Wikipedia:Reference desk/Archives/Science/2007 May 17

Science desk
< May 16	<< Apr | May | Jun >>	May 18 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

17 May

Ducks

So, what's this duck? It's on a small lake in southern England, in a relatively rural setting. The same lake has a handful of common moorhens, at least one Eurasian coot, and the usual large collection of mallards. However, it's certainly not a mallard of any form, it doesn't look much like a coot or a coot chick, and juvenile moorhens are apparently not grey (plus it's quite large - I estimated it about the size of an adult one).

The legs are clearly like those of a moorhen, as is the body shape and beak, but the colouration (see also this) seems wrong. Any idea? Is this just a moorhen of unusual plumage? Shimgray | talk | 01:01, 17 May 2007 (UTC)

On consideration, I've only ever seen coot chicks in their "little bundle of fluff" stage, never really what they look like as "teenagers", as it were. Might this just be a reasonably old juvenile coot? I can't find any pictures beyond a comment saying "is paler"... Shimgray | talk | 01:10, 17 May 2007 (UTC)

I think it's a juvenile moorhen - the shape, stance, legs and bill colour all say moorhen. If it was a coot it'd have a dark undertail whereas this has a paler patch there; Collins Bird Guide also says a young coot should have a yellow-grey collar, which the young moorhen lacks. From the general dishevelled look, I suspect it's halfway between the dark grey downy stage and its paler juvenile plumage, which would explain why it doesn't have the white line around the edge of the wing yet. But IANBO. --YFB ¿ 01:38, 17 May 2007 (UTC)

Sounds fair. I have a recollection that whilst it was still on the bank it looked a lot more recognisably moorhen-like, but the camera wasn't properly focused at that point (as the image demonstrates, I was really rather pushing it anyway...) so I can't be sure. The thing that confuses me, though, is that there were three or four adult-plumaged moorhens around, some of which I swear were noticeably smaller than this. A male/female split, perhaps? Shimgray | talk | 17:46, 17 May 2007 (UTC)

And here it is again. swimming; on shore. Pretty clearly brown when actually in the water; must be a trick of the light when on the island. Shimgray | talk | 23:51, 18 May 2007 (UTC)

Ah, seems to be fixed now... was having trouble editing this section. I've replied on Shimgray's talk page, since I couldn't post here. --YFB ¿ 02:48, 19 May 2007 (UTC)

Fructose being "better" in fruit than candy

My daughter often asks me sciencey questions at bedtime. Tonight, she asked me what the difference was between the sugar in sweets/candy and the sugar in fruit; I said "nothing, I think they're both fructose pretty much these days" (we're in the US). I asked her what made her wonder, and she told me another relative had told her that fructose that's actually in the fruit was "better" somehow; I said I'd go and ask them and get back to her. When I tracked the said relative down, they told me that HFCS is "refined" and therefore worse for you than "raw" sugar in the fruit. Is this true? I've looked at Sugar; what the relative called "raw" appears to be "natural sugars", and HFCS certainly isn't "refined sugar" as defined in that article, but I can't find anything that says that n grams of HFCS is worse for you than n grams of fructose (or even chemically different, other than whatever percentage of glucose it also contains). I stopped chemistry at GCSE, unfortunately. Can anyone give me a clue as to what to tell my daughter? Marnanel 01:43, 17 May 2007 (UTC)

The issue is complicated. In one sense the categories of "refined" vs "raw" are largely American cultural value categories like "clean" or "unclean" foods, except that the other components of fruit can slow the speed of consumption and digestion somewhat (reducing the rapdity of the effect on the blood glucose level-- i.e., the glycemic index), and may provide some additional nutritive value. In the 1970s, fructose was sometimes touted as a superior sweetener to sucrose because it also had a slightly slower impact on blood glucose levels. In the last decade, however, there is increasing suspicion that fructose (especially in the high fructose corn syrup form used in soda and many sweets) may have some unwanted attributes, such as a slower effect on hypothalamic satiety, or inhibition of insulin action in the liver, effects which may amplify either obesity risk or type 2 diabetes risks, respectively. Bottom line: fruit is likely better for her than anything containing high fructose corn syrup. alteripse 02:14, 17 May 2007 (UTC)

Fructose is much sweeter than glucose [reference needed]. Aaadddaaammm 02:49, 17 May 2007 (UTC)

Fructose is the sweetest of all sugars. http://www.answers.com/topic/fructose. According to the Fructose article on Wikipedia, the fructose in HFCS used to be glucose. some of the glucose was converted with enzymes into fructose.

While fruit and sweets may both contain significant amounts of fructose, the important difference probably lies in everything else in the foods. Two apples may have the same amount of fructose as one 12oz can of soda[1], but the soda lacks any of the vitamins and fiber you can get from fresh fruit. A gram of fructose is a gram of fructose, no matter the source; foods with significant processed sugars, however, probably tend to have more "unhealthy" or less "healthy" nutrients than those that don't. — Scientizzle 21:35, 18 May 2007 (UTC)

Easiest way to have a self-sufficient life?

