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= April 24 =
= August 17 =
== Programming Languages ==
== flocking and threshold ==
Hello. I'm a beginning programmer. Two years ago, I tried to learn Visual C++ .NET. That was really, really hard. I wasn't able to do anything besides the tutorial in the book, so I quit. About four months ago, I picked up Liberty BASIC. I am able to do a lot and understand the language. I really enjoy it and am doing a lot of fun stuff. I wondered if anyone had any suggestions on other languages to try next or any suggestions about a good progression of languages for a learning programmer. Any stories about what you did, what you wish you did, or just simply any advice you have would be great. Thanks for your help. --[[User:Think Fast|Think Fast]] 01:23, 24 April 2006 (UTC)
[[Boids]] provokes a question:
:[[FORTRAN]] would be a good next step, as it is rather similar to BASIC, but more powerful. I agree that C++ is one of the most difficult to learn. [[User:StuRat|StuRat]] 01:55, 24 April 2006 (UTC)
Each boid adjusts its position and velocity to those of (I guess) its N nearest neighbors; and/or those within a distance R. Does varying N or R make the behavior resemble that of different real bird species? [[User:Tamfang|—Tamfang]] ([[User talk:Tamfang|talk]]) 03:04, 17 August 2025 (UTC)
::But does anyone still use Fortran though? GCC still compiles it, but I can only remember one program written in it. In fact I think I've encountered more programs written in [[Ada programming language|Ada]]. I suggest [[Python programming language|Python]]. —[[User:Keenan Pepper|Keenan Pepper]] 02:21, 24 April 2006 (UTC)
:With the AI's assistance, I found this article [https://pmc.ncbi.nlm.nih.gov/articles/PMC3324025/ Statistical Mechanics for Natural Flocks of Birds] that states, based on field data, "...interactions are ruled by topological rather than metric distance." Boid models must account for these and other factors. [[User:Modocc|Modocc]] ([[User talk:Modocc|talk]]) 19:12, 17 August 2025 (UTC)
::::I do ! [[User:StuRat|StuRat]] 03:21, 24 April 2006 (UTC)
::This is a great paper, do you have any more like it? [[User:Gongula Spring|Gongula Spring]] ([[User talk:Gongula Spring|talk]]) 18:03, 26 August 2025 (UTC)
:::No, I do not. [[User:Modocc|Modocc]] ([[User talk:Modocc|talk]]) 20:45, 26 August 2025 (UTC)
:The Introduction section of the paper describing the boid model<sup>[https://dl.acm.org/doi/10.1145/37401.37406]</sup> contains this passage:
:::I still encounter it occasionally for scientific code, but it's pretty rare. Nowadays I'd use Matlab or similar for anything that could be run on a single workstation. Perhaps a lurking cluster-user can tell me if the parallelized versions are still used over there.
::"The success and validity of these simulations is difficult to measure objectively. They do seem to agree well with certain criteria and some statistical properties of natural flocks and schools which have been reported by the zoological and behavioral sciences. Perhaps more significantly, many people who view these animated flocks immediately recognize them as a representation of a natural flock, and find them similarly delightful to watch."
:In the Conclusion section, the author writes:
::"The animations showing simulated flocks built from this model seem to correspond to the observer's intuitive notion of what constitutes 'flock-like motion.' However it is difficult to objectively measure how valid these simulations are."
:Furthermore, in the description of the model, we read:
::"The flock model presented here is actually a better model of a school or a herd than a flock [of birds]."
:In particular, it appears that natural birds look further ahead than artificial boids, perceiving the approach of a 'manoeuvre wave' and anticipating its arrival.<sup>[https://www.nature.com/articles/309344a0]</sup> So there is no claim, express or implied, that this is a valid model for flocking behaviour, but merely that it looks convincingly similar. It is not a scientific article about animal behaviour but a technological article about a difficult aspect of [[Computer-generated imagery|CGI]].
:While there have been a few studies on the properties of actual biological flocks, these seem to have been with respect, each time, to a single species, reporting the observations in a non-standardized way that makes comparisons of different species almost impossible. How well turning the N and R knobs make the boid-model simulation resemble the natural flocking behaviour of different flocking bird species will depend on the subjective judgement of observers familiar with these specific behaviours. ​‑‑[[User talk:Lambiam#top|Lambiam]] 09:47, 18 August 2025 (UTC)
Thanks both! [[User:Tamfang|—Tamfang]] ([[User talk:Tamfang|talk]]) 23:43, 21 August 2025 (UTC)
::::I know that [[Folding@home]] is written in FORTRAN. As it is the oldest language, it has the best compiler and is one of the fastest available languages. Personally, I write in [[Java]], as it's what my University teaches. I enjoy it, but feel that C++ is more useful for actual, real-world, coding. Many business applications are written in BASIC. Whatever you choose, it should have some sort of [[Object oriented programming | Object]] use. --[[User:yaninass2|yaninass2]] 05:11, 24 April 2006 (UTC)
= August 19 =
:::For a learning language, Turing isn't a bad choice, but it isn't used outside of programming courses. I've heard Python recommmended, but haven't tried it myself. --[[User:Christopher Thomas|Christopher Thomas]] 03:07, 24 April 2006 (UTC)
== Is the speed of light constant, when measured by a '''remote inertial''' observer, who '''non-locally''' measures a photon traveling a long way in a '''curved''' vacuum? ==
::I too recommend [[Python programming language|Python]] even though that that wasn't my first programming language. I start with [[C programming language |C]] which I don't think that I would recommend. C could be good for understanding low level programming but otherwise I wouldn't recommend it. Python has a large standard library, a neat readable syntax and garbage collection. The major downside with Python is that the dynamical typing (which is a nice feature) makes you get more errors when running the program instead of when compiling. [[user:Jeltz|Jeltz]] [[user talk:Jeltz|<small>talk</small>]] 11:14, 24 April 2006 (UTC)
I'm asking, because our article [[speed of light]] states confusingly: {{tq|'''"In non-inertial frames of reference (gravitationally curved spacetime or accelerated reference frames)'''...the speed of light can differ from c when measured from a remote frame of reference".}} This sentence seems to ignore the situation I'm asking about, when the remote observer's frame of reference is '''inertial''', but the spacetime the light travels through is '''curved'''. [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 08:32, 19 August 2025 (UTC)
::::(after edit conflict) We've had this discussion many times before (such as [[Wikipedia:Reference_desk_archive/Science/March_2006#Learning_Computer_Programming|here]] and [[Wikipedia:Reference_desk_archive/Science/December_2005#Entry_into_programming|here]]) - it depends a bit on whether you want to learn to program (the abstract concept) or whether you want to learn to program in order to write something specific. [[Fortran|FORTRAN]] (yes, I use it too! :)) is moderately widespread in the technical and scientific community, but you may find it looks a bit 'dated' (not that that's a bad thing, depending on your tastes). On the upside, as yaninass2 points out, it's very powerful, especially for very complex (say, scientific) calculations. If you're trying to write applications for PC, then [[C programming language|C]] or [[C++]] are the standards, but beware that, as languages, they are truly evil for the beginner (C especially), and I don't recommend them if you're still learning the ropes. But it you want to write the next version of Windows, C is your baby. If such high aspirations aren't quite what you had in mind (at least not right now), I can suggest [[Python programming language|Python]] - having played with it, I think that it's a pretty good language to learn in, especially since there are many excellent free tutorials on the web. But you can still do a huge number of things with it, so it will serve you well later, too. However you won't get the raw performance out of it that you would on a lower-level language (but, as I said, it depends what you're trying to do!). In any case, good luck with your programming! :) — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 11:19, 24 April 2006 (UTC)
:The length traveled by a photo should be the path length as measured along its curved trajectory, a geodesic of the manifold that is spacetime. I am not sure how you propose the stationary observer is going to measure this. It is in fact not even clear how to ''define'' the path length (in the mathematical model of [[curved spacetime]], a [[Lorentzian manifold]]) with respect to a ''given'', fixed frame of reference. [[Inertial frames of reference]] are useful in special relativity, when objects not acted upon by a force travel in straight lines. Space curvature means that there are no "straight lines", so the inertial model for establishing a reference frame breaks down. ​‑‑[[User talk:Lambiam#top|Lambiam]] 14:07, 19 August 2025 (UTC)
:::::I would say that C++ in some ways is even more evil to the beginner than C. In C it is quite easy to understand what you are doing but it is hard to really do anything for the beginner. C++ on the other hand has more functionality but is also more confusing. [[user:Jeltz|Jeltz]] [[user talk:Jeltz|<small>talk</small>]] 11:56, 24 April 2006 (UTC)
::Let's assume we (as inertial observers) see a photon travel near the sun in a curved trajectory. Do you claim we can't use any tool (e.g. a telescope or whatever) for measuring the length of this photon's curved trajectory? [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 15:59, 19 August 2025 (UTC)
:::We can detect only photons that arrive at our ___location. If a remote photon interacts with something else in such a way as to cause emission of another photon in our direction, we can detect the resulting photon but we're not directly observing the trajectory of the initial one.
:::Saying "what if as remote observers we see a photon travel near the sun" is like saying "what if as fans watching a soccer match from 10 miles away, we get hit by the ball on its way from the players foot to the goal". A remote observer can't observe a photon's trajectory. -- [[User:Avocado|Avocado]] ([[User talk:Avocado|talk]]) 17:49, 19 August 2025 (UTC)
::::So what does the quote (from Wikipedia) in my original post mean, about when c is "measured from a remote frame of reference"? Doesn't the measurement of c made by a remote observer, mean measuring the ratio between, the photon's trajectory measured by that remote observer, and the time it takes the photon to travel this trajectory - when this time is measured by that remote observer? [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 18:29, 19 August 2025 (UTC)
:::::I'm not a physicist nor the person who wrote the article. I would assume that we can know the time of the photon's origin based on whatever caused it to be emitted also having other effects (gravitational waves, other photons, etc) that reach us directly. And that we can measure the time of the photon's arrival at another point based on the effects of its arrival (reflected or re-emitted light, for instance) that reach us directly. And that we can thus measure the time elapsed between departure and arrival and deduce its speed. But we can't observe its trajectory, only infer it. -- [[User:Avocado|Avocado]] ([[User talk:Avocado|talk]]) 20:15, 19 August 2025 (UTC)
::::::Please note that the condition of "local measurement" (as opposed to "non-local" one) is a well known requirement for the speed of light to be constant. I've asked whether the requirement of locallity of measurement is also needed when the observer's frame of referenece is inertial. [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 06:47, 20 August 2025 (UTC)
:You can imagine that you have a torch in your hand and point it towards a remote black hole. The light from the torch will travel in the direction of the event horizons but will never cross it (from the point of view of an external inertial observer). This effectively means that the speed of light becomes zero in the vicinity of the horizon. However the proper speed of light will remain ''c'' of course. [[User:Ruslik0|Ruslik]]_[[User Talk:Ruslik0|<span style="color:red">Zero</span>]] 20:33, 19 August 2025 (UTC)
::When a photon is approaching a black hole, both the distance traveled by the photon, and the time it takes the photon to travel that distance, approach infinity (from the inertial observer's viewpoint), so the "effective" velocity becomes meaningless rather than "zero". [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 06:47, 20 August 2025 (UTC)
:::Sorry, but the distance cannot become infinite because it is a known quantity. Indeed, you can measure the distance to the black hole and its mass and then calculate the distance to the horizon from the observer.
:::I think the more important thing is to program. Regardless of language choice, you have to program. Just like any skill, you have to practice. Even if you're not actaully coding all the time. Go grab the Source to any [[Open Source]] project and start to read it. It's ok that you don't know the language that it's written in, most programing concepts translate from one language to another. The concepts of programming and Computer Science are more important than the code itself.Just look at it and try to understand what the code is doing. If you have no idea, the code is usually very well documented so you can get a rough idea of what it's saying and doing. Even try to rewrite something into the language of your choice. [[User:yaninass2|yaninass2]] 12:56, 24 April 2006 (UTC)
:::Actually there is no need to use black holes at all. You can put a mirror on the Earth's surface and direct the laser beam at it from a remote ___location in space. Then since you know the distance and can measure the time when the reflected signal comes back you can calculate the speed by dividing the first quantity by the second. The result will be that the (apparent) speed of light is less than ''c''. [[User:Ruslik0|Ruslik]]_[[User Talk:Ruslik0|<span style="color:red">Zero</span>]] 10:39, 20 August 2025 (UTC)
:I would recommend [[Java programming language|Java]]. Sun tutorials are usually excellent. There is a lot of information about many common beginners problems on the net that you can google. Some people say that Java being object-oriented makes it hard to learn; but that is really not the case, since you can use a class just like a collection of functions by declaring all methods static. And IMHO doing real data structures with objects is a lot easier than handling C structs, for example. Java also offers great functionality without installing all kinds of extensions and add-ons; you can do everything from simple shell apps to graphics and database connectivity just with the basic JDK.
::::I can see some practical issues with measuring the distance to a black hole. And also some theoretical issues. ​‑‑[[User talk:Lambiam#top|Lambiam]] 16:53, 20 August 2025 (UTC)
:About taking a open source program and looking at the source of it: don't. Especially programs written in C or C++ usually have a very complex framework of compiler macros and rely very much on their own, internal application programming interface (API), which makes it sometimes hard to even recognize the language they are written in! But in Java, these APIs are usually uniform. I assume that you already know the basics such as loops and conditionals - after learning those basics, it's more about the API than the language itself whether a language is easy to learn or not.
:::::Any black hole is just a mass. You need only to measure the orbital parameters of test particles moving around it. [[User:Ruslik0|Ruslik]]_[[User Talk:Ruslik0|<span style="color:red">Zero</span>]] 17:34, 20 August 2025 (UTC)
:Java is also a great starting point if you ever want to do some professional programming. Many programmer's daily work consists of writing tailored business applications such as billing software or e-commerce web sites, and these are often written in Java. And if your interests are more on desktop software, it's easier to learn Java first and then move to C++; Java is lot like C++ made easy. [[User:Stephanos Georgios John|SGJ]] 19:10, 24 April 2006 (UTC)
::This is far from the first time I have been exposed to these facts, but this concept still breaks my brain a little. I think it's on account of how we utilize the notion of an observer from an outside frame of reference as an abstraction. Obviously, in terms actual empirical observation at this point, the photon is completely red-shifted and has no chance of ever escaping. So it can't ever be directly observed. And yet we regard it as being unable to ever being able to be observed to have crossed the event horizon. Can someone help me with the structural distinction here? Because obviously if we had a photon's trajectory bent around the gravity well of a black hole (or any mass), we could observe it only by directly interacting with it by intercepting it somewhere along its path. So what do we mean when we talk about observation in an instance that is not in any scenario actually physically possible? ''[[User:Snow Rise|<b style="color:#19a0fd;">S</b><b style="color:#66c0fd">n</b><b style="color:#99d5fe;">o</b><b style="color:#b2dffe;">w</b><b style="color:#B27EB2;">Rise</b>]][[User talk:Snow Rise|<sup><b style="color:#d4143a"> let's rap</b></sup>]]'' 06:44, 24 August 2025 (UTC)
:::Just a small remark: '''<span style="color: red">"red-shifted"</span>''' (as you say), only when it tries to ''escape'' a black hole, but here we are talking about a photon ''approaching'' a black hole, so it's '''<span style="color: blue">blue-shifted</span>'''. [[Special:Contributions/2A06:C701:745A:B800:B559:3320:A4F4:C460|2A06:C701:745A:B800:B559:3320:A4F4:C460]] ([[User talk:2A06:C701:745A:B800:B559:3320:A4F4:C460|talk]]) 10:22, 24 August 2025 (UTC)
:::Regardless of their colour (frequency), photons can only be directly observed when they hit the observer. This was already pointed out above by Avocado. They can only be observed, directly or indirectly, when they are detected by some detector, which means in quantum terminology that they are "[[Measurement in quantum mechanics|measure]]d". Measurement of a photon means a change in a macroscopic system (a [[photoreceptor cell]] in the observer's eye, a [[photographic plate]] or [[photographic film|film]], a [[photodetector]], ...) as the result of an interaction with that system. Unless the measuring system is close to where the photon is, the probability of an interaction taking place is vanishingly small. ​‑‑[[User talk:Lambiam#top|Lambiam]] 12:05, 24 August 2025 (UTC)
::::Do you claim, any measurement (e.g. by a telescope or whatever) of the length of a photon's curved trajectory - whether near the sun - or in any phenomenon of gravitational lensing, is a local measurement? [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 13:11, 24 August 2025 (UTC)
:::::Does [[Principle of locality]] help? {The poster formerly known as 87.81.230.195} [[Special:Contributions/90.210.150.115|90.210.150.115]] ([[User talk:90.210.150.115|talk]]) 18:03, 24 August 2025 (UTC)
::::I think you've mis-interpeted my inquiry here, {{u|Lambiam}}. As it happens, I'm a bit of an expert in visual cognition, and so very familiar with the physics/biophysics of photoreceptive media. That's not the part I am struggling to fix in my mind here. My epistemological confusion about the terminology is this: since a photon trapped at the event horizon never escapes to interact with such a medium, what do we mean when we talk about "observation" when, for example {{u|Ruslik0}} says {{tq|The light from the torch will travel in the direction of the event horizons but will never cross it (from the point of view of an external inertial observer).}}? Is it a conceptual conceit/misnomer for describing the relation of the frames of reference? If so, can you think of a thought experiment that would explain those interactions in such a way that accounts for the fact that, as a strictly empirical and ontological matter, no observation at a distance can be made? Maybe Ruslik0 just mixed their metaphors and terminology a bit? If not, I'm super confused as to what the act of observation means in that description. ''[[User:Snow Rise|<b style="color:#19a0fd;">S</b><b style="color:#66c0fd">n</b><b style="color:#99d5fe;">o</b><b style="color:#b2dffe;">w</b><b style="color:#B27EB2;">Rise</b>]][[User talk:Snow Rise|<sup><b style="color:#d4143a"> let's rap</b></sup>]]'' 22:10, 24 August 2025 (UTC)
:::::You are right, I misunderstood the essence of your post. My reaction was triggered by the statement connecting our inability to observe the photon to its colour, which is I think essentially correct – in the model its wavelength tends to zero as it approaches the event horizon – but irrelevant. Scenario's of a photon traveling to an event horizon can be described that conform to a mathematical model of GR, such as [[Schwarzschild metric|Schwarzschild's exact solution to Einstein's equations]]. Such descriptions need a frame of reference, preferably one that in the limit, away from the mass, is an inertial frame. I too think the wording of these scenario's is sometimes confused. The scenario may include an observer for which this frame is stationary who can observe phenomena as predicted by the model, which in real life would validate the model. But such observation can only be through information that reaches them from afar, such as transmitted by electromagnetic waves. An astronaut approaching the event horizon might broadcast a livestream witness report that reaches the observer, but a photon can do no such thing. The models do not allow an observer to observe the unfolding of the scenario with regard to the traveling photon, so describing the scenario in terms of observations is confused. ​‑‑[[User talk:Lambiam#top|Lambiam]] 23:58, 24 August 2025 (UTC)
:::::What I actually meant is [[shapiro time delay]], which can be interpreted as slowing of light in presence of a gravitational field. [[User:Ruslik0|Ruslik]]_[[User Talk:Ruslik0|<span style="color:red">Zero</span>]] 20:33, 25 August 2025 (UTC)
= August 26 =
::You bring up some good points. Compared to C and C++ Java is easy, but the are several other languages with a good standard library (no required add-ons) and object orientation (in some cases optional) like Perl, Python, and Ruby. I don't think that Java has many obvious advantages over those languages, it mostly comes down to a matter of prefernce here. Proffesional software developers seems to me to tend to prefer Java (and C++ and Visual Basic), but I think that the slighly simpler Python is better for the beginner (and not bad for advanced useers either). I'm not saying that Java is a bad choice – just adding that other languages share many of the strenghts of Java. [[user:Jeltz|Jeltz]] [[user talk:Jeltz|<small>talk</small>]] 22:46, 24 April 2006 (UTC)
== Pharmacology ==
Pascal, naturally. - G3, 07:25, 25 April 2006 (UTC)
:I for one recommend [[assembly language]].--[[User:Frenchman113|Frenchman113 ]] [[User talk:Frenchman113|on wheels!]] 00:17, 29 April 2006 (UTC)
A friend once mentioned a book similar to an Encyclopedia, describing background events behind the development of many well known medicines . Please inform if a similar book can be found and how to "custom search" at any of the sites of WIKI for such a book .
::Just don't start with i386 assmebly if you value your sanity. [[User:Plugwash|Plugwash]] 00:36, 1 May 2006 (UTC)
Thnx [[User:Dr chifti|Dr chifti]] ([[User talk:Dr chifti|talk]]) 05:05, 26 August 2025 (UTC)
:You might find such a work used as one of the many references for the article [[History of medicine]], athough what you describe would be a [[Tertiary source]] (like Wikipedia itself) rather than a [[Secondary source]] which Wikipedia prefers for article sources.
:Searching Wikipedia for the term "Encyclopedia of pharmacology" led me to the article ''[[Pharmacology Research & Perspectives]]'' whch uses as its reference 4 ''The Sage Encyclopedia of Pharmacology and Society'' – see that article for its bibilographical details. {The poster formerly known as 87.81.230.195} [[Special:Contributions/90.210.150.115|90.210.150.115]] ([[User talk:90.210.150.115|talk]]) 08:04, 26 August 2025 (UTC)
:Searching Archive.org for [https://archive.org/search?query=history+of+medicines history of medicines] turns up many candidates, including [https://archive.org/details/ourmodernmedicin0000band/page/n7/mode/2up?view=theater Our Modern Medicines] (F Bandelin, 1986) which seems to match your description. <span class="nowrap">[[User:Verbarson|-- Verbarson ]] <sup>[[User talk:Verbarson|talk]]</sup><sub>[[Special:Contributions/Verbarson|edits]]</sub></span> 15:04, 26 August 2025 (UTC)
== GolfAugust Balls27 ==
== [[Lorentz factor]] derivarion ==
Is it true that Honey is put into the centre of some golf balls?
In '''[[special relativity]]''', a common way to derive the '''Lorentz factor''' <math>\gamma</math> is via the '''[[pythagorean theorem]]''', without using the complicated '''[[Lorentz transformations]]''' (which I myself have yet to study).
Thankyou
:Not any standard, commercial golf balls. (Amongst other reasons, such as it being expensive and not doing anything useful, [[honey]] would be different from batch to batch, meaning the resulting golf balls wouldn't perform the same.) I cut one open 15 years ago, and the core was like a bunch of rubber bands, wound around a rubber ball, although expensive balls have changed since then. Our article on [[golf ball]]s has more details on the history of golf ball construction. Personally, when golfing, I use a French brand, called '''RANGE'''. --[[User:ByeByeBaby|ByeByeBaby]] 02:28, 24 April 2006 (UTC)
::Most likely pronounced "RAWNJ". [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 05:14, 24 April 2006 (UTC)
:::"La Rawnj" that is. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 05:21, 24 April 2006 (UTC)
By the equation
== Alternate Logic ==
:<math>(c\,{\rm T_s})^2=(v\,{\rm T_s})^2+(c\,{\rm T_v})^2</math>,
I'm not quite sure which desk to put this on, so I'm going with Science.
such that
Does anyone familiar with the Zensunni philosophy in the Dune books know what real-world ideas they were based on, if they were based on anything? I'm especially wondering about the anti-logic philosophy mentioned in Heretics of Dune.
:<math>c</math> [[speed of light]] in a vaccum
Same questions for the 'intuitive logic' thing in the Dorsai books (the Childe Cycle). [[User:Black Carrot|Black Carrot]] 02:16, 24 April 2006 (UTC)
:<math>v</math> speed of a '''moving observer''' relative to a '''stationary observer'''
:I've actually been meaning to re-read my Dune books for a while. I'll try to get back to you sometime this year. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 05:35, 26 April 2006 (UTC)
:<math>{\rm T_s}</math> stationary observer time
:<math>{\rm T_v}</math> moving observer time
hence
:<math>\gamma=\frac{\rm T_s}{\rm T_v}=\frac{1}{\sqrt{1-\big(\frac{v}{c}\big)^2}}</math>
My questions are as follows:
#Is this derivation actually legitimate, or does it contain any non-proven hidden assumptions?
#I have not yet seen any '''mathematical reasoning''' showing these transformations must be [[Linear map|'''linear''']].<br>In my humble opinion, most sources completely ignore this point, or treat it superficially at most.<br>I would like to know if there is any such reasoning.
#Why is the factor not written <math>\gamma(v)</math>?
[[User:יהודה שמחה ולדמן|יהודה שמחה ולדמן]] ([[User talk:יהודה שמחה ולדמן|talk]]) 15:29, 27 August 2025 (UTC)
:It is not clear where the first equation comes from. [[User:Ruslik0|Ruslik]]_[[User Talk:Ruslik0|<span style="color:red">Zero</span>]] 20:25, 27 August 2025 (UTC)
::Watch this short video [https://www.youtube.com/watch?v=67xr6EZEYV8 '''here''']. It is very common. [[User:יהודה שמחה ולדמן|יהודה שמחה ולדמן]] ([[User talk:יהודה שמחה ולדמן|talk]]) 04:11, 28 August 2025 (UTC)
:::That the equation is common doesn't mean it's clear where it comes from. It's not a priori clear that in a triangle with edges <math>cT_s</math>, <math>vT_s</math> and <math>cT_v</math> the latter two edges must be perpendicular. When I learned about special relativity, it started with the Lorentz transformations. Those aren't terribly hard; this was my first week at university. It could be done in the last year of secondary school. [[User:PiusImpavidus|PiusImpavidus]] ([[User talk:PiusImpavidus|talk]]) 09:14, 28 August 2025 (UTC)
:It's worth highlighting that the 4-space Lorenz transformations take place in is non-Euclidian. So it doesn't use the Euclidian metric, normally calculated with Pythagoras's theorem. Instead it uses a version with the squares of the three length components added but the time component subtracted.
:If you eliminate two of the length components this looks like a difference of squares. Rearrange these you get a sum and it looks like Pythagoras's theorem, but because it's been rearranged it isn't really the same thing. The minus sign in the the second expression more correctly expresses the metric. --[[Special:Contributions/217.23.224.20|217.23.224.20]] ([[User talk:217.23.224.20|talk]]) 10:38, 28 August 2025 (UTC)
:It is not clear who introduced the convention of using the Greek letter <math>\gamma</math> for the Lorentz factor (not Lorentz himself, nor Einstein, who used the letter <math>\beta</math> in "Zur Elektrodynamik bewegter Körper"*), but since it tends to be all over the place in derivations in special relativity, the one-letter notation is obviously more convenient than writing each time <math>\gamma(v)</math>. ​‑‑[[User talk:Lambiam#top|Lambiam]] 10:41, 28 August 2025 (UTC)
:<hr style="width:5em">
:{{*}}{{small|Perhaps [[Hans Bethe|Bethe]] in [https://link.springer.com/chapter/10.1007/978-3-642-52619-0_3 "Quantenmechanik der Ein- und Zwei-Elektronenprobleme" (1933)]. This is behind a paywall; I cannot check if he actually used this notation. ​‑‑[[User talk:Lambiam#top|Lambiam]] 11:08, 28 August 2025 (UTC)}}
::Bethe uses <math>\varepsilon = E/E_0</math> (his eq. 9.16; <math>E_0</math> is the rest energy), which is the Lorentz factor; I don't think he expresses it in terms of ''v'' and ''c'' anywhere. (Accessed via Wikipedia Library, which once again proved more powerful than my university account...). --[[User:Wrongfilter|Wrongfilter]] ([[User talk:Wrongfilter|talk]]) 11:34, 28 August 2025 (UTC)
'''To point 3:''' Writing <math>\gamma(v)</math> declares only that <math>\gamma</math> is a function of a variable <math>v</math> thus <math>\gamma = \gamma(v)</math>
== [[Autocunnilingus]] ==
which is true but conceals the nature of the function. Lorentz factor <math>\gamma</math> is a dimensionless ratio that is a non-linear function of a velocity <math>v</math> that for any real mass is constrained to be less than <math>c</math>. For a massless particle such as a photon, calculating <strike>a unity</strike>an infinite Lorentz factor adds no useful information.
On [[Talk:Autocunnilingus]], there's been quite a bit of difficulty coming up with evidence one way or the other on a particular debate; namely, whether such a thing is at all possible, and if so, whether there are reputable pictures or video available of it being done. Any input? [[User:Black Carrot|Black Carrot]] 02:59, 24 April 2006 (UTC)
'''To point 2:''' Given the Lorentz equation confirmed in Special relativity
:Posted my thoughts. I think finding evidence in the form of a photograph that has not been noted by a qualified source violates the [[No_original_research|No Original Research Policy]]. -Bill
:<math>\gamma=\frac{1}{\sqrt{1-\big(\frac{v}{c}\big)^2}}</math>
the OP chooses by algebraic reasoning to derive an arbitrary relation
:<math>(c\,{\rm T_s})^2=(v\,{\rm T_s})^2+(c\,{\rm T_v})^2</math>
but this result is flawed. It predicates two different observers each of whom would have to be moving at c, as only a photon can, if expressions
<math>(c\,{\rm T_s})</math> and <math>(c\,{\rm T_v})</math> are to be real distances moved in a real time interval. It is hard for me to conceive of even one photon observing another photon and somehow reporting an observed distance. I don't believe that Pythagoras who relied more on the geometrical axioms of Euclid ca. 300 BC than on Einstein publishing in 1905 would appreciate or endorse being cited here. I see no other good source for the latter "pseudo-Pythagorean" equation and I conclude that it is introduced here as algebraic sleght-of-hand. The trick is to quote a supposed definition
<math>\gamma=\frac{\rm T_s}{\rm T_v}</math>
into which the trickster plugs <math>\rm T_s</math> and
<math>\rm T_v</math> that have been synthesized to give the standard result.
'''To point 1:''' The ploy is clever but hardly legitimate. [[Special:Contributions/2A02:FE1:4088:5E00:DC53:CFFC:3F4A:F5BE|2A02:FE1:4088:5E00:DC53:CFFC:3F4A:F5BE]] ([[User talk:2A02:FE1:4088:5E00:DC53:CFFC:3F4A:F5BE|talk]]) 15:33, 28 August 2025 (UTC)
:This is not a "Pseudo-Pythagorean" equation.
::Dandy. Any suggestions on how to ''find'' a qualified source on this? [[User:Black Carrot|Black Carrot]] 11:25, 24 April 2006 (UTC)
:Perhaps [https://www.youtube.com/watch?v=qXxtqK7G4Uw&t=160s '''this derivation here'''] will be even clearer.
:::Ask around. You probably have relatives that do [[yoga]]. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 05:33, 26 April 2006 (UTC)
:I do apologise for not being able to show a geometric sketch in advance. [[User:יהודה שמחה ולדמן|יהודה שמחה ולדמן]] ([[User talk:יהודה שמחה ולדמן|talk]]) 18:27, 28 August 2025 (UTC)
::Isn't this the same derivation as given in {{section link|Time dilation#Simple inference}}?
::The presentation in the YouTube video is (IMO) in one respect somewhat confusing. There are two observers, one inside a moving train car, one standing outside next to the railroad tracks in the grass. There are two time values for the different times clocked by these observers, <math>T_{stationary}</math> and <math>T_{moving}.</math> Now in the narrative of the video <math>T_{stationary}</math> stands for the time clocked by the observer in the ''moving'' car, while <math>T_{moving}</math> is the time clocked by the observer patiently ''standing'' outside till this ordeal is over. I beg your pardon. (To be fair, the narrative gives a reasonable explanation for this choice, but note that the notation in the question has this swapped: <math>{\rm T_s}=T_{moving}</math> and <math>{\rm T_v}=T_{stationary}.</math>)
::The simple derivation given is based on vector decomposition of a velocity into a component in a given direction (in this case that of the velocity of the moving car) and an orthogonal component, and that this remains valid for a moving system observed from the outside. I don't know if this can be called an assumption – if so, it is hardly hidden — but the validity of this step may not be that obvious to the confused student all of whose implicit assumptions based on the Newtonian model of absolute time and space have lost their certainty and who may wonder what happened to length contraction.
::The presenter himself states that this is not his favourite derivation, and that there is a better, but more difficult explanation. ​‑‑[[User talk:Lambiam#top|Lambiam]] 08:47, 31 August 2025 (UTC)
== DVDAugust Ripping31 ==
I recently used DVD Decryptor to rip part of a DVD I have. It saved as a .vob file, and using VLC Media Player, I can play the file. The problem is that the file size is large. Can anyone suggest any good, free programs to convert/edit .vob to .avi or .mpg? Thanks. --[[User:Russoc4|Chris]] 05:03, 24 April 2006 (UTC)
:Videora, for computers. Handbrake, for macs. [[User:Henry Flower|Henry]][[User talk:Henry Flower|<sup>Flower</sup>]] 10:04, 24 April 2006 (UTC)
::Henry, are you suggesting that macs are not computers...? ;-) Chris, I suggest you read the forums at [http://www.doom9.org/ doom9.org], they have a whole plethora of guides on this subject. If you're just starting out, I recommend AutoGK (AutoGordianKnot), the automated newbie-friendly version of GordianKnot, the full-fledged encoder. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 10:59, 24 April 2006 (UTC)
::As I recall, VOB files are already in MPEG format. Try renaming them to .MPG and see if they play. If so, then [[virtualdub]]-mpeg [http://fcchandler.home.comcast.net/stable/ website] can directly recode them to AVI format in any [[codec]] or compression you choose. [[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 01:54, 26 April 2006 (UTC)
== Is it possible to jump out of a 747? ==
The title pretty much says it. No, I'm not looking to do it, I'm just curious if you could jump out of one and still survive. --[[User:Skull sphinx|Skull sphinx]] 06:18, 24 April 2006 (UTC)
:I suppose it depends at what height the plane is flying..or even if its flying...anyone could jump out of a plane when its on the runway and still survive... and of course, it also depends on whether you have a parachute or not.. [[User:Jayant412|Jayant,]][[WP:EA|<font color="green">17 Years,</font>]][[User_talk:Jayant412|<font color="red"> India</font>]] • [[Special:Contributions/Jayant412|contribs]] 06:23, 24 April 2006 (UTC)
::Getting the door open may be rather difficult. As far as I recall the door won't open while in flight. Of course, if you rob everyone on the plane first, you could be the next [[D. B. Cooper]]. :-) [[User:Dismas|Dismas]]|[[User talk:Dismas|<sup>(talk)</sup>]] 06:35, 24 April 2006 (UTC)
::I wouldn't say anyone could jump from the plane and survive... if you take the normal exit and there is no [[Jetway]] to step on to you will be in for a rather harrowing experience, and you could easily die from the stop at the end of the 25' fall if you land wrong on the [[Tarmac]]. --[[User:66.195.232.121|66.195.232.121]] 14:21, 24 April 2006 (UTC)
:::And your chances are even worse if you tried this from the upper deck of a [[Airbus A380]]. :) — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 14:36, 24 April 2006 (UTC)
:Not a direct answer, but interesting: [[JAT Yugoslav Flight 364]]. [[User:Notinasnaid|Notinasnaid]] 09:42, 24 April 2006 (UTC)
::"Is it possible to jump out of a 747?" While in flight? Almost impossible. Dismas is right, the pressure differential between the cabin and the outside at cruise altitude is so high that even if you were an olympic weightlifter you probably wouldn't have the strength to overcome it (airliner doors need to be pulled inward before they rotate outward, see [http://www.everything2.com/index.pl?node_id=1783222]). You ''could'' create your own door with, say, a bomb - but that entails a whole raft of other problems.
::Assuming you ''did'' find a way to leave the 747 in flight, could you survive the fall? It's very unlikely, but possible. You would probably black out from the low pressure, but are unlikely to die until you impact the ground. People ''have'' survived falls from very great heights without parachutes, but only under very special conditions. You need to land in something that would break your fall sufficiently gently - soft snow (and hope you don't get buried in too deep) or somesuch. The River Tiber (in reference to a recent popular book ;-) ) won't do. The link Notinasnaid provided is an example of a person surviving the plunge, and there are a handful of other accounts. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 12:41, 24 April 2006 (UTC)
:I think the answers above are pretty much correct. If you manage to get out of the plane you could survive but don't count on it, very few have survived. I think that falling over land would increase your chances (especially if there is snow). I don't think that water ever is soft enough, and even if it is you will most likly drown when you hit the surface of the water already unconsious from lack of oxygen. The article about [[Free-fall]] mentions three other known cases where people have survived falls at terminal velocity. [[user:Jeltz|Jeltz]] [[user talk:Jeltz|<small>talk</small>]] 11:22, 24 April 2006 (UTC)
:Also a [[parachute]] could improve the chances of surviving the landing. – [[User:b_jonas|b_jonas]] 11:05, 25 April 2006 (UTC)
:Being a [[pedant]] about the question the answer has to yes, because nowhere is it stated the plane is in motion, or in the air. --[[User:Blowdart|Blowdart]] 12:38, 25 April 2006 (UTC)
::I'm sure i heared that the early test models of the 747s were fitted with an in flight escape exit. I belive the early test models of the A380 were too. So yes with a parachute and the correct exit installed you could do it in flight but on a production airliner with no special modifications it would be very hard. [[User:Plugwash|Plugwash]] 13:01, 25 April 2006 (UTC)
If you had a gun, you could blow out a window to equalize the pressure before opening the door. [[User:StuRat|StuRat]] 00:27, 29 April 2006 (UTC)
:Why does someone want to know how to do this? I'm slightly worried.--<tt>[[User:Ikiroid/Esperanza|<font color="green">'''The'''</font>]]</tt> [[Imaginary unit|<font color="black">'''i'''</font>]][[user:ikiroid|<font color="blue">'''kiro'''</font>]][[Ego, superego, and id|<font color="black">'''id'''</font>]] <small>([[user talk:ikiroid|talk]])</small><sup>([[User talk:Ikiroid/Help Me Improve|Help Me Improve]])</sup> 19:36, 29 April 2006 (UTC)
== Early morning dilemma ==
When I arrive at my office I can either walk up four 6" steps or up a direct ramp which is about six times as long as the steps. I intuitively walk up the ramp as this looks easier than climbing the steps, but whenever I choose the steps it feels like they're less work, perhaps because the effort is expended over a shorter distance. Logic tells me I'm doing exactly the same amount of work whichever option I choose. Which would you choose and why? [[User:Shantavira|Shantavira]] 08:10, 24 April 2006 (UTC)
:Well, you do the same amount of [[mechanical work]] either way, but if by "work" you mean total muscular energy expended, then surely one option is costlier than the other. It would depend on the details of your personal gait, but in general, I would guess that the ramp requires you to burn fewer calories, simply because your velocity doesn't change as much when you use it. [[User:Melchoir|Melchoir]] 08:24, 24 April 2006 (UTC)
::Yes, that's an interesting point about the change of velocity, which I don't notice in practice. I shall try both options at an increased velocity and see how they feel. [[User:Shantavira|Shantavira]] 09:36, 24 April 2006 (UTC)
:::Another factor is that the ramp will cause you to lean slightly backwards, which causes you to expend more energy to move forward. This would actually help when walking down the ramp, though. I suggest you compare walking down the steps and ramp. I suppose I should also point out that if climbing 4 steps seems like a significant amount of work to you, you may need the exercise to get in better shape. Always taking steps (or ramps) instead of elevators and escalators can be good exercise, and taking the stairs is frequently quicker than waiting for an elevator anyway. [[User:StuRat|StuRat]] 11:21, 24 April 2006 (UTC)
::You are using different muscles, so the two would feel different, irrespective of work done "physics-wise". Have you checked if the distance - as would be measured by pedometer - is the same? --[[User:Seejyb|Seejyb]] 19:07, 24 April 2006 (UTC)
== C operator overloading doubt ==
I must write a program in C, which of course doesn't support that feature. The thing is... operator overloading would be extremelly useful since the program performs lots of operations of complex numbers, already defined in a "tool" file written by me. How can I make a*b-sqrt(a^2/2) (for example) intelligible if I have to use a lot of functions? How C programmers got around this problem? Thank you for your time.
