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April 16

World population of brown rat

What is the global population of brown rat? --Yoglti (talk) 01:49, 16 April 2013 (UTC)

Brown rat doesn't seem to have totals, but you can infer some things from the article, i.e. the estimated ratio of rats to humans. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:14, 16 April 2013 (UTC)

How are subatomic particle conceptualized?

If they cannot be seen through the most advanced electron microscope, how are they discovered? How are their properties known? How atomic structure known when it cannot be seen? --Yoglti (talk) 02:37, 16 April 2013 (UTC)

See electron#Discovery, proton#History, and neutron#Discovery, for starters. Someguy1221 (talk) 02:52, 16 April 2013 (UTC)

If I hit you in the back of the head with a baseball bat, you know roughly what happened, even if you didn't see me do it. There are ways of extracting information from the world that do not involve your eyes. To answer the question a bit more seriously, the best way to think about this is a combination of geometry and quantum mechanics.

1) We know that atom consists of a dense, highly packed nucleus and a diffuse area occupied by electrons thanks to the contributions of Ernest Rutherford and his gold foil experiment. Rutherford had a theoretical basis in models developed by Hantaro Nagaoka.

2) We know that electrons cannot be physically orbiting the nucleus like a planet orbits the sun, because according to classical mechanics, such particles should be shedding energy all the time (per the Larmor formula), and thus spiraling in towards the nucleus. We know that the atom is stable (that is, electrons don't spiral into the nucleus), so they can't work like that.

3) We know that energy is quantized (that is, energy must exist in discrete amounts, not as a continuum of values) because of the ultraviolet catastrophe.

4) Thus we know that electrons must exist as a particle "smeared out" in space, and whose energy can only have certain values. Those values are based on a set of integer values known as the quantum numbers, and if you feed those integers into the correct equations (known as wavefunctions, or the Schroedinger equations) you get geometric shapes which define the regions in space around the positive nuclei which are where the electrons are. Now, conceptually, you can think of an electron as either a) a three-dimensional standing wave anchored at the nucleus and shaped like these orbitals or b) a probability distribution graphed on a three dimensional graph with the nucleus at the origin. Either or both explanations fit with the basic theory of what an electron is and how it behaves.

5) This mathematics is weird insofar as the kind of physics it describes does not in any way match how any object behaves that your senses are used to working with. That is, what happens at the atomic level simply does not work like anything your senses have experienced. We have various models of atomic-level behavior that attempt to make analogous pictures so we can tie in behavior to experience, but these are all to varying degrees wrong (but then again all models are wrong, some are useful.) These various models, such as VSEPR theory, hybridization theory, atomic orbitals, molecular orbital theory are quite useful in describing how atoms interact with each other to produce the geometric shapes that experiments tell us that they have when they do so.

Hope that helps some. --Jayron32 04:47, 16 April 2013 (UTC)

If somebody hits you on the back of the head with a baseball bat and you ever know what happens, he had better not get a place on the team! Wnt (talk) 21:28, 16 April 2013 (UTC)

Sub-atomic particles can be detected with equipment such as cloud chambers, bubble chambers and other devices listed in Category:Particle detectors. Gandalf61 (talk) 07:52, 16 April 2013 (UTC)

At some level, you also have to ask, "what's so special about seeing?" Seeing just means your eyes are receiving photons (yet another subatomic particle) bouncing off of other things. It's just another means of detection, one that itself has its downsides (you can only see in a very tiny range of the electromagnetic spectrum, for example). Does one completely lose the ability to perceive the world when one's eyes are closed, or when one is blind? --Mr.98 (talk) 11:49, 16 April 2013 (UTC)

As a general rule you can't really "see" most sub-micron particles either (everything from large colloids, to proteins and polymers, and most small molecules fall into this category). For reference 1 micron = 1000 nm = 10000 angstroms, where your typical atom is on the order of an angstrom, thus by definition a sub-atomic particle is at least 10,000 times smaller than the smallest thing we can resolve optically. There are however plenty of non-controversial methods for detecting things we can't see. (+)H₃N-Protein\Chemist-CO₂(-) 12:58, 16 April 2013 (UTC)

A necessary clarification is that I'm referring specifically to optically resolvable phenomena here. I wouldn't count scattering and diffraction as "seeing", but they are examples of "non-controversial methods for detecting things we can't see". (+)H₃N-Protein\Chemist-CO₂(-) 13:03, 16 April 2013 (UTC)

Inter-species sexual attraction

I noticed the discussion Wikipedia:Reference_desk/Science#The_Great_Apes, a thought came into my mind. We known some species are sexually attracted to another species, this makes hybrid animals possible. For example, a zebra may be sexually attracted to a member of another species. This makes Zebroid possible. A male donkey may be sexually attracted to a female horse. If inter-species attraction exists in nature, why humans are not sexually attracted to a gorilla or a chimpanzee? --Yoglti (talk) 08:18, 16 April 2013 (UTC)

They're not? --TammyMoet (talk) 10:22, 16 April 2013 (UTC)

Bestiality is what it's called. However normal people find non-humans distinctly unenticing. If you think you might like it with a gorilla, which would most likely think you are as ugly as you think he/she is, there's probably something in the DSM (http://en.wikipedia.org/wiki/DSM-5) to cater for you - if not, there should be. Wickwack 120.145.25.214 (talk) 10:28, 16 April 2013 (UTC)

As for the possibility of hybrid, see humanzee. --Mr.98 (talk) 11:56, 16 April 2013 (UTC)

I also don't think that mules or zebroids are common in nature; they primarily come about in captivity. Consider the teals. In captivity, a green-winged teal and a blue-winged teal can successfully breed, especially if they have no conspecific mates available. But in the wild they do not tend to not interbreed, presumably because sexual selection usually works to keep reproduction occurring only between very similar mates. So, to answer your question, I think you are inferring the general from the specific. Just because something can occur does not mean it is common. And I'm sure you could find at least one human person that reports sexual attraction to chimps. SemanticMantis (talk) 15:27, 16 April 2013 (UTC)

Do the chicks come out as teal-winged teals? --Trovatore (talk) 18:22, 16 April 2013 (UTC)

Ha, no, still green, at least this for this one [1]. But a clutch of hybrid siblings will show a lot of variety, so some might have more teal coloring. SemanticMantis (talk) 19:34, 16 April 2013 (UTC)

Who is that person? --Yoglti (talk) 15:51, 16 April 2013 (UTC)

Resembles a cow. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:31, 16 April 2013 (UTC)

Changing species through genetic engineering

Is it possible to change the species of an organism through genetic engineering? --Yoglti (talk) 08:19, 16 April 2013 (UTC)

You may be interested in the definition of species, "a group of organisms capable of interbreeding and producing fertile offspring". Naturally, two species are different if their members are unable to breed and produce fertile offspring with one another. Genetically engineering an organism to be incapable of interbreeding with its original species, but still capable of breeding with other genetically modified organisms, is given a theoretical treatment in this paper, specifically the section on "extreme underdominance". Such a thing could be considered a new species, by definition. Genetically modifying an organism to be capable of breeding with an existing and distinct species (such as creating a dog that can breed with a cat) is a much more difficult proposition. Such a feat would basically require overcoming reproductive isolation. For very closely related species, this may be doable, but for distantly related species, the reproductive barrier is likely near impassible. Someguy1221 (talk) 08:55, 16 April 2013 (UTC)

I would say yes. I can't provide a reference, but only personal experience. Humans regularly turn into Trolls. --Onorem♠Dil 16:02, 16 April 2013 (UTC)

