Wikipedia:Reference desk/Archives/Science/2007 June 5

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June 5

Binary Planets

How do I figure out the relative masses and distances it would take for two planets to both:

1) Orbit each other with the barycenter outside of the larger, making them a binary planet system instead of a planet and a moon?

2) Orbit each other without spinning off to become separate planets, and without colliding?

If it matters, the small one also needs to be tidally locked to the big one. --67.110.213.253 03:20, 5 June 2007 (UTC)

For Part 1, you need to calculated the center of mass of the system, and determine if it is located inside or outside the larger mass. (The linked article has a formula for calculating the barycenter of a two-body system.) TenOfAllTrades(talk) 03:38, 5 June 2007 (UTC)

For 2): See Hill sphere. Icek 08:28, 5 June 2007 (UTC)

Questions about wasps

I have some problems with a wasp (north-european kind) in my apartment.

1) How long will it live, if it doesn't have access to food?

2) Does it eat anything which is likely in my apartment? Ie, should I assume that it will find food?

3) What are some of the best ways to get rid of wasps, assuming you are absolutely chickenshit around them?

Thanks an endless bunch. 213.161.190.228 05:14, 5 June 2007 (UTC)

Question 1 - see question 2. Question 2: it will always find food. Adult wasps can eat most human foods, cooked or raw. Larvae in nests need high-protein food (chewed-up insects by default, but any meat product seems to do just fine as long as the adult wasp has chewed on it for some time). Question 3 - do you have one wasp or a nest?! For one wasp - open the window :). For a nest, call pest control. And, BTW, there are several "north-european kinds". Try German wasp, Common wasp, European paper wasp, European hornet for the common ones. Cheers, Dr_Dima.

Question 3: For a single wasp (or a small number of them), and manageable level of chickenshit-ness:

1. Find a drinking glass or empty glass jar.
2. Find a piece of cardboard large enough to cover the glass.
3. Wait until the wasp is sitting still on some reachable, flat surface like a wall.
4. Slowly place the glass over the wasp.
5. Slide cardboard under the glass.
6. Carry glass+cardboard+wasp as a unit outdoors or to an open window.
7. Swing the glass with a throwing motion and simultaneously remove the cardboard, to fling the wasp far away.

--mglg_(talk) 17:17, 5 June 2007 (UTC)

Some additional points:

• You want the vessel you use to be large enough for it to be easy to bring down over the insect, but lightweight. A plastic wastebasket might be more convenient than a glass.
• It may be easier to slide the vessel over the cardboard than the cardboard under the vessel.
• You can reduce the fear level by wearing a heavy coat, gloves, hood, etc. while doing this. You know it can't hurt you if it can't get close to your skin.

I once had a single wasp come inside my house at night, and settle on a place where the above tactics would not work. Below is a slightly edited copy of the email I sent to some friends at the time: it's longer than the usual RD posting, but it is on-topic.

