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= June 27 =
== Aphids among the thorns ==
[[Image:Aphid.jpg|200px|right]]
On a trip to [[:Commons:Category:Nahal Peres|Peres river]], I saw plentiful [[aphid]]s on the thistly plants of the kind pictured here, but none on [[:Image:Peres river flora.JPG|adjacent flora]]. A similar phenomenon has been observed at my window box with a different specie of aphids - there were about a trillion of them on the invasive [[Hedera helix]], but none on nearby plants. What makes invasive plants so attractive, or detracts aphids off local vegetation? Thanks, [[User:Lior|Lior]] 02:10, 27 June 2007 (UTC)
:It may be that the aphids prefer to hide amongst the spikes of the thistles so as to avoid predators such as birds that might not want to be pricked. [[User:SteveBaker|SteveBaker]] 02:55, 27 June 2007 (UTC)
::maybe as is the danger with any introduced species, since the local species evolved with the aphids they adapted to a balance with both species in check, where as the introduced species has no natural protection against the aphids and is therefore overwhelmed, a similar thing could possibly happen if that aphid was then introduced into that plant's native environment, but possibly the habit there is in other ways inhospitable to the aphid. [[User:Vespine|Vespine]] 03:30, 27 June 2007 (UTC)
:::I hope other answers will be added, as I don't see how the [[Hedera helix]] case is explained by your interesting suggestions. There were some birds and [[:Image:Agama2.jpg|lizards]] around, but I wouldn't count on them to spare the aphids among the thorns. As one can see, the aphids also covered easily reachable sections. [[User:Lior|Lior]] 20:03, 29 June 2007 (UTC)
== Chief Executive Officers ==
What are the names of the past Chief Executive Officers of The Prince of Wales Hospital in Hong Kong?
:This probably does not belong at the science reference desk. The [http://www3.ha.org.hk/pwh/Index.html official website] has a [http://www3.ha.org.hk/pwh/content/about/history.html history] and a [http://www3.ha.org.hk/pwh/content/about/mgmstru.html management structure chart]. Wikipedia has a [[Prince of Wales Hospital|short article]] about this topic. [[User:Nimur|Nimur]] 06:50, 27 June 2007 (UTC)
== History of the "direct" current term ==
Would there be any science history enthusiast able to contribute somehow to the explanation of when did the term “direct current” appeared first in English, who proposed or introduced the term, and what actually the word “direct” suppose to imply in this context, meaning why and when did scientists started calling it “direct“ current instead of Galvanic current?
Was it because the graph is a straight line (cannot see any connotation), or because it is directly (!) from a battery (I doubt), or was it unfortunate mistranslation from Latin or other foreign language at the time, or is there some other explanation?
I am of electrical background and I know what direct current is, what I am after is the historical trace of the term “direct current” and its supposed meaning. I have spent many hours in libraries and on internet searching for answers, but with no luck at all. Many thanks in advance to anyone who can contribute or point in the right direction.
Did the term “alternating” current appeared about the same time?
::You may be interested in the article [[War of Currents]], probably answers most of your questions too. [[User:Vespine|Vespine]] 05:21, 27 June 2007 (UTC)
:At Google books if you specify full view you will be able to search books about electricity from the 19th century. I did not see a distinction of AC versus DC in the writings of Faraday in the 1840's or De La Rive from the 1850's. Once dynamos were invented and used for arc lighting, some were AC and some were DC. Early uses of the term "direct current {De La Rive, 1850's) were used to distinguish the battery current from the induced current, showing that the term did not then have the present sense. In 1884 I find the same Siemens dynamo described by one writer as a "constant current" machine and by another as a "direct current" machine. Further complicating things is that "constant current" often meant a DC generator with excitation such that the current stayed the same as the load was varied. I found the term "alternating current " popping up before the modern usage of "direct current." Both terms were probably known to physicists and electrical inventors in the 1870's. As Vespine said, the two terms were widely used by the war of the currents in the early 1880s. Similarly, 78rpm records were not called that until 33 1/3 rpm records were introduced; they were just called "records". DC electricity was just called "electricity" or "current electricity" to distinguish it from static electricity until AC gained some usage with transformers for sending current to distant locations. [[User:Edison|Edison]] 05:45, 27 June 2007 (UTC)
::I'm on [[User:Edison|Edison]]'s side here. I suspect that transformers created a distinction between direct current (a galvanic connection) and indirect current (through magnetic induction). But I have no reference to support my claim. [[User:Atlant|Atlant]] 12:52, 27 June 2007 (UTC)
::The [[Oxford English Dictionary]] (online subscription required) provides a quote from the ''Journal of the Society of Telegraph Engineers'' (XV p. 193): "I am glad that people are beginning to use the term ‘direct’ when they mean a current which does not alternate."; this quote dates to 1886, implying that the wide use of the term 'direct current' in the sense that we understand it today started to take hold sometime in that decade. (As others have noted, the ''first'' use of the term may well be quite a bit older.) The term was sufficiently established by 1889 to appear in Edward J. Houston's book ''A dictionary of electrical words, terms and phrases''. [[User:TenOfAllTrades|TenOfAllTrades]]([[User_talk:TenOfAllTrades|talk]]) 15:20, 27 June 2007 (UTC)
:::Our sister project - the [[Wiktionary]] says: ''From Latin directus, past participle of dirigere ‘straighten, direct’, from di- + regere ‘make straight, rule’.'' - so it seems reasonable to use 'straight' as an antonym of 'alternating'. It also provides a meaning: ''1. Straight, constant, without interruption.'' - also a reasonable use of the word. But I agree that it is almost certainly the other meaning: "directly from the battery - not indirectly through a dynamo" because early sources of AC would have come indirectly from some ultimate DC source. [[User:SteveBaker|SteveBaker]] 16:29, 27 June 2007 (UTC)
:Thank you guys, especially to [[User:Edison|Edison]] for the tip about Goggle books.
I have searched back to 1750, when Goggle gave up on me. Here is what I have found;
•Some US Government document published in1777 states: ….”direct and alternating current feeder wires shall be installed as follows:” …
•“The Discovery” published in 1763 refers to both the … “a.c. current from there to the receiver”… and further …”Low voltage alternating current is supplied”…
•“The Skipper” published 1753 provide interesting insight; …”alternating current generator, or alternator …’as is’ (my assumption)… presently called (meaning then in 1753)”….and further …. “The system is 12 volt and current is generated by what is termed a “three phase” Wico alternator.”
All this shifts the discussion a century back. It appears that both the direct and alternating current terms were well established in the mid 1700. Now, I hope there is still someone there who could dig deeper into the history and put further insight to this fascinating story? [[User:BrightSpark|BrightSpark]] 09:21, 28 June 2007 (UTC)
:A strong cautionary note here: Google books very frequently gets the date of a book wrong by hundreds of years, since apparently there is very little quality control of the people doing the data input. There is also the problem that when something is in "snippet view" you can't see the entire article to see the puiblication data. 1763 might be when "The Discovery's" first issue was published, and then Google shows you a sentence from something published 150 years later. This is shown by the supposed 1777 reference from "The Skipper" referring to "direct and alternating current feeder wires " because nothing like that existed in the world in that century, and the "US government" was more concerned with repelling the Redcoats than in a hypothetical electric power system for a hundred years or more later. As "history detectives" we may observe that it refers to the "volt" which was not a term in use until long after 1800 when Volta invented the battery. I would assign it 150 years or more later than the year you might infer from the snippet view. Another very poor feature of Google Books is that if you click onthe link to find the journal "The Skipper", apparently about sailing, at a library, it takes you to libraries that carry "Skipper" which is a different German magazine started in 2004 which is about lesbians. Likewise if you click on the link to find libraries with "Discovery: A Monthly Popular Journal of Knowledge" Google Books directs you to University of Arizona and a different journal called "Discovery." which was only puiblished from 1943-1966. All this is why I strongly encourage using only "full view" search for old public ___domain books to research 19th century technology. [[User:Edison|Edison]] 16:01, 28 June 2007 (UTC)
::Thanks a lot [[User:Edison|Edison]], after my last post I thought about all this and got to the same conclusion; something must be wrong, the language appears too modern. So, I agree fully with you, the conclusion was premature. [[User:BrightSpark|BrightSpark]] 05:24, 29 June 2007 (UTC)
== What is a 'return vector'? ==
Hi all. I was wondering what a 'return vector' is. I've heard the term in reference to 'coordinating points' (I'm not sure exactly what that means either!). It seems like a scientific term (I do know what a vector is), so I was hoping you could help me out. Much help appreciated ! <font color="#33AAAA">Xhin</font> '''<font color="#CC0000">[[User:The_Thadman/Give_Back_Our_Membership|Give Back Our Membership!]]</font>''' 08:03, 27 June 2007 (UTC)
: In what context did you hear about this? —[[User:Bromskloss|Bromskloss]] 14:03, 27 June 2007 (UTC)
::It may be the vector from Point B back to Point A (assuming that the vector from Point A to Point B is the original vector). [[User:Nimur|Nimur]] 16:12, 27 June 2007 (UTC)
:::Hmm, so it could be seen as the vector that would provide a means of getting from somewhere back to wherever the source of the original vector was? <font color="#33AAAA">Xhin</font> '''<font color="#CC0000">[[User:The_Thadman/Give_Back_Our_Membership|Give Back Our Membership!]]</font>''' 00:21, 28 June 2007 (UTC)
::::The direction you have to go to return to your starting position, perhaps. Hard to say without more context. [[User:Someguy1221|Someguy1221]] 03:18, 28 June 2007 (UTC)
== calling mobiles ==
hi,
why is that calling a mobile from a landline so much more expensive than calling another landline? Also, whilst phone companies (at least in the UK) are falling over themselves to make calling landlines free, the cost of calling mobiles doesnt seem to move- any ideas? (also, my informants tell me that this isn't the case in the US - why?) thanks..[[User:87.194.21.177|87.194.21.177]] 10:47, 27 June 2007 (UTC)
: Mobile phone networks are much more expensive to run than fixed line. Both need the same back-office equipment and trunk networking, but the mobile guys also need ''lots'' of cell towers and associated infrastructure, which have a per-user cost that's much higher than the cost of running a copper wire to your house. But moreover the mobile carriers paid ''crazy'' sums of money (in the UK, the US, and many other developed countries) to buy radio spectrum for 3G - an investment that they're struggling to pay back.
: The cost differential between the US and the UK is a function of how cellphone billing is done. In the UK mobiles have their own area codes (077xx, etc.), while in the US cellphones are tied to regular area codes ([[Area code 212|212]] for New York Cty, for example). If you call a mobile in the UK (something you can tell because of its area code) you pay more than calling a land line. In the US you can't tell you're calling a mobile, and the additional burden is paid by the mobile subscriber receiving the call. -- [[User:Synthetic element|Synthetic element]] 13:04, 27 June 2007 (UTC)
: As to why you can get free or nearly free landlines in the UK - really, you can't. You can get free or freeish phone service ''if'' you buy broadband and TV (a "triple play") from them, with the addition of mobile phone service too (a "quad play"). They do this because voice telephony is a commoditised, low-margin, cost-plus business (so there's not much to be gained from competing hard on it) while broadband, cableTV, and mobile telephony carry bigger profits and have much more opportunity for growth - so they compete on those, and chucking in telephony doesn't cost them much. For cable TV (Virgin) telephony is pretty cheap for them to provide - they own the last-mile cable and they own or lease lots of trunk network (mostly for the broadband service) so telephony is a drop in their bucket. Much the same is true for BT. Sky Broadband is really just a DSL service on a BT line, so they're having to buy the telephony function whole from someone else (either purely from BT or BT+someone's trunk). -- [[User:Synthetic element|Synthetic element]] 15:21, 27 June 2007 (UTC)
:: Actually, according to one article I read, it's not true that "mobile phone networks are much more expensive to run than fixed line" or that they have "a per-user cost that's much higher than the cost of running a copper wire to your house". They can actually be substantially cheaper. In fact, according to this article, a lot of developing countries are skipping widespread deployment of land lines and leapfrogging straight to wireless.
:: Due to mass production of microelectronics, wireless phone handsets are cheap -- not much more expensive than conventional, wired telephones, these days. But stringing copper wires all over the landscape is fantastically expensive. Sure, cell phone towers cost money, too, but -- how many of them do you need?
:: If you're using wired lines, you need to string wires to everyone's house who wants to talk. And even if not everyone wants to sign up for phone service at first, you still have to run wires down the streets of everyone who might want to talk, because new subscribers won't be willing to pay for more than the drop from the street to their house. And this model only works for relatively densely-populated areas. Even in the U.S., it was close to 100 years after the invention of the telephone before everybody in rural areas had access to phone service, -- and there are still remote areas without it.
