Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

February 12

First Ionization Energy

Hello. If helium has a wider atomic radius than hydrogen and helium electrons are farther away from the nucleus than hydrogen electrons, why does helium have a higher first ionization energy than hydrogen? Thanks in advance. --Mayfare (talk) 02:01, 12 February 2009 (UTC)

You sure about that atomic-radius comparison? But also if you like hand-waving explanations, helium as twice the nuclear charge of hydrogen. DMacks (talk) 02:04, 12 February 2009 (UTC)

Exactly. The two electrons in Helium atom (in its ground state) can not screen the nucleus completely from each-other; thus, each orbital sees, on average, a central (attractive) charge that is higher than 1. The central charge they "see" is more like 1.5, actually. So you need to invest more energy to remove one of the electons. The two electrons are indistinguishable. --Dr Dima (talk) 02:42, 12 February 2009 (UTC)

(edit conflict with Dr Dima) Actually, he's wrong about the atomic radius comparison. There are two main methods of determining atomic radius. The first is to use the average internuclear distance from covalent bonding, since helium forms no known covalent bonds, that method is pretty much out. The second method is to calculate the assumed atomic radius from the effective nuclear charge of the helium relative to its outer electron shell. From those calculations, it is assumed that helium is SMALLER than hydrogen (note that these calculations are approximations, as there are no empirical methods of determining the data for helium, but the numbers come out significantly smaller). Helium does have a larger Van der Waals radius than does hydrogen, but that really has no effect on First ionization energy. Rather, its a measure of how large the atom behaves in the gas-phase, if we treated it like a hard billiard ball. Van der Waals radius has no correlation with how the strongly the electrons are attracted to the nucleus. As Dmacks aluded to, atomic radius is a convenient hand-waving of explaining the trends in ionization energy, the REAL explanation lies in understanding effective nuclear charge. See also Atomic radius and Atomic radii of the elements (data page) for more info. --Jayron32.talk.contribs 02:47, 12 February 2009 (UTC)

Just a curiosity about diatomic helium molecules: [They exist] and have a large separation between the atoms, but they are unstable and really not relevant here ;-) Icek (talk) 14:25, 12 February 2009 (UTC)

Calling those "molecules" stretches the definition of molecule to rediculous bounds. Helium atoms, like ALL atoms and molecules, are susceptible to London forces which result from the polarizability of its electron cloud. The stuff they created was not diatomic helium molecules as much as it was an association of polarized helium atoms. Molecules specifically require "shared" covalent electrons, which this experiment decidedly did NOT produce. --Jayron32.talk.contribs 15:51, 12 February 2009 (UTC)

Mayfare, if you are serious about figuring out why the ground state energy of the Helium atom is as it is, you can work your way through problems to paragraph 69 ("self-consistent field") of the Landau-Lifshits non-relativistic quantum mechanics textbook. It deals exactly with your question. Actually, you would probably like to read the entire chapter X ("Atom"). Note: I have a Russian 4-th edition of the book; chapter and paragraph numbers may differ a bit in English translation, which is from 3-rd edition AFAIR. --Dr Dima (talk) 03:03, 12 February 2009 (UTC)

Real D glassess

So, I got two Real D glasses the other day when I went to see Coraline. The page Real D Cinema explains that they work by separating circularly polarized light. I was playing with them and noticed that if I hold one of them at arms length distance in normal position (front side facing away from me) and look at it through one lense (one at a time) of the other pair of glasses, nothing particularly special happens. But if I hold the first pair bakwards (front side facing away from towards me), when I look through the second pair (through one lense at a time), one of the lenses of the first pair looks dark while the other looks clean. I expected that phenomenon to happen in both situations, but it only happens on the second one. How comes? Dauto (talk) 03:19, 12 February 2009 (UTC)

Well - these are really just polaroid sunglasses with one lens rotated through 90 degrees.

Imagine that light is a wave that's vibrating either horizontally or vertically or both together (that's not really 'right' but it's a good way to imagine what's going on). A polaroid lens behaves like it had tiny vertical 'slots' that would let light that's vibrating vertically pass through the slot - but would block the vibration of light that's vibrating horizontally. (There aren't really 'slots' but it helps the imagination). Hence, with these glasses, one lens allows 'vertically polarized' light to pass and blocks 'horizontally polarized' light - and the other (which has horizontal 'slots') does the opposite.

I'm not sure which eye has which polarisation - but for the sake of my explanation, let's guess and say that the left eye allows vertically polarised light to pass - and the right eye allows horizontally polarised light to pass.

The movie displays alternate frames of the movie with alternate polarisation and moves the viewpoint an inch or so to the left or right on each frame. Thus when a 'right eye' frame of the movie is being projected, the light from the projector is forced to vibrate only in the horizontal direction. Your right eye lens allows the light to pass clearly but the left lens blocks most of the light and dims it down significantly. On the 'left eye' frames, the opposite happens - the projector sends out vertically polarised light and your left eye lens lets it through while the right eye lens blocks it.

One consequence of this (which was VERY noticable during 'Coraline') is that when something moves fast across the screen, it tends to double-image rather badly (this was most noticable for me during the closing credits) - that's because each eye is only seeing 12 frames per second rather than the more usual 24 frames that movies use.

So if you take two pairs of the glasses and look through the left eye or right eye of both together - nothing special happens - the left lens of both glasses allow vertical light to pass - the right lenses both let horizontal light through...things are dimmer but you can see through them both together. But if light passes through the left lens of one pair and the right lens of the other (as happened when you flipped one pair around - then only horizontally polarised light passes the first lens - and then the second lens filters that out because it has a vertically polarised lens - so everything goes very dark.

In regular polaroid sunglasses, both lenses allow only vertically polarised light through because when sunlight is reflected off of water or other flat surfaces, the glasses will dim it down. This is great for cutting out glare on the beach without making things go too dark.

Hence, if you take two pairs of regular polaroid sunglasses and rotate one of them through 90 degrees - you'll get the same effect you see with your 'coraline' 3D glasses.

SteveBaker (talk) 03:42, 12 February 2009 (UTC)

(Incidentally: If you go to see Coraline - firstly be SURE you go to a movie theatre that's showing it in true 3D...only about 50% of them are doing that - and the movie is much better that way! They use 3D exaggeration to make the parallel 'button universe' seem hyper-real and without that effect it's nowhere near so stunning. Secondly, they're going to charge you $2 of the ticket price for the glasses. When you leave the theatre they have a bin where they ask you to "recycle" your glasses. DON'T DO THAT! You bought the glasses - they are yours to keep. The theatres that bought the special 3D display equipment are ramping up for several other 3D movies coming along soon and you can save yourself $2 next time around.) SteveBaker (talk) 03:49, 12 February 2009 (UTC)

SteveBaker, your answer would have been correct 5 years ago, but now it is outdated. see the page Real D Cinema for details. You didn't really answer my question. Dauto (talk) 04:55, 12 February 2009 (UTC)

I'd give it a go, but I am unclear about the placement of the glasses and which lens you are referring to in your description. To clear this up unambiguously, call one pair of glasses Pair 1 and the other Pair 2. When you wear the glasses normally, call the lens that is on your left L and the one on your right R. (It may help to write a little L and R on the frame of the glasses.) 152.16.144.213 (talk) 06:07, 12 February 2009 (UTC)

For the situations below describe if the lens in pair 2 appears clear or dark:

a) 1 and 2 are in the normal position, looking through 1L at 2L:

b) 1 and 2 are in the normal position, looking through 1L at 2R:

c) 1 and 2 are in the normal position, looking through 1R at 2L:

d) 1 and 2 are in the normal position, looking through 1R at 2R:

e) 2 is backwards, 1 is normal, looking through 1L at 2L:

f) 2 is backwards, 1 is normal, looking through 1L at 2R:

g) 2 is backwards, 1 is normal, looking through 1R at 2L:

h) 2 is backwards, 1 is normal, looking through 1R at 2R:

The results would look like this if the lens of the glasses were oppositely circularly polarized and the polarization of 1L=2L and 1R=2R (i.e the left lens of both pairs have the same polarization. The right lens of both pairs have the same polarization, but opposite of the left lens)

a) clear b) dark, c) dark, d) clear, e) dark, f) clear, g) clear, h) dark

Thinking about it some more, I think I made a mistake above; flipping a circular polarizer around backwards will not reverse the polarity. The chirality of the filter will be preserved no matter what orientation it is in so the results should be. a) clear b) dark, c) dark, d) clear, e) clear, f) dark, g) dark, h) clear 152.16.144.213 (talk) 07:35, 12 February 2009 (UTC)

Here is what I see: a)clear, b)clear, c)clear, d)clear, e)clear, f)dark, g)dark, h)clear. Puzzling, ain't it? Dauto (talk) 06:18, 12 February 2009 (UTC)

Hmm, Now I wonder if your glasses are circularly polarized. It would seem the lenses are indeed polarized; from the two cases which you listed as dark all four lenses were involved. If the lenses were circularly polarized, results f and g indicate that 1L and 2R have opposite polarizations, and 1R and 2L have opposite polarizations. Results a and e suggest that 1L and 2L have the same polarization. d and h indicate 1R and 2R have the same polarization. The problem lies in results b and c which suggest that 1L and 2R have the same polarization and 1R and 2L have the same polarization. b and c conflict directly with f and g. So now I must ask are your glasses really circularly polarized? Take the glasses and wear them one at a time standing directly in front of a mirror. Do the lenses in your reflection appear dark or can you see through them? Linearly polarized glasses will be see-through. Reflection in a mirror reverses the circular polarity of light so that light coming out from the glasses which is polarized by them in one direction can't return once being reflected by the mirror, so the glasses will appear dark. 152.16.144.213 (talk) 07:35, 12 February 2009 (UTC)

I'll speculate that they make the circular-polarizing glasses from a quarter-wave plate (probably 15µm-or-so cellophane) oriented at 45° layered in front of a regular linear polarizer. The wave plate converts circular-polarized light to linear polarization — horozontal or vertical, depending on whether it arrived as left- or right-circular polarization.

If I'm right about that, it means that when you look through both sets of glasses forward, the light emerging from pair 2 is linearly polarized, which pair 1's quarter-wave plates convert to circular, and then pair 1's polarizers block half of (so rather than a-d being clear, they should be 50% transmission — or 25% if you count the half that gets blocked by pair #2). When you turn pair #2 backward, its polarizers let through linearly-polarized light, which #2's wave plate converts to circular (left- for one lens, right- for the other), which #1's wave plate converts back to linear (since its slow axis is at 90° to pair #2's, it essentially reverses the effect of #2's wave plate), which is then either completely blocked or completely let through by #1's polarizer, depending on whether its orientation matches #2's (i.e. left-left and right-right get through, left-right and right-left are blocked, as you report above).

(Actually, I'm oversimplifying a little by assuming the wave plates are diagonal and the polarizers are horizontal and vertical — it actually works out the same no matter what the actual orientations are as long as the relation between the wave plate and polarizer are correct in each individual lens.) -- Speaker to Lampposts (talk) 07:46, 12 February 2009 (UTC)

Meh. 3D projection through polarizing filters and the audience with 3D glasses is in no clear way advanced beyond The Stewardesses(1969), which had viewers exiting rubbing their heads with every sign of a n incipient headache. This is technology dating back to the early 1950's. It is better than black and white 3D using red and green filters, but not better than House of Wax (1953 film) or Dial M for Murder (1954 film), except for the march of progress making it harder for a stoned projectionist to reverse the projectors, causing people to look inside out, as was once done at the Biograph Theater in a revival showing of Dial M for Murder . Edison (talk) 06:22, 12 February 2009 (UTC)

It is a new technology. read the page Real D Cinema. Dauto (talk) 06:27, 12 February 2009 (UTC)

(staying with the straying from your original question) Distilling the article, the primary differences are: it uses circular polarization, so that the orientation of one's eyes does not affect the quality; it uses a single, DLP projector (which are very nice); it uses a high framerate (72fps per eye); and, mentioned elsewhere outside Wikipedia, it should be brighter, due to the screens and projectors used. The projector and framerate should reduce jitteryness and differences between the eyes' images, and the brightness helps to compensate for the loss of light associated with the polarized glasses. I've got no idea how it actually pans out, having not seen such a film, but that's the idea of it. -- Consumed Crustacean (talk) 06:38, 12 February 2009 (UTC)

Further diversion from topic : Image quality might not be effected by the orientation of one's eyes, but proper orientation of one's eyes is crucial to the stereoscopic effect. If you tilt your head more than a few degrees your brain won't be able to match up the images anymore and you'll just start see double. APL (talk) 02:07, 13 February 2009 (UTC)

It definately looked much better than the old linearly polarized 3D movies. The movie itself was also good. Dauto (talk) 06:45, 12 February 2009 (UTC)

It's getting more interesting. I decided to hold glass number one backwards too. So to

a) 1 and 2 are in the normal position, looking through 1L at 2L:

b) 1 and 2 are in the normal position, looking through 1L at 2R:

c) 1 and 2 are in the normal position, looking through 1R at 2L:

d) 1 and 2 are in the normal position, looking through 1R at 2R:

e) 2 is backwards, 1 is normal, looking through 1L at 2L:

f) 2 is backwards, 1 is normal, looking through 1L at 2R:

g) 2 is backwards, 1 is normal, looking through 1R at 2L:

h) 2 is backwards, 1 is normal, looking through 1R at 2R:

I am adding now

i) 1 and 2 are backwards, looking through 1L at 2L:

j) 1 and 2 are backwards, looking through 1L at 2R:

k) 1 and 2 are backwards, looking through 1R at 2L:

l) 1 and 2 are backwards, looking through 1R at 2R:

m) 1 is backwards, 2 is normal, looking through 1L at 2L:

n) 1 is backwards, 2 is normal, looking through 1L at 2R:

o) 1 is backwards, 2 is normal, looking through 1R at 2L:

p) 1 is backwards, 2 is normal, looking through 1R at 2R:

and I get a)clear, b)clear, c)clear, d)clear, e)clear, f)dark, g)dark, h)clear, i)clear, j)clear, k)clear, l)clear and here comes the punchline: m), n), o), and p) also look clear but if I turn one of the glasses 90 degrees around the axis of the visual path, they all turn dark!! As if they were linearly polarized. The 90 degrees turning had very small effect over the cases a) through l). I'm really puzzled. Dauto (talk) 07:15, 12 February 2009 (UTC)

Take a look at this and maybe this can help. [1] Definitely do the mirror check for circular polarizers vs linear polarizers the guy describes. You may have to hold them normally and backwards to determine what is going on. 152.16.144.213 (talk) 07:43, 12 February 2009 (UTC)

I want to thank Speaker to Lampposts. His explanation is indeed correct. The easiest way to make a circularly polarised light filter is to combine a linear polariser with a quarter plate of birefringent material (BTW that also explain the slightly purpleish shade that I had observed but neglected to mension). But unless we add the birefringent material on both sides of the lenses (and there is no reason to do that for the movie glasses since it would add cost but no added benefit), the filter works only in the forward direction (I had forgotten that). When held backwards, the filter works as a regular linear polariser. So, in configurations a) through d) I'm looking at linearly polarised light through circularly polarised blockers and should indeed always get a clear result. In configurations e) through h) I'm looking at circularly polarised light through circularly polarised blockers and should indeed get the clear-dark-dark-clear pattern observed. In configurations i) through l) I'm looking at circularly polarised light with linearly polarised blockers and see all of them as clear. Finally, in the configurations m) through p) I'm looking at linearly polarised light through linearly polarised blockers and should get either clear or dark depending on the orientation around the optical axis as indeed observed. That explains it all. Thank you. Dauto (talk) 17:25, 12 February 2009 (UTC)

milky way in the sky

A little help in mapping the skies. Can I see the milky way clearly with the naked eye? If it is, can you provide a useful map to help me find it. If it could help, I always see Orion or the Dog Star overhead or slightly near it on clear nights (I'm in the Philippines). If not then what cheap instruments should I use to see it clearly.--Lenticel ^(talk) 05:50, 12 February 2009 (UTC)

Yes you can see it, but you won't see it near a large city due to light polution. You don't need a map. it crosses the sky from side to side. Check out Milky Way. Dauto (talk) 06:07, 12 February 2009 (UTC)

It can be hard to see things that you are inside of. Edison (talk) 06:10, 12 February 2009 (UTC)

The "Milky Way" in this context refers to the disc of our galaxy, it appears as a wispy, almost cloud-like band all the way around the sky (it's more dramatic when you are facing towards the centre of the galaxy, which I think is somewhere is the southern (celestial) hemisphere. --Tango (talk) 13:58, 12 February 2009 (UTC)

You can see it by eye fairly easily, assuming there isn't too much light pollution, nor a full moon. Magnification will not help, it will only make things more difficult. A camera that handles low-light well might let you "see" it better, but if sky conditions are poor enough that you can't see it naked-eye, any photos you take may just be washed out. The "milky way" you see in the sky corresponds to the plane of the galaxy (ie. looking directly along the galactic disc rather than above or below it), so it's the region of the greatest density of stars. It appears as a bright region with many stars, and with a background haze to it from the stars you can't make out directly.

As for maps: star chart / planetarium software such as Stellarium, Cartes du Ciel and Worldwide Telescope do the best job. They let you choose your position on Earth and a time, and they show you a nice picture of the sky along with information on various features up there. Those three are free; Stellarium is the easiest to use, Cartes du Ciel is the most useful; Worldwide Telescope is probably the least easy at this point, but it does let you see actual images of the sky and various objects, which the other two don't (Google Earth has similar functionality, but I find it... lacking). -- Consumed Crustacean (talk) 06:18, 12 February 2009 (UTC)

thanks the article says it crosses Orion, Canis Major and Taurus so I think it'll be easy to spot. Its full moon tonight so I guess I have to wait a little.--Lenticel ^(talk) 11:00, 12 February 2009 (UTC)

Today's APOD has a picture of the Milky Way, here. It's the big purple thing on the right. --Sean 17:18, 12 February 2009 (UTC)

Permanent archive link: [2]. In case you happen not to be reading this on Darwin's birthday. —Tamfang (talk) 07:02, 18 February 2009 (UTC)

If you live in a region where low clouds glow orange, red, or yellow, or there are streetlights bright enough to cast a shadow from your observing location, then your limiting magnitude is probably too low to find the Milky Way. Try to find your limiting magnitude by finding nearby stars. For example, can you find the star Arneb? A limiting magnitude higher than +5.5 (with no glare is usually good enough to find the Milky Way. If the Milky Way if up on a dark night, with no objects obsucuring it, then you can't miss it. Binoculars or a telescope might aid you in finding the Milky Way, but remember that they show you a much smaller area of sky, rather than the entirety of the Milky Way. You might be able to find a light pollution map online. The Milky Way is most easily visible far from city locations. ~AH1^(TCU) 22:50, 13 February 2009 (UTC)

A map of light pollution is available at [3]. If you're in a white, red, orange, or yellow zone, the Milky Way is going to be hard or impossible to see; if you're in a grey or black zone, it'll be hard not to see. --Carnildo (talk) 00:04, 14 February 2009 (UTC)

Actually, I don't think that's a very good description. I find that the Milky Way is pretty much impossible to see from white or red areas. Orange areas are a bit iffy, if there are any lights in the vicinity, it will be difficult to see the Milky Way, but if there are no lights, then the Milky Way should be clearly visible. One time I saw the Milky Way from an orange area with no streetlights, and the sight was simply unforgettable. Yellow or green areas will produce a visible Milky Way, but likely not all visible details will be seen. Anything darker than that will produce a truly sensational sight. I live in a red area, and the limiting magnitude (for my eyes, after dark adaptation away from as many streetlights as possible) is about +4.5, and I have relatively poor eyesight. A better description of the colours is available at http://www.cleardarksky.com , but it only works for locations in North America. Hope this helps. ~AH1^(TCU) 02:15, 14 February 2009 (UTC)

What is the largest academic journal in the world

By publication volume (published papers per year), what is the largest academic journal (and how many papers do they publish)? —Preceding unsigned comment added by 24.5.116.52 (talk) 06:02, 12 February 2009 (UTC)

I don't know the answer to your question, but Journal of Geophysical Research often runs more than 30,000 pages per year. Dragons flight (talk) 06:14, 12 February 2009 (UTC)

On the other hand, IEEE would probably have more than that if they published as a single journal, but they break up in to more than 140 different sub-journals, (well, "Journals," "Transactions," "Letters," and "Magazines"). Nimur (talk) 09:12, 12 February 2009 (UTC)

I would also note there are peer reviewed academic journals outside the sciences. Since this question is on the science desk, it's more likely responders will be primarily familiar with scientific journals Nil Einne (talk) 11:18, 12 February 2009 (UTC)

Though it's likely that a science journal would probably be the winner of this question, as science articles are usually (but of course not always) quite small (unlike academic journals in the humanities). In fact I wouldn't be surprised if the winner wasn't something like Nature or Science that comes out every week and has tons of tiny articles crammed into it. --98.217.14.211 (talk) 12:52, 12 February 2009 (UTC)

Authoritative anatomy terminology

Some time ago I recall reading about a set of definitive anatomical terminology, giving precise and uniform definitions to various anatomical terms. In some sense, the official guide to anatomical terms. I can't seem to find the title now, however; does anyone know what it is? Many thanks, --TeaDrinker (talk) 07:14, 12 February 2009 (UTC)

Gray's Anatomy. --TammyMoet (talk) 08:52, 12 February 2009 (UTC)

Ah thanks! I appreciate the help. Gray's was not the one I was thinking of, but I did find the one I had in mind (Terminologia Anatomica). Thanks again, --TeaDrinker (talk) 10:16, 12 February 2009 (UTC)

Another idea would be to look for a suitable anatomy ontology which would have probably crisp definitions, too. --Ayacop (talk) 18:50, 12 February 2009 (UTC)

Darwin mechanism of evolution?

People always say that Darwin didn't propose (or even think about) a mechanism by which he thought evolution could occur. I find this hard to believe. Are there any records that hint at HOW he thought evolution might occur?

Thanks

Aaadddaaammm (talk) 13:52, 12 February 2009 (UTC)

Darwin wrote a great deal on the mechanisms of evolution. I think you mean that he did not know the underlying mechanism of heredity, which of course is required for evolution or anything like it. Our article pangenesis has some information on his (totally wrong) theory of heredity. Algebraist 14:04, 12 February 2009 (UTC)

Yes and no. Darwin didn't know about DNA molecules - so he certainly didn't have the whole picture.

He did know that offspring of parents generally inherit the characteristics of their parents - yet sometimes have one or two traits that are different from either of them. He also knew that these inherited characteristics would affect the ability of an animal or plant to survive and reproduce. Those are the only two things you need to know to formulate evolution as a hypothesis. If a particular inherited characteristic increases the probability of that organism surviving and reproducing - then there is more chance of that characteristic being in the next generation. If a heritable characteristic makes the creature less likely to survive and reproduce then that characteristic will be much less likely to be present in the next generation. Hence there is a tendency over many generations for creatures to change to be better and better able to survive and reproduce. That's evolution in a nutshell and there is nothing at all complicated about it. It's absolutely inevitable. Darwin knew that much. However, that's just a hypothesis. To become an accepted 'theory' or 'law' - the hypothesis has to be proved by experiment or observation - and (preferably) explained in detail. We can demonstrate it in action with fairly simple experiments using bacteria cultures - we can also observe it in action with (for example) Warfarin resistance in rats, antibiotic-resistance in hospitals and lactose tolerance in humans. We can explain the inheritance using what we know of DNA and RNA biochemistry. But none of those things were known to Darwin.

The fact that Darwin cannot be said to have proven his theory is rather irrelevant. It's quite common for one scientist to come up with a really good hypothesis and for others to prove it and turn it into a proper scientific law. Einstein (for example) never did a practical experiment in his life - but he turned out some very impressive hypotheses that others subsequently proved.

As for records - Darwin's books survive and you can even read them online at Project Gutenberg - here: [4] - he wrote an autobiography [5] and of course his main work on evolution The origin of species and various others [6] [7].

But (and this is important) our modern theory of evolution stands alone - it's not dependent on what Darwin did or didn't know. Even if his hypothesis was a complete guess at the time - it's been proven to be true hundreds and hundreds of times since.

SteveBaker (talk) 14:26, 12 February 2009 (UTC)

To nit-pick... the difference between a hypothesis and a theory is not experimental testing; a theory is just a testable hypothesis (but you don't have to test it and if you do test it, it doesn't have to work out... there are plenty of wrong theories which are still "theories"). Law doesn't really have a lot of real philosophy-of-science meaning, other than being some sort of simple, iron-clad relationship. (It is not higher on the truth or explanatory ladder than "theory" in any meaningful sense. Newton's Laws are still laws even though they are not as accurate an explanation of gravity, say, General Relativity.) And as to evolution... even *WE* don't know "the whole picture"—hence it's still a topic people do research and publish on to great effect.

As for Darwin's musings on heredity... it's of note that today we consider heredity to be the real underpinning of natural selection but that is not the conceptual framework that Darwin had at the time. Heredity was indeed important to him but understanding evolution as heredity-plus-time is more how Darwin's successors (including his infamous cousin, Francis Galton) thought than the somewhat more Romantic tools that Darwin used for thinking about species. Darwin did muse about heredity quite a bit but it wasn't especially systematic. (And it's of note that even Mendel, who we most of the credit for genetics to, wasn't really trying to come up with a generalized theory of genetics himself. It turns out his work serves as a great basis for doing such a thing, but that was not his research project or what he argued he had done.) --98.217.14.211 (talk) 23:17, 12 February 2009 (UTC)

To nit-pick Steve Baker, but there is no "truth" in science. Darwin's theory (hypothesis isn't quite right) was a guess, it's been tested, and the Theory of Evolution passes the tests, but science doesn't work in "truths." I would say that scientific evidence broadly supports the Theory of Evolution. OrangeMarlin ^{Talk• Contributions} 23:20, 12 February 2009 (UTC)

That's an extremely perverse usage of the word 'truth', which would disallow using it with regard to any statements about the world at all. Exactly the same could be said about the (tested, not yet refuted, supported by evidence) theory that my drinking a glass of water will not cause my head to be destroyed in an annihilation explosion. Algebraist 23:26, 12 February 2009 (UTC)

All science has is theories with varying degrees of evidence to support them. At what level of evidence do you apply the designation "true"? In imprecise everyday language, we talk about things being true and false, but they aren't well defined scientific terms. Things like "proof" and "truth" and other absolute things are the realms of mathematics (modulo Gödel), they don't exist in science. --Tango (talk) 00:44, 13 February 2009 (UTC)

Yes, exactly. As I said, this usage of "truth" leads to us not being able to assert any substantive statement as true, and thus we lose a perfectly good and useful word. I'd rather keep the word "true" and accept that the statements I assert to be true are not necessarily immune to all possible doubt. Algebraist 00:51, 13 February 2009 (UTC)

If true means "stands up to rigorous testing" then evolution is "true". If true means "unchanging and invioble statement about how things are, always have been, and always must be" then nothing in science can said to be true. Scientific truths are said to be the former, and religious truths fit under the later category. Its a shame that we use the same word to describe these two different concepts, because they really apply to very different aspects of the human experience and it would be nice to have different little words to describe these two different concepts. Alas, English is an imprecise language, and sadly the same word is used to describe both states, much as the word "theory" and other which have different contextual meanings which get bent in ways to make them fit whatever your political agenda is. <sigh>. --Jayron32.talk.contribs 02:14, 13 February 2009 (UTC)

If, on the other hand, we take 'true' to have its normal English meaning, so that 'statement P is true' is just another way of saying 'P', then scientific truths are true while religious truths are not true. Algebraist 12:50, 13 February 2009 (UTC)

<unindent>

I think we should allow 'truth' to be applied as an absolute thing in the mathematical sense of some theorem being derivable from some set of axioms. To pick an example: If we accept Euclid's axioms about geometry then "the interior angles of a triangle sum to 180 degrees" is 'true' relative to those axioms - although it's certainly 'false' if you are doing geometry on the surface of a sphere (for example) because the parallel line axiom is not true on the surface of a sphere.

Evolution is 'true' in that sense if you accept the axioms that:

• there is inheritance of traits from parent(s) to offspring
• there are sometimes mutations that result in new traits appearing
• having traits that suit the prevailing environment will result in an improved probabilty of an organism reproducing and passing those traits onto its offspring.

Accept those three axioms and you must accept that evolution is inevitable and 'true' in the fundamental mathematical sense.

To disprove Evolution in a more general sense of the word "true", you'd need to show that one or more of its axioms does not correspond to the world we live in and to the systems we apply it to. If you could show (for example) that genetics was false and that (say) Lamarckism were true instead - then evolution could be shown to be 'false' in the real world sense. However, you'd still say that it's true in the mathematical sense. If real animals reproduced in a Lamarkian manner - then evolution would be false as applied to the real world - but could still be true in the sense of generating evolutionary computer algorithms. We might well find another planet where living things don't have DNA - and it's possible that evolution would not apply there. After all - evolution doesn't apply to car manufacturing - it is false to claim that evolution explains why my car has headlights.

However, the three main axioms on which evolution sits have been shown to pertain to the real world to a highly convincing degree. So we may safely say that evolution is definitely 'true' in the mathematical sense...and as true as the theories of genetics and 'survival of the fittest' - in the more general sense of 'truth'.

The same can be said of most scientific theories and laws...if you disprove the axioms then all bets are off.

SteveBaker (talk) 05:39, 13 February 2009 (UTC)

The "Theory of Evolution" says more than just that evolution happens, it says evolution is responsible for the variety of life we see around us. Anyone denying evolution happens is just an idiot and is best ignored (you can't reason with unreasonable people). Denying that evolution caused what we see around us is rather more legitimate - the evidence is certainly extremely strongly in favour of evolution as the cause, but there are still gaps in the theory to be filled and you can come up with a vaguely reasonable argument that there must be something more too it. That evolution happens can be seen as a "mathematical truth" (given the assumptions you list, which it is completely unreasonable to deny), that evolution is responsible for the variety of life around us (for the origin of species, if you will) is a "scientific truth". --Tango (talk) 13:42, 13 February 2009 (UTC)

I don't think there is a reasonable argument that "there must be something more to it". The word must implies that we have some proof. I would be happier with some argument that says there might be more to it. Indeed - if you look at dogs, they didn't arrive at the DNA they have now by simple natural selection. Toy Poodles didn't "evolve" from wolves - rather humans intervened and produced the poodle by selective breeding. Similarly, 'starlink' corn (see Transgenic maize) did not evolve - humans implanted genes from a bacterium into the DNA of the corn plant om order to make it disease resistant. GloFish are another example.

If the people who object to evolution were indeed pointing at those weird cases, then we'd be forced to agree that not all organisms "evolved" to the state they are at now because some were intentionally designed by humans. But that's NOT what these people are arguing. They are saying specifically that humans did not arrive by evolution because that directly contradicts their religion. That's a serious problem because the genetics of humans is rather well understood and it's extremely clear that we DID evolve right along with all of the other great apes from a common ancestor - and natural selection is the sole driving force behind those changes.

If the anti-evolution people were protesting that we should not be teaching that StarLink corn 'evolved' from regular corn - then the scientific community would be happier to accept that teeny-tiny caveat...but they aren't. They are trying to use this as a 'wedge issue' to try to overturn science and any other source of information that contradicts their world-view. If we don't want the Christian equivalent of the Taliban running the place - we owe it to the world to keep this debate 'on the rails'. SteveBaker (talk) 16:35, 13 February 2009 (UTC)

Bodyhair

Which bodyparts don't have hair growing on them? —Preceding unsigned comment added by 83.80.64.227 (talk) 14:23, 12 February 2009 (UTC)

Eyes? Nails? I assume that you mean external body parts. Anything in your mouth (assuming that counts as external). A Quest For Knowledge (talk) 14:32, 12 February 2009 (UTC)

Thin particular piece of homework seem to frequently stump students. Here's a novel idea: Since you couldn't or wouldn't find it in your biology textbook, go to hair. (If you click on the blue words they will get you to the respective pages. You can also type your word into the search window in the side-bar.) There you will find many more links. One of them will be for Hair follicle. Learning how to find information without having to ask someone is an important part of what they teach you at school.76.97.245.5 (talk) 14:51, 12 February 2009 (UTC)

All of them, if you have alopecia universalis. --Sean 16:15, 12 February 2009 (UTC)

The parts of most non-mammalian bodies. —Tamfang (talk) 07:17, 18 February 2009 (UTC)

Cognation Memory

Till what age does a human memory grow123.252.230.201 (talk) 17:14, 12 February 2009 (UTC)

Death? I'm not sure that memory grows much after death... --Jayron32.talk.contribs 17:58, 12 February 2009 (UTC)

See Memory and aging. Unlike in some animals, humans' ability to form new memories merely declines with age rather than stops. 76.97.245.5 (talk) 18:00, 12 February 2009 (UTC)

Do you have an example of an animal that can't form new memories after a certain age? --Tango (talk) 19:05, 12 February 2009 (UTC)

Sorry Tango I'd love to have dragged a nice scientific article out of my google sleeve. Unfortunately nothing concise and usable came up in a quick search. So all I can give you is some murky synthesis of things I read. For quite a few animals there are things that they can't learn past a certain age. Cats e.g. can't learn how to apply a killing bite if they don't learn that at a young age. They'll catch prey, play with it, but remain unable to kill it by biting its neck. I've also read that some animals are unable to learn proper sorting of other animals into threat, food, social members and others later in life. (OR: We had a bottle-raised tom cat who was mortally afraid of mice!) And here's one example [[8]]. [[9]]. That certain birds recognize the first animal they see when they hatch as mother is well documented. I should probably have qualified my comment a bit more. Certain memories definitely get "hardwired" (imprinted) and can't be replaced with new ones. I seem to remember some reports on an overall learning cap, but can't recall any specifics to google details. One would be tempted to think that the higher developed the animal the more flexible its memory should be, but that would be wrong, considering examples like bees or parrots. 76.97.245.5 (talk) 01:54, 13 February 2009 (UTC)

I'm not sure that our memory capacity does 'grow'. I think we probably forget things at least as fast as we remember them. Old memories get less and less detailed as time goes on - and in the end, the total number of 'bits' stored there remains a constant. SteveBaker (talk) 05:14, 13 February 2009 (UTC)

So you're saying I can justifiably forget my aniversary because I had to learn my son's birthday? Cool. Someguy1221 (talk) 06:47, 13 February 2009 (UTC)

Well, since this is the Science Reference Desk, you should try the experiment and report back the results. Lotsa luck with that : ) 87.81.230.195 (talk) 07:10, 14 February 2009 (UTC)

The whole "storage" analogy unfortunately doesn't pan out. Scientist are still busy trying to figure out what's going on. What we call "memory" is actually a complex string of information. If you store pictures of a green and a yellow apple in your computer you'd have to store information on each image. Your brain may just store apple, yellow and ditto, green. But it might just as likely do something like - round fruit, color of my favorite blanket, like taste and round fruit, color of patch of lawn in the garden in sunshine, hate taste. Of course you would memorize more things that are the color of your favorite blanket so you'd only need to store that information once. And you'll always remember that blanket because so many things link there. - Until you find a color name "golden" and like that. Little by little you can forget about that blanket because all the blanket color things are "golden". Well, that particular blanket. You'll probably still remember that those square fluffy fabric things are blankets. So if your momn should call you an tell you she found "your favorite yellow blanket", your memory will happily provide a picture of a (canary) yellow full-size blanket and convince you that's it. When you then go and see the real thing you'll say "Strange I remembered it to be a different color and bigger." :) Memory is way more complicated than that (and I don't want to claim I know even the tip of that iceberg). So it's not that easy to say what has grown or not grown. If we go with computer analogies I'd liken it more to defining, linking, redefining, deleting table spaces, and writing queries in a multi-relational database. (... and the DBA won't talk to anyone:-) What I find amazing is that so many things seem to be stored in a similar fashion in different people. I remember reading that scientist were surprised to find in a study that people seem to have a "vegetable" section in their memory. A certain area of the brain lit up when test subjects were shown pictures of vegetables and asked to think about vegetables. Someone who had suffered brain damage in that same location had a good memory except when it came to vegetables. Odd, no? Sorry for (again) not linking references it's way too late and I still got work I'm trying to avoid doing. I came across these pages that you might find interesting. [10], [11] and SciAm has a whole magazine dealing with related topics: {http://www.sciam.com/sciammind/] -76.97.245.5 (talk) 08:15, 13 February 2009 (UTC)

I am old, yes, but I assure you there is nothing wrong with my short-term memory nor is there anything wrong with my short-term memory. Cuddlyable3 (talk) 21:32, 16 February 2009 (UTC)

Same-sex gametes combining to form a zygote?