Click "show" to read the long anecdote
The following discussion has been closed. Please do not modify it.
(Begin anecdote) So about an hour ago I opened the front door to put out the gray-box recycling, and I noticed that our new "neighborhood Yellow Pages" booklet had been delivered. I was taking down the old booklet, intending to add it to the gray box, when something flew by my ear with a loud buzzing sound. I looked around and there was a large insect circling around the dining-table area -- and it appeared to be black and yellow. I quickly turned the kitchen lights off, and then other lights until the only ones shining inside the house were the front lights in the living room. Both front and rear lights were on outside, as I had been about to take out the recycling through both doors. Within half a minute the wasp had done the expected thing and was circling around one of the remaining lights, and I could see clearly that it was a wasp -- a big one, body length close to 3/4 inch. After a while it got bored with this and landed on the vertical blinds near the light. But what it didn't do was go anywhere near the front door. I temporized by moving the gray box to the back door so I could take it out that way if I got the wasp to go out the front, and adding the old booklet to it. The wasp temporized by doing nothing. Now what? (Did I mention that I'm kind of terrified of wasps and such?) (Did I mention that my wife was upstairs sleeping through all this, accopanied by both cats?) I have a can of spray insecticide that I got when we were having trouble with ants this summer, but it comes with so many cautions I've never dared use it inside the house (for the ants I sprayed the front and back door sills), and I don't know how quick its action is if sprayed directly on an insect anyway. I could try killing it by swatting with a newspaper or something, and I'd probably have a good chance, but it was flying around pretty fast and I might miss, in which case I'd be setting myself up for a sting for sure. And besides, it would have to be on a hard surface -- the vertical blinds wouldn't do! I have on occasion attacked insects by spraying them with water or alcohol, whatever was handy in a spray bottle, to impair their flying ability before moving in for the swat. But this one was moving so fast that I wasn't confident enough of slowing it down enough before being stung. I could try trapping it in a wastebasket -- conveniently, I had several at hand that I'd just emptied -- but again, not on the vertical blinds. And if it went to the ceiling, it'd be hard to catch it as well, because the living-room ceiling is fairly high. Once again I might expect to be stung. I could try "herding" it with something like a magazine or a newspaper section. That might work if it was only a little way from the front door, but it wasn't; it was at least 6 feet away. I couldn't see myself herding it that far without you-know-what. Opening the front window and taking the flyscreen off was right out -- I'd first have to open the vertical blinds. Hmm. While I was thinking I put the coat I'd been wearing today back on, and my gloves. Then I put a chair by the front door and set a flashlight on it, switched on, so that it was pointing diagonally up along the plane of the vertical blinds directly at the wasp. I wasn't sure if it would respond to a bright light shining from below, but there wasn't any way to stand the flashlight at a high level in the right place. (Did I mention that I'm kind of terrified of wasps and such?) I switched off the last remaining ordinary lights inside the house, stepped back to a safe distance, and hoped to see the wasp fly to the flashlight. If it did, I would quickly open the door and so expose it to the bright porch light, which presumably is what had attracted it to the front door area in the first place. It didn't take off. I waited, keeping my eyes almost constantly on the wasp in case it flew outside of the flashlight beam and I lost track of it. I kept my hand near a light switch in case I had to find it again. And waited. The wasp had apparently reacted to the darkness by going to sleep! I mentally reviewed my other options, but nothing new emerged, so I continued to watch and wait. (Did I mention that I'm kind of terrified of wasps and such?) After about 5 minutes, the wasp slowly began to move -- it turned toward the flashlight and started walking toward it! It would have to traverse about 20 slats of the vertical blinds, one by one, moving diagonally downward all the time, if it was willing to do that. In fact it covered about 12 slats and then stopped and started moving up the slat. I realized that while the flashlight might have been a target as well, it had also been following the lighted area where the beam was playing on the blinds. But as it got closer to the light, it got to the narrower part of the cone of light, and the blinds were no longer illuminated. I could see nothing else to do. I stepped forward, picked up the flashlight, and shone it on the blinds to the right of the wasp, holding the light itself farther to the right -- and since I was holding it, I could shine it horizontally, not diagonally requiring the insect to move downward. And sure enough, this worked. The wasp turned back to the right and continued its slow walk. At least I was less afraid of it now -- apparently the darkness really had made it sleepy, or slow and cautious, or something. It wasn't making any sudden moves any more. My method worked until it reached the last slat, when I hoped to just open the door and watch it fly outside. I tried opening the door, but it appeared not to notice the lighted area -- as if it was outside its field of view. Instead, it just moved around on the slat -- and whatever I did, now it insisted on going upward. I tried taking the slat it was on and twisting it so the wasp could see the door better, but it was the wrong direction and it wouldn't move far enough. For a while the wasp stayed around the top of the blinds, just inches from the door but out of sight of it around the corner. Once or twice it even went into the vertical-blind drive track. It never took off, just kept moving at a crawl. Finally by use of the flashlight I managed to get it to come out and down again. Then I pushed the slat up against the wall, and by careful placement of the flashlight got the wasp to move onto the convex angle where the window wall meets the door wall. I now opened the door again, but the insect still didn't move toward it. I tried various things. Finally I decided that since it was usually responding to the flashlight, I would turn off the outside light as well, and use only the flashlight until I had the thing closer to the door. This was starting to work -- and then the wasp suddenly moved fast. Since I was now quite close to it, this caused the other thing I was afraid of to happen -- I lost track of where it went. I quickly snapped the inside light back on, then a couple of seconds later realized that I'd hit the wrong switch, turned it off again, and turned the outside light back on. Surely this was too quick for the wasp to react. But where had it gone? I couldn't see it outside, but I couldn't see it inside either, anywhere near where it had been. And it clearly wasn't going to move into the dark parts of the room. Had it, then, gone outside and flown away? I decided to close the door, and as I did, I glanced down at the floor where it was about to sweep across. Good thing I did -- there was the wasp! It must have fallen from the wall, too sleepy to fly right, and that was the sudden move. In retrospect I think I could have safely killed it at this point by just stepping on it, but I stayed with the original plan. I picked up a magazine and simply herded the wasp the last few inches to the door sill and out. And slammed the door. WHEE-EW! (End anecdote)

--Anonymous, June 5, 22:50 (UTC).

Exclusion principle and electrons in atoms

I may have misunderstood bits of it, but Pauli says that a system (an atom) must have half-integers that cancel one another out. What if there are three electrons, two of opposite spin to one another, and a third which has its very own kind of value? Am I to understand that the concept of zero wave function as something which is localized to only two half-integers? Otherwise the third electron would mess a bit with that. Is the wave function (and it being zero or not) directly related to how stable an atom (or electron within it) is? I'm thinking about how atoms with odd numbers of electrons seem less stable than those with pairs. Thanks for any clearing up. 213.161.190.228 05:43, 5 June 2007 (UTC)

you seem to be confused about the physical meaning of eigenvalues, or more generally of the quantum numbers characterising spatial and spin part of a single-electron wavefuncton, for an electron in an atom. Is this because of the wasp that was bothering you in the previous question ;) ? I would guess the "half-integer" you are talking about is spin (it could be total angular momentum, too, or its projection; but forget about that for a moment). There is a spin eigenvalue s which is always 1/2 for an electron, and spin projection eigenvalue s_z which can be either plus 1/2 or minus 1/2. For spatial part, there is a principal quantum number n, angular orbital quantum number l, and its projection l_z. Pauli principle says that switching any two electrons must change the sign of the total wavefunction; if the two electrons were to occupy the same state, the total wavefunction would be equal to minus itself, and thus be identically zero everywhere. Hence, two electrons can not occupy the same state. Could you please rephrase your question in these terms? Cheers, Dr_Dima.

