Wikipedia:Reference desk/Archives/Science/2010 March 2

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March 2

Solving a simplified 1-D time-independent Schrodinger-esque equation

I've been trying to solve the following equation numerically using a Python program that I've written. It works reasonably well, but not perfectly. I'm under the impression that it can be solved exactly using analytical methods and I was wondering if anybody would be able to point me in the right direction. Unfortunately, my maths and physics knowledge is very limited, so I can't guarantee I'll have a clue what you are talking about.
${\frac {d^{2}A}{dR^{2}}}={\frac {-8\pi ^{2}m}{h^{2}}}\left(E-\left(-{\frac {e^{2}}{4\pi \epsilon _{0}R}}\right)\right)A$, where m = mass of electron, h = Planck's constant, E = energy of first level in hydrogen atom, e = charge on an electron, $\epsilon _{0}$ = permittivity of free space, R = distance between nucleus and electron, A = amplitude of resulting wavefunction. Thanks --80.229.152.246 (talk) 00:04, 2 March 2010 (UTC)

See: Hydrogen_atom#Wavefunction, specifically the n = 1, j = 0, m = 0 case. Dragons flight (talk) 00:48, 2 March 2010 (UTC)

Yeah, I've looked at stuff like that before and I'm afraid it's slightly above my head. Any suggestions as to where I should start to try and learn some of the stuff? --80.229.152.246 (talk) 15:32, 3 March 2010 (UTC)

Long legged wasps

Over the last 15 years I've noticed the normal wasp being replaced by a longer legged more aggressive variety in the Pyrénées-Orientales in France. I can't seem to find it in the list of common wasp species on the wasp article, does anyone know what this wasp is? Is it another species or just a variant, it seems pretty different. As far as I can tell it's a paper wasp but the article says that they're less aggressive, not more, and also doesn't mention the fact that the yellow jackets are becoming less common compared to the paper wasps. 82.132.136.206 (talk) 00:31, 2 March 2010 (UTC)

Coreinae - Insect families/tribes

This page lists 10 tribes, Wikispecies lists a lot more than 10 tribes on it's Coreinae page ... which is correct? Should the extras from wikispecies be in the wikipedia article aswell? I'm asking because I was about to make a stub for Amorbini... Thanks. Benjamint 01:36, 2 March 2010 (UTC)

Coreinae page gives the tribes list from ITIS 2006 record, here. You can use it. However, those things tend to change every once in a while, as more studies are carried out; so don't be surprised if the tribe list changes in a couple of years. --Dr Dima (talk) 06:41, 2 March 2010 (UTC)

OK, so wikispecies is more up to date? Should I amend the wp page with the wikispecies list? I think I'm out of my depth so maybe I should just leave it. Benjamint 08:15, 2 March 2010 (UTC)

If the Wikispecies list is reliably sourced, by all means bring the WP page up to it; but you can't use Wikispecies as a reference in WP. --ColinFine (talk) 21:42, 2 March 2010 (UTC)

Speckled Bear vs. Spectacled Bear

Are the Speckled Bear and Spectacled Bear different species?

Searches on Google yield conflicting results; Wikipedia doesn't, have an article, or any reference to, a "Speckled Bear." Each name is used individually on multiple websites; but I haven't any one source that acknowledges the use of two similar, yet distinct names... let alone the resulting confusion/misinformation. Results from Google image searches are different enough that they could be of separate species, but similar enough that they could simply represent variation within one species. Aside from Wikipedia's "Spectacled Bear" article, none of the sources I've encountered offer much in the way of verification/credibility, so I figured I'd ask for feedback here.

