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Latest comment: 18 years ago2 comments2 people in discussion
unknown Insect, Costa Rica, Tapanti National Parc
unknown Insect, Costa Rica, Tapanti National Parc
These photos were taken at Costa Rica in march. It seems, one is male, the other female. On my mind, it's not a Parascopioricus. Does anyone know the name? --Ruestz00:33, 10 September 2006 (UTC)Reply
Latest comment: 18 years ago8 comments7 people in discussion
I found a partially burried pile of soft, white, oval shaped things on the ground in my yard a few days ago. The "shell" came off easily revealing a dry, yellow, oval shaped thing. Someone told me they were mushrooms but I doubted that. If they are snake eggs, is there any way to find out what kind? I live in North Carolina(eastern US) if it helps.
--Isamil00:47, 10 September 2006 (UTC)Reply
Not a very specific answer I know, but: Some animals, including some snakes, have eggs with leathery or other not-so-hard materials for the shell, so snake eggs is a reasonable first guess. Peter Grey01:11, 10 September 2006 (UTC)Reply
Wouldn't a mushroom have a 'stem' and an egg not? Also, opening it should make it very clear, or don't you want to do that (or even pick it up)? DirkvdM09:27, 10 September 2006 (UTC)Reply
Don't open them, they could be endangered. If you really want to know, you could wait 'till it hatches (that would take a lot of waiting around though). I agree with people here though, it is probably a reptile of some sort. Were they in a hole or resting on the ground? Turtles and lizards generally create a hole or burrow for their eggs. --liquidGhoul11:49, 10 September 2006 (UTC)Reply
I can't remember ever seeing a turtle in this area. They were partially buried in mulch and were not in a hole. Tomarrow, I'l see if I can take a picture of them. --Isamil 23:25, 10 September 2006 (UTC)
North Carolina has venomous snakes as well as harmless ones, so be sure not to stick them in a box under your bed and forget them. Edison04:48, 11 September 2006 (UTC)Reply
See http://wildwnc.org/natnotes/unearthly.html for info about snake egg clusters yu might find in North Carolina. This nature center in Buncombe County might be better able to advise you. Edison 05:02, 11 September 2006 (UTC)
That helped, thanks. The article says no venomous sankes in this area lay eggs, so I suppose I'l just leave them there. Isamil19:03, 11 September 2006 (UTC)Reply
Salty Fish
Latest comment: 18 years ago5 comments4 people in discussion
They don't? I think most of them taste salty to me. Anyway, the fish has a constantly active salt-getting-out system, because it would die if it had too much salt. — [Mac Davis] (talk) (Desk|Help me improve)
... because the inside and outside wouldn't be isotonic. The salty fish would absorb too much water and 'blow up'. Conversely, a sweet water fish in fresh water would shrivel. Few fish manage to migrate from one environment to the other, like salmon. I don't know how they do that, though, and the artiocle doesn't seem to say either (just skimmed through it). DirkvdM09:31, 10 September 2006 (UTC)Reply
Some birds are very difficult to tell apart externally, though I'd bet in gulls there's some very specific (though relatively small) difference, e.g. beak color, color pattern, body frame. In order to tell the difference in cases where external inspection isn't reliable, blood or tissue samples may be required. freshofftheufoΓΛĿЌ 07:56, 10 September 2006 (UTC)Reply
Maybe they don't and just give it a try. Getting it right half the time should be sufficient to keep the species alive. Of course this would also mean that male gulls get butfucked a lot, but hey, if that's their thing. Some humans even like it. (Sorry about being such an open minded Dutchman again. :) ) DirkvdM09:37, 10 September 2006 (UTC)Reply
User:Freshgavin is correct - if you watch a breeding pair of gulls (herring gulls and GBB gulls at least) stood next to each other, 9 times out of 10, the male will be longer, wider and with a slightly bigger beak. It is very hard to tell sometimes though, unless you spend a lot of time watching them - and completely impossible when there's a big flock milling around. --Kurt Shaped Box11:21, 10 September 2006 (UTC)Reply
SPSS graph
Latest comment: 18 years ago1 comment1 person in discussion
Latest comment: 18 years ago15 comments8 people in discussion
I was having a debate with my friend. He claims that music is a science, and that every song that sounds good in the world, follows the rules of musical theory. ie, every note is in the right key. Evry note is in perfect pitch. Now, I can't imagine that out of all the millions of songs in the world, there isn't at least one, that breaks at least one of these rules, while still being considered by at least some people, to be a good song.
So, my request is, does anyone know any song like this? Personally, I have no knowledge of musical theory, but I do listen to a lot of music, and I think, music, like any art form, is subjective.--Richy02:20, 10 September 2006 (UTC)Reply
Depending on what era of music you live in, there are different rules. Depending on the culture you have different tastes. In the Far East, they like pentatonal systems, in the Middle Ages, Western harmony featured the perfect intervals of a fourth, a fifth, and an octave, and the rest were called "imperfect." Western tradition focuses on harmony and counterpointing, and in recent years we have grown to place attention on the melody of the song over whatever beat or chords might be playing in the "background." Think of a favorite rock song—you can probably remember the tune, but not necessarily followed the drummer's skills the whole song. — [Mac Davis] (talk) (Desk|Help me improve)
There are not very many music theory rules, and in fact the best music is often that which artfully bends the rules. Music that follows the 'rules' can be good, for instance some of the best rock and roll is perfect 4/4 time and uses only two or three chords. But some of the best pop songs go 'out of key' and time; Peter Gabriel's Solsbury Hill and Pink Floyd's Money (song) are both in 7/8 time; Michelle (song) by the Beatles, My Little Town by Paul Simon, and lots of other famous pop songs go 'out of key' (other than modulation, going up by a half-step for dramatic tension). He's not so well-known now, but perhaps the greatest songwriter of all time, Cole Porter, was very musically complex, going out of time and key all the time. And of course classical composers did it, Beethoven in the Presto movement of his Ninth Symphony, and all our favourite modern movie composers (the Imperial March, otherwise known as Darth Vader's theme, is a great example, as is a lot of Danny Elfman's stuff). Hope that helps. Also, another John Williams example is the Across the Stars love theme, which artfully changes key about 4 times. Anchoress02:40, 10 September 2006 (UTC)Reply
Who said 4/4 is better than, say, 6/8 (favorite of Elfman if I remember correctly), which is also "standard?" — [Mac Davis] (talk) (Desk|Help me improve)
There are certainly conventions to music composition. They can and often are broken. Even the notes we define as notes (ie., what frequency we define a C to be, and so on) are not always followed, and not even in the Western oeuvre of music either. Dysprosia07:54, 10 September 2006 (UTC)Reply
About a century ago, some classical musicians decided that it was tome for 'out with the old an in with the new' because the rules were too strict (and indeed tehy were). But it was difficult to persuade composers to break with tradition, so they made new rules to replace the old ones. And some pretty stupid ones, leading to stuff like atonal music. I've heard some of it and it sounds like a pile of shite to me. DirkvdM09:48, 10 September 2006 (UTC)Reply
Of course, the absence of a Wikipedia article doesn't imply a lack of popularity in the real world; this is a whole other topic entirely. Dysprosia02:36, 11 September 2006 (UTC)Reply
To be brief on this (here is not the place to be discussing this point), it's probably for the same reason that Pokemon and other television shows are well documented while information on the arts is severely lacking. Dysprosia03:55, 12 September 2006 (UTC)Reply
As Anchoress already said, good art bends the rules. More precisely, it finds the right balance between following and breaking them. What the right balance is depends on the audience (or the artist, really). Some people prefer simple easy listening music. An extreme example is muzak, which is more a utility than art. At the other exteme you find exprimental jazz or atonal music, which I already mentioned. (btw, in pop music there is a differnce across the Atlantic, with US music being 'easier' and European music more experimental.) But there must be some rules. Take rhythm. It's usually 4 or 3 based (or multiples thereof) and occasionally you get 5 (or, rather, take 5 :) ). 7/8 is already weird, so making that work in an easy sounding pop song (as in Pink Floyd's 'Money') is a sign of sheer class. Flamenco uses some unusual rhythms too, eg 12 beat, but not quite - 3-3-2-2-2 (one, two, three - one, two, three - one, two - one, two - one, two). Indian (improvised) music seems to have very relaxed rules. I once heard a player say that if during a concert two players end up playing the same rhythm, that is a happy coincidence. I have spent about a year composing music and I like to bend the rules. One little peice I called 'blues without a rhythm', which is exactly what it is. Then agian, there is a constant hint of a rhythm, but it keeps on losing it and then finding it again, or another rhythm. If there were no hint of a rhythm at all, it would be cacaphony. But following the rhythm too precisely kills the music, a crime committed by most classical performers.
MacDavis already mentioned that almost all intervals were considered bad in the middle ages. Such as the third. Hell, you can't even make a major chord without that. Let alone a minor chord. And Mozart did something revolutionary when he used a seventh in a peice. Nowadays music that doesn't use that all the time would be considered dull. i once heard that the worst interval is the diminished fifth. So I decided to base a piece of music on it. But prettty soon I discovered that it was really based on the fifth, with the diminished fifth being a variaton of that, one that created tension that had to be resolved. And that last bit is very important. The rules are something you fall back upon, but it's the temporary deviation that makes the music interresting.
I could go on about this for a very long time. Music is the best combination of science (math) and feeling there is. It makes the basic human thought paterns (intelligence) explicit more than anything I can think of. DirkvdM11:29, 10 September 2006 (UTC)Reply
A few months ago, on NPR, they talked about music theorist Dmitri Tymoczko, who recently wrote a paper describing a new type of geometry he had created to represent music. There have been all kinds of music geometries to represent music, but none of them got it "all" right, but his apparently does. His paper was accepted to Science magazine, the first music theory paper they had ever published in 120+ years. In that paper, he says that Chopin's piano prelude in E-minor (Opus 28, No. 4) is the make-or-break song. Apparently most predictors indicate that song should sound like crap, but it sounds fairly good. Raul65417:06, 10 September 2006 (UTC)Reply
Latest comment: 18 years ago1 comment1 person in discussion
My 4th grader need to research information regarding interior plains in the United States. We were able to obtain information on the wiki under great plains. We are lookin for answers on specific questions such as:
1. What forces of nature cause the interior plains of the United States to be formed or in other words, how did it develop>
2. What is unique about the interior plains?
3. What efforts are being made to preserve the inerior plains?
My 4ht grader went to the library and they do not have any materials in plains under landforms. Please help her.
Thank you very much.
This is an encylopedia, and you can just type in "Interior Plains" in the Find box in the left. Push go, and you're there. :) — [Mac Davis] (talk) (Desk|Help me improve)
Latest comment: 18 years ago3 comments3 people in discussion
Okay, there are sequential hermaphrodites that change sex as part of their life cycle, and simultaneous hermaphrodites that have both sex organs; but is there such an organism that dynamically changes its own sex based on current population sex ratio, environment, available resources, etc. ? Phoenix-forgotten05:37, 10 September 2006 (UTC)Reply
Latest comment: 18 years ago5 comments4 people in discussion
Is it true that if your current cell phone you use breaks and it is not repairible that the battery can be placed in another phone and all your data remains or is saved on the new phone.--Biggie05:49, 10 September 2006 (UTC)Reply
No, batteries have no capability of storing information in such a way. Even if there was a battery that was for some reason attatched to a memory chip, it would probably only work in the exact model of phone that it was constructed for. freshofftheufoΓΛĿЌ 07:49, 10 September 2006 (UTC)Reply
Latest comment: 18 years ago5 comments4 people in discussion
Suppose I have a 100W amp. Does it draw 100W all the time? Or does that depend on how far I turn the volume up? Or even how loud the music is (the dynamics of the music)? I suppose the former but not the latter. If I set it at half the maximum volume, measured by subjective perception (it sounds half as loud). Is the power consumption then half of what it would be at maximum volume (so 50W). I'm pretty sure not (much less), but what is it then? DirkvdM09:08, 10 September 2006 (UTC)Reply
Yea, that's the maximum. Whether you reach the max would depend on both the volume of the recording and the volume setting on the amp. StuRat09:13, 10 September 2006 (UTC)Reply
If its class A, yes it will draw constant power wasting whatever doesnt go into the speaker. But if class AB (which has a max efficiency of 78.5%), then the power consumption is almost proportional to the power in the speakers (and hence the volume). In a class AB amp, there will be some constant power dissipation not related to the output power, but this will only be a few watts at most. See electronic amplifier--Light current09:23, 10 September 2006 (UTC)Reply
In general electronic equipment may draw far more electricity than its rated output. High fidelity is a bigger goal with audio than efficiency. Any heat given off is the result of that inefficiency.Edison19:29, 10 September 2006 (UTC)Reply
gravitational waves and propulsion
Latest comment: 18 years ago2 comments2 people in discussion
Im aware that none of the machines that claim to produce these waves have been varified, but they exist right? What is the mainstream physics communities views on gravitational waves being used for propulsion or moving objects in the future? and are these the waves produced by gravitoelectromagnetism?
Robin
Well, gravitational radiation is produced whenever a mass accelerates, but for everyday masses and accelerations the waves are unobservably small. To produce enough gravitational radiation to detect, you need huge masses accelerating very fast, like binaryneutron stars spiraling towards each other. (The reason they spiral towards each other instead of staying in a stable orbit is exactly because they emit gravitational radiation.) I did find a paper with the exciting title Gravitational radiation and its application to space travel, but it's all theoretical so far. —Keenan Pepper16:18, 10 September 2006 (UTC)Reply
Keenan Pepper is absolutely right about the mechanisms behind gravitational radiation although it's probably worth pointing out that motion in a circle is acceleration (lay-people, particularly argumentative ones, sometimes disagree with this). I haven't read the paper, but I can't imagine gravitational radiation being terrible useful for space travel as it is really rather weak. If it were to be harnessed then the first step would be to use it to transmit information. Its real worth will be (at least initially) for observation as it will allow us to see back into the radiation dominated period of the Universe.
Keenan, do you have an arXiv citation? This sounds like some presumably unpublishable (since terribly wrong) eprints I have seen there.
Robin, the mainstream view is that gravitational waves interact very, very, very weakly with matter and cannot be used in any practical way to manipulate matter or for spacecraft propulsion. There are some papers out there by physicists (and even non physicists) who are too inexperienced in the ways of curved spacetimes to avoid confusing "coordinate effects" (artifacts of a mathematical representation, which have no physical reality) with genuine physical effects. The very fact that LIGO requires such extraordinary efforts to detect even the strongest gravitational waves ought to tell you something! See for example this readable expository paper by Kip Thorne. ---CH03:47, 18 September 2006 (UTC)Reply
We're out of transcluded pages
Latest comment: 18 years ago3 comments3 people in discussion
Erm, I'm not sure I get what you mean. If you mean you can't transclude more templates than we have right now, we just archive the oldest day (it may even be done automatically), but I don't think we're out of transcluded pages. The max. limit was raised, and I doubt we hit it. - 87.209.70.23114:05, 10 September 2006 (UTC)Reply
I believe he means that none of the Ref Desk pages currently include any transcluded pages pointing to archive pages. In this case, instead of just removing the transclusion, we need to first create the archive page, then remove the day from here. I believe this will need to be done manually, as the bot that did this is no longer running. StuRat00:10, 11 September 2006 (UTC)Reply
Sexual Advice
Latest comment: 18 years ago13 comments10 people in discussion
Que: Can a curved penis be made straight with the help of surgery?
— Preceding unsigned comment added by 59.144.180.72 (talk • contribs)
I think so. Is it really worth the pain, hassle and expense though? Supposedly most men's cocks bend either to the right or left when erect. How 'curved' are we talking about? --Kurt Shaped Box16:55, 10 September 2006 (UTC)Reply
Apparently bent ones offer a better experience for the woman... obviously not to bent... but yeh, anyway, you may just be being to self conscious. PhilcTECI17:26, 10 September 2006 (UTC)Reply
Penises are rarely straight; they don't need to be for good sex. I wouldn't worry about it. If you do, bring it up with your doctor. He's the only one who can decide if surgery can be done and if it is needed. - Mgm|(talk)19:46, 10 September 2006 (UTC)Reply
Youd be surprised, doctors do have the right to refuse to perform surgery you know, their not legally bound to straighten your penis on demand you know. Ususally you wont even know if they have refused, because they would have just had a few sessions with you, and chatted about what you want done, and by the end of it convinced you that you dont want surgery, because usually they're right. PhilcTECI21:44, 10 September 2006 (UTC)Reply
let's just get something straight. The guild-like AMA and all member doctors chose their profession for the respect and the money. Trust me, you offer the money and you'll be able to find an AMA doc to do it for you. Jasbutal04:44, 11 September 2006 (UTC)Reply
Guys, we tell our ref desk clients to seek appropriate professional advice about medical, dental, or legal matters. That means that we shouldn't be entering into debates about the merits or otherwise of such surgical procedures. Shantavira's reply was the perfect one. IMO, everything since then has been inappropriate. JackofOz01:35, 11 September 2006 (UTC)Reply
Anyone with half a brain should understand that this is not a medical ref desk. If you get an expert reply you're lucky. Most answers will be educated guesses that might point you in the right direction. By your reasoning we shouldn't have any medical articles either, unless it has been established beyond doubt that the autors are true experts on the subject at hand. DirkvdM08:32, 11 September 2006 (UTC)Reply
I agree. You don't have to be a man interested in straightening his curved penis to be curious about whether curved penises can be straightened. It's an encyclopedic question, so it's within our ___domain. We should always be careful to remind people that we're no substitute for doctors, but as long as we do that, I think we should feel free to try to figure out answers. --Allen08:54, 11 September 2006 (UTC)Reply
What I'm talking about is practising what we preach. People often get abused around here when they ask a question without first doing a search. I don't agree with the abuse part of it, but the central issue is that there are guidelines that questioners are asked to read and abide by. Fair enough. Well, guidelines work both ways. The other side of the coin is that we can hardly ask them not to expect medical, legal or dental advice here, if we in fact tender such advice in response to a question. Every time we break our own rules, we undermine our credibility. That's my main concern here. JackofOz07:28, 12 September 2006 (UTC)Reply
Latest comment: 18 years ago1 comment1 person in discussion
What is the simplest way to understand the concept of space-time and its curvature?
the ? varible is part of the experiment that is affected by the independent varible.
if you could help please. thank tou
Think of it in terms of a man's penis - supposedly most men's cocks bend either to the right or left when erect. I think space-time curves in the same manner. (sorry, that was a silly answer - but I couldn't resist) --Kurt Shaped Box17:02, 10 September 2006 (UTC)Reply
Well the ubiqutius explanation of general relativity is probably found at the article. It concerns a latex sheet representing the spacetime continum, and masses bend the sheet, curving it, and that is a gravitational field. — [Mac Davis] (talk) (Desk|Help me improve)
The rubber sheet is an reasonable simplification - as with most concepts of curvature in three (spatial) dimensions removing a dimension helps people to visualise it. As an undergraduate, one of my professors told me that to visualise the curvature in three dimensions is impossible. However, I find visualising a gravitating body as stretching spacetime by pulling it towards it (pulling more strongly nearer the body and less further away - inverse square law) makes for an acceptable visualisation. I justify this by imagining a triangle being stretched in just such a manner - the internal angles will equal less than 180˚ - demonstrating just such an hyperbolic geometry as is associated with a gravitating body.
For most people it is not possible to visualize the three dimensional negative curvature, but it is better to do that if you can. I *think* the easiest two ways (I have made them myself and never told anybody before) are to imagine the flat sheet, and one that is perpendicular, along the z axis. Stick Earth right inside that corner, and see the dip. Or you could imagine something like the Earth as a spikey ball, and the (hollow) spikes being like a tangible gravitational field. Kind of like sticking your finger into the Earth and the paper turning into the shape of your finger, flairing at the edges. — [Mac Davis] (talk) (Desk|Help me improve)
I'm not sure what the advantage of having two sheets is over the single sheet - having two sheets is still a two dimensional representation just with a fold. A complication which, to me, doesn't have any advantages. As for the 'spiky ball' explanation, I have never heard of anything like that for explaining curvature and I'm not really sure what you're getting at with it (this is not a criticism). In my experience, the problem most lay-people have with visualising curvature in three dimensions is that they don't try to think of it in terms of the geometrical properties of the curvature.
Direct gene transfer using PEG and Calcium chloride
Latest comment: 18 years ago3 comments2 people in discussion
Sir/ Madam,
I will be benefitted if I get more information regarding and related to this subeject.
We don't seem to have an article on your meaning of PEG, and Calcium chloride has just a couple of sentences: "Aqueous Calcium Chloride is used in genetic transformation of cells by increasing the cell membrane permeability. This allows DNA fragments to enter the cell more readily." The reference isn't given. Melchoir21:30, 10 September 2006 (UTC)Reply
The PEG in this case is polyethylene glycol, linked from the dab page at PEG. What the original poster really needs here is either a good laboratory manual that describes the process in detail, or (ideally) a local colleague who has experience with transfections and can provide a protocol. TenOfAllTrades(talk) 21:45, 10 September 2006 (UTC)Reply
1. Unless it was quite strong, it would burst (without a bang).
2. It doesn't matter. Assuming it gets off the ground it will eventually reach an altitude at which its weight is balanced by its reduced lift in the rarefied air.--Shantavira18:19, 10 September 2006 (UTC)Reply
A helium balloon in space would inflate to the same size as on earth if the pressure differential were the same between the inside and outside. So if atmospheric pressure is 14.7 pounds per square inch or 101.325 kPa, and the balloon inflates to 1 foot diameter on earth, in space for it to inflate to 1 foot the internal pressure would have to be reduced by 14.7 PSI. Now consider temperature: if the balloon is in the shade, it will radiate off heat, become cool, and shrink. The pressure would decrease in proportion to the drop in absolute temperature, PV=nRT per the Gas laws. If the balloon is in the sun, it would heat up and expand. If it were in the International Space Station or the Space Shuttle, it would drift with air currents, with no particular tendency to rise to the ceiling or sink to the floor, since these surfaces would be interchangeable. If you untied the stem and let the helium spurt out, it would take off like a rocket, since Newton's Third Law says To every action (force applied) there is an equal but opposite reaction. The lack of a surrounding atmosphere for the balloon exhaust to "push against" would not invalidate this law. If you stuck a pin in it, it would burst, but silently,since there is no air to transmit sound. Echo 1 (seeEcho satellite) was a plastic mylar balloon put in space as a passive communication satellite in 1960 which lasted until 1968. 100 feet across, it was easily seen with the naked eye when in the right portion of the night sky to reflect sunlight. It can be seen at http://www.scienceandsociety.co.uk/results.asp?image=10300344&wwwflag=2&imagepos=1 No info on whether it was inflated with hydrogen or another gas, but a gas with larger molecules might not have diffused out through the skin as fast.Edison19:53, 10 September 2006 (UTC)Reply
It all depends on how big the ballon is, as its area (i.e. the weight of the skin of the balloon) goes up in squares, while the capacity cubes. So there is no one answer, though a formula could probably be concucted. PhilcTECI21:52, 10 September 2006 (UTC)Reply
Latest comment: 18 years ago6 comments5 people in discussion
I've had sinusitis before (eleven times in one year, at one point) and I'm fairly sure that it's not contagious, but I'd just like some verification, because this could be old information. Is sinusitis contagious, and if so, how contagious is it? Thanks in advance!! Srose(talk)19:01, 10 September 2006 (UTC)Reply
Contagiousness relates to spread of a disease from one person to another. Sinisitis can be infectious, but results mostly from bacteria already resident in the sinuses rather than "caught" from other people. You need to ask your physician what is causing you to have chronic sinusitis and what can be done about it. - Nunh-huh19:16, 10 September 2006 (UTC)Reply
Get your medical advice from a physician. 11 time in a year is way too much. See an Eye Ear Nose and Throat specialist. But from personal experience, there may be things he can do to alleviate the condition. Sinusitis can lead to some very bad things, such as meningitis.Edison19:56, 10 September 2006 (UTC)Reply
Thank you both very much! I've replied on your respective talk pages. I do get most of my advice from my physician and the specialists that I see, but of course they're unable to answer questions on a Sunday! :) Anyway, I'll repeat myself and say: thank you very much! Srose(talk)22:20, 10 September 2006 (UTC)Reply
If you have an allergic or autoimmune form of sinusitis, then it's not contagious, but it may be if you have a fungal, viral, or bacterial form. StuRat23:28, 10 September 2006 (UTC)Reply
Latest comment: 18 years ago3 comments2 people in discussion
I know mammals have hair composed mostly of keratin. Many insects, like this moth, also have hair. Is it made of chitin, or some other substance? Gary19:10, 10 September 2006 (UTC)Reply
Latest comment: 18 years ago6 comments6 people in discussion
I have this year learnt how to grow plants from seed. For fun I bought a packet of melon seeds and planted them in pots - I do not remember how long ago. I have three green melons about four or five inches in diameter.
How can I tell when I should harvest them please? As I am in the UK they may not grow as large as the watermelons for sale in supermarkets, as the latitude (or maybe I mean longitude?) here is about the same as Newfoundland and hence the sun is not as powerful.
As I noticed that something had eaten into the rind of one of them, I did cut that off the stalk and sliced it open and ate it. I realised it was a watermelon. It was pink inside with seeds, and was moderately sweet. So now I've got two left. Will they grow any more or should I harvest them now?
If the first watermelon seemed ripe, I'd harvest the other two right now, especially since it seems they may be eaten by something, if you wait. StuRat23:22, 10 September 2006 (UTC)Reply
The ones we grew were way bigger than what you described, so may be a different type. You can tell when a melon is ripe by thumping it with your knuckle. An unripe watermelon, not yet red or sweet will have a relatively high pitched clear sounding thump. A ripe watermelon will have a dull and lower-pitched thump, probably due to the appearance of cracks in the interior or to the higher sugar content. If there are smaller and greener melons, these will grow and ripen unless the temperatures have dropped. Melons ripen best on hot days with full sun. If the vines and leaves look brown and dead I would not expect any more ripening. They will eventually rot if not picked when ripe. I do not believe they continue to ripen after picking. They can be stored for days in a refrigrator. Enjoy!Edison04:42, 11 September 2006 (UTC)Reply
That thumping experiment seems nice. But if you already have you're melons ripe, what can you use as reference to whether it's dull or high pitched? --Proficient06:19, 11 September 2006 (UTC)Reply
Latest comment: 18 years ago7 comments7 people in discussion
Recently I was driving home at dusk and was surprised to see the sun sinking in the east. I thought I'd taken a wrong turn. It was a few minutes before I realised I was not looking at the sun sinking, but at a bright full moon rising.
This made me think - as the sun had just gone under the horizon in the west, then it was in the right position to shine full-on the moon in the east.
So are full moons always seen in the east, half-moons in the north or south, and new moons in the west?
And would some extra-clever person be able to calculate from the astronomical data I have given where I was in the world, or what date it was? 81.104.12.4721:21, 10 September 2006 (UTC)Reply
That sounds about right, if you mean where the moon is just after sunset. Seems to me that the full moon would also set in the west just before sunrise. Melchoir21:27, 10 September 2006 (UTC)Reply
Earlier this week I saw a huge full moon rise in the east and move across the sky to the west. It set in the west. This happened because the earth rotates. Half or quarter moons behave the same way. Edison04:34, 11 September 2006 (UTC)Reply
What I was going to say. See lunar cycle. A full moon is always "opposite" the sun (that is, 180° away from it in the 360° sphere of the sky), while a new moon is always very near the sun. You're more likely to see a thin crescent during the day than at night. --Ginkgo100talk · e@04:51, 11 September 2006 (UTC)Reply
Full moons are more usually seen in the east merely because that's the time and place where they attract attention, i.e. just after dusk and near the horizon. But then they rise and culminate around midnight and set in the west in the early morning. And no, it would not be possible to calculate your position from that information alone. The moon appears full on the same night everywhere, and always rises in a generally eastern direction (anywhere between NE and SE depending on the time of year.)--Shantavira07:56, 11 September 2006 (UTC)Reply
As Ginkgo100 observed, a moon is only truly full at the one instant when it is 180° away from the sun. When you think about that, that means that it must be midnite on that part of the Earth that is "under" the full moon. Other parts of the planet's night side will see that full moon at the same instant, but, of course, their local time will vary. For some people who are just slipping into the night side darkness, that full moon is just rising in the east. For others who are just slipping out of the night side darkness and into daylight, that full moon is just setting in the west.
Oxford UK, September 7th? ≈Eh-Steve 19:35, 17 September 2006 (UTC)
Chocolate allergy?
Latest comment: 18 years ago8 comments6 people in discussion
Hey all. Several years ago I noticed that eating chocolate would cause me to sneeze, usually only once or twice, within a minute or so of consumption. For a while now I've wondered what it is that is actually causing me to sneeze. I had a theory that how much I sneezed was dependant on the richness of the chocolate, but I can't say I've conclusively proven that. I assume this is an unusual case seeing as Wikipedia's allergy page makes no mention of sneezing or chocolate. Anyway, some answers please:
Any suggestions on what precisely within the chocolate is causing the reaction?
How unusual is it to a) have such a consistent mild reaction to something and b) to something as unusual (in terms of being allergic to) as chocolate?
Pioneer 10 and 11 are both dead. But there are a number of other active missions to Mars, the Sun, Pluto, etc. A number of satellites still in orbit are dead, either in parking orbits or just not yet fallen back to Earth. (Vanguard 1, launched in 1958 but dead since 1964, is the oldest satellite still in orbit.) Rmhermen02:40, 11 September 2006 (UTC)Reply
6Q0B44E is a recently discovered satellite in earth orbit a couple of times the moon's distance out. It is suspected to be a Saturn booster from the Apollo programs which was lost in space for 30 years or so then wandered back into earth orbit circa 2001. Ironic?Edison04:30, 11 September 2006 (UTC)Reply
Interesting. thanx for the informations guys! i never realized the number is in 4 digits!
also, why are there so many dead ones? why doesnt the owner just blast them outwards from our solar system? it wouldnt be as harmful to polute the rest of the galaxy instead of our own solar system. plus, doesnt it get too crowded? have any two satallites ever collided?
Escaping from the solar system requires a lot of fuel and is therefore expensive. It's much better to force the satellite into Earth's atmosphere and have it burn up. Also, space is huge, and a few thousand satellites aren't going to do much. (Imagine if there were only a few thousand people on Earth's surface. And Earth's surface is two dimensional, while satellites can move in all three dimensions.) --Bowlhover20:02, 12 September 2006 (UTC)Reply
Is this how to convert moles to grams?
Latest comment: 18 years ago7 comments6 people in discussion
And if you have a molecule instead of a monatomic element, then you need to add up the atomic weights of each atom in the molecule. So for H2O, you would add the weight of two hydrogens and one oxygen, to get the molecular weight. This molecular weight is then multiplied by the number of moles to get the number of grams. StuRat22:58, 10 September 2006 (UTC)Reply
Latest comment: 18 years ago8 comments6 people in discussion
Is the possibility of animals creating their own language in the next 100,000 years possible? Besides barking or meowing etc... or the fact that some birds were trained to talk. This may be more of an opinion question unless some theories have already been created by scientists. -MF14
Yes, animals already have a "language", it's just very primitive by human standards. They can manage to tell each other when they are angry, horny, hurt, etc. Communication within each species is the clearest, but interspecies communication is common, as well. You generally know what your dog or cat wants, don't you ? However, if you expect to have a discussion with your cat on the tenets of existentialism, forget it. It's not that the communication is limited, it's that they can't understand any of those concepts, as they lack basic "symbolic logic" and any potential for abstract thought. StuRat00:03, 11 September 2006 (UTC)Reply
All sorts of things are possible over the course of 100 000 years, but while animals have means of communication, none of them (except bees) currently appear to have anything ressembling the human language faculty, which combines abstraction, symbols independent of external stimulus, and grammatical structures for building complex representations out of symbols. Scientists aren't completely sure about all the issues, but human language is not simply a more complex form of animal communication, so it's not clear there would be any reason for another species to evolve the ability. Peter Grey02:00, 11 September 2006 (UTC)Reply
A relativist's observation: human language is probably pretty primitive by, say, platypus standards. They probably think humans are pretty dumb because we cannot communicate about the things that matter to them. (And don't ask me what those are because I am only human). Platypuses learning human language is as (un)likely as humans learning platypus language. DirkvdM08:44, 11 September 2006 (UTC)Reply
I don't think that's true. A platypus is not cognatically capable of wondering if the "platypus language may possibly look primitive by human standards", and thus, is more primitive. Humans are much more likely to learn platypus language than platypi are ours, because we can observe them and create models to mimic their behavior. freshofftheufoΓΛĿЌ 09:12, 11 September 2006 (UTC)Reply
How do you know? We're humans (a fair assumption :) ), so we cannot know how platypuses reason. We'd have to be platypuses for that. Even as a kid I always found the question "what animal would you like to be?" stupid. I'd have to be the animal to know what it is like to be that animal, but even if that were possible then I wouldn't know what it would be like to be another animal (or a human for that matter), so I still couldn't make the comparison. Your reasoning is the basis of xenophobia - they're different, therefore they are inferior. DirkvdM09:01, 12 September 2006 (UTC)Reply
I understand your argument, but I don't think you're taking a valid position. <OR WARNING>I believe that creature intelligence is directly related to logical thinking power, and a being that has the capability of thinking with a certain degree of logic is also capable of determining roughly the level of logic of a creature capable with a similar or lower level of logic than themselves. A creature with a significantly higher level of intelligence would be capable of concieving a strategy to fool others into believing that they were less intelligent as well as a reasoning for wanting to do so. I can only assume that platypi are not super-intelligent beings, though I do believe that is a fair assumption as well. freshofftheufoΓΛĿЌ 05:07, 15 September 2006 (UTC)Reply
I'm no expert but I do spend a lot of time watching gulls and corvids and to me, it certainly seems that they have a language - a fairly complex one too. As well as the various vocalizations, there seems to be an aspect of body language used to modify the meaning of various utterances. Seriously, just watch two (non-aggressive) herring gulls communicating sometime - it's like some strange choreographed dance. --Kurt Shaped Box14:30, 12 September 2006 (UTC)Reply
what plant is this
Latest comment: 18 years ago4 comments2 people in discussion
Are the leaves similar to grass leaves? It might be some kind of lilyturf - grasslike plants in the lily family. This one looks like it, Liriope muscari.
Latest comment: 18 years ago1 comment1 person in discussion
How and or where do you find the publication date and city of the encyclopedia?
Where do you find the author?
Where do you find the volume of the encyclopedia that you are using online?
Where do you find the copyright dates?
Latest comment: 18 years ago2 comments2 people in discussion
Can anyone identify some blurry space mission patches? [2] there are four here we haven't been able to identify, but we got all the others. They range from all over the place, Canadian Astronaut Service, Shuttle missions, Apollos. One of them looks like they have a house on it, but I haven't been able to find anything. - A.J.01:17, 11 September 2006 (UTC)Reply
Don't know any of those four, but the bottom one I can identify as that space insignia. Sometimes called a vector, or a wishbone, it is like an "A" representing the abstract of a rocket. You know what I mean? — [Mac Davis] (talk) (Desk|Help me improve)
The ship in the movie Virus?
Latest comment: 18 years ago1 comment1 person in discussion
I've been exceedingly curious for apparently no reason as to what this vessel was for. As I remember, it looked real enough in the film. The movie claims that it's some kind of Russian space agency secondary control center but I cant find anything about that.
I'm pretty sure they are reffering to the russian ship which the tug boat crew boards with the idea of salvaging for large sums of money. (Little do they know that the ship has been affected by a sentient bolt of lightning form outerspace and that all manner of mechanized zombies await them! No, seriously, that's the movie plot.) I don't remember much about the ship though. -Razma Dreizehn
Microscope Eyes
Latest comment: 18 years ago8 comments7 people in discussion
Sometimes, under the right conditions, my eyes somehow reflect light and let me see microscopic thingies on the surface of my eyes. I can clearly make out hollow cells joined together in rather short groups. It looks like this: http://img242.imageshack.us/img242/7062/untitledzz4.jpg The 'cells' move across my eyes usually from up to down. This phenomenon happens in bright light, I think. I wear persciption glasses, but I think that it has happened without me wearing glasses too. Has this phenomenon ever been reported by other people, or am I the only one? What conditions do I need to have to see this more often?--Codell[ Talk ▪ Contrib. ]03:20, 11 September 2006 (UTC)Reply
I get something like that, too. They are always out of focus with me, and I usually get them when I first wake up. I always assumed they were slime on my eyeball. After a few blinks they go away. I can't look directly at them, because moving my eyeball causes them to move. StuRat05:11, 11 September 2006 (UTC)Reply
because they're on your eyeball. And you know that, but still can't resist the urge to try and look at them, right? Btw, how was that photo in the article made? Did someone stick a camera in their eye? :) Probably not, but it looks pretty much like the real thing. DirkvdM08:53, 11 September 2006 (UTC)Reply
This is probably one of the most asked questions on the Science desk. It's still cool though, I always kept it a secret when I was a kid because I figured no-one would believe that I was seeing red sperm in my eyes. freshofftheufoΓΛĿЌ 08:56, 11 September 2006 (UTC)Reply
Under certain circumstances (usually, a bright deep blue featureless background), it is also possible to visualize the red blood cells moving in the capillaries in your retina. The Exploratorium has a gadget that can reliably provoke this effect, but given some time, you can usually see it with any deep blue featureless field. (I mention this just for completeness; your effect sounds like floaters.)
A tank is filled with 1000 L of brine, containing 15 kg of dissolved salt. Pure water flows into the tank at a rate of 5 L/min. The solution is kept completely mixed, so the concentration of salt is uniform, and the solution flows out at 5 L/min. How much salt is in the tank after t minutes? after 20 minutes?
It could also be the equation in geophysical fluid dynamics which at least one person has called "Conservation of Salt" - . Then again, thinking about it, that may just be an extension of the above problem - it's just a statement that the amount of salt in a system is based on the flow in and flow out. Confusing Manifestation00:55, 12 September 2006 (UTC)Reply
Time to freeze water?
Latest comment: 18 years ago11 comments7 people in discussion
Is there a formula for figuring how long it will take to freeze a given volume of water at a given below-freezing temperature? I couldn't find one with a brief web search, but figured there should be... -Goldom‽‽‽⁂07:41, 11 September 2006 (UTC)Reply
For one you'd have to know the starting temperature of the water. And then the contact area and the heat conductivity of the container. And the shape too, but I assume that if there will be any such formula it will assume a shape that has a simple geometric description, such as a cube. DirkvdM08:59, 11 September 2006 (UTC)Reply
You'd also need to know the pressure and the starting temperature of the water. I don't believe there is a formula as there is the unexplained (I would be delighted to hear any explanations) problem as to why hot water freezes faster than cold water when the same volumes (and shapes) are put in the same (below freezing) tempreature and the same pressure. — Preceding unsigned comment added by OEYoung (talk • contribs)
Compare this problem with that of 2 capacitors of equal value charged up to different voltages. When they are discharged thruough equal resistances, which one reaches V volts first? Certainly not the one charged higher initially!--Light current12:41, 11 September 2006 (UTC)Reply
Thanks DMacks - I couldn't remember the name. I didn't believe it myself until I tested it. If you can come up with the reason for it it'd probably win you a nobel prize! — Preceding unsigned comment added by OEYoung (talk • contribs)
Water gives up dissolved gases when heated. Dissolved gases should lower the freezing point of a solution. So if it is previously heated but allowed to cool to the same temp as the cool water, it should freeze faster.Edison19:05, 11 September 2006 (UTC)Reply
Well its not pure water then is it? Its actually a different liqiud and can be expected to behave differently. You must not compare apples and oranges. THeyre different--Light current00:20, 12 September 2006 (UTC)Reply
Pure water doesn't exist (pure anything doesn't exist). So what we call 'water' is a range of solutions. Only when the impurities become too big an ingredient will we stop calling it water. Any rules on that? DirkvdM09:06, 12 September 2006 (UTC)Reply
olympic and islam
Latest comment: 18 years ago2 comments1 person in discussion
I "created"an article concerning muslim athletes participating in olympic games.
I am unable to locate the article.
I am understanding that anyone can write an article..
please advise.
This question would be better placed at the help desk. Anyway, please sign your questions using the signature buttom or 4 tildes (~) so we can easily see who you are and what you edited. - Mgm|(talk)10:20, 11 September 2006 (UTC)Reply
Anyone can edit an existing article, but too write a new one you need to register an account and log in using the link on the top right of the page. You added this question with your IP address suggesting you're not logged in. - Mgm|(talk)10:22, 11 September 2006 (UTC)Reply
Why did nobody die of a heart attack before 1923?
Latest comment: 18 years ago9 comments8 people in discussion
Whilst perusing the Uni of Manchester website [3] I came acroos the above statement.
Anyone have any idea as to where it originates from and also, if it's true?
In the last century, heart attack has been the lay term and legal term for any type of sudden death in an adult attributable to myocardial infarction or any other heart disease. Heart attack entered common language in the first decades of the 20th century. It began to appear on death certificates in the early 20th century. The detailed concept of myocardial infarction in its strict sense (death of heart muscle because of interruption of blood supply) also dates to the early 20th century. The statement does not mean that no one ever died of a myocardial infarction before 1923 but that the cause was not recognized and described with the more familiar term. alteripse10:55, 11 September 2006 (UTC)Reply
This naturally raises the question of what it was called when somebody grasped their chest, then dropped dead, before 1923. StuRat14:22, 11 September 2006 (UTC)Reply
Well heart-failure and heart-shock go back to the 19th century, maybe English speakers didn't like to talk about it before then. Apoplexy more usually means a stoke but it sometimes refers to any fit, faint or attack. MeltBanana14:43, 11 September 2006 (UTC)Reply
I doubt it. i would say the success of identifying people with weak hearts, medication and open heart surgury are more likely to be contributing to the increase in cancer. I have no data to back up this thought though. David D.(Talk)20:50, 11 September 2006 (UTC)Reply
By that, I was trying to imply that it is the diagnosis that began in 1923, not that heart attacks didn't happen. ;) — [Mac Davis] (talk) (Desk|Help me improve)
Not semantics, this is a pair of definite history of medicine questions. How was this type of death conceptualized and understood a century ago? How much has the rate of death from this cause (regardless of what it was called) changed between the 19th and 20th centuries. The first answer I gave was off the top of my head, but I have a few late 19th and early 20th century medical texts at home and I will see if I can give a slightly more precise answer. alteripse21:01, 11 September 2006 (UTC)Reply
Usually these sorts of questions are easier to deal with if you pick more controversial "illnesses"—i.e. ADHD. Questions like the "heart attack" one are meant to destabilize even things which seem more concrete as well. The ADHD page unconsciously gives a good example of the sort of methodology that makes a historian cringe when it identifies ADHD in Ancient Greece — once you've decided on an arbitrary diagnoses, you can go back in time and read any disease into past writings, even though the conceptual/dianostic category did not exist at the time. --Fastfission22:23, 11 September 2006 (UTC)Reply
satellites
Latest comment: 18 years ago45 comments10 people in discussion
This is not homework.
Suppose there is a satellite in an orbit of 10r ( r is the radius of the earth) which falls back to earth due to a malfunction. What will be the speed with which it will impact the earth's surface ???????
Thats not necesarily true. It could reach much higher speeds in space, and then not accelerate back down to its terminal velocity in the atmosphere. If it did hit at its terminal velocity, it would be a bit of a coincidence. PhilcTECI13:58, 11 September 2006 (UTC)Reply
I disagree. With an artificial satellite, the size is small enough and the Earth's atmosphere is thick enough that it would be sure to decelerate back down to it's terminal velocity, unless it burns up in the atmosphere first. StuRat14:19, 11 September 2006 (UTC)Reply
The smaller an object is the less it will be slowed down by drag. Most physicists would use the word accelerate in this situation to mean slow down - (the magnitude of) acceleration can be positive or negative. - Not Philc. P.S. its terminal velocity.
