Wikipedia:Reference desk/Archives/Science/2011 March 6

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March 6

Better quality rest giving better quality work

Your demanding day job makes you feel tired. Is there any scientific evidence (rather than speculation please) that better rest in the evening results in better work the following day? If you spend evenings feeling bored and physically uncomfortable, is there any significant difference work-wise from evenings when you are entertained and physically comfortable? Thanks 92.29.117.180 (talk) 00:27, 6 March 2011 (UTC)

The articles Sleep deprivation and Effects of sleep deprivation on cognitive performance provide reliable sources. Cuddlyable3 (talk) 01:32, 6 March 2011 (UTC)

I think the OP is talking about how well you relax in leisure time, not how well you sleep. 90.195.179.167 (talk) 02:25, 6 March 2011 (UTC)

It is tritely obvious that the OP is not interested in how I personally sleep. Sleep is the major remedy for feeling tired and its quantitative relation to work efficiency has been studied extensively, whereas subjective evening notions of boredom, entertainment and discomfort do not provide hard scientific evidence. Cuddlyable3 (talk) 04:58, 6 March 2011 (UTC)

I was not asking about sleep, thanks. Let's assume you are getting enough sleep. 92.15.18.16 (talk) 12:16, 6 March 2011 (UTC)

On the other hand, there is this potential cycle: stress → increased stress hormones → insomnia → fatigue → decreased productivity. Try stress and productivity on Google Scholar or try these articles from LiveScience: [1] [2] [3] [4] [5]. ~AH1^(TCU) 02:38, 7 March 2011 (UTC)

Where is water taken up in the digestive system?

Where is uptake of water in the human digestive system mainly taking place? The stomach, the small intestine or somewhere else?

From digestion: "Other small molecules such as alcohol are absorbed in the stomach, passing through the membrane of the stomach and entering the circulatory system directly." The water molecule is even smaller than alcohol, so I presume water is taken up by the stomach.

From small intestine: "Water and lipids are absorbed by passive diffusion throughout the small intestine."

--Mortense (talk) 00:58, 6 March 2011 (UTC)

The stomach and the small intestine will absorb some water but the large intestine is where the bulk of the water is absorbed. Dauto (talk) 02:16, 6 March 2011 (UTC)

Agreed. Otherwise the intestinal contents would be too thick to flow around the sharp bends of the small intestine. StuRat (talk) 06:55, 6 March 2011 (UTC)

See colon, the first line confirms Dauto's answer. Richard Avery (talk) 08:51, 6 March 2011 (UTC)

Ironically, the article specifically does NOT confirm that answer. The first line makes no statement of the proportion of water absorbed; moreover, the section on colon function specifically states that 90% of the water has been absorbed prior to entry into the colon. The article might be wrong, and a reliable source would be great here, of course, but I don't think the answers above (nor our article) settle the question. -- Scray (talk) 18:40, 6 March 2011 (UTC)

The question needs to be clarified somewhat: each segment of the digestive tract deals with what arrives into it. This is complicated substantially by secretion, i.e. the mouth produces about 1 liter of saliva per day. I would guess the OP is asking about net absorption of ingested water in the digestive tract. -- Scray (talk) 19:24, 6 March 2011 (UTC)

Still looking for a reliable source, but this page states: "An important function of both small intestine and colon is the absorption of water and electrolytes. Approximately 2000 ml of food and drink is ingested daily, and the volume of gastrointestinal secretions (salivary, gastric, biliary, pancreatic and intestinal) is about 8,000 ml daily; therefore, approximately 10 liters of fluid enters the intestine each day. Of the 8 liters secreted, about 1-1.5 liters enter as saliva, 2-3 liters are secreted by the stomach, about 2 liters enter as bile and pancreatic secretion (about 1 liter each), and about 2 liters are secreted by the small intestine. (Please note that these figures are approximate, not absolute. Volumes may vary, depending on experimental method and conditions.) Of the 10 liters which enters the gut each day, only about 1 liter passes into the colon, about 90% having been absorbed across the small intestinal epithelium. Only about 150 ml is lost in the feces daily, with the remainder being absorbed by the colon. It should be obvious that any derangement in intestinal fluid absorption would profoundly influence the balance of fluid and electrolytes in the body, and that the normal functioning of the intestines plays a significant role in regulating water and electrolyte balance." This strongly suggests that the small intestine is a better answer than the large intestine/colon, but is probably not the final word. -- Scray (talk) 19:34, 6 March 2011 (UTC)