Quick question: Is HeLa still a member of the Homo sapiens species? 64.56.89.2 (talk) 17:46, 16 April 2013 (UTC)

One method is by making paracentric inversions or balanced translocations. If you have enough of these in your new lineage, it should be difficult if not impossible for it to interbreed with the original. After that, you just have to make it look cool. :) Wnt (talk) 18:01, 16 April 2013 (UTC)

HeLa#Helacyton_gartleri specifically addresses the HeLa species question. Vespine (talk) 23:21, 16 April 2013 (UTC)

Yeah, but unfortunately it gets it wrong by overemphasizing a silly suggestion by a single researcher. Chimeric human cell lines are not distinct species, and no nomenclature organization has accepted the notion that "Helacyton gartleri" is a species. - Nunh-huh 01:19, 18 April 2013 (UTC)

Orbit

According to Prime meridian, "Satellites changed the reference from the surface of the Earth to its center of mass around which all satellites orbit regardless of surface irregularities." Is that right? Would a satellite really orbit around the centre of mass of an irregular object? I understand that for perfectly spherically symmetrical objects the mass can be considered concentrated at the centre, but I thought there was no similar simplification for irregular bodies. 86.176.213.231 (talk) 11:46, 16 April 2013 (UTC)

See Center of mass, and Barycentric coordinates (astronomy). An orbiting body will be perturbed throughout its orbit by an irregular mass, but once you get far enough away, those irregularities in the gravitational field start to smooth out and the force is pretty much constant in the direction of the center of mass. 38.111.64.107 (talk) 11:54, 16 April 2013 (UTC)

In the context of that section, which is talking about centimetre-scale precision, I doubt that "pretty much" is good enough... 86.176.213.231 (talk) 11:58, 16 April 2013 (UTC)

Correct, which is why anything meant to stay in orbit for a long time has station-keeping abilities. However, the center of mass will certainly be the largest contributor to the orbit - the irregular distribution will perturb it from that orbit, but it makes a lot more sense to try to maintain an orbit around the center of mass than the center of the Earth. — Preceding unsigned comment added by 38.111.64.107 (talk) 12:07, 16 April 2013 (UTC)

Oh right, when it says "around which all satellites orbit" do you think it means that satellites are maintained in such an orbit using regular corrections, rather than that they will naturally maintain (exactly) such an orbit? If so, I think I will change the article to try to make that clearer. 86.176.213.231 (talk) 14:05, 16 April 2013 (UTC)

To first order, the satellite's orbit will naturally form an ellipse, one focus of which is at the centre of mass. Instability of the orbit is caused by second order effects which are due to the fact that the satellite is not actually a point mass. Gandalf61 (talk) 15:35, 16 April 2013 (UTC)

You meant that the Earth is not a point mass, not the satellite, right? --140.180.241.109 (talk) 16:25, 16 April 2013 (UTC)

Both. Tidal forces will apply to the satellite - consider that the far side of the satellite and the near side are forced to orbit at the same rate, even though a point in orbit at the far side should take slightly longer to complete an orbit than one on the near side. Interaction from other bodies such as the moon and sun also causes disturbances. 38.111.64.107 (talk) 17:49, 16 April 2013 (UTC)

Identification query: blue mushroom in the PNW

Here's a photo making the rounds on the interwebs, originally from a Seattle-area blogger. One tag might indicate it grows in the Pacific Northwest. I'd like to know its name, and also whether those blue-green colors are natural or were camera-enhanced. -- Deborahjay (talk) 14:17, 16 April 2013 (UTC)

It's a Trametes versicolor - and our article shows examples with all sorts of colors. SteveBaker (talk) 14:44, 16 April 2013 (UTC)

mathmetics

how we can say that 1 by infinity is equal to 0? — Preceding unsigned comment added by ARIF MIKAT (talk • contribs) 14:51, 16 April 2013 (UTC)

The limit of 1/x for x to infinity is zero. This means that for any small number epsilon, you can always find a number y such that for all x larger than y you are closer to zero than epsilon. You can easily that y can be chosen 1/epsilon. So, no matter how small you make epsilon, for large enough x, you will be closer to zero than that epsilon. Count Iblis (talk) 15:11, 16 April 2013 (UTC)

Or...you have one cake, using a very sharp knife you divide it equally amongst an infinite number of people, it's pretty clear that they each get no cake whatever. The tricky question is: "Where did the cake go?" SteveBaker (talk) 16:01, 16 April 2013 (UTC)

I wouldn't say that was in any way "clear"... 86.129.16.178 (talk) 17:00, 16 April 2013 (UTC)

I'll try to make it clearer for you. Your statement is incorrect - you mean to say that the limit of 1/x, as x approaches infinity, is zero. If you don't understand limits, i'll dissect each part for you. A limit is the value of an equation as the x variable approaches a specified number. If I say that x is approaching infinity, then I'm really asking, "What is the value of this equation as x gets larger and larger?" How large is it getting? Really large.

So let's say we plug in 10 for x. 1/10 is .1. Now let's say we increase X so that X is now 100. 1/100 is .01. Let's say that we increased x even more, so that x is 100,000. Well, 1/100,000 is .00001.

It can be seen that as we make x larger and larger (as x approaches infinity), the value for the equation is getting smaller and smaller - it's approaching zero. It doesn't become zero, but rather approaches zero. So the limit for 1/x as x approaches infinity is zero. --Jethro B 19:08, 16 April 2013 (UTC)

P.S. Limits are crucial for calculus and the definition of the derivative. Calculus itself is important for many fields of life, and can actually be a lot of fun if you understand the few basic concepts that it has (except some integrals, those can be killers). --Jethro B 19:10, 16 April 2013 (UTC)

I think the fact that they are killers IS what makes them fun. (never shy away from a puzzle). Dauto (talk) 20:01, 16 April 2013 (UTC)

Don't get me wrong - I love puzzles! One of the things I love about calculus is that you sometiesm need to piece together several concepts to answer just one question. If you're familiar with the AP Calculus AB course, for example, there are really only about 10 or so concepts in the calculus course, and the rest is just applying these concepts. For the Calculus BC Course, it's mainly applying these concepts some more, with about 2 new concepts.

However, there are year-long courses just on solving integrals, since there are so many types of integrals that have different ways to solve them. When you first learn just a few types, and you get an integral that you need to rearrange somehow or change the integrand somehow and then solve, it's a fun challenge. But when you need to recall which way out of so many different ways is necessary for solving that integral, it can get tedious! Or use Wolfram Alpha, shh!!!