The Encarta Dictionary entry on gamete says:

• male or female cell: a specialized male or female cell with half the normal number of chromosomes that unites with another cell of the opposite sex in the process of sexual reproduction. Ova and spermatozoa are gametes that unite to produce a cell (zygote) that may develop into an embryo.

With in vitro fertilization, couldn't a zygote (and viable embryo) be produced from two ova or two spermatozoa? If no, why not, and might a procedure be found to make this possible? I realize this might be common knowledge I've simply missed, but the pages on zygote and sexual reproduction aren't explicit on this point. -- Deborahjay (talk) 17:43, 12 February 2009 (UTC)

You can't combine two sperm to make a viable embryo, since sperm don't contain much more than DNA, the ovum has all the rest of the stuff needed to produce an embryo (just compare their sizes to get a good impression of how much would be missing). You might be able to fertilise an ovum with the nucleus taken from another ovum, I'm not sure. (Obviously, if you did, you would only ever get female offspring.) --Tango (talk) 17:58, 12 February 2009 (UTC)

Um. I seem to recall something with frogs for the ovum plus nucleus of another ovum arrangement; don't know about any higher life-forms. As for the males: what about emptying the genetic material from an ovum and filling it with the nucleii of two spermatozotes? -- Deborahjay (talk) 18:11, 12 February 2009 (UTC)

I'd think that's theoretically possible. But the hard part is removing only the maternal DNA. The maternal mRNA (which is derived from maternal DNA) is also important for embryonic development. I don't know how the DNA could be replaced while leaving the mRNA and other stuff in the nucleus intact.128.163.80.152 (talk) 18:19, 12 February 2009 (UTC)

Not only is this theoretically possible, it has been done. Removing the egg's nuclear material is a well practiced procedure, so that's actually the easy part. The problem in mammals is epigenetic imprinting, which renders the male and female contributions to the genome non-equivalent, even after discounting the sex chromosomes. Thus, a mammalian embryo derived solely from male or female nuclear material will be effectively homozygous lethal for a number of genes. Reading from Developmental Biology: 8th Edition (Gilbert) the earliest evidence for this came from hydatidiform mole, which can occur from the fertilization of an empty egg by a sperm. Evidence also appeared from attempts to induce parthenogenesis in mice (by suppressing the seperation of nuclear material during the second meiotic division). The embryo develops the full range of tissues and early organs, but development ceases by day 10 or 11. Attempts to fertilize eggs with two egg nuclei or an empty egg with two sperm nuclei all failed (hundreds of times), although the precise phenotypes seen in the failed embryos differed between the di-maternal and di-paternal embryos. However, female mice that are mutated to exibit DNA methylation patterns in their eggs similar to males can form a viable di-maternal zygote when artifically mated with a normal female. It should be noted that the procedures that have been developed thus far are confined to genetically manipulated mice, so men don't have to worry about becoming unnecessary quite yet. References:

• Jacobs, P. A., C. M. Wilson, J. A. Sprenkle, N. B. Rosenshein and B. R. Migeon. 1980. Mechanism of origin of complete hydatidiform moles. Nature 286: 714–717.
• Kaufman, M. H., S. C. Barton and M. A. H. Surani. 1977. Normal postimplantation development of mouse parthenogenetic embryos to the forelimb bud stage. Nature 265: 53–55.
• Surani, M. A. H. and S. C. Barton. 1983. Development of gynogenetic eggs in the mouse: Implications for parthenogenetic embryos. Science 222: 1034–1037.
• Surani, M. A. H., S. C. Barton and M. L. Norris. 1986. Nuclear transplantation in the mouse: Heritable differences between parental genomes after activation of the embryonic genome. Cell 45: 127–137.
• McGrath, J. and D. Solter. 1984. Completion of mouse embryogenesis requires both the maternal and paternal genome. Cell 37: 179–183.
• Kono, T. and 8 others. 1994. Birth of parthenogenic mice that can develop to adulthood. Nature 428: 860–864.
• Vogel, G. 2004. Japanese scientists create fatherless mouse. Science 304: 501–503.

I believe I read this somewhere on Wikipedia once too, but I can't remember what page, nor can I find it now. Someguy1221 (talk) 18:47, 12 February 2009 (UTC)

By an odd coincidence, this was mentioned today on the Straight Dope homepage. Here is the column: "Can Two Women Make a Baby". APL (talk) 19:09, 12 February 2009 (UTC)

universe expanding

is it atruth that the fact of universe expanding been known before the modern world, if so please be clear about it , need solid evidence ,, thanks..? —Preceding unsigned comment added by 86.108.60.36 (talk) 18:07, 12 February 2009 (UTC)

Considering that before the "modern world", people mostly thought that the stars were little holes punched in a black piece of paper hung a few hundred feet over their head (or something not unlike that) then it seems unlikely that anything resembling a modern scientific explanation of the universe that involved expansion existed before, say, Edwin Hubble. It may be entirely possible that we can find some ancient mythology which says something that might be like an expanding universe, but this has little correlation to actual scientific thought, and instead has a lot more to do with "making up stuff". Making up stuff was a long-held method of explaining the universe, and unfortunately it has turned out to be somewhat less accurate than the scientific methods of doing so. --Jayron32.talk.contribs 18:13, 12 February 2009 (UTC)

Somebody might have said it for all I know. However there is a great deal of difference between somebody saying something and knowing it. The only possible evidence I can think for it before the last century would be that the night sky is black, see Olbers' paradox. Someone could have formed a rational hypothesis based on that. Look for quoted evidence before agreeing someone knows something. Dmcq (talk) 18:18, 12 February 2009 (UTC)

From the article that Dmcq suggested: Edgar Allan Poe was the first to solve Olbers' paradox when he observed in his essay Eureka: A Prose Poem (1848):

"Were the succession of stars endless, then the background of the sky would present us a uniform luminosity, like that displayed by the Galaxy –since there could be absolutely no point, in all that background, at which would not exist a star. The only mode, therefore, in which, under such a state of affairs, we could comprehend the voids which our telescopes find in innumerable directions, would be by supposing the distance of the invisible background so immense that no ray from it has yet been able to reach us at all."[12]

I don't know if Poe was the first, but I'm surprised that Edgar Allen Poe of all people wrote on the topic. I'll have to look at Eureka: A Prose Poem. He was writing in the industrial revolution period though, so he seems pretty modern.65.190.207.110 (talk) 20:34, 12 February 2009 (UTC)

I must comment on the above parenthetical statement "(or something not unlike that)". Whenever you feel the urge to write something like that please repeat to yourself: "The not unbrown dog ran not unquickly around the not ungreen field." —Preceding unsigned comment added by 82.120.236.246 (talk) 20:46, 12 February 2009 (UTC)

I disagree. Litotes is an ancient and honored rhetorical figure, not without appropriate uses. Arbitrarily banning it is not harmless. --Trovatore (talk) 21:44, 12 February 2009 (UTC)

I disagree too. "Not unlike" is not equivalent to "like" - it would be if there was a perfect dichotomy between "like" and "unlike", but there isn't. There is a spectrum of likeness, and "not unlike" and "like" cover different (overlapping) parts of that spectrum. --Tango (talk) 22:23, 12 February 2009 (UTC)

It's more subtle than that. The semantics of natural language are not first-order logic, not even with fuzziness added. --Trovatore (talk) 22:33, 12 February 2009 (UTC)

Well, yes, I simplified it to make it possible to explain without writing several essays on the subject. I don't think I over-simplified it - what I said is sufficiently accurate that it does support my conclusion. --Tango (talk) 22:57, 12 February 2009 (UTC)

will .. doing some search i found this strang info ...http://www.metacafe.com/watch/933749//...follow this link ... its confusing ... what did you think...?

I don't see what's confusing. The Qur'an contains an unjustified assertion that happens to be correct. It contains lots of assertions, random chance means some of them are likely to be correct. There is a big difference between making a hypothesis with no justification and making a hypothesis based on significant empirical evidence. The former is not at all interesting. --Tango (talk) 23:13, 12 February 2009 (UTC)

There is a huge gulf between suspecting that something is true and knowing that something is true. We've only known that the universe is expanding since we discovered that galaxies are not stars and that there is 'red-shift' that increases with distance from us. That knowledge can't possibly have existed before we had spectrometers attached to telescopes and before we'd discovered things like quasars and other "cosmic rulers" for estimating distances. So we've only known that the universe is expanding for maybe 70 years. Prior to that, Einstein had math that suggested that the universe ought to be expanding - but he made the fatal mistake of disbelieving the math and sticking an arbitary term into his equations to cancel it out. So even as recently as the 1920's, we definitely didn't know that the universe was expanding. Now - it is perfectly possible that humans 'suspected' or 'guessed' or 'hypothesised' that the universe might be expanding - possibly hundreds or even thousands of years ago - but they most definitely didn't know that it did. There is no way with their technology for them to have measured the red-shift. SteveBaker (talk) 05:04, 13 February 2009 (UTC)

I just had a google on the phrase and this is what itcame up with at the top [13] It looks like it is a recent translation to be in line with science but previous translators haven't said anything like it. So, as the MythBusters say, Busted. Dmcq (talk) 13:16, 13 February 2009 (UTC)

will my clothes rot / otherwise become damaged if I leave them unwashed for a few weeks?

If I leave normal B.O. etc dirty laundry unwashed for a few weeks will it rot / become damaged in any way etc - or will the first wash (with a quality detergent) return it to the same state it would have been in if I'd have washed it just 2 days later. I'm talking about just normal laundry from being worn/in contact with body, no special stains. Thanks. —Preceding unsigned comment added by 82.120.236.246 (talk) 20:51, 12 February 2009 (UTC)

Never tried that :) but I would not be surprised if some kind of mold (fungus) would proliferate and damage the fabric irreversibly. So don't do it. On a side note, people believed for a relatively long time in the Spontaneous Generation of mice in piles of dirty laundry. That belief was eventually proved incorrect ;) --Dr Dima (talk) 21:36, 12 February 2009 (UTC)

As long as it isn't damp, I expect it would be fine. It might start to smell a bit because of the growth of bacteria, but it should be fine after being washed (maybe on a slightly higher temperature that usual). I've certainly left clothes unwashed for pretty long periods of time with no problems (there's always something at the bottom of the laundry basket that won't fit in the machine, and since laundry baskets are first-in-last-out, it tends to be the same thing! There's also the clothes you wear the day before going away for a long time - there's not much you can do about them. They've always been fine when I get home.). --Tango (talk) 21:44, 12 February 2009 (UTC)

My (scientifically nonrigorous) experience is that it can be more difficult to remove the odor after it has "set in"; several washings may be required. This is particularly true of athletic clothing, in the sense that such a shirt may smell OK right out of the dryer, but as soon as you start to sweat in it, you'll be able to tell it's not a new shirt.

But "rotting" -- no, I don't think so. Not unless you don't let the clothing dry thoroughly. --Trovatore (talk) 21:50, 12 February 2009 (UTC)

If you store them in a tight wad or plastic bag and have high air humidity they can get a bit moldy. Towels and bathrobes tossed on top can have the same effect. Spots, sweat and deodorant stains are a lot harder to get out the longer they sit there. They can be undetectable to begin with and then turn yellow or brown with time. Damage to your clothes then happens as collateral damage in the course of the chemical warfare undertaken to combat those set in stains. Food stains can attract bugs that then will find the cotton of your T-shirt quite palatable as well. Elastic waistbands and the like can become brittle (not sure due to what process, maybe deodorant residue or some acids in sweat break the cross-links). Colored clothes that are left out in a place where they are exposed to sunshine can develop faded areas. (E.g. T-shirt sleeve sticking our of the laundry basket.) Beach- and swimwear should be rinsed and dried promptly because suntan lotion will create permanent stains and salt or chlorine residue will damage clothes. Cheap jeans buttons or grommets can cause rust stains if they sit in the same position for a while and moisture gets trapped there. BTW: A "fridge pack" of baking soda tossed in the laundry basket can help prevent damage/stains caused by moisture. All of the above is the result of repeated OR experimentation. (Contract workers often stay away from their primary residence for extended periods. Catching up on the laundry beforehand isn't always an option. :-) 76.97.245.5 (talk) 23:41, 12 February 2009 (UTC)

I would expect no major problems after one or two weeks, but I'm not sure about periods longer than that. Even if clothes are damp, they usually dry out after about half a week indoors. As for rotting, clothes made from materials such as cotton would be more suceptible than polyester or nylon. I find that paper starts to rot after about one or two years, for comparison. Bacteria may start to grow on the BO, however, but they should be able to be washed off, and you could hand-wash it with hot water and soap if nessecary. If your clothes are clean but used, they should be OK for a couple of months. ~AH1^(TCU) 22:38, 13 February 2009 (UTC)

Uranus and Saturn's gravity

Why is Uranus' gravity usually less than Earth. Uranus and Saturn is much larger than Earth, so it's gravity should be like 1.05 and 1.20 at least. Some source said Saturn's gravity is 0.9 and Uranus is 0.85. And also how we know Uranus and Neptune have no solid surface when Voyager only look at it's clouds? Did Voyagers look at the bottom of the clouds?--216.100.95.90 (talk) 20:58, 12 February 2009 (UTC)

Gravity is about more than size; the strength of a planet's gravity is related both to the mass of the planet and the distance from the planet's centre. Uranus and Saturn are more massive than Earth but also have much greater diameters, and so are significantly less dense. - Eron^Talk 21:21, 12 February 2009 (UTC)

They'll have something solid if you go down far enough (or, at least, not gas any more). Uranus and Neptune may well have something not far off simple rock at their cores. Jupiter (and maybe Saturn) has such high temperatures and pressures once you go down far enough that you get weird stuff like metallic hydrogen, rather than a conventional solid. --Tango (talk) 21:32, 12 February 2009 (UTC)

Apparent surface gravity varies due to quite a few factors:

1) The mass and density of the planet are both important, as noted previously.

2) Since the material directly underfoot has a far greater effect than mass far away, local density variations are quite important, too.

3) The planet's rotation can cause an apparent reduction in the force of gravity (as opposed to an actual reduction). This will be strongest along the equator and have no effect at the poles.

4) The "atmosphere" on gas giants can be thick and dense enough to exert a significant upward gravitational pull, which must be subtracted from the normal gravitational pull to figure out the net amount. This would be much more of a factor if the "surface" on which the observer stands is solid rock underneath a liquid "ocean". StuRat (talk) 21:54, 12 February 2009 (UTC)

Assuming (as is fairly reasonable) that the atmosphere/ocean is distributed approximately spherically symmetrically, there will be no significant upward pull from it, by the shell theorem. Algebraist 22:05, 12 February 2009 (UTC)

Stop. The first question includes incorrect "information." Saturn and Uranus' gravities (ie masses) are not less than Earth's. The questiontioner should go back and check his source. Perhaps he is conflating "density" with "gravity." B00P (talk) 22:11, 12 February 2009 (UTC)

Our articles disagree with you (of course the exact value depends on where you arbitrarily declare to be the 'surface'). What's your source? Algebraist 22:15, 12 February 2009 (UTC)

Gravity does not mean the same as mass, your "ie" is wrong. Gravity is proportional to mass, but it also has other factors involved. --Tango (talk) 22:18, 12 February 2009 (UTC)

Actually, from sources and studies, Urnaus and Neptune is consider to have no solid surface level. all Jupiter, Saturn, Urnaus, and Neptune will have something solid if we go deep enough (but human will be crushed and cooked before they get to ano=ything solid.) My question is how will we know Uranus and Neptune have no solid surface between atmosphere and mantle, when they only see the clouds. I thought spacecrafts have seen somethig deeper than cloud decks of Jupiter and Saturn. From Urnausn and Neptune's mantle they call it ice, but it is superheated stuff to kill humans, when diamond decompose-this one I have no idea.--69.226.42.163 (talk) 23:38, 12 February 2009 (UTC)

We know their mass, size and some basic information about their composition (from spectral analysis and the like). Combining that with what we know of the laws of physics, we can make a pretty good guess about what's going on inside. --Tango (talk) 00:38, 13 February 2009 (UTC)

To answer your question of how scientists know Uranus and Neptune have no solid surface, they are not at all dense enough to be made out of rock. Density is a single calculation away once the mass and diameter are known. The mass of a planet can be easily determined from the strength of its gravity; the faster it makes the moons around it orbit, the more massive it must be. Diameter is directly related to how big (how many degrees) the planet appears to be at a certain distance. --Bowlhover (talk) 23:46, 12 February 2009 (UTC)

So the "Equatorial surface gravity" figures given in our articles (0.914g for Saturn; 0.886g for Uranus) are not really "surface" gravity at all, but are actually gravity at the visible top of the cloud deck. And in Saturn's case you have to make quite a hefty correction (about 15%) to account for Saturn's rapid rate of rotation - without this, the "surface" gravity would be 1.06g. So a more accurate description of these figures is "apparent equatorial gravity when co-rotating with visible surface of cloud deck". Gandalf61 (talk) 11:29, 13 February 2009 (UTC)

You should keep in mind that both Saturn and Uranus are less dense than Jupiter or Neptune. The density, along with the overall mass, contributes to the overall "surface" gravity. This exlains why Uranus's gravity is lower than Earth's, which Neptune's is just slightly higher. —Preceding unsigned comment added by AstroHurricane001 (talk • contribs)

what is Steve Baker's IQ? Why does he know so much?

What is Steve Baker's IQ? Why does he know so much? Does he know what he knows before answering the question, or do he do just-in-time (JIT) research, where he learns all that he says just prior to answering the question, through the Internet, etc? Is he a single person, or a syndicate?

Thank you! —Preceding unsigned comment added by 82.120.236.246 (talk) 21:24, 12 February 2009 (UTC)

If you want to know about Steve Baker, you should ask him. The rest of us can't really help you here. Algebraist 21:26, 12 February 2009 (UTC)

Steve Baker's IQ is as meaningless as anyone else's. I'm reasonably sure he's a single person (his writing style is definitely consistent, anyway). As for how he knows so much, you'll have to ask him - I suspect he answers questions the same way the rest of us do, a combination of personal knowledge and good research skills. But be careful - you don't want to inflate his ego too much or I'll have to go through the archives making a list of all his mistakes in order to bring him back down to Earth, and I don't really have time for that... --Tango (talk) 21:32, 12 February 2009 (UTC)

Aren't you tempting people to inflate his ego just to witness the drama? --99.237.96.81 (talk) 15:29, 13 February 2009 (UTC)

Tango: by single person did you intend unmarried or an individual? hydnjo talk 23:25, 12 February 2009 (UTC)

Individual. I try and use the same language as the person I'm talking to. The OP used "single person" to mean individual (as opposed to a syndicate), so I used the same phrase. Why would I have been discussing his marital status? --Tango (talk) 00:35, 13 February 2009 (UTC)

Dunno, just clarifying. I certainly agree that there are no signs that SB is a role account - none. hydnjo talk 00:49, 13 February 2009 (UTC)

Go and learn, and you will hopefully become as smart as Steve :) --Dr Dima (talk) 21:40, 12 February 2009 (UTC)

You don't have to research too hard to discover Steve's marital status [14]. He's a diamond geezer with platinum humour. He can sting you, teach you and make you laugh in one line. Whether he can drive well, Hmm...? Hope he's recovered. ;-)) Richard Avery (talk) 23:10, 12 February 2009 (UTC)

Hey...HEY....I was STATIONARY - my driving skills were irrelevant! SteveBaker (talk) 04:42, 13 February 2009 (UTC)

But you were stationary in the wrong place… Algebraist 18:15, 13 February 2009 (UTC)

IQ != knowledge--GreenSpigot (talk) 01:02, 13 February 2009 (UTC)

Of course, there does exist the possibility that Steve is actually a prodigious savant, where he knows and remembers all but his IQ is actually really low. Not that I think that's the case, just to outline the noncorrelation between IQ and knowledge/memory. bibliomaniac15 01:32, 13 February 2009 (UTC)

You can tell the he understands what he's talking about. You can easily tell when someone is reciting from memory without any understanding. --Tango (talk) 13:10, 13 February 2009 (UTC)

• This doens't matter if he is single or couple. These kinds of questions you do not ask users, it's personal (unless he writes it on user page). Doing so is stalking. I think he is extraordinarly intelligent, he is domineer on science. most of time, I don't even understand his post-I wish my IQ is like him, but to be like him, we have to have strong math, algebra and english art skills.--69.226.42.163 (talk) 04:04, 13 February 2009 (UTC)

• Don't be absurd. There's nothing wrong per se with asking users personal questions. If they don't want to tell you then they won't. Algebraist 18:15, 13 February 2009 (UTC)

Oh - Jeez - this is so embarrassing...but I have to be self-deprecating or Tango will go and find all of my many serious screw-ups! So this is "original research" of the worst kind!

My IQ is pretty good (I forget the score I got - but it's Mensa-level - which isn't saying that much actually) - but that's not it. IQ test scores only tell you how good you are at IQ tests.

I guess I have to reveal the trick to answering RD questions.

I read widely and I've been doing that since I was a kid and now I'm 53 years old. You should just look at the pile of books at my bedside from last month. When you do that - you end up knowing a little about an awful lot of subjects! Even more than that - from the relatively early days of Wikipedia back in 2004-ish, I decided to hit "Random article" three times every night before bedtime and NO MATTER WHAT to read every article that comes up (There are an AWFUL lot of Japanese railway stations!). So after four years, I've probably hit 'random article' and read about 1000 articles per year - maybe 4000 to 5000 articles. (And of course - sometimes I hit an interesting article and end up reading a lot of things leading from there - so probably the total number I've read is more like 15,000 to 20,000 - which is not a significant fraction of 'everything' - but it's a very BROAD look at everything we have here.

Answering questions (and reading answers) from the RD tends to make you read more deeply into areas where people commonly ask questions. Working on the RD also gives you another vital skill - the ability to Google. Quite often, knowing a little about a subject is just enough to let you find a better set of search terms than our original posters are able to do.

Combine that with the whole of human knowledge in an easily searchable form (Wikipedia and the Internet) and you can answer a broad range of questions because your little-but-wide knowledge allows you to at least know what to look for.

But I also have Asperger's syndrome. One attribute of us 'aspies' is that we are easily obsessed into doing deep-deep-DEEP research into a specific narrow area. If you are an OLD aspie (as I am) then you've probably gone through these obsessive research phases a couple of times a year since childhood. So there are probably 40 or 50 very narrow subjects that I'm truly a deep expert at. Computer graphics, Mini cars, puppetry, Lego, Software, Light and color perception...these things have been obsessions of mine for a long time - and every six months, there is a new one. Right now, I'm obsessed with tiny computers like the Arduino. Take the uber-obscure car the Mini Moke...it's a varient of the Mini and because I was trying to get the Mini article to front-page featured article status, I needed to understand the Mini Moke...but our article was just a tiny stub. So in order to write my Wikipedia article about the Moke, I bought and read every single book, repair manual, old magazine (thank-you eBay) and talked to every Moke owner I could find...now I'm something of a world authority on the car - although I've never actually owned or even driven one!

Nobody "in their right mind" does that...but that's what us Aspies are like...we're "nuts" by normal standards.

This means that on those 30 or 40 subjects I can give a really deep answer - which looks impressive when you happen to hit on one.

Very often, I answer questions by reading the relevent Wikipedia article - and merely distill and reword what it says to make it more comprehensible to our OP. You'll also notice that very often my reply is one of the last - and that's because I'm reading articles and Googling stuff that previous respondents actually already knew about...which is "cheating" - but useful to our OP's (I hope).

Being an Aspie means that I strongly dislike meeting people and going places - and the online 'world' is much more comfortable for me - so I spend a lot of time 'here'...that helps too.

So - there you go. No magic...just a thirst for knowledge and LOT of reading over a LOT of years.

SteveBaker (talk) 04:42, 13 February 2009 (UTC)

Exits stage left to loud applause. 86.4.190.210 (talk) 07:17, 13 February 2009 (UTC)

Being 53 is cheating... How am I supposed to stand a chance having only had 21 years in which to learn useless information? It's not fair... --Tango (talk) 12:10, 13 February 2009 (UTC)

Just look forward to how much you'll know at 53, what with direct brain-Wikipedia uplinks and such. Algebraist 12:45, 13 February 2009 (UTC)

Problem is, I'm an early adopter, so I'll probably get my brain fried with the beta version. I won't know anything by age 53! --Tango (talk) 13:09, 13 February 2009 (UTC)

Hey, I don't know if this is tiny enough for you, but there's an outstanding issue on the PSP article of whether the PSP's CPU is a 64-bit R4000 or a 32-bit 4K. I'm a software guy and not particularly knowledgable about non-PC hardware. The applicable reliable sources (this is a gaming system, remember) are reporting that it is a 32-bit architecture but an editor who is apparently knowledgable in this field is claiming that the reliable sources are wrong and that they have confused the difference between R4000 and 4K. This has led to two questions. 1) Are the reliable sources wrong? 2) If so, what do we do about it since Wikipedia's policy is about verifiability, not truth. The discussion is here: [15] A Quest For Knowledge (talk) 14:22, 13 February 2009 (UTC)

Maybe Steve has a photographic memory – GlowWorm —Preceding unsigned comment added by 98.17.32.201 (talk) 18:06, 13 February 2009 (UTC)

If such a thing actually exists... see Eidetic memory#Controversy. --Tango (talk) 18:12, 13 February 2009 (UTC)

See Eidetic Memory#People with eidetic memory. – GlowWorm.

I often remember things from books by associating the factoid with where it is on the page and what the headings and illustrations look like, so I will know that if I find the page with a picture at top-right and a light-purple heading halfway down, two paragraphs below that is the information I'm regurgitating. Maybe that's eidetic memory or maybe not, but it's how my own memory works and does me well. It would probably work for web pages too, but they keep changing the damn things and I can't hold them in my hands and stick my fingers in to flip back and forth. Hopefully they'll have a hand-operated web soon... Franamax (talk) 23:15, 13 February 2009 (UTC)

I do much the same. I can't actually read the text from my visual memory of the page, but I can see the general layout and know almost exactly where on the page the bit of information I want is (I notice this primarily when I can't actually remember the information - it's very frustrating!). --Tango (talk) 12:33, 14 February 2009 (UTC)

The computer manufacturers and software firms like to talk about "the paperless office". But somehow you can't seem to get along without the sheets of paper. So you use a computer where it works best, and paper where it works best. Fortunately, computers can do printouts, but you still need notepads and Post-Its. - GlowWorm.

My estimate of SteveBaker's intelligence and knowledge is approximately this number and I estimate his error rate at roughly four sigma, which is a pretty reasonable process efficiency. I would suggest that next time ToaT updates the statistics on answers, we get a separate section on how often and quickly the SteveBaker answer appears, since it is usually the comprehensive and definitive one. (And regardless of SB's intelligence level, for me they are among the answers I anticipate the most, similar to BenRG's discourses on cosmology, and a few different really good physiology answerers). We really do have some heavy hitters here, to me IQ matters much less than the quality and depth of the answers and the amount I learn by reading them! Steve does need to learn how to pop the clutch and get out of the way of large vehicles in a hurry though. :) Franamax (talk) 23:33, 13 February 2009 (UTC)

I was with you until "Steve does need to learn how to pop the clutch and get out of the way of large vehicles in a hurry though"... I'm afraid I don't follow this metaphor.. :( —Preceding unsigned comment added by 82.120.236.246 (talk) 02:18, 14 February 2009 (UTC)

It's not a metaphor. I was in a pretty nasty car wreck on sunday - rear-ended by a HUGE pickup truck...and indeed if I had teh wikkid drivin' skillz, I could have slipped the tranny into 1st, popped the clutch and redlined my way to safety. SteveBaker (talk) 04:23, 14 February 2009 (UTC)

We'll just ask JPL to send over some airbags for you and you'll be fine next time. :-) 76.97.245.5 (talk) 07:28, 14 February 2009 (UTC)

Next time

Steve, recalling a thread from a little while ago, that's another reason why I keep my car in gear with the pedal-brake depressed while stationary on the road - one less thing to do when I decide it's time to get out of the way, I just step on the gas and drop out the clutch. Luckily I've only had to use that technique when I see emergency vehicles approaching from behind, so far knock on wood. Now, Texas driving stories, and a horrific accident I witnessed and tried-but-not-rescued in Dallas, involving a large pickup truck - good to have you posting just like normal, brain apparently intact. And BTW, did your airbag deploy? (And yeah, it's Texas, I'm betting that you're fully liable for getting in the way of the 4 other cars whose forward progress you impeded - keep it in gear next time and bolt when you see it coming in your mirrors, that's what a manual tranny is made for!) Franamax (talk) 07:57, 14 February 2009 (UTC)

February 13

Post-It Note adhesive Thickness

I just got back from a trade show, and one of the bits 'o swag was a "brick" of Post-It Notes, about 2-3/4 inch (70cm) thick.

All the notes have the adhesive on one edge. It's a continuous strip of adhesive on each sheet, about 3/4 inch wide, and the paper is about 2-3/4 x 2-3/4 inch, making the brick almost a perfect cube.

I would have expected the thickness of the adhesive to be obvious along the adheded (is that a word?) edge. However, the cube looked flat. So I got out my Mitutoyo CD-6"P calipers, and took some measurements. 10 sheets measured .0415", making each sheet 4.15 mils thick. The thickness of the brick was 2.7815", meaning that (rounding off here) there were 670 sheets in the brick.

Now I admit that the caliper measurements aren't perfectly repeatable, since I can't calibrate the force I use use when making a measurement. But I was unable to detect any difference between the thickness of the adheded (there it is again) edge, and the plain edge.

If we assume that the thickness of the adhesive was a millionth of an inch, that would make a difference of .67 mils over the thickness of the brick, which would be just detectable using this crude instrument.

I find it hard to believe that such a thin coating is possible, but I hold the evidence in my hand. I checked the Wikipedia article and Googled around trying to find out the thickness of the adhesive layer with no luck. Any of y'all have an idea where I can get that information? Thanks. Bunthorne (talk) 00:03, 13 February 2009 (UTC)

oh my god do I envy the kind of time you seem to have!!! 82.120.236.246 (talk) 00:20, 13 February 2009 (UTC)

Well, you know, I don't think this took him more than five minutes with the calipers. -- Captain Disdain (talk) 02:37, 13 February 2009 (UTC)

and writing the above? and rumination ? —Preceding unsigned comment added by 82.120.236.246 (talk) 03:53, 13 February 2009 (UTC)

You're right, it was a downright Herculean effort. How did he find the time?! -- Captain Disdain (talk) 08:56, 13 February 2009 (UTC)

It helps to schedule some ruminatin' time every day. (Read, 'rite, ruminate!) —Tamfang (talk) 02:41, 21 February 2009 (UTC)

Once you start looking at scales of a millionth of an inch, the surface of a piece of paper is anything but flat. --Carnildo (talk) 01:44, 13 February 2009 (UTC)

Does the micro-weight of the sticky area vs non-sticky come into it? Julia Rossi (talk) 01:58, 13 February 2009 (UTC)

Micro weight maybe not, but macro weight they flatten the block under while producing (cutting) it. You can buy this Postit type adhesive in a spray can. Other than glue or the sticky stuff on the back of Duct tape, this type of adhesive doesn't add much if any bulk. The material will try to "even out" when pressed and so the fibers sticking out of the non adhesive part will not be depressed as much by comparison as the part with the sticky layers. 76.97.245.5 (talk) 04:09, 13 February 2009 (UTC)

Here's a side issue on this topic. The chemist at 3M who invented the Post-It adhesive was trying to develop a powerful new glue. When he came up with a weak adhesive, his cohorts laughed at him and made him the butt of jokes. However, he had the last laugh. – GlowWorm —Preceding unsigned comment added by 98.17.32.201 (talk) 18:17, 13 February 2009 (UTC)

It's interesting to note that the post-it 'brick' that I have has alternate sheets glued at alternate ends to form a 'zig zag' of sheets. I wonder whether they did that specifically to circumvent the theoretical difficulty that our OP mentions when (possibly) using less absorbant paper or something? SteveBaker (talk) 21:20, 13 February 2009 (UTC)

The alternating post-it brick is used for a post-it dispenser. If all the sheets are glued on the same side, when you pull one out the top, it will lift the whole brick, come loose, and then you'll have to hand-feed the next sheet through the slot on top. If they alternate, pulling one will lift the next sheet through the slot at the top before separating from it. -- kainaw™ 21:27, 13 February 2009 (UTC)

It's probable that the adhesive and paper are sufficiently compressible so that the "adheded" edge is of the same thickness as the uncompressed, paper-only parts of the block. As the OP mentions, "compression" force resulted in a slightly non-repeatable measurement by calipers. Though it's hard to imagine, the individual sheet of paper probably squeezes into a perfect little rectangular prism of fairly uniform thickness (height?), even though there is more material on the "adheded" edge. (Alternatively, there could be slightly thinner paper on the "adheded" side, but this would be really hard to manufacture).

Now, to verify my original assumption, you could probably perform an experiment to slice the cube into only-paper and paper-plus-adhesive blocks. Measure the mass of these, and calculate the excess mass which must be due to the adhesive. I think that there will be a serious signal-to-noise problem, bordering on the un-measurable, but for the sake of science... we must try. Nimur (talk) 18:51, 14 February 2009 (UTC)

I'd love to try Nimur's idea, which borders on genius, but the only instrument I have to measure mass is a bathroom scale. I could probably weigh myself holding the subjects, but I'm afraid the closest reliable reading is +/- 2 pounds, so I'd have to get either a somewhat better scale, or a massive number of bricks. Thanks for the ideas. Bunthorne (talk) 05:24, 15 February 2009 (UTC)

It's not the language desk, but I believe the correct word is adhered. My money is on the manufacturing process. Compressing the sticky edge with an industrial machine in a way that can't be matched by your measuring caliper. -- MacAddct1984 ^{(talk &#149; contribs)} 21:12, 17 February 2009 (UTC)

If counting thru a 2 inch brick of post-it notes takes time on one's hands, look at some of the post-it animations on www.eepybird.com and imagine what that must have taken. 207.241.239.70 (talk) 08:14, 18 February 2009 (UTC)

Sorry if it sounds like I'm nitpicking, but 2 3/4 inches does NOT equal 70 cm . . . maybe 70 mm??

Tesla, Edison, Einstein and Asperger syndrome.

Just out of curiosity, did Tesla, Edison and Einstein all had Asperger syndrome? I read that somewhere and I was wondering if it's true. Thanks in advance. ― Ann _{( user | talk )} 00:41, 13 February 2009 (UTC)

Well, Hans Asperger first described what has since become known as Asperger syndrome in 1944, a year after Tesla died and 13 years after Edison died. Einstein died 11 years after that first description, but still well before the term "Asperger syndrome" was first popularised in 1981, and even longer before it become a common diagnosis. So, anyone saying any of them had Asperger syndrome is making, at best, an educated guess based on historical accounts. To get any kind of reliable diagnosis requires an intentional assessment of a wide variety of qualities. --Tango (talk) 00:52, 13 February 2009 (UTC)

I've read a couple of biographies of Einstein and he does have a lot of the attributes of an Asperger sufferer. Comparing his story to the criteria in DSM IV, he pretty clearly could be diagnosed that way on the basis of the information in his bio's. I don't know enough about Edison or Tesla. It wouldn't surprise me if Tesla was and Edison wasn't...but I really don't have enough information. SteveBaker (talk) 03:55, 13 February 2009 (UTC)

It's tough to apply diagnoses backwards in time—heck, it's not even easy to apply them to real, living people! Einstein's a tough nut to crack in particular because everyone sees him as what they want to see him as... --98.217.14.211 (talk) 16:52, 13 February 2009 (UTC)

I agree. But from the DSM IV description, I think Einstein can easily be shown to have had:

• A2) Failure to develop peer relationships appropriate to developmental level.
• A3) Lack of social or emotional reciprocity.
• B1) Encompassing preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in intensity or focus.
• C) Significant impairment in social, occupational or other important areas of functioning.
• D) No delay in aquisition of language as a child.
• E) No delay in cognitive development.
• F) Criteria for Pervasive Developmental Disorder or Schizophrenia NOT present.

A2—the man had plenty of friends, lovers, etc., throughout his life. A3—the man was a life-long activist for the suffering, wrote passionately on the subject, got denounced by the Nazis and a 1,000 page FBI file for his troubles. B1—how exactly where his patterns of interest restricted? Patent examiner, theoretical physicist, social activist, violinist, writer, lecturer, etc.? C—what was so impaired? Are we just using the "Einstein was a weirdo" stereotype here, or are we basing this on his actual life and interactions? D,E,F—a lack of something abnormal seems hardly relevant here?