:You could just make a function named sqrtCmplx, or something like that, but the other functions, equivalent to *, -, ^, and /, would indeed be ugly. BTW, I would think you could find an include file with complex number functions somewhere, rather than write your own, but since you've already done this part, I suppose it doesn't matter now. [[User:StuRat|StuRat]] 12:54, 24 April 2006 (UTC)
You will likely need to break the expression up into multiple lines to make it easy to follow with all the new function names. As for making it readable, just include the simple version in a comment, to explain what is being done. [[User:StuRat|StuRat]] 13:00, 24 April 2006 (UTC)
:I think you'll find that if you use a lot of functions, then they become more intelligible with time. I agree that breaking down will help. Just more typing, it isn't more cryptic really. [[User:Notinasnaid|Notinasnaid]] 13:10, 24 April 2006 (UTC)
If your compiler supports the C99 standard, your expression could simply be written a*b-csqrt(a*a/2), if you use the complex types from the [[http://www.dinkumware.com/manuals/reader.aspx?b=c/&h=complex2.html complex.h]] header. [[User:84.239.128.9|84.239.128.9]] 18:53, 24 April 2006 (UTC)
:C99 even gives so called "type generic" math functions in the library, so you can say a*b-sqrt(a*a/2) if you #include <tgmath.h> – [[User:b_jonas|b_jonas]] 23:16, 27 April 2006 (UTC)
Thank you all very much.
:You're welcome. [[User:StuRat|StuRat]] 13:56, 30 April 2006 (UTC)
== Evolutionary Questions ==
What is the evolutionary fuction purpose of sleep? It seems like sleep would be a huge disadvantage as it would leave one open to predators. How & why did sleep evolve then? Also, what is the evolutionary purpose of yawning? [[User:199.201.168.100|199.201.168.100]] 12:34, 24 April 2006 (UTC)
:Check out our articles on [[sleep]] and [[yawn]] - they should answer both questions. If there is something you don't understand, feel free to come back here and ask again! :) — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 12:40, 24 April 2006 (UTC)
::I believe sleep developed because animals are specialized to be either diurnal or nocturnal. Diurnal animals (like us) are rather helpless at night without artificial light so spend the time recuperating and using as little energy as possible, during sleep. (An exception is during full moons, when we have enough light so we can go hunting at night, and hence the urge to go kill something during a full moon.) Nocturnal animals are similarly helpless during the day, in that they can be easily spotted by predators, so they sleep then. Some animals have taken the sleep concept a bit further, like cats, and sleep most of the time to limit energy consumption further. [[User:StuRat|StuRat]] 13:12, 24 April 2006 (UTC)
:Animals that saved energy by lowering their metabolism rate in a daily cycle were more successful than animals that didn't; apparently specializing for either dark or light was more successful. Once sleep existed in animals, animals that utilized this state for various internal functions (healing, reorganizing mental data, mental rehearsing of situations, etc) were more successful at surviving and reproducing than those whose genes less well utilized the sleep cycle. [[User:WAS 4.250|WAS 4.250]] 18:12, 24 April 2006 (UTC)
:On sleep leaving animals open to predators, I don't think that's very much so. I mean, animals obviously defend themselves against this, either by sleeping in an alert way and getting awake as soon as they hear any noise, or by hiding in a hole or some other safe place when they sleep. – [[User:b_jonas|b_jonas]] 11:00, 25 April 2006 (UTC)
:The brain is extremely active during sleep. It appears something important to the brain is going on, although research into exactly what is ongoing. --[[User:Ginkgo100|Ginkgo100]] 03:55, 26 April 2006 (UTC)
== Another Evolutionary Question ==
Why can't I get laid? [[User:199.201.168.100|199.201.168.100]] 12:34, 24 April 2006 (UTC)
:Because you spend your time asking questions at the Wikipedia Ref Desk instead of going out and attempting to [[preen|impress]] members of your target sex. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 12:38, 24 April 2006 (UTC)
::...and it also helps to make [[friend]]s with them first. [[User:Shantavira|Shantavira]] 13:04, 24 April 2006 (UTC)
: Perhaps you have a back problem? Try sitting down with your legs flat on the floor, and then lean your torso back slowly until it rests on the floor as well. Use your arms for support. [[User:Dysprosia|Dysprosia]] 14:38, 24 April 2006 (UTC)
:People get what they want when they tell lots of people what they want and they actively offer what those other people want. Different people want different things. Be clear about who you are and want you want. Listen carefully to what is communicated back both verbally and nonverbally. Some people want an illusion leading some to say lie to get laid; but most people just like a comfortable presentation to go along with the substance - like a meal at a restaurant looking good as well as tasting good and being nutritious. And remember, you have competition to out bid. (as do they) [[User:WAS 4.250|WAS 4.250]] 18:02, 24 April 2006 (UTC)
::That is one of the best answers I've ever read here. I think. [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 03:19, 25 April 2006 (UTC)
:::And if what WAS says doesn't work either, it may be that you're unsuccessful in getting laid because you haven't considered attempting to lay, or it may be because you are not a [[chicken]], and never will be. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 05:29, 26 April 2006 (UTC)
== Heat generated by resting human body. ==
It appears to me that regardless of the ambient temperature my body generates substantial heat when I sleep. Is this an understood bodily function?
:Your body is only attempting to keep itself at a more-or-less constant temperature (approx. 37°C) - you are a mammal, and mammals are [[warm-blooded]]. I would guess that your ambient temperature is very rarely at or above 37°C, so for any ambient temperature lower than that, your body is obviously a net generator of heat. This happens whether you sleep or not. We have a pretty good article on [[thermoregulation]], which should answer most of your questions. If anything isn't clear, feel free to come back for more clarification! :) — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 14:30, 24 April 2006 (UTC)
:Yes, it is well understood. If you too wish to understand, start here: [[Basal metabolic rate]]. [[User:WAS 4.250|WAS 4.250]] 17:53, 24 April 2006 (UTC)
:Thank you very much. I apologize for not searching more diligently; the referenced articles are excellent. --[[User:BellCurve|BellCurve]] 20:26, 24 April 2006 (UTC)
== Nutritional value of hemp seed ==
The information you provide about nutritional value of hemp seeds(http://en.wikipedia.org/wiki/Hemp) states that 100g of hemp seeds contain 2277.5 IU of vitamin D. This seems extremely hight. I have tried to verify this information and cannot find any data to support it. Can you provide your source of this information?
Thank you,
Kathy
:I have placed a note in the article for someone to provide a citation or correct this. I have copied your question to [[Talk:Hemp]] - which is the discussion page for the [[Hemp]] article, which is where the editors of this article are most likely to see it. [[User:Thryduulf|Thryduulf]] 15:16, 24 April 2006 (UTC)
== Gender Differences ==
On a first note, this question probably ''is'' going to offend someone out there, and I would apologise dearly if this is so, but I am no troll and only relating of something I have always noticed. How is it that so many modern females may excell far better than the opposite sex in their school studies, yet still produce so few works of true distinguishing excellence in their future careers? And I am not merely speaking of the scientific careers that have long leaned in favour of men, either- even some careers commonly associated with women in school curricula such as the liberal arts, are still dominated in the wider world by men! It is reported that the genders score equally well on IQ tests, but how is it that it always, as seemed to me, far easier to fulfil the higher intellectual curiosities of women than that of equally educated men? Even when given more or less similar opportunities such unusual traits would still sometimes develope. I would be deeply grateful if someone may find a way of understanding these differences. [[User:Luthinya|Luthinya]] 15:00, 24 April 2006 (UTC)
:::: Do you have any sources for actual statistics on this? It would probably help to show some real numbers, so one could trust the claim. - unsigned
:Just as human males are geneticly taller on average than females, so too males are genetically more agressive and competitive than female humans, while females are genetically more cooperative. Different social structures reward different traits just as differnt sports reward different traits. [[User:WAS 4.250|WAS 4.250]] 17:46, 24 April 2006 (UTC)
::A possible explanation is the suggestion that women have less capacity for abstract thought, which is required to make truly original and breakthrough achievements. For example, my [[cognitive psychology]] textbook in college presented women's inferior capability to rotate 3D images in their heads as fact. In a fairly recent interview, I've also heard a [[Cambridge University]] professor state that "women don't have creative minds", although the rest of the interview suggested that he may be quite biased. It's just a possibility to consider, but I can try to find out what the textbook was and where I heard the interview if you need sources for any research you're doing. In the meantime, you may want to have a look at our [[gender differences]] aticle if you haven't already. --[[User:Aramgutang|Aram]]'''[[User talk:Aramgutang|գուտանգ]]''' 18:44, 24 April 2006 (UTC)
:::"Abstract thought" is not the same as spatial reasoning. That statement is a crude generalization, and "Women don't have creative minds" even moreso. In the rush to find cognitive reasons for this perceived disparity, I think people are discounting a cultural and/or emotional one: to really excel in a field, a person needs a certain degree of dedication, and it could be that more women than men choose to sacrifice this degree of dedication in favor devoting more time to family life. [[User:Ginkgo100|Ginkgo100]] 03:50, 25 April 2006 (UTC)
:I (independantly and unjustly) attribute it to two things, one of them being sexism. It's not hard to imagine the difficulties a woman would have had trying to breach the upper levels of intellectual society in the time of Newton or da Vinci, though I don't believe it's nearly as large a factor now as it was before the 20th century.<br/>I also believe, with some evidence, that strong right-brain tendancies are more common in males than in females. Whether that really means anything is another argument, but certain "symptoms" such as left-handedness clearly indicate that women are much more left-brain dominant. If you believe in the all the right/left-brain mumbo-jumbo, then it gives you a nice way to explain why there are more well-known male [[eccentric]]s, famous male painters, gay hairdressers, and white-moustached scientists than females. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 02:42, 25 April 2006 (UTC)
:One factor (among several) is that males tend to have more diverse abilities (a greater standard deviation than females), so males do tend to be a little over-represented among the most- (and least-) capable members of society. [[User:Peter Grey|Peter Grey]] 05:30, 25 April 2006 (UTC)
::A real problem is that when you look at it from afar, things like "intelligence" and "success" and "ability" seem such obvious terms. But when you look close up, they become very 'fuzzy'. As an old teacher of mine used to say, [[shark]]s have been round a few hundred million years. They probably won't consider humans a successful species until about 300 million A.D. or so. Questions such as 'What is intelligence?' are very problematic in this sense, and the articles on [[intelligence]] and [[emotional intelligence]] will lead you to some of the debate. In the realm of the questions you are asking, a parallel question might be phrased, is it "more successful" in a "future career" to to be more commonly liable to [[sexual harrassment]] and workplace [[bullying]], and to die younger from [[stress]], as men do, and then to claim greatness for having bought career progress at such heavy cost? Success is a very arbitrary term. men and women are not only wired slightly differently, but strike slightly different balances between such things as social prestige, family, inward and outward directed motivation, and so on. What success, at what cost, by what standards, ignoring what else, and how? Thats what your question misses and where you may find more of an answer. [[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 19:11, 25 April 2006 (UTC)
: I'm not sure I completely understand the latter part of the question, or what it is based on statistically, whether from [[social psychology]] or elsewhere. One possibility is surely that women do produce as much excellence in their work but are not recognised for it, as a result of assumptions made in societies which have only recently achieved roughly equal opportunity for both sexes. You mention science, and an an example here would be [[Rosalind Franklin]], who for decades people were unaware of despite knowing about [[Francis Crick]] and [[James Watson]]. Similar work by someone like [[Dorothy Crowfoot Hodgkin]] cannot be described as anything other than excellent, and is in a field that requires advanced spatial reasoning. [[Ada Lovelace]] was overshadowed by [[Charles Babbage]] despite what may have been a greater contribution to computing. Women who enter science nowadays may do somewhat better than men on average, simply because the bar to entry is a little higher for them. Even when it was much higher, there were cases like [[Marie Curie]] and [[Lise Meitner]] that no social convention will hold back. Fine arts, literature and psychology seem to have had more time to mature as disciplines accepted for women, and it is now hard to make a case for differences in excellence there. The idea that for various biological and cultural reasons men can be more competitive, and therefore may tend to appropriate credit to themselves and self-promote, may have something behind the questioner's perception. Gingko100 is presumably also correct in that women may ''de facto'' spend more time bringing up children, acting as social glue, and so on, and thus have fewer opportunities to excel or reach a creative peak. --[[User:Cedders|Cedders]]<sup>[[User talk:Cedders|tk]]</sup> 12:25, 30 April 2006 (UTC)
== Tri-beveled needles & Anti-Coring ==
Hello, I work for a medical supply company, and I am currently doing a presentation on needles. I was wondering what Tri-beveled means as well as Anti-coring. Any help would be greatly appreciated.
Colleen
:For anti-coring, think of an apple corer. An apple corer is like a tube that punctures the apple and holds the apple core inside of it when it is withdrawn. Often it would be undesirable for a medical needle to behave like this; you want it to puncture, but not let tissue enter the needle itself. This also comes up in the context of syringes used for [[gas chromatography]]; a needle that takes a core can ruin what used to be a gas tight seal.
:I don't know about tri-beveled. Try the manufacturer's tech support. [[User:Ike9898|ike9898]] 16:33, 24 April 2006 (UTC)
:An anti-coring needle is designed to minimise the punching out of a piece of material (e.g. human tissue) which can then get stuck in the shaft of the needle, either blocking it, or depositing unwanted material at the site of injection, or leaving a punched out hole in the tissue after being withdrawn. The most commonly used medical example is the [[Tuohy needle]], used for epidural anaesthesia.
:A triple-ground, tri-bevel [[hypodermic needle]] is one with a bevel which has been ground or honed in three different planes. This is to try to achieve a compromise between cutting ability, rigidity of the cutting tip (a long bevel cuts easily but can bend or curl over at the tip), ease of introducing and advancing the needle (a short bevel feels "blunter" and the needle advances less easily), and distance from the tip of the needle to the start of the tubular shaft. This last factor is important since one does not want the tip of the needle protruding far beyond the tubing part through which the user may wish to draw blood or give an injection.
Look at the tip of one of your thicker needles, you will see the 3 planes: The bevel closest to the hub is at a relatively flat angle in relation to the shaft of the needle (that would be the start of a long bevel). About halfway to the tip of the needle you will see a change in plane (angle of bevel), with two additional ground planes (bevels) starting, one on each side of the main initial bevel, and rotated slightly, so that the very tip of the cutting edge looks triangular, not round or flat. This is the standard grind for hypodermic needles, also called a diamond bevel, or lancet. A well-made standard needle would be expected to have such a bevel (i.e. it shows compliance with accepted standards, and is not a "special feature"), and deviations from this would mostly be for special uses. --[[User:Seejyb|Seejyb]] 20:29, 24 April 2006 (UTC)
== Cryogenics ==
What was the first country to use cryogenic technology?<small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:207.28.159.13|207.28.159.13]] ([[User talk:207.28.159.13|talk]] • [[Special:Contributions/207.28.159.13|contribs]]) {{{2|}}}.</small><!-- [Template:Unsigned] -->
:I'm not sure; have you looked at [[Cryogenics]]? [[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 20:49, 24 April 2006 (UTC)
== Distribution of mass in Earth ==
Hey. So, it seems to be correct that the further into Earth you get, the less gravity is there to pull on you. Therefore, at the correct center, there's a theoretical nil-gravity. My question related to that comes from that the core must be under pressure in order to be so warm and stuff, from the particles above. Does anyone know, in theory, the distribution of MASS in earth? There are all the nice pictures with half or three quarter of a globe, showing what parts are what, but I don't see any explanations for the mass.
[[User:213.161.189.107|213.161.189.107]] 17:26, 24 April 2006 (UTC) Henning
:The article [[Structure of the Earth]] has some information on the density, but not much. You might get better results if you include the phrase "radial density profile" in your search. For example, I found: http://arxiv.org/pdf/astro-ph/9909038 —[[User:Keenan Pepper|Keenan Pepper]] 18:02, 24 April 2006 (UTC)
I have trouble understanding the question, and my main thing is geophysics, etc. Perhaps after you have looked at the above references, we can point you to some other links. --[[User:Zeizmic|Zeizmic]] 02:12, 25 April 2006 (UTC)
== The Human Genome ==
Where can I find the exact sequences for the human genome, and not just a description of the project?
:Just to make sure you're clear, there is no such thing as the "exact" human genome sequence. The genetic sequence varies by individual, otherwise we'd all be clones. To search for sequences within the human genome, look at the External links section of the [[Human Genome Project]]. [[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 20:44, 24 April 2006 (UTC)
::The [http://www.ensembl.org/Homo_sapiens/index.html ensembl] site has these, but you need to know what you are looking for. To me it's like heiroglyphics. Can one say that it will be long before all the data becomes information, or do I misinterpret the situation? --[[User:Seejyb|Seejyb]] 20:56, 24 April 2006 (UTC)
::It's like hieroglyphics to me too, but fortunately, I understand a little of both genomics and reading hieroglyphs. :) - [[User:MacGyverMagic|Mgm]]|[[User talk:MacGyverMagic|<sup>(talk)</sup>]] 07:58, 26 April 2006 (UTC)
:Visit our article on the [[Human Genome Project]] and look through the external links. There are links to [[Project Gutenberg]]'s raw text dumps of the entire genome; each chromosome is presented as one 'book'. For an annotated genome, try poking around at [http://www.ensembl.org/index.html Ensembl]. (Follow the link and click on ''Homo sapiens''; click on a chromosome and zoom in from there.) [[User:TenOfAllTrades|TenOfAllTrades]]([[User_talk:TenOfAllTrades|talk]]) 20:49, 24 April 2006 (UTC)
== POOP IS GOOD ==
My Question is why is poop brown? Because I poop alot and its always brown but sometimes its a sand color, and what determines the shape of poop? Thanks for any help. <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:68.239.192.119|68.239.192.119]] ([[User talk:68.239.192.119|talk]] • [[Special:Contributions/68.239.192.119|contribs]]) {{{2|}}}.</small><!-- [Template:Unsigned] -->
:If you had read the article on [[feces]], you would know that they get their brown color from [[bile]] and dead [[red blood cell]]s. —[[User:Keenan Pepper|Keenan Pepper]] 20:43, 24 April 2006 (UTC)
::[[Human feces]] is a better place to start. [[User:WAS 4.250|WAS 4.250]] 21:03, 24 April 2006 (UTC)
:The shape of "poop" is obviously determined by it's passage through the anus, and the texture and consistancy are determined by the character of the present material. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 02:21, 25 April 2006 (UTC)
::Think of toothpaste. It is the fact you squeeze it out through the hole in the tube that gives it its shape. (Now how will you keep from smiling when next brushing?) [[User:Shenme|Shenme]] 02:51, 25 April 2006 (UTC)
:::Are you sure about that? I'd been under the impression that it was because of the shape of the rectum. It seems too firm to have been reshaped only moments before. [[User:Black Carrot|Black Carrot]] 01:52, 26 April 2006 (UTC)
::::I understand but could not confirm that the curved shape human feces often has is a result of the curved shape of the rectum. --[[User:Ginkgo100|Ginkgo100]] 03:27, 26 April 2006 (UTC)
:::::Actually, it probably depends, like Black Carrot says (I wonder if that name is a reference to this topic), on how firm the module is. I'd say both the rectum and the anus are factors in determining the post-expulsion shape. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 05:24, 26 April 2006 (UTC)
== Brain Map showing Broca's Region ==
I'm looking for a simple sketch or drawing of the brain showing basic areas including Broca's Region. Is there a site I can find this and download it?<small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:172.185.95.29|172.185.95.29]] ([[User talk:172.185.95.29|talk]] • [[Special:Contributions/172.185.95.29|contribs]]) {{{2|}}}.</small><!-- [Template:Unsigned] -->
:See the article on [[Broca's area]]. [[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]]
: You might also be interested in [[Brodmann area]]s (though see [http://spot.colorado.edu/~dubin/talks/brodmann/brodmann.html] for better images). Broca's area comprises areas 44 and 45. Cheers, [[User:Diberri|David Iberri]] ([[User talk:Diberri|talk]]) 00:36, 25 April 2006 (UTC)
== Polarized Objects ==
Most people are firmiliar with Static Electricity, and most people know about most of it's concepts, right? Well, after looking up a problem in my homework today (Find a definition using any source) I could not find any definition for a popular term "Polarized Objects" anywhere, I have looked in many dictionaries, but it is nowhere to be found. --[[User:68.61.181.253|68.61.181.253]] 21:04, 24 April 2006 (UTC)Rachel needs Help!
:I am uncertain of what you mean by "polarized object". Perhaps you are referring to a [[dipole]]? Or perhaps about [[polarization]]? -- [[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 21:08, 24 April 2006 (UTC)
:In [[electrostatics]], any section of any object may be [[polarization (electrostatics)|polarized]]; if an object is characterized by a large amount of polarization, or is uniformly polarized, one could say that it was a polarized object. But such polarization is typically a transient thing in response to an electric field; the analog to a permanent magnet, the [[electret]], is very rare. But maybe that's what you want after all? You might also simply mean "charged object". --[[User:Tardis|Tardis]] 21:50, 24 April 2006 (UTC)
==Can you calculate orbits' stregnth?==
I found out about the gravitational formula:
<math>Force=Gravitational constant\times {Mass of object 1\times Mass of object 2 \over distance^{2}}</math>
So I calculated the force between the [[Earth]] and the [[Moon]] (1.89 X 10<sup>20</sup> N); the force between the Earth and the [[Sun]] (3.55 X 10<sup>22</sup> N); and the force between the sun and [[Alpha Centauri]], the nearest star (1.76 X 10<sup>17</sup> N).
Since the Earth/sun force is greater than the Earth/moon force, does that mean that the orbit between the Earth and the Sun is stronger than the orbit between the Earth and the Moon? Or does the force get bigger with bigger objects? [[User: Jonathan W|<span style="background:#8c6638; size:2; color:#00FF00;"> Jonathan</span>]] <sup><span style="size:-1;"> [[User talk:Jonathan W|<span style="color:#8c6638">talk</span>]] </span></sup> [[Image:Canada flag 300.png|30px]] 22:11, 24 April 2006 (UTC)
:Um... "stronger orbit" and "weaker orbit" are not phrases used in celestial mechanics, so I'm not sure what you mean. Could you clarify your question? [[User:Melchoir|Melchoir]] 22:17, 24 April 2006 (UTC)
:There is certainly more force exerted between the Earth and the Sun, as you've found out.. are you asking whether it would be harder to knock the Earth out of the Sun's orbit than the Moon out of the Earth's? The actual size of the object shouldn't really matter in any of this as far as I know, it's just that heavier objects ''tend'' to be larger. -- [[User:Mithent|Mithent]]
::Right, the important exceptions to this tendency being [[degenerate star]]s, which actually get smaller as they gain mass. [[User:Melchoir|Melchoir]] 22:44, 24 April 2006 (UTC)
:::The orbit is "stronger" in that you need more energy to tear the Earth off the Sun than to tear the Moon off the Earth. This is, however, determined by the [[potential energy]], not by the force. [[User:Conscious|Conscious]] 08:34, 25 April 2006 (UTC)
::::Conscious is right; the idea of the "strength" of an orbit is most analogous to how tightly bound the objects are. To go into the mathematical nitty-gritty, the potential energy is given by <math>U=-Gm_1m_2/r</math> (where ''U'' is the potential energy, ''G'' is the gravitational constant, and <math>m_1</math> and <math>m_2</math> are the two masses, separated by a distance ''r''). The negative of this is the work you'd need to do against the gravitational force to separate the two objects to "infinity" (but you can think of this as "arbitrarily far away" if infinity bothers you; incidentally, if you've had any exposure to calculus, because gravity is a [[conservative force]] this is just the [[integral]] of the gravitational force formula). For the Earth-Sun system this works out to <math>\approx 5.3 \times 10^{33}</math> J; for Earth-Moon <math>\approx 7.7 \times 10^{28}</math> J. So you'd need seventy thousand times as much energy to separate the Earth from the Sun as you would to separate the Moon from the Earth. --[[User:Bth|Bth]] 09:21, 25 April 2006 (UTC)
:::::Since an orbiting object already carries kinetic energy, you only need to provide 50% of that amount. In fact, if you apply it in the satellite's frame of reference, you only need 8.6%. Now, since there's nothing to push against out in space, and the various bodies are moving with respect to one another, there's no Correct Frame from which to measure the energy, and a more physically relevant measure of the "strength" of an orbit is the impulse it takes to break it. As in, how much rocket fuel would it take? But then to go from energy to impulse you'll have to divide by a speed, which will throw off the scaling relationships yet again. [[User:Melchoir|Melchoir]] 10:01, 25 April 2006 (UTC)
Thanks for all the answers, but maybe I should rephrase my question: I just want to know what these numbers mean:
[[Earth]]/[[Moon]]: (1.89 X 10<sup>20</sup> N)
Earth/[[Sun]]: (3.55 X 10<sup>22</sup> N)
Sun/[[Alpha Centauri|AC]]: (1.76 X 10<sup>17</sup> N)
I thought maybe I could use this formula to calculate and compare various orbit's strength.
And yes, what I meant by ''stronger orbit'' was ''harder to knock something out of its orbit''.
[[User: Jonathan W|<span style="background:#8c6638; size:2; color:#00FF00;"> Jonathan</span>]] <sup><span style="size:-1;"> [[User talk:Jonathan W|<span style="color:#8c6638">talk</span>]] </span></sup> [[Image:Canada flag 300.png|30px]] 16:13, 25 April 2006 (UTC)
:All that those forces mean is given by Newton's second law; they're just mass times acceleration. The numbers are great for getting an idea of the ridiculous forces at work in the sky, but I'm not sure if comparing them against each other has much of a meaning. [[User:Melchoir|Melchoir]] 16:55, 25 April 2006 (UTC)
::The formula you quote at the beginning, is the formula for the force two [[point object]]s (bodies) exert upon each other. So for example, the earth exerts a force of 1.89 X 10<sup>20</sup> N on the sun, and the sun exerts a force of 1.89 X 10<sup>20</sup> N on the earth. This force, not coincidentally, is also the force needed to keep them in an orbit about each other, which is why they have come to orbit at the exact distance they do - because its the distance where the force needed to orbit is the same as the force they exert on each other.
:: The "how hard to knock out of an orbit" is a different question. As you [[peturbation|peturb]] an orbit it becomes more and more [[eccentricity (orbit)|eccentric]], and irregular, or unstable. any amount of force applied to one or the other will affect their orbit. To "knock them out of orbit" however, the easiest way to think of it is, how much work would it take, to completely separate them, to make them move completely apart and not remain in an orbit of any kind. The velocity needed for that is called [[escape velocity]], same as for [[spaceship]]s, and so a better answer is a matter of the energy required to do so, so it will be measured in [[Joule]]s not Newtons. In other words, rather than measuring the force needed to change an orbit (because any force changes an orbit anyhow), scientists prefer to ask what is the amount of work (or energy) that must be added to the system to cause the two to be able to achieve separation. [[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 18:59, 25 April 2006 (UTC)
:::OK, so the short answer is: The Force between two object and the orbit between two objects are two different things? [[User: Jonathan W|<span style="background:#8c6638; size:2; color:#00FF00;"> Jonathan</span>]] <sup><span style="size:-1;"> [[User talk:Jonathan W|<span style="color:#8c6638">talk</span>]] </span></sup> [[Image:Canada flag 300.png|30px]] 17:08, 26 April 2006 (UTC)
==How to plot simple graphics in X-windows==
How do I get a 13 year old student to plot a simple graphics on X-windows on linux?
He wanted to be able to plot y=sin(X*2*PI/200) on a window in X-windows. At the moment he is using gnuplot to plot it but we wonder how to do it directly to a window without using gnuplot.
Can it be done in C ? Python? [[User:Ohanian|Ohanian]] 23:05, 24 April 2006 (UTC)
:To my knowledge, there is no easier way to plot graphs on X than gnuplot. --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 00:08, 25 April 2006 (UTC)
:: I'm not sure if I know one, but I hope there is. Gnuplot, for all it's good sides, is not exactly a paradigm of user-friendliness. --[[User:BluePlatypus|BluePlatypus]] 00:28, 25 April 2006 (UTC)
:::Probably want Octave or Maxima. - [[User:128.32.48.131|128.32.48.131]] 01:44, 25 April 2006 (UTC)
::::See also [[Wikipedia:Reference_desk_archive/Mathematics/March_2006#Graphing]]. – [[User:b_jonas|b_jonas]] 23:09, 27 April 2006 (UTC)
For my son, we found a Java function plotting program. Did all the sin functions, etc. --[[User:Zeizmic|Zeizmic]] 01:48, 25 April 2006 (UTC)
An excellent age to begin programming for the [[X Window System]]. To answer your question, the lowest level interface to the [[X protocol]] is [[Xlib]], a C library. There are a number of [http://www.rahul.net/kenton/xsites.html#Xtutorials tutorials] on Kenton Lee's X Window System [http://www.rahul.net/kenton/xsites.html site]. Someone who could use a C compiler and gnuplot could probably copy one of the sample programs and alter it to graph a function.
There are a number of [[widget toolkit]]s built on top of Xlib, with bindings for various languages. [[Widget_(computing)|Widget]]s are for building [[GUI]]s, but most would also allow for drawing graphics primitives (the points and lines that make up your graph) directly to an X window. Another way to render graphics on a linux box would be to use [[OpenGL]] and bypass the [[X server]] (if the [[Direct Rendering Infrastructure]] is available.) Have fun. [[User:EricR|EricR]] 02:25, 25 April 2006 (UTC)
= April 25 =
== Fractals and turbulance ==
Is there a link between fractals and turbulance? Turbulant patterns seem to be fractal but turbulance is supposed to be chaotic, is this true?
:Well, [[Fractal]], [[Chaos Theory]] and [[Turbulence]] all link to one another. And yes, I believe there's a strong connection. [[User:Black Carrot|Black Carrot]] 01:26, 25 April 2006 (UTC)
:Fractals and turbulance are both examples of chaos, at least in the mathematical sense. [[User:Peter Grey|Peter Grey]] 05:34, 25 April 2006 (UTC)
::As I recall, VOB files are already in MPEG format. Try renaming them to .MPG and see if they play. If so, then [[virtualdub]]-mpeg [http://fcchandler.home.comcast.net/stable/ website] can directly recode them to AVI format in any [[codec]] or compression you choose. [[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 01:53, 26 April 2006 (UTC)
== Do fish have lips?==
does anybody know? I'm trying to settle a bet.
:If you are referring to an opening around the mouth, yes, fish have lips. If you are referring to a ring of muscles around the mouth opening, most fish have lips. Some have hardened beak-like openings for smashing coral. If you are referring to a thin area of skin with excessive nerve endings, most fish do not have lips. If you simply mean a colored region around the mouth, many of the tropical fish have brightly colored lips - some are even pink. Of note: the product "fish lips" I've found in Asian markets is actually just shark skin (at least that is what the merchants have told me). --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 01:15, 25 April 2006 (UTC)
::My attempts to kiss fish have been somewhat unsuccessful; however, this could possibly be due to a lack of desire on the part of the fish, rather than any deficiency they may have in the lip department. [[User:Phileas|Phileas]] 06:51, 25 April 2006 (UTC)
:::Perhaps you should take advice from Peter Griffin (assuming you've see the "I've had sex with all these fish" episode). --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 13:05, 25 April 2006 (UTC)
== the date of creation ==
I have calculated the times of more than a dozen comets and they trace back to one year, this was 7205 years ago. I also found this was the same date the bible has hidden since St Jerome wrote the Vulgate in about 384 AD.These are some of the comets Haley-95 orbits of 75.63 years. Hale/Bopp had 3 orbits of 2398.66666 years, Swift-Tuttle(109p) orbited 55 times of 130.745 years, and Schwassmann-Wachmann(73p) will orbit 1327 times by next month with an orbit time of 5.42963 years. I have other proof that the earth is but 7205 years old.
:Homosayswhat? [[User:Black Carrot|Black Carrot]] 01:22, 25 April 2006 (UTC)
::Bigotsayswhat? - 18:15, 25 April 2006 (UTC)
:On a more generous note, have you tried calculating where all of those comets were 7205 years ago? If they appear to have originated from the same point, that could be a scientific discovery worth publishing. Good luck! [[User:Melchoir|Melchoir]] 01:29, 25 April 2006 (UTC)
:Oh yes. I remember it like it was 7205 years ago. I was just getting up for a morning bowl of raisin bran and I couldn't find the damn light. Then a lovely fellow - Oh, what was his name? Something like Yahoo or No Way or Yahweh - anyway, he just said "Let there be light" and I heard him flip a switch and the light turned on. I acted very impressed, but I remembered changing the bulb just a couple days earlier. I asked him to join me anyway. I was feeling very foggy from a hard day's night. I mentioned it to him and he said he'd make a song out of it later when he got around to learning the drums. Then, he gave me a couple pills and the foggy void separated into a clear view of the heavenly sky above and a firm earth below my feet. I poured him a bowl and he got all weird about it. He kept separating the piles of bran into little mounds with oceans of milk between them. He pushed the raisins in and commented how they bobbed around like little fish. I agreed, but it was getting rather trying about this time. Anyway, to make a long story short, I asked him if he remembered the date of creation. "Sure," he said. It was exactly 6.3 billion years before that. He remembered it just like it was 6.3 billion years ago. He was just getting up for a morning bowl of raisin bran... --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 01:30, 25 April 2006 (UTC)
: 7,205 years ago, yes. And on a Thursday. [[Arthur Dent|I never could get the hang of Thursdays]]. -- [[User:Filliam H Muffman|Filliam H Muffman]] 02:05, 25 April 2006 (UTC)
::Actually... assuming our unsigned friend calculated the orbits on the same day that Mr. Black Carrot replied, then the earth started on a Wednesday (5199 BCE). I'm a little confused about his calculations though. What does the origin of comets have to do with the age of the earth? I'd rather give him the benefit of the doubt and have him come back and explain his theories. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 02:16, 25 April 2006 (UTC)
::* To ''suitly emphazi'', that's 5199 BCE if you use a [[year zero]], 5200 BCE if you don't. -- [[User:Filliam H Muffman|Filliam H Muffman]] 02:53, 25 April 2006 (UTC)
:::Damn. And I feel bad for attempting to block you from using a H2G2 quote too. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 05:16, 26 April 2006 (UTC)
:What exactly are ''the times of more than a dozen comets''? [[User:Peter Grey|Peter Grey]] 05:37, 25 April 2006 (UTC)
::Like the times of exactly a dozen comets, but more! -- [[User:SCZenz|SCZenz]] 07:07, 25 April 2006 (UTC)
:::Ha, ha. Maybe this belongs in <font color=blue>Wikipedia:Reference desk/Pseudoscience</font>. --[[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 07:39, 25 April 2006 (UTC)
:Congratulations you've managed to calculate the age of recorded history. Now use your awesome powers of deduction to resolve your date of Creation with the fact that Radio Carbon-14 dating which breaks down to Carbon-12 at a fixed rate, and is renewed in living organisms dates bones and plants over 10,000 years. Not to mention several other radioactive isotopes which also have fixed rates of radioactive decay have dated rocks at around 4,000,000,000 years of age. --[[User:Tollwutig|Tollwutig]] 14:24, 25 April 2006 (UTC)
== Strings ==
Are thre anti-strings? <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:207.255.31.124|207.255.31.124]] ([[User talk:207.255.31.124|talk]] • [[Special:Contributions/207.255.31.124|contribs]]) {{{2|}}}.</small><!-- [Template:Unsigned] -->
:Your question needs more context before we can answer it. What are you talking about? —[[User:Keenan Pepper|Keenan Pepper]] 02:55, 25 April 2006 (UTC)
:If you're asking whether string theory includes antimatter states, the answer is yes. -[[User:Lethe/sig|lethe]] <sup>[[User talk:Lethe/sig|talk]] [{{fullurl:User talk:Lethe|action=edit§ion=new}} +]</sup> 03:11, 25 April 2006 (UTC)
::But there are not any "anti-strings," like how we see antimatter and matter annihilating. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 04:24, 25 April 2006 (UTC)
:::A stringy antimatter state annihilates a stringy matter state, just like regular matter and antimatter annihilate. We also have antistates of D-branes, which also annihilate with their positive counterparts. I'm not sure why you think that doesn't happen. -[[User:Lethe/sig|lethe]] <sup>[[User talk:Lethe/sig|talk]] [{{fullurl:User talk:Lethe|action=edit§ion=new}} +]</sup> 19:23, 28 April 2006 (UTC)
:The woodwind section is often very anti-string, if that's any help. [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 03:20, 25 April 2006 (UTC)
::They're really just acting that way to hide the uncontrollable physical attraction. [[User:Melchoir|Melchoir]] 03:27, 25 April 2006 (UTC)
== Aluminum- going from an ion to an atom ==
How many electrons does aluminum gain by going from an ion to an atom? <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:67.150.42.98|67.150.42.98]] ([[User talk:67.150.42.98|talk]] • [[Special:Contributions/67.150.42.98|contribs]]) 03:19, 25 April 2006.</small><!-- [Template:Unsigned] -->
:If you want to know how many electrons an [[aluminum]] ion will gain, you should look at it in reverse: how many electrons does an aluminum atom loose to become an ion? Because it is in group III of the periodic table, it has three [[valence electrons]] that are readily removed from the atom. When this happens, it becomes a Al<sup>3+</sup> ion, so the answer is '''three'''. Hope this helps.--[[User:Russoc4|Chris]] 03:23, 25 April 2006 (UTC)
== Bauxite ==
How is bauxite turned into a metal? <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:67.150.42.98|67.150.42.98]] ([[User talk:67.150.42.98|talk]] • [[Special:Contributions/67.150.42.98|contribs]]) 03:29, 25 April 2006.</small><!-- [Template:Unsigned] -->
:[[Bayer process]] [[User:Melchoir|Melchoir]] 03:33, 25 April 2006 (UTC)
:And then [[Hall-Héroult process]]. [[User:Melchoir|Melchoir]] 03:33, 25 April 2006 (UTC)
thanks!--[[User:Ll10398|Ll10398]] 03:45, 25 April 2006 (UTC)lily
== Properties of Aluminum ==
What are 10 different properties that make aluminum than other metals? <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:67.150.42.98|67.150.42.98]] ([[User talk:67.150.42.98|talk]] • [[Special:Contributions/67.150.42.98|contribs]]) 03:36, 25 April 2006.</small><!-- [Template:Unsigned] -->
:Ahem: Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please do not post entire homework questions and expect us to give you the answers. [[User:Melchoir|Melchoir]] 03:37, 25 April 2006 (UTC)
:Are you writing an essay about aluminum or something? Did everyone in your class get their own element? Anyway, I'm sure there are at least ten interesting properties in the article [[Aluminium]], so don't bother us anymore unless you really search and still can't find what you're looking for. —[[User:Keenan Pepper|Keenan Pepper]] 03:51, 25 April 2006 (UTC)
:Research is useful...--[[User:Tollwutig|Tollwutig]] 14:27, 25 April 2006 (UTC)
== would like to know anything about Arlington Chem Co. circa 1890s. ==
I would like to find out anything about Arlington Chem Co. circa 1890s if anyone knows anything I would be grateful.