That's a bit of a tangent though (see what I did there?) --Jethro B 01:26, 17 April 2013 (UTC)

One could say that 1 by infinity is an infinitesimal - some amount of cake that is less than any positive real amount of cake, but more than zero (which is where the cake goes). But this really should have been filed under WP:Reference desk/Mathematics ! Wnt (talk) 21:25, 16 April 2013 (UTC)

Prove that an infinitesimal is a nonzero number. Plasmic Physics (talk) 08:45, 17 April 2013 (UTC)

This just makes me think of people attempting to reject the idea that 0.999999999999999999999... is equal to 1. Nyttend (talk) 11:54, 17 April 2013 (UTC)

In case you're implying it: I'm not rejecting that idea. Plasmic Physics (talk) 12:03, 17 April 2013 (UTC)

Oh, no, I'm sorry; I meant that the limit-related explanations given to the original question sound like some of the proofs for 0.9999999, since both are proving that number A is equal to number B although none of the numerals in A are in B. Neither one sounds right, and I still have to fight my inclination to think of 0.9999999999 as being less than 1.00000000000. Nyttend (talk) 12:51, 17 April 2013 (UTC)

See here and here. Count Iblis (talk) 13:17, 17 April 2013 (UTC)

To be clear, I'm leaving this one up to the article. If you can resolve the point either way, by all means, cite your sources and add to it. Infinities are one aspect of mathematical philosophy that tend to arouse particular suspicion. There are so many things you can do with them that make perfect sense until they ... just ... don't. Wnt (talk) 15:04, 17 April 2013 (UTC)

In addition to the obvious mathematical flaw of "1 over infinity" as if infinity were a number... there is also the fact that there cannot possibly be an infinite number of people or of any organism... and that there is not an infinite quantity of molecules in any cake, no matter how large it might be. Even the standard phrase in limit theorems, "as x approaches infinity", is misleading. You can't "approach" infinity. It should be "as x gets larger and larger" or some equivalent phrase. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:08, 17 April 2013 (UTC)

Since maths, like geometric figures, are essentially abstractions, I don't think it matters whether or not there are infinite numbers of atoms or other objects. Perfect points, lines and circles can also be said to not exist in reality at all, yet these are very useful abstractions. Although infinitesimals are not comparable quantities (these are non- Archimedean), a sum of zeros is merely zero, but any sum of infinitesimal intervals can equal an interval: in the same sense that an infinite tree with one root can be subdivided into partitioned nodes of smaller fractional quantities an infinite number of times: {1,(a+b=1),(c+d+e+f=1),...}. With .999..., we have a very shallow tree with but one level of subdivision, although it has an infinite number of nodes: {1,(.9 + .09 + .009 + ... =1)}. It is a mistake, IMO, to claim that dividing any nonzero quantity an infinite number of times, as with the tree structure, that one will only obtain zeros though, which perhaps can be better understood with the Cantor set. With the construction of this set, there are two different entities; an infinite set of discrete points (each of these points has exactly zero width, of course, recall that any sum of zeros is zero) and a sum of excluded nonzero intervals which sum to the entire length of the original interval. -Modocc (talk) 22:09, 17 April 2013 (UTC)

1/infinity is typically undefined, but repeating the above answers: it can represent an infinitesimal and, moreover, it is only the limit of 1/x, as x approaches infinity, that is equal to zero. --Modocc (talk) 22:09, 17 April 2013 (UTC)

I think we did this one not long ago on the math refdesk. Here's one possible answer: Suppose you treat a cake as a subset of Euclidean 3-space (it isn't, of course, but if you want to make this into a math question you're going to have to make some accommodations.) Then what happens if you partition the cake into infinitely many identical pieces (say "identical" means one piece differs from the other only by a rigid motion)?

Well, if you cut it into countably infinitely many pieces, then the answer is, none of the pieces can be Lebesgue measurable. So the "pieces" are of such an unwieldy form that you cannot say how much cake is in a given piece. You can cut it into measurable pieces if you have an uncountably infinite number of cake-eaters, and in that case they might be measurable (depends on some other things), but the measure of each piece is zero. So each person gets some cake, but so little that it has precisely zero volume.

Hope this helps. --Trovatore (talk) 22:26, 17 April 2013 (UTC)

This does not make a whole lot of sense to me (I've a computer science background thus my use of a tree data structure). If you add volumes which are precisely zero volume, then certainly these sum to zero volumes which sum to a zero volume (of cake). Or not?-Modocc (talk) 22:56, 17 April 2013 (UTC)

Well, this mathematical cake is composed of points, right? Specifically, cardinality of the continuum-many points. $2^{\aleph _{0}}$ points. What's the volume of a point? It's zero. But put them all together, and you ahve the whole cake. --Trovatore (talk) 00:46, 18 April 2013 (UTC)

Aye, but not because this makes any more sense to me though. ;( With the Cantor set, an abstract mathematical cake could be made from it. But it is the excluded intervals that sum to the original interval's length (or, in 3d, the cake's volume) and not the sum of its points (again, these have zero widths and therefore sum to zero). The mathematical cake of points does not represent the intervals, volumes or quantities which must be summed, thus the mistaken summation of what ought be zero quantities instead leads to the unintended doubling of the original interval/volume, as with the Banach–Tarski paradox. -Modocc (talk) 03:36, 18 April 2013 (UTC)

Well, vaguely like that, I suppose. But Banach–Tarski is a lot more troubling intuitively because there are only finitely many pieces. Even countably many pieces means you run into trouble if you expect to expect them to be Lebesgue measurable, because Lebesgue measure is countably additive. But with uncountably many pieces, all bets are off (though you might get some uncountable additivity depending on certain set-theoretic questions, but I've already taken you pretty far afield so I won't go there unless you ask). --Trovatore (talk) 03:57, 18 April 2013 (UTC)

Let's suppose you have a cake, or whatever object, that's of finite size but is somehow "solid". Or, to conceptualize it more practically, image a finite volume of empty space, and say you're going to allocate the space to a number of persons as if it were a cake. If it's 1 person, he/she gets the whole thing. If it's 2 persons, they each get half (1/2). If it's 3, they each get 1/3. And so on. The larger "n" gets, the smaller each portion "1/n" gets. "n" can never "equal" infinity, but it can "approach" (so to speak) infinity, i.e. it can get larger and larger. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:37, 17 April 2013 (UTC)

If 1/0 = infinity (or negative infinity) then 0 * infinity = ? Well, this is why it's crazy philosophy. At least Trovatore gave us a link to read. And what he said makes some sense - if you pick a particular slice, even from an infinite number of slices, you're counting it, and if it is spread over an uncountably large number of recipients then there will be none of the infinitesimal left. Wnt (talk) 23:33, 17 April 2013 (UTC)

I heartily agree each slice is and should be counted. :-) I do not quite understand as to what is being counted though with zero volumes. To count "infinitesimal" zeros seems to be not very rigorous at all. Either we are adding together zeros or not (perhaps there is some alternate way of interpreting zero volume). In any case, counting the infinite number of infinitesimal nodes that result from an infinite partitioning, (as with (.9 + ,09 +...)), but where the numbers get infinitely small as one progresses into the tree... well at least I can comprehend a summation of such infinitesimals (because each node must become infinitely small by definition); this kind addition makes sense to me no matter what the data is representing, whether it be volumes, mass or an arbitrarily large number of nonzero likes. -Modocc (talk) 23:56, 17 April 2013 (UTC)

Isn't f(x) = x/inf a non-injective function? Take this for example: f(x) = sin (x) → x = {arcsin (f(x)) + 2kπ|for k E Z}. Plasmic Physics (talk) 04:34, 18 April 2013 (UTC)

Notice: that function is only injective, if the k term is introduced. Plasmic Physics (talk) 04:52, 18 April 2013 (UTC)

Here is a link to the previous recent discussion on a similar question (I think its the one Trovatore is referring to above). -Modocc (talk) 00:41, 18 April 2013 (UTC)

Main Battle Tank

How can the crews of Leclerc tanks extract the ammo which is not in the autoloader (from inside the tank or outside the tank like T-72) I asked this question before but I think the one who answered me did not notice that I was asking about Leclerc also not only T-72 so he answered : from outside Tank Designer (talk) 20:13, 16 April 2013 (UTC)

Here's a forum discussion (at the very bottom) that explains(?) the procedure from inside. On the top of the next page, it goes into a bit more detail, but the linked photos are blocked. Clarityfiend (talk) 00:59, 17 April 2013 (UTC)