:::If the phone was invented in the late 1870's then you are saying rural folks in the US did without phones until the 1970's? I would say rural phone service was pretty universal by the 1940, and most small towns had phone lines going out into farm country by World War 1, so all but the most isolated areas had the service available if they chose to pay for it by World War 1. Farmers would put up the wires as a cooperative effort in some cases up like they were raising a barn. As for "everybody" I am sure some never got phone service at all (Amish and dedicated misanthropes and cheapskates). Today many younger folks have only celphones and never get a land line. Where are the "remote areas" without phone lines today? Thinly inhabited swamps, forests and deserts? Mountaintops? What county has no phone lines? Maybe in the third world countries this is true. [[User:Edison|Edison]] 13:31, 29 June 2007 (UTC)
:: Using a wireless network, on the other hand, if your towers have decent range, you only have to build as many of them to take care of the number of people who are talking on the phone at a given time. At first, when you have few subscribers, you won't need very many towers. (Or even if you have kind of a lot of subscribers, but they haven't gotten into the swing of things yet, where they're gabbing on the phone or messaging each other constantly.) As your subscriber base and usage grows, you can build more towers incrementally, and only where they're needed. So it's easier and cheaper to build a wireless network incrementally, as opposed to a wired network, where nobody can talk to anybody until you first sink the huge capital expense to crisscross every populated area with wires. —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 23:53, 27 June 2007 (UTC)
:::Plus, when stringing a lot of copper wire through unpopulated areas, you have to deal with people who steal and resell the copper wire on the black market. -- [[User:Jsbillings|<span style="color:green">JSBillings</span>]] 14:24, 28 June 2007 (UTC)
== Yeast Infection ==
For [[Candidiasis]], does anyone know why or how the yeast overgrowth (or undergrowth) can be resistant to conventional over the counter treatments?
:The same basic principles as all other instances of [[antimicrobial resistance]] apply. Profligate use of antifungals lead to selection of resistant strains, increasing the probability that the species causing any given infection is resistant to the most widely used treatments. If you were asking about specific mechanisms of resistance: [1] resistance to polyene antifungals involves changes in the ergosterol content of the fungal membrane; while [2] resistance to azole antifungals involve alteration of 14-demethylase, decreased intracellular drug accumulation, and loss of function of the enzyme 5,6-desaturase. - <span style="font-family: cursive">[[User:Nunh-huh|Nunh-huh]]</span> 22:37, 27 June 2007 (UTC)
== Mars Direct ==
I find [[Mars Direct]] to be a very efficent way of getting to Mars, but my only problem is the Methane Rocket technology involved in the ERV. Have methane rockets been tested or is the propulsion system still too young?[[User:67.126.240.208|67.126.240.208]] 17:59, 27 June 2007 (UTC)
:Apparently they have been tested. This [http://www.space.com/businesstechnology/070507_methane_rocket.html] is recent, although the very first tests took place two years ago [http://www.californiaspaceauthority.org/html/press-releasesandletters/pr050831-1.html], it's even on wikipedia in the [[XCOR Aerospace]] article. Did you look in google? These were in the first page of search results on [http://www.google.com/search?client=safari&rls=en&q=methane+rocket&ie=UTF-8&oe=UTF-8 methane rocket]. [[User:Donald Hosek|Donald Hosek]] 00:32, 28 June 2007 (UTC)
== Why would spot or arc welding not electrocute someone holding non-insulated metal? ==
I've seen this a lot, usually on the Science Channel show [[How It's Made]]. A factory worker will hold two metal parts with ungloved hands while an automated spot welder fuses the parts. The weld is performed by the two copper alloy electrodes pressing against opposite sides of the part. I've also seen a robotic arc welder repair one end of a steel I-beam, while an operator standing at the other end steadies the beam, again with ungloved hands. Then there's the spot welding performed in a dentist's office. I've read that spot welding is typically low voltage while arc welding is much higher. <nowiki>
</nowiki>But in any arc welding literature I've read, safety concerns listed are blindness and chemical toxicity, but not electrocution. You're passing current through metal, butt here's no risk of shock? So, what am I missing? Bonus question. If spot welding takes one volt, how come you can't hook two copper electrodes up to an AA battery, touch them to two intersecting metal strips, and form a weld? What's the difference? [[User:97.82.254.213|97.82.254.213]] 22:36, 27 June 2007 (UTC)
:An arc welder is a powerful device which can supply a huge amount of energy, often high amperage and fairly low voltage. but enough power to melt ferrous metal or to make a heavy piece of steel red hot. An AA battery has internal resistance which prevent very much current from being drawn from it. It might just be able to spot weld small pieces of metal (That said, I must say don't try it, because hot things can burn you or start fires). As to why the people don't get electricuted, I will leave that to a welding expert, but I would look at the areas of grounding, of how the current would divide between the metal pieces and the person touching it (that is draw the circuit diagram), and at the voltage which the machine is putting out. That said, there are many different types of welding equipment and there are probably setups where a person could in fact get shocked. [[User:Edison|Edison]] 23:07, 27 June 2007 (UTC)
: When you're arc welding, the workpiece is grounded and the high-voltage arc is struck between the electrode and the workpiece. (Actually it's often not such a high voltage, after all, but that needn't concern us.) So the only way to get shocked would be to touch the electrode -- but you don't want to touch that, anyway.
: There's lots of current flowing through the workpiece back to the place where the welding machine's ground electrode is connected, but that current would much rather flow through that nice, low-resistance metal than jump out and shock you.
: Basically, you get shocked when some part of your body bridges between two spots that are at different voltages. Usually, one spot is at 0 volts ("ground"), and one spot is at some other voltage. Most of the world is grounded, and <s>most</s> much of the time, you are, too, so most of the time, touching anything that's at a voltage significantly different from 0 will give you a shock. But if you touch something that's ''at'' a voltage of 0, you don't get a shock, even if that something is carrying lots of electric current.
: The story is slightly different for spot welders. They use very high currents (at low voltages), and the current is injected very close to the point that it's collected. Away from that spot, there's very little current flowing at all. (And at any rate, the voltage is too low to shock you anyway.)
: Finally, as Edison already explained, an AA battery is simply incapable of supplying enough current/power/energy to do any spot welding. You need hundreds or thousands of amps to make a spot weld, while I think an AA battery is capable of supplying mere milliamps. —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 23:23, 27 June 2007 (UTC)
:::A AA alkaline battery can put out several amps, and I think it might be able to cause a very thin piece of iron wire to weld to another.Don't try this, because the battery might explode. [[User:Edison|Edison]] 03:43, 28 June 2007 (UTC)
::::?? several amps?? (just asking)[[User:Gzuckier|Gzuckier]] 17:40, 28 June 2007 (UTC)
::::::I just tested a well used Eveready AAA alkaline and it put out 5.3 amps. I did not want to test a newer one or a larger battery because it might blow the expensive 10 amp meter fuse. Here the current is limited by the internal resistance of the AAA cell, the contact resistance (very low) the lead resistance, and the internal meter resistance. Do not underestimate little alkaline batteries in terms of how much current thay can deliver into a low resistance circuit for a few minutes. Don;t carry one in a pocket with keys and change unless you want to start a fire or have the battery explode (I have never personally known one to explode from high discharge rate but the manufacturers say it is a danger. [[User:Edison|Edison]] 13:22, 29 June 2007 (UTC)
:: I said "most of the time, you're grounded", but that was a little too strong. If you've wearing a pair of robber-soled shoes, and not touching anything, you're effectively insulated from ground, up to a potential of a couple of hundred volts. (That is, you could probably touch a 120V wire and not get shocked. But if you tried to touch a 1000V wire, the voltage would be high enough that it would probably punch through your shoes and electrocute you.)
:: This is significant because there are sort of two different ways to get electrocuted. One is to be grounded and to touch a live wire, but the other way is to be in contact with a live wire, and then touch something that's grounded.
:: If I were wearing a pair of rubber-soled shoes, and holding a bare, live, 120V wire in my hand, I would not get a shock. My body would be raised to a potential of 120 volts, but there would be no place for the current to flow. But ''then'', if I reached out and touched a metal water pipe with my other hand, then I'd get a nasty (potentially fatal) shock. Or if you walked up, barefoot, and touched me, we'd both get a shock. (From my point of view, I'm in contact with a live wire but ungrounded until I touch you. From your point of view, you're grounded, and touching me is like touching a live wire. Now cue [[Psycho Killer]] by [[Talking Heads]]: "Don't touch me, I'm a real live wire.") —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 23:35, 27 June 2007 (UTC)
:::Whoah, careful! You mean, I take it, a 120V [[direct current]] source. Many American houses have 120V 60-cycle [[alternating current]]; that'll give you a nasty shock even in your rubber boots. The reason is that your body has significant [[capacitance]] -- the current will flow into you from the wire and then back out into the wire, over and over again, and it doesn't need an outlet on the other side. --[[User:Trovatore|Trovatore]] 00:38, 28 June 2007 (UTC)
::::Hmm, how sure are you? (I do know about capacitance, and AC current may flow into and out of ''you'' and give you a nasty shock, but I can assure you -- true OR confession here -- it doesn't do that to ''me''!) —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 00:43, 28 June 2007 (UTC)
:::::Well, I suppose I'm not terribly sure. I have gotten shocked; I don't really recall exactly what I was wearing on my feet. But I don't plan to experiment. --[[User:Trovatore|Trovatore]] 01:11, 28 June 2007 (UTC)
:::::I turn off the circuit breaker before I touch a line-wire; even then, I only touch one wire at a time in case of residual capacitance or unexpected voltage. I think it's a bad idea to touch an live AC line even if you are wearing thick rubber boots. [[User:Nimur|Nimur]] 01:21, 28 June 2007 (UTC)
::::::: If you want to work on dead electric wires safely, the most important thing is to ''make sure they're dead''. This sounds like a tautology, but the sad truth is that many people are killed by touching wires that they only thought were dead.
::::::: [[Image:Neon Test Lamp.jpg|thumb|Neon test lamp]] Get yourself a [[Test light|neon test lamp]] (right), and use it religiously. Also, unless you're working in a single-family residence where you can be sure that you're the only one who'll be messing around with the fusebox, put a note right on the fuse/breaker. The last thing you want is for some enterprising person to wonder why the lights are out, and to find the right breaker and "helpfully" turn it back on, just when you're grabbing the wire. (Professional electricians in industrial settings don't just use notes for this purpose, they use [[Lock and tag|padlocks]].) —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 11:36, 29 June 2007 (UTC)
:::::: Yeah, I got shocked by sticking my finger into a US 120V electrical outlet when I was 6 years old (on a dare, I'm not stupid or anything.. *ahem*) and I had thick rubber-soled shoes on. I assumed the shock was possible because my fingernail was touching the conductor while another part of my finger was touching the wall plate. Wow. I didn't expect so many answers on this. The welding-related ones do make sense. Sorta. I understand what you're saying, but the idea that 500A could be dumped into a girder, and I could hold barehanded onto that girder a few feet away and live just seems bizarre. It's like an electrolysis setup. Current flows all over, but some does get to each point. I'd figure at the least, there'd be enough current to give you a shock.
::::::: Think about it this way: instead of contemplating whether there's enough current to give you a shock, ask whether there's enough ''voltage''.
::::::: Whether that steel girder is carrying 1 amp, or 10 or 100 or 1000, or 0 -- as long as its potential with respect to ground is zero volts, no current is going to flow from it to another grounded object, i.e. you. And if the resistance of the girder is low enough that the voltage drop induced by the current it's carrying is near 0, then if one point of the girder is at ground potential, all of it will be. (Contrariwise, consider a piece of metal that ''is'' elevated to a high voltage -- such as, for example, one of those wires strung on insulators on poles along the street -- and suppose further that, for whatever reason, it's not carrying any current at the moment. Does that mean it's safe to touch it, since there's "not enough current to give you a shock"?) —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 04:49, 29 June 2007 (UTC) [augmented 14:03, 29 June 2007 (UTC)]
:::::: While we're on the subject, is there a law or rule that specifies what combinations of amperage/voltage are possible? If a static electricity shock can be thousands of volts, but has little amperage, is the opposite also true? That spot welding description would seem to say so. Can you really have a 1V source that, when touched, could dump 1kA and turn you to crispy human bacon? I posted a question about that before. Specifically, I can't fathom why two revisions of the same consumer product would have vastly different power requirements (12v 500mA vs. 6v 2000mA). [[User:97.82.254.213|97.82.254.213]] 04:41, 28 June 2007 (UTC)
::::::: Yes [[Ohm%27s law]]: Voltage (V) = Current (I) * Resistance (R) or V = IR -[[User:Czmtzc|Czmtzc]] 13:33, 28 June 2007 (UTC)
Any combination of current (amperage) and voltage is possible. The most obvious everyday examples:
* Low current, low voltage: most electronics
* Low current, high voltage: static shock
* High current, low voltage: car starter
* High current, high voltage: lightning
Starters draw up to about 1,000 amperes and are typically powered at 12 V. A higher voltage would be more convenient (lighter-weight wiring could be used), but the power source is a battery and that produces low voltage. In fact, 6 V was quite common a few decades ago. --Anonymous, June 28, 2007, 07:06 (UTC).