Thank you anonymous person. StuRat, Decellerate is a non scientific word coined by the US scientific community to remove some ambiguity, but has since lead to common missuse of the word acelerate, it actually means a change in velocity, which means a change in direction and/or a change in speed. The shuttle is a view of the sort of shape you need to control your decent, incredibly wide in proportion to height and weight, sattelites and meteorites, etc, are not of good proportion for slowing down, and if they are large enough to impact before they burn up, would almost always impact at a much higher speed than terminal velocity. PhilcTECI15:26, 11 September 2006 (UTC)Reply
"Decelerate" seems like a perfectly good word to me...or shall we also have the temperature "heat back down" to freezing, and the budget "increase back down" to zero ? If you want to use the phrase "negative acceleration", that's fine too, although a bit formal for common usage, for my taste. StuRat16:15, 11 September 2006 (UTC)Reply
Thats my point exactly it is incorrect to assume acceleration is an increase it is not it is a change, if their is a change in temperature it does not imply a rise, and if there is acceleration it does not imply a rise in speed or even any change in speed, but a change in velocity, wether it be a increase or decrease in speed or a change in direction. Maybe you should consuclt the article beofre speaking again. PhilcTECI16:34, 11 September 2006 (UTC)Reply
Just as a "change in temperature" does not imply a temp increase, a "change in velocity" does not imply an increase. However, if something is heated, that means an increase in temp, and when it is cooled, that means a decrease in temp, just as something which is accelerated means an increase in velocity and if something is decelerated, that means a decrease in velocity. Now, you could refer to zero acceleration or zero deceleration to mean the object is not accelerating at all, and you could even refer to negative acceleration, or even negative deceleration, if you must. But to describe an object as "accelerating" when it is slowing down is horrid, and bound to confuse everyone. StuRat12:28, 12 September 2006 (UTC)Reply
I think one problem with the term "deceleration" in physics is that in one intertial reference frame, an object is slowing down - whilst in another intertial frame, the same object is actually increasing in speed. Both reference frames are equally valid viewpoints in which the laws of physics are identical - yet one viewer is seeing the object slow down - the other speed up. The force applied in both cases is identical (it's just the same object after all) Acceleration need not refer to a change in speed as well - a planet orbiting the Sun in a circular orbit at constant speed is continuously accelerating (towards the Sun). In useage within the general public - viewing from different reference frames are not usually important as we usually have the Earth as our reference frame - but imagine flying in a plane above heavy cloud - you don't have any perception of movement other than the rumble of the engines and occasional turbulence. Another one about reference frames is in, say a car crash. Ask someone about what happens, and they'll say that loose things in the car were "flung" forwards i.e. accelerating. Measure what's actually happening from outside the car - and they're slowing down. So my point is that acceleration is just the rate of change of velocity - and it has a direction (which you could regard as being in the + or - direction for linear changes in speed). But it's odd to talk about an object simultenously decelerating and accelerating as a reaction to the same force - when they're just being viewed by 2 different observers.Richard B21:19, 12 September 2006 (UTC)Reply
Ok, if dealing with an acceleration in a constantly changing direction, I take your point. However, acceleration may also refer to a scalar, where the direction doesn't change. In such a case the term "deceleration" for negative acceleration is perfectly clear. StuRat22:37, 12 September 2006 (UTC)Reply
That's not quite correct. Acceleration does not vary between reference frames - only uniform motion does. In your car crash example, the loose objects would not accelerate (ignoring gravity and air resisitance). The passengers would decelerate (disambiguation) - they would feel the force of the seatbelts slowing them down. From their reference point they will decelerate, the objects will continue in uniform motion. The same will apply to the observers standing outside the car - they will see the passengers decelerate and the loose objects continue. Your arguements about the relative motions are perfectly acceptable for special relativity, but when dealing with changes in velocity one must use general relativity. The fundamental principle of relativity does not apply to accelerating frames.
I have no idea why you're so bent out of shape over the use of the term decelerate. I have a B.Sc. in physics and don't recall ever being told it was a naughty word. In any case, you're getting off the topic. It boils down to whether there's enough time for the object to decelerate, negatively accelerate or just plain slow down to terminal velocity before it burns up or hits the ground. Drag and barometric formula seem to have some pertinent equations, if somebody has the inclination to work on it (hint, hint). Clarityfiend19:51, 11 September 2006 (UTC)Reply
Decelerate is a scientifically incorrect term coined and regularly used by the american scientific community. It, like many other words, despite being officially useless, is commonly used, amongst those in that community. Its not a taboo word, it just inst a proper word, its fine to use it because everyone knows what it means, but my original point was, that you can accelerate so that your speed drops. Which is perfectly true, and I'm sure if you do have a BSc that you will know this. PhilcTECI20:26, 11 September 2006 (UTC)Reply
Speaking as a physicist, (in scientific use) accelerate does not always mean to increase speed. It means change in velocity - that's increase in speed or decrease in speed or change in direction of motion (or any combination). While to say decelerate is not incorrect, to assume accelerate means speed up is wrong (as is to correct peoples usage of the word).
Ur such an ass have you not tagged onto the fact were talking about physics terminology, not english words, and in physics, accelerate = changin velocity. FINAL!,(you cant have a rise in velocity, as you can change velocity while travelling at a constant speed, so is this a rise or a fall?). maybe this site would be of more help, it is an idiots guide to physics. [5] i linked to the section acceleration. For gods sake people. Get over yourselves, decelerate is used in common english, in which it is a word, but in science, it is basically scientific slang. Mate, get over yourself, its ok to be wrong. PhilcTECI17:49, 12 September 2006 (UTC)Reply
Philc, you are resorting to personal attacks and name-calling, which are completely inappropriate in Wikipedia, and not permitted. Please behave in a civil manner.StuRat22:18, 12 September 2006 (UTC)Reply
Interesting. The entire American scientific community is using an incorrect term? Sez who? (And yes, I know quite well that acceleration is a vector quantity yadda yadda yadda.) Clarityfiend22:11, 11 September 2006 (UTC)Reply
The smaller an object is the less it will be slowed down by drag ... umm ... surely the opposite is true ? For an object travelling much faster than terminal velocity, magnitude of acceleration is approximately proportional to drag divided by mass (assuming drag >> weight); drag is proportional to cross-sectional area; mass is proportional to volume; so magnitude of acceleration is proportional to cross-sectional area divided by volume, and this ratio goes up as size of object decreases (assuming we keep shape and density fixed). Gandalf6115:58, 11 September 2006 (UTC)Reply
Agreed, I picture small grains of "sand" landing at thousands of miles per hour, and killing anyone they hit, if that was actually the case. Meanwhile, the meteor that killed the dinos would have just settled down like a feather. :-) StuRat16:06, 11 September 2006 (UTC)Reply
Assuming that objects of different volumes have a constant mass is not reasonable. You should assume a constant density, instead. StuRat06:18, 12 September 2006 (UTC)Reply
THis thread seems to have veered off topic. THe initial answer I gave was more than sufficient. I suggest a new hdg if you all want to discuss the correctness of the term 'deceleration'. --Light current21:17, 11 September 2006 (UTC)Reply
Depends. How does the malfunction alter its intial velocity. Does the malfunction cause it to leap into an elliptic orbit with astoundingly good impact parameters to allow a simple atmospheric reentry. Or does the malfuction cause the satellite to explode into <1 cm3 debric that rains down over an entire hemisphere? Does the malfunction cause the satellite to suddenly accelerate towards the planet at nearly the speed of light?
If we posit that the malfunction causes no initial acceleration of the satellite, then the dynamics are one of orbital decay which strongly depends on solar activity and sunspots. Especially at an altitude ot 64 Mm (earth radius times 10). At such an altitude, the density is very low (q.v. Image:Atmosphere model.png), we may read off < 1 microgram per cubic meter (achieved at 0.15 Mm) and (wildly) extrapolate (-9 orders of magnitute per 0.15 Mm) ~10-3800 gram per cubic meter (with a huge irrelevant error, because...). This is lower bounded by the solar atmosphere. The solar wind is ~1 Tg/s of material moving at 450 km/s. At the orbital radius of the earth (150 Gm), the density of the material is ~5 proton masses per cubic centimeter. However, the satellite's original orbit is inside the Earth's magnetosphere, so the density is assumed to be a bit lower, by cyclic. Kepler's third law tells us that the satellite at 10r will orbit once every (384 Mm / 64 Mm)-3/2 * 27 days ~= 1.8 days (Q.v. the Moon's orbital radius and period). The rate of decay will be negligible (due to the very low atmospheric density).
Satellite Orbital Decay suggests that the densities may be higher than expected from the above considerations (due to temperature fluctuations and mass fraction considerations not present in the above). This paper describes in some detail the effect of solar activity on the drag force, even for low-orbit sattelites like the Hubble Space Telescope and therefore should be a good starting point on the problem you've posed. -- Fuzzyeric22:31, 11 September 2006 (UTC)Reply
Hmmm...now that I think about it, it seems to me that there's a simpler way of looking at it. Just imagine a rocket leaving the Earth. It has to be going just over 11 km/s (about 36,000 km/hr) to get away. Reverse it and a satellite (ignoring for the moment whatever orbital velocity it has) would return at about that speed. Now, I remember from an earlier question posed here, that astronauts report that atmospheric drag is noticeable at about 120 km up. So, it seems unlikely that an object travelling at that speed would be able to decelerate to terminal velocity in that short a distance and time (it would probably come in at an angle, but still). My conclusion is that one of three things would happen: (1) it could come in at too shallow an angle and bounce off the atmosphere (as discussed in the movies Apollo 13 and Space Cowboys), (2) burn up or (3} hit at considerably in excess of terminal velocity. Clarityfiend17:15, 12 September 2006 (UTC)Reply
I don't think there's any easy way to calculate the answer. You'd need to know whether the malfunction caused its thrusters to activate. If it's a homework question, then it's probably after the difference in the potentials between r = 10R, and r = R, starting at v = 0, neglecting air resistance. Richard B21:24, 12 September 2006 (UTC)Reply
Sorry to bring up a topic that seems to have run its course, but I can't help but find the whole "accelerate/decelerate" debate quite amusing. I may not have a BSc, but I do have an LLB/BCL, so I'm familiar with the way members of certain disciplines tend to "borrow" words from the English language, mangle and distort their original English language definition, and then claim that they're using the word correctly, and you, a simple English language speaker are wrong in using its original, true definition. Let's be clear, science, like law, uses the English language, NOT the other way around. An example I always bring up is that according to "legalese", the English word "person" has been extended to include non-human entities such as corporations. According to "legalese", a corporation is a person! We actually had a rather funny discussion about the whole thing in law school. The professor stated, with a straight face, "If the law defines you as a carrot, you're a carrot!" The same thing seems to be going on here. I would never be so arrogant as to insist that a corporation, in reality, is an actual person. Sure, it may be the way we've twisted and contorted the English language to suit our needs, and that's ok. But all due deference must be given to the actual, real life, language from which we've borrowed, mangled and distorted certain words to suit our needs. I will never be a carrot, no matter what the law says. Perhaps the law may decide to consider me a carrot, but the English language does not. Likewise, in the English language, a person is a human being and a human being only. The "law" may consider a corporation to be a person, but the English language does not. Similarly then, to accelerate is to increase velocity and to increase it only. Sure, the scientific community may decide to define "acceleration" as whatever the hell it wants, and that's ok, if it contributes to a better understanding of science. But again, science uses English, not the other way around. Due deference must be given to the original source of the word. If you choose to mangle it, that's ok, but never be so arrogant as to forget its original source. To me, the only acceptable approach would be to say: "true, to accelerate indeed does mean to increase in velocity and to increase only, however, for scientific purposes the scientific community has chosen to define it differently". Loomis22:06, 12 September 2006 (UTC)Reply
I used the word accelerate in its physics meaning, in physics context, and was told I was wrong. I was not, and that basically the jist of it, languages have words, science has words, but accelerate in a context of physics is defined by physicists, in other contexts you can claim it means whatever you want, but the simple fact is, I was told I was wrong, when I was right. PhilcTECI22:19, 12 September 2006 (UTC)Reply
I must take issue with you here, Phil. You've proven to me in the past that you're a good guy, so I'm not exactly enjoying contradicting you. The fact is, though, that you didn't merely state that you were using a scientific definition of the word that differs from its true English language meaning. Rather, you did the opposite. You accused the "US scientific community" of "coining" a "non-scientific word", and further, you argued that it has "since lead to common misuse of the word accelerate". Phil. C'mon. That's ridiculous. You make it seem like English speakers should thank scientists for inventing the word "accelerate", and then humbly submit to their understanding of the word. The word "accelerate" is an English word. So is the word "decelerate". It's the scientists who are deliberately misusing the word, not the other way around. But as I said, there's nothing wrong with that, as long as the original source of the word is acknowledged. Loomis22:44, 12 September 2006 (UTC)Reply
Ok, I got a bit het up after the way in which it was implied I was wrong showed little or no understanding or acceptance of what I had said, and I will admit to knowing next to nothing about the origin of the word decelerate, I was told it was coined by the US scientific community, I cannot verify this though. But what I do know about is the physical meaning and in a physical context, I dont see how I said anything wrong. But anyway, I'm pretty sure decelerate is a pretty recently made up word, and fair enough, Im sorry, but accelerate just does not in a physics context imply a rise in speed. So yeh sorry for anythin else. PhilcTECI18:08, 13 September 2006 (UTC)Reply
I didn't mean to speak on your behalf, Stu. You have every right to demand an apology. What happened, though, is that I saw a silly little argument blow up into a shouting match based on practically nothing. With all the terrorism, war, disease, bigotry and all the other nasty things going on in this world, I just thought it was a bit silly to get into such a heated, personal argument over such a silly topic as the definition of a word. It's true, Phil said some nasty things and should apologize, but on the other hand, my experience with him is that like me, he can put his foot in his mouth or over-react in some situations, but on the other hand, he's proven to me that deep down he's a good person. I say this because I was particularly touched one time when he actually took the trouble to write a clarification/apology on my userpage in another situation where he put his foot in his mouth. He was under no obligation to do so, but was decent enough to take the trouble to do it anyway. What I'm saying, as "referee" is that you're both good guys, and it would be a shame for either of you to hold any grudges. As such, I'd humbly "suggest" that Phil apologize for the harsh words, but it's really between you two, and I already feel like I'm sticking my nose too far into other people's business, so I'll leave it at that. Loomis14:34, 14 September 2006 (UTC)Reply
Well, you're almost there, now if you can just manage to apologize without actually calling me a dick during the apology, I'd be happy. StuRat07:19, 15 September 2006 (UTC)Reply
(After edit conflict)Just another little thought so perhaps Phil can understand things better. I'm no scientist, but it would seem that the scientific community depends heavily on the use of formulas (or formulae for all you pedantic linguists!) to study and to expand their knowledge. Formulas, in turn, require very well defined variables. Again, I'm no scientist, but at the risk of sounding like a clueless moron concerning physics, I would imagine that scientists would have come up with such formulas as: Where V = velocity, T = time, A = rate of acceleration and Δ = change: ΔV = T x A. (I'm just guessing here! The whole thing is likely nonsense! Please be gentle! I'm just a simple lawyer, not a physicist!) In any case, whether the formula makes sense or not isn't really all that relevant. The relevant point is that to have a coherent formula, the variables must be defined as simply as possible. If scientists used the original English language meaning of the word "acceleration" they'd be forced to have two rather redundant formulas when only one is necessary, and to complicate matters worse, they'd have to add an additional variable. So instead of the simple:
Where V = velocity, T = time, A = rate of acceleration and Δ = change: ΔV = T x A.
They'd be forced to say:
Where V = velocity, T = time, A = rate of acceleration, D = rate of deceleration, in cases where velocity is increasing: ΔV = T x A, however in cases where velocity is decreasing: ΔV = T x D.
Makes the whole thing so much more complicated than it has to be, doesn't it? Instead, it was just taken as a given, for scientific purposes, that the variable "A" can have a negative value. Why not? Makes the whole thing so much simpler. I've got no problem with it. The mistake, though, was when scientists began to believe that their redefinition was actually more authoritative than the original English language definition that they had originally borrowed the term from.
Anyway, it's a big mess, but definitely not nearly important enough to warrant descending into a vicious shouting match with personal attacks and all. Loomis20:33, 14 September 2006 (UTC)Reply
Ok I tried Phil, but you simply don't seem to understand my point. You simply don't seem to get what I'm saying. SCIENCE borrows words from ENGLISH. ENGLISH doesn't borrow words from SCIENCE. The English language is the origin of the word ACCELERATE. In the English language, ACCELERATE is defined by an INCREASE in velocity, and by an INCREASE ONLY. Scientists, for GOOD REASON, have chosen to DISTORT the TRUE meaning of the term ACCELERATE. That's how scientists have invented the counterintuitive notion of NEGATIVE ACCELERATION. It's all ok, but if you don't recognize that it's the SCIENTIST'S who are distorting the word, you're not giving due respect to its ORIGINAL English language meaning. Loomis03:37, 15 September 2006 (UTC)Reply
I don't see a conflict. Positive acceleration means to increase speed or velocity. Negative acceleration means to decrease speed or velocity, and a less formal synonym for this is deceleration. Zero acceleration/deceleration means to maintain constant speed or velocity. There is no need to use a "d" in the formula, as an "a" with a negative value has the same meaning. If you don't know if an object is increasing, decreasing, or maintaining speed or velocity, then just call it an unknown acceleration. Where I disagreed with Philc is that, if an object is known to be slowing down, I would ALWAYS say it is undergoing negative acceleration (or deceleration), I would NEVER just say it is accelerating, as that is bound to cause confusion to those who are using the ENGLISH meaning of the word (which will be many of the readers here). The only time such usage would be permissible, in my opinion, is if you are certain your audience is only scientists, which is not the case here. StuRat07:33, 15 September 2006 (UTC)Reply
Ummmmm... Guys? Many, many terms have a common English meaning and a more precise scientific meaning. To speak about one being more "true" or "correct" is kind of silly. Which one you use depends on how well your audience will understand what you're saying and how precise you need to be. Case closed. -- SCZenz07:40, 15 September 2006 (UTC)Reply
Loomis I do understand your point, but words dont really have a true meaning in the way you seem to mean, all words meanings change, so do the words themselves, new words come and old words go, I wouldnt agree that any word has a true meaning, just a meaning that is commonly agreed on. There was no need to get shouty. PhilcTECI13:44, 16 September 2006 (UTC)Reply
OK, OK. The shouting thing is definitely contagious! First I try to calm things down, then I myself get in on the act. How hypocritical can I be? How about we just forget about this one and move on, ok? :--) Loomis07:06, 17 September 2006 (UTC)Reply
Latest comment: 18 years ago10 comments7 people in discussion
I already asked this question in great detail in August but I got no responses and then the question just got deleted off the wikipedia. So I'll try again but I am reluctant to write as copiously a≈s before. Also I was told there was nothing ever on about "solution of vessels" so maybe I'm not using the system correctly.
Basically, I was requesting information about the relative solubility of vessels (eg.wood, plastic, glass etc) containing (to make it simple) water (tho that is obviously not a constant as varies according to acidity, temperature etc.)
My query arose out of comments of a fastidious niece that she would not drink anything out of plastic bottles, because the "water got contaminated", but glass was OK. A retired scientist said that all this is a waste of time as the rates of solution are so miniscule as to be insignificant, "like glass flowing down a window pane!".
Although we never came up with any stats, this issue was discussed extensively, and was archived after 7 days (not deleted), here:[7]. StuRat13:51, 11 September 2006 (UTC)Reply
Agreed; but the rest do, with plastic being the worst, then metal, then wood. StuRat 16:00, 11
September 2006 (UTC)
Glass also does not flow downward in window panes. That is a myth resulting from blobby old blown glas being mounted in windows. There are ancient Roman bottles which have not shown any tendency to melt into a puddle like Silly Putty, but people assume 300 year old glass in a church window is melting.Edison19:10, 11 September 2006 (UTC)Reply
One way to come at this problem is to investiage hoaxes related to water containers leaching materials into their contents. This Snopes article describes a hoax claiming that the reuse of plastic water bottles can leach plasticizers into their contents. This is false. This article debunks the claim that microwaving in plastic containers will release carcinogens into food. -- 205.162.232.25421:27, 11 September 2006 (UTC)Reply
Those Snopes articles do say "FALSE" at the top, but that really isn't what they say in the body. On microwaving, for example, they said something closer to "when using a microwave safe rated plastic according to the manufacturer instructions, there is currently no evidence that dangerous levels of toxic chemicals are released into the food". This leaves open the possibilities that there are toxic chemicals, in dangerous levels, but this has not yet been established, or that using improper plastics or microwaving improperly will generate toxic levels of chemicals in the food.
Moreover, they seem to approach all questions with the attitude that "let's assume everything is healthy, unless we have evidence to the contrary", while many people, myself included, would say "let's assume everything (especially relatively new things) is dangerous unless we have specific evidence to the contrary". Obviously eating or drinking from plastic isn't immediately 100% fatal to everyone who does so, but if it caused a 10% increase in cancer, after 20 years, this wouldn't be easy to isolate as having been caused by plastic containers. So, I prefer to play it safe. If I can taste the plastic in my food or drinks, I don't eat it, for both safety reasons and because it's quite unpleasant. StuRat06:11, 12 September 2006 (UTC)Reply
Which leaves the question how much harm it could do. Some people don't rinse after washing the dishes. How much washing up liquid do they consume in a lifetime and how much harm can that do? Of course, all this is probably negligible compared to the exhaust fumes a city dweller inhales. And there are many other things that will have a negative effect (do you ever drink alcohol?) and the negativest effect might verry well be worrying too much about it all. I'm a happy smoker, for example. But I also take the stairs in stead of the lift, so that should compensate. :) DirkvdM09:26, 12 September 2006 (UTC)Reply
Need full citation for Gibbard and Kolfschoten chapter (glaciation timeline ref)
Latest comment: 18 years ago1 comment1 person in discussion
Hi,
I wondered if you could send me the full citation for the reference you use for the glaciation timeline. I was able to download the book chapter, but I have no idea where the chapter came from. Can you send me the title of the book, the year published, publisher, and ___location of publisher?
Now published - A Geologic Time Scale 2004 Felix Gradstein, Jim Ogg & Alan Smith. **The Quaternary chapter [pdf] by P.Gibbard & Th. van Kolfschoten, which includes a CORRECTED version of the correlation chart, including the term QUATERNARY. pdf
Latest comment: 18 years ago10 comments8 people in discussion
Any eds who know anything about this topic are welcome to look at this recently created article. As a definite non-scientist, I can't begin to tell if it's nonsense or original research (or not). --Dweller14:31, 11 September 2006 (UTC)Reply
Speaking as a scientist, a definate non-scientist you shouldn't have a problem with this definately non-scientific article. For a more scientific approach to something similar the wormholes article should answer the questions posed in title article or else demonstrate that, even in principle, the situations presented are flawed.
It appears to be referring to some type of portal from a video game, not a science topic at all. Unfortunately, they don't identify the game. StuRat15:52, 11 September 2006 (UTC)Reply
erm... they did. I came across the article when patrolling new articles. I deleted the advert. Twice. But left the article, feeling out of my depth on deciding if it was or wasn't guff. Anyway, thanks to those in the know for confirming it is, indeed, a load of tosh. --Dweller16:26, 11 September 2006 (UTC)Reply
Well, as I said, it is scientifically worthless, but, if it's accurate info for a particular video game, it could still be "encyclopedic", provided it identifies the game. After all, we have many articles on other games, like countless articles on Pokemon characters. StuRat16:53, 11 September 2006 (UTC)Reply
Well somebody better merge some of it in fast than! I can't do it now because I should be doing work that is not Wikipediaing. — [Mac Davis] (talk) (Desk|Help me improve)
Isnt all this stuff covered in Wormhole? Oh yeah, just seen ref to that ^. THis page is pure fantasy nad of course should be deleted. But why are we discussing deletion here may I ask?--Light current00:47, 12 September 2006 (UTC)Reply
Latest comment: 18 years ago11 comments8 people in discussion
A friend of mine is on sertraline for bipolar disorder, and has an intimate relationship with rum. I think the sertraline is taken once a day and then he drinks a 700ml bottle of rum (37.5% alcohol) on a single day. Every week. How big of a risk is there that he will become an alcoholic and/or bust his liver due to combined pill/liquor use? Jack Daw15:47, 11 September 2006 (UTC)Reply
Drinking spirits is the worst thing for the liver, I saw a documentary once and the doctor doing the liver transplant said that binge drinking spirits once a week was enough to do the damage and worse than say the equivalent alcohol dosage in beer/larger. Dont know anything about the drug.
As for the alcoholism thing - someone who drinks a bottle of rum a day probably is an alcoholic already (though, of course, there's more to alcoholism than just drinking). Like any drug, sertraline takes its toll. Of course, if you're self-medicating that heavily, the antidepressant probably isn't working for you. Guettarda17:49, 11 September 2006 (UTC)Reply
He's been doing this stuff for maybe two years now, then stopped for two months (of course that was only what he told me), but telling from the alcoholism article I don't think there's any alcoholism yet. Jack Daw20:30, 11 September 2006 (UTC)Reply
Come off it! Anyone whose drinking a bottle of sprits a day is obviously an alcoholic! You should force your friend to see a doctor (or if you cannot afford that then at least AA for example) and get him treated to stop the drinking. With that amount of drinking, and the other drug, then its obvious that if he dosnt stop drinking he's going to be dead soon. Harsh words, but they need to be said to save your friend. 81.104.12.6122:14, 12 September 2006 (UTC)Reply
Liver impairment can affect the elimination of this drug from the body. If someone with liver impairment is treated with sertraline, lower or less frequent dosage should be used.
Patients should limit their alcohol intake while on sertraline (or any antidepressant). Because the liver is doubly taxed with processing both substances (in addition to any other drugs the patient may be taking), alcohol remains in the bloodstream longer, so the effects of alcohol may be more strongly and quickly felt by people taking sertraline or other antidepressants.
Yes? Unless you have some kind of evidence that it's me rather than said friend who has these problems, please refrain from that kind of comments. It would be pretty useless to denote my friend by any other "name" than 'my friend'. Jack Daw20:30, 11 September 2006 (UTC)Reply
Latest comment: 18 years ago36 comments7 people in discussion
I searched wiki but could not find the relevant information. My specific questions are — who can manufacture (specifically, can Pakistan do it on its own?) 99.9% enriched U-235 and what are its implications. What will be the critical mass for Atomic bomb with this purity. {enrichment for little boy was just about 80%.}
Background for this question is that two Muslim terrorists were arrested on suspicion in Bareilly, India about a few years ago. Police found a white powder with them. They initially thought it to be a Drug. But, when they sent it to the Lab, they were shocked at the results, as it was 99.9%pure enriched U-235. Nuclear Submarines just use 90% EU. Remeber that This news was highly censored in India, so you wont find much about it in the archives. But it was once the front page news in The Times of India.nids(♂)21:30, 11 September 2006 (UTC)Reply
Well the obvious answer is that any one with the right plant and raw materials can do it. As you need enriched uranium for nuclear power stations, I would think most countries who have these, also have the enrichment facilites. THeres one just down the road from me! Iwould think tho that the stuff must have been made in a proper plant rather than in someone's shed. I dont know what compound of uranium is a white powder, but Im sure someone will tell us--Light current21:37, 11 September 2006 (UTC)Reply
You cant enrich to 99.9% in a shed. The One used in Nuclear power plants is enriched just about from 3% to 40%. Never more. 85% or more enriched EU is always called Weapons Grade. Most submarines just use about 50%. 90%(in special cases).nids(♂)21:42, 11 September 2006 (UTC)Reply
Im not aware of any specific problems in making more highly enriched uranium above the 50% you quote for sub use. Surely, you just leave it in the 'enricher' for longer?--Light current21:52, 11 September 2006 (UTC)Reply
it is not as simple as you think. Perhaps you would like to go through Enriched uranium. remeber that the critical mass reduces with enrichment and it is dangerous to enrich it beyond certain levels.nids(♂)22:00, 11 September 2006 (UTC)Reply
Its the amount with 85% enrichment. Remember that Uranium is extremely dense metal. So the volume of 50Kg. is just about a litre and a half, (i.e. with 85%). Efficiency of critical reaction increases with enrichment.nids(♂)22:16, 11 September 2006 (UTC)Reply
(edit conflict due to fire drill) the story sounds like bollocks to me, like most stories that invoke a grand conspiracy. For starters, uranium is a silvery metal which gains a black oxide coating, not a white powder, and compounds of uranium, such as uranyl nitrate, which aren't used in fission, are yellow. and the methods for isotopic refinement of uranium are complex, and require difficult to obtain equipment, and highly toxic materials. not beyond a state, but look at how much trouble iran is having. Xcomradex21:55, 11 September 2006 (UTC)Reply
I am sorry i cant quote much about the news as i told you that it was immediately censored. Nothing came again on TV or any news channel about it and they never published a disclaimer either. I doubt it to be completely wrong as it was the front page headline (atleast for a day).nids(♂)22:02, 11 September 2006 (UTC)Reply
I request you to leave out the background for this question as i cant defend it. Please answer the specific questions that i posted. Can pakistan do it on its own????nids(♂)22:04, 11 September 2006 (UTC)Reply
99.99% would be remarkably high enrichment; there wouldn't be many countries that could get it that high, if any can at all (I doubt it). After some point, you are really wasting resources to get that extra .01% enrichment—there are better, and easier ways to improve efficiency if you are resource conscious. Judging from that description it doesn't sound legitimate to me — the powder sounds wrong, and enrichment level sounds wrong.
Back to the original question—many types of reactors require at most 3-4% enriched uranium. Some don't require enriched uranium at all (i.e. a heavy water reactor like a CANDU). Reactors which require very highly enriched uranium are usually quite small — research reactors and submarine reactors, for example. I don't know how many places can enrich to 90%, but any enrichment facilities which can go up to that amount are usually under heavy IAEA safeguards, unless the nation in question is not a signatory of the NPT (like Pakistan and India).
Pakistan has a number of unsafeguarded uranium enrichment facilities, all using gas centrifuge technology, and their P-2 centrifuges are recognized as relatively advanced. The country certainly has the ability to enrich uranium to bomb-grade level—its tested nuclear weapons were uranium-core, if I recall. --Fastfission22:18, 11 September 2006 (UTC)Reply
I have a background knowledge about this subject and i know that it is illegimitate to waste resources after a certain point. But its benefit (for terrorists) are that the critical volume required could be as low as 80 ml (by my estimates). Pakistan for sure can do it to 90%, but i doubted about the figure i gave you in the beginning. With these outdated P-2 Techniques, i dont think that they can even go beyond 50%.nids(♂)22:26, 11 September 2006 (UTC)Reply
Yes, Pakistan can and did enrich uranium to bomb-grade. The other countries with known uranium enrichment facilities include the big 5 (USA, UK, France, Russia, China), India, and presumably Israel. Brazil has recently opened a centrifuge enrichment plant for making reactor fuel; however, a plant for making reactor fuel could probably be used to make HEU with some reconfiguration (Brazil's centrifuges are reportedly very advanced, as good as European and American ones). As well, Germany, Japan, and the Netherlands have centrifuge enrichment plants, and could also start turning out HEU if they really wanted to.
For completeness, there are a number of other countries who have developed enrichment technology such that they could make nuclear weapons, but haven't done so or have stopped doing so. To take the best known example, South Africa built an enrichment plant, and half a dozen nuclear weapons, but abandoned the program and dismantled both the enrichment system and the weapons when the apartheid state ended. To take another, Australia built a pilot-scale centrifuge enrichment plant, but did not progress beyond that stage by choice.
But could terrorists do it without the support of a state backer? Pretty unlikely. An enrichment plant is a very considerable industrial operation; the parts have to be made with very, very high precision or the centrifuges will simply disintegrate. Gas diffusion enrichment would require so much electricity that it would be obvious to all and sundry that there was something going on in the building concerned.
Nids' comment of a risk of a criticality accident when trying to reach HEU is interesting. I would have thought myself that it wouldn't pose that much of a problem in the centrifuges or the piping, as they are both very long and skinny. I could see that subsidiary parts of the plant might need to be carefully designed though. --Robert Merkel23:10, 11 September 2006 (UTC)Reply
I am skeptical of a 99.99% enrichment. 85% would be just fine, 95% is weapons grade isn't it? — [Mac Davis] (talk) (Desk|Help me improve)
(FYI, Mac Davis, you appear to have accidentally increased the purity by an order of magnitude - the question has three 9s but you wrote four 9s in several places.) —AySz88\^-^04:07, 12 September 2006 (UTC)Reply
I think when you are talking about enrichment levels below 93.5% you are essentially asking about the difference between a nuclear weapon and a dirty bomb (assuming you do not have other very high-level technologies—I imagine that there are ways to increase the efficiency of a lesser enriched bomb if you could do things like use very reflective tampers and fusion boosting). --Fastfission00:31, 12 September 2006 (UTC)Reply
I was going off of this article by a number of ex-nuclear weapons designers, though with them again one has to wonder what they consider the line to be between a "successful" nuke and an "unsuccessful" one (if you are just trying to make a relatively large explosion and a big mess, even a fizzle can be worthwhile). 80% is not technically weapons grade — I don't know what the predicted yield would be, but my guess it that we're talking about five kilotons or two at most, depending on the assembly mechanism. Very inefficient for such a large device but again it all depends on what you are looking for. It is hard to find values on the low-end of nuclear weapons work (Carson Mark has written a number of articles about low-grade nukes) in part because that's the sort of information they consider to be the most valuable to terrorists today (the irony is the big, complicated nuclear secrets of yesteryear are totally useless to terrorists, while the simple things, like "can you use research reactor plutonium in a nuke?", suddenly become very relevant). --Fastfission12:02, 12 September 2006 (UTC)Reply
The Bin Laden terrorists supposedly laughed at José Padilla (alleged terrorist) when he proposed to centrifuge weapons grade uranium by swinging it in a bucket which he would hold while he spun around. Superman might have better luck, because he could turn coal into diamonds by squeezing it in his hand. Edison17:15, 12 September 2006 (UTC)Reply
You are taking the subject too lightly. Are you forgetting that all the terrorists have Pakistani support. Anything that Pakistan can do, is what that Al-Qaeda will have access to. I dont think it will be hard for a suicide attacker to diffuse a bomb from 99.9% Enriched Uranium. They will just need about 100ml volume of U-235.nids(♂)20:30, 12 September 2006 (UTC)Reply
Yes Dubya knows it. The details for the answer why he isnt attacking Pakistan are for the Humanities desk. But i think that Pakistan is now a nuclear power, so this isnt possible.nids(♂)23:17, 12 September 2006 (UTC)Reply
So you are not actually asking a question here, but are making some sort of political statement as you seem to know all the answers anyway and just want conformation of your beliefs. Is that right?--Light current23:35, 12 September 2006 (UTC)Reply
Leave these questions. I was interested in knowing the critical mass for the HEU of 99.9%, and whether the pakistan has openly accepted that it has facilities to enrich U to 99.9%.nids(♂)23:49, 12 September 2006 (UTC)Reply
Physical Characteristics of Uranium Hexafluoride
As it can see from the phase diagram In figure 10, UF6 is characterised by an unusually high vapour pressure for a solid, e.g., 24 mbar at 0 °C, 107 mbar at 20 °C and approximately 1 bar at 56 °C. At this temperature UF6 is a white crystalline solid. The melting point of UF6 is 64 °C, with a vapour
pressure of approximately 1.5 bar. The density of solid UF6 at room temperature is around 5 g/cm3. There is a large change in density to 3.7 g/cm3 when UF6 turns from the solid into the liquid state (diagram 11).
The physical data of UF6 are given in the following table:
Another answer is that it's the speed something is going at a given moment, as opposed to its average speed over time. --Allen22:06, 11 September 2006 (UTC)Reply
I'd say the best one can do, physically speaking, is to compare the position of an object at two times that are very close together. Its speed is then the distance traveled, divided by the time passed. In order to be truly instantaneous, mathematically one would like to pass to the limit, but in the real world one doesn't have that luxury. Melchoir22:17, 11 September 2006 (UTC)Reply
Well... "Instantaneous velocity" is defined by taking the limit. Q.v. formal description of velocity. It is the rate of change of the displacement, where the test time during which the displacement is allowed to occur is reduced. This process (in a macroscopic experiment) will asymptotically approach some value as the test time is allowed to go towards zero. Extrapolated to "test time = 0", we get the instantaneous velocity.
This is by analogy to defining the electric field. The electric field is defined according to the force a fictional test charge would experience when placed into the field at the position at which the field intensity is to be known. Similarly, we measure a displacement that would occur during a fictional time period as that period skrinks down to the instant at which the instantaneous velocity is to be known. -- Fuzzyeric22:48, 11 September 2006 (UTC)Reply
Shamelessly copied from the wiki page:
The instantaneous velocity vector (v) of an object that has position at time (t) is given by x(t) can be computed as the derivative:
Perhaps a simple example is in order - suppose your car goes from zero to 100 mph in 10 seconds, and further suppose that the acceleration is constant over that time. Then your average speed over that time is 50 mph, but your instantaneous speed goes from 0 at the beginning to 100 at the end. For another example, which also highlights the difference between the speed and velocity, get your car up to 100 mph and drive it in a circle. Your average velocity over the whole circuit is zero - you wind up right where you started. Your instantaneous velocity is 100 mph in whatever direction you are travelling at a particular moment, and your instantaneous speed is just 100 mph. In fact, your average speed is also 100 mph, since your displacement from the starting position is 0, but your distance travelled isn't. Confusing Manifestation00:45, 12 September 2006 (UTC)Reply
further gravitational wave questions
Latest comment: 18 years ago3 comments2 people in discussion
I have read here that high frequency gravitational waves could be used for propulsion and moving objects, and that they could be created by quantumm effect http://arxiv.org/pdf/physics/0410022#search=%22high%20frequency%20gravity%20waves%22
Can anyone explain to me firstly how a gravity wave could move something, secondly is there even any proof that gracity waves with the force to move things [high frequency ones] even exist?
No, LIGO is a (big budget) mainstream physics project; the cited eprint (surely unpublishable!) is another example of the kind of nonsense which is promoted by cranky websites like American Antigravity and GRAVWAVE LLC.. Some time back we had an article on somewhat similar claims by someone named Franklin Felber, which was deleted on the grounds that such crackpottery is very obscure and would never come up again :-/ In fact, people with more enthusiasm than knowledge keep tossing up stuff like this. See also Eugene Podkletnov.
According to general relativity, gravitational waves exist, possess energy, and can transfer momentum, but they interact very weakly with matter and are very hard to generate, for fundamental reasons. Mainstream physicists do not expect to be able to exploit them for manipulation of laboratory objects or for purposes of spacecraft propulsion. Rather, the goal of observatories like LIGO is to use (extremely weak) gravitational wave signals from very distant and very violent events to learn more about these interesting events. For a variety of reasons, gravitational waves should yield information not obtainable from electromagnetic waves. Try this.
Bottom line: just because you found it in the arXiv doesn't mean it isn't nonsense. There are many very good eprints there and unfortunately also some very bad ones.---CH11:22, 12 September 2006 (UTC)Reply
The big problem with using gravitational waves for propulsion is that they interact very weakly (as stated above). Some serious research has gone into the practicalities of using gravitational waves (well the fabric of spacetime really) for one very good reason. Spaceships using such a technology would not need to carry their fuel with them. Personally, I don't think it'll work. LIGO, however, might work. At the moment all we use to observe the Universe is electromagnetic radiation. Before the Universe was a certain size it was in the radiation dominated epoch. We have been unable to see anything in this epoch - it's like trying to see stars at midday. Gravitational waves wouldn't be (very much) effected by ambient radiation so we could actually 'see' objects.
Hmmmmm the article seems mainstream, do you have background in physics CH that you can say for sure that what they are proposing is crackpottery? heres another one that was apparently accepted for publication by American Institute of Physics http://www.gravwave.com/docs/Am%20Inst%20of%20Phys%20007.pdf and surely if gravitational waves usually interact waeakly surely high frequency ones would interact more strongly? since they can transfer momentum? so all EM waves can transfer momentum then?
Robin
EM radiation can and does transfer momentum (p=h/λ), but from your question at the end so all EM waves can transfer momentum it sounds as if you are considering gravitational waves as a type of EM radiation which is not the case (although if you could prove it was you'd almost certainly win a Nobel Prize for your efforts). Higher frequency gravitational waves would not interact more strongly than lower frequency ones, although they would transfer more momentum in the same time period as lower frequency waves as more gravitons will be transferring momentum. The problem is actually generating these high frequency gravitational waves. Having read only the abstract of the paper to which you linked, they don't seem to be trying to use gravitation to propel spacecraft, they are looking at using it as a method of observation/information transfer.
but if you read further they claim that high frequency gravitational fields could cause peturbations or even move objects, its in the abstact as well also move down to aplications under propulsion.. So you are saying that it is possible to move objects with an EM wave that can cause momentum tranfer of the air thus pushing the object. If high frequency gravitational waves do not work this way how wouild they move an object?
Robin
Electromagnetic radiation can transfer momentum straight to the object it is moving. The articles on radiation pressure and solar sail should contain more information about that. In a quantum mechanical treatment of gravitational radiation, they would work in a similar way (although quantum gravitation is, at best, poorly understood) but this does not mean they (gravitation and electromagnitism) are part of the same phenomena. A general releativistic explanation is given in the paper.
Robin, the website you mention, gravwave.com is maintained by Robert M. L. Baker, Transportation Sciences Corp. in Playa Del Rey, CA. IMO this is indeed a crackpot website. Some clues: Baker's affiliation is apparently with Department of Information and Communication Technology, University of Trento, Italy, not with a physics department at all. (For some reason, I have noticed that Italy seems to have more than its fair share of fringe physics activity---I don't know why. There is a small group of physicists there who regularly post arXiv eprints which flatly contradict various elementary textbook computations; these eprints are flat out wrong, as any good student can easily verify.)
The site promises "important practical, commercial and military high-technology applications for HFGWs". This is rather a tall order, and the fact that it mentions "patented technology" should be an indication that the website is engaged in PR designed to attract investment. If you compare with mainstream sources such as this paper by Bernard Schutz or this paper by Kip Thorne, you should quickly find grounds for suspicion, even if you don't know much about physics, that something is probably wrong with Baker's claims. Note that Schutz and Thorne are the authors and coauthors respectively of two widely used general relativity textbooks, and are leading physicists who have affiliations with two of the most prestigious places in Germany and the U.S. respectively. As for "apparently accepted for publication by American Institute of Physics", I think you might be misinterpreting something. Can you cite an arXiv abstract page? Be aware that some "journals" actually accept almost anything, so "publication" need not imply at all that any paper represents mainstream physics. For example, the abstract page of the eprint by Fontana mentions "Space Technology and Applications International Forum-STAIF 2004". FYI, this conference (not a journal) often features some very oddball talks. In general, conference proceedings are not refereed publications and this series is particularly notorious.
I think I already said that gravitational waves can transfer energy and momentum (see the textbook by Schutz for a fine introduction to the basic theory of gravitational waves as treated in "linearized gtr"). See my user page for more about my training and background. Since I have solved the Einstein field equation thousands of times and am familiar with hundreds of exact gravitational wave solutions, including CPW solutions and exact solutions to the full EFE, you should probably assume that I am not misleading you here. Sorry if this is bad news. ---CH04:12, 18 September 2006 (UTC)Reply
Robert Boyle
Latest comment: 18 years ago2 comments2 people in discussion
Latest comment: 18 years ago2 comments2 people in discussion
- Recently, someone I know was diagnosed with a serious disease. After some time, i di research on how organs can be transplanted and everything I could in my power to help. But in all seriousness, even if the information was useful, there were still some questions to ask, and my doctor would not answer:
1) How long do transplants last?
2) How effect are they?
3) What are the long term affects?
4) How much do they cost? Are there any help plans?
5) What are the chances for rejection?
6) What are the options for a person who's body is rejecting an organ?
7) If that person's body is rejecting an organ, how long do they live?
