Wikipedia:Reference desk/Science

July 21

Cough cough

Can any animal cough in its sleep? —Pengo 00:35, 21 July 2007 (UTC)

Yes - my dogs do. SteveBaker 01:01, 21 July 2007 (UTC)

So why don't humans if dogs do? —Pengo 15:16, 21 July 2007 (UTC)

My wife does.

So now we have anecdotal evidence on two species of animals. --Halcatalyst 21:23, 21 July 2007 (UTC)

Economics Question

Just a bit stuck. What possible circumstances could lead to there being a concave curve of production possibility, i.e., circumstances in which the opportunity cost of a product falls as its production increases, I am only looking in simple 2-product systems, but I cant quite grasp this. Philc 01:27, 21 July 2007 (UTC)

I'm no economist, but I'd assume any situation involving economies of scale could easily make at least part of the curve concave. —Ilmari Karonen (talk) 11:26, 21 July 2007 (UTC)

Agreed. Let's say you need a fweeble to make a fwap and need a fwizzle to male a fwaz, and both fweebles and fwizzles are quite expensive (same high price) if you buy them retail, but you can only buy them wholesale (same low price) if you buy 1000 at a time. Then let's say you can afford 1000 of one at the wholesale price, but not 1000 of both. In that case, you would do best to build only fwaps or fwazzes, not both. StuRat 00:39, 23 July 2007 (UTC)

Is this proof of seagull intelligence?

http://news.bbc.co.uk/1/hi/scotland/north_east/6907994.stm

The bird has a favourite flavour of Doritos, it knows what's in the bag and it knows how to open the bag. Any thoughts? --84.64.224.162 01:42, 21 July 2007 (UTC)

One of my dogs is fairly adept at opening food packaging without tearing it, never seen a bird do that though...My own thoughts, the bird probably figured it out by trial and error. It has to figure out what normal seagully foods to eat anyway, so they must have an ability to learn things of that nature. Someguy1221 01:57, 21 July 2007 (UTC)

Gulls clearly do have a concept of 'things inside other things' - they routinely rip open rubbish bags and discarded takeaway containers to see if there's anything edible inside (I once saw a gull open a margarine tub, have a look inside, then start pecking away at the scrapings that were left inside). So, here we have a gull demonstrating that it understands the concept of of 'things inside things inside things' - tasty corn treats inside a shiny plastic bag, inside that strange cave that the apes use. --Kurt Shaped Box 08:32, 21 July 2007 (UTC)

While seagulls may have a fairly good understanding of human packaging equaling food (they often scavenge garbage dumps), I recall, as a young boy I'd add, feeding a seagull a whole stick of butter. He/She ate it up in one gulp, now how intelligent is that? --Cody.Pope 10:14, 21 July 2007 (UTC)

Pretty smart, IMO. Get it down his neck quickly so he doesn't have to share it with the other gulls against his will. He can digest it later... :) --Kurt Shaped Box 10:37, 21 July 2007 (UTC)

Swallowing impossibly large objects is something many gulls do. I suppose that it is an adaptation to being a scavenger and eater of carrion. I have often seen gulls with entire sea stars jambed halfway down their throats walking around for hours and finally swallowing it. These are sea stars 4 or 5 inches in diameter! This is on the central coast of California and the gulls are usually the large Western Gulls.--Eriastrum 15:39, 21 July 2007 (UTC)

Were they actually in the bird's crop, or do you mean that the gull was walking around with the thing half-swallowed and hanging out of its mouth? Gulls can fit enormous amounts of food into their crops - sometimes it looks like they've swallowed a baseball whole. It's pretty normal for them - if they discover that an item of food is slightly too big or hard, they vomit it back up immediately. --Kurt Shaped Box 21:01, 21 July 2007 (UTC)

The gulls with the sea stars have initially 2 or 3 arms hanging out of their beaks. After an hour or more there is just a big lump in their throat. I've never actually timed this, but I've never seen that they vomit it up again. If you do an image search on google using keywords gull and starfish, you will see what I'm talking about.--Eriastrum 18:20, 22 July 2007 (UTC)

Interesting, thanks - I see what you mean. I'm quite surprised that the other gulls don't follow the one with the half-swallowed crustacean and try to forcibly yank the thing back up out of its throat... --Kurt Shaped Box 20:28, 22 July 2007 (UTC)

(re-indent)Remember that seastars are not delectable, crunchy, yummy crustaceans! They are spiny, hard echinoderms. So my guess is that it is not looked at by other gulls as especially desirable: it's hard to digest and obviously takes a considerable investment in time to fully swallow.--Eriastrum 22:31, 22 July 2007 (UTC)

So Kurt, would you please stop organizing the gulls into a master criminal conspiracy? Thank you. Dragons flight 22:35, 22 July 2007 (UTC)

Don't say that I didn't warn you. --Kurt Shaped Box 21:09, 23 July 2007 (UTC)

I don't think it's anything special. Lions know what's in the Zebra "bag." They selectively chase it down, open the "bag" and eat the goods. Seagulls eat shellfish which they drop from the air to open on the rocks below. this behavior seems pretty common. --Tbeatty 05:48, 24 July 2007 (UTC)

Ice hardness

Is water ice harder at -40 degrees than it is at -5 degrees, or is ice the same hardness no matter what? 68.231.151.161 01:47, 21 July 2007 (UTC)

I'm guessing but from experience in both refrigeration work and in winter environments, yes. (Also vehicle travel over frozen lakes would also attest to the fact that sustain warm periods can greatly reduce both the thickness and the hardness of ice.) Clem 03:03, 21 July 2007 (UTC)

Yes, the "hardness" of ice is inversely proportional to the temperature (i.e. harder ice at lower temps). Here is a ref that claims ice at 0°C is a 1.5 on the Mohs hardness scale, while its Mohs 6 at -70°C - about 50х harder. -- MarcoTolo 03:12, 21 July 2007 (UTC)

"Harder ice at lower temps" I believe; "inversely proportional", don't be ridiculous. Where do you see a ratio of 50 between the two temperatures you cite? --Anonymous, July 21, 07:22 (UTC).

Don't worry, anon, you can always concoct a scale on which it works (provided you ignore all other temperatures). Someguy1221 08:29, 21 July 2007 (UTC)

"Is inversely proportional to" is not the right language here; "varies inversely with" should be used instead. (As I understand it, hardness scales are ordinal scales, not ratio scales.) --72.78.102.77 11:26, 21 July 2007 (UTC)

Moh's is indeed an ordinal scale, its values are based on the hardness of various readily-available minerals, which is of great utility for mineralogical diagnosis, but less so for engineering purposes. Other hardness scales include the Vickers hardness scale. DuncanHill 15:49, 21 July 2007 (UTC)

Skaters report that skating at very cold temperatures is harder, supposedly because the thin film of water melted under the pressure of the blade doesn't melt when it's too cold. Gzuckier 15:46, 23 July 2007 (UTC)

Sky colour question

Within an atmosphere humans can breathe without difficulty, is it possible for the sky to be a colour besides blue (during the day)? If it can, which colours? I checked the Rayleigh scattering article, but the relevant information was written too technically for me to get anything out of. 142.59.225.165 04:46, 21 July 2007 (UTC)

Yes - it's possible. If the earth was orbiting a red giant like Betelgeuse or something - we wouldn't have a blue sky because there would be no blue light there in the first place - so it's clearly possible to have a different coloured sky. I suppose it's possible that the particles that are doing the scattering could be a dramatically different size on some different world - that would result in a differently coloured sky too...but that's a harder sell because dramatically bigger particles would probably just settle out leaving a black sky. Obviously the sky can be grey or white - it is right here on earth on cloudy days. Imagine a planet with permenant cloud cover and you have a white/grey sky. SteveBaker 05:26, 21 July 2007 (UTC)

feline table manners

Do cats other than housecats (F. silvestris catus) play with their prey? —Tamfang 07:47, 21 July 2007 (UTC)

Yes they do. What better way to learn about the behaviour/movements of your prey? —The preceding unsigned comment was added by Canis sylvaticus (talk • contribs) 08:24, 21 July 2007 (UTC)

I believe the cubs of most if not all felidae play with their prey — it's how they learn to hunt. The mother brings live prey to the cubs and lets them play with it, thereby showing them what to hunt and how to catch it. As Canis sylvaticus points out, I'd expect this to be common behavior for most at least moderately intelligent predators. The persistence of this behavior to adulthood in housecats may simply be a symptom of the neoteny associated with domestication, although I believe I've also heard of wild adult felines playing with prey when they're reasonably sated and in no hurry to kill and eat it. —Ilmari Karonen (talk) 11:41, 21 July 2007 (UTC)

Barium

Does Barium conduct sound? 168.209.97.34 12:05, 21 July 2007 (UTC)

other metals conduct sound, I'd imagine barium is no different - the only possibility for it's not conducting sound would be if it was a rubbery material.

Does anyone know if barium has a rubbery texture?83.100.251.27 12:15, 21 July 2007 (UTC)

http://www.allmeasures.com/Formulae/static/formulae/speedofsound/97.htm

Barium is not like rubber - it is a metal! GB 01:54, 23 July 2007 (UTC)

centrifugal pump

after priming why do we close the outlet valve of a centrifugal pump?59.92.74.83 12:05, 21 July 2007 (UTC)

Do we? If we do, it is to stop anything getting in or out. The purpose of priming a pump is to fill it with liquid, since attempting to pump air could damage it. If you have been instructed to close the outlet valve, this will presumably be to stop air getting into the pump while it is not in use.--Shantavira|^{feed me} 13:32, 21 July 2007 (UTC)

sorry, i did not put it clearly.After priming till the pressure reaches it's rated value , the outlet valve is kept closed and then opened slowly,why?

Mouth-movements of puppets or animations

I assume that the voices of animations like the Simpsons are recorded first, and then the animations are fitted to the voices. I wonder how they decide when to open and close the mouths? But this Supermarionation article, talking about Thunderbird puppets, says:

"The heads contained solenoid motors that created the synchronised mouth movements for dialogue and other functions. The voice synchronisation was achieved by using a specially designed audio filter which was actuated by the signal from the pre-recorded tapes of the voice actors; this filter would convert the signal into a series of pulses which then travelled down the wire to the solenoids controlling the puppet's lips, creating lip movements that were precisely synchronised with the dialogue."

What would the audio filter consist of, and what features in the sound signal did it pick up on? Thanks 80.0.110.193 13:27, 21 July 2007 (UTC)

There is certainly computer software out there that attempts to do at least a basic fit of lipsynch to sound - but generally you need an animator to come in and fix up errors at the end. The special features in the Thunderbird DVD set talks about the automatic gadget - but doesn't go into details. Since they only had to open and shut the mouth, they didn't have to have anything anywhere near as sophisticated as modern animators expect. They were doing this stuff in the early 1960's well before Thunderbirds - Stingray, Fireball XL5 and Supercar all seem to use the same techniques - but I don't think Four Feather Falls did (although the mouths were still moved by solenoids). That pre-dates most fancy modern electronics so it couldn't have been much more complex than a set of filters. It would be really interesting to know what they did in detail. SteveBaker 14:09, 21 July 2007 (UTC)

Indeed, I believe the Teddy Ruxpin doll also used a technology somewhat similar to this. Though the mouth motions themselves were recorded on the tape in a "hidden" track and not made on the fly, he probably represented the nascent stages of a consumer version of such technology. --Cody.Pope 14:33, 21 July 2007 (UTC)

I had a toy which also "spoke" but it was just in response to sound. You could make it "talk" by just speaking very close to its little microphone. It wasn't discerning — if you clapped your hands it would also "speak". It's probably a very simple sound-detecting circuit. --24.147.86.187 20:25, 22 July 2007 (UTC)

In a related field, Daleks have lights on their dome that flash with each syllable; I was surprised to learn that even today the lights are manually controlled, rather than by a volume-threshold switch. —Tamfang 17:18, 24 July 2007 (UTC)

Honeysuckle species

I'm looking for a species name on this picture: http://www.flickr.com/photos/skenmy/864121885/in/photostream/ - I know it's a Honeysuckle but I'm wondering which species of honeysuckle it is, any help would be much appreciated! --Skenmy^(t•c•n) 15:26, 21 July 2007 (UTC)

There are quite a few species and cultivars of Lonicera. Where did you take the photo? Europe, Britian, Australia, the U.S.? Was it growing in a garden or was it a native plant? What are the leaves like?--Eriastrum 15:33, 21 July 2007 (UTC)

The photo was taken in a British garden today, as far as I know it's a native as it's not in a pot. The leaves are dark green, opaque, oval shaped, few on the stalk. A picture of the same plant earlier in the year is here: http://www.flickr.com/photos/skenmy/488629643/in/set-72157594370422977/ --Skenmy^(t•c•n) 17:25, 21 July 2007 (UTC)

I'm certainly not familiar with Lonicera species native to Britain (I live in California), but I doubt it is a native species. It looks to me like the hybrid Lonicera X heckrottii, known as Goldflame Honeysuckle. It is commonly grown in the U.S. and in Europe, I believe. It is indeed a beautiful type of Honeysuckle. Try doing an image search on Google to see if it matches your plant.--Eriastrum 19:23, 21 July 2007 (UTC)

That looks perfect to me! Thanks guys! --Skenmy^(t•c•n) 21:55, 21 July 2007 (UTC)

colour of compounds

i have learnt something in chemistry which goes lke this: the colour of a compound is the complementary of the wavelength of photon absorbed, when an electron jumps to a higher energy state. but in equilibrium, the no of electrons jumping up have to be equal to the no of electrons falling back, emitting the same wavelength photon(corresponding to the energy difference), so shouldnt the net result be white always? —Preceding unsigned comment added by 59.180.4.84 (talk • contribs)

Yes, but not all electrons will "fall back" through the same path. Some will jump up and then down, but some will jump up, change vibrational states, change multiplicity, and/or release the energy at other wavelengths or with no radiation at all. I am looking for a diagram on Wikipedia that is printed in almost every chemistry textbook, but I can't find it. I used a version I made in a report once and may post it, although I'm afraid it may not be 100% completely right. It would certainly help spruce up the articles on phosphorescence, fluorescence, intersystem crossing, etc, which look like they could use some help. --Bennybp 18:16, 21 July 2007 (UTC)

I posted the diagram on my webpage here. I think it needs a little touching up and updating before adding to Wikipedia, but the general ideas are there. Just a note, ISC stands for intersystem crossing, IC stands for internal conversion. The "up then down" you are thinking of is fluorescence I believe. Let me know if you have any more questions :) --Bennybp 18:33, 21 July 2007 (UTC)

Note that color of compounds involves human perception. Human eyes/brains see color, but they cannot see frequency. For example, a compound which passes a narrow band in the yellow frequencies would look just like a compound which passes two narrow bands; one in red, one in green. And humans have trouble seeing narrow absorption bands, while such bands are glaringly obvious on a specrum graph. If you don't want to involve human eyes and psychophysics, then you want to concentrate on the spectrum of a compound, and not on it's perceived color. --Wjbeaty 14:52, 22 July 2007 (UTC)

thanks. so the electron follows an alternate route back which loses energy at wavelengths which the human eye cannot percieve, to give the compound a specific colour. is that right? 59.180.19.231 17:59, 22 July 2007 (UTC)

Also, if a photon is absorbed and then emitted even at the same wavelength, it may be emitted in a different direction than the incoming photon. As a result, one can stand at a right-angle to a focused light-source on an object and see certain colors emitted (and those photons are hence not propagated in the incident direction). This is in addition to those photons being color-shifted due to various phenomema that occur between absorption and emission. See Raman scattering. DMacks 17:08, 23 July 2007 (UTC)

DNA and its being double-stranded

As I understand it, only one strand of the DNA can have functional genomic function? (Either the 5' strand or 3' strand.) I'm not saying that only 3' or 5' strand exclusively in the entire DNA can have all the genes. Rather, when a specific sequence on a strand contains a gene, the complement strand can't contain a gene. Am I getting all of the above correct?128.163.171.68 20:27, 21 July 2007 (UTC)

More or less. There is no "3' strand" and "5' strand", these are the names of the termini of each strand, named after the deoxyribose carbon molecule at the end. Genes may only be read from the 5' to 3' direction on either strand, but where a coding sequence is found on one strand, the other (complementary) strand is nonsense. So there are genes on both strands, but not at the same time. To form a functional protein from antisense RNA is as probable as reading a poem backwards and finding it makes perfect sense in another language. Protein function is far too complex for that to happen. Bendž|Ť 21:22, 21 July 2007 (UTC)

Should be noted that when the coding strand contains one gene the complementary strand can contain a different gene. This is quite evident in prokaryotes where there is a very high gene density.PvT 21:36, 21 July 2007 (UTC)

Believe it or not, the backwards poem happens more often than you'd think. Every genome so far studied has several: [1]. In addition, there are quite a few genes that partially or completely overlap other genes in the same direction, but frameshifted. (To continue the poem analogy, it's like moving every space in the poem one letter to the right and still getting a poem that makes sense.) They're particularly common in organisms like viruses where there's a strong evolutionary pressure to keep the total amount of genetic material carried compact. TenOfAllTrades(talk) 22:03, 21 July 2007 (UTC)

One example of overlapping genes on opposite strands is the mammalian melanin concentrating hormone gene (MCH) and the antisense-RNA-overlapping-MCH gene (AROM). [2]

Wow, I didn't know that. I guess the flexibilities of the genetic code make this possible; the poem is written in hieroglyphics. Bendž|Ť 07:53, 22 July 2007 (UTC)

I have a vague recollection from when I was in grad school of them finding some virus where both strands of the DNA were coded, so as to give the minimum possible size chromosome. Gzuckier 15:48, 23 July 2007 (UTC)

Viruses are excellent examples of effeiciently packed genomes--many viral genes include sections that are antisense to other genes. — Scientizzle 21:39, 23 July 2007 (UTC)

Thanks for the answers. Any official terms for this phenomenon so I can look it up? 128.163.245.26 10:03, 24 July 2007 (UTC)(question poster)

ethanol production

≥Can Distillers yeast be frozen to remove the ethanol and reactivated? If so what are the temperature limits. —The preceding unsigned comment was added by 207.199.249.186 (talk • contribs) 21:11, 21 July 2007 (UTC)

Freezing is deadly to most organisms, and I would expect yeast to be among them, unless we have evidence to the contrary. StuRat 14:46, 22 July 2007 (UTC)

That's not really true. Cold in itself doesn't really destroy cells the way heat does — any cellular damage from freezing is mostly caused by the uncontrolled formation of ice crystals, and there are many ways to prevent that from happening. In fact, quite a lot of organisms, even multicellular ones, can survive being cooled below the freezing point of water, in some form or other — if they didn't, things would be pretty barren here come spring. Even for organisms that can't do so normally, appropriate freezing techniques can allow succesful revival after freezing. As for yeast, I'm not sure about the fresh kind, but dry yeast can certainly revive and start growing happily after being frozen, thawed and rehydrated. (You could also try Googling for freezing yeast.) —Ilmari Karonen (talk) 16:45, 22 July 2007 (UTC)

You've interpreted frozen to mean "below the freezing point of water", while I took it to mean "has become a solid", which is the more usual definition, I believe. StuRat 00:13, 23 July 2007 (UTC)

For organic materials, "has become a solid" doesn't seem a very useful definition of frozen. For example, isn't the fresh live baker's yeast usually sold in blocks already pretty solid to begin with? As for mixing the yeast in water and freezing the water solid, this doesn't really imply anything about the state of the water inside the yeast cells, which is what matters for their survival.