I think the net absorption of water in each part of the digestive tract is the relevant info we need here. You listed 1 liter going into the large intestine, and 0.15 coming out, so that means 0.85 liter of net absorption. That, divided by the 1.85 liters that enters the mouth and doesn't leave the other end, gives us approximately 46% of water being absorbed by the large intestine. If we can come up with comparable figures for the stomach and small intestine, we will then have a way to determine where the net absorption of water is greatest. StuRat (talk) 20:34, 6 March 2011 (UTC)

Well, if we stick with stomach vs small intestine vs large intestine, the answer is pretty clear - the stomach secretes 2-3 liters and is well-known to absorb very little, so its net absorption will be nil. That leaves 54% to the small intestine. -- Scray (talk) 20:41, 6 March 2011 (UTC)

Absorption of nutrients often depends on whether they are water-soluble or fat soluble and this also applies to vitamins. ~AH1^(TCU) 02:19, 7 March 2011 (UTC)

Two questions about filters

(1) Why do filters for digital cameras exist? Can't you process the pictures after shooting them with a software filter?

(2) Is there a filter for glasses to make everything look black and white? Quest09 (talk) 02:26, 6 March 2011 (UTC)

1)You can process color images with Photoshop or other software and gain many of the advantages of using color filters, such as if the image is transformed to black and white, after a yellow filter effect is used to emphasize clouds in an outdoor color photo. Actual filters can achieve some effects which would be difficult or impossible with Photoshop, since a filter might have a very narrow bandwidth, while the three channels of color info in a digital image are very broadband. 2)Kodak produced a "viewing filter" which made it easier to visualize how a B & W image of a color scene would look. The name of it is a "Kodak Wratten 90 filter." If memory serves, it might have been brown or orange. The scene did not really look black and white through it; that is impossible. See also [6]. Edison (talk) 03:07, 6 March 2011 (UTC)

UV, infra-red and polarizer filters cannot be emulated in software. Cuddlyable3 (talk) 05:17, 6 March 2011 (UTC)

1) One other advantage would be to get the filtered results immediately, and thus know if another photo should be taken, while the subjects are present and the lighting is still the same. Here I'm assuming that the software filter is used later on. If you apply it as the picture is taken, then that's good, too. StuRat (talk) 06:43, 6 March 2011 (UTC)

As the preceding responses note, there are some filter effects that cannot be employed after the fact, because the camera doesn't record the information required to reconstruct the 'filtered' image. Typically, the camera will collect just three pieces of information about each pixel: the intensity of light in that spot as seen through a red, a green, and a blue filter (built into the camera's sensor). This is usually enough to reproduce the color and brightness of the pixel as our eyes would see it, but can still leave much to be desired. For instance, specular reflections of light will be polarized to some degree; a suitable polarizing filter allows the photographer to suppress (or enhance) the appearance of this reflected light. Here are some examples. Since your digital camera's sensor doesn't record polarization information, you cannot reconstruct the polarized-light image in software.

Similarly, with only three color channels recorded, a great deal of information about the spectrum of the light observed is lost. This is usually not particularly important, but it can have significance under unusual lighting conditions or with particularly novel subjects; astrophotographers can have a particularly complicated toolbox here. To take an extreme example, look at the sun. (Figuratively only — don't actually go out and stare at the sun, please.) If you photograph the Sun – with appropriate filters so that you don't cook the camera's optics – you'll get a yellow-white blob, which may have some discernibly-darker patches: sunspots. Photograph the sun through an H-alpha filter (which extracts just a narrow window of light around 656 nm wavelength) and you'll get a much more richly detailed image. TenOfAllTrades(talk) 16:41, 6 March 2011 (UTC)

A graduated neutral density filter can help digital cameras with a restricted dynamic range cope with a bright sky etc. If the sky gets burnt out, then no amount of post editing of the RAW file will bring it back. Yet if the sky is brought within range, the ground can become too dark and noisy. WP as ever, even has an article on filters in general.--Aspro (talk) 19:28, 6 March 2011 (UTC)

Alternatively, some digital cameras have settings to enhance colour contrast in a live photo or to make it appear B&W or sepia. ~AH1^(TCU) 02:06, 7 March 2011 (UTC)

If there's a heart defibrillator, why isn't there a brain defibrillator?