Well guys you are right and you are wrong. How could that be? OK, there are situations where for whatever critical reasons the maintenance or repair have to be done on live electrical equipment, and sometimes at much, much higher voltages than 120V. In these situations maintenance crew will use special (!) safety (!) equipment; rubber boots, rubber gloves and special mats and platforms, not to mention strict procedures and compulsory presence of a co-worker during the procedure. All this is exactly for the reason you mention, to isolate the person from the ground or earth potential so the current that develops through the serviceman body and the protective equipment is so insignificant that the person can work safely.
Where you go wrong is assuming that wearing any (!) rubber boots will always (!) protect you. At 120V, it may or may not, and the fact that it protected you once does not really mean it will maintain the protection the next time. Electrical safety equipment is made from special (!) rubber like materials, using special design and manufacturing processes, and for that reason it is usually quite expensive. The fact that something is made of rubber or plastic does not automatically mean it is electrically safe! Dielectric properties of such materials vary significantly, though they may look alike. On top of that, all electrical safety equipment is subjected to strict safety tests, is rated at specific maximum voltage it will provide the protection and is given an attest; you may see that electrician’s screwdrivers or cutters, or the multimeters are all marked accordingly, usually 1000V. Further more the equipment is subject to regular maintenance and tests regime during its service life to ensure that its protective ability did not deteriorate over the time or due to accidental damage.
The rubber boots you buy at you local hardware shop are not intended for that purpose. They may possibly protect you at 120V when new and dry but I would not dare to test their ability at any voltage. With time and wear the insulating properties will change significantly. The thickness of the sole will reduce, micro-cracks will develop and moisture from perspiration will accumulate; all this will reduce significantly its protective ability and suddenly the current will find its way to the earth exactly the same way as lightning finds its way from a cloud to the earth; you may be unpleasantly surprised if not harmed. So here is where you go wrong.
I too think, it is a bad idea to touch a live AC line even if you are wearing thick rubber boots, and I am saying this from my past experience. To ensure safety more than that is needed. It is not that I am in any way giving you support but if you ever consider, for whatever reason, to do such an exercise ensure that you have someone responsible with you at all times. Such a person must know where and how to isolate quickly the right circuit and what to do should the unthinkable happened, and without exposing any one to further danger. Live wires are dangerous and there are good reasons for all the warnings.
And, on the other issues mentioned earlier;
Generally, international standards quote the “Extra Low Voltage” limits as being 120V for DC and 50V for AC (mind you the 50V is RMS value). Voltages below and up to the above limits are generaly considered safe to touch under normal conditions!!! (You do not stand barefoot on a wet floor in the bathroom or in the rain; you do not have cuts to you fleshy tissue where you touch the wire, etc. under such abnormal conditions you can be assured you won’t be safe). These limits are summary of statistical tests and the limits may be slightly different in various standards or countries..
Typically human body under normal dry conditions have adequate resistance (primarily due to the dry skin which acts to our fleshy tissue like an insulation on a wire) so the current that develops through you body when you touch voltages below the above limit is so insignificant that it won’t affect you.
Safety standards further quote current limits for what is known as “Threshold of Perception” (lowest current which causes any sensation to a person through which it passes). These are 0.5mA for AC and 2 mA DC. Further more there is another yet limit called “Threshold of “let-go” (highest current at which a person holding electrodes can let go of the electrodes). These are about 10 mA for AC and approximately 300 mA for DC.
These figures are based on statistical data and are not absolute limits. Different people will respond differently under different circumstance, and there are many factors that affect this. So, one must be knowledgeable to interpret them. I have quoted them here to give you some understanding while you can safely touch the car battery or welding equipment, but should not touch the mains at 120V AC.
With the AA battery, yes it will give you a spark, but it will be so minute that you will be lucky to spot it in a dark room. It acts the same way as the arc welder. It simply does not have ability to maintain the current long enough; it wasn’t designed for that purpose. You will probably have more luck with a car battery. Remember however, such experiment is likely to damage the battery due to long term rapid discharge, especially repeated; again this battery was not intended to be subjected to such a torture. And one more, never ever leave a battery short circuited, even the AA. It will overheat due to excessive short circuit current and may explode!!!
And final one; the body capacitance is really of no consequence at 50 or 60 Hz and the theory expressed there appears to be confused.
Sorry, I thought I will do it in three sentences. As the subject is rather crucial it took me a while so, here we are. [[User:BrightSpark|BrightSpark]] 09:06, 28 June 2007 (UTC)
:Um, I wasn't confused, just (apparently) wrong. I hadn't done the actual calculations (and still haven't, but assuming the ones given here are correct then) that wasn't the reason I got the shock. But it could have been, in principle. --[[User:Trovatore|Trovatore]] 06:32, 29 June 2007 (UTC)
::According to [http://www.aecouncil.com/Papers/aec1.pdf] the capacitance of the human body is 60 to 300 picofarads. Static electricity to as much as 15,000 volts can be stored in this capacitance just by walking across a carpet on a dry day. The electrostatic discharge when you then touch a grounded object or a metal pobject at a lower potential can amount to "tens of millijoules" of power, with a peak current of 7.5 amps and a peak power of kilowatts. An IEEE paper[http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=737028] gives 100-150 picofarad as the measured human body capacitance tested with an AC bridge and higher for static electricity, 200-400 picofarads. These amounts of capacitance, with 120 volt electricity at 60 Hertz would produce a very small amount of capacitive current, so the hazard would be conduction from the source of electricity through the body, to a grounded object or another conductor. Capacitive current would be (voltage)*2 π*frequency*capacitance. Now to calculate the current for 120 volts, 60 hertz and for 240 volts 50 hertz, since these are found in most residences of the world (remember this is capacitive current only, and the electrical conduction is a great hazard beside this).
*120 volts, 60 Hz, capacitive current for a 300 picofarad person= 14 microamperes
*240 volts, 50 Hertz, capacitive current for a 300 picofarad person= 23 microamperes.
*(This is presented for discussion only and is not to be relied on for any safety related matters such as doing electrical wiring or experimentation. Do not try the experiment because any inadvertent contact with a grounded object or conductor could be fatal while in contact with something electrified). [[User:Edison|Edison]] 15:56, 28 June 2007 (UTC)
#I've been zapped when I tried to do TIG welding without wearing a glove. The voltage is somewhere below 110, so you live, but you remember to wear a glove.
#You can't get zapped from just one pole of the AC line, body capacitance or not. Both theoretically, and practically. In my stupid youth I had occasion to work on the electrical system of apartments where I didn't have access to the circuit breakers, involving occasional skin contact with one side of the line, and nothing happened.
#There are websites which describe how to weld with car batteries.
#There was a case years back where an electrical lineman was electrocuted, despite wearing insulating gloves. Turned out a nearly invisible pinhole in the glove was directly over his wedding ring, and when he grabbed the conductor with that glove so that the hole was proximate, that was it.
:[[User:Gzuckier|Gzuckier]] 17:40, 28 June 2007 (UTC)
::You most certainly can get zapped from one pole of an AC line, if it is sufficiently high voltage. In high school I hooked up an induction coil (19th century device which has a step up transformer to change 6 V DC to several thousand volts AC with an internal interruptor), a 6 volt battery, and a swith, to build a spark radio transmitter. The problem was, when I turned it on the voltage would come arcing out from the light switch, which was only in the 6 volt DC primary circuit, and cause an excruciating shock. It was capacitive coupling from the ungrounded circuit. Likewise a utility high voltage line will arc impressively to an ungrounded helicopter when the workman repairing equipment on the line first makes contact. (They wear metal suits and have special training for live line work). [[User:Edison|Edison]] 13:11, 29 June 2007 (UTC)
:: Let me clarify, I don't want to try welding with a battery or car starter. That was just a hypothetical example given for comparison. BrightSpark's answer was very informative, but one point given confused me. Specifically, the section about the “Threshold of “let-go”. If the let-go threshold for DC is 300mA, does that mean if one were to clip the plug off a puny 3.5V 500mA AC power adapter adapter (or any standard wall wart), strip the wires and grab them, they wouldn't be able to release? Similarly, the anonymous post before BrightSpark said "Starters draw up to about 1,000 amperes and are typically powered at 12 V" Does that also mean that if one were to grab those leads, the car starter would instantly kill them?
:::I'll break in here to answer that point. If you broke open the starter circuit while the starter was in operation, you might get an impressive arc, but once the gap was opened wide enough, the arc would stop and then there would be zero current flowing. If you then "grabbed the leads" and put yourself in the place of the starter, which I think is what you mean, that would be a different circuit with a much large resistance in it, namely your body. The current that would now flow would be determined by the 12 volts and the resistance of the skin contact and your body in that configuration (plus the internal resistance of the battery, and the restistance of the wiring, but those are both too small to matter). In a worst case it might still be enough to hurt or kill you; this I can't say. But I can say it would be just about 1/10 of the amount of current you'd get if you grabbed two leads that were live with a 120 V household power supply, so the chance of it being lethal would be less. --Anonymous, June 28, 2007, edited 23:50 (UTC).
:::To the other two points:
:::#You can certainly weld with a car battery. A few years ago, some friends of mine built a go-kart powered by car batteries and starter motors. The fancy high-current solid-state motor controller they'd bought, the one whose specs said it could ''theoretically'' handle the currents involved, fried the very first time they used it. So they were reduced to using a little accelerator-pedal-like strip of metal which you pressed with your foot to complete the circuit. Trouble was, it tended to weld itself in place, so while you were zipping around in this thing, trying to not steer into trees or telephone poles or anything, you'd be madly trying to pry the "accelerator pedal" back up with the side of your foot...
:::#A "puny 3.5V 500mA AC power adapter adapter" can supply a ''maximum'' of 500 mA. It's not some magical device that shoves 500mA through anything it touches. (Though there are constant-current supplies which try to do this; more on them later.) —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 04:43, 29 June 2007 (UTC)
::I've seen conflicting posts that state the threshold for death is 2A, or around 60mA (I think. Could have been 600mA) across the heart. The former was on Wikipedia, and the latter was on the TV show Mythbusters. Anyway, the arc welding and rubber boots explanations make sense now, though it is a difficult concept for me to wrap my brain around. I do a lot of work with electronics, and always try to make safety a priority. But these simple parts of EE theory always manage to elude my understanding. For example, If I were designing a DC electrical device, and assuming the components could handle it, what would be the difference in supplying 6VDC @ 200mA or 12VDC @ 100mA? Isn't the output identical? As another example, what would happen if a consumer electronic device came with a 12VDC 1250 mA AC adapter, but it was swapped with, say, a 30V 500mA AC adapter? Isn't the output also identical? If not, that's what I just don't get; that there's more than one way to accomplish the same output, but those other ways fail. I know there's a way I can understand this. As I said before, I'm definitely not stupid. Hell, I once quit Mensa. :) [[User:97.82.254.213|97.82.254.213]] 21:52, 28 June 2007 (UTC)
:::: If you think that 12 volts at 1250 mA should be the same as 30V at 500mA, ask yourself this: if the recipe says to bake for 30 minutes in a 350 degree oven, does that mean you could also cook it for 350 minutes in a 30 degree oven? (This isn't an exact analogy, but it has the same, er, flavor.) —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 01:10, 29 June 2007 (UTC)
::: The "3.5V 500mA" rating means that it will provide a nominal voltage of 3.5 volts, and a ''maximum'' of 500 milliamps. To determine the actual current, you divide the voltage by the resistance of the load across the terminals. Since intact human skin has a fairly high resistance, the actual current flowing will be under a milliamp.<p>If, on the other hand, you were to connect a one-ohm resistor across the terminals of the power supply, it would try to provide 3500 milliamps, overheat, and catch fire. --[[User:Carnildo|Carnildo]] 22:58, 28 June 2007 (UTC)
:::As I recall, the lethal current ''directly through the heart muscle'' is down in the tens or low hundreds of milliamps. And for this reason, pedants are find of saying, "It's not the voltage that kills you, it's the current." But this is a terribly misleading statement. The implication is that a 1 milliamp power supply wouldn't kill you, but that a 1 amp supply would. But you very rarely find true 1 milliamp or 1 amp power supplies. So what we need to understand is why a 12 volt battery almost certainly won't kill you, and a 120V wall socket might, and a 1000 volt power line almost certainly will.
:::Let's suppose that the resistance across your body is 1000 ohms. (I think that's about right, if you overcome the higher resistance of normally dry skin. Perhaps your hands are wet, or you're applying the electrodes to open wounds.) Suppose further that if you pass a current from one hand to the other, across your chest, one tenth of the current flows through your heart, and the other nine tenths flow through other parts of your chest. (This is a number I just made up; I have no idea what the real current distribution through your chest might be. But this is just a thought experiment; we're not going to try this or anything; we're just getting a rough feel for what the numbers might look like, to mix a metaphor.)