Re-reading the original question, it does strike me that it may be somewhat misguided to begin with. What the original poster apparently wants is to separate the yeast from the ethanol it produces; while this could be done by freezing the water and the yeast and draining away the ethanol, it would seem more convenient to simply filter out the yeast and then separate the water and the ethanol any way you like (such as by distillation). —Ilmari Karonen (talk) 13:54, 23 July 2007 (UTC)

Since yeast multiplies rapidy, you can take a small sample to keep alive, and process the rest by freezing. GB 02:45, 23 July 2007 (UTC)

Not sure how you intend to separate the alcohol and water by freezing. ?? Gzuckier 15:49, 23 July 2007 (UTC)

Alcohol and water are seperated by freezing in the process known as Freeze distillation or Fractional freezing. DuncanHill 00:11, 24 July 2007 (UTC)

July 22

Aliens

What are the chances that extraterrestrial life would live off of oxygen? Is it possible/likely that they would use a different substance to breathe, because the chemical makeup of the atmosphere of wherever they live would most likely be different than that of Earth. —Preceding unsigned comment added by 68.190.122.58 (talk • contribs)

What makes you assume aliens would need to breathe? Dragons flight 04:56, 22 July 2007 (UTC)

There are even organisms on Earth that don't breath oxygen, see Anaerobic organism. Someguy1221 06:03, 22 July 2007 (UTC)

Oxidation is a good way to get lots of energy out of your "food". (If you doubt this, look at all the energy a fire gives off, which is rapid oxidation.) However, there are other processes for releasing chemical energy from food that don't require oxygen, and free oxygen is also rare in the cosmos (we only have it on Earth due to plants), so those points would support aliens possibly using some other method. StuRat 06:05, 22 July 2007 (UTC)

Iy you are looking for life on other planets, looking for oxygen in the atmosphere is a sensible thing to do. That's not because life needs oxygen to breath, but because life makes oxygen gas as a biproduct of photosynthesis. Theresa Knott | The otter sank 09:26, 22 July 2007 (UTC)

Is it possible? Of course. Is it likely? Difficult to say. We don't have too much evidence to the contrary here of anything larger than bacteria which live off of anything but oxygen. It's hard to make odds when you have a sample size of 1 (for the planet as a whole, anyhow). --24.147.86.187 14:35, 22 July 2007 (UTC)

Depends on how you define life, which is not so easy. For their space program, the USSR once built a robot that was designed to look for life. When they tested it here on Earth it found no signs of life. :)

But one aspect of life must certainly be that it has some form of organisation and for that it needs energy. Oxygen is pretty reactive stuff (as StuRat pointed out), but there are other reactive substances. A chemist had better fill that in. But another thing is that that source of energy needs to be replenished or the environment will run out and the life wil perish (which Theresa hinted at). On Earth, one way that is done is through the interaction between animals and plants, with the animals getting energy out of oxidisation of carbon and the plants using energy from the Sun to reverse that. Without the plants, the animals would run out of oxygen and without animals the plants would 'drown in their own shit', so to say (the way yeast does in a brew, which is why you can never get above 12% with a normal brewing process). Actually, they almost did long ago, until animals came to the rescue.

So you'd need an energy-carrier that is somehow replenished by some other process, be it life or a simpler chemical process. And I have understood that there are not many such cycles possible, but again, you'd better ask a chemist. DirkvdM 19:23, 22 July 2007 (UTC)

Part of this is misleading. Most animals can tolerate 100% oxygen atmospheres, and plants can handle nearly pure oxygen provided small amounts of CO2 are there for metabolism. Life actually flourished during past periods with higher O2 levels, as that could accommodate larger animals. So we don't actually drown in high O2. However, we would burn really really well, which is speculated to be one of the feedbacks that limits oxygen levels on geologic timescales. Dragons flight 20:27, 22 July 2007 (UTC)

Dirk is right (except that plants and animals as we know them came later; it was anaerobic and aerobic microorganisms); he's referring to the Oxygen Catastrophe. Dragon is referring to life of a later time. --Anonymous, July 23, 2007, 01:05 (UTC).

The lack of CO₂ would be the problem for plants, though. StuRat 00:08, 23 July 2007 (UTC)

You can look at life on earth to see other ways for organisms to oxidize. Some bactera convert H₂S to sulfur. Others can change Fe²⁺ to Fe³⁺. Other element conversions are possible, such as producing Chlorine, Bromine or may be even Fluorine as an oxidation waste product. If you found a planet with a Fluorine atmosphere you would have to ask how did this come about? GB 02:04, 23 July 2007 (UTC)

I have to add that oxygen is quite a common element, and so it is quite likely to be used by life. Other common elements in stars are carbon and nitrogen, but not so common on the earth. GB 02:08, 23 July 2007 (UTC)

Herms

Are human Hermaphrodites real? Or are all of those pictures just photoshopped? --59.180.4.84 06:12, 22 July 2007 (UTC)

Yes, there are hermaphroditic people. Many of the pictures you see could be faked, though. Try searching on medical websites for real pictures. A Very Noisy Lolcat 07:27, 22 July 2007 (UTC)

I think the better question is, is there an actual documented case of a human succesfully reproducing (or at least getting an embryo out of it) with him/herself, to which the answer is no (to my knowledge, though I imagine this would be kind of a big thing, so I'll presume no). Alternatively, is there a documented case of a human siring two children, once as a father, and once as a mother, to which, again, the answer would be no. In all cases of human hermaphroditism that I have read of, many of which are heavily documented, only one set of genitalia is functional, or neither is. The problem with human hermaphroditism is that the testicles and ovaries are produced from the same base organ in developing embryos, so unless there is something truly bizarre going on, you can't get both. However, it is possible for a human to have both male and female external genitalia (this has been documented to varying degrees of development thereof), but at least one will be useless in all cases. On there other hand, this paper describes something truly bizarre going on, cases in which children have developed ovaries and testicles. It mentions, however, that such patients are prone to a great manner of abnormalities in these organs, and removal of one is usually performed. It further does not give a positive answer to either of my above rephrasings of the question. It does discuss some of the children reaching puberty and completing development of only one set of genitalia, not both. Someguy1221 20:42, 22 July 2007 (UTC)

Savage Love [3] has a letter from a woman who just discovered that she has two vaginas. It is thought to be “didelphic uterus” in which there are two complete female reproductive systems. Just seemed worth mentioning. She had only had one lover, so apparently was still a virgin in the less used vagina. Edison 21:44, 22 July 2007 (UTC)

172" or 17.2" pipe @ 3,740 psi

One might be surprised how gruesome a totally professional report can be without going into much detail:NIOSH FACE case titled:

Maintenance Man Dies After Being Drawn Into 172-Inch-Diameter Positive Pressure Intake Pipe--Virginia

I'm having a hard time picturing the events described occurring in a pipe 14.3 feet in diameter. Did they forget a decimal point or do they really use pipes that huge at paper processing plants? Anynobody 07:29, 22 July 2007 (UTC)

While I can't speak to paper plants, one way to create high pressure is to have a very large fan directed at a small pipe. So it could be that this opening is specific to the fan drive segment creating the large overpressure. Dragons flight 09:51, 22 July 2007 (UTC)

Yes, I believe you're right, it's likely 17.2 inches inner diameter. The "smoking gun" for me is that it said "the vacuum suction pulled his chest against it" and that "the victim was doubled over backwards and pulled 38 feet through the pipe by the vacuum". This means the pipe would need to be about the size of a man's chest. They apparently repeated the error everywhere they mentioned the pipe, which seems odd based on the level of detail in the rest of the article. I suspect that a spellchecker is to blame, which probably said "Did you mean 172 inch" when it found "17.2 inch". The editor then likely picked "Replace All" when they meant to pick "Skip All". Since the spellchecking was the last process in the checking process, they likely never read it after running the spellcheck, or would have spotted this obvious error. (Interesting that we a have serious human error in an article about a deadly human error.) StuRat 14:38, 22 July 2007 (UTC)

172 inches isn't the only number I'm suspicious of; I don't think I believe that "3,740 psi" figure, either. If the pipe is 17.2" in diameter, that's 400 tons of force on the end of it, or if (somehow) the pipe is 172", it's 40,000. With 400 tons on a 17" pipe, I don't think the poor guy would have been "stuck" long enough for his buddies to try to pull him off; I think he would have been sucked completely in in an instant.

3,740 psi is huge. You'd need special, small-diameter, thick-walled, high-pressure piping for it; there's no way you could sustain that kind of pressure in a 17" diameter pipe, unless it were constructed and machined like a submarine hull. —Steve Summit (talk) 15:22, 22 July 2007 (UTC)

Clearly the victim of this industrial accident was in the atmosphere on the outside of the building before he was pulled into the pipe, whatever its diameter. Therefore there could only have been 14.2 psi of "vacuum pressure" even if the other end of the pipe were connected to perfect vacuum. Air pressure pushed him into the pipe, rather than "vacuum pressure" pulling him into the pipe. It scares me that either a government or an industry would issue such an addled report. A 17.2 inch pipe is believable. The area is such that atmospheric pressure could apply 2200 pounds of force. The same phenomenon would apply as when a window of an airplane blows out at high altitude and a passenger gets sucked out (this happens less often than movies would imply). Why would they have attempted to replace the blower without shutting down the flow of air through the pipe? The whole story is senseless. Edison 21:20, 22 July 2007 (UTC)

Argh! You're right, of course. I was worried about the report's use of the perplexing term "positive-pressure vacuum pipe" also, but I didn't think it through far enough to remember that you can't have more than 14.2 psi of suction.

(I'm not sure I believe "17.2 inch", either -- would they really use that much precision? Wouldn't they just say "17 inch"?)

Addled and senseless, indeed. —Steve Summit (talk) 22:29, 22 July 2007 (UTC)

For 14.2 above, read 14.7. --Anon, July 23, 2007, 01:18 (UTC).

I've explored other case reports on the page, and get the impression that at some point in the late 1990's they finally started submitting these electronically. Which made me theorize earlier reports were transcribed. Would 374 psi be more reasonable for the pressure? Anynobody 23:25, 22 July 2007 (UTC)

No, it's still way too much. Most steam locomotives had boiler pressures less than that, and besides, as noted, 14.7 psi is the greatest possible suction. I wonder if they had something in mind with pounds? Let's see, the cross-section of a 17.2" pipe is pi*8.6^2 = 232.35 square inches... so it would take over 16 psi for the total pressure on one end to be 3,740 pounds. So that's not it.

Another thought: maybe the comma should be a decimal point. 3.74 psi. That still seems a lot for the stated purpose, but at least it's physically plausible and enough to suck someone in. But why would it be stated to such a high precision, if that was it?

--Anonymous, July 23, 01:18 (UTC).

People make dumb mistakes all the time, myself included if you've seen my user page. Reading not only this one, but several more senseless reports, this is simply what happens when people make dumb mistakes in a hazardous environment. I don't just mean the guy who got sucked to his death but whoever should have shut down the other blowers and appointed a safety manager. (I had no idea how dangerous it is to be a farmer, or the horribly disgusting fates possible.) Anynobody 23:41, 22 July 2007 (UTC)

Rather than attribute the death to a "dumb mistake" I would review the whole process for possible failures to follow standard OSHA safety procedures. The job as described was a literal deathtrap. There would normally be a job briefing, reviewing the possible dangers to avoid, with appropriate barriers, tagout procedures, safety harnesses, barriers, etc. I still do not understand why the intake of air through the 17 something pipe wasn't stopped while they were trying to mount a new blower over the opening. How did they get the old blower off the opening with that much pressure pulling it in? I just don;t see the need for all the alleged vacuum pressure to move wood chips into a machine, when a backyard leaf blower or vacuum cleaner would be adequate to move them, as soon as the air was moving at 3o miles per hour or so. Edison 15:07, 23 July 2007 (UTC)

Well, I contacted the NIOSH via the form on their web site, and got a prompt reply from the senior investigator in the case.

There was some sort of character-set problem: the pipe diameter was not 172 or 17.2 inches, but 17.5 inches, i.e. 17½. The report on the web site has now been corrected.

As for the huge pressure, that is correct, but it is the pressure on the output side of the blower. (I think this means some of the report's wording is misleading.)

--Anonymous, July 24, 2007, 14:42 (UTC).

Well done! (I've got a barnstar here for ya, but alas, you've got no user page to put it on.) --Steve Summit (talk) 23:54, 24 July 2007 (UTC)

[Still scratching my head over that pressure, though -- that ain't no "blower"; that is a compressor!]

Common knowledge in 2007 that would be insanely valuable in 1807.

If I -- a moderately-educated Australian adult of average intelligence -- woke up tomorrow to find I'd been warped to the year 1807, what knowledge of mine would be most valuable to the doctors, scholars, etc of the time? My first thoughts were of bacteria, psychotherapy and Franz Ferdinand's assassination. A Very Noisy Lolcat 07:35, 22 July 2007 (UTC)

Ones that spring to mind for me are advanced methods for producing steel, controlled steam locomotion (it was in its early stages in 1804-1810), internal combustion using stuff like diesel, electrical currents, vaccination methods, and the concept of the elevator. Inventing high grade steel for building materials, bio diesel, and an electrical generator would see the railways and business jump significantly ahead if started that early.  ALKIVAR™ ☢ 09:13, 22 July 2007 (UTC)

Ones that jump to my mind are the principles of electricity generation and that bacteria causes disease. Somewhat more esoteric, but highly practical would be dynamite, antibiotics and pasteurization. Dragons flight 09:33, 22 July 2007 (UTC)

This is a question I have thought about too and realised that unfortunately

• some things, I know can be done, but can't do them myself (e.g. making steel)
• some things I can do are useless without some other knowledge, that I lack (I could use transistors in a circuit, but I couldn't make them).

—Bromskloss 10:21, 22 July 2007 (UTC)

I'm not sure the 1807ers would be impressed by word of an event you claim will occur 107 years in the future. Algebraist 11:35, 22 July 2007 (UTC)

Photography and phonography would be pretty valuable, and at heart are both relatively simple - plus, bring them together and you've got talking cinema 120 years early! Laïka 12:22, 22 July 2007 (UTC)

Convincing them to look for Brownian Motion earlier, and experimentation with Uranium salts, in order to discover radioactivity, would have allowed remarkable advances in physics to have happened a hundred years earlier. Similarly, pretty much everything that became encapsulated in the Maxwell Equations could have been discovered and published in 1807. But in terms of common-place stuff, really simple things like hygiene - convincing people to wash their hands, boil their food and chlorinate their water - would have been hugely beneficial. Batmanand | Talk 13:56, 22 July 2007 (UTC)

Convincing people to be better stewards of the earth would be insanely valuable from 1807 to 2007.--138.29.51.251 14:00, 22 July 2007 (UTC)

When I consider this "time traveller problem" I realize that the main challenge would be to convince anyone to try your ideas. Hygiene for example was rejected by the experts time and again, and only tested and accepted after a long bitter battle. Remember that Semmelweis ended up in an insane asylum after a lifetime of failure at convincing doctors to wash hands. So, the most valuable tidbits in 1807 would be those things which would imediately make you fantastically wealthy. Having gotten rich, you could then fund all sorts of research and manufacturing based on 2007 knowledge, and those many who try to stop you would fail. In other words, you don't want to be a Ignaz Semmelweis who knows that surgeons should wash pus off their hands before the next surgery... and you don't want to be a Nikola Tesla whose amazing advances are sometimes accepted but usually ignored. Instead you want to be a Tom Edison who uses his income from ticker-tape machine sales to rapidly achieve any damn revolutionary idea he wants. --Wjbeaty 14:36, 22 July 2007 (UTC)

A knowledge of the Geology of Australia, particularly its gold deposits, would enable you to become insanely rich and thus fund your good works. DuncanHill 14:49, 22 July 2007 (UTC)

Or you could come up with some inventions that were expected in the 1810's. Inventions farther in the future likely wouldn't work due to lack of infrastructure. Airplanes, for example, wouldn't work in 1807 due to the lack of lightweight, powerful engines. StuRat 14:55, 22 July 2007 (UTC)

Makes sense, but then by definition, these inventions were about to come out anyway, so how valuable would introducing them a few years earlier (best case scenario) be? (Worst case scenario is getting attacked by irate 19th c. inventor for stealing their idea.) TresÁrboles 04:22, 24 July 2007 (UTC)

Psychotherapy would not be that valuable at that time. Most people would not believe it. It was an uphill struggle for Freud even a few decades later. You'd have a similarly difficult time convincing people about bacteria. Basically, in Kuhnian terms, you are talking about showing up with knowledge specific to a particular paradigm and trying to force it onto people who are not in any way prepared for accepting such a paradigm. What you want is someting that will easily assimilate into existing understanding; something that does not require extensive belief in certain abstract modes of thought (anything relating to things people cannot see is pretty tough to sell to people, even today, if they have not been taught to have faith in that matter of thinking); engineering advances would be the easiest in this respect, far easier than theoretical advances. Personally, I think the suggestion of dynamite was particular good (hell of a lot safer than traditional explosives at the time, requires no paradigm that people would find inaccessible in the early 19th century). The internal combustion engine could potentially work out as well — you'd need to develop an infrastructure which could take advantage of it but again the engineering and chemistry is not beyond their comprehension, just skill. With an effective knowledge of airplane design you could easily be quite valuable to any government, but you'd have to demonstrate it first. --24.147.86.187 16:48, 22 July 2007 (UTC)

Weaponry is another obvious one, for a man concerned only with getting rich. AK-47s, pump-action shotguns, semiautomatic pistols, napalm, plastic explosives, mustard gas, etc. --Kurt Shaped Box 17:23, 22 July 2007 (UTC)

While all of the above would be usefull, keep in mind that they're no immunity from sharpers or proficient confidence men and/or embezzlers. That said, Do you know anyone who was assassinated? The two dudes who saved that German Emperor from an anarchist got a dukedom each out of it (I think). If you happen to remember certain political trends, you could ride the waves and stay in office for years on end. 68.39.174.238 18:34, 22 July 2007 (UTC)

Copper wire was widely available in 1807, and the innovation of insulating it with cotton, then building telegraphs, electric generators and electric motors would be immediately feasible in 1807, if one had a high school physics understanding of these devices. A blacksmith or machinist of that era such as a gunmaker coud make the iron parts needed if you could describe them and provide drawings. A big 19th century electrical breakthrough was cutting the cost of a kilowatt hour of electricity by an order of magnitude or more by making it with a generator powered by a steam engine rather than zinc and copper plates in a battery. Next step: arc lighting. Then telephones. Then incandescent light bulbs (harder to get working with commercially useful lifetime and brightness than the aforementioned devices). Electric railways. Transformers and AC for long distance transmission of electricity. Household appliances. Then X-ray tubes and vacuum tubes, as soon as the light bulb technology is working, and the whole world of early 20th century electronics, up through radio. television and computers, but over a century earlier. Certainly a machine shop in 1807 could have built you phonographs and movie cameras and projectors if you could draw plans. I think you would have to be quite a specialist to know how to make transistors in 1807, much less integrated circuits, with the micro-etching and clean room crystal growing required.but knowing transistors are possible and the basic principles of doping semiconductors and biasing junctions should make it possible to kick start semiconductos solid state electronics if you developed a few hundred thousand dollars profit from the earlier ventures and could hire a research team. On the dark, side, certainly machine guns would be hugely valuable, as would land mines. A very high degree of specialized knowledge would be needed to get avation working. Even by the 1880's very silly things were written in the leading scientific journals about how airplanes of the future might work. Edison 20:57, 22 July 2007 (UTC)

Ah, any links regarding those silly airplane things? —Bromskloss 22:01, 22 July 2007 (UTC)

I could not find the articles I saw in Science in the 1880's issues. Indexing sometimes leaves much to be desired. But I found the steel balloon "aeroplane" with a vacuum inside, 1887 [4] , Aeropaedia from the Dublin Review [5](p 95) describes aeroplanes with screw propellors, proposed steam airplanes, and interesting acounts of balloon ascensions (1890). Steam airplanes are discussed (p302) in The Gentleman's Magazine (1888)[6] . If a time travellor built a working airplane in the 1880's or perhaps a few decades earlier, the notion would not have been novel to the educated person of that age. They would just have seen it as the culmination of research then in progress. Edison 14:52, 23 July 2007 (UTC)

If I could, I would bring a copy of Wikipedia! :-) —Bromskloss 22:01, 22 July 2007 (UTC)

That could be challenging without at least a computer and power. As I recall, we would fill something like 300 volumes. Dragons flight 22:28, 22 July 2007 (UTC)

If I found myself in the situation you describe I think I would keep very quiet about my ideas and knowledge. People of all ages seem to be very superstitious of people who have a great deal of strange information. The last thing I would want to do would be to give people the idea that I’m a sorcerer or demon. --S.dedalus 00:11, 23 July 2007 (UTC)

So, how was 1807? —Bromskloss 08:48, 23 July 2007 (UTC)

Lovely, thank you! Although having Bonaparte charging all over the place was slightly disconcerting. --S.dedalus 02:03, 24 July 2007 (UTC)

I suspect that most of these suggestions fail because most people from 2007 don't actually know how how most of the wonders we have work. To take the first few suggestion - how many of us could actually describe how these things work?