8) What steps must I take in order to prevent anything from happening ( to the person and to myself, it runs in the family)?
Please, no pictures
- Thank you ---Sam
What do you mean how long does it last? You mean the operation to take an organ out (could be any organ), or to put it in, or how long will the organ last? If the doctors know what they are doing the organs will be 100% effective, because it is a new one. Cost depends on the organ, rejection possibilities depend on the organ, options, depend on the organ, lifespan after rejection without a new organ depends on the organ and their condition... we need more information. — [Mac Davis] (talk) (Desk|Help me improve)
Here are accurate answers to your questions based on the information you provided us. Now do you understand why your doctor didnt give you specifics? Best wishes to both of you. alteripse01:47, 12 September 2006 (UTC)Reply
Depends on the organ. If it is working at a year, chances are good for a couple of decades, more or less. #Usually if it works, it works adequately.
Many long term effects. Damage from malfunction before transplant. Peri- and postoperative injuries & residual effects. Long-term immunosuppression increases cancer and infection risk. Drug side effects. Long term change of life perspective from life-threatening illness.
Depends on where you live. Depends on where you live.
Chance for rejection ranges from 10 to above 50% depending on the organ, the combination of immunosuppressive drugs, the quality of the match.
Artificial organ substitution (various methods depending on organ) or a new transplant.
How long they live depends on the organ and the effectiveness of the substitution methods and any other coexisting medical problems.
Steps to take to prevent something happening to the person? Depends on the organ, the disease, the available treatments, and the person's access to the treatments. Steps to take to prevent something happening to you? Depends on the inheritability of the disease and your genetic relationship, or on the contagiousness of the disease and your physical relationship and infection prevention measures, or on the other effects the person's disease might have on you (missed work, expense, cancelled plans, stress, etc etc).
Just to echo the above, it really depends on the transplant. A bone marrow transplant that works lasts a lifetime. A lung transplant may only last 5-10 years. Kidneys last decades. Etc. InvictaHOG02:45, 12 September 2006 (UTC)Reply
Sinusitis
Latest comment: 18 years ago3 comments2 people in discussion
Quite a few years back I had serious upper respiratory problems and a medical doctor decided to run x-rays of my sinuses. One of his comments was that I have a congenital defect: both of my frontal sinuses are absent. I never learned a technical term for this condition, which I understand is unusual. He mentioned that the absence of a sinus (or in my case a pair of sinuses) is associated with sinus problems, but the causal connection was unknown. What would be the medical term for this and how would I learn more? Durova03:24, 12 September 2006 (UTC)Reply
bilateral frontal sinus aplasia. If you look up "paranasal sinus aplasia" in Medline you may get some articles of interest. (The relationship between anatomic variations of paranasal sinuses and chronic sinusitis in children, "Benign" imaging abnormalities in children and adolescents with headache, Anatomic risk factors for sinus disease: fact or fiction?, etc.) Medline. - Nunh-huh03:46, 12 September 2006 (UTC)Reply
Thank you very much. Some of the abstracts were confusing - I'm not really sure how frontal sinusitis could be associated with frontal sinus aplasia (unilateral cases?) but it seems my abnormality is far more common than I had thought. Durova04:01, 12 September 2006 (UTC)Reply
What did I see on September 10?
Latest comment: 18 years ago13 comments5 people in discussion
On September 10, I went outside to see the Messier 27. I sketched the nebula as well as the stars around it. Using Cartes du Ciel, I identified all but one of the stars. Here is the star I couldn't identify:
This star was about magnitude 9.7, but Cartes du Ciel showed no stars in the region brighter than magnitude 10.8. So what was the object that I saw? If it's a star or asteroid, why didn't Cartes du Ciel show it? If it's a variable star, which variable star is it? If it's a supernova (this is extremely unlikely), why isn't there a nearby galaxy in this region of the sky? --Bowlhover04:14, 12 September 2006 (UTC)Reply
I've just made a comparison image between Cartes du Ciel, and your drawn diagram. The ringed star is there - as SAO 88052 - about 8th magnitude. I've ringed in white on your diagram the mystery star. It's interesting that there's an 8th mag star missing from your diagram that is there on Cartes du Ciel. I've checked the minor planet database, and the brightest object that's on that portion of the sky at the moment is about 15th magnitude - so it's unlikely to be that. I'd say it might be a drawing error - and that the missing star on Cartes has actually been drawn - and the extra star on the diagram is probably one of the ones on the Cartes map. It's easy to get stars in the wrong place on the diagram - as you are usually drawing the position relative to some other star - and these stars are all similar in brightness and easy to confuse with each other. Richard B20:57, 12 September 2006 (UTC)Reply
Hmmm...I was observing with a diagonal (sorry I didn't mention that!), so did you remember to flip the image horizontally? If not...
Latest comment: 18 years ago3 comments3 people in discussion
How the control unit of a CPU/PROCESSOR/MICROPROCESSOR works ?
I've cearched in wikipedia and in other sites but they all provide me with the information that microprocessors are made of IC/logic gate ; several electronic gates like and,or,not are described .
What's the minimum number of logic gates that can form a microprocessor of embedded system(no matter how low the processing power/speed is) ?
I want to know the process by which microprocessors control an electronic devie ; how I/O ports are connected with logic gates ? How logic gates are placed in a microprocessor ?
Does the control unit of embedded system do the same work done by the microprocessor of a pc in the same way ?
I want to construct a control unit(something like used in embedded system)using IC/logic gate (no problem if the processing power/speed is low) for experimental purpose ; how the IC/logic gates have to be configured ?
If I recall correctly, the control unit typically impliments microcode to control the processor. As far as the minimum number of gates - I suppose there are some processors that do not have any centrally located control unit, so 0 is the answer. Raul65405:35, 12 September 2006 (UTC)Reply
I find it has a taste, although not very much, but maybe this is to do with impurities. Perhaps it could be linked to ph value.
Your mouth is always full of the stuff. You could say that you've gotten used to the stuff, since it's the solvent that all of your cells are perpetually bathed in. TenOfAllTrades(talk) 13:37, 12 September 2006 (UTC)Reply
(edit conflict)What would be the evolutionary advantage of tasting, or smelling, water? If it had a taste, that taste would run the risk of overpowering any impurities you wish to taste. When water tastes, or smells, when it shouldn't, you spit it out. Saving you from possible illness. --liquidGhoul13:41, 12 September 2006 (UTC)Reply
Many gases are odorless, even when they are in extreme concentration compared to their concetration in air. See hydrogen and helium. --Russoc423:55, 12 September 2006 (UTC)Reply
Aren't elephants supposed to be able to smell water many miles distant? I can certainly smell the sea when I get near it, not to speak of the local canal. Seriously though, I can smell and taste water quite easily. Sheffield water tastes much better than Birmingham water, and Norwich water tastes dreadful.--Shantavira14:50, 12 September 2006 (UTC)Reply
Have you tasted distilled water? The stuff I have tasted all tasted like plastic, as that is what it was in. What you are tasting between different towns is just the different salts and impurities in the water. I love the water at my mum's house, which is tank water, and is close to rain water, probably with some rust from the tank and dilute bird crap from the roof. However, town water is terrible. It reminds me of pool water. Also, the smell of the sea is the fish, salt etc. --liquidGhoul14:57, 12 September 2006 (UTC)Reply
Salt most definitely does have a smell. We are able to detect many things in the air in extremely minute quantities, especially when doing so is, or was, necessary for our survival. Since lack of dietary salt was apparently quite a common problem for primitive people, the ability to detect salt was quite critical. Also, I believe that wave action causes tiny droplets of sea water to become airborn. The water then evaporates, leaving a tiny grain of salt floating in the air. Corrosion on metal roofs close to ocean water (but not in contact with the water), is known to be a problem, and building codes account for this. StuRat02:45, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago6 comments5 people in discussion
If north of the equator a toilet flushes clockwise and south of the equator it flushes counter clockwise, what happens if you flush a toilet on the equator?
I always liked this line of thinking as a way of dispelling the myth. Physics (the simple kind) isn't discontinuous, so there must be a band of uncertainty around the equator where the effect is too weak to determine toilet flow. And once you admit the existence of that band, why shouldn't it cover the whole globe? Melchoir16:05, 12 September 2006 (UTC)Reply
Yes yes, I know. But the Coriolis force is elementary stuff. It doesn't involve any complex systems, nor is its magnitude prevented from falling to zero. So it really should be overpowered by other effects at the equator, and lo and behold, it is. Melchoir16:47, 12 September 2006 (UTC)Reply
I think you'll find that "designed-in swirl" from the toilet's washdown jets probably overcomes the Coriolis Effect many times over. Tubs would be a different story, but you would need to take great care to assure that there's no residual swirl left over from the filling process, else the conservation of angular momentum from that initial motion would again swamp the Coriolis Effect.
According to our article on bird anatomy, "Birds have acute eyesight, with raptors having vision eight times sharper than humans. This is because of many photoreceptors in the retina (up to 1,000,000 per square mm in Buteos, against 200,000 for humans), a very high number of nerves connecting the receptors to the brain, a second set of eye muscles not found in other animals, and, in birds of prey, an indented fovea which magnifies the central part of the visual field. Many species, including hummingbirds and albatrosses, have two foveas in each eye, and the ability to detect polarised light is also common."--Shantavira15:38, 12 September 2006 (UTC)Reply
Please take a moment to review with the instructions at the top of the page. We're pleased to help out with most questions, but I'm afraid that we have to ask you to Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please do not post entire homework questions and expect us to give you the answers. TenOfAllTrades(talk) 16:31, 12 September 2006 (UTC)Reply
you dont know that thats a homework question. many questions asked here are far more complicated and homework looking. hes only asked 1 question and the reason why.--86.141.230.12917:14, 12 September 2006 (UTC)Reply
I beg to differ. Asking whether rubber or steel is more elastic is a transparently obvious homework question. That said, the answer is easily found in your textbook or a dictionary. — Lomn | Talk17:25, 12 September 2006 (UTC)Reply
If you're really stuck, click on the links I put in your question, or use the search box. Or just look up elasticity in a dictionary.--Shantavira17:29, 12 September 2006 (UTC)Reply
Come on people. You dont get an 800 on your SAT unless you immediately recognize that the only possible answer to this question is the counterintuitive one, or it would not have been asked. Don't waste time, move on to the next question, recognize the pattern in the future. alteripse02:35, 13 September 2006 (UTC)Reply
Yeah if its a rubber band, you can deform that all you like and it wont come back; but steel would. BTW alterprise youre supposed to smile if youre joking! You were joking werent you?--Light current02:39, 13 September 2006 (UTC)Reply
I guess I am not sure if you are joking. I was speaking truth in jest but I will spell it out. The common immediate answer is that in the usual sense of the word elastic, the rubber elastic band is more elastic than steel and everyone knows it, but there would be no point in asking such a question if the academic answer were not the other. Understanding that this kind of question needs no more than one second of consideration is how you ace the SATs and get to leave first (it helps to know a lot of junk too). alteripse02:48, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago4 comments4 people in discussion
As a health precaution, until there is further clarification on if acrylamide is carcinogenic or not, I'm trying to avoid things containing it.
Can anyone tell me please how much acrylamide there is in sultanas - a form of dried grape. I have searched on the internet and emailed a sultana wholesaler about this without success.
There is a lot of acrylamide in prune juice - a prune is a dried plum. The browning process - possibly the Maillard reaction - creates acrylamide. Sultanas are dried grapes and undergo browning - they could also have similar levels of acrylamide (yes, I know grapes are otherwise good for you). Does anyone know for sure please? 81.104.12.3918:39, 12 September 2006 (UTC)Reply
Almost all natural food contains some sort of carcinogen. It's just that the other stuff usually makes up for it. Prunes are one of the healthiest things going (if consumed as part of a varied diet). To avoid all bad stuff, I suggest that you just eat highly purified sucrose. --Zeizmic20:04, 12 September 2006 (UTC)Reply
I disagree with all of your assertions. I'm looking for facts rather than homely armchair speculation please.
The fact of the matter is you would have to work rather hard to get all the acrylamide out of your foods. but from memory acrylamide is mainly an issue in foods cooked at high temperatures eg deep fried foods. the levels in most fruits etc seem to be quite low, [10], but sultanas aren't listed. Xcomradex22:18, 12 September 2006 (UTC)Reply
"The fact of the matter is you would have to work rather hard to get all the acrylamide out of your foods" - not true. If you avoid baked and fried foods, avoid coffee and chocolate, stick to either raw foods or foods cooked by boiling - then you can avoid acrylamide. You should also avoid olives and prunes and possibly other dried fruits. It is apparantly carbohydrates that are bad when fried or baked - some other foods seem to be OK according to the link you supplied. Bread can be replaced by mantou which should be OK as it is cooked by steaming at atmospheric pressure.
"but from memory" - you mean you havnt bothered to read the article acylamide?
"acrylamide is mainly an issue in foods cooked at high temperatures" No, really?.
"the levels in most fruits etc seem to be quite low" Yes for unprocessed fruits, but the question is about dried fruits.
Also, there is a great difference in toxicity and carcinogenicity between free acrylamide and polyacrilamide. If it is in the polymer form in the fruit you mention, the acrylamide will be harmless.Tuckerekcut22:53, 12 September 2006 (UTC)Reply
Thanks for an informative reply for a change.
Myocardium (heart muscles)
Latest comment: 18 years ago2 comments2 people in discussion
72.70.136.19518:50, 12 September 2006 (UTC)How would aerobic excercise strengthen the heart? Is the heart muscle fast or slow twitch?There is an excercise movement called "Superslow" that teaches that aerobics are more harmfull than good, but that to build and strengthen skeletal muscles will make the heart efficient. This philosophy also teaches that the heart of an athlete pumps very little more blood per beat than a couch potatoe's heart. I know aerobics can do a lot of harm to joints. The aerobics also train the muscles in motor skills that make it "seem" like the heart is stronger. The point is, if the "Superslow" people are correct, then aerobics would definitley be unecessary. However, it seems walking is good for stress reduction, and a small amount of calorie burn.
Bottom line is, "How" does aerbic activity really help the heart? Thanks to those who know the answer.
Rich StoneReply
Aerobic exercise increases vascularization and (to a lesser extent) density of heart muscle. The increase in vascularization allows increases anastomization (redundant blood flow) and imparts resistance to ischemia (loss of blood perfusion). The amount of blood pumped by the heart depends on a lot of factors and is not a good indicator of overall health. The isolation of skeletal muscles in any exercise routine will not develop the heart muscle properly, and in extreme cases will be detrimental, as the increased stress introduced by growing muscles will not be matched by a stronger heart. In general, the heart will do its job just fine as long as it is "fed" properly. See myocardium, smooth muscle, atherosclerosis, aerobic exercise, and anaerobic exercise for more information.Tuckerekcut22:48, 12 September 2006 (UTC)Reply
Inertia
Latest comment: 18 years ago6 comments4 people in discussion
Is inertia a property of matter, or a force of some kind?
Inertia is a property of matter. It is the property by which a body continues to move with constant velocity unless acted upon by an external force and comes from Newton's first law.
What is said there seems to supoort my thought that inertia is a property of mass. Or vice versa. In other words, they're two aspects of the same thing (which is yet to be named?). DirkvdM07:36, 13 September 2006 (UTC)Reply
"X is a property of Y" becomes a model-dependant statement at a certain point. In newtonian mechanics, the inertial mass (i.e. the mass that relates the force on an object to its acceleration) of an object turns out to be (for no particular reason) always the same as the gravitational mass, causing all objects to accelerate the same way under gravity. In General Relativity, as Allen notes above, this happens automatically because gravity isn't really a force after all and everything travels along null geodesics. -- SCZenz15:32, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago3 comments3 people in discussion
I need help to explain my son's homework. A common saying goes," it's not the fall that hurts you; it's the sudden stop." Can you translate this into Newton's laws of motion? THANKS.
An object in motion tends to stay in motion. When you hit the ground, whatever body part touches first stops first. But the rest of you keeps going, tearing and crushing your organs. (The fall itself (through the air) is no problem -- you're changing speed as you fall, but your different body parts are changing speed together, so your body stays intact.) --Allen19:32, 12 September 2006 (UTC)Reply
It's even worse. While your body stops when you hit the ground, your organs (which are mainly lying loose in their place) keep moving and hit all sorts of things. The organs stay in motion while the body stops moving. - Mgm|(talk)08:05, 13 September 2006 (UTC)Reply
Newton's second law says that the rate of change of velocity (acceleration) is proportional to the force. In a fall, the rate of change of velocity (g) is 9.8 m/s per second and the force acting on the body F=mg. This can be comfortably tolerated by people. Let us say that you have reached a velocity of 19.6 m/s, after a fall for 2 seconds. But when you reach the ground, the velocity reduces to zero. When you fall on solid ground, the time taken to reduce the velocity may be as small as 0.5 sec. Now calculate the decceleration. It is (19.6-0)/0.5 = 39.2 m/s per second. The force experienced by the body (F=m*a ) is now 4 times greater that that of free fall and this hurts. When you fall on sponge, the time taken for decceleration may be 1 second in which case, the decceleration will be 19.6 m/s/s and the force is twice as strong but it is more comfortable than landing on solid ground. Hope this helps and hope it is not too late for the homework :-) -- Wikicheng13:01, 15 September 2006 (UTC)Reply
velocity
Latest comment: 18 years ago9 comments7 people in discussion
When your car moves along the highway at constant velocity, the net force on it is zero. Then why do we continue running our engine?
Think of it like this: The car is moving at a constant velocity because the engine is pushing it forwards, while friction is resisting this movement. The two forces are balanced, if they weren't, the car would either speed up or slow down. Gary19:42, 12 September 2006 (UTC)Reply
In fact, your highway gas mileage is almost totally dependent on the air friction. That is why sports cars with huge engines are very thrifty on gas on the highway. --Zeizmic20:06, 12 September 2006 (UTC)Reply
The Drag equation approximates the force experienced by an object moving through a fluid at relatively large velocity. The equation is attributed to Lord Rayleigh, who originally used in place of (L being some length). The force on a moving object due to a fluid is:
The reference area A is related to, but not exactly equal to, the area of the projection of the object on a plane perpendicular to the direction of motion (ie cross-sectional area). Sometimes different reference areas are given for the same object in which case a drag coefficient corresponding to each of these different areas must be given. The reference for a wing would be the plane area rather than the frontal area.
The power required to overcome the aerodynamic drag is given by:
Note that the power needed to push an object through a fluid increases as the cube of the velocity. A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). With a doubling of speed the drag (force) quadruples per the formula. Since power is the rate of doing work, exerting four times the force at twice the speed requires eight times the power. Of course, if you are going twice as fast, you would get to your destination in half the time. Thus the total energy consumption would be 4 times higher (instead of 8 times higher).
Ceterus paribus, that is. Most car engines are, however, designed to be most efficient at very high speeds. The SmILE is different in that respect, and it has a very low drag coefficient, resulting in a very fuel efficient car.
Extremely efficient cars, as used in fuel efficiency races (no article on that?) don't leave the engine running all the time. If I remember correctly, the engine is turned on for a short while to get to a certain speed and then turned off to let it roll untill it drops below a certain threshold speed. I can't find any info on this in Wikipedia. DirkvdM08:15, 13 September 2006 (UTC)Reply
I like this quote: "it would be possible for the winning Shell Eco-Marathon UK car to travel three times around the equator on the same amount of fuel that Concorde needed to reach the end of the runway." DirkvdM08:57, 14 September 2006 (UTC)Reply
If you stop the engine, it takes much energy to restart it. That's why you don't stop it when you have to stop at a red traffic lights, and also why you don't stop it on the motorway. – b_jonas07:45, 14 September 2006 (UTC)Reply
Yes, I wondered about that too, but I have heard that that was done. Maybe a fly wheel is used? Or a different type of engine? Electric? DirkvdM08:57, 14 September 2006 (UTC)Reply
Inorganic Chemistry
Latest comment: 18 years ago5 comments4 people in discussion
What would be the transition energy in units of eV from the ground state to the second excited state of the Li(2+) ion? I'm more interested in an explination than an answer. Thanks! 130.207.180.3720:02, 12 September 2006 (UTC) DaveReply
Look at the Bohr model of the atom, since this ion is "hydrogen-like" (has precisely one electron). All you have to do is note that the nucleus has thrice the charge of hydrogen; the change in mass is irrelevant since that model assumes an infinite nuclear mass anyway. Hope this helps. --Tardis15:03, 13 September 2006 (UTC)Reply
I haven't studied it in detail recently, but that's how I understand it. All I meant was that you consider the nucleus entirely fixed when working out the dynamics, so its mass doesn't matter. --Tardis17:01, 14 September 2006 (UTC)Reply
This is a hydrogenic atom (one electron) as Tardis noted. The ground electron configuration is then 1s. The first excited state (Aufbau principle, ibid.) is 2s and the second excited state is 2p. (Unless there's a strong magnetic field which would induce the Zeeman effect.) By reference to the Lyman series, we may estimate the change in potential energy of the electron in the potential of a single proton (a.k.a. Hydrogen) between the 2p and 1s states. The potential in the given atom is greater because the charge is greater, so the energy is greater (by three times). -- 66.103.112.14003:47, 14 September 2006 (UTC)Reply
Question about energy states / emission spectrum of hydrogen
Latest comment: 18 years ago2 comments2 people in discussion
What is the position of the third line in the visible portion of the emission spectrum of atomic hydrogen, ie in Angstroms in wavenumbers? I just need a helping hand with this question more than anything else. Thx in advance! ~ Mark P.
Latest comment: 18 years ago13 comments6 people in discussion
I lost my brother about two and a half years ago in a car crash. He was driving alone and no one else was hurt. He simply lost control of his car on a patch of black ice and crashed into a utility pole. The attending doctor at the ER told me that the "cause of death" was a heart-attack. Yet my brother was in his 30's, and had no previous heart condition whatsoever. I wasn't in the mood to ask questions so I just left it at that. But over the past while I've been wondering about exactly what he meant when he said that the "cause of death" was a heart-attack. At first I assumed what appeared to be the most obvious: he was driving, had a heart-attack for whatever reason, and as a result of his heart attack he was inacapacitated and could no longer effectively control his car.
But then it occured to me that I may have it all wrong. Perhaps, when a healthy person suffers such a severe trauma to his body, perhaps the trauma causes the heart-attack. In other words, first he lost control of the car, then smashed into the pole, and only then, due to the trauma of the crash, did the heart-attack occur. Or perhaps even more simply, due to the crash, his heart simply stopped for whatever reason, and therefore, the "cause of death" was considered to be a heart-attack.
I'm wondering if there's anyone out there who may work in an ER, or somehow have knowledge of this sort. If a healthy person gets into a fatal car crash, what are the most likely terms used for the "cause of death"? Excluding instances where the heart-attack actually occurs prior to the trauma, is it rather common for a heart-attack to be considered the "cause of death" after the trauma occurs? Thanks. Loomis21:07, 12 September 2006 (UTC)Reply
It is likely that the ER doc was talking about a pericardial tamponade. This is a catastrophic bleeding into the sac surrounding the heart which rapidly causes cardiac arrest. Tamponade occurs frequently in car crashes because the ligament (the ligamentum arteriosum) which connects two large blood vessels just above the heart often rips a hole in one of those vessels when the heart itself jerks out of place at the moment of impact. Blood fills the sac and prevents the heart from stretching and relaxing as it should. This is by a wide margin the most likely cause of cardiac arrest after trauma.Tuckerekcut22:37, 12 September 2006 (UTC)Reply
The heart attack suffered by Harry Whittington was due to a pellet from Cheney's shotgun that lodged in the outer tissues of his heart. Probably the metal in the pellet altered the endogenous electrical ativity therein, causing atrial fibrillation. This is a completely different pathology, and can only loosely be considered "trauma".Tuckerekcut23:02, 12 September 2006 (UTC)Reply
How was your brother's death officially filed? 1.2 million people die each year of car accidents. If some cases are filed as 'heart attack', the number might be even worse than that. DirkvdM08:25, 13 September 2006 (UTC)Reply
I mentioned that the gunshot wound in this case would only loosely be considered trauma because the underlying pathology was, in my relatively uninformed opinion, more likely due to chemical differences introduced by the pellet than by the physical trauma. That is, the atrial fibrilation was caused by the presence of exogenous conductive material near the elecrical fibers of the heart, and not by the introduction of physiologically damaging forces to the tissues of the area. In this way, his disorder would have been more like hypercalcemia (or hyper-steel-ball-in-the-heart-ia) than physical trauma. There was surely some damage caused by the pellet on its way to the heart, and by the other pellets as they penetrated the skin, but the life threatening detail, as far as I have read (which is not much), was a conduction syndrome.Tuckerekcut21:56, 13 September 2006 (UTC)Reply
Dirk, I'm really not sure exactly how it was filed. But I would only imagine that the heart-attack "cause of death" was more for the medical files and that the death would have been included as a "car accident" death for the purposes you're speaking of. When you think about it, the simple term "car accident" can't possibly be considered a "medical" cause of death, for "medical" purposes. I would only imagine that deaths like this are included as "car accidents" in the 1.2 million stat you mentioned. It's just that doctors have to be a bit more precise as to exactly how the car accident, medically speaking, caused the death. That's just my best guess.
You're welcome. As for the question, I've often thought that, instead of a single "cause of death", a death cert should permit a "chain of events leading to death". Take my grandfather's death, for example:
He had diabetes.
That caused circulation problems.
He also had an ingrown toenail.
That combo caused an infection.
If younger, his immune system could have fought off the infection.
Failing to have the toenail removed caused the toe to turn gangrene.
Refusal to have the toe amputated caused the foot to turn gangrene, and could also be considered suicidal.
The gangrenous foot caused blood poisoning.
This caused a heart attack and death.
So, when asked to pick just one cause of death you have a choice of "diabetes", "poor circulation", "ingrown toenail", "infection", "old age", "suppressed immune system", "negligence", "suicide", "blood poisoning", or "heart attack". Obviously none of those alone is sufficient to describe what happened. And, since funds are allocated based on number of deaths from each cause, we really should document all causes of death, not just one. StuRat09:53, 14 September 2006 (UTC)Reply
Death certificates do allow for enumeration of contributory causes of death (there's usually space for three) as well as the (one) proximate cause. But "heart attack" does not mean "his heart stopped" and shouldn't be used on a death certificate unless a myocardial infarction is suspected (and then it should be called a myocardial infarction!). Similarly, "heart failure" also does not mean "his heart stopped". But the accuracy of a death certificate depends on the experience of the person filling it out. As to Loomis, what he is hinting at is the distinction between "mode of death" (suicide, homicide, accident, natural causes) and "cause of death". In StuRat's hypothetical, the death certificate really should read something like:
PART I. Enter the chain of events--diseases, injuries, or complications--that directly caused the death. DO NOT enter terminal events such as cardiac arrest, respiratory arrest, or ventricular fibrillation without showing the etiology. DO NOT ABBREVIATE. Enter only one cause on a line. Add additional lines if necessary. Sequentially list conditions, if any, leading to the cause listed on line a. Enter the UNDERLYING CAUSE (disease or injury that initiated the events resulting in death) LAST.
IMMEDIATE CAUSE (Final disease or condition resulting in death) --------->
Thanks to all of you for your contributions. It's really helped me in better understanding something that I've been wondering about for a while, but only lately felt comfortable asking about. I'd just like to summarize what I've gotten out of all your contributions, and if you can, tell me if I've got it right or where I may still have it wrong:
Although it is of course technically possible for a person to have a heart-attack while driving, and due to the incapacity caused by the heart-attack lose control of his vehicle and end up dying in a fatal car accident, in my brother's case, it is FAR more likely that when the ER doc spoke of him dying of "a heart attack", what he meant is that the crash caused the heart-attack, not the other way around.
It is quite common for victims of fatal car crashes to be deemed to have died "due to a heart attack", when it was obviously the crash, not some underlying heart problem that caused the heart-attack.
In general, what Nunh-huh terms "mode of death" is never a medically satisfactory way of defining the "cause of death". As extreme examples, take the Challenger or Columbia tragedies. In both cases, a pure layman (such as myself) would describe the deaths of all of those on board as being caused, very simplistically, "because the shuttle blew up", and just leave it at that. After all, if you're in something like the Space Shuttle, and it blows up (before you have any chance to escape), there's pretty much zero chance of survival. The thing blows up, and so you die instantly (as a layaman such as myself would put it). No need to go into the gory details. However, am I right to assume, that even in tragic situtation like that, someone truly dedicated to the medical sciences would, at least in his own mind, look at it differently? Would s/he, for purely scientific purposes, describe the blowing up of the shuttle as merely the "mode of death", yet the actual "cause of death" would have to be some direct traumatic effect on the persons of the crew due to the explosion (and being a layman I won't even try to guess how that can be described!)?
Actually, that last paragraph was more out of general curiousity, and not nearly as important as the first two. I'm much more interested in knowing if I'm pretty much understanding things correctly about what happened to my bro. Thanks again to all of you. Loomis19:45, 14 September 2006 (UTC)Reply
In the absence of an autopsy, the "cause of death" is necessarily a "best guess", and is not necessarily correct; it's only as good a guess as the person making it can give. We don't know on what basis the ER physician in question made his assessment: was there an autopsy? was there a diagnostic EKG before death? Or was it a more seat-of-the-pants guess than that? We really don't know enough to say.
"Mode of death" is indeed not a strictly medical determination, but a medico-legal one, usually made by a coroner or inquest. "Cause of death" and "mode of death" are separate determinations.
Yes, the exploration of the deaths of the shuttle accident went beyond their modes of death and characterized their causes of death. Three, at least, survived the explosion proper and were alive at the time they impacted with the surface of the ocean. - Nunh-huh01:56, 15 September 2006 (UTC)Reply
Io MOTH
Latest comment: 18 years ago1 comment1 person in discussion
We have an Io Moth which has made a cocoon withing the oak leaves I gave it. It has been wrapped up in cocoon since Saturday, Sept 2. How long will it remain in the cocoon stage before it erupts and becomes the adult moth? We want to prepare it a branch that it can climb upon.
The only information I can find is in the pupa article, which states that the pupation stage can take anywhere from 2 weeks to many months. I assume in your case that you won't have to wait until the end of winter. freshofftheufoΓΛĿЌ 02:41, 15 September 2006 (UTC)Reply
PSS World Medical
Latest comment: 18 years ago1 comment1 person in discussion
Hey I was wondering if there was any information about PSS World Medical Inc, which is an organisation in America that supplies doctors and hospitals with medical supplies that they need?
Latest comment: 18 years ago6 comments5 people in discussion
Why do parrots like having their heads stroked but freak out if you touch their backs, wings or stomaches?
My bird loves to have her beak stroked, but not he rwings or stomach. Some birds like to be pet anywhere. It all depends on how the bird was handled after they hatched. If they get used to certain touches, they will be more accepting, but if you get a parrot after they have been raised for a few months or so, and it wasn't made acustom to certain touches, then it never will get used to them. My bird also fears gloves and socks, leaving us to believe that she may have been handled by someone wearing gloves and has had a bad experience. Just an assumtion, not necessarily true. --Russoc423:52, 12 September 2006 (UTC)Reply
It is also species specific. Cockatoos love to be scratched on the skin, you have to go under the feathers. I have also heard that the skin around the beak is particularly sensitive, and a lot of birds like that. But mostly it is learnt behaviour, I used to have a Crimson Rosella (who we got as an adult) who would bite like crazy, and almost bit one of the cat's tails off! --liquidGhoul02:50, 13 September 2006 (UTC)Reply
I've been guessing that they don't like being touched on the back because that's where birds of prey slam into them when they catch them. But that's just me --Bmk15:36, 13 September 2006 (UTC)Reply
Birds don't seem to actually like being 'stroked' (i.e. smoothing the feathers down) and some birds just don't like being touched at all. Have you tried rubbing the feathers up the 'wrong way'? They get itchy sometimes and they find this soothing, especially on top of the head where it's quite difficult for them to reach. --Kurt Shaped Box17:40, 13 September 2006 (UTC)Reply
Getting my head shaved - pros and cons?
Latest comment: 18 years ago8 comments8 people in discussion
(edit conflict) Do you mean actual head shaving, where all the hair is shaved off, or a buzz cut, where hair is cut very short (usually 2cm or less), or a "high and tight" which is sort of a mixture of the two? If you are balding, you may want to go with the first option. A buzz cut is vary easy to maintain (low maintenance). —EdGl23:34, 12 September 2006 (UTC)Reply
Pros:
You'll look like a tough guy.
You can wash your hair with a sponge.
No more messing around with combs and gel.
Cons:
Some drunken arsehole might try to start a fight with you because you look like a tough guy.
What is your hair like? When my grandfather started getting bold he decided to shave his head every spring and then let it grow for the rest of the year. That is even lower maintenance than never cutting your hair, as I do, because I spend most of the time under the shower washing my hair. A nephew of mine, however, decided to shave his head and it turned out he had a really ugly skull. A bit of an oops experience that lasted several weeks. DirkvdM08:31, 13 September 2006 (UTC)Reply
I've shaved my head a couple of times and I loved it. Some other posters seem to have assumed you're a man, and if so, I don't know if my advice applies, but I found that almost everyone treated me differently. I would be bald now except that I got tired of every single staff person in every single store I entered watching me like a hawk the whole time I was there, people calling me a dyke, security staff asking to see inside my bags, teenagers throwing things at me as they drove past, people trying to buy drugs off me on the street, etc. Anchoress06:31, 14 September 2006 (UTC)Reply
Here's a con for you: Some people (such as myself) think that shaved heads are unattractive. If you're trying to look good for someone or just in general, I'd get their opinion first. --Niroht00:25, 18 September 2006 (UTC)Reply
Small bass cab
Latest comment: 18 years ago3 comments2 people in discussion
Anyone know of a commercially available bass cabinet (or combo), less than 1 cu ft, that will reproduce frequencies down to about 40 Hz @ -3dB?--Light current23:31, 12 September 2006 (UTC)Reply
This would be a good time to say that my headphones go from <10 Hz to >10,000 Hz. :D Good luck with your woofer man. Everybody except neighbors and sleeping people appreciate them! Don't find yourself with a combination. — [Mac Davis] (talk) (Desk|Help me improve)
Latest comment: 18 years ago3 comments3 people in discussion
I was thinking about how the Blood-brain barrier prevents polar molecules from entering the brain (e.g. glucose have to be transported to the other side). But how can then red blood cells reach the brain to deliver it's need for oxygen? Is there a way for these cells to circumvent the BBB? I cannot believe that oxygen is diffusing from the BBB to reach all areas of the brain, it's not likely. /80.217.232.21714:00, 13 September 2006 (UTC)Reply
Perhaps a clarification of the BBB is in order: the barrier isn't really some wall at the bottom of the brain or something. Blood-brain_barrier#Physiology has more, but here's some info...There are numerous blood vessels and capillaries throughout the brain, but the capillary beds are a little different than elsewhere in the body--the capillaries in the body are relatively "loosely" surrounded by cells and there is a lot of easy passage of fluids, large proteins and cells between the blood and the lymph/interstitial fluid; in the brain, the endothelial cells are packed very tightly together, forming an effective barrier against anything of moderate size or polarity. Oxygen still freely diffuses accross the cell membranes of the endothelial cells and beyond, and it really doesn't have to diffuse that far. Additionally, the brain uses something like a quarter of the oxygen taken in by the lungs, so there's a hefty concentration gradient that allows diffusion to happen quite easily; and since the brain receives a large share of the body's blood circulation, there's no shartage of oxygen availability, either. This should provide some handy graphical representation, too. -- Scientizzle19:46, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago7 comments6 people in discussion
I read the article about Pica and I want to know more about this disorder. I know a lot of people who like to eat stuff that normally would be considered gross, like raw potato and powdered milk. Is it always a disorder when you eat things like that? I like to eat paper, in little bits at a time. Is this Pica? Should I stop doing it? Even if it is Pica, is paper dangerous to eat? --Jonathantalk00:06, 13 September 2006 (UTC)Reply
Does it decrease your quality of life? If not, don't worry about it. But please, stay away from bleached paper. Paper itself is pretty much just insoluble fiber (cellulose) but the chemicals they use to bleach it include some pretty nasty species (most famously, members of the dioxin family).Tuckerekcut01:48, 13 September 2006 (UTC)Reply
It's not always a sign of an underlying disorder such as iron deficiency anemia, etc. It can be a manifestation of a psychiatric disorder, though. Or, it can just be that a person likes to eat a certain thing, such as paper. If it bothers you, stop. If not, I wouldn't worry. InvictaHOG10:05, 13 September 2006 (UTC)Reply
Eating real foods in preparations you consider "gross" is not necessarily pica. There is a cultural component for starters. For instance, many Westerners would think it "gross" to eat raw fish, while many Japanese consider it "gross" to eat greasy-gravy foods like chicken fried steak. True pica is actually pretty rare. I can't say whether your paper eating qualifies. --Ginkgo100talk · e@22:09, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago6 comments5 people in discussion
I am in the 12th grade and I am very interested in Human Viruses. Now i need to write a paper in Psychology about theories such as Gestalt Theory, Psychology of Lieing "Why people lie" and "Nature vs. Nurture" and such. It can basicly be anything that involves psychology. Now I wanna tie in Psychology and human viruses such as I dont know, How they form or the affect of the human body from human viruses. I believe I need a theory that I need to disprove/prove. As long as it involves human viruses and I can write a paper about it im fine with it. So basicly my question is, Is there any psychological theory about human viruses? and what is it?
One of my favorite psychologists, Claude Steele, once did a study on alcohol and safe sex. Basically, he was trying to show that alcohol, rather than being simply a disinhibitor, more accurately serves to narrow one's attention. Narrowing one's attention generally has a disinhibitory effect, but not always. Steele showed that if you put an card with warnings about HIV in front of a drunk, they'll actually be less likely (at least according to their own predictions) to have unsafe sex that night than a sober person presented with the same card. (HIV being a virus. :-))
Another angle: even though almost all medical scientists are sure that the benefits of immunization (against viruses) far outweigh the risks, a lot of parents won't allow their children to be immunized. What motivates these anti-vaccinationists? --Allen00:56, 13 September 2006 (UTC)Reply
People live with bacteria and viruses all their life. Psychology could tell plenty of things, viz. -
When you're unhealthy and those little beasts attack you, instead of living peacefully within or outside, it is because you're in a bad mood.
If the great idea in our societies is to cure people, is it better to cure the mind by psy means, to build healthy houses and towns, or to attack our mini friends and destroy a little our bodies ? (I'm not 100% of an antivaccin', I'm writing this for the general idea). -- DLL .. T19:12, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago2 comments2 people in discussion
Following up on my question from the other day, Wikipedia's article states that a significant portion of migraines may be misdiagnosed as sinusitis. Migraine patients often perceive pain in the sinuses and migraines themselves may be accompanied by increased mucus production. So...how would I determine the difference? I do experience severe headaches that last 4-72 hours, often accompanied by nausea (although not actual vomiting) and have a family history of severe headaches - which might have been migraines misdiagnosed as sinusitis? I'd always thought my headaches were due to airborne allergens (dust or pollens) but the worst episodes seem to occur without any relation to seasonal weather. I'm thinking of trying the "ice cream headhache" treatment the next time I feel one coming on - just to test whether that helps. Is there any other way to test the hypothesis? Durova02:19, 13 September 2006 (UTC)Reply
See a migraine/headache specialist. It's really, really difficult to self-diagnose types of headaches and causes. Particularly since some causes of severe headaches are life-threatening problems (like tumour, stroke, meningitis, etc). But there are classes of drugs (triptans, vascular constrictors, etc) that will relieve migraine symptoms but not those of other types of headache, so get yourself a prescription for Imitrex and try it out. Anchoress07:12, 14 September 2006 (UTC)Reply
Preserve human tissues
Latest comment: 18 years ago7 comments7 people in discussion
I'm getting some organs surgically removed, and I may consider the option of preserving them. What is the easiest and best way to preserve them? Should I buy 95% pure alcohol, something like Everclear_(alcohol)? Or where would I buy formaldehyde? Maybe at the university? I hear it's toxic though? What are the pros and cons of various methods of preservation in a jar? I wish I had the equipment for plastination, LOL. --Sonjaaa03:11, 13 September 2006 (UTC)Reply
Formalin (37% aqueous formaldehyde) would be the gold standard, talk to a local university biology department nicely and see how much luck you have. Alternatively ask the doctors at the hospital. its generally used as a 2% formalin solution in ethanol. it is also rather toxic, so don't spill it on yourself, or try to have the organ put back in. You could have a peek at embalming chemicals too.Xcomradex04:21, 13 September 2006 (UTC)Reply
I really doubt any University would give you anything toxic. I can't buy fix, or anything for that matter, from my University stores without having the appropriate paperwork in hand. Initial fix in formalin, then store in paraformaldehyde, just guessing. Pete.Hurd05:35, 13 September 2006 (UTC)Reply
Well it is a fairly special case here, c'mon. I know several guys that just go ask for some liquid nitrogen to take home from their University. — [Mac Davis] (talk) (Desk|Help me improve)
Avoid preserving tissues in ethanol. Just Google "Nelson's Blood" and see what might happen.Maybe your local undertaker would give you a little jar of embalming fluid, to build good will against the day all your organs need a bit of preserving. Then you could put the little jar in the casket so you will be all in the same place and require less reassembly on judgment day. Also having your removed organ handy will lessen the tendency to fulfill the campfire ghost story of the thumping sound coming up the stairs and a voice asking "WHERE'S MY GOLDEN ORGAN?" http://www.evboard.com/archive/index.php/t-33740.htmlEdison15:09, 13 September 2006 (UTC)Reply
Patient rights vary by country, but if you're in the United States you have the right to demand your own organs back. It helps to state your intentions in advance (or as soon after the surgery as possible) and it helps to have a relative act as an advocate. I did get a relative's body part from a hospital in formalin, but in practical terms the pathologist was very concerned to make certain there were no children in the home - it's highly toxic stuff. Hospitals legally have to comply with the demand, but they might "accidentally" dispose of the organ before they process the request. Durova17:04, 13 September 2006 (UTC)Reply
Last week in my anatomy lab some techs came in and made us wear exposure badges which measured ethanol, formaldehyde and phenol concentrations in the air, so I would guess that those are the main chemicals used in preserving semi-dry bodies (it may differ from the solution used for liquid-suspended preservations). You mentioned in passing that you were having some organs removed, dare I say how many, or even which ones?Tuckerekcut21:41, 13 September 2006 (UTC)Reply
Why do you want to preserve the material? If you want to preserve it for cultural or religious reasons (e.g. you want it buried with you later), you may have more luck convincing someone (embalmer, someone at the hospital) to provide you with what you need. Failing that, you could simply request the unpreserved item(s) and use any of the usual methods people use to preserve meat - freezing, canning, smoking, salting, pickling, etc., although none of those will perfectly preserve it for (hopefully) decades to come. If you just want a keepsake, then the suggestions above sound good. Matt Deres03:48, 15 September 2006 (UTC)Reply
'Sulfisomezole Sodium'
Latest comment: 18 years ago2 comments2 people in discussion
Hi
In front of me I have eye drops. On the bottle I see that it contains, 'Sulfisomezole Sodium'. I can't find it here (or anywhere else). So I went to the request page but can't figure out how to go about making a request. I am assuming that by making a request it is meant, that I would like someone who knows anything on it to hopefully provide info on it and put this info on this site.
Thanks
You've tried google? That exact phrase didn't get me much that seemed useful, but just searching for "sulfisomezole" taught me a lot. DMacks04:42, 13 September 2006 (UTC)Reply
You put this on the help desk, and I asked you to leave me a message on my talk page. I'll write the article (stub) tomorrow (unless somebody else wants to first!), which is faster than making a request. Good idea for asking here though. — [Mac Davis] (talk) (Desk|Help me improve)
Latest comment: 18 years ago10 comments4 people in discussion
I wrongly posted this elsewhere:
Just a question.