Well, I do like the idea of being green, but I also like the idea of being reliant on myself, so I was thinking about going (at least somewhat) self-sufficient. I figure the easiest way to do this without a huge lifestyle change would be to create a sturdy, economical, efficient, and eco-friendly house (i'm looking at a monolithic dome, which fits at least three of those), use natural power, and use all electrical appliances. That takes care of 99% of things, but I do have questions on that:

• Where in Canada would be the best place for a building like this? Preferably somewhere without a lot of building codes or permits needed, but still near towns or cities. I say Canada because there's always been a part of me that wants to leave the states, and it's the closest I could be to family, not to mention I have friends in Canada.

• In general, which is cheaper/more efficient, solar power or wind? Also, which is easier to maintain? Solar seems like it's less of a hassle, but then you have to have more batteries to power your house at night, and i'm not sure which is cheaper.

• Slightly off topic, but what electric car is the best mix of price, performance, and efficiency? By performance, I mainly mean how far it can drive on a charge. I'd probably have three vehicles, a small gas powered car for trips, such as something from japanoid.com, an Obvio, or a Smart, a small electric car for every day things like groceries, and an electric bike, for getting around town (driving to town in a car and parking and going around on a bike is a good way to not run out of fuel, I figure)

• Also off topic, but is it as much of a PITA to get odd/foreign cars street legal in canada? Japanoid.com makes me think it isn't, but it would be nice to know.
  

And then of course, to be more self-reliant, I'd have my own water and food supply. I figure gardening isn't too hard, and i'll probably still get most things from a supermarket, at least at first, but how would I handle water? I figure I'd need a well, is there any way to get this automagically? as in, have it made with the house, so it handles your water supply? And how would you purify it? I'm going to have a water purifier even for a government tap, I can't stand hard water, but I figure this makes it more complicated. Am I just being silly, and should I get a water line, since it would be impossible for me to be truly self-sufficient? thanks for reading all this, -- Phoeba Wright^OBJECTION! 02:11, 17 May 2007 (UTC)

Would your ethics allow you to just buy a house with existing well and septic tank ? Many exist in isolated rural areas, which are losing population, so they should be available cheap. StuRat 02:20, 17 May 2007 (UTC)

It's not really about ethics, more about just being able to live by myself without making a huge impact on the enviroment. That's probably a good idea, but I don't know how easy either of those are to use (mainly, how to maintain a septic tank, and how to get a water supply for your house out of a well), and I want to make a monolithic dome home (see monolithic.com). I have extremely messed up ethics, they aren't a concern for me -- Phoeba Wright^OBJECTION! 02:41, 17 May 2007 (UTC)

A small electric pump (or solar powered or wind powered, if you prefer) can move the water from the well to a water tower whenever energy is available. It can then be used as needed. A good septic tank might need to be serviced periodically, but should otherwise be trouble-free. Also keep in mind the huge difference in harm to the environment between reusing an existing home and building a new one. StuRat 23:08, 18 May 2007 (UTC)

Electric bike? What about a traditional bike? Also, I have my doubts that an electric car + electricity + all the infrastructure you're going to need to keep it charged + a spare gas powered car for trips is more economical than just having a gas powered car, and electric car batteries are extremely difficult to dispose of in an eco-friendly manner. I don't think it's that big of a deal to dig a well. --froth^t 03:51, 17 May 2007 (UTC)

Comment - Self-reliance and environmentalism are separate ideas, and often even mutually exclusive. Nimur 04:26, 17 May 2007 (UTC)

Very True. Anyway, I was thinking a spare car would probably be something old, but still fairly cheap, like the ones I listed. I didn't think digging a well would be a big deal, it was using one to run a house (dishwasher, laundry machine, shower) and having pure water from it, and septic system maintenence. A traditional bike would work, but an electric assist is never a bad idea to have when you're tired. The infrastructure would mainly be for the house, not the car, I don't get out much, so I doubt an electric car would be sucking very much juice. I've also wondered, in Canada, if you hook your house up to the power grid, but generate all your own power, are they required to pay you for the electricity you're pumping back into the grid? I'm fairly sure they are in most parts of the US, but it would be nice to know if it works elsewhere. -- Phoeba Wright^OBJECTION! 07:28, 17 May 2007 (UTC)

I think winnipeg has the "windiest corner in North America" [2] so, if you built there, I think wind power might prove effective. Edmonton is also high ranking in terms of hours of sunshine if you'd rather go the solar route, but land around that city's crazy expensive.