• advanced methods for producing steel - I have no clue.
• controlled steam locomotion - I have some approximate ideas, but I don't know the details.
• internal combustion using stuff like diesel - I understand the principles - but how to make the fuel?
• electrical currents - This is probably the one I could help most with - but even so, to make anything beyond an fascinating toy...tricky.
• vaccination methods - How the heck do you make a vaccine? No clue.
• the concept of the elevator - emergency fallback braking systems - and I'm not 100% sure how those work.

Sure we all have a vague idea - but outside of our own specialities, could we really offer much help? SteveBaker 01:27, 23 July 2007 (UTC)

You should read up on smallpox, anyone with access to dairy farms can make a crude version of that vaccine (though it was invented before 1807). As a physicist, I might fail metallurgy, but I bet I could get the others to work given enough time and period materials. Dragons flight 02:22, 23 July 2007 (UTC)

But if you wait a few more years, you could bring back the recipe for transparent aluminum. "Computer? Hello computer..."

Atlant 16:27, 23 July 2007 (UTC)

If you knew your history well, you could possibly turn the tide in the Naopleonic War to which side you chose if you could convince the right people.

You might be interested in this (fake) game show: "Phone Call to the 14th Century". You get 60 seconds to impart as much knowledge as you can. --TotoBaggins 18:48, 23 July 2007 (UTC)

Almost zero. The question isn't what you know is possible, but what can you build? Can you build an internal combustion engine and make the iron and steel necessary? Can you produce the kerosene? I can speculate about what might happen in 2107 but without the ability to actually build any of it, you might not be any different than anyone else. da Vinci proposed all sorts of things that he lacked the ability to build. But perhaps there is one thing you may know: boil your water. You may even be able to build a toilet as it is a simple mechanical device. --Tbeatty 20:12, 23 July 2007 (UTC)

Of course simply knowing that a given technology is possible is often all that is needed to spur innovation in the field. --S.dedalus 02:07, 24 July 2007 (UTC)

But see above the response by Wjbeaty, i.e. you will not be believed especially if you haven't the foggiest on how a particular technology actually works in any useful way. Remember, we are talking about the average person. TresÁrboles 04:22, 24 July 2007 (UTC)

It's a more interesting problem to consider the what the average person knows in detail and can demonstrate convincingly -- not much I'm afraid! (I include myself in this!)

Specifically for 1807 in the U.S. ... just brainstorming...

I know in the U.S., there's supposed to be a war with the U.K. in a few years. I don't know how that simple knowledge can help anything.

I know there's gold in California... yeah! Although... I'm not sure where to look (was it near Sacramento? Maybe an average Californian would fare better here). Likewise for the future gold rushes of the Yukon and Australia. For the Yukon, at least I know you can go from Skagway up across some insanely steep hill.. and then what?

I know about the airfoil, but I don't know that I could make anything other than a toy (if even that), and I'm sure they would already have flying toys.

Photography? Put some kind of chemicals on paper somehow and expose it to light just so, and ... never mind.

It's starting to look like there would be zero effect!

I 'm not sure if it would be different for a 2007 Australian person going back to 1807 Australia either. Maybe the average Australian knows where all the gold was? TresÁrboles 04:22, 24 July 2007 (UTC)

I would suggest sleeping from now on clutching a scientific encyclopedia, just incase of such an eventuality. (And hope that whatever transports you transports the encyclopedia with you). Capuchin 08:12, 24 July 2007 (UTC)

'You can't take it with you.'

Spider identification

Hi, I took this shot of a spider in my appartment : [7] and I would have liked to identify its species so as to be able to upload it to commons and include it in relevant wikipedias. The size was about 2mm and it weaved a pretty impressive web of about 30cm diameter. I am living in Sweden. Any help is welcome. --Nattfodd 11:39, 22 July 2007 (UTC)

After looking at some galleries, it seems to be of the "long-jawed" kind, but I couldn't find the exact family. --Nattfodd 11:34, 22 July 2007 (UTC)

To summarize: 2mm long, north-european, brown colouring, probably long-jawed, weaves ~30cm webs. --Nattfodd 11:39, 22 July 2007 (UTC)

Turned out to be Uloborus walckenaerius. I found the answer on [8]. --Nattfodd 13:17, 22 July 2007 (UTC)

Wow that thing looks evil. Are there any better pictures of it? That one you found is in a strange posture. Or is it really like that? Capuchin 14:33, 23 July 2007 (UTC)

Tree rain

Is there a formal name for this phenomenon ? After a brief rain storm (during which time there may have been no rain under a large tree), the rain drops, which have been slowly falling from leaf to leaf, start to fall to the ground from under the tree, leading to a time when it is raining under large trees and nowhere else. This could also happen from dew after a wind gust. StuRat 16:10, 22 July 2007 (UTC)

yes, but I've forgotten what.

—Preceding unsigned comment added by 172.207.154.122 (talk • contribs) 20:24, 22 July 2007

I can't find this anywhere, the only word I can think of is "dripping". Sorry if this doesnt help. Maybe it would do better on the language desk. Capuchin 11:28, 23 July 2007 (UTC)

On the funnier side, we used to call this the "capacitor effect", imagining that the tree stores the "charges" and releases them later -- WikiCheng | Talk 05:16, 24 July 2007 (UTC)

Isn't it more like an inductor...? :p --antilived^{T | C | G} 06:08, 24 July 2007 (UTC)

I would suggest that it is more like lots of little capacitors (leaves) forming a bucket brigade delay line. The buckets empty when they get too full. So the term for this could be: Leaf delay.--SpectrumAnalyser 14:55, 24 July 2007 (UTC)

Visible Insect With Large(st) Population

I am looking for a source on the worldwide population of an insect species which is very populous. I prefer an insect that is at least 2-3 mm long and is not eusocial. Really anything with a population higher than 10 billion would do.

I would also like to know the length of one generation of that insect.

The point of this is to provide an example of a species that would, on average, mutate every base pair in its genetic sequence in a relatively short period of time, given a mutation rate of 10^-10 to 10^-12. If you could find the population of an insect that has been observed to evolve either in nature or experimentally, that would be even better.

Thank you

I humbly suspect that most insect species have a population far greater than 10 billion. I know nothing of mutation rates and so on, but a classic example of an insect evolution observed "on-the-fly" is the Peppered moth. See Peppered moth evolution. Unfortunately it's much bigger (in it's adult phase) than the 2-3mm you specify, but it is a fascinating example. I'm sorry I can't give you a more specific answer - anyone else? Best regards, TreeKittens 02:04, 23 July 2007 (UTC)

A classic insect species for evolutionary and genetic studies is Drosophila melanogaster. It is usually 2-3mm in length, and I guess it's population to be utterly vast, but I have no evidence for this. It's generation time is about 2 weeks, depending on temperature etc. Hope this helps a little. Best regards TreeKittens 02:39, 23 July 2007 (UTC)

You could go for the plague locust. GB 02:44, 23 July 2007 (UTC)

I didn't figure finding a species with a very large population would be hard. But I can't find any references to even estimates of insect populations.

Hmmm, neither can I offhand. I suspect this is because the total world population of a particular insect would not be a very useful figure for ecologists and biologists as they would normally be interested in the population within a particular ecosystem. One way to derive an estimate may be to use any biomass figures you can find, and simply divide them by the mean mass of the organism. I think that may be your best bet. Sorry I can't help you with the specific figures. Best regards TreeKittens 21:34, 24 July 2007 (UTC)

You are aware I hope, that it is rather unlikely that a mutation in every base pair would be seen given that certain single point mutations will result in a change too critical for the resulting organism to survive? Nil Einne 12:40, 23 July 2007 (UTC)

I am not suggesting that all the mutations survive. Just that for these types of species, it is not unreasonable for random mutation to find the changes that lead to adaptive changes fairly quickly if there are any.

Castor oil on eyelashes

Hi, I apply castor oil daily on my eyeleashes in order to make them thick. Is there any harm in doing that daily?? Thank you

If you are looking for medical advice, we can't answer you, as Wikipedia does not give medical advice. As for beauty tips, I have no idea, but perhaps someone else will. Dragons flight 20:36, 22 July 2007 (UTC)

Whether or not this is a request for medical advice, it can be answered without giving any! Our own article on castor oil discusses it's many uses in medical treatments and folk treatments. It was even commonly believed long ago to treat burns. The only adverse effect from castor oil, it appears, would come from consuming very large quantities of it (I have no idea what a large quantity would be for castor oil), but consuming anything in large enough quantities will kill you. Further, considering that castor oil is an ingredient in some foods, perfumes and even some modern medical treatments, I think you can make your own judgement on this. Someguy1221 21:42, 22 July 2007 (UTC)

Be aware that anything liquid applied to the eyelashes may regularly end up on the eyes and most perfumes, foods and medical treatments don't tend to end up on the eyes regularly. Nil Einne 12:34, 23 July 2007 (UTC)

I doubt that it hurts anything - but I'd be very surprised if it helped. Once a hair has sprouted from the follicle, it's dead material - more hair is added at the root - but the part of the hair you can see is just a dead thing. All of these shampoo adverts that talk about feeding and nourishing your hair are more 'sham' than shampoo. So the only things the olive oil could possibly be doing to 'thicken' your eyelashes would be to somehow cause the Keratin to swell up and thereby gain thickness (which sounds possible, I suppose) - or perhaps it might cause the follicle to grow a thicker hair (seems very unlikely to me). What I think you should do (for the good of all mankind) is to do a careful experiment. Put castor oil on your left eye lashes - and don't put any more on your right eyelashes. It takes 4 to 8 weeks for an eyelash to grow and then fall out - so if the oil is making a difference, it should be obvious within two months. If you can tell the difference between your left and right eyes after that amount of time then it works! Otherwise - not. To be really sure, you should ask other people (preferably those who don't know you) whether they can tell the difference - because you are bound to be a bit biassed. Please tell us what happens! SteveBaker 20:52, 23 July 2007 (UTC)

In some parts of south India, there is a practice of applying castor oil on the eyelids to get a 'cooling effect' (whatever it means). They also apply it on the eyelids if there is irritation in the eyes, as a home remedy. I am not sure if this really helps. I personally have felt that it makes you slightly drowsy, may be because you tend to close your eyes to get over that funny feeling after it is applied. I also agree with SteveBaker (to make the hair look thicker), because castor oil is also applied on the head -- WikiCheng | Talk 05:08, 24 July 2007 (UTC)

Binturongs

I was unable to track down the original reference that contains the information regarding the reproduction parameters in binturongs in the article. Could you please post those or direct me to the person that posted it? Thank you, Amoresco 21:05, 22 July 2007 (UTC)AMoresco

This information was in the original version of the article, as created by 64.63.221.115 (which IP has not edited for three years). The original article cited [9] and [10]. These source more-or-less corroborate the information given, though neither seems to give the estrus period. None of the currently listed references appear to give this information. Algebraist 14:14, 23 July 2007 (UTC)

Google gives this article on JSTOR: [11]. The abstract is kind enough to give all the facts. Algebraist 14:21, 23 July 2007 (UTC)

July 23

Hereditary talent?

(Following up on a question asked here.) Is there any evidence of a genetic link to artistic talent? Can a predisposition towards a specific field be hereditary? Thanks! --S.dedalus 00:03, 23 July 2007 (UTC)

For sufficiently varied choices of possible field, I'm sure it can be. Height and weight are genetically influenced and can affect who is more likely to succeed as various sorts of athletics (think basketball players, for example). For artistic talent, I don't know, but I wouldn't be surprised if there were a weak genetic association (coupled to a strong environmental/experience component). Dragons flight 00:08, 23 July 2007 (UTC)

Note that some conditions (not diseases !), like left-handedness, manic depressive disorder and homosexuality, may be both inherited and a cause of correlated with an "artistic temperment". StuRat 03:03, 23 July 2007 (UTC)

Be careful of the word "cause." correlated and causal are tricky things. --Tbeatty 03:06, 23 July 2007 (UTC)

Good point, I fixed it above. StuRat 03:22, 23 July 2007 (UTC)

Inherit... homosexuality... interesting theory there. Anyway, I'm not sure if it's nature or nurture, but I'm sure genetics have some effect on the brain and the way it forms and works, which could easily make someone like a certain thing their biological parents do, without even being exposed to them. At the same time though, artistic parents will probably expose children to art from a young age, so they will form their minds to that --L^augh! 03:57, 23 July 2007 (UTC)

Definitely you could say that there are hereditary traits which might be extremely useful for someone who happened to be disposed towards a certain career path and having these traits might even influence that person towards a particular career, playing to your strengths and all, but I don't know about being heriditarily "predisposed"; I doubt we will ever discover the astronaut or fireman gene. For example, there seems to be a genetic component to having absolute pitch, which could in turn be useful if one decided to become a musician. As to the first question, researchers have tried to answer it by searching for a "creative gene/s" or some evidence of heritability of creative talent, with apparently mixed results. This 1973 twin study, "failed to provide convincing evidence of a genetic component in creativity" [12]. However, this more recent '93 one (login needed for full article) presents a case that the genetic component of creativity has been overlooked and that, "creativity is an emergenic trait of moderate heritability" [13]. Even if creativity does have some genetic component, which seems likely in my opinion, environmental influences still must be accounted for, and this says nothing really about how the trait might be expressed; could just as easily end up with a creative janitor than with a brilliant artist. Interestingly the same study refrences a previous familial study which looked at a bunch of professions within families, finding that, "only judges seemed to aggregate within families," so maybe there is a "judge gene". -- Azi Like a Fox 05:08, 23 July 2007 (UTC)

Well, there's the remarkable Bach family. Clarityfiend 08:43, 23 July 2007 (UTC)

Some serial killers and the like seem to be creative too so any creativity could be expressed via such an outlet Nil Einne 12:30, 23 July 2007 (UTC)

The trouble with examples like the Bach family is that you can't separate nature from nurture. That is to say, you can't tell whether the younger Bach's inherited their talent from the older Bach's in their genes - or whether simply spending all of their youth amongst amazingly talented parents and other relatives caused them to learn those skills at an early age. To test the theory properly, you'd want to look at sons and daughters of musicians who had been separated from their parents at birth and who grew up with foster parents who were not musically inclined - and also at children of non-musicians who had been brought up by musically talented foster parents - and compare their abilities with offspring of musicians who lived with their parents. However, there is strong evidence that babies hear (and possibly even enjoy) music in the womb - so even separation at birth is not necessarily enough to show that there is a genetic basis. If I had to guess, I'd bet that musical ability would be a bit of both...but that's just a guess. Musical ability is composed of so many separate skills: good dexterity, an acute sense of pitch, a creative spark, possibly an interest in mathematics - it seems impossible that ALL of those would be genetically based - or that all of them would be as a result of nurture. SteveBaker 20:42, 23 July 2007 (UTC)

Chickenpox

Hi, does anyone know why chickenpox is more active in adults than in children? Thanks. —The preceding unsigned comment was added by 58.153.96.148 (talk • contribs) 07:00, 23 July 2007.

If you get chickenpox as a kid, you retain the antibodies in your system into adulthood - so any adult who had chickenpox as a child is effectively immune to the disease. Since it's a common childhood disease, very few adults succumb to it. The disease is mild in childhood - but much nastier for adults, so this is just as well! SteveBaker 11:11, 23 July 2007 (UTC)

I think the OP wanted to know why it is nastier in adults. Capuchin 11:27, 23 July 2007 (UTC)

Oops! I misread the question. Our chickenpox article offers some suggestions, it says that people with weak immune systems, the elderly and pregnant women are all at serious risk - I guess most children don't fall into that category. SteveBaker 12:45, 23 July 2007 (UTC)

I wouldn't think that a healthy adult would have a weaker immune system than a child. But chickenpox definately would affect them more. I'm curious to see if someone can explain it :) Capuchin 12:52, 23 July 2007 (UTC)

I've always heard that chickenpox is more serious for adults than children (which leads to the practice of sending children to visit those with chickenpox so they will get it when they are young). I asked three doctors in dermatology (because I felt it was in their field). Each one said it was far more severe in adults. I asked why and they didn't know. That led to a discussion of how severe it is and the conclusion is that they've always heard it was more severe, but none of them ever had an adult patient with chickenpox. -- Kainaw^(what?) 13:29, 23 July 2007 (UTC)

From my reading of the article, it appears that chickenpox is uncommon in adults, as most will have acquired immunity through childhood infection, however adults are liable to shingles which can be excruciatingly painful. DuncanHill 13:40, 23 July 2007 (UTC)

I've heard chickenpox can be a problem during or after puberty (rather then simply for adults) but no idea why. The article suggests it's true although also doesn't say why. Google doesn't help much, several sources say it's more severe but don't explain why. Some even suggest sterility in males is a possibility but this appears to be a confusion, that's mumps not chickenpox. As DuncanHill may said, it's possible some sources are confusing shingles and chickenpox which are 2 different diseases even if caused by the same virus. You can only get shingles AFTER you've had chickenpox. You rarely have chickenpox more then once. Nil Einne

Philaethria dido page and butterfly identification

Hi, while checking "Uncategorised pages" on Commons, I came across Philaethria dido, which was blanked by user not logged in, it seems from the history that the image on the page was not a Philaethria dido (Scarce bamboo page) but a Siproeta stelenes (Malachite butterfly). I don't know the first thing about butterfly species, can someone more knowledgeable than me clear this up? (I will then either nominate page for deletion or not and/or upload the image again with a correct name). Thanks in advance. Deadstar 08:18, 23 July 2007 (UTC)

I think our anonymous editor has it right. Philaethria species lack the clearly visible spur on the rear wing and the entire forewing extend considerably farther, rather than having that lobe on the anterior. Go ahead and tag the page for deletion. Bendž|Ť 10:14, 23 July 2007 (UTC)

Thank you for your help! Deadstar 10:58, 24 July 2007 (UTC)

TECH CHALLENGE ! Need source for 12 v Non-Lead acid Battery of the golf cart size ? This for some reason is very hard to find?

Need source for 12 v Non-Lead acid Battery of the golf cart size ? This for some reason is very hard to find?

If anyone can give me a concrete lead (ie verified phone or email or website ) of anyone or any company that can provide a Battery of the golf cart sizes (ie 10" long x 7" wide x 9"-11" tall) that is NOT- Lead Acid, I would really appreciate the information.

I am trying to test my patent on golf carts more than I have in the past and need to use non-lead acid types. The maximum battery size is 10.3" long x 7.3" wide x 11.6" tall but can use somewhat smaller if necessary. GOD BLESS YOU FOR HELPING! ! P.S. 10.2"= 260mm, 7.1"= 180mm, 11.6"= 295mm TripleBatteryLife 18:08, 23 July 2007 (UTC)

A quick google found this site, which will make you a custom battery pack. It might not be cheap, but they do offer alkaline, Ni-Cd and NiMH in addition to lead-acid batteries. grendel|khan 19:18, 24 July 2007 (UTC)

Moving Energy

Is there any means of moving energy out of a gravitational field without gaining or losing any energy or potential energy? Philc 16:00, 23 July 2007 (UTC)

If you count Gravitational potential energy, you could do it by converting some form of energy besides kinetic into potential energy. If you don't (and you probably don't), I think you could do it by using gravitational potential energy holding the energy you're transporting apart i.e. compressing it under its own gravity, but you wouldn't get very far, and it's pretty useless. What I think you actually mean is impossible, because if you could do it you could drop the energy and create kinetic energy from nothing, disobeying the law of conservation of energy. If you could create energy, this would be trivial, since you could just create the energy used to move your energy. — Daniel 18:22, 23 July 2007 (UTC)

Creating energy from nothing is impossible no matter where it is done. But, maybe the OP means providing an energy source for space stations without having to lift heavy batteries or power plants into orbit. I once read about a plan to capture sunlight using huge solar panels in orbit and transmit the power to the Earth's surface using microwaves. I don't see any reason why that could not be reversed with power being generated on Earth and transmitted to a space station using microwaves. Of cource there would be major concerns with safety (we wouldn't want to cook any astronauts!), cost, efficiency, etc. and something would still need to be consumed to provide the energy in the first place. 87.113.3.139 13:34, 29 July 2007 (UTC)

Double Pendulum

I was wondering how the time period of a double pendulum depends on the mass of the intermediate object and its distance from the main bob?

