Wikipedia:Reference desk/Archives/Science/2010 October 9

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Science desk
< October 8 << Sep | October | Nov >> October 10 >
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.

October 9[edit]

Why do parrots live such a long time?[edit]

Why is it that the large parrots (e.g. macaws, cockatoos, Amazons, African greys) have a life-span comparable to humans? Is it not a general rule that the smaller the animal, the shorter the average lifespan? Even large parrots are not particularly large in the scheme of things (what, about the size of a chicken or so?). I don't know if there has ever actually been a verified, documented case of a parrot living 100+ years but I know that there have been many that have reached their 70s. Is there anything specific about a parrot's lifestyle that makes such longevity advantageous? -- (talk) 07:24, 9 October 2010 (UTC)

Well longevity in general is always advantageous, because it means each individual has more chances of producing more offspring. So why aren't all species long-living? One answer is predation: animals which have a lot of pressure from predators will have shorter life spans, because they have to hurry up and reproduce before they're eaten. Larger animals tend to have fewer predators and so longer life spans. Physchim62 (talk) 12:10, 9 October 2010 (UTC)
But that doesn't really answer the OP's question. Aren't parrots subject to as much pressure from predators as other similarly sized birds? —Angr (talk) 17:00, 9 October 2010 (UTC)
Longevity is not in general advantageous. Older animals are more likely to produce genetically defective offspring, and are less capable of raising their offspring. As a species, it's often better to just spend the resources to make new individuals who can do the job better and more efficiently than to spend on prolonging the life of old and damaged ones. Besides, most birds don't live that long even in the absence of predators. Rckrone (talk) 20:08, 9 October 2010 (UTC)
Well, parrots can get pretty large, which may help with the predation thing, Macaws, for example, can have a wingspan over 1.25 meters or so, meaning they may be as large as any predatious birds, and being able to fly tends to keep away the ground-based predators. --Jayron32 03:00, 11 October 2010 (UTC)
I challenge the idea that size is related to longevity. Elephants, for example, despite being much larger than humans, live only 50-70 years, according to elephant. Chihuahuas have twice the average lifespan of Great Danes. Chinchillas and Giraffes have comparable lifespans according to my roommate, a chinchilla owner. There is a lot more that goes into it than pure size. Falconusp t c 04:13, 11 October 2010 (UTC)
Comparing dog breeds might be a little misleading since the dogs were selectively bred by humans. I mean some of those dog breeds can't even reproduce properly without human intervention. Googlemeister (talk) 13:18, 11 October 2010 (UTC)
Ok, the short but uninformative is 'because natural selection favored longevity in parrot ancestors.' The reasons for this probably have to do with R-k_selection. Parrots have low clutch size compared to other birds, and high levels of parental involvement in raising of young. Also anomalous is parrot intelligence. They have varied diets, and must learn (from parents) how to find appropriate food in different seasons. Since parrots spend so much time with young, they cannot raise many at once. Thus, to have a high lifetime reproductive output, they must live for a long time and reproduce in small clutches over many years. Hope this helps. --SemanticMantis (talk) 15:02, 11 October 2010 (UTC)
I don't know if this could possibly be relevant to the question at hand, but I think research has indicated that having 3 generations alive at the same time has proved advantageous to humankind. See here. Also see here. Note where it says:
"One more distinction between Neandertals and moderns deserves mention, one that could have enhanced modern survival in important ways. Research led by Rachel Caspari of Central Michigan University has shown that around 30,000 years ago, the number of modern humans who lived to be old enough to be grandparents began to skyrocket. Exactly what spurred this increase in longevity is uncertain, but the change had two key consequences. First, people had more reproductive years, thus increasing their fertility potential. Second, they had more time over which to acquire specialized knowledge and pass it on to the next generation—where to find drinking water in times of drought, for instance. “Long-term survivorship gives the potential for bigger social networks and greater knowledge stores,” Stringer comments. Among the shorter-lived Neandertals, in contrast, knowledge was more likely to disappear, he surmises."
At least in the case of humans, this is indicative of a species-wide advantage in longevity, at least up to a point. Bus stop (talk) 15:16, 11 October 2010 (UTC)