Being self-sufficient is WAY harder than you make it sound. Let's just think about one teeny-tiny part of your plan...So you have an electric car - and let's just suppose you have enough solar panels to recharge it (you won't - but we'll assume that you do for the sake of argument) - what happens when it breaks down? If you are self-sufficient, you need to be able to fix it - but how do you replace that dead microprocessor and rewrite all of the software? What do you do about a broken axle? Heck - have you even thought about how you replace worn out tires and replenish the lubricants? How do you cope with the fact that solar panels start to lose power after a few years? The fact is that going this route is a million miles from self-sufficiency. If you plan on being self-sufficient you need a sufficiently low-tech vehicle that you can repair or replace every single part of it yourself. I suggest getting a horse...well, several horses because you'll need to breed them. You'll need a lot of acreage to feed them through the winter - so plan on using them to do the ploughing too. ANd that's just to get transportation together. How are you going to keep your food fresh? You can't have a refrigerator because you have no way to repair it when it stops working - yet your pathetically small fields and limited range of livestock won't produce food all year round - so storage and preservation becomes a HUGE problem if you don't want to starve. Just think of any one aspect of your live and think about it that way - even the smallest problem becomes a nightmare once you are doing it without external help.

It's totally unrealistic to consider being 'high tech' and self sufficient. You need to go back to medieval standards of farming, weaving, healthcare, nutrition, etc. You have to do that because that was the last time in history when it was possible to be even close to self-sufficient. It's just wishful thinking to imagine otherwise. SteveBaker 03:26, 19 May 2007 (UTC)

Steve, my point is about a mile back, you might want to turn around -- Phoeba Wright^OBJECTION! 02:26, 20 May 2007 (UTC)

I live outside Calgary on 8 acres. Our house is too big to be self-suficient at this point but we have a well and septic field and a garden. We recycle (to community recycle bins) as we do not have garbage pick-up. I have a large compost pile which can then be recycled into the garden. Our garden grows plenty of veggies which I freeze, pickle or dehydrate. I have a smoker and make my own sausage and jerky. My herb garden grows peppermint and camomile for tea. I also make my own soap & lotions. There is alot you can do with a little practise and instruction from the internet. Go for it. It might be a good idea to look for a small homestead or acreage to start with and see what you can do from there. Enjoy! - NiteRN

Hovering Shoes

Above there is a thread about "shoes/skis" that float on water...what about ones that work on land? They would essentially be frictionless, or floating a few inches off any ground. Lean in the direction you want to go, and a sensation similar to running and sliding on a patch of ice would occur, moving you long distances with little effort. How would this be accomplished technologically? 140.180.11.227 03:03, 17 May 2007 (UTC)

With great difficulty. You could probably achieve that effect with high-pressure air or some sort of jet propulsion, but it would be very heavy, consume a great deal of energy and probably be difficult to control. Get a Segway. --YFB ¿ 03:24, 17 May 2007 (UTC)

Fill them with vacuum such that they displace a weight of air equal to that of the person plus accouterments. Eldereft 05:00, 17 May 2007 (UTC)

They'd need a volume of somewhere approaching 50m^3 for a 60kg person. Not very practical? Capuchin 12:00, 17 May 2007 (UTC)

50 cubic meter shoes would need a surface area around 60 square meters - with air pressure at around 10 tons per square meter - the shoes would have to be able to withstand 600 tons of pressure. We're talking heavy steel structures here! Oh - but wait - isn't steel rather heavy? You are much better off filling them with helium or something. "Vacuum balloons" sound like a great idea - but you can't make them strong enough to resist air pressure. SteveBaker 13:12, 17 May 2007 (UTC)

Rollerblades? "Heelys" (my son had those - they were very cool!) They are pretty close to frictionless. I don't see how 'leaning in the direction you want to go' helps though. Wheels work well because they offer little rolling resistance in one direction - yet you can push sideways on the shoe to get some thrust to get you moving. Totally frictionless shoes would be impossible to walk in. SteveBaker 13:17, 17 May 2007 (UTC)

You could hold a lot of helium baloons, and therefore reduce the force pulling you toward the ground. This would reduce friction a lot. If you had enough balloons

Black holes again!

If you're falling feet first into a black hole and you're past the event horizon, could you look down and see your feet? Or would it be a slightly delayed image of your feet (until your eyes could overtake the light rays)? How far could you see down into the black hole? Could you even see the singluarity, or would your eyes actually have to be on it to see it? It's a very large one, so you don't have to worry about spaghettification :) --froth^t 03:40, 17 May 2007 (UTC)

Surely something would kill you before you would be able to recognize it. Are you asking whether light could travel radially outward from the singularity towards the eyes, which are closer to the event horizon? Probably not, since it is gravitationally captured by then. More to the point, even if any light could travel back outward (even if it never re-crosses the event horizon boundary), the amount of distortion of the rays would preclude image formation. Nimur 04:16, 17 May 2007 (UTC)