:::Suppose you touch the two posts of a 12V car battery, one with each hand. [[Ohm's law]] says that a current of 12V ÷ 1000Ω flows, or 12 milliamps. If one tenth flows through your heart, that's 1.2 milliamps. Not enough to kill you.
:::Suppose you put yourself across 120V. Now the current is 120V ÷ 1000Ω, or 120 milliamps. A tenth of that is 12 milliamps, and we're definitely in the danger zone.
:::Now suppose the voltage is 1000 volts, or one kilovolt. The total current is 1000V ÷ 1000Ω = 1 amp, and a tenth of that is 100 milliamps, and you're probably dead. —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 04:43, 29 June 2007 (UTC)
::: P.S. A 500 milliamp power supply that's trying to source 3.5 amps will "overheat and catch fire" only if it's poorly made. Most power supplies limit their output current to their safe limit somehow (perhaps with a [[fuse]]), since [[short circuit]]s are so easy to accidentally complete.
:Sounds like you need to consider the difference between [[voltage]] and [[current]]. The total power might be the same, but a small amount of flow with a lot of force behind it is quite different from a large flow with very little force. Sometimes it's better to be shot by a BB gun vs caught in a car crusher, however, a water jet cutter can cut stone but Hoover Dam is just a giant stone holding up a lake. [[User:DMacks|DMacks]] 22:38, 28 June 2007 (UTC)
There's one more point that's worth making, although we've drifted pretty far afield from the original question about arc and spot welders.
Some of you may be wondering, why is there this asymmetry between voltage and current when it comes to power supplies? Why does a five volt, 1 amp power supply always try to give exactly five volts, but is perfectly happy delivering any current less than 1 amp?
The answer is that we're talking about constant-voltage power supplies, which are by far the most popular kind. But there is such a thing as a constant-current power supply, and for those, the situation is exactly reversed. The supply will do whatever it takes to make sure that the desired ''current'' flows, regardless of the resistance of the load. The higher the resistance of the load, the higher the supply's output voltage goes. But constant-current supplies have a maximum voltage they're capable of delivering. If the output resistance goes so high that it would take more voltage than the rated maximum to induce the requested current, the supply ends up breaking its promise, and supplying less current than requested. —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 04:58, 29 June 2007 (UTC)
:Fascinating stuff. It's interesting how, despite the fact that electricity has been around so long, there's still so much debate with respect to its effects on bodies. On its face, the apparent simplicity of Ohm's Law belies the actual complexity of the subject. It seems like there's a different answer for every scenario. And let me tell ya, for those of us who tend to learn by thinking in absolutes, this stuff can drive you insane. I do understand the concept of nominal voltage/current from power adapters, as well as the concept of actual current passed in the event your body becomes part of a circuit. It makes sense when I think of it like this: Say I'm swimming in the ocean and a lightning bolt hits nearby. Despite the massive amount of power and decent conductivity of saline water, my chances of survival would be based upon how far away I was from the strike. The arc welder and girder scenario seems to be no different. If I understand the answers correctly, assuming the girder isn't grounded, any current traveling to the end of the girder (where the hand was) is overcome by the girder's resistance, gradually dissipates and is just converted to heat?
:I guess my main problem is, as someone new to hobbyist-level electrical theory, all the variables make it difficult, if not overwhelming to reliably assess the danger potential for a given situation. For example, I do know that shorting a capacitor from a TV is a good way to make yourself quite dead, but for smaller, or less power-hungry electronics, (Ionic Breeze, clock radio, or an audio mixing board), finding the crossover from instant death/major pain/minor pain/no effect is a big gray area. Obviously, safety precautions should not be scaled down for perceived "safer" projects, but even with consistent safety, all these variables (moisture, temperature, proximity to, size, resistance & conductivity of the object, etc.) make it way more difficult than it probably should be. :)
: One last question regarding differing voltage vs amperage values in power supplies. Would it be correct to think of a device's voltage requirement as being the average voltage required to complete the circuit (by overcoming the cumulative resistance of all the components) and amperage being the power required to bring all the components in that circuit to a functional power level? That's the best description I can think of that makes sense.
:Anyway, thanks again for all the answers, they will definitely be kept and studied, probably repeatedly. :) [[User:97.82.254.213|97.82.254.213]] 00:32, 30 June 2007 (UTC)
= June 28 =
== Are all flamingos pink? ==
Are all [[flamingo]]s pink? --[[User:HappyCamper|HappyCamper]] 00:15, 28 June 2007 (UTC)
:Apparently not - [[Flamingo#Colour]] [[User:DuncanHill|DuncanHill]] 00:24, 28 June 2007 (UTC)
::OK, maybe I don't know how to ask this. Is there such a thing as a yellow flamingo, or a blue flamingo? --[[User:HappyCamper|HappyCamper]] 00:28, 28 June 2007 (UTC)
:::From the information I can find on the different species on Wikipedia - they are all pink (subject to diet and age), but the Andean Flamingo has yellow legs. [[User:DuncanHill|DuncanHill]] 00:33, 28 June 2007 (UTC)
::::If the flamingo ate blue food, would it become blue? [[User:Nimur|Nimur]] 01:03, 28 June 2007 (UTC)
:::::The color comes from particular compounds in their food, [[carotene]] if I recall correctly. -- [[User:Jsbillings|<span style="color:green">JSBillings</span>]] 01:16, 28 June 2007 (UTC)
::::According to [http://www.straightdope.com/columns/010518.html], blue algae contains carotene, and turns the flamingos pink anyway. [[User:Nimur|Nimur]] 01:18, 28 June 2007 (UTC)
:::::In zoos you'll often see whitish flamingos, since artificial dyes turning them pink are costly. Normally the dye is made from carrot oil and a substance derived from shrimp skins. '''''[[User:Bibliomaniac15|<font color="black">bibliomaniac</font>]][[User talk:Bibliomaniac15|<font color="red">1</font><font color="blue">5</font>]]''''' <sup>[[User:Bibliomaniac15/Enlarge your edit count|BUY NOW!]]</sup> 02:45, 28 June 2007 (UTC)
::::::OK, so the explanation for the color of flamingos has to do with their diet...I suppose, similar to why salmon are colored the way they are? --[[User:HappyCamper|HappyCamper]] 04:48, 28 June 2007 (UTC)
:::::::Red [[Domestic Canary|canaries]] too.[http://www.avianweb.com/redfactorcanaries.html] --[[User:Kurt Shaped Box|Kurt Shaped Box]] 08:24, 28 June 2007 (UTC)
:::::::According to the [[Salmon]] article, the red color in Salmon does come from [[Carotenoid|carotenoids]] in shrimp and krill. -- [[User:Jsbillings|<span style="color:green">JSBillings</span>]] 14:21, 28 June 2007 (UTC)
::::::::Have you ever seen ''[[Pink Flamingos]]''? If not, be warned - see Trivia, dot point 2. -- [[User:JackofOz|JackofOz]] 11:01, 28 June 2007 (UTC)
::In a zoo in Hungary they feed the flamingos with [[paprika]] to keep them pink because they can't afford shrimp. They looked fairly white to me though. —[[User talk:Pengo|Pengo]] 16:20, 28 June 2007 (UTC)
== Bird first aid ==
I have a cat and occasionally need to rescue birds or mice that she has caught and brought into the apartment. I want to do something to help the injured ones before releasing them back outdoors, but at the same time, I don't really want to do more than the minimum. I have an injured bird in a cage (actually a hamster carrier) and intend to release it as soon as it seems able to fly. Any suggestions on simple (i.e. inexpensive) things that might help a convalescing bird? [[User:Peter Grey|Peter Grey]] 05:01, 28 June 2007 (UTC)
:There is some advice from the RSPB [http://www.rspb.org.uk/advice/helpingbirds/health/injuredbirds.asp here], but its prospects of returning successfully to the wild are not good and if you can reduce or prevent injuries, for example by putting a bell on the cat, the birds will fare much better.--[[User:Shantavira|Shantavira]]|[[User talk:Shantavira|<sup>feed me</sup>]] 08:07, 28 June 2007 (UTC)
:::A bell on the cat would be very cruel to the cat - just imagine how big and noisy it is if you scale it up to human size. [[User:80.0.109.226|80.0.109.226]] 00:20, 30 June 2007 (UTC)
::The Quebec Society for the Protection of Birds may be able to help, website here [http://www.pqspb.org/] [[User:DuncanHill|DuncanHill]] 11:15, 28 June 2007 (UTC)
:::I mis-read your userpage, you are in Ontario. The Ontario Society for the Prevention of Cruelty to Animals has some factsheets, see [http://www.ontariospca.ca/4-wildlife-guidelines.shtml Guidelines for helping wildlife]
== Is this game a pyramid scheme? ==
How closely does a game such as [http://world5.knightfight.co.uk/?ac=vid&vid=115197120 this one] resemble a [[pyramid scheme]] or [[MLM]], keeping in mind that:
#Clicks on a link are AFAIK much less rivalrous than cash.
#Even if and once nobody was going to click any more recruit links ever, the game could still be succeeded at by the newer players. Although the players who had gotten the clicks would have a substantial advantage, this is probably true in most MMOGs anyway for the established players versus the new ones.
[[User:NeonMerlin|<span style="background:#000;color:red;border:#0f0 solid;border-width:1px 0">Neon</span>]][[User talk:NeonMerlin|<span style="background:#0f0;color:#000;border:red solid;border-width:1px 0">Merlin</span>]] 06:47, 28 June 2007 (UTC)
== Fibroblast growth factors (FGF) ==
Can anyone tell me when is the production of FGF in the body increase, ie other words, under what conditions? Also, where is FGF produced. Thanks for helping me out.
: I believe the article on [[Fibroblast growth factor]] and [http://dx.doi.org/10.1210/er.2003-0040 the review article] it refers to may satisfy your needs. Anything else? [[User:Lior|Lior]] 09:09, 28 June 2007 (UTC)
== recovering from nail-biting ==
hi,
For a long time I have bitten my finger nails excessively to the stage where now, the distance from my cuticles to the end of my nail doesnt reach the end of my finger, not even close. its pretty ugly. anyway, i'm trying to give up but have a niggling question. On perfect nails, the red bit (apologies for not knowing any medical terms) extends to the end of the finger and the "over hanging" nail is white. Now, on my nails when i allow the nail to grow it is also that white colour, but as my nails grow longer, will the red bit grow longer as well? or will i end up with ridiculous looking nails where the nail is normal length but half of it is white as opposed to just the end bit like most people. if this is the case, is there any, um, corrective surgery? basically, i want non-repulsive nails, how can i best acheive this. thanks! [[User:130.88.243.227|130.88.243.227]] 14:29, 28 June 2007 (UTC)
:The line between red and white on your nail is governed entirely by where your nail loses contact with the flesh below. For instance, after some injury that pulls the flesh and nail apart (thus turning red bit into white bit) the nail color will go back to normal not long after flesh and nail are back together. Even when an entire nail needs to be removed, it grows back normal. So I would expect your nails to eventually look perfectly normal once they grow back out. — [[User:Laurascudder|Laura Scudder]] [[User talk:Laurascudder|☎]] 21:35, 28 June 2007 (UTC)
::I wouldn't be so sure, after years and years of nail biting, the bit that used to be red would now be completely healed over, your nails may not go back to normal, or it may take a long time before they do, at any rate, having a slightly longer white bit then other people doesn't make you a freak. if you've stopped biting your nails, then they will get better, if you keep biting your nails they can only get worse.[[User:Vespine|Vespine]] 00:07, 29 June 2007 (UTC)
== toxic/ heavy metals ==
I need the introduction of toxic/ heavy metals.
Also i need the literature on method of separation toxic/ heavy metals by liquid membranes.
: A lot of the 'toxic heavy metals' are found in computers, so [[E-waste#Chemical_elements_contained_in_electronic_waste|here's]] a good place to start. Just click on each of the elements, see if they are heavy metals, and read about the ones that are. I was shocked to learn that about 90% of an old-style CRT monitor's weight is comprised of lead. Yuck![[User:Vranak|Vranak]]
:: The lead shielding was there to protect you from the radiation generated by the elecron gun/beam. So it's a good thing. Lead's also beneficial for optical quality--they use a small amount in eyeglasses.[http://www.drakehs.com/archive/05_29_07_tip.asp] — [[User:RJHall|RJH]] ([[User_talk:RJHall|''talk'']]) 22:44, 28 June 2007 (UTC)
::The good news is that the lead in a CRT is in the form of [[lead glass]], and [[vitrification]] is a very effective way of isolating toxic metals. --[[User:Carnildo|Carnildo]] 21:10, 29 June 2007 (UTC)
== Einstein's Concept of relativity.... ==
Hai Master minds.... I have a doubt in Einstien's Concept of relativity.I find that in my textbook,Under the heading [[Non Inertial Frames]]I find the following wordings
"A frame of reference is said to be a non inertial frame,when a body not acted upon by an external force,is accelerated".