As with anybody as "iconic" as Einstein there is an elaborate mythology and stereotypes of his behavior that have percolated throughout culture. The idea that Einstein had his "head in the clouds" and thought of nothing but physics is plainly false (it is easy enough to see if one reads his collected essays—the man had tons of interests, was extremely cultured, was very "down to earth" on a wide variety of things).

My point in being contrarian here is not to make strong statements about Einstein, but to point out that each of those criteria are extremely subjective. Even in a living, breathing, non-famous person they can be quite ambiguous in everything but the outlier, extreme cases. With a historical figure around which an expansive mythology has been built—one that is demonstrably not even close to being accurate, like the one of Einstein as being a spaced out mystic old grandpa—it seems rather impossible to me to make a retrospective analyses unless of course they are one of the outlier cases (and Einstein doesn't seem to be one of those). For example, the fact that Einstein was a subversive civil rights activist and an unapologetic socialist is something that has long been underemphasized, as it for decades made people politically uncomfortable (even today, while his civil rights work is now much more paid attention to, his socialism is downplayed, though it is clear it was important to him for most of his life). He's not as simple as the caricature of him makes out. --98.217.14.211 (talk) 19:23, 13 February 2009 (UTC)

Where do people get this idea that Einstein had Asperger's? Never mind a detailed look through a list of symptoms, who would ever come up with this idea in the first place? It seems to be based on nothing more than the idea that smart people must be "different from the rest of us". People seem shocked that a smart person might go to clubs or be a surfer or womanize. The perception of intelligence as a kind of mental abnormality is a threat to the future of the human race. We should be fighting these nonsense diagnoses, not entertaining them. -- BenRG (talk) 13:56, 14 February 2009 (UTC)

Indeed. Asperger's is a very fashionable diagnosis at the moment, and it's common for people (not doctors, so much, they know a little better) to diagnose every smart person that has difficulty making friends as having it. I'm a smart person that has difficulty making friends, I do not have Asperger's (I was tested for it). I put my difficulty making friends down to two things, difficulty finding people I have something in common with (that gotten easier as I've moved up through education, there are plenty of smart people around once you get to Uni), and the fact that I was bullied in school because of my intelligence and as a result I tend to be quite closed off emotionally (a couple of pints helps with that!). I expect those reasons apply to a large number of smart people. (I should make it clear, I do have plenty of friends, it's just difficult to form that initial bond.) --Tango (talk) 14:20, 14 February 2009 (UTC)

The initial bond thing is key here. If someone struggles to make friends, but once made, can chat away easily with them, then the person probably has trust issues _{(awaits big pharma companies to start pushing oxytocin reuptake inhibitors or the like).} If the person just cannot empathise with people and doesn't chat to those they know well, then it is more likely Asperger's. --Mark PEA (talk) 12:40, 15 February 2009 (UTC)

• I have never seen strong indications that Thomas Edison had Asperger's syndrome. He was a personable and charismatic leader of a research group, able to impress financiers, writers and the general public. He always had a group of close friends, contra-indicating Asperger's. He could be quite manipulative, indicating an understanding of the inner thoughts of supporters and competitors. He liked to experiment as a child with chemicals, but was not the overly verbal "little professor." An Aspie would not have been able to set up a business selling treats and self-published newspapers on a train as did the young Edison. "The wizard who spat on the floor" was one characterization.He was a deaf gadgeteer and his one great emphasis in life was inventing for the sake of inventing. Tesla, on the other hand seemed obsessive-compulsive and psychotic/delusional more than Aspie. Einstein was pretty odd in his lack of interpersonal loyalty towards spouse or offspring,and had some oddities in his childhood, but I have no strong opinion as to whether he had Asperger's. It does seem a bit grasping for Aspies or their family members to try and claim historical figures as fellow non-neurotypicals. Edison (talk) 02:08, 17 February 2009 (UTC)

comb attracting little pieces of paper

Classic physics example: A comb that's been rubbed can attract little pieces of paper. The explanation I've read is that the comb becomes charged, and it causes the neutral paper's atoms to be polarized. The positive ends of the atoms in the paper are attracted to the negatively charged comb. But that doesn't seem to make sense, because the negative ends of the atoms would equally be repelled by the paper. Since there are equal #s of negative and positive on the paper, shouldn't there be zero movement (no attraction/repulsion)? Also, the paper sometimes are repelled? Why? Thanks in advance. 128.163.224.222 (talk) 03:38, 13 February 2009 (UTC)

I can't really recommend our pages Static electricity and Triboelectric effect. The simple Wikipedua version is shorter, but I can't say I find it more enlightening [16]. Nevertheless you might find them useful. 76.97.245.5 (talk) 04:25, 13 February 2009 (UTC)

Similarly to the recent question about Saturn's gravity, the answer lies in the fact that the electric charge is only one of the factors governing the strength of the electic force. The other factor is the distance. As the negatively charged comb atracts the positive charges in the paper and repells the negative ones, those charges separate and the positive charges come closer to the comb. That way the atractive force becomes stronger than the repulsive force and the paper ends up being atracted. Dauto (talk) 05:52, 13 February 2009 (UTC)

I think something like that would be good on our pages. Would s.o. have the time to write it up? 76.97.245.5 (talk) 08:29, 13 February 2009 (UTC)

That doesn't make sense to me. If the comb attracts the positives, it should repel the negatives an equal amount for a net of zero. I thought that the presence of the electrons on the comb (or absence, I don't know which) would make it have a net charge with respect to, well, the rest of the universe, basically. Let's say the comb has excess electrons (it doesn't matter); the paper bits would have a positive charge with respect to the comb and would be attracted. A pile of lead shot would be equally attracted to the comb but would be too heavy to be lifted or even moved by the feeble forces involved. --Milkbreath (talk) 13:21, 13 February 2009 (UTC)

If the comb has excess electrons, they will repel the electrons (it's the electrons that are mobile) in each bit of paper. So the electron cloud around each atomic nucleus in the paper is very slightly displaced - it is no longer centred on the nucleus. The net effect over the whole piece of paper is that there is a slight deficiency of electrons nearest the comb and a slight excess furthest away. Force dimishes as the square of the distance, so the attraction of the positive end of the dipole is greater than the repulsion of the negative end. Philip Trueman (talk) 13:31, 13 February 2009 (UTC)

If I remember correctly, it's called electrostatic induction. (Just giving a name to Philip's explanation) --Bennybp (talk) 13:57, 13 February 2009 (UTC)

Further proof that I'm seriously stupid. If the comb is pushing the electrons in the paper away, that force is pushing the paper away, or those electrons would go right back where they were. The reason that that force doesn't make the paper move away is that the now-exposed positive charges attract the comb, for a net force of zero. I must be thick as a brick. --Milkbreath (talk) 14:31, 13 February 2009 (UTC)

The comb will now actually attract the paper, since now the positive charge is closer to the comb, and the negative charge is farther away (Coulomb's Law). I've never seen it done with a comb and paper, but balloons (one charged will actually attract a neutral one). --Bennybp (talk) 16:22, 13 February 2009 (UTC)

Paper is (very) slightly conductive. When the comb becomes charged, the difference in charge between it and the bit of paper causes the paper to be attracted to the comb. When the charge on the paper becomes equal to the charge on the comb, it is strongly repelled. Try this with a bit od cereal(slightly conductive) suspended from a silk or polyester thread(insulator), and a rubber (insulator) comb or PVC pipe rubbed with wool or silk or whatever. The bit of cereal will be strongly attracted to the comb until it gains charge, then strongly repelled. It is not necessarily a matter of polarization. It is a matter of different charges attracting, and transfer of charge. For a polarization demo, bring the charged comb near, but not touching, an insulated piece of metal. The far end of the metal object will then repel a Cheerio charged from the same comb. This is just stuff Steven Gray discovered in the early 18th century. Electroscopes work nicely by induction.Edison (talk) 02:17, 17 February 2009 (UTC)

Syndrome or Disorder?

In order to respond to our previous question about Asperger syndrome and Einstein - I looked up the precise symptoms in the 'DSM IV' (which is the 'bible' of psychiatric diagnosis).

Why is it that DSM IV describes Asperger's as "Asperger's Disorder" and not "Asperger's Syndrome" as everyone else seems to do? Is there some important difference between a "Disorder" and a "Syndrome" in psych terminology?

SteveBaker (talk) 04:01, 13 February 2009 (UTC)

In technical discussions, a "disorder" or "disease" refers to the underlying condition or malfunction, while a "syndrome" refers to a collection of co-occurring symptoms or signs. A syndrome need not have unique cause, as the same constellation of symptoms might be caused in multiple different ways. In practice, the distinction may be abused or ignored, especially since many syndromes actually do only point to one unique cause. Dragons flight (talk) 04:16, 13 February 2009 (UTC)

So DSM is saying that Asperger's has a single underlying cause? Interesting. SteveBaker (talk) 04:50, 13 February 2009 (UTC)

Not quite, it's thought to have seveal underlying causes. We're just not entirely sure what they are yet, most likely genetics. —Cyclonenim (talk · contribs · email) 07:39, 13 February 2009 (UTC)

Well, that's what I thought - so back to the original question: Why 'disorder' and not 'syndrome'? In fact - a quick skim of the DSM IV index suggests that they never call anything a 'syndrome'. On the other hand we have 'AIDS' which is a syndrome (that's what the 'S' stands for). SteveBaker (talk) 08:05, 13 February 2009 (UTC)

I was doing a project for a client that had me read up on a medical topic. I then started work on a related wikipedia page and after a while was happy if I had a term where there were not at least 2 different versions describing the same thing with factions warring whose term was the better one. (First prize went to 5 varieties for one item.) Mental disorder and Classification of mental disorders say there are two accepted systems ICD and DSM. So maybe they are using different terms to reflect different views. Or they're just defending their turf. 76.97.245.5 (talk) 08:47, 13 February 2009 (UTC)

There's a desire in the community at large to "de-perjorify" language in an imprecise way. The word "disorder" implies a negative thing, that there is a normal (i.e. order) way to be, and that if you have a condition, that condition represents a "dis"-order, i.e. not normal, i.e. you are broken. Over time, there has been a trend in society to change the terms to remove distinctions that imply "brokenness" or "less than normalcy" for all sorts of conditions. Consider the spectrum of terms: mentally retarded-slow-mentally handicapped-mentally challenged-mentally different-exceptional. Over the past 30 years or so, these terms have been used to describe the exact same set of conditions in an individual. Look at the early end of the spectrum compared to the modern term, "exceptional". Exceptional even sounds like its a benefit. Does little Joey have a learning disability? No, he's "exceptional". Same deal with disorder vs. syndrome. A disorder implies that something is broken that requires modification in order to work. A syndrome merely sounds like a set of differences that requires no intervention. We need to fix a disorder. You need to learn to live with a syndrome. The medical professionals who wrote the DSM IV sound like they aren't necessarily caving to political pressures to use imprecise or cuddly language. These are real problems, and require real interventions in order to help people cope with them. Asperger's is not like being left handed; it's not a neutral condition with regards to how people interact socially in the world, and it requires serious minded people who are willing to approach it in a way that helps people who have it integrate in the world in a meaningful way. Changing its name does not change the need to deal with it properly. --Jayron32.talk.contribs 17:24, 13 February 2009 (UTC)

Hmmm. Somehow I doubt that all (or even most) people with Asperger's would agree that their condition is something that "needs to be fixed". Gandalf61 (talk)

Indeed no! I'd be violently opposed to anyone trying to 'fix' my Asperger's - for me, the benefits outweigh the losses. Not all aspies feel that way though. I wouldn't object to 'disorder' though - there is definitely something wrong with my brain - it's just that the consequences of that 'wrongness' are a mixed bag of benefits and down-sides. What I would wish for is MUCH earlier detection - and proper training to help aspies know what their limitations are and how to work around them. I didn't find out until maybe 10 years ago - and knowing what I know now, I just cringe at some of the things I totally screwed up as a kid and young adult. SteveBaker (talk) 17:56, 13 February 2009 (UTC)

Is there anybody without a 'disorder' at that rate? Just because a greater percentage of people do a thing doesn't mean it is the better way. For instance it is quite normal to get in a huff when criticized and ignore any practical lessons that there might be. It is quite normal to follow a leader and do what they do even if it is wrong and bad. Yes normal is a whole mixed bag of contrary ways of doing things, social anthropology may be a bit unscientific but appealing to the behaviour of bunches of ape men in caves seems about the best explanation. I wonder though what types of people the future belongs to. Dmcq (talk) 10:06, 14 February 2009 (UTC)

asexual reproduction

is it possible (for women) to reproduce asexually using the power of the mind alone? If so, are there any documented cases? If not, what physical constraints in the human body would prevent this effect? Thank you. —Preceding unsigned comment added by 82.120.236.246 (talk) 05:34, 13 February 2009 (UTC)

Short answer: NO. A woman's body cannot produce the sperm necessary to fertilize one of her eggs in order to create a diploid cell. Other dipoid cells of the woman's body do not have the right genes activated in order to start a new embrio. Dauto (talk) 05:58, 13 February 2009 (UTC)

Not in humans (although I'm not sure if it's technically impossible) and definitely not related to the power of the mind, but see parthenogenesis. Zain Ebrahim (talk) 09:07, 13 February 2009 (UTC)

Also see the section Wikipedia:Reference_desk/Science#Same-sex_gametes_combining_to_form_a_zygote.3F. Mammals take two to tango. Even those genetically modifed mice that let you make a viable embryo out of two eggs doesn't make asexual mammals possible. Someguy1221 (talk) 09:18, 13 February 2009 (UTC)

Fingerprints

i always had doubts about this ..is it an absolute truth that finger prints are unique for each one , isnt been recoreded even for once that two indivisiuals has the same finger print , and when was the first time this finger print thing was mintioned ..??????? —Preceding unsigned comment added by Mjaafreh2008 (talk • contribs) 11:20, 13 February 2009 (UTC)

Have you read Fingerprint#Validity_of_fingerprinting_for_identification? 130.88.151.87 (talk) 11:31, 13 February 2009 (UTC)

It depends on what level of accuracy you look at. Have there ever been two fingerprints from different people which were exactly alike ? Probably not. Have there been two different prints which were close enough to be mistakenly taken to be the same print ? Absolutely. This is especially true if fingerprints are smudged or partial, as they frequently are at crime scenes.

Another factor that comes into play is use of fingerprint databases. Let's say that a match can be found with only a 1 in a million rate of misidentification of the wrong person. If fingerprints are used to compare a crime scene print with a suspect seen leaving the premises around the time of the murder, then it's very unlikely the print will be found to match if it doesn't. So, that's a good usage. But now let's imagine that nobody was seen leaving the scene, and instead they run the print against a database that contains millions of fingerprints. With that 1 in a million failure rate, you'd expect one or more to match, just based on chance. Arresting such a person, based solely on their fingerprint, would not serve justice. Investigating people further who match might make sense, though. If one of them was an acquaintance of the murder victim, and has a record of performing similar murders, then an arrest would make sense. StuRat (talk) 15:52, 13 February 2009 (UTC)

WILL ... mabey op should look in the link he listed beforehttp://www.metacafe.com/watch/98111/miracles_of_the_quran_12/ i dont think this is a coincidence too , dont you think —Preceding unsigned comment added by 94.249.98.74 (talk) 19:36, 13 February 2009 (UTC)

The article cited above on validity and reliability of the method noted that the FBI incorrectly said there was a match between the prints of an innocent man (as later determined) and prints left by a terrorist bomber. The validation of the methodology has apparently been mostly by handwaving assertions rather than scientific and objective testing. Edison (talk) 01:00, 14 February 2009 (UTC)

Note that many of the failings of fingerprints can also apply to DNA testing. That is, while both prints and DNA are supposedly always unique (although, in the case of identical twin DNA, you'd need to look in great detail to find mutations, etc.), they can both still fail to identify, with either false positives or negatives, for similar reasons:

1) Poor quality prints or degraded DNA can both result in people declaring a match, when they really don't have enough data to say with any certainty.

2) Both are subject to simple human error, like accidentally submitting the same sample as if were both prints/DNA samples, resulting in a false match.

3) Both are subject to the expert lying on the stand about there being a match, due to bribes, pressure from the prosecution, threats from the defense, etc. Prints aren't quite as bad, in this respect, though, as jurors are more able to judge for themselves whether a match exists (provided they are actually shown the correct samples). StuRat (talk) 14:46, 14 February 2009 (UTC)

Snowflake symmetry

Why are snowflakes symmetrical? How does one leg know to become exactly like the others? --Milkbreath (talk) 12:04, 13 February 2009 (UTC)

I think the answer (i.e. I read it somewhere once - but here's a link) is that in general they aren't: it's just that the pretty symmetrical ones are those whose photos get into the books. AndrewWTaylor (talk) 13:02, 13 February 2009 (UTC)

Indeed. Our article on snow says "The most common snow particles are visibly irregular, although near-perfect snowflakes may be more common in pictures because they are more visually appealing". Gandalf61 (talk) 13:18, 13 February 2009 (UTC)

I've looked at a lot of snowflakes over the course of a life lived mostly at 40 North. When you do get individual snowflakes, they are quite regular. I don't know what those articles are talking about. But, leaving that aside for the moment, let me rephrase the question: In the not uncommon snowflake that in gross structure is radially symmetrical, what forces are at work in creating the symmetry? How can one leg know what the others are doing, so to speak? --Milkbreath (talk) 13:28, 13 February 2009 (UTC)

See http://www.sciam.com/article.cfm?id=why-are-snowflakes-symmet Cheers.--Fuhghettaboutit (talk) 13:42, 13 February 2009 (UTC)

Good link. So, nobody knows. I can live with that. --Milkbreath (talk) 14:37, 13 February 2009 (UTC)

I don't think there is any mystery here. The six branches of the snow flake presumably grow radially outwards at the same rate, and the length and breadth of side branches or plates depends on the temperature and humidity that the snowflake is experiencing at a given point in time, so it is not surprising if all branches show similar sequences and patterns of side branches. Observer bias then makes us focus on the symmetries and ignore the imperfections. If you look closely at the photographs here or here or even in the iconic Wilson Bentley photographs, you see that the symmetry is far from perfect. Gandalf61 (talk) 15:20, 13 February 2009 (UTC)

I think we know. The core ice crystal is hexagonal - as the crystal is swirled around inside the cloud, it accretes more ice until it becomes too heavy to stay inside the cloud and then falls to earth. In general, whatever humidity/temperature/pressure changes happen to one face of the crystal happen identically to the other five faces - so however one side grows, the other sides tend to grow the exact same way. What makes them slightly asymmetrical is that the conditions may not be PRECISELY the same on all six arms and also, sometimes they are damaged by collisions with other snowflakes. SteveBaker (talk) 15:30, 13 February 2009 (UTC)

(ECx2) They gave a good explanation, the same one I thought of:

1) Different temp/humidity combos result in many different types of branching.

2) Since the conditions are likely to be identical on all sides of the flake, the branching is likely to be the same on all sides.

3) When temp or humidity do change, during snowflake formation, the type of branching changes on all sides of the flake. The result is a complex, yet symmetrical, formation.

4) So, then why are so many not symmetrical ? I suspect that collisions are the main culprit, allowing flakes to break or stick together.

It also seems to me that this is part of a larger question: Why do crystals, under ideal conditions, tend to form symmetrical shapes ? The explanation would be similar to that for snowflakes. StuRat (talk) 15:33, 13 February 2009 (UTC)

Why are snowflakes flat? Most crystals have substantial amounts of material in three dimensions. Does the thickness vary in different snowflakes? Are there bumps or other extrusions on the flatness that vary in size and placement in different snowflakes? If there are bumps, do they form a pattern, perhaps hexagonal? Has anyone photographed, or even examined, snow flakes viewed on edge? – GlowWorm —Preceding unsigned comment added by 98.17.32.201 (talk) 17:08, 13 February 2009 (UTC)

One of the links Gandalf61 posted lists a variety of snowflake types, many of which are far from flat. Depending on the temperature the snowflake forms at, it may grow primarily along the c-axis ("vertical"), and come out as something like a thin needle; or it may grow primarily along the a-axes, and come out flat. Take a look at the morphology diagram here. Also, snowflakes generally don't form at constant humidity and temperature — so for instance if one starts forming at a temperature that drives c-axis growth, then (because of a temperature change) switches to a-axis growth, you'll get something like a capped column. -- Speaker to Lampposts (talk) 08:07, 14 February 2009 (UTC)

I missed that link. I'll order a couple of those books. – GlowWorm. —Preceding unsigned comment added by 98.17.32.201 (talk) 10:16, 14 February 2009 (UTC)

Was Banting really the first to discover insulin?

People in Romania believe otherwise !They say it was Palescu!(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk) 13:22, 13 February 2009 (UTC)

And was it Best or MacLeod who should be credited as his partner in discovery?(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk) 13:24, 13 February 2009 (UTC)

Our article insulin says that Nicolae Paulescu was the first to isolate insulin, both those articles, and the references cited in them, should be of interest to you. DuncanHill (talk) 18:06, 13 February 2009 (UTC)

Freemartin

What does the term freemartin mean relating tocattle prodution and what causes this condition ? —Preceding unsigned comment added by 66.244.104.243 (talk) 16:26, 13 February 2009 (UTC)

Have you found our article freemartin yet? DuncanHill (talk) 18:03, 13 February 2009 (UTC)

Faster-than-light communication idea

I believe physicists that nothing can travel faster than light, c, at 300,000 m/sec. But what nothing actually had to move for something meaningful to be transmitted superluminally?

Here's my idea: (see picture here) A giant rigid cylinder made of super-strong material extends between two points in space that are one light-year apart, A and B. (Disregard the engineering infeasibility, gravitational influence of stars, galaxies, dark matter, etc.) At each end of the light-year long cylinder is a wheel with a peg to turn it. Initially, the peg at A is exactly at A and the peg at B is exactly at B. If I turn the peg from A to A', how long does it take for B to go to B'?

I see two possible outcomes:

1. Holy cow it's the answer to superluminal communication! (unlikely)

2. The rotation from the A end of the cylinder will "travel" across to point B over time, probably taking a little more than a year.

What do you folks think? —Preceding unsigned comment added by Marskid2 (talk • contribs) 16:57, 13 February 2009 (UTC)

Sorry. -- Coneslayer (talk) 17:03, 13 February 2009 (UTC)

(EC with coneslayer. I will assume his answer was similar to this). In any real material (i.e., one made of atoms which obey the laws of physics in this known universe) there is no such thing as a "rigid" cylinder. Rigid is only relative, and at the sizes you describe, there will be some deformation along the rod. When you turn A towards A', the rod in the middle begins to twist torsionally. Think if you had a piece of clay in your hands, and held one end steady while the other end you twisted. The rod will do the same thing. Now, over time, the "twist" will travel down the rod towards B, however this obviously will occur at some rate slower than the speed of light, the movement of A towards A' will not occur at the B side until the "twist" arives there. Thus, the laws of the universe are safe from giant imaginary rods. --Jayron32.talk.contribs 17:12, 13 February 2009 (UTC)

Ah that makes sense now. I definitely didn't realize how big of an assumption "rigid" was. Thanks for the quick answers! =) marskid2 (talk) 17:15, 13 February 2009 (UTC)

To elaborate a bit further: Your rod's stiffness is caused by chemical bonds, i.e. electromagnetic forces. These are communicated via photons. So any disturbance of the rod can at most travel down it at the speed of photons (i.e. the speed of light). --Stephan Schulz (talk) 17:26, 13 February 2009 (UTC)

Is anyone collecting these? In the past few years, I've seen suggestions that we use long ropes, metal bars, crystal rods, long nano-tubes... etc. I'm waiting for "What if we used a really long fish?" -- kainaw™ 19:07, 13 February 2009 (UTC)

We already know the whole idea is fishy, these are just specific variations. DMacks (talk) 19:21, 13 February 2009 (UTC)

Here [17] is a fish-powered perpetual motion machine. You have to scroll through dozens and dozens of other ideas but eventually:

"If we made a fishing rod with a tiny motor-battery combo, and it would cast out til it caught a fish, and the fish when caught was pulling against the motor til it ran backwards and recharged the battery for the next cast, we would have made another perpetual activity er motion. It would, of course, have to sense the battery charged up & generate a lure-release."

(You can tell it's a crackpot site because it's using LOTS of color/italics/underlining)

SteveBaker (talk) 21:06, 13 February 2009 (UTC)

To give him credit I think it lost something in translation from the original schizophrenia. --98.217.14.211 (talk) 04:53, 14 February 2009 (UTC)

I had a tube full of marbles yesterday. --Carnildo (talk) 00:51, 14 February 2009 (UTC)

I thought I had one also, but everyone says I lost mine years ago... DMacks (talk) 01:52, 14 February 2009 (UTC)

Just for the record, the speed of light is about 1000 times faster than what you said. :) -- Aeluwas (talk) 16:55, 14 February 2009 (UTC)

Indeed. I expect the OP meant km/s. --Tango (talk) 17:38, 14 February 2009 (UTC)

Just to answer Marskid2s original scenario, the torque on the cylinder will travel along its length at the rate of shear waves in the material, which is a little less than the rate of (longitudinal) sound waves. Assuming the cylinder is made of steel, for which the speed of sound is about 5930 m/s, the twist will travel from one end of the light-year long cylinder to the other in a little more than 50,600 years. --Chetvorno^TALK 07:10, 15 February 2009 (UTC)

PROPELLER ENGINE VS JET ENGINE AT HIGHER ALTITUDE

IS THERE MATHEMATICAL PROVE FOR DECREASE IN PROPELLER ENGINE EFFICIENCY AT HIGHER ALTITUDE IN COMPARISION TO JET ENGINE —Preceding unsigned comment added by 114.31.179.11 (talk) 18:34, 13 February 2009 (UTC)

First, typing in all caps is the equivalent of screaming at everyone. Would you walk into a library's reference desk and immediately start screaming at the poor woman behind the counter?

Second, check Newton's laws of motion. How does a propeller work? It forces air in one direction, causing the propeller to move in the opposite direction. If there is less air, there is less are to move. How does a jet engine work? Fuel is placed into a confined area. Combustion causes thrust to escape. The thrust is channelled in a specific direction, causing the engine to go in the opposite direction. The air is not used, fuel combustion is. If you take oxygen with you, you can continue using a jet engine at any altitude you like, but a propeller engine will fail at rather low altitudes for aircraft flight. -- kainaw™ 19:04, 13 February 2009 (UTC)

Forces on an aerofoil

Well, that's not the full story, as the illustration of a wingform shows. Rotate that illustration 90 deg anticlockwise and you get a propellor blade, and the lift becomes the thrust. Also, your explanation of how a jet engine works is a bit off too. The thrust created in a jet engine is not just the escaping gases rushing out the back. Remember when you were a kid you blew up a balloon, then let it go and it flew crazily around the room? That same balloon will behave in exactly the same way if you let it go in a vacuum where the escaping air has absolutely nothing to push against. The pressure inside the balloon creates the thrust, not the air being expended, and the balloon moves away from the point of low pressure (where the air is escaping). If that didn't happen we couldn't steer/guide vehicles in outer space which is a vacuum.

I don't think it is necessary to be quite so sniffy with people who type in all caps. Its not really the same as shouting in a library and their typing skills may not be as good as yours. SpinningSpark

Most people mean by jet engine a turbofan engine as used on commercial aircraft. These engines require an air intake for the compressor and have a definite altitude limit. Although technically the term includes rockets which carry their own oxidizer I think the OP probably meant turbofan. You can find a comparison of the altitude records for both types of aircraft at Flight altitude record. Both types will lose efficiency as air density decreases but I don't think you are going to find a simple formula to compare them as it depends on many aircraft design factors. SpinningSpark 22:47, 13 February 2009 (UTC)

2009 satellite collision relative velocities

Hi guys. I'm trying to add some detail to 2009 satellite collision and I'm looking for reliable sources on the relative velocities of these satellites. I've found a few sites [18] but these are "amateur" estimates fraught with speculation. Has anyone got any good sources for the relative velocity of the strike? Nimur (talk) 19:47, 13 February 2009 (UTC)

This forum seems to use more rigorous math to ge 3.4 km/s. Still hardly a reliable source. Nimur (talk) 19:57, 13 February 2009 (UTC)

I do not understand why the relative velocity would be so high (26,000 mph per the article, or een the 3.4 km/sec estimate above). If they were in circular orbits at the same height, and in the same orientation, the relative velocity should be zero. In a given orbit, satellites could be placed at the same height and orientation, spaced around the earth. Eccentricity of orbit would introduce some relative velocity. Orbits at different orientation would introduce additional velocity. Why would the launching countries place satellites in conflict orbits, where high speed collisions are likely? If a satellite is defunct, shouldn't the launching country be responsible for controlled de-orbiting (by retrorocket on board or by their or others' robotic deorbiting mission? Isn't there some coordination of orbits, to avoid the proliferation of long lasting space junk in valuable orbits, like airliners do not fly around willy-nilly ? Is there the likelihood of this debris hitting other satellites and causing even more hazardous space junk? These orbits are high enough that the junk might not reenter for a very long time. Edison (talk) 00:56, 14 February 2009 (UTC)

All of these are very valid points. When I first heard of the collision, I presumed the satellites must have been in the same orbit, with a slight separation of distance; and I assumed that the relative velocity must have been a "slow drift" on the order of meters per second that never got noticed until the two collided. However, this diagram seems to show that the two orbits were quite different ("so they cross paths at a 12 degree angle" of orbital inclination). (The map doesn't look like 12 degrees to me, but I'm not so sure the math was done right). As you say, how could this conflict of orbits have been overlooked when deciding the orbit for the launch planning for the Iridium satellite? Nimur (talk) 04:37, 14 February 2009 (UTC)

The orbits of spacecraft are affected by a multitude of factors which are very difficult to model. The satellites aren't traveling in perfect circles, the orbits change due to the effect of maneuvers, solar radiation pressure, atmospheric drag, effects of a non-spherical earth, third body effects from the moon and sun, etc. This means that orbits cannot be predicted with a high level of accuracy for long periods of time, and certainly not 12 years. Simply put, the two orbits didn't intersect when Iridium 33 was launched (in 1997), and it's likely no orbit could be chosen such that it doesn't intersect with some known object. Orbits are chosen to meet a large number of requirements, and like everything in engineering there is a trade involved. An orbit with very low risk of collision could be chosen at the expense of other requirements, or a higher risk orbit could be used and other requirements met.

It is difficult to predict when a conjunction will occur, and even then it is still probabilistic (a 1 in 25 chance of collision, for example). According to Space Debris, there are around 13,000 cataloged objects in orbit, and collision with almost any of them would be at high relative velocity, and thus catastrophic. To foresee any possible collision, conjunction analysis must be performed for every object which passes through the same altitude as Iridium 33 (or any other object you're interested in protecting), and there are probably thousands in this subset. Since the orbit of any object cannot be reliably predicted for a long period of time, this analysis has to be performed often, which is computationally intensive. When you run the analysis, all you get is probability; it isn't yes or no.

Suppose there is a conjunction with some probability of collision (1 in 25, for example). Do you maneuver to avoid the debris? A maneuver has costs, both in consumables (fuel) and potentially downtime for the satellite (a maneuver might require pointing antennas away from their targets, or some other interruption to service). The line has to be drawn somewhere, and perhaps they chose wrong.

Predicting events like this isn't cut and dried. It is a tradeoff between the risk and the cost of mitigating that risk. Perhaps Iridium didn't find it worthwhile to go through all of this, and mitigated the risk in other ways (on-orbit spare satellites). Perhaps their analysis was insufficient, or perhaps they chose to take their chances and the dice came up snake eyes.

Of course there was little Russian Space Forces could have done since Kosmos-2251 was not functioning at the time. A spacecraft can stop functioning for many reasons, either predictably or unpredictably. Thus it is not always possible to deorbit a non-functioning satellite since it may stop working without warning. To foresee a collision is difficult, as illustrated above, and it's unlikely they would undergo all of the required analysis for a non-functioning spacecraft.

As for the original poster's question, here is a picture showing the orbits of the two spacecraft. Unfortunately I can't find a good source on the relative velocity. My back-of-the-envelope number is about 10,600 m/s, or about 24,000 mph. To arrive at this I assumed two circular orbits at 776 km altitude, which gives an orbital velocity of about 7,500 m/s. The picture shows approximately 90 degrees between the two velocity vectors, making the relative velocity around 10,600 m/s. anonymous6494 07:08, 14 February 2009 (UTC)

Wow - at those speeds, the odds of a collision with 90 degree orbital inclination is astoundingly small. The circumpherence of those orbits is around 40 million meters - if the spacecraft are (say) 10 meters long - then the odds of them colliding - even if their orbits do intersect is about 8 million to one against per orbit. At 8,000 m/s orbital speeds - each orbit takes a couple of hours - so you'd expect a collision like this about once every 400 to 500 years - even if they were both at the exact same altitude! SteveBaker (talk) 23:56, 14 February 2009 (UTC)

This is exactly what I was thinking, with similar back-of-envelope probability calculation. That's why I assumed the satellites were in an almost identical orbit, with much slower relative velocity - hence my original question. Of course, the slower the relative velocity, the more time would have been available to all parties to notice an impending collision and possibly avert it. But, the more I dig in to the actual orbits, I find a lot of different orbit diagrams and a wide variety of parameters described. Hopefully a post-incident press release will come out in a while with some more reliable numbers. Nimur (talk) 14:35, 16 February 2009 (UTC)

Well, you might expect a collision between these two specific spacecraft to take place after 400-500 years. But a collision between any pair of satellites would have been reported on the news, and if we take 6000 as the number of satellites orbiting Earth, the number of pairs would be 5999+5998+...+1=18 million. Obviously it is much more likely than not for two randomly-picked satellites to have orbits that never intersect, but when the number of chances for failure is in the millions, one would expect something to happen pretty often. --Bowlhover (talk) 04:04, 15 February 2009 (UTC)

It would happen pretty often if measures weren't taken to avoid it. I'm not sure how often collision avoidance manoeuvres are made, but I know they certainly happen. --Tango (talk) 14:57, 15 February 2009 (UTC)

As I suggested above, there could be an international convention that any country or group launching a satellite is liable for any collisions it causes with preexisting and still functioning satellites. A defunct satellite could be seized and deorbitted by a robotic retrieval satellite, at the expense of the party launching the dud, to avoid the proliferation of space junk. So it is not correct that "There is little Russian Space Forces could have done." The U.S has discussed robotic deorbitting of the Hubble Space Telescope, for instance. Edison (talk) 14:47, 15 February 2009 (UTC)

Such a deorbitting mission would be very expensive and would take significant time to plan. It seems that these satellites were in polar orbits - it would be next to impossible to arrange polar orbiting satellites in such a way that their orbits never intersected any other satellite. Better tracking of satellites seems to be the answer - the commercial satellite was operational and should have been able to avoid the collision if it had been predicted. At those speeds a tiny course correction just a hour or so before the collision would probably be enough. --Tango (talk) 14:57, 15 February 2009 (UTC)

Have scientists tried mixing every combination of chemicals, elements, etc. together?