This is how I think it must work (somebody more knowledgeable please correct me if I'm getting it wrong): Yes, you would see your feet. The photons leaving your feet "trying" to head outward would actually fall backwards toward the center, but your eyes would be falling faster and would catch up with the photons. However, the image you would be seeing at any one moment would depict an event (the moment when the photons left your feet) that occurred when the feet were located further away from the center than your eye is when you see the event. Same thing with your unfortunate friends who fell in immediately before you: you might see them, but only as they were at a time when they were not yet as far in as you are when you see the image. Thus you are, in a strange sense, not really looking "in" toward the singularity, but back outward. In particular, you could not "see the singularity". In fact, I think what you would see at the furthest apparent distance in front of you would be a (very darkened, for all practical purposes invisible) image of events that happened at the event horizon behind you a long time ago. For you, however, in your local reference frame, everything would feel rather like normal... for a while, until the tidal forces would start to rip you apart. --mglg_(talk) 04:33, 17 May 2007 (UTC)

Looking at the same thing in a totally different way: once you are inside the event horizon, your local spacetime coordinate system has been rotated so that all positions (events) that lie closer than you to the center (spatially closer according to the coordinate system of a distant observer) are in the future for you. (More precisely, your whole past light cone lies outside of you.) You cannot see events that lie closer than you to the center, for fundamentally the same reasons we cannot see into the future in everyday life either. But, again, from your perspective your local spacetime is perfectly normal, and you don't feel anything funny (yet). --mglg_(talk) 04:50, 17 May 2007 (UTC)

It may be enlightening to think about the moment when your eyes pass the event horizon. Any light that was ever emitted straight outward exactly at the event horizon will remain hovering at the horizon forever, eternally trying to escape. And that is all the straight-outward-directed light that will be there: light emitted outward from outside the horizon will escape, and light emitted from inside the horizon will fall inward. Therefore all the events that you see, when your eye is at the horizon and you are looking straight inward, actually happened at the same spatial point, namely that point on the event horizon where you are, but at different times (all according to the distant observer's coordinate system). Recent events will look close, and early events will appear to be further away. But to you it will look normal; according to your local (co-moving) coordinates, the events that look like they are located toward the center from you actually are. The difference of opinion between you and the distant observer is not all that different from a "normal" Lorentz transformation between the coordinates of different reference frames that move relative to one another, as encountered in special relativity. --mglg_(talk) 16:03, 17 May 2007 (UTC)

Biochemistry Universities

In your opinions, what are the leading universities in the world in terms of biochemistry research? Aaadddaaammm 04:05, 17 May 2007 (UTC)

This is a very tough thing to answer because biochemistry is such an immense field. You could start with silly and useless comparisons of research-dollars, number of faculty, and other "marker" statistics, but you should think about narrowing your focus. Any top research university will certainly have a strong biochemistry program, with specialization in some areas. Nimur 04:09, 17 May 2007 (UTC)

Addendum - However, if I had to name favorites, I would pick any university with a good balance between work and aesthetics. Good science is everywhere; good weather is not. Nimur 04:11, 17 May 2007 (UTC)

I sincerely doubt that cutting edge biochemistry research is found at every college where there is a balance between work and aesthetics. [3] lists the top biochem grad programs in terms of NIH research grants, and [4] is U.S. News list of a variety of schools with biochem undergrad programs. Although they list the ranking of each, I did not see a way to sort by the ranking of the biochem program. If an undergrad, you might consider the overall quality of the school, its location, its costs, etc. Edison 13:47, 17 May 2007 (UTC)

Edison, my comments were meant to illustrate the fallacy in a total order ranking of "merits" or "cutting-edge-ness." Cutting edge in industrial applications is very different from cutting-edge academics; and funding dollars are only one way to gauge the performance and quality of work. I believe it is more advantageous to consider the quality of a specific sub-discipline, if a student is pursuing research work. Nimur 21:09, 17 May 2007 (UTC)

McGill -Arch dude 02:58, 18 May 2007 (UTC)

Traditionally, University of California, Berkeley is considered the top biochemistry school. Other institutions with reputations as leading places for biochemistry include the Pasteur Institute (not a university), Cambridge University, Harvard, and Caltech. Such reputations probably don't mean very much from an undergraduate perspective, while from a grad school perspective, having a good advisor is far more important than the overall departmental research picture.--ragesoss 01:43, 20 May 2007 (UTC)

Random v. linear evasion

A few years ago, I recall reading, or possibly hearing in a lecture, that some species of rodent (?) had shifted its behavior due to collision with cars. This species previously ran in a randomly shifting path, but generally in a line. This strategy worked well for evading predators, but not so much for cars. In recent times, repreated collisions with cars had selected for a more linear evasion path. My question, does anyone have more information on this, possibly even a species or (blessed be) a citation? Many thanks, --TeaDrinker 04:49, 17 May 2007 (UTC)