:[http://www.google.com/search?q=%22Arlington+Chemical+Company%22&sourceid=mozilla-search&start=0&start=0&ie=utf-8&oe=utf-8 start here] [[User:WAS 4.250|WAS 4.250]] 15:56, 25 April 2006 (UTC)
:"John Andrus (1841-1934) was born in Pleasantville, New York, graduated from Wesleyan University and soon moved from teaching school to pursuing his talents as an investor and businessman. His primary operating business, the Arlington Chemical Company, manufactured typical medicines of the late 1800s and distributed them worldwide." [http://www.surdna.org/about/about_show.htm?doc_id=314235] [[User:WAS 4.250|WAS 4.250]]
== Physics Dilemma ==
I have a question that's based on theory of physics.
Suppose you have a person of a certain weigh in a bucket where he/she is pulling themselves up by tugging on the other rope. So that's a pulley, he/she is on one side in the bucket, and the rope is over the pulley, and then they pull the other end, just to clarify.
So, my physics teacher told me that if the person was to pull at the force of gravity on the person going up, that the person would go up in a constant speed, no acceleration. So, if the tugging action is equal to the weight, it moves up in a constant speed. But how would you pull yourself have way up for example, and then stay in that position? What force is keeping you balanced? She told it was the same force, except that the rope was exerting the force up when it was moving, and then when it was motionless, that the same force was being directed into a different direction. Class was over and I didn't get the last bit.
So if someone could explain this well as they can it would be greatly appreciated. Thanks a lot.
[[User:C-c-c-c|C-c-c-c]] 05:11, 25 April 2006 (UTC)
:If all the forces on a body sum to zero, then it doesn't accelerate; this is universally true whether the body is moving or not. If you're not accelerating, then the rope/bucket must be exerting an upward force equal in magnitude to your weight. It'll never be in any other direction.
:On a different note, "force of gravity" is misleading. Sitting in the bucket, you don't have to pull the other side of the rope down with a force equal to your own weight; you only need to exert half of that force. This example is actually touched on at [[Mechanical advantage]]. [[User:Melchoir|Melchoir]] 05:35, 25 April 2006 (UTC)
Thanks, but I was wondering if you could explain the idea behind that, why would it be half your weight? I've never seen any of those equations in the link you put up. Thanks again.
[[User:C-c-c-c|C-c-c-c]] 05:47, 25 April 2006 (UTC)
:Hmm, interesting. I haven't thought about this problem before. Assume that you are standing in a bucket. There is a rope tied to the bucket, looped over a fixed pulley, and which passes by you again on its way down. You're holding on to the rope.
:For our example, all forces will be in the vertical direction; assume negative forces point down. The force of gravity on you (your weight) will be -''m·g'': your mass ''m'' times the gravitational acceleration ''g''.
:If you pull on the rope with a force ''f'', you'll be directly exerting that force to lift your body. In addition – and this is the important trick – the rope (in tension) will be exerting an additional force ''f''. To remain steady, the forces acting on you must sum to zero, so:
::0 = -''m·g'' + ''f'' + ''f''
::''f'' = (1/2)·''m·g''
:Conceptually, you could also think of it has being a bucket with a rope looped over a pulley where ''both'' ends of the rope are tied to the bucket. (Here, your arms just act as the knot that ties the other end of the rope down.) Your weight is supported by two ropes; each rope holds half the weight. [[User:TenOfAllTrades|TenOfAllTrades]]([[User_talk:TenOfAllTrades|talk]]) 06:05, 25 April 2006 (UTC)
Wow! That actually makes sense! And it's so simple too, but not obvious at all at first. Thanks a lot![[User:C-c-c-c|C-c-c-c]] 06:18, 25 April 2006 (UTC)
=== what's definition of tension? ===
in the question above why's it 0 = =mg + f + f & not mg - (f+f) because the tension is opposite direction of gravity rite? what's tension exactly how would u define it. also its always opposite of gravity rite? or no? can some1 explain thanks
06:37, 25 April 2006 (UTC)
*[[Tension]] is the force experienced when a rope is pulled, and is equal and opposite at the ends. If something is hanging from a rope, then tension is balancing the vertical force of gravity. Try a [[free body diagram]] of a section of the rope. [[User:Peter Grey|Peter Grey]] 06:52, 25 April 2006 (UTC)
== Psychiatrist's view of a religious person ==
Assume for a moment that people believing in a god isn't a common thing. Instead it's the kind of thing that may make someone proclaim, "That there is crazy talk!". With that in mind what would a psychiatrist's diagnosis be of a person who believes in an omniscient and omnipotent god who nobody has ever been able to prove exists? [[User:Dismas|Dismas]]|[[User talk:Dismas|<sup>(talk)</sup>]] 08:02, 25 April 2006 (UTC)
:There are people who believe in [[Ufology|aliens amongst us]], but mostly they're just living otherwise normal lives. In your scenario, people believing in a god might be regarded as eccentric, but not requiring treatment unless they believe their god requires them to, for example, kill all non-believers.-[[User talk:gadfium|gadfium]] 08:09, 25 April 2006 (UTC)
:It would depend on the patient's behavior. Example: saying Heaven is better than Earth is not considered "crazy"; but trying to go there ''now'' on purpose because it is better (by suicide) is considered crazy. [[User:WAS 4.250|WAS 4.250]] 15:38, 25 April 2006 (UTC)
::Under the DSM-IV, probably "delusional disorder". The current definition of the symptom is a "fixed false belief, excluding those that are part of a religious movement". If you remove that religious caveat, you have a delusion, a symptom of psychosis, and the diagnosis would depend on the presense or absense of other symptoms (such as hallucinations). In the absense of other symptoms, probably "delusional disorder" would win the day. - [[User:Nunh-huh|Nunh-huh]] 18:13, 25 April 2006 (UTC)
:::Of course, the other opposite question arises. [[mysticism|Mystics]] would consider that ''not'' being aware of more than the [[consensus reality]] we see around us, is somewhere between ignorance, [[delusion]] and [[illusion]] too. [[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 18:42, 25 April 2006 (UTC)
::::Fortunately, mystics can't civilly commit anyone, so their opinion matters mainly to themselves. - [[User:Nunh-huh|Nunh-huh]] 20:07, 25 April 2006 (UTC)
:::::Thanks for the replies, everyone! [[User:Dismas|Dismas]]|[[User talk:Dismas|<sup>(talk)</sup>]] 01:40, 26 April 2006 (UTC)
== Insane Psychiatrist ==
Is it true that an insane person isn't allowed to study psychiatry/psychology? --[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 11:32, 25 April 2006 (UTC)
:That is not true. [[User:WAS 4.250|WAS 4.250]] 15:38, 25 April 2006 (UTC)
::Recently I came across a study which suggested that an above-average percentage of those studying psychology is made up of mentally instable persons, however you define that; a number mentioned was 60%, whatever that is worth. I have also been told that the curriculum is made up so as to ''not'' appeal to that type of person who wants to get in because he is obsessed with his own disorders, at least at my university. Apparently they try to bore them out :D --[[User:Dr. Zarkov|Dr. Zarkov]] 17:27, 25 April 2006 (UTC)
:For what it's worth, I'm currently applying for a master's degree program in clinical psychology, and so far there's been no mention of psychological screening for applicants. --[[User:Ginkgo100|Ginkgo100]] 03:18, 26 April 2006 (UTC)
I'd be very skeptical of this rumor. It has [[urban legend]] written all over it. [[User:Bhumiya|Bhumiya]] ([[User talk:Bhumiya|said]]/[[Special:Contributions/Bhumiya|done]]) 04:46, 26 April 2006 (UTC)
*You might not be allowed to practice phsychiatry, but I don't see why they should stop insane people from studying it. - [[User:MacGyverMagic|Mgm]]|[[User talk:MacGyverMagic|<sup>(talk)</sup>]] 08:03, 26 April 2006 (UTC)
This is '''NOT''' true. My girlfriend is majoring in psychology. [[User:12.183.203.184|12.183.203.184]] 04:20, 27 April 2006 (UTC)
== Netherlands And Rising Sea Levels ==
Based on the threat of rising sea levels and the Dutch government's plan to give some land to the sea in coming decades, would you agree that property in The Netherlands would be a bad investment? Culturewise, what where would be the next best place? Belgium? -[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 08:06, 25 April 2006 (UTC)
:I have not heard about this, but I suppose waterfront property may not be the best investment. Nevertheless, as we have seen in Vancouver, BC, Canada, when space is limited, prices go WAY UP, so investment would be a ''good'' thing. As for the culture... that's hardly a scientific question. [[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 08:21, 25 April 2006 (UTC)
:The threat is unknown. Sea level is largely dependent on local pressure, temperature, salinity, etc. Some parts of the ice on Earth are melting, some are freezing, some are not doing anything, and some are just moving. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 10:44, 25 April 2006 (UTC)
::Sorry, MacDavis, I have to disagree with you there. The threat is definitely there, take a look at [[sea level]] and [[sea level rise]], especially the first graph on both pages. Sea level change is global (because water is a liquid and so spreads itself out evenly), and it is definitely rising, there is no debate about this - satellites can measure sea level to an accuracy of a millimeter, and data collected over the past decades shows a steady rise of about 3mm a year (see [[Sea_level_rise#Satellite_sea_level_measurement|here]]). There are several low-lying islands in the Pacific which have seen their land area greatly reduced over the last fifty years because of this. The question is ''how much'' it will rise, but even the lowest estimates put a significant strain on the Dutch sea defences over the next decades. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 11:44, 25 April 2006 (UTC)
:While it is a concern, do not forget that the Netherlands is already for over 50% below sea level, and dykes, levies and dunes have kept it dry in the past few centuries with only one major flooding(The one in zeeland in 1953). Most prognosis for the rise of sea level talk about 30cm to 70cm until 2100, something that should be manageable, although quite costly. Do not confuse this with the other waterworks project currently going on, which is to create basins for the 3 major rivers because altered weather has increased the chances of flooding from those. However, i'm not sure i'd advice anyone to invest in property in the Netherlands, since 60 years of housing shortages have pushed house and land prices to very high levels. As for what are related cultures, i'd guess that Belgium, Germany and the scandivian countries would probably be closest. [[User:SanderJK|SanderJK]] 11:56, 25 April 2006 (UTC)
:This is getting slightly offtopic, but you might be wise to look at [http://www.economist.com/finance/displayStory.cfm?story_id=4079027 this article] before you think too hard about buying investment property ''anywhere''...--[[User:Robert Merkel|Robert Merkel]] 05:05, 26 April 2006 (UTC)
== Refering To A Research Group ==
During my reading I've read of a research group refered to as the "Pabo group", being lead by someone called 'Pabo'. I need to refer to three papers published by
DAVID J. SEGAL, BIRGIT DREIER, ROGER R. BEERLI, AND CARLOS F. BARBAS III
Birgit Dreier, Roberta P. Fuller, David J. Segal, Caren V. Lund, Pilar Blancafort, Adrian Huber, Beate Koksch,
and Carlos F. Barbas III
Birgit Dreier, Roger R. Beerli, David J. Segal, Jessica D. Flippin, and Carlos F. Barbas III
Segal and Drier occur in all instances, but some of the work was carried out at more than one laboratory. So can I refer to a specific group? --[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 09:36, 25 April 2006 (UTC)
:Hrm. I'd say something like "Segal, Dreier and collaborators (Segal et al XXXX, Dreier et al YYYY, Dreier et al ZZZZ) [did whatever they did]" where XXXX etc are years (if YYYY=ZZZZ then use YYYYa and YYYYb). If I needed to refer to the same work repeatedly I'd do "Segal, Dreier and collaborators (Segal et al XXXX [SXX], Dreier et al YYYY [DYY], Dreier et al ZZZZ [DZZ])" at the first appearance and use the abbreviations I'd established thereafter to refer to whichever paper was relevant for the point I was making, probably treating the abbreviation as I would the names written out in full (eg, "DZZ showed [some exciting result]" for "Dreier et al (ZZZZ) showed ..."). But that's because I'm used to (the astronomy variant of) [http://www.lib.ohio-state.edu/sites/guides/chicagogd.html Chicago-style science citation]; I don't know how similar that is to biochem. I'd be wary of deciding that they were "the Someone group" unless they're already widely referred to as that and/or one of the people is very clearly much more senior. --[[User:Bth|Bth]] 12:25, 25 April 2006 (UTC), not logged in
: Scientific publications list the group leader as the corresponding author, who is typically marked with an asterisk. [[User:Dr Zak|Dr Zak]] 20:20, 25 April 2006 (UTC)
::yes and no - it depends on the type of scientific publication - there are many different formats for referencing and citation. Psychological journals use APA, for example, which is different from the method you mention. [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 02:24, 26 April 2006 (UTC)
If there is one person marked out to whom correspondence should be sent, would it be correct to assume that they were the group leader? -[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 05:04, 27 April 2006 (UTC)
:mmm. usually, but not always. [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 08:37, 27 April 2006 (UTC)
== Microprocessor Programming ==
I am currently syuding microprocessor programming.We can multiply two numbers by repeated addition of one number;
other number of times.But then how does the scientific calculator do decimal multiplication and all as the numbers dont consist of integers??Ex 2*3=2+2+2 or 3+3 but 2.3*5.6???
:A calculator will store decimal numbers as either fixed point or floating point. These are special ways to store information about a number. Fixed point allows a certain fixed number of decimal places, while floating point stores an exponent and mantissa. If a microprocessor chip does not include direct support for floating point, it is a huge project to create it, but the principles are fairly simple, so long as you understand what the arithmetic rules would be for arithmetic on two numbers in exponent and mantissa form. [[User:Notinasnaid|Notinasnaid]] 12:25, 25 April 2006 (UTC)
:[[Multiplication algorithm]]s are executed by [[Arithmetic logic unit]]s. [[User:WAS 4.250|WAS 4.250]] 15:30, 25 April 2006 (UTC)
::Repeated addition is about the worst method of multiplication. Long multiplication is very simple in binary and this is the method most computers use for normal multiplication. It can be implemented in either hardware or software (software being the norm on some very low end microcontrollers hardware on anything else)
::As for non-integer types the basic idea is you multiply the mantissas and add the exponents. then if nessacery you normalise.
::e.g. in decimal (most computers would do this in binary but the principles stay the same) 2.3*5.6 = 23*10<sup>-1</sup>*56*10<sup>-1</sup>=23*56*10<sup>-2</sup> [[User:Plugwash|Plugwash]] 15:42, 25 April 2006 (UTC)
The answer is it depends on the calculator. It's important to distinguish between [[Integer (computer science)|integer]]/[[Fixed-point arithmetic|fixed point]]/[[floating point]] representation, [[Binary numeral system|binary]]/[[decimal]] representation, and for decimal the encoding of digits ([[Binary-coded decimal|BCD]], [[Densely Packed Decimal]], [[Chen-Ho encoding]]). For instance, a floating point number may be stored with a binary integer [[significand]] and densely packed decimal integer [[exponent]]. Also keep in mind that a number may be represented in one form, but arithmetic may be performed in another, see: [[Intel BCD opcodes]].
If you are looking at a scientific calculator, you are probably dealing with some kind of floating point decimal and IBM has a great [http://www2.hursley.ibm.com/decimal/ site] with links about decimal representations and arithmetic. [[User:EricR|EricR]] 16:32, 25 April 2006 (UTC)
The representation of a number can undergo many changes prior to and after the multiplication. I once saw a computer program that converted numbers back and forth between ASCII, BCD, and binary as the data passed between subroutines written by diferent people and this was just for small integers! A handcrafted program in assembly I saw went right from the keyboard-key-identify-buffer-contents passed by the keyboard-control chip to binary integer representation it sent to a multiplication-register in the CPU chip. (ok, ok, "right from" condenses a lot of get interupt, get byte & store, type detail...) [[User:WAS 4.250|WAS 4.250]] 18:30, 25 April 2006 (UTC)
:See also the chapter 4.2 ([[floating-point]]) in [[Knuth]]'s [[The Art of Computer Programming]] (it's in volume 2). It explains how you can calculate 2.3*5.6 based on integer arithmetic. – [[User:b_jonas|b_jonas]] 22:54, 27 April 2006 (UTC)
== Anyone run a website? ==
That is not computer related (and is in English). If you have a counter on the front page, I would like to know what statistics you have on the various operating systems that computers visiting your website run. I write a blog, but have contaminated the stats by visiting it myself. Presumably your site will not be contaminated to any large degree, if you don't visit it often or have a large number of visitors. Thanks heaps.
:The last data we seem to have on Wikipedia can be found [[Wikipedia:Browsers|here]], but this is over two years old - Wikimedia hasn't has the stats accessible for some time. However, this might be interesting for you, on a global web perspective: [[Usage share of web browsers]]. -- [[User:Mithent|Mithent]] 13:36, 25 April 2006 (UTC)
:I have a website [[http://hellrazor.cybergoth.ca/]] that uses a free counter by sitemeter.com. An example of statistics it generates from hits from my page are here [[http://www.sitemeter.com/?a=stats&s=sm2hellrazor]]. - [[User:Cybergoth|Cybergoth]] 21:48, 25 April 2006 (UTC)
:Thanks Cybergoth, that's exactly what I'm after. Didn't realise visitors could see other webcounters stats, very handy. ''Bladerunner'' is in my top 3 films, although I haven't ever seen The Directors Cut, never will, think it will ruin my enjoyment of the film. [[User:218.101.92.181|218.101.92.181]] 22:36, 25 April 2006 (UTC)
I have a tracker on my site from eXtreme Tracking, but I'm pretty sure my results are skewed due to small sample size and a selected population [geeks mostly :P]. You can see it [http://extremetracking.com/open?login=ilyanep here] though. — [[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">Ilyan</span>]][[User:Ilyanep/Esperanza|<span style="font-variant:Small-caps;color:green;">e</span>]][[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">p</span>]][[User talk:Ilyanep| <span style="font-variant:Small-caps;color:#808080;">(Talk)</span>]] 23:27, 25 April 2006 (UTC)
:I never knew that you could view site stats for another site, now I know that you can seek out (ie google) specific sites running extreme tracking (high levels of resolution) and see what sort of bias the site is getting. Yes lynanep, you do seem to have a geek bias, Linux users are about 4 times the proportion at your site than another site which is a blog about someone's thoughts. I was in a round about way wanting to know Linux market share (of web browsers) and the other site gives 0.65%. That means the only way is up.[[User:218.101.92.181|218.101.92.181]] 01:08, 26 April 2006 (UTC)
== Bohrs radius in Plancks units. ==
Dears,
In line 34 of the sub-article "Plancks units and the invariant scaling of nature" of the main-article of "Plancks units" is after the normal equation of Bohrs radius used in NIST's CODATA and Wikipedia article about Bohrs radius an other equation in Plancks units namely:
a0 = mp.lp / (me.alpha)
whereby mp and lp are Plancks mass and length, me is the electron mass and alpha is 1/137.
My question is where does this equation come from and what is its derivation from the "normal"
equation?
Boy Boer
Breda
the Netherlands
:It's a simple set of substitutions. Starting from the [[Bohr radius]] <math>a_0={4\pi\epsilon_0\hbar^2 \over m_ee^2}</math>, we substitute in the [[fine structure constant]] <math>\alpha = {e^2 \over 4\pi\hbar c \epsilon_0}</math> to get <math>a_0={\hbar \over m_e c \alpha}</math>. Now, from the definitions of the [[Planck units]] <math>m_P=\sqrt{\hbar c \over G}</math> and <math>l_P = \sqrt{\hbar G \over c^3}</math> we get <math>m_Pl_P=\sqrt{\hbar c \over G}\sqrt{\hbar G \over c^3}=\sqrt{\hbar^2 \over c^2}={\hbar \over c}</math>, which we substitute in to get <math>a_0={m_Pl_P \over m_e \alpha}</math> as you wanted. --[[User:Bth|Bth]] 14:37, 25 April 2006 (UTC), still not logged in
::Ah, you beat me to it. Here's the same in Gauss units: <math>a_{0} = {\hbar^{2} \over m_{e}e^{2}} = {\hbar \over m_{e}c} \times {\hbar c \over e^{2}} = {\hbar \over m_{e}c\alpha} = {m_{p}l_{p} \over m_{e}\alpha}</math> [[User:Conscious|Conscious]] 14:48, 25 April 2006 (UTC)
:::I have to say, I'm rather dubious about the claim in the [[Planck units]] article that this definition of <math>a_0</math> is somehow fundamental, dimensionless, etc. -- the mass of the electron still sneaks in as a parameter, which isn't a combination of the five constants used as the basis of the system. Indeed, the equation explicitly uses the mass <math>m_P</math> which ''is'' such a combination. --[[User:Bth|Bth]] 07:15, 26 April 2006 (UTC)
== Electron acceptors for photosystems ==
Okay, I give up on trying to find this. Does anyone know if [[potassium ferricyanide]] is an electron acceptor for [[photosystem]]s I and II, or only photosystem I? I believe that phenyl [[quinone]] is an acceptor for only photosystem II, though I could be wrong. Thanks in advance, if anyone can tell me! -- [[User:Mithent|Mithent]] 13:54, 25 April 2006 (UTC)
: I'm not sure what you're asking? If K3Fe(CN)6 can oxidize PS I/II? That would depend entirely on the redox state of the enzyme. There's plenty of experimental data on the redox potentials of PS I and II out there. --[[User:BluePlatypus|BluePlatypus]] 20:25, 25 April 2006 (UTC)
== Calculating escape velocity - simpler method ==
In Y.Perelman's book '''physics for entertainment'', he shows a much simpler way of calculating the escape velocity. It goes somewhat like this:
Stand on a hill of height say h metres. Throw a ball horizontally with a velocity v. The ball will fall towards earth. In 1 second, the ball would have fallen 4.9 meters [s=ut+(1/2)at^2]. If it is still h metres from the surface of earth (i.e. if it has fallen just enough to follow the curvature of earth), then v is the escape velocity.
I don't remember the exact argument and I am not able to derive it. I try and end up with a velocity of about 7.9 km/sec. Can anybody tell me where I am going wrong ? Do you know how he derives it ? [[User:Wikicheng|Wikicheng]] 19:41, 25 April 2006 (UTC)
:It sounds like that v is actually the circular-orbit velocity, not the escape velocity. As you've discovered, the two differ by a factor of sqrt(2). But to order of magnitude, an estimate of one is an estimate of the other. [[User:Melchoir|Melchoir]] 19:49, 25 April 2006 (UTC)
:Also, for good accuracy you'll need to consider an infinitessimal time instead of "1 second", because that standard gravitational acceleration expression applies at finite time only when the velocities are small (so the orbit is effectively parabolic). --[[User:Tardis|Tardis]] 19:51, 25 April 2006 (UTC)
Even if I use the time of 0.1 sec, I still get about 7.9 km/s. Looks like Melchoir's is right. 7.9*sqrt(2)=11.2 approx. Anyone who has read this in the above mentioned book? -- [[User:Wikicheng|Wikicheng]] 20:12, 25 April 2006 (UTC)
== Black hole horizon problems ==
I get the feeling that these are a common misunderstanding-driven question, but oh well.
#Objects falling into a black hole will redshift out of visibility, and appear to slow to a stop as they approach the event horizon. If it takes an infinite amount of time (as viewed from far away) for anything to actually fall in, how is the black hole ever observed to grow (or even to really form, for that matter)?
#Similarly, if I recall correctly, an object falling into a black hole will have its entire rest mass released as lost gravitational potential energy. Since rest mass is invariant, shouldn't the object be able to observe its own energy loss -- down, even, to 0 energy at the event horizon?
#I saw recently (at [[photon sphere]]) that the circular orbital velocity at 1.5 [[Schwarzchild radius|radii]] is ''c''; obviously the escape velocity is less than ''c'' there. So is it yet another [[general relativity|GR]] revelation that with sufficiently intense gravity, the ratio of orbital velocity to escape velocity crosses 1?
GR is really too much; thanks for any clarification. --[[User:Tardis|Tardis]] 20:08, 25 April 2006 (UTC)
:For #3, isn't the escape velocity always less than any orbital velocity? —[[User:Keenan Pepper|Keenan Pepper]] 20:54, 25 April 2006 (UTC)
::Never mind me, I don't know what I'm talking about. —[[User:Keenan Pepper|Keenan Pepper]] 21:02, 25 April 2006 (UTC)
Point 3 is really strange; I'd like to hear about that too. That must mean that (differently from the Newtonian case) the speed required to escape to infinity from near a black hole depends on direction. Which of course in the extreme case is obvious; if your [[perinigricon]] is below the event horizon, you ain't coming out.
What happens when perinigricon is near the event horizon, but above it? Are you accelerated to relativistic speeds? Do you lose significant energy to gravitational radiation, which might drop you below the event horizon on a trajectory that you thought was safe, if you hadn't taken that energy loss into account? --[[User:Trovatore|Trovatore]] 22:36, 25 April 2006 (UTC)
:The physics outside a black hole are actually qualitatively not too different from the Newtonian case. There's still a conserved energy and angular momentum, and you can construct a one-dimensional potential that describes the radial motion of a test particle. The major difference is that this potential no longer has an infinite centrifugal barrier at r=0; instead it goes to negative infinity at r=2. (G=M=c=1) If the particle has an angular momentum greater than sqrt(12), the potential has a ''maximum'' somewhere between r=3 and r=6.
:So no particle can escape with a peringricon less than r=3, which is apparently called the photon sphere. If you cross that photon sphere in the wrong direction, you're not coming out unless you light the fires. (And, of course, if you cross r=2 you're not coming out no matter what.) [[User:Melchoir|Melchoir]] 23:24, 25 April 2006 (UTC)
::A more qualitative way of putting this is, "closer than the photon sphere, moving tangentially around the hole pushes you in, instead of out". You get very interesting optical effects too, due to the way light rays curve (the black hole looks like it takes up more than half the sky, with your view of the universe looking like a ball). --[[User:Christopher Thomas|Christopher Thomas]] 21:46, 26 April 2006 (UTC)
:As to the first two points, my extremely limited understanding is as follows:
:1) We need a consistent definition of "fall in" here, I think. Crossing the event horizon counts, as far as I can see. As such, when something hits it, even if it takes an infinite time for us to observe the falling-in, it's already part of the mass of the black hole from the POV of the gravitational effects of the hole. AIUI, if it weren't for the infinite redshift part, a black hole would maintain the appearance of the last sphere of star material to cross into it during formation indefinitely. (But of course we've never actually observed any of this directly.)
::I had thought of this explanation; the problem I have with it is that the black hole could then become asymmetric if, say, everything were to fall in on one side. That seems to violate the [[no hair theorem]]. --[[User:Tardis|Tardis]] 15:47, 26 April 2006 (UTC)
:2) This is one of those things that boils down to "the far-away and falling-in viewpoints see the same physics from very different perspectives". IIRC, it's been shown that for a black hole with minimal tidal forces (eg the supermassive ones in galactic cores) the observer crossing into the black hole barely notices the point of crossing the event horizon, so it seems they wouldn't get to notice their energy dropping to zero. However, they are now in a situation where all their possible worldlines contain a singularity in the future. But from the perspective of an external observer, what happens to them is forever inaccessible, shrouded by the event horizon, and so their mass has just become part of that of the black hole.
:Most of that probably makes no sense, and anything that does make sense is probably wrong. --[[User:Bth|Bth]] 07:35, 26 April 2006 (UTC)
== Physics of cutting ==
It says on the article on [[cutting]], that an object can be cut with an appropriately hard tool with such a force, that the resultant stress exceeds the strength of the material in question - "The simplest applicable equation is stress = force/area".
Is it possible to arrive at a lower limit for the said area? I.e. to the point, where you are cutting just one atom wide? (and at arbitary length)
One could use the equation stated above to calculate the minimum energy requirements to cut through an object, supposing that you could use an impossibly sharp tool. In such a case, would there be other factors to consider, in addition to strength of the material and the area being cut?
This is my curiosity working again. Thanks for any responses. [[User:Santtus|Santtus]] 20:58, 25 April 2006 (UTC)
:Material properties such as strength are based in [[continuum mechanics]], and don't apply on length scales not much larger than atoms. Moreover, it's very hard to define an area of contact when the edge is essentially one-dimensional, so the concepts of pressure and stress are not very applicable at all. Still, it would be possible to cut with a monolayer, although the knife would be quickly blunted by abrasion even if it were harder than the substrate -- one line of atoms cannot have the strength (hardness) associated with the bulk material. If the knife survived, it would indeed require very little force to make the cut. The difficulty might be expected to depend on whether one was cutting "between" atoms or "through" them with an edge that small, but the amount of energy required to shift and/or compress the material by half a bond length would probably be negligible compared to the energy required to break the bond. --[[User:Tardis|Tardis]] 21:55, 25 April 2006 (UTC)
::Thanks! So I'll be looking at [[bond energy]] and similar concepts, maybe measured in J/mol, or something like that. I'll look around. With few other numbers I can convert it into J/m^2 of cross section of area cut with the "perfect knife". I got suddenly interested of how far the current technology is from the "perfect" in that area, and I wanted to calculate that myself. Maybe I'll get a somewhat accurate estimate now. [[User:Santtus|Santtus]] 00:15, 26 April 2006 (UTC)
:::And then you can get to work on a prototype of those laser whips they had in [[Johnny Mnemonic]]. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 05:00, 26 April 2006 (UTC)
:::Remember that a lot of the effort involved in cutting, say, cheese is friction between the substrate and the sides of the knife. This is one reason (along with uniformity of slice thickness) why some [[cheese slicer]]s use wires, and it might affect your judgment of what counts as a "perfect knife". --[[User:Tardis|Tardis]] 16:14, 26 April 2006 (UTC)
== Can electricity be converted to kinetic energy?? ==
I heard that electromagnetic energy can be converted into kinetic energy and move things around. If this is true how come background Em from things like powercables and TVS etc dont hit us all throughout the day?
Jonothan pritchard 23:00
:The best way to convert electricity into kinetic energy is probably with an [[electric motor]]. [[User:Johntex|'''Johntex''']]\<sup>[[User_talk:Johntex|talk]]</sup> 22:03, 25 April 2006 (UTC)
:If you are asking why the EM energy emitted by power cables and TVs don't move anything, it is just that the waves emitted are too weak to move anything. But they do hit us. Powerful EM waves inside [[Microwave ovens]] can heat things up. Haven't you heard the argument that EM waves emitted by [[mobile phones]] are dangerous ? Being in the vicinity of high tension power cables for a long time is supposedly dangerous too --[[User:Wikicheng|Wikicheng]] 22:43, 25 April 2006 (UTC)
::Also take into account that most of the EM waves (sunlight/starlight/space radiation) are slamming down on you from above at about 299,792,458m/s. By comparison, very little comes from earth-bound items (unless you happen to be near a nuclear explosion). I'll never fully understand why physicists are absolutely certain that wave after wave of billions of electromagnetic particles slamming into you every millisecond of the day has absolutely no effect on your momentum. It seems logical that the high excess of EM waves coming from above would result in an overall momentum downward. --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 23:23, 25 April 2006 (UTC)
:::Actually, it's closer to 299,702,547m/s, unless you live in a vacuum bubble. Coincidentally, radiation from earth bound sources ''also'' strikes you at the same speed. Hm....? When it comes to sunlight, personally, I'd be most concerned at sunrise... perhaps that's why I stumble so much when I wake up early compared to later in the day. [[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 23:41, 25 April 2006 (UTC)
::::Actually, I do live a vacuum bubble, void of facts, statistics, and responsibility. That is why it is so easy to answer all the questions here. Regardless, my point was the quantity of EM coming from above compared to the quantity of EM coming from Earth. Everything I've read has claimed that even in the dead of night, the EM from Earth is insignificant compared to the EM coming from above. That did just spark a memory - is the Earth bright or dark? Most think that it has a bright side and a dark side - but that is because we only see visible light. With all our radios, televisions, cell phones... even in the dark we emit a hell of a lot of EM waves. So, for a radio-seeing being, it would be rather bright all the time. Of course, that has absolutely nothing to do with this question. --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 23:47, 25 April 2006 (UTC)
:::::Not to mention the infrared energy that is given off naturally. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 04:52, 26 April 2006 (UTC)
:::See [[light pressure]]: sunlight on something facing directly into it is 4.6 [[micropascal|μPa]]. So (being very generous with the size of the person and very conservative with their mass) there'd be something like 10 billionths of your weight added onto you while, say, sunbathing at noon. Entirely irrelevant, regardless of the direction it's applied. --[[User:Tardis|Tardis]] 13:46, 26 April 2006 (UTC)
== Synthesizer how-to==
I have just downloaded a soft synth. Can anyone recommend me a good source of information of using (general) soft synthesizers? Thanks.
:See our article on [[Software synthesizer]]s. -- [[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 00:16, 26 April 2006 (UTC)
Soft synths are standardized so as to be supported by the largest number of programs possible. If you're running Windows, the soft synth is probably a VSTi, Macs are usually audiounits. Most programs either want you to put the softsynth file in their plugin folder, or you can specify a directory or set of directories to scan for soft synths. The software one would use soft synths with is called a [[Music sequencer]]. So the sequencer sends the data like note, duration, velocity and tons of other midi-like data to the soft synth, which returns audio. [[FL Studio]] is one of the most powerful, and one of my favorite sequencers. [[User:TheDapperDan|TheDapperDan]] 02:22, 26 April 2006 (UTC)
:Try [http://www.soft32.com/download_77484.html Musical Keys] --[[User:Russoc4|Chris]] 02:26, 26 April 2006 (UTC)
== Physics Textbook ==
Hi, my physics teacher mentioned a textbook a while back but I can't remember the name (something and Johnson's) that he recommended. It's probably a university level one since I'm in AP, if anyone knows what I'm talking about or has info on any good textbooks it be great. thanks
23:17, 25 April 2006 (UTC)
:Hm, [http://he-cda.wiley.com/WileyCDA/HigherEdMultiTitle.rdr?name=cutnell try here]. [[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 00:14, 26 April 2006 (UTC)
== Mac OS X ==
How easy is it to learn the Mac interface for a fairly advanced Windows User?
I'm asking because I want to get the Macbook pro when Mac OS 10.5 comes out, so that I can get boot camp and boot both Windows and Mac OS on the same computer [which would be mega-awesome considering some things you can do so much easier with a mac and because their hardware is better manufactured in my opinion. Plus, I like their user interfact. The only reason I never got a Mac was because they used to be very incompatable].
Also, what are other people's opinions of the Macbook Pro? Would it maybe just be better to skip this and get a good laptop when Vista comes out? — [[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">Ilyan</span>]][[User:Ilyanep/Esperanza|<span style="font-variant:Small-caps;color:green;">e</span>]][[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">p</span>]][[User talk:Ilyanep| <span style="font-variant:Small-caps;color:#808080;">(Talk)</span>]] 23:25, 25 April 2006 (UTC)
*As for the interface question: it's not very hard. Mac OS X is pretty easy to use and in many ways is similar to Windows XP. If you use it for a few days you'll get the hang of it. I siwtch between the two regularly without much confusion (except that for certain things, such as non-English characters, Mac OS X is a million times easier). --[[User:Fastfission|Fastfission]] 23:35, 25 April 2006 (UTC)
:Max OS is similar to Linux desktops (KDE/Gnome) which are similar to Windows. Everyone steals the good ideas from everyone else. However, your idea that dual-booting a computer would be "mega-awesome" is flawed. Consider this: You are in Mac and you need to run a Windows program. You must reboot. You are then in Windows and you need to run a Mac program. You must reboot. It is far better to have some sort of embedded system. A popular one is VMWare (install Windows inside of Mac). Since I have plenty of computers at my disposal, I have a Win2003 box sitting in a corner and I rdesktop it when I need Windows. --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 23:50, 25 April 2006 (UTC)
::I don't see myself switching between apps very often. On a computer, I'm usually either in game/goof off mode [Windows] or office/internet/homework mode [Mac]. Most design would somehow continue going on on Windows [as my copies of Photoshop, Flash, etc. are all Windows], and some things might become Mac-only [calendar management through iCal and GCal, etc.] If I were someone who made frequent use of both at the same time, I'd agree with you.
::An annoyance I might see is having to configure wireless networking twice. But ''c'est la vide''. Thanks for the answers. — [[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">Ilyan</span>]][[User:Ilyanep/Esperanza|<span style="font-variant:Small-caps;color:green;">e</span>]][[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">p</span>]][[User talk:Ilyanep| <span style="font-variant:Small-caps;color:#808080;">(Talk)</span>]] 23:54, 25 April 2006 (UTC)
:Mac OS X is probably the easiest OS to learn, and it ripens the more you explore. There are a lot more applications you can download than you think. Boot Camp is better than nothing, and I think they will soon be able to have you switch between Windows and Mac OS X like application switching, or user switching. Usually I just want to see what is in the exe file, or something like that. If you get [[Apple Pages]] you can view .docs well, and with [[Apple Keynote]], you see .ppts well. -- [[User:Mac_Davis]] 00:13, 26 April 2006 (UTC)
::That's cool. I'll probably get iWork (Pages + Keynote) because it seems useful (looks like very nice presentations and documents there) -- although probably not Office (I can just use oo.o if i ever need a bread and butter office). All the rest will probably be freeware and downloaded, because I don't have money to buy a $2.5k laptop and then rebuy my expensive library of software :P which is why having Windows as a fallback is very nice (plus games).