Levitating animal[edit]

When was the first animal levitation experiment happened? Is there any side-effect of being levitated? I read that actually every animal has magnetic property, is this true? Is it done only using strong magnet? When will human able to experience levitation? Thanks for the answers. roscoe_x (talk) 09:03, 9 October 2010 (UTC)

The research paper was submitted in 1997 Of flying frogs and levitrons, The Levitating frog itself See also our article Magnetic levitation--Aspro (talk) 10:02, 9 October 2010 (UTC)
All animals (and most other things as well) are diamagnetic, that is they are slightly repelled by a magnetic field. However, the effect is usually very small, so you need a very strong magnet to be able to use it to levitate things. As far as I know, the largest animal that has been levitated to date is a hamster called Tisha: see A.K. Geim and H.A.M.S. ter Tisha, Physica B 294–295, 736–739 (2001) doi:10.1016/S0921-4526(00)00753-5. Physchim62 (talk) 11:52, 9 October 2010 (UTC)

Radio-controlled watch exactly 40 minutes fast[edit]

My radio-controlled wristwatch is exactly 40 minutes fast today. I live in Germany and it should be receiving DCF77. I have reset it twice and it keeps going to a time exactly 40 minutes ahead of where it should be. Any ideas/suggestions as to what's going on and how to fix it? —Angr (talk) 16:57, 9 October 2010 (UTC)

Look for timezone settings in the manual for your watch. Check that it is set correctly. –Henning Makholm (talk) 05:15, 10 October 2010 (UTC)
The time zone is set correctly. There's no time zone 40 minutes ahead of Central European Time anyway. —Angr (talk) 14:58, 10 October 2010 (UTC)
Can we accredit this to "mysterious implementation bug" inside the watch? The radio synchronization signal is probably correct (if not, thousands of other clocks would be off by 40 minutes, spurning some kind of public attention and a quick fix from the responsible agency to correct the transmitter. The watch, however, might be cheaply designed and poorly tested; it could have a software glitch, a hardware imperfection, or could have been damaged by some mechanical or electrical event. It's possible that a dying battery is providing insufficient power, resulting in a brownout to some digital electronics or even a software/CPU inside the watch. (Brownouts are notorious for yielding bizarre sorts of unintuitive failure cases - there's really no way to know which circuit starts shutting down first unless we have a complete engineering-plan of the watch's software and circuitry - for all we know, there might be a separate circuit to "calculate minutes" which has the least-robust connection to power). Because there really are no user-serviceable parts except the battery, consider changing that, and see if the watch repairs itself. Nimur (talk) 15:56, 10 October 2010 (UTC)
Since I bought the watch new only a month ago, I rather doubt it's the battery. But it was quite inexpensive and doesn't seem to have any brand name, so "cheaply designed and poorly tested" is a distinct possibility. —Angr (talk) 16:41, 10 October 2010 (UTC)
Could there be radio interference? Computers, TV monitors etc. produce quite a lot of noise, especially at lower frequencies. Count Iblis (talk) 17:03, 10 October 2010 (UTC)
You haven't yet said, if you have done the basic first step of removing the battery so that the internal registers can empty. Then after a few minutes (say 15) replace it, then watch and see if all the hands zero to twelve o'clock. If you do this a few minutes before its scheduled daytime sync time, you will see it sync __ or not. The you can come back and tell us what it did, or did not do. If you do not know its sync time, then just do it and wait twentyfour hours. Or if it has manual sync, activate it that way. --Aspro (talk) 18:02, 10 October 2010 (UTC)
I haven't tried that, because I'm not really sure how to open it to get to the battery, and I'm afraid of voiding the warranty if I try. —Angr (talk) 20:21, 10 October 2010 (UTC)
How far are you from CERN? Perhaps they've made a black hole and you're experiencing relativistic time distortion? see occam's razor for more details--Ludwigs2 20:26, 10 October 2010 (UTC)
A CERN created black hole would vacillate down toward the centre of the Earth and back up again... and then back down again... and then back up again.... So the time distortion would not stay in synchronisation with UTC time. No! the only time distortion that the Swiss have succeeded in creating, is with their cuckoo clocks that sing approximately between 23 and 25 time a day. But then I suppose that most people know that already :)--Aspro (talk) 20:42, 10 October 2010 (UTC)

