Wikipedia:Reference desk/Archives/Science/2009 February 12

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February 12[edit]

First Ionization Energy[edit]

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. 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. 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[edit]

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.) (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 (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. (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. (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[edit]

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 , 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[edit]

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 (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. -- (talk) 12:52, 12 February 2009 (UTC)

Authoritative anatomy terminology[edit]

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?[edit]

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?


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.) -- (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>. 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)


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)


Which bodyparts don't have hair growing on them? —Preceding unsigned comment added by (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. (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[edit]

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... 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. (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. (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 : ) (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: {] - (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?[edit]

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. (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[edit]

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 (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. 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. (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 (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 ... 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?[edit]

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 (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. :-) (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[edit]

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?-- (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. - EronTalk 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.-- (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 (talkcontribs)

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

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 (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? -- (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 placeAlgebraist 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.-- (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'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 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. (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 (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 (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. :-) (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)