::I'd love to see a fast switch between OSes. And hopefully I can learn Mac OS X quickly, because I'm sure I'd feel quite set back after being an advanced user of Windows (been using it since 1994, as a 3-year-old). — [[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">Ilyan</span>]][[User:Ilyanep/Esperanza|<span style="font-variant:Small-caps;color:green;">e</span>]][[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">p</span>]][[User talk:Ilyanep| <span style="font-variant:Small-caps;color:#808080;">(Talk)</span>]] 01:19, 26 April 2006 (UTC)
::See [http://guides.macrumors.com/Booting_Windows_on_the_Mac]. Parallels lets you run WIndows within the Mac OS, so you have both running simultaneously. It's free in beta, will be about $50 when it is commercially released [http://www.macrumors.com/pages/2006/04/20060406081519.shtml] - 05:39, 26 April 2006 (UTC)
:::The thing is that you get a performance hit because you're running a windows app on top of windows dlls on top of mac os dlls. — [[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">Ilyan</span>]][[User:Ilyanep/Esperanza|<span style="font-variant:Small-caps;color:green;">e</span>]][[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">p</span>]][[User talk:Ilyanep| <span style="font-variant:Small-caps;color:#808080;">(Talk)</span>]] 12:07, 26 April 2006 (UTC)
Another question: If I have a Windows XP disc but it's an original XP [no SP2] disc, will it work with Boot Camp? If not, is there a way I can get an XP/SP2 disc from Microsoft? Perferably from the internet for free. — [[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">Ilyan</span>]][[User:Ilyanep/Esperanza|<span style="font-variant:Small-caps;color:green;">e</span>]][[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">p</span>]][[User talk:Ilyanep| <span style="font-variant:Small-caps;color:#808080;">(Talk)</span>]] 01:32, 26 April 2006 (UTC)
:You should be able to download SP2 from Windows Update for free. The issue here is that your copy of Windows XP was probably authorised to run on your existing PC only. You'll have to ring Microsoft and arrange for the authorisation to be cancelled so you can authorise your Mac to run it. --[[User:Canley|Canley]] 03:17, 26 April 2006 (UTC)
::In fact, bundled copies of Windows cannot be moved to another computer. This is part of the deal: in return for being a fraction of the retail price, they go to landfill with the computer. If of course the spare Windows XP disk was a retail copy, never installed, that doesn't apply, so I don't want to jump to conclusions. [[User:Notinasnaid|Notinasnaid]] 11:29, 26 April 2006 (UTC)
:::Oh no no no, it's a different retail disc copy of Windows XP that has long since been removed from the original computer. I also found how to slipstream SP2 onto a disc along with XP — [[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">Ilyan</span>]][[User:Ilyanep/Esperanza|<span style="font-variant:Small-caps;color:green;">e</span>]][[User:Ilyanep|<span style="font-variant:Small-caps;color:black;">p</span>]][[User talk:Ilyanep| <span style="font-variant:Small-caps;color:#808080;">(Talk)</span>]] 12:05, 26 April 2006 (UTC)
= April 26 =
== For you Physics People ==
Question: When you are running and want to stop quicikly, must decelerate quickly. a) What is the origin of the force that causes you to stop? b) Estimate the maximum rate of deceleration of a person running at top speed to come to rest.
Does anyone know what they are asking for in part A? I don't quite get it, I mean I understand the question but I'm having a hard time visualizing how this would work. Any help would be appreciated thanks.
01:06, 26 April 2006 (UTC)
*The force is mostly friction between your feet and the ground, although there is some small contribution from air resistance as well, I suppose. ([[User:ESkog|ESkog]])<sup>([[User talk:ESkog|Talk]])</sup> 01:07, 26 April 2006 (UTC)
*Unless you hit a wall, in which case it's more of a [[normal force]]. [[User:Melchoir|Melchoir]] 02:04, 26 April 2006 (UTC)
:To help you visualize the answer, imagine yourself running top speed, and then imagine what you would do to try to stop yourself. Most... humans extend one of their feet (most likely right foot for righties) and slam it down putting a lot of pressure on the one leg. By slamming your foot down, you are transferring your kinetic energy into the earth (the same energy transfers when objects crash), and since the earth is essentially stationary (relative to you running) and heavy enough so as not to be moved much by such a relatively small amount of energy, it will eventually take all of your previous kinetic energy and you will come to a stop.<br/>If you stop by taking a few heavy steps as opposed to sliding your feet along the ground (like the way a hockey skater stops) then friction shouldn't be the major force, though there certainly is some friction force involved too.<br/>Though the question may seem to be worded awkwardly, the origin of the force that stops you is the Earth. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 04:46, 26 April 2006 (UTC)
:The major part is played by friction, even if you slam your foot down. If the surface on which you are running is smooth, no matter how hard you slam, you still will not be able to stop quickly. You are basically trying to prevent your body from continuing to move forward, by applying a backward force, using the friction between your feet and the earth. Even when the hockey player slides to a stop, he uses friction. If there was not friction, a moving body will not stop, unless it hits something else. I wouldn't be wrong in stating that all moving bodies in contact with other bodies slow down mainly due to friction between the bodies. (Ignoring other obvious cases like a direct collision and influence of other forces like gravity, magnetism etc) -- [[User:Wikicheng|Wikicheng]] 13:49, 26 April 2006 (UTC)
:About part b)- To calculate the rate of deceleration you'll have to use this formula: v=u-(a*t). Where, v=final velocity (in this case 0, beacuse the man is coming to a stop), u=initial velocity, -a=decelaration (+a for acceleration), t=time. If you know the amount of time taken by the man to stop and the initial velocity of the man, you can calculate the rate of deceleration (a). If you know the distance the man covered before he came to a stop, you can use the following formula: v^2=u^2-2aS, where S is the distance, v=0, if you know u(initial velocity) then you can find the rate of decelaration. (Note: ^ is to the power and * is multiplication sign).--[[User:DIGIwarez|DIGIwarez]] 15:54, 26 April 2006 (UTC)
== Problem with Rope having a Mass ==
Suppose the cord is a heavy rope of mass 1.0 kg. Calculate the acceleration of each box and the tension at each end of the cord.
I can't for the life of me get the diagram on here, I've tried for the last half hour and I get
"The file is corrupt or has an incorrect extension. Please check the file and upload again". I'll try describing with a bit of drawing on my part. I don't know how to do this because of the 1 kg rope, and most likely without it either. But we've never done any with ropes having a mass.
----- |-----|
m2= |T2 T2 Cord T1 T1| |FP 40N(force of pull)
12kg |--> <---++++++++---> <--|m1= |--->
| MC = 1.0kg |10kg |
-----| |-----|
This is just the free body diagram:
The thing actually looks like:
Rope
BOX------BOX
in which the boxes are connected with the rope, and are in contact, unlike the top picture.
Thanks for any response.
02:53, 26 April 2006 (UTC)
:I took the liberty of fixing your formatting. If you want preformatted text, you have to put a space at the beginning of each line. —[[User:Keenan Pepper|Keenan Pepper]] 03:21, 26 April 2006 (UTC)
Thanks a lot for that. 03:34, 26 April 2006 (UTC)
:Is there gravity? Are the boxes sliding around on an air table, or out in space, or is there friction from something...? [[User:Melchoir|Melchoir]] 03:42, 26 April 2006 (UTC)
The boxes are on the table and the question makes no mention of friction or gravity, but I believe it wouldn't need gravity because it's asking for movement along the x-axis, it shouldn't make a difference I would assume. 03:48, 26 April 2006 (UTC)
:Well, it looks like all the elements accelerate equally. You can find that acceleration by considering the whole system as a single body with whatever total mass. Then determine, algebraically, the forces on all the elements of the system as a function of the tensions, and set those forces equal to the forces required to move them under Newton's second law.
:By the way, if you don't like to deal with massive ropes, you can think of the rope itself as a box made of rope! You're only asked for the tension at either end, so conceptually there's a very short, massless rope that connects the rope-box to the box on the left, and another very short, massless rope that connects the rope-box to the box on the right. These new imaginary ropes will be under different tensions; you're asked to find them. [[User:Melchoir|Melchoir]] 04:01, 26 April 2006 (UTC)
::So would you have a different answer for the tension if you didn't consider the rope a box itself? how would you do the question then? Thanks again. 04:11, 26 April 2006 (UTC)
:::No, the laws of physics are blind to the difference between boxes and ropes. (Well, they are up until you get to engineering mechanics.) A rope, like anything else with mass, accelerates if and only if a net force acts on it. I'm just saying that whatever conceptual model helps you solve the problem, go with it. [[User:Melchoir|Melchoir]] 04:21, 26 April 2006 (UTC)
::::Except that you can't push with a rope. (Or at least not normally. I once used a rope that had been soaked in water and frozen to push my physics teacher.) --[[User:Serie|Serie]] 22:35, 26 April 2006 (UTC)
A rope with mass means that there will be a linear tension distribution throughout the rope. Think of a heavy rope just hanging vertically. --[[User:Zeizmic|Zeizmic]] 12:13, 26 April 2006 (UTC)
Assuming no friction and no stretching:
Once the ropes are fully extended (under tension), all the boxes and ropes will accelerate at the same rate. Call that 'a'. There will be tensions in the ropes too, marked in as T1 and T2. So we can calculate the forces on each object:
''Forces on m1:''
* m1 has forces of FP RIGHT and t1 LEFT. So the total force is (FP - T1) RIGHT
* It has mass m1 and the forces make it accelerate at 'a'.
* So F=ma ==> (FP - T1) = m1 x a
''Forces on cord:''
* cord has forces T1 RIGHT and T2 LEFT. So the total force is (T1 - T2) RIGHT
* It has mass MC and the forces make it accelerate at 'a'.
* So F=ma ==> (T1 - T2) = MC x a
''Forces on m2:''
* m2 has forces of T2 RIGHT only.
* It has mass m2 and the forces make it accelerate at 'a'.
* So F=ma ==> (T2) = m2 x a
''Solving these equations:''
*We have been TOLD that FP = 40, m1 = 10, MC = 1 and m2 = 12
*So if we substitute these numbers in, we get:
:* (FP - T1) = m1 x a ==> (40 - T1) = 10 a
:* (T1 - T2) = MC x a ==> (T1 - T2) = 1 a = a
:* (T2) = m2 x a ==> T2 = 12 a
# You now have 3 equations in 3 unknowns.
# Rearrange the 1st and 3rd equations to get T1 and T2 in terms of 'a'
# Substitute these into the 2nd equation to get an equation that has one unknown, 'a'.
# Solve it to find 'a', the acceleration of the objects
# Substitute again to find T1 and t2, the tension at each end of the cord.
[[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 00:10, 27 April 2006 (UTC)
== Global Heating ==
In discussions of Global Warming, I am curious why there is so little focus on heat (as opposed to temperature). Temperature is important of course, but the transition of ice at 0°C to water at 0°C requires a lot of heat, implying that the polar ice caps, for example, are buffering the temperature rise. Then the question arises, if the total heat content of the planet is increasing, where will all that heat go when the ice has melted? Is this unimportant with the Greenhouse Effect? Is that heat just a very small part of the picture? Or is there enough ice that it's not an issue (yet)? [[User:Peter Grey|Peter Grey]] 04:48, 26 April 2006 (UTC)
:I have no idea. That said, I'm going to guess that measurements focus on temperature changes because they can be directly measured, while heat fluxes cannot. Behind the scenes, when one models climate change, I assume that latent heats and so forth are duly taken into account. And, to add the obligatory joke answer: because Global Heating sounds like an appliance manufacturer. Or maybe they lay gas pipelines? Who knows. [[User:Melchoir|Melchoir]] 05:02, 26 April 2006 (UTC)
:Global warming is an issue because of expansion of the ocean. Think of it this way. An ocean might be 1000 m deep. If water expands 0.1%, that's 1 m. Goodbye Florida (joke). But yes, melting polar icecaps are heat sinks. But they only need to melted once and they're gone. I assume that the energy needed to melt them is relatively small. Lets do a small calculation on the back of a napkin. To Melt 1 million square kilometres with a depth of 100 m over 100 years. That's 10^6 x 10^6 x 100 = 10^14 cubic metres. 100 years = 10^2 x 4*10^2 x 2.5*10^1 x 4*10^3 = 4*2.5*4 (40) times 10^8 = 4*10^9 seconds. Dividing, 10^14 / 4*10^9 = 2.5*10^5 cubic metres a second. That's quite a bit. But that's only 2.5*10^5 / 10^12 = 2.5*10^-7 m = less than a micron per second. And no, I don't have a calculator on me as you guessed! [[User:153.111.60.15|153.111.60.15]] 07:50, 26 April 2006 (UTC)
::Without factoring in latent heats and heat capacities of various reactions and reservoirs, these numbers mean nothing. [[User:Melchoir|Melchoir]] 21:36, 26 April 2006 (UTC)
:A related question, would this mean that once most of the Earth's ice has melted, we should expect the temperature to increase at a faster rate? [[User:Peter Grey|Peter Grey]] 00:52, 27 April 2006 (UTC)
::Yes, but... Given an extra input of a few W/m^2, a density for ice of 0.9 g/cm^3 and a latent heat of 300 kJ/kg, you'd expect a melting of ~30 cm/yr if all the local excess heat were going solely into melting ice. This is about 5 times greater than the observed mass loss in Greenland but still in the same ballpark. If we say that about 20% of the local excess energy from global warming goes into melting ice and note that ice covers about 3% of the Earth, then without the process of melting ice, global warming might progress ~0.5% faster. This is of course only a very crude estimate. More important is the fact that ice is shiny and white, and once you remove the ice the ground is dark. By changing the [[albedo]] in this way you absorb more sunlight after the ice is removed, which would be a much more important factor in amplifying global warming. [[User:Dragons flight|Dragons flight]] 16:39, 28 April 2006 (UTC)
== My theory on obesity and height ==
For a while now, I have come to the conclusion that shorter women are more likely to be obese/overweight than taller women. Of course, this can easily be proved/disproved if I had gender/age/height/weight for a random sample of people in a Western country with obesity issues. What are peoples thoughts? Does anyone have any actual research on this or stats? Thanks. BTW, I'm looking at, say age 30-40. [[User:153.111.60.15|153.111.60.15]] 07:29, 26 April 2006 (UTC)
: Maybe its just that taller people dont look overweight even if they are... as i understand being obese depends on the genetics and how much they exersice... not necessarily on the height of a person... (i am not completely sure about that last point) [[User:Jayant412|Jayant,]][[WP:EA|<font color="green">17 Years,</font>]][[User_talk:Jayant412|<font color="red"> India</font>]] • [[Special:Contributions/Jayant412|contribs]] 10:39, 26 April 2006 (UTC)
:I think Jayant's point about perception is sound. A quick Google brings up two studies:
:[http://www.jacn.org/cgi/content/full/23/1/51 Height-Related Changes in Body Mass Index: A Reappraisal] gives a slight positive correlation between [[body mass index]] (a popular measure of whether someone's overweight) and height for men (ie taller men are "fatter") and a slight negative correlation for women (which fits User:153's belief). That's for data from people coming out of the Israeli army just over the age of 20, so it may not be that similar to 30-40 year olds in other contexts.
:[http://biostat.stat.fsu.edu/documents/AJPAWtHtRevisedApr04.pdf These guys from FSU] (warning: pdf doc) examine a wide range of populations and generally find a negative correlation for both men and women (again in line with the User:153's theory). But they use it to argue that a blanket application of BMI is therefore not a good way to determine whether someone's overweight, rather than that shorter women are more likely to be overweight.
:Note that in both cases the correlation coefficients, while statistically significant, are small in absolute terms -- the effects are there, but they aren't all that large. --[[User:Bth|Bth]] 11:42, 26 April 2006 (UTC)
Thanks for the comments, I still think my theory has validity, if only I had data! Have downloaded the .pdf but yet to digest. [[User:153.111.60.15|153.111.60.15]] 08:49, 28 April 2006 (UTC)
== Turbine engineering ==
How is it possible to maintain a seal between the shaft of high pressure turbine and the chamber it is enclosed in?
:Turbines are a complex bit of engineering. I know that we always have trouble with the monster turbines. I suggest you brush up on your Google skills. --[[User:Zeizmic|Zeizmic]] 12:17, 26 April 2006 (UTC)
== PVC substitutes ==
I am wondering what materials may be used in place of PVC in its main applications (Namely construction, housing, toys, cars and medical use). Thanks in advance.
...
:Polyethylene and polypropylene for toys, cars, diapers and medical use I believe. I would imagine most types of relatively harmless polymers could be used for any of those categories. -[[User:Snpoj|Snpoj]] 11:37, 26 April 2006 (UTC)
:Wrong question. The right question to ask is "Why is PVC used in so many applications despite its being so poorly suited to the purpose at hand?" The answer is that in the process of alkali electrolysis [[sodium hydroxide]] is the sought-after product. Chlorine is producted in equal amounts and is really an unwanted byproduct. Converting it into PVC is one way to dispose of what really is a waste product. [[User:Dr Zak|Dr Zak]] 11:45, 26 April 2006 (UTC)
: You could use pretty much anything non-toxic for toys. For medical use biocompatibility is of primary concern, common polymers used in hospitals (for IV tubes and the like) include polyethylene (PE) and silicone. In construction, I can't think of any alternatives that are used (particularly with a high volume area like construction, price is a mjor factor in choosing a material). There is lumber made from recycled plastics, but that doesn't replace a PVC application. Polymethylmethacrylate (PMMA) is a strong, fair enivronmentally material that is used for greenhouses and architecturally. The plastics used in cars include polyurethane (PU), polypropylene (PP), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), and PVC. Generally, PU, PS, ABS, and PC are the most commonly subsituted polymers for PVC. --[[User:Chapuisat|Chapuisat]] 14:42, 26 April 2006 (UTC)
::I always think of something to add write after posting a reply. I should have mentioned that all polymers have advantages and drawbacks, many of the alternatives to PVC (such as ABS) also use hazardous chemicals. Polymer engineering hasn't always been the most environmentally friendly field, but over the last decade or so I think it has improved quite a bit. --[[User:Chapuisat|Chapuisat]] 14:48, 26 April 2006 (UTC)
::Leather and latex. Oh, constructions purposes. My bad. --[[User:Blowdart|Blowdart]] 17:39, 26 April 2006 (UTC)
== Redirect From Incorrect Spelling? ==
Is it appropriate to make a redirect from for example, [[Pyramidine]] (incorrect spelling) to [[Pyrimidine]]? -[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 10:36, 26 April 2006 (UTC)
:It usually is, yes, though someone's already done that one. This was more of a question for the [[Wikipedia:Help desk|help desk]], though, since it's about editing Wikipedia rather than a specific question about science. -- [[User:Mithent|Mithent]] 11:05, 26 April 2006 (UTC)
:It usually is, yes, but somebody has already done so. Ask at the help desk next time, but how you do it is: <nowiki>#REDIRECT[[Page name you redirecting to]]</nowiki> -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 12:22, 26 April 2006 (UTC)
::Did you guys plan that or something? --[[User:Chapuisat|Chapuisat]] 13:40, 26 April 2006 (UTC)
::Sorry, I did go to the help desk, and didn't realise I could post there. I just saw the humanities, science options etc. and thought I had no other choice. Btw, the somebody who did it was me, I just wanted to make sure I was doing the right thing. --[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 15:12, 26 April 2006 (UTC)
:Just make sure to add the template {{tl|R from misspelling}} so that no-one would think it's a legitimate alternate spelling. See [[Wikipedia:Redirect]] for more info. – [[User:b_jonas|b_jonas]] 22:45, 27 April 2006 (UTC)
== long term memory ==
'''characteristics of long term memory'''
1 The ability to receive and store information during observation.
2 The ability to trace and recall information stored in long term
memory.
3 Like sensory storage, long term memory has a large capacity.
4 Long term memory is usually well organised.
5 It is a relatively permanent form of memory.
6 The information is sifted,coded and stored and thus form a
components or part of all experience that can be remembered.
7 Information is rearranged when new material is added.
8 The process is not static, but dynamic.
9 Information obtained through any of the senses can be stored.
10 New meterial can be arranged meaningfully together with the old
meterial.
11 Familar meterial or information is easier to process or arranged
than unfamiliar material.
DESCRIBE AN EVENT OR WRITE A STORY (ROUGHLY 200 WORDS) ABOUT SOMETHING THAT YOU HEARD ABOUT OR EXPERIENCED YOURSELF ABOUT A YEAR AGO. NOW ANALYSE YOUR PIECE OF WRITING IN TERMS OF THE ELEVEN CHARACTERISTIC OF LONG-TERM MEMORY AND TRY TO DETERMINE THE DEGREE TO WHICH YOUR WRITING SATISFIES THOSE CRITERIA.
*Please read the instructions at the top of the page. This page is to ask questions, not to set assignments. I wonder what your short term memory is like...- [[User:131.211.210.13|131.211.210.13]] 12:45, 26 April 2006 (UTC)
*Ok, I did that: I wrote a story of roughly 200 words, and analysed it. Thank you for the suggestion. [[User:Notinasnaid|Notinasnaid]] 14:16, 26 April 2006 (UTC)
== can you tell me how to install windows XP in a newly brought system ==
:Take your newly purchased copy of Windows XP (not one reused from an older computer, unless it was purchased retail), put it in the CD drive, and boot. The system will boot from the CD and install Windows XP after a few questions. [[User:Notinasnaid|Notinasnaid]] 14:14, 26 April 2006 (UTC)
::If the computer is set-up to boot from CD, you will see "press any key to boot from CD"; you'll then have a window of a couple of seconds in which to press a key, so make sure you're paying attention. If you don't see this message on the screen, come back for more help. -[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 15:09, 26 April 2006 (UTC)
== Virtual Memory ==
I've heard in the past that your virtual memory should be set to 1.5x your physical memory. I just upgraded from 512mb RAM to 1024mb RAM, but it doesn't look like my virtual memory went up. Can anyone with 512 or 1024 RAM let me know how their settings are in WinXP SP2? Thanks. --[[User:Russoc4|Chris]] 15:49, 26 April 2006 (UTC)
:You can set your VM to whatever you want; so long as you don't find that you're running out (angry dialogs and crashing applications), you're fine. You don't get any benefit from having "extra". But for what it's worth, the system I'm currently using (though it's not Windows) happens to have approximately equal amounts physical and virtual: about 1GB each. If you have the hard drive space to spare, set it to 2GB or more if the system will let you, and then you won't worry about it. But if you want to conserve space, and haven't had any trouble, just leave it alone. --[[User:Tardis|Tardis]] 16:19, 26 April 2006 (UTC)
::This is known to be very poor advice, regularly criticized on IT forums. Read [[virtual memory]] to understand what VM does. Basically, your computer will use X amount of memory to work, the exact amount varying depending what you are doing. It uses all the [[RAM]] it can, the rest is made up using VM. So in fact the more physical memory you have, the ''less'' VM you need and vice versa!
::As a rough rule of thumb, unless you're doing complex processing (video editing, photoshop etc), and given how cheap physical memory is today, I'd use this for a rule of thumb with Windows XP: as you have, use between 512 MB and 1024 MB of physical memory (not less than 256 MB), and then set virtual memory to use a set (fixed) size of around minimum 512 MB and maximum 1536 MB (if your [[hard drive]] allows it). The fixed size stops Windows having to extend the file quite so often. That should fix it up nicely.
::If you do intense work on photoshop or video work (not just DIVX coding!), eg professionally, then get more RAM (1-2 GB is not uncommon) a fast modern [[dual core]] processor, a solid and stable [[motherboard]] (eg [[ASUS]] which I use and have never had a problem with) and a huge hard drive ([[Seagate]]'s 'Barracuda' range currently offer the best price/quality/warranty/speed balance). [[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 19:58, 26 April 2006 (UTC)
== Running a local server... issues ==
I'm using Mac OS X Tiger, and I'm running a personal web server (Apache) off of my local machine which I use while writing PHP. Normally this is fine -- I point the page to the local address (http://mycomputer.local/~myusername/) and it runs fine. However just today it has, without me changing the settings, redirected from mycomputer.local to the local IP that my university has assigned for my computer's internet access. In fact, if I type in the address as http://127.0.0.1/~myusername/ it will automatically substitude it with http://net-23295456.myuniversity.edu/~myusername/. Some of my scripts execute fine, despite this, but some give me a 404 error. What gives? --[[User:Fastfission|Fastfission]] 16:22, 26 April 2006 (UTC)
*The more I tinker with this... I think the latter "net-2323" bit still goes to my local computer. Yet it sometimes will, sometimes won't run a script. I haven't had this issue before. I've tried restarting the web server, restarting the computer, disconnecting and reconnecting it to the internet, using different browsers, resetting my cache, clearing the dynamic DNS, etc., to no respite. Argggg. --[[User:Fastfission|Fastfission]] 17:06, 26 April 2006 (UTC)
*Actually, now it's only failing whenever I try to open a new locally hosted script in a javascript window, and try to pass GET arguments to it in the URL. What the hell. If I ''don't'' try to pass arguments, it executes the script just fine. Why is my computer being such a pill? --[[User:Fastfission|Fastfission]] 17:13, 26 April 2006 (UTC)
What is the [http://httpd.apache.org/docs/1.3/mod/core.html#servername ServerName] set to in apache? [[User:EricR|EricR]] 17:36, 26 April 2006 (UTC)
*Nevermind, I figured it out! Not a big deal, I was confused about something, please ignore. --[[User:Fastfission|Fastfission]] 01:30, 27 April 2006 (UTC)
==Direct ancestor of Homo sapiens?==
I'm trying to trace an approximate timeline between modern humans and the [[dawn of life]]. For example, who are the direct ancestors of Homo sapiens? Would it be erectus? And what is the ancestior of primates, e.g. the "protoprimate"? and then the ancestor of all mammals, before mammals branched out into all the different kinds we know today. And so on and so forth to the earliest known life forms from which presumably all life evolved. For example is [[Tiktaalik]] a possible ancestor of humans? Or a [[cynodont]]? etc. What's the most accurate line as we know it?--[[User:Sonjaaa|Sonjaaa]] 16:57, 26 April 2006 (UTC)
:Well you can't think of lines as just being straight shots, first of all. They get all mixed up with themselves and look more like bushes than trees. Secondly, we don't have straight genealogies available anyhow. Anything could be a "possible" ancestor of humans if you are talking about as far back as Tiktaalik. Take a look at our [[evolution of homo sapiens]] article for an overview of what is known and what can be said about it. --[[User:Fastfission|Fastfission]] 17:04, 26 April 2006 (UTC)
:Also look up [[Y-chromosomal Adam]] and [[Mitochondrial Eve]], [[Most recent common ancestor]], and [[Last universal ancestor]]. [[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 20:08, 26 April 2006 (UTC)
:Also, a good article to get acquainted with some of the conceptual difficulties making sense of this sort of genetics is Troy Duster's "[http://www.longviewinstitute.org/research/duster/deeproots Deep Roots and Tangled Branches]". --[[User:Fastfission|Fastfission]] 01:32, 27 April 2006 (UTC)
== Who designed Monobook? ==
Who designed the Monobook skin, initially, for Wikipedia? We need this in relation to a media outlet's request. -- [[User:Zanimum|Zanimum]] 17:38, 26 April 2006 (UTC)
:[[User:Gwicke]]. --''[[User:Nrcprm2026|James S.]]'' 18:06, 26 April 2006 (UTC)
:: But I believe he based the design (and may have used some of the collateral, such as images and styles) on a weblog skin (I'm afraid I forget which). -- [[User:Finlay McWalter|Finlay McWalter]] | [[User talk:Finlay McWalter|Talk]] 18:11, 26 April 2006 (UTC)
==Are centipedes [[arachnid]]s?==
This spider book I'm reading mentiones that scorpions, mites, and '''centipedes''' are all arachnids. But according to Wikipedia, [[centipede]]s belong to the Subphylum [[Myriapoda]], while arachnids belong to the Subphylum [[Chelicerata]]. Can someone explain this to me? Maybe scientists can't agree where centipedes belong? [[User: Jonathan W|<span style="background:#8c6638; size:2; color:#00FF00;"> Jonathan</span>]] <sup><span style="size:-1;"> [[User talk:Jonathan W|<span style="color:#8c6638">talk</span>]] </span></sup> [[Image:Canada flag 300.png|30px]] 17:44, 26 April 2006 (UTC)
:Wikipedia's articles place Class Chelipoda (centipedes) in Subphylum Myriapoda, as do some other sources (try Googling "Myriapoda"), but I found a source placing them in Arachnida ([http://hbs.bishopmuseum.org/good-bad/centipede.html Hawaii Biologial Survey]). Another source ranked Myriapoda as a class, equal to Arachnida ([http://www.kendall-bioresearch.co.uk/class.htm Kendall Bioresearch Services]). So it appears there's no firm consensus where they belong, but placing them in Arachnida seems outdated at best. --[[User:Ginkgo100|Ginkgo100]] 18:13, 26 April 2006 (UTC)
:Wikibooks has a [[dichotomous key]] for arthopods, the place where centipedes and arachnids are thought to diverge. You can read it [http://en.wikibooks.org/wiki/Dichotomous_Key:Arthropoda here]. The key is based on morphological features (antennae, number of feet, etc.) which is popular among some biologists, while other prefer genetic sequence analysis or using other types of distiguishing features. That may be why there is not an agreement on the exact phylogenetic tree. You may also enjoy looking at the wikispecies entry on [http://species.wikipedia.org/wiki/Craterostigmus_tasmanianus centipedes]. --[[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 19:21, 26 April 2006 (UTC)
Shhh...don't tell them anything useful or they might never post again on reference desk. Jonathan, Andrew was just lying ok?You never hear erm... read that 'k?
== Different prongs on electrical plugs ==
The lamp on my desk has a plug with two flat parallel prongs. One of them is wider than the other, and I believe it to be a Type A Nema 1-15. see [[Domestic AC power plugs and sockets]]. My question is, why do the prongs differ from one another? In my youth common electrical plugs had prongs that were identical in shape. They carry alternating current, so what is going on electrically at the two prongs are the same, and one is not "hot" and the other "neutral" at least in any electrical sense, it seems to me. Electrons are moving alternately into and out of each prong during the cycles. I've taken graduate courses in E&M, but still wonder at this...--[[User:DonSiano|DonSiano]] 18:21, 26 April 2006 (UTC)
:You are mostly correct. However, although the electricy is alternating current, one pole remains roughly neutral (relative to ground) while the other alternates on average 120V (relative to ground). Keep in mind that I am discribing the ''voltage'' of the plug relative to ground, not the ''current'' running though an appliance. -- [[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 18:54, 26 April 2006 (UTC)
I have 'unconsciously internalized' this from somewhere: Polarized plugs have a wide neutral prong and can only plug one way into a receptacle. In a properly wired lamp, the polarized plug ensures that the hot wire energizes the metal tab at the bottom of the socket, which is less exposed to fingers than is the threaded shell. --[[User:Zeizmic|Zeizmic]] 19:46, 26 April 2006 (UTC)
== Radishes ==
Really random but I need to know for my A2 Biology coursework, are radishes leguminous nitrogen fixing plants or non-leguminous nitrogen fixing plants? I have looked on this site and others and cannot find an answer! I would really appreciate it if you could get back to me asap on this as my coursework needs to be handed in shortly and I've nearly done the rest of the project!
Thank you for your assisstance!
Dee x x x
You should at least have looked at [[radish]], [[legume]] and [[Nitrogen Fixation]] before asking us to do your homework. (though I think the answer to the question you posed is "no"). [[User:Malcolm Farmer|Malcolm Farmer]] 19:10, 26 April 2006 (UTC)
== PCL6 ==
I am trying to investigate the contents of packets being sent to an HP IP printer using PCLXL (now called PCL6). Upon viewing a packet capture of the data I find very little, if any, information that is readable/useful. I have a white paper on PCL6, but I find it to be less that helpful. If anyone could provide some insight on what steps to take to extract the print data please let me know. Ideally I would like to have some sort of break down of field sizes and possible values, but it looks to me like the data need to first be converted into some other format.
Below is an example of the data that goes across the network when printing a file. It is compiled from several packets and derived with the "Follow TCP Stream" functionality in Ethereal. I didn't include all the output to help keep it short. In addition, some data that could be used to identify me has been removed. If it would be helpful to have the full capture please let me know.
.%-12345X@PJL SET STRINGCODESET=UTF8
@PJL JOB NAME="Document"
@PJL COMMENT "HP LaserJet 2420 PCL 6 (60.42.108.11); Microsoft Windows XP 5.1.2600.1; Unidrv 0.3.1296.4"
@PJL COMMENT "Username: REMOVED; App Filename: Document; 4-21-2006"
@PJL SET JOBATTR="JobAcct1=REMOVED"
@PJL SET JOBATTR="JobAcct2=REMOVED"
@PJL SET JOBATTR="JobAcct3=REMOVED"
@PJL SET JOBATTR="JobAcct4=REMOVED"
@PJL SET JOBATTR="JobAcct5=REMOVED"
@PJL DMINFO ASCIIHEX="0400040101020D101001153230303630343231313532363133"
@PJL SET USERNAME="REMOVED"
@PJL SET DUPLEX=OFF
@PJL SET ECONOMODE=OFF
@PJL SET RET=MEDIUM
@PJL SET RESOLUTION=600
@PJL SET BITSPERPIXEL=2
@PJL ENTER LANGUAGE=PCLXL
) HP-PCL XL;3;0;Comment Copyright(c) 1999 Microsoft Corporation
.X.X...........A........H...(...&...LETTER.%C.d.d..*u....?...?.+w....j...-x...-|......Lk...,{....c....y...........B.....,{.....c........MS PCLXLFont 001..O.....P.........p.....P..GT...d.....P.........@... .`...P.`cvt .......l...0fpgm...........pgdir............head......
....8maxp......
D... prep......
d.....0...P.0................&...............i.......i.....................i.....................D...|.......Z.....R.R...D......./...........W.~...................
.".A.P.o...L.u.\.....7.L.n.p...X...................c.c.........-.\...........@.W.......r...]...g.....!.w.....M.....+.L.e.....|.C.............].h.....5.G.!.\.M.....-.x...........................,.I.............?.......).9.I.o.......#...o...2.@.z.....1.U.W.........~.~.....F.B................./.O.V.).o...r...,.1.1.d.i.........+.....................&.......
... .s.......C._...........a...^.m.........
And it goes on...
Thanks for your time.
--Daniel
:Get the source for [[ghostscript]], it includes a PCL driver, study that and you can figure it out. Try printing a simpler document, like a single letter 'a', and see what gets sent over ethernet and see if you can figure out the translation. Try asking in the right newsgroup. See [[Printer Command Language]] and various links to documents attached thereunto. --[[User:GangofOne|GangofOne]] 18:59, 26 April 2006 (UTC)
:What you are seeing there is a fairly simple PCL stream, or the start of one. After the setup commands, it begins to download a font, which will go on for quite a long time. The specification for this print language should have the information you need to break it down - but be sure it is exactly the right specification, as HP updated it regularly. Parsing the full range of PCL is hard work - I'm not sure what you are trying to achieve with this analysis? If how to write PCL, don't do it that way! [[User:Notinasnaid|Notinasnaid]] 20:20, 26 April 2006 (UTC)
Thank you for your input. Starting with the "specification" for PCL, this is actually my problem. I have been unable to locate any specifcation that would allow me to adequately parse through bytes and retrieve meaningful data. I don't need to parse ALL of the stream, just the data intended for printing. The end goal of the analysis is the extract data for input into another program. My goal is not to write PCL. As for sending a "simple" text document across the wire and view the traffic, this is it. Actually, this is it, or rather almost it. My first attempt was the word "hello" sent across all by itself. This stream was for a document reading "hellohellohello...." The data is obviously encoded in some format, I just don't know, and can't figure out exactly what it is.
:I'd expect there's a good chance of seeing the "hello" somewhere down towards the very end, after the font downloads. PCL has the potential to be simple, unlike some other printer formats which simply take a binary bitmap. It is the ability to download fonts which makes simple printing possible: otherwise, the requirement to match a font would make it compulsory to print a page as a bitmap. Though some print methods will still turn out an entire page bitmap in PCL (e.g. GhostScript's PCL driver). Traditionally the format of PCL was something like
stream: [ plain text | escape sequence ] *
escape sequence: escape character , arbitrary characters, length defined by context
If the real question is: where is the latest PCL specification, the answer might be "HP keep it proprietary and only license it" ... and that would make sense because HP don't want the whole world to copy their printer technology. But that would be a guess. A good way to find people who might know is to post on the [[PCL]] article's talk page. But there is an encouraging find: in Usenet I found the comment "You can order the PCL specifications including PCL 6/XL from HP. But it can sometimes be a little problematic, as it seams not all sales people at HP know this ;) But it is possible, I succeded." [[User:Notinasnaid|Notinasnaid]] 07:09, 27 April 2006 (UTC)
== Leaves in Georgia ==
In my Science class, our teacher gave us a project that is due May 10,2006. We have to find 15 different leaves, seal them in wax paper, give the accurate name and tree where found,etc... I needed help because the leaf examples have been located on your site in another part of a state and I need different leaves inside Covington Georgia. Area code:30016. I would greatly appreciate it if you guys can please locate some leaves in this area and send me a reply!
danielandtay@GA411.org
:You could go to the library, check out one of the Peterson's guides or similar tree identification book, go to a forest preserve or large park, look up the trees in the book, and then do the picking, sealing, etc. [[User:Dismas|Dismas]]|[[User talk:Dismas|<sup>(talk)</sup>]] 21:06, 26 April 2006 (UTC)
::Let me point out that there are two ways to do this, either start with the leaves you found, then try to identify them, or start with a list of leaves in your area, then look for each. You might want to focus on leaves with highly distinctive shapes, like maple leaves, as they are easier to identify. Also, if you have a guide book with you when you pick the leaves, you can also check the tree height, bark, etc., against the descriptions in the guide. [[User:StuRat|StuRat]] 21:51, 26 April 2006 (UTC)
:library's for chumps. Do as Calvin did and [[Secondary_characters_in_Calvin_and_Hobbes#Other_characters|sell the earth for alien leaves]]. -[[User:Snpoj|Snpoj]] 21:53, 26 April 2006 (UTC)
== Solar Power Cars ==
Could a car whose surface area is covered in solar pannels produce enough electricity to run? If not, how efficent do the S. Pannels need to become before this can be possible? The current efficency rate is ~15% [[User:199.201.168.100|199.201.168.100]] 21:13, 26 April 2006 (UTC)
:Try [[Solar car]]. [[User:Melchoir|Melchoir]] 21:15, 26 April 2006 (UTC)
:Short answer is, "never as well as a car with a gasoline engine". Even perfectly efficient solar panels give you 1 kW/m^2 under direct sunlight at high noon (or about 1.3 HP per square yard, for Americans reading this). So, an ordinary-sized car with perfect solar panels would give you somewhere around 10 horsepower under ideal conditions. Generally 100 horsepower is considered the minimum for an ordinary car. --[[User:Christopher Thomas|Christopher Thomas]] 21:53, 26 April 2006 (UTC)
== If a tree falls in the woods, does it make a sound? ==
Why is this a popular question? Clearly sound waves are produced, so it becomes nothing more than a petty arguement over the definion of sound. Sort of like if "If all humans became extinct, would puppies still be 'cute'?" [[User:199.201.168.100|199.201.168.100]] 21:13, 26 April 2006 (UTC)
:It's said to be a [[koan]] (although I'm not sure where it comes from; it's not in ''[[The Gateless Gate]]''). The point is not to have a petty argument about semantics, the point is to think deeply about the role of the observer in all forms of experience and perhaps get closer to [[enlightenment (concept)|enlightenment]]. —[[User:Keenan Pepper|Keenan Pepper]] 21:21, 26 April 2006 (UTC)
::I agree with Keenan. This is not a purely ''scientific question.'' But, some might argue it's relevance to [[Observer effect]]. Like, if you don't look at an electron, is it really there? Or for that matter, is it ever really [[Uncertainty principle|anywhere]]? --[[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 21:50, 26 April 2006 (UTC)
:::"Some" might only be me. --[[User:Andrewjuren|Andrew<font color="lightblue">jur</font>]][[user:Andrewjuren/Esperanza|<font color="green">e</font>]][[User talk:Andrewjuren|<font color="lightblue">n</font>(talk)]] 21:50, 26 April 2006 (UTC)
:'''Do Your Own (Dharmic) Homework'''! Snide comments on the RD from people like me are no substitute for proper meditation on koans and the meaning of 'mu'. --'''[[User: Sam Pointon|<font color="#98285C">Sam</font> <font color="79ABDC">Pointon</font>]]''' <font color="#F0D207">United FC</font> 21:27, 26 April 2006 (UTC)
:Today we have a simple answer. Once upon a time, people didn't know as much about physics, and they didn't actually know the answer, and it would require a lot more thinking. [[User:Peter Grey|Peter Grey]] 23:34, 26 April 2006 (UTC)
::It is simple if ''sound'' is clearly defined; under the primary definitions, the answer appears to be ''no''. — [[User:Knowledge Seeker|Knowledge Seeker]] [[User talk:Knowledge Seeker|দ]] 04:51, 27 April 2006 (UTC)
See [[Mysticism]] for more. This is a famous "pointing out" exercise. Its intention is not to exercise the intellect, but to throw a question at it that helps it think "[[lateral thinking|outside the box]]". The question was never intended literally as a physics quiz. [[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 00:16, 27 April 2006 (UTC)
This long predates western knowledge of zen and it is not mystical. It is more related to the philosophical arguments (after [[Berkeley]]) about whether things exist apart from our perception of them. I suspect you could find some 19th century English or American usage of this particular version of it. [[User:Alteripse|alteripse]] 00:55, 27 April 2006 (UTC)
A few years ago in a philosophy class, I heard an interesting answer: It does not, because "sound" is defined to be something like "that which we can hear." Personally, I prefer a less biased definition, though. [[User:Ardric47|Ardric47]] 02:48, 27 April 2006 (UTC)
:Sound is defined as the disturbance of mechanical energy that propagates through matter as a wave. If the question is taken from a purely scientific point of view, the answer is a resounding yes. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 04:25, 27 April 2006 (UTC) re''sound''ing. *wink*
::That is one definition, yes, although not the primary definition either at [[wiktionary:sound|Wiktionary]] or at ''Merriam-Webster''. Following the primary definitions (auditory perceptions or sensations), then quite clearly the tree does ''not'' make a sound if no one is around to perceive it. It depends how you wish to define ''sound''. — [[User:Knowledge Seeker|Knowledge Seeker]] [[User talk:Knowledge Seeker|দ]] 04:51, 27 April 2006 (UTC)
And that pun is resoundingly lame :) [[User:12.183.203.184|12.183.203.184]] 04:31, 27 April 2006 (UTC)
The way I typically interpret this riddle is that it's something that simply can't be proven one way or another. While you can talk about stuff like defining sound, etc., the bottom line is that you can't prove whether a tree makes a sound if no one is around to hear it because any proof would involve someone actually being around to hear it. Obviously as scientists we know that it must make a sound (or not, depending on how you define sound), but this is simply an argument that's impossible to win against a skeptic. [[User:EWS23/Esperanza|<font color="green">'''E'''</font>]][[User:EWS23|WS23]] | [[User talk:EWS23|(Leave me a message!)]] 05:00, 27 April 2006 (UTC)
:No, the definition of sound is in fact the important thing. Proving that the tree did the thing with the air vibrating that people can usually hear if they're close by is easy, at least as a thought experiment: the sound decays into heat as it's absorbed by the forest. In other words, while we may meaningfully argue that perception is an important property of the world and helps define it, no one seriously argues that the lack of observers actually affects the physical occurrence (including what anyone present would have labelled as sound) except for certain real but wholly unrelated issues of measurement in [[quantum mechanics]].