It's a little bit like the game of Set: no two electrons can be the same in every way, but they have several independent properties to think about. Just like set cards have color, hatching, number, and shape. Electrons have "quantum numbers" n, l, m, s. The n, l, and m are the "spatial part" of the wave function, as Dr Dima described, and the s is the "spin part," which is totally independent and can be ±½. If you have two electrons, they can both have the same lowest-energy value of n, l, and m, with s=+½ and s=-½. As you add more, they have to have higher n and higher energy to satisfy the principle that each one has to be different from all the others in at least one respect. --Reuben 06:44, 5 June 2007 (UTC)

For electrons, spin is only one of four properties. Only when all four are the same does the Pauli exclusion principle apply (i.e. they can;t iccupy the same space). Also see Fermions and Leptons and Bosons--Tbeatty 06:55, 5 June 2007 (UTC)

That's exactly why I mentioned the game of Set: four properties, and no pair of cards can share all four. --Reuben 17:25, 5 June 2007 (UTC)

Greenland map, no ice

Like 5 or 6 years ago, in my oceanography class in high school, my teacher had on the wall a map showing greenland under its ice sheet, as well as naming all the sea floor expanses and trenches around it. Not a 'if the ice melts and sea levels rise' map, but just, it lifted off, photo snapped map. The image was spectacular, Greenland looked like a giant backward 'C' with a huge bay in the middle. I want to try to find an image of that map, or any one done the same way (no ice on top, just the land under the ice). After months of on and off Google image searches for awkward combinations of greenland, no ice and map, I decided to give my fellow editors a shot. Anyone able to find such an image? The map in the classroom was published by the Navy Press or something similar out of Annapolis, Maryland, but im not hung up on that particular map so long as it is the same style. -M^ask? 06:07, 5 June 2007 (UTC)

Something like this? Try a Google image search for Greenland subglacial topographic map and variations thereof. Maelin (Talk | Contribs) 09:30, 5 June 2007 (UTC)

Exactly! Thank you, I'll do my own poking with the new terms looking for a more detailed image. Thanks a bunch! -M^ask? 16:35, 5 June 2007 (UTC)

Earth's hot core.

Why is the core of the Earth so hot? Is it just a pressure thing? Chemical reactions? 213.48.15.234 07:06, 5 June 2007 (UTC)

Great question! There is a short section addressing it in Structure of the Earth. My understanding is that radioactive decay of unstable elements, along with pressure due to gravity keep the Earth's interior heated. --TeaDrinker 07:12, 5 June 2007 (UTC)

Constant pressure does not create heat. It's thought to be mainly radioactive decay. Icek 08:32, 5 June 2007 (UTC)

Very interesting, thanks. It's amazing how little we know about the termperature and its causes, and the material of the core. 213.48.15.234 09:10, 5 June 2007 (UTC)

Radioactivity (along with crystalization of the inner core and primordial heat of formation) provide the energy, but the main reason it is hot is because it is surrounded by thousands of kilometers of poorly conducting rock. The energy sources involved are actually quite puny (much much weaker than sunlight, for example), but because the rock is a poor conductor the heat accumulates. It's like wrapping yourself in many thick blankets. The blankets don't generate heat, but they trap the heat you do generate and cause temperatures to rise. For the Earth, the end result is temperatures in the core that are similar to temperatures at the surface of the sun. Dragons flight 09:20, 5 June 2007 (UTC)

Thanks, I had realised this, my first reaction was "wow, that much heat from radioactive decay?!", but then realised that the energy doesnt really have anywhere to go. (I'm a physicist by training). Does this mean that a few billion years ago the core was significantly cooler? Is it still getting hotter? Or has it reached the equilibrium point and is slowly cooling as the radioactive sources get less active? 213.48.15.234 09:38, 5 June 2007 (UTC)

No, we are cooling, just very slowly because of all that rock. Radioactivity and the latent heat of crystalization of the inner core slow the process, and arguably there is still a component of primordial heat of formation (though not everyone agrees on that). Primordial heat and radioactivity both diminsh with time. At the present time, the growth of the inner core provides a thermal buffer, but eventually the entire core will solidify. This is believed to have already happened on smaller bodies, like Mars. For the sake of scale, the Earth currently dissipates about 40 terawatts of geothermal energy to the surface (where it eventually radiates into space). Dragons flight 10:12, 5 June 2007 (UTC)

You can have one too: *. 213.48.15.234 10:18, 5 June 2007 (UTC)

That is an excellent question indeed, and one that was discussed in depth by the leading scientists after the Stefan-Boltzmann law discovery but before the extent of Potassium-40 and heavy element radioactive decay in the core became apparent. Indeed, people know for nearly 100 years now that Earth radiates more heat into space than it receives from the Sun; too much to be explained by the thermal energy reserve left over since the Earth formed and compressed. So the answer to your question is no, it is not just pressure (that was most important while the Earth was forming and compressing rapidly), and it is not chemical reactions. It is mostly radioactive decay, as TeaDrinker and Icek told you already; plus a minor contribution from tides, converted to heat by viscosity and friction. BTW, research into exact heat balance of the core is still very much ongoing, there are new findings being published rather regularly on the science news sites. Cheers, Dr_Dima.

The answer to your second question (regarding the equilibrium or, strictly speaking, the steady state) is not really known, since the core temperature can not be directly and precisely measured. The leftover heat is slowly dissipating, and radioactive material quantity in the core is slowly dwindling; so there is a consensus saying that eventually, in billions of years, the core will cool down and solidify completely. (Actually, the Sun will probably become a red giant and engulf the Earth sooner than that). But I do not know of any reliable measurement or simulation of recent history of core tempeartures. I would expect the temperature to fluctuate slightly, on the same time scales as the Earth magnetic field; but to decrease on the largest time-scale. Dr_Dima.