Or do they work this out mathematically, because of the obvious dangers? Maybe this sounds impractical. I just figured that most scientists felt they had a duty to uncover and report every secret that nature has tucked away in it's emergent property quantum realm. And to find out what blows up and shit.TinyTonyyy (talk) 22:11, 13 February 2009 (UTC)

I just love how the question ends with "..and shit.". -Pete5x5 (talk) 00:42, 15 February 2009 (UTC)

No to both questions. First off, over 40 million CAS registry numbers have been assigned to known compounds, so combining any two all possible pairs (without even considering such variables as temperature and pressure) would be an daunting task. And I'm fairly certain that modeling reactions computationally is quite difficult (otherwise drug companies would have a much easier job). Clarityfiend (talk) 23:05, 13 February 2009 (UTC)

There is often more to producing compounds than just mixing chemicals. There are certainly new compounds being discovered all the time (check out a Chemistry journal sometime), so they can't have got them all yet! --Tango (talk) 23:17, 13 February 2009 (UTC)

Two more things to consider why it's an emphatic no. Even things that have been combined before sometimes create different compounds under different conditions. Think of temperature, distribution, pressure, agitation and the like. Even computer modeling doesn't help getting things down to size. Folding@home uses huge amounts of computer resources donated from all over the world and they aren't even combining anything. They are modeling at what proteins look like when they are folded in different ways. Depending on what's sticking out where they behave quite differently. 76.97.245.5 (talk) 00:24, 14 February 2009 (UTC)

Imagine if you merely tried that with just a chemistry set containing 32 chemicals. How many mixtures would be required, ignoring order (with 1 to 32 components)? http://en.wikipedia.org/wiki/File:1940s_Gilbert_chemistry_set_04.jpgEdison (talk) 00:43, 14 February 2009 (UTC)

Like 32 with one chemical, 601,080,390 with 16 chemicals, etc. Edison (talk) 02:04, 14 February 2009 (UTC)

In chemistry, atoms of elements combine to form moleculess. Depending on the type anbd position of th ebonds between the atoms, the same bunch of atoms can create completely differnt molecules ("chemicals") with completely different properties. Furthermore, there is no upper bound on the size of a molecule, so there are infinitely many different "chemicals." For example, there are zillions of different moleculres that are composed exclusively of atoms of carbon and hydrogen, and they have have radically different properties. These include gasses (methane, acetelene) liquids, (pentane, hexane, benzene) and solids (Paraffin.) So there are an infinite number of different molecular combinations of just these two elements. No, we have not yet discovered tehm all. -Arch dude (talk) 02:31, 14 February 2009 (UTC)

For a simple explanation of scale, say you have everyone in the world working to combine every pair in the CAS registry. There's 40 million of them, so that's 800 trillion. There are about 6.5 billion people, so that's over 100,000 pairs per person. If each person lives 70 years, that's about 25,000 days, so you'd have to have everyone in the world mix four chemicals a day for their entire lives. That's just every pair. If you want to mix every combination, that's 2^40 million, or about 10^12 million. For comparison, there's about 10^80 to 10^85 particles in the universe. — DanielLC 19:19, 14 February 2009 (UTC)

That's only scratching the surface though - many chemicals require three ingredients in order to react - or special temperature/pressure/agitation - some require specialized catalysts. Then you get things like polymers and proteins that form bit by bit rather than all at once. Truly, the number of possibilities is beyond measurement. Then you have isomers and isotopes. Isomers are chemicals with the exact same 'ingredients' - but different shapes. Something as simple as a benzene molecule can have several 'foldings' ("chair" and "boat" forms of the benzene ring) - others exist in left and right-handed forms - one of which will be biologically active and the other not. With proteins, this 'folding' is absolutely critical. There could be hundreds, thousands, maybe millions of "different" proteins that have identical formulae but are simply folded up differently and therefore have quite different properties. Then most elements have several stable isotopes (ie larger or fewer numbers of neutrons). These have very similar (but not identical) properties - so you might well find that to try everything, there would be a few odd versions of compounds that have the same formula but are built from unusual combinations of isotopes. So doing chemistry by making some of everything and testing it is a dead end. SteveBaker (talk) 03:08, 15 February 2009 (UTC)

Imagination "like becoming someone else" to some people?

My friend has Asperger's Syndrome, so I think I understand why he said this, but he recently remarked to me that when he tries to put himself in another person's shoes, he literally feels like he becomes that person, in a way. Even if it's someone in the past.

Is this because of the autism spectrum rendering normal imaginative play in children - and hence imagination in adults, I presume - hard if not impossible? So that a person with an ASD must practically feel like they become someone else to "imagine themselves" like that?

I'll note that I looked at the imagination article, and it's a little complex, but it almost seems like it's saying that is possible, since imagination is a created world.

Of course, I'll also grant that I probably shouldn't presume that he's using words in the same way I do, either.209.244.30.221 (talk) 22:12, 13 February 2009 (UTC)

Somehow when I read your post I was immediately reminded of the writings of physicist Richard Feynman. Although certainly not in a field you'd think of in this regard he studied and described his ability to multitask. He compared that to what others described/displayed in that regard. People differ in their ability to e.g. listen and read at the same time. Some can write and speak at the same time. You can do your own experiments and compare your and your friend's results with Feynman's. While some people when reading a book hear the text read to them in their head, others see the words float off the page. So there is already a lot of variation in people not described as having any "syndrom" (or "disorder" :). If I'm not mixing things up I think I read that "Aspies" have a very visual memory. So your friend is probably creating a visual picture of the things he reads about in a book. Another thing usually described is the ability to "focus" excessively. So just the opposite of muuti-tasking. So your friend's brain may just not be able to process the information of the imaginary world and the real world at the same time. Empathy may interest you. I must say though that some of the things on that page rubbed me the wrong way. Our resident expert SteveBaker will probably be able to shed a lot more light on things. 76.97.245.5 (talk) 00:07, 14 February 2009 (UTC)

My understanding is that the underlying cause of Aspergers and Autism (and other things along that spectrum) is most likely to be due to a failure or some kind of inadequacy of the mirror neurons. These neurons are the ones that let normal humans understand how other people are thinking by literally modelling a simplified version of their thought processes in your own head. I have Aspergers - and it seems almost like everyone else has some kind of telepathy that lets them all know what each other are feeling! This seems like magic to me! Kinda like the empathic Deanna Troi on Star Trek.

The response your friend gives seems almost completely opposite to how I feel - which is that I'm simply unable to think about how someone else thinks or feels. I would speculate that perhaps your friend has discovered a way around not having a decent set of mirror neurons with which to model the other person's mental processes - but instead literally has to imagine that he is the other person and thereby use his regular neural capacity to model the other person's mental state. So for as long as he does this, he IS the other person. That's a very strange and interesting thing. If that is indeed what is going on, it would definitely be a neat trick...one that I'd very much like to learn. (Presuming it is learnable...not everything is).

I suppose it's also possible that his diagnosis as an Asperger syndrome victim is incorrect.

SteveBaker (talk) 00:45, 14 February 2009 (UTC)

I'm autistic. I have put myself in people's shoes by pretty much imagining I was them, though I'm perfectly capable of empathy without that. I don't know if it works better, but it presumably varies how well it works with the person, so it's possible that your friend finds that it works much better, and does that a lot. When I read, I imagine what it sounds like, so there's at least one Aspie with auditory memory, though I don't see how that's relevant. Also, I don't have any problem imagining things. In fact, I commonly have a problem of getting lost in my thoughts, and imagining stuff when I should be doing something. — DanielLC 19:08, 14 February 2009 (UTC)

Error measurement question

The manual for the equipment says "Accuracy specifications are given as: ±([% of reading] + [number of least significant digits])". Then it gives, for example for one measurement, "0.5% +/- 1". Does that mean I have to multiply 0.5% by my measurement, then add 1? But where does the number of least significant digit come into the calculation?128.163.224.240 (talk) 22:30, 13 February 2009 (UTC)

That kind of expression is usually found on instruments that have a digital readout and is due to an uncertainty in the last digit which is present no matter what the size of the reading. For instance, consider a frequency counter with a six-digit display reading 173.624 MHz. An error of ±0.5% is ±86,812 Hz. To this must be added the uncertainty of the last digit, which in this case represents kHz (1000 Hz) so a ±1 uncertainty corresponds to ±1000 Hz making the total accuracy limits ±87,812 Hz. We can round this to ±88 kHz since the instrument on its current range is only measuring to a resolution of 1 kHz, making the limits for the measurement 173.536-173.712 MHz. SpinningSpark 23:31, 13 February 2009 (UTC)

Isaac Asimov quote on the fractal nature of discovery

Can anyone point me to the quote of Asimov's in which he talks about how every discovery opens a whole new series of questions - he compares the process to the recursive nature of fractals.

Thanks Adambrowne666 (talk) 22:55, 13 February 2009 (UTC)

I believe that scientific knowledge has fractal properties; that no matter how much we learn; whatever is left, however small it may seem, is just as infinitely complex as the whole was to start with. That, I think, is the secret of the Universe.

- Autobiography I, Asimov: A Memoir (pub. post. 1994) - Azi Like a Fox (talk) 23:51, 13 February 2009 (UTC)

Wonderful. Thank you. Adambrowne666 (talk) 02:45, 14 February 2009 (UTC)

Resolved

-Pete5x5 (talk) 00:46, 15 February 2009 (UTC)

February 14

Questions about catnip

1. Is catnip an addictive substance (for cats)?

2. Is it possible for a cat to OD on catnip?

3. What recreational drug, when taken by a person would most closely mimic the psychoactive/physical effects of catnip on cats?

Just curious after watching videos of cats getting high on the stuff on YouTube. Thanks. --84.68.107.30 (talk) 00:27, 14 February 2009 (UTC)

1. catnip is not addictive

2. not by rolling in it or smelling it. If the cat eats too much catnip (some cats like to eat fresh catnip, mine does), it may become ill.

refs for these two answers: [19], [20]

3. hard to say, catnip affects different cats differently. Some get loopy, some get aggressive, some get a little sexual. I'd say marijuana, for its euphoric effect, but I don't know a lot of marijuana users that get hyper or aggressive. There's probably not a really analogous human drug. Alcohol is euphoric, but its effect lasts longer and it's addictive. - Nunh-huh 00:49, 14 February 2009 (UTC)

1 How would you define "addictive" in cats. I have had cats do serious damage to containers or cabinets to get at the stuff.

2 Some cats become over excited and can "conk out" from catnip. Others just get extremely tired in a hurry and wander off for a cat-nap. Reactions vary greatly between different cats. Lots of kittens and some older cats aren't affercted at all. BTW: I've seen several cats get the same reaction from elderberry.

3 Androstadienone and/or Musk probably come closest, although not in intensity. We haven't discovered a pheromone for humans that has that strong an effect (thank goodness). Maybe it's just that cats don't care about indulging. After all they are not the ones who have to go out and earn for the tuna cans. Mrrow. Also see [21] - 76.97.245.5 (talk) 02:26, 14 February 2009 (UTC)

Why do cats need a special definition of addiction? I suppose because of the muddled popular meaning of the word, we should specify that we're talking about physical dependency manifested by withdrawal symptoms or increased drug tolerance, and that catnip doesn't cause either. - Nunh-huh 03:17, 14 February 2009 (UTC)

Well caught I was thinking of the other use for psychological addiction. 76.97.245.5 (talk) 07:32, 14 February 2009 (UTC)

According to the second link above, "It is possible for cats to become immune to its effects if exposed too often". Or could it be the case that the regular dose just isn't enough to cause a high any more? How on earth do you determine if a cat is jonesing or not anyway? --Kurt Shaped Box (talk) 09:03, 14 February 2009 (UTC)

Reading a little about the effects of catnip and the short-lived - but seemingly intense high, it reminds me somewhat of the effect that freebasing crack has on a human... --Kurt Shaped Box (talk) 09:11, 14 February 2009 (UTC)

Neanderthals, Humans and Chimps

I was just reading the artical on the Neanderthal genome project. In the artical, there is reference to the Chimp's DNA being 18.77%98.77% identical to modern human DNA. What is it about the remaining 1.23% of the chimp's DNA that makes it impossible for humans and chimps to interbreed (aside from the ethical objections we may hae)? Could modern humans and neandertha;s inter-breed? —Preceding unsigned comment added by 209.161.215.58 (talk) 04:23, 14 February 2009 (UTC)

I'm not sure it's true that chimps and humans can't interbreed. It's not easy because we have one less chromosome than chimps. Two of the great-ape chromosomes are fused together in humans. So while most of the DNA is identical - the way it's glued together isn't. But that doesn't make it completely impossible. Humanzee explains all of the horrible details. It's widely assumed that humans and Neanderthals would have been able to interbreed. SteveBaker (talk) 04:33, 14 February 2009 (UTC)

The degree of identity between human and chimpanzee genomes is not easy to estimate. Figures like the one to which you refer ("98.77%") are fraught with serious problems, as discussed in many papers including this one [22]. The differences go much deeper. --Scray (talk) 05:03, 14 February 2009 (UTC)

Representing the similarity of genomes in term of percentages is very, very misleading. Yes, we share about 98.4% of our genome with chimps, but we also share about 90% with mice and 50% with bananas[23]. First, as mentioned above, percentages don't take into account structural chromosomal differences (fusions, inversions, and the like) that may exist, making interbreeding difficult or impossible even between otherwise closely related species. Second, there is a great deal more information in a genome than just the genes themselves. One major example would be how the genes themselves are regulated: how strongly they are expressed, in which tissues they are expressed, and when. Complicating things further, altering a single base may result in a major change in how the gene product itself functions. One gene often given credit for providing humans the ability of language is FOXP2, which contains 3633 bases in its coding regions. The human and chimp versions differ by only 3 (0.008%) of those bases. Clearly, when it comes to genetics, a little difference can go a long way. – ClockworkSoul 06:26, 14 February 2009 (UTC)

Despite what SteveBaker said, the question of wheather Humans and Neanderthals could interbreed is still an open one and the lack of evidence that any interbreeding took place may indicate that interbreeding was not possible. The only honest answer is that we don't really know yet. Dauto (talk) 18:42, 14 February 2009 (UTC)

Regardless of whether "modern" humans tens of thousands of years ago and neanderthals had viable offspring, there is no reason to believe they did not have sex. Modern humans have been known to have sex with sheep, cows, donkeys, horses, dogs, geese and chickens. Kinsey found that 8% of men and 3.6% of women reported such sexual relations with animals. It strains credulity that early humans and neanderthals never danced the horizontal bop. Edison (talk) 14:39, 15 February 2009 (UTC)

And goats. Don't forget the goat. Very important. BrainyBabe (talk) 15:47, 16 February 2009 (UTC)

So did the Sudanese man and his goat-wife have any kids? Edison (talk) 16:43, 17 February 2009 (UTC)

From what I've heard (which may be very incomplete), the only attempt to find surviving Neander genes was to look for N. mitochondria in a sample of modern humans. The negative result suggests that interbreeding was rare, but doesn't establish that it never happened: the female-line descendants could have died out by chance. (Many family names, i.e. someone's male-line descendants, have died out in the few centuries since they were adopted.) —Tamfang (talk) 18:17, 18 February 2009 (UTC)

Or not died out, but just become rare enough that none were present in the sample. (If only a few dozen or a few hundred existed, they would be unlikely to be found...) 128.194.250.39 (talk) 06:53, 19 February 2009 (UTC)

Scientific name

Does the scientific name Cacops aspidephorus mean "bad-face shield-bearer", or is there a more subtle meaning I may have missed? And, if so, why did Williston call this animal "bad-face"? Thanks a lot to anyone who can help. --83.57.77.67 (talk) 07:41, 14 February 2009 (UTC)

Our article on Dissorophidae (which is the family from which Cacops comes) says that all dissorophidae had armored plates over their spines...which explains "shield bearer"...and it says that Cacops is specifically known for having a "relatively huge head". I'm not sure that "bad-face" applies - but I wonder whether "big-face" might not be a better translation? (I long ago forgot any latin I might ever have been taught). It's also possible that the discoverer found this dissorophidae and found that it fitted in with other species in that family - except that the head didn't fit the pattern of the other species. I suppose it's then possible that the head/face was considered "bad" because of that failure to match the other species in that family. SteveBaker (talk) 02:42, 15 February 2009 (UTC)

Your Latin wouldn't help even if you could remember it Steve, I do believe that is Greek. Aspis=shield. The Latin for shield is scutum. SpinningSpark 15:08, 15 February 2009 (UTC)

Mental illness and "colorful" writing

A few questions ago, SteveBaker wrote "(You can tell it's a crackpot site because it's using LOTS of color/italics/underlining)", and I knew (even before I followed the link) exactly what he meant. I've noticed the phenomenon in web pages, I've noticed similar things in flat-text fora (e.g. Robert E. McElwaine's tendency to RANDOMLY capitalize WORDS...) and my father once told me that the American Institute of Physics used to have a special category for crackpot letters they received written with a variety of different-colored pens. My question is: is this writing quirk associated with any particular mental illness? I'd think it would be a symptom of schizophrenia and/or thought disorder, but I haven't seen it actually listed as such. -- Speaker to Lampposts (talk) 09:12, 14 February 2009 (UTC)

I guess emphasis ("shout when argument is weak") takes all forms but you might be interested in the article about green inkers. Another tic is to pad out a erm, "certain articles" with excessive C-quotes. Julia Rossi (talk) 09:16, 14 February 2009 (UTC)

It seems to be quite common on Usenet for the crackpots to pad out their posts (often several, one after the other, crossposted, saying pretty much the same thing, as is the custom) with weblinks and random cut+pasted excerpts from websites which are seemingly unrelated to the topic of the screed. --Kurt Shaped Box (talk) 09:32, 14 February 2009 (UTC)

The best crackpot site of all time has to be Time Cube. A Quest For Knowledge (talk) 11:19, 14 February 2009 (UTC)

I second that. -Pete5x5 (talk) 01:16, 15 February 2009 (UTC)

Closely followed, of course, by stopabductions.com, a website claiming that telepathic aliens can be thwarted through the use of a telepathy-blocking helmet... *ahem* this is a quote from their testimonials section:

“I am happy to report that the Thought Screen Helmet has been performing beautifully! It’s been over six months now and NOT ONE INCIDENT! Aside from some of the naive neighborhood kids and their taunting it’s been a blissful period.”

This. Is. Insane. Also: see aliensandchildren.org , another (equally ridiculous) site run by the same person. Ilikefood (talk) 23:01, 20 February 2009 (UTC)

Alex Chiu and the 'Anus 100' guy deserve honourable mentions for their incomprehensibility and sheer dogged determination to defend their theories in the face of overwhelming criticism and ridicule. --Kurt Shaped Box (talk) 11:58, 14 February 2009 (UTC)

At first I thought you meant Frank Chu, with whom I've futilely attempted conversation. —Tamfang (talk) 18:22, 18 February 2009 (UTC)

Immortality devices! LOL. I love it! (Those are sentences that deserve exclamation points.) A Quest For Knowledge (talk) 17:37, 14 February 2009 (UTC)

I remembered the anus guy's name now, FWIW. Hiroyuki Nishigaki. Check out some of his musings/ramblings if you can find them online (his website seems to have gone now). His main theory (from what I could understand of it) combined 100-times-daily anal constriction with various other religious, spiritual, alien, pseudo-scientific or downright crackpot concepts to produce a truly (sometimes literally) incoherent wholeness. IIRC, he was also trying to encourage mentally ill people to stop taking their meds on Usenet - which would've been dangerous, if the guy didn't come across as *more* insane than everyone else there present. --Kurt Shaped Box (talk) 22:21, 14 February 2009 (UTC)

Children also tend to randomly write in multiple colors, so I associate that with "immaturity". There are places where color is used to actually mean something, though, like Bibles which use red text for supposed quotes from Jesus. StuRat (talk) 14:27, 14 February 2009 (UTC)

Ding! Ding! We have our explanation! --Kurt Shaped Box (talk) 22:07, 14 February 2009 (UTC)

And don't forget about exclamation marks ! Every sentence should end in at least one, no matter how dull ! It is now 9:30 AM ! And, when the reader gets used to every sentence ending in an exclamation mark, it's time to escalate to several !!!!!!!!! StuRat (talk) 14:31, 14 February 2009 (UTC)

When I was a lad, many of the newspaper comic strips ended every sentence (except questions) with a bang. Is that still true of any? —Tamfang (talk) 18:34, 18 February 2009 (UTC)

This will go way over your head as my research into this area is decades past general scientific understanding (let alone that of lay people) but here goes: the reason crackpots write with different colors is because they are approaching science with their right brain hemisphere. It is also the reason they fixate on the intuitive meaning of scientific terms (i.e. the impression the term would make before you ever learn what it means), with a seeming inability to internalize the technical definition. This is a style of thinking -- its more useful in some areas of life and science and less useful in others. That's all I will say, because my research on this subject is so far ahead of science that trying to explain it to you in a Reference Desk response would be hopelessly quixotic. —Preceding unsigned comment added by 82.120.236.246 (talk) 15:22, 14 February 2009 (UTC)

Come on, everyone knows any sentence containing the phrase "far ahead of science" HAS to end with an exclamation mark! --Tango (talk) 15:39, 14 February 2009 (UTC)

Then I would have had to say "the reason crackpots write with different colors is because we are approaching science with..." —Preceding unsigned comment added by 82.120.236.246 (talk) 15:53, 14 February 2009 (UTC)

I don't know why they do this - but it's a dead giveaway when you open a web page that looks like that. As for excessive exclamation marks, it helps to pretend that each "!" is really a "?". I doubt that this is a mental illness per-se - but there is certainly a correlation between crackpot theories and tasteless web sites. However - correlation is not causation. SteveBaker (talk) 19:22, 14 February 2009 (UTC)

I guess that depends on whether you count being a complete idiot as a form of mental illness. I've never been quite sure how you distinguish between "learning difficulties" and "stupidity". In cases where there is a definite cause for the learning difficulties, it's pretty simple, but in other cases I'm not sure there actually is a distinction. --Tango (talk) 20:07, 14 February 2009 (UTC)

Another common 'red flag' for these quacksites seems to be the overuse of mid-90s-web-style animated gifs and stock clipart. Has anyone else ever noticed that? --Kurt Shaped Box (talk) 22:38, 14 February 2009 (UTC)

Pretty much everything about their webpages boils down to them being stuck in the mid-90s (you forget to mention <blink> and <marquee> tags!). I have no idea why... --Tango (talk) 23:25, 14 February 2009 (UTC)

They like <center> tags too. SteveBaker (talk) 23:45, 14 February 2009 (UTC)

The use of several different fonts, bold/italic styles and text sizes within the same paragraph/block of text too. I wonder if they're deliberately trying to give the impression to their readers that they were chewing the keyboard when working on the site? --Kurt Shaped Box (talk) 00:44, 15 February 2009 (UTC)

Another dead giveaway to me for a crackpot letter is its ending. It's usually "Think about it!"

Think about it!. Bunthorne (talk) 21:48, 14 February 2009 (UTC)

Thought-terminating cliché#Non-political examples. Most of these websites will also have a colourful array of fallacies within them (no pun intended). --Mark PEA (talk) 12:29, 15 February 2009 (UTC)

Yes, such as circular logic. The reason that circular logic tells us these sites are run by crackpots is that, as previously established, circular logic tells us these sites are run by crackpots. StuRat (talk) 17:31, 15 February 2009 (UTC)

I guess you are arguing that there is no evidence that the sites are run by crackpots, but the definition of crackpot could be "someone who uses colourful writing and talks crap", which would mean it is not circular logic. Although hasty generalization is still possible. --Mark PEA (talk) 18:28, 15 February 2009 (UTC)

Is there any way to repair a cracked DVD?

I have a dual-layer DVD-Video disc with a full-thickness crack running from the centre, to about 1cm into the data area. Is there any possible way that I could either fix the disc, or even just render it readable for long enough for me to make a copy?

I guess that the answer's going to be 'no' - but hey, it's worth a try if it saves me having to buy the movie again... ;) --Kurt Shaped Box (talk) 13:04, 14 February 2009 (UTC)

If it's full-thickness, then probably not (surface scratches are another matter). Almost certainly not easily (you might be able to pay a specialist company lots of money to get the data off, like you can with broken hard drives, but I doubt that's worth it). You might be able to get the DVD replaced for free (or maybe for a small admin/p&p fee) from the manufacturer, though - if all the DRM and EULA stuff is to be believed, what you bought wasn't the DVD but rather a license to the content that is on the DVD, so it makes absolutely no sense for them to charge you for the content again just to replace the DVD (of course, sense doesn't really come into it!). Try asking at wherever you bought it. --Tango (talk) 13:12, 14 February 2009 (UTC)

I wouldn't count on them replacing it for free. They conveniently either say you are buying the disc or the content on it, whichever way will get them the most money. Can we get free DVDs by turning in old VHS tapes ? I doubt it. StuRat (talk) 14:22, 14 February 2009 (UTC)

DVDs usually contain additional content that wasn't on the VHS version, so almost certainly not. --Tango (talk) 15:45, 14 February 2009 (UTC)

Even if it isn't, the idea that the content and the medium are totally separable is certainly not part of the EULAs. --98.217.14.211 (talk) 00:39, 15 February 2009 (UTC)

As for the original Q, I'd guess that there is some way you could "fix" the DVD. By this I mean glue it together so it won't fall apart when played. However, the data in the vicinity of the crack will still be lost. This is merely annoying for music and video, but will make any program on the disk completely unusable. StuRat (talk) 14:22, 14 February 2009 (UTC)

It may be worth writing to the publisher. I did this once with a similarly damaged CD and they replaced it for the cost of postage after I had sent them the damaged original. -- SGBailey (talk) 18:41, 14 February 2009 (UTC)

There's some stuff you can buy to repair plastic eyeglass lenses that might work to repair the plastic part. The data as Stu said is another matter. Try opticians for the chemical (comes in a very small tube.) I came across it once and stocked up. I haven't seen it since. 76.97.245.5 (talk) 22:36, 14 February 2009 (UTC)

Have you tried playing it? DVDs have a lot of error correction and it may still be playable. In that case (if you can break the copy protection, which is possible) you could copy it to a new disc. --Chetvorno^TALK 07:49, 15 February 2009 (UTC)

Let me say right off that there is no way you'll be able to 'repair' the disk. Forget it - it's not gonna happen. Even if it did work, the extra weight of the glue on one side and not the other would unbalance the drive and either prevent it from playing or damage the bearings in the DVD drive. However, I would expect the error correction systems to be able to recover data from the DVD so it should play OK providing that's the only damage. If it also has some fine scratches, dust or fingerprints then there may just be too many errors for it to recover from. But there is another problem. A crack that goes all the way through the disk will have a very good chance of spreading and eventually causing the DVD to shatter while it's spinning. I would STRONGLY advise against playing it in a computer DVD drive because those can spin a lot faster than a Video-only DVD player and if a DVD comes apart at high RPM, it can do some serious damage. (I refer you to a Mythbusters episode where they tried playing various optical disks to make them fly apart). The trouble is that the other advice I'd like to offer would be to suggest 'ripping' the movie off of the DVD and writing it onto a blank disk using your computer...but with the risk of the disk shattering when you do that...I'm beginning to think that this is actually a bad idea. IMHO, you should first contact the company that made the disk and ask for a replacement. I think they'll probably give it to you - although they might want to charge for shipping & handling. SteveBaker (talk) 17:00, 15 February 2009 (UTC)

so cola is TERRIBLE for your teeth. Does swishing with water immediately afterwards help?

I heard cola is terrible, horrible for your teeth. Drinking thru a straw helps, but I wonder: would swishing your mouth thoroughly with clear water immediately afterwards also help any? I am not asking for medical advice! —Preceding unsigned comment added by 82.120.236.246 (talk) 15:09, 14 February 2009 (UTC)

Saying "I am not asking for medical advice" doesn't make it true. This is quite obviously a request for medical advice. Ask a dentist. --Tango (talk) 15:43, 14 February 2009 (UTC)

Yes, actually, it does -- saying, in bold, "I'm not asking for medical advice" means I'm not asking for medical advice. —Preceding unsigned comment added by 82.120.236.246 (talk) 15:53, 14 February 2009 (UTC)

No, it doesn't. You're asking for something which requires expert medical understanding and could easily lead you to behaviors which are not safe. Appending a contradictory statement to the end of it doesn't change that fact. It just makes your bolded statement false. --98.217.14.211 (talk) 00:42, 15 February 2009 (UTC)

Cola is no worse for your teeth than other soft drinks. For healthy teeth it's best to avoid drinks with added sugar. Rinsing your mouth thoroughly might remove some of the sugar.--Shantavira|^{feed me} 16:03, 14 February 2009 (UTC)

The carbonic acid, citric acid and phosphoric acid isn't good for them. There are plenty of soft drinks that aren't anywhere near as acidic. There are also plenty of soft drinks that aren't high in sugar. --Tango (talk) 16:30, 14 February 2009 (UTC)

Then what are you doing? --Tango (talk) 16:26, 14 February 2009 (UTC)

This possibly? SpinningSpark 16:33, 14 February 2009 (UTC)

Aside from everything else: Drinking through a straw WILL NOT AFFECT chemical or biochemical behaviour of a substance! That is a very frequent misinformation. (Assuming you arent drinking harzardous chemicals which actually react with the plastic) --91.6.7.232 (talk) 17:58, 16 February 2009 (UTC)

Don't be silly. Drinking through the straw isn't supposed to chemically change the drink. No one in the world believes that. The point is to stop the soda from repeatedly eroding your front teeth.

Who knows how much difference that makes, but some dentists seem to believe that it is significant. 21:10, 17 February 2009 (UTC)

Verifying that a CO detector works

Is there an easy and safe way to verify the correct functioning of a CO detector? --173.49.17.152 (talk) 19:33, 14 February 2009 (UTC)

Does it have a "test" button? That will verify that the batteries aren't flat. As for verifying that it actually detects CO, I'm not sure... you could try holding it up to your car's exhaust pipe while it's running (outside, otherwise you'll end up giving yourself CO poisoning while testing your CO detector, and that would just be silly!). But really, I think if you have reason to doubt your CO detector is working, you should just get a new one. It's not worth the risk. --Tango (talk) 20:05, 14 February 2009 (UTC)

That, of course, would be the easy answer. From what I understand, CO detectors have a finite lifetime, but some fail earlier than others. Although early replacement would be a (somewhat expensive) solution, it would still be nice to be able to verify that a CO detector is actually working even when its age suggests that it should. Like you pointed out, the test button merely tells you that the battery is not dead. With a smoke detector, you can use a smoke pencil to verify that it does detect smoke. I was hoping that there's a similar solution for CO detectors. --173.49.17.152 (talk) 20:23, 14 February 2009 (UTC)

Some CO detectors have self-diagnostic modes which give a more detailed test than simply "is the battery ok". For example, some have a test involving lighting a cigarette near to it, while in the test mode. The instructions supplied with the detector will have further information. DuncanHill (talk) 20:34, 14 February 2009 (UTC)

If you have cigarettes around, you probably don't need the detector to know you're getting too much CO. What are normal people supposed to do? Run out and buy cigarettes just to test the detector? --Trovatore (talk) 21:35, 14 February 2009 (UTC)

Normal people already have cigarettes available, we just prefer not to waste them testing electronic equipment! DuncanHill (talk) 21:38, 14 February 2009 (UTC)

Ah, read the manual... Can we pretend that my first recommendation? --Tango (talk) 20:36, 14 February 2009 (UTC)

(ec) There may well be, I don't really know how CO detectors work (although, knowing me, I will now compulsively find out!). I do, however, know how nasty CO poisoning is, which I why in the absence of a definite answer to a contrary my advice is to risk wasting money rather than risk wasting your haemoglobin. --Tango (talk) 20:36, 14 February 2009 (UTC)

I could be wrong but I'm doubtful that any manufacturer (at least in any country with strong and enforced consumer protections) would give device intended to be life-saving a lifespan that's likely to result in a substanial number of devices 'expiring' before then. In other words, if the manufacturer says you should replace the device in 6 years (random guess) only a tiny number of devices are likely to fail before then (and it not be detected by the self diagnostics). So it's not so much replacing the device early as on time Nil Einne (talk) 05:08, 15 February 2009 (UTC)

Try a smoldering incense stick. This will work for smoke detectors too. If it sounds the alarm, OK. If it doesn't, the stick is either not emitting enough CO or the detector is not working. A smoldering incense stick is also useful for revealing drafts, and does not leave the unpleasant smell of a cigarette. Check ebay for sources of incense. – GlowWorm. —Preceding unsigned comment added by 98.17.32.201 (talk) 23:46, 14 February 2009 (UTC)

Or ask your friendly neighborhood pyromaniac for assorted substances of ambiguous legality :-P Ilikefood (talk) 23:03, 20 February 2009 (UTC)

Mysterious Dead

Recently someone, who in turn got it from anonymous source, sent me a photograph of a dead animal that seems to be something between a bear and a dog. I could not find any refernece on Wiki. I have verified that actually the picture comes from a blog, but that damned blog has only pic and no explanation. Since I do not have the copyright and don't know who the author is, I cannot put it on Wiki. Instead I am putting it on my website : http://www.khurmi.com/sqyy.jpg. Courageous Wikipedias are urged to have a look at it and tell me what the hell it is. Please reply on my talk page.  Jon Ascton  (talk) 21:45, 14 February 2009 (UTC)

We'll reply here, we always do. --Tango (talk) 21:47, 14 February 2009 (UTC)

It's not a great picture, most of the nose is covered by grass, which doesn't help. It looks like a dog to me, though (probably an unusual crossbreed). --Tango (talk) 21:48, 14 February 2009 (UTC)

Looks like a black Chow-Chow mix. Compare [24]. Poor dog. 76.97.245.5 (talk) 22:25, 14 February 2009 (UTC)

(For some reason, the OP deleted this question and all of it's answers. Please don't do that.) SteveBaker (talk) 23:40, 14 February 2009 (UTC)

Whatever it is, it's been photoshopped pretty significantly. If you zoom in on the thin blades of grass over the animal's head, you can see that quite clearly. All bets are off. It could be anything - or nothing. SteveBaker (talk) 23:33, 14 February 2009 (UTC)

I don't see it... what am I looking for? --Tango (talk) 00:07, 15 February 2009 (UTC)

I don't see anything like canine teeth. And it's blue?? Cuddlyable3 (talk) 00:12, 15 February 2009 (UTC)

It's not just that - but look at the 'specular' highlight on the animals' black nose...the reflection is blue...it should be white. If you blow up the region around the grass blades, there are whole pixels of green and whole pixels of blue - and other than the color bloom that's caused by JPEG encoding, there is no soft average of grass-color and fur-color. There is no camera data in the EXIF data. It's eyes are blue too...it's a crappy photoshop job - it just screams it. SteveBaker (talk) 01:49, 15 February 2009 (UTC)

That's not a crappy Photoshop job. This is a crappy Photoshop job. The image under discussion is either a pretty good Photoshop job or real. The blue tint is presumably due to poor color balance in the camera, which has no analogue in computer graphics—and anyway, the light on the nose looks more diffuse than specular to me. The image was clearly cropped and probably resized (I don't think any digital camera takes photos in that aspect ratio), which would explain the lack of EXIF data. The green-blue boundaries don't look suspicious to me. Read the story of the Lumber Car as a cautionary tale. It looks implausible on the face of it, so people pore over the image for evidence of Photoshopping, and they find it, because most images of this (rather poor) quality have features that can be ambiguously interpreted as Photoshopped. That way lies conspiracy-theorist madness. -- BenRG (talk) 15:23, 15 February 2009 (UTC)

I've seen the 'lumber car' pictures before - they didn't strike me as photoshopped at the time - and it's good to hear that they were genuine. In order to discover whether an image might have been tampered with, you have to look at the subtle signs of color, lighting, shadows, etc. Those are all as they should be in the lumber car picture - but they most certainly AREN'T right in this one. SteveBaker (talk) 16:48, 15 February 2009 (UTC)

Diffuse light takes on the color of the object (which in the case of the nose - is black) and reflects more or less equally in all directions - specular light is constrained to a region where the angle of the incident light is roughly the same as the angle of the camera to the object. In this case, the parts of the nose that are angled away from us are black - so there is little if any diffuse reflection going on - the bright spot is therefore a SPECULAR glint. Specular reflections take on the color of the light source (which would have to be blue in order to make a blue splotch on a black object). The only way a 'shiney' spot on a black object could be blue would be if the photograph was taken in blue light - or if the camera was not registering red and green very well. However, the grass is green and there are other white things in the scene - ergo neither the light nor the camera was favoring green. It WAS tampered with. If there was excessive blue balance in the camera then you'd wouldn't have such bright green grass. I have some considerable experience with computer graphics, lighting and coloring and I can assure you that image was messed around with by someone who didn't know how to do it well. As for conspiracy theories - which is more likely - that someone (inexpertly) messed with the photo - or that there really are blue dog-bear hybrids running around loose unknown to modern science? SteveBaker (talk) 16:43, 15 February 2009 (UTC)

NOW you're really extrapolating, Steve. The only evidence we have is of blue dog-bear hybrids lying on the ground looking dead. Did I miss the photo or other evidence of one running around? You really should stick to the 'facts'. ;-) --Scray (talk) 17:23, 15 February 2009 (UTC)

I realize that specular highlights in computer graphics are usually independent of the color of the object, but as our specular highlight article mentions, in real life it depends on the material—it's true of colored plastics but not colored metals. Whether it's true of rhinariums I don't know, but anyway it makes no difference because that's obviously not the origin of the blue tint here. Surely you've noticed before that black objects in photographs very commonly have a blue tint. Here's a great example from the rhinarium article—would you say that image was photoshopped to make the monkey look blue? I don't think the blue tint in this image was even an issue until you and Cuddlyable3 brought it up. The original poster wasn't asking about a mysterious blue animal, but about a mysterious seeming hybrid of different species. I assume that he interpreted the blue tint the same way I did, as a color-balance problem. It is, as I said, very common and I'm amazed you haven't noticed it before. This is the most similar image I could find in a quick search of the Commons. Does that also have the sudden green-blue transition that you were talking about (look at the forelegs)? Here's another example of a blue nasal highlight (although I admit I'm linking it more because it's friggin' adorable than because I think another example is needed).