:Look at [[archaeology]] for a science that never involves "being there to see it"; did the Egyptians really build the Pyramids, or do we just suppose that because big rocks are arranged in neat shapes, had we been there, we might have seen someone working on it? It's silly to be skeptical about things that obviously did in fact happen, even if no one saw them. After all, if someone shows up and points out that they in fact cut the tree down and quite clearly haerd it fall, why not label it as [[hearsay]] and continue to refuse the sound, and everything else you're not currently watching, existence? And then keep going and posit that you may in fact be only imagining that the world exists... This too has been done, but the original question presupposes that trees do in fact fall in forests, so it's wrongheaded to apply the unanswerable questions in the philosophy of existence itself to the question. --[[User:Tardis|Tardis]] 07:27, 27 April 2006 (UTC)
::Well, there is a school of thought that the only thing you can be absolutely sure of is ''[[cogito ergo sum]],'' and that anything else could simply just be the the work of some evil scientist or something like [[The Matrix]]. That wasn't really where I was going with my original post (though heading toward those lines, I suppose); I was just saying that if you neglect the ''cogito ergo sum'' argument, there are quite a few things that you can physically prove to a casual observer, but the tree falling in the forest example isn't one of them. (I guess what I'm going for here is that I was taking more of a philosophical interpretation of the famous riddle than a scientific one.) [[User:EWS23/Esperanza|<font color="green">'''E'''</font>]][[User:EWS23|WS23]] | [[User talk:EWS23|(Leave me a message!)]] 08:34, 27 April 2006 (UTC)
:The same (rather unoriginal IMO) question was asked about two weeks ago at the Humanities desk: [[Wikipedia:Reference_desk_archive/Humanities/April_2006#Question_on_subjectivism]]. That provided some intriguing answers, too. [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 08:48, 27 April 2006 (UTC)
== Last Question for today ==
If all humans suddenly became extinct, would puppies still be cute? [[User:199.201.168.100|199.201.168.100]] 21:13, 26 April 2006 (UTC)
:No, but the reason is one that you wouldn't have guessed. I happen to operate a [[dead man's switch]] that, in the event of my own incapacitation, will release an army of robot laser cats to obliterate the world puppy population. They know why. [[User:Melchoir|Melchoir]] 21:29, 26 April 2006 (UTC)
I presume there would be some time between your death, and when the switch activates, as well as some time between the switch's activation and the time the cats finish their work. Durring this time, would the puppies be cute? [[User:12.183.203.184|12.183.203.184]] 22:57, 26 April 2006 (UTC
:No, because I have an army of [[neutrino]] triggered [[nanorobot]]s that hop like [[flea]]s from dog to dog, and which are transmitted by birth. So every puppy has one. At the time I die (and I will die no later than the last human), a neutrino-modulated signal will be released which before I even draw my last breath will activate all nanorobots and almost immediately turning every puppy on the planet into [[grey goo]]. During this process I can assure you that a hundred million rapidly-melting puppies in crisis will be anything but [[cute]]. [[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 00:22, 27 April 2006 (UTC)
::Excellent, now my army is free to pursue other ends... [[User:Melchoir|Melchoir]] 00:28, 27 April 2006 (UTC)
:Adult dogs react emotionally to puppies. If that falls under your definition of 'cute', then they're still cute. If 'cute' is only a cultural concept of humans, then it ceases to have meaning if humans become extinct. Unless whoever made us extinct thinks puppies are cute. The cuteness of kittens, of course, is objective fact. [[User:Peter Grey|Peter Grey]] 00:34, 27 April 2006 (UTC)
::The answer is ''undefined''. Humans won't be confirmed extinct until the [[World Conservation Union]] deems them to be, and I have a feeling that the leftover puppies won't be willing to do all the paperwork. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 04:21, 27 April 2006 (UTC)
== Alternate Launching techniques ==
This was a type of launch platform used in an episode of [[Star Trek: Enterprise]]. Would this work in today's times, and if not why not.
[[Image:Enterprise_first_flight.png]]
[[User:Chcknwnm|Chuck]] 22:05, 26 April 2006 (UTC)
:What is it? How does it operate? We can't really tell these things from a picture. [[User:Isopropyl|Isopropyl]] 22:43, 26 April 2006 (UTC)
:Without seeing it in action, I can't be sure, but that looks like a [[maglev]]/[[linear motor]] track with a ski jump curve on the end. It's a pretty popular alternative launch system in science fiction: accelerate the spacecraft down the ramp until it reaches orbital velocity, then use the ski jump curve to turn a little bit of that velocity into altitude. The spacecraft then fires its engine once it reaches [[apogee]] halfway around the world to circularize the orbit. It would be possible to build one today, but it would be extremely expensive.
:As a bit of science-fiction trivia, Mount Wilson is a popular place to put this sort of launcher. --[[User:Serie|Serie]] 22:58, 26 April 2006 (UTC)
:Is this on Earth? It's effectiveness would depend on the local gravity and atmospheric density. As I understand it, building one is technically feasible, but you also have to consider whether it's economically feasible, given that the actual designs of the linear and curved sections will be limited by the how much acceleration whatever you're launching can survive. [[User:Peter Grey|Peter Grey]] 00:24, 27 April 2006 (UTC)
::Theres actually some interwting science about these kind of things. First, read up on [[escape velocity]]. Basically, if we could ignore the atmosphere, then any object travelling under escape velocity will remain on (or return to) earth, and any object over escape velocity will either escape from earth (if pointing above the horizon) or hit earth (if pointing down). It does not matter if the object is pointing up, at an angle, or horizontal. If you ignore atmospheric effects, the ONLY question is, if it is pointing above the horizon (nothing in the way!) and above escape velocity, it escapes, otherwise it returns or crashes to earth. Its that simple. Direction has nothing to do with it. Its purely the [[potential energy]] needed to escape earth, and the [[kinetic energy]] given to it by escape velocity, and which is bigger than the other.
::HOWEVER... if you take into account the atmosphere, the atmosphere applies [[friction]] and [[air resistance]] to moving objects, strongly slowing them down. Imagine walking into a strong wind. The atmosphere is [[Earth's_atmosphere#Thickness_of_the_atmosphere|denser]] near the ground. So it pays to get above the lower atmosphere as fast as possible, to minimize the loss of energy. A horizontal track would work, but would have to launch a vehicle faster to allow for this loss, than a vertical or tilted take-off. And so yes, this design is feasible. [[Robert Heinlein]]'s book ''[[The Moon is a Harsh Mistress]]'' describes one of these and some of the science. [[user:FT2|FT2]] ([[User_talk:FT2|Talk]]) 00:33, 27 April 2006 (UTC)
Wow...great answers. Thanks everyone! --[[User:Chcknwnm|Chuck]] 02:07, 27 April 2006 (UTC)
:You often hear about jump launches like this as being good solutions for launching [[RAMJET]]s or other high-speed craft that can't operate properly at low speed. After accelerating down a long maglev (or similar) track (a very wide circle track might work even better) the craft launches off the final ramp and the engines engage. The main problem with this is that if the track isn't circular, you will almost certainly be subject to very high g-forces from acceleration, and engaging the engines after flying off a ramp probably isn't the most comfortable experience either. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 04:16, 27 April 2006 (UTC)
::It's the acceleration on the tightly curved ramp at the end that would keep me from getting on this thing. If the device were launching objects without their own propulsion into orbit, and had them moving at escape velocity (many thousand mph) by the time they reach the curve, there would be preposterous force on both the track and projectile, whether the curvature is circular or not. The only way to practically build something like this is to lay the entire track (or at least the highest-speed portions) on a straight line. As noted above, even a horizontal track would work, provided there are no mountains in the way. '''''×'''''[[User:Meegs|Meegs]] 06:30, 27 April 2006 (UTC)
== baseball problem ==
A 0.145kg baseball travellng at 30m/s strikes the cathcesr mitt bringing the ball to a stop. The glove recoils back 11cm. What is the average force applied by the ball on the glove?
Confused since the distance (11cm) is after the ball is at rest. then I don't enough info to do it, but yeah if someone could show me thanks.
[[User:C-c-c-c|C-c-c-c]] 22:44, 26 April 2006 (UTC)
F = ma
A = 30/t
D = 11 = VT + .5AT^2
Two equations, two unknowns. Solve for F&T. [[User:12.183.203.184|12.183.203.184]] 22:53, 26 April 2006 (UTC)
:To address the fundamental problem, try spending some more time visualizing the situation before deciding you don't understand it. Clearly the glove didn't move 11cm after it was at rest. [[User:Melchoir|Melchoir]] 23:07, 26 April 2006 (UTC)
:Although, actually, there's a second problem with the question. To determine the time-averaged force, you'd have to know the time it took to stop the ball, which you're not given. So you can really only determine the space-averaged force. One way is to assume a constant force, as 12.183.203.184 suggests. [[User:Melchoir|Melchoir]] 23:23, 26 April 2006 (UTC)
For the heck of it I did v2^2 = v1^2 + 2ad with V1 being 30m/s and V2 0 and I get twice the correct answer.
v2^2 = v1^2 + 2ad
(v2^2-v1^2)/(d) = a
(0 - 30^2)/(0.11) = a
a = -8181.81m/s^2
F = ma
F = 0.145(-8181.81)
F = -1186.36
The answer I was given was 588.6. Anyone know why this happens? Thanks. --- [[User:C-c-c-c|C-c-c-c]] 01:46, 27 April 2006 (UTC)
:When you know you're off by a factor of 2, that's a good time to step back through your work and determine where you dropped it. [[User:Melchoir|Melchoir]] 01:52, 27 April 2006 (UTC)
I think your equation is off by two. VT +1/2 AT^2 = D
:The first equation is fine. [[User:Melchoir|Melchoir]] 08:47, 27 April 2006 (UTC)
== How much does a flea weigh? ==
What is a ballpark figure for the weight (or mass) of a typical flea, say for concreteness a hungry adult Pulex irritans? The relevance of this itching question is that the article [[Planck mass]] states (without source) that "the Planck mass is on a scale more or less conceivable to [[human]]s, as it is roughly the mass of some [[flea]]s." The article [[Flea]] sheds no light on the issue. I put this question on the [[Talk:Flea|talk page of Flea]], but in more than a month there has been no reaction – no-one wants to talk about fleas. [[User:Lambiam|Lambiam]][[User talk:Lambiam|<small><sup>Talk</sup></small>]] 22:40, 26 April 2006 (UTC)
:(Heh, after reading just your first sentence, I was about to answer "oh, about a Planck mass". Guess that doesn't cut it?) [[User:Melchoir|Melchoir]] 23:34, 26 April 2006 (UTC)
:[http://dermatology.cdlib.org/DOJvol3num2/fleas/fleas.html This page] indicates that females can consume up to 14 μL of blood per day, amounting to about 150 times their body mass. Assuming a density of blood of a bit more than 1 g/cm<sup>3</sup> (close enough for our purposes) 14 μL of blood would weigh about 15 mg. Divided by 150, that's a weight per flea of about 100 μg—I don't know if that would be the dry or full weight, however. Given a Planck mass of about 21 μg, I'd say we're getting well into the realm of 'close enough'. [[User:TenOfAllTrades|TenOfAllTrades]]([[User_talk:TenOfAllTrades|talk]]) 00:32, 27 April 2006 (UTC)
::Update. Guess what, the value for Planck mass quoted in the article was just corrected by an anonymous editor; it was off by a factor of 1000. It's 21 pg, not μg. While not as unimaginable to us as the Planck length, fleas would then be a whopping 5000 Planck masses. Although, is the Planck length so unimaginable? Lambiam's Law: If you have to walk the plank, it will appear a Planck length. [[User:Lambiam|Lambiam]][[User talk:Lambiam|<small><sup>Talk</sup></small>]] 20:55, 30 April 2006 (UTC)
== [[Rail gun]] ==
Is it possible with todays technology that a actual mass driver such as a railgun could be built? If it was then what would it be made out of and how could the required amount of energy be produced to send a vehicle speeding out of our atmosphere at escape velocity? <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:68.120.231.85|68.120.231.85]] ([[User talk:68.120.231.85|talk]] • [[Special:Contributions/68.120.231.85|contribs]]) 23:25, 26 April 2006.</small><!-- [Template:Unsigned] -->
:No, it's not currently possible. One problem is that a projectile (like a rocket) needs to move slower in the thick lower atmosphere to avoid burning up. However, I can imagine a setup where you give a conventional rocket a bit of a push-start with such a device. Some other technology, like compressed air, would also allow you to give a rocket a head start and thus save on fuel it needs to keep onboard. This would allow for much lighter, smaller rockets. It's also far easier to store large quantities of energy as compressed air than as electricity, and electromagnetic interference isn't an issue. [[User:StuRat|StuRat]] 02:10, 27 April 2006 (UTC)
::Also see [[mass driver]], [[rail gun]], and [[coil gun]]. [[User:StuRat|StuRat]] 02:26, 27 April 2006 (UTC)
Thank you that actually was the answer I was looking for. Patrick Kreidt
:You're quite welcome. [[User:StuRat|StuRat]] 15:03, 27 April 2006 (UTC)
= April 27 =
== Hydrogen as energy source/fuel ==
Hydrogen is praised as the fuel of the future for it's non-polluting properties, but nowhere have I found how much energy is required in producing a given quantity of energy in hydrogen. The process of hydrogen production can't be better than 100% efficient, and if it uses oil or coal we are just transferring the problem from the end-consumer to the producer.
I would like to know something about the efficiency of hydrogen production, and the method(s) used.
Researching this subject and publishing the results may clarify the situation, and your efforts would be sincerely appreciated.
Henry Boessl <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:63.22.138.50|63.22.138.50]] ([[User talk:63.22.138.50|talk]] • [[Special:Contributions/63.22.138.50|contribs]]) 01:02, 27 April 2006.</small><!-- [Template:Unsigned] -->
:You're correct that it takes a considerable amount of energy to produce hydrogen gas. And, of course, there aren't vast quantities of it sitting around like petroleum and coal (although not as huge quantities as there once were). However, hydrogen is a reasonably good way to store and distribute energy. Compared with coal, for example, it can be shipped through pipes and used in cars, while coal isn't suitable for either purpose. So, burning coal and using the energy to produce hydrogen, say by the electrolysis of water, allows you to distribute hydrogen for fuel cells or direct combustion in cars and eventually for other purposes, like home heating. Another advantage is that the pollution created by the coal is at the power plant, and very little pollution is released from the car. By placing the power plants away from dense population centers you can thus reduce pollution in populated areas. Another competing temporary way to store energy is as electricity stored in batteries in the car. At present, however, batteries don't carry much energy relative to their weight, so this may give hydrogen gas the advantage. Energy produced by other non-portable sources, like nuclear, hydro, geothermal, etc., may also be converted into hydrogen gas. I don't see it being worthwhile to convert other portable energy sources, such as petroleum, to hydrogen gas, however. The advantage of moving the pollution away from cities doesn't seem to be worth the energy loss incurred in such a conversion. [[User:StuRat|StuRat]] 01:32, 27 April 2006 (UTC)
::Hydrogen can be produced by reducing steam with [[coke (fuel)|coke]] (the latter being produced from coal). That does make CO2, but possibly less than you'd produce by burning gasoline to power a car to go the same distance. (I say "possibly" because I don't really know; anyone who ''does'' know should feel invited to jump in here.) If that's true then total greenhouse emissions could be reduced; even if it isn't, it's still a way to use coal, which the US has a lot of, to power cars. It's surely better than burning it for electricity and then hydrolyzing water.
::The only solution I can think of, though, that uses hydrogen to let us keep driving while eliminating greenhouse emissions is to make it using nuclear power. (Yes, the full cycle of nuclear power production does currently produce some greenhouse gases, but that's because mining, construction, etc use fossil fuels; they could be switched over to nuclear-generated hydrogen as well.)
::But there is an issue that hasn't yet drawn a lot of attention, but will have to be dealt with if the hydrogen thing really gets going: Hydrogen could cause ozone depletion (hope I don't have to explain why :-). Just how serious the problem is, or how hard it would be to keep the hydrogen from leaking, I don't know if anyone really knows. --[[User:Trovatore|Trovatore]] 02:15, 27 April 2006 (UTC)
:::The two answers above are excellent, you may also be interested in reading our article on [[hydrogen economy]]. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 09:44, 27 April 2006 (UTC)
I was researching this a few years ago and came up with the same problem. However, I then found that there are algae which can be induced to produce hydrogen, and if stimulated correctly will hopefully produce sufficient quantities to be worthwhile. The info I found suggested 10 years as the time frame before they had good results, but that was about 3 years ago. Anyway, if it worked you could get your hydrogen from algae, inputting only sunlight and a few chemicals to up the prduction. [[User:88.144.79.120|88.144.79.120]] 16:39, 27 April 2006 (UTC)
:This new technology could be considered a more efficient form of solar energy, which is sorely needed. I hope it works out. [[User:StuRat|StuRat]] 00:40, 29 April 2006 (UTC)
This was my first attempt at using Wickipedia and I am amazed how quickly and thorough the response was. Many thanks to those who took the time to reply; irelly appreciate their effort. HB
:You're quite welcome. [[User:StuRat|StuRat]] 18:16, 29 April 2006 (UTC)
== Electroysis to breath underwater? ==
Please help
I am still in grade school and very interested in electricity, and i've read a few books on electricity and i cant seem to really understand if anything answers my question; '''Is it possible to make an underwater breathing apparatus using materials such as an electrolysis device with like a mouth piece or something that 1 person could use and operate, like a scuba tank, so they could breath underwater? And would it be safe?'''
Thank-you in advance for you help.
--[[User:216.197.232.142|216.197.232.142]] 03:43, 27 April 2006 (UTC)Gus
:I imagine it is technically feasible with an adequate power source, but you would need to think through a few more points, like where is the hydrogen going to go, and how do you safely handle pure oxygen. I think a more interesting question is the ''that 1 person could use'' part, whether or not it would be less massive/bulky/dangerous than a simple tank of compressed oxygen. [[User:Peter Grey|Peter Grey]] 05:21, 27 April 2006 (UTC)
:The power source is probably the biggest problem. If you were going to carry a lead battery to power your electrolysis, it would probably outweigh an equivalent air tank by a large factor (but how large, I don't know). -[[User:Lethe/sig|lethe]] <sup>[[User talk:Lethe/sig|talk]] [{{fullurl:User talk:Lethe|action=edit§ion=new}} +]</sup> 05:24, 27 April 2006 (UTC)
::You're right. Basically, the energy density of a lead battery is not very good; the energy you got out of 1 kg of battery is enough to electrolyse only a small fraction of 1kg of water. To do the calculation yourself, you need to know the energy density of a lead-acid battery and how much energy it takes to electrolyse water; both statistics shouldn't be too hard to find. It's unlikely that any conventional power source is likely to be dense enough to pull this off; the latest and most efficient thing in "conventional" submarines is powering them with [[fuel cell]]s, which is essentially electrolysis in reverse! Nuclear-powered submarines have fuel with enormous energy density, so they indeed use the scheme you describe (as well as devices to remove carbon dioxide, carbon monoxide, and other contaminants from the atmosphere) to provide breathable air on their very long voyages.
::--[[User:Robert Merkel|Robert Merkel]] 06:28, 27 April 2006 (UTC)
::Maybe I can make a rough stab at the math. From [http://www.lsbu.ac.uk/water/data.html] I get that, say, 1 kg of water would require <math>1.59\times10^7\mbox{ J}</math> to dissociate into an atmosphere (in other words, into your helmet or so). From this, you'd get 889 grams of oxygen. That much energy at, say, the 1.6 [[electron volt|eV]] per electron in a [[silver-oxide battery]], is <math>6.19\times10^{25}</math> electrons. You get two per reaction, and each reaction involves 297 [[amu]] of reacting material (not counting [[catalyst]]s, but in theory they can be [[amortization|amortized]] over many reactions). So that's 15.3 kg of reactant to "power" 889 grams of oxygen (factor of 17.2). You're probably better off just carrying the oxygen; while the oxygen tank adds some weight, the battery structure and electronics and electrolysis equipment would add a good bit too. --[[User:Tardis|Tardis]] 07:12, 27 April 2006 (UTC)
Followup: As Peter Grey touched on, can you, in fact, create a breathable mixture solely from hydrogen and oxygen (and compounds of the two)? If not, this device would presumably have to process and recycle the diver's exhaled air just as the submarines. '''''×'''''[[User:Meegs|Meegs]] 08:02, 27 April 2006 (UTC)
:That's a very creative idea, although I don't think it could be made to work no matter how it was engineered. The reason is that people normally ''don't'' breath pure oxygen. This can cause [[oxygen toxicity]]. SCUBA divers breathe compressed air, which about 78% nitrogen and only about 21% oxygen. See also [[breathing gas]] and [[air]]. --[[User:Ginkgo100|Ginkgo100]] 18:31, 27 April 2006 (UTC)
::Hey, the article on [[breathing gas]]es mentions hydrogen as component of deep-diving mixes! Just an aside, [[cyclopropane]] and [[acetylene]] used to be used in anesthesia, if it weren't for the fact that they are explosive they would be great anesthetics - no liver and kidney toxicity, fast equilibration with lung air. [[User:Dr Zak|Dr Zak]] 19:38, 27 April 2006 (UTC)
Aren't there bacteria that produce oxygen (though I'm not sure if they exist anymore)? If they are still around, could they produce enough oxygen to make it possible to breath underwater, seeing as you would only have to caarry traces of other gases and a tank to hold your carbon dioxide. Might not make any sense, I'm still in grade school too.
:Recycling exhaled air is nothing new in serious diving so that wouldn't be an issue though you may have to carry a small ammount of your mixer gas to make up for losses. As already mentioned the issue with anything that depends on splitting water is power. Fossil fuels are pointless as you'd have to carry oxygen to burn them with. Battries are too low energy density. A [[RTG]] might work but you'd probablly have difficultly getting it past the authorities. [[User:Plugwash|Plugwash]] 01:11, 1 May 2006 (UTC)
== Dimensionally prove the simple pendulum equation! ==
Sir, there is the prove of simple pendulum equation or formula but there is no dimensional analysis of this formula to check weather it is correct dimensionally or not, For just studing for college--[[User:80.231.14.119|80.231.14.119]] 06:58, 27 April 2006 (UTC)
:What? [[User:Melchoir|Melchoir]] 07:02, 27 April 2006 (UTC)
:Er, if it's been proven, you don't need to do dimensional analysis. Dimensional analysis finds bugs, but proof precludes them (notwithstanding any bugs in the proof!), so the analysis would be redundant. Why would you want it specifically? --[[User:Tardis|Tardis]] 07:14, 27 April 2006 (UTC)
Sir i want for studing for college.i know its all right proof but for my personal studies i want proof of Dimensional analysis. If u write for me i am very thank ful to you--[[User:80.231.14.119|80.231.14.119]] 07:31, 27 April 2006 (UTC)
:Since it's so insanely easy we may as well do it for you. You haven't specified which formula you want, so I'm going to do the period for the small angle approximation, <math>T_0=2\pi\sqrt{l \over g}</math>.
:<math>T_0</math> is a time, so it has dimensions of T. <math>2\pi</math> is a dimensionless constant. <math>l</math> is a length, dimensions of L. <math>g</math> is an acceleration, dimensions of LT<sup>-2</sup>. So, <math>l \over g</math> has dimensions of L/(LT<sup>-2</sup>) = T<sup>2</sup>, and its square root therefore has dimensions of T, as required.
:If it's some other formula you wanted have a go at it yourself. --[[User:Bth|Bth]] 07:37, 27 April 2006 (UTC)
Thanks sir i am very very thankful ,remmember that this is the only site which help me in studies! whole google search not give me such type of intresting site Sir--[[User:80.231.14.119|80.231.14.119]] 07:46, 27 April 2006 (UTC)
Give the drawbacks to use the time period of pendulum as a time standard--[[User:80.231.14.119|80.231.14.119]] 07:54, 27 April 2006 (UTC)
:OK, see, if you're going to get us to do your homework, you have to work hard at pretending that it's not. Quoting the next question in such obvious "this is a question" form is a dead giveaway. I'm sorry I helped you now. --[[User:Bth|Bth]] 08:15, 27 April 2006 (UTC)
"Give the drawbacks to use the time period of pendulum as a time standard"if any--[[User:80.231.14.119|80.231.14.119]] 08:23, 27 April 2006 (UTC)
:Erm, you seem to have misunderstood - please read the rules at the top of the page, we are here to help with concepts and try and answer general questions, but we strongly object to doing your homework for you. Your question "Give the drawbacks to use the time period of pendulum as a time standard, if any" smells very strongly of homework, so we won't help you, as it won't do you any good to have others do your work for you. Please come back when you have finished your homework. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 08:32, 27 April 2006 (UTC)
::But do you know the application of simple pendulum? [[User:Ngocthuan 06]]03:38, 27 April 2006 (UTC)
:::I relent, I'll give you the answer. Think about the equation that you are working with...it's a ''simple'' pendulum. What assumption was made to derive the equation? Hm...I wonder... --[[User:HappyCamper|HappyCamper]] 02:51, 30 April 2006 (UTC)
== photons ==
Anything that moves at light speed has infinite mass.The photon has no mass.How does this explain RADIATION PRESSURE?
:Anything with a [[rest mass]] cannot ''reach'' light speed in the first place, because to do so would require infinite energy. Anything with a zero rest mass can ''only'' travel at light speed. Photons still have energy (equal to Planck's constant times their frequency), and it's the transfer of that energy that ultimately accounts for [[radiation pressure]]. --[[User:Bth|Bth]] 08:24, 27 April 2006 (UTC)
:Moreover, radiation pressure is a classical effect of electrodynamics that doesn't even require photons. Ah well... how many times have we gotten this question now? Maybe we need a FAQ. Seriously. [[User:Melchoir|Melchoir]] 08:58, 27 April 2006 (UTC)
I'm well versed with the fact that only particles can interact because of change in momentum.Is there something im missing here?
:Photons have momentum. It's [[Planck's constant|h]]/[[wavelength|λ]]. —[[User:Keenan Pepper|Keenan Pepper]] 14:00, 27 April 2006 (UTC)
:Have a read of [[Optical tweezers]]. -- [[User:SGBailey|SGBailey]] 08:30, 29 April 2006 (UTC)
== Hepatits School Project ==
I need to find out specific numbers of the incidents and deaths for most of the countries of the world. If anyone can help please I really need it. Thanks
For every single country in the world there are some incidents and deaths from the disease Hepatitis. I require the specific number for each country. Anything Helps!!
--[[User:204.218.240.30|204.218.240.30]] 08:20, 27 April 2006 (UTC)
:I think you will struggle very much to get [[morbidity]] rates: [[hepatitis]] (which is a symptom, not a disease: it refers to several different conditions, including a number of viruses, damage from too much alcohol and prescription drug side-effects) is not necessarily even diagnosed, and if it is, not all countries will have any system of counting incidents, and of those that do, not all will publish the data. Even getting [[mortality]] figures is questionable for most countries. Where information is published it may well be in medical journals for which you would have to visit a medical library - assuming you can find the existence of the article. I think you either need to find an easier project, or be satisfied with a much simpler lot of information to collect. [[User:Notinasnaid|Notinasnaid]] 08:41, 27 April 2006 (UTC)
There is no single disease "hepatitis". There are many causes of infection or inflammation in the liver, which is what hepatitis means. To get a sense of your challenge google [hepatitis] and [epidemiology]. For example, see [http://www.brown.edu/Courses/Bio_160/Projects2000/HepatitisB/epi.html], which gives some vague statistics for endemicity of hepatitis B. Those percentages on the map refer to the percentages of people thought to be infected. Hep B is the most well-known kind of hepatitis. There is much less info available for the other types. After you have a sense of what is available through Google, go to [[medline]] or [[Pubmed]] with the best terms. Good luck. [[User:Alteripse|alteripse]] 10:31, 27 April 2006 (UTC)
BTW, you are talking about "[[incidence (epidemiology)|incidence]]", not "incidents", and you may find it easier to look for [[prevalence]] figures. - [[User:Nunh-huh|Nunh-huh]] 19:29, 27 April 2006 (UTC)
'''Symptoms of hepatits'''<br>
The principle symptom of hepatits is the spontaneous appearance of five extra nipples on the patient's chest area.
Sorry, it's so late it's early and I couldn't resist. [[User:Offtherails|Howard Train]] 09:48, 30 April 2006 (UTC)
== Mobile mouse cursor ==
I'm using a Mini Optical 3D mouse by A4Tech.
Firstly,what's with it being 3D?Secondly,sometimes the mouse cursor suddenly starts moving on its own,without any physical force being applied on the mouse.Why and how does this happen and how can I prevent this?
Thanks in advance.
:3D is probably why "2000" is added to waterguns. Or maybe the company is reminding you of the mouse's three dimensional features. The mouse cursor is moving around (like jumping? or slowly moving like how fast you contorl it) because of the surface your optical mouse is on. Put it on a mousepad or something less rough or shiny. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 10:19, 27 April 2006 (UTC)
It '''is'''on a clean mouse pad already.
:In that case you have perhaps been infected by malware. Someone outside your computer could be taking control of it. No joke, this happens. [[User:Notinasnaid|Notinasnaid]] 12:49, 27 April 2006 (UTC)
:If it is an optical mouse it may not have to do with it being ''clean'' or not. Some surfaces provide better reflection than others. But in any case -- you might try fiddling with the mouse settings and reducing its sensitivity. While it's always possible that you are suffering from malware, if by "moving on its own" you mean just random little movements and not purposeful moving, then it is probably just being overly sensitive and/or on a surface which is confusing it. --[[User:Fastfission|Fastfission]] 15:41, 27 April 2006 (UTC)
I think I have a pretty good defence against all sorts of malware,adware and spyware.Have d/loaded plenty of softwares to protect my system.
I was thinking more along the lines of some physical damage to my mouse maybe.
And when I say "moving on its own",I mean that it can cover the whole length of my monitor screen in 20 seconds,if I don't stop it from doing so.It's a minor problem,but sometimes disturbing.Its like phantom movement by my mouse.
== ion wind effects ==
Does the pressure force created by ionised air, or ion wind effect only conductive materials or can it lift non-conductive materials such as wood. not generating it but just being pushed up or sideways by it?
Edward knott 11:43
:[[Ion]]s are just atoms or molecules with a net charge. They can exert pressure on anything just like a normal gas. —[[User:Keenan Pepper|Keenan Pepper]] 14:03, 27 April 2006 (UTC)
::Go to a Sharper Image and put your hand in front of the Ionic Breeze. You can feel the wind blowing out on your hand - which isn't very conductive. --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 15:08, 27 April 2006 (UTC)
:::I'm not sure that either of the two posters above looked at the relevent articles. As the [[Air ioniser]] article itself states, such machines have nothing to do with [[ion wind]]. The [[Ion wind]] article is not very clear, but it stresses that any force is not due to a tranfer of moment to another body, but from the impulse of the ions leaving the generator. In which case, I would assume that an ion wind can only cause thrust in the generator, which must itself be conductive. — [[User:Asbestos|Asbestos]] | [[User talk:Asbestos|<FONT COLOR="#808080">Talk </FONT>]] [[User:Asbestos/RFC|<FONT COLOR="#808080"><small>(RFC)</small></FONT>]] 16:49, 27 April 2006 (UTC)
Uuuuum so are we gona get a concencus here? some say one thing, others say another. So which is it exactly?
Edward
:My opinion is that Asbestos and I read your question differently. In my reading, you ask if an ion wind genererator can generate enough wind to move wood. Yes. I gave an example - the Ionic Breeze (which is a very weak ion wind generator) creates enough of a breeze that you can feel it. If you use a much better generator, you'll get more wind, and more wind will move larger things. Asbestos appears to have read it as: Can an ion wind generator attached to some wood device be some sort of lift engine? Not effectively. Lifters (made with very light weight wires, foil, and toothpicks) use ionic wind engines to lift a wood (toothpick) structure. They are very weak and fragile. I've seen models with dozens of lifters connected together to lift a small object, but the power generator is far to heavy to be contained on the lifter. Instead, it sits on the ground and is just wired to the lifter (which usually lifts, gets pulled towards the generator by the cables, hits the generator, sparks, then bursts into flames.) --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 02:43, 28 April 2006 (UTC)
Thank you, i was not asking about this because i want to build a lifter, i was just wondering if the force used in them, if generated some other way could lift all kinds of objects rather than just metal ones.
Edward
==animal/plant/fungus/protist==
I'm trying to write the start page on a wikibook called [http://en.wikibooks.org/wiki/Dichotomous_Key Dichotomous Key]; you have to answer a certain number of questions to determine the species of an animal. (For example, I would ask: ''Does it have a nucleus? If not, it's a bacteria. If so, go to section #3 for the next question.'')
But I'm not quite sure what questions to ask to determine: [[Animal]], [[Plant]], [[Fungus]], and [[Protist]]. I looked at the corresponding Wikipedia articles but they're not much help. The Protist article says that protists are the "left-over" kingdom; if a eucaryote isn't an animal, plant, or fungus, it's a protists. The animal, plant, and fungus articles are not much help at all and I'm not sure what questions to ask for the Wikibook. [[User: Jonathan W|<span style="background:#8c6638; size:2; color:#00FF00;"> Jonathan</span>]] <sup><span style="size:-1;"> [[User talk:Jonathan W|<span style="color:#8c6638">talk</span>]] </span></sup> [[Image:Canada flag 300.png|30px]] 14:10, 27 April 2006 (UTC)
:There's no such thing as "a bacteria". --[[User:Trovatore|Trovatore]] 14:48, 27 April 2006 (UTC)
:Hmmm... You aren't working from an existing Dichotomous Key? They can be very complex, precise and intricate. Unless you're working from a source, or have more than a working knowledge of the distinctions, I'd say you're in for many headaches... The Protist would be the easiest to define — if you knew the definitions for the rest of the categories... Animals are typically defined at least in part by their locomotive ability. Fungi can be separated from plants by not being heterotrophs. — [[User:Asbestos|Asbestos]] | [[User talk:Asbestos|<FONT COLOR="#808080">Talk </FONT>]] [[User:Asbestos/RFC|<FONT COLOR="#808080"><small>(RFC)</small></FONT>]] 15:41, 27 April 2006 (UTC)
::Thanks for the answers. And when I said ''a bacteria'' I meant ''eubacteria'' or ''archaebacteria''. [[User: Jonathan W|<span style="background:#8c6638; size:2; color:#00FF00;"> Jonathan</span>]] <sup><span style="size:-1;"> [[User talk:Jonathan W|<span style="color:#8c6638">talk</span>]] </span></sup> [[Image:Canada flag 300.png|30px]] 17:14, 27 April 2006 (UTC)
:::Still wrong. The singular is "bacterium". --[[User:Trovatore|Trovatore]] 17:32, 27 April 2006 (UTC)
::::Oops, sorry.