So a defib paddle can restart a flatlined heart; why isn't there a defib device that restarts a flatlined brain?

What would it take to invent a device that would restart a flatlined brain? What obstacles would it have to overcome and how would it overcome them? --70.179.169.115 (talk) 03:39, 6 March 2011 (UTC)

The heart has a beat to restart, the brain doesn't. Clarityfiend (talk) 04:31, 6 March 2011 (UTC)

CF, what does the brain have to restart then? It must have something to keep going. --70.179.169.115 (talk) 04:34, 6 March 2011 (UTC)

DISCLAIMER: I'm no expert, so take the following with a boulder of salt. Compared to the brain, the heart and its operation is a lot less complicated. It follows a repetitive, relatively simple cycle, which somebody has discovered that a jolt of electricity can restart. Various areas of the brain, on the other hand, fire off at different times, intensities and combinations depending of the stimulus. There is no set pattern AFAIK for you to kick start. Also, I'm guessing that neurons are a lot more fragile than heart muscle, and would not take kindly to being zapped. As a rough analogy, kicking a malfunctioning washing machine has a much better chance of working than (physically) booting your PC. Clarityfiend (talk) 05:16, 6 March 2011 (UTC)

Actually, this question isn't entirely off base. The heart doesn't usually stop beating entirely, but rather goes into an abnormal contraction pattern, called fibrillation, and the shock stops that and allows the normal beat to return. Similarly, the brain sometimes has abnormal electrical patterns, and some attempt has been made to stop those and allow the brain to "restart", via electroshock therapy. While this therapy has a bad reputation from being used improperly, it still has it's advocates, especially when compared with brain surgery. StuRat (talk) 06:37, 6 March 2011 (UTC)

It's an interesting question. I know little about it other than you would need to get the the neuronal ion pumps to start working again but the IP may be interested in having a read around the subject of cortical spreading depression in the visual cortex. It's kind of like part of the brain flatlining for a while (in the sense that neurons remain excessively inhibited) after a hyperexcitability phase (a spreading jolt of electricity). Sean.hoyland - talk 07:09, 6 March 2011 (UTC)

What does it mean to re-start a brain? We re-start heart because they are fibrillating and you could die. If the brain is not working properly there are other means to 're-start' it. If you mean re-starting a brain without activity, I have to say that you should have re-started the heart earlier. —Preceding unsigned comment added by 212.169.187.20 (talk) 13:08, 6 March 2011 (UTC)

I will note parenthetically that a defibrillator cannot restart a 'flatline' rhythm (asystole). This is a popular myth perpetuated by the lazy or inept writers of movies and televised medical dramas, where the flat EKG and beeeeeeeeep of the monitor are a convenient and widely-recognized device for plot advancement. TenOfAllTrades(talk) 16:08, 6 March 2011 (UTC)

This is one of the reasons why a brain dead person is often considered deceased even in cases when the heart continues to beat. The brain and heart are also co-dependant in some processes. ~AH1^(TCU) 02:03, 7 March 2011 (UTC)

weather

If we wanted to know everything about the weather to predict it w/ 100% accuracy, would it be better to ask all the inhabitants to hold their breath and stop moving or include those interactions in our analysis? by better i mean to predict the weather, not for the inhabitants. —Preceding unsigned comment added by 98.221.254.154 (talk) 04:42, 6 March 2011 (UTC)

What about the animals, continental plate movement, variable solar activity, the odd earthquake, even plant growth? Clarityfiend (talk) 05:21, 6 March 2011 (UTC)

How would you even model interactions between humans and the atmosphere? Titoxd^{(?!? - cool stuff)} 07:39, 6 March 2011 (UTC)

You could build a scalar field of global baked bean sales. That would be a start. Sean.hoyland - talk 07:56, 6 March 2011 (UTC)

To actually answer the question, no, because of the butterfly effect.--Shantavira|^{feed me} 08:18, 6 March 2011 (UTC)

Yes all those things also. how can you answer no to an "either or" question? Just b/c it might be totally impossible to do does nto change whether we would need it for the 100%. —Preceding unsigned comment added by 98.221.254.154 (talk) 17:33, 6 March 2011 (UTC)

