Wikipedia:Reference desk/Archives/Science/2007 December 7

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December 7

Need to burp!

I wonder if this counts as a medical question. Whenever I have a stomach full of gas, I have a hard time burping it out, so it ends up being very uncomfortable and painful until it finally happens.

What are best ways to stimulate burping? — Kieff | Talk 00:57, 7 December 2007 (UTC)

With babies you pat them on the back for a while, maybe it can have the same effect on you? —Preceding unsigned comment added by 128.101.53.177 (talk) 01:08, 7 December 2007 (UTC)

Eno's Fruit Salts. DuncanHill (talk) 01:25, 7 December 2007 (UTC)

Yes it does. This could actually be a medical condition (a feind of mine had similar condition). Please see a doctor.--TreeSmiler (talk) 03:17, 7 December 2007 (UTC)

As far as my understanding of our policies is concerned: a) we can tell you how to induce burping, but b) we can't tell you if it's healthy to do so in your case. If this (epigastric discomfort) is a problem for you, you should see a physician or other health care worker, as it may be a sign of a serious condition (or it could just be gas, but since it's causing you grief, why not look into a solution with a doctor that will stop the gas from forming, rather than finding ways of relieving it?) (EhJJ) 04:15, 7 December 2007 (UTC)

Just as with the question "How do you get to Carnegie Hall?", the answer is "Practice!". Drink something highly carbonated such as seltzer. Learn to relax the muscles in your throat and contract the muscles in your abdomen. Seriously. You can train yourself. People who have had their larynx surgically removed learn to swallow air and burp it out to simulate the buzzing of their now-missing vocal cords; you can probably Google up more info regarding how they train themselves. And then there's the contest in Revenge of the Nerds...

Atlant (talk) 14:08, 7 December 2007 (UTC)

Dear Reference Desk: Does telling someone how to make it worse count as medical advice? I'm uncertain. SteveBaker (talk) 16:16, 7 December 2007 (UTC)

Questioner: Remove the opening sentences and just leave your question. "What are best ways to stimulate burping?" is in no way a request for medical advice. Adding personal history confuses some people and makes it difficult for them to see the question. As with any abnormality, you should seek professional medical advice to ensure that you are healthy. Answering the question - as with babies, patting someone on the back and rubbing the center of the back in circles helps with burping. -- kainaw™ 17:28, 7 December 2007 (UTC)

Wikipedia talk:Reference desk

Hydrogen Peroxide

Does anyone know what the heck is that white gunk you get from hydrogen peroxide you put on any unsterile surface (i.e. sink, tub, bathroom floor), or on raw meat? --Agester (talk) 01:19, 7 December 2007 (UTC)

Beyond "white", tell us something about this "gunk". Is it a solid, liquid? Does it dissolve if you pour some water on it? Does it disappear after sitting for a while? Is it foamy (H₂O₂ decomposes to H₂O and O₂ and this reaction is strongly catalyzed by several common biological materials). DMacks (talk) 02:41, 7 December 2007 (UTC)

It sounds like bleached scum. Graeme Bartlett (talk) 21:22, 7 December 2007 (UTC)

Not quite too sure what it is. But it seems very similar to the foamy stuff if you put hydrogen peroxide in a open cut / wound. I figured it might be the dead bacteria, because when i put it in a clean bowl that i just washed it doesn't build up that foamy stuff, but if i accidentally drip some in my sink it'll foam up similar to it being applied to a cut. And if it isn't assumed I'm talking about the hydrogen peroxide you can get in your local pharmacy for antiseptic uses. --Agester (talk) 01:09, 8 December 2007 (UTC)

The hydrogen peroxide article mentions that the human body, most animals and nearly all aerobic bacteria use catalase, which is an enzyme that speeds the reaction 2H₂0₂-->2H₂0+0₂. I assume you use your sink (bathroom one) to brush your teeth and your tub to wash, right? And there's always bacteria there just growing on the water left over and any biological material. So all this bio-matter in those places has catalase, which decomposes the hydrogen peroxide, which gets caught up in any sort of proteinaceous stuff on the surfaces, creating a foam. Same on the meat---it's like the frothing when it is poured on an open wound.Aquaman590 (talk) 00:38, 9 December 2007 (UTC)

Malt liquor

Is malt liquor sweet? Heegoop, 7 December 2007 (UTC)