::::I still need help! (You can see the page I created on the wikibook [http://en.wikibooks.org/wiki/Dichotomous_Key:Start here].) I can classify animals, plants, and fungi well enough, but some protists can move around too, right? And some protists get energy from the sun, and some get energy from other organisms! Some protists are unicellular and some are multicellular! Does anyone have any more characteristics that separate animals, plants, and fungi from protists for me please? --[[User: Jonathan W|<span style="background:#8c6638; size:2; color:#00FF00;"> Jonathan</span>]] <sup><span style="size:-1;"> [[User talk:Jonathan W|<span style="color:#8c6638">talk</span>]] </span></sup> [[Image:Canada flag 300.png|30px]] 17:43, 27 April 2006 (UTC)
:::::I assume you are familiar with [[Wikispecies:Eukaryota|Wikispecies]], right? You may also find the excellent [http://www.tolweb.org/tree/ Tree of Life] project helpful. — [[User:Knowledge Seeker|Knowledge Seeker]] [[User talk:Knowledge Seeker|দ]] 03:19, 28 April 2006 (UTC)
==Solar Powered Cats==
If I had an army of solar powered laser cats, whose surface area is covered by enough solar pannels to produce enough electricity to run 1.1 jigawatt lasers, would you still hear a sound if a flea landed on a cute puppy in woods, while being propelled into orbit by a cyclic path? and would it allow me to breathe underwater with the aid of my solar powered laser cat army whose 1.1 jigawatt laser would allow me to transport oxygen free radicals from the year 1885 directly to my breathing apparatus in the year 2007? assuming of course that the force felt by photons impacting on the surface of the water, allowed for enough solar energy to penetrate the depth of the water, and reach the solar pannels, of course--[[User:Nullity|Nullity]] 15:45, 27 April 2006 (UTC)
:No, you can't breath underwater in any case, because "breath" is not a verb. --[[User:Trovatore|Trovatore]] 15:54, 27 April 2006 (UTC)
::nitpicker--[[User:Nullity|Nullity]] 15:57, 27 April 2006 (UTC)
:''if a flea landed on a cute puppy in woods... would it allow me to breathe underwater with the aid of my solar powered laser cat army'' What's the distance from the flea to the water? [[User:Peter Grey|Peter Grey]] 17:08, 27 April 2006 (UTC)
::Why do you say 2007, not 2006? [[User: Jonathan W|<span style="background:#8c6638; size:2; color:#00FF00;"> Jonathan</span>]] <sup><span style="size:-1;"> [[User talk:Jonathan W|<span style="color:#8c6638">talk</span>]] </span></sup> [[Image:Canada flag 300.png|30px]] 17:11, 27 April 2006 (UTC)
:::Isn't it obvious? The solar powered laser cats are still in R&D. They won't be ready until 2007. --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 17:36, 27 April 2006 (UTC)
::::It's true. My current models are nuclear-powered, but fuel is so expensive these days. [[User:Melchoir|Melchoir]] 18:27, 27 April 2006 (UTC)
:::::Have you considered training the cats to use public transportation? --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 18:31, 27 April 2006 (UTC)
::::::That was the 1994 model. I admit, they were efficient, and they kept a low profile, compared to streaking across the sky at Mach 2 to engage my enemies. But wouldn't you know it, the damn things achieve self-awareness and suddenly it's me, me, me. ''We want turreted lasers, we want a sexier means of transportation, we want full dental.'' And if you try to say no, they morph into kitten mode and stare at you with those eyes... [[User:Melchoir|Melchoir]] 18:48, 27 April 2006 (UTC)
:::::::Please, please stop...these threads are so hilarious that I am getting Wikipedian stomach aches from laughing...someone needs to archive these at [[WP:-)]] for sure!!! --[[User:HappyCamper|HappyCamper]] 00:40, 28 April 2006 (UTC)
:It's a well-known fact that cats are solar powered gravity machines. They find a sunny spot to sleep in all day, and then at night they climb on top of you in bed and weigh approximately seventy three times what you'd expect. --[[User:LarryMac|LarryMac]] 00:43, 28 April 2006 (UTC)
:''photons felt enough force'' Photons can't feel force. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 01:35, 28 April 2006 (UTC)
:If humans became extinct, would laser cat kittens still be cute? (Are they cute now? I've never seen one) [[User:Peter Grey|Peter Grey]] 04:34, 28 April 2006 (UTC)
Do they ever feel melancholy?
:Have they ever felt lonely? Heve they ever felt blue? Oh, and is there an equivalent of BJAODN for the Reference desks? [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 03:10, 28 April 2006 (UTC)
::It may not be B, or ODN, but it's definitely a J and it's been moved to BJAODN...! :) — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 08:18, 28 April 2006 (UTC)
Cats are like Goths. No matter how else they feel, there is always an element of melencholy.
Solar powered [[WP:CAT|cats]]? Sounds good to me. [[User:EWS23/Esperanza|<font color="green">'''E'''</font>]][[User:EWS23|WS23]] | [[User talk:EWS23|(Leave me a message!)]] 03:22, 28 April 2006 (UTC)
Bah, solar powered ones are so usless. Those mouse power ones are 10 more reliable and the fuison ones go boom and kill you if you get them mad.
== Hair ==
How does hair 'know' when to stop growing. If I shave my arm, the hair will grow back to the former lenght, how does it know what length to grow to--that is, how does it know it has reached the previous length?? [[User:Ztsmart|Ztsmart]] 19:00, 27 April 2006 (UTC)
:In [[hair]] it mentions that hair growth is timed. A folicle grows hair for a preset time and then stops. --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 19:03, 27 April 2006 (UTC)
so if I cut it, how does it know to start growing again? [[User:Ztsmart|Ztsmart]] 19:19, 27 April 2006 (UTC)
:I don't know the "real" answer to this, but it's partly an illusion. Hairs are falling out and growing back all the time. When you shave, some notable portion of the hairs were already near the falling out/regrowing point, so they immediately start growing. Since some of them, at least, will reach very nearly their "full" length, it can easily look like they all grew back even if some of them were severely stunted for that cycle. --[[User:Tardis|Tardis]] 21:15, 27 April 2006 (UTC)
:The brief answer is that the cut hair has no way of 'knowing' that it has been cut. A hair follicle will crank out hair for a fixed period of time, after which the hair (eventually) falls out; the cycle then repeats. Since your hair follicles are ''not'' sychronized with one another, you will have some hairs that are growing, some that have reached their full length, and some that are just getting started. The overall impression, however, is of a uniform, average length and thickness of hair.
:If you cut your hair, inactive follicles won't reactivate ahead of their normal schedule—those hairs will stay short until the fall out. Growing hairs, if cut, won't recover the length that was cut off; they'll continue growing for the usual length of time and be missing whatever length was removed. The newest hairs, however, will be short enough to remain uncut. It is this last population of hairs that will be first to regain the full, normal length in the area that was trimmed. [[User:TenOfAllTrades|TenOfAllTrades]]([[User_talk:TenOfAllTrades|talk]]) 23:33, 27 April 2006 (UTC)
:Also, I remember reading in the [[androgenic hair]] article that, say, why your pubic hair stops growing, is because something measures the weight of the hair, after it is great enough it will stop growing. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 00:47, 28 April 2006 (UTC)
In my case, my giant hogg creates an intense gravitational field due to it's mass. This likely increases the weight my pubic hairs feel. How does this effect my pubic hair growth? [[User:12.183.203.184|12.183.203.184]] 04:00, 28 April 2006 (UTC)
:If your hog was large enough to create its own gravitational field, your hairs would likely grow to a short length before plunging back into the skin of your hog, causing serious irritation and swelling, leaving you vulnerable to infection. I suggest cutting short, or getting a smaller hog. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 07:08, 28 April 2006 (UTC)
::Or entering it as a prize pig at a farmer's market. — [[User:Asbestos|Asbestos]] | [[User talk:Asbestos|<FONT COLOR="#808080">Talk </FONT>]] [[User:Asbestos/RFC|<FONT COLOR="#808080"><small>(RFC)</small></FONT>]] 11:36, 28 April 2006 (UTC)
== Amides ==
i know that when i react a carboxlyic acid or an ester with a primary amine i will form a amide, now will these instantly form peptide bonds and create long chained polymers? or would i have to do something to the mixture to get it to? i'm thinking along these lines becuase i need to find something that proves theres been a positive test, cheers
--[[User:Colsmeghead|Colsmeghead]] 19:59, 27 April 2006 (UTC)
:If you have an [[amino acid]], or a diamine and a dicarboxylic acid, then yes, it will polymerize to a [[polyamide]] if you heat it up enough. —[[User:Keenan Pepper|Keenan Pepper]] 21:00, 27 April 2006 (UTC)
::If you're curious, the reaction is called [[condensation reaction|condensation]]. [[User:Isopropyl|Isopropyl]] 21:42, 27 April 2006 (UTC)
== Sound formats and such.... ==
I have a sound-file encoded in [[a52]] format (which wikipedia tells me is Dolby format...not surprising since it came from a movie I guess). I'd like to have it in mp3 format, or any other nice format which my ipod will play. Suggestions? [[User:Oskar Sigvardsson|Oskar]] 20:04, 27 April 2006 (UTC)
:[[Audacity]]! [[User:Isopropyl|Isopropyl]] 21:05, 27 April 2006 (UTC)
:[http://www.doom9.org doom9.org] has guides for working with and converting AC3. (Does Audacity support AC3?)- [[User:Mako098765|mak]]''[[User_talk:Mako098765|o]]'' 22:30, 27 April 2006 (UTC)
== World time ==
What is the "world time" that is mentioned here in this book? [http://www.amazon.ca/exec/obidos/ASIN/079235737X/701-4035402-1961125] --[[User:HappyCamper|HappyCamper]] 21:06, 27 April 2006 (UTC)
:Never heard that one before. Could it be the [[proper time]] along a [[world line]]? [[User:Melchoir|Melchoir]] 21:22, 27 April 2006 (UTC)
::I don't think it is...it's some sort of formalism that is useful for addressing many body problems I think. But that's about it. I'm not really sure actually. --[[User:70.50.34.181|70.50.34.181]] 00:41, 28 April 2006 (UTC)
:::Sigh...does anyone know? :-) --[[User:HappyCamper|HappyCamper]] 03:02, 28 April 2006 (UTC)
== Physics ==
I would like to know the Hamiltonian for the 2-Dimensional
[[Hubbard model]].
Denis Lieberman
-- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 00:45, 28 April 2006 (UTC)
== latex snippets for windows ==
I use a mac, and for the mac, there are these wonderful programs [[Equation Service]] and [[LaTeXiT]] which allow you to input a snippet of [[LaTeX]] code and it gives you a cropped PNG or jpeg, which you can drag into an email or something. It's pretty much the same thing that [[texvc]] does for [[MediaWiki]], except with a [[drag and drop]] [[GUI]]. I'd like this email conversation to be two-sided. Is there any equivalent program for windows? -[[User:Lethe/sig|lethe]] <sup>[[User talk:Lethe/sig|talk]] [{{fullurl:User talk:Lethe|action=edit§ion=new}} +]</sup> 23:35, 27 April 2006 (UTC)
Not sure it has a GUI, but it is built for Windows, it's free and it's open source. It's called MiKTeX. [[MiKTeX | Here]] is the Wikipeida article about it and [http://www.miktex.org/Default.aspx here] is the direct link to its development page. It is a lather large download, weighing in at just over 33MB, just as a warning. Hope this is helpful. [[User:yaninass2|yaninass2]] | [[User talk: yaninass2 | talk]] 00:26, 28 April 2006 (UTC)
:MikTex is a port of the standard teTeX distribution to windows. This is a necessary prerequisite before doing any latex rendering. People often use an IDE as a frontend to MiKTeX, which provides an environment for composing full LaTeX documents. There are many Windows IDE frontends available such as TeXnicCenter. What I'm looking for is a program that will allow you to input a single equation in LaTeX markup and will return a small PNG or GIF no larger than the equation. This doesn't require a full IDE like TeXnicCenter, but does require some automated image cropping and conversion tools like [[imagemagick]]. Miktex is a prerequisite for this, but I'm looking for something much more specific. Thanks anyway, though. -[[User:Lethe/sig|lethe]] <sup>[[User talk:Lethe/sig|talk]] [{{fullurl:User talk:Lethe|action=edit§ion=new}} +]</sup> 01:19, 28 April 2006 (UTC)
= April 28 =
==Getting frozen==
Would it be possible in the near future to freeze myself at near absolute zero, and wait until my investments have grown to the point that I would be wealthy, then have myself 'thawed' out? I would love to be a Billionaire (inflation adjusted) in 3000 AD.
:See the article on [[cryogenics]]. Also consider the fact that you'd need a fair amount of money to get yourself frozen to start with (assuming a workable freezing process existed), and that any investment designed to grow faster than inflation (as well as covering the costs of keeping you frozen but alive for 1000 years) would have to have a very high risk associated with it. [[User:ConMan|Confusing Manifestation]] 00:34, 28 April 2006 (UTC)
::Maybe someone watched too much [[Futurama]].... ;-D ....[[User:Jayant412|Jayant,]][[WP:EA|<font color="green">17 Years,</font>]][[User_talk:Jayant412|<font color="red"> India</font>]] • [[Special:Contributions/Jayant412|contribs]] 10:11, 28 April 2006 (UTC)
::You'd lose all your money. Most courts would declare a person cryogenically frozen to be dead, and your investments would go to your living relatives (or whoever), who would do with them as they wish. [[User:Zafiroblue05|zafiroblue05]] | [[User talk:Zafiroblue05|Talk]] 11:23, 28 April 2006 (UTC)
:::That doesn't seem like an insurmountable problem. Simply set up a [[trust fund]], which can easily continue to exist past one's death, and specify in the trust fund that the money gets transferred back to you at some point in the future, if you are alive then. [[User:Chuck Carroll|Chuck]] 18:37, 28 April 2006 (UTC)
:There's a very good book on this and similar topics, which talks not only about the biological but economical or social implications of newer biological developments. It's [[Gordon Rattray Taylor]], ''[[Biológiai pokolgép]]''. Medicina Könyvkiadó, Budapest, 1973; original [[The Biological Time-bomb]], Thames and Hudson Ltd., London. – [[User:b_jonas|b_jonas]] 15:19, 28 April 2006 (UTC)
== Blimps ==
I have recently been researching ways of getting into space. One way that I particularly enjoyed and licked was the use of a blimp. I am still cofused on a couple small things one is could a blimp actually continue out of the atmosphere into space and the other is if a blimp where to be in low Earth orbit or if it actually could continue into space how would the ballon be kept from popping from the high pressure? Thanks in advance for any help.
:Blimps, or lighter-than-air craft in general, can't float above the atmosphere, because it's precisely the atmosphere that holds them up. However, some of them can go pretty bloody high, higher than any civilian airplane. See [[radiosonde]]. --[[User:Trovatore|Trovatore]] 02:05, 28 April 2006 (UTC)
::At 100km you've still got 497µg of air per m<sup>3</sup>, you just need a realy big balloon. [[User:EricR|EricR]] 04:46, 28 April 2006 (UTC)
I have read propositions for using blimps as launch platforms for Pagasus-style launch vehicles. It would be much less expensive than using large jets for a launch platform, since much less fuel is required, wouldn't it?
:Since the atmosphere is relatively thin compared to the radius of the earth, I don't think escape velocity is that much lower at the edge of it and I can't see why there would be any benefit to launching a Pegasus from a blimp. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 07:03, 28 April 2006 (UTC)
Seems like a blimp using a vaccume instead of gas would be effective at getting you close enough to launch into orbit. [[User:12.183.203.184|12.183.203.184]] 03:54, 28 April 2006 (UTC)
:See [[orbital airship]], where this is discussed. The short version is that, aside from the guys that announced its development, nobody can figure out how the hell it's supposed to work. But, if you look at [http://www.jpaerospace.com their website], the JP Aerospace guys seem to still be working away at it, so ''they'' think they've figured out how to make the whole crazy scheme viable. --[[User:Robert Merkel|Robert Merkel]] 07:24, 28 April 2006 (UTC)
:Could a sufficiently streamlined vessel, dropped from a sufficiently high blimp, reach escape velocity before either hitting the ground or reaching terminal velocity? If so, the work is done: you just need to make a sharp turn and you're in orbit! [[User:Notinasnaid|Notinasnaid]] 11:33, 28 April 2006 (UTC)
For a free falling object to reach escape velocity, it needs to be dropped from infinity (see [[escape velocity]]) and hence an object dropped from a blimp will never reach the escape velocity. [[Terminal velocity]] being lower than the freefalling velocity in vaccuum, is much less than the escape velocity. But good idea though !! -- [[User:Wikicheng|Wikicheng]] 15:07, 28 April 2006 (UTC)
:Hm—but you do get more increase in kinetic energy, for burning the same amount of fuel, after you're already moving fast, so there's ''something'' to it. (It's not something for nothing; you're just avoiding burning fuel to accelerate the rest of your fuel, which you're then going to throw away.) The problem is that, while it might be easier to reach escape velocity, you'd be headed straight for the Earth. All you need is a hole through the planet, and Bob's your uncle. --[[User:Trovatore|Trovatore]] 15:22, 28 April 2006 (UTC)
== Trouble in Physics ==
I've heard that physicists have trouble understanding what happens in places such as the centre of a black hole and at times such as right after the Big Bang.Why?
[[User:60.241.30.237|60.241.30.237]] 02:54, 28 April 2006 (UTC)
:Because the equations which describe the physics in these situations sort of breaks down...simply put, we don't have an adequate theory to address these extremes - yet. --[[User:HappyCamper|HappyCamper]] 03:03, 28 April 2006 (UTC)
:Check out our [[quantum gravity]] article, which is relatively clear for a physics article. --[[User:Fastfission|Fastfission]] 03:39, 28 April 2006 (UTC)
:If you want the quick answer, it's that the equations that are currently used to model these things reach a [[singularity]] at those points (notice that there are articles on both [[mathematical singularity]] and [[gravitational singularity]], and there is a strong connection between the two). [[User:ConMan|Confusing Manifestation]] 04:14, 28 April 2006 (UTC)
Phisicists don't call this trouble. They call it job security.
::Regarding the unsigned job security comment, physicists don't know everything, and that's what they are trying to do. Job security? Why don't you try to be a theoretical physicist. One sounds like a bit of a crazy conspiracy theorist who says that Einstein didn't say everything or guessed so he could keep his job.
:::I don't believe the former anonymous comment was meant to critical. It's perfectly reasonable to point out the fact that the only reason physicists still have a lot to work to do is that they still don't know a lot about the universe. I'm sure they're all working really hard in the meantime and deserve every penny they earn. [[User:Freshgavin|<font size="-2" color="white" style="background:blue"> freshgavin</font>]][[User_talk:Freshgavin|<font size="-2" color="blue">ΓΛĿЌ </font>]] 06:58, 28 April 2006 (UTC)
:::Yeah, geez, it's funny. Laugh. Theoretical physicists make that exact joke all the time. -[[User:Lethe/sig|lethe]] <sup>[[User talk:Lethe/sig|talk]] [{{fullurl:User talk:Lethe|action=edit§ion=new}} +]</sup> 07:24, 28 April 2006 (UTC)
== Hexahelicene chain ==
Has any long chain molecule been made, based on [[Hexahelicene]]? —[[User:Masatran|Masatran]] 04:32, 28 April 2006 (UTC)
: You mean by continuing the helix shape? It doesn't seem like it. Sooner or later they're going to start [[Pi stacking]] and break the helix shape. (What a bad article that is, btw.. Pi-stacking is in no way specific to DNA.) --[[User:BluePlatypus|BluePlatypus]] 07:40, 28 April 2006 (UTC)
::Yes, there are. According to the article, it has 14 hexagons in it. These compounds rotate extremely plane polarized light. --[[User:HappyCamper|HappyCamper]] 14:57, 28 April 2006 (UTC)
::: Huh? The chirality question is down below. 14 rings doesn't qualify as a "long chain" in my book. I'd say you need about 50 units, that's where they draw the line for peptides-to-proteins. --[[User:BluePlatypus|BluePlatypus]] 20:30, 28 April 2006 (UTC)
== Why is Twistoflex chiral? ==
Why is [[Twistoflex]] chiral? —[[User:Masatran|Masatran]] 04:38, 28 April 2006 (UTC)
:What is twistoflex's [[IUPAC]] name? I can't find any information on it. [[User:Isopropyl|Isopropyl]] 04:44, 28 April 2006 (UTC)
:Also, I know this isn't the answer you want, but the molecule most likely satisfies the conditions of [[chirality]]. [[User:Isopropyl|Isopropyl]] 04:49, 28 April 2006 (UTC)
:: The structure is in Jones' ''Organic Chemistry'' 3, page 652. It gives a WWW link, but it requires a plug-in not available on Linux. —[[User:Masatran|Masatran]] 04:58, 28 April 2006 (UTC)
:::I found the site too, but as I am running [[Debian]], I am also unable to view Shockwave pages. :( [[User:Isopropyl|Isopropyl]] 05:00, 28 April 2006 (UTC)
:::From the name, can we assume that the molecule is a spiral? If that's true, spirals do have chirality, as do staircases and DNA helices. [[User:Isopropyl|Isopropyl]] 05:02, 28 April 2006 (UTC)
:It sounds like it's related to [[hexahelicene]]. Oh man, we don't have an article on that either? —[[User:Keenan Pepper|Keenan Pepper]] 12:50, 28 April 2006 (UTC)
::Oh, sure we do. I've redirected it to [[helicene]]. —[[User:Keenan Pepper|Keenan Pepper]] 12:52, 28 April 2006 (UTC)
== LyX and LaTeX ==
Today, I discovered the next best thing since sliced bread: [[LyX]]! Now, I am trying to figure out how to make my LyX file so that all the front matter has page numbers in Roman numerals, and the rest in Arabic numerals. How do I do that? Using
\renewcommand{\pagenumbering}{arabic}
\setcounter{page}{1}
doesn't seem to work...--[[User:HappyCamper|HappyCamper]] 05:38, 28 April 2006 (UTC)
:If your document is a book you can just do
\frontmatter
I'd like to thank the Academy...
\mainmatter
blah blah blah
\backmatter
appendix stuff (usually the largest part of my documents despite all my good intentions)
:I don't know a way to make article class documents do the Roman and Arabic numerals. — [[User:Laurascudder|Laura Scudder]] [[User talk:Laurascudder|☎]] 22:39, 28 April 2006 (UTC)
== pepper pad ==
I heard that the size of screen in pepper pad is 8 into 6 inches. Will it be enough to view web pages? Or should we have extraordinary eyesight to read using pepper pad?
:While not speaking from seeing it in person, the picture on the [http://reviews.cnet.com/Pepper_Pad/4505-3126_7-31661238-2.html?tag=nav review] of it at CNet shows the [[Yahoo!]] homepage, and it mentions have a Mozilla-based browser. Seems a safe assumption that it will at least be able to handle HTML without too much diffculty. <b>[[User:Tijuana Brass|<span style="color: #FF4500; font-family: Times New Roman; font-variant: small-caps;">Tijuana Brass</span>]]<sup>[[User talk:Tijuana Brass|<span style="color: #228B22;">¡Épa!</span>]]-[[User:Tijuana Brass/EA|<span style="color: #228B22;">E@</span>]]</sup></b> 06:51, 28 April 2006 (UTC)
There is actually a neat hacker blog on the pad. [http://www.pepperhacks.com/]. This is run by somebody from Pepper. Seems you can use if for all types of special duties. --[[User:Zeizmic|Zeizmic]] 14:09, 28 April 2006 (UTC)
== the movie xmen and the real science behind it ==
Is human mutations possible such as the charactor mutations in the movie XMEN? Why and Why not?
What does the first law of therodynamics have to do with the XMEN?
What does human evolution have to do with it?
What are the human limitations if they were to have the same types of mutations as the movie characters in the movie the XMEN?
:At the top of the page it says do your own homework. The mutations are not possible, the [[first law of thermodynamics]] should help you for the second question. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 06:33, 28 April 2006 (UTC)
:Exactly what course do you think this might be homework for, Mac? "Do your own homework"may be an appropriate guideline, but it is an inappropriate response to questions. If you don't want to answer a question, then don't. But there's no need to be gratuitously rude whether you want to answer or not. - 12:32, 28 April 2006 (UTC)
:I think the thoroughness of the question was what triggered the homework-detector, IMO it sure sounds odd that someone would throw down such a pointed question without at least starting the discussion, making it very likely homework of some sort. However I agree that it's not good policy to bash people on this rule, just vote with your feet and don't answer it. <p>That being said, I do find [[Conservation of energy]] to be the biggest problem with the plausibility of mutants like the [[X-men]]. Unless something in their mutation causes them to interact with [[String theory|another dimension]] that allowed for transferring of energy back and forth from our observable world. The possibility of this surfacing in the process of [[Human evolution]] seems *extremely* unlikely... Heck most people can't be convinced that [[Intelligent design|evolution is possible]] to begin with! Although that raises another point, what if a [[Deity|supreme being]] were to intelligently design some enhancements into a few people, and let them sort themselves out?
:We also have a good if somewhat technical article on [[mutation]]. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 07:31, 28 April 2006 (UTC)
:Hmm, maybe it would be ok to sketch out the answer of this.. I think major points you would need are:
::Evolution doesn't let you break the laws of physics. It isn't magic - new organisms have to be biologically plausible.
::Note that evolution needs 3 things to happen. Are they present in X-Men?
::#Random mutations
::#Selective pressure
::#A very long time
--[[User:212.241.231.52|212.241.231.52]] 17:41, 28 April 2006 (UTC)
:::For #3, I would say, "a large number of generations" instead of "a very long time." Sure, for organisms like humans where the time between generations is on the order of decades, evolution only operates detectably on the scale of thousands of years. But when you have bacteria, where the time between generations can be as little as forty minutes, you can get a thousand generations in a month. [[User:Chuck Carroll|Chuck]] 18:46, 28 April 2006 (UTC)
== Cancer and viruses ==
Is it possible that all cancers are caused by viruses? The more I read around, the more it seems that way. For e
:According to our article on [[Cancer]], some cancers are caused by viruses, but others are caused by [[carcinogen]]s, which are physical/chemical agents. So the answer to your question is no. -- [[User:Daverocks|Daverocks]] ([[User_talk:Daverocks|talk]]) 12:00, 28 April 2006 (UTC)
== High BP and athletes ==
From what I understand, athletes that have conditioned hearts have less beats per minute because each beat pushes more blood. So does this mean they have higher blood pressure?
:Athletes have a ''lower'' incidence of high blood pressure. While blood pressure during exercise is increased, their blood presure at rest is generally normal or lower than usual. An athlete in top condition may have a blood pressure of 200/120 during peak exertion and a pressure of 90/60 in the morning before getting out of bed. - [[User:Nunh-huh|Nunh-huh]] 12:41, 28 April 2006 (UTC)
== Talking buderigars and problems with their pronunciation ==
Why is it that many [[budgerigar]]s that learn to speak the English language struggle with pronouncing certain words and parts of words? In my experience, they tend to find it difficult to correctly vocalize anything containing containing a hard consonant sound and they also draw out their vowels.
e.g. I have a budgie called Joey at the moment. When he says his name, he pronounces it as "owwwweeeeeeeee" most of the time, occastionally with a throaty 'click' at the beginning to represent the 'J' (he really seems to be strugging). "What you doing?" comes out as "whayooooooin?", etc.
Any ideas?
:Isn't it actually more surprising that they can produce anything resembling human speech - with a vocal apparatus markedly different from human, and so one for which human language sounds are foreign -- than that they fail to do it perfectly? I think a linguist might be able to tell you which particular phonemes produce problems (plosives, perhaps?) and you could plan the bird's vocabulary accordingly. - [[User:Nunh-huh|Nunh-huh]] 12:47, 28 April 2006 (UTC)
::I heard somewhere (don't ask me where - I can't remember now) that talking parrots cannot pronounce the word 'red' at all. Apparently, it comes out sounding like the bird is clearing its throat. --[[User:Kurt Shaped Box|Kurt Shaped Box]] 22:57, 28 April 2006 (UTC)
:[edit conflict]Budgies don't have lips, and their beaks are more rigid than your mouth. I believe they basically make all their sounds through whistling and clicking, because those are the sounds the setup allows. You would make much the same sound if you tried to speak without using your tongue. I'm sure someone else can give a more detailed answer. [[User:57.66.51.165|57.66.51.165]] 12:50, 28 April 2006 (UTC)
:They don't "speak the English language" either (or any language, for budgies living in places like France, China or Madagascar). They are good at mimicry, and can be trained to respond in certain ways, but to call it language is quite a leap. There is a short discussion of this at [[African Grey Parrot]]. --[[User:LarryMac|LarryMac]] 15:29, 28 April 2006 (UTC)
To answer the original question, it seems your particular budgerigar has problems with the letters "J" and "T". The J is formed by the action of air around the teeth - the T is formed by touching the teeth with the tip of the tongue. From this I suspect there may be something wrong with your budgerigar's teeth. [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 09:07, 29 April 2006 (UTC) <small>(but... but... budgies don't have...)</small>
== regarding dentistry ==
i want to know all the developmental disturbance which will occure in oral cavity,as in tooth development ,tongue,palets,and......?
:That sounds like the sort of thing you'd need to go on a course in Dentistry to learn... [[User:Notinasnaid|Notinasnaid]] 11:27, 28 April 2006 (UTC)
: or [[embryology]], which oddly, doesn't link to [[cleft|cleft palate or cleft lip]] - [[User:Nunh-huh|Nunh-huh]] 12:34, 28 April 2006 (UTC)
::It is impractical to expound on '''''all''''' the developmental derangements in the oral and peri-oral areas; as Nunh-huh said, this would take a course in embryology in order to do justice to the subject. However, there are several developmental anomalies that are interesting in the way they reflect on normal embryological development. For example:
::*[[craniopharyngioma]] as it relates to [[Rathke's pouch]]
::*[[Cleft|Cleft lip and palate]] and [http://www.usc.edu/hsc/dental/opath/Cards/GlobulomaxillaryCyst.html globulomaxillary cysts] as they relate to the fusion of the embryonic [[premaxilla]]e and [[maxilla]]e
::*[http://www.emedicine.com/derm/topic61.htm Branchial Cleft Cysts]
::*[[Thyroglossal cyst]] and [http://www.ghorayeb.com/LingualThyroid.html lingual thyroid]as they relate to the migration of the embryonic [[thyroid]] gland.
::--[[User:Markitos76|Mark Bornfeld DDS]] 18:57, 28 April 2006 (UTC)
== Anatomy ==
Why do men have nipples?
12:13, 28 April 2006 (UTC)
:Nipples are a vestige of our androgynous appearance lasting up to 15 weeks after conception, where both men and women develop almost identically. Nipples develop before this period and are hence present on both sexes. Approaching adolescence, the average male (while bearing nipples) lacks the hormones to develop breasts. This can however happen, a condition called [[gynecomastia]] in which a reduced amount of testosterone (for varying reasons) can cause growth of fatty tissue around the nipple, appearing similar to the female breast. Rare cases of male lactation have also been reported. [[User:Anand Karia|Anand]] 14:23, 28 April 2006 (UTC)
::Apart from those unusual cases, the primary use of nipples on most males is sexual excitation. [[Sexual arousal|This article]] suggests that when a male is sexually aroused, the nipples become erect - which is true, but it's only half the story. The nipples can be directly stimulated in order to ''produce'' or assist in male sexual arousal. Mysteriously, many men don't seem to be aware of this. [[User:JackofOz|JackofOz]] 22:18, 28 April 2006 (UTC)
:::Actually, if you are not gay, the primary use of nipples are the grabbing and pulling of other men's, known as a tittie twister or purple nurple. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 06:18, 29 April 2006 (UTC)
::::You seem to be ignoring the fact that members of your preferred gender can stimulate ''you'' using your own male nipples. --[[User:Bth|Bth]] 08:45, 29 April 2006 (UTC)
:::::Indeed so. You don't need to be gay to enjoy having your nipples excited. [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 09:09, 29 April 2006 (UTC) <small>(I can't believe I wrote that)</small>
== Magnetic field ==
How does quantum mechanics describe a magnetic field? <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:219.78.36.146|219.78.36.146]] ([[User talk:219.78.36.146|talk]] • [[Special:Contributions/219.78.36.146|contribs]]) {{{2|}}}.</small><!-- [Template:Unsigned] -->
:[[Quantum field theory]] describes it as [[virtual particle|virtual photons]]. —[[User:Keenan Pepper|Keenan Pepper]] 12:58, 28 April 2006 (UTC)
== boxer engine ==
does the boxer engine require more maint. than the V6 engine . Does the Cam shaft have to be changed every 48,000 miles or there will be damage to the engine. thank you paul
:The engine you speak of is the [[Flat-4]]. Compared to a V6 it probably has similar maintenance schedules, barring any specific design issues which require more frequent preventative measures. It is generally regarded as more costly to maintain compared to an [[Inline-4]] due to it having two [[Cylinder head|heads]] and therefore twice the number of moving parts in the assembly. If there is a specific engine you are inquiring about, you may wish to include that information in your post.
== Flower name ==
[[Image:UnknownFlower.jpg|thumb|200px|Name this flower and make me happy!]]
Does anybody recognize this flower? If it of any help, it was taken in Malaysia. So, most likely a tropical flower though I have no idea if it's native. [[User:Earth|__earth]] <sup>([[User talk:Earth|Talk]])</sup> 15:29, 28 April 2006 (UTC)
It looks like Celosia Cristata (Yellow Toreador). Just a guess...--[[User:Markitos76|Mark Bornfeld DDS]] 19:20, 28 April 2006 (UTC)
:The leaves [http://www.ag.auburn.edu/hort/landscape/441.html look different]. So, I don't think it is =( [[User:Earth|__earth]] <sup>([[User talk:Earth|Talk]])</sup> 04:00, 29 April 2006 (UTC)
:That's a nice picture, maybe you should put it up for Featured Picture. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 06:19, 29 April 2006 (UTC)
::Thanks. Maybe I will but I need to find a page for it first. In order to do so, I need to find out that name of the flower first =( [[User:Earth|__earth]] <sup>([[User talk:Earth|Talk]])</sup> 09:11, 29 April 2006 (UTC)
== cholesterol in food oils ==
hi! i want to do a project on cholesterol content in various food items, like: butter,cator oil,etc. but i don't know how to carry it out.
one of the requirements of this project is acetic anhydride which is banned in india. so can you let me know the requirements and the procedure for conducting out this experiment.
thank you!
:First of all, who told you that "one of the requirements of this project is acetic anhydride"? You must have some kind of instructions that told you that, and we'd be better able to interpret them for you if we knew what they were. For another thing, [[acetic anhydride]] isn't banned for no reason; it's very flammable and corrosive. Um... that's all I have really, sorry for not being more helpful. —[[User:Keenan Pepper|Keenan Pepper]] 17:41, 28 April 2006 (UTC)
== Toshiba laptop boot problem ==
My Satellite A20-S103 Toshiba had a memory module corrupt, I switched it with an exactly the same but new one and it just won't boot. I can see the green light of power on but it won't do anything, even no fan activity. Even if if I switch back to the old 266MHz 256MB DDR RAM module, it just won't do anything. Maybe it's a "hibernation" problem? Please, this is urgent, help.
:Have you done all this after removing the battery and disconnected the notebook from any power source? --[[User:Gennaro Prota|Gennaro Prota]] 18:40, 28 April 2006 (UTC)
:Are you getting any [[Power-on self-test|POST]] beeps from the [[BIOS]]? If you are figure out what BIOS you are using and what the beeps mean. If you get no beeps, i would remove all the memory and cards from the machine. If you still don't get any message from the POST it's probably a power supply or motherboard problem. [[User:EricR|EricR]] 19:46, 28 April 2006 (UTC)
::It's possible that I forgot to remove the battery, but the system was definitely wasn't on, of course. What are the consequences?
:::Hi, since you asked on my talk page to give a further reply here we go: basically, as [[User:Zeizmic|Zeizmic]] hints at too, removing any power source is a 101 rule for any electronic equipment repair. For a laptop (and many other devices), if you violate the rule you can permanently damage it. In fact that's not a *very likely* possibility (though not rare either). That's why I didn't reply, at first: I didn't want to be scary for nothing (it astonished me, anyway, to read that you were not sure if "you forgot the battery": did you perform the replacement years ago?). Your problem could be due to static charge (your memory module should have been kept in its anti-static bag until installation and you should have grounded yourself, but I guess you didn't). If your laptop experienced freeze/reboot problems before (a defect many Toshiba laptops have had in the past, usually showing itself when moving your fingers from the touchpad to the keyboard) that could be more likely. Another possibility could be that you damaged the memory socket: did you *rotate* the module before extracting it? Please, also reply to others (in particular to the question about POST beeps, though I think your problem lies earlier and you don't even get to POST). --[[User:Gennaro Prota|Gennaro Prota]] 13:52, 29 April 2006 (UTC)
Number one thing with laptops is to remove the battery if there is any trouble (or fixing it), and re-insert. A laptop is always on, and just powering off is not the same as a hard power-off on a desktop. --[[User:Zeizmic|Zeizmic]] 23:26, 28 April 2006 (UTC)
== Black holes and apples ==
If I threw an apple into a black hole, will it land in the black hole? Is a black hole solid, or is it just some quantum mass of existence in space? :-) --[[User:HappyCamper|HappyCamper]] 19:46, 28 April 2006 (UTC)
:Without a [[theory of everything]], I guess we can't answer that question without making playing hypothesis and conjectures. --[[User:GTubio|GTubio]] 21:15, 28 April 2006 (UTC)
:The apple would fall into the black hole and disappear forever. Black holes are neither solid, liquid, or gaseous, because of the [[no hair theorem]]. —[[User:Keenan Pepper|Keenan Pepper]] 21:23, 28 April 2006 (UTC)
::The no hair theorem only applies to outside observers doesn't it? But for them the apple won't actually make it past the event horizon. [[User:EricR|EricR]] 21:37, 28 April 2006 (UTC)
:::Just because we can't see it after it gets near the horizon doesn't mean we don't know what happens to it afterwards. We do: it falls into the singularity. Every atom of it. I guess we don't know what will happen when it gets within a couple of Planck legths of the singularity. So I would say that black holes are empty "space" except for the singularity, which you could call "quantum weirdness of spacetime" if you liked. Or some such weirdness. I put "space" in quotes because inside the horizon, spacetime is quite different from what we normally consider empty space. The radial coordinate becomes timelike. As for Keenan's mention of the properties of black holes, don't forget that a black hole also has a temperature something the no hair theorem can't tell you about (it only knows about classical black holes). -[[User:Lethe/sig|lethe]] <sup>[[User talk:Lethe/sig|talk]] [{{fullurl:User talk:Lethe|action=edit§ion=new}} +]</sup> 21:45, 28 April 2006 (UTC)
::::Okay, so it seems a better way to think of this question is to think of the apple as a bunch of matter in a certain state. As it approaches the singularity, the state of the apple changes in a manner that it loses all the information that is stored in it: the chemical bonds, its structural form, etc...and I suppose hypothetically speaking, at some point, it would be meaningless to consider the apple as anymore than a quantum field of stuff ripped to shreads? Is the state of the black hole comparable to such a thing as the ground state of something? If so, would a black hole be cold? Or would the notion of temperature not even make sense? --[[User:HappyCamper|HappyCamper]]
:::::Well, any two black holes with the same mass have the same temperature, so that doesn't really count as "hair". The temperature is proportional to the surface gravity. See [[Hawking radiation#Emission process]]. —[[User:Keenan Pepper|Keenan Pepper]] 22:52, 28 April 2006 (UTC)
==Help with reflection==
Ok, what is the mirror fomula and how do you use it? My physics books saids it is 1/p+1/q=1/R where p=object distance, p=image distance, and R=radius of curvature, but the sheet my teacher gave me saids it's 1/p+1/q=1/f where p=object distance, q=image distance, and f=focal length. Which is it? I'm trying to study by doing problems that have answers in the back of the book but I can't seem to get the right answer with either forula.
Here's an example problem:
"If you have a concave mirror with a focal length of 8.5cm, where would you place a sheet of paper so that the image projected on onto it is twice as far from the mirror as the object is? Is the image upright or inverted, real of virtual? What would the magnification of the image be?"