Here's a more-convincing-sounding and easier-to-understand explanation[2] from someone claiming to be a French tank commander. Search for 09:37 (reloading from outside), and 09:39 and 09:44 (theoretically from inside). Clarityfiend (talk) 01:17, 17 April 2013 (UTC)

Thank you very much Tank Designer (talk) 08:00, 17 April 2013 (UTC)

Planck microwave background data

I notice that the Planck microwave background data shown in [3] isn't in our article yet (neither Planck (spacecraft) nor Cosmic microwave background radiation). There is an image at [4] but it is unsatisfying for a few reasons: the left edge is cropped off, and weirdly, when I click on "view image" (and presumably when I save it) I go from a reasonable-looking graphic to one that is slightly smaller with obvious jpeg damage. Above all, however... this time I want more than just one single Mollweide projection - I want the data itself, with the full spherical accuracy available, viewable from every possible perspective. That way if, say, I am hallucinating, say, a giant pentagram centered somewhere around 45N 5E, I can (in concept, at least, and ideally by some practical means) rotate to look straight up at it. So ... what options are available for actually seeing this data? Wnt (talk) 22:05, 16 April 2013 (UTC)

I haven't actually done it, but you should be able to download the data from here and then use a HEALPix viewer like SkyViewer. -- BenRG 00:31, 17 April 2013 (UTC)

The player works, and I found the map .. but the download is 1.7 GB! I may not actually look at it right this minute, but thanks! Wnt (talk) 15:02, 17 April 2013 (UTC)

April 17

Water ya doin'

some water on earth does not change into water vapor for hundreds or thousands of years what water is this--71.164.242.116 (talk) 00:54, 17 April 2013 (UTC)debbie smith

I would assume it's the water frozen deep inside glaciers and ice sheets? This sounds a little like a homework question... Brambleclawx 01:55, 17 April 2013 (UTC)

(edit conflict) There's also ground water (see hydrogeology) and lots of water which is trapped in rocks themselves, chemically bound up as water of hydration and could be very deep within the earth's crust. --Jayron32 02:32, 17 April 2013 (UTC)

Also, there might be locations deep underground where water is sealed in by impermeable rocks on the sides and bottom. StuRat (talk) 02:32, 17 April 2013 (UTC)

Fossil aquifers. Nimur (talk) 18:53, 17 April 2013 (UTC)

Magnolias in southern Illinois

Visited Metropolis, Illinois last week and spotted a tree that looks like a magnificent Magnolia grandiflora, but I get the impression from the article that this species doesn't get very big so far north. Are there other magnolia species that (1) resemble Magnolia grandiflora in appearance, and (2) would be likely to grow to full size in southern Illinois? I can upload a photo if you want it; besides the leaves, the photo shows a massive (and differently colored) version of one of these. See File:Curtis House Metropolis IL.JPG, if that helps at all; it's the same tree, as my photo was taken in front of the Curtis House. Nyttend (talk) 02:50, 17 April 2013 (UTC)

I don't see why it wouldn't be a cultivated Southern Magnolia. Sure, it's natural range doesn't extend as far north as Illinois, but the article you linked at Magnolia grandiflora notes a rather grand Magnolia in Nantes, which isn't exactly in its native range. --Jayron32 03:19, 17 April 2013 (UTC)

In short, if you thought it was a magnolia, it almost surely was. But keep in mind there are zillions of magnolia cultivars, and it can be difficult to ID down to the species/strain. I currently live in central IL, and can attest (WP:OR) that there are many beautiful magnolias around, but I don't think that many are pure grandifloras. For instance, Magnolia_×_soulangeana varieties are very common. They just started blooming last week or so. Some of them are quite old, and I think this year is giving a better than average display. There are a few magnolias in my neighborhood the size of the one in your link. SemanticMantis (talk) 03:59, 17 April 2013 (UTC)

The thing is that the article mentions magnolias getting farther north in the USA but says that they normally end up being stunted, not grand like this one; I can easily understand them flourishing in non-native climes that have weather similar to "home". But since SemanticMantis has them in central Illinois, I have to admit that I misunderstood something; Metropolis is just about as southern as you can get. Nyttend (talk) 11:58, 17 April 2013 (UTC)

I'm not sure what's really going on either. We definitely have some GIANT magnolias. But I'm thinking now that the biggest ones are not the wild-type grandiflora, but some cold-adapted hybrids or domestic strains... and central IL is certainly not much like the south! If you really want to get to the bottom of this, you might ask at the gardenweb forums, or contact a university extension in the region. SemanticMantis (talk) 14:06, 17 April 2013 (UTC)

We have "domestic" magnolias in the Detroit area as well - some of them as tall as two-story houses as not exactly stunted. A long drive (mostly north) from Metropolis and a bit colder in winter. Rmhermen (talk) 15:38, 17 April 2013 (UTC)

john s bergheim

this man was an oil man who lived in Belsize Court, Hampstead. He went to canada and started up a partnership with a Mr McCauley, together they found oil in germany, canada, russia and iran. He died in 1903 in a taxi cab accident. I cannot find any more information than this and would be grateful for your help. — Preceding unsigned comment added by Janeward (talk • contribs) 09:59, 17 April 2013 (UTC)

His partner appears to have been named either McGarvey or MacGarvey. The first article is more informative about their partnership. Searching for "John Bergheim" and "oil" brings up lots of useful hits (more than I can easily list here), although they can't seem to decide if he's a "Viennese banker" or a "British engineer". I may get around to writing a bio of one or the other or both. Clarityfiend (talk) 10:26, 17 April 2013 (UTC)

Focal length and "Focus" difference.

I know that focal length is the distance between the camera and the lens, changing it, will "zoom" the image, focusing will change the distance from the lenses which is being focused that can range from 3 ft to infinity, now what does focus exactly physically does to the lengths? Does it moves the length too? Changing focus will change the focal length?, Thanks. 190.60.93.218 (talk) 13:45, 17 April 2013 (UTC)

This question is not well written, so some guesses or assumption must be made about what you are really asking. The following points may be relevant:-

1. The focal length of a simple lens is a fixed property of that lens, is a measure of the lens focusing power, and is determined by the optical properties of the lens material (the refractive index) and the curvature of its surfaces. Focusing a camera does not therefore, and in fact cannot change the focal length.
2. When you focus a camera, you are moving the lens toward or away from the film/image sensor. When the lens is set for infinity, the distance to the film/image sensor is equal to the focal length - this means that incomming parallel light rays are brought to a point on the image sensor. For objects closer, such that focsing for them is needed, you move the lense further away from the film/image sensor, so that light rays for any point on the object still converge on a point on the image sensor, even though they don't get bent to the same angle after passing thru the lens.
3. In a zoom lens system, there is more than one actual simple lens present, and it is possible to alter the distance between lenses so that the aparent focal length of the lens system is changed. This alters the distance from the film/sensor that is required for focus, thus changing the image size. Zoom lens systems are designed so that when the focal length is changed, the whole lens system is moved as well, so as to maintain focus.