Then take it back to the retailer, as you have one duff watch. Don't forget to take along your receipt. Good luck--Aspro (talk) 20:26, 10 October 2010 (UTC)

I tried another manual reset and now it's back to normal. Which is good, because I have absolutely no idea where I put the receipt. Thanks for y'all's help! —Angr (talk) 20:50, 10 October 2010 (UTC)

Dead transistor radio[edit]

I've had a cheap portable small battery-powered transistor radio for several years. Recently it stopped working. I put in new batteries, still dead. All batteries have been aligned correctly. It has not been dropped or knocked. It has not got wet or damp. Is there any other explaination of why it should stop working? Is there anything in it that wears out with time? Thanks (talk) 19:39, 9 October 2010 (UTC)

Capacitors, especially electrolytic ones are the weakest link. Check also for broken wires or corrosion on battery connectors. Edison (talk) 20:14, 9 October 2010 (UTC)
Further to the post by Edison: Look for broken connections due to hairline cracks in the circuit board or "dry" solder joints, particularly where there is extraordinary mechanical stress, such as where a switch is mounted on the circuit board. If it is an old radio that consists of a printed circuit board carrying only small 2-wire and 3-wire components, it can probably be repaired by someone able to use a test meter to check discrete transistor circuits. If the price of the work will exceed the value of the radio, or it contains integrated circuits (8 or more connections on a component ) then throw it away.Cuddlyable3 (talk) 23:47, 9 October 2010 (UTC)

Making selections in Pymol[edit]

I'd like to select the backbone of a double-stranded DNA helix which I have open in Pymol. According to a tutorial I found on the 'net, I can select protein backbones with the command 'select backbone=(n;CA,C,O,N)' - what command would one use to select a DNA backbone, leaving all the bases? ----Seans Potato Business 19:53, 9 October 2010 (UTC)

It's fiddly as frick, but in the end I determined the code I needed was: select backbone=(n;1H5*,2H5*,C5*,O5*,H5T,C4*,H4*,C3*,H3*,O3*,O1P,O2P,O3P,P) — Preceding unsigned comment added by (talk)

I had to zoom right in, go 'label > atoms' and then type in the names of each atom which I wanted to be placed into the selection 'backbone'. A right kerfuffle. ----Seans Potato Business 22:14, 9 October 2010 (UTC)

Why are we not researching this?[edit]

Researchers are busy working on treatments for obesity, including some to increase metabolism (such as increasing the amount of brown fat in the body, using antiobesity drugs, or giving leptin infusions), but why is there no research on decreasing metabolism to help end starvation? Overpopulation, like obesity, is an important issue today. We heard about an antiobesity drug to increase metabolism on the news a few years ago (Does anyone remember Excalia?), but I have never heard a news story about decreasing metabolism. I have not been able to find one article about this subject on the Internet (outside of two pathetic how-to articles both entitled “How to Decrease Metabolism”). Why have experts never addressed this subject, if not just to say that it cannot be done and explain why? I know that there is a great deal of interest today in raising metabolism to combat obesity (and a slow metabolism is often considered a curse), but surely I am not the only person who has ever wondered about increasing the energy efficiency of the body. The only book that I have ever seen that has mentioned this is How to Think like Eistein, which mentioned “genetically lowering metabolism” as one hypothetical way to reduce starvation.