Maybe I'm missing something, but your suggestion that a blue tint might mean that "the camera was not registering red and green very well" makes me think you don't understand real-world color at all. In computer graphics white is just an equal combination of red, green and blue, but in real-world imaging it's a considerably more complicated concept. The world isn't sRGB, and our eyes don't see in sRGB. There've been a bunch of good color-vision threads in the Ref Desk—they're worth a(nother) look. Also see color balance, white point, CIE 1931 color space, etc. -- BenRG (talk) 22:18, 15 February 2009 (UTC)

How fair is a coin?

How fair is a physical coin? I mean, what by percentage does it favor heads or tails, when flipped in the standard way -- it must by SOME amount, since there must be more material on one side than the other. Also, how many standard deviations away from the average would this favor be? Thanks! —Preceding unsigned comment added by 82.120.236.246 (talk) 21:57, 14 February 2009 (UTC)

Slightly different, I know, but careful analysis suggests that a coin will land the same way it started about 51 percent of the time. In reality, this probably favours heads. The weighting issue - which would differ based on the coin used - pales in comparison to human jitteriness (which is what actually introduces the randomness), I'm afraid. - Jarry1250 ^{(t, c)} 22:18, 14 February 2009 (UTC)

Is there really a standard way to flip a coin? It can't be completely standardised or the result would be predictable. Cuddlyable3 (talk) 00:10, 15 February 2009 (UTC)

The coin will always favour the side which it was flipped from. This is because the spin is unbiased only if the coin rotates about an axis that is orthogonal to its normal. Otherwise it favours the face starting on top. There are a lot of recent studies that suggest this bias is indeed close to 1%. (Too lazy to find any links). —Preceding unsigned comment added by 99.255.228.5 (talk) 00:44, 15 February 2009 (UTC)

Assuming that each coin flip has the same bias and is independent of all other coin flips, you can correct the bias using some unbiasing procedure. Here's one way to do that:

1. Starting with the head side up, flip the coin once.
2. Starting with the head side up (again), flip the coin a second time.
3. If the two coin flips come out different, take the result of the first coin flip.
4. Otherwise, start over.

This will work so long as the coin flips don't come out the same way 100% of the time. --173.49.17.152 (talk) 17:18, 15 February 2009 (UTC)

You don't even need that many steps - just one:

1. flip twice until you get different results then use the first

Tested like this

C:\>perl -we "$numHeads = 0; $numTails = 0;
   for (1..1000000) {
      while (
         ($first_is_heads = (int rand 10? 1:0)) ==
         (int rand 10? 1:0)
      ){};
   if ($first_is_heads){$numHeads++} else {$numTails++}
   }
   print qq/$numHeads heads - $numTails tails\n/"
500014 heads - 499986 tails

-- good enough for me!

Bias reduces the probability of getting two different results in succession from the ideal 50%. However the bias that affects every individual flip still affects the coin (first) that you choose. A way of reducing the bias is to toss a second coin to choose whether to take the first or second flip of the first coin. Cuddlyable3 (talk) 18:34, 15 February 2009 (UTC)

Actually most coins are heavier on one side than the other.--GreenSpigot (talk) 00:03, 16 February 2009 (UTC)

I'm not so sure I like this "bias preconditioning." I'm not an expert in statistics, but the way I read these prior responses goes something like this: "We have a (semi) non-random set of numbers. We perform a conditioning algorithm. The result is a more-random set of numbers." That would be fine (pseudo-random number?) except it sounds like the algorithm suggested above (only accept the toss if the value changed since last time...) is just a high pass filter. This won't eliminate all bias, it will just eliminate low-frequency biases. Maybe I'm mistaken, maybe the definition of randomness, pseudorandomness, and unpredictability are all worth checking again... Nimur (talk) 16:10, 16 February 2009 (UTC)

Here's an explanation of why the unbiasing procedure doesn't work, not using the concept of frequency. Consider our biased (to fall "heads", say) coin is tossed many times in its lifetime and our first toss is an entry into the stream of results. The bias means we are more likely to enter into a string of recurring heads ...HHHHH... than of tails. Therefore as we repeat tosses, the first time the algorithm finds two different successive results will be at the end of this string i.e. ...HHHT. Encountering TTTTH is less likely. Therefore the first toss selected by the algorithm is still more likely H than T, due to the bias.

Using a second coin as I described reduces but does not eliminate the bias. Tossing an infinite number of times would be the only way to eliminate bias. Cuddlyable3 (talk) 13:21, 18 February 2009 (UTC)

No, using the approach described above ("always flip twice in the same manner, repeat until the results are unequal, then pick the first") will produce heads and tails with exactly 50%. That is a well-known result from probability theory, and it holds for any biased coin as long as the results of the two coin tosses are independent. Note that you have 4 possible results, HH, HT, TH, TT. You throw out HH and TT, leaving you with TH and HT. The probability for the first sequence is P(H)*P(T), the one for the second P(T)*P(H), and since * is commutative, they come out the same. Note also that you do not throw until you detect a change - you always throw pairs. --Stephan Schulz (talk) 15:57, 22 February 2009 (UTC)

Energy vs mass

Does something have energy because it has mass? Or does something have mass because it has energy? Or do the two exist because of some higher attribute?128.163.224.222 (talk) 23:02, 14 February 2009 (UTC)

Both, the two are really just different manifestations of the same thing. Einstein's famous equation, E=mc², tells us how they are related. The c² part is really just there to convert the units - from kilograms to joules or whatever (just like you have to multiply by 2.54 to convert inches to centimetres, you have to multiply by 3x10⁸ to convert kilograms to joules). Essentially, energy and mass are equal. We often talk of rest mass, which is the mass something has when it doesn't have any other energy (what gives things their rest mass is something of an open question, see Higgs mechanism if you want the technical details of the most popular theory). When you move an object you give it kinetic energy, that results in it having a greater mass (we call it relativistic mass). It's that greater mass that makes it impossible to accelerate something to the speed of light - as it gets faster and faster and gets heavier and heavier and takes more and more energy to accelerate it, it would take an infinite amount of energy to get it all the way to the speed of light. Does that help at all? --Tango (talk) 23:22, 14 February 2009 (UTC)

In ordinary experience mass and energy are independent properties that co-exist. Only extreme cases such as nuclear fusion or fission, such as in the sun or A- and H-bombs, demonstrate that one can convert into the other. Whether there is some higher attribute than these in the universe sounds like a religous question. Cuddlyable3 (talk) 00:06, 15 February 2009 (UTC)

It's a perfectly reasonable scientific question - if two things are related, it's sensible to ask if perhaps they have a common cause. --Tango (talk) 00:16, 15 February 2009 (UTC)

Electric fields and magnetic fields can be converted into one another—because they are basic components of a single electromagnetic force. Asking the underlying connections between related quantities is one of the fundamental physics questions, nothing to do with religion. --98.217.14.211 (talk) 04:02, 15 February 2009 (UTC)

The illustration I like is that a hot cup of coffee is slightly heavier than it is when it has cooled off. --Chetvorno^TALK 07:57, 15 February 2009 (UTC)

Just because we can write down an equation which relates two quantities by nothing but a constant of nature does not mean that these two quantities are the same. In fact, energy and mass are two different things, in relativistic as in Newtonian physics. That's relatively easy to see mathematically (energy is the time-component of a particle's four-momentum, mass is the four-momentum's invariant length, hence the full connection is $E^{2}-p^{2}=m^{2}$, where I have set c=1), and somewhat harder to describe in words. I like to put it as follows: Energy (along with its companion, momentum p) describes how a particle is moving. This should make it obvious that the energy of a particle depends on the reference frame in which it is measured, as is the case for kinetic energy in Newtonian mechanics. The mass of a particle puts constraints on the motion that is possible for that particle (because the relation $E^{2}-p^{2}=m^{2}$ has to be fulfilled). Famously, particles with zero mass always travel at the speed of light, particles with mass have to travel at less than the speed of light. $E=mc^{2}$ is a special case of the relation quoted above, and is valid in the particle's rest frame. It says that even when a particle is at rest, we have to attribute an energy (numerically equal to its mass, multiplied by c², although that's just a matter of the units we use) to it, something that is not the case in Newtonian mechanics. --Wrongfilter (talk) 12:42, 15 February 2009 (UTC)

That's rest mass, of course. The now unfashionable relativistic mass is just the same thing as energy. Algebraist 13:58, 15 February 2009 (UTC)

Indeed. It's unfashionable because it isn't actually very useful when doing calculations, and whatever. It is, however, quite a good way of thinking about it when you are trying to get your head around why the speed of light takes infinite energy, and related concepts - that's why I answered the OP's question in terms of it. --Tango (talk) 15:01, 15 February 2009 (UTC)

Above, it was mentioned that "Only extreme cases such as nuclear fusion or fission, such as in the sun or A- and H-bombs, demonstrate that one can convert into the other". This is a common fallacy! A 25 keV cathode ray such as the one in your old cathode ray tube television could easily impart enough potential energy to introduce a mass artifact on the electrons as it hurtles through the unit. This can and does introduce a noticeable shift in the trajectory of the beam, which must be compensated for by the controlling electronics, else the raster scan doesn't work properly. (Reference: Cathode Ray Tubes, R. Casanova Alig, Sarnoff Corporation, 1999). "The electrons leave the gun at speeds of 5% or more of the speed of light. This speed is high enough for the theory of relativity to change the electron path perceptibly from that expected from Newtonian physics. The CRT is unusual, perhaps unique, among household objects, in that relativistic effects are significant." Perhaps mass-energy equivalence is not such an extreme case after all! Nimur (talk) 16:18, 16 February 2009 (UTC)

Runaway propeller

I am listening to A Case for Dr Morelle on the BBC iPlayer, and an aeroplane in the story suffers from a "runaway propeller". What might this be? DuncanHill (talk) 23:52, 14 February 2009 (UTC)

If the governor associated with a constant-speed propeller fails, the propeller blades may feather to an extremely fine pitch. This will sharply reduce the load on the engine, and – unless corrective action is taken immediately – the engine may redline. Damage can occur to the overspeed prop itself, to the engine, or both. (A rough analogy from the driving world — imagine driving at highway speed and suddenly shifting down into first gear.) TenOfAllTrades(talk) 04:05, 15 February 2009 (UTC)

If the engine speed is constant and the pitch is automatically controlled, what is left for the pilot to control? How does he adjust the thrust? —Bromskloss (talk) 12:26, 15 February 2009 (UTC)

The name 'constant-speed prop' is a tad misleading. It shouldn't be read to mean that the prop maintains a constant speed at all times during the flight; as you've quite correctly surmised, that would leave no obvious way to control thrust. Instead, the pilot has a second control in the cockpit (usually adjacent to the throttle) which allows for selection of the target engine speed (RPM). On takeoff and climb, the pilot will choose a high speed, corresponding to finer prop pitch and greater power. During level flight, the pilot will move to a lower speed, corresponding to greater prop pitch, lower engine speed, and better fuel economy.

Here are a couple of links that go into a bit more detail: [25], [26]. TenOfAllTrades(talk) 14:16, 15 February 2009 (UTC)

Aha! Thank you. —Bromskloss (talk) 10:58, 16 February 2009 (UTC)

• Excellent, many thanks! DuncanHill (talk) 15:46, 15 February 2009 (UTC)

Can we create giant insects like those that lived during the Carboniferous period?

During the Carboniferous period, insects could grow much larger than today due to the high oxygen levels. So, why can't we breed insects under high oxygen conditions and select for size, or use genetic manipulation techniques to create large insects? Count Iblis (talk) 23:57, 14 February 2009 (UTC)

We probably could if we really wanted to. I'm not sure selective breeding would get us anywhere near those sizes in a reasonable amount of time, but genetic engineering might be able to. --Tango (talk) 00:04, 15 February 2009 (UTC)

The American cockroach can grow to amazing size. (Not quite big enough to saddle, despite the common saying.) Which leads to the question what you'd do with your giant bug and what would it feed on? There may be some use in the entertainment industry (Godzilla vs Ibis bug). Our next problem, though, is going to feed the steadily growing human population, not entertaining them. If your bugs were edible, could be fed on something that would not have a negative net food value it might be worth the resources expended to create and maintain it. All that would be left to do would be to train humans not to get the creeps when they find out what's in that hot dog. But then there are cultures who eat bugs.76.97.245.5 (talk) 02:24, 15 February 2009 (UTC)

There is a perfectly extant and very large terrestrial arthropod, the Coconut crab. It's not an insect, and its respiratory system is quite different from that of the modern insects; but it is still an arthropod (so same basic body arrangement, exoskeleton, open circulatory system, etc...). Does it fit your bill? Or are you rather asking about "breeding back" Meganeura and such? --Dr Dima (talk) 03:54, 15 February 2009 (UTC)

Probably a major reason those insects were able to grow bigger was because there was more oxygen in the air. Which is good for the rest if us as you'll have to keep them in a special enclosure. I've seen the effects when such creatures are released.:) Dmcq (talk) 12:25, 15 February 2009 (UTC)

Yes, I think that is understood to be the primary reason they were bigger. The OP said as much. --Tango (talk) 15:03, 15 February 2009 (UTC)

We still have a few moster flying insects around: Attacus atlas the Atlas Moth for instance, and Ornithoptera alexandrae the Queen Alexandra's Birdwing butterfly. Although neither of them comes anywhere near Meganeura's 30 inch wingspan. SpinningSpark 16:13, 15 February 2009 (UTC)

February 15

How do I genetically engineer the world's best sports team?

I was thinking thru cloning. Like chip some skin off our top baseball and football players and thier offspring's genetic code would be the same, right? So they would have an excellent chance of being athletic in a superior way, I take it? Then in about 20 years,-"And now,- presenting the only 162-0 baseball team in history,-". They would then take the field proudly and win another 27-0 shutout. Is this dream possible?Baseball and and and Popcorn Fanatic (talk) 00:17, 15 February 2009 (UTC)

How do you genetically engineer the world's best sports team? You begin by getting a degree in genetic engineering and hope that by the time cloning techniques are advanced enough to allow such a thing, that it is legal to do so in whatever country you plan on cloning your humans. In addition, you also need to make sure that for whatever sport you plan on having your players compete in, that cloned humans aren't banned similar to doping. There's also the question of whether your human clones will actually want to play for you and not other teams. Finally, if you plan on having your players compete in a professional league, you may find it useful to buy a franchise. But be forewarned that such franchises are cost-prohibitive. The Chicago Cubs, for example, are currently being sold for $900 million. A Quest For Knowledge (talk) 01:18, 15 February 2009 (UTC)

You may also wish to consider what makes you enjoy watching your team win. Is it the elegance of each batter's swing and the movements of the catchers (sort of like ballet?) or is it the uncertainty of the outcome of the game? A majority of spectators would abandon the game if your team so far outperforms other teams that the outcome is a given. So your franchise would go broke and your perfect players would have to go work in jobs they weren't engineered for. 76.97.245.5 (talk) 02:04, 15 February 2009 (UTC)

Your clone breeding project comprises a violation of Equal opportunity that not even eugenicists contemplate, and which would raise issues of medical ethics and legality in athleticsCuddlyable3 (talk) 18:17, 15 February 2009 (UTC)

speeding up human gestitation

is there any way to speed up the 9 months? how about in non-humans? —Preceding unsigned comment added by 82.120.236.246 (talk) 00:52, 15 February 2009 (UTC)

It seems very unlikely. Any effort to mess around with the cell division rates would likely screw up the development in one way or another. Perhaps you could do it in VERY primitive organisms - but not in 'higher animals'. SteveBaker (talk) 01:44, 15 February 2009 (UTC)

That's only if you want the newborn to be normally developed, of course. It's easy enough to induce birth early if you don't mind an underdeveloped baby. Algebraist 02:53, 15 February 2009 (UTC)

You could always have nine women work on one baby, they should be able to get it done in about a month.--OMCV (talk) 02:56, 15 February 2009 (UTC)

You, sir, should work in management. You would go far. -- Captain Disdain (talk) 09:06, 15 February 2009 (UTC)

As far as non-humans go, in viviparous reptiles it is possible to reduce the gestation length by increasing the ambient temperature, up to some point. For mammals, esp. placental mammals - I doubt it. --Dr Dima (talk) 04:18, 15 February 2009 (UTC)

Travel in a spaceship and come back. You will notice time dilation. But don't go too far or too fast or you'll miss a birthday or few.Cuddlyable3 (talk) 17:51, 15 February 2009 (UTC)

Most non-humans already gestate in fewer or more than 9 months, presumably for their own good reasons. Cuddlyable3 (talk) 17:54, 15 February 2009 (UTC)

An unfortunately serious answer follows. By definition, a human baby that is born early is a preterm birth and will probably suffer from a large number of mild to serious medical complications, mostly relating to underdeveloped systems. Low birth weight is already a problem, and accelerating the birth to an even younger gestational age would severely increase the numerous accompanying conditions, infant mortality, and long-term problems like cerebral palsy, mental retardation, and other developmental disorders. Speeding up a human birth would have serious medical ramifications. Nimur (talk) 16:37, 16 February 2009 (UTC)

Yellow Sodium Light

Hello. Why is yellow sodium light the reference point in determining refractive indices? Thanks in advance. --Mayfare (talk) 05:13, 15 February 2009 (UTC)

Until an expert comes along, all you'll have is an educated guess. Yellow is kinda in the middle of the optical spectrum, the sodium output is very bright and unambiguous, and a yellow sodium light emitter should be readily available to any researcher (if nothing else, salt sprinkled in a Bunsen burner flame). Bunthorne (talk) 05:46, 15 February 2009 (UTC)

Sodium has a bit of info on the history. Also see Fraunhofer lines 76.97.245.5 (talk) 06:04, 15 February 2009 (UTC)

(EC) note by unambigious a key point may be it's fairly monochromatic Nil Einne (talk) 06:09, 15 February 2009 (UTC)

Indeed, the key point is that it emits light at one very specific and precisely known frequency. --Tango (talk) 12:39, 15 February 2009 (UTC)

Think about white light (eg sunlight). If you shine white light through a narrow slit and into a triangular slab of glass (a 'prism') it spreads out into a broad rainbow-like spectrum. It's hopeless to try to measure the angle the light was bent by because each of the colours got bent by a different amount. When you measure refractive indices, you are measuring that angle - and you get a different answer for different frequencies of light - so if you want to express it as a single number, you need a very pure light source. Sodium emits an almost pure yellow light - there are actually two frequencies but they are very close together. When you shine sodium light through a slit and into a prism, it doesn't split up - you get just two bright yellow lines (which are very close together) instead of a rainbow. It's easy then to measure the angle between the incoming and outgoing light and calculate a simple refractive index. If you used white light, you'd have to guesstimate (say) the middle of the fuzzy red/orange/yellow/green area and that would produce hopelessly inaccurate results. SteveBaker (talk) 15:25, 15 February 2009 (UTC)

For those who are interested, our article on sodium vapor lamps has a pretty picture of the low-pressure sodium emission spectrum. Check out the article or jump directly to the image: File:Low-pressure sodium lamp 700-350nm.jpg. (The image has been somewhat overexposed to make the other emission lines visible; this also causes the sodium D line to 'bloom' out a bit.) TenOfAllTrades(talk) 16:59, 15 February 2009 (UTC)

science/geology---tides!!!

If moon's attraction causes tides during nighttime,,, but why they not occur during daytime,, even if moon is present at that time? —Preceding unsigned comment added by Nilesh raj (talk • contribs) 06:39, 15 February 2009 (UTC)

Who says they don't? See the graph or the daytime pictures of the Bay of Fundy in the Tide article. Also, surfers don't go out only at night. Clarityfiend (talk) 07:35, 15 February 2009 (UTC)

There are definitely tides during the day. You usually get one high tide about every 12 hours (it's not exactly 12 hours since the Moon is orbiting as well as the Earth rotating - that's what causes the tides to be at different times each day). --Tango (talk) 15:11, 15 February 2009 (UTC)

Oh cool! I can use the word! Can I say 'syzygy'? Can I please? ... Oh good - thanks!

The tide is at it's highest when there is a syzygy - which is when the sun, moon and earth are all in a straight line. That happens during the day and during the night when there is either a total solar eclipse or a total lunar eclipse.

SteveBaker (talk) 18:40, 15 February 2009 (UTC)

How long have you been waiting to use that word? I think that was rather a stretch - the OP didn't ask about the maximum tides, just tides in general. --Tango (talk) 18:56, 15 February 2009 (UTC)

I was pointing out that not only do tides occur during the day - but the highest tides happen at midday during a...a...well, I'm just not going to say it now...you've taken ALL of the fun out of it. SteveBaker (talk)

Don't worry, Steve. He's just jealous because he didn't get to say 'syzygy'. — DanielLC 21:05, 15 February 2009 (UTC)

Lies, lies! --Tango (talk) 21:29, 15 February 2009 (UTC)

Oh, stop being such a syzy (gy whiz). Clarityfiend (talk) 02:00, 16 February 2009 (UTC)

At least you got to say it. I'm still waiting for my chance with Gegenschein. Algebraist 21:43, 15 February 2009 (UTC)

ENGINEER'S HELP NEEDED

HI FRIENDS

I AM RESIDING ON GROUND FLOOR OF A 3 STOREY APARTMENT.

THE PERSON RESIDING ON 1ST FLOOR ABOVE MY HOUSE HAS GOT HIS BATHROOM LEAKING IN MY HOUSE.

I TRIED HARD TO PURSUE HIM BUT HE IS NOT WILLING TO MAKE REPAIRS & ALSO IS NOT ALLOWING ME TO DO SO.

WHAT SHGOULD I DO?

I HAVE HEARD OF CHEMICALS(FOSROC HYDROPROOF)WHICH CAN HELP IN THIS BUT DONT KNOW MUCH.

ALL THAT CAN I DO IS TO MAKE REPAIRS FROM MY HOUSE ONLY, THAT IS, FROM THE BOTTOM ONLY.

IS THIS POSSIBLE?

PLEASE SUGGEST. —Preceding unsigned comment added by Saurabh85 (talk • contribs) 10:31, 15 February 2009 (UTC)

PS: On the user page of user:Milkbrath the OP mentions that he ad his / she and her neighbour are owners the apartments. --Cookatoo.ergo.ZooM (talk) 16:04, 15 February 2009 (UTC)

First of all, I suggest you turn off your caps lock key.

Secondly, to begin with, I suggest you contact the owner (or owners) of the building, or the building's manager, or some comparable party. Water damage can get very expensive if the problem isn't addressed, and it's likely to affect a lot of people other than just the people who live in the apartments in question. You don't mention whether you own the apartment or are renting; if you're renting, contact your landlord. The Wikipedia Ref Desk is probably not a good place to get help with this; you really should notify the building's owner or owner's.

Thirdly, I very much doubt that any chemical could fix this problem. I guess it might keep the water from your apartment, but it's not going to make the water go away: it's still going to be up there, leaking and doing damage. It will rot wood, rust steel, cause molds to grow, etc. You really need to move on this now; the longer you leave this, the more damage there will be. The leak needs to be fixed.

Fourthly, your neighbor is not only an asshole, but -- depending on where you leave -- probably also in a bad position legally; if he's aware of the problem but refuses to do anything about it, he's probably going to end up with a pretty hefty bill. We don't do legal advice, but let me put it this way: it's probably not a good idea for you to be aware of it and not report it to anyone, either. -- Captain Disdain (talk) 11:32, 15 February 2009 (UTC)

You state that you both are the owners of your respective apartments. As such, there must be an occasional meeting of owners to agree on communal matters where this problem should be discussed. Alternatively, as CD points out, there must be an appointed manager who looks after groundkeeping / general repairs / lift maintenance / etc.

You may also consider to call a plumber to determine the cause of the problem and to have an expert witness at hand. If nothing else helps, take a few photos of the damp patches / dripping water / mould / whatever and contact a lawyer. Finally, you may consider the benefits of having an apartment with an indoor swimming pool. --Cookatoo.ergo.ZooM (talk) 12:04, 15 February 2009 (UTC)

You don't need an engineer's help. You need legal help. Dmcq (talk) 12:06, 15 February 2009 (UTC)

Maybe it'll help you if you do a little experiment to visualize your problem. You'll need 2 or 3 slices of bread. Spread a good layer of butter or margarine on two of them. Turn your faucet to a slow drip and hold the piece of bread without any spread underneath. The bread will get soaked and sooner or later water will drip from the bottom. That's your ceiling now. Next turn one of the buttered slices upside down so that the side with the spread on it faces away from the faucet. Hold that one under the faucet. That's what you'd get if you tried to seal your ceiling from below. Not satisfactory, is it? The only way to solve your problem is to stop the leak or seal the ceiling from the top. (i.e. your neighbor's floor). If there still was a leak in his bathroom (e.g. from a leaky gasket or runoff from a shower curtain) the water would then collect on his floor and he could mop it up. That is the idea behind the products you read about. They are intended to prevent the water from leaking into the ceiling. Once it's in there it will have to go somewhere. If you'd block the ceiling it would just run into your walls into your closets and under your flooring and damage those, too. It's not that we wouldn't want to help you, it's just that sealing your ceiling from the bottom isn't an idea that would work. Don't know where you are, so I can't tell you what's available in your area. You may qualify for free legal assistance from some organization. Check your condo contract and your insurance policy and follow the advice the others have given. OR We have an occasional leak in our basement and are now into our third expert trying to find and remedy the cause. This kind of thing isn't a job for DIY even if you had better skills and knowledge than you seem to have. 76.97.245.5 (talk) 14:07, 15 February 2009 (UTC)

You don't say where you are from - and you don't say whether you and your neighbour own the apartments or are renting them - so it's hard to guess what legal options might be open to you. For sure there is no technical/engineering solution. That water is landing on your ceiling and that's that. If your ceiling is showing damage - and presuming you have insurance on your apartment - then I would make a claim on your insurance for the damage. They will come and investigate - they'll realise that your neighbour is at fault and will make a claim on him. Then there will be action. If you are renting the apartment - then you need to talk to your landlord. Whatever you do - you need to do it soon because your ceiling will collapse...and you'll also be getting mold growing up there which could have serious effects on your health. You should also talk again to your neighbour - explain clearly that if he doesn't fix the leak - and quickly - he will be responsible for all of the damage AND the leak will have to be fixed. If he fixes the leak now - then he's saving himself money. You might also check whether there is a home-owners' association for your apartment block - they would be able to help you too. SteveBaker (talk) 15:16, 15 February 2009 (UTC)

One comment: Just because there is water leaking from your ceiling doesn't necessarily mean it's coming from the apartment directly above yours. Water can leak from another apartment or even a roof ice dam, travel down the walls until it reaches a barrier, then travel between the upstairs floor and your ceiling until it finds a spot to leak through. StuRat (talk) 17:20, 15 February 2009 (UTC)

THere's some excellent advice above. In your situation I would I would contact your building insurer immediately in the form of a letter, marked Urgent, that states that you observed a water leak start, you believe it originates from Floor #1 and that you have informed (by a copy of the letter) the resident of the danger of damage. The logic here is that if damage and argument do arise, you have proof that you took steps to limit damage, and there is no accusation that provokes the other resident. Good luck. Cuddlyable3 (talk) 17:37, 15 February 2009 (UTC)

Is there any Green Agency at India

There are agencies that help corporates move towards achieving energy efficiency like 1 degree in Australia that helps News Corp. to reduce green house gas emition.

Is their any such service at India? or other parts world wide? —Preceding unsigned comment added by 117.196.164.211 (talk) 16:24, 15 February 2009 (UTC)

This might be a start [27].76.97.245.5 (talk) 23:59, 15 February 2009 (UTC)

Past weather data

Please, is there an internet source for detailed past weather data? I'm looking for specifics (e.g., weather in Wales on a specific date), not long-term weather records. I realize that what I am looking for would require a large database.

Thank you, Wanderer57 (talk) 16:39, 15 February 2009 (UTC)

Try searching newspaper sites. If they've got their archives online, just pick the date you're interested in. B00P (talk) 17:26, 15 February 2009 (UTC)

TuTiempo. I found it a couple of months ago looking for historical weather data for Cape Town. The site is amazing, it has daily weather data for seemingly every city in the world going back decades, and not just temperatures, it has precipitation and cloud cover and everything. Knock yourself out! Zunaid 17:51, 15 February 2009 (UTC)

p.s. you have to click on the "climate" section in the left-hand column. The link for the UK is this. Zunaid 18:45, 15 February 2009 (UTC)

In the U.S. Weather Underground is very similar. I don't know what its like for locations outside the U.S. however. --Jayron32.talk.contribs 18:35, 15 February 2009 (UTC)

For locations (airports) in Canada, The Weather Network has historical weather data for most dates in the current millenium. ~AH1^(TCU) 16:41, 16 February 2009 (UTC)

The National Weather Service provides recent and current archives, and also has an FTP server with long-term archives, for all US locations and many many world-wide locations. They are a little "more official" than WeatherUnderground, but their database requires a bit more technical savvy to access. Nimur (talk) 16:45, 16 February 2009 (UTC)

For specialist only...!

I'am working at construction feild , as asite engineer

now we're filling the spaces between the foundation according to cast the (slab on grade ) , to save time we are using single size aggregate instead of selected natural material , now and according to the plans there is a 15 cm layer of basecoarse under the slab , the question is this ...?

if i execute this layer , and we assume some how water did find its way to this layer , dont you think that the water will carry the fine material contained in basecoarse and move it down ward through the voids between single size agg. particles ,leading to deflection in the slab.

and , is the only purpous of (15 cm layer ) of single size to protect the slab concrete from being in contact with the natural fill material , and why ...?

i know its hard to understand all of this but i hope to get an answer ... ? —Preceding unsigned comment added by 94.249.40.92 (talk) 17:34, 15 February 2009 (UTC)

This is, essentially, a legal question. At least, it is a question which requires knowledge of building regulations in Jordania, knowledge of the plan of the building, the specifics and substrate of the buidling site, the reinforcement of the slab, the aggregate you are using for the fill, data on precipitation / groundwater and a few details more. I can´t imagine that you will get useful answers from a distance, even from static engineers. --Cookatoo.ergo.ZooM (talk) 18:34, 15 February 2009 (UTC)

we are using BS standards , we dont have our own i thought its going to be the same detailes for concrete structures assume , ordinary building use , low water table , warm claimate , crushed stone fill ( course aggregate used in concrete casting ). you will find a very excellent answers at www.contractortalk.com . thanks —Preceding unsigned comment added by 94.249.40.92 (talk) 18:51, 15 February 2009 (UTC)

Do British standards contain a section on earthquake engineering or earthquake construction? I hope we aren't going to get any more of those reports like 1999 İzmit earthquake on bad construction. Cheaper isn't always better. 76.97.245.5 (talk) 07:59, 16 February 2009 (UTC)

is it a coincedence too

I want you to follow this link , after you watch the video , please i need your objective opinion ...http:/www.metacafe.com/watch/98111/miracles_of_the_quran_12/

be objective .... thanks . —Preceding unsigned comment added by 94.249.40.92 (talk) 18:41, 15 February 2009 (UTC)

Many of us do not go to off-WP sites that could be anything. You can help us help you by asking your question, please, and by telling us what the link purports to show. We prefer to deal with facts, not opinions, objective or otherwise. Thanks ៛ BL ៛ (talk) 18:47, 15 February 2009 (UTC)

That's not a coincidence, it's just nothing at all. So the Qur'an mentions the tips of the fingers, who cares? I'm sure people noticed that fingers had tips long before the Qur'an was written. It's just a reference to putting together the whole body, it makes no reference to using fingerprints for identification, or even a mention of fingerprints at all. --Tango (talk) 18:53, 15 February 2009 (UTC)

will ... this link will show avideo talking about finger print and that quraan referred to it and that each person do have a unique finger print from evry one else ... will how do they knew that ... ? —Preceding unsigned comment added by 94.249.40.92 (talk) 18:56, 15 February 2009 (UTC)

The quote from the Qur'an doesn't mention uniqueness at all. It doesn't even mention fingerprints, just the tips of the fingers. --Tango (talk) 19:03, 15 February 2009 (UTC)

And even if it did, the observation that fingerprints are unique is something that anyone who looked at them would be able to figure out. It doesn't require any scientific theory to understand this, so I see no reason why this couldn't be known, even to prehistoric people.. StuRat (talk) 19:46, 15 February 2009 (UTC)

Well, it's of note that it took quite a bit of time before this was really proven to be true. They look superficially similar to one another—you have to really look at them closely to see that they are in many ways very different from one another, and you have to extrapolate a bit further beyond that to think that such is a meaningful observation (why does it matter that fingerprints are unique, vs., say, noses, which are also unique). The modern significance of fingerprints for forensic criminology was not surprisingly only figured out in the 19th century or so—it requires a concept of forensic criminology first. --98.217.14.211 (talk) 20:29, 15 February 2009 (UTC)

Yeah - this is nuts. The whole thing is based upon one line - whose English translation is: "Yes, We are able to put together in perfect order the very tips of his fingers.". This doesn't say - or even imply that "everyone's fingerprints are unique" - it says that fingertips are "in perfect order" - which I would more likely assume to mean that all fingertips are perfectly smooth - or they all have nice regular 'ordered' stripes or concentric circles or something. Fingertip patterns are a result of 'chaos theory' - which is about as mathematically 'unperfect' as you can get. So FAR from assuming that this book says that we all have unique fingerprints, I'd go so far as to say that the existance of totally different fingerprints is yet another thing proving the Quran is wrong (and lest I appear to have a western bias here - let me also point out that the christian Bible and the Tanakh and the Sefer Torah are also filled with just as much nonsense and untruths). Besides - there are many other aspects of humans that are just as unique as fingerprints. Our toeprints are also different. Our retinal patterns are different...pick the ratios of the sizes of any few dozen physical features, round them off to the nearest 1% and you'll have a number that's unique to every human on earth. There are any number of other things that are unique. Why does the Quran not mention that chimpanzees also have unique fingerprints too? Dogs have unique nose-prints. The only reason people find human fingerprints in any way 'notable' is because we leave behind little greasy patterns when we touch things with our hands - and that provides a means to tie a criminal to some place or object. I guess the Quran failed to mention that too. Furthermore - fingerprints were used as identification by the Babylonians around 4,000 years ago. Since the Quran is supposedly only about ~1400 years old - this hardly constitutes a prediction! I'm sorry - but when religious nuts of all kinds come to the science desk in an effort to impress us - they are going to get torn to shreds by actual FACTS. This is no different. SteveBaker (talk) 19:58, 15 February 2009 (UTC)

See Fingerprint#History_and_validity for some very old uses of fingerprints. — DanielLC 20:55, 15 February 2009 (UTC)

See, this is what irks me about people's misunderstanding of science. You can blindfold a man and ask him to throw darts at a dartboard. Every once in a while, he will hit a bullseye. Merely because he does so does not make him a good dart player. Darts is a game which requires a certain set of skills and talents and needs practice to play right, and merely because dumb luck resulted in a blindfolded man hitting a bullseye does not mean that being blindfolded and throwing random darts is a valid way to win the game. Likewise, science is a process and not a collection of facts. Just because someone randomly makes a statement, without going through the scientific process, which happens to match what rigorous scientific study has shown to be true; does not mean they got it right, and more than we can say that playing blindfolded is the "right" way to play darts. --Jayron32.talk.contribs 21:01, 15 February 2009 (UTC)

I kind of doubt that you're interested in our "objective opinion". Essentially, you keep on coming at us with various "amazing" things from the Qur'an -- the development of the fetus, fingerprints, all of that -- and we keep explaining to you why it doesn't mean that the Qur'an is the best science book you could possibly have. It's not hard to identify you, even though your IP address changes, because... you have a very distinctive... style of writing. You keep presenting these things from the Qur'an to us, as if they were proof of something, when, in fact, all you do is either demonstrate your own ignorance (at worst) or misconceptions (at best) of science and history, or misrepresent what the Qar'an actually says.

The ridiculous thing is, you keep doing it, and let me predict something here: if you manage to get one right and come up with an example of the Qur'an coming up with some great scientific discovery, then you'll probably hold that up as some kind of proof. That's a case of counting the hits and ignoring the misses, and frankly, I find it a little sad that you're trying to use the Ref Desk as a tool in this campaign of validation. -- Captain Disdain (talk) 21:46, 15 February 2009 (UTC)

That is harsh and I would grant some WP:AGF to the questioner who I think honestly needed objective input. Cuddlyable3 (talk) 22:11, 15 February 2009 (UTC)

If you read the original poster's comments -- including the one below directly below -- and believe that he has no agenda, okay, that's fine with me. I disagree, and I think his own comments back me up. But please understand that I'm not really assuming bad faith as such, either. I'm not saying he's dishonest here, because that implies some kind of a malevolence... but I don't think he really wants objective opinions or knowledge. I think he wants to present us with something that proves his faith, and that doesn't really go well together with being objective. I can understand why he does that, but the end result is that we jump through hoops. And I wouldn't mind that as such, but when he ignores what he's told and keeps hoping for that hit, it's not a very fair setup -- if he was trying to understand or looking for knowledge, that'd be one thing, but he isn't. He's looking for validation.