Is this correct,and how can a body be accelerated without an external force?
:It means accelerated relative to the frame. So for example, in a car turning a corner, you feel pushed outwards. There is no force pushing you, but in the frame of the car you are being accelerated (i.e. if the car could see it would see you being accelerated and not know why.) Therefore a rotating frame (the turning car) is non-inertial. An accelerating frame (i.e. one not moving in a constant speed and direction) is non-inertial. This outwards 'force' you feel is called [[centrifugal force]] and is often said not to exist, or to be virtual, as it results not from a real force but from the movement of the car, and is only seen from the car's point of view. Hope that helps. [[User:Cyta|Cyta]] 16:58, 28 June 2007 (UTC)
:Yeah, like he/she said. You seem to have the correct instinct, i.e. that in a normal well-behaved frame of reference that can't happen; a non-inertial frame has to be funky is some way. Typically, it's because the frame of reference is being accelerated, like being rotated, or falling down a gravitational field. You can see how from the point of view of whoever is being accelerated, an object that is just sitting there looks like it's being accelerated the other direction. [[User:Gzuckier|Gzuckier]] 17:47, 28 June 2007 (UTC)
== Bohr Model ==
I'm wondering how the Bohr Model of the atom explains the reactivity of the alkali metals. I have already read the article on bohr model and alkali metals.
Is it something to do with the electrons?
Thanks [[User:217.41.217.24|217.41.217.24]] 16:53, 28 June 2007 (UTC)
:Yes chemistry is all to do with electrons! Basically atoms are stable with a full shell of electrons, the alkali metals need only lose one electron to get a full shell, so they are very reactive. There reactivity increases as you go down the group as the electron you lose is further from the positive nucleus attracting it, which is also shielded by the electrons in between. This makes it easier for the outer electron to be lost. That's obviously a very basic description, but it should explain the main features. The reactvity can be explained using this shell picture, but strictly speaking the [[Bohr model]] is a mathematical model referring to hydrogen. It is also requires a full quantum mechanical model to make any numerical predictions about reactivity ([[quantum chemistry]] might cover this.) [[User:Cyta|Cyta]] 17:03, 28 June 2007 (UTC)
== Our solar system. ==
Does our solar system have a name of its own, other than "our solar system"?
:I've seen a lot of science fiction call it Sol, the [[IAU]] seems to refer to it at [http://www.iau.org/SPELLING_OF_NAMES.240.0.html ''the'' Solar System] -_<sub>[[User Talk:Feba|ʇuǝɯɯoɔ]]</sub>[[User:Feba|ɐqǝɟ]] 17:43, 28 June 2007 (UTC)
:Hmm. more to the point, if our sun is Sol, what do we call the solar systems of other stars? [[User:Gzuckier|Gzuckier]] 17:48, 28 June 2007 (UTC)
:::We already call them "The XXX system" where 'XXX' is the name of the star. So, if we found planets orbiting Alpha Centauri, we'd talk about "The Alpha Centauri System". [[User:SteveBaker|SteveBaker]] 21:04, 28 June 2007 (UTC)
::I get the feeling we'll cross that bridge when we get to it --<sub>[[User Talk:Feba|ʇuǝɯɯoɔ]]</sub>[[User:Feba|ɐqǝɟ]] 17:53, 28 June 2007 (UTC)
:::[[Science fiction]] frequently uses [[Earth]] and [[Terra]] for our planet, and [[Sol]] for our sun; and hence "Solar" would probably refer to the system around Sol (presumably other star systems are not "solar systems" at all). However, since these are fictional works, there is significant room for [[artistic license]]. [[User:Nimur|Nimur]] 18:07, 28 June 2007 (UTC)
::::I suspect the reason SciFi uses "Terra" is because the name of the people who live here can be "Terrans" - which is much nicer than "Earthlings" which somehow makes us sound small and weak (like "Ducklings" or something!). The word "Sol" is widely used outside of SciFi - go to NASA's Mars rover web site for example - they talk about "Sols" - meaning one solar day on Mars. To complete the set - we now often call our moon "Luna" to distinguish it from other moons. This is a good way to think about things because if we ever do end up living on a planet orbiting another star, we're going to want to talk about "Sunshine" and "Sunrise" and not have to get into messes like "AlphaCentaurishine" or "Starshine". I doubt that people living on mars will talk about burying things in "regolith" - they'll still say "earth" (lowercase) as a synonym for "soil". I suspect that wherever humans live we'll end up talking about "The Sun" and "The Moon" as being the ones in the sky of wherever we live. But it's hard to guess what might happen that far into the future. [[User:SteveBaker|SteveBaker]] 21:04, 28 June 2007 (UTC)
:::::Maybe in the centuries it will take to perfect interplanetary / interstellar spaceflight, we'll make progress towards a universal language that makes sense. I've been a little disappointed with the [[Lojban|efforts]] [[Esperanto|so]] [[COBOL|far]]. [[User:Nimur|Nimur]] 05:23, 29 June 2007 (UTC)
:::::: (Please don't use the word ''[[COBOL|far]]'' - some of us are still trying to supress the terrible memories of that particular linguistic effort!) But I wonder who it will be who'll undertake to translate 1.8 million Wikipedia articles into this future universal language? The arrival of the Internet has done a lot to cement English as the universal language - and projects like Wikipedia can only serve to accentuate that. Any new language has an even larger uphill struggle than before to gain ascendancy - it's hard to imagine how that can happen. [[User:SteveBaker|SteveBaker]] 14:49, 29 June 2007 (UTC)
:The ''our'' in ''our solar system'' is redundant. We call the nearest star as Sun (or Sol). Solar system refers to the planetary system around Sun. The planetary systems around other stars wouldn't be called ''solar'' systems. I agree with SteveBaker ("the XXX system") -- [[User:wikicheng|Wiki'''''Cheng''''']] | [[User talk:wikicheng|Talk]] 05:10, 29 June 2007 (UTC)
::It's all the fault of those stoopid aliens who insist on saying things like "We'll be back in three of your earth days"...<sigh>. [[User:SteveBaker|SteveBaker]] 14:49, 29 June 2007 (UTC)
:::Doesn't the Astronomical Union have a standard for this? [[User:Retarius|Retarius]] 03:14, 30 June 2007 (UTC)
== Twin paradox ==
this is a spesific example of the twin paradox...
<blockquote>
Specific example
''
Consider a space ship travelling from Earth to the nearest star system: a distance d = 4.45 light years away, at a speed v = 0.866c (i.e., 86.6% of the speed of light). The round trip will take t = 2d / v = 10.28 years in Earth time (i.e. everybody on earth will be 10.28 years older when the ship returns). Those on Earth predict the aging of the travellers during their trip will be reduced by the factor \epsilon = \sqrt{1 - v^2/c^2}, the reciprocal of the Lorentz factor. In this case ε = 0.5 and they expect the travelers to be 0.5×10.28 = 5.14 years older when they return.
The ship's crew members also calculate how long the trip will take them. They know that the distant star system and the earth are moving relative to the ship at speed v during the trip, and in their rest frame the distance between the earth and the star system is εd = 0.5d = 2.23 light years ("length contraction"), for both the outward and return journeys. Each half of the journey takes 2.23 / v = 2.57 years, and the round trip takes 2×2.57 = 5.14 years. Their calculations show that they will arrive home having aged 5.14 years, in complete agreement with the calculations of those on Earth.
If a pair of twins were born on the day the ship left, and one went on the journey while the other stayed on earth, the twins will meet again when the traveller is 5.14 years old and the stay-at-home twin is 10.28 years old. This outcome is predicted by Einstein's special theory of relativity. It is a consequence of the experimentally verified phenomenon of time dilation, in which a moving clock is found to experience a reduced amount of proper time as determined by clocks synchronized with a stationary clock. Examples of the experimental evidence can be found at Experimental Confirmation of Time dilation.''
</blockquote>
My question is, wouldn't the people in the spaceship age twice as fast as the people on earth if one looked at the relative roles in reverse?(say that earth is moving at .866E and that the ship is stationary)
Im just curious as to why this situation cannot have reversed motion/benchmarks like other ones can./ cant the same thing apply to the people on earth making them age 10 years and those on the spaceship 5?
:It could be reversed if everyone was initially on the ship and then some hopped out and got on the Earth and then the Earth fired rocket blasters and accelerated off into space and returned 10 years later. The problem you are having is that you feel it is fine to jump from one point of reference to another. That makes it difficult. Instead, simply ask - which object has energy added to it? The ship is the one with the added energy for acceleration. The Earth stays the same. So, the ship is the one in which time slows down. -- [[User:Kainaw|Kainaw]]<small><sup>[[User_talk:Kainaw|(what?)]]</sup></small> 19:34, 28 June 2007 (UTC)
: Special relativity talks about how the world behaves as seen from an [[Inertial frame of reference|inertial reference frame]], i.e., one that doesn accelerate. We can do calculations with quantities (lengths and times) as measured from Earth since it is not accelerating (not very much at least). The spaceship, on the other hand, has to accelerate to get up to speed, turn around at the destination and slow down when it comes back. The formulas of special relativity can therefore not be expected to yield correct results, which is the reason we cannot simply swap the roles. —[[User:Bromskloss|Bromskloss]] 19:41, 28 June 2007 (UTC)
== Atomic Radius and Melting Point ==
What is the relationship between atomic radius and melting point? Why is this?
Thanks [[User:217.41.217.24|217.41.217.24]] 20:45, 28 June 2007 (UTC)
:Both are properties of chemical elements? Both are numbers? There are patterns to each, but no easy relationship or trend between these two properties. See our article about the [[Periodic table]] to learn about trends of various properties, and the [[atomic radius]] and [[List of elements by melting point]] for actual numbers to look for anything of interest. [[User:DMacks|DMacks]] 22:43, 28 June 2007 (UTC)
::But why for the alkali metals does the melting point decrease as the atomic radius increases?
I'm making a guess here and assuming someone credible has stated to you that there IS a relationship. With a large atomic radius, the electrons in the outermost shell are less strongly bound to the atom. This may mean covalent bonds between atoms are more easily broken up, lowering the melting point. But this is just a guess [[User:EverGreg|EverGreg]] 08:37, 29 June 2007 (UTC)
== Audubon copyrights ==
Are images of Audobon birds and animals now in the public ___domain since they are so old? Or has the Audobon family kept up with the copyright and owns all the images? I want to use a few audobon images in my artwork, but want to make sure its legal. thanks for your help with this.
:This is a legal question, which we're not supposed to answer. I will anyway; use this information at your own risk. [[John James Audubon]] died in 1851 and that means the [[United States copyright law#Duration of copyright|copyright in the U.S.]] on any work he did in the U.S. has expired long ago. Other countries have their own rules but I haven't heard of any ordinary copyrights lasting that long.
:By the way, please include a title so your questions are separated from the one before. I've added one for you. --Anonymous, June 29, 2007, 00:00 (UTC).
:[http://www.copyright.cornell.edu/training/Hirtle_Public_Domain.htm Copyright Term and the Public Domain in the United States]. [[User:152.16.59.190|152.16.59.190]] 06:30, 29 June 2007 (UTC)
= June 29 =
== One really strange effect... ==
Hello, I own one of those plasma bulb things, (you know what I'm talking about) and I noticed a really strange effect with it that doesn't make sense to me. If you turn on a plasma bulb and put something on it that can conduct electricity (metal works best) anything that touches the metal and can also conduct electricity has a static shock/charge with the metal. I was wondering if whether the electrons in the plasma bulb flow through the metal and jump to another object or if the plasma bulb negatively/positively charges the metal and it creates a charge similar to that of [[Lightning]] but on a much much smaller scale. Thanks for your time!- [[User:ECH3LON]]
:[[Capacitance]] allows high-frequency electricity ([[alternating current]]) to flow "through" [[Electrical insulation|insulator]]s such as the glass bulb of the [[plasma lamp]]. Enough electricity flows through that, concentrated by the metal rod onto a small area of your hand, you perceive it as an [[electric shock]].
:[[User:Atlant|Atlant]] 12:32, 29 June 2007 (UTC)
== hydrometallurgy in situ leaching ==
[[User:Eskall|Eskall]] 02:19, 29 June 2007 (UTC)What are the environmental or other hazards or risks, e.g. health and safety, associated with in situ leaching in mining operations?