I believe 98.221.254.154 is making a valid point if he/she is saying that all factors would need to be accounted for if we are to achieve 100% accuracy in a prediction. By the way, please "sign" your posts with 4 Tildes. See WP:SIGN. (Bus stop (talk) 17:41, 6 March 2011 (UTC)). Bus stop (talk) 17:37, 6 March 2011 (UTC)

If you wanted to lift Mount Everest, would it be better to remove the snow from the top or lift harder in order to take the snow into account? There is no sensible way to answer questions such as this. Looie496 (talk) 19:03, 6 March 2011 (UTC)

If by better you mean easier (less work), then most likely lifting harder, because it is extremely unlikely that the work needed to remove the snow before lifting it would be equal or less than the same work associated with the snow portion when lifting it with the snow in place.98.221.254.154 (talk) 04:02, 7 March 2011 (UTC)

If both methods are 100% accurate, then they are equally good at predicting the weather. Your question makes no sense. --Tango (talk) 22:17, 6 March 2011 (UTC)

I am asking if attempting to artificially isolate certain phenomena at the expense or exclusion of other valid ones in order to only understand the isolated ones is as fruitful (if at all) as attempting to identify and combine all possible phenomena as they exist entangled.98.221.254.154 (talk) 04:02, 7 March 2011 (UTC)

The effects of human breathing are typically considered negligible on global weather and thus are not included in numerical weather forecasting methods, even as it contributes to the butterfly effect. Human-made contrails, effects of greenhouse gas emissions, Arctic haze, dust from overgrazing, reduced evaporation from deforestation, the Asian brown cloud, soot in the atmosphere, the ozone hole and even wind farms likely have a much greater effect on weather than breathing, and those are usually not included either. It's not useful to consider any and all possible influences on weather, as that would amount to trillions of co-interacting and co-evolving factors even boiling down to the movement of every individual organism in microscopic gut flora in each of the nearly 7 billion humans on Earth having an effect on weather...so you get the idea. ~AH1^(TCU) 01:59, 7 March 2011 (UTC)

Just b/c those are not usually included doesn't mean they shouldnt be.

Just because they do not feature explicitly in the equations doesn't mean that human breath and a thousand other factors are not implicitly included in the mathematical model. All such factors contribute to the initial conditions that are used as a starting point for the forecast, and they are possibly included in the constants of the equations. Perhaps an expert in weather forecasting can confirm this? The forecast might be rendered inaccurate if the whole population of a large city decided to take vigorous exercise simultaneously for a few hours, but I expect that the effect would be more from the extra heat generated than from the breath, unless they all faced in the same direction and blew hard! Dbfirs 17:20, 7 March 2011 (UTC)

(ec) Reputable scientists are in agreement on this one: there is no practical benefit to over-parameterizing global models of climate. See, for example, our article on Global climate model. Here are several actual models in use. If you can extend any of those models, or the computer-code implementations of them, you can probably make a career for yourself as a climate scientist. But if your suggested model extension is totally infeasible and incompatible with today's theory and practice, (like your current suggestion to model microscopic effects due to human breath), you will have a hard time making a scientific case that you are modeling and predicting meaningful parameters. Being able to test your model against some parameter is a requirement for scientific research. Nimur (talk) 17:21, 7 March 2011 (UTC)

Testosterone as an anti-depressant in men

Has any research been done on using testosterone as an anti-depressant on men with or without low testosterone levels? —Preceding unsigned comment added by 76.169.33.234 (talk) 05:55, 6 March 2011 (UTC)

There's plenty of research showing a small but statistically significant decrease in bioavailable testosterone levels correlated with depression (such as [7]), but the only research I can find on treatment of depression with testosterone has actually been done on women to treat symptoms of menopause (such as [8], if you're allowed to access it). Someguy1221 (talk) 06:05, 6 March 2011 (UTC)

Chemicals that mimic testosterone are used in anabolic steroids. ~AH1^(TCU) 01:51, 7 March 2011 (UTC)

Period & Bloating

When a woman gets bloated during her period, is the bloating all blood or water? —Preceding unsigned comment added by 76.169.33.234 (talk) 05:57, 6 March 2011 (UTC)

It's water retention. Surprisingly little blood is lost during the menstrual period - about a teacup over the average 5 days. Most of what you see is endometrium, or the lining of the womb. --TammyMoet (talk) 09:13, 6 March 2011 (UTC) Edit: Sorry, I meant an eggcup. The Menstrual cycle article says 10 - 80 ml. (Note to self: wake up before you start posting!) --TammyMoet (talk) 11:32, 6 March 2011 (UTC)

Life on meteorites?