Ajburket (talk) 02:21, 2 March 2010 (UTC)

There is no speckled bear. See our Bear article which lists all eight surviving species. Rmhermen (talk) 02:46, 2 March 2010 (UTC)

There are several videos[1] [2] [3] at YouTube with "speckled bear" in their titles. This seems to be just a misnaming of Spectacled bears by zoo visitors. Cuddlyable3 (talk) 19:11, 2 March 2010 (UTC)

magnetic field

Would a magnetic field generated around a space ship or space station protect it from radiation, particles or anything else or just make radio transmission more difficult. 71.100.5.197 (talk) 02:49, 2 March 2010 (UTC)

Yes, it is one option that has been considered. Here is one reference that discusses it: [4]. --Tango (talk) 03:57, 2 March 2010 (UTC)

The Maxwell equations are linear, therefore a static magnetic field does not make radio transmission more difficult. —Preceding unsigned comment added by 83.134.160.138 (talk) 06:41, 2 March 2010 (UTC)

It would protect the ship from alpha particles, beta particles and proton radiation, but not from neutrons or gamma rays. Clear skies to you 24.23.197.43 (talk) 07:04, 2 March 2010 (UTC)

Cosmic rays are almost all charged particles, so we're ok. --Tango (talk) 07:06, 2 March 2010 (UTC)

A magnetic field wouldn't have much affect on large particles unless thay were ferrous would it? And then wouldn't it tend to attract them? (I'm not thinking of sub-atomic here as above, tell me if I'm wrong!) These may be of interest Scientists Designing "Ion Shield" To Protect Astronauts From Solar Windsourced from Sun shield to let space crews boldly go to Mars and Spacecraft Shielding —220.101.28.25 (talk) 17:06, 2 March 2010 (UTC)

Ferrousness (is that a word?) applies only to lattices of atoms, we're talking about individual particles. The key concept here is whether they are charged or not. A charged particle (electrons, protons and alpha particles, primarily) travelling through a magnetic field will be deflected. --Tango (talk) 18:22, 2 March 2010 (UTC)

Ferocity ? :-) StuRat (talk) 18:42, 3 March 2010 (UTC)

I wonder how powerful a magnetic field should be to deflect protons coming at relativistic speeds. The LHC article says dipole magnets at the field strength of 8.3 teslas keep 7 TeV proton beams in their orbit. As some cosmic particles are much more energetic than man-made ones, is it feasible to maintain such a field for long durations, in a small spaceship? 88.242.228.248 (talk) 17:56, 2 March 2010 (UTC)

Change Simulink Algebric Loop Solver Props

I have a simulink model consisting of feedbacks. After a few iterations, simulink shows up a "cannot solve algebric loop" error for a block. I noticed that for that time instant (0.24), it had already found out converging values of the block (within my accuracy requirments). How do I modify its algebric loop solver configuration ? —Preceding unsigned comment added by 218.248.80.62 (talk) 08:01, 2 March 2010 (UTC)

I'm not familiar with that software, but I suspect it must have some setting for how many iterations to try before giving up. If not, you could manually copy the results from one run as the starting conditions for another run, and thus get a better result (assuming it is a converging case). Also, you might try the Math Desk. StuRat (talk) 18:39, 3 March 2010 (UTC)

plasma

does plasma take an indefinite article, (such as 'a lake') or not (such 'as water'). The article was inconclusive. —Preceding unsigned comment added by 129.67.116.170 (talk) 18:05, 2 March 2010 (UTC)

It depends on context. Is there a particular sentence you are wondering about? --Tango (talk) 18:25, 2 March 2010 (UTC)

... like soup! Dbfirs 19:02, 2 March 2010 (UTC)

Or, indeed, like "solid", "liquid", and "gas". ("The bottle contains 200 cc of liquid"; "The bottle contains a liquid") Probably a question that's better for the language desk; see mass noun. Tevildo (talk) 19:27, 2 March 2010 (UTC)

No it doesn't -- you can't say "a plasma", it would be wrong. The only exception is if you specify a particular type of plasma (e.g. you could say "a xenon plasma"). 24.23.197.43 (talk) 05:06, 3 March 2010 (UTC)

You (or at least I) might say "when heated, the material formed a plasma", or some other construction. I agree that it depends on the context, just as other states of matter do. Buddy431 (talk) 06:31, 3 March 2010 (UTC)

Yeah, 24.23.297.43 is wrong. There's nothing about plasma that forbids taking an indefinite article. In fact it's (much) easier to find correct, natural sentences that include a plasma than it is to find ones that include a water. But even a water is possible in the right context. --Trovatore (talk) 19:27, 3 March 2010 (UTC)