I think WP:AGF is a kind of a problematic guideline a lot of the time. It's great when you run across something that makes you angry or looks weird or suspicious for the first time, but it often gets twisted into a free pass. -- Captain Disdain (talk) 08:05, 16 February 2009 (UTC)

iam not trying to press my opinions , its afact its your choise not to belive . when i talked about univers expanding ,some said it was acoincedence , and talking about finger prints some talked about darts game , and steve say it was used 4000 years ago (prove it , put some links at least ). the statment was that god will recreat us that he will even rebuild our finger tips , because they didnt have the term finger print back then , if he say finger print they are'nt going to understand , because simply they didnt have that word . i do have more , alot more and if you can make me belive this all just luck or wrong i will become atheist . and if you say it was used 4000 years ago (please prove it ). about the different addresses , will i use alot of computers ,its not even mine . have faith people ,even if thier's a probabilty about 1/1000000 that your wrong it does worth it,dosent it i dont understand why you are so angry , you should be more tolerance . excuse my english , iam not an english native ,thank you any way ... —Preceding unsigned comment added by 94.249.40.92 (talk) 22:30, 15 February 2009 (UTC)

You seem to be referencing Pascal's wager, a seriously flawed argument. The expanding universe thing was an intentional mistranslation and the fingerprint thing is just reading more into a quote than is actually there. These aren't coincidences, they're just very poor attempts at making it look like the Qur'an is saying things it isn't. --Tango (talk) 22:36, 15 February 2009 (UTC)

You requested a link in respect of the use of fingerprints in antiquity. See Fingerprint#History_of_fingerprinting_for_identification for statements, with sources, about the use of fingerprints as identification on legal documents as early as 1900 BCE, which is just shy of 4000 years ago. ៛ BL ៛ (talk) 22:44, 15 February 2009 (UTC)

we are using a very advanced technology to identify finger prints , and some time we have errors and your telling me that 4000 years ago they were using it to the same purpose . will .. is this make any sense , mabey they notice the shape,mabey they assume that its unique , but use it to identify people in thieft cases ... iam sorry this is too mush ...??????????? —Preceding unsigned comment added by 94.249.40.92 (talk) 23:03, 15 February 2009 (UTC)

We use ink and some kind of powder - not very advanced, really. You don't need computer analysis for fingerprints to be useful, it just makes it quicker and more accurate. --Tango (talk) 23:10, 15 February 2009 (UTC)

I noted that fingerprints were being used for identification instead of signatures. I said nothing about criminal use. Muslim tradition dates the Koran from around 610-630 CE. From the article "Fingerprint" linked above comes: In China around 300 C.E. handprints were used as evidence in a trial for theft. From the remainder of that paragraph, it appears that at least one other culture knew about fingerprints at the time the Koran was compiled, and this knowledge was a part of the Chinese criminal-justice system some 300 years prior to the dates of the Koran. It is fact. ៛ BL ៛ (talk) 23:23, 15 February 2009 (UTC)

I apologize for leaving off the link - but (as others have pointed out) it's right there in our Fingerprint article. Fingerprint#History_and_validity to be precise. It says (with LOTS of impeccable references) that the Babylonians were fully aware of the uniqueness of fingerprints around 4,000 years ago. The didn't use ink - they used soft clay which was then baked into pottery to make it permenant. They used them in place of signatures. So without any doubt whatever - the Quran didn't predict or explain anything that wasn't already well-known. If you were honestly curious - you could have looked at that article and discovered precisely what I discovered. But even if we somehow deny all of these older instances of an understanding that fingerprints are unique - you can't claim that this one sentence in the Quran says ANYTHING about fingerprints being unique. Just read the darn thing! It says that they are in "perfect order" - I can't make my brain go from "perfect order" to "completely and utterly random and different on every single person in the world"! How can those two things POSSIBLY mean the same thing?! So the Quran didn't predict or explain ANYTHING - in fact (if we are to believe that it's talking about fingerprints at all) it stated completely the opposite of the truth! I don't know whether you plan to drop these supposed "facts" from the Quran on us every few days in the hope that one of them will be convincing - but honestly, it's pointless - I can tell you - in advance - that not one of them will turn out to be true...not one. So if you really must - why not get it over and done with in one go. Just list the whole phreaking list in one question and I promise that I'll personally go through the list disproving every single one of them - with references. If you're honest - then you'll have to admit that this stupid book is as big a pile of crap as all of the other "great" religious books of the world and then we can go back to answering questions from people who aren't trying to push an agenda. Sadly, I know you won't do that because you're brainwashed. You don't give a damn about the answers - you just have some vague hope that we'll be dazzled by the impressiveness of a 1400 year old book...but we're not going to be. If the Quran contained all of these deep scientific and technological truths - how come none of the consequences of that was ever discovered by the people who live and die by that book? Most of math, science and technology comes from the christian world...and mostly from atheists living within the christian world. Religious teachings ALWAYS act to suppress advances in science and technology...the Quran is no different. SteveBaker (talk) 02:58, 16 February 2009 (UTC)

dear Mr steve .. you hav'nt disprove any of them . about finger print ... the statment says that god will recreat evry one of us that he will even rebuild his finger tips ... god want to show you that he is cabaple of reproducing your body after its turned into ashes that he will even build your finger tips back .... translation may not give the same meaning , because languages are different , that i can't help you with . and why the people who lived by the book had'nt dicover any thing , because they are no ascientiests , they are an ordinary people , what its gonna mean if they discover it 1400 years ago . arab world became the most advanced in the world , because they lived by the book , bibble and tawrah is the book of god as mush as the quraan , but we missed the two up , that god send the last one (quraan) to be the last , surly god didnt leave people before islam lost in the world . and finally , i will list up what i know , and wait for your answers , and before you answer read the explanation of it , and dont expect to find some mathmatical expression in it , such science could'nt be expressed by arabic language that time , the word was'nt enough . i look at indian scientist worshiping caws , mabey i'am justlike them and maybe not , at least i considering the possibility , why dont you , you could be wrong either Mr steve . —Preceding unsigned comment added by 79.173.227.192 (talk) 07:34, 16 February 2009 (UTC)

So you've changed what you were saying. You asked us to comment on a video that said that the Quran predicted that fingerprints are unique. I clearly showed that not only does it not say that - but also it didn't say whatever it actually DOES say until a couple of thousand years after the fact was already well known. Now you are just saying that the Quran tells us that god will rebuild us or something - that's a completely different matter - it doesn't say anything about predicting that we all have unique fingerprints - which is what you asked us to discuss. So did we answer your question by proving that the Quran DOES NOT predict unique fingerprints? If so - then we're done here. SteveBaker (talk) 15:45, 16 February 2009 (UTC)

You're not listening and I'm not going to repeat it all. You clearly aren't here to learn, you just want science to prove Islam right, and that's not going to happen. Please stop posting here. --Tango (talk) 12:04, 16 February 2009 (UTC)

And what does this book say about aggregates (previous question above)? Bazza (talk) 14:54, 16 February 2009 (UTC)

What's the point of debating this? Either the Quran did have scientific facts in it, or it did not. Lots of books have lots of important information buried in lots of noise, and suffer from widely interpretable translation artifacts. But you don't see scientists running around quoting Principia Mathematica verbatim (Quantitates materiae in corporibus funependulis, quorum centra ossillationum a centro suspensionis a qualiter distant, sunt in ratione composita ex ratione ponderum & ratione duplicata temporum oscillationum in vacuo!) We have better ways to say the same thing, rendering the original text obsolete, and as a scientific community we can move forward. If the material is relevant, the truth of it will be self-evident. The mindless task of deciding attribution, or assuming that the author was divine, divinely inspired, etc., is a question for the humanities desk, because that sort of thing is not a science question. Nimur (talk) 16:59, 16 February 2009 (UTC)

On ancient languages being incapable of saying "fingerprints are unique"

You made an assertion at one point that they had no way to say "fingerprints are unique", so said the closest thing they could in the language at the time. I disagree. If they didn't have a word for fingerprints, they could have said something like "the patterns on the skin on tips of the fingers, on the underside, opposite the nail, are different for each person and each finger". This would work without the words "fingerprint" or "unique". Most concepts can be described without words needed for the concept itself, by using more words. This is what a dictionary or encyclopedia does, after all (or at least what they're supposed to do). StuRat (talk) 16:44, 16 February 2009 (UTC)

our discussion is if the quraan is god word or not , so we will assume that it was made by god , which lead to the fact that these is gods word not ours . i can give you alot of similar examples , but assuming that god want to talk about the earth , god mentioned that he had created seven earthes , its not clear unless you search for it to find that earth is made of seven layers , not three as we use to know , it was meant to remain unexplained until we explain it , so to be like aguide , aprove that this book is the word of god . will the question is is it acoincidence that seven earths were used , or mabey the fact is just wrong, or what and finaly , even if any one could proof that there is ascientific facts in quraan , its very easy to say , avery advanced civilisation had lived before us and this is just their remains . its easy to ignore it , to assume any thing . my friend , i'am not arelegious man , yes i'am amuslim but i'am not really amuslim if you know what i mean , just like chrestians these days , i'am just trying to find the truth , no thing i said were disapproved , they all make assumptions , like coincidences and such , from where did we come , evolution , mabey ,its just theories . all i'am asking is try to be neutral , admmit the possibility that this could be true . and please dont get angry , i'am not your enemy , thank you any way . —Preceding unsigned comment added by 86.108.53.185 (talk) 18:20, 16 February 2009 (UTC)

I don't see why "words having come from God" would mean that they must be so vague they could be interpreted to mean just about anything. Why exactly would God want to give us confusing descriptions instead of clear ones ? As for your example of "7 Earths", it's quite a wild assumption to take that to mean "one Earth with 7 layers". And, even if you did (mis)interpret it that way, you could say the Earth is made of just about as many layers as you want. Just the atmosphere could be said to have 7 layers, if you wanted to define it that way. So, if you combine being able to interpret holy words in any way convenient and being able to interpret science in any way possible to get a match, you will find you can "prove" just about any holy words you want. StuRat (talk) 19:19, 16 February 2009 (UTC)

Islam teaches that only the original Arabic is God's word - you're talking about translations of God's word, and often serious mistranslations. --Tango (talk) 22:50, 17 February 2009 (UTC)

On the predictive nature of good theories

While it's one thing for a theory to be able to be adjusted to fit data that doesn't fit initially, it's certainly not a proof that the theory is correct. What would be a partial proof is if the theory allows us to predict things accurately. For example, was there anything in the Koran which clearly pointed to the date of the tsunami ? (I mean so clearly that everybody reading it would have been sure that it could only mean that date, before the event occurred.) No, of course not. If so, then all believers would have evacuated the coastal areas on that day, but they didn't. StuRat (talk) 19:29, 16 February 2009 (UTC)

Question about the nature of the expanding universe

Hi, my question is ver stupid but here it goes. What is beyond the expantion? 1) Nothing?? in this case we can say that "the expantion of the universe" is creating "space" as it keeps going. 2) Empty space? in this case we can say that our big bang could be just one of "many big bangs" going on at other points of that "empty space" I think this question is a little confuse.. sorry about that and thanks for the future answers. --Starlingmaximilian (talk) 20:28, 15 February 2009 (UTC)

There are two acceptable answers. One is "nobody knows and we don't have any good way of knowing." Not very interesting but technically true. The other is "nothing is necessarily beyond it, as far as we understand it"—that is, the expansion of the universe is creating "space" as you put it, it isn't expanding into anything. Whether people lean towards one or the other interpretation seems rather arbitrary to me, but in any case the answer given isn't ever going to be "empty space", at least, other than that being a possible answer in the "nobody knows" sense (which would make it as valid an answer as, say, "butterflies"). --98.217.14.211 (talk) 20:36, 15 February 2009 (UTC)

Neither. It's not really clear whether the universe is infinite or whether it 'wraps around' in some manner...but in either case, there is no "edge" of the universe - and therefore no "beyond". We've tried to explain that here MANY times - but the thing people don't "get" is that it's not that objects in the universe are moving apart so much as it is that space itself is stretching. This gives the impression that things are moving apart - but essentially, they are staying still while space itself stretches. SteveBaker (talk) 20:41, 15 February 2009 (UTC)

SteveBaker has it right. Try it from this perspective. The simplistic view is that the Big Bang was a singular event. People often view it as a massive explosion which "pushed" objects outward, and that the expansion we see is merely the inertia of these objects which they carry from this initial push. Its a nice, easy to understand image, and like most of "real" physics, it doesn't match what is really going on. The more complete view is that the Big Bang is the process of space creation. Under this understanding, space is created between the galaxies; they don't actually move of their own accord. The Big Bang is not a singular event, its an ongoing process. The problem with the "explosion" explanation is that, if it were true, we could observe the motion of the galaxies, and identify a "center" of the Universe from which the matter was moving away from. Except, when we look at the whole observable Universe, the grand picture is not of galaxies moving away from a central point of explosion, its of all galaxies moving away from each other uniformly. That only makes sense if there is no center of expansion; and the "creation of space" model fits the observations much better than the "big explosion" model. --Jayron32.talk.contribs 20:53, 15 February 2009 (UTC)

Could we not be in a volume of space that is shrinking in a pervasive way such that none of our local measurements seem to be affected, embedded in a static infinite Universe ? Cuddlyable3 (talk) 21:54, 15 February 2009 (UTC)

How are you defining "shrinking"? If our measurements of its size are staying the same then, by any reasonable definition I can think of, its size is staying the same. --Tango (talk) 21:56, 15 February 2009 (UTC)

By shrinking I mean you, me and all our tape measures getting smaller. An astronomer on a distant galaxy who is also shrinking could be looking towards us right now, measuring our sun's red shift and calculating how much closer we are than them to the time of their equivalent B. Bang concept.Cuddlyable3 (talk) 19:12, 16 February 2009 (UTC)

Universe can't be infinite, it must be an "edge", call it "end of the space" or "Matter moving from initial inertia". If space is tretching is because it has a limit!! and if is being created it has a limit as well!!! I found 98.217.14.211's answer very satisfactory, cause i don't know about phisics but is philosophically impossible that the universe doesn't have a "dinamic edge" —Preceding unsigned comment added by Starlingmaximilian (talk • contribs) 22:04, 15 February 2009 (UTC)

It's difficult to get your head around, I know, but the universe doesn't have an edge. Either it's infinite (trying to understand how the big bang works in an infinite universe is a sure fire way of giving yourself a headache!) or it has a closed shape - think of the surface of a balloon, as you blow it up the surface expands, but it doesn't have an edge. --Tango (talk) 22:10, 15 February 2009 (UTC)

In the baloon example the "edge" would be the last layer of rubber of the ball, and the "beyond" the air surrounding it... sorry... i'm very troublesome :)

No, we're just considering the surface of the balloon - the idealised 2-dimensional object. --Tango (talk) 22:32, 15 February 2009 (UTC)

Ok, In the baloon example the "edge" would be the unique layer of the ball (sphere), and the "beyond" is whatever outside the ball, it may be "the nothing" "the lack of space" call it as you like. —Preceding unsigned comment added by Starlingmaximilian (talk • contribs) 22:47, 15 February 2009 (UTC)

Inside and outside are references to the 3rd dimension, we're just talking about the 2D surface. Imagine you are a tiny ant walking around on the surface, there is no edge that you can fall off. --Tango (talk) 22:54, 15 February 2009 (UTC)

the body of the aunt is in "the nothing" in your example (obviosly impossible) and only the feet of the aunt are in contact with the sphere, but yet, outside. —Preceding unsigned comment added by Starlingmaximilian (talk • contribs) 23:16, 15 February 2009 (UTC)

Indeed, as with any analogy it breaks down if you look too closely. The ant is meant to be infinitely thin - it's just an analogy to help make it easier to understand. Obviously, the universe is 3D, not 2D, but the principle is the same. --Tango (talk) 23:37, 15 February 2009 (UTC)

I told you that this was going to be the problem! We've explained this at least a dozen times - and every time our OP gets stuck at the same point. We explain the balloon analogy and it doesn't help. How about the chocolate chip cookie analogy? If you buy raw cookie dough - a blob about an inch across can be placed on a baking sheet and after you bake it, you have a cookie that's about four inches across. With chocolate chip cookie dough, you start of with something that seems to be almost all chips - but after you bake it, they are quite far apart. So - the chocolate chips are...galaxies say...the dough is space. As the dough cooks every chip gets further from every other chip. No matter which chip is "you" - it seems like all the other chips are moving away from you - and the further they are at the outset - the faster they'll seem to recede. Now - if your original piece of cookie dough was infinitely big - and you baked it in an infinitely large oven - the result would still be infinite and every chip would see every other chip receding from it. SteveBaker (talk) 02:29, 16 February 2009 (UTC)

The problem is that REALLY BIG PHYSICS and really small physics work very non-intuitively. That is, the laws which govern the way the REALLY BIG THINGS (like Galaxies) and the really small things like atoms, do not obey the same basic laws which govern the medium sized world we live in. Basic Newtonian physics, where infinity has no meaning, where I push something and it behaves as I expect it, where waves are waves and objects are objects, describes the medium-sized world very well. However, when we actually make observations and measurements of the REALLY BIG STUFF (like galaxies) and of really small stuff (like atoms) the laws that seem to work well for the medium-sized world just don't apply. So entire new sets of laws and theories needed to be created to account for these differences in observations.

Now here's the kicker, these new laws and theories work perfectly well, they are mathematically and observationally consistant, they just don't make any sense. By that I mean that our unaided senses give us certain information about the world. That information leads to an intuitive model of how the world is supposed to work. It's almost subconsious; a 6-year old probably has the same intuitive model that a 30-year old does. The problem is that this model we have created for ourselves does not match the way that the REALLY BIG STUFF and the really small stuff works. So, you get the sort of incredulity that the OP expresses. At some point, if you are going to understand how the universe works on a cosmological level and on a subatomic level, you are just going to have to ditch everything you intuitively understand and accept what the actual data and observations are really telling us about how it really works. --Jayron32.talk.contribs 04:04, 16 February 2009 (UTC)

Well, it may be true that my intuition is playing me tricks... and i cannot accept examples like the balloon or the cookie... they always have a catch... but even if my intuition is making me unable to understand i can't let it apart.. i cannot accept something that don't makes sense, even if observations and maths tells me the oposite. Lets just keep it like this guys :), but one last thing, if any of you knows about any documental video explaining this subject please post it here and i will watch it. Also i want to thank 98.217.14.211 SteveBarker, Jayron32 and Tango for all the time you took in order to explain this subject to me, thanks to people like you wikipedia is as big as it is, thanks a lot guys. --Starlingmaximilian (talk) 10:05, 16 February 2009 (UTC)

Yes - there is a very real sense in which our minds are not evolved to deal with Quantum physics and the various large scale weirdnesses. However, if all else fails, you can punt on the idea of having a mental picture of what's going on - and instead just rely on the observations and the math. Sadly, you have to accept the reality of it because it is true. Nothing else can explain the observation that every object in the universe is moving away from us - and the further they are from us, the faster they are moving away. You can prove that with a spectrometer and a backyard telescope - so there is really no doubt that it's true. But getting your head around the concept that something can be both infinite and expanding is tricky. Then when you're told that it's space itself that's doing the expanding and all of the objects within it are more or less stationary...that is REALLY tough to envisage. So you have to believe it's real - even though you can't envisage a nice analogy. Trust the math. SteveBaker (talk) 15:22, 16 February 2009 (UTC)

Most scientists consider the universe to be "flat" - that is, if you were to look at the edge of the universe, it would be exactly flat. So it's an open universe, not round or closed, and it has infinite size. However, the "edge" would still be expanding "outward", that is, away from itself and its contents. ~AH1^(TCU) 16:36, 16 February 2009 (UTC)

There are empirical limits on how curved the universe can be, but I'm not sure it's true to say most scientists think it is completely flat. Even if they do, it doesn't follow that it's open - a 3-torus is closed and flat (when we think of it as embedding in higher dimensional space it has an extrinsic curvature, but it doesn't have intrinsic curvature which is all that matters in this context). --Tango (talk) 19:02, 16 February 2009 (UTC)

Okay, first, there was no big bang. Big Bang cosmology isn't about a big-bang event and doesn't say that there was one. It's misnamed. Second, we don't know whether there's an edge. The cosmological model we use doesn't have an edge in it, but there's no reason to think that it models the whole of existence. We already know it doesn't work farther back in time than ~14 billion years, and it doesn't necessarily apply further than some finite distance in space either. It's a mistake to assert that the universe has no edge just because the model doesn't have one. We couldn't directly see or otherwise detect any edge because of the light speed limit anyway. Third, as I keep saying, the cosmological expansion is just galaxies moving apart. It is not galaxies standing still while space is created between them. There's no way to invent a coherent concept of "creating space" because space doesn't have the properties of a substance. There's no conservation law for space. All of the space at any given time is brand new: it's all-new points in spacetime. The principle of relativity implies that you can't associate any particular point in space right now with any particular point in space at an earlier time (in contrast to ordinary matter, where you can trace back the worldlines and tell which matter is new and which has been around for a while). The other reason you can't talk about creating space is that the physics governing the separation of the galaxies is exactly the same physics governing the separation of any other two objects. These situations aren't distinguished in any way in the mathematics, and there's no natural dividing line you can draw between them. When an astronaut on a spacewalk drifts away from the shuttle, space is being created between him and the shuttle in exactly the same sense that space is being created between the galaxies in the cosmological expansion. It's all relative motion. If we knew the volume of the whole universe, and it was finite, it would be increasing with cosmological time, and you could describe that as an "overall expansion of space", but I would still strongly discourage that because everything I said above still applies. Physics is local; the universe doesn't care about quantities obtained by integrating over large quantities of space at a fixed cosmological time. Each bit of spacetime is doing its own thing, whether or not an overall volume can be defined. -- BenRG (talk) 18:24, 16 February 2009 (UTC)

I still don't get that. How does that work for, say, a 3-sphere? What are the momentum vectors for each galaxy at a given moment of time (in a given reference frame, it doesn't really matter which)? I can't see any way they can all be pointing away from each other. Somewhere you would need to have a region of space that is contracting, which doesn't fit with any theory of cosmology I've heard (except for contractions on very small scales, which don't help here). --Tango (talk) 19:02, 16 February 2009 (UTC)

Okay, here's the best answer I can come up with for this. The key points are: 1. The relative motion of galaxies and the relative motion of astronauts are essentially the same. This doesn't mean they're both special relativistic—they're not, they're both general relativistic. It's like saying that separation at 1 m/s and separation at 299,000,000 m/s are essentially the same, even though Newtonian physics gets one of them right and not the other. Think of the small-scale stuff in general-relativistic terms, not the large-scale stuff in special-relativistic terms. 2. Physics is local—the spacetime over here doesn't care about what the spacetime over there is doing, at least not directly. Suppose first of all that space has an edge. An edge of space, unlike the bulk, would have to have a state of motion. Suppose it's moving in roughly the same way as the galaxies in that region. Then, since the galaxies are moving away from neighboring galaxies, which are moving away from..., etc., all the way across the universe, the distance between the edges is also increasing, so the overall volume of space is increasing. However, the universe doesn't "know" this—all evidence suggests that different parts of the universe evolve independently. Locally, objects are just moving apart in the same way they would otherwise. In the case that space doesn't have an edge but closes around on itself, it's the same story. Locally, you have a net positive curvature that's due to the density of matter being a bit higher than the critical density. As matter continues to separate and thin out that density decreases and so does the curvature, though it remains positive. Global consistency requires that the total volume of space increased, but locally it doesn't matter. Locally there might as well be an edge moving "inward" at such a speed that the total volume remains constant (and eating up galaxies in the process, I suppose). In that case you might interpret it as galaxies flying outward through fixed space until they reach the edge instead of as fixed galaxies on an inflating balloon, but the universe doesn't care one way or the other.

The other thing is that it's somewhat arbitrary how you define the volume of space in the first place. Everyone knows that space is flat when the matter density equals the critical density and hyperbolic when it's lower than that. In particular, space is hyperbolic when the density is zero. But given that curvature is supposed to be due to the presence of matter, shouldn't it be flat in that case? In fact what's going on is that the Ω=0 limit of the FLRW cosmology is just a part of (flat) Minkowski spacetime, but the coordinates are such that the ones interpreted as "spatial" happen to cover a hyperbolic surface in Minkowski space for any given value of the "time" coordinate. If you look at the same cosmology in Minkowski coordinates, taking Minkowski x,y,z to be "space" and t to be "time", it looks like a finite flat space with a spherical boundary that's growing with time (at the speed c), instead of an infinite hyperbolic space with no boundary. Same physics, different coordinates. The Euclidean analogy for this is Cartesian versus polar coordinates. If you take Cartesian x,y to be "space" and z to be "time" then space is flat and infinite, but if you take θ and φ to be "space" and r to be "time" then space is spherical and finite and growing with time. A similar thing happens with de Sitter space, which is the exponentially inflating spacetime that was the past of our universe (according to inflationary cosmology) and also the future (according to ΛCDM). Cosmologists like to say that it's spatially flat (and infinite) and exponentially expanding (i.e. the scale factor goes like e^t), while mathematicians are more likely to say that it's spatially spherical (and finite) and the scale factor goes like cosh t. This is two different coordinate descriptions of the same thing. The universe doesn't care about global coordinate systems, and we probably shouldn't either. -- BenRG (talk) 23:19, 17 February 2009 (UTC)

Ok, i really like the point of view of BenRG, but if theres no space creation what do you understand with "origin of the universe"? i mean, if space is not "created" that means that the "origin of the universe" is just matter getting separated from his original point and that space was always there. But if you say that that would mean that many "origins of the universe" might be happening really far away of us, and maybe in an uncertain future colide with our "universe", but if we believe this, the word "universe" doesn't aplly anymore... do you really say that there was no "space cration" at the origin of the universe?? or maybe i got you wrong. --Starlingmaximilian (talk) 00:29, 17 February 2009 (UTC)

Our current theories only explain things back to a tiny fraction of a second "after the big bang", we don't know what happened before that (we talk about there being an "infinitesimal singularity" that went "bang", but "singularity" is just what physicists say when they don't actually know what's going on). --Tango (talk) 15:55, 17 February 2009 (UTC)

That was the traditional big bang, but in modern inflationary cosmology they do think they know what was going on and it's not a big bang singularity. The ΛCDM scale factor at very early times looks something like $a(t)\propto {\sqrt {t}}$, which obviously goes to 0 at t=0. That's the big bang. However, in inflationary cosmology there's a time t_R > 0 before which the scale factor is exponential instead due to non-ΛCDM physics, so overall you have something like

$a(t)\propto {\begin{cases}e^{{\frac {1}{2}}t/t_{R}}&t\leq t_{R}\\{\sqrt {et/t_{R}}}&t\geq t_{R}\end{cases}}$

where I put in factors of e and 1/2 to make a and a' match up at the crossover point. Real inflationary models are not this crude—there's a gradual transition between the models, not a grafting together of two different functions—but I think this gives the right general idea. The interesting thing here is that this new function never reaches zero, no matter how far to the left you go, so this model no longer has a natural beginning-of-the-universe. That doesn't mean there wasn't a beginning of the universe, but it does mean you should forget about the idea that there was a big bang at t=0. Nothing special happens at t=0; it's just a mathematically convenient origin point for the ΛCDM part of the model.

Incidentally, it's worth pointing out that the inflationary expansion is slower than the ΛCDM expansion in the regime where it actually takes place (i.e. before t_R). People are fond of saying that inflation causes the scale factor to increase by a factor of $10^{10^{10}}$ in 10⁻³⁰ second, but they neglect to mention that the ΛCDM expansion would have increased it by a factor of infinity (from 0 to a nonzero value) in an even shorter time. In fact, inflation is so slow that it takes literally forever to get from zero to a(t_R) (not that anyone thinks this simple model is valid arbitrarily far back in time). Inflation solves the horizon problem by being enough slower than ΛCDM that causal influences have time to cross the whole observable universe (which was very small back then, but not small enough to compensate for the quickness of the ΛCDM expansion). Also note that the duration of inflation is much longer than the "time after the big bang" at which it ends (in other words, inflation starts at t/t_R << 0). Or so it would seem, anyway. I don't think I've ever seen a description of inflation that mentioned either of these things explicitly, so I may be missing something, though I don't know what it is I could be missing. It would be nice to have some sources so I could either fix my thinking or fix Wikipedia's cosmology articles. -- BenRG (talk) 23:19, 17 February 2009 (UTC)

Coming from the inflation page, if space grew at a speed faster than the speed of light, then even though at a time before inflation light could travel across the whole universe, wouldnt info still not reach the edges of the universe (if there even is one) even traveling at the speed of light?--GundamMerc (talk) 15:44, 17 February 2009 (UTC)

It's not true that inflationary expansion is faster than light (a lot of books claim it is; they're all wrong). It is true that causal influences can't necessarily cross the whole inflating spacetime, but they only need to cross a part somewhat larger than our present-day observable universe to explain what we see. The uniformity that we see doesn't necessarily extend forever. -- BenRG (talk) 23:19, 17 February 2009 (UTC)

Boiling to Death

I read our article on the concept, my question is though, what is the cause of death?

Does the skin slough off? Can the lungs not take in air if it's too hot? Does the blood boil in the veins?

Why would being immersed--not drowned, just immersed, in boiling hot water--kill someone?24.91.161.116 (talk) 21:34, 15 February 2009 (UTC)

Warning, the following link contains explicit images of a decomposed human corpse which may be distressing to some readers

If you really have to see. Please don't try this at home. Cuddlyable3 (talk) 21:44, 15 February 2009 (UTC)

That link is not safe for... um... anywhere from where you can see the computer screen... --Tango (talk) 21:50, 15 February 2009 (UTC)

I am apalled that the police could even consider releasing that picture on to the internet. The man must have relatives. SpinningSpark 00:53, 16 February 2009 (UTC)

I just feel bad for whoever cleaned up. Zain Ebrahim (talk) 15:00, 17 February 2009 (UTC)

An interesting question... Obviously your skin would burn, but I'm not sure that would be the cause of death (death from skin burns usually takes some time, as I understand it, I expect death by boiling to be reasonably quick). Boiling water entering the mouth or other orifices could cause internal burns, which could be more fatal (causing internal bleeding, damaging lung tissue and causing suffocation, etc.). Or, death could simply be by hyperthermia, getting too hot - if your core body temperature gets above about about 40 degrees, you're in real trouble, and I guess it wouldn't take long to get up to such temperatures when immersed in boiling water. --Tango (talk) 21:46, 15 February 2009 (UTC)

Quite simply, the cause of death would be the symptoms pertaining to hyperthermia. Your blood pressure would drop like a stone, dehydration, tachycardia (this could be the big killer here) etc. When your heart fails, you can no longer supply cells with oxygen and you will essentially die from that. Also, when you become unconscious, there's a risk of drowning. —Cyclonenim (talk · contribs · email) 23:18, 15 February 2009 (UTC)

One time, a girl fell into an area where the water was boiling in Yellowstone, after getting out of a hotspring. She was in the boiling water for seven seconds, and then she was dragged onto a cold river to cool for 45 minutes. She didn't survive. ~AH1^(TCU) 16:33, 16 February 2009 (UTC)

That probably wasn't the best treatment... In just 7 seconds I expect the only damage would be burns, hyperthermia wouldn't have set in yet. The first aid for burns covering more than about 1% of the body (and 100% is more than 1%!) is not to cool it since that will just cause hypothermia, but rather to go straight to hospital (after wrapping the effected area in cling film). Of course, this should not be taken as medical advice - if you want to learn first aid, take a first aid course! Even with correct treatment, though, her chances of survival would have been pretty slim. --Tango (talk) 18:42, 16 February 2009 (UTC)

Cream Smell

My girlfriend uses a skin cream which reminds me of doctors. Just smelling it immediately makes me think of hospitals.

I'm wondering which ingredient in this cream is the cause:

they are as follows: Aqua, Glyceryl, Stearate SE, Glycerin, Lanolin, Alcohol, Benzyl Alcohol, Cetearyl Alcohol, Oleic Acid, Triethanolamine, Stearic Acid, p-Chloro-m-Cresol, Parfum (Fragrance), Linalool, Limonene, Citronellol, Courmarin, Geraniol, Anise Alcohol, Benzyl Cinnamate

is one or several of these a main component of the bandages/first aid/ointment smells of hospitals?24.91.161.116 (talk) 21:39, 15 February 2009 (UTC)

The alcohol (ethanol) and benzyl alcohol are both common solvents and disinfectants that are found in many medical products; they both have a fairly distinctive odor that you may associate with hospitals. Triethanolamine also has an ammonia odor which again could be associated with all sorts of medical products. p-Chloro-m-Cresol, if I recall right, has a distinct odor of phenol, which is another common disinfectant which has a very distinctive smell - if I had to bet, I'd say that is likely to be the culprit. Phenol makes me think of hospitals too, it's a very horrible and very distinctive medicine-like smell. The last eight ingredients are all substances specifically added for their smell; and are all common components of perfumes and cosmetics - it's unlikely you'd associate any of those with hospitals, though again it's possible. ~ mazca ^t|c 23:29, 15 February 2009 (UTC)

^{yes, I've spent too much time sniffing chemicals at university. I'm surprised I'm not dead.} ~ mazca ^t|c 23:29, 15 February 2009 (UTC)

Mmmm I would say the alcohol would definitely be methanol and its unlikely you are smelling that over the Parfum (which means perfume) or the Lanolin. The methanol that normally goes into these products has almost no smell. I know you may be thinking 'Hey, I've smelled rubbing alcohol before and I know it has a smell,' but that isn't the methanol you are smelling; it is an additive to make sure you don't try and drink it. Benzyl alcohol is just a preservative and while it is found in IV solutions to keep them sterile, I don't think you could pick that out either. I have compounded many similar creams and would say that you could smell the lanolin. Most lanolin that goes into cheaper OTC products isn't necessarily medical grade and contains a lot of smelly fatty acids. Whether or not those smell like a hospital, I'm not sure. Mazca probably hit on the answer in one of his other suggestions, but I'll rule out methanol as a possibility. --Mrdeath5493 (talk) 01:30, 16 February 2009 (UTC)

Yeah, you're correct on the topic of those alcohols - regardless of whether it's ethanol or methanol, in retrospect I doubt either would smell strongly enough to overpower the perfume ingredients. Benzyl alcohol does have a noticeable smell, I personally find - but again, you're right that it probably isn't strong enough. I hadn't thought about the lanolin - in its pure form it's basically odourless, but it's true that impure stuff could have all sorts of distinctive smells. ~ mazca ^t|c 10:50, 16 February 2009 (UTC)

Actually I don't know what I was thinking with methanol. I was truly thinking isopropyl alcohol.

--Mrdeath5493 (talk) 21:12, 17 February 2009 (UTC)

The night sky

Is it possible to have a faint glow in the night sky around the moon during a lunar eclipse? There, you can both have your moments now. --Tango (talk) 21:48, 15 February 2009 (UTC)

If you're referring to what I think you are, then I don't think a lunar eclipse is a very good time to look for it, as the eclipsed moon is still quite bright. According to Google, the best time is in the middle of a clear moonless night in late February (the time of year is relevant because you don't want the milky way to obscure the view). You realize it's no fun this way, don't you? Algebraist 21:57, 15 February 2009 (UTC)

I know it's no fun, I just wanted to stop you two complaining... Shall I log out and word the question less obviously? --Tango (talk) 21:59, 15 February 2009 (UTC)

Best wait a few months first. Algebraist 22:02, 15 February 2009 (UTC)

But then I have to put up with you complaining for a few months... --Tango (talk) 22:03, 15 February 2009 (UTC)

how i make small text? —Preceding unsigned comment added by 194.80.240.66 (talk) 13:20, 16 February 2009 (UTC)

Uh, perhaps you could've looked at how Tango and Algebraist did it? In any case, anything you write between <small> and </small> is rendered in a smaller font size -- so typing "<small>small text</small>" results in small text. -- Captain Disdain (talk) 13:40, 16 February 2009 (UTC)

Do you have an account? If you do, login and you get an expanded toolbar that includes a button with that feature. Or try Captain Disdain's suggestion. A Quest For Knowledge (talk) 13:43, 16 February 2009 (UTC)

February 16

Time

Why do AM and PM start at 12:00 instead of 1:00? JCI (talk) 03:50, 16 February 2009 (UTC)

Because they stand for "before noon" and "after noon" in Latin. See 12-hour clock. --98.217.14.211 (talk) 04:33, 16 February 2009 (UTC)

Can I also add that am should be thought of as starting at 0:00 (just the maths does) CipherPixel (talk) 08:54, 16 February 2009 (UTC)

When does 12 a.m. mean noon?