A black hole singularity is an infinitesimally small, two dimensional ring that spins at the speed of light and its surface wiggles with quantum foam. Wouldn’t this pretty much describe a closed string as well? Especially since closed strings describe fermions and the shorter the wavelength at which they oscillate, the greater the mass of the particle of matter they represent. Wouldn’t this prove that strings do exist?
To which I got this:
A black hole's singularity is 0-dimensional, and its event horizon is 2-dimensional. Strings are 1-dimensional. So there certainly isn't a direct analogy. Brian Greene does discuss the relationship between strings and black holes in one of the later chapters of The Elegant Universe, though. (A caveat for my own piece of mind: Mr. Greene is a little bit overenthusiastic about the prospects for proving/solving string theory in the near future. Regardless of what impression you're left with if you do read his book, nobody has a clue if string theory is real, and there are no clear prospects for resolving the matter anytime soon.)
However:
"When a spherical non-rotating body collapses under its own gravitation under general relativity, it is usually supposed to collapse to a single point. This is not the case with a rotating black hole (a Kerr black hole). With a fluid rotating body, its distribution of mass is not spherical (it shows an equatorial bulge), and it has angular momentum. Since a point cannot support rotation or angular momentum, the minimal shape of the singularity that can support these properties is instead a ring with zero thickness but non-zero radius, and this is referred to as a ring singularity, or Kerr singularity." (from the Wiki)
"A closed string looks like a small loop." (from anyone)
I know that particles have zero dimensions and strings have one, still, a really small ring and a really small loop have nothing in common? Just intuitively, shouldn't gravity crush the contents of a black hole into a string?
--208.15.6.16205:53, 13 September 2006 (UTC)Arch LittleReply
Hurray for good questions. Who said a black hole was two dimensional? The mathematical singularity exists there because what we know of physics breaks down, because things get so extreme. There may or may not be actually an infintesimally small piece of matter there. The black hole does not spin at the speed of light, because a mass just can't do that. Then again, I guess physics breaks down because of the extremes, and we don't really know. The event horizon is three dimensional, as far as we know. — [Mac Davis] (talk) (Desk|Help me improve)
What you seem to have hit upon is the very reason string theory can include GR where quantum mechanics can't. In string theory, the smallest any object can be is the size of a string (~the planck length) whereas in QM objects can be of zero size. If ST is correct then the singularity would not be a string, but it would be string size. An event horizon is two dimensional - it is a surface. The black hole itself is three dimensional, but its surface is two dimensional.
Thanks, but if a string is the building block for everything and the ring singularity is shrunk to the size of a string, then the ring singularity is its own building block and it must be a string. That's just geometric logic. NASA has found proof of Kerr ring singularities by observing matter in acretion disks. The matter could only be falling into a singularity that was spinning. Such a ring singularity would be proof for the ST.208.15.6.16203:59, 14 September 2006 (UTC)ArchieReply
The least wrong way to think about the singularity in a black hole is "the place where everything inside the event horizon is going". In GR, the coordinates become degenerate at the event horizon -- in particular the forward time direction is a spatial direction. In a non-rotating black hole (q.v. Black hole, Schwarzschild black hole, Kerr black hole, and Charged black hole) the forward time direction is towards a point. Thus, anywhere inside the event horizon, waiting will result in moving toward that point. This point is a singularity because, for instance, the forward time direction is discontinuous there. In a rotating black hole, the forward time direction points slightly outward from the center (centrifugal force) and inward from everywhere else. This "extrudes" the singularity into a ring -- i.e. there is a set of points homeomorphic to a circle where the forward time direction is discontinuous. Waiting around in this event horizon causes inexorable motion towards this ring.
As an interesting side note, from the point of view of an observer far away from the black hole, it takes an infinitely long time for an object to follow those forward in time vectors all the way to the singularity. Of course, from the object's point of view, the time to arrive is finite. This is one of those wacky consequences of trying to compare clocks at places where the forward time directions aren't parallel.
Equivalently, there's no physical thing at the singularity. It's just where all the time vectors point. Since it's not a physical thing, it would not be composed of strings in ST. A successful ST may also encompass a loop quantum gravity, but this is by no means currently clear. So we can't currently say that there are special forms of loops near the singularity (and thus we cannot say that there are special strings there). -- 66.103.112.140 04:14, 14 September 2006 (UTC) a.k.a. Fuzzyeric02:48, 15 September 2006 (UTC)Reply
No physical thing at the singularity? Well something has a great many solar masses at the singularity. Hawking radiation converts this mass slowly as this very real physical thing melts away. (BTW, strings also make up non-physical things, like forces.)
I'm saying that the ring singularity is a string loop. Closed strings that represent fermions vibrate in correlation to the mass of the particle they represent. A ring singularity spins near the speed of light (thanks Mac), which should cause some pretty good vibration related to its extreme mass. If its the size of a closed loop string and it behaves like one, maybe it is a special looped string. It doesn't take a lot of hand waiving to look at a drawing of a ring singularity and a closed loop string to see the similaities. 208.15.6.16209:41, 14 September 2006 (UTC)ArchieReply
Remember also that Hawking radiation has a problem if all the interior mass is at the singularity. The probability of mass tunnelling from the singularity to the surface (i.e. backwards in time and several meters) is so low that the universe wouldn't last long enough to let any non-microscopic black hole evaporate. The external pair production event has to interact with matter frozen just inside the horizon, which is fine because it is as far as the external observer is concerned. For matter to reach the singularity, it would have to never escape as Hawking radiation, implies that so much of the mass doesn't evaporate that the black hole is never microscopic, implies that Hawking radiation is strongly inhibited for that black hole for a very long time, (seems to) imply vacuum pair production has been turned off near the horizon. How does one turn the vacuum off
Also, if it's spinning so fast, then from the point of view of an observer not at the singularity, its vibrational frequencies are extremely retarded by special relativity. The local gravity is doing that also. So it's not observably vibrating. -- Fuzzyeric03:00, 15 September 2006 (UTC)Reply
The explanation given by 66.103.112.140 is very good from the point of view of GR. A singularity in GR is a slightly abstract notion in exactly the way the above user explained. I evidently didn't make my point very well. I was trying to say that it is impossible to compress anything down below the size of a string. The GR singularity would be at the (mean) centre of this string sized lump of matter. GR can't really tell us what happens at this point - it just doesn't work when gravity is not the dominant force. My explanations are based on what we know about ST (we know that according to ST no actual thing can be smaller than a string), assuming it is correct. I suppose this wouldn't really clash with the GR version of a singularity - perhaps a new word is needed. If (big if) ST is correct and there is this string sized thing round a singularity, we wouldn't be able to see it to prove ST because of cosmic censorship.
We already know what a ring singularity would look like and we know what a closed string would look like. We know a lot of other details about them, too, many of which coincide. GR describes a ring singularity without too much argument. Independently, ST has described something very similar as the basic building block of everything. The size of a string was arrived at intuitively from QFT. Nothing can be smaller than the Plank length because of the Heisenberg uncertainty principle. Thus anything smaller than a string would supposedly explode to the size of a string. Also, this puts a bottom limit on what gravity should do to a singularity. Detective work isn't about seeing the crime, its about recognizing the evidence.208.15.6.16211:11, 14 September 2006 (UTC)ArchieReply
Having seen the article on ring singularities, it all seems far too definate. I find it hard to imaging we really know that much about them. From my understanding, a ring singularity would be a one dimensional circle, whereas (it string theory is correct) the matter would form a two dimensional surface around a singularity. A colleague of mine did a lot of work on Kerr black holes some time ago. I'll ask them for more information next time we meet.
I've finally remembered the name (Samir Mathur) and therefore the whimsical name they gave to their ST model of a black hole. Fuzzballs. In their model, using the language I introduced in the GR answer above, the strings are extruded into the positive time direction, with one end at the event horizon and the other end at the singularity. The theory didn't explain in detail how a heterotic string was suddenly cleaved into an open string, but this may be the route to understanding the ST prediction of the boundary conditions of the universe. Of course, one can add a one-point compactification and attach the two ends of the string (one at the Big Bang and the other at the singularity) together, incidentally creating a new non-self-interference condition. Anyway...
So even under the current best guess of ST black holes, there is no physical object at the singularity; it's still just a place where the normal rules don't work and there's no ultra-condensed mass there, it's distributed around the interior of the event horizon (from the point of view of an external observer) or reached its final condition in finite time (from the point of view of an internal observer). -- Fuzzyeric02:48, 15 September 2006 (UTC)Reply
Hi Fuzzyeric. A star bulges at its equator and spins. When and if it collapses into a singularity the mass collapses around the bulge and forms into a ring. It spins ever faster to conserve angular momentum. This initial mass makes it to the singularity. That's what creates the event horizon. That's when time dialation kicks in. In a Schwartzschild singularity a non-spinning mass collapses uniformly into an ever smaller point that rips through space time. I think that a lot of people have the misconception that the singularity must always vanish because of this. However, a ring singularity should be crushed down to the size of a string (Plank's length) by gravity and then stop for the reasons I've mentioned. NASA released info over a year ago that matter observed in an acretion disk could only be falling in to a spinning singularity. If it is spinning, then it is still there. You seem to be stuck on what is happening in between the inner and outer event horizons and not the singularity itself.208.15.6.16204:25, 15 September 2006 (UTC)ArchieReply
From Black hole: "From the viewpoint of a distant observer, an object falling into a black hole appears to slow down, approaching but never quite reaching the event horizon. As the object falls into the black hole, it appears redder and dimmer to the distant observer, due to the extreme gravitational red shift caused by the gravity of the black hole. Eventually, the falling object becomes so dim that it can no longer be seen, at a point just before it reaches the event horizon." and "At the center of the black hole, well inside the event horizon, general relativity predicts a singularity, a place where the curvature of spacetime becomes infinite and gravitational forces become infinitely strong." Thus, from the point of view of an external observer, no matter added to an existing black hole can ever reach the singularity. It can't even reach the horizon.
Gravitational collapse collapse describes the formation of the black hole both from the point of view of an observer on the star and from a remote observer. Note that the two stories need not appear compatible becuase one observer's forward time direction becomes orthogonal to the other's. The article describes a scenario similar to the above: "As the free falling observer (in his time) falls faster and faster toward the Schwarzschild radius, the stationary observer sees him progressing slower and slower towards the Schwarzschild radius and will never see him passing that stage."
I fully understand the idea that the mass collapses into a singularity. This is just incompatible with any observable history. In fact, the time dilation caused by the stupendous curvatures near the singularity ensure that no test matter can ever arrive in finite time, even from the point of view observers inside the event horizon (and "above" the test matter). So there is no hypothetical observer that ever sees matter reach the singularity. (Well, okay... an observer already at the singularity, who necessarily has nonphysicality problems, can see material falling to himself in finite time, but only because his clock is stopped.)
Ultimately, the problem is that the singularity is a problem of coordinate charts. Outside the event horizon, our atlas contains a chart that's flat except near the black hole. Then it's progressively non-flat as it approaches the event horizon. At the event horizon the coordinates "break", similar to the problem of Mercator projection necessarily omitting two points (classically the north pole and south pole). However, much like analytic continuation, we can augment our atlas with the charts local to observers falling through the event horizon. These have to be constructed to provide compatibility with the chart inside the event horizon. My copy of Misner, Charles; Thorne, Kip S. & Wheeler, John Archibald (1973). Gravitation. San Francisco: W. H. Freeman. ISBN 0-7167-0344-0.{{cite book}}: CS1 maint: multiple names: authors list (link) describes these "Novikov coordinates" in section 31.4 (p. 826, et seq.). Every atlas for this manifold has a common feature: the charts can't cover the entire interior of the event horizon. There is always a singularity (q.v. hairy ball theorem for an example) somewhere in the interior and for some atlases, this singularity is not of measure zero. Thus, there is no coherent sequence of local coordinates that allow anything to reach the singularity.
Really. It is very fundamental that nothing ever reaches the singularity. Also, nothing ever has to. Collapsing the star to the event horizon will produce an object externally indistinguishable from the one you're imagining. The only difference is in the interior. The coordinate systems in the interior are so unfamiliar that it is easy to draw incorrect conclusions without careful analysis. -- Fuzzyeric02:46, 16 September 2006 (UTC)Reply
Arch Little, you wrote "A black hole singularity is an infinitesimally small, two dimensional ring that spins at the speed of light". I don't know where you got that, but in classical gtr, this is not right. As Fuzzyeric suggested somewhere above, I think, in gtr the singularity cannot be easily treated as if it were part of spacetime or as if it had a well defined dimension.
Be careful in reading too much into popular books, even those written by competent physicists. Physics can be pretty subtle and often resists translation into non-mathematical language. I'd go further: generally, almost everything is lost in the translation. I've seen dozens of popular books on relativity, and think only three are of any value at all. I like the way Fuzzyeric put it: "The least wrong way to think about the singularity..." :-/ The right way is of course to bite the bullet and learn the math. In the long run this also turns out to be the easy way, for those of you who can't stop banging your head against the weird-sounding claims you read about in popular physics book :-/
In the interests of ridiculously complete disclosure: I went to the same high school as Brian Greene, but am not acquainted with him.---CH04:24, 18 September 2006 (UTC)Reply
Be careful in reading too much into popular books, even those written by competent physicists. Physics can be pretty subtle and often resists translation into non-mathematical language. I'd go further: generally, almost everything is lost in the translation. I've seen dozens of popular books on relativity, and think only three are of any value at all. I like the way Fuzzyeric put it: "The least wrong way to think about the singularity..." :-/ The right way is of course to bite the bullet and learn the math. In the long run this also turns out to be the easy way, for those of you who can't stop banging your head against the weird-sounding claims you read about in popular physics book :-/ Well said, sir!
science
Latest comment: 18 years ago8 comments6 people in discussion
If the observer is on or near the ground, a circular rainbow will be truncated where it appears to hit the ground. If the observer is at a high altitude, however, it will be seen as a full circle. StuRat14:20, 13 September 2006 (UTC)Reply
The rain within the bow is continuing to fall. But as droplets pass through that region of space that forms the correct solid angle with your eyes and the sun, they contribute, for just an instant, to that part of the rainbow. And each rain droplet, of course, gets to contribute to the full spectrum as it falls into different angles with your eyes and the sun.
And furthering StuRat's point, you can see a fuly circular rainbow if you're willing to stand on a ladder while spraying downwards with a garden hose.; the (primary) rainbow always occurs at a certain angle from the sun (and the secondary rainbow, if present, always occurs at another, different angle).
I saw an OU prograqmme once on tv about how rainbows form. It was quite a complex phenomenon and mind bendingly difficult to understand at the time. Im afraid my brain glazed over!--Light current19:42, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago4 comments4 people in discussion
Can anyone tell me how do computer read the data from the thumb drive (or pen drive) we use daily?Unlike the CD, VCD, DVD even the hard disk have the driver or ROM to read the data from the them, the way of the data read by the computer is confusing.
Particularly USB flash drives implement the USB mass storage device class protocol - which means the OS is responsible for knowing how to talk to a generic USB-MSD but it's the responsibility of the flash drive's onboard controller to implement that interface. It's a nice division of labour - the OS doesn't need to know all the horrid complexities of working with flash memory, and by implementing one simple interface the drive can work in any compatible OS without the need to author device drivers for each one. -- Finlay McWalter | Talk12:00, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago12 comments7 people in discussion
A girl standing at the equator is in circular motion about the earth's axis .Calculate the angular speed of the girl.
The radius of the earth is 6400km .the girl has a mass of 60kg .Calculate the resultant force of the girl necessary for this circular motion
If the girl were to stand on eighing scales calibrated in newtons,what reading would it give?
The top of this page states Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please do not post entire homework questions and expect us to give you the answers. This sounds awfully close to a homework question so try it yourself first. We will however, be glad to help you should you encounter any problems. - Dammit09:53, 13 September 2006 (UTC)Reply
<--rant-->Why do teachers think up these ridiculous questions? How about preparing kids for the real world? She got hold of some eighing scales calibrated in Newtons??? And surely angular speed should be angular velocity.<--end rant-->--Shantavira10:05, 13 September 2006 (UTC)Reply
I suspect it does mean angular speed. It sounds like a GCSE question and they probably don't need to know about vectors.
Everybody loves the GCSE! Nobody is going to help? Ok well I will have to than, because the three people above me couldn't <appropriate smilie> ...wait, what are eighing scales? — [Mac Davis] (talk) (Desk|Help me improve)
Obviously, eighing scales measure how much Tim Horton's coffee you can drink in a blizzard, while waiting for the roads to be opened up. --Zeizmic15:24, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago3 comments2 people in discussion
Our Endoplasmic reticulum article has been getting a lot of edits recently, many apparently from silly schoolkids. The section on "smooth ER" says "The smooth ER has functions in several metabolic processes, including synthesis of lipids, metabolism of carbohydrates, and detoxification of drugs and poisons" (my emphasis). That last part sounds very strange to me: it sounds like a vast oversimplification of a highly complex physiological process, and something that one wouldn't expect would be so easy to locate to a specific structure. Unfortunately the article, while quite elaborate, is entirely unsourced, so it's hard to check this. Thoughts? -- Finlay McWalter | Talk12:06, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago13 comments7 people in discussion
I've been reading about how one can make a compound of gold and xenon, two apparently unreactive elements. Do we have an article on this? What's its chemical name? It could be AuXe4 or Xe4Au, or something much more complicated. Is there a picture anywhere? And there's no point in asking me to look it up, I've been looking at gold and xenon and their compounds pages and have no idea where to begin, and looking up 'gold xenon compound' on Google yields nothing that can help me (I'm a cripple when it comes to chemistry). Help plz? Vitriol13:01, 13 September 2006 (UTC)Reply
I've only heard of that as a divalent cation, AuXe42+, not a proper compound itself, and never seen a name for it. For some "food for thought", here's an overview of some recent noble-gas chemistry. DMacks13:34, 13 September 2006 (UTC)Reply
No, but the concepts are similar. A hole is a missing covalent bond in a crystal lattice which causes that particular atom to become a cation. But a cation itself is just a positively-charged atom, and it need not have any bonds, nor be in a crystal lattice. If a cation is sitting alone in solution, it is NOT a hole. And if a cation is in a crystal lattice with equal numbers of anions, they are bonded by electrostatic (ionic) bonds and not by movable covalent bonds, so we still wouldn't call the cations by the name "hole." --Wjbeaty18:28, 13 September 2006 (UTC)Reply
A small addition to answer the rest of the asker's questions, [13] mentions Tetra Xenono Gold(II) as the name for the ion. The molecular configuration is pictured here. - Dammit14:11, 13 September 2006 (UTC)Reply
Forgive me if I am outside of my expertise, but I don't think it is completely accurate to polarize (snicker) the issue with respect to ionic versus covalent bonds. I have been taught to think of these types of bonds as extremes on a spectral scale, rather than opposites on a quantal one. That is, "ionic" and "covalent" describe attributes of a bond, but not the bond itself (and that there is indeed a middle ground). As such, ionic:covalent::velcro:glue, as opposed to ionic:covalent::velcro:magnetic attraction (if that was confusing, ignore it...)Tuckerekcut21:33, 13 September 2006 (UTC)Reply
Obviously the crystals aren't of the isolated AuXe42+ ion, they are of one its salts. one salt containing the ion is [AuXe4][Sb2F11]2. And the other partner isn't just sitting there, gold-fluoride interactions stabilise the whole assembly. If you have acess to more traditional (non-free) sources of information, see: Angewandte Chemie, International Edition (2002), 41(3), 454-456. i could post an image from this paper if you guys think it falls under fair review in copyright terms, showing the arrangement of atoms. and if someone shows me how to upload an image. Xcomradex22:14, 13 September 2006 (UTC)Reply
As a sidenote, I've started an article about Tetra Xenono Gold (actually a substub, but feel free to change that). Maybe you can include the photo there if it falls under fair use. You can upload via [15] - Dammit23:00, 13 September 2006 (UTC)Reply
Latest comment: 18 years ago3 comments3 people in discussion
My mother-in-law has had chronic chest congestion for many years. She was recently advised by her physician that the results of a sputum test shows she has congestion due to the presence of "sutomonus" bacteria (or virus?) in her lungs, and that it is untreatable. I do not know if this is the correct spelling of the bacteria, and I am unable to find any information about it using this phonetic spelling. Any information on this subject would be appreciated.
Thank you.Spokaloo16:27, 13 September 2006 (UTC)Reply
Unquestionably Pseudomonas, probably Pseudomonas aeruginosa. The organism is often found colonizing the sputum of people with chronic lung disease, such as bronchiectasis. There are instances where prophylactic treatment of the organism (by such means as aerosolized antibiotics) can be helpful in preventing further lung damage; if your mother-in-law has not consulted a lung specialist (pulmonologist), it might be useful to obtain another opinion as to the advisability of treatment. - Nunh-huh19:29, 13 September 2006 (UTC)Reply
dna
Latest comment: 18 years ago6 comments5 people in discussion
i think you guys might remember me i was the one who asked the question about the extraction of dna from pea soup , even after i tried it with my father's help i couldn't get it right , so i have decided to make a model of the structure of dna or a working model on dna , since the topic given to me was dna , therefore could u help me witha few ideas on what to make so that i can expand on that .forgive me for my naiveity but is it possible to make a working model on dna , im not talking about an experiment or activity, thank you Mightright19:34, 13 September 2006 (UTC)Reply
Sorry the extraction didn't work out for you. There are lots of DNA-modeling kits available from science education stores; just do a google search on "DNA model" and poke around. This website on about.com has instructions for building your own without a kit, although they look like they might be rather crude. A good simple physical model of DNA "works" in the sense that you can see why the molecule has a double helical shape, you can compare the major groove to the minor groove, you can see why A pairs with T and G with C, and you can see how an accidental pairing of A with G can create a bulge in the molecule. I don't know if there are models that can easily demonstrate replication and transcription and things like that, but at least with a physical model in hand you can point to things while explaining those processes to people. --Allen20:29, 13 September 2006 (UTC)Reply
If you're interested in spending some money, you might check out this page from sciencekit.com. I've ordered a couple things from them; they're kind of expensive, but at least they cater to individuals interested in buying just one or two things, rather than teachers ordering in bulk. --Allen20:32, 13 September 2006 (UTC)Reply
Hold on: you tried to get DNA out of pea soup!? I think I remember your original question, and if you did say "soup", I misread it. As I remember (im sure somebody with a little more skill in wikipedics can link it...) I briefly described the marmur technique (which I called the marburg technique, sorry), in which DNA is extracted with cold EtOH. This would not have worked for pea soup. To make pea soup, one must cook the peas for a long time to get a proper consistency, and canned varieties are also flash heated or irradiated to avoid spoilage. This processing would destroy, or at least severely fragment all of the endogenous DNA material. The metals in the can would do a number on it too. In order to get macroscopic amounts of genetic material, you really need to start with fresh or flash frozen cells. Tuckerekcut21:23, 13 September 2006 (UTC)Reply
i just called the goo like liquid, soup (pea soup !yuck), actually these projects are supposed to be hand made not ordered from amazom because threr is every chance that my bio teache could flunk me for that 212.72.0.19003:52, 14 September 2006 (UTC)Reply
Woman/man physiological difference in body structure and movement
Latest comment: 18 years ago10 comments10 people in discussion
Is there a verified exemple of a woman/girl beating a boy/man in a fight without any weapon or it's just another urban legend?
Don't get me wrong, I'm no mysoginist!
This is a REAL (amateur) quasi-scientific inquiry based on an hypotesis that :women/men physiological differences(like better height ,better muscles,more grey matter in brain cells)are not innate but acquired via "darwin natural selection"-type genetic mutations throughout the years of human evolution.
As a counter exemple of man superiority,you can check the "black widow" spider case.
--SamiKaero19:59, 13 September 2006 (UTC)Reply
It is very hard to determine which components of observed sexual differences in humans are "caused by" genes or by social circumstances. (I use quotes here, because in a certain sense everything is caused by both genes and the environment.) Determining which characteristics are a result of selection pressures would be even harder because that study would require more detailed understanding of human evolution than we are ever likely to have. (For conflicting views, see evolutionary psychology and sociobiology). Your question suggests, however, that you over estimate the actual sexual differentiation in humans. Although, ON AVERAGE men may be stronger than women, there are certainly many women who are stronger than most men. I feel confident that in all of human history many women have defeated many men in hand to hand fighting. --best, kevin[kzollman][talk]20:34, 13 September 2006 (UTC)Reply
It's hardly scientific, but some of the most formidable sparring opponents at my kung fu school are women. (Alas, I am not among these Amazons, but I hold my own.) --Ginkgo100talk · e@20:46, 13 September 2006 (UTC)Reply
There's a book (probably long out of print) called Her Wits about Her that documents instances of women who successfully fought away violent assailants. Durova22:13, 13 September 2006 (UTC)Reply
How about two weeks ago's news?[17] It is possible for a woman to beat a man in a fight, just look at it as if the woman was just a smaller man. In this situation we can approximate it. A more skilled fighter can win a fight over a larger fighter. — [Mac Davis](talk) (New!SUPERDESK|Help me improve)22:43, 13 September 2006 (UTC)Reply
photo review
Latest comment: 18 years ago7 comments6 people in discussion
recently i returned from the phillipine islands on a diving trip. part of my objective was to photograph sea slugs or nudibranches. i have many photos that i feel would enhance the articles to sea slugs. all are of large format size and excellent quality. my question is and understand that i am a first time visitor to this site, who do i send the photos to for evaluation? i am not certain after reading the section on photos excatly what the process is. your help is greatly appreciated as i feel i can add to a small section of this site. the photos i have may prove to be useful for a student doing research or some other worthy cause.
thank you for your assistance
Golfdog
Scientifically, this sounds interesting. You really have to go through the whole Wikipedia bag, starting with the general help, and editing information. You can donate extra pictures in their general archive (you have to find out how!) This is a fun hobby, and I was generally proficient in a few days. Good luck! --Zeizmic22:03, 13 September 2006 (UTC)Reply
There isn't really an evaluation process at all. If you think your photos can help an article, add them. If you think they're considerably more helpful than an image already there, then replace it. It might be more helpful to ask (in the talk page, probably) if others agree before you do this, though.
If you want to upload all the pictures right away but are unsure if all or any of them should eventually be included in the Wikipedia, then try uploading to the Wikimedia Commons, which is a sister project of the Wikipedia. You can display pictures from the commons here, so you only have to upload the images to one site. -- Consumed Crustacean (talk) 22:04, 13 September 2006 (UTC)Reply
How many pictures do you have? Do you know what species each is of? If you feel very uncomfortable (uploading was difficult for me the first few times), you can read the guide on it (which someone else will hopefully supply), or I can do it for you. — [Mac Davis](talk) (New!SUPERDESK|Help me improve)18:53, 13 September 2006 (UTC)Reply
To clarify why it is a good idea to upload to Wikimedia Commons, there are several Wikimedia projects, such as the different language Wikipedias, which can't use each other's photos, so they would have to be uploaded to each separately. That's why this central repository was made. You can place the photos here at the English Wikipedia like this: A nice photo by me (check the source (click 'edit' to the top right) to see how I placed the photo). For an upload manual see http://commons.wikimedia.org/wiki/Commons:First_steps/Upload_form. If you need help identifying what's on the photos, see http://commons.wikimedia.org/wiki/Category:Unknown_species and follow the links to as specific a category as you can find. DirkvdM09:49, 14 September 2006 (UTC)Reply
Latest comment: 18 years ago10 comments7 people in discussion
My question is one regarding my science fair project topic (obviously). I am looking for a science fair project related to or with computers. Why? I guess because I think computers are so interesting, but anyways, I'd like to know if you could kind of help me find some computer science fair projects also please let it be one that an 8th grader is capable of doing.
Thank You
Sincerely,
Raoul Frere
Get yourself some educational software intended for little kids (say first graders). Figure out what each one is supposed to teach them (reading, arithmetic, colours, whatever). Then persuade the first-grade teacher to lend you some of her little charges, and let them loose on a computer with the educational software. Watch what they do, and after a time (say 15 minutes) talk to them and ask them about the program - did they enjoy it? did they learn how to do the thing the program was supposed to be helping them with? could they work it themselves, or did they need someone to help them? Then you can analyse your findings and present your results,and say what kinds of educational software actually work and which (hint: it's most of them) are really just junk. But make sure to have a proper hypothesis and a scientific way of measuring your results (otherwise you're just doing market research, which sure ain't science). -- Finlay McWalter | Talk21:28, 13 September 2006 (UTC)Reply
I've always thought it would be cool to build a family of logic gates from basic components, but I've never done it so I don't know how much time and money it takes. Finlay's idea is probably a lot better, but I thought I'd mention mine in case you're more into the technical side of things. Another idea might be to learn how to use a programming language to do simple image processing with bitmaps. When I was in college, I took an intro course in C, and really simple image processing turned out to have a pretty high impressiveness-to-difficulty ratio. --Allen22:21, 13 September 2006 (UTC)Reply
It's cynical, but science-fair stuff should be attention catching - pity the poor judges who have to thole endless papier-mache volcanoes and potatoes/fungus/cress growing crudola. My next-door neighbour (who is about Raoul's age) was going to do a rotting-sandwiches experiment (yawn) but I suggested chucking eggs out of windows wrapped in various kinds of packing materials (and with a nice naked egg as a control). He made a bunch of different packages (bubblewrap, newspaper, polystyrene beads) and took photos of the results of each droptest. He had fun doing it (especially the smashing parts), much more so than he'd have had watching sandwiches rot. Better yet (well, worse for him, 'cos he's shy) he won the fair and had to present it at some regional fair (much to his excruciation). I had worse luck persuading his older brother, however. Said teen was scheduled for medical school, and his bio project was something dull involving the nitrogen metabolism of soil bacteria. My idea was altogether more fun (and more attention-grabbing-science-fair-ey) - buy a sheep's heart from the butcher and (armed with some plumbing supplies, a fishtank aerator, a bottle of lucozade and a car battery) see how many beats we can get out of the old ticker. For some odd reason that idea was decried as "sick". -- Finlay McWalter | Talk23:00, 13 September 2006 (UTC)Reply
It's fairly trivial to build the basic logic gate types using one or two transistors each. One such circuit is even linked directly from the logic gate article. I've seen articles from back in the 80s (perhaps in the "Amateur Scientist" column in Scientific American?) in which logic gates were constructed using ropes/struts/pulleys, and using billiard balls on pool tables with specially-arranged bumpers. DMacks22:54, 13 September 2006 (UTC)Reply
Not a debunk, but the Apraphulian computer (near Pullleg Mountains...) was an April Fools' joke ("Computer is unearthed in the jungle of Apraphul, An ancient rope-and-pulley.", Scientific American, April 1988, p. 96). 123 . Despite this, it could make a good science fair project, especially if you use the logic to *do* something. -- Fuzzyeric03:52, 15 September 2006 (UTC)Reply
I don't know how it could be made into a science experiment (and it might be outside your realm of computer experience), but something that is not nearly well-enough known, and it always of interest, is how easy it is to get data off a supposedly cleaned or erased disk. I'd suggest going to a 2nd hand computer store or a big second hand store (where they often have old hard disks at $1 a pound or $1 a gig), and show how the data can be retrieved despite the previous owners' erasure efforts, or your own. Anchoress00:11, 15 September 2006 (UTC)Reply
KW Vs HP
Latest comment: 18 years ago6 comments5 people in discussion
I once learned a simple mnemonic for this: "In Fourteen-hundred and ninety-two / Columbus sailed the ocean blue / Divide that son of a bitch by two / And that's how many watts are in a horsepower". You're welcome. -- Plutortalkcontribs19:05, 14 September 2006 (UTC)Reply
That's priceless!!! I usually just round this in my head by figuring 100HP is 75KW, you can rough out numbers either way pretty easily. --Jmeden200020:42, 14 September 2006 (UTC)Reply
Latest comment: 18 years ago2 comments2 people in discussion
Someone who looks like they have ESL has added a bunch of stuff to the Crest (bird) article. At the moment, I'm trying to read through it, try to get the gist of what the anon was trying to say and see if any of it is salvagable. There is a reference in the article to Rooster of Bankiva. Anyone know what the heck that is? Cheers. --Kurt Shaped Box00:31, 14 September 2006 (UTC)Reply
Latest comment: 18 years ago15 comments14 people in discussion
The Northern Hemisphere is located between ______ and the _______? I think the second blank in the equator but I am not sure what the first blank may be.
If you are complaining about far Western Europe and Africa, then you're right, we lump those in with the Eastern Hemisphere, since they are geologically, physically, politically, socially, and economically tied to the Eastern Hemisphere. The line really should have been drawn between Iceland and Greenland, that would have been far more logical. StuRat16:40, 14 September 2006 (UTC)Reply
Latest comment: 18 years ago9 comments4 people in discussion
I am seriously confused on some things on the topic of craft moving near the speed of light. I would like to know first does time slow down for the passengers in the craft as they approce light speed? Second If so would they barely age on lets say a fifty year mission traveling at about 90percent the speed of light compaared to the same fifty years on earth which people aged fifty years? Once again I'm seriously confused thanks for all the help.68.120.224.21904:32, 14 September 2006 (UTC)Reply
Assuming constant motion, the passengers would not notice anything different in the spacecraft. If they looked out of the window however, they would see everything aging more slowley. The twins paradox is very confusing for people who only understand special relativity. This confusion arises from there being no preferred inertial frame of reference (it is not possible for an observer to tell if he is moving or or everything else is moving). This, however, only applies to constant motion frames of reference. It is possible for an observer to tell if he/she is accelerating (changing their velocity - yes this could mean slowing down). In the twins paradox, the twin on the spaceship will be younger on the return because he/she will have accelerated.
If one has accelerated from the other, why not has the other accelerated away from the one? (as measured by determining the red shift of their beams of light pointing at each other?) 8-)--Light current02:50, 15 September 2006 (UTC)Reply
Gravitational time dilation describes the differential time effect for an accelerated twin. As described in introduction to general relativity gravitational acceleration is indistinguishable from any other form of acceleration. (Think about being in the opaque box and trying to tell the diffrence.) So, we have this timline:
Traveling twin experiences a force, after which he knows that his reference frame is moving relative to his initial frame. The stationary twin is unaccelerated and therefore knows that his reference frame is not moving relative to his initial frame.
Traveling twin hurtles through space, his clock running slow relative to his initial frame and (equivalently) the stationary twin. The stationary twin knows that his clock is right (as long as he feels no forces).
Traveling twin has a big acceleration turning around. His clock runs even slower during the acceleration.
Traveling twin returns, with a slow clock.
Traveling twin decelerates, his clock running even slower due to the acceleration.
When traveling twin arrives back, his clock has been running slow the entire time. Stationary twin has experienced no accelerations, so both twins know that the traveling twin's clock was running slower pretty much all the time.
The situation isn't symmetric. One twin has been pressed to the walls of his black box several times and the other has not. This is explained at twin paradox as referenced above. -- Fuzzyeric02:59, 16 September 2006 (UTC)Reply
So its accn that slows the clock. OK Say the traveller accelerates away at only 1g. The stay home twin also experiences 1 g on earth. How now? Whose time is going slower?--Light current03:46, 16 September 2006 (UTC)Reply
Is it really that difficult to read the referenced articles? And no, the traveling twin originally experiences > 1 g as he accelerates out of the potential well the stationary twin is stuck in. However, the situation you're tring to describe, where each twin experiences 1 g acceleration continuous is still discriminable because one twin experiences the acceleration in the same direction all the time and the other does not. Really, go read the articles. Right now. Don't delay. -- Fuzzyeric04:18, 16 September 2006 (UTC)Reply
Latest comment: 18 years ago15 comments7 people in discussion
Anybody know any good ones? I've been doing some of my own devising, and they're working, but I'd like to know of others. The google sites I found were all commercial. Anchoress05:03, 14 September 2006 (UTC)Reply
No I haven't, but thanks for the link. I'm not trying to wean myself off glasses/contacts, I'm just trying to restore the full range of functional motion (focus) to both my eyes. I've just noticed that my peripheral vision is asymmetrical, there's a few degrees in the range where I can't focus, and my dominant eye is becoming more dominant, my weaker eye weaker. Anchoress08:49, 14 September 2006 (UTC)Reply
My general impression from years of experience and research is that there is nothing you can do. My optometrist said that, years ago, myoptic vision used to improve as you went over 50, due to shrinkage of the eyeball. Now, with computers, it rarely happens. --Zeizmic17:11, 14 September 2006 (UTC)Reply
Huh? LOL. As I said above, I'm not trying to fix myopia. I'm trying to strengthen my eye muscles, which (again, as above) seems to be working. What I meant by 'too much computer work' was not that it was causing myopia, but rather that (esp with my coke-bottle glasses rather than contacts), I was using a smaller range of motion and less varied focus lengths. Anchoress17:15, 14 September 2006 (UTC)Reply
As we sgould always say with Wikipedia, this is not the place for medical advice. But if you have noticed changes in your vision, it might be a sign of something needing medical attention. An optometrist or opthalmologist can test your peripheral vision. Changes in your visual field can be a sign of some neurological serious conditions. Vision changes can also be a sign of diabetes. Edison18:05, 14 September 2006 (UTC)Reply
Yeah I know all that, but I'm just asking if people know any good eye exercises :-). I've had a recent eye exam. I'm not asking for medical advice. Anchoress18:08, 14 September 2006 (UTC)Reply
Hey, I’m the one asking for help, lol. But it’s probably a good idea for me to write them down, I’ll do my best to describe them.
OK, so some caveats; first, this is not medical advice. For medical advice, consult an Optometrist or Ophthalmologist. :-) Second, I have no idea if I’m using the right words to describe what I’m doing, so please don’t flame me if I describe something in a goofy way.
All the exercises I do are to stretch the boundaries of my peripheral vision and to strengthen the muscles that control movement and focus.
Imagine the outer boundary of your vision as a big clock. Sitting comfortably, preferably somewhere where your view to both sides is symmetrical (I sit in the middle of a room), look along the boundary of your vision in overlapping 90 degree arcs. First look up at 12, then carefully along the boundary down to 9, then back to 12. Repeat 6 times. Rest and take a breath. Then do 12 to 3 six times, then 6 to 9, then 6 to 3, with a break and a breath in between each. Make the movement slow and smooth like a fastish second hand. Note any places where your eyes jump or fail to focus. Gently push to keep your vision as far out as you comfortably can. Note and correct the tendency to move your head. Then overlap by going from 10:30 to 1:30, 4:30-7:30, 7:30-10:30 and 4:30-1:30.
Now go in straight lines, from 12 to 6 and back six times, 9 to 3, 10:30 to 4:30, and 1:30-7:30. Don’t just jump from one to the other, focus on all the objects along the path. Take a breath break between each pair of coordinates. Take a second to do your best to focus at each end. Keep your head still.
Now go in a big circle, three times clockwise, then 3 times anti-clockwise, then repeat. I don’t cover an eye each time, but I do concentrate on switching between my dominant and subordinate eyes. Meaning, the first six times around I’m concentrating on using my left eye, then the last 6 times my right.
I do some crossed-eyes stuff, just fooling around, that’s difficult to describe. If you ever saw Madeline Kahn in the credits of – Blazing Saddles I think – it’s like that.
I should also say that the first few times I did these exercises they made me kinda nauseous.
I’d like to learn some other exercises, particularly the ones that are supposed to be so good that utilise differing focus distances. I just don’t know how to do them, so I’m not bothering to make up any exercises for them.
I see. Yes it does help, thank you. FWIW, I try to perform (very rudimentary) focus exercises daily. I always sit near a window when using the computer and, every half hour or so, I look outside for a minute (it helps when there's daylight outside). I try to focus on things in the distance and observe them consciously without thinking of anything else, watch clouds, mountain tops, buildings, cranes. While commuting, I sometimes look outside the train window and switch back and forth from close to distant without moving my eyes or head by focusing on a smudge on the window and the distant horizon respectively (and perhaps an intermediary target as well). I used to enjoy looking at the Magic Eye Autostereogram books, but got tired of all the dolphins and dinosaurs after a while. ---Sluzzelin02:02, 16 September 2006 (UTC)Reply
Cool, glad it was of interest to you. I do a couple of little focus exercises every now and then, one of them in the loo, :-). But unlike the other exercises I do, which I can 'see' the results of very very clearly, I have no idea if the focus exercises are helping, which is why I'd love to find some that have had actual results, or that were developed by experts. Anchoress20:33, 18 September 2006 (UTC)Reply
Gravitational pull between moving objects
Latest comment: 18 years ago9 comments7 people in discussion
Is it possible that I can detect a small attractive force between two staffs when I spin them close and parallel? They are made of aluminium, so are fairly light, about 5 feet long and two centimetres in diameter. It feels, once I have them close and parallel, like it suddenly requires less effort to keep them there. The 'spinning' I describe is a little like Chinese stick fighting manouvres, one staff in each hand.
No, you wont be feeling the gravitational force between them. Without actually being there and seeing what is going on I doubt I can help explain it much. Hopefully someone else has experienced this same thing and can explain it.
First of all, spinning will not have any effect on the gravitational pull between bodies. Secondly, the force of attraction between any 'normal' (not massive) bodies will be very very less and can be detected only with precise measuring instruments. So I don't think that you can actually feel the attraction between the staffs - Wikicheng07:11, 15 September 2006 (UTC)Reply
You can even do it mathematically - the gravitational force between two objects is (from gravity). Plugging in some reasonable numbers (each staff weighs about 0.5 kg, and say they are 20 cm apart) and the force between the staffs is 4.2x10-11 N. This is 200,000 times less than the weight of a flea. So, really, not very much... — QuantumEleven11:10, 15 September 2006 (UTC)Reply
Ok, I accept that the maths above is probably accurate - Thanks. But another phenomenon, which I have observed but never had explained, might be related - That is, when two streams of water are falling close to each other, the streams seem to come closer to each other the further the water falls. So if they are, say, a half a centimetre apart at the top, they come together to form a single stream after a metre of falling. To me it seems there is some kind of attraction going on, but the water must have a similar mass to the staffs. Does that help at all?
It is starting to come together - the fluid theories would also apply to fire? I didn't say earlier, but there is a burning wick each end of the staff. Maybe that is the key ingredient, rather than the staffs themselves. I am thinking along the lines of - the burning wicks comsume oxygen in the local area, resulting in an area of low pressure. This would occur equally all around each wick, but when two wicks are close to each other, the area between them would be the lowest, resulting in a tendancy for the wicks to move towards each other. If this occurs at both ends at the same time, the staff draw together. If that sounds completely wrong, I welcome further criticism. Thank you all for your help so far!
Sulphur
Latest comment: 18 years ago2 comments1 person in discussion
Why is sulphur used for making skin ointments? Thanks!
In the 1940s before modern antiseptics became available, I think sulphur was used. Perhaps it is used for this reason, and to stop things growing in the ointment. But I'm only guessing.
earth science
Latest comment: 18 years ago4 comments3 people in discussion
what are the composition of lithosphere
?kellane hannam
Latest comment: 18 years ago4 comments4 people in discussion
Could anybody tell me how many tentacle housefly has does spider, earthworm ??
Do you mean how many legs do they have ? Insects (including flies) have 6, arachnids (including spiders) have 8, and worms have zero. StuRat13:49, 14 September 2006 (UTC)Reply
Latest comment: 18 years ago1 comment1 person in discussion
Henry Ford introduced the Fordson tractor in 1917 but started experimental work in 1915 - 1916. I have a picture of one of these experimental tractors and it looks diffrent than the production model, it appears to have a diffrent engine. Do you have any information about what engine was used? Did Ford buy some engines from other companys such as continantal for the experimental tractors? Thank you for any help you can give me.
Actually Ford built his first prototype "automobile plow" in 1907 (See image at [18]) Since Ford was the probably the largest single maker of engines in the world and that Ford's policy was devoted to producing every part in shop from raw materials (except tires), it is hard to imagine them going to another supplier for an engine, even for a prototype. Rmhermen15:50, 16 September 2006 (UTC)Reply
Is this a Dracaena?