Male and female human voices

It's an easily observable, almost universal, fact that almost all female humans have higher-pitched voices than male humans. This is already noticeable with children, but even more so with adults. Most people accept this as natural and don't think twice about it. But what exactly causes it? JIP | Talk 20:04, 2 March 2010 (UTC)

Puberty#Voice change has some information about the mechanism of it. I don't know what, if any, evolutionary benefit it has. --Tango (talk) 20:16, 2 March 2010 (UTC)

Human voice may also be of interest to you. Vimescarrot (talk) 20:17, 2 March 2010 (UTC)

I imagine that sexual selection is at play here. Different pitches are a sexual characteristic magnified by puberty, I think. Imagine Reason (talk) 15:41, 3 March 2010 (UTC)

Super-fast spaceship

Wouldn't it be in practice impossible to have extremely fast space ships such as you'd need to get humans to other stars, because they would go so fast that the tiniest specks of space-dust would go through them like bullets and cause lots of damage? —Preceding unsigned comment added by 84.13.29.241 (talk) 21:41, 2 March 2010 (UTC)

Yes, relativistic effects can make the interstellar medium deadly. You'd need some sort of shielding mechanism to counteract it. — Lomn 21:50, 2 March 2010 (UTC)

Then there is also the practical problem of being able to accelerate your spacecraft at about 1g for a full year, and having a full year of fuel to decelerate once you arrive (well a year before). Googlemeister (talk) 21:55, 2 March 2010 (UTC)

There are possible methods. The acceleration can be done by pushing the ship along with a laser beam from Earth if you can't take enough fuel with you. There are ways of slowing a ship down the same way, but you would be so much further away that it would be hard - a laser could be sent in advance as part of an unmanned probe that can take decades to arrive without it being a problem. --Tango (talk) 00:09, 3 March 2010 (UTC)

The Bussard ramjet is an idea for using the interstellar medium as fusion fuel on your spaceship. In practice, "go slow" is our only recourse. --Sean 22:01, 2 March 2010 (UTC)

It is unclear if a Bussard ramjet could actually generate more thrust than drag. --Tango (talk) 00:09, 3 March 2010 (UTC)

Only as impossible as a deflector dish! TastyCakes (talk) 22:59, 2 March 2010 (UTC)

The shielding could be done, the real question is whether it can be done without adding so much weight that the ship is impossible to accelerate. --Tango (talk) 00:09, 3 March 2010 (UTC)

Here's my approach:

1) Start with a spaceship which is a massive linear particle accelerator, using matter/anti-matter engines with tanks full of anti-matter in a magnetic containment "bottle".

2) Go to the asteroid belt and clamp onto a huge asteroid.

3) The ship will then slowly mine the asteroid, which is positioned in front of the ship to act as a shield.

4) A particle stream (consisting of particles mined from the asteroid) zips out of the linear accelerator at the speed of light, driving the ship ("be careful where you point that thing !", the Sun might be a good choice).

5) When the ship nears it's destination, a hole is drilled through the asteroid, and the particle accelerator is reversed to send particles through the hole at the speed of light. Alternatively, the ship can be turned 180 degrees. The particle stream will act as a shield to prevent dust particles from getting to the ship during decel. There will be a short period of vulnerability while the reversal occurs. It may be possible to scan for approaching dust particles and time the reversal for a clear period, or they may just have to take their chances.

6) When the ship stops, discard whatever remains of the pitted and hollowed-out asteroid and pick up a new asteroid for the trip home (you might want to make sure the target system has asteroids before you set out). You should have a good 5 minute period before the kids return to asking "Are we there, yet ?".