I suggest you read the article on Double pendulum. -- JSBillings 17:17, 23 July 2007 (UTC)

Beyond fairly small swings, a double pendulum is a classic example of a chaotic system - as such it doesn't even have anything you could reasonably describe as a period. SteveBaker 20:31, 23 July 2007 (UTC)

Rolling Up Projection Screen

I pulled down a projection screen and now I want to make it go back up. When I pull on it again, it goes down a bit and then will go back up that same amount (i.e. not rolling all the way up like I would expect). Has anyone encountered this before? What should I do? --82.171.103.231 17:38, 23 July 2007 (UTC)

WD40? But keep it away from the screen itself and any plastic parts. Wipe off any surplus.--Shantavira|^{feed me} 19:36, 23 July 2007 (UTC)

The screen is quite new. I'm not sure it needs WD40. I was wondering if there's some technique to getting it to go back up again. --82.171.103.231 19:55, 23 July 2007 (UTC)

Oh, those things always bugged me. I've found that you have to push up on the screen as it starts back up, which helps it start it's roll-up. -- JSBillings 21:21, 23 July 2007 (UTC)

We had a recent question about a stuck starter rope on a generator, and the same answer applies here: I have corrected this problem in the past by giving the screen a jerk and quickly releasing it or pushing it upwards (you might want to "escort it " up rather than releasing it completely, so it does not get going too fast. The screen, like a roller blind, must have a brake which keeps it from rolling up, but which is released by movement upward at some speed. Of course it could have a broken spring or other fault. Edison 21:41, 23 July 2007 (UTC)

I suggest a quick tug

If you can, look inside the mechanism and see if you can work out how it works. Then you should be able to see what you are doing wrong.

In school a little jerk would often fix audiovisual equipment. Edison 20:11, 24 July 2007 (UTC)

Hey, that's no way to talk about the janitor:)) Richard Avery 07:24, 27 July 2007 (UTC)

I would suggest the highly technical procedure known as jiggling it about a bit. DuncanHill 20:24, 24 July 2007 (UTC)

Insulin

• why in humans insuline is less in non-vegetarians ?
• what are the reasons ?
• And what is the funtion of insuline in the body?
• why do docters suggest to not to take sugar content food or high carbohydrate food to diabetic patients?
• why weak or lean persons must take high carbohydrate food to become fat ?
• why fat persons must take protineious to become slim or lean or for there physical structure?

—Preceding unsigned comment added by 210.211.231.203 (talk • contribs) 19:44, 23 July 2007

Please understand that Wikipedia cannot provide any medical advice. I do not understand exactly what you are asking in the first 2 questions. Are you saying that vegetarians need more insulin or less insulin than non-vegetarians? The 6th question is also unclear. The answers to some of your questions can be found in Insulin. For the third question, see the section on "Regulatory action on blood glucose" in that article. Food is converted into glucose (a sugar) in the blood. Insulin allows the body's cells to use the sugar. You can find information related to the third and fourth questions in the insulin article and in the article about Diabetes mellitus, a disease in which carbohydrate metabolism is impaired. A diabetic person who eats an excess amount of sugary food or carbohydrate may develop blood sugar levels that are dangerously high. Under proper control, a wide variety of foods in moderation can be part of a diabetic diet. A doctor, nurse, dietician or diabetic educator can advise a diabetic on what kind of foods to eat, how much and how often, how to monitor blood sugar levels, how to correct high or low blood sugar levels, and the proper medications to take depending on the type of diabetes. See also Nutrition , Healthy diet and Dieting articles relevant to questions 4 and 5. If English is your second language, you may prefer the Wikipedia in "simple English" which has an article on Diabetes at [14]. Edison 20:34, 23 July 2007 (UTC)

I believe the last question is actually referring to the Atkins diet. The intake of protein does not make a fat person thin, but rather the complete lack of carbohydrate uptake causes their bodies to burn more fat than they normally would. 151.152.101.44 20:48, 23 July 2007 (UTC)

Sounds suspiciously like homework; I must remind you that Wikipedia does not do your homework, but if you have a specific part you're having trouble with (after you've done research and looked first), we'd be more than happy to help you. --71.98.4.68 00:02, 24 July 2007 (UTC)

This is not anyone's homework, as the answers to some of the questions are not straightforward. I am not sure what the first two questions mean and suspect the answer is likely to be different in a westernized culture and non-westernized culture. In a westernized culture, a vegetarian diet may still be high in carbohydrates, which provokes and requires more insulin secretion, while in non-westernized cultures, a vegetarian diet may be associated with reduced body fat and greater insulin sensitivity. People with diabetes often stay healthier if they reduce carbohydrate intake somewhat, and especially if they avoid eating much sugar, because both types of foods are likely to raise their blood sugar levels further. Insulin promotes fat storage, so it is often easier to gain weight with a high carbohydrate diet and easier to lose fat with a lower carbohydrate diet. alteripse 02:54, 24 July 2007 (UTC)

Acoustic inertance of a long thin slit in a wall of negligible thickness

Im trying to find the inertance of a long thin slit in a thin walled cavity for a speaker deign problem. Inertance is m/S^2 (where S is the area and m is the mass of the air) but 'm' cannot be defined as there is negligible wall thickness. Or should I also use an end correction for my slit? If so, what is the end correction for a slit? Is it the same as for a cylindrical tube?--SpectrumAnalyser 20:42, 23 July 2007 (UTC)

OK let me pose the question in another way. In a bass reflex loudspeaker cabinet, if you just have a port (vent) opening (square round or slitty) but no tube (ie no depth to the hole), how do you work out the area of the port knowing the volume of the cabinet and all the Thiele-Small parameters of the speaker. This info is in none of the articles on cabinets or speakers or Thiele Small parameters. Do you need to include(like you do for cylindrical tubes) some sort of end correction that gives you the 'effective' length of the tube. If not, how is the area of the port calculated?--SpectrumAnalyser 14:27, 24 July 2007 (UTC)

nobody seems to be touching this question! Perhsp no one here knows anything about it, I don't either. Do you have the formula for a cone? a hole in a thin wall would be like a cone with sides at a 180° angle. Else you could approximate the slit as infinite in length, and calculate a two dimensional result, and then multiply by the length of the slit. You may have to integrate nested semicircles centred on the slit. GB 02:04, 25 July 2007 (UTC)

I have the formula for a slit but it requires the depth of the slit but doesnt seem to need any end correction. I understand that (I think). What I wanted to know was how you calculate the area of a port for a certain box frequency if it has no depth (and therefore contains no mass of air). Do you then need to use some sort of end correction to get the effective 'length' of the port so you can then calculate the mass of the air that gives the inertance?--SpectrumAnalyser 22:18, 25 July 2007 (UTC)

Is Teflon safe to cook with?

I read the section of 'Teflon' concerned with safety, and I don't know what's true and what isn't. All the sources cited are either studies funded by DuPont or what looks like paranoid woo. (Previously, tuberose.com was used as a source; note the bits about "jagged, scary-looking chunks of synthetic chemicals that have no place in the human body" and the expression of surprise at discovering that using metal implements on nonstick cookware is destructive.) I was hoping for some kind of objective answer here, and I've been unsuccessful at finding anything. It seems ridiculous that there's no good study of the safety of such a widely-used chemical; it also strikes me as odd that there are "many published cases of health effects" related to the use of nonstick cookware, none of which I've been able to dig up. It's, of course, quite possible that my research skills are rusty, and so I come to you, the reference desk, because I'm honestly very, very confused about where the truth lies. grendel|khan 22:02, 23 July 2007 (UTC)

This is one of "those" topics where it's very hard to sort the facts from the paranoid woo, but Teflon has been around long enough that one would think that if it were really trouble, we'd have some pretty strong indications by now. On the other hand, it does seem clear that when it's overheated, its decomposition vapors are bad. And the perfluorooctanoic acid precursor/relative is bad. But the finished product, used properly, seems okay.

Atlant 01:00, 24 July 2007 (UTC)

As Atlant says, it's a controversial topic. If the Wikipedia editors who've worked hard at providing a nicely balanced and accurate presentation at the Teflon article haven't managed to give you quite the answer you're looking for, I'm afraid we duffers here at the Reference Desk aren't likely to be able to, either. (My own belief, for what it's worth, is that Teflon is metabolically a rock and is perfectly safe to ingest in small quantities.) —Steve Summit (talk) 01:08, 24 July 2007 (UTC)

The thing is, I was one of those editors (I made the decision to can the tuberose.com article) and I came here because I was looking for solid information and came up blank. I want the article to lay out the known facts rather than a list of allegations that have been made, but said facts seem awfully slim. grendel|khan 18:49, 24 July 2007 (UTC)

Okay, here's the longer answer I didn't have time to write up last night.

The impression I get (though I haven't researched it) is that this is a tough question to answer, in part because it's right on the edge of what we can detect and analyze. Epidemiology is a tricky subject.

I'm reminded of the (alleged) higher incidence of Leukemia and perhaps other cancers among people who live, work, or attend schools beneath high-voltage electric power transmission lines. Someone did a review of the 200 or so papers that had been published on this question, and found that something like 197 of them demonstrated no correlation, and three of them demonstrated a very slight correlation, right at the edge of statistical significance -- with the level of statistical significance used being 95% or 97% or something.

The thing is, if you run 100 carefully-controlled surveys observing some phenomenon, all at a 97% confidence limit, and even if there is (in reality) no correlation at all, you can expect to have three positive findings, just by random chance. Statistically speaking, those 100 studies might together show that there is a correlation, or that there isn't -- either hypothesis fits the observed data to the limit of our ability to statistically analyze it. (Actually, given that there were 200 studies surveyed, with only 3 positive outcomes, I think this lends more credence to the "no correlation" hypothesis, but I'm not a statistician so I can't say this with any, er, confidence.)

This is one reason that many people's formulation of the scientific method includes a clause stipulating that you must propose a mechanism underlying your hypothesis, not just present statistical evidence showing correlation. If you can suggest how a higher-than-usual 60 Hz AC electric field might induce leukemia, or how ingestion of PTFE could have toxic effects, people will take your right-on-the-edge-of-significance statistical observations much more seriously.

None of which really answers your question, I know... —Steve Summit (talk) 02:31, 25 July 2007 (UTC)

Serious side question, what do people know about the risks posed by decomposing Teflon at 400 C? Dragons flight 01:11, 24 July 2007 (UTC)

What food doesn't turn carcinogenic at 400°C for prolonged period of time anyway? --antilived^{T | C | G} 06:03, 24 July 2007 (UTC)

Most food isn't packed full of flourine... It's a serious question because I've been in the room with Teflon that was baking off and still have the results (which will never be used for food again). Dragons flight 06:24, 24 July 2007 (UTC)

I wrote a Teflon flu stub, which has since been deleted and made into a redirect to polymer fume fever. StuRat 07:15, 24 July 2007 (UTC)

Wikipedia cannot give cooking advice. Please consult your food care professional if you have any concerns. --Trovatore 07:39, 1 April 2525 (UTC)

He/she is not asking for a recipe here. I think she is justified in asking the question. It is as good as asking "Is it safe to cook in a microwave oven?". Go ahead and ask any other doubts you may have, Grendelkhan -- WikiCheng | Talk 14:45, 24 July 2007 (UTC)

I think Trovatore was just roasting us, but I know how that sort of remark can really burn one up, with some construing it as a raw deal ;-).

Atlant 17:33, 24 July 2007 (UTC)

But I just know someone here makes a decent Teflon salad! grendel|khan 18:49, 24 July 2007 (UTC)

Yes, but it doesn't really stick to your ribs. (Translation for Brits: "stick to your ribs" = "is filling"). StuRat 06:18, 25 July 2007 (UTC)

July 24

Diabetes

Hi, I know that hyperglycemia is a symptom of diabetes, what about hypoglycemia, is it also classified as diabetes, or is there another disease for it? Thanks. 58.153.97.9 01:42, 24 July 2007 (UTC)

Hypoglycemia#Causes. Someguy1221 02:45, 24 July 2007 (UTC)

Hyperglycemia is the central manifestation of diabetes mellitus, the core pathophysiological condition that distinguishes diabetes from other diseases. Hypoglycemia is a common complication of treatment of diabetes, because insulin and other agents that lower the blood sugar occasionally "overshoot" and bring the blood glucose too low. Whether hypoglycemia is ever a prodromal manifestation of diabetes is unsettled; a few case reports suggest it, but it is uncommon and difficult to prove that the hypoglycemia was an integral part of the process of developing either type 1 diabetes or type 2 diabetes. You might have found the answers in the articles linked, but I suppose asking here is easier. alteripse 02:45, 24 July 2007 (UTC)

Transsexual

I know that I am not suppose to ask any porno questions, but I want to know that is there a slang for a transsexual man who doesn't have a penis? because his female counterpart is called a shemale because she has a penis.—The preceding unsigned comment was added by 76.64.55.150 (talk • contribs) 02:25, 24 July 2007 (UTC)

Your question is legitimate and not "porno", According to the Transwoman article the term you are looking for may be post-op. -hydnjo talk 04:34, 24 July 2007 (UTC)

Wouldn't the appropriate article be transman? grendel|khan 19:15, 24 July 2007 (UTC)

You might also want to look at the article on Buck Angel, a transman pornstar. grendel|khan 19:15, 24 July 2007 (UTC)

effect of acid on plant life!

We had many plants around us in our university...it was merely like a forest with grasses, weeds, herbs, shrubs & trees! & everyday atleast a hundred (or even more) people urinate randomly around those plants (all varities)..now i wonder why not even a single plant is getting effected with such continuous urination. We know that human urine was highly acidic& it should definitely affect the plants..but not even a single grass or any big tree is getting affected..can u explain me why? Temuzion 04:05, 24 July 2007 (UTC)

Check out some of these links. - hydnjo talk 04:43, 24 July 2007 (UTC)

Most plants prefer a slightly acid environment, preferably to alkaline anyhow. The worst thing urine could do to a plant is if it gets on the leaves directly, eutrophication will allow mildew will grow on them. Bendž|Ť 08:44, 24 July 2007 (UTC)

Urine can kill grass, especially if it's too concentrated. I've heard this can problem especially with dogs. (Googling shows a lot of people complaining) Not because of of the acidicity or alkalinity of the urine but because of an overdose of nitrogen. This was in the "last word" column of the New Scientist a few months back. BTW urine is not always acidic and pH 6 is not exactly 'highly acidic' Nil Einne 16:01, 24 July 2007 (UTC)

extraction of hydrogen from methane

i want tht topic —The preceding unsigned comment was added by Deepikavoona (talk • contribs) 05:43, 24 July 2007 (UTC)

Go read the articles on hydrogen and methane, both of which discuss the methane → hydrogen conversion. DMacks 06:05, 24 July 2007 (UTC)

(edit conflict)

Here is something for you: In extremely high temperatures methane will decompose into Hydrogen and Carbon gas. This happens in stars. When methane burns in oxygen it will form carbon monoxide, steam and hydrogen for a short period, before the hyrdogen is burned up. Steam reforming reacts methane with steam to produce carbon monoxide and hydrogen. Nickel is used as a catalyst. The water gas shift reaction can covert some more of that carbon monoxide to Hydrogen. GB 06:13, 24 July 2007 (UTC)

I doubt that anything short of alchemy can turn carbon monoxide into hydrogen. The water gas shift reaction turns carbon monoxide and water into carbon dioxide and hydrogen. grendel|khan 19:07, 24 July 2007 (UTC)

lol...

Do Electrons in an atom slow down in lower temperatures?

Will electrons in orbit in an atom slow down when the temperature is decreased? (I'm guessing no)

--wj32 ^{talk | contribs} 08:11, 24 July 2007 (UTC)

No, not really. Temperature is approximated by the kinetic energy of a group of atoms(/molecules). You have to remember that the electrons don't really orbit, they are defined by a fuzzy probability cloud, they don't really move in a classical way like atoms do (mostly). You can knock electrons to a higher energy level through providing heat energy, but they're normally unstable and will re-emit back down to a lower energy level. I assume that you haven't studied quantum mechanics yet, so i'll leave it at that. Capuchin 08:15, 24 July 2007 (UTC)

Thanks. Also, what force makes electrons stay in different energy levels? I mean, just because theres protons and neutrons in the center doesn't mean electrons should stay in orbit... Protons attract electrons, but why don't the electrons stick to the protons? --wj32 ^{talk | contribs} 08:34, 24 July 2007 (UTC)

I don't think there's any way to explain that without invoking quantum mechanics. In classical mechanics, the electron should radiate energy in the form of electromagnetic waves and continue to get closer and closer to the nucleus. The amount of energy radiated is infinite because the integral of 1/r² diverges as r tends to 0. This is obviously unphysical.

In quantum mechanics, the ground state is the lowest energy state, and the electron cannot decrease its energy by getting closer to the nucleus. If the wavefunction got smaller, it would have to be more strongly curved, and since the kinetic energy is directly related to the wavefunction, it would go up. The electron cannot get closer to the nucleus without vibrating faster, and the energy cost of the vibration exceeds the potential energy. The ground state wavefunction is a perfect balance between potential energy (distance from the nucleus) and kinetic energy (quantum fluctuation).

Note that this "vibration" can never be directly observed: it's not that the electron moves to one side and then the other; it's that it's always vibrating in all directions in a spherically symmetric manner. —Keenan Pepper 09:14, 24 July 2007 (UTC)

This is why I was having trouble answering. Unless you have studied quantum mechanics, it's very difficult to see these things in a way that is not newtonian motion. When you're talking about electrons, you have to drop most of the assumptions (and lies-to-children) that you have been taught. Electrons are too small to be described by Newton's laws. Capuchin 09:18, 24 July 2007 (UTC)

Actually, the electrons kind of do stick to the protons. In the ground state of hydrogen the electron is not orbiting the proton at all—its orbital angular momentum is zero. Hydrogen in its ground state is basically just an electron superimposed on a proton. The size of the electron cloud is defined by the uncertainty principle, not by an orbital distance.

Starting with boron, at least one electron does orbit the nucleus in the ground state, because of the Pauli exclusion principle and the electron shell filling rules. -- BenRG 00:44, 26 July 2007 (UTC)

Well, its a kind of a degenerate orbit, but I don't think the "superimposed" image is a good one, because the expected value of the magnitude of the momentum is not zero. I think a better picture is more like this: Imagine a sort of a "ghost baseball" that's attracted by the Earth's gravity, but otherwise doesn't interact with the Earth's mass -- it just falls straight through to the other side. When it gets to the other side, it falls back again. That's an orbit, of a sort, even though it has zero angular momentum.

Now destroy all your information about what point in the cycle the baseball is currently at, and you have a picture of the electron in the ground state of the hydrogen atom. --Trovatore 01:25, 26 July 2007 (UTC)

Girls vs Boys

Is there any reason for girls (as a trend) to prefer pink while boys prefer blue? Just curious, thanks!

There are extensive discussion on this in Talk:Pink and Talk:Blue. I guess it's a form of stereotyping. Lanfear's Bane

I could have sworn I read that a long time ago, baby girls were given blue and baby boys were given pink. If so, then yes, it's definately some sort of society thing. This site isn't a perfect reference, but it's a start.--Wirbelwindヴィルヴェルヴィント (talk) 15:12, 24 July 2007 (UTC)

Your comment brought to mind a Dear Abby piece I'd read two months hither, and, overcoming my profound general contempt for Abby, I would adduce her column of 31 May toward the proposition that, at least in the nineteenth and early twentieth centuries, the societal understanding of the color dichotomy was apparently the reverse of our current understanding. If the Google answers, Talk:Pink, and Talk:Blue pages are of insufficient help, one might also query the humanities reference desk on the issue of the history of baby colors as a social, as against a psychological, construct. Joe 04:48, 25 July 2007 (UTC)

hey, I like pink. :( They like what they are told to like, especially boys, who don't want to be thought of by their friends as being like girls.

I like green. What does that make me?? HYENASTE 23:01, 24 July 2007 (UTC)

Greedy? --Trovatore 23:13, 24 July 2007 (UTC)

Environmentally friendly? --SamSim 11:23, 27 July 2007 (UTC)

Wirbelwind is right. Until about 1930, blue (the color of the Virgin Mary) was the color designated to colors, while boys were given the more "masculine" pink. The change occurred inexplicably in the 30's, and caught on in the 50's. 24.1.137.20 04:25, 25 July 2007 (UTC)

Tusks

Why do elephants have tusks? What purpose do they serve?

Have you read the Tusks section of our Elephant article? — Matt Eason ^{(Talk • Contribs)} 12:02, 24 July 2007 (UTC)

Blood serum vs blood plasma

I am confused with the 2 terms as I don't see their difference, even after I've read the related articles. Thanks.