Latest comment: 18 years ago2 comments2 people in discussion
Latest comment: 18 years ago8 comments6 people in discussion
Could someone explain why certain colours when put together, form patterns? Specifically I'm referring to Image:Visiblecolour.svg on Commons, small version: , which I can see a kind of + (plus) shape when looking at the yellow hue values and the cyan. I thought it might have been just me but asked others who said they could see them too. It's not very pronounced but is definitly visible. Why do those particular colours create the illusion of that shape? (I don't see it on any other parts). Or is it a flaw in the image? - Рэдхот21:50, 14 September 2006 (UTC)Reply
It's an artifact in the image. The person who made that image made it out of a single gradient object, but the object has 7 points on it, and the colour curve is kinda flat at those points. -- Finlay McWalter | Talk22:07, 14 September 2006 (UTC)Reply
It's an artifact of the way colour is displayed on an RGB monitor. To make red, green, or blue, you crank up that single colour of pixel up to 100%. To generate cyan or yellow you combine green and blue or red and green—in this case, it was done using the 100% maximum intensity of both component colours. Consequently, the yellow and cyan appear very bright. TenOfAllTrades(talk) 22:11, 14 September 2006 (UTC)Reply
There may be artifacts in the image, but I have noticed that some color regions seem wide, like blue, red and green, while others seem narrow, like yellow, orange, cyan and violet. Does everyone see this same difference ? I've noticed the same thing when looking directly at a rainbow. StuRat07:43, 15 September 2006 (UTC)Reply
Yeah, I've wondered about that too. If this image shows an objective representation of colours and we see green as a broader band then the logical conclusion would be that we don't differentiate very much between the different shades of green. But that doesn't make sense if our specific colour perception evolved when we were swinging around in trees. Wouldn't it make more sense for us to actually differentiate better between those shades of green, helping us to disitnguish the various types of vegetation that surround us? DirkvdM08:29, 15 September 2006 (UTC)Reply
I'm sure Wikipedia has an article on it somewhere. Try Color space or gamut or XYZ colorspace. Basically, computer monitors cannot display the full range of colors that humans can see, and because of the way they work, they've got better coverage of the greens than of any other color. --Serie21:45, 15 September 2006 (UTC)Reply
Cool thanks for all the answers. I actually made the image myself which is why I wanted to know. I checked several times to make sure there wasn't a flaw in the gradient and couldn't find one, so thought it might have been the screen. - Рэдхот11:59, 15 September 2006 (UTC)Reply
Expanding universe
Latest comment: 18 years ago17 comments9 people in discussion
Eternity? I guess once the universe has expanded into it, it's called outer space. I don't know what it's called before the universe got there though.---Sluzzelin22:46, 14 September 2006 (UTC)Reply
(edit conflict) No the huge vacuum is the universe, outside the universe the are no dimension (no spacial or time dimensions) so it is impossible to exist outside of it, so there is not anything outside of, not just space, there is no space outside of it, there isnt anything for it to expand into, its not expanding into anything, its just getting bigger. The outside of the universe is not atached to the universe by a time structure, so there can be no concept of movement of the boundary. And anyway the universe doesnt have edges. The whole thing is pretty complicated really, but here goes;
the universe in a boundary-less, yet finite in size object.
it is getting bigger
there is nothing outside, not because it hasnt got there yet, but because it is impssible to exist outside of it
Basically anything that is possible for you to percieve is inside the universe. All the space and time are inside (various) universe(s) but, these universes, are all the same universe, which ahs collapsed, and expanded an infinite amount of times, but, due to the fact that time structures were destroyed every time aswell, there is no relation in time between these universes, so every universe is happening ate every point. Hmm, basically, yeh its expanding, nah theres nothing out there (atall, not even a vacuum, because thats something). PhilcTECI23:11, 14 September 2006 (UTC)Reply
So is the universe expansion due to the galaxies moving away from each other (due to the initial big bang etc) OR is it just the space between them expanding for some reason? --Light current23:17, 14 September 2006 (UTC)Reply
Even if nothing exists outside the universe, as explained above, can we still have a word for it (something better than 'non-universe' perhaps)? After all, we human beings like having names even for things that don't exist.---Sluzzelin23:23, 14 September 2006 (UTC)Reply
The real answer is this: nobody knows. However, there is one thing that we can be fairly sure of: space isn't static. That is, the galaxies, when we speak of the expanding universe, are not actually hurdling through space, but rather space itself is expanding. In addition, this expansion appears to be accelerating. One might expect the universe to either slow down, or stay at constant speed. Yet this is not what is observed. Things appear to be speeding up, which may in time clue us in to exactly what is going on "beyond" our universe, if there is such a thing. - R_Lee_E (talk, contribs) 23:26, 14 September 2006 (UTC)Reply
Not 100% true. The various galaxies are moving with respect to each other, in addition to the expansion of the universe. I think we're scheduled to gulp down (yeah, that's the scientific term) the Magellenic Clouds at some point. Clarityfiend01:37, 15 September 2006 (UTC)Reply
It's expanding into the future. Really. Consider the common "surface of an inflating balloon" model. Run the film backward and it contracts into the past. Run it forwards and it expands into the future. This really is what's going on.
Of course, there are two things going on... The observable universe has a radius of ~13.7 Gly (billion light years) because our past light cone extends far enough to see that far away/back. Inconveniently Hubble's law induces in-place expansion and details of that theory lead to estimates of 46-78 Gly. The first effect is similar to the balloon model. The second would be similar to some weird force causing the surface of the balloon to get wrinklier and wrinklier. -- Fuzzyeric04:11, 15 September 2006 (UTC)Reply
I also wondered about the (im)possibility of expansion of something that has to be assumed to be of fixed size when I was a kid and that (plus other thoughts) eventually led to my alternative to the Big Bang theory. But assuming the correctness of the theory of a Big Bang leading to an expanding universe, it is quite immaginable that there is another 'universe' that grew from another Big Bang. If they both expand, then could these ever touch? If so, how could their distance be expressed if there is nothing between them? And if there is no 'expressable distance', then how could their approach be expressed? And if that can't exist, then how can they ever meet or have been apart? DirkvdM08:45, 15 September 2006 (UTC)Reply
Two parallel patches of Flatland can approach each other and (perhaps) pass through each other. The distance between them is inexpressible because the only directions in which there is distance in either universe is perpendicular to the direction of separation. Imagine that the answer to the principle question were "3 meters"; then the follow-up question is "in which direction", which is unanswerable. Now, if there is brane cosmology then this could be exactly the situation in which we find ourselves, but (hopefully) measurable dynamics would set a metric in the direction of brane separation and so "distance" could be meaningful, i.e. would set a norm (mathematics). -- Fuzzyeric03:06, 16 September 2006 (UTC)Reply
brain disorder
Latest comment: 18 years ago2 comments2 people in discussion
my sister had a CT of her brain and they found dark area in the frontal lobe. Is there a specific disease that this is a symptom of? She has frequent "migraines" which they have been treating for yrs. She has some speech difficulty, ex; finding the right words, etc. Any info will be greatly appreciated Thanks ahead of time.24.118.93.15823:58, 14 September 2006 (UTC)Reply
There's no single disease that's associated with a "dark area" on a CT: there are lots of different problems that might cause such a finding. A dark area is an area that is relatively more permeable to x-rays than the light areas. You need the radiologist or neurologist who actuallu looked at the x-ray to tell you what they think it might be, there's no way to tell from just a description. They will also be able to suggest if there would be any value to further studies like a CT scan with contrast, or an MRI. - Nunh-huh04:36, 15 September 2006 (UTC)Reply
September 15
To the ends of spacetime itself!
Latest comment: 18 years ago21 comments11 people in discussion
On a related note, (and I'm sure this is already adressed elsewhere, sorry) if I could travel for any set amount of time in one direction as fast as desired, would I come to some boundry-like feature? If I come to such a feature, what would its nature be? --Amanaplanacanalpanama00:19, 15 September 2006 (UTC)Reply
Hopefully with a lot of frequent flyer points and a T-shirt that says "I went to the edge of the universe and all I got was this lousy shirt." Clarityfiend02:10, 15 September 2006 (UTC)Reply
Because the three dimensional universe has a fourth-dimensional fold upon itself, right? Are we quite confident about that? Are there alternative ideas? What if I could travel in the fourth dimension too?--Amanaplanacanalpanama02:12, 15 September 2006 (UTC)Reply
There are plenty of alternative ideas: see Shape of the Universe. I think modern observations support a spatially finite universe, but I'm not sure. It's absolutely conceivable that the universe doesn't fold upon itself, and we probably need better observations to prove it or rule it out. Melchoir02:22, 15 September 2006 (UTC)Reply
There are three definitions of universe floating around here. Observable universe, accessible universe, and Universe. The first is what we can see. If we wait, the observable universe expands because our past light cone includes more and more space. The accessible universe could be defined as the set of all points with a connected path to them (the canonical path is one that goes backwards in time to nearly the Big Bang, travels a little sideways (in space), then forward in time to the destination point. Thus, the accessible universe is larger than the observable universe but should have the same physics and similar structure as our observable universe. The capital Universe is everything, which might include higher dimensions, superstrings, branes, parallel universes, and even weirder things. The Universe as just defined has ontological problems, much like rank-into-rank cardinals, largely as a reflection of our ignorance about the subject.
Currently, if you were to travel at a feasible velocity (less than the speed of light), we can show that even if the Universe were closed, bounded, and connected, you'd never return to your starting point because of a Hubble expansion and the acceleration of the metric expansion of space. To be blunt, space is appearing faster than you could possibly cross it. -- Fuzzyeric04:29, 15 September 2006 (UTC)Reply
Right. If spacetime has either an edge or "wraps around," these features are currently completely inaccesible to us. In principle, if the universe collapsed again this could change. -- SCZenz07:26, 15 September 2006 (UTC)Reply
When you say "the observable universe expands because our past light cone includes more and more space" that sounds as if space = time. DirkvdM09:05, 15 September 2006 (UTC)Reply
I don't think that was what was meant. Since light travels at a finite speed, it takes a certain amount of time for light from distant parts of the universe to reach us. The longer we wait, the more light from ever more distant parts of the universe reaches us - that's why the observable universe (not the universe itself) can be said to be expanding over time. -- Ferkelparadeπ09:15, 15 September 2006 (UTC)Reply
So I believe the question can be rephrased as this: theoretically speaking, could there be a galaxy somewhere in which the inhabitants look towards one side of their sky and see stars and galaxies (everything that we see when we look up) and on the other side of their sky, do they see blackness (the edge)? I find this unlikely, but I can't quite justify why. Thoughts? - R_Lee_E (talk, contribs) 14:15, 15 September 2006 (UTC)Reply
There sure doesn't appear to be any such place, at least not for 13 billion light years in any direction. There are some vague ideas that maybe the universe's fundamental physical constants could be different in other Hubble volumes, and then presumably on the border there'd be galaxies on one side and crazy-go-nuts chaos on the other; but there's no obserervations that confirm this, and the details of the transition would vary tremendously from model to model. -- SCZenz19:51, 15 September 2006 (UTC)Reply
Latest comment: 18 years ago3 comments2 people in discussion
Why, for example, is glass see-through, and a material like iron a metallic grey? What physical or chemical properties determine that difference?
Ellen U.
Probably for the same reasons we discussed a few days ago on this same wiki page here, and that's even very near the top of the table of contents? DMacks03:03, 15 September 2006 (UTC)Reply
Latest comment: 18 years ago4 comments3 people in discussion
In the electrolysis of a solution of baking soda (sodium bicarbonate, NaHCO3) in distilled water, is caustic lyme (sodium hydroxide, NaOH) produced? If so, is there any way of neutralizing it, so as to make the solution safe again for ingestion?
Yes. NaHCO3 -> Na+ + HCO3- q.v. carbonic acid. The formation of NaOH will be limited by the concentration of OH- (one part in 107 by default (q.v. pH)) and competition with the formation of Na2CO3 (q.v. soda ash) and NaHCO3 (q.v. baking soda) as mentioned in the sodium article.
The sodium hydroxide article references an external MSDS which should give toxicity information. Together with your estimate of the concentration of NaOH based on the three-way race above, you should be able to judge if the concentration is unsafe. -- Fuzzyeric04:42, 15 September 2006 (UTC)Reply
Yup. List of Latin phrases (P–Z) has "quod vide (q.v.)" -- "which see". Although the notes there claim that this should be a suffixed annotation, I've never seen it used other than as a prefix, like "e.g." ("exempli gratia" in the "E"s). -- Fuzzyeric03:13, 16 September 2006 (UTC)Reply
Battery Capacity
Latest comment: 18 years ago2 comments2 people in discussion
How is it possible to measure the capacity of low voltage high current devices?
First determine what final voltage constitutes the battery being discharged. Then determine your discharge rate. You can connect it to a constant resistance load, and the current will drop as the voltage drops. Or you could discharge it at a constant current draw. If it is driving an uninterruptible power supply, the discharge current may actually increase as the battery discharges, as the inverter draws more current at lower voltage to maintain constant power output.Edison23:49, 15 September 2006 (UTC)Reply
Computer Software
Latest comment: 18 years ago2 comments2 people in discussion
How does the computer distinguish between shutdown and restart command from software?
The "o" and "p" refer to the positions of the Cl atoms on the benzene rings relative to the position where the rings bond to the central carbon (the standard "ortho" and "para" substituent designations). I added a note about it to the DDT article. DMacks06:25, 15 September 2006 (UTC)Reply
Latest comment: 18 years ago17 comments11 people in discussion
Hi, I would like to know YOUR opinions on diet coke and its effect on health. Please dont just send me a link to the coke page or aspartame page! I drink about 1-2 litres a day every day. There seems to be one camp that saas its bad for you and one camp saying its as harmless as water. please dont quote the penny cleaning story either as our stomachs secrete hydrochloric acid anyway!!
Please help as Im very confused about this issue.
As you say, there are different opinions, no doubt here on the reference desk as anywhere else. If you've thoroughly read up on the subject you will have to decide for yourself. Personally, I wouldn't touch the stuff, but that's just because I don't like it. I don't think you can beat a good cup of tea. I start with three mugs of tea every morning, drink coffee in the afternoon, and fruit juice in the evening, or hot chocolate depending on the weather. There will be people who don't think that's a good regime either.--Shantavira11:01, 15 September 2006 (UTC)Reply
Those artificial sweeteners are nasty chemicals, I would ban them. Or, if a neutral research firm had 1100 test subjects exposed to those chemicals daily, then studied them over the course of their lifetimes, and showed no increase in any major diseases over the control group, then I might accept them as safe. Short of that, I would drink something natural and known to be safe, not take my chances on those artificial chemical cocktails. StuRat12:19, 15 September 2006 (UTC)Reply
That article shows that it does not pass right thru the system, but is broken down into all sorts of nasty chemicals in the body, like formaldehyde. Even those who support using aspartame admit that these breakdown products exist, they just deny that they are harmful in those quantities. StuRat23:56, 15 September 2006 (UTC)Reply
As Shantavira said, there is differing opinion on the subject, and you seem to be quite well read on this topic. Irrespective of that, something to consider: yes, your stomach does produce acid. But it's also well known that increasing the acidity of your stomach contents does bad things for you (why do you think people take antiacid tablets?). Coke is moderately acid stuff, and if you're drinking 1-2 liters of the stuff a day it will make your stomach more acid. Do that continuously and you'll probably get heartburn and other ailments unless you have also taken a liking to bicarbonate of soda. Is that such a good idea? Baseline, if you want my (non-expert) opinion is that Coke is fine in reasonable quantities, but if I were you I'd cut down. Try fruit juices, or simply water (with a bit of flavouring, such as a bit of lemon juice, if the taste is too bland for you). Plus, you won't have to go to the bathroom so often (Coke is a strong laxative, as you've no doubt noticed) — QuantumEleven13:04, 15 September 2006 (UTC)Reply
and yet artifical sweetners are safer than natural orange juice. Xcomradex
(edit conflict) I don't want to get into a war about natural vs artificial, and I'm no expert on the subject, but that would surprise me greatly. Do you have any sources to back that up, XComradex? — QuantumEleven13:25, 15 September 2006 (UTC)Reply
Go by QuantumEleven's advice. I ised to drink coffee but stopped for some reason and switched(?) to plain water. Now I do enjoy just plain water. I do take a cup of coffee when it is too cold but otherwise it is just water for me. I really like it. Try it. -- Wikicheng13:21, 15 September 2006 (UTC)Reply
While I'm unsure of the health effects of drinking large amounts of diet soda, anything taken to excess is bad for you. I recommend drinking water. When I left home to go to college, I gave up soda, as I had sold my car, and soda took up too much space in my backpack when I rode back to my dorm from the grocery store. I started drinking Tang, and then later I started just drinking water. Since then I've lost thirty pounds and I've never been healthier. I would attribute the lost weight not just to the lack of soda, but from getting exercise by riding my bike. I also found that it was easy to drink water often if you have a Brita filter in the fridge. That way, you always open the door and are greeted by a container of cold water. Gary15:05, 15 September 2006 (UTC)Reply
I think aspartame has a relatively good track record, but 1-2 liters a day of anything that's not just plain-ol' water is probably a bad idea...moderation would be my advice. Of all the studies I've looked at, excessive aspartame = bad in certain model systems. (but who is surprised by that? show me a chemical given in high doses that doesn't cause negative effects...) It can't be bad for you to consume less aspartame, though, right? Try to limit your consumption a bit--if you can get down to a can a day (replacing some or all of the volume with water) you might reap the benefits of less caffeine, healthier teeth and a fatter wallet. -- Scientizzle18:39, 15 September 2006 (UTC)Reply
1)The question was about diet coke, which would not affect sugar metabolism much; 2)Not much evidence that sugar consumption causes diabetes, other than it causing obesity which makes Type 2 diabetes more likely. 3)I believe constant consumption of diet coke can discolor your teeth and tends to etch away enamel. Carbonated beverages are also said to produce flatulence. Edison23:55, 15 September 2006 (UTC)Reply
I can't believe no-one's come up with this yet. Most artificial sweeteners in soft drinks are derived from phenylalanine. It is metabolised, otherwise there would be no problem with phenylketonuric people consuming it. Thats what I know. This is my opinion: I've also heard that some people believe that it increases total body phospate somehow. If thats true, then it could possibly also lead to osteoporosis in the longer term (look up the physiology of calcium-phosphate regulation if you don't follow) - although I don't know if theres any studies around that lend any credible evidence to that. But as the others have said - you can't go too far wrong with good ol' water. Mattopaedia08:49, 16 September 2006 (UTC)Reply
Digital camera image size ratio
Latest comment: 18 years ago8 comments5 people in discussion
After some browsing of the relevant articles I couldn't find the answer to this, so I'm hoping one of the Ref Desk wizards can help me. Why is it that most (I think all except digital SLRs, but I could be wrong since I've never owned a digital SLR) digital cameras take images that have a size ratio of about 1.3 to 1, whereas film cameras (specifically, 35mm) take pictures that are about 1.5 to 1? This has gotten me into trouble several times when developing photos, as I have to remember if I have to develop them at 10x13cm or 10x15cm. Is there any reason for this discrepancy? Thanks! — QuantumEleven11:15, 15 September 2006 (UTC)Reply
I would guess that's so they will more closely match the common computer monitor aspect ratios:
Academy ratio (1.375:1) was established for movies in 1928 and Academy ratio was essentially the only ratio used until 1952. This ratio was adopted for television and then monitors. For stills, 135 film was a cartridge format introduced in 1935 that has a 24 x 36 mm ratio (1.5:1). See film formats to be astonished by the wide range of film formats that have been in use since 1895. APS for instance is a still film format that is designed to accept all three aspect ratios (4:3, 3:2, 16:9). -- Fuzzyeric05:06, 16 September 2006 (UTC)Reply
Impregnating the female population of Europe
Latest comment: 18 years ago10 comments9 people in discussion
For some time it's been accepted that every man has enough sperm in a single ejaculation to impregnate all the women in Europe. What would be the consequences if one did. The practicalities of how are unimportant (as it's impossible), just assume its magic or sufficiently advanced technology. I know there would be major social & economc upheaval, litigation, divorces, etc but what I'm interested in is the long term evolution of the people of Europe. If all the women of childbearing age in Europe (I estimate female population of Europe to be around 355,000,000 & child bearing women to be half this at 177,500,00) were to get pregnant with the same man's child there would be a lot of duplication of genes across the population so how would this population develop (assuming that it isn't possible for all the children to breed with someone outside Europe) over the course of several generations? Would they develop into another species through the accumulation of certain genes or combinations of genes? AllanHainey11:24, 15 September 2006 (UTC)Reply
In the short term you'd see an increase in recessive genetic disorders. In the long term, the defective recessive genes would be largely removed from the gene pool. Of course, if the father was a particularly good genetic specimen, you would also dramatically improve the European gene pool, while, if he was a rather poor specimen, then you would seriously degrade the European gene pool. In any case, Europeans would be more homogenous (similar), as a result. StuRat11:58, 15 September 2006 (UTC)Reply
Actually, total scum are the best at impregnating large numbers of women, by promising them everything, impregnating them, then dumping them immediately and moving on. This has rather negative implications for the genetic future of the world. StuRat17:10, 18 September 2006 (UTC)Reply
Not really. It's true that some percentage (5%? 20%? i can't be bothered looking it up) of people in the UK have Genghis's genes, but that number is more a matter of statistics than of his sexual prowess. That is, the same stat would be true of many other people who were alive at the time of Khan. Simple the DNA has diffused throughout the population. I could probably explain this better but it's 3am. As for the original question, yes, as mentioned there would be many recessive traits coming out as Europeans would have no one to breed with but their half-brothers and half-sisters unless they left Europe. These don't get bred out that quickly as that's the nature of resessive traits. It would be similar to the founder effect. —Pengotalk · contribs17:26, 15 September 2006 (UTC)Reply
If the single man was the bearer of any low-frequency alleles (which, statistically, any single person is likely to have a handful), you'd have a most profound disruption of genetic drift. As Stu pointed out, if any of those alleles are associated with autosomal recessive diseases, the overall incidence of such diseases would increase. If he's got an autosomal dominant condition, it could have even more drastic effects on the overall poplulation. Overall, though, there will be a dramatic increase in the frequency of each of his alleles in the general population.
Now, looking at future generations: the production of a roughly a 170 million half-siblings would lead to increased consanguinity in the production of future generations. This could potentially lead to something akin to a founder effect under the right circumstances (small rural areas of Europe, especially). A hundred generations later, our Don Juan's genetic effect would still be noticable, but probably mostly in isolated regions. With increased globalization, the effects of pseudo-random assortive mating would smooth out many of the negative consequences of a drastic decrease in genetic variability within the European population. -- Scientizzle18:27, 15 September 2006 (UTC)Reply
If the Great Impregnator were Prince Charles, the population of Europe would tend to have ears that stuck out a bit. There was a sci-fi story aboout a world where one man's dream was to have sex with all the women. He got his wish, and only he could father children. It got old after a whileEdison23:58, 15 September 2006 (UTC)Reply
Latest comment: 18 years ago9 comments3 people in discussion
I was wondering if someone might (gently) explain "msin i" as a formula for determining planetary mass boundaries. The only answer I've found is this but I'm still befuddled. The sentence it pertains to (that I'd like to unpack in an article): "Throughout the habitable zone around Barnard's star, i.e. 0.034-0.082 AU, we exclude planets with msin i> 7.5 mEarth and m> 3.1 mNeptune." Marskell14:33, 15 September 2006 (UTC)Reply
The article is describing the detection of extrasolar planets by "wobble". The magnitude of the wobble is proportional to the mass of the planet and the sine of the (edge on) angle of the orbit, called "iota" there. A better way to write your expression is "exclude planets with and ." This means that they're ignoring planets producing wobbles bigger than would be produced by a planet 7.5-times as heavy as the Earth in an orbit that was perpendicular to the line of sight to the planet and ignoring planets more than 3.1-times more massive than Neptune. -- Fuzzyeric03:25, 16 September 2006 (UTC)Reply
If a planet's orbit is perpendicular to the line of sight its detection is much more difficult, correct? If it's perfectly perpendicular there will be no red/blue shift at all relative to the observer and thus no radial velocity detection available (?). How, in this case, is the measurement for an orbit perpendicular to the line of sight so precise? I'm no doubt ass-backwards, but I'd expect the more precise boundary for a parallel orbit as this would create a maximal "wobble" to the observer. Marskell05:57, 16 September 2006 (UTC)Reply
You're right (your reference even says so in the first sentence). But I have a question for you: why does sin(i) appear only in one of the inequalities? Clarityfiend18:42, 16 September 2006 (UTC)Reply
The primary source [19] states "determine upper limits to the projected mass msin i and to the true mass". The second figure is true mass: no body >3.1 Neptunes, period. Marskell09:32, 17 September 2006 (UTC)Reply
Extrasolar planets describes both transverse wobble (photographically detected) and longitudinal wobble (Doppler shift detected). The article's abstract isn't sufficiently detailed to indicate which is being talked about. It would make as much sense using appropriate combinations of "orbit vector defined by displacement vector most parallel to line of sight", "orbit vector defined by angular momentum covector", "wobble measured photographically", "wobble measured spectrally". -- Fuzzyeric21:46, 17 September 2006 (UTC)Reply
Latest comment: 18 years ago3 comments3 people in discussion
Can people in their 80s live with CF all there life without knowing it?
My 83 year old brother-in law has terminal CF, is at home and administered Hospice care. He never smoked, is a WW2 combat vetran, and was an avid walker till recently when, after short walks, he began labored breathing.
I have read most of Wikipedia articles concerning CF, but don't find any referance to late diagnosis, for the first time, of CF at his age , hence, my question.
Well, usually cystic fibrosis is diagnosed very early and, without dedicated treatment, is still largely fatal by young adulthood. The list of notable people with cystic fibrosis has some examples of folks that have lived relatively long and successful lives with CF.
If I were to hazard a guess here, perhaps the CF alleles your brother-in law possess are of the relatively healthier variety. There are effectively five classes of CFTR mutation (more info here) that range from defective protein production with premature termination of CFTR production to simply reduced overall synthesis of CFTR. A person's two alleles will combine to determine overall CFTR function and symptoms follow from there. There are also at least four knownautosomal dominant alleles that confer relatively minor effects. Whatever the combination, maybe it took eighty years to do what often happens to children and teenagers with the most common mutations.
It is unusual to have such a late diagnosis, but there seems to be plenty of genetics info that would suggest it's not unlikely. Best of luck to your brother-in law. -- Scientizzle18:07, 15 September 2006 (UTC)Reply
While exceedingly uncommon, it's certainly possible to have mutations which are mild enough to give a mild disease which doesn't present until late in life. Some people have mutations with no pulmonary symptoms (such as those diagnosed after infertility evaluations). Maybe it occurs more often than we know and no one checks for it! InvictaHOG22:44, 15 September 2006 (UTC)Reply
mesotechnology
Latest comment: 18 years ago1 comment1 person in discussion
what exactly is the principle of mesotechnology?if i am to do a seminar on this topic from where can i achieve enough and more information regarding this technology? — Preceding unsigned comment added by 220.226.49.86 (talk • contribs)
Latest comment: 18 years ago1 comment1 person in discussion
I would like to know if there is and honest/ethical source that does studies on the benefits of vitmins and supplements. I am looking at hsn right now and Andrew Lessman is giving some very interesting information on supplements... I would like to know if there is an support for the statements he is making and where a average person can look for an unbiased/ researched opinion... thanks
The problem, I think, is that there is really nowhere an "average person" can go look for unbiased research opinions. A lot of medical literature on the subject will have improtant confounding biases (which may not easily be observed) such as one or more of the authors receiving some benefit form a large vitamin company, for example. Advertising and advertorials are more about marketing than good scientific evidence. You can search public ___domain medical databases like pubmed if you like, but if you're not au fait with medical terminology and statistics what you find may be hard to interpret. Much of what I've read over the years in the medical literature about vitamin and mineral supplements suggests there is no evidence they are any more effective at improving health & well-being than placebo. This is for the average, well nourished, western civilisation adult. There is evidence to suggest vitamin supplementation is important in certain health conditions, such as Iron and vitamin C in anaemia, zinc and vitamin C for wound healing, thiamine to limit chemically induced brain damage, vitamine B6 for leg cramps in pregnancy. General supplementation is also believed to benefit chronically malnourished individuals such as those with anorexia nervosa. So if you're fit & well, eat fresh friut & veg, don't eat many processed foods or fast foods, don't smoke & don't drink too much alcohol, you are probably wasting your money buying supplements. And anything some guy on TV tells you that sounds too good to be true, probably is. By the way, don't forget to sign your posts. Mattopaedia03:14, 16 September 2006 (UTC)Reply
I take a vitamin and mineral supplement every day, so I'm biased. Vitamin D has been recently shown to reduce many cancer rates, as has selenium. British people are thought to be deficient in selenium since we not longer import bread-flours from selenium-rich areas of North America. But selenium can also be obtained in abundance by eating one brazil nut a day, and there is firm evidence that people who eat nuts regularly (unroasted, non-salted) live longer. I choose a pill that includes iodine, as I wonder I might be otherwise deficient, but iodine can be found in seafood. The bad and dangerous thing to do is to consume more than the recommended daily allowance (RDA), since some vitamins such as Vitamin D for example are dangerous at only a little above the RDA, or can result in deficiencies in other nutrients. Vitamin C in unnaturally high doses causes kidney damage. So stick to a pill with only the RDA or less in it. And pregant women or those seeking to become so, should seek medical advice, including regarding folic acid.
Seagulls and slightly past-the-date sausages?
Latest comment: 18 years ago3 comments3 people in discussion
I have a pack of sausages in my fridge that I didn't manage to eat by the expiry date and they have started to go slightly 'off' (turned greyish with a little bit of mold starting). Are they safe to feed to the seagulls like this (raw too)? I don't want to see food go to waste but I don't want to make the gulls sick either. --84.67.70.18516:41, 15 September 2006 (UTC)Reply
I'd cut off the moldy parts, then cook them, then give them to the seagulls. If that's too much trouble, just toss them in the garbage. StuRat17:30, 15 September 2006 (UTC)Reply
I'm pretty sure the sausages would eventually be eaten by something (perhaps seagulls, perhaps another animal or insect) even if you just toss it out. Maybe let the gulls decide if they want it (i.e. leave it outside on the ground or something). —AySz88\^-^18:27, 15 September 2006 (UTC)Reply
I believe most food molds are carcinogenic, except presumably those in cheese. I remember reading a detailed article in the online Spiked magazine written by a professor who said that although mold may only appear on a small part of the fruit or vegetable, the carcinogens will have spread through most of it. I expect the same is true with sausages. I think it would be ethical to feed the sausages to gulls, as they won't live long enough to develop cancer. My guess is they may prefer them uncooked, as this is closer to their natural food, but who knows?
Recharging NiMH batteries
Latest comment: 18 years ago2 comments2 people in discussion
Hello. I have a set of NiMH batteries. I also have a charger that states: "Use only with nickel-cadmium batteries." I think that the charger is from before NiMH batteries were commonly commercially available here in the Netherlands. What is the risk if I try to recharge the NiMH batteries with this charger? Could they explode? :wimdw: 16:54, 15 September 2006 (UTC)
You'll wreck the batteries. If you're unlucky, the batteries will leak acid or catch fire. NiCd batteries are very durable when it comes to charging, while NiMH batteries aren't. --Serie21:52, 15 September 2006 (UTC)Reply
Thanks. :wimdw: 18:51, 16 September 2006 (UTC)
It relates to how the charger senses when to stop charging. One way that works for NiCd cells is to sense the rate of change of the cell voltage as a function of time (dv/dt). This voltage will increase as the battery charges (so dv/dt > 0), but when the battery is fully charged it will start to decrease (dv/dt < 0), and you can sense this and terminate the charge. NiMH cells still do this to a certain extent, but the effect is much smaller. An NiCd charger that looks at dv/dt might therefore overcharge an NiMH cell, which could destroy it, or at least shorten its life.
A lot depends on how much life you're expecting to get out of the set of NiMH batteries and how sophisticated your charger is. The warning probably refers to the idea that the charger is completely unsuitable for recharging primary batteries.
Now whether or not you could charge NiMHs is a somewhat different question. Very old NiCd chargers were not automated at all; you simply charged batteries for a certain number of hours and hoped a) they were "topped up" and b) if they ran "over the top", that the recombination catalyst within the cells was recombining the hydrogen and oxygen that was being evolved by electrolysis. The charge current was usually quite low (<= 1/10 C) so the power that was dissipated by a fully-charged cell wasn't very much. Such a charger could probably do about as good a job recharging NiMH cells as it did with NiCd cells (which was "okay" but not great and certainly not "automatic".
Automated chargers would run into the problems described above by other editors: the "terminal" (end-state) conditions for NiMH batteries are different from NiCd batteries. But it still might be possible to recharge NiMH cells if this is a conventional "slow" charger and you considered the charger to be manually operated and were careful to end that charge cycle after some calculated period of time. If you were to try this, monitoring the cell temperature sounds like a really good idea. I suspect it would be a very bad idea to try this with a "fast" NiCd charger as finding the "end moment" would be too tricky and the results of miscalculation too dangerous.
Latest comment: 18 years ago4 comments3 people in discussion
What's the correct plural of brille? (in the sense of the article).
It could be brille (no plural), brilles, or brillen (from German). I'm not sure which is correct in English, or if multiple are. Most mentions seem to avoid using a plural. —Pengotalk · contribs17:10, 15 September 2006 (UTC)Reply
From the use in the article ("All geckos except those in the subfamily Eublepharinae (eyelid geckos) possess brille."), the singular and plural appear to both be 'brille'. -- Plutortalkcontribs17:15, 15 September 2006 (UTC)Reply
Latest comment: 18 years ago2 comments2 people in discussion
I have a question about the ice core examinations and how increasing temperatures correlate to increased CO2. In years when the temperature and CO2 are high, doesn't the ice melt--loosing an important piece of the record? Wan't the temperature in the 13th century high enough to melt the ice even on the GISP2 site in Antartica? During interglacials, how can scientists distinguish between years of ice strata when the depth of the ice is unlikely to increase due to summer melting? Is geothermal heating an issue with the 800,000 year old ice core? I'm having trouble understanding the science. Thank you!
CCM
At most of the sites where cores are located it never gets warm enough to melt (or only very infrequently). Consider that Antarctica has been ice covered for 10s of millions of years, and a warm summer at Vostok Station is a balmy -30 C. At sites where melting does occur, the resulting melt layers are very easy to distinguish from ice formed by compacted snow. Geothermal heating can be an issue and is partially responsible for the formation of subglacial lakes, like Lake Vostok, but I don't believe it is an issue with the recent 800,000 year Dome C core. Dragons flight17:38, 15 September 2006 (UTC)Reply
In Earth's history, 800.000 years is nothing.That's less than one thousands of its age. And there have only been four major ice ages in the sense that the polar caps melted (wat is coloquially known as an ice age is really a glaciation). The present ice age started 40 million years ago. That's 50 times longer ago than the age of those cores. DirkvdM07:10, 17 September 2006 (UTC)Reply
Coins
Latest comment: 18 years ago7 comments4 people in discussion
I've been to a mall in the Northeast US where there were these trash can-shaped receptables that people were supposed to put coins into for charity. There was a small slot outside of the can you put the coin into that would align the coin, so that after it dropped out of the slot, it would rotate around and around the upper lid of the bin until it dropped into its hole in the center. Does anybody know if there is a special mathematical curve for this type of lid, and if I can easily make/obtain this as a scientific curio? Thanks, JianLi22:22, 15 September 2006 (UTC)Reply
I'm imagining a 3D spiral (something between a 2D spiral and a helix). As long as the slope is sufficient to overcome friction, excess slope would just accelerate the coin further. You would have to be rather generous on the slope, though, as the friction may vary quite a bit, depending on the size of the coin and how sticky it is. StuRat23:21, 15 September 2006 (UTC)Reply
It actually wasn't spiral. Rather, it was merely a curved surface. I think it's called a "coin vortex." Here are some pictures of it on Google [20]. There are references to a "hyperbolic tunnel," but I am skeptical that that is its actual shape. JianLi01:11, 16 September 2006 (UTC)Reply
They're not just in the Northeast. We have them all over the U.S. And not just at malls, although that is likely where you'll find one. Charities often put them in public places because kids want to see coins go down them so they pester their parents for the coins. It gets more money than just setting a bucket up somewhere with a big sign that says "please give". Dismas|(talk)17:30, 16 September 2006 (UTC)Reply
I'm not sure that it's a hyperboloid because the website that said it was hyperbolic was a commercial, rather than academic, website. So you think a hyperboloid would work? Could it be any other shape, or any type of hyperboloid? And yes, the path of the coin was spiral; I was just saying the shape of the curve was not spiral since it was a solid surface. JianLi18:40, 16 September 2006 (UTC)Reply
Latest comment: 18 years ago4 comments3 people in discussion
I recently read two articles one was about acoustic levitation the other about a vortex ring cannon, the vortex ring cannon claims to use momentum tranfer to accelerate air at such speeds and concentration that it can knock a man down. i am wondering if this is how acoustic levitation works [sounds transfers momentum to air, air pushes object] and if there are other methods for producing momentum transfer on air molecules, and how is this different from levitations that transfer momemtum directly to the object?
blow the man down??? yea, but the question was does acoustic levitation produced pressure on objects because it is causing momentum transfer between air molecules , and the air pushes the object,
Robin
So acoustic levitation is not the same as levitating something by superfocussed high intensity momentum transfer in air molecules. i dont think this method exists yet however, but it seems possible vortex rings focuss air enough to repulse even large objects. and apparently this is not acoustic in nature. What are the methods for producing momentum transfer in air molecules
Robin
A vortex-ring is more than just a ring, it also carries some surrounding air, and the whole blob is roughly spherical. The whole blob moves along. So if you could fill the whole thing with smoke, it would resemble a travelling sphere with a ring-shaped flow in its center. If you were struck by a fast-moving sphere of air, as with any other collision you'd absorb momentum. Perhaps it would help your understanding if you imagine the whole thing taking place under water. If you collide with a fast-moving ball of water while under water, it's not much different than colliding with a ball of ice while under water. --Wjbeaty06:11, 17 September 2006 (UTC)Reply
Best guess based on what definitions I can find of the terms in "superfocussed high intensity momentum transfer in air molecules" is no. Acoustic levitation is based on caoustic waves, which produced a zero expectation displacement in the participating air molecules. (They displace approximately sinusoidally, but they don't have a constantly increasing displacement.) The momentum transfer method is similar to directing a hose at the object -- the participating molecules have constantly increasing displacements (until they hit something in the way).
The momentum transfer method requires a constant supply of air to replace the air that's being jetted away. Acoustic levitation does not because no air is (net) pushed away. -- Fuzzyeric22:00, 17 September 2006 (UTC)Reply
September 16
Gull
Latest comment: 18 years ago19 comments7 people in discussion
(okay, so there was a question in there...) ;)
Not really a question - but I just saw this photo and it took my breath away. How cool is this? Even the gull I raised from a couple of days old won't do this... --Kurt Shaped Box01:00, 16 September 2006 (UTC)Reply
Anybody notice how the bread looks like it was toasted with a clothes iron ? So we know the guy is a bachelor trying to lure young gulls into his grasp... :-) StuRat02:42, 16 September 2006 (UTC)Reply
THe question I have is : who is taking the picture. If it's the person holding the bread, how the hell did s/he keep the camera so steady/ focussed etc?--Light current20:51, 16 September 2006 (UTC)Reply
Weird! Not the photo, but the response here. If you throw some bits of bread to gulls on the beach, a big flock gathers. Hold up bread, gull flys up to get it, snap picture. If it didn't turn out well, do it again and again until you run out of bread and/or fingers. The gulls aren't easily bored if there's food involved. I guess the equivalent for a city-dweller would be a pigeon or squirrel eating peanuts right at your feet, where you could reach out and touch it. --Wjbeaty06:06, 17 September 2006 (UTC)Reply
The gulls around here would never actually take food from a human's hand on the wing. They'll catch food in mid-air if you throw it to them and they'll come quite close if you place it on the ground but they are *very* careful never to enter our 'striking range'. When on the ground, they seem to calculate the distance that I'd be able to cover with a full length dive and stay just outside of that. Very wise birds - "beware the hand of man". The only one that comes closer is a gull that knows and trusts me... --Kurt Shaped Box06:39, 17 September 2006 (UTC)Reply
Photographing birds on the wing is very difficult, even at a distance. Imagine getting a good shot at a short distance like that. But photographing gulls like that under windy conditions (such as on a boat or a cliff) isn't too hard. They just hang in the air, inching closer to the person holding the bread.
Gulls are the masters of the updraft - it's like they're just floating there without any effort whatsoever. Forwards, backwards, sideways, they can just sort of 'slide' around in the air without flapping their wings at all (if you look closely, they do it with tiny flicks of the 'wrist'). On a hot summer's day, they love to ride the thermals and go so high as to be tiny dots in the sky. Then they glide slowly down. Thinking about it, in my garden, with nothing to catch a ride on, they'd have to swoop, dive and pull up at the last moment to take food from my hand - which is probably a pretty tricky manoeuvre for the sake of a piece of bread... --Kurt Shaped Box12:39, 17 September 2006 (UTC)Reply
Onions going green
Latest comment: 18 years ago5 comments3 people in discussion
There's a way to preserve onions that involves peeling the onions, and then leaving them in a jar filled with pure vinegar (normal vinegar, not white vinegar).
The vinegar soaks into the onions, and the onions are ready to eat after about a year. At the end, the onion pieces turn black (obviously due to the black color of the vinegar that gets soaked in.) After a few month, the onion pieces started turning black. However, i noticed many of them also turned green before going to black. Not like a dull green, but a bright and almost flourscent green. They'd stay green for a few weeks before starting to turn black also.
And before anyone tells me the onions have gone mouldy - i can assure you that's not the case. They're supposed to turn green. When preserving onions in vinegar, it's normal for them to start turning green.
I can't quite figure out why, no one really knows...and i'm having a bit of a hard time trying to get intelligent results by googling keywords like "green onions" Yaksha02:02, 16 September 2006 (UTC)Reply
Garlic I've pickled has gone blue. The main changes a chemist would expect would be due to the acid of the vinegar causing changes or maybe something to do with metal ions bonding / breaking free from / swapping with different metal ions on organic molecules. Have a look at pH, denatured, chelate, chlorophyll, and colour for some background reading. Rentwa07:21, 16 September 2006 (UTC)Reply
Yeah..i know it happens to garlic too. I've seen garlic turn green when preserved in vinegar too. I pretty much guessed it was due to the acid in the vinegar and all, i'm a chem student myself. I had hoped someone here would be able to give a precise answer about exactly what in the onion did what to produce what product that caused the green-ness. thanks anyway Yaksha12:05, 16 September 2006 (UTC)Reply
Latest comment: 18 years ago14 comments7 people in discussion
My sister needs to build a catapult for physics class. For her project, she needs to build a catapult that will be able to launch a tennis ball sufficently farther than the competition (her other classmates). Interestingly, grades will be determined by one's rank in distance compared to the competition. She needs to help with concepts and such, to keep this safe from that homework rule. :p
Here are the main points and rules:
Size restrictions: The maximum size of the base is 0.75 meters by 0.5 meters.
The maximum size of the movable rigid throwing arm cannot exceed .5m.
There must be a safety switch to ensure the mechanism can be fired from 2 meters away.
There are no weight restrictions. (This seems pretty important and useful.)
Any materials can be used.
Here are some questions:
What is a good place to start at when building the catapult?
What materials would be best for such a catapult? (springs, etc)
What are some sources (websites) that provide detailed instructions on creating a catapult that maximizes distance?
What are some general rules to follow?
And lastly, what are some good tips that can give the highest opportunity to have the best distance?