That verfies what I was thinking about it too. Thank you for this discussion. Have a text-barnstar. Because I can't work out how to do barnstar stuffs: *. 213.48.15.234 10:03, 5 June 2007 (UTC)

You are welcome! Thanks, Dr_Dima.

I wonder (without much evidence) whether tidal friction due to the moon and friction due to coriolis effects in the spinning liquid core have a measurable effect too. Some of the moons of Jupiter are heated by tidal friction that way (although the effect is likely to be much bigger when Jupiter is doing the pulling compared to the moon!) (Ooohhh - Jupiter made the Wikipedia front page today! Well done all you Jovian editors out there!) SteveBaker 20:18, 6 June 2007 (UTC)

Ping times towards a destination in Africa

When experimenting with "ping" towards a destination in Africa, I saw a 450 ms delay between two routers (adding to the overall round-trip-time). The obvious hypothesis is a satellite link. A geostationary orbit is about 36000 km above the equator; thus a ballpark estimate for round-trip time of radio signals is 240 ms 480 ms if I could total RTT (I'm a fool). Of course, the stations are not exactly on the equator, so it is normal that it should take longer, but it does not explain such a large increase. Is the difference due to error-correcting codes, error correction protocols or similar? (I know error correction explains the latency on ADSL lines.) David.Monniaux 08:46, 5 June 2007 (UTC)

Is the 450ms one-way or return? --antilived^{T | C | G} 10:24, 5 June 2007 (UTC)

Yes, how did you get the $450\,\mathrm {ms}$ number? —Bromskloss 10:32, 5 June 2007 (UTC)

Most round-trip ping times are nowhere near the speed-of-light transit times. Most of the time elapsed has nothing to do with the amount of time the bits are actually moving from place to place. Instead, longer ping times result from the time required for your data to queue up and be transmitted from one server to another, and on how rapidly the final destination server responds to your request.

The ping time to my local ISP is about 10 ms, but that shouldn't be interpreted to mean that my ISP's office is 3000 km away. Incidentally, it is my understanding that the bulk of transoceanic data now travels via submarine fiber optic cables; satellite links don't have nearly the capacity of optical fiber. TenOfAllTrades(talk) 13:48, 5 June 2007 (UTC)

Er... I get 1ms ping times or so when I'm at work, because we have an optic fiber connection to the backbone. I get ping times of several dozen ms to my ISP because the ADSL box has big internal queues, which are necessary for error correction (my ISP offers the possibility of "fast path" ADSL, which reduced latency / ping times, for people who have a good and short phone line and thus do not need complex error correction.

You are correct in stating that most intercontinental traffic goes through fiber optic cables. However, they yield much shorter ping times, which are in my experience nearly consistent with the speed of light in optic fiber (300000km/s over the optical index, which is around 1.5). David.Monniaux 19:37, 5 June 2007 (UTC)

Satellite links also have much longer round-trip delays than do submarine cables, owing to the unavoidable speed-of-light problem travelling 22,000 miles up then 22,000 miles down, then back 'round again. That's about 470 ms of delay, minimum.

Atlant 15:59, 5 June 2007 (UTC)

Bear in mind that there are often silent routers and the like. Also, it's easily possible the link is satured. Nil Einne 17:23, 5 June 2007 (UTC)

For a geostationary satellite, the minimum one-way delay is 238ms, where both hub and remote are directly under the satellite. The maximum one-way delay is about 280ms (where the satellite is on the horizon from both hub and remote.) Thus, the minimum round-trip delay with a satellite link is 476ms. the maximum can be any number greater than this based on the terrestrial part of the path. Since your delay is less than 476ms, you are not using a satellite round-trip. It is possible that you are using a satellite downstream with a terrestrial upstream. -Arch dude 18:31, 5 June 2007 (UTC)

Argh! I'm a fool! I did 2*36000/300000 instead of 4*36000/300000, which gives .480 and is fully consistent. Silly idea: round-trip-time includes 4, not 2, trips and from the satellite... The "about 450" was a difference between ping times and is thus not very precise, it's most probably more. David.Monniaux 19:37, 5 June 2007 (UTC)

arunbrainy

I have some ques. 1.what is crystal axis? 2.when one substance is rubbed against another substance,frictional electricity is produced.then from which substance the electrones are transferred to the other substance?

I'm going to guess you need to read up on piezoelectricity and maybe crystallography As far as actually answering your questions, I'm not sure I can be of any help, Sorry! Root⁴(one) 15:55, 5 June 2007 (UTC)

Ooops, after rethinking what you might be asking, I note when charge is built up due to increased surface contact via friction, and not stress on a crystal (piezoelectricity), that is static electricity. As to knowing which of two substances will get the negative charge, that's a good question! (Again, I can't help out). Root⁴(one) 16:02, 5 June 2007 (UTC)

The article you need to read for question 2 is triboelectric effect. For question 1, crystal structure and its "see also" links may be helpful. --mglg_(talk) 17:05, 5 June 2007 (UTC)

Prozac

I understand that I am not allowed to ask for medical advice, but wanted to ask about Prozac. My GP prescribed me Prozac this morning and this afternoon I feel lightheaded, giddy and nauseous. Does Prozac take effect this quickly or are these more likely to be side affects - I understand the lightheadedness and giddiness could be connected. 194.168.231.2 13:12, 5 June 2007 (UTC)Wes.