It says on the disambiguation page serum that blood serum is "Blood plasma, with clotting factors removed". This would seem to explain the difference quite well. The clotting factors being Fibrinogen. Capuchin 12:24, 24 July 2007 (UTC)

Fibrinogen is just one of many clotting factors, but you've got the right idea. --David Iberri (talk) 15:37, 24 July 2007 (UTC)

RepHresh

Does anyone know what are the ingredients in the product RepHresh? How does it normalize the pH balance in the vagina? --WonderFran 12:39, 24 July 2007 (UTC)

From the first hit on google (an Internet search engine):

INGREDIENTS: RepHresh Vaginal Gel contains purified water USP, Glycerin, Polycarbophil, Carbomer 934P, Ethylparaben Sodium, Methylparaben Sodium, Propylparaben Sodium.

Our patented vaginal gel is made of two polymers, polycarbophil and carbomer. Polycarbophil is an acidic molecule that adheres to the vaginal epithelial cells until they turnover (3-5 days) and buffers vaginal secretions near the natural physiologic level. This restores the vaginal pH to its optimum balance of 4.5 and helps to maintain good vaginal health.

--TotoBaggins 15:44, 24 July 2007 (UTC)

To clarify on that, the gel is a buffer solution; it can change from an acid solution to a salt solution; adding more acid causes the buffer to turn back into a salt, so it counteracts changes in pH. Technically, polycarbophil is actually a salt, not an acid; the acid is carbomer, which confusingly is not a carbomer, but is another name for poly(acrylic acid); if the secretions become more acidic, the acrylic acid turns into polycarbophil, reducing the overall pH and maintaining balance. Laïka 17:00, 24 July 2007 (UTC)

coal crisis

Hi. I'm just wondering, what would happen to global temperatures, if we burned 98% of the oil, 95% of the natural gas, and 70% of the coal we had? I mean, what would happen if we burned all these, not counting any of the global warming that would occur anyway without the consumption of fossil fuels? I've heard somewhere that if we burned all the coal we had, we'd have a climate like venus. Is this true? The main part of my question is regarding the temperature rise globally solely based on the burning of these amounts of fossil fuels. Thanks. ~AH1^(TCU) 14:33, 24 July 2007 (UTC)

No. In the real world, as measurable by science, CO2 in the atmosphere and in the ocean reach a stable balance when the oceans contain 50 times as much CO2 as the atmosphere. "The IPCC postulates an atmospheric doubling of CO2, meaning that the oceans would need to receive 50 times more CO2 to obtain chemical equilibrium," explains Prof. Segalstad. "This total of 51 times the present amount of carbon in atmospheric CO2 exceeds the known reserves of fossil carbon-- it represents more carbon than exists in all the coal, gas, and oil that we can exploit anywhere in the world. Models trump measurements, National Post, July 7, 2007 Saturday National Edition. - MSTCrow 17:40, 24 July 2007 (UTC)

Segalstad's facts are coprrect, but his conclusions are misleading. Take a look at this diagram of the carbon cycle, which accompanies our carbon cycle article. The deep ocean carbon reservoir does indeed hold about 50 times as much carbon as the atmosphere - 38,100 billion tonnes versus 750 billion tonnes. But look at the annual rates of exchange - the figures in purple. They are much smaller numbers. So if atmospheric CO2 doubled, it would take many years before the deep oceans reached equilibrium with the atmosphere. And if atmospheric CO2 is being continually increased by burning fossil fuels, then the system is being forced away from equilibrium. So an argument based on a hypothetical equilibrium state that is never reached is fallacious - it is like saying you cannot run a hot shower unless you switch off your fridge first. Gandalf61 12:35, 25 July 2007 (UTC)

Synonym of "potential"

I'd like to compare two materials X and Y, saying that X has the same potential as Y for doing this-and-this. However, it is in a discussion about corrosion properties. Since I do not want the reader to be confused with the electric potential, I would like to use a synonym for "potential". The word "possibilities" popped into my mind, but this may be not "strong" enough for saying what I want to say. Is there anyone with suggestions, please? In return, I promise to write something about the extrusion of metals on wikipedia after I've finished my report. SietskeEN 14:50, 24 July 2007 (UTC)

ability, aptitude, capability, capacity, potentiality.... [15] aptitude would be my preference. Philc 15:10, 24 July 2007 (UTC)

Thanks for the help, I'll take that one! The link is in my bookmarks now. SietskeEN 15:48, 24 July 2007 (UTC)

I disagree! Aptitude is something people have. "Capacity" makes much more sense. --Anonymous, July 24, 2007, 23:25 (UTC).

Whole wheat and multi-grain

Why, ceteris paribus, does a product made with multi-grain have slightly more calories than whole wheat? - MSTCrow 17:24, 24 July 2007 (UTC)

As a wild guess, it's possible that some of the other grains are oilier (soy, for example); fat is about twice as energy-dense as carbohydrate, so grains containing more fat and less carbohydrate will contain more energy per unit mass. Just a guess, though. grendel|khan 19:10, 24 July 2007 (UTC)

Another possibility is that you're comparing against that phoney sort of "whole wheat bread" that feels and tastes like white bread with a little brown food coloring. Appalling stuff, just horrible. It may just have less bread in it than your typical multi-grain.

Genuine wheat bread should be dense enough to stand up to genuine peanut butter, which is the kind you have to put in the refrigerator to keep it from separating. Whether that phoney plastic peanut butter that you don't have to keep refrigerated was invented so you could spread it on the phoney bread, or whether the phoney bread was enabled by the phoney peanut butter, I'm not sure. --Trovatore 22:38, 24 July 2007 (UTC)

Question about E=mc^2

According to E=mc^2, as an object goes faster (gets more energy) its mass will increase. I'm wondering if that means that the objects volume increases or its density.

If you are watching an object go faster and faster, it will shrink along it's direction of travel by the Lorentz contraction, so in fact the apparent volume will decrease. No other dimensional changes occur. As for the mass, each and every particle making up the object becomes more massive. Protons, neutrons, electrons...all will be more massive than they were when the object was stationary relative to you. 151.152.101.44 18:07, 24 July 2007 (UTC)

It depends on exactly what you mean by "mass." Popular writing on relativity often describes mass increasing as you get closer to the speed of light, and asymptotically approaching infinity at exactly v=c. According to this definition, the mass of any object depends on the reference frame you're viewing it from. This mass is just m=E/c^2. However, that's not what physicists usually mean by "mass" in a relativistic context. Instead, we usually talk about invariant mass, or rest mass. It's defined by m^2 = E^2/c^4 - p^2/c^2, and it has the useful property that it comes out the same in all inertial reference frames. This means that different observers can agree on the invariant mass of an object. I think this is a more useful concept of mass. Using this definition, the volume decreases (Lorentz contraction), mass stays the same, mass density goes up, and energy density goes up more. You can read all about it in the article Mass_in_special_relativity. --Reuben 18:30, 24 July 2007 (UTC)

Just curious, is there a speed at which a particle will be fast enough and short enough to create a black hole with an event horizon beyond it's contracted length? What particle would be able to do that? --Tbeatty 06:01, 25 July 2007 (UTC)

If it's a perfect point particle, then you can calculate its event horizon even at zero speed. Otherwise, you need to take into account the entire stress-energy-momentum tensor, and something that's a black hole in one frame of reference will be a black hole in any frame of reference. That means its speed doesn't matter. --Reuben 06:58, 25 July 2007 (UTC)

But that's my question. Does adding energy in the form of momentum increase mass with decreasing volume (i.e. increase density) and could the end result be a black hole that's brought into existence? It seems that even if a black holes are frame invariant, their event horizon would depend on their relative velocity as the momentum is part of the tensor equation you mention above. take the earth, accelerate it at 1G until the Lorentz contraction makes its combined energy/restmass and length within it's event horizon. Possible? --Tbeatty 07:57, 25 July 2007 (UTC)

As I said, no, if it's a black hole in one frame of reference, then it's a black hole in any frame of reference. Since the Earth isn't a black hole in its own rest frame, it also won't be a black hole in a frame of reference where the Earth is moving at 99.999999999% of the speed of light. --Reuben 23:21, 25 July 2007 (UTC)

Centre of mass of the universe

Is there of a centre of mass of the universe, and if so is there anyting other significant about it. Would it be the basis of some special frame of reference, it being the centre of the universe? Thanks Stanstaple 18:30, 24 July 2007 (UTC)

As far as we know, there's no center or center of mass of the universe. On large enough scales, all parts of the universe are pretty much equivalent. However, there is a special frame of reference, defined by the cosmic microwave background. It's actually one special frame of reference for each location in the universe, and you can stitch together all these local frames to make a global coordinate system. You can read about it in comoving distance. --Reuben 19:25, 24 July 2007 (UTC)

But assuming there is a finite amount of matter (and hence mass?) in the universe, and that matter doesn't extend indefinetly in any direction, then surely there is a centre of mass. I only studied physics to secondary school level so anything beyond classical physics is beyond my ken. The question dawned on me when i read that the earth and moon were revolving around their common centre of mass and likewise the sun and earth and so on. I had started to believe there was no priveleged frame of reference when I (thought) realized that there was no place in the universe you could take to be more at rest or central than any other. Is there something I'm missing, or this there a centre to the universe? Thanks for the link Reuben, but it didn't seem to shed any light on what i was wondering. Stanstaple 20:25, 24 July 2007 (UTC)

Well, first of all, it isn't known whether there's only a finite amount of matter in the universe. But if there is, and if its distribution is uniform throughout the universe, then that implies that the global topology of the universe is a compact manifold (like, say, a 3-sphere). Well, "implies" might be too strong, but I can't think of another obvious possibility.

So by analogy, consider the surface of the Earth, and suppose it were completely covered by people at a uniform density. Then ask yourself where the center of population would be. --Trovatore 20:50, 24 July 2007 (UTC)

The centre (as in the core)? [I'm being slightly sarcastic] Are you saying that the universe is curved, in the sense that if you head head in a literaly straight forward direction through space you could end up here? I can't believe i'm a flat universer, I should know better ;)

Well, again, this isn't known. That's the simplest possibility if the global curvature of the universe is positive. But it could also be negative (in which case the simplest model has infinite extent in all directions) or zero (in which case the universe is asymptotically flat, and again the simplest model is infinite in all directions). --Trovatore 21:18, 24 July 2007 (UTC)

I appreciate your reply but I don't really understand it. My limeted mental model of the universe is in 3 dimensions. Could you point me in the direction of how i could understand positive -v- negative global curvature. I would have thought, given big bang theory (and my simple understanding of) that there was a definite extent to which matter extended.

Well, this is the kind of thing for which direct observation is not available, but if we assume that the universe is pretty much the same wherever you are in it (I think this is called uniformitarianism; haven't looked at that link and don't know if it's helpful), then it's wrong to think of the big bang as a little dot that blew up into (pre-existing) empty space. If the inflaton was a little dot, then so, at that time, was the whole universe. On the other hand, if the universe is infinite (and uniformitarianism is correct), then it must contain infinitely much matter, and (presumably; I'm a little out of my depth here) the inflaton itself had infinite extent. --Trovatore 21:39, 24 July 2007 (UTC)

Take a two dimensional model; a flat sheet universe. Has a center, if it's not infinite. However, imagine that flat sheet is actually the skin of a balloon. The "center" is not actually "within" the universe; and furthermore, as the balloon inflates, the universe expands, evenly, without being able to find a center to the expansion within the universe. Gzuckier 14:41, 25 July 2007 (UTC)

Lightning/sand/glass

Can a lightning strike generate sufficient heat to fuse sand into glass? DuncanHill 21:40, 24 July 2007 (UTC)

So you're a reader of xkcd too? TenOfAllTrades(talk) 21:48, 24 July 2007 (UTC)

No, but the X-Files are on TV, and Mulder says lightning can't do it. Struck me as an interesting question.DuncanHill 21:50, 24 July 2007 (UTC)

Oh, and yes—lightning can indeed fuse sand into glass; see fulgurite. Small ones are available for purchase from a number of web sources. (This is the first I ran across; it has some pretty pictures.) (after edit conflict) It looks like Mulder is full of it. TenOfAllTrades(talk) 21:52, 24 July 2007 (UTC)

Magnificent - thank you TenOfAllTrades. Mulder should use Wikipedia. DuncanHill 21:54, 24 July 2007 (UTC)

If you're watching the same episode of X-files that I'm thinking of (had some kid receiving binary code through the TV), Mulder says that because the fused sand he notices doesn't resemble the spires of fulgurite, but is more of a solid mass. HYENASTE 23:00, 24 July 2007 (UTC)

I wasn't really watching, had it on in the background as I edited and cooked. The Brandenburg Concerto was involved at one point, as was a lake called something like obikenobe (I may have misheard that bit). DuncanHill 23:32, 24 July 2007 (UTC)

That's the same one. Coincidentally, its the only episode I've seen in years. HYENASTE 23:38, 24 July 2007 (UTC)

The Boston Museum of Science has (had?) a very nice, quite large piece of fulgerite on display in their Thompson Electrical Theatre, right near the 2 megavolt Van de Graaff generator.

Atlant 11:57, 25 July 2007 (UTC)

Didn't this also happen in Planet of the Apes? Somehow I trust Planet of the Apes to be more scientifically accurate than X-files.

Lithium ion battery

What happens when I put an AA Li-ion battery (3.7volts each) into a camera designed for 1.2v AA Ni-MH battery? AA Li-ions aren't enormously popular, but available. I want to know what happens in practice: does it work, and are there any side effects (eg a battery explosion or depleted life).81.168.125.154 23:18, 24 July 2007 (UTC)

If you use a 3.7 volt battery in something designed for a 1.2 volt battery, you may well knacker the camera, and certainly invalidate your warranty. DuncanHill 23:42, 24 July 2007 (UTC)

Are you sure you have something claiming to be an AA battery, that's supplying 3.7 volts? That sounds like a tremendously bad idea for someone to have manufactured, and it really shouldn't be called an AA battery. --Steve Summit (talk) 23:57, 24 July 2007 (UTC)

I haven't got one, but the web is swimming in them if you look - see, for example, http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1336. The reading around I did on it seemed to suggest that there used to be many safety hurdles which needed to be passed before they could be made at AA size. To me, it looks as though we're approaching that point. $3.30 is rather expensive for only one, but if they are relatively new technology, and Lions were always expensive anyway. 82.153.73.50 09:17, 25 July 2007 (UTC)

Huh. Shows what I know. (I stand by my point that it was a tremendously bad idea, but alas, no one asked me. :-) )

In any case, DuncanHill is right, definitely don't use such a battery in a device designed for use with normal, 1.2 to 1.5 volt AA batteries. —Steve Summit (talk) 11:59, 25 July 2007 (UTC)

FYI: There are AA batteries that use some sort of lithium chemistry but still put out about the usual 1.6 volts. They apparently have greater capacity and lighter weight than ordinary "alkaline" batteries.

Atlant 12:02, 25 July 2007 (UTC)

I will check that out. Surely a 1.6v battery in a camera designed for 1.5 will make little difference. Are they rechargeable (and therefore, probably Lion?82.152.199.26 12:38, 25 July 2007 (UTC)

can't find any atlant. Can you give the link to an example?82.152.199.26 12:44, 25 July 2007 (UTC)

The Google query "lithium AA battery" fairly quickly yielded http://www.energizer.com/products/lithium/default.aspx . I'm pretty sure this is the brand that came with my Apple wireless Mighty Mouse.

Atlant 15:15, 25 July 2007 (UTC)

YIKES! This does seem like an extraordinarily dumb battery design. They could have made it just a bit fatter or shorter or longer so that people wouldn't screw up their delicate electronics! But AA cells of different technologies have always been around that work between 1.2v and 1.6v and most devices are happy to work over that range without problems. The only device I've ever had trouble with was my Lego Mindstorms computer that didn't like me using six 1.2v NiCd's instead of six 1.5v alkalines - it worked fined with NiMH's. It mostly worked but was kinda intermittant. But as others have said - you DEFINITELY don't want to go sticking anything much over 1.6v per cell into a camera or anything else that's designed for a regular AA. SteveBaker 15:19, 25 July 2007 (UTC)

Don't Panic! As I said, I think the battery chemistry was chosen to work out to a voltage compatible with the typical 1.6V alkaline battery.

Atlant 22:00, 25 July 2007 (UTC)

I see. Helps if you search for "lithium" rather than assuming all lithium based batteries are lions. That said, making them a slightly different size would actually have worked very well for safety... because no-one would be using them, given that nothing currently comes in double A and a bit size. Other than that, my question has been well and truely answered: not quite adviseable. Anyway, given that we are dealing with a camera (did I mention that?), which is a high drain device, I would expect it to cope better than some devices going A LITTLE over the limit.81.5.171.223 17:00, 25 July 2007 (UTC)

Also, please note that "lion" is an animal, as Li-ion would have two is. If you've been searching for "lion", you might want to try changing it to "li ion" or something. --Wirbelwindヴィルヴェルヴィント (talk) 17:20, 25 July 2007 (UTC)

Of course. I abbrev. bcos i cnt b bothrd 2 type it al out. Would something like this [16] go ok - I mean, are batteries like that supposed to replace two AA Alkalines or NiMH? I expect, even if it were 3.7v, it should go ok because if a 2x 1.6v batteries would be alright, it's not far behind a 3.7. The battery in question is a lithium ion, and not a lion or tiger, just to be sure :-) 81.5.171.223 17:25, 25 July 2007 (UTC)

July 25

Technetium

Having read the article, I see that Tc does not occur naturally on the earth, but it never says why. Of all the lower elements, what makes Tc so unspecial that it doesn't naturally form? HYENASTE 01:34, 25 July 2007 (UTC)

Technetium is radioactive in all its isotopes, the halflife is short enough that any original has all decayed away. No isotope of technetium has a half-life longer than 4.2 million years. And also note that on Earth, technetium occurs in trace but measurable quantities as a product of spontaneous fission in uranium ore or by neutron capture in molybdenum ores. (lifted from that article) GB 01:39, 25 July 2007 (UTC)

Technetium says "Since technetium is unstable, only minute traces occur naturally in the Earth's crust as a spontaneous fission product of uranium." So natural uranium fissions spontaneously, forming natural technetium. But it's unstable, and has in general a short half life (see Isotopes of technetium), so that technetium in turn spontaneously fissions into something else. -- Finlay McWalter | Talk 01:41, 25 July 2007 (UTC)

I suppose I should rephrase thusly: why does Technetium, an element with considerably fewer subatomic particles than other radioactive elements, decay so quickly? HYENASTE 01:49, 25 July 2007 (UTC)

The article has a "Stability of technetium isotopes" section, which explains. -- Finlay McWalter | Talk 01:54, 25 July 2007 (UTC)

Thank you, Finlay. I can't believe I missed that the first time though. HYENASTE 02:04, 25 July 2007 (UTC)

Constant laws of physics?

Also based on Tc: What if Tc does form naturally somewhere in the universe? Is it possible, then, that certain truths in our part of the universe don't hold elsewhere? Could it be that beyond our realm of the universe, our accepted laws of physics do not apply? HYENASTE 01:34, 25 July 2007 (UTC)

Well, it would depend. If the reason there's no Technetium on Earth is (in effect) a coincidence, then if it appears somewhere else, there's no problem. Or if we know that the conditions for it to "form" were never found on Earth or in our Solar System, but they do elsewhere, then still no problem. Or if the reason there's none is that it's all decayed away by now, as Finlay McWalter just explained, then still no problem.

As far as we know, the Laws of Physics (as we know them in our Universe) apply everywhere. As far as we know. Obviously we can't prove that they apply beyond the realm of our knowledge and experience. (Except maybe by Occam's Razor. Which is actually a pretty good argument.) —Steve Summit (talk) 01:43, 25 July 2007 (UTC) [edited 01:46, 25 July 2007 (UTC)]

It does form naturally. It forms on Earth, as mentioned above, and in red giant stars. All of this is in the Technetium article. -- Finlay McWalter | Talk 01:45, 25 July 2007 (UTC)

Yes, stars that we have observed. I'm imaging a distant area where Technetium is as common as iron (figuratively). HYENASTE 01:46, 25 July 2007 (UTC)

You're not asking a science question, then, but postulating some figurative imaginary land where different laws of nature apply. -- Finlay McWalter | Talk 01:52, 25 July 2007 (UTC)

As in the Isaac Asimov novel The Gods Themselves. But that's, y'know, science fiction. --Anonymous, July 25, 07:17 (UTC).