The closest thing I can find in relation to this topic is the effect of fencing along roadways, which can create geographic separation of the population, leading to evolution and eventual speciation. I tried this google scholar search which resulted in mostly unrelated biochemistry subjects. Maybe you can further refine it? Nimur 05:31, 17 May 2007 (UTC)

I've been told (no RS, unfortunately) that this is because it's easier for drivers to predict the path of something moving with constant speed and direction (velocity), as opposed to something that's randomly jerking around. I've also heard this is the best way to avoid getting run over if you feel you must cross against traffic, but I would not recommend testing this. Someguy1221 09:42, 17 May 2007 (UTC)

Thanks all, for the insight. I will keep on searching. --TeaDrinker 09:31, 19 May 2007 (UTC)

the presence of melanin(pigment) in human skin is determined by human gene . presence of melanin makes skin look darker .

it is seen that when a person exposes his skin long time under sunlight his skin becimes darker . my question is how is this possible while his gene remains the same ? is this process reversible ? what can one do to regain the skin colour that he had while he born ?

I believe it is because the sun's rays cause the person's skin to produce more pigment, although that's not a very precise answer. I think if you just avoid sunlight for awhile, tans will go away, in slightly more extreme terms, you could try skin bleaching or other cosmetic surgery -- Phoeba Wright^OBJECTION! 07:46, 17 May 2007 (UTC)

When human skin is exposed to sunlight (in particular, Ultraviolet radiation) a pigment called "melanin" is released that makes the skin darker. Melanin comes from cells called Melanocytes. Differences in genes, however, affect the activity of these cells. So a person who, without the effect of the sun, has darker skin is likely to possess melanocytes that are more active than someone who has naturally light skin. I would say that after exposure to the UV radiation has ceased the melanin may begin to break up and disappear. More information can be found at Sun tanning. Vvitor 07:52, 17 May 2007 (UTC)

Great question, and the very good answers above lead to a couple of braoder ideas that might interest you: The physical characteristics (phenotype) of a person (or any living thing) are affected by both their genes (genotype) and their natural environment, which includes things like diet, lifestyle, and in this case, exposure to the sun. The perfect human would have skin that would darken and lighten instantaneously in response to their environment, because although too much sun causes cancer, some is still required for vitamin D production, so a happy medium is needed. This is homeostasis. We haven't evolved to travel to different continents on holiday, so our genes give our skin just enough plasticity to cope with the changing seasons, which is why we need sunscreen to supplement our skin's natural protection when travelling to places sunnier than our ancestral lands. You may have noticed that equatorial Africans don't get lighter living in Scandinavia; this is because there are no seasons on the equator so have little evolved plasticity! Bendž|Ť 14:42, 17 May 2007 (UTC)

Well, you seem to be puzzeled that it's in the genes but depends on sunlight. Have a look at Regulation of gene expression. 84.160.208.134 18:29, 17 May 2007 (UTC)

Conservation of Mass - kids

By what age do children develop an understanding of conservation of mass?—Preceding unsigned comment added by 122.169.10.154 (talk • contribs)

When they can feed themselves and use the lavatory unassisted.--Shantavira 13:24, 17 May 2007 (UTC)

The Theory of cognitive development of Jean Piaget (1896-1980) says that children go through a series of stages, although not all at the same age. In the third of these, the Concrete operational stage, at about age 7 to 11, they develop notions of reversibility (things can change shape and return) and conservation. Anecdotally, I remember when I was younger than this, an older child who was sharing a bottle of Coca Cola with me would offer me a choice of a thin tall glass or a short wide glass, and it really looked like there was more in the tall glass, but I knew from his smile that there was a trick to the process. Similarly, a child before this stage will think there is really more clay when modelling clay is rolled out thin. Of course there are also post-Piaget theorists. Edison 13:31, 17 May 2007 (UTC)

Acidity of "Special Parts"

Dear Wikipedians,

Wat is the acidity of a human vagina?

The normal vaginal pH is 3.8 to 4.5. --BenBurch 15:52, 17 May 2007 (UTC)

Lightning

What would happen if a nuke was hit by lightning in mid flight?

It might short out the detonation circuits so the bomb wouldn't go off, or screw up the onboard navigation technology, but it's extremely unlikely that the strike would detonate it. Anchoress 15:53, 17 May 2007 (UTC)

Disclaimer - Under carefully controlled conditions, Lightning does whatever it feels like doing... However Apollo 12 I think it was was hit by lightning shortly after lift off and survived. Nuclear weapons are designed to withstand EMP from nearby nuclear detonations, and so I would expect lightning to have little effect. However, it might kill the bird at which time it would most likely fall inert. --BenBurch 15:57, 17 May 2007 (UTC)

lightning is trying to find the easiest way to the ground, so I doubt it would hit a flying object, even if it is much higher than any trees/buildings around it :) HS7 17:28, 17 May 2007 (UTC)