Our article on malt liquor doesn't really answer the question, aside from mentioning that sugar is sometimes added. I would guess that it would depend on the particular brew, as it is essentially beer with a little more alcohol (like they sell in Canada and Europe). As a scientist, I'd like to suggest a simple experiment :P (EhJJ) 04:20, 7 December 2007 (UTC)

The article says sugar is sometimes added before fermentation, "to boost the beverage's alcoholic strength". Adding sugar before fermentation has somewhat the opposite effect to adding it afterward, because the yeast use up all the sugar present and turn it into alcohol. —Keenan Pepper 06:17, 7 December 2007 (UTC)

Malt liquor is really little other than distilled beer, and as a brewer I can tell you that beer can be made sweet or not so. Depending on mash temperatures (the temperatures at which the malt is steeped), sugars in the grain are broken down to various degrees. At some temperatures you end up with much of the sugar of the kind yeast likes, and little of the stuff yeast can't easily digest; and at other temperatures, the opposite. Any sugars the yeast doesn't digest to ethanol+CO₂ increase the sweetness of the finished product. Psud (talk) 10:09, 7 December 2007 (UTC)

What?!? Maybe this is a difference in terminology between different places, but around here, what we call "malt liquor" is beer that's a bit stronger than typical beers. It is most emphatically not distilled! It's still just beer. The article Malt liquor also does not mention distillation. If it's distilled, it's not beer. Friday (talk) 16:38, 7 December 2007 (UTC)

Ooops. Brain not switched on (never is at 10:00Z). The stuff I was talking about is properly called "Whiskey". Oh well. We call malt liquor "barley wine" here. Being beer, nothing more, nothing less, it can be naturally somewhat sweet, or its sweetness can be increased by adding lactose (which sacromyces cerviseaSaccharomyces cerevisiae can't digest) or an artificial sweetner. It's all up to the brewer. ----Psud (talk) 13:09, 8 December 2007 (UTC)

As with anything that's brewed, the amount of sugar left at the end of fermentation depends on how much you put in at the outset and how long the fermentation went on. Fermentation stops when either the yeast runs out of sugar to convert - or it poisons itself with it's own alcohol production (or maybe if someone stops it prematurely by messing up the temperature or something). So there are a range of possible outcomes here. Obviously, the manufacturers can also alter the final sweetness by adding more sugar after fermentation is complete. So it's not true to say that because something sweet went in at the outset, that the result will be sweet...but "it depends". SteveBaker (talk) 16:11, 7 December 2007 (UTC)

How much sugar went in; how long it fermented for; and how fermentable the sugars are:

• Starting with unfermentable sugars makes the result sweeter
• Adding unfermentable sugars after fermentation makes the result sweeter
• Killing or filtering the yeast then adding fermentable sugars after fermentation makes the result sweeter
• Adding artificial sweeteners makes the result sweeter
• Stopping fermentation early is wrong and bad and only suitable for childrens' drinks, but does make for a sweeter, lower alcohol drink

--Psud (talk) 13:23, 8 December 2007 (UTC)

• You might be thinking of Malt beverage, which is a little different from malt liquor. In the United States, makers of Alcopops such as Mike's Hard, Zima, etc. refer to the drinks as "flavored malt beverage" or "premium malt beverage". These drinks are very different from malt liquors, which more often taste like smooth beers, as Steel Reserve and Hurricane High Gravity Lager do. Also, don't forget Low-end fortified wine like Mad Dog and Thunderbird -- these are often sold in the same section as the malt liquor, and most of them are very sweet to cut the harsh taste. --M@rēino 19:01, 7 December 2007 (UTC)
  • Never heard of those. Surely Colt 45 is the typical malt liquor? Rmhermen (talk) 19:32, 10 December 2007 (UTC)

Gene transfer a mutation?

Would horizontal gene transfer be considered a mutation for the organism that receives the transferred gene? I'm confused. I stumbled across a PNAS article which seemed to refer to it as a "mutational process," [1] but sometimes the two terms may be observed contrasting with eachother (e.g., [2] , scroll down to the section that says "evolutionary genetics in bacteria"). Thanks! Schmitty120 (talk) 01:33, 7 December 2007 (UTC)