The best people to ask about this would be your GP or your pharmacist. Give them a call; they're there to help—and they're actually qualified to give this sort of advice. We're not able to advise you on what your symptoms may mean here at the Reference Desk. TenOfAllTrades(talk) 13:37, 5 June 2007 (UTC)

If you want a list of side effects, see Fluoxetine#Side effects. --Kainaw ^(talk) 13:39, 5 June 2007 (UTC)

See all the blah-blah disclaimers, but I can give my personal experience. I was on everything, including Prozac, but now I'm on Celexa. I found the Prozac effect was instant, including the symptoms you mentioned. It goes away in a day or so. The first week will tell if you can take it, then you will notice the positive effects in a month. It takes several months for full effect, and then you can evaluate with your doctor. If you find you are having trouble, you can ask for a specialist psychiatrist. Most people go through several dose attempts, and several types of anti-depressants. --Zeizmic 14:52, 5 June 2007 (UTC)

Thanks Zeizmic, I don't believe I am feeling an instant effect, probably the light head caused dizziness and made me feel giddy coupled with the relief of receiving a perscription. I already see a clinical psychologist but progress feels painfully slow. Doctor warned me of nausea and headaches but that was all the information I received and nothing with the pills. Had read the article but guess I just wanted the reassurance that someone else had experienced similar side effects. Silly I guess. Cheers again people. 194.168.231.2 15:19, 5 June 2007 (UTC)Wes.

For perspective, a psychologist and psychiatrist are significantly different (each has their own article!). Psychiatrists are medical doctors with a specialization in mental health and well-being. (Clinical) Psychologists are not medical doctors but often have advanced degrees (such as a Ph.D) in psychology. Psychologists can not usually prescribe medicine directly. Some individuals qualify as both psychiatrists AND psychologists, though this is rare. Good luck with your medication, Nimur 17:06, 5 June 2007 (UTC)

Should zeaxanthin and lutein be called vitamins?

As far as I know, animals, at least mammals, are not able to synthesize carotenoids. I think it is strongly suspected that low blood plasma levels of lutein and zeaxanthin lead to illnesses of the retina, where these carotenoids usually occur in larger concentrations. Then why are they not "officially" declared vitamins? Icek 16:54, 5 June 2007 (UTC)

I don't know the answer for this. But the symptoms of most vitamin deficiencies are quite severe and so they were usually recognised fairly early on. Also, these vitamin deficiencies (and therefore the syndromes associated with them) were common enough that they could be recognised. From the sound of it, the symptoms of lutein and zeaxanthin deficiencies are either not that severe or so rarely observed that they are still only beginning to be understood Nil Einne 17:17, 5 June 2007 (UTC)

According to Wiki, lutein and zeaxanthin, as well as lycopene, are included in the vitamin list under vitamin A definition. Please see Vitamin and Carotenoid. Dr_Dima.

According to which Wiki? Lutein and Zeaxanthin are not pro-vitamins. Icek 01:27, 7 June 2007 (UTC)

Dead Gill

For the last what ever my fish has stop all use of one gill! Im afraid something maybe wrong! can ya help?--Lolichan4u 17:05, 5 June 2007 (UTC)

Universe

How did the universe start? Where did all of the matter that makes up planets come from?

Is there a God?

See History of the universe and Existance_of_God for encyclopedia articles on these topics. Friday (talk) 17:53, 5 June 2007 (UTC)

As far as what can be verified through personal experience, the universe began when you were born. It ends when you go to sleep and begins again when you wake up. Or, the more scientific view is that it began with the Big Bang. Vranak

There is no way of telling :( For all we know time could be going backwards and the big bang was when everything was destroyed :] HS7 14:52, 7 June 2007 (UTC)

Starvation in cats causes liver disease?

I read an article the other day about overweight cats, and what to do and what not to do. The article said that one should never starve a cat because they could develop deadly liver disease. Why? How? After how long starvation? Thanks in advance for answers. Jack Daw 18:44, 5 June 2007 (UTC)

It's called fatty liver disease, or hepatic lipidosis, and it usually only happens in overweight cats. Generally it takes at least a few days of starvation (or anorexia secondary to stress or diet change) to occur. It's caused by mobilization of fat for energy, which subsequently accumulates in the liver and causes liver failure. It is reversible, but treatment is intensive and usually involves a feeding tube. Here's more information [1]. --Joelmills 20:12, 5 June 2007 (UTC)

Ichthyosis vulgaris

I have a mild form of Ichthyosis vulgaris. I read the article in Wiki about it however I read somewhere that there are additional symptoms that one can have such as hyperlinear hands and feet and rhinitis. Are there any others that I am missing? --Juliet 19:01, 5 June 2007 (UTC)

• Check the third reference (MedlinePlus) at the end of the article. 69.201.182.76 22:19, 5 June 2007 (UTC)

Do you have a link? --Juliet 12:42, 6 June 2007 (UTC)

If I reduce the pressure of a packet of air in space, will it still get colder?

From either the ideal gas law or adiabetic cooling, we know that if we decrease the pressure of a packet of gas the temperature should drop. Supposedly, this is because the air is doing work on its surroundings as it expands, or something.

If I take a box of air into space and make a hole in it, the pressure will decrease very rapidly. But it won't, as far as I can tell, be doing any work on its surroundings. Will the temperature of the air decrease? If it does decrease, can someone please explain it to me without using abstractions, but actually from an atom's-eye view: how is an individual atom losing kinetic energy? As far as an atom's concerned, it was just heading towards a wall that was suddenly not there anymore!