Such a design might be able to do maybe 10% of the speed of light, so it might take some 45 years to reach the nearest stars. Unless you freeze the people, they likely would die during the return trip. So, I'd either have them stay there or do the whole thing robotically, and don't worry about a return trip. StuRat (talk) 15:49, 3 March 2010 (UTC)

That's all great except for the "matter/anti-matter engines" bit. We have absolutely no idea how to generate antimatter in such a way as to get positive net energy. Oh, and the dust is pretty constant (although very low density), so you aren't likely to find any gaps. If you put the sensitive stuff in the middle of the asteroid, it won't matter which way it is facing. I can't see how a particle stream would act as a shield, though, the density of the stream wouldn't be high enough to stand a good chance of intersecting much of the dust. --Tango (talk) 04:44, 4 March 2010 (UTC)

The antimatter wouldn't be generated on board, but would be created and placed on the ship prior to launch, similar to how rocket fuel is loaded now. The energy source used to produce the antimatter at the launch base might be a series of nuclear reactors (hopefully fusion). I like the idea of putting the ship completely inside the asteroid. I'm hopeful that the matter stream could be kept narrow and at a high density, at least a small distance ahead of the ship. Remember, it only has to protect the hole from which the matter stream flows, while the asteroid will protect the rest of the ship. StuRat (talk) 15:35, 4 March 2010 (UTC)

Are chickens intelligent enough to suffer?

This afternoon I was faced with the dilemma of buying six free-range eggs for £1 or ten battery-hen eggs for 78p. Are tiny-brained chickens intelligent enough to suffer in a battery cage, or realise that they are missing out on going free-range? Are they smart enough to have any conciousness at all, or have any sense of self? I did buy the free-range eggs. Thanks. 84.13.29.241 (talk) 22:02, 2 March 2010 (UTC)

There is, in principle, no way to know anything for sure about the qualia of chickens (or, for that matter, any being other than yourself). But to me it seems very likely that they are capable of suffering. I also prefer to buy cage-free eggs. --Trovatore (talk) 22:10, 2 March 2010 (UTC)

Unfortunately I think "cage-free" is likely to mean hens that spend all their lives in pernament darkness or almost-darkness in a large modern barn while packed in shoulder-to-shoulder with a sea of other chickens. 84.13.29.241 (talk) 22:18, 2 March 2010 (UTC)

Having raised chickens in my youth, being a free range chicken would not be all fun and games either. Chickens can be quite brutal to each other. Googlemeister (talk) 22:15, 2 March 2010 (UTC)

Though this may not answer your direct question, I'm sure you'd be interested to know that there is literally no (US) federally mandated standards with which a chicken/egg/ect. producer needs to meet in order to call their product "free range". In every meaningful sense it means nothing besides it being a fantastically effective marketing scheme. Chris M. (talk) 22:20, 2 March 2010 (UTC)

This is a very complex issue and my personal jury is still out on the subject. Unfortunately one of the main factors to consider is that "free range" is not very well regulated in the US or Australia, I'm not sure about the UK, but I'd be surprised if it was much different. This means that there is actually no "standard" that a producer has to follow to label their product "free range" and "some" free range labelled eggs come from very similar conditions to battery eggs, except maybe they have a "window" or something equally as superfluous. In Australia we have brands which are RSPCA certified free range eggs which I believe is well monitored and enforced but there are other eggs labelled "free range" which are not as enforced. That doesn't actually answer your question. Yes chickens are stupid but I just can't see how that gives us a right to exploit and abuse them to the fullest possible extent for our benefit. Chickens are easily the worst abused animals we farm, just google clips of battery hen condition, and don't do it with kids around, it's like a horror movie. Or maybe don't if you don't have a strong resolve and don't want to be a vegetarian. ;) Vespine (talk) 22:24, 2 March 2010 (UTC)

There are regulations for free-range in the EU, see Free-range eggs. Four square meters per hen for "free-range". ten square meters per hen for "organic free range". However the current photo in that article does not look like free-range to me, but barn-hens. The free-range commerical hens I've seen from the roadside here in the UK were similar to this http://www.youtube.com/watch?v=gS78WhX2ubY and could have been organic-free-range. 84.13.29.241 (talk) 22:37, 2 March 2010 (UTC)

Part of this requires a definition of suffering. They certainly feel pain. They certainly feel stress. They certainly have some type of consciousness, though they don't appear to be sentient. (I say "certainly" in these instances to mean, "within a reasonable physiological definition," not to indicate I know what chicken qualia is like.) They probably don't know they are "missing out" (but then again, a human raised exclusively in such conditions would probably not know they were "missing out" on a wide world of options, either). Is a sense of self required for suffering? --Mr.98 (talk) 22:29, 2 March 2010 (UTC)