Wickwack 120.145.130.241 (talk) 14:20, 17 April 2013 (UTC)

I thought, the focal length was the distance between the length and the film, which changing makes the image "zoom", thanks for the clarification, but what I'm asking is how you "set" the lens to focus on something while keeping the same "zoom"/FOV. 190.60.93.218 (talk) 15:53, 17 April 2013 (UTC)

Focusing is done by moving the lens or lens assembly toward or way from the image plane, as I explained. However, an undesirable biproduct of doing this is a (generally small) altering of the field of view, as Nimur pointed out. It would be possible to construct a multi-lens system to automatically hold the field of view constant while focusing (just as zoom lens systems are constructed to hold the image in focus while the zoom ratio is changed), however I have never seen nor heard of such a thing - there is no commercial need. If the field of view is not as desired after focussing, move the camera and refocus as necesary. Your English is none too good, so I hope this answers the question you were trying to ask. Wickwack 120.145.20.216 (talk) 01:00, 18 April 2013 (UTC)

Thank you for your answer, forgive my English. 190.60.93.218 (talk) 12:12, 18 April 2013 (UTC)

(ec) For very simple lens assemblies, changing the focus also changes the field-of-view. This works by moving the lens without changing its optical properties, which moves the focal plane; the effective focal length of the imaging system (not the lens) is changed. Because the field of view changes, this means that every focus change is also a slight zoom. That behavior is undesirable, which is why expensive camera lens assemblies have multiple lens elements. Some elements move during focus to counteract the focal length change due to the movement of the focal plane. As always, here's a pitch for the go-to reference for practical lens assemblies: Applied Photographic Optics, which is unfortunately still very expensive. Nimur (talk) 14:23, 17 April 2013 (UTC)

Caesarean

During a C-section, what is used to stitch the mother back up? Pass a Method talk 15:15, 17 April 2013 (UTC)

Surgical sutures and/or Surgical staples. Rmhermen (talk) 15:30, 17 April 2013 (UTC)

Non-black-body emission.

Our article on black-body radiation says that "...a black body is a diffuse emitter (its emission is independent of direction)". But that's an ideal black-body. Do non-ideal real-world materials also emit light independently of direction - and if not, is there any information about how directional that emission might be? (I know that they certainly reflect light in a directional fashion). Also, if it matters, I'm most interested in emission in the infra-red rather than the visual part of the spectrum. SteveBaker (talk) 16:11, 17 April 2013 (UTC)

I would expect the shape to have an effect, both on a macro scale and on a microscopic scale. That is, a direction with more material "pointed at it" should receive more radiation than others. For example, a long rod would presumably radiate less axially. StuRat (talk) 17:05, 17 April 2013 (UTC)

Steve, we use Lambert's cosine law for ideal materials, and variations on it for non-ideal materials. It can be used to model emission or reflection.

An integrating sphere nearly perfectly approximates a diffuse emitter, even though it is built from real-world material.

In computational imaging, you already know all the ways standard APIs model surfaces for reflection - and you know ambient and specular illumination.

You'll probably find tables and approximations of real-world illuminators; keywords that will help: radiation patterns, lambertian surface, antenna gain. When I learned all this stuff, I learned the theory for RF - and later applied it at visible/optical frequencies. As you know, infrared, optical, and radio light are all just electromagnetic waves of different frequencies - so the theory is identical. The practical parts - answers to questions like "how lambertian is a surface" vary quite a lot: at radio frequencies we almost always say "perfectly Lambertian."

Of course, the model for specularity is scaled by wavelength. If you're using very long wavelengths, every surface has roughness relative to the size of the wave! At infrared and optical wavelengths, this is less likely to be true.

Finally, keep in mind that an emitting or reflecting surface can be specular and non-specular independently of its lambertian or non-lambertian property.

As an example - humans are darned near perfect lambertian surfaces, even though some parts of them are more specular than others. This is (or ought to be) common knowledge amongst photographers; the mathematics are all over the internet, too. Here's one for optical models of human reflectivity, geared towards machine-vision applications - using physics to help robots identify human skin by sight!. From the standpoint of physical principles, if we reflect with that pattern, we probably emit our infrared according to the same law. Nimur (talk) 19:02, 17 April 2013 (UTC)

I thought the Lambertian stuff was about how objects reflect light - I'm interested in how they emit light...and specifically, IR light...due to their temperature. Are you saying that the radiation is also much greater in the normal direction than off at an angle?

Specifically: Suppose we have a heated cube, made of some uniform real-world material, out in the darkness of deep space. If I point an IR camera at it, will I see the various facets of the cube having different brightnesses due to their angle to the camera (which is what I'd see in reflected light) - or will I see a seemingly flat surface of uniform brightness as black body suggests? Could ask the same question of an object heated until it's white-hot, viewed in a conventional camera. SteveBaker (talk) 20:42, 17 April 2013 (UTC)

Correct, you can apply the cosine equation to emitted light in the same way you apply it to reflected light. That would be a perfectly diffuse reflector. The derivation of the lambertian equation is strictly from geometry - it has to do with the projection of the ray onto the unit-area of emitting (or reflecting) surface. Nimur (talk) 00:01, 18 April 2013 (UTC)

Oh - I see what you're saying. I normally think of using the term "lambertian" to describe a surface who's reflected light is in proportion to the cosine of the angle between the normal and the light source. You're right that it also alters (as a strictly geometrical matter) the light reflected from each unit area of the surface as a function of the angle between the normal and the camera/eye/detector...but in practical matters, that's perfectly cancelled out by the fact that the number of unit areas emitting light towards the same "pixel" of a camera increases by the exact inverse of the way that the cosine law is reducing the output of each unit area.

So, indeed, a sphere that's emitting IR light in a cold/dark vacuum would look like a perfectly evenly glowing circle - getting neither brighter nor dimmer at the edges as angle between the surface normal and the camera gets closer to 90 degrees...right?

SteveBaker (talk) 14:23, 18 April 2013 (UTC)

Yes right. There is an easier way to see that. If that was not the case, than a carefully placed mirror reflecting light from the edge of the glowing circle to its center and vice versa would transmit more energy one way than the other causing a net transfer of thermal energy between two objects that are at the same temperature. Turns out that that can be used to make a perpetual motion machine and is therefore forbidden by the second law of thermodynamics. Since the 2nd law of thermodynamics also applies to non-black body objects, that makes for an ironclad argument. Dauto (talk) 16:01, 18 April 2013 (UTC)

Wow! I love that answer. Clever. Thanks. SteveBaker (talk) 19:51, 18 April 2013 (UTC)

And any deviations from that perfect uniform flat-looking emitter would be caused by non-idealities: perhaps each surface-element is not emitting with the same intensity (due to thermal variations in the object, for example - maybe the corners of the cube are not as hot as the center of each cube-face). Or perhaps the light that the viewer sees is passing through an imperfect medium whose transmittivity is directional; (or even isotropic, but non-negligible over different path-lengths). There are hundreds of other reasons why optical depth might vary across a scene in the real-world. Nimur (talk) 17:44, 18 April 2013 (UTC)

Yep - I'm aware of the other things that are going on - it was just this one thing that I was hung up on. Many thanks! SteveBaker (talk) 19:51, 18 April 2013 (UTC)

Better than a laser printer?

Can something be improved in a laser printer? (besides the price). It seems to me to be the perfect solution, both relating to quality and simplicity. Is there any new technology, with a complete new architecture being developed? OsmanRF34 (talk) 17:24, 17 April 2013 (UTC)

Well, you still have the potential problems from feeding paper in with rollers, which can lead to paper jams. And those moving parts are likely to wear out, eventually. Hopefully some steady-state solution will eventually become available, where you place paper on a flat bed, it prints to it, and you then remove it, with no paper feed mechanism required. (It could still have a paper-feed mechanism for multiple pages, but I typically print one page at a time, so would like this option.)