The key question that she wants to know is what is the best way to build a catapult that will allow her to win. :)
Please tell me if you have questions. Hopefully there are loopholes in the project that can be exploited. :P
I don't see a rule prohibiting tennis ball launchers, baseball launchers, nor any design like them. Also, backspin is a good thing. A friend built a fixed-arm catapult with approximately these dimensions that would through tetrahedral packs of four tennis balls ~300 meters (of course, the arm tended to bend slightly on these maxed-out throws). -- Fuzzyeric03:58, 16 September 2006 (UTC)Reply
I would use bungee cords for the energy source. You can buy them at many stores, typically in the hardware/automotive section. Use a peg to hold the throwing arm in place, then add the bungee cords one at a time (you will need to have eyelets on the throwing arm for the bungee cord hooks, and eyelets on the base for the other end of the bungee cords). Make sure the base is very heavy, so it won't tip over when you pull the lubricated peg out with a rope from several feet away. You should have a "stop" that assures the object is launched at a 45 degree angle for max distance, this will take some testing. StuRat06:10, 16 September 2006 (UTC)Reply
Here is a rough sketch:
+-+
|S| \
|T| \BUNGEE CORDS
|O| \
|P| \ BALL
+-+--ARM---+------+
+-+----------+
| HEAVY BASE |
+------------+
Keep in mind that the more bungee cords you add, the harder it will be to pull the throwing arm down to the ready-to-fire position. One thought is to buy a boat trailer winch (the manual hand-crank kind) at a hardware store, and use it for cocking the firing arm. I bought one a few years ago for a project, and it was pretty inexpensive. Speaking of cost, though, what's your sister's budget? I suspect that every other student in the class is also turning to the internet, and researching old Roman catapults and stuff, and will come up with the same basic design. Want something different, and more dangerous? Use the power of compressed air for firing the thing. A big accumulator (air tank), some large-diameter hoses and a poppet valve, and a big pancake cylinder will generate way more force than a few bungee cords. It'll also make an exciting, loud noise and scare the crap out of the competition. It may be beyond your sister's technical abilities though... is she handy with tools? Does she have a MIG welder or know someone who does? --192.168.1.1 8:33 16 September (PST)
My instructions are to attach one bungee cord at a time, while the throwing arm is already in the firing position. Thus, you can apply maybe a dozen bungee cords, each stretched to the maximum, for a great deal of total force. StuRat01:29, 18 September 2006 (UTC)Reply
OMGLOL MIG Welder!! THis girls probably in primary school!(and probably doesnt understand the meaning of the term welding) I think Stu's idea is probably the most practical for a young girl.--Light current16:49, 16 September 2006 (UTC)Reply
Well, she wants to win, doesn't she? :) I was going to ask what grade she was in, but forgot... I can see a high-school student maybe having access to one (a neighbor, a friend in shop class... ) A third-grader, though, probably not. Anyway, my competitive streak came out (and my innate tinkerer). Can I build this for her? We won't tell anyone! But if she wins, I get to share the prize. --192.168.1.1 11:03 16 September (PST)
She is a junior in high school (physics). I will tell her of these suggestions. I thank each one of you. Please feel free to add more comments and such. --Proficient19:15, 16 September 2006 (UTC)Reply
What scares me about this is that an unlimited amount of stored energy can be put into the device. With no material or weight limit, it could be powered by a piston driven by high pressure compressed air, with a pilot valve manually triggered which opens the large main air valve very quickly. A high voltage electrical circuit breaker in a substation uses such technology. Or it could be powered by a coil spring or by a torsion spring, also like used in substation circuit breakers and automatic throwover gear. Either the compressed air or the spring could have enough energy to lift a car off the ground, so the transfer of that energy to a tennis ball could result in perhaps lethal speed at launch, which would decay rapidly due to air resistance. One could build a catapult, the firing arm of which was capable of knocking off the head of anyone in its way if it fired inadvertently. If I wanted to win this contest at all costs and regardless of risks, I would get a spring such as is used on a car, and use a ratchet and windlass, or perhaps a car hydraulic jack, to cock it. Think a classic crossbow made into a catapult. If it came apart or fired prematurely, it could sever limbs. It would be apt to break and throw deadly parts in various directions to considerable distanced. The firing arm would be low mass to allow max acceleration, but strong enough to stand the acceleration and deceleration. A damping device would be needed to absorb the impact when the firing arm stops. The whole device would tend to jump in the air when fired, so I would design for low center of gravity with a massive baseplate. When the trigger released the firing arm, which would probably require a clever trigger mechanism to avoid binding, the firing arm would rotate from its rest position to, say, a 45 degree angle or something between 45 and 90, selected to achieve maximize range. It would stop by hitting the arresting device and the tennis ball would continue. The limiting launch velocity would be that which breaks the tennis ball or the mechanism. Design conservatively with a large safety margin. I would have written the rules to limit weight and materials to avoid the hazards inherent in this very open statement of rules. As always, these comments are purely theoretical: don't try this at home. Edison19:41, 16 September 2006 (UTC)Reply
You could also take some pointers from the recurve bow. That's basically the thing that made mongol bows so dangerous. Basically, if you just use one half of it you get a catapult, right? Btw, I once saw a video of atrebuchet flinging a car into the air. It landed tens of metres away. Pretty potent stuff! DirkvdM07:41, 17 September 2006 (UTC)Reply
Trebuchets don't scale linearly: throwing power increases somewhere between the square and the cube of size, so while a large trebuchet is more powerful than a large catapult, a small catapult is more powerful than a small trebuchet.
Back to the original competition: the rules limit the rigid part of the throwing arm to half a meter, but there's no mention on a limit on a sling. All medaeval throwing weapons had a sling on the end of the arm to increase range. Calibrating the release hook for the sling is something of an art, but if you get it right, you can easily double the range of your catapult. --Serie19:38, 19 September 2006 (UTC)Reply
Effects of using spent perlite as soil conditioner to improve yield of corn
Latest comment: 18 years ago2 comments2 people in discussion
one of the by products in the manufacture of carrageenan is perlite - predominantly Si02 used in the filtration process. do you have technical papers citing the benefits of usig perlite as soil conditioner to improve yeild of corn? we generate about 3-4 mt/day and it will also help transform the waste into agricultural purposes and help the local farmers.
Perlite is used to lighten (improve drainage, aeration etc) heavy soils. I'm sure it would help agriculturally, although I think most of the data available will be from horticultural sources, try searching for perlite as a compost additive / ingredient for more info. It may be contaminated (depending on the details of your process). If the contamination is with organic matter it may encourage excessive microbial growth, which may be harmful. Rentwa07:38, 16 September 2006 (UTC)Reply
Black Rain
Latest comment: 18 years ago5 comments5 people in discussion
The GE-600 series (a.k.a. "Honeywell 6000 series") and the PDP-10 were 36-bit computers. The Ge-600 also had 6- and 9-bit addressables (which can make the second definition of byte difficult to apply). The CDC 6000 series used 60-bit words. The IBM 7030 had variable length bytes (1-8 bits). During the relevant time period, bytes can in all kinds of sizes, leading to the use of the phrasing n-bit-byte ("8-bit-byte").
The Motorola 68000 was degenerate in that there was no address pin zero, so the minimal actually addressable was 16-bits although the pointers had 8-bit resolution. (Dereferencing an odd address threw an exception.)
See Category:Data unit. There are certainly quite a few computer architectures which use data sizes which are not a power of two bits, but 31-bit is the only one I'm aware of which isn't an even number.
The main reason why a 64-bit processor is "better" than a 32-bit one is that it can address (or "use") more memory. A 32-bit processor can only use 4 GB of memory unless certain work-arounds are used; a 64-bit one can use 4 billion times as much. For current personal computers, there isn't much demand for more than 4 GB, but for servers and some scientific applications, the extra memory is very useful.-gadfium05:20, 16 September 2006 (UTC)Reply
help me to know more about the colour of the urine
Latest comment: 18 years ago9 comments7 people in discussion
I want to know what are the unnormal clours of the human 's urine ? Can it be green? does it's colour depend on what has been drunk?
Yes, it can be green, and it does depend on what you eat and drink, but it's not as simple as always being the same color as what you eat or drink. It can also be clear if you drink a lot of water. Yellow, of course, is normal. Red or brown indicates blood in the urine, and merits a visit to the doctor (hopefully it's just a bladder injection and some antibiotics will fix you right up). StuRat06:40, 16 September 2006 (UTC)Reply
Normal urine is a pale yellow: that color is a result of the presence of urochrome. Dilute urine, caused by increased fluid intake, can be colorless; concentrated urine, caused by decreased fluid intake, can be dark yellow
There are two relatively common abnormal colors that correspond with physical disorders. Dark brown ("tea-colored" or "Coca-Cola") urine can indicate a problem metabolizing bile in the liver - if this is the case it can be accompanied by a yellowing of the skin and eyes (jaundice), and by pale feces. Red or pinkish urine can indicate the presence of blood in the urine, which can be the result of urological probem.
Also, a "cloudy" urine may indicate an infection.:There are less common abnormal colors as well. Some of them are related to foods, vitamins or medications such as beets, B vitamins, pyridium, or rifampin
Green urine is very unusual, but can result from artificial colors such as methylene blue, or pigments produced by certain microorganisms that cause urinary tract infections.
Obviously, if anyone has an abnormally colored urine that isn't linked to an obvious specific cause, they should talk to their doctor about it. - Nunh-huh06:43, 16 September 2006 (UTC)Reply
Porphyria (the madness of King George) can cause purple-pink urine, but most bizarely of all, the flourescent microbes found in seawater can give sea travellers glow-in-the-dark urine even if the sea water is thoroughly treated before drinking. smurrayinchester(User), (Talk)21:22, 16 September 2006 (UTC)Reply
Asparagus will often cause urine to be green colored. Check this link for all urine color changes, and also this page, which says that other foods, as well as some medicines, including Risanpin, an antibiotic, will cause urine to be green (or blue). BlankVerse05:18, 17 September 2006 (UTC)Reply
I recently saw a documentary on the possibility of missions to Mars and the preservation of water. Of course that meant distilling the urine for reuse. The leftover concentrated urine was gathered in a transparent (!) tank and looked very dark yellow of course, but with a definite reddish hue to it. Is that blood or what? DirkvdM07:53, 17 September 2006 (UTC)Reply
Latest comment: 18 years ago6 comments3 people in discussion
I added the following to Barnard's star yesterday: It has a "visual luminosity just 4/10000 of solar, corresponding to a bolometric or absolute luminosity of 3.46/1000." This is based on this and this paper within it. But I'm uncertain if I have this right, as it suggests the first figure is a relative value and the second absolute, while our page on solar luminosity mentions no distinction. Also don't no why there's an order of magnitude difference, though I think I'm reading it write. Marskell07:15, 16 September 2006 (UTC)Reply
So do I but its not always possible. Just edit in good faith OR put a question on the respective talk page pending your edit (or even afterward)--Light current14:31, 16 September 2006 (UTC)Reply
The visual luminosity is the total amount of visible light output from a star. The bolometric luminosity (which, I believe, is what astronomers usually talk about when discussing luminosity) is the total radiated energy output: visible light, ultraviolet, x-rays, infrared, radio, etc.
Barnard's star is smaller and cooler than the Sun, which means that its light output is redder than the Sun's and that it radiates less energy per unit of surface area. Also, a larger fraction of that output is down in the infrared, rather than visible light. So the total energy output of Barnard's star is about 0.346% that of the Sun. Because a larger portion of that output is in the infrared, Barnard's star's visual luminosity is even lower—0.04% that of the Sun. TenOfAllTrades(talk) 17:37, 16 September 2006 (UTC)Reply
OK, thanks. I assumed something like this, but it often doesn't seem to be made clear when detailing luminosity. When luminosity states "In astronomy, luminosity is the amount of energy a body radiates per unit time" it makes no mention of the distinction, which is fine I suppose, insofar as the generic term is taken for absolute output. But the characteristics in star tables on our pages use the other figure and say "luminosity", not "visual luminosity", which strikes me as an error. Marskell19:47, 17 September 2006 (UTC)Reply
Weird strings during nuclear explosions
Latest comment: 18 years ago9 comments7 people in discussion
Yeah, they are smoke trails from rockets that go off right before the blast. You can measure blast effects with them which would otherwise not appear on film in a quantitatively measureable fashion (like the shock wave and changes in air pressure). --Fastfission17:21, 16 September 2006 (UTC)Reply
If this is about the vertical striations each side of the cloud, I used to think this was an electrical discharge phenomenon due to the intense emp generated by the blast but looking at the photos linked to, it appears I was wrong.--Light current01:21, 17 September 2006 (UTC)Reply
You are all wrong, if you are talking about, as I suspect, pictures of early "ground burst" tests which sometimes show bright more less diagonal lines. In such pictures, you can sometimes see the vaporized remnants of cables which had been used to anchor the tower holding the bomb, or to anchor (un-manned!) blimps which held scientific instruments. This is discussed in Richard Rhodes, The Making of the Atomic Bomb.
It is true that some pictures also show electrical discharges related to atmospheric disturbances resulting from an nuclear explosion; these tend to look like lightning flashes, not straight line segments. ---CH22:36, 19 September 2006 (UTC)Reply
Sorry, just noticed that someone already linked to Rope trick effect. I think the mention of rockets is a third possible correct explanation. Looks like you would have to provide a link to a specific picture.---CH22:40, 19 September 2006 (UTC)Reply
name of species - or common name
Latest comment: 18 years ago3 comments3 people in discussion
resembles - to me at least - a snail, is very large - maybe 10" across, lives on land, only seen photo long ago, remember it being quite colorful
Sounds perhaps like one of the West Indian land snails famously studied by Stephen Jay Gould. Possibly either the genus Cerion or Poecilozonites. They don't have specific Wikipedia articles, but you can look at Bermuda Land Snail or try a Google search (e.g., cerion snail). --jjron16:35, 17 September 2006 (UTC)Reply
On Glass Cleaners, Ammonia.
Latest comment: 18 years ago6 comments4 people in discussion
So is ammonia used as a glass cleaner or not? If I just wanted to read a static answer in the article, I wouldn't be here on the ref desk. I'm looking for a more dynamic answer that doesn't just aimlessly redirect me to an article.--Russoc418:27, 16 September 2006 (UTC)Reply
Latest comment: 18 years ago1 comment1 person in discussion
Where would I find a list of top incidents of cancers (prostate and breast) per county in the U.S.?
By county, I'm not sure, but the American Cancer Society has a load of US cancer statistics by state at the very least. I have seen by-county maps out there before (they are sometimes quite remarkable) but I don't know offhand where they are. --Fastfission17:29, 16 September 2006 (UTC)Reply
Psychopathy prevalence
Latest comment: 18 years ago9 comments6 people in discussion
I am taking a criminology course in college and recently learned from the professor that statistics show psychopathy is more prevalent in the united states than in japan and other asian countries (controlled for population). I asked the professor why this was and the theory he came up with is that it could be genetically less prevalent in ethnic asians or that a more individualistic culture might be correlated with a higher incidence of psychopathy. Is there any statistical evidence for or against this theory (possibly the percentage of asian peoples diagnosed as psychopaths in the US)? Thank you very much for your time, any evidence would really liven up class discussions!
-Timothy
One potential confound to researching genetic differences among ethnic groups is that even in one country, different ethnic groups generally have cultural differences. Most clinical psychologists would point to a cultural explanation rather than a genetic one to explain differences among ethnic groups; this approach even has a name -- the sociocultural model. Also note it is simplistic to say that the U.S. has a higher prevalence of psychopathology; this may be true overall (I don't have it in front of me), but different disorders have different prevalences around the world. Schizophrenia has similar rates in all cultures. Also, there is a cultural component to the symptoms of some diseases -- for example, with major depression -- and some disorders are peculiar to certain cultures. --Ginkgo100talk · e@19:44, 16 September 2006 (UTC)Reply
Whoa, I just realized I mistook the work "psychopathy" for "psychopathology". Very different things! Psychopathy, of course, is aka antisocial personality disorder, one of many types of psychopathology (mental disorders). --Ginkgo100talk · e@00:41, 18 September 2006 (UTC)Reply
I suspect that the incidence of psychopathy is either overreported in the US (say by criminal lawyers hoping for leniency) or underreported in Japan (possibly due to the shame associated with such a diagnosis). StuRat23:44, 16 September 2006 (UTC)Reply
Two words: ascertainment bias. What an astonishing question. There are enormous cultural differences between the two societies. It is hard to think of a more culture-dependent imputed category than "psychopathology", which is originally a European concept wholeheartedly adopted and elaborated in North America. How could anyone imagine that the classification and ascertainment procedures would be the same in the two countries. Find another professor if he really believes that. alteripse00:11, 17 September 2006 (UTC)Reply
There is an essential difference between psychopathology – the study of various forms of mental illness – and psychopathy – a presumed personality disorder characterized by the inability to experience compassion or remorse. I doubt that the latter concept is originally European. --LambiamTalk20:00, 17 September 2006 (UTC)Reply
Thanks for pointing out that I wrote psychopathology when I meant psychopathy. The former is a very broad category roughly equivalent to "mental illness", while the concept of psychopathy (and the more common term psychopath) derives from European and American psychiatry. See Werlinder H (1978) Psychopathy: A History of the Concepts. Uppsala: Almqvist and Wiksell if you dont believe me. However, my answer does apply to psychopathy not psychopathology. alteripse02:36, 18 September 2006 (UTC)Reply
Thanks for the information guys. And no thanks for the completely unhelpful trolling alteripse.
-Timothy
Geez, Timothy. alteripse is the only self-identified medical professional who responded to your question, and s/he said exactly what I was going to say (but didn't because it'd already been said). Maybe some of it was strongly worded, but it wasn't trolling, IMO. No need to take offence for a WP editor casting aspersions on your prof. Anchoress17:39, 17 September 2006 (UTC)Reply
Project management
I would like to know of existing or recent case studies or experiences from community based projects in some Developing Nations with respect to methodologies in project management and evaluation. Preferably in the building/construction area.
Micro-climate in Nigerian houses
Latest comment: 18 years ago1 comment1 person in discussion
Please help me with information on housetypes of the pre-colonial Nigeria and how the various types of architecture of the three major geo-political zones (north, southeast and southwest)as well as the materials used helped in creating a tolerable micro-climate within the building.
There's no physical reason why you can't have ABS on a manual; most cars in the UK are manual and it's legally mandated that all new cars are fitted with ABS. I don't know why you can't get that combination from your dealer. --Yummifruitbat20:35, 16 September 2006 (UTC)Reply
To cut production costs, manufacturers like to limit the number of available combinations of options. For example, power windows and power locks almost always come together, even though there is no technical reason preventing one from being offered alone. StuRat23:31, 16 September 2006 (UTC)Reply
I have a 2000 Dodge Dakota pickup truck with manual transmission and 4-wheel ABS, so I know for a fact there is no incompatibility between a manual transmission and ABS. --Gerry Ashton03:59, 17 September 2006 (UTC)Reply
Toyota is playing games here, I have cars from 1992, 1997, and 2003, all have manual transmissions and ABS (none are Toyotas). And to Smack, what he meant by 'no stability control' was that no ABS system usually means the car has no way to meter the wheels for electronic traction control. To Ravedave, cars require a master cylinder for brakes whether there is ABS or not, the ABS mechanism is actually often far away from the pedal mechanism, so they would have to offer manual transmissions only on cars without brakes... hmmmm... --Jmeden200015:04, 18 September 2006 (UTC)Reply
histologia
Latest comment: 18 years ago4 comments4 people in discussion
CualSeptember 17September 17on las diferencias entre mastocitos y celulas cebadas?
You can ask a trick question in Spanish at the English science ref desk, mutilate it by replacing a letter with the date (twice) and still get an answer. Is that cool or what? DirkvdM08:36, 17 September 2006 (UTC)Reply
Most references give 0.9%-1.1% as the range of acceptability. The acidification of yogurt continues during storage, so I assume that commercial yogurt has around 0.9% lactic acid when it leaves the factory. This UCLA link has a table showing the postacidification of yogurt for different storage temperatures.---Sluzzelin02:27, 17 September 2006 (UTC)Reply
How does radar work?
Latest comment: 18 years ago7 comments4 people in discussion
Let's say we send some radar waves toward an object, like so:
If radar waves obey the law of reflection, how can the object be detected in the above situation? None of the radar beams are reflected back to their source.
Also, our article on radar says that the received power (that's reflected from the object) decreases with the fourth power of the distance. Why is this? I know that since the radar emitter sends out waves in all directions, the intensity of the waves decrease with the square of the distance. But since the target object reflects the waves directly back, and does not send it out in all directions like the emitter does, why does the intensity of the reflected beam decrease with the square of the object-receiver distance (instead of the emitter-object-receiver distance)? --Bowlhover05:01, 17 September 2006 (UTC)Reply
The diagram depicts "stealth technology" where an aircraft is covered with flat facets. As long as none of the flat mirrors face the emitter, and as long as none of the flat mirrors reflect each other (so they don't create "corner reflectors") ...then there will be very little reflected waves. And the 4th-power stuff only works if we model the distant target as a point-like reflector. Of course if the object is covered with curved metal surfaces, it will be a curved mirror, and will create virtual images which act as point-sources. --Wjbeaty05:55, 17 September 2006 (UTC)Reply
You unwittingly discovered one aspect of stealth it seems. :) Most surfaces will scatter the radio waves, so some of it will come back to the source. As for the fourth power, imagine looking at a light source through a cloud. The intensity will decrease with the distance, but also because of the scattering. I don't know why this would amount to the fourth power precisely (or is that an estimate for practical purposes perhaps?). Also, doesn't the intensity decrease with distance to the third power because the beam gets emited in three dimensions? DirkvdM08:49, 17 September 2006 (UTC)Reply
Suppose the target were a sphere, roughly the size of the wavelength of the RADAR wave. The intensity of the radiation incident on the sphere falls off like . That radiation is then reflected over just less than steradians (grazing waves are barely reflected). Thus, the reflected energy also falls off as . Since the round-trip energy is attenuated twice this way, the result is .
Now, why is this a reasonable model? Note that very few surfaces are optically reflective. Most surfaces have semi-transparent surfaces, so incident waves are incoherently scattered from several different depths in the material. This happens for RADAR waves and metals. The penetration depth is proportional to the wavelength, so a real surface looks like a bunch of randomized scatterers at variuos depths in the skin. Thus, the reflected radiation pattern is not purely specular but contains a large diffuse reflection component. This is captured at radar as , a coefficient indicating the tendency for the target to scatter incident radiation. Common radar wavelengths now are a few millimeters to a few centimeters, or equivalently gigahertz frequencies. So current radar will treat any rough features with these dimensions as a re-scatterer. So bolts, plate seams, and other similarly small features will act as scatterers (not reflectors). -- Fuzzyeric22:31, 17 September 2006 (UTC)Reply
Thanks to Fuzzyeric for explaining why power decreases with the fourth power. Also thanks to Dirk and Wjbeaty for telling me what's going on in my diagram. However, I have a question: in the example of the sphere, shouldn't radiation be reflected over just less than steradians (instead of ), because only half of the sphere is facing the radar emitter? --Bowlhover01:21, 18 September 2006 (UTC)Reply
Well, I hinted why this is the case ("grazing waves are barely reflected"), but ... Take a test ray and point it at the sphere. When the test ray passes through the center of the sphere, it will be retroreflected. We will measure displacements from this ray by measuring the angular displacement of the point of incidence at the center of the sphere. Move the ray slowly towards the edge of the sphere. When the displacement is less than 45-degress, the reflection is to the same side of the sphere as the incoming ray. When the displacement is 45-degrees, the reflection is at right angles to the incident ray. At larger displacements, the ray is "nudged" out of line, but ends up in on the other side of the sphere from the incoming ray. The only part of the forward scattering hemisphere that does not receive a reflected ray is the shadow of the sphere. (And, in Mie theory, even this isn't true due to diffraction around the edge of the sphere.) -- Fuzzyeric13:17, 18 September 2006 (UTC)Reply
Forgive my lack of knowledge, but I still don't quite understand. I'm pretty sure this is what you meant with the example of the sphere (am I correct?):
Latest comment: 18 years ago2 comments2 people in discussion
Are chemical computers and molecular computers the same thing? If not, then what's the difference between them? Are all molecular computers DNA computers? If not, then apart from DNA computers, what other types of molecular computers are there (or will there be)?
(I've read the articles on them but I still don't understand.)
Latest comment: 18 years ago5 comments5 people in discussion
My biochemistry is from a while ago. Am I correct in assuming 1 g carbohydrate = 4 kcal, 1 g protein = 4 kcal and 1 g fat = 9 kcal of energy when metabolized in humans. Anyone remember the value for glycogen? Thanks -- Samir धर्म08:18, 17 September 2006 (UTC)Reply
BINAS tells me that Cod liver oil is pure fat and 100 g metabolises to 3762 kJ. So that would be 37,62 kJ/g. I don't know what kind of calorie you're talking about (there's a small one and a large one - weird unit!), but assuming it's the large one, then it would be 37,62/4,185 = 8,989 kcal. Close enough. DirkvdM09:10, 17 September 2006 (UTC)Reply
My chemistry book confirms this: 1 gram of fat = 9.3 kcal (39 kJ), 1 gram of carbohydrate = 4.06 kcal (17 kJ). It doesn't give values for proteins, but I wouldn't be surpirsed if it was about the same as that of carbohydrate. It's only approximate though; it depends on the type of carb or fat (in this case glucose and glyceryl trioleate (olive oil) respectively). smurrayinchester(User), (Talk)14:49, 17 September 2006 (UTC)Reply
The problem with glycogen is that it is never eaten in a pure form, which would theoretically be about the same in terms of caloric value as starch. alteripse17:22, 17 September 2006 (UTC)Reply
Long ago, I memorized the values you gave (1g carb = 4 kcal, 1g protein = 4 kcal, 1 g fat = 9 kcal) from a nutrition book. So my memory at least matches yours. --Ginkgo100talk · e@00:38, 18 September 2006 (UTC)Reply
energy
Latest comment: 18 years ago3 comments3 people in discussion
i want to know about energy so that i can put it as the introductory part of my project -"conservation of energy"
Latest comment: 18 years ago4 comments4 people in discussion
I was attempting to explain the concept of Time to my son today. I went your search engine, typed in the word "Time" and was floored by what I read. You guys better take a real good look at what some individual(s) wrote about what time is. The reference to George Bush and Dick Chenny (while comical) do not belong in Wikipedia. Just thought I would send this msg. your way.
Latest comment: 18 years ago9 comments6 people in discussion
After reading about the twin paradox at http://en.wikipedia.org/wiki/Twin_paradox, I think I have a problem with the resolution. It says that the knoticable time delation of the moving object compared with the none moving one would distinguish which one it is that is moving only because of the acceleration of one twin in a switch in time frame.
What I don't understand is what if the space has a ring topology, then there would be no nessessary acceleration for the two objects to move in seperate directions, then to meet again and compare time. The topology of the universe seems not to be coverd in the artical.
Is it iMpossible for space to have a ring topology or is there a much simpler answer that I'm missing?
Thank you for your time in answering.
Colin
Curved space alone couldn't account for the time dilation without relativity, because the space would still need some kind of discontinuity in it for the dilation to occur. Rentwa17:43, 17 September 2006 (UTC)Reply
In flat, cyclic time (no accelerations, but if you go long enough in finite time you meet someone going the other way (which is a weaker requirement than "you get back to where you start")), if both participants accelerate with identical magnitudes but opposite directions then when they meet again, their clocks agree. However, in the twin paradox, only one twin experiences any acceleration at all (first to get up to speed, second to turn around, and third to stop) and the other experiences no acceleration at all. In the loop universe, the second twin accelerates to get up to speed and to stop, so we can still tell whose clock is slow. -- Fuzzyeric22:46, 17 September 2006 (UTC)Reply
I don't get what the paradox is in the "twin paradox". One ages more than the other, where's there a paradox in that ? If one could be frozen and thawed out later, the same thing would occur. Or, if one lives a rough life exposed to the elements they will also appear to age faster than one in a protected environment (although this is just the apparent age, not the true age). StuRat01:18, 18 September 2006 (UTC)Reply
It's called a paradox not because it's a logical error, but an apparent impossibility - "What? Two people born at the same time, in the same place, now have a thirty year age gap? That's impossible!" Confusing Manifestation01:35, 18 September 2006 (UTC)Reply
(Addendum) Oh, and then once you've had the concepts of special relativity explained to you, your next response is "ok, I'll accept that, but then if everything's relative to each other, how come if we look at it from the other twin's viewpoint we don't see the exact opposite happening?" - The answer to which is that the other twin has to accelerate and thus special relativity doesn't apply to him. Confusing Manifestation01:37, 18 September 2006 (UTC)Reply
THe conclusion from this is that altho velocities can be relative, accelerations are absolute in the universe. So you dont need to accelerate wrt anything-- you just accelerate! So in special relativity, I dont think an accelerating frame can be compared to a non accelerating one. Actually in the twins thing, its probably more to do with momentum.--Light current01:42, 18 September 2006 (UTC)Reply
I am distressed to see there is a lot of misinformation in the "answers" to several earlier questions involving relativistic physics, but since I am a latecomer, and tend to try to mention subtle points, perhaps there is no point in my trying to go into any detail.
Colin, your question involves taking a "discrete quotient" of Minkowski vacuum to "roll up" ("compactify" is the fancy term) one spatial dimension. "Twin paradox" thought experiments (of course, the "paradox" here is more apparent that real!) in such spacetimes have been considered by various authors. Try [24] and [25]. The correct short answer to your question is that global Poincaré group symmetry is broken by taking the quotient, while local Poincaré group symmetry is preserved. The local versus global distinction is fundamental in the theory of smooth manifolds.---CH03:27, 18 September 2006 (UTC)Reply
Do animals prefer raw or cooked food, and can evolution cope with cooking?
Latest comment: 18 years ago15 comments9 people in discussion
A comment above about feeding sausages to gulls made me wonder what animals prefer. Has anyone any practical experience of gulls, dogs, cats, birds and so on prefering one or the other?
And since cooking is a very recent invention in evolutionary time, would anyone else agree or disagree with my hunch that since apes, mammals, and all predecessors back to single cells have not evolved to dealing with cooked foods, then we humans may not be able to totally cope with the carcinogens and acrylamide that is in food, not just burnt or browned food? 81.104.12.5216:05, 17 September 2006 (UTC)Reply
I think your postulate reflects a naive and overly simplistic understanding of evolution, cooking, and the differences between people and animals. Sorry. alteripse17:19, 17 September 2006 (UTC)Reply
Hey there! If you're gonna pick on the guy's theory, at least offer a reason why you find it so "naive and overly simplistic"! Seems like an interesting thought to me! In fact, the only "simplistic" notion expressed here is that there is some fundamental, physiological difference between people and animals. Of course, neurologically we may be vastly superiour to our closest cousins, but physiologically ... human beings are basically nothing more than another species of animal, and a rather weak, fragile species at that. In fact, (with the exception of our manual dexterity), we're actually physiologically inferiour to many animals in practical every sense. Loomis18:01, 17 September 2006 (UTC)Reply
How do you know? They may go home and have a really bad stomach ache after eating those manky sausages. I believe it may be called ' **** stomach' 8-)--Light current20:59, 17 September 2006 (UTC)Reply
I should have just passed on answering it, but you are right, if I criticize it I should at least explain. The simplistic notions that seemed embedded in the question were the following:
1 Animals cannot eat cooked foods. What's simplistic? Of course they can eat it; they just can't build the fire to cook it.
Huh? I cannot see why I am supposed to believe that animals cannot eat cooked food: I've just asked if they prefer it, for goodness sake.
2 Animals would not prefer cooked food. What's simplistic? It's an untested hypothesis and I have a hunch that carnivores would prefer heated meat if given a choice. Someone somewhere has probably done the research and I will gladly admit I am mistaken if it showed otherwise.
Huh? again. I've just asked if they do prefer it or not. ?????
3 Evolution has selected us to be able to deal with carcinogens from cooking better than animals. What's simplistic? Evolution selects reproductive fitness and most effectively selects out traits likely to interfere with reproduction. With some exceptions, cancer (especially carcinogen-linked cancers) are diseases of the post-reproductive years and the assumption that evolution had made us less vulnerable to old-age cancers is pretty questionable. Secondly there is no evidence that we are less susceptible to cancer produced by cooking carcinogens than animals-- zero evidence.
Huh? yet again. I'm concerned that humans havnt had time to evolve to fully cope with cooking. I am aware that evolution is less forceful post-reproduction. Also my hunch is that human are still susceptable to cooking carcinogens. Why do you believe I believe things I dont believe? This is very bizarre.
4 Ability to deal with carcinogens is the largest survival effect of cooking. What's simplistic? The major advantages of cooking are enhancing flavor, killing parasites, denaturing bioactive proteins, retarding spoilage, and reducing the energy required for chewing and digestion. I suspect those advantages outweigh carcinogen risks as pro-survival factors by orders of magnitude. Armchair speculation about evolution requires thinking through all the likely effects at different stages in the life history.
No I don't. You've confabulated the assumptions out of nowhere. Surely you can't be a know it all.
OK, if you don't see the points it actually confirms my first suspicion when I didnt list the reasons, but you asked. Others can judge whether they find them convincing. At least I hope you dont mind that I reformatted slightly since you interpolated in my message and it messed up the numbering and flow. alteripse01:59, 18 September 2006 (UTC)Reply
You've invented out of thin air "the simplistic notions that seemed embedded in the question" which are pure baloney and which I don't in fact believe, and then you've used them to condem me. This does not make any sense at all. It is analogous to hearing someone remark for example they would like to go on holiday in Germany, inferring with your superior intellect that this must be because they are a covert-nazi and anti-jewish, and then condemning them on this basis. What utter nonsense.
Alteripse said what I was going to say. :( Oh well, I second everything he said. Doesn't it seem blatantly obvious to everybody?? That was actually pretty confusing. I was going to say all those things that had numbers. — [Mac Davis](talk) (New!SUPERDESK|Help me improve)23:23, 17 September 2006 (UTC)Reply
There is certainly a raw food diet/movement which believes humans are better off eating raw foods. I think most raw fooders are vegetarian, but there is mention of raw meat on the page. Cooked food certainly does contain carcinogens, and the benefits listed for cooking are mostly irrelevant for fruit and vegetables. —Pengotalk · contribs02:33, 18 September 2006 (UTC)Reply
Ah-ha! It has just occurred to me that the bizzarre remarks above may be due to one or two people who have quite wrongly and incorrectly decided that I am suggesting that people should eat only raw food. This is not the case - I eat plenty of cooked food myself. I'm going to eat some now.
I'm not sure why, Alterprise, but you seem to have COMPLETELY misread the questioner's question. You make four points. The first two are based on a complete misreading of his/her question. S/he never said anything about animals prefering raw food over cooked food. Quite the contrary. The first paragraph of the question bears repeating here: A comment above about feeding sausages to gulls made me wonder what animals prefer. Has anyone any practical experience of gulls, dogs, cats, birds and so on prefering one or the other?. You then proceed with a brief summary of what you got out of the questioner's question in your first two points: "1 Animals cannot eat cooked foods." Huh? S/he just ASKED that question! "Do they prefer one or the other?" How can the question "do they prefer one or the other?" be transformed into the simplistic assumption that they do prefer one over the other? I'm afraid you've misread the question.
Same goes for the second point. "2 Animals would not prefer cooked food." Again: A comment above about feeding sausages to gulls made me wonder what animals prefer. Has anyone any practical experience of gulls, dogs, cats, birds and so on prefering one or the other? What the...? I'm afraid that once again you've misread the question. Again, I can't imagine why. It's written in such a simple, commonsense manner.
3 Evolution has selected us to be able to deal with carcinogens from cooking better than animals. No! That's the exact OPPOSITE of the point the questioner was making! "[W]e humans may not be able to totally cope with the carcinogens..." (emphasis added). Did you miss the "not" part?
4 Ability to deal with carcinogens is the largest survival effect of cooking. Once again, in the questioner's words: "have not evolved" (emphasis added). "Not evolved!" Again, the complete opposite of what the questioner is asking.
I'm really at a loss as to how such a relatively easy to understand question could be so badly and completely misread.
So let me (with the permission of the questioner) rephrase his/her question in even simpler terms: "Is it not a reasonable hypothesis, that the particular vulnerability to cancer in humans (as against other animals), can be attributed to the fact that we learned to cook our food, (and learned to prefer it that way,) much faster than evolution has allowed our bodies to physiologically adapt and defend against those particular cancer causing agents that naturally occur due to the "cooking" process?" Seems like a reasonable hypothesis to me. Of course it could be completely false, that's why it's simply a hypothesis. But I definitely don't see how the hypothesis "reflects a naive and overly simplistic understanding of evolution, cooking, and the differences between people and animals." Loomis00:00, 20 September 2006 (UTC)Reply
Speed of Radio
Latest comment: 18 years ago17 comments8 people in discussion
The speed of light is clocked at just under 300k metres per second. Yet when scientists speak of sending and receiving radio signals from spacecraft or perhaps even from places further distant, it always seems as if they're using the speed of light as a measurement of the speed at which radio signals travel. I'm no scientist, and I'm not quite sure exactly how radio signals travel, and what their relationship is to the speed of light. I've always been told that the "speed of light" is the maximum speed that anything can travel. If anything, I would only imagine that radio signals, would, at most, travel at speeds slightly less than the speed of light. Is this true? If so, how fast do radio signals travel? If they travel at the speed of light, how is it that they match this speed? Thanks. Loomis16:28, 17 September 2006 (UTC)Reply
Radio energy, like light, is carried by photons, and they always travel at the speed of light. Now the speed of light in a vacuum is the highest speed, but the speed of light in other media is a bit lower. For spacecraft in stellar space the two speeds are, essentially, the same. -- Finlay McWalter | Talk16:32, 17 September 2006 (UTC)Reply
Those photons tend to travel at the speed of light because THEY ARE light. Finlay says the speed of light in different media varies. Pretty much the denser an object is, the longer it takes light to get through it, if at all. The photons kind of go in one atom, and come out the other side to continue on its way. The more atoms, the longer it takes. — [Mac Davis](talk) (New!SUPERDESK|Help me improve)16:42, 17 September 2006 (UTC)Reply
Visible light is one part of the Electromagnetic spectrum, radio waves are part of the same spectrum (with lower frequency and longer wavelength). Everything in the electromagnetic spectrum travels at 'the speed of light'. Don't confuse the term 'radio signals' with the sound you hear from your radio - in simple terms, the signal is carried to your radio at the speed of light, but the sound you hear travels very much slower, at the Speed of sound, which is about 340m/s in air. --jjron16:56, 17 September 2006 (UTC)Reply
Ok, I may be no scientist, but I do know the difference between the speed of light and the speed of sound! No worries though, you couldn't have known that, so thanks anyway, you're help is much appreciated! Loomis17:10, 17 September 2006 (UTC)Reply
It doesn't. But if you are here to learn (what else?) then isn't it nice if people point out to you you made a mistake and that the way you phrased the question doesn't make sense? Well, in scientific lingo, anyway. Using 'k' for 'thousand in other combinations has become colloquially accepted and actually does make some sense. DirkvdM18:24, 18 September 2006 (UTC)Reply
My mistake was akin to a typo. I saw nine digits, but mistakenly wrote a "k" for "thousand" rather than just writing "million". Also, as I said, I'm no scientist, and so "scientific lingo" is somewhat of a foreign language to me, albeit one that I'm reasonably familiar with. Take yourself, (please! Apologies to Henny Youngman!:-). Your mother tongue is Dutch, but at the same time you have an excellent command of the English language. I only wish I had as much fluency in my second language (French) as you seem to have in English. Yet occasionally, you do make the odd linguistic error, the type that only a non-native English speaker would make. Of course I understand what you're saying completely, so I'd consider it rather rude to correct your English, and I'd feel like quite the ass for doing so, so I just leave it alone. True "learning" is one thing. Pointing out other people's typos and the most minor of linguistic errors is quite another. Loomis23:06, 19 September 2006 (UTC)Reply
I would consider a correction of my English by a native speaker a great help. It's a courtesy, not at all rude (depending on how it is brought, of course) and I wish more people would do it. Especially if I make the same mistake more than once. Eg, StuRat recently pointed out to me that 'instead' is one word, not two ('in stead'), as it is written in most languages. I had always written it that way as I consequently noticed. I was thankful for the help. DirkvdM07:39, 20 September 2006 (UTC)Reply
Loomis, I wasn't typo-flaming you, and I'd appreciate it if you'd AGF a little bit, instead of being so sensitive. I truly didn't know whether or not the way you wrote it was correct, and just not familiar to me, OK? That's why I commented. Because I am here to learn. Just like everyone else here.Anchoress07:51, 20 September 2006 (UTC)Reply
Anchoress, even if I was being overly sensitive, my reaction wasn't directed at you at all. Only to those who assumed I didn't know the difference between a thousand and a million. Loomis09:41, 20 September 2006 (UTC)Reply
Huh? You said in the post just above (addressed to Dirk) that you considered it rude to point out people's typos. Since I was the one who pointed out the typo, who else could it have been referring to but me? Anchoress18:34, 20 September 2006 (UTC)Reply
Look. An order of magnitude out isnt bad for a non scientist. Even scientists are out by more than that some times. I dont know why you are arguing about it, but I do know its taking up a lot of space in the wrong place! 8-(--Light current18:45, 20 September 2006 (UTC)Reply
Faster than light???
Latest comment: 18 years ago12 comments7 people in discussion
Hi
I am reading a book on the creation of the Universe. According to Inflationary Theory, at a certain point in time, there was an "explosion" that created an expanding Universe. What i dont understand is that within a fraction of a second after this "explosion", it seems that the Universe has expanded to a size larger than can be explained/allowed by the speed of light (because nothing can travel faster than it).
What i mean to say is...the universe seems to have expanded faster than the speed of light and thus something must travel faster than light?
Hope someone can help me out
Cheers
Gregory J Davies
17/09/06
It is accepted that during the inflationary epoch the universe expanded faster than the speed of light. The short answer for why this doesn't violate relativity is that no information or 'actual stuff' moved faster than light. You may also be interested in entanglement
Moving the speed of light practically breaks the universe, I cant see how it is possible.... but if it was 0 at one point, through e=mc² you would get infinte mass from any energy, which could explain the big bang and stuff I guess. PhilcTECI20:32, 17 September 2006 (UTC)Reply
Erm... You'd get zero rest mass contribution to energy, but the inertial terms would still appear, so you'd have the rest of the Taylor series expansion at Relativistic mass#kinetic energy, most of which would diverge, suggesting the need to renormalize.
The fine structure constant is a constant that is one of the more famous candidates for non-constancy. This is still controversial and the best data so far is consistent with no change. However, there should be new data late this year that should finally be fine enough :-) to resolve the issue. -- Fuzzyeric23:06, 17 September 2006 (UTC)Reply
Inflationary epoch address this in its first titled section ("Explanation"). The observation is that space expanding is not the same thing as something (even light or information) moving and so the speed of light is not a limit to the effect. -- Fuzzyeric22:53, 17 September 2006 (UTC)Reply
Doesn't the speed of light depend on the medium in which it is traveling? For instance, light travels faster in a vacuum than it does in, say, water... correct? - R_Lee_E (talk, contribs) 01:41, 18 September 2006 (UTC)Reply
Yes it does, but I dont think thats relevant to this argument. THe speed of light depends upon the medium constants mu_nought and epsilon_nought. These may have had different values at the beginning.--Light current01:51, 18 September 2006 (UTC)Reply
Variable speed of light theories? No, no, no. You should all read this excellent popular book:
Weinberg, Steven (1977). The First Three Minutes. Basic Books. ISBN 0-465-02435-1.