Hi. Could this be evidence of panspermia? Please refer to this unpublished article from the Journal of Cosmology (no Wikipedia article), as well as this older similar discovery from 2004. I'm not asking for opinions here, just an overall analysis of the articles presented here (is JoC a reliable source?), and comments on whether any information from these studies once peer-reviewed and published are to be included in Wikipedia articles. Thanks. ~AH1^(TCU) 15:58, 6 March 2011 (UTC)

If they are truly bacteria (a big if there) which really originated from outer space (another big if), and if they appear to be based on the same "code" as we are (e.g. they look more or less like life on our planet), I'd say that would be pretty suggestive towards panspermia, assuming that the probability of us finding similar designs on meteorites is low (which I think is a reasonable assumption at the moment, but it might be the case that our "template" for life is more common than we realize). If they don't look like they're on the same template as the rest of Earth, then probably not — could be independently developed somewhere else. I lack the technical ability to judge the article, but as a layman I would worry that humans are extremely good at looking for recognizable patterns, and are seeing bacteria where they might otherwise just see random structures. Lots of things look like bacteria at scales like that, when all you have access to are morphological structures and relatively clunky things like how much nitrogen or carbon are in them. But again, I'm no scientist — but these seem like the obvious things to be concerned about. The JoC looks legit as far as I can tell — peer-reviewed, non-nuts running it, etc. --Mr.98 (talk) 17:38, 6 March 2011 (UTC)

The Journal of Cosmology looks extremely non-legitimate to me. Did you look at the other articles it's published, such as these ones? The editorial board includes Subhash Kak, who also frequently publishes in the journal (as do other board members). The board also includes Roger Penrose as a "guest" editor, whatever that may mean. The "author guidelines" page contains the remarkable phrase "Do Not Use "Latex" Word Processing Programs". The "manuscript preparation" page says that authors should include with their submission a list of qualified reviewers. And they charge for submission and publication. This looks for all the world like a vanity journal for crackpots. -- BenRG (talk) 20:21, 6 March 2011 (UTC)

I can't speak to the crackpottery (not yet having investigated the journal), but charging authors for submission and publication has long been the norm in academic journals. Typically, charges are made per page, for preparation of illustrations, and so on, and are quite steep. 87.81.230.195 (talk) 15:30, 7 March 2011 (UTC)

Check out: Fox News Publishes Fake ‘Exclusive’ About Discovery of Alien Life for a bit more on this subject, this scientist and the journal. Rmhermen (talk) 19:10, 6 March 2011 (UTC)

That link doesn't take me to a specific story. It also seems to be a gossip mag. I think relying on a gossip mag to debunk Fox News is a sure route to madness! --Tango (talk) 19:21, 6 March 2011 (UTC)

Link takes me directly to the story. To summarize, he appears to have already announced this discovery on panspermia.org in 2004 and in 2007 in a paper at a conference for the Society of Professional Instrumentation Engineers. But necver in a top-line journal like Nature. He also appears to have claimed that the fossils are older than the solar system. Rmhermen (talk) 19:43, 6 March 2011 (UTC)

The only thing that gawker is saying is that Fox is ridiculous for calling this "new" or "exclusive." That the guy has been shopping this theory for years doesn't really count against him. JoC seems to have reviewed it rather thoroughly before publication, if one takes their editorial note as being accurate. That doesn't mean it is right, but it also means that it shouldn't just be dismissed out of hand because it is unusual. The gawker criticism of the JoC is entirely on the basis of their webpage design — I hate to inform them that most academic journals have pretty lousy web designers. They then back up their evidence by linking to another blogger (who is a biology professor, good for him) who says it is not true. All in all, fun commentary, but not science. --Mr.98 (talk) 20:10, 6 March 2011 (UTC)

The article can also be found here. -- BenRG (talk) 20:21, 6 March 2011 (UTC)

Some ways in which the bacteria may not be extra-terrestrial:

1) Fraud. They could have been placed there by the scientist who "found" them.

2) Accidental contamination. It's difficult to prevent Earth bacteria from getting onto a sample. Even with careful decontamination procedures, bits of bacteria may remain.