One could argue the semantics of describing the effect of horizontal gene transfer as a mutation. From a strictly technical point of view, it could be considered mutational. For instance, if the gene integrated into the recipient genome it would result in a "mutation" of the genetic insertion site. Likewise, of you wish to use the term to describe the phenotype affected then the recepient could be described as having a "mutant phenotype" and it follows that must have occured by a mutational process. In the link where you suggest it is used in a contrasting manner, I think the use of the term "mutational process" is really a shorthand for "classical mutational processes in vertical gene transfer" (meaning indels and point mutations) in contrast to horizontal gene transfer and recombination. I don't think in calling them "mutations" (or not) the author is attempting to make a point about whether they are involved in the evolutionary process (or not). It is fairly well established that both types of genetic changes have driven evolution (at least in bacteria, see Horizontal gene transfer#Evolutionary theory). Rockpocket 08:15, 7 December 2007 (UTC)

Neurobiology: Effects of decreased membrane capacitance

My script says that Myelination reduces the leakage current and decreases the axon's membrane capacitance. By this the speed of signal propagation is increased. However, I do not see which effect decreasing the membrane capacitance has on the speed of signal propagation in addition to reducing the leakage current. Can somebody please explain this to me? Falk (talk) 08:27, 7 December 2007 (UTC)

We are propagating a potential difference up the axon. By $Q=CV$, we see that for this potential to stay constant, there must be a buildup of charge difference on each side of the membrane, and to get this charge difference there must be an ion flow toward the membrane, which takes time. By reducing capacitance, the necessary charge difference becomes lower. Otherwise, we could say $I=CdV/dt$, in which case reducing the capacitance for a given ion current (the rate of flow of ions we'll assume is constant) increases our voltage propagation speed $dV/dt$. SamuelRiv (talk) 13:27, 7 December 2007 (UTC)

Cold Car Experiment

Two identical cars are started, and their heaters turned on, on a cold wintry morning. One car is encased in half an inch of ice; the other car was covered and is clean. In which car will the internal air temperature rise faster? We've come up with several hypotheses:

a) The icy car will warm faster, because it is insulated with an extra layer of ice.

b) The clean car will warm faster, because the ice on the icy car conducts heat away from the windows faster than air could, due to ice's higher thermal conductivity.

c) It depends on how close the ice is to the freezing/melting point, since

d) It depends on the air temperature or velocity outside -- if the air is significantly colder than the freezing point of water, it will cool the windows faster than melting water.

e) More than one of the above are true, and the problem is too complex to definitively answer.

Your thoughts? jeffjon (talk) 14:07, 7 December 2007 (UTC)

Assuming the outside air temperature is the same as the temperature of the ice (which is reasonable) and that it's a lot colder than zero centigrade (ie well below freezing): I think the one covered in ice will win - ice is a reasonably good insulator - but not as good as air. However, with air, as soon as you heat it up just a bit, it drifts upwards to be replaced with new, cold air. Hence any heat that leaks out of the second car is lost immediately. With first car, with an icy jacket, the heat you radiate goes into warming up the ice - at least until it reaches it's melting point - and that warmth is retained close to the surface of the car. Since the rate of heat loss is proportional to the square of the temperature difference (Newtons law of cooling), the ice-encased car will do better.

If the air around the second car was retained close to the car though (eg if it had a loose car-cover thrown over it) then the superior insulation value of air would win out.

SteveBaker (talk) 15:55, 7 December 2007 (UTC)

I agree with Steve. There would be several minutes of ambient temperature air coming out of the vents until the engine warmed up, then the ice-encased car would have less heat loss due to convection, leading to a faster rise from the assumed below zero C interior temp and temp of the ice. Of course if it were warm outside, then the ice-free car would warm up faster. Edison (talk) 23:55, 7 December 2007 (UTC)

Not so fast. If one car is literally encased in half an inch of ice, then you can't get in to start it at all. It will just sit there cold while the other warms up! :-P More seriously... should any thought be given to the blanket of ice essentially acting as a heat sink - for the engine if nothing else? I agree with the theory that the ice will act as an insulator, but the interior of most cars is composed of cloth, plastics, and foams - surely that degree of internal insulation would minimize any difference to heat loss caused by the ice? Matt Deres (talk) 15:52, 8 December 2007 (UTC)

You can't refer to the car's own insulation, as it's the same between the two cars, and insulationA + insulationB is better than insulationA + nothing. --Psud (talk) 16:54, 8 December 2007 (UTC)

I understand that (I think). I'm just saying that the effect of insulation B isn't going to be much compared to the effect of insulation A and in fact might be completely overshadowed by the heat sink effect. Just a guess on my part, though; I assume Steve is probably correct. Matt Deres (talk) 22:02, 8 December 2007 (UTC)

Let us not forget that if the car were encased in ice, the HVAC air intake would be blocked. The heater core itself would warm up faster because there'd be no airflow through it, but the cabin temperature would not, for the same reason.--Scheinwerfermann (talk) 16:30, 8 December 2007 (UTC)

This sounds like a question for Mythbusters.  :-D -- HiEv 06:11, 9 December 2007 (UTC)

Hovercar?