A picture is worth a thousand words, so look for the figure illustrating "light cones in the large" in an expanding FRW dust model. The same point is made with more mathematics in books such as
d'Inverno, Ray (1992). Introducing Einstein's Relativity. Oxford: Oxford University Press. ISBN 0-19-859686-3.{{cite book}}: CS1 maint: publisher ___location (link)
Hawking, Stephen; and Ellis, G. F. R. (1973). The Large Scale Structure of Space-Time. Cambridge: Cambridge University Press. ISBN 0-521-09906-4.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: publisher ___location (link)
Latest comment: 18 years ago4 comments3 people in discussion
I recently went backpacking in the Sierra Nevada (US), in the John Muir Wilderness. We spent three nights in two places at about 10,000 feet, near the treeline. There was a sparse forest there, consisting mostly of one particular species of tree. I believed it to be some kind of fir, but after perusing our various articles on firs, I found that I was mistaken. The best picture that I have is this rather blurry one. Does anyone know what kind of tree this is? --Smack (talk) 17:33, 17 September 2006 (UTC)Reply
Your link doesn't work, maybe you could upload your picture to Fileanchor? It is free and easy to use. Wikipedia also has an article on the Biology of the Sierra Nevada, with pictures, maybe one of the pictures will be your plant and you will be able to identify it from that. Gary18:20, 17 September 2006 (UTC)Reply
Burmese python is not specific on the matter, but it does say "As Burmese Pythons are opportunistic feeders, they will typically eat almost any time food is offered, and often act hungry even when they have recently eaten. This often leads to overfeeding, and obesity related problems are common in captive Burmese Pythons", which seems to suggest that they are not picky. ColinFine18:11, 17 September 2006 (UTC)Reply
With snakes, this often depends on what the animal is accustomed to. A python raised in captivity on dead prey may not even know how to kill live prey, and may be injured by it. Other animals may refuse anything not alive. --Ginkgo100talk · e@00:13, 18 September 2006 (UTC)Reply
Fact check me?
Latest comment: 18 years ago4 comments3 people in discussion
Latest comment: 18 years ago3 comments2 people in discussion
Hi there.
I'd like to find out what the normal broadcast range is for DAB radio, as I'm considering purchasing a unit. I live in Ireland (east coast), but I'd like to pick up UK stations too. I can't pick these up on FM, so would I be able to receive them on DAB?
Yes, I always use internet radio, but it's a bit of a pain having to listen off the web the whole time; it's not much good for the kitchen! Thanks for the help NaLaochra00:22, 18 September 2006 (UTC)Reply
September 18
Future of plant genetic engineering
Latest comment: 18 years ago16 comments6 people in discussion
What do you think is the future of plant genetic engineering? I've read things about the dangers of GM crops, such as golden rice that has become prevalent in china, and a type of corn made by a company called epicyte that can be used as a contraceptive. What are some active GM plants out there, and does anyone know any GM horror stories (or potential GM horror stories?) Thanks! Dave 130.207.180.2700:28, 18 September 2006 (UTC)Reply
You seem to be looking for horror stories and totally look over the tearing greatness that genetic engineering has brought us. Aside from the fact that the "unscientific" genetic engineering that brought us apples, and oranges, pumpkins, and cabbage, detoxified almonds (they used to have a compound that when digested produced 10x the lethal dose of cyanide for an adult), genetic engineering is possibly the greatest technology that has ever evolved from the human race. Read a bit on Norman Borlaug, easily one of the greatest people who ever lived, credited with saving billions of lives through genetic engineering. It is easy to complain and talk about the bad things, when you know you have at least one meal per day, and are not among the 25,000 to die of starvation everyday. Also, what is wrong with the golden rice, that is to help with the problem of VAD? — [Mac Davis](talk) (New!SUPERDESK|Help me improve)02:43, 18 September 2006 (UTC)Reply
Mac Davis, genetic engineering has a specific meaning. Please do not confuse it with plant breeding or artificial selection — which are NOT genetic engineering by any stretch of the imagination. Norman Borlaug, although a proponant of GMO, worked largely on HYVhybrid varieties without the use of genetic engineering techniques. The other benefits you talk of are not from genetic engineering but from ordinary plant breeding. To say we should turn a blind eye to the problems of genetic engineering because of the benefits is plain stupidity. —Pengotalk · contribs03:00, 18 September 2006 (UTC)Reply
One "horror story" is that of the weed Lactuca serriola, which gained herbicide resistance from being contaminated by GMO lettuce. It's not that much of a horror story really. Another is of some GMO corn produced in the US (See Bt_corn#The_StarLink_corn_controversy). There are probably not many real horror stories relating directly to GMOs. The key issues, in my mind, is that of the patenting of life (biopiracy); the loss of genetic diversity (countered partially by seed banks and seed exchange groups and networks); and the placing of a large amount of trust in seed corporations, which farmers have become reliant on as they cannot replant their own seed. These issues are the same for hybrid varieties as much as they are for GMO, and are not safety issues as much as they are food security issues. —Pengotalk · contribs03:14, 18 September 2006 (UTC)Reply
The potential of any GM plant spreading worldwide without any ability to stop it is indeed frightening. Even if grown in a greenhouse, preventing workers from taking out pollen on their bodies or clothes or carrying a seed in the tread of their shoes is nearly impossible. Such crops would need to be given the highest levels of biocontainment treatment, similar to how anthrax and bubonic plague are treated in research labs, to prevent dispersal. Such treatment would make GM foods completely impractical. StuRat06:42, 18 September 2006 (UTC)Reply
The potential could be good or bad. If it were doing more harm than good (who could be the judge of that?), than that would be "bad." But if it was a vitimin-rich protein-packed, high calorie crop, that didn't kill off too many species (who could be the judge of that?), than that would be "good." — [Mac Davis](talk) (New!SUPERDESK|Help me improve)15:22, 18 September 2006 (UTC)Reply
I agree that most GM modifications are beneficial, but the potential for such GM plants to spread uncontrollably is still troubling. This can lead to wiping out non-GM varieties, thus forcing people to consume the GM variety, against their will. If some negative side effect is later found in the GM variety, it may be difficult to get the original variety back. Perhaps an "assassin virus" would then need to be programmed to go after the GM variety to wipe it out in the wild. StuRat16:45, 18 September 2006 (UTC)Reply
I have a cure for this problem, from the movie Jurassic Park. In that movie, the "lysine contingency" refers to the fact that the cloned dinosaurs were genetically engineered to lack the normal ability to synthesize lysine, a critical amino acid. While captive, these animals would be provided with lysine in their diets. If they escaped, however, they would die in short order from a lysine deficiency. Similarly, some defect (perhaps multiple defects) should be programmed into the GM plants, so that escaped varieties would die naturally. Legislation should be passed making such protections mandatory, preferably at the worldwide level. StuRat16:59, 18 September 2006 (UTC)Reply
Most GM plants are prisoners of their poor design. Built to resist one and only one species of insect or fungus, they are more able to get attacked by another pest, or by any mutation of the original ones : what do you think happened before in South America : people bought GM seeds, their plants were soon attacked and the people are poorer. Now when you buy stocks of GM engineering companies, you get rich. Right ? See also [27] -- DLL .. T18:28, 18 September 2006 (UTC)Reply
The problem is we know so little of what we're doing in that field that we don't even know what the horror stories might be. If you do something bad you can usually rectify it with equal effort. But some things propagate themselves in a feedback loop. And life is the greatest expert at feedback. Once something starts it can be unstoppable, spreading exponentially. That's why we still haven't managed to exterminate loads of diseases - miss one bacterium and in a few years it will be all over the place again. And if we inadvertently create some disease (or something that creates a disease or gives it a breeding ground to evolve or something I can't think of (!)) then that can be as hard to stop as malaria. Of course I'm talking about plant diseases here. And if farmers the world over would switch to certain plants because they give a much bigger yield then that will reduce biodiversity, nature's best counterforce against the spread of diseases, because some varieties might not be affected and thus take the place of the ones that died - the same mechanism that diseases use to become resistant to antibiotics. Life is a constant battle between species and the ones with the greatest biodiversity stand the best chances of survival.
As an illustration think of what has happened with the introduction of species to new environments (rabbits in Australia, that sort of thing). Most will not survive in the wild, but the ones that do won't have any natural enemies and will spread like wildfire. And with gm we may create species that don't even come close to what life on Earth has seen so far. Maybe not yet, but if we continue we'll get there for sure. DirkvdM18:57, 18 September 2006 (UTC)Reply
I think there may be a misinterpretation here about GM plants. They aren't completely new plants engineered from scratch, but more typically very close to an existing plant, with perhaps one gene added to provide disease resistance, produce a valued nutrient, etc. Therefore, they retain all other characteristics of the original plant, such as resistance to all the same diseases as the original. However, if the new, more disease resistant plant becomes widespread, this will put pressure on the disease causing organisms to evolve a counterattack. The original plants will be particularly susceptible to these new "super bugs". StuRat19:11, 18 September 2006 (UTC)Reply
Yeah, I know, I was just taking it a little further. GM is sort of evolution on steroids. So if it becomes popular, a new species may be created in a much shorter time. And if that is taken further still, we might create something that would normally never have evolved (on Earth), something that not only has no natural enemies in one spot, but anywhere on Earth, so we couldn't even introduce one. Of course we could fabricate one, and that will lead to a 'natural' selection of who is the cleverest GM engineer. Of course this could also be used for warfare, so we had better start with it real quick before 'the enemy' beats us to it (who is it this time? Oh yeah, terrorists). DirkvdM06:27, 19 September 2006 (UTC)Reply
Turpentine
Latest comment: 18 years ago4 comments3 people in discussion
I went to the article on turpentine looking for some sort of confirmation of the story that the stuff can enter through your skin and stays in your blood (or collects in your ankles) and never leaves your body.
A. Is this true? Or where does this idea originate?
However, looking at the article, I discovered that Wood turpentine and Mineral turpentine are different things, and looking at the shelf of my local hardware store, I notice that there is also Mineral turpentine substitute which is different again from mineral turps. (The article seems to confuse the two — which is partially my fault).
B. What's the difference between these substances?
C. And does anyone feel like sorting out the articles to reflect these differences?
I looked around and didn't find this particular myth, but if it exists, it probably comes from painters and their practice of mixing turpentine with all sorts of nasties, such as lead. --Zeizmic12:08, 18 September 2006 (UTC)Reply
Mineral turpentine substitute just sounds to me like a sloppy way of saying "mineral turpentine (substitute for wood turpentine)". I can't think of many instances in life where I've needed a substitute for a substitute. Well there was this one time in grade 5... freshofftheufoΓΛĿЌ 14:27, 18 September 2006 (UTC)Reply
The labels of the two seemed to have different ingredients, but i only glanced. There's also "low odor turpentine" which may or may not be the same as any of the above. —Pengotalk · contribs09:04, 19 September 2006 (UTC)Reply
Metals, non-metals, and semi-metals
Latest comment: 18 years ago2 comments2 people in discussion
Looking at the Periodic table, it's pretty clear which elements are considered metals, non-metals, and transition metals. After all, there's a big old streak running from Boron to Polonium. What I'm not entirely clear on is why, that is, why those guys on the top like covalent bonds and the guys on the bottom like metalic bonds. At first I thought that it could be electronegativity -- maybe the higher electronegativities would favor covalent bonds because in covalent bonds, the electrons are more localized -- but a quick look down one of the columns refutes this.
My next thought was that as you go down a column, the atom gets larger and larger and has more and more complex valence shells -- maybe the fact that the shells are held further away from the nucleus allows the electrons to be shared more easily amongst all the nuclei (leading to a metalic bond), and maybe as these shells get more full, this has less of an effect (an attenmpt to explain why lead is metalic while polonium is not). This explanation seemed plausible, but not great.
Any ideas?
for a start...i think Polonium is sort of metallic, or at least metalloid. I don't think it's a non-metal.
But Polonium would be less metallic than lead. this is because lead is physically smaller than Polonium. Polonium has two more protons than lead, and two more electrons. The two extra protons make the nucleus stronger. However, the two extra electrons go into the same shell...meaning Polonium has the same number of shells as lead.
This means in Polonium, there is a stronger nucleus holding on to the same number of shells of electrons. This means the outer shell of Polonium is held more tightly than the other shell of lead...hence Polonium would be less inclined than lead to shed off its valence shell electrons (which is what metallic bonding involves.)
Classification as metal/semiconductor/insulator is based on band gap and valence band. The effect is primarily one of delocalized bonds and their energy spectra. The physics of electronic band structure is not simple. In metals, the conduction band has no gap separating it from the valence band, so electrons may be promoted from a localized orbital (essentially attached to a single nucleus) to a delocalized orbital (essentially smeared out over a large volume). In semiconductors, valence electrons may be promoted to the conduction band by providing a small energy, for instance thermal energy at room temperature. Insulators have such a large bandgap that essentially no electrons are in the conduction band at room temperature. -- Fuzzyeric14:06, 18 September 2006 (UTC)Reply
Latest comment: 18 years ago4 comments4 people in discussion
I was diagnosed with an allergy to penicillin (and another drug, sulfa) at a young age. My father recently suggested that the diagnosis might have been wrong, and that I should get tested again, because penicillin is such a useful drug and so on. Is it likely that it could have been misdiagnosed? (He claims that the doctor seemed rushed and "unprofessional".) Alternatively, is it possible to "grow out" of such an allergy? Would re-testing be worthwhile?
Second, my boyfriend is allergic to most seafood (with exceptions for some processed fish, like canned tuna) and some nuts (allergic to almonds, brazil nuts, and walnuts, but not pistachios, peanuts, macadamia nuts or cashews). Do you see any connection between these allergies? Fish and nuts are said to have high levels of omega-3 fatty acids. Is it possible that that's the allergen? If so, is he in danger of not getting enough omega-3? What sort of factors would cause him to be allergic to some nuts, and some fish, but not others?
I agree that you should be retested, as allergies do change with age, and the doctor might have misinterpreted the results originally. StuRat10:06, 18 September 2006 (UTC)Reply
Reactions to substances vary and not all are "allergic". Reactions which indicate an allergy with a high degree of certainty include hives and swelling of mouth or throat, especially with a change of voice or narrowing of the larynx. The likelihood of a similar or worse reaction upon next exposure is fairly high. At the opposite end of the spectrum in terms of risk is a vague red rash which is a common part of many viral infections and which is sometimes amplified by concurrent use of ampicillin. The problem with labelling someone penicillin-allergic is that the penalties for being wrong in either direction are so asymmetric. If someone is erroneously told she is allergic to penicillin, there is rarely any penalty for avoiding it and lots of people react positively to their "specialness". If someone is erroneously told she is not allergic to penicillin and is prescribed it in the future she could develop a worse reaction with throat swelling and very rapid death. This severe reaction is called anaphylaxis and doctors consider contributing to someone's avoidable death a Bad Thing. So this enormous asymmetry of consequences leads to many people being labeled penicillin allergic erroneously. This is well-recognized by doctors and there are published guidelines for deciding how likely it is that a person is really allergic based on the nature of the original reaction (not based on the parent's estimate of the "professionalness" of the doctor). The major disadvantage of being erroneously labeled penicillin-allergic is that you get prescribed more expensive antibiotics which migh incur other risks. There are ways to test for penicillin exposure with small risk if someone needs treatment and no alternative antibiotic seems appropriate. Why not have this conversation with your doctor?
As for your second question, allergies seem to be formed primarily against specific proteins in foods rather than against omega-3-fatty acids, so your boyfriend has many other possible sources of the fatty acids. We have no idea why people become allergic to certain food proteins and not others-- be glad it is limited. Best wishes. alteripse10:33, 18 September 2006 (UTC)Reply
Your boyfriend is allergic to some of the most common food allergens. Besides tree nuts, fish, and shellfish, the other most common food allergens are peanuts, soy, milk, eggs, and wheat. I sympathize, having certain shellfish allergies myself. One of the hardest things about it is explaining it to restaurant staff. You would think they would hear it all the time, but they are frequently rather stupid about it, either not understanding the concept of a food allergy or acting "put out" that you ask for special non-deadly food. --Ginkgo100talk · e@04:34, 19 September 2006 (UTC)Reply
Fishy coincidence
Latest comment: 18 years ago13 comments10 people in discussion
Take two rivers not too far away from each other, say you consider the Po and the Rhône River, which both give water to the Mediterranean Sea. You have a look at what fishes live in these two rivers, and say you discover that the carp lives in both rivers. Question: how is this possible? With the exception of salmons, no fish can live both in fresh water and in the sea (I am not sure if NO fish can, but of course SOME fish cannot). So how is it that two rivers which are not connected by some fresh water channel contain the same species of fish? Of course this does not depend on Man. I have asked a biologist friend, but her answer does not really satisfy me, so I am posting it here. And I will tell you what her answer was, but I would like to see some other opinion first. Cthulhu.mythos08:55, 18 September 2006 (UTC)Reply
Well for the example you give, the Alps are only ~15 million years old, so the freshwater fish could have been part of a connected watershed earlier than that. Though I haven't checked on carp in particular, most fish families are far older (100s of millions of years), so it wouldn't be surprising to find carp on both sides. After ~15 million years though, you'd expect to see a variety of descendant species unique to each side as well as a few ancestral species that survived in both places. Dragons flight09:22, 18 September 2006 (UTC)Reply
I agree. The two rivers may have had a confluence at some point in the past, such that one was a tributary of the other. I suppose that, if it can be established that the same species existed in both rivers prior to development of boats by people, this would even constitute evidence that the two bodies of water were, indeed, once connected. StuRat10:02, 18 September 2006 (UTC)Reply
Mmmmh. I see. Now I will tell my friend's answer. She said: well, once upon a time during Pangea, or anyway durind a time when the two rivers were somehow connected, there was the carp's great-great-great-granmother, which was not yet a carp. Then continents drifted and blah blah and the two rivers became separated. So we have two ancient rivers with the same archeofish. As the two rivers wetre once connected, they cannot be too much far away, hence the climate must have been about the same in the two rivers, hence the two archeocarps will undergo the same evolutionary processes, as they live in very similar environments. What you get is the same carp in the two rivers.
Now what does not satisfy me is that I do not believe that the same evolutionary processes must happen, of course the two great-great-great-granchildren will be similar species, but I see no reason for them to be the very same species (interfecundity, in perticular). Then what she replied was: they will just like two different races of carp, not really the same carp but very very similar, like "Caucasian" and "Asian" for Man. Cthulhu.mythos10:24, 18 September 2006 (UTC)Reply
Agree, especially if you're talking about a length of time like that since Pangaea. In cases like this there are often more simple explanations that are easily overlooked, e.g., major and rare floods allowing the rivers to be temporarily connected, rising and falling sea levels, coming and going of ice ages, etc. Whether these can necessarily explain this specific example I don't know, but they do explain a lot of similar cases. While these things may be rare or a long time ago on our time scale, in geological and evolutionary terms they are not - a once-in-a-thousand-years flood is actually pretty common, and the last ice age at about 10,000 years ago was a mere eye-blink ago. --jjron13:46, 18 September 2006 (UTC)Reply
Why does evolution or connection have to be involved? What about the possibility of a visitor from Po to the Rhone becoming interested in the carp, and then bringing a few back with him to place in the Po? Man could have easily accomplished this thousands of years ago. - Rainwarrior15:54, 18 September 2006 (UTC)Reply
I believe the original question was asking for reasons that didn't involve human interference. Of course human involvement is a possibility in a case like this, but if there was evidence that the fish were in both rivers prior to human occupation of the region then there would have to be a natural cause. --jjron16:19, 18 September 2006 (UTC)Reply
Freshwater systems used to be a huge source of diversity, and endemism was common within them. However, man has basically destroyed the fresh water systems of the world, and most are overrun by introduced species which outcompete native species. Naturally, crossing to different river systems occurs through large flooding (which can occur to a huge scale, but is rare), and previously connected rivers. Remember that rivers are constantly changing, and can split apart, merge, or whatever. They are rapidly changing, much faster than continental change. --liquidGhoul16:30, 18 September 2006 (UTC)Reply
It is still possible to see man as the origin of a plain identity of carps in both rivers. They belonged to the same empire during centuries, and you may carry freshwater fish a long time in a bucket. I'm thinking of a Roman war veteran who was allowed some part of Provence and wanted to fish his old Po carps to have his foreign wife accomodate them in the Po valley fashion. -- DLL .. T18:38, 18 September 2006 (UTC)Reply
Arowanas are obligatory freshwater fish; they cannot tolerate sea water, yet they are found on different islands and continents around the world. They evolved long ago, when the landmasses were connected, and were carried along when the continents and islands broke apart.[28]Cutthroat trout, an American species, diverged into numerous subspecies, each peculiar to a separate river basin, more recently. During the Ice Age, their ancestor was able to travel "over the mountains" into different rivers.[29] By the way, many other fish, such as the barramundi perch, can tolerate both fresh and salt water. See fish migration. Of course, the carp themselves could be introduced species, not natives. --Ginkgo100talk · e@20:09, 18 September 2006 (UTC)Reply
Flies
Latest comment: 18 years ago7 comments6 people in discussion
I read the article on here about flies. I was wondering if anywhere in the article does it say if they go to the bathroom at all? I'm just curious about this.
Latest comment: 18 years ago6 comments2 people in discussion
Hello everyone,
does anybody knows the thermal conductivity of indium (III) oxide around room temperature ? I already searched in a few scientific databases and handbooks without results... Thank you ! David Berardan11:56, 18 September 2006 (UTC)Reply
I imagine I will have too ^^. I am just a bit impatient, cause my thermal conductivity measurement device is currently broken down ! When I can measure it I will complete the article (but In2O3 being very hard to densify, it probably won't be a very precise value). David Berardan19:49, 19 September 2006 (UTC)Reply
Are you talking about squeezing a pimple ? I understand how they would be filled with puss, as this is left over from your skin fighting the small bacterial infection which caused the pimple. I'm not sure why their would be air inside a pimple, as seems to be described, as well. StuRat16:32, 18 September 2006 (UTC)Reply
I can't believe I've put any thought into this at all, but I'd guess that there are two factors coming into play here: one would be the size of the pimple (or specifically the amount of pus that is trapped) and the second would be the hardness of the plug that has formed at the surface. If the material blocking the pore has hardened significantly, it will not be easily dislodged. Exerting additional pressure when squeezning the pimple might cause it to pop, with the result that the additional pressure also causes the pus to shoot out with more velocity. --LarryMac19:18, 18 September 2006 (UTC)Reply
ISO/IEC 7810:2003 specifies:
* four different sizes of identification cards with a nominal
thickness of 0,76 mm and dimensions of:
o ID-000 25 mm x 15 mm,
o ID-1 85,60 mm x 53,98 mm,
o ID-2 105 mm x 74 mm,
o ID-3 125 mm x 88 mm;
* the conditions for conformance;
* the dimensions and tolerances of the identification cards;
* the construction and materials of the identification cards; and
* the physical characteristics of the cards such as bending stiffness,
flammability, toxicity, resistance to chemicals, dimensional stability,
adhesion or blocking, warpage, resistance to heat, surface distortions,
and contamination.
ISO/IEC 7810:2003, together with a standard for test methods, provides
for interchange between various types of identification card
processing devices and systems.
I'm sure that the logic behind those numbers is "that's the size almost all ID cards were when they officially wrote up the standard". Credit cards and ID cards and whatnot have been essentially standardized for decades, and everything from wallets to card readers to the little static-proof ATM card sleeves all assumed the sizes would stay that size. This is kind of a cop-out answer, but it would take a lot of research to figure out who used that size first and how it became a widespread standard. I wouldn't be too surprised if it was the first social security cards or some such. -- Plutortalkcontribs13:54, 19 September 2006 (UTC)Reply
Especially the senseless precision – 53,98 mm instead of 54 mm, a difference of 20 µm and less than 0.04% – is curious. Assuming a modest variation in the measured heights of existing ID cards, on the order of 1 mm, would require averaging over several thousands of measurements before the estimated average gets a precision anywhere near that. While very close to 2⅛ inch (= 53,975 mm), the width 85,60 mm is clearly less than 3⅜ inch (= 85,725 mm). If we stick to powers of two for the denominators, it could be 3451/1024 inch in mm, rounded to two decimals, but no lesser power will do. --LambiamTalk20:50, 19 September 2006 (UTC)Reply
Hot and Cold as Sensations...
Latest comment: 18 years ago8 comments5 people in discussion
Has there been any research done as to how exactly the sensations of hot and cold manifest themselves? Clearly, with sufficient exposure, either can be quite painful. Yet the sensations are vastly different. Something that is hot is, well, a burning sensation. And something that is overly cold is a kind of biting sensation. Why is this? There must be some explanation on both a cellular and neurological level. After searching for a bit, I still wasn't able to find the answers I was looking for. Maybe you guys can help. Thanks. - R_Lee_E (talk, contribs) 16:36, 18 September 2006 (UTC)Reply
The archive doesn't answer why we perceive the feeling of hot and cold as we do (i.e. burning vs biting). That is an interesting question and more to do with interpretation of the signal in the brain, rather than nociception at the periphery. Interestingly, though, when human skin is exposed to extreme noxious cold (like, of example, dry ice or liquid nitrogen), the resulting pain is often descibed as a "burn" and, i can confirm, the immediate acute pain is "burn like". Thus, my hypothesis is that the human thermosensory system is more "tuned" to warn us of hot temperatures, since we are more likely to be exposed to noxious heat in a natural environment, than noxious cold. Consequently "hot" is more immediately painful than "cold", within the ranges we are normally exposed too. Its only when you get to extremely cold temperatures, that the cold interpretation becomes as acute as the hot response. Why then, as Seejyb reports, we have "about 30 "coldness" nerves for every "warmth" nerve", is a puzzle, however. But this expanded "thermo-space" for cold detection, could provide a mechanism through which a more moderate cold respose is mediated. Rockpocket04:43, 19 September 2006 (UTC)Reply
Thanks for the response(s). Makes alot of sense. Though, I suppose all of existence must be regarded as an "interpretation of (a) signal in the brain." Much respect to the Man, Descartes. - R_Lee_E (talk, contribs) 01:46, 20 September 2006 (UTC)Reply
When you're talking about "burning" and "biting", you're not just talking about heat and cold perception. A stimulus that is sufficiently severe to be perceived this way is also provoking a pain response, which is conveyed by means of sensory neurons that are morphologically different from heat and cold afferent neurons, to different centers in the brain. In other words, extreme heat and cold evoke more than one type of sensation at once. Interestingly, temperature and pain perception follow the same neural pathway from the peripheral nervous system to the diencephalon-- the spinothalamic tract.--Mark Bornfeld DDS17:39, 19 September 2006 (UTC)Reply
Yes, that is a very good point. I was oversimplifying. Clearly there is cross-talk between the thermosensation and pain sensation signaling. Rockpocket07:35, 20 September 2006 (UTC)Reply
Solvents
Latest comment: 18 years ago1 comment1 person in discussion
It is not 'safe' but I would call it a 'rule of thumb'. There are some organic compounds which will not dissolve in any of those.
watts into kwh
Latest comment: 18 years ago4 comments3 people in discussion
My alarm clock runs at 5 watts, or 5 joules per second. Would this mean that it consumes 1/200 kwh?— Preceding unsigned comment added by ChowderInopa (talk • contribs)
Usually people count kWh when they receive their monthly electric bill, so kWh/month may be a more useful unit. Your clock uses .005 kWh/hour * 24 hour/day * 30 day/month, or 3.6 kWh/month. If electricity costs you $0.10/kWh, that's a whole $0.36 you spend every month keeping your clock going. Foobaz·o<02:13, 19 September 2006 (UTC)Reply
First you divide the Joule by seconds. Then you multiply that by hours. And then you divide by months again. Or days. Or years. This is almost as bad as the imperial units system. Just stick to one unit for time, the SI unit 'second'. Then you'll only have joules and watts and it's clear what you are talking about (energy and power). DirkvdM06:35, 19 September 2006 (UTC)Reply
Unfortunately, no electric company actually bills in Joules, which is the real measurement. If I have the math correct, 1 kwh = 3600 seconds × 1000 joules/second = 3,600,000 Joules. Kind of a difficult conversion factor in calculating your bill. Fan-196714:10, 19 September 2006 (UTC)Reply
butterflies
Latest comment: 18 years ago5 comments5 people in discussion
Ok, since the reference desk has wandered into chaos, and primally contains sarcastic and rude remarks for plain and simple questions (this question/answer-thread isn't that bad...Just look at the above entries) - I will try to answer your question. At least the easy answer: Both male and female nipples develops at a stage in the pregnancy when the babys gender is still undetermined. The genitals develop later. --Petteroes11:57, 19 September 2006 (UTC)Reply
Freudian slips are very telling. "Primally" is spot on when it comes to nipples. My contribution, fwiw, was not meant flippantly, which is why I said "seriously". Whenever this question comes up, I remind folks of the sexual function of men's nipples. I know, I know, there's a difference between the biological purpose behind how they developed, and what they're good for now that we've got them. I'm more interested in the latter question. JackofOz13:15, 19 September 2006 (UTC)Reply
Stephen Jay Gould discussed this in an essay entitled Male Nipples and Clitoral Ripples in which he basically explains that the fetus has to have the roots of both genders' characteristics, so men have nipples because women have breasts, and women have clitorises because men have penises. Fan-196714:15, 19 September 2006 (UTC)Reply
Info on an american polar-expedition...
Hope you guys could help me out here. A long time ago I read an article in a science magazine about an american expedition with an exceptionally big tank, an armoured wagon that weighted too much for the enviroment it was going to explore, and eventually got itself stuck in the snow. I reckon it was during the early stages of The Cold War - around 1946 - 1956. I think the target for the expedition was to reach the central parts of Greenland, or the North Pole. The expedition was widely concidered a failure.
Does anyone know the name of the expedition?
fluid behind our cats ears
Latest comment: 18 years ago7 comments3 people in discussion
moved from Wikipedia talk:Questions
We have a four year old golden calico male.Our cat goldie keeps building up pockets of fluid behind his ears.He has had three hematobin operatoins.He also has asthma.He has been on full time antibiotics and prednisone.I hear that they are a very rare species because of their genetics.Can you please help us solve this problem.We love this cat very dearly and hate to lose him.We have heard rumors that golden calico males usually only live up to five years old.Please help SINCERELY JIM KERR. —The preceding unsigned comment was added by 24.105.219.35 (talk • contribs) .
First, let me clarify that a Golden Calico is a breed, not a species. Second, this "fluid behind the ears" doesn't sound like a life threatening issue from your description. Can you describe the quantity ? I would think the treatment would be to lance the skin and allow the fluid pockets to drain. StuRat23:55, 18 September 2006 (UTC)Reply
Calico is not a breed, it is a description of a coat pattern, and it only occurs in females. You see, the colors are on the X chromosome, and the calico patchiness comes from the alternating patches of x-chromosome silencing (i.e. barr bodies) in the young embryo. Thus Goldie could only be a "he" if he has klinefelter's syndrome, and Golden Calico can not be a breed unless this particular breed is parthenogenic...Tuckerekcut01:36, 19 September 2006 (UTC)Reply
Now that I have read your question more closely (sorry Jim), I have decided that your cat probably is a klinefelter male, which would corroborate your details. You can read about klinefelter's syndrome here on wikipedia, perhaps a description of the human phenotype will help you better understand the prognosis of your cat, there is also some info at Tortoiseshell cat. It may very well be that the problems you mentioned regularly go along with being XXY and a cat. I will also add that your cat's condition would probably be better described as a genetic disease than as a "rare species" or otherwise.Tuckerekcut01:46, 19 September 2006 (UTC)Reply
There's more than one way to have a male tortoiseshell (see Laura Gould's Cats Are Not Peas for the story of George, a rare fertile male calico who turned out to be an XXY/XY mosaic). On the more serious question, it sounds like the cat in question needs a vet more than Wikipedian's opinions. (By "hemotobin" do you mean "hematoma"? Your vet should be able to tell you why this is recurring), - Nunh-huh06:49, 19 September 2006 (UTC)Reply
I suppose thare are many possibilities, but straight klinefelter's is the most likely, at about 1/1000 live births. (How much more likely? I don't know how many chromosomes a cat has, but the likelyhood of being mosaic for two karyotypes like this is about 100 times the number of chromosomes in a typical cell, if this cat were a human, that would be about a 1 in 4600 chance, giving a total chance of having an mosaic x nondisjunction in a male of about 1 in 4.6x10^6.) If this cat were a human, I would recommend having him karyotyped, but that is not particularly cheap. As Nunh-huh said, a vetrinarian is your best bet, she will know if these symptoms are normal for your cat's disease.Tuckerekcut11:57, 19 September 2006 (UTC)Reply
38 chromosomes for cats. I can't see much benefit in karyotyping, other than assuaging an intellectual curiousity. Better to spend the bucks getting veterinary care.- Nunh-huh16:49, 19 September 2006 (UTC)Reply
About the same benefits as with a Down's patient. With a full karyotype you know exactly what's going on (i.e XXY vs X/XY mosaic in the cat, as with 47 X(x/y) +21 or 46 X(x/y) der(N;21) or some mosaic with one of those in the Down's patient). Sometimes it helps the family to get a solid, definite cause. But sometimes even that results in little benefit.Tuckerekcut02:40, 20 September 2006 (UTC)Reply
September 19
Work, lifting vs walking - 7th Grade Physics
Latest comment: 18 years ago14 comments8 people in discussion
Yes, this is a homework problem for the kiddo; however, I am not understanding the concept trying to be taught here, so thought I'd see if someone can lead me in the right direction (38 Yr old CompSci Major slinks off to the corner and cries....) The problem is this - A woman lifts her 100-netwon child up 1 meter and carries her a distance of 50 meters to the crib. How much work does the woman do?
Because of Work = Force x Distance, I can see that the woman lifting her child exerts 100 joules by lifting the child 1 meter. How do we account for the 50 meters that she walks? Surely she is doing some work? But would the work exerted simply be 100 newtons times the 50 meter walk? 100100100:56, 19 September 2006 (UTC)Reply
While the horizontal movement requires energy, it is not work in the physics sense, except for the acceleration and deceleration of the combined mass of woman and child, which are probably only over short distances. If there are no figures for the mass of the woman, or the accelerations, (and it 7th grade) it's probably meant to be assumed negligible. (Probably bonus points for identifying the assumption.) Peter Grey01:56, 19 September 2006 (UTC)Reply
Peter, I basically agree with you, but I would say that most of the work she does is due to microscopic accelerations and frictions in her muscle cells, and that this does count as physics work (in real life, not for the kid's class). I would also argue that the work she does carrying the child probably far outweighs the work she does lifting the child. Almost certainly, though, the teacher wants the student to pretend no work is being done in the carrying. (Not that going for the extra credit isn't a good idea.) --Allen02:25, 19 September 2006 (UTC)Reply
I pretty sure that the question is asking how much work is being done only against gravity, and only whatever affects the baby - which I personally think should be stated very clearly in the question. Of course, some energy is expended in the part of the force that's counteracting friction in the vertical and horizontal directions, as well as all those biological processes mentioned before, plus the work necessary to lift the weight of her arms and etc. This was one of the toughest things for me to understand myself in middle school, because you have to understand that all of that "off-to-the-side" work is being ignored. All that they care about is the work against gravity. As another example, holding a pen up needs impulse and energy is being used in your hands/arms to create the impulse, but none of that energy is actually going into the pen (neither potential nor kinetic), so it doesn't count as work. Also note that heat transfer is being ignored too (though it'll eventually start playing a role in a future course, once you get into heat engines and gas laws and such). —AySz88\^-^04:25, 19 September 2006 (UTC)Reply
Well put, AySz88. In my opinion, trying to teach kids, without explanation, that they're not doing any work as they carry things around, even though they intuitively know they are, is an unhelpful oversimplification. Light current, that's why I don't think it really is TMI. It's just enough "I" that kids can understand what the lesson is driving at without being sidetracked by apparent absurdities that aren't really there. --Allen04:51, 19 September 2006 (UTC)Reply
Just wanted to add my thanks to this - I really didn't understand what the question was going for, but it makes sense now. I think that I can even explain it to the kiddo now. (and they say raising kids doesn't generate work, HA!) 100100105:08, 19 September 2006 (UTC)Reply
Isn't this a nice (and educative) example of how physics is a model of reality and not reality itself? An much used modelling 'error' is to assume no friction. Let's say the baby is lifted onto a table on wheels. Assume no friction in those wheels. It takes energy to get the table going, but stopping it 'releases' that energy again. In a modelled world, that is. I'm no physicist, so I'm not sure if that example was a good one, but the first sentence touches on the core of the problem, right? DirkvdM07:08, 19 September 2006 (UTC)Reply
Hmmm, one thing still bugs me about my example. If there were any energy lost by friction, that would go into heat, but what about the 'releasing' of energy by stopping. Where does that 'come from'? I assume this depends on which system you look at and whether it is open (to what?) or not, but I can't wrap my head around it. (Suppose my head isn't big enough. :) ) DirkvdM07:12, 19 September 2006 (UTC)Reply
THe energy of motion is of course 1/2 mv^2 and when you stop the trolley the energy goes into stretching your arms or dragging you across the floor creating heat by friction. And no, I woulddnt agrre with your last statement. 8-)--Light current07:41, 19 September 2006 (UTC)Reply
Yeah, I understand that. That's the reality bit. But I meant that in the model, if you pick up the baby and then put it back down, you end up with the old situation. But if you move the table and stop it, something has changed, namely the ___location of the table. Also, you excert energy twice. Maybe I should be thinking about energy as a vector. The model sort of assumes that the energy is 'won back' because it worked in opposing directions. (And in reality that would (to some extent) be possible if you slowed down with a dynamo.) So the two situations are 'energetically equal' (or how should I put that), despite the fact that a change has occured. This makes me think of something different, which I will ask a separate question about below (space travel). DirkvdM08:45, 19 September 2006 (UTC)Reply
You should certainly not think of energy as a vector. If you're thinking that energy has a direction, you're probably thinking about momentum instead (which does). If I may quote myself here, I discussed some of the physiological aspects of this situation about two months ago. In this case, the important thing to say is that the woman does so much work on the child. She may do plenty more work on her own tissues, the floor, the air, etc., but that's not the (implied) question. --Tardis16:41, 19 September 2006 (UTC)Reply
Tylenol Overdose
Latest comment: 18 years ago8 comments5 people in discussion
A health question:
I was recently told that taking more than the extra dose as said on the bottle of tylenol is a serious health risk; I have been feeling bad lately so I have been taking 4 Tylenol extra strength 500 mg tablets twice daily, double the twice daily two tablet dose...is this a health hazard? Thanks! ChowderInopa03:03, 19 September 2006 (UTC)Reply
Yes, taking more than the recommended dose is a health hazard, so is not going to the doctor when 1g of acetominophen/day is not enough to alleviate your pain. You should schedule a visit with a physician. In case you are curious, acetominiphen overdose has a slow onset and can lead to a very slow, very painful, very irreversible failure of the liver.Tuckerekcut01:26, 19 September 2006 (UTC)Reply
Thanks, this is only for today though...As in, for months I have not had any medicine, now when im feeling sick I took double starting this morning, then a friend said that was crazy and I should throw it up...but then i responded that it was just 8 pills in one day. All I am asking is, a one or two time double dosage during one day isnt a serious problem is it? By the way I am a 200 pound male, so the effects should be dampened. I mean it sounds like you are saying continual abuse hurts the liver, which i of course agree with, but just doing so today isnt horrible correct? This is not merely a context specific question, I am curious for general double doses with any medicine. Thanks! ChowderInopa03:03, 19 September 2006 (UTC)Reply
In your case, I would not recommend taking a double dose again, in some people without other obvious pathologies, taking the dose that you took even one time could cause clinically relevent, albeit minor and ephemeral, symptoms, especially if compounded by alcohol (be it in your beer or your cough syrup). The general case is even more fuzzy. For instance lithium can cause severe life threatening complications in certain circumstances if a patient takes a double dose. Other medicines have an even smaller theraputic ratio, (adriamycin/doxyrubicin comes to mind, but these things are not likely to be self-administered). In general, monoamine oxidase inhibitors and drugs for bipolar disease have some of the narrowest theraputic ratios, I believe. This information is all trivial, though. If you feel that you have a medical problem, see a doctor. She will be in a much better position to tell you what is healthy for you specifically. Also, please sign your edits with four tildes in the future. Tuckerekcut02:12, 19 September 2006 (UTC)Reply
No, I feel great and feel no problems whatsoever, I was just curious to make sure I hadnt done something completely stupid, like knock myself into a coma. How many would that generally take? 10 pills? 20? In the movies you always see a bottle full, but that seems to be way too much compared to what you are saying could hurt me... ChowderInopa03:03, 19 September 2006 (UTC)Reply
I have heard of people dying from as little as 8, which is only double what you're taking. You're at a much higher risk of harming yourself if you are in a weakened state (i.e. if you are sick) because your body is weak and may react strongly to the drugs that you (over) induce. Tylenol are generally pretty safe, which is why they're so easy to put on the market, but there is a reason that the warnings are there in the first place so there's no reason to deliberately put yourself in danger. I'm the kind of person that refuses to take any medicine, especially pain killers, unless it is really needed to help increase the speed of recovery. I can handle a little bit of pain and discomfort, and when it get's bad enough that I can't, I know that it's time to get some kind of treatment. freshofftheufoΓΛĿЌ 03:27, 19 September 2006 (UTC)Reply
I don't know if you've actually received a medical opinion or not yet. In Australia, acetaminophen is known as paracetamol, and the typical healthy adult dose is 1 or 2 500mg tablets 4 times daily, with a maximum dose of 8 tablet (or 4g) daily. If you have other health problems the safe dose for you may be less than this. Read the packet instructions on your tylenol. It will probably say something like this. If you exceed the dose, it means at least 2 things: 1.) it is not treating the illness you are using it for; and 2.) you risk toxicity, including irreversible liver damage. Either way - the most sensible course of action is to see your doctor. Best wishes, Mattopaedia04:10, 19 September 2006 (UTC)Reply
Latest comment: 18 years ago3 comments3 people in discussion
Is the image in our MPTP article correct? If not, what needs to be done to fix it? On the talk page, a visitor has called the image's accuracy into question, but no one watching the article is qualified enough to fix a chemistry diagram. Thanks for any help you can give! Foobaz·o<02:00, 19 September 2006 (UTC)Reply
Latest comment: 18 years ago8 comments7 people in discussion
Would a warm or cold blooded animal (assuming that they are the same size, like a large toad and a rat) freeze first?--Peta04:32, 19 September 2006 (UTC)Reply
I figure the toad would freeze first, because it isn't producing as much heat of its own, and is probably starting from a lower temperature to begin with. But it might not freeze to death first, because some toads have weird abilities to live through freezings. --Allen04:58, 19 September 2006 (UTC)Reply
It depends, in part, whether the Ectotherm/poikilotherm was warmer or colder than the homeotherm at the time of the competition. The terms warm- or cold-blooded refer to the mechanism of thermoregulation, not the actual temperature of the organism itself. (that said, its likely the toad would freeze first, unless it was particularly toasty to begin with). Rockpocket05:06, 19 September 2006 (UTC)Reply
As Allen said, there are some cold blooded animals which can freeze, and still live (I know of snakes and frogs). So the question as to which would die first, it is dependent upon the species. It would be interesting (though horrible and cruel) to see which would die first between the Wood Frog and the Arctic Fox. --liquidGhoul05:47, 19 September 2006 (UTC)Reply
Warm blooded animals have a constant temperature. Cold blooded ones don't. So the toad's temperature seems to be one piece of information that's missing. But even if they started off at the same temperature the rat would use its metabolism to keep it warm, so the toad would freeze faster. All this assuming were talking about live animals here and I don't know how much heat a toad can store. It would have to be one hot toad to compensate for the rat's metabolism. That said, I wonder what happens to coldblooded animals under freezing conditions. Do they all manage to survive freezing? Or do they dig themselves in at a warmer spot or something? DirkvdM07:24, 19 September 2006 (UTC)Reply
I can't speak for all, but it is certainly true for frogs. During winter, the tree frogs in my area will bury themselves under leaf litter, compost to keep warm. A lot of the ground dwelling frogs bury themselves underground, and some can just take it (Common Eastern Froglet seems to be able to live in absolutely freezing conditions). Mind you, this isn't Canada, the coldest it gets is -7 celcius. --liquidGhoul08:47, 19 September 2006 (UTC)Reply
Some cold blooded animals use antifreeze to keep from freezing, some find warm spots to survive, others die, but leave eggs that can survive freezing temps. However, the evidence that warm-blooded animals can handle cold better is in the relative scarcity of cold blooded animals in arctic environments. The problem with cold-blooded animals is that, while they may survive freezing temps, they can't do anything at those temps, like eat, breed, migrate, etc., which is a problem in places where temps are almost always below freezing. StuRat12:38, 19 September 2006 (UTC)Reply
Space travel
Latest comment: 18 years ago16 comments9 people in discussion
In the 'walk, lifiting vs walking' questions a few posts back it is claimed that it requires no more energy to move a baby than the energy needed to pick it up. In reality energy is expended because of friction. But take space travel, where the friction is negligible. Would it be possible to make a spacecraft that consumes no energy because it can regain the stopping energy when it reaches its destination? Of course, energy has to be put into the sytem for the first acceleration, but if the spacecraft shuttles back and forth it can use it's stopping energy to start again in the opposite direction and thus consume no more energy than for the first flight. This sounds wrong, but I can't find the flaw. DirkvdM08:54, 19 September 2006 (UTC)Reply
Is it possible? No. Hmm… *thinks again* Well, yes, actually. If the spacecraft could use its kinetic energy to "charge its batteries", or something, when it slows down at the destination, it could use that energy for going back. This is what electric automobiles usually do when you brake – instead of using the brakes, they start to charge the batteries with the movement of the wheels (which also slows the vehicle down). —Bromskloss10:19, 19 September 2006 (UTC)Reply
No, it's not possible, for two main reasons: The first is theoretical, no energy conversion is 100% efficient (second law of thermodynamics). Your theoretical spaceship would have to perform several energy conversions to 're-use' its deceleration energy, so something will always be lost in the process. The second is practical - I know of no technology which allows you to 'recover' some of the energy used for deceleration in space. Remember that, in space, there is no difference between decelerating and accelerating, both use energy. You need a certain amount of energy to accelerate to your 'cruise speed', and the same amount again to decelerate. And even if you did come up with a technology which would allow you to 'recover' some of your energy (perhaps some kind of drag against the magnetic field of a star which would induce a current in a wire?), the second law will still get you in the end.