Thanks so much for any help! --Mike 19:49, 5 June 2007 (UTC)

It sounds like what you're describing might be a hypothetical case where the pressure and number of moles of gas in a system are decreasing in equal proportion while the volume and temperature of the gas remains the same. In terms of the ideal gas law, PV=nRT, you might be seeing P and n decrease in the same proportion, leaving V and T constant.

I don't think this is the same as expanding gas in a cylinder piston. In that case the gas molecules are expending their kinetic energy to expand the volume of the cylinder by pushing the piston. So if the temperature rises, then either the pressure or the volume or both will increase. And if you manually raised the piston from outside to increase the volume, then you'd probably see the temperature remain constant but see the pressure drop in proportion to the increase in volume.

Of course that's all hypothetical, and I can't claim to be an expert. But basically variables other than temperature in PV=nRT can change when you change something in the enclosed system. Dugwiki 21:18, 5 June 2007 (UTC)

By the way, as long as I'm speculating, I should mention that it also follows that when you open a valve to let gas out of a system, it's quite possible that the most energetic gas molecules will be the ones most likely to escape the system. After all, the faster an individual molecule is moving the more likely it is to be able to escape through the open valve before the valve shuts. Therefore when you open the valve to space it's quite possible that on average you have shunted off molecules on the higher end of the kinetic energy spectrum of the gas, thereby lowering the total average temperature of the remaining system. That would be, I think, a case of adiabetic cooling where the temperature and pressure and number of moles of gas all change simultaneously. Dugwiki 21:28, 5 June 2007 (UTC)

See this article: [2]. Seems you're right, no work, so no decrease in temperature for ideal gases. (Real gases can give a different result!) Also see Boomerang nebula, which is similar but actually has cooled itself to ~1K. --Reuben 21:30, 5 June 2007 (UTC)

You thinking is correct. In the case of an ideal gas, each gas molecule would keep its original kinetic energy as it zips off into space. The process is called adiabatic free expansion. (I note this is currently a requested article. Any volunteers?) The process is adiabatic, in that no heat is transferred to or from the gas, but it is neither reversible nor isentropic: the entropy of the system increases greatly as the gas increases in volume without cooling down. For a real (rather than ideal) gas, interactions between the molecules can cause either cooling or heating to take place; see Joule-Thomson effect. This cooling or heating can be understood as kinetic energy being lost to, or gained from, potential energy, by the gas molecules' pulling or pushing on each other as they move apart. --mglg_(talk) 22:43, 5 June 2007 (UTC)

Eh, no, I don't think that's quite right. It's true that the average kinetic energy of the atoms, in the frame of reference of the original box, remains the same. But it isn't random kinetic energy anymore; some of it is now part of the energy of motion of a clump of gas all moving in one direction. So the gas does in fact become cooler. --Trovatore 06:07, 6 June 2007 (UTC)

I should say that I'm talking about an ideal gas. I looked up the Joule-Thomson thing; my guess is that the experimental setup must not permit the expelled gas to keep moving; that's why the distinction regarding "external work" as opposed to simply "work". The gas does work -- on itself -- when it escapes; it's that work that causes it to go fast, and the gas will cool as a result of doing that work. But if you then stop the gas before measuring its temperature, you change that energy from the energy of motion of a clump of gas (which is not heat) back into heat, and that annuls the cooling due to the work the gas did on itself. In the "outer space" scenario, though, there's nothing to stop the gas -- it just keeps on moving, having done work on itself and therefore cooled off.

This is all a bit off the top of my head, and I'm not a physicist, so I hope I haven't made any embarassing blunders. --Trovatore 07:10, 6 June 2007 (UTC)

Jatropha Energy

Jatropha seems to be the perfect solution for energy use. It is not a food like corn. Why don't more countries produce jatropha energy? It seems like a perfect green energy.

The reason for "corn" ethanol is because corn husks and stalks are currently a waste byproduct in corn production. So, they are (inefficiently) converted into ethanol. In Brazil, it has been demonstrated that sugar cane is far more effective, but it doesn't make use of an existing waste product. That is the point behind corn ethanol - it is an attempt to get rid of the waste. --Kainaw ^(talk) 21:46, 5 June 2007 (UTC)

Kainaw, you are unfortunately mistaken: what is currently referred to as corn ethanol is made from the kernels themselves, not from the husks or stalks [3]. Using the husks and stalks, or other cellulose-containing plant matter, to produce cellulosic ethanol would be a much better idea, but that is not what is being done so far. --mglg_(talk) 23:48, 5 June 2007 (UTC)

Will jatropha survive a Kansas winter (for example)? If not, will it grow fast enough to be planted and harvested annually in areas with a short growing season, as corn does? Sugar cane can't be used in most parts of the world because of its particular growth needs. Farmers and ethanol producers know what they are doing.

The concern about using a food crop to make ethanol is misplaced. If some other (non-food) crop becomes more popular, so farmers will find it more profitable than growing food - and food prices still go up. SteveBaker 02:24, 6 June 2007 (UTC)

General Mills announced cereal price increases today [4], attributed in part to the demand for corm to make ethanol, along with higher energy and transportation costs. Of course, the grain is a tiny part of the cost of a box of cereal, probably far less than the cost of making the cardboard box, or the cost of transporting it to the store from the factory, or the cost of advertising it. Edison 15:28, 6 June 2007 (UTC)

Can there possibly be a cure for cancer?