3) The meteorites may have come from Earth, as a result of an ancient meteor strike, similar to the one that may have hit to form the Moon, and only recently have fallen back to Earth. I'm unsure if the composition is consistent with a meteorite from Earth. StuRat (talk) 19:32, 6 March 2011 (UTC)

I say JoC looks about as genuine as a thirteen dollar bill. But don't take my word for it - read PZ Meyers at [9]. Note, however, that the scenario of finding life preserved in just the right meteorite is genuine - this was claimed before for a Martian meteorite - but this just isn't meeting the threshold. Wnt (talk) 05:54, 7 March 2011 (UTC)

Why take PZ Meyer's word on it? He seems to me as partisan as any blogger, and willing to make gigantic claims that he doesn't bother to support with evidence. His objections to JoC is "it's online", "it has stuff in it I don't like", and "it has an ugly website." That's not exactly a scientific critique. It might be fringe, but I don't think you can tell that from its webpage alone. --Mr.98 (talk) 01:14, 9 March 2011 (UTC)

Hi, did you actually read PZ's article? He's taking the paper apart. He might be a bit loud at times, but his objections are much deeper than "I don't like the website". PervyPirate (talk) 06:51, 10 March 2011 (UTC)

weird question about evolution

Did Human being become more sophisticated and intelligent by becoming omnivores? —Preceding unsigned comment added by 1.23.4.211 (talk) 17:04, 6 March 2011 (UTC)

Do you have reason to believe that being omnivorous leads to intellectual attainment? You may be right—I don't know. But we have List of omnivores with a mix of creatures of various intellectual capacities. I'm curious to know how being omnivorous may have spurred on humans to evolve to have intellectual capacities at the upper end of the range. Bus stop (talk) 17:12, 6 March 2011 (UTC)

There's some discussion on the evolution of eating meat by humans here and here, without any reference to cranial capacity. Personally I kind of doubt it — it's not clear to me when you want to say that "humans" evolved to be omnivores anyway, and we have evidence from other great apes that being an omnivore or a vegetarian doesn't seem to push you into the human range at all. (Chimps are omnivores; gorillas are vegetarians. Bugs not included.) It's clear that evolving to eat meat was important for human evolution more generally, especially by allowing them to expand into different ecological niches, but I'm just not sure it can be called a main or prime motivator for our big brains. --Mr.98 (talk) 17:27, 6 March 2011 (UTC)

I'd rather say humans are omnivores (= opportunistic feeders) because they are intelligent. However, I don't see how diet can have an influence on your intelligence as a species. Proper diet is determined more by your intestinal track than by your brain. And along evolution, you tend to adapt to be able to digest the food available to you. Quest09 (talk) 17:43, 6 March 2011 (UTC)

Isn't there an argument that by eating meat, and/or by inventing fire and cooking, humans have been able to get more nutrition from a given quantity of food, and thus spend less time foraging for food, and more time in activities that would make use of their bigger brains? (not sure how that would impact the evolution of the brain, however). --rossb (talk) 17:55, 6 March 2011 (UTC)

Any change that requires an increase in the complexity of behavior and of decision-making ought to generate evolutionary pressure for an increase in the sophistication of brain structure. Since omnivorous behavior is more complex than consistently eating a single type of food, it ought to create a pressure for increased intelligence. Whether this pressure is significant in comparison to other factors, though, is far from clear. Looie496 (talk) 18:59, 6 March 2011 (UTC)

The point is that being omnivore, as I said above, is not exactly our nature. We are opportunistic feeders, so there is less pressure on us, since we can eat what's available. Quest09 (talk) 20:26, 6 March 2011 (UTC)

Animals that have always been herbivores (meaning no omnivores or carnivores in their evolutionary past) do tend to be less intelligent than omnivores and carnivores (or those species descendant from them), but there doesn't seem to be as much difference between omnivores and carnivores. I'd say that this is because hunting requires more skill than foraging. StuRat (talk) 19:21, 6 March 2011 (UTC)

Elephants are reputed to be herbivores, and are very clever animals, as apparently are many parrots. However, I should say that I am always skeptical of claims of absolute herbivory in any animal. An angry elephant can supplement its diet with more than a bit of meat,^[10] and as we know from the mad cow disease outbreak, even cattle feeding can involve substantial amounts of animal byproducts. Wnt (talk) 19:32, 6 March 2011 (UTC)