It is not at all uncommon for lightning to strike an airplane in flight. There is a potential difference between an uncharged metal airplane and a charged cloud. If it is large enough, the air will become ionized and voila a lightning strike. On May 8, 1996, Illinois Governor Jim Edgar's plane, a Beechcraft King, was struck by lightning while in flight, per [5] and he lived to tell about it. It started a small fire inside. No ground wire necessary. Edison 20:42, 17 May 2007 (UTC)

Actually I think it is highly likely that if lightning strikes nearby that it will hit a falling bomb, since the metal of the bomb would offer much less resistance then the equivalent amount of air the lightning would have to travel if it didn't hit the bomb. But as above, I don't think lightning would do anything to a nuke, like a plane, the lightning would just pass through. Vespine 22:46, 17 May 2007 (UTC)

Have you not seen the holes in aircraft lightning can cause? (See [6]) Yes, most likely no effect, but there is more energy in a stroke than you can easily imagine. --BenBurch 05:15, 18 May 2007 (UTC)

Marx generator?

Can I make a functional marx generator with only a 35 volt DC power source? Or is that voltage too low to make a working spark gap?

If you run the DC through a vibrator and the resulting pulsed DC through a transformer to step up the voltage, you can likely make it work. --BenBurch 16:02, 17 May 2007 (UTC)

To get a spark in air you need a field strength of about 3 kV/mm, see electrical breakdown, so for any reasonable gap spacing you would need very much higher voltages than 35 V. There are ways to create such voltages, but please do not do this. High voltage backed by significant capacitance is an excellent means of getting yourself killed quick. --mglg_(talk) 17:26, 17 May 2007 (UTC)

Agreed, but there are ways to work with this safely. I mean, I'm still here after 40 years of electrical tinkering. You just have to learn the safety precautions to take and never, ever fail to take them. --BenBurch 17:29, 17 May 2007 (UTC)

OK, if you do know what you are doing, see DC-DC converter. You can buy ones that put out 6kV. Some of these actually work much the same way as the Marx generator, on a smaller scale, with FETs instead of the spark gaps. You could use one to charge your Marx generator with, or hand-build a long one instead of the Marx--169.230.94.28 20:25, 17 May 2007 (UTC)

Use of Jasmine and Rose flowers

Kindly let me know the method of pollination in the above two flowers(Jasmine and Rose). Please tell me if in these plants seeds are produced? Where are thwe seeds found? Can new plants be grown from these seeds? Are these seeds sold? 202.71.137.235 16:12, 17 May 2007 (UTC)Hemchandra

You can in fact grow roses from seed, see [7]. Most often it is done by cuttings though so as to preserve particular traits that would likely be lost in sexual reproduction. --BenBurch 16:52, 17 May 2007 (UTC)

The rose seeds are found inside fruits known as rose hips. --mglg_(talk) 21:10, 17 May 2007 (UTC)

Ashwagandha

Please tell me are Ashwagandha leaves used for weight loss? And please tell me the different types of Ashwagandha plants?

Ashwagandha#Medicinal use doesn't seem to mention weight loss specifically. Algebraist 16:33, 17 May 2007 (UTC)

(after edit conflict) Ashwagandha = Withania somnifera. Seems to be used a lot in traditional medicine, but I could not find any indications in literature that it induces weight loss. In fact, this reference [8] (which deals with carcinogenegis ihibition in lab mice) specifically states that the mice did not lose weight when fed Withania somnifera. Most important, we do not give any medical advice!. No, really, we don't. And, ingesting medicinal plants without consulting a certified physician first is a really, really bad idea. Take care. Best regards, Dr_Dima.

To amplify, there are very few medicinal plants that can be safely used as a medicine. This is because the medicinal effect depends on the amount of whatever active ingredient is in the plant and this can vary greatly. Most medicinal plants have a toxic dose level, and often this isn't far from the clinical dose level. In addition medicinal herbs can pick up traces from the soil of heavy metals and herbicides and other things that are simply no good for you. Unless we are talking about something very safe like Camomile tea or eating Marijuana, I'd stay away from herbal medicines entirely. --BenBurch 16:58, 17 May 2007 (UTC)

Ramdev baba(Yoga teacher) says that when the leaves of this plant are consumed weight is lost but when thw churan(powder)of this plant is eaten weight is gained. Is it True?

blood system

how long does morphine stay in blood system?

Until it's gone

Our morphine article says it has a half-life of 2-3 hours, so its concentration in your blood stream halves every 2-3 hours. (Be sure to also see Biological half-life.) In theory, it's never actually gone, but in practice, by 10 half-lives later, it's down to 0.1% of its original concentration and so is certainly no longer clinically effective. But if the question is really "how long till one can pass a drug test?", that's probably a lot longer, depending on the sensitivity of the drug test and which metabolytes it's looking for.