But printers themselves may become obsolete. In the future, a digital copy on your portable device may serve the same purpose. We already have some digital coupons, allowing us to skip the printing step. StuRat (talk) 17:30, 17 April 2013 (UTC)

Right, eventually there will be usable e-paper. Looie496 (talk) 17:35, 17 April 2013 (UTC)

Perfect solution for what? Laser printers are great for text and simple artwork like charts, graphs so therefore excellent for most documents, fliers are similar things. They aren't quite so good for reproducing photos or some types of artwork so with those, in cases where you care more about quality than cost or time (and possibly water resistance) they aren't really the perfect solution. In addition, while some laser printers can handle banners or continuous feed paper, it's more difficult to implement so is significantly less common then with a number of other forms of printing. Large format (I'm thinking A1 or larger) laser printers are also AFAIK a lot less common then inkjet ones I think for a mix of consumer demand and construction difficulty reasons. Laser printers are also still crap for very large scale jobs. P.S. I'm assuming by laser printer you mean one using toner not Digital printing#Digital laser exposure onto traditional photographic paper Nil Einne (talk) 18:13, 17 April 2013 (UTC)

Perfect for private and office use. For printing docs, not meant to be a big scale enterprise, like book printing and such. I'm not sure that inkejet printers are more common in this context. All people and companies around me user laser printers only since several years, as far as I am aware. OsmanRF34 (talk) 18:19, 17 April 2013 (UTC)

The examples you describe fit with the cases where laser printers work well, that doesn't change the fact laser printers aren't perfect for all uses. No one ever said inkjet printers were more common in the examples you describe although I think inkjets still have a reasonable market share in home use, probably more for printer purchase cost reasons then any of the ones I mentioned. Nil Einne (talk) 18:25, 17 April 2013 (UTC)

I didn't say anyone "ever said inkjet printers were more common in the examples [I] describe." OsmanRF34 (talk) 18:29, 17 April 2013 (UTC)

If the lasers were focused with perfect lenses to carve diffraction gratings into the paper that would act as structural color, so they never needed ink, I would be more impressed. Wnt (talk) 21:35, 17 April 2013 (UTC)

I think you are setting your expectations a little high - a printer that didn't regularly break down, jam or leak toner would be enough to impress me! Equisetum (talk | contributions) 00:01, 18 April 2013 (UTC)

My point is I don't get the relevance of your comment 'I'm not sure that inkejet printers are more common in this context' which was made in reply to me, since this was not something I was discussing at the time although as I later mentioned, I don't think your claim is entirely accurate anyway (as with your first post, problem is you seem to be applying what you know or think you know about one segment of the market too widely). I should also mention that the existence of CISS printers from manufacturers like Epson in parts of Asia, coming after the wide availability of aftermarket modifications to support CISS, is another indication that there is fair demand for inkjets in some sections of the home/office market, and I don't believe this demand is entirely coming because of photo/artwork printing. BTW, I should clarify when I mentioned continuous feed paper, I was also thinking of Continuous stationery. I also forgot to mention that laser printers are unsuitable for multipart stationery and copy paper (whether carbonless or not) that requires impact printing. And laser printers also doesn't work well for stuff like small receipts. (Note that in my first reply I intentionally avoided using the term inkjet, only mentioning it once, for a reason. There are several different methods used nowadays for printing for different purposes. Inkjet is probably the most common alternative to laser printing, but other methods are used for other purposes.) Nil Einne (talk) 07:17, 19 April 2013 (UTC)

Not only are laser printers not a good choice for large formats (e.g., A1 and A0 drawings for engineering) due to technical difficulties, inkjets are far cheaper and, for the last 10 years or so, offer resolution sufficient to make your own eye the limiting factor.

Laser printers are not generally acceptable for contract documents and drawings because their output is not archivable. All of us who have photocopied or laser printed (it's the same technology inside) a manual several years ago know that - the image is not permanent and comes off on adjacent pages. You can inkjet print with HP and Cannon technology printers and come back 200 years from now - if the paper has survived the image printed on it will.

A4 laser printers has become cheap enough, due to volume production (and the practice of manufactuers to sell at a loss and make money on the toner) to make them very common in homes and offices. But they are not built to last - you generally won't keep them more than just a few years. But the enginering/drawing office market is quite different - large format printers built to professional standards last a very long time.

I have an A0 inkjet in my office that has been turning out engineering drawings every day for 15 years (and, yes, we have a driver for it under the currently supported Windows). and the cost of ink (approx $500 a year) is far far below what laser toner would cost. I get to see lots of customer and co-contractor drawing/engineering offices - they all have inkjets, I have never seen a large format laser printer.

So, to answer Osman's question, what improvements are desirable in laser printers:-

1. Make them archivable - image stable for decades, not years
2. Either make them cheap in large formats or make them built to last
3. Reduce the cost of toner so they are competitive with ink for large format high volume applications.

I don't see any of this happening anytime soon.

Wickwack 120.145.20.216 (talk) 00:32, 18 April 2013 (UTC)

Did you move straight to inkjet from plotters? I've seen some quite old plotters still in service (indicating reliability), and to me their output for technical drawings still looks great. I can't imagine dot matrix technology doing well in large format vector graphics, but I don't know much about old printers, or what else might come in between. SemanticMantis (talk) 01:07, 18 April 2013 (UTC)

Yes, I did. Plotters were a very slow technology, did not have the resolution of inkjets, and of course could not do photo images. You can still buy the pens (though not from Hewlett-Packard), which must mean a fair number of plotters still in use. I also use my inkjet to print out project gantt charts generated from Microsoft Project. Plotters could not handle that. Large format dot matrix printers were made before inkjet technology was refined. I saw a colour one in operation once, about 1990. I hated the raggedy screaming noise they made. One of the nice things about large format inkjets is that you can include on the technical line drawing a CAD rendered semi photo-realistic image of the part(s) described. Wickwack 120.145.20.216 (talk) 01:40, 18 April 2013 (UTC)

Surely the perfect solution is the paperless office. HiLo48 (talk) 06:40, 18 April 2013 (UTC)

Greatest joke of all time. In my experience, the amount of paper used in offices since the advent of the so-called "paperless office" has burgeoned beyond all reason. -- Jack of Oz ^[Talk] 07:07, 18 April 2013 (UTC)

Yep. Too true. Partly my reason for mentioning it here. Much of what is printed doesn't need to be. My suggestion is a serious one in this thread. HiLo48 (talk) 07:13, 18 April 2013 (UTC)

I suppose the true paperless office is going to come eventually, but not in my working lifetime. iPads and kindles are ok for novels, emails, and photos of friends. But there's are darn good reason why commercial spreadsheets, gantt charts, and engineering drawings are produced on A1 and A0 size paper (or 36 x 42 inch if you are American) - you need it to convey the complexity with a font or line size big enough for the ordinary human eye to see. Looking at gantt charts and engineeing drawings on an iPad or even an ordinary desktop PC is like looking at the World through a keyhole. And a 42 inch wide iPad is just not in any way practical - not technically, and not ergonomically. And scan-reading a scientific or engineering textbook and extracting the specific understanding you need is far far quicker with a printed book than it is on a computer, even with the search tools you can use on a computer. I use an iPad for entertainment, but would never consider it for work. Not forgetting that if you give a tradesman a paper drawing and ask him to weld it up, machine it, cast it, or whatever, he'll take that paper drawing into the dirty, dusty oily workshop with him and do a fine job. Give him a iPad with the drawing loaded in it, and what you'll probably get back is a load of abuse and a dirty, dusty, oily busted iPad. Wickwack 120.145.68.159 (talk) 08:55, 18 April 2013 (UTC)

A0 and A1 sized prints are not the issue. It's the masses of stuff printed on A4 (or US Letter size) that's the biggest waste of paper. HiLo48 (talk) 22:09, 18 April 2013 (UTC)