First off, do I convert the 8.5cm to meters, or does it matter? which of the fomulas that I gave above should I use?
thanks
:IIRC, for a spherical mirror, the radius of curvature equals the focal length, so the two formulas are equivalent. --[[User:Serie|Serie]] 23:13, 28 April 2006 (UTC)
::I don't think so. A spherical mirror reflects light from its center of curvature back to itself, not to infinity. So assuming an analogue of the thin lens formula for mirrors, we should have 1/R + 1/R = 1/f and so f = R/2. [[User:Melchoir|Melchoir]] 23:33, 28 April 2006 (UTC)
::Ah yes, see [[Focal length]], particularly the bottom. [[User:Melchoir|Melchoir]] 23:34, 28 April 2006 (UTC)
::...and Pedrotti and Pedrotti's ''Introduction to Optics'' says (although they technically use a different sign convention):
:::<math>\frac1p+\frac1q=\frac2R=\frac1f.</math>
::Note the all-important 2. So, what can I say, your book is on crack. [[User:Melchoir|Melchoir]] 23:39, 28 April 2006 (UTC)
:Although not an answer to your question, http://webphysics.davidson.edu/Applets/optics4/ may be a useful java applet for you. -- [[User:SGBailey|SGBailey]] 08:16, 29 April 2006 (UTC)
:: First of all, Melchoir is right.
:: Then, ''here'' it doesn't matter which system of units do you use. But once you chosed one, stick to it.
:: Your teacher must be very lazy. These things are actually simple. OK. Consider this: 1/q + 1/p = 1/f, for a mirror.
:: This formula is very wise. In it, p,q and f may be positive as well as negative. (I suppose, it isn't tricky for you, that e.g., 1/(-0.5)=-2 ?) There are cases, for mirror:
* f is positive for concave mirror and negative for convex one.
* p is positive if image is ''in front of'' the mirror(real image), and negative if image is ''behind'' mirror(virtual).
* q is positive for real object, and negative for "virtual object". (i'll explain this later)
::This formula also works for lenses, just similarly:
* f > 0 for a converging lens and f < 0 for a diverging lens.
* p is positive if image is ''behind'' lens(real image) and negative if image is ''in front of'' the lens (virtual image).
* Again, q is positive for real object, and negative for "virtual object". You'll probably meet this thing in more complex tasks, involving systems of lenses. It's just that light from any real object always diverges, yeah? But when you have a system of lenses, it may occur so, that a '''converging''' beam will fall on a lens. It couldn't be emitted by any real object. But you can consider it as "virtual" object, and q is just minus distance from the point where this beam WOULD converge if there were no this lens to the lens itself.
::These questions are actually simple. The idea is so: imagine you have a set of lenses and an object. You use formula of lens for the first lens, and, knowing q and f, you'll find p. Positive or negative. Image for first lens is object for second. You know where it lies -- at distance p to the left or to the right of first mirror. It's just a matter of adding two numbers (in ''algebraic'' sense, i.e. 4 + (-5) is adding in algebraic sense).
::Also you should know that a parallel beam is a object at infinite distance, q=inf, so 1/q=0.
::Now let's look at your problem... Those guys are f*ckers. Not good to say so about teacher, but... They don't give you a problem with actual physical meaning, but cover real problem with words like "where you should place a piece of paper".
**I think, they want you to place an object in such a point that distance from image to mirror will be twice distance from object to mirror. Let's designate q the distance from object to mirror. So, the image could be real(in front of the mirror) or virtual:
***1_a) Real. So p=2q. Now, substitute p and q in formula of lens: 1/q + 1/(2q)=1/f => (1/q) * (1 + 1/2)=1/f => q=f*1.5, p=3*f; substitute values by yourself, ok?
***1_b) Virtual. So p=-2q. Doing the same, 1/q + 1/(-2q) = 1/f => (1/q)*(1 - 1/2) = 1/f => q=f/2 => p=f.
***So, the answer is p=3f and p=f.
***Magnification is just p/q. Real image is inverted, virsual is not. You can see it, if you draw an object, a vertical line, beginning from optical axe, and will draw a couple of rays from each end of the line; they contact mirror, and reflect due to [[laws of reflection]]. For real image, the rays themselves will intersect. For virtual, only prolongations of rays beyound the mirror will intersect.
***If you have questions, you can ask me on my talk page. [[User:Ellol|ellol]] 01:58, 30 April 2006 (UTC)
== Neon bulbls ==
why do neon bulbs stop functioning of they have no wearable parts?
:A little bit of the cathode vaporizes every time the lamp is turned on. When it's used up, the lamp no longer lights. —[[User:Keenan Pepper|Keenan Pepper]] 00:31, 29 April 2006 (UTC)
= April 29 =
== (Sea)gulls ==
How many gulls (counting all species) are there in the entire world? Does anyone have an approximate figure? Just to settle a debate I'm having with someone - he thinks that there is 'a gull for every human on earth'. I think that there are considerably less.
Thanks. --[[User:Kurt Shaped Box|Kurt Shaped Box]] 00:36, 29 April 2006 (UTC)
:Tout humain a une gueule (face)! --[[User:Harvestman|DLL]] 19:31, 29 April 2006 (UTC)
:And : She gulps sea gulls on the sea. Gore! --[[User:Harvestman|DLL]] 19:32, 29 April 2006 (UTC)
== Keeping an oxpecker as a pet? ==
Just thinking about a question that I saw someone ask on [[Usenet]] once (that didn't get a serious answer). Would an [[oxpecker]], kept in one's home as a pet, be any use as a natural method for controlling any hair/body lice or fleas that the bird's owner might have? --[[User:Kurt Shaped Box|Kurt Shaped Box]] 00:52, 29 April 2006 (UTC)
*Well, maybe, except for this one sentence in both of our oxpecker species articles: ''its useful parasite control is partially negated by its tendency to keep wounds open or create new ones.'' I don't think anything more need be said. --[[User:Jpgordon|jpgordon]][[User talk:Jpgordon|∇∆∇∆]] 06:17, 29 April 2006 (UTC)
*Do you want to get rid of those lice and fleas, or don't you? Just try to keep your screams to a minimum as they will scare the bird.-[[User talk:gadfium|gadfium]] 06:49, 29 April 2006 (UTC)
== Gamecube, etc. memory cards ==
Are the [[memory card]] formats used by [[Gamecube]], [[PlayStation]]s 1 and 2, or [[Xbox]] related to any broader standard, or are they completely unique/limited to their particular video game systems? [[User:Phoenix-forgotten|Phoenix-forgotten]] 02:18, 29 April 2006 (UTC)
:I'm not sure, but I have a friend who had what looked like an unofficial, third-party memory card for his Gamecube. It worked perfectly, but measured its capacity in [[Megabyte|MB]] (that one was 64 MB) rather than Nintendo's usual measurement of "blocks". I don't think Nintendo has explained what the format of its memory card is, but if a third-party can do it, then it must be related to something. -- [[User:Daverocks|Daverocks]] ([[User_talk:Daverocks|talk]]) 12:40, 29 April 2006 (UTC)
== film of aurora borealis ==
When you see film of the aurora borealis, and it is rapidly changing - are these films in real time or are they speeded up? [[User:Bubba73|Bubba73]] [[User talk:Bubba73|(talk)]], 03:04, 29 April 2006 (UTC)
:The few times I've seen the [[Aurora Borealis]] (in person) it's been changing continously, I don't think they need to speed up the films. Our article also sugguests that it's rapidly changing. --[[Wikipedia:Esperanza|<font color="green">E</font>]][[User:EivindFOyangen|ivind]][[User talk:EivindFOyangen|<sup>t</sup>]][[Special:Emailuser/EivindFOyangen|<sup>@</sup>]][[Special:Contributions/EivindFOyangen|<sup>c</sup>]] 08:31, 29 April 2006 (UTC)
::They do change very rapidly. I suspect the films are sped up slightly, but it wouldn't need to be by much (twice normal speed, perhaps, but that's all that would be needed - certainly time lapse wouldn't be necessary). They do change very fast. (and yes, to be pedantic, I'm far more used to Aurora ''Australis'' - like the one i photographed as [[:Image:Auroradunedin.png]]. [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 09:14, 29 April 2006 (UTC)
::: OK. the two times I've seen aurora down at my latitudes (30-something degrees) it didn't look like that. It was a large red area that changed slowly. [[User:Bubba73|Bubba73]] [[User talk:Bubba73|(talk)]], 15:28, 29 April 2006 (UTC)
::: No need for speeding up. Aurora can shift both at immensely slow speeds (meaning only that there's a steady, uniform stream of particles) or really fast (suggesting atmospheric turbulence and whatnot). I live around N70, and have seen most of the aurora that is to be seen here. I wish I could give some kind of objective measurement about the rate of change for some of the fastest ones, perhaps in terms of hertz, but I don't see how I could do that. I don't know what films you have seen, but I know from television that in the case of slowly shifting light, one speeds it up unless there are moving objects in the picture (which in the case of moving unnaturally fast destroys all the romance and such). So really, this boils down to us not knowing how fast the light you watched, shifted. :)
== Windows small text problem ==
I'm having a huge problem, all of the text on all my files and folders, and even "file" "edit" etc. in programs is really really small. Is there anyway to fix this? It happend out of nowhere, thanks.
:Assuming it's a relatively modern Windows variant, here a couple of things you could try: Right click on an empty spot on your desktop and choose "Properties" from the menu that appears. Go to the "Appearance" tab, which has a Font size option down the bottom. There you can choose a larger font size. Alternatively, you may have accidentally set yourself on a very high resolution (which makes everything correspondingly smaller), especially if you changed the resolution in a game or something -- this can be fixed on the "Settings" tab. --[[User:Bth|Bth]] 07:25, 29 April 2006 (UTC)
== The Pharmacy Blues ==
When I go to the chemist to pick something up, what takes so damn long? For example, say you want pills for arthritis... if it was MY pharmacy, they'd come in with the perscription, pay if necessary, and I'd take the pills of the shelf and give them to the customer. What on earth are they doing behind that counter? Just give me the pills!! -[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 07:42, 29 April 2006 (UTC)
:What? You don't know? At most pharmacies there is a contest between the workers. Workers win a pot if they can get somebody to piss in their pants because they're waiting. Nice title too—creative and original. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 07:54, 29 April 2006 (UTC)
:If it was MY pharmacy, I would first check the perscription, make sure the pills are the right ones and the right doseage, double check the perscription, double check the medicine, make sure the customer is the same person that was issued the perscription. All in all I think my pharmacy would have smaller chance of being: sued/closed down by the police/responsible for countless fatalities. --[[Wikipedia:Esperanza|<font color="green">E</font>]][[User:EivindFOyangen|ivind]][[User talk:EivindFOyangen|<sup>t</sup>]][[Special:Emailuser/EivindFOyangen|<sup>@</sup>]][[Special:Contributions/EivindFOyangen|<sup>c</sup>]] 08:42, 29 April 2006 (UTC)
::Right on, brother. That's got to be it. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 11:58, 29 April 2006 (UTC)
::I've worked in a pharmacy, and we were required to double-check the pill count, as well has have our double-checked pill count be checked again by the head pharmacist. Pharmacies receive an extraordinary amount of complaints from people issued controlled substances who claim that the wrong number of pills was issued; notice that it's never too many pills they complain about. Triple-checking with multiple inspectors guarantees that the count is accurate. [[User:Isopropyl|Isopropyl]] 15:53, 29 April 2006 (UTC)
::Well, here is the explanation of ''that'' particular [http://placebojournal.com/narcotic_mystery.htm phenomenon]. [[User:Alteripse|alteripse]] 16:41, 29 April 2006 (UTC)
:::What if I just want an inhaler or tube of ointment? --[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 16:19, 29 April 2006 (UTC)
::::You wouldn't want to get out of the store and discover that they gave you one too few, would you? [[User:Alteripse|alteripse]] 16:41, 29 April 2006 (UTC)
:::Maybe you are waiting while they count someone else's pills. And they will be entering everything they dispense into a computer system, which will cross check against your other prescriptions for side effects, and no doubt the computer will crash when you don't want it to. [[User:Notinasnaid|Notinasnaid]] 21:44, 29 April 2006 (UTC)
== Holly tree leaves ==
On a recent walk, I came across a [[holly]] tree where the lower branches all had 'coarse spikey' leaves whilst the upper branches had smooth leaves. I saw one branch which had spikey at the tip and smooth a little further back.
What if anything is the significance of this? I wondered if it is plant sexuality, but being [[dioecious]] it presumably isn't.
-- [[User:SGBailey|SGBailey]] 08:10, 29 April 2006 (UTC)
:That's standard on holly. ISTR this is an evolutionary adaptation - early species of it are believed to have had entirely smooth leaves, but in order to protect itself from herbivorous animals like horses, over the hundreds of millennia holly has produced spikier leaves close to the ground to stop itself being eaten. [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 09:18, 29 April 2006 (UTC)
:Also, as the holly tree evolved cuteness, which means that human beings will tolerate it in contexts where it would otherwise be removed as a weed, there is no need to generate cute leaves above the level where householders will cut their Christmas harvest of decorations. [[User:Notinasnaid|Notinasnaid]] 10:44, 29 April 2006 (UTC)
== Electrical Usage In Stand-by ==
When my CRT goes into stand-by, it takes just as long to start up again as if it was switching on from a state of off-ness. If energy isn't being used to keep the CRT warm for quick image display then where's this energy going that people always moan about? Is it the 50W blinking LED? -[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 09:43, 29 April 2006 (UTC)
:From [http://ergo.human.cornell.edu/Pub/LCD_vs_CRT_AH.pdf ] (PDF): "[typical] 17" CRT that uses 80 watts when operational and 5 watts in standby mode." Still, hundreds of millions of CRTs in standby do use an awful lot of electricity. [[User:Notinasnaid|Notinasnaid]] 10:41, 29 April 2006 (UTC)
::But I wonder what those 5W are doing? -[[User:Username132|Username132]] ([[User talk:Username132|talk]]) 11:33, 29 April 2006 (UTC)
:Among other things, keeping a light on, and running some circuitry that is continually monitoring the signal cable to see if it has to switch back on. Also some part of it will be transformer losses. Most domestic equipment in standby also has to run an infra-red receiver waiting for a remote control signal. [[User:Notinasnaid|Notinasnaid]] 11:46, 29 April 2006 (UTC)
::Quite a few also have timing mechanisms (either visible as clock displays or otherwise) that need to be kept regulated. [[User:Grutness|Grutness]]...''<small><font color="#008822">[[User_talk:Grutness|wha?]]</font></small>'' 03:05, 30 April 2006 (UTC)
==Electrical Usage In Charging Devices (Cell phone charger etc.)==
Someone told me yesterday that in order to save electricity, one should unplug the charger from the wall socket once your cell phone is charged. They are under the impression that the charger contines to use just as much electricity when charging as when not charging. I would think the charger does not use any electricity after the charge is complete since these chargers are really only transformers and if their is no draw on the charger (from the phone trying to recharge), no watts would be consumed. Who's right? Does charger keep wasting electricity after battery is charged? {{unsigned|72.79.99.199}}
:As usual the truth lies between the two extremes. It will almost certainly waste some power when plugged in but not attatched to a phone. It will also almost certainly not draw as much as it will when charging the phone. Exactly where in between it lies depends on the quality of the design and can only really be found out by measuring. [[User:Plugwash|Plugwash]] 22:25, 30 April 2006 (UTC)
This answer does not evince a lot of confidence. It's easy to say "It will almost certainly waste some power" but what about some hard facts? Is it using only 5% of what it would if connected to a phone that is charging or is it using 75%???
==Stargazing==
Hi, I am from India, I am greatly interested in star gazing. I can't help noticing that there are fewer stars nowadays and I've noticed this for a couple of months. Is it normal to see fewer stars?.
Thank you. --13:07, 29 April 2006 (UTC)
:If you live in a fairly urban area, one possible cause would be [[light pollution]], or just general [[smog]] obscuring the night sky. [[User:GeeJo|<font style="padding : 0px 1px 1px 1px; border : 1px solid #809EF5; background: #FFFFFF ; color: #99B3FF">GeeJo</font>]] <sup>[[User talk:GeeJo|(t)]]</sup>⁄<sub>[[Special:Contributions/GeeJo|(c)]]</sub> <small>•</small> <small>13:48, 29 April 2006 (UTC)</small>
:: There are several factors - light polution mentioned above, air polution or haze, your eyes have to get used to the dark, and the brightness of the moon. [[User:Bubba73|Bubba73]] [[User talk:Bubba73|(talk)]], 15:30, 29 April 2006 (UTC)
If you are in [[Bangalore]], it is definitely because of pollution and [[smog]]. :-( But if you go anywhere near the outskirts, say about 20 km from the city, you can see the sky in all its grandeur --[[User:Wikicheng|Wikicheng]] 18:46, 29 April 2006 (UTC)
==Visibility at sea?==
How far away can a ship's lights or a signal mirror be seen on calm, open ocean in clear weather? [[User:Brian G. Crawford|Brian G. Crawford]] 17:28, 29 April 2006 (UTC)
:When you have calculated the earth's curvature effect and you know the height of the light, think that the light is dispersed and that atmosphere shall dim it with distance. Maybe we should devise a ship laser beam for a better visibility. --[[User:Harvestman|DLL]] 19:19, 29 April 2006 (UTC)
:Well, assuming that the light is sufficiently bright, we need to know when the curvature of the earth will interfere. This depends on the height above the water of the light source and of the observer. But the greatest distance that still works will be when the horizon-circles of each are tangent, so that the sightline from the observer just grazes the water but still makes it up (having reached the horizon, the line is now increasing in altitude) to the light source. See the [[horizon]] article for formulas; you'll need to decide whether you mean ground (or sea) distance or the actual (shorter) distance the light travels, but for this sort of application the difference is trivial. For reference, putting the light at 10m off the water, the horizon is at 11.3 km distance; the straight and curved paths differ by 1.2 cm. (Remember to add the horizon distance for your observer; it'll be comparable if the height is similar.) Hope this helps. --[[User:Tardis|Tardis]] 19:21, 29 April 2006 (UTC)
Thanks! [[User:Brian G. Crawford|Brian G. Crawford]] 00:09, 30 April 2006 (UTC)
== Spaceship ==
If a craft was attached to blimp of somesort and it made to low earth orbit could the gas in the blimp be used to push the craft well out of earths low orbit into space if mixed with oxegen from an on board tank. Patrick Kreidt
:We had a discussion on a very similar topic a few days ago: [[Wikipedia:Reference_desk/Science#Blimps]]. Your theory has several problems: First, a blimp can't reach low Earth orbit for the simple reason that it needs atmosphere in order to stay aloft (see [[balloon (aircraft)|balloon]] and [[blimp]]) - it stays aloft by being lighter than the air it displaces ([[Buoyancy|Archimedes' principle]]), as the air thins at altitude, the blimp needs to be even less dense to rise higher, and even Helium (the gas used in blimps) can only take you so far (weather and research balloons can reach about 100000ft, but that's nowhere near low Earth orbit). If you mixed Helium (which is what blimps and balloons are filled with) with Oxygen, you get.... nothing. Helium isn't flammable. And no-one in their right mind would fly a blimp full of hydrogen (see [[Hindenburg disaster]]). Plus, even if you were nuts enough to try it, the ''amount'' of hydrogen in a blimp is very little (hydrogen is very very light), and nowhere near enough to run a rocket engine for any decent length of time. There is a reason why rockets carry hydrogen and oxygen in very dense liquid form.
:Fast answer: No. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 19:49, 29 April 2006 (UTC)
== REGENERATION OF TONGUE ==
whether tongue regenerates after operating the tongue for squamous cell carcinoma where about 50% of the tongue has been removed from the right side leaving the small portion of the tip? Does the tiisues develops after healing? Is there any artificial way of forming the removed portion of the tongue? How the speech can be improved after such operation? <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:220.224.20.97|220.224.20.97]] ([[User talk:220.224.20.97|talk]] • [[Special:Contributions/220.224.20.97|contribs]]) 17:47, 29 April 2006 (UTC{{{3|}}})</small><!-- [Template:Unsigned2] -->
:My uncle bit the end of his tongue off when he was a child. It never grew back. Because he still had most of his tongue, he had no trouble learning to talk with what was left. --[[User:Kainaw|Kainaw]] <small><sup>[[User_talk:Kainaw|(talk)]]</sup></small> 22:20, 29 April 2006 (UTC)
:from what i've heard regeneration is quite easy ............ if you're a [[time lord|''time lord'']] that is [sic] --23:12, 29 April 2006 (UTC)
:Humans can't regenerate hardly anything. Including their tongue, any part of it. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 00:14, 30 April 2006 (UTC)
::Generally speaking, skeletal muscle does not regenerate after removal, and this would apply to both the intrinsic muscles of the tongue (those within the body of the tongue itself) and the extrinsic muscles that connect the tongue to neighboring anatomic structures. The severity of functional loss would depend both on the amount of tissue removed and the ___location, as well as the amount of scar tissue adhesions. It is common for partial glossectomies (tongue resections) to also involve dissection of the deeper muscles of the floor of the mouth, which would further compromise tongue mobility. Depending on the severity of motor deficits, glossectomy patients adapt and compensate for their loss to a lesser or greater extent, often without intervention. However, speech therapy is also an option. There are surgical procedures available that are intended to restore a measure of motor function to the tongue. Interestingly, one study suggests that these types of interventions may actually hinder recovery of speech. See [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WKF-45V27WN-G&_coverDate=04%2F30%2F2002&_alid=396462304&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=6905&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7465a3beb43aae16bd78df1e4ff5c6cd Speech after partial glossectomy: A comparison between reconstruction and nonreconstruction patients]--[[User:Markitos76|Mark Bornfeld DDS]] 01:53, 30 April 2006 (UTC)
== Hypothetical navigation in space ==
Earthbound navigation, say for a ship or plane, can be done using the stars as a reference, or using GPS, or by using an intertial guidance system. The Apollo missions to the moon used inertial guidance and reference stars, as far as I know.
Hypothetically, if one had a faster-than-light spaceship, what practical method(s)would be used to navigate in interstellar space? If I understand right, the stars serve as a reference here on earth because of two things- they're fixed in relation to each other, and over time navigators have developed tables (ephemeris) of the positions of the stars. So if one knows the date and time, a ship or plane on Earth can be navigated using a compass, a sextant, and the tables.
But if you could hyperspace your way around the universe, the stars would no longer be in fixed positions, right? So you want to go to your summer home that's on a planet that's several light-years away (or further)... The star that that planet is orbiting is not where it appears to be from earth, since we're seeing it's position several years distant, right? So you'd need tables of true positions relative to visible positions as seen from Earth. But then to go from that star to a third star, you'd also need tables with true vs. apparent positions respective to that second star, wouldn't you?
:There might be other options, but you could easily just use a 3D map of whatever area of space you wanted, including the motion of stars (since they'd appear to be at different points along their trajectory depending on where you were). Then use [[inertial guidance]] and/or [[dead reckoning]] to keep your rough ___location in it (especially if in your [[FTL]] travel mode you couldn't see for whatever reason). Then re-calibrate your position by comparing to the star chart (using the approximate position and/or spectrum information to determine which stars correspond). In other words, you'd never use the apparent position of anything except to determine your own position, and navigate based on that. --[[User:Tardis|Tardis]] 19:28, 29 April 2006 (UTC)
:(edit conflict - darn you for being a faster typist, Tardis!) Erm..... no. You can navigate perfectly well through measuring the positions of the stars - our own interplanetary probes do this all the time. Whether or not you'll be able to take measurements ''in transit'' while flying your faster-than-light spaceship I can't answer (because we have no idea how such a spaceship would operate), but once you've arrived you can get a pretty accurate position fix by seeing where various prominent stars are.
:Navigating on Earth by means of the stars is (relatively speaking) easy, because they are so far away that the [[parallax]] you get by moving around on the Earth's surface is negligible compared to the distance to the stars, hence they can be treated as being infinitely far away - and this means you only need to know their angular position on the (hypothetical) stellar sphere. How far away they ''actually'' are doesn't matter.
:However, once you leave the solar system, then the parallax is no longer negligible, and you need to start dealing with each star's 3-dimensional position in space - basically, you are [[triangulation|triangulating]] your position based on known points of reference. We have pretty good measurements of the distances to most nearby stars, so your measurements will be pretty accurate. I hope this answers your question - there are bits of it where I'm not sure what you're referring to... — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 19:34, 29 April 2006 (UTC)
I guess that's what I was getting at: How does the parallax error affect one's ability to navigate once one is large distances away from Earth. So would the difficulty increase with the distance traveled? That is, a trip to, say, Alpha Centauri which is only about four light years away wouldn't result in much parallax error with the position of reference stars. But (assuming the FTL drive is very fast) what about a trip to a star system that is a great many light years away? Wouldn't the parallax error be large? How would one find the reference stars, especially if it was the first trip to that star system, and no star charts existed for that area?
And, sort of a separate question, once one arrives in the vicinity of the star system, how would one actually find and navigate to a particular planet?
* I'm not following what you mean by "parallax error". But I think what you're getting at is that when you depart from Earth using some mystery FTL method, you program your computer to take you ''X'' light years in direction Y, and you want to be sure that ''X'' and ''Y'' are the right numbers. And in that case, yes, you would naturally have larger distance errors the further you travel. If, say, ''Y'' is off by an [[arcsecond]], that means you'll be off by an [[AU]] for every [[parsec]] you travel. I remember [[Isaac Asimov]] got around this by having people travel across galaxies by making many short jumps, measuring their positions in between each. -- [[User:Filliam H Muffman|Filliam H Muffman]] 02:54, 30 April 2006 (UTC)
:"That is, a trip to, say, Alpha Centauri which is only about four light years away wouldn't result in much parallax error with the position of reference stars."
:Actually, it would result in a huge parallax error. The position of Sirius, the nearest bright star besides Alpha Centauri, would be off by 26.2 degrees. Even the position of a star 240 light-years away would be off by 1 degree.
:"How would one find the reference stars, especially if it was the first trip to that star system, and no star charts existed for that area?"
:You can simply track the reference stars while you're travelling. Also, calculating the positions of the stars (and making a star chart) is easy, as long as you know where you are. [[Celestia]] is a program that can determine what the sky looks like in other star systems.
:"And, sort of a separate question, once one arrives in the vicinity of the star system, how would one actually find and navigate to a particular planet?"
:Look for points of light that aren't stars. Once you've found one, see if it moves (relative to the stars) or not--if it does, it's probably a planet or asteroid. Then navigate to the planet by pointing your spacecraft there and making sure that it's always pointed in the planet's direction. --[[User:Bowlhover|Bowlhover]] 05:41, 30 April 2006 (UTC)
:''So would the difficulty increase with the distance traveled?''
:Slightly - it would depend on how far you want to go. Going back to basics, you are trying to navigate in a full three-dimensional environment. In order to determine your position by triangulation (probably the best method), you need to know the relative angles to several (three at least) fixed points in space (ie stars). The accuracy of your position measurement will depend on 1) how well you measure your angles, and 2) how well you know the ''3D'' position of each of the points (stars) you are measuring angles between. 1) is trivial - we've been measuring angles very accurately for hundreds of years. For 2), in nearby space (say, out to a few hundred light-years), we know the distances (and hence the 3D positions) of stars pretty well - the errors in our measurements are relatively small, so you should be pretty safe. For stars further away, our readings aren't quite as good, so if you travel further away, your position could be off by a bit - but you'll always know more or less where you are.
:One problem I forsee is that, if you can't take measurements while in FTL travel, you need be very careful that you don't lose track of which star is which - they don't exactly carry labels. You can get some ideas by looking at their spectra, but it's not foolproof, and if you measure an angle to a star you thought was Rigel when it's actually Sirius, your position will be completely out.
:As Bowlhover said, install Celestia and play with it. It allows you to 'be' in any place in the galaxy and see what the stars would look like from there. You can simulate one of your trips - fly out from Earth (speeded up, of course :)) and see how the sky looks like from other places in the Galaxy, to get a good idea of what future space travellers would see.
:As for navigating to a planet in another star system - it's a bit more complex than what Bowlhover said, as you need to take into account not just where the planet is but also how (and how fast) it's moving, otherwise, you could well either never catch up to it, or fly right past it. You'd probably need to either observe it for a few weeks to get an idea of its orbit, and then adjust your course so that you 'intercept' it at some point. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 09:00, 30 April 2006 (UTC)
Excellent answers, everyone. Thanks for taking the time to explain this.
One more question: Reminded by the second post above. Nasa diagrams of their probes and manned spacecraft often point to an object labeled a "star tracker". I assume that it's the part of the navigation system that does track one or more stars while the craft is in flight. What happens if the spacecraft, either intentionally or by accident changes its orientation? Can the star tracker re-acquire the target star? If so, how does it discern the target star from others?
== Licking lips ==
This is a very odd question, but here goes: if you lick your lips too much (eg to moisturise them if they've become dry) they start to become irritated (a slightly brighter shade of red, and you experience mild discomfort). Further licking only makes the problem worse. Does anyone know why this is so? Why should excessive salive on the lips cause them to become irritated? — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 19:23, 29 April 2006 (UTC)
:::: Could it have anything to do with enzymes? Other than that, saliva consists of mucus and some antibacteria. Is this documented to more than one individual, if I assume that you speak from personal experience?
:Oh, sorry - yes, this is personal experience, and happens to the rest of my family as well. I guess I made the assumption that it was universally applicable, sorry if this isn't the case...! (how sloppy of me). — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 21:21, 29 April 2006 (UTC)
::The vermillion, or red part of the lip, lacks much of the tough keratin layer that is typically found on the surface of the skin. Prolonged exposure of this tissue to moisture causes it to absorb water, which makes it more fragile and vulnerable to maceration and microtrauma, ultimately leading to inflammation and the typical symptoms of chapping.--[[User:Markitos76|Mark Bornfeld DDS]] 01:17, 30 April 2006 (UTC)
== If a blimp was attached to a ship ... ==
Would the ship travel faster ? Has this been experimented ? --[[User:Harvestman|DLL]] 19:24, 29 April 2006 (UTC)
:Why would you want to do this? A blimp attached to a ship would essentially be a large, non-orientable sail - it would always push the ship in the direction away from the wind. The engine power on a blimp required to make it fly at a different speed / a different velocity is far too small to move a ship mich faster than it can under its own power - remember that, for ships, once you try to exceed a certain velocity (the hull speed), the power requirement goes up enormously, unless you do a fancy hull design (such as a planing hull, or, even fancier, a hydrofoil - but both only works for small to medium-sized boats). And if the wind was blowing in the opposite direction, or, worse, if a storm came up, the blimp would be nothing but a liability for the ship. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 19:39, 29 April 2006 (UTC)
::Thank you. I just thought of a [[NKS]] (a new kind of sail) without motors and all : anyway, any sail needs to do with the contrary winds. The storm is a problem in that method indeeed - we can go back to motors and free the blimp but the issue is not guaranteed. --[[User:Harvestman|DLL]] 06:35, 30 April 2006 (UTC)
== Computer Overhaul ==
We have an old computer, and we're adding a hard drive, and replacing the motherboard and CPU, and upgrading from Windows 98 second addition to Windows XP. What order would I do this is in? Start adding hardware and then upgrade, or upgrade and then replace hardware?--<tt>[[User:Ikiroid/Esperanza|<font color="green">'''The'''</font>]]</tt> [[Imaginary unit|<font color="black">'''i'''</font>]][[user:ikiroid|<font color="blue">'''kiro'''</font>]][[Ego, superego, and id|<font color="black">'''id'''</font>]] <small>([[user talk:ikiroid|talk]])</small><sup>([[User talk:Ikiroid/Help Me Improve|Help Me Improve]])</sup> 19:30, 29 April 2006 (UTC)
:If you're changing the motherboard and CPU, you almost ''certainly'' need to reinstall Windows anyway - that's virtually a new computer! So, upgrade hardware first, then reinstall. — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 19:53, 29 April 2006 (UTC)
::Do you have a full version of XP or an upgrade only version? If you have the full CD I'd recommend a clean installation (format or exchange hard drive first to get rid of 98) as you are less likely to run into compatibility problems and semi-functional leftover programs that are a pitfall of upgrading. If your CDROM drive is bootable you should be able to just put the CD in and restart (set the BIOS to boot from CD first), then follow the instructions and the setup will do everything else for you. Also, you'll need to be careful that your old memory (and graphics/peripheral cards if any) are compatible with the new board and CPU. Even if the RAM works, you may find it acts as a major performance bottleneck with your new kit. [[User:Yummifruitbat|Yummifruitbat]] 21:55, 29 April 2006 (UTC)
:::So, I have a full cd, not an upgrade. But is there a way and can have my new XP hardrive coexist with the old 98 one? Or if not, can I salvage the files on the old hard drive, other than burning all the info to a CD?--<tt>[[User:Ikiroid/Esperanza|<font color="green">'''The'''</font>]]</tt> [[Imaginary unit|<font color="black">'''i'''</font>]][[user:ikiroid|<font color="blue">'''kiro'''</font>]][[Ego, superego, and id|<font color="black">'''id'''</font>]] <small>([[user talk:ikiroid|talk]])</small><sup>([[User talk:Ikiroid/Help Me Improve|Help Me Improve]])</sup> 01:48, 30 April 2006 (UTC)
::::I'm not entirely sure what you're trying to do - are you trying to have ''both'' Windows 98 and Windows XP (ie both [[operating system]]s) installed on your computer? If so, that's a difficult proposition and beyond the scope of my knowledge - and there are few good reasons to do want to do it. Are you trying to just save the ''files'' on your old (don't think of them as the XP and the 98 disks, just as the 'old' and the 'new' - it will make things a lot easier) hard disk, eg your documents, pictures and so forth? Yes, that can be done - the easiest thing would be to burn them to CD, but if you really don't want to, you can do it by a bit of juggling. I'll explain in a minute. Just to get things straight - unless you want to keep both operating systems on the computer (my first point), you will ''not'' be able to re-use the programs you had installed under Windows 98 (eg Microsoft Office) straight away - they will need to be reinstalled under Windows XP.
::::But now to how to save your files. I'm not entirely sure how much you know and how much is obvious to you, so I'll do my best to explain and if anything isn't clear, come and ask again. The trick to saving your files will be to have them on the disk that is ''not'' reformatted when you install XP - so, you upgrade your computer, plug in the second disk, and make sure you plug in the ''new'' (ie empty) hard disk as the master (if you're using [[ATA]] - likely if your PC is more than two years old) and the other as the slave. Then, insert the Windows XP CD and install Windows on the ''new'' hard disk, making sure that the installer doesn't try to reformat the old hard disk (to be safe, unplug the old hard disk - we'll add it again later). Once Windows XP is installed, turn the computer off, reconnect the old hard disk, and restart. Windows XP will recognise there is a second hard disk and set itself up to read from it automatically. Voilà! You now have access to all the files you had on your old hard disk (which should now be labelled D: in Windows). Note that there will be a lot of stuff on the old hard disk that you can now delete - everything in the old Windows directory (D:\Windows, by default) as that's your old Windows installation, all your old programs (as you need to reinstall them to get them to work, you can't just run them), basically everything except your documents, pictures and so forth.
::::To get your old programs back under XP, you now need to find the install CDs they came on and install them again - most of them should work just fine under XP. Good luck! — [[User:QuantumEleven|Quantum]]<i>[[User_talk:QuantumEleven|Eleven]]</i> 08:42, 30 April 2006 (UTC)
:::No, I don't want both OS's on my computer, only XP. I can reinstall Office if I have to, I have a copy of the 2003 version that still has two uses left. So I suppose that means I can follow the directions within the latter paragraph of your response. Thank you very much for your help.--<tt>[[User:Ikiroid/Esperanza|<font color="green">'''The'''</font>]]</tt> [[Imaginary unit|<font color="black">'''i'''</font>]][[user:ikiroid|<font color="blue">'''kiro'''</font>]][[Ego, superego, and id|<font color="black">'''id'''</font>]] <small>([[user talk:ikiroid|talk]])</small><sup>([[User talk:Ikiroid/Help Me Improve|Help Me Improve]])</sup> 01:29, 1 May 2006 (UTC)
== Windows XP and removeable media ==
I haven't researched this usinghelp files etc because I can't think how to phrase the search. In English, when I insert an SD card in my PC ruuning XP, a popup dialog appears asking what I want to do with the files on the card. How do I stop this happening? -- [[User:SGBailey|SGBailey]] 20:13, 29 April 2006 (UTC)
:There should be an option to do nothing. Select this and check the box that says "always do this" or something like that. [[User:Isopropyl|Isopropyl]] 21:33, 29 April 2006 (UTC)
== baths ==
lets say for instance that the hot water was broken in my house and i wanted a bath. so i decide to fill the bath with hot water from a kettle. now to fill the bath up with water, and keep it at the maxium possible temperature would it be better to top the water up in a few big goes ie a full kettle however the time between each filling is long or fill the kettle say 1/4 the way but the time between each filling is shorter? we assume that the keetle heats the water to the same temperature each time
:I would say fill the kettle as full as possible, as this will limit time between refills. During refills of the kettle (while carrying it to the tub, dumping it, refilling it, and putting it back on the stove), no heating occurs, so you want to minimize this. For the same reason (to minimize refills), I would heat the water to just short of boiling. Of course, if you have a new kettle filled with cold water and ready to heat as soon as you remove the hot kettle, then it makes no difference how often you dump each. I would still heat the kettle to as hot as possible and as full as possible, just to limit the amount of work you need to do to fill the tub. [[User:StuRat|StuRat]] 21:23, 29 April 2006 (UTC)
:I've actually had to do this, and no matter what you do, it's difficult to get the water much warmer than room temp. The capacity of a tub is so much larger than the kettle, and it loses heat so rapidly, that the heating efforts are in vain. It also seems to take forever to fill a tub using a kettle. The boiler in my apartment complex was being replaced, and we were without hot water for a couple weeks, giving me a chance to develop another strategy. I ended up just filling the tub the day before with cold water, allowing it time to warm to room temp, then I would heat water on all 4 stove burners at once to boiling, dump it in, then take my bath. It wasn't exactly warm water, but this method made it bearable without me wasting hours filling a tub from a kettle. [[User:StuRat|StuRat]] 21:23, 29 April 2006 (UTC)
::Using a 9KW electric shower unit to run a bath is painfully slow and most kettles are only a couple of kilowatt at most! even fairly large gas combi boilers are annoying when you are used to tank fed hot water. Immersion heaters work because they heat a lot of water slowly in a well insulated container without any intervention and then dump it all into the bath quickly. [[User:Plugwash|Plugwash]] 00:34, 1 May 2006 (UTC)
==Combined Oral Contraceptive Pill & DVT predisposition==
I have been researching the clinical findings that the Combined Oral Contraceptive Pill increases the risk of a Deep Vein Thrombosis, however, I have been unable to find the biochemical mechanism by which this occurs (other than possible link to the Factor V Leiden inherited disorder). I was hoping someone may be able to find a good reaseach link that would shed some light on this...