Atlant 17:24, 17 May 2007 (UTC)

Torch testing In Software Jargon

hi, recently i came across torch testing, wud really be helpful if anyone cud explain what is torch testing in software testing scenario??

Sounds similar to a smoke test. DMacks 18:20, 17 May 2007 (UTC)

OK this really is the final starch question

So I have basically decided there are clearly no quantitative tests for starch. You could have told me a few weeks ago then I wouldn't have wasted my time. But nevermind. I still need to test for starch quantitatively, but it appears I will have to use iodine to do it. So, are there any ways that I can do something to the iodene so that it only reacts a little bit to the starch, so that I can see how much starch there is by how much or how quickly the iodine changes, without it all going dark blue as soon as it gets near any starch? I really need help here and as soon as possible.

A little bit of starch makes a lot of darkness with iodine, and it's a fairly fast and complete reaction. If you want gradations visible to the naked eye, your best bet would be to use very small or dilute samples. DMacks 17:11, 17 May 2007 (UTC)

Small samples of starch? I don't think I can do that. Basically I have a leaf, and I need to know how much starch there is in it at a specific time.

Would cutting a very small bit off of the leaf, and only testing that for starch help :) I really wouldn't know as I am not a very good scientist, (as any regulars here will tell you) :( HS7 17:19, 17 May 2007 (UTC)

I think something like (testing a small cutting instead of a whole attached leaf) that would have to done anyway...I think the iodine test is a destructive test on the sample. DMacks 17:31, 17 May 2007 (UTC)

I do have lots of leaves I can test if each one gets damaged. How small would it have to be for the starch to not change totally?

I am going to go with cutting a very small bit off. Someone tell me quickly if this is wrong.

I have no idea "how much" of the things you'll need here to get a good visual gradation. I guess that's why they call it an experiment. DMacks 18:04, 17 May 2007 (UTC)

One final last thing would I be able to test for starch without boiling the leaf for a few minutes first? Would it continue photosinthesizing during this time? How long will it take to prepare a leaf for the test?

A few minutes is unlikely to make a huge difference in your detection data...since you're looking for (I assume) differences among different leaves, you'll still see the same differences as long as you are consistent in your timing and preparation process. A few minutes probably won't affect the data that much; if you're concerned about having photosynthesis stop at a precise time (vs continuing during the prep), do the prep in the dark (or very dim light) and get the leaf into very hot water very quickly (destroy the biological starch making and using processes). DMacks 18:18, 17 May 2007 (UTC)

This might well be totally wrong, but could you test the leaf without boiling it, therefore making it difficult for the iodine to get into the leaf, and thereby making the test take longer :? Would the Iodine acyually be able to enter the leaf through stomata and the cut edge :) HS7 18:21, 17 May 2007 (UTC)

Does a thermodynamic capacitor exist?

Can anyone explain me The mechanism by which could a capacitor absorb sunlight-generated heat and convert it to electricity? JammieJammiefungt 17:47, 17 May 2007 (UTC)

I don't think capacitor is the name for such a thing. Maybe solar panel or Solar cell would help? Friday (talk) 17:49, 17 May 2007 (UTC)

Of course you could always connect a regular capacitor to a solar cell

Have a look at Thermoelectric effect 84.160.231.206 18:41, 17 May 2007 (UTC)

So a thermodynamic capacitor does not exist....

Ok. Is there nothing pther than solar panels? A Thermo-Transducer or something simpler as to not make-up words?

If you're asking about devices that convert solar energy into electricity, there's no need to invent new names for them. See solar cell for a large informative-looking encyclopedia article on this topic. Friday (talk) 18:19, 17 May 2007 (UTC)

The thermoelectric effect was already linked for you. As far as devices that convert electromagnetic energy from the sun into useful energy for humans go, three main options come to mind: photoelectric (quantum) effects (optical to electrical direct conversion), purely thermal effects like the aforementioned thermoelectric effect and things like solar water heating (this covers a broad range of devices), and chemical (such as the useful chemical energy plants store just for your consumption). -- mattb 22:51, 17 May 2007 (UTC)

Can a lake have two outlets?

Can a lake have two outlets? So that it creates an island in between? Why or why not? --Spoon! 19:10, 17 May 2007 (UTC)

If you want to create an island - yes. It is not uncommon. A mound of earth forms in a single outlet, trapping sediment, and grows. The two outlets go around the mound and rejoin. This also happend right in the middle of rivers (I can see one from my office window - it is called Drum Island, a little island in the middle of the Cooper River). As for two outlets that do not create an island between them, that is also possible, but less common. High altitude lakes can form more than one outlet river and the rivers do not have to join together downstream. --Kainaw ^(talk) 19:17, 17 May 2007 (UTC)

Of course assuming the rivers end up in the sea and don't flow through tunnels and you define an island as a peice of land surrounded by water than two outlets have to create an island it just might be a rather big one ;) Plugwash 19:20, 17 May 2007 (UTC)

If you do a Google search on "lake" and "two outlets", you will find many examples. The first hit that's in Wikipedia is Highland Lake (Stoddard, New Hampshire). Of course, when a lake is artifically made or its flow is controlled by dams, it has as many outlets as the dam engineers want. A notable example is Gatun Lake in middle of the Panama Canal, which supplies water to both parts of the canal. --Anonymous, May 17, 2007, 22:57 (UTC).