I belive the term you're looking for is sapience (when you say a chicken doesn't have it). the sentience/sapience confusion is remarkably common. Chris M. (talk) 15:03, 3 March 2010 (UTC)

I would note here that sentient means "capable of feeling", not "capable of thinking". I don't know what you mean by saying they have consciousness but are not sentient. --Trovatore (talk) 00:52, 3 March 2010 (UTC)

Hmm, I meant in the sense used at Sentience: "the ability to feel or perceive subjectively". Apparently the term has a number of meanings depending on the field it is being used, though. The article itself brings up some useful points for thinking about it. --Mr.98 (talk) 00:57, 3 March 2010 (UTC)

If you don't have subjective experience, in what sense can you be said to be conscious? --Trovatore (talk) 01:11, 3 March 2010 (UTC)

I think you probably need a concept of emotion - do chickens feel happiness and sadness? I'm not sure we'll ever really know... --Tango (talk) 00:13, 3 March 2010 (UTC)

Here's an interesting quote from Cecil Adam's treatment[5] of the subject : "UK researchers studying commercial poultry farms say only 15 percent of chickens who have the opportunity ever leave the henhouse." APL (talk) 00:37, 3 March 2010 (UTC)

This video seems somewhat informative. Bus stop (talk) 00:54, 3 March 2010 (UTC)

Please understand that regulations and conventions are different in different parts of the world even in english speaking countries. The regulations for "free range" seem more hen-friendly in the EU than they are in the US - see above. 78.151.146.204 (talk) 01:09, 3 March 2010 (UTC)

Is opposition to suffering, as such, morally correct, and if so why? ...Is a question you might ask next. 213.122.45.10 (talk) 02:05, 3 March 2010 (UTC)

A chicken will undoubtably experience everything that you yourself would experience if you were put in its position. the only real difference between animals and humans (cognitively speaking) is that humans are capable of a high level of abstraction: You can sit in a cage and imagine all sorts of alternate situations (how you might escape, what you'll do if you get out, whether or not being stuck in a cage is justified, how you might pass the time each day). Chickens can't - they are simple stuck experiencing whatever it is they experience while stuck in the cage. I don't know if that's more misery or less misery, but I think you can judge by the fact that most chickens would run away from a cage if they could that it's probably not a lot of fun. --Ludwigs2 02:17, 3 March 2010 (UTC)

I've thought a lot about these sorts of issues, and in my opinion that only sensible approach is to look for signs of distress. Do the chickens fail to care for themselves, or peck at themselves, or make attempts at escaping, or squawk, or otherwise fail to thrive? I don't know the answer, but in my opinion any approach that isn't based on looking at behavior leads to answers that are purely based on preconceived beliefs. Looie496 (talk) 02:29, 3 March 2010 (UTC)

The assumption that brain size has anything to do with depth of feeling is a specious one. After all, Neanderthals had a much larger cranial capacity than extant humans. Did they have a richer experience of the world as a result? Who knows -- but I for one very much doubt it. SortedButter (talk) 03:09, 3 March 2010 (UTC)

Not sure what you mean by "depth" of feeling but, given that these feelings originate in the brain, I would expect that brain size is relevant. If a hypothetical animal had a tiny brain composed of 5 neurons, would you say that it is capable of suffering or feeling distressed at being locked up? Zain Ebrahim (talk) 08:10, 3 March 2010 (UTC)

Yes, but you cannot honestly say that a fly has a weak or negligible response to finding something sweet to eat, because it has only a tiny fraction of the 'brain cells' that a human has. Who knows how anything feels that is not you. SortedButter (talk) 13:34, 3 March 2010 (UTC)

• The field of animal cognition is a very interesting one and still a matter of considerable debate. It used to be that animals were considered automatons with no emotions, which reacted to stimuli. Some older scientists still hold onto this, but the depth of animal behaviour is slowly being explored. Alex (parrot) is a good place to start (although the article doesn't really examine the impact he had on the science in general... something I may have to rectify). While crows, parrots and tits are reckoned to be the brightest of birds, that doesn't mean that dumber birds are less capable of complexity and feeling. The extent to which humans can relate to the moods and lives of chickens is evident in how many chicken behaviours have influenced our own langauge. Sabine's Sunbird talk 03:43, 3 March 2010 (UTC)