Technetium has been detected in other parts of the universe. However it can be explained in terms of physical laws also used on earth. This is part of science to find out what is the same on earth as the rest of the universe. Some things are different, and then the laws have to be generalised - eg air pressure, day of 24 hours. GB 01:49, 25 July 2007 (UTC)

Rephrase

I believe my example overshadowed my question. To rephrase:

In the observable universe, all laws of nature do apply consistently. Could it be possible, in part of the universe unobserved, billions of light years away, that certain inalienable laws here do not apply? A fair example is: what if the gravitational constant G was not constant, but depended on the objects' distances from the center of the universe if the universe has a center. HYENASTE 02:12, 25 July 2007 (UTC)

Well, yes, it's possible, in the sense that just about anything is possible. The general trend of science, though, is to say "there should be one set of laws governing everything we can observe" and then try to find that set of laws, or a reasonable approximation to it. When scientists observe something that doesn't follow the current theory, they look for a more expansive theory that explains both the previous observations and the new one (a good example is how we went from Newtonian gravitation to General Relativity). That said, I think I've read somewhere about the possibility that if there are sections of space expanding away from each other faster than light, so that they can never communicate, then certain aspects (I can't remember if they talked about physical laws, or constants, or something else) could be significantly different. Confusing Manifestation 02:34, 25 July 2007 (UTC)

There is some discussion of whether such physical parameters do vary within the observable universe (e.g. Fine-structure constant#Is the fine structure constant really constant?). Beyond the observable universe, we have few theoretical constraints, so it is not really science in the usual meaning; however, there are some theories that would predict that physical parameters vary on scales much larger than the current observable universe. So yes, it is possible. Is it necessary? No. Right now there is no conclusive evidence that would require the parameters of physics to be anything other than constant. Dragons flight 02:45, 25 July 2007 (UTC)

Alot of science is actually based on the assumption that certain laws and characteristics of the universe are the same everywhere.

For example, cosmology is based on the "Cosmological Principle." That article says:

The Cosmological Principle is not a principle, but rather an assumption or axiom that, when applied, severely restricts the large variety of possible cosmological theories. It follows from the observation of the Universe on a large scale, and states that:

On large spatial scales, the Universe is homogeneous and isotropic.

In laymen's terms, (I quote ISBN 0471265187) At any given time, the distribution of matter is the same everywhere in space, and the universe looks the same in all directions. So in the field of cosmology, scientists tend to ignore notions like "what if the laws of physics are completely different over there?" It's justifiable to ignore ideas like that (as we can't study things we can't see), and those "what if"s aren't strictly scientific. So, to answer your question: yes, it is possible for certain physical laws to be different in unobservable reaches of space, but there's no evidence to support that claim, and cosmologists tend to quickly rule out ideas like that. Jolb 05:25, 25 July 2007 (UTC)

Yes it's possible - in the same way that anything is possible until proved or shown otherwise. It is however usual to assume that behaviour in one place is the same in any other place unless there is a reason to believe otherwise (it's simpler that way).87.102.10.79 12:39, 25 July 2007 (UTC)

Of course if our 'laws of physics' don't apply it would be fair to describe such a place as a different (new) universe.87.102.10.79 12:41, 25 July 2007 (UTC)

We really only know what we can observe - so we have two hypotheses: One says that the universe has the same laws and constants everywhere (evidence for which is that for every experiment we have ever done - and every observation no matter how distant a galaxy we look at - those numbers are still correct). The other hypothesis is that these numbers change - but so gradually that we can't observe it with any existing equipment or theories. Since we have at least some evidence for the first theory - and no reason to suspect the second, all we can do is employ Occams razor and say that in all likelyhood, the simplest explanation is the right one. The simplest is that everything is the same everywhere. So that's what we go with...but knowing, in the backs of our minds, that MAYBE we're wrong about that. There have been lots of scientific papers written about this kind of thing and it's definitely taken as a serious possibility. The Universal Gravitational Constant and the Fine Structure Constant are the two that are most often questioned. We don't (for example) often ask whether the charge on the electron might vary - although I have no clue why not! Obviously there are mathematical constants like 'pi' that we know for sure can't vary. Another possibility (much more likely IMHO) is that these 'constants' are only constant under a certain set of circumstances - maybe they are actually variable depending on the curvature of space or the intensity of an electromagnetic field or something. This kind of thing was initially suggest as a 'get out clause' to avoid the need to hypothesise black holes. SteveBaker 15:09, 25 July 2007 (UTC)

A third possibility is that things are the same everywhere but our understanding is only local. The world is measurably flat on very small scales, for example. --140.247.238.102 15:22, 26 July 2007 (UTC)

A rephrase seems to be, is it possible our scientific model is wrong? and yes would be the answer, as all the previous ones were. Philc 19:28, 25 July 2007 (UTC)

It's a good idea to note, however, that many previous models were largely untested before their acceptance, while the existing base laws of physics have been well tested since their creation starting a century ago. The well tested models that were thrown out (but still used today! Newtonian mechanics, and Maxwell's theory) failed testing only once sufficiently accurate analytical devices were created, non-existent when said theories were invented. But then this just brings us back to the one of the original, and most basic answers, which is that our current model of the laws of the universe are almost certainly accurate, to within our ability to test them. 151.152.101.44 21:10, 25 July 2007 (UTC)

Well, the philosophy of science generally accepts that its a bit more complicated than simple test/verification/falsification in most cases, but in any case, I think the most safe way to pose the positive statement is as far as we know, our current scientific model is correct, and we do not have compelling evidence that it is exceptionally wrong, though that doesn't apply to some fields (e.g. we know that something must be exceptionally wrong/incomplete in our understandings of General Relativity and/or Quantum Mechanics, because they aren't compatible). --140.247.238.102 15:22, 26 July 2007 (UTC)

Climate Change

I'm confused about why scientists are so concerned about climate change. If the Earth is warming, why can't humans just cool it down to solve or at least mitigate damage done by greenhouse gasses? We've all heard of nuclear winter, another kind of man-made climate change. Why don't scientists look into using aerosolized dusts (like in a nuclear winter) to reduce the amount of solar radiation reaching Earth? I'm not suggesting nuclear winter to prevent global warming, but, for example, couldn't we spray aerosolized sulfur dioxide or aluminum oxide into the upper atmosphere to reflect solar radiation to counteract greenhouse gasses? Jolb 05:02, 25 July 2007 (UTC)

And have you considered the consequence to your solutions? Do you want to smell like Rotorua get acid rain or get lung cancer from breathing in microscopic pieces of aluminium oxide? It is simply easier to prevent climate change than to let it happen and undo its damage. --antilived^{T | C | G} 05:18, 25 July 2007 (UTC)

Antilived, I don't feel like the examples I gave are necessarily sound ecological solutions. Instead, I merely use those examples to illustrate the point that humans are capable of REVERSE climate change, not necessarily in the same way or with those exact chemicals. Also, preventing climate change has eluded us thus far, so I don't think it's as easy as you seem to think. I also don't suggest that we "let it happen." Jolb 05:29, 25 July 2007 (UTC)

Climate change is very small over a long period of time. It would be very difficult to respond over such a long period of time with the minute changes necessary to counteract it. Secondly, the law of unintended consequences would most likely impact the earth in an unexpected fashion. Third, the mechanism of global warming is not completely understood nor is the man-made contribution to global warming fully understood. --Tbeatty 05:53, 25 July 2007 (UTC)

The short answer is that yes, there are people who are paying serious attention to geoengineering approaches to combating climate change. As Antilived suggests, so far these proposals are either extremely impractical/costly or carry significant negative effects on their own. As a result, most people feel that focusing on preventing/limiting climate change is probably the better opinion of those that have been presented. Dragons flight 05:58, 25 July 2007 (UTC)

There is a proposal in the scientific community right now too possibly use a shield of dust in orbit abound earth the shade us as a last ditch solution. (The article is from a recent New Scientist. I’m not sure which issue.) However, the proposed method is apparently only an absolute last resort, since it would probably cause an ice age or other unintended disaster. --S.dedalus 06:00, 25 July 2007 (UTC)

The question whether global warming could be reduced by technical means is, of course, a valid one, and hence actively researched since quite a while. So far, however, all ideas seem to be quite dangerous, in that they may pose risk for even bigger disaster. Even the simple idea of capturing and storing the carbon dioxide has its problems: the storage might malfunction and release giant amounts of CO2 in one go. Other scientists test whether one could increase the growth of algae in the oceans by iron fertilization. When the algae die, they sink down and take with them the carbon that they took from the athmosphere while growing. But will they stay down there? That's far from clear given the little we know about deep ocean currents. And recently, Paul Crutzen sparked a major debate with his idea of artificially introducing sulphur dioxide into Earth's upper athmosphere to cause a cooling effect similar to that following major volcano outbreaks. Most scientists, however, consider this way too dangerous. The problem with all this geoengineering is always that it is hard to judge effects and side effects from small-scale experiments, and large-scale experiments may cause irreperable damage. Simon A. 07:39, 25 July 2007 (UTC)

This is the kind of optimistic can-do thinking that made the former Soviet Union into the veritable paradise it is today, both economically and ecologically (note to origial poster, please don't take this as condescencing or insulting, it's not intended as such). Whereas our government is largely formed of lawyers who couldn't get lawyer jobs, with all the problems that brings, lawyers didn't have the same clout in the USSR (defense lawyers vs. the USSR; yeah, right), so the majority of the lawmakers were engineers. And the attitude was, we'll make it work; and if something breaks we'll patch it, and if that breaks something we'll patch that, etc. and like i said, that led to economic and ecological disaster. At the current state of human competence, best we not screw with things too much, and always with a clear pathway for rolling things back to The Way They Were In The First Place rather than patches on patches on patches.Gzuckier 14:36, 25 July 2007 (UTC)

Your 'our government' sounds a lot like my 'our government'. :) DirkvdM 06:32, 26 July 2007 (UTC)

The problem with these kinds of intervention is that they all too often do more harm than good. We didn't understand the atmosphere well enough to avoid getting into this mess in the first place - it's unlikely we could safely take such drastic action to reverse it. For example (and I have no clue whether this is a real issue or not) - the CO₂ in the atmosphere predominantly blocks re-radiation of infrared light back out into space. Regular visible light is not much affected. If we put up some kind of cloud to reflect sunlight away, maybe it would reflect visible light away as well as infrared. Lack of sunlight in the green region of the spectrum would cause plants to do less photosynthesis - which would cause them to absorb less CO₂ - which would result in global warming getting worse - not better (and incidentally probably cause global crop failure and starvation). I'm not saying that's definitely what would happen - but you have to see that it's plausible. If I can imagine a problem that serious with just 10 seconds thought (and I'm no climatologist), just imagine how many other nasty possibilities there might be after 10 years of experts looking into it! Think about the number of cases where we've tried to "fix" ecological problems and made things worse in the past. We introduce some kind of animal or plant into a non-native habitat - it goes nuts and takes over from the native species - so we find the natural prey for that thing and introduce that - only to find that it's extra food for some native species that then undergoes a population spike that causes some other native species to go bust. If there is anything we've learned over the past 40 years it's that intervention of any kind is dangerous. By far the safest thing to do at this point is to drop the outflow of CO₂ into the atmosphere as fast as is reasonably possible - and to let nature do the best it can to clean up and restore balance to the system. SteveBaker 14:55, 25 July 2007 (UTC)

It's interesting that you should ask this question today. Wired News just posted this article up. In it, scientists suggest that pumping 20 to 25 litres of aerosols into the stratosphere per second would be enough to reach the temperatures of 1900 in five years. Unfortunately, this pumping of aerosols would have to remain constant. If it was stopped, temperatures would dramatically increase to the level governed by carbon dioxide levels. --80.229.152.246 22:02, 25 July 2007 (UTC)

Steve, your problem would be solved if the sunlight were not 'caught' before it reaches the Earth but when it reaches the Earth. We might do that with solar panels and create electricity at the same time. Two for the price of one!

Of course, those shouldn't be placed on rooftops in cold climates, because that would take away the natural heating of the house, increasing the necessity for burning fuel. But that's just another side-effect I happen to think of. Damn side-effects. DirkvdM 06:32, 26 July 2007 (UTC)

No - that doesn't work. If you absorb the sunlight, turn it into electricity, then use the electricity, the sunlight turns back into heat (eventually) and ends up warming the earth. You have to reflect away the sunlight so that its energy is shed back out into space. This is one reason why the melting of the North Pole is so serious. Snow and ice are white and reflect sunlight back out into space. Open ocean is dark and absorbs sunlight - making the world warmer. As the polar ice retreats due to greenhouse effects - it actually accellerates global warming. So you can't absorb the sunlight and claim to be helping. Of course replacing fossil fuels with solar electricity may not be such a terrible thing - so long as your solar panels don't absorb more sunlight than the ground beneath them did. Putting a huge array of solar panels on snowy ground (for example) is likely to be counter-productive. SteveBaker 11:58, 26 July 2007 (UTC)

Friction Ridges / Finger Prints

I was told that finger prints are formed by pressure in the womb, yet the Wikipedia article on skin suggests that it is genetically determined. Which one is right, or both?

AFAIK it's genetics, but I'm not an expert. Gzuckier 14:43, 25 July 2007 (UTC)

If it were pressure in the womb, wouldn't we have fingerprints all over? Naegeli syndrome is a genetic disease that results in people being born without fingerprints - which also says it can't be due to pressure in the womb because that couldn't depend on the genetic makeup of the baby. Nope - I don't buy the 'womb pressure' theory at all. Who told you this? SteveBaker 14:43, 25 July 2007 (UTC)

The fact that fingerprints fall into discrete patterns (spiral, whorl, etc.) implies a genetic cause, but identical twins have distinct fingerprints, so that implies an environmental cause. These links give that same (non-)answer: it's both nature and nurture. [17], [18] --TotoBaggins 19:59, 25 July 2007 (UTC)

The article says that patterns are partly inherited but ridges are not. --Kjoonlee 20:47, 26 July 2007 (UTC)

which is more durable:metal or non metal?

which is more durable?metal or non metal?

it depends on the context. please elaborate. --Russoc4 13:46, 25 July 2007 (UTC)

Yep - more detail please! It depends on whether you are talking about resistance to abrasion or tensile strength or ductility or compressive strength, tendancy to crack formation and propagation. At what temperature range? Pure metals versus pure non-metals - there are some pretty durable compounds that contain both metals and non-metals. We certainly need more information about the context. Ceramic heat tiles on the space shuttle are much more durable than aircraft-grade aluminium under circumstances of re-entry into the earths atmosphere, but a bone-china (ceramic) teacup is no match for a stainless steel coffee mug if you drop them both from 6 feet onto a concrete floor! Diamond is much harder than steel - but at high enough temperature the diamond will catch fire long before the steel will melt. The answer can only be: "it depends". SteveBaker 14:36, 25 July 2007 (UTC)

Skin. In the bible it states that Moses tied his ass to a tree and walked for a day and a night. (haha). Gzuckier 14:44, 25 July 2007 (UTC)

Diuretics and potassium

Why is it with diuretics that potassium is the only ion that is lost? Why don't diuretics result in a loss of sodium, calcium, magnesium and so forth? I read the diuretic article but couldn't make much sense of it, so I was hoping that someone here might be able to provide with information that is easier to understand. Thanks in advance, Jack Daw 13:50, 25 July 2007 (UTC)

See Loop of Henle: "K⁺ is passively transported along its concentration gradient through a K⁺ channel in the basolateral aspect of the cells, back into the lumen of the ascending limb. This K⁺ "leak" generates a positive electrochemical potential difference in the lumen. The electrical gradient drives more reabsorption of Na⁺, as well as other cations such as magnesium (Mg²⁺) and importantly calcium Ca²⁺." Thus potassium is "sacrificed" to allow for more reabsroption of the other ions.-- Flyguy649 ^talk _contribs 17:20, 25 July 2007 (UTC)

It actually depends on the diuretic used. Loop diuretics affect the Na-K-2Cl symporter, and can indeed cause hyponatremia (low sodium) and hypomagnesemia (low magnesium) as well as hypokalemia (low potassium).

On the other hand, potassium-sparing diuretics operate on other ion transport channels. For example, amiloride and triamterene inhibit the epithelial sodium channels, preventing the resorption of sodium from urine. TenOfAllTrades(talk) 17:28, 25 July 2007 (UTC)

Eating excess sugar?

What are some health problems that can result from eating too much sugar?

You can see the appropriate article on sugar, specifically the sugar and health section. While that entry seems to be sadly lacking in necessary citations, it should be able to give you a start to looking into it in more depth. ◄Zahakiel► 18:04, 25 July 2007 (UTC)

There are a variety, but it basically boils down to this ------->

--TotoBaggins 20:09, 25 July 2007 (UTC)

You mean sugar mutates the ob gene? alteripse 02:26, 26 July 2007 (UTC)

Or this -------->

--DuncanHill 22:59, 25 July 2007 (UTC)

Type II diabetes. Aaadddaaammm 01:27, 26 July 2007 (UTC)

Air speed and PSI

How fast does air have to be traveling to create pressures of up too 10 psi [pound per square inch], such as would be in a shockwave etc ?

Thank you - — Preceding unsigned comment added by 80.6.36.200 (talk • contribs)

I got a figure of 294mph from The Atomic Archive using the following google query: overpressure mph "10 psi" - But you'll probably have to show your work. - CHAIRBOY (☎) 20:49, 25 July 2007 (UTC)

Ha! Flyguy649 ^talk _contribs 21:11, 25 July 2007 (UTC)

Name for a filtering problem formulation

Say I'm building some active noise control system, for example a noise-canceling microphone system in which one microphone faces the source of the sound, and a second microphone faces away from the source to pick up the ambient noise. So I have two different input streams: a noisy signal, and another stream that's correlated with the noise, and I want to clean up the first stream by subtracting out some estimate of the noise derived from the second stream. The problem is, I can't just subtract out the second stream as it is, because it's facing a different direction, and it might be a different kind of microphone with a different frequency response or whatever, so I have to filter it first. How do I design a filter that is optimal in the sense that the signal resulting from the noise subtraction process has the minimum possible power, i.e. it is most effective at removing noise?

I don't want a detailed answer (it would be too long and there are probably many different ways to attack the problem); I just want some keywords I can use to search for this problem. The book I have here (Optimal Filtering by Anderson and Moore) mentions three problems: filtering, smoothing and prediction, but they all use only one input stream, so they're not what I'm looking for. —Keenan Pepper 22:07, 25 July 2007 (UTC)

Presumably you have looked here? [19] or here [20]--SpectrumAnalyser 22:28, 25 July 2007 (UTC)

Um, yes. And don't use external links to link to Wikipedia articles. For example, instead of [http://en.wikipedia.org/wiki/Noise-cancelling_headphone], use [[Noise-cancelling headphone]]. —Keenan Pepper 23:43, 25 July 2007 (UTC)

Oh sorry. So what your problem? You dont need a filter, you just need to capture the noise in the same phase as it would appear at the main microphone then subtract it from th e main signal. The trick is to get it in the right phase, but you would n use a filter to do that. You dont say what type of noise you are trying to eliminate. If its higher frequency stuff, the phase errors will stuff you.--SpectrumAnalyser 00:26, 26 July 2007 (UTC)

I beg to differ. You do need a filter. How else would you "get it in the right phase"? Ever heard of an all-pass filter? Also, as you say, active noise control is less effective for high frequencies, so if you didn't use a filter, you would end up increasing the power at high frequencies rather than reducing it. The optimal filter would automatically incorporate a low-pass filter.

None of which answers my question, which was: what is the name of this problem formulation? —Keenan Pepper 05:06, 26 July 2007 (UTC)

I dont think there is a specific name for this sort of system. You will have to treat it as any other system with two inputs. The main input will be S+N and the other input will be f(N). You have to create the inverse function (with your 'filter' as you call it) before you can subtract the noise (N) from S+N. Since you are likely to have little control over f(N) you must create a versatile system to obtain its inverse. If you new the exact nature of the noise (say a single sine wave) then of course it would fairly easier. But with broad band noise, I dont think you have a chance unless you were to utilize spectral subtraction methods. These methods may be too slow to perform in real time for all but the lowest frequencies of interference. None of which answers your question sorry.-- I dont think there is an answer.--SpectrumAnalyser 12:40, 26 July 2007 (UTC)

Related question

OK - so I have a related(ish) question. Why do this electronically at all? Why not have a microphone that's just a hollow tube with a diaphragm blocking the tube halfway down it's length. Sound that's coming from all directions would enter both ends of the tube and the pressure changes would cancel out - someone singing into one end of the tube would create a pressure differential on that side that would vibrate the diaphragm. Noise cancelling without the electronics! Clearly this doesn't work in practice or that's the way everyone would be doing it - but why would it be worse than two microphones pointing in opposite directions with electronics subtracting one signal from the other? Noise cancelling headphones are a different matter of course...not at all the same thing! SteveBaker 01:47, 26 July 2007 (UTC)

Ding ding ding! Correct answer! Highly-directional microphones are the way everyone does it, using techniques such as "shotgun" microphones and parabolic reflectors plus microphones. Our microphone article discusses this.