Elephants are not going to eat too much meat. They don't have the teeth or habits for it. I do think, though, that in general, hunting requires more brain power than running away, though there are some important exceptions where the impetus for more brain power seems to have come from elsewhere. (And comparing it with cows is a complete non sequitur. Cows are herbivores. That we feed them meat tells us only about us and nothing about them.) --Mr.98 (talk) 20:05, 6 March 2011 (UTC)

Regarding "hunting requires more brain power than running away"; that's an invalid comparison, as being a hunter does not exclude one from being hunted, and vice versa. I would also argue that being hunted is important to developing intelligence, and humans likely were considered prey for large predators for most of our evolution. Thus, being both hunter and hunted might lead to the most intelligence with being neither predator nor prey leading to the least, such as the infamous dodo. StuRat (talk) 18:17, 8 March 2011 (UTC)

There are some stupid hunters, like crocodiles, which would eat more intelligent animals like zebras. Quest09 (talk) 20:26, 6 March 2011 (UTC)

Some would take exception to your claim that crocodiles are stupid hunters. See here. Lsfreak (talk) 23:31, 6 March 2011 (UTC)

"Although we classify them as herbivores, hares occasionally eat meat." Bus stop (talk) 20:19, 6 March 2011 (UTC)

Some pretty vicious rabbits have been observed, too. --NorwegianBlue ^talk 21:38, 8 March 2011 (UTC)

Being intelligent also implies having a big brain, which implies lots of energy, which implies some calories rich diet, which contains at least some meat. Quest09 (talk) 20:34, 6 March 2011 (UTC)

The troodon was considered the smartest dinosaur prior to its extinction, and it was also omnivorous. Feral cats eat both meat and grass. ~AH1^(TCU) 01:49, 7 March 2011 (UTC)

I don't think that grass is part of the normal diet of cats. Both feral and domestic cats do eat grass, but probably only as a medicine? Can an expert comment on this? From observation, domestic cats eat grass only when they are about to be sick! Dbfirs 09:46, 7 March 2011 (UTC)

These cat experts give several theories as to why cats eat grass, of which one is that it induces vomiting which helps the cat bring up hairballs. Other sources including The new Encyclopedia of the Cat (Fogle) advise offering grass to indoor cats for this purpose. Cuddlyable3 (talk) 10:44, 7 March 2011 (UTC)

While a common claim, I think the 'sick' part is perhaps a little simplistic particularly if you're thinking they do it because they need to or are about to or already have thrown up. Plenty of cats seem to eat a blade of grass without outward signs of being sick and not all seem to vomit afterwards. A lot of claims are made of the reasons why, but as with many claims about pets, I think there isn't actually much evidence or research. See also [11]. More interesting is [12] which is also covered in [13] and while primarily about dogs they do mention cats, in particular an ongoing study is mentioned (I didn't find evidence has been published yet but didn't look that hard). The hypothesis presented would support a 'medicinal' function I guess. In any case while eating grass is apparently 'natural' and not that uncommon, I wouldn't call cats omnivores and would be careful about giving too much emphasis to them eating grass. Nil Einne (talk) 10:52, 7 March 2011 (UTC)

When talking about carnivores, perhaps a distinction should be made between predators, scavengers, and others, like filter feeders (or are they considered to be omnivores ?). Predators presumably would be more intelligent, as hunting requires more brain power than the others. Note, however, note that baleen whales are filter-feeders, which doesn't seem to require much brain power. I believe, however, that they evolved from fish-eating whales, and retained the brain structure developed for that. StuRat (talk) 18:06, 8 March 2011 (UTC)

lamps

what material are lamp shades made from? — Preceding unsigned comment added by Wdk789 (talk • contribs) 18:05, 6 March 2011 (UTC)

The variety would be very vast. Bus stop (talk) 18:06, 6 March 2011 (UTC)

We could roughly cover the entire spectrum of material science: fiber, polymers, glass, or metal. Almost all day-to-day materials fall into one of those categories. Nimur (talk) 20:30, 6 March 2011 (UTC)

... and bacon! --DI (talk) 22:00, 6 March 2011 (UTC)

Human skin (must be jewish). Cuddlyable3 (talk) 09:38, 7 March 2011 (UTC)