You might also ask yourself whether you actually want to eat an egg that came from a chicken covered in feces, which breathes fecal dust its whole life, which must be fed antibiotics due to all the feces in its life, which in many cases is sharing a cage with a partially decayed hen that is left to rot through the wire floor, and on and on. I personally don't buy eggs unless they came from chickens I can actually see (friends with hens, etc.). The alternative is too repugnant, and not just morally. --Sean 16:38, 3 March 2010 (UTC)

In my youth we had hens who slept in a large henhouse, but ran around in a large fenced enclosure during the day, free to scratch for bugs, and free to flap their wings and fly a bit. Some of the birds could fly out and explore the woods, but came back for dinner. A pigeon also moved in and stayed for a couple of years, so that "free-range" setup was clearly preferable to some birds than "unlimited freedom." I cannot honestly say the eggs tasted any different from those I buy at the store which are "cage free" or eggs produced in typical abusive commercial operations. I just prefer to pay several times as much for the cage free ones. I certainly believe that birds can be happy or unhappy, calm or distressed, and that they can suffer. Edison (talk) 19:47, 3 March 2010 (UTC)

I have no direct experience, but from what I've been reading it seems that what is called "cage free" in the US is not the same as what we'd call "free range" in the UK. I fear that "cage free" in the US may simply mean that the chickens are kept all their lives in darkness in an enclosed barn packed with a huge crowd of other chickens, possibly de-beaked too. Nearly as bad as being in a cage. 89.243.73.49 (talk) 22:50, 3 March 2010 (UTC)

thermoelectric generators

It would seem like the relatively extreme difference in temperature of an object's surface that faces the sun and the surface that faces the stellar background would be ideal for generating electricity both from thermoelectric generators and closed system liquid/gas phase generators. Are they ever used in space or are solar panels that conver solar radiation the only choice? 71.100.5.197 (talk) 23:41, 2 March 2010 (UTC)

Solar heat is used on Earth (a rather extreme example). In space it may be used as well, but it isn't used because we don't have anyone that far out in space. I do not believe it is possible, at this time, to make an educated claim about what exactly will be used when manned spacecraft go well beyond the Moon and need plenty of methods of generating electricity and heat. -- kainaw™ 23:46, 2 March 2010 (UTC)

Actually I was thinking on a much smaller scale that the terrestrial based systems your link points to. I was thinking on the order of solar panels used to power the International Space Station for instance. I'm asking because such terrestrial systems used to heat and cool homes are far more limited in terms of efficiency due to the slight temperature differences between hot and cold whereas in space the very opposite is true. 71.100.5.197 (talk) 01:05, 3 March 2010 (UTC)

I would think that the issue is one of relative efficiency in terms of power generated per unit area and, more importantly, power generated per unit mass. I suspect that photovoltaics (given how thin they can be) come out on top over solar thermoelectric generation, but I don't know the numbers. 124.157.249.27 (talk) 01:03, 3 March 2010 (UTC)

For craft in a low orbit around a major body like a planet or a moon, the assertion that the plate would see the heat of the sun on one side and the cold of space on the other only applies for a small fraction of their orbit. When they are behind the body - then they are seeing only the temperature of the dark side of the planet on one side of the plate - and the temperature of space on the other. When they are between the planet and the sun, they'll see the temperature of the sun on one side and the temperature of the sun multiplied by the albedo of the planet on the other. That's much less effective than the ideal case. So it seems to me that this idea might be more useful for craft that either have very high orbits or are out in deeper space - than for the ISS - which orbits at only 300km or so above the earth and is only rarely in that ideal situation. Deep space missions tend to use radioactive heat sources to generate power if they are going far from the sun - and I presume the thermoelectric effect would be vastly less efficient out at the orbit of Jupiter and beyond - where the sun is a tiny dot in the sky and solar panels aren't a great deal of use. SteveBaker (talk) 13:38, 3 March 2010 (UTC)