Atlant 15:54, 26 July 2007 (UTC)

Why do you assume the noise on either side of the diaphragm would be perfectly out of phase? It could just as easily be perfectly in phase (doubling the amplitude and therefore increasing the power by a factor of four), or, more likely, incoherent (doubling the power). Electronics simply "subtracting one signal from the other" would suffer the same problem. You have to filter the noise to make the phase correlate before you can achieve destructive interference. At high frequencies it's hopeless and the best you can do it avoid increasing the noise by adding to it incoherently. —Keenan Pepper 05:06, 26 July 2007 (UTC)

I notice that expensive cell phones do a much better job of blocking ambient noise than cheap cell phones. I assume it's due to some intelligent acoustic engineering. Gzuckier 19:19, 26 July 2007 (UTC)

Medical Illness

When I was younger, I contracted a virus which gave me these weird red dots all over my skin that turned purple when pressed. It also affect my joints, making them so swollen I could barely move. I've heard that it could also cause kidney problems/failure. The only thing is, I don't know the name. I suppose I could ask my doctor, but I was wondering if this was a somewhat common infection that someone else knew. According to my mother, it was named after someone. Thanks! Delta 23:15, 25 July 2007 (UTC)

Rubella?

Henoch-Schonlein purpura? alteripse 02:25, 26 July 2007 (UTC)

metal

is there any metal on earth that can conduct lightning and not get super heated, with out it being grounded? —The preceding unsigned comment was added by Jeff1133 (talk • contribs) 23:38, 25 July 2007 (UTC)

I dont think the metal body of an aircraft gets super heated when struck. And thats not grounded (when flying of course)--SpectrumAnalyser 00:31, 26 July 2007 (UTC)

Yikes! That's not true! This 707 wingtip [21] (for example) shows a nice scorch mark on the wing where it took a mid-air lightning strike. The electrical discharge takes the (electrically) shortest path. It's easier for the electricity to pass through the body of the plane and out the other side than it is to go through the air nearby. Immense amounts of current flows through the metal - and current flow heats metal...so yeah - it'll zap the plane pretty efficiently.

To answer the question, all metal conducts electricity to some extent - but all of them offer some resistance to the flow. Resistance means heat. Some (eg silver) conduct better than others (eg aluminium). The degree to which the metal gets heated depends on it's total resistance. The larger the chunk of metal, the lower the resistance - the better the conductivity - the lower the resistance. The most conductive metal known is silver - and a really large ingot of the stuff ought to conduct lightning without getting too hot. As to whether grounding it helps - you have that backwards. You're interested in what the potential difference is between the ends of the metal - grounding the metal helps to ensure it presents the easiest path to ground (that's why we carefully ground lightning rods) - and therefore that it'll experience a bigger potential difference than if it were suspended in the air. So a grounded metal rod would heat more than one sitting out in the air. But both get heated! SteveBaker 01:32, 26 July 2007 (UTC)

Generally superheating only occurs in liquids. I think that lightning would probably disturb the liquid enough (through air-shockwaves) for this to not happen. Out of interest, could it happen in a perfect crystal? Should this be added to the article? Capuchin 06:50, 26 July 2007 (UTC)

The questioner didn't say "superheated", but "super heated". Slang. very; extremely or excessively: super classy; a super large portion of food. —Keenan Pepper 10:19, 26 July 2007 (UTC)

You just need a thick enough piece of metal to conduct all the current safely. The current could be about 1000 amps, so a one inch diameter copper cable should be able to do the job. However where the lightning strike goes from air to copper it will be plasma temperture and will cause excessive heating at that spot. GB 21:56, 26 July 2007 (UTC)

Yeah, it's mostly just a matter of having enough metal in a lump. Big buildings get struck by lightning all the time without damage, as you see here and here and here. If the metal main structure got super-hot, it would set something on fire. --Anonymous, July 27, 00:34 (UTC).

July 26

Lettuce in the dishwasher

Why is it that when I don't completely rinse off all of the scraps of lettuce from a utensil, or plate, or anything, it won't come off in the dishwasher but will easily come off by just rinsing it under the sink? 68.231.151.161 02:10, 26 July 2007 (UTC)

In the sink, a very clever intelligence is controlling the washing action and the lettuce-loaded water goes down the drain. In the dishwasher, the lettuce-loaded water just goes round-and-round again, potentially redepositing the lettuce elsewhere. (The water does go through a built-in garbage grinder, but it may not handle 100% of the flow and the grinder may not be 100% effective.) Also, depending on how you load your dishwasher, there may be lots of "shadows" that aren't effectively washed by the water blasts, forming sorts of hydraulic Lagrangian points for food debris.

Atlant 16:00, 26 July 2007 (UTC)

Hah, nice one I like it =) --froth^t 02:16, 27 July 2007 (UTC)

Identify this insect

What kind of bug is this?

http://www.flickr.com/photo_zoom.gne?id=900187829&size=o

Foobody 02:33, 26 July 2007 (UTC) (edited to add sig)

Well, the image is somewhat blurry and small, but they look like wood lice to me (or, more generically, the woodlouse article). -- MarcoTolo 03:47, 26 July 2007 (UTC)

The skin beetles or Dermestidae. The picture is from german article - Gemeiner Speckkäfer.--Stone 12:32, 26 July 2007 (UTC)

Looks like a carpet bug sometimes known as 'wooly bears'?213.249.237.190 13:04, 26 July 2007 (UTC)

I agree with Stone that the "bugs" are probably the larvae of a Dermestid. They look like one of the species in the genus Anthrenus, commonly called Carpet Beetles. They can be serious problems in homes or museums because they can severely damage textiles and other organic substances. --Eriastrum 16:11, 26 July 2007 (UTC)

what percentage of bone is carbon?

Hi I'd love to be able to find out what percentage of bone is carbon ? I'm interested in calculating how much greenhouse gases are "fixed" into bone when farm animals grow. Cheers 61.9.137.86 05:41, 26 July 2007 (UTC)DaveBeggs

Farm animals don't get their carbon from greenhouse gases so "0". But water is the biggest greenhouse gas and animals are about 70% water I believe. --Tbeatty 06:26, 26 July 2007 (UTC)

Yeah um, animals get their carbon from food, not from air. Only plants fix carbon from the atmosphere. —Keenan Pepper 10:22, 26 July 2007 (UTC)

Cows get carbon from grass, grass gets carbon from the air - so although the cow doesn't fix carbon from the air, it does incorporate atmospheric carbon through the intermediary of grass. DuncanHill 10:45, 26 July 2007 (UTC)

The problem is that it's a zero sum game. When the animal dies, the bone's organic content is metabolised by bacteria, etc - only the calcium content remains. So burying bones isn't really locking away much (if any) carbon. I'm pretty sure that no useful dent in global warming could be made in this manner. Having animals eat carbon-laden plants then 'sequestering' the animal corpses is a lot worse than just sequestering the plants directly. Note particularly that animals produce methane as well as CO2 - and methane is an even nastier greenhouse gas than CO2. Having fewer domesticated animals in the first place would go some way reducing the greenhouse effect. SteveBaker 11:49, 26 July 2007 (UTC)

I remember seeing some little blurb in a NYT article, where some biologist calculated the net effect on global warming the increasing obesity in the United States was causing. By storing away carbon in the form of fat instead of burning it off as carbon dioxide, a continuously fattening populace actually slows the rate of temperature increase. Unfortunately, he calculated the effect to be on the order of billionths or trillionths of the total temperature change. We clearly aren't eating enough. 151.152.101.44 19:39, 26 July 2007 (UTC)

Cute. But of course the fatter we are, the more gasoline our cars use to haul us around -- and the more likely we are to drive rather than walk or bike. I'd expect that this effect outweighs the other one by quite a few orders of magnitude. --Trovatore 19:54, 26 July 2007 (UTC)

This claim that America's increasing waistlines were causing us to burn some outrageous amount of extra gasoline was in the press recently - the debate came up at work and I showed that it was utterly negligable. Filling your gas tank only half full and stopping off for gas twice as often will probably save you the weight of 10 gallons of gas (60lbs) on the average - nobody is telling us to do that! Toss out your 25lb spare wheel, carry a AAA card instead. Unbolt and remove the passenger seat when there's nobody sitting in it and you've saved another 25lbs. We don't consider doing these things because their effect is rather negligable compared (say) to driving a 1,300lb Mini instead of a 8,000lb SUV. 02:06, 27 July 2007 (UTC)

By the way, I notice that no one has even attempted to answer the literal original question. What percentage of bone is carbon? By the way, I doubt Steve's claim that the carbon in bone is metabolized by bacteria -- my guess is that it's in the form of calcium carbonate or some such, not counting the marrow as part of the bone, of course. --Trovatore 20:46, 26 July 2007 (UTC)

I'm working on it. It's surprisingly difficult to find! Flyguy649 ^talk _contribs 21:05, 26 July 2007 (UTC)

From this ref: Bones are 20% water, and 75% of the dry weight is organic matter, and while there is some carbonate in the inorganic, we'll ignore it. Proteins are ~45% carbon by mass. So roughly speaking, wet bone is 25% carbon. Flyguy649 ^talk _contribs 22:27, 26 July 2007 (UTC)

Bone is about 50% protein - mostly collagen. GB 22:28, 26 July 2007 (UTC)

Charge buildup through friction with air

Friction between materials can cause the build up of a charge (triboelectric effect), but are there materials that build up a charge when air (wind) rushes past them? DirkvdM 05:42, 26 July 2007 (UTC)

I suppose that's how thunderstorms are made. Bo Jacoby 06:59, 26 July 2007 (UTC).

You mean lightning, yeah, I thought about that too, but that seems to be a different effect (although it doesn't have to be the same effect). Anyway, I'm looking for a solid material, at least something one can build something out of, so to say. DirkvdM 07:48, 26 July 2007 (UTC)

What is your project? A wind-driven electrostatic power plant? That's a great idea. Bo Jacoby 08:01, 26 July 2007 (UTC).

Unless you happen to live downwind of the thing and are concerned about lightning damage! But one assumes the amount of energy you could extract this way would be small - so my concern is probably more theoretical than real. SteveBaker 11:41, 26 July 2007 (UTC)

I seem to remember some concern over using dust blowers on static sensitive circuitry due to the fact that the air got charged up, but I cant remember where I saw it. If the air got charged, then presumably an insulated nozzle would get charged the opposite way?--SpectrumAnalyser 12:46, 26 July 2007 (UTC)

I have a faint memory of reading in a book or seeing in a documentary about building skyscrapers that static electricity buildup is a problem due to wind blowing past the building and the electrical potential between the air at the top of the building and the air at the bottom of the building. It led to an experiment I tried - putting an antenna on top of a 13-floor building and another in the ground and measuring voltage/amperage between the two (connected by thickly insulated wiring. The amperage was negligible, but the voltage was measurable at only 13 floors. I wouldn't be surprised if it was much higher at 100 floors. -- Kainaw^(what?) 19:07, 26 July 2007 (UTC)

Well that's promising. A building isn't designed to build up a charge - it might even be designed not to. So if it already works there, then what if the building were coated in the right sort of material? Btw, I want a charge in the material, not in the air, but I suppose that comes down to the same thing. DirkvdM 19:14, 26 July 2007 (UTC)

SpectrumAnalyser, is or the air and the circuitry that creates the charge? Instinctively I'd say plastic sounds like a good material. DirkvdM 19:14, 26 July 2007 (UTC)

I presumed it the friction between the air and the nozzle that charges them both when I read the advice, but my memory is very vague --SpectrumAnalyser 22:55, 26 July 2007 (UTC)

Steve, why do you say the charge-buildup would be small? The surface of a windmill isn't too big, yet it can generate several MW. Imagine this stuff on the roof of a factory. That's quite a surface and would have a great potential for slowing down the wind, which is basically the source of wind-energy (and it would be right where a lot of energy is needed). DirkvdM 19:14, 26 July 2007 (UTC)

You are all making the common error of confusing voltage and current. Sure, you can build up enormous voltages - but you aren't extracting much power because it's just a static charge. Sure, you'll get an occasional impressive spark - but the total current flowing (and therefore the total energy extracted from the wind) is tiny compared to what a windmill could produce. Static-sensitive circuitry suffers horribly from a huge voltage - even if the current flow it tiny and brief - but you can't build useful powerstations that run on static electricity. SteveBaker 01:53, 27 July 2007 (UTC)

Wait a minute, Steve, I distinctly remember hearing about a guy who had a house powered by static electricity. To get the living room lights to go on, he'd shuffle his feet on the carpet. To operate his television, he'd pet his cat. In fact, I think his name was Steve. Oh, wait, it was Steven Wright. "Never mind." —Steve Summit (talk) 02:56, 27 July 2007 (UTC)

Sorry, but Wikipedia cannot offer advice on how to create machines to use in your diabolical plans to take over the world. Please consult with your doctor. Thanks. kmccoy (talk) 23:09, 26 July 2007 (UTC)

Glad you brought that up. I'm not asking for the design of infernal machines or such. :) I just want to know what material would build up a charge when air rushes past it. And I'm quite serious by the way. I really want to know this. DirkvdM 06:34, 27 July 2007 (UTC)

Iron ore

Why iron -ore deposits on hill tops occur only in sedimentary form ?

Most of the time sedimentary, but pyrite for example is not sedimentary but created by hot water transport.--Stone 13:01, 26 July 2007 (UTC)

We have quite a good article at Iron ore which discusses some of the different ores and their modes of formation. DuncanHill 16:47, 26 July 2007 (UTC)

Exotic or Negative Mass to reduce net mass?

Picture of the object

Assuming one could create and use exotic matter or negative mass, would it be possible to reduce the "net mass" of an object made of both mass and exotic mass (as shown in the picture)? If so, would that not mean that the net mass of an object could be reduced below that of a photon (or all together negate the effective mass of the object) so that higher-than-lightspeed-travel would be possible? --Demonesque 07:30, 26 July 2007 (UTC)

Yes, assuming the impossible, anything is possible. Bo Jacoby 07:55, 26 July 2007 (UTC).

Thanks, so very, very, extremely helpful. I realize that my question is speculative, since exotic matter itself is speculative, but what I am trying to find out is whether or not the two bodies would negate each other's mass as described or if it would be no different than two objects of different types of mass (or in other words, if the exotic mass would just be adding to the mass of the object.) --Demonesque 14:22, 26 July 2007 (UTC)

Seriously, the answer is yes or no depending entirely on the assumed properties of the exotic matter and how it interacts with normal matter. As we have no examples of exotic matter, we have no constraints. Hence you are free to assume it to be true if you want to. That said, I think it would be far less weird if exotic matter had a positive inertial mass and only a negative gravitational mass. My opinion on what is asthetically pleasing would exclude your scenario. Dragons flight 14:43, 26 July 2007 (UTC)

I'd agree, looking at the articles, only negative gravitational mass appears to have been postulated, negative inertial mass appears to be paradoxical in its very concept, that applying a force in one direction would provide acceleration in the other, I cant see how that could possibly fit in with conservation of energy and momentum. Philc 14:28, 27 July 2007 (UTC)

automobile steering

after an automobile initiates a turn ,its steering automatically aligns or comes back to its initial position even without our effort.how does this happen? 210.212.228.8 07:58, 26 July 2007 (UTC)

see caster angle. It is actually more complicated than that, but only at a level way more complex than wiki can stand. Greglocock 08:33, 26 July 2007 (UTC)

A couple of ways to do it.

Caster: First, by tilting the steering axis, it can be set up so that the contact point of the tire with the ground is actually behind the steering axis, rather than right on it as when the steering axis would be vertical through the centerline of the hub. Since there is some drag, the contact of tire with road will naturally attempt to place itself as far back from the steering axis as possible. (look at the steering axis of a bicycle for example; i.e., the headtube, the bearings right below the handlebars that the fork pivots in. They're not vertical, they're tilted so that the line through them hits the floor forward of where the tire hits the floor. The curve in the bicycle's forks that moves the wheel forward is to reduce the self straightening action of this. The further back the contact point is from the axis, the more "relaxed" the steering is, wanting to just stay straight. the closer the contact point is to the axis, the more twitchy the steering becomes. If the contact point is moved forward of the steering axis, the steering is unstable, it has to be constantly prevented from deviating from straight.). Same reason "casters" on furniture or suitcases or grocery carts get called that; in that case, the steering axis that the whole thing swivels on is vertical, but the whole wheel is offset so that the steering axis doesn't go through its center; when you push the cart or whatever, the wheels naturally lines up so that it's straight back from the steering axis.

That all works, as you may have noticed, on wheels that are not powered, i.e. not front wheel drive. You can imagine that if the wheel is pulling the car forward, the tendency for the wheel to be pulled straight back from the steering axis is reduced. So, another way to do it is having it set up so that when the wheel is turned, it raises that corner of the car up a tiny bit; the weight of the car will then tend to pull it down, and keep the wheels straight. Luckily, this is accomplished by... tilting the steering axis.

The other thing that is partially related is toe-in. The front wheels are sort of pigeon toed, i.e. the fronts are closer together than the rears. If you fiddle with that for a while, you see that if the car is turned in one direction, that makes one wheel run straighter, while the other wheel is more "crooked". This generates a force that tends to push the car back to where both wheels are equally crooked, in opposite directions. Again, this doesn't work for front wheel drive, where they are often toed out.

So, combining all these things to the proper amount depends on fwd vs rwd, the weight of the car, and a dozen other things. Gzuckier 19:35, 26 July 2007 (UTC)

Tilting Immersion blenders

While mixing some food with an immersion blender, I noticed that whenever the device was tilted and spinning, there was a powerful force trying to bring it back to vertical. I thought at first that it was some kind of gyroscope effect, as it only happened when the blades were spinning, but found that on further investigation, the blender tried to return to vertical even when started at an angle. Any ideas what could have been causing this effect? (If it helps, I was blending tinned tomatoes) Laïka 13:07, 26 July 2007 (UTC)

Does it do this when not placed in the food ? I'm thinking you have it at an angle, partly in the food and partly out, causing it to pull down in the food where you have contact, which would tend to make it go vertical. StuRat 15:17, 26 July 2007 (UTC)

It does only happen in the food, but the bowl is much deeper than the height of the blades; the tomato covers the whole apparatus even when at an angle. Laïka 15:42, 26 July 2007 (UTC)

Is it not just pressure differences? The spinning blades accelerate the food being blended so that it exits the blender through the slits in the side of the round head. This lowers the pressure in the round head, so the higher pressure in the rest of the bowl pushes the food into blades; at the same time, the lower pressure below the head compared to above means the head gets pushed down. People often think of this as the lower pressure 'pulling' the round head down and the food up into the blades. The head of the blender gets 'pulled' towards the position of vertically standing up on the bottom of the bowl; if you put it in that position, you'll find it hard to lift up as well as tilt. Thinking about it, I hope you can see that tilting the blender leads to it 'pulling' more strongly one way than the other; I hope you can see it, because I can't think of a good way to describe it over the internet! Skittle 21:05, 26 July 2007 (UTC)

That makes sense; I hadn't thought about the pressure differences caused by the blades. Thanks! Laïka 21:40, 26 July 2007 (UTC)

Nano tubes synthesis

Is it possible to synthesise nanotubes of CuS using dimethyl glyoxime as a capping agent?If yes what are the reagents to be used? Its a project requirement.