Think these would ever be viable? How would one break or slow down in one? 64.236.121.129 (talk) 14:19, 7 December 2007 (UTC)

Presumably by reversing the means of propulsion (a fan or whatever). If you can figure out how to make it go forward, you can figure out how to make it slow down. And I would think they would break the same way regular cars do—when it's least convenient, and at great expense. -- Coneslayer (talk) 14:23, 7 December 2007 (UTC)

I reckon they'd be too expensive in fuel. Hovering is very energy intensive, especially when compared to rolling. As to braking, consider an already existing vehicle that can hover - the helicopter. Helicopters brake by vectoring their thrust forward, a hover car would presumably do the same. --Psud (talk) 14:39, 7 December 2007 (UTC)

I think by the time the technology is good enough and reliable enough and they are cheap enough to be somewhat popular, there will be other, far better forms of transportation people will use instead. Recury (talk) 14:41, 7 December 2007 (UTC)

Actually, I like the idea of travel by rocket - a short high acceleration burn; a ballistic arc; a short high acceleration burn to stop. Fun and quick whether across town or across continents! --Psud (talk) 14:45, 7 December 2007 (UTC)

Hovering as in hovercraft? The trouble with hovercraft is that they are very unmanouverable - you don't have friction with the ground - hence you have no brakes. Redirecting thrust to slow you down means that you can't slow down any faster than you can accellerate and if there is even the slightest deviation from aiming the thrust dead straight, there is a tendency for the craft to spin or slip sideways. Stopping at traffic signals would be tough. Energy-efficiency-wise, they aren't so good either. The lack of friction with the ground is a net win - but it's very expensive to maintain the hover thrust - so you end up needing more power than with a car. It's nice to be able to travel over water and to not need paved roads (it would be nice if all of our roads could be turned into lawns - or farmed for grain!). Hovercraft are impractical for other reasons: If your lift motor fails, you can't push the vehicle off the road - if your thrust motor (which is also doing the braking remember!) fails then you have a dangerously uncontrolled vehicle on the streets. At stop lights, or in heavy traffic, everyone has to land and lift off again because, again, there is no way to keep a hovercraft stationary. Even the slightest breeze would be enough to blow you onto the sidewalk if you continued to hover.

Using propellors to direct thrust has another set of problems in that the 'blow back' from the rear of the craft will tend to knock pedestrians off their feet and blow out windows! Also, if two or more hovercraft are manouvering close together (again, think busy city streets with people turning, parking, stopping and starting) - then there are lots of dangerous cross-winds induced by one craft turning that would tend to blow other craft sideways.

All in all, hovercraft just aren't really practical in tight areas. Great for lakes and open grassland and such though. SteveBaker (talk) 15:43, 7 December 2007 (UTC)

• my hovercraft is full of eels --M@rēino 19:07, 7 December 2007 (UTC)

You can buy a hovercar today: the M200G Volantor or the Moller Skycar M400. Rockpocket 19:19, 7 December 2007 (UTC)

That's not really true. They are offered to sell one of their prototypes - on the condition that you basically use it as a museum piece and promise not to fly it - but the price was so high, I don't think they actually managed to find a buyer. You can't actually buy a working, flyable, usable flying/hovering car from them - it's always "a few years away"...which is why Moller are being dragged through the courts over it by their investors. SteveBaker (talk) 19:48, 7 December 2007 (UTC)

Also those are flying cars. That's a bit different. A hovercar doesn't lift off the ground by too much, while a flying car can fly very high. 64.236.121.129 (talk) 19:57, 7 December 2007 (UTC)

"The computer system also prevents the machine from flying higher than 10 feet (3 m) above the ground." - sounds like a hover car to me. I didn't say you should buy one, just that could could buy either of those functional prototypes if you had enough money. It would then be up to you to find somewhere to use it legally. ;) Rockpocket 01:14, 8 December 2007 (UTC)

No, no, no! You can't buy a flying/hovering car that you can actually use - at least not from Moller. The company only ever had ONE flying/hovering car for sale - it was their first prototype - and nobody bought it. BUT you had to sign some kind of legal document promising that you would only use it for display purposes and NEVER attempt to fly it. So if you had a HECK of alot of money (it was in the millions of dollars), you could own a car that was theoretically capable of flying/hovering - but you couldn't actually use it. Check the Moller FAQ if you don't believe me. SteveBaker (talk) 03:33, 8 December 2007 (UTC)