After reading 12-hour clock#Confusion at noon and midnight, I was quite surprised to find that the US Government Printing Office defines 12 a.m. as noon. (See this document and scroll down to section 12.9 or search for "noon".) I know that going back to the Latin, noon is neither ante- nor post- meridiem. But it seems when it is used, common modern interpretation is that 12 a.m. is midnight and 12 p.m. is noon. Is there any historic precedence for the GPO definition? Is there any other entity in this world that uses this convention? -- Tcncv (talk) 07:43, 16 February 2009 (UTC)

I'm more used to 24 hour time but the US GPO actually makes sense to me, since it goes 1am - 10am then 11am, it only follows that next is 12am followed by 1pm. Vespine (talk) 08:40, 16 February 2009 (UTC)

If you wish to communicate clearly and logically, say 12 noon and 12 midnight. Use of a.m. & p.m. after 12 is ambiguous and needs context to assist a correct interpretation. Even those who know the modern convention often get it wrong! Dbfirs 09:11, 16 February 2009 (UTC)

The problem with your definition is 12:00:00.00000000000000000000000000000000000000000000000000000000000001 p.m. is clearly intended and logically can only be 0.00000000000000000000000000000000000000000000000000000000000001 seconds after noon. If you use 12 am to mean 12 noon then you have the oddity of suddenly changing to pm with the smallest measurable time interval afterwards which IMHO makes no sense. As I've remarked before when this came up, 12 pm as noon therefore makes a lot more sense and it seems to me outside of the US there is little ambiguity or confusion. Definitely when I searched, by and large the vast majority of sites used 12 pm to mean noon and 12 am to mean midnight. Google searches are of course hardly scientificly compelling but given the evidence, I see little reason to presume there is any real common misconception. Of course, I'm not denying that strictly speaking, the terms are ambigious or just plain wrong but then again, this is hardly uncommon with a lot of the English language. After all, most of us can survive when we say 'the weight is 80kg' even though they're really talking about mass. For that matter, as I've remarked before elsewhere on wikipedia, I personally don't care if people say their timezone is -5 GMT or -5 UTC. The fact that GMT is ambigious and they probably mean UTC but could mean UT1 is no concern of mine. I don't need that level of precision. I just don't want to have to work out or remember WTF EST is. This doesn't mean of course there aren't cases when you need to be completely unambigious or that even in general, it may not make more sense be accurate and avoid unambigious terms. Simply that it isn't really IMHO that big a deal. P.S. I originally had a lot more zeroes but for the sake of the reference desk, I reduced it Nil Einne (talk) 10:40, 16 February 2009 (UTC)

If it's 0.0 seconds after noon, it's equally 0.0 seconds before noon. I don't see any compelling reason that it's more reasonable for AM to be a half-open interval closed on the left, than a half-open interval closed on the right. The only correct (and only safe) approach is to say "12 noon" or "12 midnight", and we ought to insist on these terms.

Except of course that a general switch to 24-hour time would be even better. I made the switch long ago because I was irritated at having to get up at 7 AM (or whatever) and sleeping through it because I'd set my alarm for 7 PM. --Trovatore (talk) 10:48, 16 February 2009 (UTC)

I usually use 24 hour alarm clocks for that reason. However I have never really found the need to use 24 hours clocks in general usage. It's not that hard to use both, as it suits you. P.S. You haven't explained what happens at 12:00:00.00000000000000000000000000000000000000000000000000000000000001. Clearly 12:00:00.00000000000000000000000000000000000000000000000000000000000001 noon or midnight make little sense. P.P.S. Again I don't deny that a general switch to 24 hours may be better, simply that it doesn't really cause that many problems using both. Of all the confusing problems we have in the world, there are far bigger ones like the way some people insist on using customary units in everday life when most of the world has moved on Nil Einne (talk) 10:53, 16 February 2009 (UTC)

I missed this because of the anon intervention. Sure, epsilon after noon is PM. Just like epsilon before noon is AM. And noon itself is neither, just like 0 is neither negative nor positive. --Trovatore (talk) 11:56, 16 February 2009 (UTC)

Nil Enne has a point. It makes sense for pm to start 1 second after 11:59.59. Rather than 1 second+some arbitrary infintesimely small unit of time. The fact is the minute where the clock read 12:00.xx is in the pm, why not make the whole minute in the pm, rather than all of it except one infintesimal instant? —Preceding unsigned comment added by 129.67.37.225 (talk) 11:36, 16 February 2009 (UTC)

Assuming (and it's actually quite an assumption) that time is modeled by the real numbers, then the "1 second+infinitesimal" is not an option. The boundary point of AM, and the boundary point of PM, are both noon; the only question is which set noon actually belongs to, if either.

But there is no truly standard convention. The only safe course is not to depend on how the phrases "12 am" or "12 pm" will be understood (which means not using them at all). These locutions should simply not appear; they should be considered incorrect. --Trovatore (talk) 11:44, 16 February 2009 (UTC)

Nobody can ever agree on what 12am means, so just use 12 noon or 12 midnight as appropriate. There is also confusion about when "midnight on Sunday" is. Is it the end of Sunday or the beginning? This confusion is so great that it's very common to see events advertised as being at either 11:59pm or 12:01am so there isn't any doubt. --Tango (talk) 11:51, 16 February 2009 (UTC)

I believe I am right in saying that trains in Britain are never timetabled to depart or arrive at midnight, for this very reason. DuncanHill (talk) 14:57, 16 February 2009 (UTC)

Why doesn't the whole world go onto UTC and be done with it. That will not only eliminate the a.m./p.m. ambiguity, it will eliminate time zone confusion as well. After all, the US is moving to metric measurements. While we're at it, let's eliminate the 50 -States- State governments of the US, each with its own legislature and set of laws - it's clumsy, expensive, and confusing (though it's a lawyer's paradise in disentangling inter-State affairs. - GlowWorm. —Preceding unsigned comment added by 98.17.32.201 (talk) 14:53, 16 February 2009 (UTC)

I don't believe that 12:01am is confusing - you simply have to think for a moment. The number indicates the number of hours that have elapsed ante-meridiem. Hence 12:01am and 00:01pm are simply two different expressions of the same moment. The 24 hour clock is just a system where all hours are conventionally expressed ante-meridiem. Treating 12:01am as being shortly after midnight is silly. SteveBaker (talk) 15:10, 16 February 2009 (UTC)

What does "number of hours that have elapsed ante meridiem" mean? "Ante meridiem" means "before noon", "hours elapsed before noon" doesn't make sense. The only way I can see to interpret it is as "hours until noon", in which case 12:01am should mean one minute before midnight, which is certainly doesn't. --Tango (talk) 17:17, 16 February 2009 (UTC)

The way I see it is this: We divide the daylight hours into morning and afternoon, but we don't divide the night-time hours. There are no words for "before midnight" and "after midnight"; both before and after midnight are still parts of "night" - except that the date changes, but it's still "night" at 12:05 am. The morning ends and the afternoon begins at noon. The precise point of noon (if such a thing even exists; it's gone as soon as it arrives, not a second later, not a milli-micro second later, but instantenously) is probably in neither camp, but noon is when the afternoon begins. We start books on page 1; we start months on the 1st; so if noon is when the afternoon starts, then it makes sense to consider it part of the afternoon, rather than the very end of morning. It has intuitive sense, but may not appeal to scientists. -- JackofOz (talk) 23:12, 16 February 2009 (UTC)

But the start of a book isn't the end of something else. The hour from 12 noon to 1pm is certainly part of the afternoon, just as the 1st of March is part of March (the fact that we say 1st March, not 1 March is relevant here, and there's lots of interesting stuff about how time was measured and referred to in the past, but I won't get into it), but the instant of 12 noon and the instant at the beginning of 1st March are boundary points and it's completely arbitrary to assign them to either interval. It's far better just to leave them as separate points, hence "12 noon" rather than either "12 am" or "12 pm". --Tango (talk) 14:42, 17 February 2009 (UTC)

It seems to me that the 24 hour clock begins at 0.000000000000001 and continues to 24.000000000000000000000. By contrast the 12 x 2 hour clock talks of 12.02 am/pm instead of 00.02. I still think of noon as 12.00pm. Kittybrewster ☎ 14:56, 17 February 2009 (UTC)

Academia at present

How could anyone be so complacently content with how the education system is today honestly? It's become more closed than actually being uneducated, as it seems. First of all, isn't there clearly a monopoly in nations? How could you monopolize knowledge? (That, of course, depends on whether 'education' still cares about knowledge nowadays.) How could you necessitate huge fines just for these bureaucratically-sanctioned 'educators' to 'teach' you? (Which mostly means shoving their own opinions on theories and whatnot down throats.) How could it be so tense? All of this wasn't founded like this though, was it? 94.196.67.254 (talk) 12:17, 16 February 2009 (UTC)

What country has a state monopoly on teaching? Every country I know allows for private schools... --Tango (talk) 12:21, 16 February 2009 (UTC)

No... I'm talking about something deeper than that. A monopoly on knowledge itself that the education system as a whole creates that makes it seem like knowledge couldn't possibly exist outside it. —Preceding unsigned comment added by 94.196.67.254 (talk) 12:43, 16 February 2009 (UTC)

In that case, I don't have the faintest idea what you're talking about. Do you actually have a factual question? --Tango (talk) 13:09, 16 February 2009 (UTC)

Perhaps you could be more specific in your question. What for instance would I be able to see that was different if things were the way you wish they were? Dmcq (talk) 13:36, 16 February 2009 (UTC)

It is possible that the OP refers to fringe areas of knowledge (spiritual, esoteric, psychoceramics, etc) which are excluded from mainstream education. There are, after all, folks who think that creationism should be part of the curriculum in physics and biology. If so, the question may be better placed at the humanities desk. --Cookatoo.ergo.ZooM (talk) 13:40, 16 February 2009 (UTC)

The education system certainly doesn't have a monopoly on knowledge - after all, there are public libraries, Wikipedia, the Internet - all of those are sources of knowledge that lie outside of the education system. If as Cookatoo suggests you are asking why the people in control of the education system act to limit what knowledge they teach - then that also is true, simply because there is more knowledge in the world than one person could possibly ever learn - and someone has to decide what subset of all knowledge is most important for people to know. Hence (for example) we teach basic algebra in schools - but we do not teach the proof of the three color map theorem. The reason for this should be self-evident - algebra is useful to everyone (eg I know my car just travelled 300 miles on 10 gallons of gasoline - how good is my mpg this week?) - but knowing WHY the three color map theorem is true is pretty much useless for every day life - and only a very few mathematicians really need to know it. So yeah - they limit what is taught to a reasonable set of things that the average person has time to learn and will find useful later in life. SteveBaker (talk) 15:03, 16 February 2009 (UTC)

Perhaps the other reason we don't teach the proof of the "three color map theorem" is because it doesn't have one, seeing as it isn't true... ;) --Tango (talk) 15:16, 16 February 2009 (UTC)

Spoilsport! --Stephan Schulz (talk) 15:28, 16 February 2009 (UTC)

Duh! The "three colour map theorem" works perfectly well. I once tried it out on the map of Down Under and had one colour left. --Cookatoo.ergo.ZooM (talk) 16:44, 16 February 2009 (UTC)

D'oh! How stupid we mathematicians have been all these years... why didn't you tell us?! --Tango (talk) 17:08, 16 February 2009 (UTC)

Do'h indeed. Sorry - I meant four-color...not three. You see what happens when they don't teach you stuff! I should have gone with Fermat's Last Theorem. SteveBaker (talk) 21:48, 16 February 2009 (UTC)

Teaching the only known proof of the four-color theorem would be like teaching the phone book — it has a huge section of tedious, mechanical checking of an enormous number of cases; thus far, AFAIK, no human has ever gone through the whole thing — it's been verified only by computer. Of course arguably the "real" proof, from the perspective of a human mathematician, is the part that reduces the problem to those machine-checkable cases, and that could possibly be taught. I don't know whether it would be an undergrad or grad level course, as I don't know how difficult that part of it is. --Trovatore (talk) 21:56, 16 February 2009 (UTC)

I believe it's still way beyond the lecture-course level, in terms of size if nothing else. The five colour theorem, on the other hand, was on my undergrad course, and takes about half a lecture. Algebraist 22:02, 16 February 2009 (UTC)

Academia as we know it in western culture arose from the Medieval university system of Europe. The OP's assertion that academia "wasn't founded like this..." is astonishing, considering that the medieval university was intended as the exclusive mechanism for passing literacy and historical knowledge to the next era of monks, selectively excluding the masses. As the system progressed, (a few revolutions later), academic institutions changed focus pretty significantly, and the philosophy of education changed dramatically. "The role of religion in research universities decreased in the 19th century, and by the end of the 19th century, the German university model had spread around the world." That is to say, students participated in four years of focused "undergraduate" curriculum with a major specialization, instead of five or seven years of religious, liturgical, and philosophy training in Greek and Latin, with the occasional mathematical theory course. Most prestigious American universities did not switch to the "German" model until around the first World War (Academic major attributes this to Harvard in 1910, but I have heard differently). In any case, it has been a fight uphill for centuries against the "establishment", with effort to liberalize the system. In my experience, the more rigorous scientific disciplines suffer less from the "shoving of theories and opinions", because most of science is pretty self-evident if you know where to look for evidence. Nimur (talk) 17:24, 16 February 2009 (UTC)

"most of science is pretty self-evident if you know where to look for evidence." goes into the quote-file:) DMacks (talk) 01:29, 17 February 2009 (UTC)

Just as an addendum, the first university in the US to really emulate a German model in terms of an undergraduate/graduate division was Johns Hopkins University. (There is more to the European model than just academic majors.) It's also of note that America was a considered largely a scientific backwater until the 1920s or so. --98.217.14.211 (talk) 01:54, 17 February 2009 (UTC)

Hmm, the US was a scientific backwater but at the forefront of technological (in things like engine design, flight, the work of Edison...). Sounds like the way we thought of Japan in until the 1990s. Seems like there is a story there.--OMCV (talk) 04:16, 18 February 2009 (UTC)

quantum mechanics(a particle in box)

It is possible that a particle in a box is equaly likely to moving in either direction. Iwant a disscation on it.Supriyochowdhury (talk) 14:03, 16 February 2009 (UTC)

You say "either direction", does that mean you are talking about a 1D box? If the scenario is symmetric, then the solution will be. I don't know what you mean by "disscation", do you mean "dissertation"? If so, we're not going to write your dissertation for you. --Tango (talk) 14:07, 16 February 2009 (UTC)

I think the OP meant "discussion". A Quest For Knowledge (talk) 16:11, 16 February 2009 (UTC)

Try google with your question title "quantum mechanics(a particle in box)" and and one of the first entries it comes up with is the wikipedia article Particle in a box. It is worthwhile learning how to use search engines like this. Dmcq (talk) 14:14, 16 February 2009 (UTC)

It is almost certain that your particle in a box is equally likely to be moving in both directions. If not then it will be drifting in one direction and ending up at one side of the box. Graeme Bartlett (talk) 20:25, 16 February 2009 (UTC)

Terpenes

are Terpenes base or acidic and can they be turned solid? —Preceding unsigned comment added by 76.14.124.175 (talk) 16:35, 16 February 2009 (UTC)

It all depends on the Terpene you mean. Isoprene will neither be acidic or basic nor will it be solid at 25°C as the article states. Of course a long enough Polymer of Isoprene units will turn solid at room temperature, as will substituted Isoprenes. For all other Information see Terpenes or ask a more specific question. --91.6.7.232 (talk) 17:38, 16 February 2009 (UTC)

Vision, light pollution, and the Milky Way

Hi. Let's say someone had 20/1 vision. Now let's say that another person with 20/40 vision, after dark-adapting their eyes away from as many streetlights as possible, at a given location, at night, can see objects up to a limiting magnitude of +4.5, without wearing glasses. Now let's say that the subject with 20/1 vision looks at the sky under the same conditions, would the subject be able to see the Milky Way (the subject with 20/40 vision cannot see the Milky Way under these conditions, but is able to from a location with less glare and light pollution)? Thanks. ~AH1^(TCU) 16:50, 16 February 2009 (UTC)

I don't visual acuity is the right measure of quality of eyesight for this. Visual acuity is about how well you can resolve small things, you're talking about how well you can see dim things, they are completely different abilities. Also, does anyone actually have 20/1 vision? That would be extremely impressive. --Tango (talk) 17:07, 16 February 2009 (UTC)

Resolving small things is the same as resolving dim things for a camera or a telescope. Is the human eye any different? Nimur (talk) 17:31, 16 February 2009 (UTC)

On second thought, probably not. The size parameter is dictated by the angular area of a single pixel; the dimness is more of a signal-noise question or quantization size per-pixel. Nimur (talk) 17:33, 16 February 2009 (UTC)

Sensitivity comes from the number of rods & cones, resolution from that too, but mostly from lens shape (i. e. I have 20/30 vision because my lenses are a little deformed). It is possible that the pixelation from a finite number of rods/cones could start to blur images at 20/1 vision (certainly it would before you got to 20/0.00001, for instance). As above, I don't think there are likely to be many people with 20/1 vision (although it may be possible - one must remember that people exist who are nine standard deviations from the mean). WilyD 18:03, 16 February 2009 (UTC)

According to our article on visual acuity, 20/10 or possibly 20/8 is about the limit for humans. I'm not sure visual acuity follows a bell curve (I believe there are more people with worse than 20/20 vision than there are with better - 20/400 (uncorrected, which is what we're talking about) isn't very uncommon, the equivalent in the other direction would be 20/1, which is unheard of), so the 9SD thing doesn't necessarily apply. --Tango (talk) 18:09, 16 February 2009 (UTC)

It should be noted that the Earth is part of the Milky Way Galaxy. Just about everywhere you look, you're looking at the Milky Way. Now if you want to look at the rest of the Milky Way Galaxy, that's a different question. Sorry to be anal, but it always bugs me when I hear people say things such as "I can't see the Milky Way Galaxy". I always want to say back, "You're looking at it right now.". Whew! That felt good to get off my chest.  :) A Quest For Knowledge (talk) 18:17, 16 February 2009 (UTC)

"Milky Way" in this context (which is the original context) refers to the disk of the galaxy, which appears from our perspective to be a band of densely packed stars going all the way around the sky. --Tango (talk) 18:38, 16 February 2009 (UTC)

Well, the thing is, I have relatively poor vision, and wearing glasses allows me to see more stars in the night sky. For example, just today, I was able to see Venus in glasses 1 minute before sunset, but not without glasses until about 2 mintues after sunset. Maybe visual acuity is a measure of myopia or non-myopia-ness? Or, would someone with 20/1 vision see objects 20 times "closer" than people with 20/20 vision, meaning that astronomical objects seem "closer", and thus brighter as well? I came up with this (hypopthetical) question after a friend claimed he had 20/1 vision (being able to see the entire eye testing chart as well as all the copyrights), and he also claimed that he has never looked up at the night sky (I don't know if either one is true or not). I find that a limiting magnitude of about +5.5 is sufficient to glimpse the Milky Way. Would people with a higher-than-average visual acuity be able to see down to a better limiting magnitude under identical conditions? Thanks. ~AH1^(TCU) 23:30, 16 February 2009 (UTC)

First, visual acuity is how small of an object, in terms of angular size, that you can see. So yes, myopia directly decreases visual acuity by preventing the lens from focusing correctly. People with better vision certainly don't see objects as if they were closer; all objects appear to be of the same size to you and your friend. If he has 20/1 vision (I doubt it; why not test him?), he can see something of a certain size, say 1 mm, from roughly 20 times the distance somebody with 20/20 vision can. But that's just because his eyes can focus more accurately, not because of anything mysterious.

Second, it makes sense that you can see more stars with your glasses than without. Stars are point sources, and the better the eye focuses, the smaller the area it takes up on retina. A small circle of confusion is good because more light is being focused on fewer rod cells, so the star needs not be as bright to be detected. A large circle of confusion has the opposite effect. For an extreme case, imagine finding a star using a telescope and throwing the instrument way out of focus. You won't see a thing.

The Milky Way, however, is anything but a point source. Blurred vision should not be much of an impediment to seeing it because it's always "blurred" in the sense that it has no sharp edges. Smoothening out the transition from the Milky Way to the rest of the sky by a tiny bit can't have much of an effect. --Bowlhover (talk) 02:27, 17 February 2009 (UTC)

hydroponics

do hydroponicaly grown plants grow faster than dirt grown plants? —Preceding unsigned comment added by 76.14.124.175 (talk) 18:11, 16 February 2009 (UTC)

According to our article, yes. A Quest For Knowledge (talk) 18:21, 16 February 2009 (UTC)

sudden freezing

i noticed that some times that while opening abottle of water (in liquid state) after take it out from afreezer it suddenly start to freez , do this have some thing to do with pressure ,,, ? —Preceding unsigned comment added by 86.108.53.185 (talk) 18:32, 16 February 2009 (UTC)

Supercooling. DMacks (talk) 18:34, 16 February 2009 (UTC)

Supercooling is a possibility, but the more likely explanation is the one you came up with, that the water is pressurized and that it is therefore able to stay liquid at a colder temp. Releasing the pressure allows it to freeze quickly. StuRat (talk) 19:03, 16 February 2009 (UTC)

(edit conflict)Well, I guess supercooling can be a factor as well, but if it's a pressurized container -- say, a can of soda -- that's not the reason. Rather, that'd be the CO2 in carbonated drinks. You don't mention if the water is carbonated, 86.108.53.185, but you do mention pressure, so I'm going to assume that that it is -- and you're correct, it does have something to do with the pressure. When you open the bottle, the CO2 gas suspended in the liquid expands and the pressure between the contents of the bottle and the atmosphere outside is equalized... and when gases expand, their temperature drops. Since you've kept the bottle in the freezer, the temperature of the water is already very close to its freezing point; when you open it and release the pressure, it cools down a little bit more, and that's enough to make a difference: it freezes. You don't get a solid block of ice, of course; it's more like a bottle filled with slush, because the temperature drop isn't that dramatic... but ice is ice. -- Captain Disdain (talk) 19:15, 16 February 2009 (UTC)

Water freezing up in an ice cube tray

I've noticed something strange a couple times when I made ice cubes. Normally, when you freeze water in an ice cube tray, I would expect that the surface of the ice cubes to be (more or less) flat. However, a couple of times, towards the centers of the several of each ice cubes' surfaces, water had apparently frozen up. They sort of looked like inverted icicles. I'm using a standard ice cube tray and a plain old refrigerator. How is this possible? A Quest For Knowledge (talk) 19:00, 16 February 2009 (UTC)

See ice spike. StuRat (talk) 19:04, 16 February 2009 (UTC)

That's it! Thanks. A Quest For Knowledge (talk) 19:12, 16 February 2009 (UTC)

Water has many unusual and mysterious properties, some mysterious even to science. I've read that one experiment suggested water to be H_1.5O! ~AH1^(TCU) 23:21, 16 February 2009 (UTC)

Do you have a source for this? That doesn't make much sense to me.. there are Non-stoichiometric_compounds but water isn't one. Friday (talk) 17:51, 17 February 2009 (UTC)

See Water (molecule)#Quantum properties of molecular water. DMacks (talk) 19:02, 17 February 2009 (UTC)

Percent of people infected by the "common cold" each year in US

About what percentage of people are infected with the common cold each year in the US? I'm looking for an authoritative source -- a peer-reviewed journal or NIH website, for instance, would be great. I was able to find one here that said 90%, but I also found another (can't locate it at the moment) that said 35%.

Any help would be greatly appreciated!

— Sam 72.248.152.57 (talk) 20:07, 16 February 2009 (UTC)

The CDC page links to a huge number of academic and medical sources. "HPIVs are ubiquitous and infect most people during childhood. The highest rates of serious HPIV illnesses occur among young children. Serologic surveys have shown that 90% to 100% of children aged 5 years and older have antibodies to HPIV- 3, and about 75% have antibodies to HPIV-1 and -2." The difficulty is in defining the "common cold" - depending on how widely you categorize ailments as "common cold", you will get incidence estimates that vary by orders of magnitude. Nimur (talk) 21:12, 16 February 2009 (UTC)

Hmmm... the 90-100% figure would appear to be the total number of children exposed to the viruses at some point in their lives, not the total number of infections per year. But thanks for the sources. If anyone sees anything else, it would also be helpful. Thanks, Sam 146.115.120.108 (talk) 23:51, 16 February 2009 (UTC)

As soon as I read this question, I wonder what do you mean by 'infected'? Does the person have to show symptoms, or just come in contact with the virus? I don't know if refining the question like this will get you a better answer (maybe scientific journals all define infected the same way), but it might help (and I'm curious). -Pete5x5 (talk) 05:59, 17 February 2009 (UTC)

Sex hormones in ham?

Does ham sold in Canadian markets naturally or artificially contain human sex hormones or any substances with similar effects on humans? NeonMerlin 21:27, 16 February 2009 (UTC)

I would seriously doubt it. This sounds to me like an urban myth. That said, I believe that some plastics can degrade into chemicals similar to oestrogen. That may not be true, however -It's only half-remembered.--NeoNerd 21:36, 16 February 2009 (UTC)

NeoNerdi you're probably thinking of Bisphenol A We haven't had a question mentioning that for a while. Waiting for Benzyl butyl phthalate to take off. Use of growth hormones in pork production is prohibited in the US and Europe AFAIK. I found this study which you might find helpful [28]. You might also have found [29] or [30]. Estrogens naturally occur in pigs. We need industrialized agriculture to feed our masses. Unfortunately that comes at the price of sometimes having undetermined health effects. I's good to be vigilant, but the media scare waves based on some poorly represented study are rarely helping. 76.97.245.5 (talk) 23:41, 16 February 2009 (UTC)

New colours

Could there be colours waiting to be discovered / thought up by our minds / whatever? - Jarry1250 ^{(t, c)} 22:01, 16 February 2009 (UTC)

Just a guess, but I'm going to have to say no. Every 'colour' in the sense we think of (the visible spectrum) is dependent upon wavelength, and I'm guessing we know all the individual wavelengths which produce different shades of different colours. The only way you could alter this is by going outside the visible spectrum, and then the product wouldn't be defined as a colour, per se. —Cyclonenim (talk · contribs · email) 22:29, 16 February 2009 (UTC)

You also have combinations of those wavelengths to consider. --Tango (talk) 22:38, 16 February 2009 (UTC)

No you dont, waves superpose. —Preceding unsigned comment added by 129.67.37.225 (talk) 00:10, 18 February 2009 (UTC)

You could make new colours be fiddling with how the human eye works, but I think that's it. Pretty much all the colours possible are shown in the CIE 1931 color space chromaticity diagram (pictured here, but it won't be displayed correctly by your monitor). It doesn't correspond to precisely how the human eye sees colours, but it's designed to be pretty close (it's meant to be the "chromatic response of the average human viewing through a 2° angle" - what "average" means in that context, I don't know). --Tango (talk) 22:38, 16 February 2009 (UTC)

(ec) Human perception of colors correspond with how our visual and neural hardware perceive wavelengths of light. It's a finite range of possible perceptions—with the "standard hardware". There are some people who apparently have non-standard visual hardware who can see more colors than the majority of us can (see tetrachromacy), and of course there are those with non-standard visual hardware who perceive less colors than the majority of us (see color blindness). Other than those possibilities, there's no way for humans to experience more colors than the standard "visual spectrum". --98.217.14.211 (talk) 22:40, 16 February 2009 (UTC)

(triple edit conflict!) You may want to look at tetrachromat. If tetrachromacy in humans exists, then the trichromatic colors won't cover all the colors tetrachromats can see. 152.16.144.213 (talk) 22:41, 16 February 2009 (UTC)

On the other hand, not all colours appear in the spectrum. Brown, for example. We perceive this as a colour separate to anything else, even though we know it's some combination of spectral colours. The spectrum would have infinite gradations (not all discernible to the human eye, admittedly), so theoretically there's an infinite number of ways of combining two or more spectral colours to come up with a complex colour (again, not all separately discernible to the human eye). Have all of these possible combinations been recorded and named? I very much doubt it. -- JackofOz (talk) 22:54, 16 February 2009 (UTC)

I could imagine that evolution or genetic engineering may expand the sensitivity of human eyes, say, into the infrared spectrum. There may be significant benefits if folks could see a warm (edible) rat in some post-acocalyptic scenario in the middle of the night.

There may also be significant advantages if humans could "see" ultrasound or gravity waves or whatever. It would make sense to invent terms of pseudo colours for these new sensations. If you can visually interprete the bits and bytes generated by the graphic card of your PC you have already saved €250 for a useless monitor. --Cookatoo.ergo.ZooM (talk) 22:57, 16 February 2009 (UTC)

Also, as Steve alluded to recently (though I don't recall that he brought up this specific aspect), certain wavelengths in the near UV are invisible not because the retina doesn't respond to them, but because the lens filters them out. If your natural lens is removed (e.g. for cataracts) you will be able to see this light, and as it has a different mix of responses from the three sorts of cones than any other wavelength, you may perceive a color that no one with normal eyes can see.

(also don't forget the hooloovoo). --Trovatore (talk) 22:58, 16 February 2009 (UTC)

The IR emitted by a rat is very distant IR. About 10µm, I think, compared to the limit of human vision of about 700nm, so that's more than a ten-fold increase, whereas the current range of human vision is less than a factor of two from one end to the other. So engineering human eyes to see those wavelengths would be very difficult. Other animals can do it, though, see Infrared sensing in snakes. I guess we could try and add some snake DNA to our genome... --Tango (talk) 23:08, 16 February 2009 (UTC)

The question also is one of language. You might be able to imagine a new color, but how do you communicate that to others? See Minor Discworld concepts#Octarine.76.97.245.5 (talk) 00:24, 17 February 2009 (UTC)

It's quite complicated - there are at least four ways to answer this question:

• There are colors we can't perceive because our retina is not sensitive to them (eg InfraRed). You can see infrared using night-vision equipment - but that works by turning the IR into shades of green. You aren't 'seeing' the colors as different (it's just plain old green) - but you can see things that you wouldn't ordinarily be able to see like that a car has recently been driven because the engine bay is hot and therefore emitting IR "light". Without this extra 'sense' we can't tell the difference between a car with a hot engine and a car with a cold engine - they look EXACTLY the same.
• There are colors in the near UltraViolet that we can't perceive with normal eyesight because there is a protective sun-screen over our eyes that protects the retina from sunburn. However, some people have that protective layer removed as a result of cateract surgery. After surgery they can see light in the near ultra-violet - but it just looks blue. However, you can see blue-ish spots and stripes on flowers - which are really ultraviolet spots and stripes that the flower has evolved to attract bees (which can see into the UV). But just as with night-vision - it doesn't seem to be anything amazing - just shades of blue.
• We only have three kinds of 'cone' sensors in our eyes - so we see all colors as if they were mixtures of red, green and blue. But in the real world, there are (for example) 'kinds' of yellow that are mixtures of red and green and 'kinds' of yellow that look absolutely identical to us - but which are really pure frequencies of yellow light with no trace of red or green. If we had the eyes of certain species of freshwater shrimp - we'd have as many as twelve different cone types and the world of color would be VASTLY richer and different than we can actually see. In that sense, there are vast ranges of color that exist physically - but we just can't tell the difference. It's like we're all somewhat colorblind. So there are "more" colors out there - but to see them, you've somehow got to become a shrimp...unless...
• There are very, very few women who are 'tetrochromats' who have a fourth kind of green sensor - they see colors in a richer way than we do - and they could distinguish colors that we consider to be identical as if they were very different indeed. Just two such people have been identified as a result of genetic studies. They have to have both parents who are colorblind in very specific ways. But they TRULY see colors that we can't even imagine.

SteveBaker (talk) 01:22, 17 February 2009 (UTC)

Steve: Brown is a desaturated, dark red. It is not somewhere outside the CIE diagram. Edison (talk) 01:52, 17 February 2009 (UTC)

Edison: There are different browns. Some are more a dark orange, or even dark yellow, than dark red.

Yeah - brown is nothing particularly special - it's a word we use to mean various dark shades of red/orange/yellow.

Speaking (typing) as a colour blind person, I see a lot more brown than normally sighted folk. I take this to mean that we tend call things brown when they don't have a 'clear' colour. Mikenorton (talk) 14:04, 17 February 2009 (UTC)

When you say you see more brown, what that means is you can't distinguish between brown and certain other colours (red and green?). That doesn't mean brown is any different to any other colour, it just happens to be the one you have difficulty with. Basically, you see all combinations of red and green as the same thing, brown is one of those combinations. Why you describe it as seeing lots of things as brown, rather than lots of things as red, or lots of things as green, I don't know... convention, maybe? Or is there some underlying reason? Anyone? --Tango (talk) 14:12, 17 February 2009 (UTC)

Not exactly, I have problems generally with any mixed colours that involve red or green, e.g. mauve looks blue to me, but all 'muddy' reds and greens look brown to me, if I can't see a distinct colour, I call it brown. Mikenorton (talk) 16:43, 17 February 2009 (UTC)

It sounds like your response to red and green are the same as each other and significantly reduced from normal (you can't distinguish brightness of the colours you see as the same colour). The fact that they're the same is why anything that's just made up of red and green looks the same, and the reduction from normal levels is why it looks brown (rather than yellow, say - I'm assuming you see yellow as brown, yes? Whereas someone with normal colour vision sees bright yellow and yellow and dark yellow as brown (ish)). --Tango (talk) 18:01, 17 February 2009 (UTC)

Just to clarify, I see pure red as red, pure green as green and indeed bright yellow as yellow. I have the most common red-green colour blindness with a reduced sensitivity to red and green. It's worth remembering that, just like everyone else, I learned to call colours by particular names, whether I actually 'see' red as other people see red is impossible to tell. Mikenorton (talk) 18:11, 17 February 2009 (UTC)

So it's when red and green are mixed that you can't tell how much of each there is? So essentially you can't distinguish different shades of brown - reddish-brown, greenish-brown, yellowish-brown and anything inbetween all looks the same? And you call them all brown because that's what the rest of us call them - we just use the word to describe lots of colours which to you are just one colour. If my understanding is right (scientific method: Make observations, form theory, make prediction, test prediction!) you should have difficulty distinguishing bright orange and bright yellow, is that correct? --Tango (talk) 18:20, 17 February 2009 (UTC)

Better finish this off now, I'm having trouble counting the colons. Yes I have problems with that pair (more with yellowish orange and yellow) and similarly yellow and yellowish green. Otherwise your description seems about right. Mikenorton (talk) 18:35, 17 February 2009 (UTC)

My theory stands up to empirical testing (to an acceptable margin of error), fantastic! Thanks for helping me get my head round this. --Tango (talk) 19:07, 17 February 2009 (UTC)

Steve: I thought I had read somewhere that the UV color was at least a little outside of normal experience. It certainly seems possible a priori — say, if a certain near-UV wavelength produced a larger ratio between the blue-cone response and the green-cone response than any normally visible wavelength, then you wouldn't be able to reproduce that signal by any combination of normally visible light. (I suppose people could see it if you shined that wavelength at them at such high intensity that enough of it came through the protective layer — good luck getting that past the ethics committee!) --Trovatore (talk) 02:02, 17 February 2009 (UTC)

The problem is that you only have three color sensations (Red,Green,Blue) - and all color perception is mixtures of those sensations. Ultraviolet light (for people who have had cataract surgery) stimulates the blue sensor and does not stimulate either of the other two - so the sensation is no different from a rather pure blue. My mother had cataract surgery and she wasn't aware of having seen amazing "new" colors - but rather she sees blue in places where she didn't before. She's an avid gardener and was somewhat surprised at how formerly uniformly colored blooms now had spots or stripes or other markings. But sadly (and predictably) no 'new' colors. Presumably objects with large amounts of UV reflectivity would also change hue slightly - but still, she's unable to perceive 'new' colors. That's not possible without having more color sensors - and for that to happen, you'd have to be born as a tetrachromat or a freshwater shrimp. SteveBaker (talk) 03:18, 17 February 2009 (UTC)

Well, you seem to have skipped over my point, though. It may be true that your mother doesn't see any new colors; I don't know. But if it were the case that one of these wavelengths she now perceives could get a higher ratio of blue-to-green, or blue-to-red, or blue-to-(0.3*green+0.7*red), or something like that, than any normally-visible light — then she theoretically could, because no linear combination with positive coefficents of normally-visible light could get you that ratio.