You've addressed just one of my points, but I think you are only partly correct anyway. When computers (and photocopiers) first became common, so called experts started predicting the paperless office, but the reality was a big increase in paper use, because people could. In recent years, the consumption of paper has remained high. But the productivity of workers has dramatically increased. The consumption of paper per unit of work has gone down. Years ago, all written business communication was by formal letter and minute, on paper. Now its via email and almost never printed. Obtaining supplies was done by paper requisitions sent by snail mail. Most companies are now using electronic purchasing systems. I remember working in offices 30 years ago - there were lots and lots of filing cabinets storing all the paper. We still have filing cabinets full of paper, but not many of them. But the amount of real work pumped out per worker has gone up enormously. I work as a consulting engineer. I work mostly in my home office and sometimes I'm allocated a desk at a customer's office. I do everything myself, using email, MS-Word, spreadsheets, and certain CAD software. 30 years ago, an engineer like me would have been supported by a secretary, part of a typing pool, and a couple of draftsmen. And work harder to get a heck of a lot less done. If you just look at the (A4 even!) paper consumed by myself, it hasn't dropped that much. But all those other folk consuming paper are gone! Post offices around the World are strugging to remain financially viable now, because there has been a dramatic reduction in the volume of letters. Wickwack 121.221.217.72 (talk) 00:47, 19 April 2013 (UTC)

In the old days people worked harder to get less done... for more money in fewer hours. Either worker productivity isn't really going up or else it doesn't really seem to matter. Wnt (talk) 03:21, 19 April 2013 (UTC)

You must be joking! It's blindingly obvious productivity has improved enormously! What kind of work do you do, Wnt? Productivity-wise, the introduction of mainframe computers (1950's and 1960's) didn't do much. The introduction of DR-DOS and MS-DOS computers (1980's) only improved things slightly. But the introduction of email (~1990), web-enabled business-to-business transactions, and Computer Aided Design and Computer Aided Manufacturing has been a revolution at least as great as the industrial revolution, and it's still evolving. Wickwack 120.145.203.15 (talk) 12:46, 19 April 2013 (UTC)

So where are the wage increases to match this increase in productivity? Where are all the extra products being made going to? Wnt (talk) 16:59, 19 April 2013 (UTC)

Which planet have you been living on? Worker wages have been going up exponentially for at least the last several decades, as measured by the Social Security Administration's wage index: [5]. This rise significantly outpaces inflation, which you can check for yourself using this CPI data from the Bureau of Labor Statistics: [6]. --140.180.254.78 (talk) 01:50, 20 April 2013 (UTC)

Wnt can't have been on this planet. Here's a couple of examples, out of a multitude:-

1. 30 years ago, cell phones were available. They were available in two kinds: mobile, which was installed in the boot of a car, or behind the seat in a truck, being the size of 3 or 4 housebricks; and portable, which meant it had a carry handle and also was the size of 3 housebricks, and nearly as heavy. The only function provided was voice calls. No texting, no web services, just talking. They were very expensive, so only folk who had a real business need had them. Today, cell phones are the size of a cigarette packet, only thinner. You can still use them for talking. You can also text, take, send, and recieve photos, access the internet, listen to FM radio broadcasts, get the time, etc etc. And they are so cheap that just about every one over the age of 9 has one.
2. 30 years ago, you could watch a movie at home. Typically you rented a VHS tape for about half or 3/4 the price of seeing it in a theater, ie about $10, and watched it on a player that cost you $500 to $800, and a TV costing about the same. You watched a blurry picture that was a poor cousin to analog broadcast standard (625 or 525 line) with medium fidelity mono sound. Today, you buy a DVD for about $5, and watch the movie in high definition equivalent to 1080 lines or better, with 5+1 high quality sound. And you watch with a player worth at most $150. Assuming you didn't just download the movie via your internet connection of course. Outside of the universities and some Telco's, there was no internet 30 years ago. Actually, a few months ago, I bought a TEAC full-HD digital TV with built-in DVD player for $149.99.

Wickwack 120.145.69.179 (talk) 12:16, 20 April 2013 (UTC)

biology

Is acid rain and normal rain same?If not,then compare the climate before and after the acid rain. — Preceding unsigned comment added by Titunsam (talk • contribs) 18:09, 17 April 2013 (UTC)

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Nil Einne (talk) 18:14, 17 April 2013 (UTC)

BTW, is it possible you could use a more descriptive title for your questions then the 'biology', 'chemistry', 'physics' you seem to use every time? As an example, in a case like this you could use 'Acid rain' or 'Acid rain compared to normal rain'. Nil Einne (talk) 18:16, 17 April 2013 (UTC)

Yet another Titunsam's question that looks like homework. OsmanRF34 (talk) 18:35, 17 April 2013 (UTC)

You do realise that Wikipedia has a very informative article on acid rain? It even has a very informative article on ordinary rain.--Shantavira|^{feed me} 19:53, 17 April 2013 (UTC)

Um, exactly what kind of "biology" is acid rain? (+)H₃N-Protein\Chemist-CO₂(-) 13:52, 20 April 2013 (UTC)

Climate and its effects on biomes might be taught as part of a school biology class. OP's question asks specifically about climate. 151.225.115.232 (talk) 17:31, 21 April 2013 (UTC)

Fair enough. I suppose in that case it might have made more sense for the question to be titled "climate". If they're going to ask us to do their homework for them the least they could do is make an effort to identify the subject of their homework. Calling it "biology" just because it's homework for a biology class is a bit silly. They may as well have titled this section "school", would have been equally informative. (+)H₃N-Protein\Chemist-CO₂(-) 18:58, 21 April 2013 (UTC)

Can you identify these Prunus species?

1. 16 and 17
2. 18

I would be very grateful. Surtsicna (talk) 19:54, 17 April 2013 (UTC)

For some reason 16 and 17 won't open for me but I think 18 might be Prunus cerasifera 'Atropurpurea'. Richard Avery (talk) 21:56, 17 April 2013 (UTC)

Thanks for your input! Can you open these: 16 and 17? If not, I'll have to try something else. Surtsicna (talk) 22:44, 17 April 2013 (UTC)

Yes, I can see 16 and 17 now and to me they are the same species, although it is difficult to be exact because the image is not sharp and the backgrounds are different. Furthermore there are literally dozens of varieties of prunus species and it is normally necessary to be able to view the whole plant so that the size, shape, bark, fruit, leaf and flower detail can be considered in detail to make a sure and accurate identification. On the grounds of probability I would say that 16 and 17 are possibly Prunus avium or some variety of this species. About a 70% degree of confidence. Richard Avery (talk) 07:31, 18 April 2013 (UTC)

Yes, 16 and 17 are the same species, with 18 being a different one. I suppose this information increases the degree of confidence a bit :) Surtsicna (talk) 16:38, 18 April 2013 (UTC)

salt storing tissue?