Yes, yes, yes! I can't find anything in the FAQ that says you would be legally restricted from attempting to use it, could you elaborate? This suggests the auction was for a car that is "suitable for test and evaluation only." That sounds like you could happily attempt to "hover" your $3.5M "car" under the guise of an evaluation/test, as long as the local air authorities could be convinced to permit it. Rockpocket 21:39, 8 December 2007 (UTC)

Chemical(s) responsible for Pine/Christmas Tree Scent

Can anybody inform me of the name(s) of the chemical(s) responsible for the fragrance associated with Christmas/Pine trees? --Mark PEA (talk) 16:00, 7 December 2007 (UTC)

I presume pine oil. Someguy1221 (talk) 17:54, 7 December 2007 (UTC)

Most fragrances are very complex mixtures of chemicals - I doubt there is one particular one that produces the "Pine tree" smell. SteveBaker (talk) 19:44, 7 December 2007 (UTC)

Okay, thanks for the answers. I thought maybe there would be some research into the constiuents of pine oil but I can't seem to find any without digging deep. --Mark PEA (talk) 23:51, 7 December 2007 (UTC)

There is certainly scientific literature on this because I have seen it. I think that many of the priciple aroma compounds are monoterpenes such as pinene. ike9898 (talk) 13:12, 8 December 2007 (UTC)

Indeed, the igredients have been identified. [3]. 57% alpha-pinene, 8% beta-pinene, 26% carene, 6% limonene and 3% other hydrocarbons. I don't know if the article identifies the other hydrocarbons, as the only online version I could find was here, and I don't have a subscription to that service. Someguy1221 (talk) 22:38, 8 December 2007 (UTC)

I would have thought of esters. 86.150.30.106 (talk) 19:51, 10 December 2007 (UTC)

Testosterone Question

I read something about testosterone and how bodybuilders have to keep using more and more each time they use it to get the same effect. Does that mean, that when your off of synthetic testosterone, the testosterone that is body makes is less effective then it used to be before you started using synthetic testosterone? (assuming your body is making the same amount of testosterone as it did before you started using synthetic testosterone) —Preceding unsigned comment added by 71.106.34.15 (talk) 17:18, 7 December 2007 (UTC)

This is a phenomenon known as downregulation, which occurs when any receptor is overstimulated by a ligand. I've never answered a question here before, so maybe someone else can put more effort into it and explain it better. See also: Desensitization (medicine), Drug tolerance, Physical dependence. --Mark PEA (talk) 23:49, 7 December 2007 (UTC)

With testosterone it's more complex than mere downregulation. In fact, when you massively flood your system with artificial testosterone, your endogenous production is completely knocked out. This is what causes rather extreme withdrawl symtoms for several weeks after going cold turkey from steroids, as your body takes that long to regain normal production levels. Additionally, your body will initiate processes to convert excess testosterone into other hormones, including estrogen (if I recall correctly). I'm not sure if these two processes in combination are the complete reason for any apparent drug resistance seen in steroid abusers. Someguy1221 (talk) 23:57, 7 December 2007 (UTC)

Just a little correction, most people dont know this, especially the media and the people that give steroids a bad rep. Educated steroid users (not the little 17 year old kids, im talking about the people that do research and are parts of different steroid or bodybuilding forums), take drugs such as clomid,nolvadex, etc.. or shoot some HGC to restore natural testosterone production, they dont go cold turkey. If they were dumb enough to not use these drugs to restore natural testosterone fuction, they would lose most the muscle they gained and be depressed, and thats not the case with educated users. —Preceding unsigned comment added by 76.167.132.90 (talk) 03:13, 9 December 2007 (UTC)

Autothermal Reforming and Modelling Software

Okay, this is possibly a little specialised but I'm losing track of what reasonable values are for things and nobody else around me seems to be doing better with the software. I'm modelling autothermal reforming of methane with oxygen and steam using PRO/II (pro2), which has to be the most irritating piece of software ever coded. Putting 16152.7060 kmol/hr of my reactants into a Gibbs reactor, at some temperatures the reactor is giving out 3,000 million kJ/hr in heat. At some lower temperatures it requires nearly 300 million kJ/hr heat to be put in. Now, pro2 being as erratic as it is (and given the weird way the duty is varying with the pressure), I'm suspicious of these values. Are they, in fact, reasonable?