:Typically the obvious problem is if the leached liquid runs off (heavy rain etc) it can contaminate nearby streams, soil contamination is also a possibility.[[User:87.102.4.153|87.102.4.153]] 12:01, 29 June 2007 (UTC)
::Normaly heavy metals are present as unsoluble sulfides or oxides and therefor are not mobile in the water (ground water), by leaching you mobilize them. The two incidents which makes the problem clear is the leaching of gold by [[potassium cyanide]], which is a really very toxic substance, and the other was tests with uranium leaching in east Germany which can create a poblem if by exident the now soluble and mobile heavy metal reaches the ground water.--[[User:Stone|Stone]] 12:13, 29 June 2007 (UTC)
== Largest cow ==
[[Image:Cow highland cattle.jpg|thumb|This [[Highland cattle|highland cow]] may not be the largest, but it is certainly the most attractive. [[User:Nimur|Nimur]] 16:52, 29 June 2007 (UTC)]]
Which is the biggest cow and cow race in the world? In terms of height, length, mass... I'm aware about the massive [[Piedmontese]] and [[Belgian Blue]] but was wondering if others were even larger though less muscular. --[[User:Taraborn|Taraborn]] 06:50, 29 June 2007 (UTC)
:According to this [http://www.lynehamvillage.com/news/misc/biggestcow270406.html Lyneham News] article Charolais are the largest breed. There is a [http://www-staff.it.uts.edu.au/~don/big/cow.jpg giant cow] near [[Nambour]] in Australia and [[Salem Sue]] in North Dakota, but these aren't what you are looking for. --[[User:TrogWoolley|TrogWoolley]] 09:53, 29 June 2007 (UTC)
::Strictly speaking, you are looking for [[cattle]]. A female African [[elephant]] seems to be the largest terrestrial cow, and the [[blue whale]] the largest sea-going cow, but those aren't what you're looking for either.--[[User:Shantavira|Shantavira]]|[[User talk:Shantavira|<sup>feed me</sup>]] 10:45, 29 June 2007 (UTC)
== If a Butterfly Flaps its Wings ==
I have heard a saying that goes something like this: if a butterfly flaps its wings in Mexico, that creates a hurricane in Japan (or something like that). Is there any truth to that, or is it an old wives tale / urban legend? If it is true, can you please explain the science behind it (in elementary terms). If it is not true, what is the origination of that saying and why does it persist? Or is it just a metaphor for something else? If so, what? Thanks. ([[User:JosephASpadaro|JosephASpadaro]] 07:37, 29 June 2007 (UTC))
:What you are referring to is the so-called [[butterfly effect]]. It is an expression which should by no means be taken literally, but the story is that the atmosphere is such a complex fluid environment that something as minor as the flap of a butterfly could determine (some time later, mind you) whether or not a major storm system will develop. This phenomenon is known as [[chaos]], or extreme sensitivity to initial conditions, first discovered by meteorologist [[Edward Norton Lorenz|Edward Lorenz]] in the 1960s. In a nutshell (sorry if I use too much math language), some systems (such as the earth's atmosphere) are governed by [[non-linear differential equation]]s. In an ideal mathematical situation, where you know the conditions at ''all'' points in a situation, it is possible to predict its future behavior accurately. However, since the supercomputers which simulate the weather take data from weather stations which are spread far apart, they must estimate the conditions between weather stations, and so do not know the exact conditions of the earth's atmosphere. Because the atmosphere is chaotic, the small difference between the actual atmosphere and the computer simulation compound to become large differences as the simulation wears on, making even rough weather prediction more than 10-14 days in advance practically impossible. One estimate is that even if we had weather monitoring stations every 1 meter in all directions, feeding data simultaneously into an infinitely powerful supercomputer, that computer could still not predict the weather with any certainty 30 days later. Hope I've helped, feel free to ask for clarifications! -<b><font color="black">[[User:Runningonbrains|Running]]</font><font color="blue">[[WP:METEO|On]]</font><font color="green">[[User talk: Runningonbrains|Brains]]</font></b> 07:50, 29 June 2007 (UTC)
:We have an article on the [[Butterfly effect]] which covers this, but it may be somewhat too technical. In short, for a complex, non-linear system like the weather, a very small change (a butterfly flapping its wings) may be magnified over time to a huge effect (a hurricane). --[[User:DrBob|Bob Mellish]] 07:48, 29 June 2007 (UTC)
:: Hmmmmmmmm. So, taken literally, it is or it is not true? That the butterfly's flap causes the hurricane ... ([[User:JosephASpadaro|JosephASpadaro]] 07:57, 29 June 2007 (UTC))
::: No. --<sub>[[User Talk:Feba|ʇuǝɯɯoɔ]]</sub>[[User:Feba|ɐqǝɟ]] 08:00, 29 June 2007 (UTC)
:::One way of thinking about chaos is to imagine a steep hill that has a ball precariously balanced at the very top. The slightest difference in the way you touch it will send it on its way downhill to a much different destination. So too with a butterfly's wings and the hurricane. Is it likely? No. Is it possible? Yes. [[User:Clarityfiend|Clarityfiend]] 08:19, 29 June 2007 (UTC)
:::I think we can say it's literally true that a butterfly flap may influence when and where a future hurricane or tornado starts and where it's heading. This takes into account conservation of energy. There's a whole lot of energy in a hurricane and that energy would have had to go somewhere, regardless of the butterfly flapping or not. [[User:EverGreg|EverGreg]] 08:31, 29 June 2007 (UTC)
::::My understanding of it is that every major event is underpinned by so many seemingly unconnected albeit equally prerequisite minor events that there is no way of determining what they all are as an exact science, hence chaos theory. Some may wonder whether if [[Franz Ferdinand]] had been shot, would there ever have been two world wars at all, but think of all the minutest changes in events preceeding that day in 1914 that may have spared his life and changed the course of the twentieth century. A butterfly perching on his shoulder, distracting him enough to move his jugular out of the bullet's trajectory perhaps? [[User:Bendzh|Bendž]]|[[User talk:Bendzh|Ť]] 08:45, 29 June 2007 (UTC)
:::::Well that's a more philosophical approach, I think Bendzh, and many would argue the long term causes of war would have been sparked by some other incident. But the real point is the mathematical one, that small changes in initial conditions lead to large changes in outcome. One problem is that the relation between accuracy of input (i.e. measurement of initial conditions) and accuracy of prediction are logarithmically linked. Which basically means (roughly) that increasing your accuracy of input by a factor 10, may only improve your predicition by a factor 2, increasing it by a factor 100 might only improve your prediction by a factor 3. We'll never know if an individual hurricane was caused by a butterfly Rather like global warming, although the tendency is to blame every bit of extreme weather on climate change, all we can really see are long term trends. [[User:137.138.46.155|137.138.46.155]] 11:42, 29 June 2007 (UTC)
:::::::A [[Paul Harvey]] news report yesterday marked the anniversary of the shootong of [[Franz Ferdinand]] in 1914. He said the motorcade route for the Archduke had been changed at the last minute due to security concerns after a bomb explosion earlier in the day, but his driver was not informed, and took the original route, carrying the car right by where the assassin was waiting. Perhaps someone forgot to mention it to him because of being distracted (maybe by a butterfly or a bumblebee?). In the Wikipedeia [[Assassination of Archduke Franz Ferdinand|article]] on the assassination there was a paragraph previously about chaos theory and the event, but it was removed. [[User:Edison|Edison]] 12:48, 29 June 2007 (UTC)
: The [[Fauna_of_the_Discworld#Quantum_Weather_Butterfly|Quantum Weather Butterfly]] has a lot to answer for! [[User:DuncanHill|DuncanHill]] 13:04, 29 June 2007 (UTC)
:In chaotic systems (like the weather) we find large scale stabilities (eg I'm guessing that there have been no hurricanes sweeping over the Sahara desert in all of recorded history - yet we can be fairly certain that at least a handful of them will be sweeping across the Atlantic on the next hurricane season) - but there are small-scale events that are utterly unpredictable (eg will it rain at the Town Hall in Cedar Hill, Texas on July 17th at precisely 2:43pm?). Even in theory, we cannot know enough information about the atmosphere to make even rather general predictions at this fine scale more than a day or so into the future. The position and momentum of every single atom in the entire earth, sun, moon system (and beyond) has a bearing on the weather - and a change in any one of those things could change precisely when and where a hurricane might happen at some time in the distant future - although we can be pretty sure that no matter what, it won't happen over the Sahara. But we can't say for sure which butterfly, on which wingbeat in which part of China is the cause of what future event. In a sense, they all have an influence - so it's true to say that things would have come out differently at some very fine scale of measurement if that butterfly hadn't chosen that moment to flap. But it's not really true to say that (for example) Hurricane Katerina was directly caused by a butterfly ten million years ago, because it was also caused by you failing to have an attack of hiccups on your third birthday because your mother wouldn't let you eat that extra slice of cake - and that cometary fragment that just missed the moon 10,000 years ago was also 'the cause'. This sensitivity to long-past events is the key here - but its' essentially INFINITELY sensitive - to the point where the [[uncertainty principle]] of quantum theory ends up being responsible (in part) for that same hurricane. The point here is that the butterfly wing analogy is not meant to be taken literally to be true - it's just a handy shorthand for chaos theory and sensitive-dependance-on-initial-conditions. [[User:SteveBaker|SteveBaker]] 14:36, 29 June 2007 (UTC)
:: This is probably obvious by now, but the point of the argument is obviously not that any butterfly flapping its wings necessarily will cause a hurricane, but that it ''might''. And even if, via some kind of total meteorological omniscience, we were to determine that a particular butterfly flapping its wings had caused a hurricane that otherwise would not have happened, we would also find that it was equally caused by (for example) a particular [[Bumblebee#Flight|bumblebee]] that did not flap its wings, and a particular passenger jet shedding some ice from its wings, and a particularly ravenous baseball fan wolfing down some [[Buffalo wings]], and a particular oldies fan fondly listening to [[Paul McCartney and Wings]]. So we can hardly blame the butterfly, let alone go after its liability insurance carrier to try to recoup the hurricane damage... --[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 14:51, 29 June 2007 (UTC)
== The Flight of the Bumblebee ==
When I was younger, I was told that aerodynamically speaking, a bumblebee should (theoretically) be unable to fly (due to some physics principles and the anatomy of the bee). Yet, bumblebees do in fact fly. Is there any truth to the statement that theoretically their anatomy should render flight impossible? Or is this an old wives tale / urban legend? If the statement is theoretically true, have scientists reconciled that with the reality that the bees do fly? How so? Please keep the science / physics explanations at an elementary level. Thanks. ([[User:JosephASpadaro|JosephASpadaro]] 07:37, 29 June 2007 (UTC))
:[[Bumblebee#Flight]] --<sub>[[User Talk:Feba|ʇuǝɯɯoɔ]]</sub>[[User:Feba|ɐqǝɟ]] 07:51, 29 June 2007 (UTC)
: Urban legend - perpetuating a pile of steaming nonsense - dating from a 1934 book (think about the state of the aeronautical sciences in 1934!) - that incorrectly applied the physics for a fixed wing aircraft to an animal that flaps its wings [http://www.paghat.com/beeflight.html]. Similar arguments were applied to the 'fact' that Dolphins can swim faster than physics says is possible. That one turned out to lead to some very interesting discoveries about micro-turbulance caused by the ingenious fine surface texture of the dolphins' skin. No laws of physics were broken - but it took some effort to understand why not! On a more serious note - if there is an outstandingly counter-example to a physical law - then that law has been overturned and it's no longer considered a law. If the bee's flight truly violated physics then you could be very sure that physicists would be working very hard indeed to understand what was wrong with those laws and coming up with new ones to replace them. Scientists get very excited indeed on those rare occasions when this happens because that's where the big breakthroughs and the Nobel prizes can be found! If something as easy to study as a bee lead to that kind of thing - they wouldn't be interested in billion dollar telescopes and atom smashers. [[User:SteveBaker|SteveBaker]] 14:09, 29 June 2007 (UTC)
::It's been said that the "payoff" sound in science isn't someone shouting "Eureka!" but is, instead, someone softly saying "How odd..."
::[[User:Atlant|Atlant]] 16:57, 29 June 2007 (UTC)
== When you push your eye... ==
What is the little black spot you can see on the other side of the eye? Also, I had an impact to my eye once (It's fine now though) that causes a large one of those. What are they? <font color="#33AAAA">Xhin</font> '''<font color="#CC0000">[[User:The_Thadman/Give_Back_Our_Membership|Give Back Our Membership!]]</font>''' 12:01, 29 June 2007 (UTC)
:I can't see one here, but are you referring to an [[entoptic phenomenon]]? --[[User:Shantavira|Shantavira]]|[[User talk:Shantavira|<sup>feed me</sup>]] 13:13, 29 June 2007 (UTC)
::I can't recommend poking your eye, but what you describe shows that the light sensitive receptors in the retina on the inside of the eyeball are also sensitive to pressure and produce [[Phosphenes]]. A professor once said that pressing on the eyeball could cause damage, but I don't have a source and we cannot give medical advice. Why do you see a spot at the left when you push on the right side of the eyeball? remember that the eye. like a camera, or a lens, makes an image that is upside down and backwards on the retina, so the right side of the retina "sees" things that are on the left. The "wiring" in the optic nerve and brains is such that we see things correctly. [[User:Edison|Edison]] 14:37, 29 June 2007 (UTC)
:::I've heard that pressing on your eye can briefly change its shape enough to improve performance on an eye exam. Again, definitely not recommended though. [[User:Dragons flight|Dragons flight]] 14:42, 29 June 2007 (UTC)
::::I suspect that pressing on your eye changes its shape, causing some of the light passing into your eye to be focused somewhere other than your [[retina]], causing a dark spot in your vision. I may be wrong, I have wondered this myself in the past.-<b><font color="black">[[User:Runningonbrains|Running]]</font><font color="blue">[[WP:METEO|On]]</font><font color="green">[[User talk: Runningonbrains|Brains]]</font></b> 18:15, 30 June 2007 (UTC)
== What's up with lightning? ==
I heard from a rather unreliable source that lighning today is stronger than it ever was before. I laughed at the time, but it got me thinking...