However, I have read that a genetically slow metabolism basically does not exist ( Variation in metabolism between humans is small (according to recent studies, , and it appears that weight gain is caused by underreporting food intake, not having a slow metabolism. The closest that we can get to a genetically slow metabolism is genetic hypothyroidism. Therefore, if there is a way to decrease metabolism, we certainly cannot use genes. Our inability to always keep problems such as tachycardia and hypertension in check adds to the evidence that there is basically no way to slow down someone’s metabolism (outside of drinking and becoming impaired), or that scientists are very limited in their knowledge of how metabolism really works. However, when researchers write papers about treatments to increase metabolism (sometimes referred to as “exercise in a pill”), they do not talk about using genes from a person with a fast metabolism (a fast metabolism basically does not exist either). If we can manipulate metabolism to help prevent obesity, why are there no papers about manipulating metabolism to help prevent starvation? Why have none of the experts written an article about how this might be done or why it would be impossible? I should be interested in any articles written by an expert. (talk) 20:43, 9 October 2010 (UTC)

Fat people are not fat because they have "low metabolism"; they're fat because they eat too much. Starving people are not starving because they have "high metabolism"; they're starving because they don't have enough to eat. The bodies of starving people already lower their metabolism it as much as possible - lower it any further and they die. The solution to starvation is food, not drugs. -- Finlay McWalterTalk 21:07, 9 October 2010 (UTC)
That isn't true in general (obviously in some cases it is, but not in most of them). And if you do any research on the subject at all you will see that. It's not a low metabolism exactly, it's more along an incorrectly set setpoint that the body keeps returning too. Ariel. (talk) 00:51, 10 October 2010 (UTC)
If we can manipulate metabolism to help prevent obesity, why are there no papers about manipulating metabolism to help prevent starvation?
If the rate of metabolism is reduced, so is the rate of energy production in the mitochondria, which are the cells powerhouse -- especially the muscles. The people who are in the greatest threat of starvation do not have petrochemical fuelled tractors to help them produce food. Instead the need to be able to metabolise food fast enough to have the strength to be able to work-the-land fast enough, that by the end of their agricultural year the have enough food to sustain them, for the lean times, in the following year. If you were to slow their metabolism down, you would only succeed in ensuring that they staved to death sooner, than they would have down without your help, because they would no longer have the energy, to put aside enough food for the lean times.--Aspro (talk) 21:19, 9 October 2010 (UTC)
I think starvation has been a common occurrence during the evolution of humans and the body is therefore probably prepared to handle the situation as god as possible.
On the other hand evolution has not prepared us to almost unlimited supply of tasty and energetic food since it almost never occurred for long periods before the industrialization. Another aspect is that starvation often affect young people at fertile age or younger while obesity often kills slowly and after the fertile period so it wont affect the evolution of humans.
It is much easier to improve something in a aspect that is not already “optimized”.
And then there are the economic aspect also starving people are often poor and it is hard to make profit by selling medication to them whille many obese people are richer.
--Gr8xoz (talk) 22:05, 9 October 2010 (UTC)

Snakes can go a long time without food because they don't need energy to keep their blood warm. What about hydrogen sulfide induced hibernation in humans? However such extreme technology would be more expensive than food. [Trevor Loughlin] (talk) 09:30, 10 October 2010 (UTC)

If I understand this Victorian mystery story, its theme is that a person can by hypnotism be prevented from dying, though he/she will not be very happy about it. Cuddlyable3 (talk) 12:39, 10 October 2010 (UTC)

It would be far more feasible to make humans transgenic for cellulase, or design a gut bacterium that expresses it stably. But I think anyone can predict what will happen, in a highly inegalitarian social system, when you make it so that the poor can eat grass: in no time at all, their combination of pay and spare time will be just barely insufficient to allow them to consume the grass they need to live. Because how can capitalism work without the exemplary starvations to put the fear of the Lords into the populace? Wnt (talk) 18:38, 10 October 2010 (UTC)

Wouldn't it just be cheaper to give starving people food then the give them a pill to lower their metabolism? Googlemeister (talk) 13:14, 11 October 2010 (UTC)

Ideal Springs[edit]

Hello. Hung vertically, a massless spring extends by 2.00 cm when a mass of 802.0 g is attached to its lower end. The same mass and spring are then placed apart on a table. The spring is fixed in place and then the mass is given a velocity of 0.900 m/s towards the spring. Find the maximum compression of the spring when the mass runs into it.