• Lake Michigan has two outlets. The Chicago River was reversed many years ago and now flows out of the lake rather than into it. --BenBurch 23:58, 17 May 2007 (UTC)

Flower identification

I posted this a few weeks ago without success in identifying it. I had suggestions of foxglove, snapdragon, and Texas Bluebonnet, none of which quite seems to match. Can someone help identify it? J Are you green? 20:35, 17 May 2007 (UTC)

Could you give us some more information, such as on what continent and in what environment the flower was found , whether it grew wild there or might have been planted, etc.? --169.230.94.28 20:44, 17 May 2007 (UTC)

From afar it looks like one of the many, many variants of Impatiens. Could be tricky to find the right one and verify it. 84.160.231.206 20:53, 17 May 2007 (UTC)

I'm almost certain it was not wild. It was in a garden in mid-eastern United States. J Are you green? 21:03, 17 May 2007 (UTC)

Penstemon?

A gardening friend agrees that it is one of the many, many plants of the Penstemon family, though which one she does not know. It is not a variety found in eastern Canada, for example. Bielle 20:43, 19 May 2007 (UTC)

I think it is Angelonia--try googling name as image

Thank you. Angelonia seems to fit well. I would be very appreciative if someone could verify this, though. J Are you green? 21:48, 19 May 2007 (UTC)

Your picture seems to match exactly Angelonia angustifolia Angel Mist Dark Rose (google image), so I don't think there is any doubt about your image being Angelonia--63.201.4.254 23:27, 19 May 2007 (UTC)

Sounds good to me. Thank you for your help. J Are you green? 02:01, 20 May 2007 (UTC)

Relative Speed

If an object is going at or close to the speed of light and another object is going in the opposite direction at the same speed.

Wouldn't the second object be going faster than the speed of light relative to the first object or vice versa? --M.A.D.M.D. 21:49, 17 May 2007 (UTC)

See velocity addition formula. Short answer: no. --Tardis 22:17, 17 May 2007 (UTC)

It actually depends on in whose frame of reference you are interested. If you stand next to the railroad and observe two trains going by in opposite directions, each with a speed close to $c$ (in your frame of reference), then yes, their relative speed is greater than $c$, as far as you are concerned. But for an observer on one of the trains, the other train does not have a speed greater than $c$ relative to the train with the observer. The rule is that whenever you measure the speed of an object, you will find that it moves with a speed less than $c$ relative to you, the observer. —Bromskloss 23:18, 17 May 2007 (UTC)

That's a fair point, but the trick is to define "velocity relative to". When considering just two objects, it's somewhat odd to define the velocity of one relative to the other as being the simple subtraction of their velocities as measured by an third party (because it depends on which third party!); of course, M.A.D.M.D. implicitly introduced that third by giving both objects a velocity to begin with. It still strikes me as more fundamental to take "relative to" to mean "as measured in the frame of", even though in this case that's largely discarding part of the question, at which point my simple answer applies. --Tardis 15:45, 18 May 2007 (UTC)

100% reflextion

is there a material that reflect 100% light and absorbs nothing from it ?

Every material has a critical angle at which it reflects all of the light. --M.A.D.M.D. 22:12, 17 May 2007 (UTC)

The best we've got is dielectric mirrors. The percentage of light reflected and not absorbed has a lot of nines in it. [Mac Δαvιs] ❖ 22:32, 17 May 2007 (UTC)

Note that these very high reflectivity mirrors are typically fairly narrow-band. See distributed Bragg reflector. Incidentally, I have to disagree that light incident beyond a critical angle will experience truly total reflection. Some small amount will still be lost, just as the second sentence of that article hints at. -- mattb 22:43, 17 May 2007 (UTC)

What loss mechanism are you thinking of here? --Prophys 11:41, 19 May 2007 (UTC)

Sure: see Unobtainium. -Arch dude 02:31, 18 May 2007 (UTC)

mouse

what would a mouses nipples look like if its suckeling babys because ive never seen what a mouses nipples look like normal compaerd to a mouse that isnt suckleing young i would rather have a image thank u for your time --Sivad4991 23:00, 17 May 2007 (UTC)

I didn't have much luck, but did find this site showing the diff between male mouse nipples and female mouse nipples (near bottom of page): [9]. It seems to imply that, as adults, you won't be able to see the nipples unless the female mouse is nursing. StuRat 05:18, 18 May 2007 (UTC)