[[User:66.155.141.135|66.155.141.135]] 14:17, 29 June 2007 (UTC)
:[http://www.grida.no/climate/ipcc_tar/wg1/092.htm] says that a 1999 study found, based on 3 years of observations, that with "a 1°C increase in global wet-bulb temperature there is a 40% increase in lightning activity, with larger increases over the Northern Hemisphere land areas (56%)." But the data do not go back far enough to make me confident and clearly more recent data and analysis would be needed. Weather services installed a network of electromagnetic lightning detectors about 40 years ago [http://www.csu.edu.au/special/bushfire99/papers/brookhse/other/] , which allow them to record the ___location, polarity, and intensity of lightning strikes in the US. An accurate computerized system went in service in 1991[http://ghrc.msfc.nasa.gov:5721/sensor_documents/NLDN_antenna.html] to replace earlier less accurate manual plotting. The cited source says that the strokes which cause fires are the 20% which are positive, and of those the lower intensity, longer duration ones are the major starters of forest fires. [http://www.netweather.tv/index.cgi?action=lightning;sess=] is a live plot of lightning in the UK. The data exist to say whether the number and intensity of lightning strikes in the US is greater or lesser than when the network was put in service, but I haven't heard one way or the other. Data about the intensity of selected strikes, and the number of strikes st selected locations, (like the [[Empire State Building]]), and high voltage electrical lines and facilities, goes back for several decades, but again I don't know what trend they show. I know the number and intensity of lightning strikes varies wildly from day to day and year to year, so a seeming trend might be spurious and just part of normal variation. [http://thunder.msfc.nasa.gov/bookshelf/docs/white_paper_driscoll.html] is a global satellite lightning detection system which went in service in 1997, and the site says "The global lightning flash rate is on the order of 40 flashes per second (fps) as compared to the commonly accepted value of 100 fps, an estimate that dates back to 1925." Of course they had no satellite in 1925 so that figure was a pretty wild guess. This would allow trend tracking as we go forward, but an accurate large scale baseline does not go all that far back.[http://thunder.msfc.nasa.gov/bookshelf/images/white_paper_large_images/OTD1year.gif] is an interesting plot of lightning frequency worldwide. Lots in some areas, very little in others, such as Europe. [[User:Edison|Edison]] 14:52, 29 June 2007 (UTC)
::You can [http://nova.stanford.edu/~vlf/haarp/live.php WATCH] live lightning strikes detected on radio receivers! Most of these stations are located in Alaska, but they detect lightning strikes from all over the planet, because signals can travel very far via the [[skywave]] effect. Large vertical lines in these graphs indicate lightning strikes, and horizontal lines typically indicate AM navigation beacons. [[User:Nimur|Nimur]] 17:01, 29 June 2007 (UTC)
== Liquid metal technology ==
I need to have as much as information on Liquid metal tecchnolgy as possible. Its very less available on Wikipedis itself and on internet. Plz help me in that.
Thanks
:What happened when you searched Wikipedia for "liquid metal"? I just tried it and got an interesting page about [[liquid metal]]. Is that page not clear, not enough info, too advanced, or some other problem? The phrase "liquid metal technolody" can have many meanings, hard to provide specific info without knowing what meaning you have in mind. [[User:DMacks|DMacks]] 15:59, 29 June 2007 (UTC)
::Maybe you could read the [[Mercury (element)]] article? It is a liquid metal at room temperature and it can be used to make [[mercury thermometer]]s. [[User:Nimur|Nimur]] 17:04, 29 June 2007 (UTC)
:::Me, I assumed he was talking about the technology behind the [[T-1000]]. --[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 23:39, 29 June 2007 (UTC)
::::Which, to make the point explicit, is entirely fictional. --Anonymous, June 30, 2007, 01:30 (UTC).
== What is this plant? ==
Hi
I have taken a photo of a plant in my garden in Surrey, England[[User:Dp1st|Dp1st]] 18:23, 29 June 2007 (UTC) which can be viewed here:
http://en.wikipedia.org/wiki/Image:Exoticplant.jpg
Can anybody tell me what this plant is. I've never seen one like it before.
Thanks
David Furst
:Looks like some kind of [[anthurium]].--[[User:Shantavira|Shantavira]]|[[User talk:Shantavira|<sup>feed me</sup>]] 18:49, 29 June 2007 (UTC)
::I think it is Dracunculus vulgaris, known as the Voodoo Lily, Dragon Lily or Dragon Arum. It is native to the Mediterranean and a member of the Araceae (Aroid Family). Anthurium is also an aroid. The family is distinguished by the unique inflorescence consisting of a spathe and spadix. Very peculiar. --[[User:Eriastrum|Eriastrum]] 15:37, 30 June 2007 (UTC)
== How to explain holding a balloon in an air stream? ==
A friend of mine asked me if I know the reason why a balloon can be suspended oscillating slightly up and down in a constant air stream. For example, if you place a fan pointing at an angle up, and a balloon at just the right distance in the air flow, the balloon will be suspended relatively in place in midair even when the fan isn't pointing straight up. I've seen a similar demonstration at a science museum where a person moved a dodgeball around in midair using a nozzled leaf blower.
I wasn't sure what the exact mechanism is, though. I think it's related to the Bernoulli Effect or the Magnus Effect (as the balloon moves in the air flow the velocity and hence pressure of the air around the balloon is different on different sides), but I was looking for a more detailed explanation. Thanks! [[User:Dugwiki|Dugwiki]] 20:02, 29 June 2007 (UTC)
:Consider the fan-pointing-up case: the way it works is that when the balloon starts to drift to the left, say, the air on the balloon's right will cling to its right side (due to the [[Coandă effect]]), snake around the top of the balloon, and then jet off to the left. While doing so, the air [[Newton's third law|pushes back]] on the balloon's right side, so imparts a rightward force which will send it back to the center.
[[Image:Coanda_Spoon.jpg|thumb|right|100px|Coanda effect as demonstrated with a spoon and a water stream. ]]
:Consider the spoon at right. As the water jets off to the left due to the Coandă effect, a (tiny) equal and opposite force pushes the spoon to the right.
:[http://www.flyingcircusofphysics.com/News/NewsDetail.aspx?NewsID=24 Here's] a blurb about it from the author of the *wonderful* book "[http://www.amazon.com/Flying-Circus-Physics-Answers/dp/047102984X/ref=si3_rdr_bb_product/102-2464019-1357708 The Flying Circus of Physics]", which has several hundred answers to questions along these same lines. --[[User:TotoBaggins|TotoBaggins]] 20:55, 29 June 2007 (UTC)
::Such a device is commonly known as a [[Bernoulli blower]] ([[Chad (graffiti)|wot, no article?]]). A Google search comes up with quite a few interesting articles about them... [[User:Smurrayinchester|<span style="color:#00BB55">Laïka</span>]] 23:51, 30 June 2007 (UTC)
== Can tooth enamel be restored? ==
A brand of toothpaste claims "Liquid calcium (r) technology fills in tooth surfaces to naturally restore lost surface enamel for whiter teeth". Comparing the list of ingredients with another toothpaste suggests that the active ingrediants are [[calcium sulphate]], [[sodium carbonate]], and possibly [[dipotassium phosphate]] - which seem to be [[plaster of paris]], [[washing soda]], and fertiliser.
Is this just a [[gimmick]] or is there any scientific support for this claim please? [[User:80.0.109.226|80.0.109.226]] 23:20, 29 June 2007 (UTC)
:See [[tooth enamel]] -- [[User:Kainaw|Kainaw]]<small><sup>[[User_talk:Kainaw|(what?)]]</sup></small> 23:29, 29 June 2007 (UTC)
:Does anyone remember the toothpaste ad in the UK that claimed that the stuff advertised worked by splitting water molecules during brushing and releasing 'active oxygen' into the mouth for a deeper clean? That was probably the clearest example of 'bollocks science' I've ever seen in an advert - even moreso than some of the claptrap that the hair and skincare ads come out with. --[[User:Kurt Shaped Box|Kurt Shaped Box]] 23:47, 29 June 2007 (UTC)
I have read the article on tooth enamel and it does not answer the question. The same toothpaste company is now advertising a slight variation on "liquid enamel" which is now said to be "zinc activated". As tooth enamel naturally thins and cracks as you get older (one of the reasons why younger people have whiter teeth) then it would be great if it could in truth be restored.
:I believe the article clearly states there is no way currently to "regrow" enamel. - [[User:Dozenist|Dozenist]] <font color="darkgreen" size="1">[[User talk:Dozenist|talk]]</font> 02:14, 30 June 2007 (UTC)
I cannot see where in the article it says that. In addition, its not true. As my experienced and highly-qualified [[NHS]] dentist told me some years ago, that used to be what was thought, but more recently it has been found that teeth can naturally repair small (probably very small I imagine) amounts of enamel damage, which was why she was not being so gung-ho with the drill as previously. In fact the article on [[Fluoride therapy]] says "The presence of this fluoride in turn attracts other minerals (such as calcium), thus resulting in the formation of new tooth mineral", implying that tooth enamel can increase. Whether "liquid enamel" is a gimmick or not is another matter. Looking in a supermarket this morning found another variant of the same "liquid enamel" toothpaste, so its got at least three different formulations. [[User:80.2.194.68|80.2.194.68]] 10:15, 30 June 2007 (UTC)
:Though [[User:Dozenist|Dozenist]] says he is a dentist, and I'd hate to argue this with a dentist, I too had heard from reputable sources (including my own dentist on my last visit a month ago) that it is possible to reverse minor damage before cavities form with careful, thorough brushing. Perhaps this is a different thing than ''regrowing'' enamel? --[[User:Jjron|jjron]] 12:11, 30 June 2007 (UTC)
== Shaggy cows? ==
Just seen the picture of the [[Highland cattle|highland cow]] above. Question. How on earth is the cow able to see where it's going with all that hair hanging down over its eyes? I suppose that I could ask the same thing about [[dulux dog]]s... --[[User:Kurt Shaped Box|Kurt Shaped Box]] 23:35, 29 June 2007 (UTC)
:I guess they can see through the thatch adequately for their needs, i.e. "there's some grass, there's another cow, oh there's a rambler...." Now you know why [[bull-fighting]] never really took off in the [[Scottish Highlands]].--[[User:Shantavira|Shantavira]]|[[User talk:Shantavira|<sup>feed me</sup>]] 07:05, 30 June 2007 (UTC)
Oh I've had my hair like that, it's not a big deal. It's kinda like when you're taking off a t-shirt, and it gets so close to your eyes you can see through it, except even more transparent. It's nature's sunglasses! --<sub>[[User Talk:Feba|ʇuǝɯɯoɔ]]</sub>[[User:Feba|ɐqǝɟ]] 10:23, 30 June 2007 (UTC)
It's like net curtains, where you can see out, but not in.
Actually, looking carefully at the picture, it looks like it's eyes aren't actually covered by the hair. Being a herbevore, its eyes are on the sides of its head, where the hair is slightly shorter.
= June 30 =
== Black spots in front of eyes after vigorous coughing? ==
I got some food stuck in the wrong pipe this evening and was coughing and spluttering hard for several minutes. After I managed to dislodge the morsel, I sat around to catching my breath and clearing my throat. It was then that I noticed (whilst staring at a white wall) many tiny black spots swimming around and blinking in and out of existence in front of my eyes. What was that all about? Does WP have an article on this phenomenon? --[[User:Kurt Shaped Box|Kurt Shaped Box]] 00:42, 30 June 2007 (UTC)
:You were '[[seeing stars]]'.[http://www.medhelp.org/forums/eyecare/archive/142.html] So no article under that title--[[User:Tugjob|Tugjob]] 00:49, 30 June 2007 (UTC)
::The article is called [[phosphene]]. [[Seeing stars]] should redirect there, and now does. --[[User:mglg|mglg]]<sub>([[User talk:mglg|talk]])</sub> 01:22, 30 June 2007 (UTC)
:::Some people notice that phenomenon in the presnece of low blood sugar or low blood pressure. Don't know how that relates to coughing. [[User:Edison|Edison]] 05:20, 30 June 2007 (UTC)
== manufactured prescription drugs ==
I am trying to find out in what year was the first manufactured prescription drug made and wha was it, like the name of it and who manufactured it and what was it for?