[14] confirms human skin but suggests it wasn't possible to determine the ethnicity of the human. Given the source, Jewish is probably more likely to be right then wrong, but we still can't be certain. Nil Einne (talk) 10:28, 7 March 2011 (UTC)

Human skin (goys OK). --Sean 15:23, 7 March 2011 (UTC)

florida homes

do florida homes have insulation in walls — Preceding unsigned comment added by Wdk789 (talk • contribs) 20:35, 6 March 2011 (UTC)

A quick google search for "Florida building code" + "insulation" provides several hits that suggest that insulation is required to meet the building codes. Such as: http://www.dca.state.fl.us/fbc/committees/energy/energy_forms/New_Energy_forms/600C_04Nrevised.pdf

--DI (talk) 21:56, 6 March 2011 (UTC)

Many Florida homes however do not seem to have basements. ~AH1^(TCU) 01:43, 7 March 2011 (UTC)

I live in Florida and I can attest that basements here are exceedingly uncommon. Dauto (talk) 03:42, 7 March 2011 (UTC)

Interesting I'm sure but I don't get the relevence. No one mentioned basements before you. Nil Einne (talk) 10:58, 7 March 2011 (UTC)

The presence or absence of insulation would depend on when the home was built, and that would apply anywhere - insulation did not come into general use until the 1920s, and wasn't required until the 1940s or 50s in most of North America. In Florida, I'd suspect it wasn't required until somewhat later. Acroterion _(talk) 05:16, 7 March 2011 (UTC)

Energy Densiy of Vacuum Quantum Fluctuations

How can I calculate the energy density of vacuum quantum fluctuations using quantum electrodynamics? Luthinya (talk) 22:31, 6 March 2011 (UTC)

First of all, understand that quantum electrodynamics is a very difficult and subtle subject. If you aren't familiar with it, it will be unwise to try to learn a small piece of it, and attempt to apply some textbook-equation to a particular problem where it might be invalid. Next, have a read at vacuum energy for a conceptual overview of the topic; and read the research publications and textbooks at the bottom of our article. The key is to apply physical constraints to calculate an upper bound on the energy density; our article suggests that modern researchers use the cosmological constant as the upper bound constraint on the vacuum energy. Finally, note that different approaches result in estimated values that differ by hundreds of orders of magnitude. As a general rule, when separate well-known physical theories disagree so significantly, it is a clue that our current theoretical understanding of the relevant process is incomplete - in other words, even the best and brightest physicists who specialize in this field don't know the answer to your question with a great deal of certainty.

As a consequence of this question, I am now reading The Structured Vacuum: Thinking About Nothing. This monograph was written by a professor of physics at University of Arizona, and seems to be an excellent resource for the advanced undergraduate physicist. Without solving the Dirac equation, the chapter on vacuum polarization describes the necessity of a virtual particle plasma of virtual electrons and positrons; these inherently have a statistically fluctuating vacuum polarization (and hence, embodied energy); I suppose to solve for the magnitude of that energy, you must solve the Dirac equation for the virtual particles, subject to physical constraints. Nimur (talk) 00:55, 7 March 2011 (UTC)

Nimur, I see that The Structured Vacuum is over 25 years old. Has the subject evolved much since it was written? -- 119.31.121.84 (talk) 02:20, 9 March 2011 (UTC)

Absolutely - the subject has surely evolved. I am not an expert in this field, but as I understand, recent experimental measurements of the casimir effect were made in the last few years (our article mentions a 1997 experiment, but I seem to vaguely recall some more recent "earth-shattering" news on this subject). The Rafelski book is very entertaining, but it's probably the most up-to-date or mathematically-rigorous text on the subject. Nonetheless, I don't think anything is invalid in what I've read so far. The authors present a bit of speculation about how a high-energy particle collider could be used to experimentally verify some energy-bounds assumptions - and now that we have a Large Hadron Collider, I bet there's some related work on that area. Nimur (talk) 14:43, 9 March 2011 (UTC)

The vacuum energy of electrodynamics like the vacuum energy of most quantum field theories is formally divergent. That is not a serious problem for a theory that does not include gravity. That is one of the many theoretical reasons that make supersymmetry a popular subject. Supersymmetry allows theories with finite vacuum energy to be built through a careful cancellation of formally divergent terms with opposite signs. These cancellations depend on the existence of superpartner particles that are yet to be detected experimentally. Dauto (talk) 04:12, 7 March 2011 (UTC)