With the new technological advancements and many pills to alleviate the damage cancer soes, is there an end in sight?

A "cure for cancer" is too general a term: cancer is a term that encompasses hundreds of different diseases that, while they share some commonality in terms of dysfunctional cell regualtion leading to malignant tumors, have widely different etiologies, symptoms, progression patterns, etc. governed by the type of initial DNA errors and the cell types affected.

That said, some cancers already have very high survival rates with effective medical treatments readily available (at least to patients in modern Western nations that catch the disease relatively early). It's certainly plausible that eventually every type of cancer will have highly successful treatment options, but some cancers have far more difficult paths towards a "cure" than others and may be many, many years away from the type of success you're probably asking about. — Scientizzle 22:04, 5 June 2007 (UTC)

You do have to take some of these increased survival rates with a pinch of salt. Many of them are the equivalent of "By catching this 2 years earlier, we've improved life expectancy after diagnosis from 3 years to 5 years!", others can involve catching and removing tumours that would otherwise have lain dormant for years, not causing any problems. Our actual ability to improve the lifespans of people with cancer has not greatly improved for decades. We are making progress, but very slowly. Once something other than cutting the tumour out or basic, indiscriminate chemotherapy turns out to be successful, and goes mainstream, maybe we'll see a big improvement. I like the sound of the various targeted chemos that are being worked on. (Oh, and if you have a New Scientist subscription, you can see I'm not just making this stuff up here "Yet it has been known for 100 years that cancers are generally curable if they can be removed while still in their early stages. When somebody dies of cancer it is usually because it has spread from one site in the body to another, yet over the past 35 years the death rate from most of these metastatic cancers has remained largely unchanged.") Skittle 23:14, 5 June 2007 (UTC)

Definitely not. Cancer is a lifestyle issue, and there's no cure for a malignant lifestyle. Vranak

You know, as horrible as Vranak's statement sounds, he has a point. How many cancers have been caused by smoking, alcohol, or drugs (person's lifestyle), or pollution (related to the lifestyle of a group of people over a long period of time)? Probably a very large majority of them. Of course, I've always been fond of the idea that all of us have some sort of cancer, we just die of another cause first. (Getting down from the soapbox) Root⁴(one) 17:53, 6 June 2007 (UTC)

A point, yes, but poorly made. I have no problem with a statement along the lines of "generally better lifestyle choices are a currently readily available "cure" for cancer in the sense that quitting smoking, wearing sunscreen, eating more fiber, etc. will lower anyone's risk of developing cancer". Such a statement is factually correct and to be encouraged! The absolutist position that cancer is a lifestyle issue, however, is intractable and can be perceived as insulting to those who have experienced cancers that appear independent of your standard "bad", cancer-promoting choices.

If the human race manages one day to rid the world of pollution, smoking, food additives, drugs, viruses, etc. (and everyone wears SPF 900), there still would be a significant cancer rate (albeit much lower) because, as I said below, DNA errors can happen independent of these external (and variably controlable) sources of mutation. — Scientizzle 18:16, 6 June 2007 (UTC)

Sounds like you are blaming the victim. Some cancers just occur, due to random mutations, and are not the result of unprotected sun exposure, radiation exposure, smoking, asbestos exposure, pesticide exposure, or other lifestyle choices. Do not point a finger at a child who is dying of leukemia and say "Malignant lifestyle!" Edison 15:32, 6 June 2007 (UTC)

Sure, but when's the last time you heard a child talk about a 'cure for cancer'? They are not so naive. Vranak

I, too, recoiled at your ridiculous throwaway line, Vranak. To generalize cancer as a "lifestyle issue" is a pretty stupid statement. There exist many examples of cancers (often so-called "childhood cancers") that strike those who haven't even had the opportunity to make the "malignant lifestyle" choices we are all familiar with. Additionally, the cruel reality with cancer is that anyone can get it: a handful of genetic mutations in sensitive segments of the genome (particularly proto-oncogenes and tumor suppressor genes), be those mutations inherited or acquired during one's lifetime, in the right cell type can induce a tumor. Certainly lifestyle choices (smoking, UV exposure, etc.) are associated with cancer because they increase the liklihood of such mutations, but they are not necessary to develop those mutations, nor are they sure to cause them--that is, there is certainly not a 1:1 correlation between the quality of one's lifestyle choices and the liklihood of devloping cancer.

Finally, if you honestly believe "there's no cure for a malignant lifestyle", you could do with a dose of good literature & philosophy... — Scientizzle 15:58, 6 June 2007 (UTC)

You're stretching the definition of 'cure' a little far there. Self-improvement is not a cure per se. Look at the original question. The poster is not asking if there will one day be a book of spiritual enlightenment that will rid man of his woes, he's asking about pills to pop.Vranak

[EC] And cures for various cancers may well be developed into various pills to pop...and "technological advancements" is as broad a brushstroke as medical research can be. Your original response was flippant and unhelpful in regards to that question. A general discussion on the etiology and treatment of cancer seems far more appropriate than reading a negative societal connotation into a 20 word question and replying with terse condemnation. — Scientizzle 16:56, 6 June 2007 (UTC)

What lifestyle are you talking about? Respiration produces free radicals that are dangerous, so of course there can be no cure for lifestyle since life itself is toxic. David D. (Talk) 16:47, 6 June 2007 (UTC)