Also, to be pedantic, there is some (very very small) amount of friction in space. Space contains particles, and these hitting your ship will slow you down. However, there are very few particles in interstellar space (tens of atoms per cubic meter, if I remember the figures correctly off the top of my head), so the friction they exert is nearly negligible. — QuantumEleven11:40, 19 September 2006 (UTC)Reply
Oh, come on. Of course the energy conversion isn't perfect, we all know that. I don't think the questioner was thinking of actually go out and build the spaceship! As for deceleration is acceleration, that is very true, but this time we might have a planet to crash into – freeing a lot of energy. You might wan't to "crash" smoothly, of course, but if done well (again, perfect conversion) you would still get the same energy. —Bromskloss12:49, 19 September 2006 (UTC)Reply
Yes, but that's exactly the problem - crashing on a planet will stop you, obviously, but I know of no way how this energy can be 'recovered', it's wasted as heat and terrain deformation. The energy is there, but it's not in a useable form (unless you want to use the heat of re-entry to boil water to turn it to steam to turn a turbine to produce electricity... but then you have to carry all this extra equipment around, so your ship is heavier, which needs a bigger heatshield... you can see where this is going, it's just not practical). — QuantumEleven15:09, 19 September 2006 (UTC)Reply
OK, you're clearly on a more practical level in this discussion than I am. Boiling water with the heat would have been perfectly satisfying for me. One could also imagine landing on a very high (many kilometers) platform that is not firm (as to avoid a crash), but gives way with only a little resisting force and takes care of the energy the spacecraft gives to it by pushing it down. —Bromskloss21:32, 19 September 2006 (UTC)Reply
This reminds me of a quite funny thought experiment: suppose you were to bore a tunnel straight through the earth that came out at exactly the other side of the globe (assuming this would be possible, of course). You could then jump into the tunnel and be accelerated until you passed the center of the earth, from which point on you would be decelerated by exactly the same amount. At the other end of the tunnel, you would stop and could just step out into the open. -- Ferkelparadeπ11:50, 19 September 2006 (UTC)Reply
Actually, it is possible, and it's being done for ages now. The moon's been going to and fro from Earth's sunside to the other side without ever having needed to charge it's batteries. It is, maybe, not a very practical way of making space ships fly, but it is certainly very economic. David12:12, 19 September 2006 (UTC)Reply
Note that spaceships do reuse the energy going one way and use it for the return trip, by using the destination star's, planet's, or moon's gravity to turn the ship around (possibly after many orbits). Also, the ship may even gain velocity by using the slingshot effect. They don't come to a "stop", of course, in either case, but can get close enough to make good observations and maybe drop a probe, then return back home. StuRat12:15, 19 September 2006 (UTC)Reply
That's true, you can use gravity assist to get some "free" (it's not completely "free" as you alter the trajectory of the body you're passing near, but the effect is so small it can be ignored) acceleration or deceleration. However, you can't slow down very far this way, so you still have to shed the rest of your speed some other way, either with rocket engines or aerobraking, neither of which obviously nets you any energy. — QuantumEleven15:09, 19 September 2006 (UTC)Reply
What do you mean when you say that you can't slow down very much? Relative to the body you use for gravity assist, you can't slow down at all, actually. You can only change the direction of your movement. —Bromskloss21:32, 19 September 2006 (UTC)Reply
Gravity slingshots do address this when you can use them, but it's important to realize that you always have the problem of conservation of momentum. If you're going to stop when you get to Alpha Centauri, something else has to gain that momentum. If this is fuel that you carry with you, you'll have to give it energy to get it moving (in your reference frame). What you'd "want" to do would be push off of a counterweight you left behind at Earth, and then pull on it again when you got there. But this would require a light-years-long tether, or else some magic like a tractor beam, and so has its own problems. --Tardis16:30, 19 September 2006 (UTC)Reply
The reason it is impossible is that, even theoretically, energy will be lost (due to the second law).
Um, what do you mean? I can't see why you would loose energy (apart from practical imperfections, of course) or what Newton's second law has to do with it. —Bromskloss21:32, 19 September 2006 (UTC)Reply
The third answer is that, due to the absence of appreciable friction, accelerating an object in space requires using Newton's third law. (See the second paragraph in the Overview at rocket.) That is, fling something backwards away from the ship. Since the center of mass of the rocket/exhaust system is unaccelerated by this maneuver, if you want to travel arbitrarily great distances, you have to let the exhaust escape. Having done this, your ability to subsequently accelerate (to stop at the destination, for instance) is reduced because you have less stuff left to use as exhaust. If, for example, your exhaust were a lead brick and you attached an infinitely long, internally frictionless rope to it, you could throw it away at the start of a maneuver, then grab the rope at the end and recover (most) of your kinetic energy. But the example is strongly unrealizable except for very short maneuvers (say, the length of the capsule).
If there is a large mass at the point of destination that can be used as an anchoring point, then you could stretch a large rubber band between two poles and have the ship fly into the band. Just as the ship would be about to be catapulted back, you secure the stretched band, storing energy. At departure time, use as a catapult. --LambiamTalk21:19, 19 September 2006 (UTC)Reply
Global Warming/ Ozone layer
Latest comment: 18 years ago14 comments7 people in discussion
Seeing as the ozone layer is closing, does that mean global warming will stop? If not, what does it have to do with global warming?
thanks!
The hole in the ozone layer has nothing to do with global warming. The ozone layer is a region of the atmosphere that shields us from ultraviolet radiation coming from the sun, and prevents you from sunburning too easily and getting skin cancer (amongst other things). Global warming is the result of increased amounts of greenhouse gases (such as CO2) which 'trap' more of the sun's heat, changing the global climate. I recommend you browse through some of the articles I've liked to for more info. Hope this helps! — QuantumEleven11:33, 19 September 2006 (UTC)Reply
The confusion is that both are caused by air pollution. The hole in the ozone layer was caused by CFCs, which used to be in every spray can and air conditioner. They have been largely eliminated now due to government actions, and this explains why the ozone hole seems to be closing. The greenhouse gases which cause global warming have not been stopped, however, thus global warming continues to worsen. There are two main reasons why there is no agreement to reduce greenhouse gases:
The Bush administration is denying that anything needs to be done and has rejected the Kyoto Protocol, which would have addressed this issue.
Unlike CFCs, a significant portion of greenhouse gases are produced by third world countries, which can't afford to eliminate them. They are produced by agriculture, heating homes, etc.
However, since action on stopping the use of CFCs did fix the ozone hole, it's reasonable to think that reducing greenhouse gases would reduce global warming. We've now seen evidence that human intervention can affect the atmosphere, for good or for bad. StuRat11:59, 19 September 2006 (UTC)Reply
Of course the ozone hole had decreased in some years before CFC's were discontinued, and the Earth has been warmer than this before the industrial age began adding more greenhouse gasses. The Climate is more complex than many are willing to admit.
No no it wasn't. The ten year average is the highest in history, as far back as reliable estimates can be made via the current methods. And we are indisputably at the high point of recorded temperatures. --DarkfredTalk to me16:22, 19 September 2006 (UTC)Reply
Most people seem surprised when to find that current levels are relatively low, at least from a long-term perspective - understandable considering the constant media/activist bleat about current levels being allegedly "catastrophically high." Even more express surprise that Earth is currently suffering one of its chilliest episodes in about six hundred million years.[31] On the 650,000 year time scale, it is following pattern remarkably well.[32] On the 20,000 year time scale it is pretty hot.[33] Regarding post-Industrial Revolution[34], this is for sure the hottest time (how hot is disputed). However, the point is often brought up that only a few decades before the Industrial Revolution was the CO2 ppm measured as higher than current. (Thenard, 1812 Traité élém. de chimie, 5 edit., vol1, p. 303. | Value: 385.0 ppm) (W. Kreutz 1941, Kohlensäure Gehalt der unteren Luft schichten in Abhangigkeit von Witterungsfaktoren,” Angewandte Botanik, vol. 2, 1941, pp. 89-117 | Average 1939-41: 438 ppm) The current value is around 381 ppm. I see you have mentioned "as far back as reliable estimates can be made via the current methods"—that is where opinon comes into play often more than scientific objectivity.— [Mac Davis](talk) (SUPERDESK|Help me improve)16:53, 19 September 2006 (UTC)Reply
The problem with examining the whole 650,000 year timescale is that different studies have had radically different results. As far as the last 20,000 years the results are undeniable. You mentioned C02 levels, according to ice cores testing, (where the granularity of testing is in 10-100 year range) we are at a 300,000 year high. The high 1800s numbers are during the heydey of Coal consumption, the problem is the numbers have never returned to their pre-coal/pre-industrial levels. By propping up the less reliable statistics you are basically just giving political ammunition to the "do-nothing" crowd, when there IS a concensus on the danger even from the scientists who have recorded the outliers. --DarkfredTalk to me14:54, 20 September 2006 (UTC)Reply
Although the Bush administration has its own motives for denying, there is an extremely heated controversy on almost all parts of the anthropogenic global warming hypothesis. Back to the original question, the ozone layer is a thin dynamic blanket that absorbs some parts of the ultraviolet spectrum. Relation to climate seems negligible at current. — [Mac Davis](talk) (SUPERDESK|Help me improve)16:46, 19 September 2006 (UTC)Reply
While there have certainly been climactic variations in geologic history, that fact is unrelated to human-caused global warming, which most scientists and national governments accept as a serious problem. If the scenario is true, then failure to heed the warning signs in time would have serious consequences. Oceans could rise due to melting glaciers and ice shelves: just a few feet of rise could destroy the fresh water reservoirs for the country of Kiribati. The city of Venice would become uninhabitable. Other inhabited lowlands such as coastal Louisiana and parts of Florida would have to be evacuated. Durova22:27, 19 September 2006 (UTC)Reply
Also note that the rate of change of global temps is at least as significant as the current level of global temps. Normally, global temps would only change slowly, allowing people time to adapt (moving slowly inland as the coasts flood, for example). However, rapid change can lead to disasters. There may be some rare natural causes of such rapid temp changes, too, such as a supervolcano or large meteor. Of course, those events can be catastrophic to life on Earth too, just ask the dinosaurs (oops, you can't !). :-) StuRat00:33, 20 September 2006 (UTC)Reply
A clue: Volcanic activity releases about 130 to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year. SO2 output shown here: [[35]] Looks like at least 10 megaton per year to me --Light current04:21, 20 September 2006 (UTC)Reply
Latest comment: 18 years ago1 comment1 person in discussion
does magma contain magnetic material?
It can. For example, moving molten iron can react with the Earth's magnetic field and cause a weak magnetic field to form. Most magma, however, is not magnetic. StuRat11:49, 19 September 2006 (UTC)Reply
Fidel Castro's eyes
Latest comment: 18 years ago1 comment1 person in discussion
Why do the irises of Fidel Castro's eyes appear completely black in recent pictures? Does some drug dilate the pupils that much? If so, how can he stand daylight?
Ken
The man is barely alive. 'Intestinal surgery' usually means something really bad, like stomach cancer or some such thing. As well, he might be on a hose-pipe of morphine. --Zeizmic12:59, 19 September 2006 (UTC)Reply
the magnetic field can effect to FO ( mazut oil) using in burner
Latest comment: 18 years ago7 comments5 people in discussion
My manufacturer has one boiler made in UK, produced by Wellman Robey, this boiler uses FO (mazut oil) for burning, I make the maximum magnetic field by the Neodyme magnets in the input type of the oil line to the boiler , I hear that this system will be saved the oil after the magnet treatment ,but the oil used the same, not reduced.
For the burner using the DO, it's OK, Why? Please give me the answer. Thanks. Ngocthuan_06 , 13:30 (UTC) 19,SEPT,2006
The "magnets on a fuel line" scheme is an urban legend at best. They never have any effect. There are, of course, countless shady companies with these worthless products. DMacks14:17, 19 September 2006 (UTC)Reply
I have the fuel saver from USA for the truck used the Diesel Oil, this product uses the magnet treatment for reducing the dimension of the fuel drop, from 300Micron into 3 micron, the fuel will be burned completely.The fuel reduced about 15% for my truck in highway
You can find out it by go to google.com, type fuel saver
[[User:Ngocthuan_06] 14:30, 19 september 2006 (UTC)
I'm not really sure why you appear to be answering your own question, but DMacks has summed up the situation nicely. Magnetic "fuel savers" are hoaxes. If they weren't, they'd be standard equipment with every car manufacturer who likes bragging about fuel economy. — Lomn15:57, 19 September 2006 (UTC)Reply
I think that any products are selling in USA, it must be checked the quality and purpose. I bought one fuel saver for fuel car, and one for truck, my truck is OK , it reduce 15% of DO in the highway, and 6% in city.But my car, it can not go over 70km/h, the speed can not increase but I still open the throttle(it means the fuel is increased but the speed is saturated), but if below 65km/h, it can reduce 20% of fuel in the highway. And now I get this for the FO burner, but no effect . I pose the question, why is it the difference of the same hydro carbon molecules but one is effected with magnetic field, one don't >User:Ngocthuan_06 00:51, 20 September 2006 (UTC)
The additive is reducing the octane of your fuel, destroying its performance while slightly increasing mileage rating. This will also damage your engine, your manual states a minimum octane. Plus, for a 6% increase in fuel efficiency (which I doubt) you are paying $15. This is NOT a good deal, you could simply have paid for 50% more fuel. --DarkfredTalk to me14:59, 20 September 2006 (UTC)Reply
Ayup. Can't rule out observer bias in the driving case: you know the magnet's there, and you unintentionally drive in a more fuel-efficient manner. OTOH, you could believe all this hooey, and think about the differences between what form of energy you get from a piston engine and a combustion furnace: maybe magnets increase the expansion that occurs during burning but don't increase the heat output. "I think that any products are selling in USA, it must be checked the quality and purpose" is entirely false—there are as many unscrupulous quack vendors selling useless, counterproductive, dangerous, and even illegal things are there are gullible people willing to pay for them. DMacks01:53, 20 September 2006 (UTC)Reply
Latest comment: 18 years ago6 comments5 people in discussion
I bought some superglue with instructions along the lines of applying glue to both of the surfaces to be affixed, waiting 10-40 minutes and then pushing both surfaces together. I want to know what is going on here - why can't I just apply glue to one surface, push the other suface against it and leave them overnight to get acquainted. --Username132 (talk) 14:12, 19 September 2006 (UTC)Reply
The strength of the bond depends on the amount of pressure the two objects are under whilst the glue dries. The stronger the pressure, the stronger the bond.
What you're talking about isn't superglue, but a type of contact glue (I haven't found a Wiki page on it yet). I have used it for many years, and, yes, it does work best if you apply it to both sides, leave them both to dry for a little bit (10-40 min sounds good, less if the ambient temperature is warm) and then press them together hard. The strength of this type of glue depends on the force with which the two objects are pushed together. After you've pressed them together you then need to leave it for a bit to set properly. You can, of course, just apply the glue to one side, press the two together without waiting, and leave it overnight, it will still work, but the joint won't be as strong. — QuantumEleven14:51, 19 September 2006 (UTC)Reply
The products I've used call themselves "contact cement" and several wiki pages (including glue) have redlinks to contact cement as well. So I guess: 1) that's this thing's official name, and 2) we there isn't a wiki page for this thing. DMacks18:51, 19 September 2006 (UTC)Reply
The "why" is that glues set by evaporating solvent and polymerizing (or engaging in other, more complicated chemistry). If you press the parts together soon, then the evapoartion can take a long time and therefore the time to set can become unduly long (possibly infinite). -- Fuzzyeric18:42, 19 September 2006 (UTC)Reply
Latest comment: 18 years ago10 comments8 people in discussion
An adult human can grow only 2 sets of teeth...Why is this? And why can animals (e.g. A shark), grow many sets of teeth?
Presumably, due to evolution. Some animals (i.e. shark, crocodile) lose their teeth a lot because they like to feast on large, live prey. They have to bite down on an animal struggling for it's life, and some of the teeth or lost. If the teeth didn't grow back, that would be one toothless shark. For humans, we don't have to worry about that problem. We never bother to grow teeth after they've been lost.— [Mac Davis](talk) (SUPERDESK|Help me improve)17:05, 19 September 2006 (UTC)Reply
I've actually heard speculation that wisdom teeth were evolved in order to replaced lost teeth. This explains why many modern day humans don't have room for these teeth, because they haven't lost any others. --best, kevin[kzollman][talk]19:29, 19 September 2006 (UTC)Reply
"and the people did feast upon the lambs and sloths and carp and anchovies and orangutans and breakfast cereals and fruit bats and large chu--" – b_jonas14:21, 20 September 2006 (UTC)Reply
I understand what you guys are saying, yet it still doesn't tell me why we don't grow more than two sets. IS there a reason? Or is it something no one can explain? Its very weird and I have no idea what the answer is! HELP MEEEEE!
It's not that humans don't grow more than two, it's that other animals do. We don't grow more because we don't need to. That is to say, evolutionary pressures are not sufficiently strong to have mutant genes like mine more reproductively advantagious. Although I do attribute my attractive set of straight cavity-less teeth to the fact that my last set came in when good dental hygiene practices were finally engrained into my prepubescent psyche. AEuSoes121:47, 19 September 2006 (UTC)Reply
Are your last teeth falling out? What sense of "why" do you mean? After all, why don't we grow an extra set of eyes for when the first set starts failing? And why don't we grow a pair of eyes in the back of our heads? Why can't we fly? It's so very weird. WHY? WHY? --LambiamTalk22:01, 19 September 2006 (UTC)Reply
Evolution is based on epending the minimum amount of energy, whilst spending it well so that it increases the chances of survival to the point that it was worth the change. Since we have survived just fine as a species with only 2 sets of teeth, we have no need for any more. PhilcTECI22:08, 19 September 2006 (UTC)Reply
I would say the cost of growing new teeth includes the possibilities of impacted teeth, infection, abscess, and death. We need to grow one new set of teeth, or else either babies would have impractically large teeth or adults would have useless tiny teeth. (I know someone who never got their adult teeth, and those baby teeth are almost useless as an adult.) But, growing more teeth would have more of a cost (potential death) than a benefit, so we don't do it. StuRat00:01, 20 September 2006 (UTC)Reply
Are you saying that if a bitter liquid somehow got past the eardrum, a bitter flavor would be tasted? Do you have a source for that? It is interesting if true, and if so I'd like to read more about it. Gary00:16, 20 September 2006 (UTC)Reply
Many people have a perforated eardrum. Via the Eustachian tube, material from the external ear can enter the mouth and be tasted. Contrariwise, some of them can puff on a cigarette and blow smoke out their ear. Edison04:54, 20 September 2006 (UTC)Reply
Here's your reference:
the middle ear lies in the petrous part of the temporal bone. It contains the three ossicles. Laterally lies the tympanic membrane (eardrum). Medially lies the inner ear. … Anteriorly, the Eustacian tube communicates with the pharynx. Oxford Hadbook of Clinical Specialties 4th Ed. 1995. ISBN 0-19-262537-3
So, yes, things can pass from the middle ear to the pharynx, and thereby the mouth, where they may be tasted. If the eardrum is perforated, it follows therefore things placed into the external auditory meatus (ie your earhole) will be able to be tasted should they pass through to the mouth. The quandry arises in the case of an intact eardrum - how do you get the taste to go through? Light current's idea of permeation is interesting, but I don't know that enough would get through to have an appreciable taste in the throat - so I don't think that's the whole story. My theory is neurological. The mucous membrane of the middle ear is supplied by a bunch of nerves called the tympanic plexus, which mainly originates from the tympanic branch of the glossopharyngeal nerve, and, you guessed it, the glossopharyngeal nerve also carries sensory information from the pharynx and the posterior ⅓ of the tongue. That is, a lot of taste information gets to the brain via the glossopharyngeal nerve. Now, here's where Light current's idea kicks in. Any substance that can diffuse through the eardrum, (and it really only has to get to the inner surface of the eardrum, which is covered by the mucous membrane of the middle ear, and therefore innervated by the glossopharyngeal nerve) might cause a degree of chemical irritation to the mucous membrane, which would generate a sensory impulse the brain could well interpret as a taste - the brain's differentiation of smell, taste and oropharyngeal stimuli being a bit fuzzy. --Mattopaedia13:30, 20 September 2006 (UTC)Reply
Gold reacting with Mercury
Latest comment: 18 years ago11 comments6 people in discussion
Dear Sir,
Gold whien in contact with Mercury is changing the colour to silver.
What is to be done to get back the colour of Gold.
With Regards,
Ajaya Babu Potluri
The gold metal isn't just turning a silver color, it's actually dissolving in the liquid mercury, forming an amalgam. The "Mining" section of that article mentions distillation as a way to remove the mercury. Google for gold mercury separate for more info. DMacks16:19, 19 September 2006 (UTC)Reply
Is this a homework question of a practical question, if practical DO NOT attempt to repair this yourself, you are obviously not a metallurgist, attempts to do this at home could result in permanent brain damage. --DarkfredTalk to me16:26, 19 September 2006 (UTC)Reply
In seriousness now. If this is damage to a family heirloom cause by breaking a thermometer, a jeweler could fix this by reforging the item, basically heating it till it glows, the mercury will boil off. This should be done under a vapor hood, while wearing a mask. --DarkfredTalk to me23:00, 19 September 2006 (UTC)Reply
I'm going to interpret the question as "do satellites in orbit travel along a constant vector (straight line) ?". In that case, under Newtonian physics, the answer in no, they follow an elliptical orbit. According to relativity, however, I believe space is curved (by gravity) around massive objects like planets, and the path they follow is actually straight, so could be called a "vector". StuRat14:55, 20 September 2006 (UTC)Reply
laws of motion
Latest comment: 18 years ago9 comments8 people in discussion
if you were to push an immovable object with all your might, how hard would it push back?
With the exact same force as you were applying to it. However, this would never really happen so I suppose you could say it could push back with any force as it is outside the scope of the laws of physics (as far as I know) 80.229.152.24620:08, 19 September 2006 (UTC)Reply
See Newton's laws of motion. It's not possible to have an immovable object. By Newton's 2nd law, if you apply a force to an object, it will accelerate. By Newton's 3rd law, it will push back as hard as you push it - as the first reply said. Whilst it's not possible to have an immovable object, it is possible to have an extremely heavy one, say a large wall connected to the Earth - where the acceleration caused by your muscular force will be miniscule. Richard B21:49, 19 September 2006 (UTC)Reply
Presumably you'd be pushing the Earth with your feet in the other direction with the same force. Otherwise, you'd also be accelerating in the opposite direction. So effectively you're keeping the Earth in its place. --LambiamTalk22:19, 19 September 2006 (UTC)Reply
If you take the reference frame of the object (so it doesn't seem to be changing its motion), if you push on the object, it would appear to push back with more than the force that's pushing it. It also would seem like the entire universe accelerated - but that's only because your reference frame is accelerating. An accelerating frame of reference makes things strange. —AySz88\^-^22:35, 19 September 2006 (UTC)Reply
Yes, but it's not like the Earth moves all at once as a rigid body. It's probably better to say that anyone can launch seismic waves into the Earth by jumping up and down. Melchoir05:43, 20 September 2006 (UTC)Reply
"In order for life to have appeared spontaneously on earth, there first had to be hundreds of millions of protein molecules of the ninth configuration. But given the size of the planet Earth, do you know how long it would have taken for just one of these protein molecules to appear entirely by chance? Roughly ten to the two hundred and forty-third power billions of years. And I find that far, far more fantastic than simply believing in God."
So I have a couple questions. What exactly is a protein molecule of the ninth configuration? Do we have any articles that talk about these kinds of proteins specifically? And does anyone know if what the character claims has been proven/disproven/discounted since then (the book the movie is based on was written in 1978)? Recury19:56, 19 September 2006 (UTC)Reply
I have never heard of a protein molecule of the ninth configuration. I am thinking this figure comes from the 9 human essential amino acids. Also, the figure cited I would think is not very reliable ("the kind that you make up, not look up"). Besides, it wouldn't take that long for a few atoms to hook up in the right way—that's 10251 years. That's several orders of magnitude greater than the estimated lifespan of the universe. Heh. — [Mac Davis](talk) (SUPERDESK|Help me improve)20:31, 19 September 2006 (UTC)Reply
It might be useful to look at what the Intellegent Design folks have to say about this. This is a film, and the purpose of films are to entertain, although they can have the effect of provoking thought. I always ask people who calculate these odds exactly how did they do these calculations. How do you compute the odds of something when you do not know what the conditions are. What are the odds of rolling dice and coming up seven? What are the chances of throwing a peice of metal in water and having it catch fire? What are the chances of a planet existing with an oxygen atmosphere? How do you calculate these odds without knowing the conditions?
Having read the essential amino acids and Levinthal paradox articles, it seems pretty likely to me he is applying the Levinthal paradox to essential amino acids to make his argument for ID. If my memory of the film is right, he does mention that the amount of time it would take is longer than the lifespan of the universe, which I guess is the point of the argument. Which "configuration" is supposed to be ninth out of nine is beyond me. Recury22:07, 19 September 2006 (UTC)Reply
In addition to the other flaws already mentioned, limiting the places where life could possibly evolve in the universe to just Earth is also wrong. Life could evolve anywhere in the universe with the proper conditions. Had it evolved somewhere else, instead of on Earth, we would be on that planet and the silly ID folks there would then limit their calcs to that planet, and not include Earth as potential site for life to evolve. StuRat23:51, 19 September 2006 (UTC)Reply
Depends whether the questioner is looking for something about the sinking, or about the design of Titanic. We need more info from the questioner.--Light current21:56, 19 September 2006 (UTC)Reply
This isn't the homework-helpers'-hut, mister. I'm wondering, is that a potassium ion (K+) or the potassium metal (K2)? I haven't worked with theoretical redox equations in a year so I might be wrong in thinking that it should be either one. Hyenaste(tell)23:21, 19 September 2006 (UTC)Reply
Dude, we don't do your homework for you. Try the redox reactions page. It shows you how to do it. And make sure you get different charges at the end. Potassium should be oxidized and sulfer should be reduced.
Is potassium metal K2? i did not know that, and can't help but suspect it false. why does elemental potassium exhibit metallic properties on the bulk scale if the bonding is localised into K2 units? these bulk properties suggest delocalised bonding, like the other metals. Xcomradex00:16, 20 September 2006 (UTC)Reply
Oops, I was wrong. I saw a K and S and jumped straight into K2SO4, got frustrated with my inability to still be able to solve it in my head, and my response fell apart from there. Hyenaste(tell)00:32, 20 September 2006 (UTC)Reply
Did not! Clearly cars, like television, represent intelligent design and content. Thus cars and television were invented by God and anything found in or on them is the literal truth of God. (<sprain> Ouch!) -- Fuzzyeric23:26, 19 September 2006 (UTC)Reply
Karl Benz in 1885 received a German patent for adding a gasoline engine to a carriage. More specifically for making and selling it to the public, but custom carriages had already been made by others, and steam cars were commercially available even earlier. --DarkfredTalk to me23:14, 19 September 2006 (UTC)Reply
September 20
Health Care Supply in Canada 12 years ago and today
Hello,
Thank you to anyone willing to help me out.
I'm looking for the number of medical school seats in canada in 1994, and the number available now. Does anyone have that information or a lead on where I can look for that information?
A most sincere thank you,
Matthew LR
Breast removal
Latest comment: 18 years ago9 comments8 people in discussion
If I cut off a girl's breasts, what will happen to her? What will she look like? (Yes, I know she's not going to be able to breast feed, but are there any other negative effects?) --Bowlhover04:19, 20 September 2006 (UTC)Reply
Surgery should only be done with the informed consent of the patient, and only by those medically qualified, using all applicable standards of sterile technique and anesthesia. And what would happen to you if she cut off your breasts?Edison05:05, 20 September 2006 (UTC)Reply
Yes, I believe that is a myth, that Amazon women removed one breast to improve their ability to pull back an archer's bow. The existence of the Amazons may even be a myth, although there does seem to be some supporting historical and genealogical evidence. StuRat13:01, 20 September 2006 (UTC)Reply
That particular part of the myth is particularly hard to believe. It would take enormous breasts to interfere with archery at all, and in those rare instances they could be bandaged. Durova13:31, 20 September 2006 (UTC)Reply
Latest comment: 18 years ago3 comments3 people in discussion
it is known about watson and crick base pairing in DNA molecules but are there any other non watson and crick base pairing in DNA molecule
please give me some informations on it.
it is quite common in RNA. not sure about in native DNA, but it can obviusly occur in DNA-like molecules containing unnatural bases. Xcomradex07:20, 20 September 2006 (UTC)Reply
Can you prove existance of colors if you can only see B/W?
Latest comment: 18 years ago8 comments8 people in discussion
I was wondering on the subject on how the design of our human sensors and brain affects our understanding of the universe. Related to this I came up with this abstract question and would like ask the world for input:
If I have nothing but a black & white television, is it possible to prove the existence of color transmission? -- Let's say I suspect that there is a television transmitter sending out in full color somewhere, could I prove its existence using only my B/W television?
No, not with a b/w television. Reception in colour requires a very different technology. That was a very practical question. The abstract question you hinted at in the title would be a more interesting one.--Shantavira09:28, 20 September 2006 (UTC)Reply
To answer the abstract question, yes, a color blind person can prove the existence of color, by looking at a spectral analysis of various colors. That is, they can see that different frequencies are produced by different light sources. Now, they might have no idea how these frequency differences are perceived by those with normal vision, but they would certainly know that color (frequency differences in light) do exist. StuRat12:02, 20 September 2006 (UTC)Reply
Color does not exists. It's a sensory fiction created by the biological system known as the eye and the brain. Just ask yourself this question: if no living creatures have eyes, does color exists?210.49.155.13412:14, 20 September 2006 (UTC)Reply
The universe does not exist. It's a fiction created by information processing systems. Just ask yourself this question: if no living creatures exist, does anyting exist? --LambiamTalk17:02, 20 September 2006 (UTC)Reply
This is as much a question of philosophy as it is of science. With the television example, no, a B/W television can’t prove the existence of color transmission. However, televisions aren’t such a good analogy for eyes.
Firstly, we have to look at how color is seen. Color is the result of different waves lengths of light. Our eyes has cells which can respond to certain specific wave lengths. Information from many, many cells which respond to certain wave lengths are passed into our brain, where the brain puts together the information and tells our conscience mind what ‘color’ something is.
Now, if we defined color as being the different wave lengths of light, than the existence of color can be proven to a color blind person, as explained by StuRat.
However, if we define color as being the perception of color. So that it is an illusion created by our brain (based on the information received from the eyes) for our conscience mind, then color is completely meaningless for a color blind person. And it would be impossible to prove this perception to be color blind person, since color would be a creation of how the mind interprates sensory information.
In biology, color is defined in terms of the wave lengths of light – so yes, scientifically, ‘color’ can be ‘proved’ to a blind person. And yes, even if no living creatures have eyes, color would still exist because light still has different wave lengths.
But in some schools of thought – people will say that yes, science explains to us what color is in terms of light, but people define what color is. And if color cannot be perceived, then it is not color.
A good question to consider is, do you believe 'ultraviolet' exists? What does it take to prove ultraviolet rays exist to you? After all, ultraviolet refers to light of certain wavelengths. Just like the way “green” refers to light of certain wavelengths. But...is ultraviolet a color too then? you are blind to ultraviolet rays like the way a blind person is blind to the difference between different colors, what would you accept as a proof for the existence of ultraviolet? Yaksha12:50, 20 September 2006 (UTC)Reply
Perhaps not a very satisfying answer, but if you were to filter the colour signal to show only the red, then only the blue, then only the green, you could see each layer of the colour image on your black and white set. This answer, of course, doesn't look at the perception side of colour. However, we seem to believe bees can see ultraviolet colours even if we have no concept of what that perception may be like (or even if bees "perceive" anything, or if they're some sort of automata). Science is pretty shakey on the subject of consciousness and qualia. All we can do in that department is infer along the lines of "my brain looks like this when I see pink, so if that fish over there has a similar brain pattern when it sees pink, then we must be on the same wavelength." (no pun intended) —Pengotalk · contribs15:05, 20 September 2006 (UTC) (my RfA)Reply
Perceived colors do not map monotonically to the spectral wavelength of electromagnetic energy. Metameres are colors perceived identically, but having different physical bases. Many colors, defined by hue and saturation, are in the interior of the CIE color space, and can be created by mixtures of 2 or more spectral colors. These combinations are infinite in number. Also, color perception is influenced by prior exposure of the observer's eye. Stare at a color for say 30 seconds, and you will perceive its complementary color in an afterimage. Repeat the experiment, and after staring at a color, stare at the complementary color, and you will perceive a supersaturated color, more vivid than the pure spectral wavelength pruduces. Add a surround of the original viewed color, and the perceived color becomes even more vivid. Perceptual psychologists have techniques of convergant and discriminant validation to investigate the validity of sensation and perception experiences. They can determine that the same observer reports the same physical stimulus with the same label "red" and applies different color labels to different physical stimuli, and that different observers apply the same labels. They can systematically map stimuli to responses.Edison17:00, 20 September 2006 (UTC)Reply
Surface area of a pin
Latest comment: 18 years ago3 comments3 people in discussion
Hii my physics teacher asked me how to calculate the surface area of a pin, how the heck could u do that!!
Take a close look at it, is it a series of cylinders and cones ? If so, draw a diagram, then take measurements and do calcs for those primitives, being sure not to count areas twice where the primitives meet. Here is one possible way to model it (not drawn to scale):
I hope it's not a safety pin () but more like a standard pin. The task can be split in three parts: (Step 1) deciding on an appropriate geometric model for your pin (for example the one suggested above by StuRat); (Step 2) estimating the parameters of that model (lengths, diameters, ...), preferably by taking measurements; (Step 3) doing the actual calculation using formulas for the surface areas of various geometric shapes. For step 1, stick to shapes for which you have a formula (see the article on surface area and various articles on shapes). You could go for a standard pin with a spherical head. I'd include a picture in the written report. Since the assignment is about calculation, I would not go overboard in doing the measurements with ultra-high precision. --LambiamTalk14:20, 20 September 2006 (UTC)Reply
Physics professors often give students questions like this to teach them how to do back-of-the-envelope calculations. My professor once asked on a test how much water a person drinks in a year, and there is a famous story about a mathematician who calculated the number of piano tuners in Chicago. Here's an article about these types of calculations:
http://en.wikipedia.org/wiki/Back_of_the_envelopeGary18:22, 20 September 2006 (UTC)Reply
What kind of bug is this?
Latest comment: 18 years ago3 comments2 people in discussion
As both you and the random university entomologist that I emailed concur, I shall be fixin' that image to illustrate the article. Thanks! grendel|khan18:11, 20 September 2006 (UTC)Reply
Latest comment: 18 years ago8 comments5 people in discussion
Yesterday I was cycling along a route I normally run, when I started wondering - why is cycling easier than running? You're going faster, and carrying more weight (moving the bike frame as well as yourself), but using the same legs and cardiovascular system to generate the energy - so surely you should get tired more quickly. Yet it feels easier. Obviously there's some energy not-loss, in that your energy is just going into moving forwards, wheras running also uses energy to push upwards with every step, but is that all the difference? Or is cycling more efficient/am I just imagining the difference in tiredness? Our article on Cycling didn't seem to cover the energy input. --Mnemeson13:10, 20 September 2006 (UTC)Reply
As long as you don't ride up an incline, the weight of the bike is not directly relevant to the amount of work needed. You have to counter the force of friction and of the deformation of the tubes, which is higher for a heavier bike, but still small if the bike is in good condition. On the other hand, when walking on a strictly horizontal plane, various body parts also have an up-and-down motion component, which does involve work, and this gets stronger with a running gait. Going up a steep incline, walking is easier than running or cycling (at least for me). --LambiamTalk13:32, 20 September 2006 (UTC)Reply
(edit conflict) :Walking requires constant lifting and lowering (or bobbing) of the body to swing the legs. THats where the energy goes in walking (on the flat)--Light current13:35, 20 September 2006 (UTC)Reply
Yeah but it took him a while to realise it should be round. The square wheel he first invented still required extra energy. We still have some of those original wheels on out local buses. 8-)--Light current15:16, 20 September 2006 (UTC)Reply
Which reminds me of a B.C. cartoon in which we are in the waiting room of the patent examiner's office. Through a window we see carts with square wheels go by in the streets; in the room someone is sitting with a model cart on his lap that has triangular wheels. As the proud inventor explains to his neighbour: "It eliminates one bump." --LambiamTalk16:49, 20 September 2006 (UTC)Reply
Square wheel production continues today but they are used mostly on shopping carts. I believe there was a Scientific American article in the 1960's looking at the efficiency of bicycling versus running or walking, which showed the calories burned by mile to be way lower for the cycle. For one thing, you are not having to move your center of mass up and down with every step like running.Edison17:04, 20 September 2006 (UTC)Reply
Latest comment: 18 years ago3 comments3 people in discussion
After doing much research on Glycemic index at WP and other sites, a question seems to emerge. Is there any way for a person who suffers from exaggerated insulin response but is otherwise healthy to improve their response to normal foods, aside from reducing glycemic load in meals? --Jmeden200014:40, 20 September 2006 (UTC)Reply
As always, get your nutritional info from a registered dietitian and your medical advice from a doctor , nurse, or diabetes educator. Now what do you mean by "exaggerated insulin response?" Are you diabetic? How do you know your body has an abnormal insulin production after a meal? Do you have hypoglycemia, diagnosed by yourself or a doctor, and how was it diagnosed? Anyone can buy a glucose meter for $30 or so at a drugstore and do a finger-stick to test blood sugar premeal, say an hour after, and 2 hours after, etc. Never use someone else's meter or lancets, since hepatitis and other illnesses have been spread thereby. Edison17:13, 20 September 2006 (UTC)Reply
a question about seed
Latest comment: 18 years ago2 comments2 people in discussion
can u tell me what sort of plant has the biggest seed and where they r found?
Latest comment: 18 years ago4 comments3 people in discussion
What formula should be used to solve the following ?
An open circuit exists with a 500 kOhm resistor and 35 microfarad capacitor in series with a 30 volt battery. Once the switch is closed and the circuit is energized, how long until the circuit will acquire 63.2% of it's final charge ?
This is a homework problem, although not mine, but somebody I'm helping. Also, I want the formula, not the answer. (However, if you want to give the answer, I won't object too strongly.) :-) StuRat15:38, 20 September 2006 (UTC)Reply
THe formula for voltage across the capacitor is Vc= 30* [1-exp(-t/RC)]. The figure of 63.2% is a special one as you may see from the equation and the cap charges to this level in a time that is known as one time constant which is equal to RC (ie t=RC). Because [1-1/e]= 0.632.--Light current15:50, 20 September 2006 (UTC)Reply
Latest comment: 18 years ago5 comments3 people in discussion
In the UK/Netherlands, the cheapest bread money can buy is 28p/€0.39. Is this bread nutritionally inferoir to bread of two or three times the price? --Username132 (talk) 15:43, 20 September 2006 (UTC)Reply
We have always referred to cheap fluffy white bread as "balloon bread" and buy whole wheat instead. "Wheat bread" is a misleading advertising trick term, since balloon bread is made of wheat. The whole grain is supposed to have some nutritional value, but at least it is higher in fiber. Still, cheap white bread will keep body and soul together and if money is tight, something is to be said for the most grams of complex carbohydrate per unit cost. Bakery outlet stores sell all kinds ofday old bread for a small fraction of the grocery store cost, and most bread is day old by the time it is consumeed anyway.Edison17:18, 20 September 2006 (UTC)Reply
Water window ph4 - ph 9
Latest comment: 18 years ago1 comment1 person in discussion
Water window or de:Wasserfenster from pH 4 bis 9, we need help on the discussion here [[40]],
The pH of wastewater leaving manufacturing plants and wastewater purification
plants, as well as potable water from municipal drinking water
plants, must be within a specific pH "window" as set forth by
local, state or federal regulatory agencies. This value is typically
between 5 and 9 pH, but can vary from area to area. source, :[[41]].
Your links answer your question. The Apollo missions were short. Note that the "from space" example (not the lab example) is a 1mm "crater" after 6 years of exposure, and the Apollo missions spent around a week outside of the Earth's magnetic field. — Lomn18:17, 20 September 2006 (UTC)Reply
Yes the Apollo astronauts were incredibly lucky:
not to have been hit by micrometoeries of any damaging size
not to have been out and about during a solar flare
not to have got more of a dose (a life times worth wasnt it?) of radiation than they did.
However this points up the difficulties of long spaceflight: something that seems to have been forgotten by the general pubic most of whom think that holidays on the moon are just around the corner. 8-(--Light current18:28, 20 September 2006 (UTC)Reply
unknown Insect, Costa Rica, Tapanti National Parc
unknown Insect, Costa Rica, Tapanti National Parc
(talk, contribs) 03:51, 13 September 2006 (UTC)
, which I can see a kind of + (plus) shape when looking at the yellow hue values and the cyan. I thought it might have been just me but asked others who said they could see them too. It's not very pronounced but is definitly visible. Why do those particular colours create the illusion of that shape? (I don't see it on any other parts). Or is it a flaw in the image? - Рэдхот 21:50, 14 September 2006 (UTC)
(talk, contribs) 01:44, 15 September 2006 (UTC)
12:12, 19 September 2006 (UTC)
) but more like a standard pin. The task can be split in three parts: (Step 1) deciding on an appropriate geometric model for your pin (for example the one suggested above by StuRat); (Step 2) estimating the parameters of that model (lengths, diameters, ...), preferably by taking measurements; (Step 3) doing the actual calculation using formulas for the surface areas of various geometric shapes. For step 1, stick to shapes for which you have a formula (see the article on surface area and various articles on shapes). You could go for a standard pin with a spherical head. I'd include a picture in the written report. Since the assignment is about calculation, I would not go overboard in doing the measurements with ultra-high precision. --LambiamTalk 14:20, 20 September 2006 (UTC)
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