Thanks for any help. I've just reached the stage where I'm so frustrated with the software I can't think clearly about the actual process. Skittle (talk) 17:31, 7 December 2007 (UTC)

I really have no knowledge whatsoever of your problem domain. So I'll respond anyway (that's what teh Intarweb is for!). 3,000 million kJ/hr is 833 megawatts, which is pretty close to the electrical output of Three Mile Island's remaining nuclear reactor. Do you anticipate that what you're trying to do should have energetics on the same scale as a power plant? -- Coneslayer (talk) 17:44, 7 December 2007 (UTC)

Hmm, thanks. I wasn't really expecting to get nuclear power plant levels of heat :) Although, it would provide excellent heat integration opportunities. That was the sort of reality check I needed; I was starting to doubt the size of a kilojoule. So, pro2 screws up again. Hooray! Skittle (talk) 18:05, 7 December 2007 (UTC)

BTW, Google is good for quick unit conversions... 3000 million kJ/hour in watts is what I used. -- Coneslayer (talk) 18:29, 7 December 2007 (UTC)

Yes, but without someone who isn't me to tell me 'that's like a power plant', I couldn't be sure I wasn't just being stupid :) Skittle (talk) 18:31, 7 December 2007 (UTC)

We all came from the sun?

Would it be a fair statement to say that we all came from the sun? The matter in our bodies came from the sun, and the energy that sustains us also came from the sun in one form or another. 64.236.121.129 (talk) 19:37, 7 December 2007 (UTC)

That assumes (incorrectly in my opinion) that absolutely no matter from outside the solar system or matter that existed in the ooze that became the solar system made it to Earth. -- kainaw™ 19:44, 7 December 2007 (UTC)

That's true, but how much matter from outside the solar system contributed to the ooze? 64.236.121.129 (talk) 19:47, 7 December 2007 (UTC)

The matter in our bodies did not come from the sun. It came from the Earth (and the stuff on the Earth's surface) and thus (ignoring meteorites and so on as negligable), it came from the cloud of gas and dust that collapsed into the solar system. Some or all (not sure which) of this cloud came from a previous supernova, so we come from a star, but not from the sun in any literal sense. See formation and evolution of the solar system. Algebraist 20:16, 7 December 2007 (UTC)

No, little of you came from the Sun. Much of your body consists of hydrogen (either in the water that comprises much of your body, or in the many compounds that comprise the solid bits), which was formed in the aftermath of the big bang. Almost all of the remaining atoms were made in a sun, but not our Sun. Right now the Sun is turning hydrogen into helium; much later in its life it'll make a few heavier elements. The atoms that comprise your body (bar the aforementioned hydrogen) were made by old suns that have since exploded, the wreckage of which condensed to form the planetary nebula from which the Sun, the Earth, and the rest of our solar system formed. Our Nucleosynthesis article is a good place to start. -- Finlay McWalter | Talk 20:12, 7 December 2007 (UTC)

"Us from the sun"? No way…planets and sun all came from a common origin, not one from the other. See Solar System#Formation. DMacks (talk) 20:14, 7 December 2007 (UTC)

As for the energy that sustains us, virtually all of this comes from the sun. The energy contribution of extra-solar sources is truly negligable in comparison. Some primitive organisms, however, obtain their energy from geothermal sources, which certainly didn't originate from the sun. Someguy1221 (talk) 20:17, 7 December 2007 (UTC)

It would perhaps be better to say that we came from A sun - but not from THE sun. Everything we are made from came from the remnents of one or more dying stars someplace. SteveBaker (talk) 03:35, 8 December 2007 (UTC)

As Carl Sagan puts it "We are made of star stuff". I'd say "some suns" rather than "A sun". And of course, those suns were made of the generation of stars before them, with each generation of stars made of heavier elements than the one before. --Psud (talk) 13:30, 8 December 2007 (UTC)

It should be the big bang and suns, right? The stars aren't producing hydrogen. As Finlay pointed out - that was there before the stars were born. -- kainaw™ 19:40, 10 December 2007 (UTC)

Gravity fields, mass, volume, density

Lets say we have two objects. Jupiter, and Mini Jupiter. Jupiter, is the planet Jupiter. Both have exactly the same mass. However, Mini Jupiter has a radius of only 500 miles. As such, Mini Jupiter has less volume, but is much more dense. How do their gravity fields compare? Which is stronger? Which is larger? 64.236.121.129 (talk) 19:45, 7 December 2007 (UTC)