I am a certified pharmacy technician and I think this would make a great trivia question to discuss with my pharmacist.
:[[Medical prescription#History]] claims that prescriptions have been around since "the beginning of history." This section could use some copy editing! [[User:Nimur|Nimur]] 01:39, 30 June 2007 (UTC)
::See also [[Galenic formulation]], named for [[Galen]]; [[Hippocrates]], even earlier... and of course, [[Timeline of medicine and medical technology]]. [[User:Nimur|Nimur]] 01:42, 30 June 2007 (UTC)
:::This is actually a reliable source, being an accredited, degree-granting institution with a college of Pharmacy... but I can't help but wonder if they are seriously suggesting [http://www.pharmacy.wsu.edu/History/history01.html that cavemen were pharmacists]... [[User:Nimur|Nimur]] 01:49, 30 June 2007 (UTC)
::::Pharmacists and doctors in the 19th century had little machines to compress medicine into pills. Does this amount to manufacturing? In the 19th century, companies put "patent" medicines, which might contain alcohol and opiates, into bottles with labels expounding all the things the medicine "cured." Was that manufacturing? [[User:Edison|Edison]] 05:19, 30 June 2007 (UTC)
== Job ==
I have a job that involves me being on my feet nearly the entire time and crouching down. Is there any way I can avoid hurting my feet or back while at work?[[User:71.218.35.192|71.218.35.192]] 03:22, 30 June 2007 (UTC)
:Softer shoes perhaps? --[[User:JDitto|JDitto]] 04:14, 30 June 2007 (UTC)
well, i have to wear dress shoes[[User:71.218.35.192|71.218.35.192]] 04:32, 30 June 2007 (UTC)
:If you have to stay standing for long periods, its best to try to lean forward a little while you are standing so your weight is more on the balls of your feet than the heel. It really works, especially if you're in smart shoes. [[User:Tree Kittens|Tree Kittens]] 06:16, 30 June 2007 (UTC)
::As for back pain, I find back exercises such as [[pull-ups]] (or if that's too easy for you, pull-ups with weight) to cure it really fast. Of course, I'm not a physician and I can't see your particular case, I just dropped it here because it may be useful for someone. --[[User:Taraborn|Taraborn]] 07:06, 30 June 2007 (UTC)
:::You may need to see a doctor and get [[orthotics]] fitted and made for you. My niece had to do this - they're not cheap (over AU$300 plus the doctors fees), but she says they do work and can be worn with most shoes, other than open shoes. --[[User:Jjron|jjron]] 13:39, 30 June 2007 (UTC)
:I had a job that involved me standing and walking all day (it was in the back room of a store). I found that bringing an extra pair of tennis shoes helped a lot — when I was out of sight of customers, I would slip into them. --[[User:24.147.86.187|24.147.86.187]] 14:47, 30 June 2007 (UTC)
== If a Tree Falls in the Forest ... ==
Perhaps this is a naive question, but ... how has science resolved the dilemma presented in "If a tree falls in the forest, and no one is there to hear it, does it make a sound?" ...? Thanks. ([[User:JosephASpadaro|JosephASpadaro]] 04:33, 30 June 2007 (UTC))
:See [[If a tree falls in a forest]]. [[User:152.16.188.111|152.16.188.111]] 04:46, 30 June 2007 (UTC)
::Ignoring the human-centric philosophical mumbo-jumbo in the article that underlies and 'explains' this 'dilemma', if you want a simple answer, think about the physics. A falling tree needs to convert a lot of [[Potential energy#Gravitational potential energy|gravitational potential energy]] into other forms of energy. As it falls this will be largely (but not entirely) [[kinetic energy]], when it hits the ground, this will then be converted again, mainly to [[heat]] and [[sound]] energy. So there's the answer, ''of course it makes a sound'', physics couldn't give a damn whether or not there's a human there to hear it. Oh, BTW, I always liked Bart Simpson's solution to that other dilemma, [[Koan#The sound of one hand|what is the sound of one hand clapping]]. --[[User:Jjron|jjron]] 13:08, 30 June 2007 (UTC)
::Strictly scientifically, [[sound]] is the vibration of matter. When a tree falls, it most certainly creates vibrations in the ground, in the air, and as a propagating [[sound wave]]. The question at hand is a philosophical inquiry against the rigid definition of sound by bringing in the element of "human perception." Science neatly sidesteps this issue with a careful definition. '''Without doubt, sound is produced.''' [[User:Nimur|Nimur]] 17:06, 30 June 2007 (UTC)
It's very simple: if by "sound" you mean "sonic vibrations trough air or another medium", then yes, clearly sound is produced. If you mean "perception of sonic vibrations by a human being", then equally clearly, there is no sound. If you're not sure what you mean, you can debate this forever. There's probably a lot of similarity to the debate over whether animals feel pain. —[[User:Ummit|Steve Summit]] ([[User talk:Ummit|talk]]) 17:19, 30 June 2007 (UTC)
== Blood-sampling for measurement of sex-related hormones ==
How can we measure sex hormones and other sex-related hormones, like hormones related to sex-attraction and sex-excitement at the time of sexual intercourse, such as testosterone, adrenaline, etc.? In other words, when during the day and where in the body can we measure these hormones?
After extracting the blood sample, how long it can be preserved by freezing and on which temperature?
I hope you'll answer my question soon. Thank you
[[User:217.132.193.68|217.132.193.68]] 12:14, 30 June 2007 (UTC)
== FGFR ==
When is there an overexpression of Fibroblast Growth Factor Receptor in our body, as in under what circumstances or any stimuli?
:This sounds like '''homework.''' But maybe not, and I will [[WP:AGF|assume you are just curious...]] we have an article about all of the following:
*[[fibroblast]]
*[[fibroblast growth factor]]
*[[fibroblast growth factor receptor]]
:Maybe the answer will be self-evident if you even very briefly skim any of these articles... [[User:Nimur|Nimur]] 17:10, 30 June 2007 (UTC)
== event horizon ==
Where does all the energy come from to keep the last image of something falling into an event horizon frozen on the surface? Surely there are only so many photons bouncing off it when it passes the event horizon- wouldn't they basically all be escaped or sucked in within a very short time?
Also what would happen if you sent a giant clump of antimatter into a black hole? A giant enough clump that not enough matter is left to trap light and maintain an event horizon. Would it still be considered a singularity even if the remaining piece of the black hole is still solid matter? --[[User:Froth|'''froth''']]<sup>[[User_talk:Froth|<small>t</small>]]</sup> 15:05, 30 June 2007 (UTC)
: Sounds like you're basing your definitions of an [[Event horizon]] off of science fiction rather than science. Any thing passing the event horizon would not be viewable to someone outside of it, since light wouldn't be able to escape. Also, if you dropped a lot of antimatter into a black hole, you'd just be adding mass, not removing it. The [[First law of thermodynamics]] still holds. -- [[User:Jsbillings|<span style="color:green">JSBillings</span>]] 19:25, 30 June 2007 (UTC)
:From the viewpoint of a distant observer, time slows down for the object falling into the black hole. It is true that the distant observer will never see the object cross the event horizon. However, as it approaches the event horizon its image will undergo increasing [[gravitational redshift]], so fewer and fewer photons with less and less energy reach the distant observer. [[User:Gandalf61|Gandalf61]] 19:44, 30 June 2007 (UTC)
:To amplify what the previous posted said: a black hole messes with ''time'' in a big way. Infalling stuff appears to be "frozen" only from the point of view of an outside observer, since time runs at very different rates very near vs. very far from a black hole. Regarding the second question, for stuff inside an event horizon, distinctions between matter, antimatter, and energy lie somewhere between irrelevant and nonexistent. If you dump ''anything'' into a black hole, you just end up making it bigger. --[[User:Tugbug|Tugbug]] 20:06, 30 June 2007 (UTC)
:To answer the antimatter question more concretely: When matter and antimatter come into contact outside of a black hole, they produce gamma rays which then escape. The energy content of the gamma rays is the same as the total energy content of the matter and antimatter. If the same thing happened inside a black hole, the gamma rays wouldn't be able to escape, so all the energy would remain inside the black hole and its gravitational field wouldn't change. (Remember, in general relativity, all energy creates a gravitational field, not just energy in the form of matter.) —[[User:Keenan Pepper|Keenan Pepper]] 21:37, 30 June 2007 (UTC)
== water purification of plants ==
how plants can discern the particles of substances and elements , with what special characteristic of them?
and it would be nice if there is useful links and references.
:It is a simplification to assume that plants purify toxins out of the ecosystem. In fact, [[biomagnification]] discusses the rapid concentration of heavy metals by accumulating in algae and upwards through the [[food chain]] - a convenient counterexample to the common idea of "purification". However, wetlands do serve as a sort of eco-filter. You may also want to read about [[wetlands]] and [[wetland#Wetland functions|their function]] in an ecosystem. "[[Denitrification]] is arguably the most important of these reactions because humans have increased nitrate worldwide by applying fertilizers."
:How does it work? At the cellular level, [[facilitated diffusion]] is about the simplest mechanism that enables plants to "discern" particles; more advanced control and selection can be obtained with more complex cellular processes. [[Plant anatomy]] discusses the structures in a plant; [[vascular plant]] discusses a more elaborate structural level. [[User:Nimur|Nimur]] 17:15, 30 June 2007 (UTC)
== TV letterbox and 16:9 TVs ==
We have conventional 4:3 TVs. Some programs are in letterbox, for instance on [[The History Channel]] right now is one in an aspect ratio that I measure as 1.62. If we get a 16:9 TV (a 1.78 aspect ratio), will the picture fill the screen vertically, and have black bands on the sides? [[User:Bubba73|Bubba73]] [[User talk:Bubba73|(talk)]], 20:26, 30 June 2007 (UTC)
:It depends on your settings. Usually, Wide screens have settings for Normal: what a 4:3 looks like; Stretch: a 4:3 made to fit the entire screen; Zoom: zoomed in to the image, so it takes the entire screen, which is what wide screen format uses in my experience (which isn't much, I just own one, i'm not technically inclined with TVs), and zoom stretch, which is just painful --<sub>[[User Talk:Feba|ʇuǝɯɯoɔ]]</sub>[[User:Feba|ɐqǝɟ]] 20:55, 30 June 2007 (UTC)
== Microwave oven accident ==
(silly thing to ask but) I've accidentally placed in my [[microwave oven]] some food which was rolled in an aluminium foil and paper container (one side paper, the other alu). It was touching the door, it caught fire and scolded the inside of the door. Is my oven now safe to use? From what the oven article says, I guess it is ie there won't be any wave leakage or something but i'd like your take. Thank you!
:We can't give advice on something which could very well post a medical (and property) hazard. Your best bet is probably to buy a new one, they aren't so expensive that it's worth the risk IMO --<sub>[[User Talk:Feba|ʇuǝɯɯoɔ]]</sub>[[User:Feba|ɐqǝɟ]] 20:53, 30 June 2007 (UTC)
:Is that ''scolded'' is a typo for ''scorched'' or something? —[[User:Keenan Pepper|Keenan Pepper]] 21:29, 30 June 2007 (UTC)
::I assumed they meant [[wikt:scald|scald]]ed. --[[User:ColinFine|ColinFine]] 22:08, 30 June 2007 (UTC)
:::Generally, any damage to a microwave oven, especially the door, should be treated as a [[catastrophic failure]]; the door contains a very cleverly designed shield to prevent the microwaves from escaping, and damage to that means that the whole kitchen is potentially at risk from the possibly dangerous levels of microwave radiation (in particular, damaged microwave doors can cause cataracts)[http://www.informaworld.com/smpp/content~content=a769886983~db=all]. Replace it. [[User:Smurrayinchester|<span style="color:#00BB55">Laïka</span>]] 22:59, 30 June 2007 (UTC)
::::The door contains a metal mesh between two glass plates. As long as the metal mesh and the rest of the metal casing is fully intact, the microwave is safe. If there is any hole in the shielding, the microwave is dangerous. So if you just have a layer of ash on the inside of your door, clean it and thats it. There is no clever designed shield, unless you call a plate with small holes a clever design.
== Hybrids different... how do you call this? ==
[[Hybrid]]s may vary in [[phenotype]], depending on the respective sex of the parent species. A [[Mule]] and a [[Hinny]] are different, as are a [[Liger]] and a [[Tigon]]. But how do you call this kind of differences? Are they investigated and analyzed? How do you call the science doing so? --[[User:Thick Peter|Thick Peter]] 23:31, 30 June 2007 (UTC)
= July 1 =
== Why are antistatic bags pink? ==
Why are antistatic bags pink? Yes there are blue/silver ones too but pink I dont get. Is there a reason or not?
Studying Comptia A+ and questions keep coming up like "what colors are antistatic bags" -- why pink?
wikipedia link [http://en.wikipedia.org/wiki/Antistatic_bag]
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