Note that just because she hasn't seen any such colors doesn't refute the idea, because she presumably has not been exposed to pure light of such a wavelength.

Whether this actually happens, as I say, I don't know. But it's not as simple to refute as you're making it out to be. --Trovatore (talk) 03:40, 17 February 2009 (UTC)

Indeed - she should be able to distinguish things as being different colours when we see them as the same colour, that's seeing new colours. The new colours will just be new shades of blue/violet, since it's only pretty near UV so isn't that different from blue, but it's still new colours. It will be rather difficult to distinguish them, since the human eye isn't very sensitive to differences in wavelength towards the ends of our usual range, but it will distinguish them a little. --Tango (talk) 13:34, 17 February 2009 (UTC)

That isn't the point. Being able to distinguish things that we see as the same color is not perceiving new colors — you might be able to distinguish A and B even though a person with normal lenses couldn't, but you'd maybe see A the way you used to see C and B the way you used to see D, so there's no new color being perceived.

The point is that maybe, for every wavelength that you and I can see, whenever the blue cones are firing at 100%, the green cones or the red cones are also firing, say at at least 5% and least 7% (these are just made up numbers).

Whereas maybe when Steve's mom looks at this new light, when it fires her blue cones at 100%, it's only firing her green cones at 2% and her red ones at 8% (again, made up).

In that case she would have a mixture of signals from the cones that is not possible, with any light, for a person with natural lenses. --Trovatore (talk) 19:25, 17 February 2009 (UTC)

But if you distinguish colours by seeing them as other colours then you lose the ability to distinguish those colours, so that doesn't help - that's just seeing different colours, not new colours. Someone without the filtering lens can distinguish between, say, "blue+UV" and "blue", two colours which the typical human can't distinguish between. (Perhaps I'm using the word "colour" slightly differently to its standard definition.) --Tango (talk) 19:45, 17 February 2009 (UTC)

I get the feeling neither you nor Steve has read what I actually wrote. --Trovatore (talk) 20:47, 17 February 2009 (UTC)

I read it. That's distinguishing new colours. If it was monochromatic UV, then it would be distinguishing UV from black, if it's UV+something visible then it would be distinguishing that from just the visible part. When you see extra strips on petals, that's distinguishing the colour of the strip from the colour of the rest of the petal, which the human eye can't usually do. --Tango (talk) 21:43, 17 February 2009 (UTC)

I read it too - and I didn't reply immediately because I wanted to check my sources to be absolutely sure. I don't think there is a 'new' color there. UV light starts at 400nm. When I look at higher resolution plots similar to the diagram above I find that the red receptor doesn't function to any measureable degree at 400nm. Green and blue are both tailing off - but green hasn't completely gone away the ratio of green and blue at 400nm is not a whole lot different than in the "indigo" blue region right next to the 400nm cutoff. It's possible that the precise shade of blue you'd see wouldn't be identical to any 'normal' shade of blue - but the difference is right down in the noise. I don't think there is a noticably new color there - although I'll admit that it's mathematically possible. Most important of all - LOTS of people have had this surgery and I can find no references to anyone seeing anything stunningly novel - they mostly report seeing new patterns and that some 'normal' objects seem to have shifted color - but not one (that I could find) report anything "new". SteveBaker (talk) 22:50, 17 February 2009 (UTC)

Wait a minute — you're saying the red cones don't respond to 400nm light? Then why does it look purple? --Trovatore (talk) 23:28, 17 February 2009 (UTC)

No, what I'm talking about is actually seeing new colors (or at least, new ratios of signals from the cones, that are not possible for a person with natuarl lenses). What you were talking about, in the 13:34 17 Feb post, was only making different color distinctions, which is not the same thing. --Trovatore (talk) 21:49, 17 February 2009 (UTC)

Well, it's just going to look like a slightly different shade of violet (as Steve says), you're not going to notice it as being new if you're just looking at it in isolation. You'll only realise it's new when you compare it to existing shades of violet. --Tango (talk) 22:54, 17 February 2009 (UTC)

And how exactly do you know that? --Trovatore (talk) 22:59, 17 February 2009 (UTC)

Because I've looked at the graphs and can see that the green and red lines are pretty much flat by that point. --Tango (talk) 23:00, 17 February 2009 (UTC)

Well, those graphs are obviously wrong (or, let's say, "incomplete") because they don't show the response of the red cones to violet light. The red line should start turning upwards again towards the left edge — that's why you see violet light as "purple". --Trovatore (talk) 23:05, 17 February 2009 (UTC)

See "List_of_colors#Fictional_colors". The article describes ulfire and jale as shades of ultraviolet, but in reality (in fiction, actually) they are two more primary colors that can be seen by a race whose eyes can see well into infrared and ultraviolet (a very good sci-fi book, by the way, that). Carlos Castaneda reports an indefinable color in one, I forget which, of his hallucinatory tours-de-force; a monster guarding a path shows him its colored back. --Milkbreath (talk) 02:25, 17 February 2009 (UTC)

It may be possible to stimulate the cones in different ways, for example the green cone absorption spectrum overlaps the red substantially and the blue somewhat, so there is not normally a pure green cone stimulation. If a pattern of light could illuminate the retina so that only green cones were stimulated you would get some form of ultra green colour sensation. Graeme Bartlett (talk) 03:23, 17 February 2009 (UTC)

Or even better, infragreen. The color of the Mushroom Planet. --Trovatore (talk) 03:41, 17 February 2009 (UTC)

Yes, you could (theoretically) connect electrodes to the retina/optic nerve and make all kinds of weird things happen, but you couldn't do it by shining light into the eye (which is what we usually mean by "seeing"). --Tango (talk) 13:34, 17 February 2009 (UTC)

Another idea for ultragreen is to bleach the red and blue cones with bright deep red and violet light, and then look at green spectral colour and see what it appears like. Graeme Bartlett (talk) 20:42, 17 February 2009 (UTC)

February 17

CIE 1931 color space chromaticity diagram equivalent tending towards black

The color question above made me think that there should be a triangle - analogous to the one above - with black at the center. Is there such a thing and what is it called. The two together should come closer to covering all colors visible to humans. I didn't want to stick this on to the above question because the two are only related. 76.97.245.5 (talk) 00:13, 17 February 2009 (UTC)

Only in a subtractive color model do colors converge on black (which is not used for light). So I doubt you'll find a colorspace diagram for it, as they are modeled on light, not paint... --98.217.14.211 (talk) 00:43, 17 February 2009 (UTC)

Provided you'd consider no light as black wouldn't different intensities of colored light give different results. The triangle seems to be all with the same intentity. (Oops there's two. Don't know in a hurry which one I should link.) 76.97.245.5 (talk) 01:19, 17 February 2009 (UTC)

The chromaticity diagram covers only 'chrominance' (ie 'color') and doesn't include 'intensity' or 'brightness'. To show all of the colors that humans can see you need a three-dimensional diagram with red, green and blue as the three axes. I have one of these on my desk at work - it's a perfect demonstration of 3D color space. You could certainly produce other diagrams as 2D slices through that cube at different angles. SteveBaker (talk) 01:28, 17 February 2009 (UTC)

The OP may also find Munsell color system (and some of the articles linked therein) of interest. Deor (talk) 12:53, 17 February 2009 (UTC)

Matter and Anti-Matter creation from energy

When matter is created from energy, is the outcome randomly determined (of it being matter or anti-matter)? And if so, would this explain the predominance of matter over anti-matter in this universe? 70.171.16.131 (talk) 06:19, 17 February 2009 (UTC)OP

As far as I know, which isn't much compared to some refdeskers, energy can ONLY be converted to matter if the corresponding antiparticles are created at the same time. You can't pick on or the other; that would violate conservation of charge, etc. (Please correct where necessary.) -- Aeluwas (talk) 09:41, 17 February 2009 (UTC)

When matter is created from energy, such as in the photon-photon collisions or from matter particles colliding at high speed at CERN and elsewhere, conservation laws specify that some quantities stay the same before and after the collision. Importantly, the number of particles minus the number of antiparticles must stay constant, so if 2 particles collide, you could for instance get 8 particles and 6 antiparticles out of that collision. Known violations of these laws are heavily studied but so far noone has been able to fully explain the predominance of matter over antimatter in the universe, it's one of the big questions in physics today. If you want to learn more, CPT symmetry or books on quantum mechanics may help. EverGreg (talk) 11:32, 17 February 2009 (UTC)

protein to build muscle mass

Hello Wikipedia,

In order to comply with current gay body-fascist requirements, i'm looking to build muscle-mass so would like to know what i should eat. The supplements people say about 1g of protein per pound of body weight but others suggest that this is cobblers and i should just eat sufficient calories so that i'm rarely hungry. My problem is that these people have an agenda to either sell me supplements or magazines and i don't know who i should believe. Does anyone know any objective figures? (ideally based on good ol' fashioned peer-reviewed science?)

Many thanks, 81.140.37.58 (talk) 11:16, 17 February 2009 (UTC)

The gays have created a body-fascist movement? Or the body-fascist movement itself is inherently homosexual? Or perhaps it's just disdained? Maybe the fascists just like gay bodies? This is all very confusing...

Regardless, "objective" advice (of which there is effectively none -- I doubt that peer-reviewed science is in agreement on this one) is likely to stray into medical advice. If you don't trust the subjective advice of magazines, I suggest you try the subjective advice of a doctor, physical therapist, and/or other health professional who can take your personal circumstances into account. — Lomn 14:19, 17 February 2009 (UTC)

The gay mafia must be behind the gay fascists. :-) But seriously, you need to exercise to build muscles. This will make you eat more and possibly crave protein (if you aren't already getting enough). You don't have to take any supplements or force yourself to eat more of any item to gain muscle mass, just eating what you want to eat will be sufficient. The exercise is the key. Eating more or taking protein/carb supplements without exercise will only make you fat. Unless you're going for the bear look, that probably won't help. StuRat (talk) 14:37, 17 February 2009 (UTC)

Do you go to a gym? If so, you can probably book a few sessions with a personal trainer and they will be able to give you nutrition advice (or, perhaps, refer you to a nutritionist) - they will be able to tailor it to your current diet, build, weight and your planed training routine and desired results. We can't do that. --Tango (talk) 14:45, 17 February 2009 (UTC)

So there's no general rule? Ho Hum... —Preceding unsigned comment added by 81.140.37.58 (talk) 17:09, 17 February 2009 (UTC)

When I researched this a few years ago, I didn't find much if any reliable scientific evidence in support of protein supplementation or even high protein diets. There seemed to be a minimal amount of scientific evidence in support of creatine supplementation. A Quest For Knowledge (talk) 17:10, 17 February 2009 (UTC)

Also, you might want to check out our Bodybuilding supplement article. A Quest For Knowledge (talk) 17:15, 17 February 2009 (UTC)

Most complex formula in Physics

What is the most complex formula that you know in Physics?--Mr.K. (talk) 11:55, 17 February 2009 (UTC)

The complex ones are boring, it's the simple ones that are interesting. You can get as complicated a formula as you like by just coming up with a really complicated problem to solve. --Tango (talk) 13:49, 17 February 2009 (UTC)

Yeah, you can make arbitrarily complex equations for whatever you want. However, you asked which is the most complex equation in physics that I know, so I'll tell you the most complex equation that I remember actually using. It is as follows:

$\rho {\frac {\partial ^{2}{\vec {\zeta }}}{\partial t^{2}}}=-\nabla (-\gamma p\nabla \cdot {\vec {\zeta }}-{\vec {\zeta }}\cdot \nabla p)-{\vec {B}}\times (\nabla \times (\nabla \times ({\vec {\zeta }}\times {\vec {B}})))+(\nabla \times {\vec {B}})\times (\nabla \times ({\vec {\zeta }}\times {\vec {B}}))+(\nabla \Phi )\nabla \cdot (\rho {\vec {\zeta }})$

(reference) which is the linearized magnetohydrodynamic equation of motion for plasma in terms of the plasma displacement vector, ${\vec {\zeta }}$. Of course, there are always more complex equations, but that's probably the longest one I've ever used. --Bmk (talk) 15:17, 17 February 2009 (UTC)

Magnetohydrodynamics will rank high on many people's lists because it has a lot of terms, effectively building up from "F=ma" for a single particle, accounting for all the forces involved. Plasmas encompass the many different domains of electromagnetism and Newtonian statistical mechanics, encompassing half of the fundamental forces recognized by the Standard Model. In some extra-special space-plasma cases, there can even be relativistic magnetohydrodynamics, adding another few terms. Other disciplines, such as subatomic physics, often introduce new conceptual ideas rather than adding additional terms to an equation. "Complexity" of a formula is sort of tough to decide; for example, if you wanted to solve the simple ballistic trajectories for thousands of catapults, the individual equations would be trivial but the implementation details to solve the equations simultaneously could be quite complex. At a certain point, physical equations cease to be represented as closed-form expressions, and will probably be represented as a computational physics simulation, numerical solver, or computer program. The complexity of such a representation can range in to tens of thousands of lines of computer code for numerical processing, data management, and user interface. Nimur (talk) 16:16, 17 February 2009 (UTC)

As I'm not a physicist, I don't have much experience of long formulae, but this one is pretty nasty (Continuous Fourier transform#Spherical harmonics)):

$F_{0}(r)=2\pi i^{-k}r^{-(n+2k-2)/2}\int _{0}^{\infty }f_{0}(s)J_{(n+2k-2)/2}(2\pi rs)s^{(n+2k)/2}\,ds.$

The Laplace transformations and Laplace's equation articles will give you ammunition to impress the ladies at parties. --Mark PEA (talk) 21:40, 17 February 2009 (UTC)

It's been a while since I used it, but $R=\kappa T$ (see Einstein's field equations) still gives me nightmares. Don't think it's complicated? It's actually (if I remember correctly) 4-dimensional, 4th order non-linear differential equation, with the only saving grace being a couple of symmetries. Confusing Manifestation(Say hi!) 22:52, 17 February 2009 (UTC)

Hmm, how about the Standard Model Lagrangian? -- BenRG (talk) 23:35, 17 February 2009 (UTC)

Microsoft Office Live Workplace for Linux users

This question has been moved to the Computing Desk, Nimur (talk) 16:31, 17 February 2009 (UTC)

Liquid density

How can this problem be solved: A mass of a liquid of density ρ is thoroughly mixed with an equal mass of another liquid of density 2ρ. No change of the total volume occurs. What is the density of the liquid mixture?

A.4/3 ρ      B.5/3 ρ
C.3/2 ρ      D.3ρ  —Preceding unsigned comment added by 116.71.33.96 (talk) 13:12, 17 February 2009 (UTC) 

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. SteveBaker (talk) 16:53, 17 February 2009 (UTC)

The Reference Desk will not do your homework for you. That said, I'll offer some pointers: Consider the volume of the first liquid to be x. What is the mass of the first liquid (there is a density-volume-mass relationship)? What is the mass of the second liquid? What is the mass of the mixed liquid? Now solve for density. — Lomn 14:14, 17 February 2009 (UTC)

Event horizon and neutron star crushing question

A recent Scientific American article about the possible existence of naked singularities got me wondering about neutron stars and event horizons. Specifically, there is a certain amount of gravitational force across the spherical boundary of an object needed to overcome the nuclear forces that keep a neutron star from collapsing into a singularity. There is also a certain amount of gravitational force to bring a sphere's surface area escape velocity to the speed of light, turning the sphere's boundary into an event horizon.

What's not clear to me is that those two levels of gravitational force are equal. So my question, then, is how much gravitational force is needed to start the process of crushing a neutron star into a singularity, and how much gravitational force is needed to create an event horizon around the surface of a collapsing object? And if those two numbers aren't equal, could it be possible to have an object that is, at least temporarily, significantly denser than a neutron star but whose escape velocity is less than the speed of light and thus is not a black hole? (A naked singularity is presumably one such object.) 63.95.36.13 (talk) 15:19, 17 February 2009 (UTC)

You may find Quark star interesting, but it's not entirely relevant to your question. For a object of a given mass you have something called the Schwarzschild radius. This depends only on mass, so for the neutron star/black hole in your scenario, it is constant. Once the neutron star collapses to smaller than its Schwarzschild radius, it is a black hole and has an event horizon, before then it isn't and doesn't. The gravity of a black hole isn't any stronger than the gravity of anyone else of the same mass, the only difference is that you can get closer it its centre of gravity. Therefore, it is meaningless to ask how much gravity is needed to create an event horizon, the correct question is how small does an object of a given mass need to be to form one. If the gravity is great enough to overcome degeneracy pressure and collapse the star, then sooner or later it will get small enough to form an event horizon and become a black hole. Its density will continue to increase until it passes that point (after which it becomes rather meaningless to talk about density). --Tango (talk) 15:30, 17 February 2009 (UTC)

Thanks for the tip about Quark Stars; that's the first I've heard of them, and it's actually related to my question in that it sort of shows an example of a star that is in an intermediate phase matter (at least at its core) between that of a neutron star and a singularity. As far as whether all singularities are black holes, though, that's precisely what the naked singularity article in SciAm was discussing (ie scenarios in which a singularity for one reason or another is not within an event horizon). Interesting stuff. 63.95.36.13 (talk) 18:30, 17 February 2009 (UTC)

Incidentally, have you read our articles: Naked singularity and Cosmic censorship hypothesis? (Lots of tags at the top of them both, so they may not be very good - I haven't read them recently.) --Tango (talk) 18:41, 17 February 2009 (UTC)

I did, but unfortunately they didn't really deal with the question above (or if they do it was in an over-my-head technical area). 63.95.36.13 (talk) 22:50, 17 February 2009 (UTC)

Coincidentally, we covered a similar question in january EverGreg (talk) 18:16, 17 February 2009 (UTC)

Nuclear submarine crash

What could actually happen if two nuclear-powered and nuclear-armed submarines crashed into each other way beneath the sea? On the one hand we have PR flaks saying, oh, nothing to worry about, the tea sloshed out of the mugs and we'll have to re-paint, that's all. At the other extreme we have ... nuclear war, possibly? (Worst case scenario: If one of the bombs were accidentally activated, and then another nation felt called on to respond.) Or the in-between possibility, of the vehicle being totalled, shades of Texas road crashes. BrainyBabe (talk) 16:40, 17 February 2009 (UTC)

Hmm. Are you asking because you've read this article (or another one on the same subject) or is this just a great coincidence, considering that was published yesterday? -- Aeluwas (talk) 17:00, 17 February 2009 (UTC)

Yes, I was in fact trying to tie together X and Y, but I guess absolute explictness trumps collegial allusiveness. BrainyBabe (talk) 17:12, 17 February 2009 (UTC)

I'm just surprised there was not a need for a major rescue. When Kursk (submarine) hit a rock (or blew a dud torpedo, as the current consensus seems to hold), everyone perished despite best efforts to send help. To me the most amazing thing about such a scenario is the total information-vacuum. The capacity for a submerged submarine to communicate with the surface is limited (exact data rates are probably classified), but I suspect we are talking about a few hundred bits per second as an absolute maximum. This is barely enough to even send a distress call, let alone a full explanation of the scenario. And to imagine that these guys must have a special bit-sequence to initiate second strike! Let's all hope their bit-error rate is REALLY low. Between the highly-classified nature of submarines and simple logistics which limit the number of witnesses, I think the truth of any submarine accident is always pretty elusive. Nimur (talk) 17:20, 17 February 2009 (UTC)

The chance of a nuke detonating accidentally is close enough to zero as makes no odds. Smashing them, shooting them, blowing them up, whatever, won't have any effect, you have to fire neutrons into a critical mass of fissile material - that just doesn't happen unless someone makes it happen. The real risks (to the world - obviously there are risks to the submariners) are leakage of radioactive material (pretty unlikely) and loss of nukes which could then be recovered by terrorists or rogue nations (everything is so top-secret that they would have to have spies in just the right places to find out where to look, so this is a pretty low risk too). There is also a risk that one side may not believe that it was an accident and retaliate, but they wouldn't retaliate with nukes (loss of a submarine does not warrant mutually assured destruction), so you're just looking at a regular war, at worst. --Tango (talk) 17:55, 17 February 2009 (UTC)

Delving away from the scientific aspects of this question into the political aspects, it should be noted that France and UK are allies and have been for quite some time. It is unlikely a war would erupt between these two nations even if a nuke were detonated. Had this occurred between the US and the Russia, the situation might be quite different. I suspect a war would not break out, but there would be accusations and counter-accusations. Of course, if this had happened during the middle of Cuban Missile Crisis, all bets are off. A Quest For Knowledge (talk) 18:18, 17 February 2009 (UTC)

It was only after the collision and reports started coming in that it was worked out what had happened - neither knew who or what they had crashed into at first. If a nuke had gone off, there would never have been any reports and the UK and France would each have simply seen a nuclear detonation at the approximate location of one of their nuclear subs. What conclusions they would have drawn from that, I don't know, but they might well have acted before letting the other know they had a nuclear sub in the area, so before anyone could work out what had happened. --Tango (talk) 18:28, 17 February 2009 (UTC)

You may be amused/terrified to learn that deliberate provocations along these lines *did* occur during the Cuban Missile Crisis, including forcing Soviet missile subs to surface, and actually test-firing an ICBM! That's what you get with the Buck Turgidsons of the world running the show. --Sean 21:59, 17 February 2009 (UTC)

OK, so far so good, but I posted on the science desk deliberately. What happens when a sub hits something (another sub, or a mountain for that matter), at various velocities? What would it take to knock a hole in one? What sorts of damage could an undersea collision cause? Could it become "stuck" down there, without massive other damage? BrainyBabe (talk) 19:05, 17 February 2009 (UTC)

I heard on the BBC Radio 4 this morning some submarine walla talking about a submarine that several years ago crashed into an undersea pinnacle at 30 knots. A crew member was killed and several others received serious injuries but the shell of the submarine remained intact and there was no damage to the nuclear fuel cell on board. Funny that we didn't hear about it. Richard Avery (talk) 19:50, 17 February 2009 (UTC)

You're referring to USS San Francisco (SSN-711)#Collision with Seamount? --Carnildo (talk) 02:18, 18 February 2009 (UTC)

Failure modalities:

• the sea-hull is damaged, and/or control surfaces are damaged and function improperly: the sub must limp to its home port; if the damage is bad, it must surface and call for a tender
• the prop is damaged, the driveshaft or its bushings bent or damaged, or the gearbox damaged - mild gearbox damage may be reparable or patchable at sea, for everything else the sub cannot make way and must call for a tender (it can remain submerged while it waits)
• the sea hull is deformed to an extent that the hatches to the pressure hull (man hatches, torpedo tube hatches, missile tube hatches) leak, seals for the prop shaft leak, and/or the ballast system piping and its valves are damaged and leak - pumps can handle small leaks (if the sub remains at shallow depth); for more serious leaks the affected compartments must be evacuated and sealed, and the sub must surface
• large scale damage to the pressure hull, or major damage to the ballast system - compartments flood and must be quickly sealed off to prevent the sub sinking. With more than a few areas waterlogged, or if the balast system is badly damaged or inoperable, the sub cannot surface. Crew must be rescued (the US Navy uses a DSRV, I don't know what arrangements if any the British and French navies have). 12-36 hours pass before rescue begins, and as the DSRV has a capacity of ~8 people, rescue of the boat's 100+ compliment takes some time. If the electrical systems have failed the air is not reprocessed and becomes rich in exhaled CO2; the crew resort to breathing apparatus with wearable scrubbers. If these become exhausted, or if insufficient are available (particularly if many crew are trapped in a small compartment) crewmembers begin to die from CO2 poisoning (it's my understanding that you die from CO2 poisoning before the hypoxia kills you).
• damage to the pressure hull affects many compartments; too much of the boat floods for the ballast system to lift, and the boat sinks to the bottom of the ocean. In sufficiently deep water the remaining pressure hull fails under the pressure and the crew is killed.

Submarines are always very sturdily constructed to withstand the pressures they must face; military submarines (which must also withstand violent maneuvers and near-misses from depth charges) particularly so. Naturally they don't publish crash-test results, so we can't say which of the above scenarios are likely to result from collisions of a given speed. As noted above, it is very unlikely that a nuclear warhead will explode. There is a larger chance that the solid rocket motors of an SLBM will explode, or that the reactor encapsulation would be torn open to the sea, but it's difficult to imagine a non-explosive impact that could trigger either of those without also shattering the pressure hull and killing the crew anyway.

87.115.43.168 (talk) 20:19, 17 February 2009 (UTC)

The film Gray Lady Down gives a fictional account of the rescue of the crew from a striken US attack submarine; despite being a "disaster movie", it's probably rather optimistic. Some of the crew of Kursk were alive for days after she was damaged; it would appear the Soviet->Russian Navy did not have an effective rescue technology (a DSRV sounds great on paper, but if the sub's hatches are damaged, or if she is lying at a funny angle, or if she's taking on water faster than the rescue equipment can arrive, then things are more complex). 87.115.43.168 (talk) 20:28, 17 February 2009 (UTC)

Wow, 87.115, you sure know your stuff! I'd buy you a drink if I could. BrainyBabe (talk) 21:17, 17 February 2009 (UTC)

Resolved

The road to Xibalba

The lead section of Xibalba states: Another physical incarnation of the road to Xibalba ... is the dark rift which is visible in the Milky Way. Is this an example of a dark cloud constellation? Astronaut (talk) 18:03, 17 February 2009 (UTC)

The dark rift is nothing more than gas and dust obscuring our view of the lens-shaped galaxy. Because we're on the outer edge of the galaxy - we're seeing all of this 'stuff' edge-on and we're looking through a lot of it. Just as humans have often discerned patterns in stars ('constellations' - the 'signs of the zodiac', etc) - we also see shapes in the clouds (it's ALWAYS a "bunny"!), in the pattern of marias on the moon, faces on Mars - and so it's no surprise that people have seen (and named) patterns in these gigantic dust clouds. It's an example of pareidolia. SteveBaker (talk) 22:35, 17 February 2009 (UTC)

Health: green tea leaves v. cabbage leaves

I've been drinking green tea recently. In the teapot, after a while the dry tealeaves swell up and can be clearly seen to be parts of a leaf. I'm wondering if there is anything special about the tea plant: would infusing or even eating the same amount of eg cabbage leaves be as good for you as green tea is supposed to be? 78.151.117.148 (talk) 19:07, 17 February 2009 (UTC)

I can't directly answer your question, but I went to school with our local swimming champion, who drank a litre of cabbage water every lunchtime: the school dinner ladies saved it for him! When I asked him why, he told me that the vitamins from the cabbage were actually in the water rather than in the cooked cabbage, and it was better for you than eating the cooked cabbage!--TammyMoet (talk) 21:25, 17 February 2009 (UTC)

Potential effects of tea on health makes many claims for green tea's health benefits; Cabbage makes fewer. They are quite different plants and they presumably contain many different trace chemicals. Tempshill (talk) 21:27, 17 February 2009 (UTC)

Gold in volcano

I recall reading about an active volcano in Antarctica that has a large amount of gold in the volcanic ash. Is this just a tall tale, or does such a volcano exist? If so, which volcano is it? 65.167.146.130 (talk) 20:04, 17 February 2009 (UTC)

"Large amount" is rather overstating the case, and our article on Mount Erebus doesn't mention it, but see this New Scientist article (which is the first hit in a Google search for Antarctica volcano gold). Deor (talk) 20:16, 17 February 2009 (UTC)

sort of alchemy

Ok, the ancient alchemists dreamed about turning lead into gold. I have heard that this is now possible using a particle accelerator or something and bombarding lead to break off protons and neutrons. Is the gold created in this manner a stable isotope, or will it be radioactive? 65.167.146.130 (talk) 20:13, 17 February 2009 (UTC)

I believe you are referring to nuclear transmutation. Yes, it is possible but is too expensive to be worth the cost. A Quest For Knowledge (talk) 20:35, 17 February 2009 (UTC)

And if it were inexpensive to do, the supply of gold would increase substantially, which would lower the price of it. --Mark PEA (talk) 21:28, 17 February 2009 (UTC)

yes, but is the resulting material radioactive, or stable? —Preceding unsigned comment added by 65.167.146.130 (talk) 21:34, 17 February 2009 (UTC)

Per our article on the synthesis of noble metals, Au₁₉₇, the only stable isotope of gold, can be produced from mercury. Likely there exists a path from lead to Au₁₉₇, but it's also quite likely more complicated. — Lomn 22:01, 17 February 2009 (UTC)

Why is there a high concentration of catalase in the liver?

What specific purpose does the liver serve by having a high concentration of the enzyme catalase? Does the body pump most of the waste hydrogen peroxide produced to the liver to be treated there? Or is there another reason?

22:01, 17 February 2009 (UTC) —Preceding unsigned comment added by Scofield Boy (talk • contribs)

I don't know for certain, but it may play a role in detoxifying potentially harmful compounds and/or removing peroxides from the blood. – ClockworkSoul 22:34, 17 February 2009 (UTC)

I can't find a definitive answer, but I believe, essentially, what Clockwork says. Peroxisomes are responsible (in whole or in part) for some functions that take place mainly in the liver (gluconeogenesis and fatty acid metabolism). I suspect this means the liver needs more peroxisomes, and also more catalase (many of the reactions involved in those processes are oxidative, and so could create free radicals and superoxides that would also lead to peroxide). Someguy1221 (talk) 23:14, 17 February 2009 (UTC)

Hodgkin's lymphoma and GHB?

While searching on the internet about Hodgkin's lymphoma I found on wikipedia an article saying that one of the risk factors is "Prolonged use of human growth hormone". I kept searching clicking on "human growth hormone" and found maybe a relation between GHB abuse and lymphoma. Why isn´t this mentioned? Am I wrong, has someone studied about this?

When I heard about GHB, 10 years ago, it was said that there were still no known long-term secondary effects of it´s use. But if now it´s getting clearer, please inform people. My friend suffers from Hodgkin's lymphoma and he used regularly GHB but he also has Aids. So, where´s the connection? Is the lymphoma related to Aids or the abuse of GHB? Are we blaming AIDS for it forgetting the risks of using GHB? and because both diseases have the fact of being gay (aids & lymphome) or a man (lymphome) as one of the risk factors (although to say this is politically incorrect, I apologise, but it´s true) aren´t we mixing up things and making people believe that GHB has no long term severe secondary effects. Every website I found about GHB doesn´t mention this relation, but it mentions it´s use as rape drug. I know many cases of lymphome and a few of rape. Are we not making patients irresponsible? In the process of living with a cancer and facing it´s treatment it´s important not to blame yourself but at least know that your behaviour can deeply affect your health - a change of behaviour will help to cure. I wish I could say all this to everyone with the same problem in order to motivate a behaviour change to a healthy lifestyle and the strong belief in a cure, especially with withdrawing toxins and cancer agents and bringing in anti-oxidants through food. (we are what we eat/consume). I would much appreciate scientific answer/ explanation about this matter. And if there is a relation between and no one found out, I should get a prize. 217.22.90.231 (talk) 00:15, 18 February 2009 (UTC)

First thing, human growth hormone is completely different from and unrelated to GHB, which is a date rape drug. The acronym used for human growth hormone is HGH, not GHB. The following scientific articles I found address the issue of HGH and leukemias and lymphomas.

1. Critical evaluation of the safety of recombinant human growth hormone administration: Statement from the Growth Hormone Research Society. J Clin Endocrinol Metab 2001;86:1868 – 187025.. I would like to note that according the Growth Hormone Research Society webpage they are sponsored by a variety of corporate entities and thus may have outside interests. I do not know enough about the sponsership to make that call.
2. I found the following medical case report which requires a subscription to read. Nicola Magnavita, Luciana Teofili, Giuseppe Leone: Hodgkin's lymphoma in a cyclist treated with growth hormone. American Journal of Hematology, Volume 52 Issue 1, Pages 65 - 66. One quote is "The suspected relationship between GH use and hematological malignancies represents a further, strong reason to discourage this [doping using HGH] practice."
3. This paper found that HGH stimulated the growth of fresh patient-derived lymphoblastic leukemia and myelogenous leukemia cell lines. This paper and papers citing it seemed to conclude leukemia and lymphoma patients on an HGH treatment should be closely monitored, and that giving HGH to patients in remission is probably not a good idea since relapse risk increases.
4. This well cited paper collects various leukemia cases that have occurred in people treated with growth hormones. I can't read it so I'm not sure what it concludes.
5. Finally this commentary evaluates the scholarly writing and information available since 2004 and concludes the following:"There are no data to prove that the intrinsic risk of leukemia is further exacerbated by GH treatment, particularly if the dose of GH is at the level of physiologic replacement. Never-theless, this possibility requires serious consideration by the physicians and the families involved, and absence of data should not necessarily be construed to mean absence of an effect."' (Blanche P. Alter: COMMENTARY: Growth Hormone and the Risk of Malignancy. Pediatric Blood & Cancer, Volume 43, Issue 5 (p 534-535) )

I personally liked number 5 on my list of papers. From the limited exposure I have had to this topic from researching your question it seems like there is reasonable evidence that human growth hormone use (what level of use?) may increase the risk of relapse among leukemia/lymphoma patients. There is less than conclusive evidence that HGH use (what level of use?) may increase leukemia/lymphoma development risk in predisposed people but not enough research has been done to nail down whether this is true and to what extent if it is. I get the feeling that the most endocrine researchers do not think that human growth hormone increases the risk of leukemia/lymphoma development in healthy unpredisposed people. Concerning diet, you should look at Diet and cancer. Barring obesity, eating a well balanced diet at best only slightly reduces cancer risk. Other factors are more important in the development of various cancers than diet. 152.16.253.109 (talk) 03:53, 18 February 2009 (UTC)

AIDS and Non-Hodgkins Lymphoma (NHL) are certainly associated. NHL is the most common lymphoma affecting people with AIDS; NHL is an AIDS-defining illness in the presence of a positive HIV test. - Nunh-huh 04:37, 18 February 2009 (UTC)

A side note here: GHB is an extremely important pharmaceutical in the management of narcolepsy and cataplexy. It is very unfair to stigmatize it as a "date rape drug"; this tends to result in onerous regulation that makes it difficult for sufferers to get the medicine they need. --Trovatore (talk) 04:47, 18 February 2009 (UTC)

Ionic Strength: am I doing it right?

I'm trying to figure out the ionic strength of a solution used for inducing insect flight muscle contraction. My PI couldn't help me with this, so I'm asking here. In short, my question is am I doing this ionic strength calculation right? The formula for ionic strength is given here. The components of the solution with concentrations are listed below. I included relevant pKas for the weak acids/bases. I can't figure out if pKa matters in this context since pKas are affected by ionic strength.

15mM Na₄ATP (ATP pKa = 6.5)

15mM Mg(OAc)₂ (acetic acid pKa = 4.76)

5mM CaCl₂

20mM NaMOPS (Mops pKa = 7.20)

5mM EGTA (EGTA pKa = 6.91) (I have no clue whether or to what extent a chelator of calcium will affect the ionic strength contribution of calcium present)

5mM NaN₃

Below I have separated the above into ions assuming complete dissociation for the salts and that the concentration of dissociated EGTA is negligible.

species	concentration	charge	ionic strength
Na	85mM†	+1	42.5 *10-3
ATP	15mM	-4	120 *10-3
Ca	5mM	+2	10 *10-3
Cl	10mM	-1	5 *10-3
MOPS	20mM	-1	10 *10-3
Mg	15mM	+2	30 *10-3
OAc	30mM	-1	15 *10-3
EGTA	5mM	0	0
N3	5mM	-1	2.5 *10-3

† That 85 mM is from 4*15mM + 20mM +5mM

The sum of all of those is 235 *10^-3. Did I do the calculation right? If it helps, I know from experience the pH winds up being between 5.3 and 5.8 (I think 5.6?) and if I replace the 5mM CaCl₂ with 10mM NaCl (a sum of 230 *10^-3) the pH winds up being between 6 and 6.5 (I think 6.3?). I pH the solutions to 6.8 using sodium hydroxide afterwards, but I'm not going to worry about this yet because I want to make sure that I am doing the ionic strength calculations correctly in the first place. And a bonus question: If I have an enzyme that is in the form of a disodium hydrated salt, is it safe to assume for the purposes of ionic strength calculation that the enzyme will act as a divalent anion when in solution? 152.16.253.109 (talk) 02:42, 18 February 2009 (UTC)