This is the first I hear of anything other than carbon nanotubes. anyway - Dr N S Xu of Zhongshan University grew copper sulfide nanowire by treating copper foil with hydrogen sulfide and oxygen mixture for 10 hours at room temperature. No solutions were involved.[22]. GB 11:42, 27 July 2007 (UTC)

Future of Key Boards

In the future, will the standard keyboard be replaced by another method of communicating?-— Preceding unsigned comment added by WonderFran (talk • contribs)

Probably, but the Reference desk, despite what you may have been told, hasn't had a working crystal ball since the TimeQuake of 2005. - CHAIRBOY (☎) 15:59, 26 July 2007 (UTC)

Although not terribly new (patented in 1936), there's the Dvorak Simplified Keyboard, which a lot of people are starting to use instead of the standard QWERTY keyboard. -- JSBillings 16:37, 26 July 2007 (UTC)

I've tried to use the Dvorak, but I've had difficulty finding a dumbed-down howto for getting the OS (Fedora in my case) to accept a Dvorak keyboard for input. -- Kainaw^(what?) 16:57, 26 July 2007 (UTC)

There's a line you can put in /etc/sysconfig/keyboard that'll tell it to use dvorak. I think it's something like KEYTABLE="dvorak" -- JSBillings 17:02, 26 July 2007 (UTC)

"A lot" is not that many people, no doubt less than 1% of computer markets worldwide (remember that OS X, which you can see in practically any coffee shop, is still only around 5% of the market share!). It's not going to become truly popular anytime soon, because its purported advantages are not enough to overcome the disadvantages of trying to change the input devices for an entire technology. --24.147.86.187 21:54, 26 July 2007 (UTC)

Ah, that's for a different reason. People take laptops to coffee shops to show off and be snooty- thus OS X --froth^t 02:14, 27 July 2007 (UTC)

This guy who had equipped his bicycle with pc hardware, satellite uplink, etc. way back when and roamed the US writing columns about it for a living had set up eight switches, four for the fingers on each hand, so that he could type while biking, in raw Ascii 8 bit digital. Now that is cool. Gzuckier 19:39, 26 July 2007 (UTC)

That sounds like a great way to have a biking accident... --24.147.86.187 21:54, 26 July 2007 (UTC)

The odds are the standard keyboard will not. It allows for precise input of written alphabetic languages at relatively high speeds (with practice, obviously). There is no serious competitor to this sort of functionality at the moment. Voice-to-text technology might increase its ability to replace it but I doubt it will ever be anything more than a supplementary technology — even assuming that it was made far more precise and generalizable than it currently is, strictly speaking you often don't want to have to speak to write things down. (If you think people talking on cell phones is annoying, imagine how it would be if everyone was dictating their e-mails!)

That being said, here are two futuristic speculations:

• What if alphabetic languages become economically less important? Imagine that a language like Chinese, which is not alphabetic, became a prerequisite for global commerce and communication? Keyboards are notoriously more difficult for non-alphabetic languages than for alphabetic ones, so I could imagine some other technology more suited to non-alphabetic languages becoming popular and supplanting the traditional keyboard.
• What if we had a way to directly receive signals from the brain and transfer them into writing? You could skip the hands altogether as a way of translating thought language into written language. Is this ever going to be possible? Probably — if the brain can tell the fingers how to use a keyboard, then there is likely going to be some way to intercept that same sort of set of instructions. The real question, as I see it, as to whether it would become a realistic and popular technology is whether or not it could do this easily and non-invasively — I don't think most people are going to want to have things embedded in their bodies just to take care of the chore of not typing (some no doubt would, though — aside from cyberpunk fetish geeks, I could imagine parapalegics, sufferers from repetitive strain injuries, etc. finding this sort of technology useful even if it is invasive). Anyway, advances towards this sort of thing are going pretty well at the moment, I believe, though anything rivaling the precision/speed of a keyboard is still some time off, I think.

Just some food for thought... --24.147.86.187 21:54, 26 July 2007 (UTC)

Speech is handy in niche markets - phone response systems, hands-off stuff in cars, that kinds of thing. The human voice has some advantages and some disadvantages - firstly, it works at a distance and it works around corners. It's a broadcast mechanism - one person talks and everyone in the room can hear. It's very error-prone (we mis-speak and mis-hear all the time) - but that doesn't matter too much in most conversation because the person you're talking to can generally ask questions to clarify. These are all great things in some sorts of situation - but they are nothing short of disasterous when interfacing to computers - every computer in the room might respond to your command to copy the file named "reformat" onto the disk - but then the computer you were actually talking to might hear this as a command to "reformat the disk". Humans know that eye contact contains information about who within a conversation is being addressed and who is merely listening in. Offices are annoyingly noisy places - speech input will make that vastly worse. You want to work on your computer while watching TV or listening to music? Dangerous! Who knows what some actor on TV is telling their computer and getting picked up on your microphone? It's notoriously difficult to do something as conveying your email address by voice - mine used to be sjbaker1@airmail.net (not anymore) - the number of times I had to tell people "no that's the digit '1', not the word 'one'" - and correct people who thought 'airmail' was 'air male' or something. Just try reading a C++ program source to people:

  #include <stdio.h>
  #define pythag_rule(x,y) sqrt((x)*(x)+(y)*(y))
  void main ( int argc, char **argv )
  {
    const char helloWorld[] = "Hello World.\n" ;

Reading a million lines of that stuff to the computer ACCURATELY - where a missing semicolon can take you a week to track down...I don't think so!

Keyboards are a pain - but there is very little sign of them ever going away. SteveBaker 01:43, 27 July 2007 (UTC)

There's a bit of a fallacy in your argument, though: "Today's computer languages all require utterly precise placement of semicolons and other punctuation, ergo keyboards will never go away for programming." —Steve Summit (talk) 02:34, 27 July 2007 (UTC)

Speaking of the computer-controlled-by-speech-on-the-TV issue, I once heard a (possibly apocryphal) story where a kids show host said "hey kids, hold your phone up to the TV if you want to talk to Krusty!", and they played the touch-tones of a 900 (pay) number on the air, which dialed all these kids' phones and made Krusty (or whoever) a bunch of money! --TotoBaggins 14:16, 27 July 2007 (UTC)

Salmonella odds

So I've always eaten raw eggs -- in mayonaises and various other things -- and I now work in a restaurant that keeps its raw egg mayonaisses and other possibly salmonella-risky things for up to a week. The restaurant's in Italy, so nobody cares. And I'm becoming convinced, because nobody cares, that my squeamishness about leaving raw eggs for a week in the fridge is ridiculous. The question I'm getting at is a) whether Salmonella is still so much of a risk as it was, say ten years ago, and b) whether the eggs I and the restaurant use -- organic eggs that have never seen one of those gigantic chicken coups they show in vegetarian horror propaganda movies -- have any risk at all for salmonella. Oh. And also, what is the risk even for mass-produced eggs? If I were, say, to eat a raw egg every day for a year, is it at all likely that I'd get Salmonella? And what are the odds of Salmonella, if I do get it, causing any sort of permanent damage or death? I did look at the Salmanellosis or whatever article, but it was kind of vague where I was concerned. Thanks, Sasha — Preceding unsigned comment added by 151.28.233.89 (talk • contribs)

I can't vouch for Italy, but in the UK, all poultry is vaccinated against Salmonella (see Egg (food)#Edwina Currie, Salmonella and the UK Lion Mark); indeed a random test of 28,000 eggs, a grand total of 0 eggs had Salmonella. Laïka 21:38, 26 July 2007 (UTC)

The CDC says there are 1.4 million cases of salmonella in the USA each year. Presumably some non-trivial percentage of that is from eating raw eggs, so I'd say at least in this country it's a not-insubstantial risk. Italy is probably similar. --TotoBaggins 14:18, 27 July 2007 (UTC)

aids

can someone get effected by aids through licking? — Preceding unsigned comment added by 217.69.178.16 (talk • contribs) 21:44, 26 July 2007 (UTC)

Wikipedia cannot dispense medical advice. Please consult a doctor if you have a question. For purely informational purposes, you should read the article about AIDS -- JSBillings

Licking what? Skin, genitals, an open wound? --24.147.86.187 21:56, 26 July 2007 (UTC)

Deer? Capuchin 07:57, 27 July 2007 (UTC)

July 27

random number generation by the human mind

How does the mind do it? And have there any been any experiments to see just how non random they are? When I rattle off a few they tend to end in a multiple of 3 and they're all decimal numbers from 10-99.. --froth^t 01:51, 27 July 2007 (UTC)

Not exactly a study, but I do know that what humans think of as random often doesn't match with something that's actually random - for example, I recall reading about a professor (of statistics, I assume) who got his class to write down a "random" string of fifty coin tosses either by making it up or by actually flipping the coins, and he could tell which was which by the fact that the real ones often had long strings of either heads or tails (say 5 or 6 in a row), whereas the made-up ones didn't, because we don't think a string of HHHHH in the midst of fifty trials appears "random". Confusing Manifestation 02:23, 27 July 2007 (UTC)

I concur with Confusing Manifestation.

I suspect that humans are less likely to pick "special" numbers, so the digits 0, 1, 5 and 9 might be underrepresented. Your own experience tends to show this: you tend not to pick 0 as the first digit of a two digit number.

There is a parler trick where one is asked to pick a number from 1 to 50, with the conditions that both digits are odd and they are not the same. Then they are told "your number is 37." It works surprisingly frequently. But I think I understand why: only 8 numbers pass both conditions: 13, 15, 17, 19, 31, 35, 37 and 39. The only one that does not contain a "special" digit is 37.

I do not have a reference to the psychology, but David Blaine performed the trick live on his TV show Street Magic. Baccyak4H (Yak!) 03:04, 27 July 2007 (UTC)

You might be interested in W.A. Wagenaar,Template:PDFlink, Psychological Bulletin 1972, Vol. 77, No. 1, 65-72. Rockpocket 07:12, 27 July 2007 (UTC)

If you know that you aren't going to manage to produce a series of random heads and tails, is there any easy "mechanism" one could apply mentally to make your results random? One thought that occurred to me is to use odd/even distance between vowels in some text to determine change/repeat. Thus "And dId thOsE fEEt In AncIEnt tImEs" generates 44221223142 which might be HHHHTTTHTTT. ? -- SGBailey 13:35, 27 July 2007 (UTC)

When I am asked for just one digit, I wait a few seconds, then look at the second hand of my watch, modulo whatever appropriate number to get the right range. While this is hard to generalize to more than one digit (in a short length of time), it does avoid any artifacts caused by nonuniformity and nonindependence of letter distributions in the English language. You win some, you lose some...Baccyak4H (Yak!) 13:45, 27 July 2007 (UTC)

Well, if you're allowed to use some text, why not RAND's compelling 1955 magnum opus "A Million Random Digits with 100,000 Normal Deviates"? --TotoBaggins 14:26, 27 July 2007 (UTC)

Using the ground for a ground

Surely there are more ideal electical grounds than just running a pipe into the dirt.. do laboratories and things use big water pools or hunks of metal or something to take care of dangerous electrical potentials? --froth^t 02:19, 27 July 2007 (UTC)

As far as I know, and unless the ground is dry, a nice hunk of metal (doesn't have to be a pipe, but doesn't have to be anything too elaborate) gives you as good a ground as you're going to get. (And stop calling me Shirley.) —Steve Summit (talk) 02:31, 27 July 2007 (UTC)

For modern buildings, see Ufer Ground.

Individual Timeline

My understanding of general relativity is that an object moving at near the speed of light in relation to a stationary object, would return to find that his native environment has far exceded his own. My question is what defines "near" the speed of light? Assuming my understanding is correct; wouldn't a fixed individual observing another individual simply walking away, or some other commonly exercised speed, differentiate the individual timelines of the two people? So therefore, isn't every individual living in their own personal space/time?
75.134.4.229 04:04, 27 July 2007 (UTC)Alan

This question is coming up on a near-daily basis and I would like to correct one misconception right away. While the "two twins" example refers to one twin traveling at high speed, general relativity refers to high energy and low energy objects. Traveling at high speed is merely one concept of a high energy object. So, "near the speed of light" means that the object contains more energy than mass. "At the speed of light" means that the object is all energy (no mass). Absolute zero (a complete state of rest) means that the object contains all mass (no energy).

As for time-lines, they do not exist. Time is merely a dimension. I can walk down the street. You can run. It doesn't mean we have our own individual streets. We just walked down the same street at different speeds. The concept of time-lines (aka world-lines) is used in science-fiction to do magic and make impossible things possible. -- Kainaw^(what?) 04:12, 27 July 2007 (UTC)

I don't know about your background, but worldlines were used in my graduate general relativity course to describe the motion of relativistic particles. Dragons flight 04:29, 27 July 2007 (UTC)

Note - you are not using the science-fiction version of world-lines. You do not use a concept that every particle exists in an infinite array of worlds and infinite number of times. While the names are the same, the concepts have nothing in common. I read the question as asking if each person on earth has their own little pocket of time that they carry around with them. I have my little version of time. You have yours. You can't see mine. I can't see yours. There is nothing in common between the two. That is why I thought of the science-fiction version of time and space. -- Kainaw^(what?) 05:11, 27 July 2007 (UTC)

Most relativistic corrections are proportional to something like $\beta -1$, where $\beta ={1 \over {\sqrt {1-{v^{2} \over c^{2}}}}}$, so relativistic effects become important when $\beta$ becomes larger than 1 to whatever degree of precision one cares about measuring. And yes, everyone has a slightly different experience of time, but the difference is miniscule for everyday speeds. Dragons flight 04:29, 27 July 2007 (UTC)

World lines only do impossible things if you decide to ignore the laws of physics. And to say a complete state of rest equates no energy, it would be more proper to say "no kinetic energy" (provided you're ignoring thermal and other fluctuations, but these would mainly apply to individual particles). "No energy" is also a meaningless concept. Everything has energy, always. There are many kinds of energy besides that of motion, and even vacuum has energy. Also, saying no mass at the speed of light, you must specify that you mean "no rest mass" (ie, if you were to slow the object down below the speed of light, it would have no mass, related to why it can't slow down). Someguy1221 05:00, 27 July 2007 (UTC)

As I stated above, I was referring to the science-fiction use of timelines, which are often called world-lines. I was not referring to the scientific term "worldline". As for "no energy" - it is, in my opinion, easiest to explain to a person who is grappling with the basic concepts of the theory of relativity that anything traveling at the speed of light is all energy and anything at absolute zero is no energy. If they take an interest in the topic, they can later work on determining the mass of a photon or the energy of an absolute-zero particle. Basically, I do not find it helpful to throw equations and complicated details at a newcomer to scare them away from the topic. -- Kainaw^(what?) 05:22, 27 July 2007 (UTC)

Theory Of relativity

Friends, Can any one explain the Theory Of Relativity in the most simplest way, B'cos any article I Read looks too complicated ??? Thank u.

You might be interested in this. Someguy1221 05:12, 27 July 2007 (UTC)

or this --Philc 14:18, 27 July 2007 (UTC)

Sea water

Why is Sea Water Salty, While rivers and Ground Water are perfect and have no Saline Charecterestics ??

Rivers are fed by rain and melting snow - which is mostly water. As it flows out to the ocean, it will pick up sediment, minerals, salts, and all. But, it will remain mostly water. The oceans are full of salt (have been for a very long time). It comes from the animals/plants living in it and the salts coming in from the rivers. Mostly, the salt just stays there. You can look at trapped salt lakes which were once parts of the ocean. Many years have gone by and the salt is still just sitting in the lake. -- Kainaw^(what?) 05:26, 27 July 2007 (UTC)

Agreed. Rivers with a tiny amount of salt flow into oceans, where the water then evaporates and leaves the salt. Over time, the salt content thus builds up in oceans and "dead seas", until it reaches the point where it precipitates out as salt beds and formations. Note that oceans and terminal lakes are also higher in many other dissolved minerals, for the same reason. StuRat 06:57, 27 July 2007 (UTC)

Is there any way to stop my budgerigar 'pleasuring himself'?

This sounds like a silly question and it's embarassing but I swear that I'm not making this up. I have an 14 month old male budgerigar who has recently started to masturbate using various objects in his cage. He'll hook his rear end under his perch, swing or ladder and hump away until he gets himself off. He's doing it several times a day now.

Is there any way to stop him or put him off from doing this?

Buy a female budgerigar and a bigger cage. ugen64 06:34, 27 July 2007 (UTC)

Looking after baby budgies is a big, big responsibility. I'm not ready to breed him yet. --81.76.8.159 07:01, 27 July 2007 (UTC)

On the bright side, the behaviour is probably seasonal; it's "high season" now in the Northern Hemisphere, but it will pass.

Atlant 12:30, 27 July 2007 (UTC)

Buy a webcam and make a little seed money. --TotoBaggins 14:29, 27 July 2007 (UTC)

FTL

I don't understand why FTL travel implies time travel. Okay, it's fairly obvious that physically moving through space at a faster velocity than light is a scientifically meaningless notion. And clearly, any journey you make into your own past light cone results in a causality violation (which is what I understand as time travel). But what if I just instantly blip from here to Mars - specifically, a version of Mars which is currently "elsewhere", neither in my past nor future light cone? I can see why this would result in apparent time travel from the point of view of, say, an observer on Mars, who would see me arrive there before she the light of my departure from Earth reached her. But I don't see that apparent time travel is a contradiction and I don't see how a causality violation would arise. -- SamSim 09:26, 27 July 2007 (UTC)

But in some other reference frames, you will appear to have arrived before you left, according to special relativity. --Spoon! 13:30, 27 July 2007 (UTC)

Which is not a logical contradiction, just a possibly surprising result, like the twin paradox. You can add FTL travel to special relativity without contradiction. What you can't do is have a notion of FTL cause and effect (sending and receiving) which doesn't break Lorentz invariance. It should be easy to see why: you can always construct a trip of two consecutive FTL jumps which take you into the past light cone of your starting point. Nobody really understands the thermodynamic arrow of time, so it's not entirely clear what's really going on here. -- BenRG 14:24, 27 July 2007 (UTC)

primitive Weighing scale ?

What is the most primitive or rudimentary type of scale that a pre-metal or stone age society could invent? Something portable and easy to make from raw materials found in nature, but not metals. Maybe not so accurate, but better than nothing. For weighing herbs or drugs, not for entire humans. Maybe something using sand or a liquid?--Sonjaaa 11:07, 27 July 2007 (UTC)

The traditional scales is a wooden rod with a weight suspended at one end and held up by a string in the middle. At the other end is suspended the material that you want to weigh. The supporting string can be moved around against various marks to get a read out of different weights. This could have been made in the stone age, but probably wasn't. It seems that there is no picture of it in the weighing scales article! GB 11:29, 27 July 2007 (UTC)

Commons (http://commons.wikimedia.org/wiki/Weighing_scale) has a bunch of pictures (although the one I was really hoping for, with a witch on one end and a duck on the other, wasn't there).

Atlant 12:34, 27 July 2007 (UTC)

Hahah, I get it! Capuchin 12:38, 27 July 2007 (UTC)

PINE TREE

HOW MUCH WATER DOES A PINE TREE TAKE UP FROM THE GROUND? Jamec IT LOOKS LIKE WHEREVER PINE TREE IS PLANTED, THE SOILS BECOME TOO DRY, E.G IN AUSTRALIA THE PLACE IS GETTING DRIER, IN S.AFRICA THEY STARTED UPROOTING IT AFTER KNOWING ITS BAD EFFECTS, ARE THE COUNTRIES PLANTING IT SAFE IN THE NEAR FUTURE OR THEY ARE ABOUT TO FACE CLIMATE CHANGE?

It depends on the type of pine, size and environment of the tree. -- SGBailey 13:23, 27 July 2007 (UTC)

Solid bloodveins

Hey

I was wondering, why does some people, especially men have very visible and "strong" bloodveins that is visible through the skin over the biceps, and down over the underarms and at the backside of their hands?

I see that especially those who train and exercise alot tends to have this, while many other people again do NOT have visible bloodveins at all... I was thinking maybe it is because those people with "strong" and visible bloodveins have more oxygen in their blood - and it has always been said that it is a sign of good health a strong body. Something which to me sounds correct as I have learned that the more oxygen our blood are capable of taking in the better, for those with much oxygen in their blood often have good stamina and constitution and are stronger in sports/physical activities. And then it makes sense i guess that these things will improve by exercising, running or training in various ways that will improve our fitness and form. But we also see this often at older people that they have much visible bloodveins as well, so I don't know...

So, what is the reason for those strong visible bloodveins that some of us have? Is it indeed because we have more oxygen in our blood than some other people? I know that both things are normal, I'm just curious what is the reason, what makes it so? and does strong solid and visible bloodveins mean anything, like that we have good bloodcirculation or something?

Thank you, Krikkert

Krikkert7 14:08, 27 July 2007 (UTC)