You can use simple Newtonian gravity and the shell theorem to figure this out. Outside the radius of Jupiter, the gravitational fields are identical. Inside the radius of Jupiter, Jupiter's own field weakens, its strength now directly proportional to the radius (if you assume Jupiter's density is irrespective of radius, so this is a very very bad assumption. It's assumed for simple physics problems, and I don't know the actual density vs. radius of Jupiter). MiniJupiter's gravity, on the other hand, keeps getting stronger right up until you reach it's edge. Inside of here, it also decreases as you approach the center, under the same bad assumption for density. So MiniJupiter will have stronger gravity inside Jupiter's outer radius, and outside of that radius, they will have equal gravity. Someguy1221 (talk) 19:59, 7 December 2007 (UTC)

Are living beings mostly comprised of water and carbon?

^Topic 64.236.121.129 (talk) 19:49, 7 December 2007 (UTC)

The average organism is said to be about 70% water. In a sense, living organisms are just aqueous chemical reactors. There are some insects that are considerably less that 70% water (as low as 15% if I recall correctly) as an adaptations for dry environments. There are also plants that contain significantly higher than 70% water. As for carbon, well, carbon is a main constituent of every major chemical group in a living organism. Reading from my years old biochemistry notes, living organisms are 1-3% carbohydrates (made mostly of carbon, oxygen, and hydrogen), 2-3% lipids (mostly carbon and hydrogen), 15% protein (mostly carbon, nitrogen, hydrogen, and oxygen), and 7% nucleic acids (mostly carbon, oxygen, nitrogen, hydrogen, and phosphorus). Carbon, oxygen, hydrogen, and nitrogen constitute 96% of living matter (I believe this number is by mass). Someguy1221 (talk) 20:08, 7 December 2007 (UTC)

The Carbon page tells us that that element "is ubiquitous in all known lifeforms, and in the human body it is the second most abundant element by mass (about 18.5%) after oxygen." DMacks (talk) 20:11, 7 December 2007 (UTC)

See also an elemental breakdown at: [4]. Maybe someone who remembers their chemistry class a little better could figure out how much water might be present based on the H & O content. jeffjon (talk) 21:19, 7 December 2007 (UTC)

Large trees have more carbon than water. Inside the tree is dead wood which contains a massive amount fo carbon but no water. David D. (Talk) 23:41, 7 December 2007 (UTC)

I call that cheating. Someguy1221 (talk) 23:54, 7 December 2007 (UTC)

Maybe but lets not let people think that a whole tree is 70% water. David D. (Talk) 03:05, 9 December 2007 (UTC)

Jellyfish are on the other end of the spectrum with up to 98% water. —Preceding unsigned comment added by 84.187.84.147 (talk) 03:52, 8 December 2007 (UTC)

Grammar note: "comprise" doesn't make sense here. You mean "Are living beings mostly composed of water and carbon?" (If you *really* wanted to use "comprise" you *could* instead ask something like "Does the group of water and carbon-based life forms comprise [exhaustive list of living beings]?", but obviously that would be hugely awkward.)--TyrS (talk) 08:05, 15 November 2010 (UTC)

UK telephone extension wiring

I bought a standard UK telephone extension kit (Homebase), wired it up according to the simple instructions, and plugged it into the master socket. (There are no other extensions.) I have two handsets, an old one (maybe ten years old or more) and a new one. Plugging either handset into either socket on its own works just fine: both handsets will ring and give me a dialtone. Plugging the new handset into the master socket and the old one into the extension works just fine too. However, when I set up the configuration I want, with the old one in the master socket and the new one on the extension, the old handset works but the new one is dead. The old handset seems to be somehow blocking the extension. Any ideas how to solve this? Will I have to get another new handset or can the old one be fixed?--Shantavira|^{feed me} 20:10, 7 December 2007 (UTC)

The description you have given of the problem seems to mean that there is a difference between the two sockets. They should be the same. Me, I would double-check my wiring job, with reference to this site and this one. --Milkbreath (talk) 00:12, 8 December 2007 (UTC)

See Ringer equivalence number. This may ring some bells (or not)--TreeSmiler (talk) 01:11, 8 December 2007 (UTC)

REN matters when you have a lot of phones - but it shouldn't be a problem with just two - and it certainly shouldn't matter if you just swap them over. It kinda sounds like a dodgy connection of some kind or another. SteveBaker (talk) 03:39, 8 December 2007 (UTC)