I applied the Law of Conservation of Energy to find the spring constant. (I didn't apply Newton's second law since the mass can accelerate up and continue dropping.) Since gravitational potential turns into elastic potential, . I solve for k, and . In the table scenario, I apply the Law of Conservation of Energy. Since kinetic energy turns into elastic potential, . I simplify and substitute k; . I isolate for x; . So = 0.0287 m. LON-CAPA says it's wrong. What have I done wrong? Or have I? Thank you! —Preceding unsigned comment added by Mayfare (talkcontribs) 22:08, 9 October 2010 (UTC)

When you assume that all gravitational energy turns in to energy in the spring you interpret the distance 2 cm as the maximum distance the mass will fall when released before returning upwards. It is possible that the 2.00 cm meant the extension of the spring after the oscillations has disappeared.
In that case k is calculated from F=k*h => .
If you think of the case were you hold the mass so the spring is not extended and slowly move your hand down half the gravitational energy difference will end up in the spring the other half will act on your hand. Also you assumed this is only valid on earth and no location are given in the problem formulation. --Gr8xoz (talk) 23:02, 9 October 2010 (UTC)

Have you tried using the equations for simple harmonic motion? In the presence of gravity it's a little more tricky, but you can still use them, with modifications, because the force of a spring is a conservative force (and so is gravity). John Riemann Soong (talk) 09:42, 10 October 2010 (UTC)

Whole grain on the food pyramid[edit]

The government recommends three servings of whole grain per day. The website says each slice of whole grain bread is one serving. So is half a cup of brown rice. It seems the former is much easier. Why such a big difference? (talk) 23:39, 9 October 2010 (UTC)

Both a half a cup of rice, and a slice of bread, supply about 100 calories. Ariel. (talk) 00:53, 10 October 2010 (UTC)
Ariel, calories don't have a lot to do with serving size in this context. There is a relation, yes, but serving sizes when dealing with specific food groups are more about geeting a certain amount of--in this case--dietary fibre. → ROUX  19:53, 10 October 2010 (UTC)
Actually that's not how serving sizes are set. They are set based on how much people eat, and it's more or less calories, unless the specific food is different for some reason. Do a random survey of food near you, they are all around 100 calories ±50. Ariel. (talk) 06:39, 11 October 2010 (UTC)
I said in this specific context. Meaning, something like whole grains, where the point is not caloric but aimed at a specific substance. In this case, whole grains. There has been a trend for serving sizes, at least in Canada for official purposes (not the ridiculous nonsense 'serving sizes' manipulated on packaging by food companies), to be largely predicated on amounts that everyday reasonable people will understand; one egg, a slice of bread, or as the Canada Food Guide also says--a deck of cards, a golfball, etc. That then gets backed out into X number of servings per day. → ROUX  06:50, 11 October 2010 (UTC)
Is the website referring to cooked or uncooked rice? Nil Einne (talk) 07:52, 10 October 2010 (UTC)
If I remember my nutrition course correctly, most food guides are predicated on post-cooking sizes (for items which require cooking). Thus, 1 slice bread (not 14 grams flour 1/8 egg etc etc) or 1/2c cooked rice, but 1 apple or 3 carrots. → ROUX  07:55, 10 October 2010 (UTC)
Oh, that'd make a bit more sense. But how much of uncooked rice would that be, then? (talk) 18:55, 10 October 2010 (UTC)
My packet of Sainsbury's wholemeal brown rice says that 40g of uncooked rice produces 100g of cooked rice. Since the density of cooked and uncooked rice is probably different, I cannot translate that into those quaint American "cups". (talk) 19:43, 10 October 2010 (UTC)
Rice approximately doubles in volume when cooked, and slightly more than doubles in weight. (Give or take; we're not at Alinea or El Bulli, we don't need to be that precise.) → ROUX  19:53, 10 October 2010 (UTC)