I just noticed you amended your post to clarify wrt the pill popping. I still don't understand the malignant lifestyle comment. The question relates to either killing cancer cells (could be possible) or drastically reducing chances of getting cancer (also could be possible) with medication. Certainly such a magic pill is not currently available, and maybe never, but that does not mean impossible. The key is to be able to target cancer cells specifically or reduce mutation rates. Both are feasible goals. David D. (Talk) 16:54, 6 June 2007 (UTC)

There's two ways to approach the cancer issue: with the mega-industrial pharmeuctical complex, and preventive measures (lifestyle changes). There's no money to be made in the second, which is why we have our dear friends Scientizzle, David, Edison et al who fiercely defend the first. Vranak

I replied on your talk page. This line of discussion is not appropriate for the ref desk. David D. (Talk) 17:08, 6 June 2007 (UTC)

Cancer is a part of evolution, which is a very inefficient process, and there are often mistakes, many of which cause cancer. We can't stop evolution, and in the long run it isn't a good idea even if we could.

But of course there is a difference between prevention and cure :) We can't prevent cancer occuring, but we can do a lot to stop it spreading or getting worse if it does :) Three problems with removing cancer are finding out who has it, getting to cancerous cells deep inside someone and removing every damaged cell :( HS7 14:49, 7 June 2007 (UTC)

Altering DNA

Is there a way to alter you're skin color, eye color, hair color,or race from altering DNA?

Maybe in a century or two. ---CWY2190^TC 21:57, 5 June 2007 (UTC)

As an adult it may prove difficult, as you'd have to modify the DNA structure of many existing cells. It may be easier to modify such attributes for an embryo. But first scientists would need to identify what characteristics of the DNA produce those attributes, and that will take many years of research. — RJH (talk) 22:18, 5 June 2007 (UTC)

It has been done on fishes, see GloFish and genetically modified organism. --Vsion 05:11, 6 June 2007 (UTC)

I think the OP wants to know whether such modifications can be done after conception. —Tamfang 05:46, 6 June 2007 (UTC)

It would be very difficult and take a lot of work, but if you really wantyed to and had a ridiculously huge amount of money, there might be a way. An easier option would be to prevent dominant genes being expressed, I expect someone could make a drug or a GM virus to do that soon.

People of India contrasted to Caucasian

Apart from the lighter skin, variety of eye colors and hair what elese makes them different. What lead to these traits, biotic factors,abiotic factors, people?

Can you briefly explain the history/evolution between these groups of people.

Start by reading about Race, and also try Category:Race. 69.201.182.76 22:15, 5 June 2007 (UTC)

Recently in the ref desk, the topic of lactose intolerance came up. Asians (including India) are more prone to lactose intolerance than Europeans. --Kainaw ^(talk) 23:39, 5 June 2007 (UTC)

Flame temperature increased by electric arc?

See Talk:Brown's gas#To do. According to U.S. patent 4,014,777, oxygen and hydrogen gas can be passed through an electric arc, whereupon they absorb electrical energy from the arc and split into lone atoms. The patent says that when H₂ molecules are split into 2 H, the atoms absorb 101,000 calories per gram mole. O₂ → 2 O absorbs 117,000. (What's the metric equivalent?) On recombination into water, the temperature of the flame produced will then be hotter due to the more energetic particles than if they had not passed through the arc.

Is this legit? — Omegatron 23:16, 5 June 2007 (UTC)

Well, perhaps - very briefly...see Nascent hydrogen. SteveBaker 02:21, 6 June 2007 (UTC)

How do you determine the ka value of a substance

Hi, Omegatron. Calorie says that in scientific use "calorie" means the gram calorie, the amount of energy needed to raise one gram of water one degree C, which 4.184 Joule. There are at least 3 slightly different values for the conversion factor given in the article, depending on temperature. Things that are patented are not always practical, since there is no longer any requirement that a working model be demonstrated. Given that all it takes is a spark to cause the exothermic recombination of H₂ and O₂ into water, it is hard to see how one could take the mixed gases and pass an electric arc through them to split the strong covalent bonds in the H₂ into monotomic Hydrogen and do the same to oxygen, as in Brown's 1977 patent, without immediately producing H₂O. Maybe he found a way. In a different talk page I mentioned a high school chem book "Modern Chemistry" by Charles E. Dull et al, published by Holt Rinehart and Winston, NY 1962, which on page 129-130 described the "atomic hydrogen torch" which passes an arc through the hydrogen before mixing it with the oxygen, using tungsten electrodes, to break down the hydrogen covalent bond. In the diagram, the torch appears to supply only hydrogen to the flame, and achieves a 4000 degree C flame. The monatomic hydrogen appears to burn immediately after it is split. The arc method is attributed to Irving Langmuir(1881-1957). [5] is a website which discusses Brown's gas and HHO and says the Langmuir invention dates to 1926. An H₂ molecule effectively has the s orbital of its K energy level filled, and thus has the stable K shell configuration of a helium atom. The electric arc would have to supply substantial energy to break the bonds in the hydrogen or oxygen, so it would appear to be a process for achieving a high temperature flame at an energy cost, more than a process to get more energy out of the gasses. If oxygen went through its own arc before combining with the separately split hydrogen, it makes sense that a very hot flame should occur as it gives up the energy which had just been added to it by the arc. Edison 16:12, 6 June 2007 (UTC)

Wait a second. Didn't you vote to delete this article? — Omegatron 02:51, 7 June 2007 (UTC)