Do you have any6 extra phone wire? Coil it up and connect the old phone to the master through the extension wire. I suspect the ring circuit inside the old phone clamps the ring voltage so that it doesn't get to the extension. Putting more wire between the master socket and the old phone may fix it. --DHeyward (talk) 05:19, 8 December 2007 (UTC)

How many wires did you connect when installing the extension lead: 2,3 or 4?--TreeSmiler (talk) 07:11, 8 December 2007 (UTC)

Four.--Shantavira|^{feed me} 09:59, 8 December 2007 (UTC)

Maternal depressions effects on the Family

What are the effects of maternal depression on the spouse and children, especially teenagers? —Preceding unsigned comment added by 75.131.194.201 (talk) 21:24, 7 December 2007 (UTC)

Wikipedia has postnatal depression. A starting point in the research literature: Do Parenting and the Home Environment, Maternal Depression, Neighborhood, and Chronic Poverty Affect Child Behavioral Problems Differently in Different Racial-Ethnic Groups?
--JWSchmidt (talk) 00:49, 8 December 2007 (UTC)

Photographs

If I point a camera at a brick wall, I see straight lines of bricks running left and right. I really don't understand how this is possible. Since the far corners of the wall are farther away from the camera than the brick directly in front of the camera, they should logically be both out of focus and smaller than the center. I believe our eye corrects for this because it projects the image on a curved surface, but the film in a camera is flat, so this shouldn't affect it. How does this work? 72.155.209.101 (talk) 21:44, 7 December 2007 (UTC)

The focus is due to the depth of focus (dependant on the aperture). In short there can potentially be a wide range of distance that remains in focus. David D. (Talk) 23:38, 7 December 2007 (UTC)

It does get out of focus, if you're shooting with 85mm f/1.2 at 1m away from the wall, or try some macro photography. Point and shoot cameras usually has enough DOF (which is also dependant on the focal length is well) to get pretty much everything in focus. --antilived^{T | C | G} 01:41, 8 December 2007 (UTC)

That's not what I am saying. There is a focal plane, here represented by the wall - DOF does not factor in if the object is flat. Try shooting a grid; if I'm right, the corners squares will be smaller than the center squares and not on the focal "plane" (since they are farther away from the lens). Even if I have your 85mm f/1.2 pointed at this hypothetical wall, the wall would all be in focus, since it is flat. However, the far corners of the wall are farther away from the lens than the part directly in front of the camera. Thus, rather than a focal plane, should we not be seeing a focal sphere, where the points in focus lie at equal distance from the camera? And since the points farther away from the camera are, well, farther away, should they not be rendered smaller? 72.155.209.101 (talk) 02:32, 8 December 2007 (UTC)

(edit conflict) It all depends on the projection. Normal camera lenses are designed to give a rectilinear projection, which has the desirable property that the resulting image looks "right" (as in undistorted) when displayed on a flat surface (such as a piece of paper or a computer screen) — assuming the viewing distance and angle are correct. (Fortunately, our brains also tend to mostly ignore the small distortions that result from viewing such images from a wrong distance or angle, as long as the mismatch isn't too severe.) Essentially, this is because the rectilinear projection is exactly what you'd get if you, say, held up a flat transparent sheet in front of your face and traced the scene onto it as you saw it.

However, the rectilinear projection does have some disadvantages, particularly in wide-angle photography. One is that it can't possibly produce a field of view wider than 180°, and even at much lower fields of view (say, anything over 60°) it tends to look distorted unless projected on a very large canvas and/or viewed from a very close distance. Another problem is that, contrary to what you might expect, if you rotate the camera the image will not simply scroll left or right — rather, horizontal lines will appear to rotate. This is the price one has to pay for keeping straight lines straight, and is related to the effect known as the corner illusion (or I thought it was, but I can't find an article on it — perhaps I'm misremembering the name). There are alternative projections, commonly used in panoramic photography, which avoid this at the cost of making some straight lines appear curved. —Ilmari Karonen (talk) 02:38, 8 December 2007 (UTC)

Molecular solution

From [5], a distinction is made between a solution and a molecular solution. I have never heard of this before, but I am not a chemist. Can anyone clarify this? If this is important, maybe we should have an article on molecular solution ?--Filll (talk) 23:12, 7 December 2007 (UTC)

They seem to be referring to ionic organometallic compounds. Unlike an inorganic salt, these compounds don't fully dissociate in solution, and instead form complexes of several carbanions and metallic ions. However, I've never heard this term used to describe it. Someguy1221 (talk) 23:27, 7 December 2007 (UTC)