I have heard of a paper by a Dr Jordon, but been unable to find it. If anyone can help I would be most appriciative
:You may already realise this, but just because a study finds that X increases the risk of Y, there is no guarantee that there is any idea of the biochemical mechanism. Initial results like this are generally based on statistical analysis; causes come much later, if ever. I am deeply suspicious of results based only on statistics, I might add, but the press report them as if they were the word of God. [[User:Notinasnaid|Notinasnaid]] 21:41, 29 April 2006 (UTC)
== Diluting Acids ==
What is the simplest way to dilute 2M Hydrochloric acid down to just 250ml of 1M Hydrochloric acid?
are there any specific calculations that need to be carried out?
thanks in advance! <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:172.203.232.109|172.203.232.109]] ([[User talk:172.203.232.109|talk]] • [[Special:Contributions/172.203.232.109|contribs]]) {{{2|}}}.</small><!-- [Template:Unsigned] -->
:Add 125cm3 HCl to enough water to make 250cm3<br>To work it out u need to know number of moles which is given by conc = moles/ volume (dm3) so rearrange ur 250cm3 and 1M to get number of moles which is 0.25/1 = 0.25 moles oh HCl, which then rearranging again using the 2M gives 0.25/2 = 125 cm3 so thats how much 2M acid u need to make 250cm3 of 1M acid --[[User:Colsmeghead|Colsmeghead]] 22:16, 29 April 2006 (UTC)
::No, you don't need to know the number of moles. 125 ml of 2M acid, when diluted to 250 ml, will have a concentration of 1M. It's a simple proportion. The important thing is that you have to measure the amount of acid precisely, and then dilute it so that the total volume of the solution is also a precise volume. And of course, you must "do as you oughta, add acid to watah". So I would say:
::* Measure 125 ml of the 2M acid with a graduated cylinder.
::* Add that to, say, 100 ml of water in another graduated cylinder.
::* Then add water until the total volume is 250 ml.
::You can't just measure 125 ml of water, because the volume of the solution can be different from the volumes of its components. —[[User:Keenan Pepper|Keenan Pepper]] 22:25, 29 April 2006 (UTC)
:::Mind you, regarding "add acid to water", 2M HCl isn't very concentrated acid — and it certainly isn't that much more concentrated that the about 1.1M HCl solution into which you'll be adding the rest of the water anyway. So I'd say in this case the acid-into-water rule could be safely broken. It would, however, be much more important if you were starting with concentrated acid, and especially if you were working with a [[hygroscopic]] acid like H<sub>2</sub>SO<sub>4</sub>. In that case the procedure given above is pretty much how you should do it — first dilute the acid to approximately the desired concentration by pouring it into water, then measure the volume of the solution and adjust the concentration as required. Oh, and don't forget to keep your goggles on. —[[User:Ilmari Karonen|Ilmari Karonen]] <small>([[User talk:Ilmari Karonen|talk]])</small> 17:48, 30 April 2006 (UTC)
:The 'M' number refers to the molarity of the solution. 2M means that there are 2 moles of HCl in 1 litre of the solution. You don't say how much of the original solution you are starting with but you need to take 125 ml of it and make it up with water to 250 ml to get the result you want. The equation is: Molarity (M) = number of moles / litres of solution. [[User:Yummifruitbat|Yummifruitbat]] 22:20, 29 April 2006 (UTC)
== Cleaning up fat ==
What is the most efficient, or any efficient mix against stains/remains of fat which can be made from traditional kitchen ingredients (milk, baking powder, etc etc)? Water is of course not very efficient, not on its own, but hot water mixed with soap traditionally does the work. Spit (1,5l produced per day by a normal person :)) would probably be smashingly good to rub in at it, but I was searching for something in place of the soap. [[User:213.161.189.107|213.161.189.107]] 22:22, 29 April 2006 (UTC)Henning!
:My first thought would be that you need a natural [[emulsifier]], (also known as a surfactant) which breaks up the oils/fats and makes them easier to remove. Your household washing up detergent contains synthetic surfactants which do this job. A quick browse of the article on emulsifiers says that egg yolk is one, so perhaps that would help... assuming it does act as a surfactant in this context there are always the disadvantages of a) having to separate out the yolk from the white; b) the hygiene issue of cleaning things with raw egg and c) the fact that it's orange. Out of interest, is it being used to clean dishes or clothes? [[User:Yummifruitbat|Yummifruitbat]] 22:33, 29 April 2006 (UTC)
::Since egg yolks contain lecithin, an emulsifier, I was thinking along the same lines ... but they do also contain a lot of protein, which is sticky. Maybe egg yolk plus a whole lot of water, but you'd still have the problems you mentioned. I can't think off the top of my head of any other food-based emulsifiers common in home kitchens. Stick with soap is my advice. By the way, I doubt [[saliva]] would work well on fat, even though it contains a lipase, since it also contains so much other stuff ... again the same problem as with eggs. Milk has no fat-fighting or binding capability that I know of, and I'd say baking powder would be no better than water since the acid and base in it are polar and fat is non-polar. Chemistry people, can you help? --[[User:Ginkgo100|Ginkgo100]] 02:53, 30 April 2006 (UTC)
:::[[Baking soda]] and [[washing soda]] are supposed to break down fats. They're [[basic]], so they [[saponification|saponify]] them. --[[User:Heron|Heron]] 15:04, 30 April 2006 (UTC)
== Gender ==
Does anyone know ''WHY'' do the 2 sexes exist? I mean... couldn't reproduction have been produced by a single androginous sex? and why not 3 different sexes?, it sounds weird since we are used to only 2, but what is the science behind it, I mean, is it a mysteri? or is there an explanation. --[[User:Cosmic girl|Cosmic girl]] 23:14, 29 April 2006 (UTC)
:We have a whole article devoted to this: [[Evolution of sex]]. —[[User:Keenan Pepper|Keenan Pepper]] 23:24, 29 April 2006 (UTC)
Thanks Keenan, I'll read it. --[[User:Cosmic girl|Cosmic girl]] 00:25, 30 April 2006 (UTC)
::If the question is asking why ''gender'' exists, not sex, I might have some leads. One reason that I am looking for some information to back is that different sexes allow specialization. In hermaphroditic species, a single individual must seek out a mate and then after doing so expend the energy to produce offspring. By having a male and female gender, only one in a pair of individuals needs to seek out a mate while the other one just needs to focus on having offspring. With two genders, the risks associated with one of these roles can then be accommodated for by allowing each gender to specialize so that the seeking gender [usually the male] can expend energy on adaptations that allow him to seek while the impregnated sex [female by def] can specialize in producing viable offspring. This is called [[sexual dimorphism]]. In birds, the males have a bright coloring which allows him to be easily recognized and the females have a dull one which allows her to hide. Seeking a mate is a dangerous task because that individual will be more noticeable to predators in the process. In a hermaphroditic species, individuals lose the ability to specialize but they benefit when a pairing occurs because two individuals become pregnant rather than one. If the risks of searching for a mate are low, it is to the benefit of the organism to be hermaphroditic. There is one additional benefit to having two genders. The male can seek out additional members of the opposite sex with whom to mate. Hermaphroditic species tend not to do this because if they are already impregnated, they need to save the energy to produce viable offspring. Seeking out another mate is less beneficial at this point because the individual must face the risks associated with seeking again and only one of the individuals in the next meeting will be impregnated instead of two.
::As to why there are not three, it is because it is too hard to get three individuals together at the correct time and place. It is true in chemistry as well. Reactions where three molecules must meet in order to react happen slowly and few reactions take place in this manner. Nature likes coming in twos. [[User:Sifaka|Sifaka]] 23:44, 29 April 2006 (UTC)
:::Not finding any sources that are discussing the topic at this point... [[User:Sifaka|Sifaka]] 23:55, 29 April 2006 (UTC)
The question was why gender exists, since sex is a byproduct of gender... wouldn't a species be more competent if it had mode genes to chose from? like with 3 'parents'? lol! like, a mom, a dad and a mom-dad (the 3rd sex hypothetically needed to produce better offspring).
and also! wouldn't there be more creatures if both male and female got pregnant simultaneously?... it's so weird...I mean, the logic behind it :|.--[[User:Cosmic girl|Cosmic girl]] 00:25, 30 April 2006 (UTC)
:If by ''sex'' you mean ''sexual intercourse'', then I think it is quite likely that sexual intercourse evolved first; only later did the two ''genders'' become specialized. — [[User:Knowledge Seeker|Knowledge Seeker]] [[User talk:Knowledge Seeker|দ]] 01:10, 30 April 2006 (UTC)
:Quite a few creatures such as [[clown fish] can change their gender. I don't know about at will but I am sure that there are one or two out there that can change back and forth. [[User:Sifaka|Sifaka]] 01:30, 30 April 2006 (UTC)
:If there were three genders which each contributed to an offspring's genes, then each parent would get to contribute only 1/3 (on average) of its genes, which is a higher cost than the current 1/2 [[Evolution_of_sex#The_two-fold_cost_of_sex|cost of sex]] (with two genders). Plus, the logistics of getting all three genders together to mate would be a lot more complicated than getting only two together. With no real selection pressure for it, such a complex system would be pretty unlikely to evolve. The anonymous responder answered pretty well the question why all species are not simultaneous [[hermaphrodite]]s when such a system elminates the cost of sex. [[User:Ginkgo100|Ginkgo100]] 03:00, 30 April 2006 (UTC)
== Q about conservation of momentum ==
While watching [[CSI: NY]] with a friend (who happens to be a physics graduate), a phrase along the lines of a "zero-recoil bow" came up. This led to a discussion about recoil from firing a bow. We discussed a hypothetical free-floating bow-wielding astronaut, who fires off an arrow. My understanding would be that the astronaut would then move backwards with momentum opposite to that imparted to the arrow, per [[conservation of momentum]]. My friend, however, asserted that this would not be the case with a sophisticated modern [[compound bow]], and that the momentum could be absorbed by the pulleys and what-not within the bow. Moreover, he said that it could even be possible that the astronaut would end up moving in the same direction as the arrow was fired. Whose (if anyone's!) interpretation is correct? And is a zero-recall bow possible[http://www.fastestbows.com/press/2003/bowtech_extreme_vft.htm]? (I discover that [[recoilless rifle]]s are possible, but only because something goes out the back...). [[User:Matt Crypto|— Matt <small>Crypto</small>]] 23:50, 29 April 2006 (UTC)
Your friend is wrong. If you were floating exactly still in a vacuum when you fired you would recieve momentum equal and in the opposite direction as the arrow went. As long as the compound bow does not drop anything out the back like a recoilless rifle, it doesn't matter. I am not sure about how a compound bow works but it doesn't even matter. Summing up the forces and the tension produced will yield the same result: Newton holds. Just don't go firing a quantum mechanical bow at relativistic speeds and you should be alright. [[User:Sifaka|Sifaka]] 00:04, 30 April 2006 (UTC)
::By the way, sometimes when some archers fire it seems like the bow appears to be jerked forward after the shot. It is because the archer was pushing against the force of the leaving arrow and overcompensates once the [[impulse]] has finished been imparted. [[User:Sifaka|Sifaka]] 00:09, 30 April 2006 (UTC)
:Your friend makes an interesting point about the way a compound bow works, but as Sifaka pointed out he is wrong. Work backwards, consider the closed system before the astronaut fired the arrow. He draws the bow with arrow back, but does the system move? No, he has not transferred energy in any unbalanced way by drawing the bow, so when he lets go and energy is imparted into the arrow, there is now an imbalance due only to the departing of the arrow from the bow. If you think of the arrow as still being in the system, and remember that the laws of physics declare that the center of gravity must remain fixed, ask yourself what must the astronaut do now that the arrow is moving very fast away from his ___location?
Your friend is wrong. He wants to violate the law of conservation of momentum with ropes and pullies, but ropes cannot outsmart mathematics. It is sometimes possible to give the appearance of violating these laws. For example, it is possible using a technique called [[tacking]] for sailboats to be driven against the wind by the force of the wind, but the whole principle rests on using a tack into the wind, which imparts momentum to the water, enough to propel the boat forward. In a vacuum, however, there are no shortcuts. If the projectile goes forward, you go backwards. Perhaps your friend should consider switching majors. -[[User:Lethe/sig|lethe]] <sup>[[User talk:Lethe/sig|talk]] [{{fullurl:User talk:Lethe|action=edit§ion=new}} +]</sup> 02:44, 30 April 2006 (UTC)
:Devices called "recoilless stabilizers" for bows exist [http://www.toxonics.com/stabilizers.html (example here, but beware slow, crufty website)], but they don't violate the conservation of momentum. They transfer the momentum to some damped moving weight that keeps the bow steady for the duration of the shot. After the arrow has left the bow, the weight eventually has to transfer its momentum back to the archer, but by that time it doesn't matter if the bow twitches. --[[User:Heron|Heron]] 14:58, 30 April 2006 (UTC)
= April 30 =
== Tight foreskin ==
Embarassing problem, I know but here goes. The foreskin of my penis is too tight to retract properly when I have an erection (it will go back all the way when flacid but not comfortably). I have been told by my doctor that I may need to be circumscised if it proves to be a problem for me and that I should work on stretching it manually. So far, it doesn't seem to be doing much good.
I *really* don't want to be circumscised, except as a last resort and I was wondering if anoyone knew of a (proven to work) mechanical device that I could wear over my penis and under my clothes to gradually stretch the foreskin widthways as I go about my daily routine. Any advice would be appreciated. --[[User:81.77.187.20|81.77.187.20]] 00:57, 30 April 2006 (UTC)
:No need to be embarassed - it is something that bothers you, and it is not often that people will feel comfortable enough to talk to their doctors about it. I would say that Wikipedia doesn't offer medical advice (see the top of this page), so you are probably better off trying to find out more options with your health care provider. Tell your doctor your concerns and considerations you've voiced here so they can help you better. --[[User:HappyCamper|HappyCamper]] 01:06, 30 April 2006 (UTC)
See our article on [[phimosis]], but be careful, there are editors around here crazed on this. [[User:Alteripse|alteripse]] 02:49, 30 April 2006 (UTC)
:Surely this is fairly normal when erect? As long as you can retract it when flaccid (i.e. for washing) it is not necessary to retract it for sex, unless it is painful. If it is painful I suggest using plenty of lubricant or a condom to reduce the friction. --[[User:Shantavira|Shantavira]] 08:30, 30 April 2006 (UTC)
::My only knowledge of other men's erect penises is from pornography. Their foreskins seem to fully retract behind the head of the penis when it's erect (when the woman is jacking off the man, she slides the foreskin up and down the full length of the head). I've never really had a problem with having sex myself but I have heard horror stories of torn forskins (and heavy blood loss) from vigorous shagging if the skin won't retract fully. There is so much info out there for women concerned about their genitals but so little for men - I have no idea what's 'normal' and what isn't. --[[User:84.68.221.14|84.68.221.14]] 20:40, 30 April 2006 (UTC)
Ehm, WHEN is it (too) tight? My skin won't retract like all the way, but where does the border go? As a virgin I can't honestly say I know if it's uncomfortable in any way during sex. õò
== Bouncing Pencil ==
Suppose you have a massive, fixed, inclined plane and a thin (may be regarded as infinitely so) rigid rod of finite length. The thin rod is launched at the inclined plane along the rod's axis. The rod makes contact with the plane at an angle and ''without sliding'' bounces off. Assuming an elastic collision, how does it bounce? Does it bounce straight back up or does it acquire angular momentum and begin to spin? The issue I am having with this problem is that a particle would simply bounce off at the angle it entered in. A thin rod though, coming in with no angular momentum, would gain angular momentum if it behaved in the same manner. I am not suitably well versed in physics yet to know if the conditions I set void the conservation of angular momentum law. I spent a couple hours approximating this by dropping a pencil eraser side down under the force of gravity onto by a book propped up on one side covered in newspaper. When I managed to drop it so that I did not impart any spin, many times it bounced straight back up, but on quite a few drops I thought were good it also ricocheted off with angular momentum. That could be attributable to irregularities in the eraser and my judging of drops. It seems like if it was not supposed to bounce straight back up that it would never do so. Perhaps my biggest problem is understanding how to visualize the rod and how the forces are acting on it. Do you visualize the rod as a rigid body or a connected line of particles that influence their neighbor or what? [[User:Sifaka|Sifaka]] 01:09, 30 April 2006 (UTC)
Ascii diagram of the pencil and the inclined plane
/| Inclined plane
rod moving --> / |
'''__________''' / |
/ |
/ |
/_____|
**Note the contact will be at an angle**
* I would suggest treating the rod as a rigid body, but keeping in mind that when it strikes the plane, the [[normal force]] will not be through the centre of mass. That means [[torque]]. -- [[User:Filliam H Muffman|Filliam H Muffman]] 02:44, 30 April 2006 (UTC)
== bandicoots: how do they get water from their food? ==
i am doing an essay on bandicoots for science and i need to know how they get water from their food.
if anyone could help me, it would be greatly appreciated.
Samantha
:Hello Samantha, welcome to Wikipedia! Bandicoots get water from their food through their digestive system. Their [[intestine]] absorbs water out of the [[digestive juices]]. Just the same as we do. ''See also'': [[GI tract]]. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 03:17, 30 April 2006 (UTC)
thankyou!!
== Instantanenous Speed ==
I really do not understand how to find it except drawing lots of tangents. This probably stems from the idea I don't understand limit but can anyone help me?
-What is a limit? How does it work?
-Using that, how do I plug that into the formula. I would write but I don't know how to use the math tools
basically it goes that v-inst is equal to delta x/delta t with lim delta t approaching zero
I know that this sounds like a hw problem but it is things my parents are trying to teach me and they gave me a physics books that does not really explain well, nor provide any examples. Any help will be appreciated.
:First off have you looked at the [[Limit (mathematics)|limit]] article? A limit just means, what happens to a function/equation as some variable approaches some number (in this case the change in time approaches zero). To find instantaneous velocity you take the first derivative of the position. That is, it equals the [[slope]] of the position function at a certain point (the slope of a line that is tangent to the curve at that point). The limit definition you saw in your book is in effect the definition of a derivative (if you have calculus then it is easier to explain) which is based upon the formula for slope where the change in t (in this case delta t or dt) approaches zero (see [[Velocity#Formal_description|this]]).
::<math>f'(x)=\lim_{h\to 0}{f(x+h)-f(x)\over h}.</math>
:This is the definition of a derivative (f' is the notation for a derivative). You can convert it to your terms by realizing a few things. f(x) is a function of the objects position over time. So f(x+h)-f(x) is the change in position. Dividing by h gives the slope. If h is zero then you have the instantaneous speed (because the change in time is zero it happens in an instant). As h approaches zero, you should see that both the bottom and the top approach 0 (because f(x+0)-f(x)=0). In calculus you find ways to figure out what 0/0 equals (ex. canceling). Anyways with a bit of mathematical stuff you can figure out what the limit equals and you have the instantaneous speed. Sadly Wikipedia doesn't have the nice graphs it should to explain how instantaneous position, velocity, acceleration and jerk are related. Maybe i'll make them sometime in the future. Did I help you (I'm not sure if I'm being too simple or too sophisticated)? [[User:BrokenSegue|''B''roken]][[User talk:BrokenSegue|''S''egue]] 04:20, 30 April 2006 (UTC)
After reading that only 10 or so times, I have a bit of a better understanding. Thing is I'm only learning Geometry (I'm in 7th grade in American{ewwww) public schools. And you wonder why we are falling behind in math and science.
:In my (American public) school, I didn't even get to Algebra until 8th grade, and that was an 'advanced' class. Sigh. So this instantaneous stuff is pretty heavy by typical 7th grade standards. What book are you using? - [[User:Mako098765|mak]]''[[User_talk:Mako098765|o]]'' 08:42, 30 April 2006 (UTC)
::This is off topic, sorry, but I thought I would just point out that not reaching algebra until 7th or 8th grade (8th in my case) is also common in countries like Norway. I don't know about the practise in other countries, but I know that English students learn about algebra and pythagoras and whatnot at least a year ahead of us (me).
== Glass slippers.......... ==
is it possible to walk or run in glass slippers?
what is the density and brittle nature of glass?
thanks--[[User:Vpearlinewiki|Vpearlinewiki]] 04:38, 30 April 2006 (UTC)
i think that they would have to be pretty thick glass if u were going to run in them
lol
i really dont know much about glass but i hope someone else can help you
sorry
--Sammie_hero
er..... thanks..--[[User:Vpearlinewiki|Vpearlinewiki]] 04:54, 30 April 2006 (UTC)
can sumone pls help me........???,..
DesPerAte >>>...--[[User:Vpearlinewiki|Vpearlinewiki]] 04:55, 30 April 2006 (UTC)
:Shoes could be made out of thick glass but their rigidity would make them uncomfortable, perhaps even more so than [[clogs]]. Keep in mind that the "glass slippers" in [[Cinderella#Discussion|Cinderella]] is probably a mistranslation of the French for "fur slippers". —[[User:Keenan Pepper|Keenan Pepper]] 05:22, 30 April 2006 (UTC)
But no one said she did not pad them...
but the article in this website proves that it is indeed glass slippers , not furslippers.
'''[[http://itre.cis.upenn.edu/~myl/languagelog/archives/002886.html]]'''
what is ur response now ?
pls hav a look at the article ,\\\
thx--[[User:Vpearlinewiki|Vpearlinewiki]] 07:09, 30 April 2006 (UTC)
pls help me .....reply soon.....--[[User:Vpearlinewiki|Vpearlinewiki]] 07:17, 30 April 2006
(UTC)
can some body out dere pls help me >>>>>>...1!
i am waiting so long 4 a repy >>!.>..!
--[[User:Vpearlinewiki|Vpearlinewiki]] 07:55, 30 April 2006 (UTC)
:Question 1: No. Question 2: There are many types of glass. See [[glass]]. --[[User:Shantavira|Shantavira]] 08:34, 30 April 2006 (UTC)
:Actually, I'd say one could walk. Perhaps not easily. Probably no worse than diving boots. [[User:Notinasnaid|Notinasnaid]] 08:59, 30 April 2006 (UTC)
:Trying to answer the question in a semi-sensible fashion, what is it about glass slippers that differs from normal slippers? The obvious characteristics are: flexibility, transparency and brittleness. I see no issue with transparency. Brittleness is a possible safety issue. Flexibility is surely the key issue. Any shoe I have ever seen has some part flexible, a standard slipper has a soft flexible sole with a soft flexible upper part. The closest match is probably wooded clogs (as mentioned above). Here the flexiblity is provided by the foot at the time of putting the show on and if incorrectly sized will readily fall off or be extremely uncomfortable. So if we assume a correctly fitted. molded, with patterns acting as grips on the soles; and if we assume thick enough glass to not readily break I consider you would have a heavy pair of slippers in which you could do anything that can be done in clogs. -- [[User:SGBailey|SGBailey]] 16:59, 30 April 2006 (UTC)
== What article articulates about [[Square lights]] found on vehicles? ==
I'd like to know about the history of the vehicular square light. At first, the lights were circular, and sometime in the 70s, they switched shapes to square. I hope to know why, so I tried looking up [[Square light]] but alas, it's a red link. (I'd also like to know what vehicle had the square light the earliest.
Therefore, if simply I didn't type in the right keywords, what's the true name of the article I'm looking for? --[[User:Shultz IV|Shultz IV]] 05:33, 30 April 2006 (UTC)
:''[[Headlight]]'' probably answers your questions. [[User:Melchoir|Melchoir]] 05:37, 30 April 2006 (UTC)
::Thank you! I will make a redirect. <!--Why did "headlight" not cross my mind fast enough? I might be having a [[brain tumor]] or some [[degenerative brain condition]].-->--[[User:Shultz IV|Shultz IV]] 05:47, 30 April 2006 (UTC)
:::haha, [[brain tumor]] -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 08:36, 30 April 2006 (UTC)
==Metadata==
Is it possible that somebody else can poke around and find out if I had cropped a digital photograph that I took? -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 08:36, 30 April 2006 (UTC)
:Possibly, if the original picture metadata was in place and gave that information. But the expectation is that any reasonable digital photographer will crop almost every photograph, since framing by eye is not as accurate as the check on the computer, so I'm not sure what your point is. [[User:Notinasnaid|Notinasnaid]] 11:00, 30 April 2006 (UTC)
::I can only think of three ways someone else can 'poke around' to find that out.
::* They have a copy or have seen the original and can compare and see that your new picture is a crop.
::*As Notinasnaid states, if you keep the EXIF info on the picture and the pictures size does not match.
::*Your picture is of an 'impossible' size, say e.g. that you crop it to be 10x1000 pixels, we can be pretty sure that no such camera exists, so therefore it must be cropped. [[User:Stefan|Stefan]] 11:18, 30 April 2006 (UTC)
::*Actually a fourth way exists but is a bit complicted, it would be to see if the picture is more distorted or vinjetted on one side than the other, if so we can also assume that it is cropped but then it might also just be taken with a lousy lens :-)
::But I would also wonder why is this importaint, as Notinasnaid states it is very common to crop. [[User:Stefan|Stefan]] 11:18, 30 April 2006 (UTC)
::Wow, I like the fourth way. It has real [[hack value]]. Something I would be proud to think of! Anyway, what do you mean "keep the EXIF info on the picture?" -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 11:54, 30 April 2006 (UTC)
:::Thanks! :-) A digital camera will save info about the picture taking in something called [[EXIF]], when you edit the picture in a picture editing application it can keep that info or discard it or save its own info. Depends on which application you use. You can often check this info in you picture showing application, it will tell you which camera was used, what focal length, shutter speed and so on, including the PixelXDimension and PixelYDimension. If you want to remove that info i'm sure there are application out there that can remove it (even edit them :-)), use google. Older versions of photoshop used to remove the info, not sure about the last versions. [[User:Stefan|Stefan]] 12:47, 30 April 2006 (UTC)
==Focal Length==
This photograph says its focal length was 6. What does that mean? -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 08:36, 30 April 2006 (UTC)
:That the [[Focal_length]] of the lens used was 6 mm. Read the article on focal length. Short summary. "For a thin lens in air, the focal length is the distance from the center of the lens to the principal foci (or focal points) of the lens." [[User:Stefan|Stefan]] 11:09, 30 April 2006 (UTC)
== why exactly do snakes slither? ==
why exactly do snakes slither?
:Can you suggest any other options for a legless creature to get around? [[User:Notinasnaid|Notinasnaid]] 10:58, 30 April 2006 (UTC)
:Rolling. [[User:Ohanian|Ohanian]] 12:50, 30 April 2006 (UTC)
But perhaps the question is: why did they evolve to slither? Or to put it in a Soviet way: why did they choose to lose the legs? If you ever came back, you could tell us how [[snake]] educated you, but I think we'll just see you in the form of another silly anon question. --[[User:Zeizmic|Zeizmic]] 13:02, 30 April 2006 (UTC)
:Good question! -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 20:51, 30 April 2006 (UTC)
== Take-Out Heat or Taking Out Heat? ==
Why is it that [[Aluminum foil]] is often used, it is claimed, to keep take-out food warm? How can a heat conductor serve as heat insulator?--[[User:JLdesAlpins|JLdesAlpins]] 11:58, 30 April 2006 (UTC)
:It is is use because it is cheap. The customer finds a container still hot at home and is satisfied, even if food is everything but warm : that's psychology. --[[User:Harvestman|DLL]] 12:25, 30 April 2006 (UTC)
:::[[Heat]] can be transferen in a few means, conduction and radiation beeing the most common according to the [[heat]] article, [[convection]] not beeing applicable to take away food. Since Aluminum foil will reflect radiated heat it will insulate the food from heat beeing radiated away, and since when you wrap food in Aluminum foil most of the food is not in contact with the foil but with air, the heat can not be transfered by [[conduction]] to the foil so it does not matter much that Aluminum foil is a good conductor, it is the air that the food have to conduct to and air is a quite good insulator when it comes to conduction. So therefore using Aluminum foil you have a good insulator agains both radiation and conduction, convection not haveing any effect (unless you spill your takeway soup :-) ). See also [[Vacuum_flask]] which works the same way except that it have glass and vacuum instead of air and [[Thermal_insulation]]. [[User:Stefan|Stefan]] 12:38, 30 April 2006 (UTC)
::::Convection '''is''' applicable to take-out food, in that it can be the primary mode of heat transfer from the food itself to the top surface of the container. Going back to the original question, one should keep in mind that merely putting food in a covered container lowers the rate of heat loss. With a covered container, the upper surface of the food is "insulated" by a volume of warm air in the container, which is not a good conductor of heat. If, on the other hand, the warm air is allowed to escape (as would be in the case of an uncovered container), the warm air "cover" is continuously being destroyed and replaced with cooler air from the environment. In this case, the greater temperature difference between the food and the (now cooler) air above it is responsbile for a greater rate of heat loss. In this particular mode of heat loss reduction, the material of the cover is unimportant. --[[User:68.238.254.236|68.238.254.236]] 13:21, 30 April 2006 (UTC)
90% of the heat saving is from sealing it (to avoid evaporative cooling). As said, foil is cheap and recyclable. They could use foam containers, etc, but it probably wouldn't make much difference. (and Saran wrap gets all gummy and yucky with hot food, as I have found out) --[[User:Zeizmic|Zeizmic]] 13:06, 30 April 2006 (UTC)
== lpg for cooking ==
can the use of lp gas for cooking leave black residue on saucepans & pots <small>—The preceding [[Wikipedia:Sign your posts on talk pages|unsigned]] comment was added by [[User:Fordhamw|Fordhamw]] ([[User talk:Fordhamw|talk]] • [[Special:Contributions/Fordhamw|contribs]]) {{{2|}}}.</small><!-- [Template:Unsigned] -->
:Not if the equipment is in good working order. If you are getting a residue you should contact a competent service engineer and have it checked urgently. Carbon monoxide, a deadly poison, could also be being produced if the gas is not burning fully. However, make sure you are not mistaking the effect of burning spilled food on the bottom of pots. Test by taking a clean pot, and boiling a full pan of water. Do not boil it dry: check the bottom. Also, never use a pan that is too small for the flame, nor turn the flame too high: you should not see a flame up the side of the pan. (If you do, this is probably not a fault, but the pan is too small). [[User:Notinasnaid|Notinasnaid]] 15:39, 30 April 2006 (UTC)
== Diesel Engine Low Load performance ==
What are the disadvantages of Diesel engine when operating continously at about 50% rated load?
Continuous operation of less rpm (1000 rpm) of diesel engine is advisable?--
:Do you mean 50% of the red line on the tach? Nobody runs any engine like that continuously. --[[User:Zeizmic|Zeizmic]] 13:08, 30 April 2006 (UTC)
== gram staining tecnique ==
why does gram positive bacteria retains the dye while gram-ive bacteria doesnt?
:The relevant articles are [[gram staining]] and [[gram-positive]], possibly [[gram-negative]] as well. [[User:Isopropyl|Isopropyl]] 16:52, 30 April 2006 (UTC)
== Crystallography (thin Films) ==
I developed ZnCdS thin films, varying the Zn content. While doing structural analysis using XRD, I find that CdS thin film peaks coincide to the peaks available in XRD database but for ZnCdS films' peaks, though present on same ___location as that available in database, but the intensity of the peaks is not the same. For example for my films intensity of the (002) peak is maximum, whereas database shows maximum intensity for 001 and 101 peaks, and small intensity for (002) peak. My results though tele with the results reported in literature. Many researchers have reported that the (002) is prefered orientation. How can I explain this anomaly as I have to quote the card number with which I am comparing my results.
:Just to be clear, you are referring to orientation of the Bragg plane, right? [[User:Isopropyl|Isopropyl]] 18:11, 30 April 2006 (UTC)
==Chemistry Software==
Does anyone know any good, free software that is able to draw bonds for compounds, like the images we have on our articles? Thanks, '''[[User:Kilo-Lima/Esperanza|<font color="green">K</font>]]'''[[User:Kilo-Lima|ilo-Lima]]|<sup>[[User talk:Kilo-Lima|(talk)]]</sup> 18:02, 30 April 2006 (UTC)
:Personally I use [http://www.mdli.com/downloads/downloadable/index.jsp ISISDraw] 2.5, though it requires you to fill out a (free) registration. If you don't find that one to your liking, take a gander at some of the programs listed at [[Molecule editor]] [[User:GeeJo|<font style="padding : 0px 1px 1px 1px; border : 1px solid #809EF5; background: #FFFFFF ; color: #99B3FF">GeeJo</font>]] <sup>[[User talk:GeeJo|(t)]]</sup>⁄<sub>[[Special:Contributions/GeeJo|(c)]]</sub> <small>• 21:08, 30 April 2006 (UTC)</small>
== origin of matter? ==
im not looking for a definate answer, but rather theories on my question. they say the universe is expanding and that outward motion of matter was created by the big bang theory. thats all good cause it makes sense. however i read the law of matter that says, "matter cannot be created nor destroyed." take everything today back in time to its origin point of the big bang. other than god or faith, what could be the origin of matter? im i waisting my time putting these theories together or is there something in all this?
:See [[Baryogenesis]] and [[Leptogenesis]]. —[[User:Keenan Pepper|Keenan Pepper]] 18:53, 30 April 2006 (UTC)
== Removing smell from microwave oven ==
Several months ago someone burnt something in my microwave oven, but the smell is still there. Can someone please suggest how I can get rid of this smell? Thank you.
:The plastic liner has absorbed (adsorbed?) the nasty molecules. Try cleaning with baking soda, or an oxygen cleaner. You could also boil a mixture of one of those commercial smoke odour remover products (no scent), but that goes into the plastic as well, and might not be food grade. --[[User:Zeizmic|Zeizmic]] 18:34, 30 April 2006 (UTC)
== Global Warming ==
What is the simple explanation for global warming. How does it work? I know about fossil fuels and methane and cabon dioxide or whatever, but how does that make the earth warmer. What about turning the oven on, or sweating? Why doesn't that make the world warmer. Is a possible solution to pump cold air into the world? Can you put ice on mountains or something?
:Did you look at [[global warming]]? The addition of [[carbon dioxide]] to the [[atmosphere]] results in something called the [[greenhouse effect]]. As for your suggestion of a massive [[air conditioning]] system, consider how much electricity a household unit uses, then imagine using a million times more. That energy has to come from somewhere, and most energy generators in the [[United States]] run on [[coal]], which would sort of compound the issue. [[User:Isopropyl|Isopropyl]] 18:45, 30 April 2006 (UTC)
== stem cell therapy for bone cartilage ==
Hello,
I'm 56 ys. female with onset of osteoarthritis in both hip joints.I work as a physiotherapist and "use" my lower extremities quite a lot.
Are there any advanced treatments, stem cell technique for instance, in order to avoid hip replacement surgery?
In case there are some special (not invasive ) treatments, will you kindly refer me to specialists?
Thanks very much for your help
Irit Levinton
== What is the importance and function of the digestive system and the excretory system as a whole? ==
What is the importance and function of the digestive system and the excretory system as a whole?
:Is this, by any chance, a ''homework question''? [[User:Notinasnaid|Notinasnaid]] 19:56, 30 April 2006 (UTC)
:You die without them. That's how important. [[User:Peter Grey|Peter Grey]] 20:09, 30 April 2006 (UTC)
This if for a project in my biology class.
:Ok, if they didn't teach that in class, see [[digestive system]] and [[excretory system]]. [[User:Notinasnaid|Notinasnaid]] 20:27, 30 April 2006 (UTC)
thank you
Hematuria affects what organs/organ systems?
:See that little box that says "search"? Not only does it go a lot faster than we reference desk helpers, it's also less liable to be rude to you for asking silly questions. —[[User:Keenan Pepper|Keenan Pepper]] 20:42, 30 April 2006 (UTC)
:They're meany heads. But yes, just type in "[[hematuria]]" into the box and click go. That will bring you to the article about it; this is an encyclopedia too. -- [[Image:Flag_of_the_United_States.svg|17px]] '''[[User:Mac Davis|<span style="font-family:Times;color:navy;cursor:crosshair;"><em><font color=#006600>Mac Davis</font></em></span>]]]''' ⌇☢ [[User talk:Mac Davis|ญƛ.]] 21:13, 30 April 2006 (UTC)
thanks
== Renal Failure ==
My friends father died from accute renal faliure. How can it be prevented and how is it caused and what organs are affected by renal failure?
:Type [[Renal]] into the search box for a reasonable overview. -- [[User:SGBailey|SGBailey]] 20:59, 30 April 2006 (UTC)
Thanks now i know what he was talking about?
== Help with science project ==
I need to do a display board,my science project is a telegraph or telegram,but i don't know what to put,should i put things like history of the telegraph,materials used,photos of one?
: Yes, those are great ideas. --[[User:Diberri|David Iberri]] ([[User talk:Diberri|talk]]) 02:13, 1 May 2006 (UTC)
== The existence of Gravity ==
What possible reason is there for gravity to come about? Other than it's obvious utility (the cosmos, natural phenomenon, life), what reason would it be for it to even happen?
:This is one of those questions that, at least for now, are better answered by religion and philosophy than by physics. If a successful theory of [[quantum gravity]] is developed, it will likely explain gravity as the transfer of [[virtual particle|virtual]] [[graviton]]s, but that immediately leads to a different question: why do gravitons exist? —[[User:Keenan Pepper|Keenan Pepper]] 00:14, 1 May 2006 (UTC)
<eliminated accidental duplication caused by an edit conflict which confused me heaps> [[User:The Mad Echidna|The Mad Echidna]] 23:38, 30 April 2006 (UTC)
:An argument due to [[Weinberg]] shows that an interacting spin-2 massless particle must obey the [[Einstein field equations]]. Massless spin-2 particles are part of the spectrum of excited string states in any string theory, so you could say that the existence of gravity is a consequence of the kinematics of excited stringy states. -[[User:Lethe/sig|lethe]] <sup>[[User talk:Lethe/sig|talk]] [{{fullurl:User talk:Lethe|action=edit§ion=new}} +]</sup> 01:43, 1 May 2006 (UTC)
== Is there a psychological term for True Believer Syndrome? ==
Is there a formal psychological term for the informal [[True-believer syndrome]], in which people continue to believe something that is false after it has been conclusively demontrated to them that it is false? [[User:Bubba73|Bubba73]] [[User talk:Bubba73|(talk)]], 23:39, 30 April 2006 (UTC)
= May 1 =
== Animal survival in winter ==
How do animals obtain water in the winter when water sources are frozen.
:Some [[hibernation|hibernate]]; that's all I know. [[User:Melchoir|Melchoir]] 01:09, 1 May 2006 (UTC)
Although this is a very silly question for us Canadians, I actually found a quote: "''Studies in Canada have shown some cows have gone 50 to 60 days with snow as the sole water source without any adverse effects.''" However, it quite uncomfortable to take a shower in snow. --[[User:Zeizmic|Zeizmic]] 01:13, 1 May 2006 (UTC)
::Cows shower? [[User:Zoe]]|[[User talk:Zoe|<sup>(talk)</sup>]] 01:51, 1 May 2006 (UTC)
:::A cow shower is a brief or small area of precipitation that is heavier than "raining cats and dogs." For more information, see [[Raining animals]]. </official meteorologist opinion> [[User:EWS23/Esperanza|<font color="green">'''E'''</font>]][[User:EWS23|WS23]] | [[User talk:EWS23|(Leave me a message!)]] 02:23, 1 May 2006 (UTC)
== Fullerene Formation ==
How are fullerene molecules formed? Is there a reaction mechanism process that creates them or is it something else. I am particularly interested in buckminsterfullerene and its formation. Thankyou. [[User:Vollsa|Vollsa]] 01:05, 1 May 2006 (UTC)
:I know nothing on this topic beyond [[fullerene purification]]. [[User:Isopropyl|Isopropyl]] 01:48, 1 May 2006 (UTC)
::Basically, you just zap graphite with lots of electricity (in a vacuum), which makes a messy mixture of all kinds of fullerenes and nanotubes. That's why the purification process is so important. —[[User:Keenan Pepper|Keenan Pepper]] 02:09, 1 May 2006 (UTC)
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