Hi, I wondr if some organisms could have cells analogous to fat cells, but for salt instead of energy?thanks76.218.104.120 (talk) 23:52, 17 April 2013 (UTC)

Some animals have Salt glands. This is a gland which gets rid of excess salt. I've not heard of anything that stores it for later, but I'm not a zoologist or anything. Vespine (talk) 01:22, 18 April 2013 (UTC)

The problem with salt (NaCl) is that it is water-soluble, so hard to store in the organism. Animals that live in the high-salinity environments have salt glands that excrete excess salt ingested with food or water; they don't normally store the excess salt internally. Animals (fish and amphibians) that live in low-salinity environment rely on their kidneys to remove the salt from the urine; this protects them both from the electrolyte loss and from the osmotic bloat. I am not aware of any organism that would store solid salt (but that, of course, doesn't mean there aren't any!). --Dr Dima (talk) 01:24, 18 April 2013 (UTC)

• Note that "salt" is a little ambiguous. If it includes potassium, then basically all cells store it -- the intracellular concentration of potassium is much higher than the extracellular concentration. But if "salt" means sodium (the usual meaning), then as far as I know there are no animal cells that maintain high intracellular concentrations. It seems unlikely to be possible, because basic mechanisms of cell metabolism would break down if you had high intracellular sodium concentrations. Sodium is essentially stored in the bloodstream instead. I also spotted one recent paper that claims to have seen relatively high sodium concentrations in the skin, but that would be a minor effect. Looie496 (talk) 15:15, 18 April 2013 (UTC)

thanks.76.218.104.120 (talk) 05:49, 24 April 2013 (UTC)

April 18

How to destroy a planet in star completely

From i have learned the way scientist predicts inner planets to get swallowed up is to telltrace the chemicals, for example lithium and sodium. But if we get a hypothetical planet in the star how would I destroy it? I learned when a hypothetical rocky planet gets in the sun, they will not instantly get destroyed, they won't completely get destroyed until it gets to the sun's core. So when earth gets in the sun, will earth wait until it gets to hotter layers of the sun to get destroyed completely (only the crust to core) all at once, or it will first eat away the crust and erode the planet progressively (through the mantles to earth's core) as earth gets deeper in the sun. For scientist to predict the inner planets to get swallowed up to they try to find the missing planets and compare their solar system planets to our solar system's planets, or they always find the chemicals inside the star like sodium, lithium rocks which got evaporated into gas. Is this possible other sun-like solar systems might have planets closer to sun like Mercury or much closer to sun than Mercury, like 0.05 AUs away from their sun.--69.226.42.134 (talk) 00:39, 18 April 2013 (UTC)

As a rocky planet approaches the star, the solar wind, and radiational heating, will erode the atmosphere of the planet. Once the planet is close enough to the star, those same processes will start to significantly melt and evaporate the planet progresively. This will continue as the planet enters the star. Since heat transmission is not instantateous, the planet may sink well into the star, where temperature is tens of thousands of degrees. The greater temperature only affects the rate at which the planet evaporates completely. A planet may exist close a star, but not indefinitely, as it experiences errosive processes as described above. It is even possible for a planet to orbit within a star, if it has sufficient orbital velocity. Plasmic Physics (talk) 04:07, 18 April 2013 (UTC)

Also note that in the red giant phase a star expands out to some of it's planets, making the density of the star extremely low (the mass is the same, but the volume is far greater). So, while still quite hot (although not as hot as the original star), the density is so low that it takes a long time to heat up those planets. On the other hand, if something caused the planet to fall into a normal-sized star, the much greater density would make short work of the planet.

Something else to note is that the heavier elements in a planet would cause it to eventually sink into the core of the star, whether it was solid or vapor when it got there. StuRat (talk) 04:58, 18 April 2013 (UTC)

Thermal convection currents will slow down the net movement of heavy elements towards the core consideably, and may even prevent it. I believe that most stars would be hot enough at the centre to cause a planet to simply smear out and dissolve before reaching the actual core. Now that I think about it, what kind of turbulance would it cause if a solid object the size of several thousand kilometres colides with the core of a star which is itself a dense object? Somekind of star quake? Plasmic Physics (talk) 05:17, 18 April 2013 (UTC)

I can see them being delayed, but heavier elements must eventually sink to the center, I would think. I wonder if these elements would have an effect of reducing nuclear fusion, and thus reducing the star's output. StuRat (talk) 07:28, 18 April 2013 (UTC)

One other consideration is how hot the planet is to begin with. The Earth has a molten core/mantle, so only the crust would need to be melted. StuRat (talk) 04:58, 18 April 2013 (UTC)

The mantle is not really molten as it is, that is a common misconception. The mantle is infact a type of hot solid, called a rheid. Plasmic Physics (talk) 05:17, 18 April 2013 (UTC)

I was using "molten" to describe it's temperature. That is, it would be liquid, were the pressure not so high. Thus, once the outer layers melt away, the core will be liquid. It won't need to heat up. StuRat (talk) 06:27, 18 April 2013 (UTC)

Yeah, that's right. I should have thought it through. Can the mantle temporarily cool down as the planet is eroded away? Plasmic Physics (talk) 08:26, 18 April 2013 (UTC)

No — something as nearly incompressible as solid/liquid rock will not do any appreciable P-V work on its surroundings as it expands, and so its temperature will not drop significantly. (In particular, not enough to counteract the external heating!) --Tardis (talk) 01:45, 19 April 2013 (UTC)

The thing to remember is that the solid lithosphere of the earth is only 20 to 60 miles thick...much thinner in some places. As a mental image of this, think of the earth shrunk to the size of an apple...the skin of an apple is about as thick as the solid part of the earth on that scale. The remaining 4,000 miles down to the center (the white flesh of the analogous apple) is hot enough to be molten if the pressure were any lower. So only the top 20 miles of rock has to be melted/vaporized to get to the mantle - that reduces the pressure on the mantle - so some of that turns to a true liquid...and when that's boiled away, the pressure further in is reduced still more. Ultimately, the rest is only held together by gravity - and as it's eroded, the gravity (and therefore the pressure keeping it solid) would be shredded/dispersed more and more quickly as it boils away.

The friction with the sun's atmosphere alone would be horrific - the sun rotates every 25 days, the earth orbits in 365 days. The surface of the sun right now is moving at about 7,000 kph - and conservation of angular momentum suggests that it would slow down dramatically as the diameter of the sun increases. The earth is moving around an orbit at 100,000 kph...so there would be a 93,000 kph "wind" of solar atmosphere blowing past the earth's surface. Quite aside from the heat - that wind alone would remove a liquified surface material at an impressive rate as soon as any significant amount of the sun's atmosphere reached our orbit.

The details of what will ultimately happen depends in great detail on things we're not 100% certain about. How fast will the sun expand? How much will the sun's upper atmosphere and radiation affect the earth before we're physically close enough to be "swallowed up"?

There are at least four possible scenarios:

• The earth is actually far enough from the sun that it doesn't get "swallowed up" at all - but continues to orbit - albeit with atmosphere stripped, oceans boiled and molten surface.
• That the earth is slowly eroded over centuries to millenia as the temperatures rise...before the sun gets large enough to swallow it up.
• That something disturbs the earths orbit enough to cause it to spiral into the sun - which would blast it to atoms relatively quickly...depending on the rate of descent.
• The earth isn't the only body being messed with as all of this happens - so other gravitational disturbances might even fling the planet away from the sun...with all manner of possible consequences.

Any of those things seems possible on the basis of the evidence we have - and the rapidity with which the events unfold make a huge difference to the outcome - so it's really tough to describe what will happen in any kind of detail.

SteveBaker (talk) 13:52, 18 April 2013 (UTC)

There are a huge number of archived threads about this stuff, for example [7]. Wnt (talk) 21:44, 18 April 2013 (UTC)

Lever frame, again

Is it possible in principle, using a mechanical lever frame, to "clear" the interlocking signals even though the points are set for the siding? Or do the signals themselves have to be cross-wired to achieve this? (Note that in France, a dark signal is a clear signal -- completely contrary to American practice -- so shooting them out would also be an option.) Thanks in advance! 24.23.196.85 (talk) 05:49, 18 April 2013 (UTC)

I'm not familiar with the details of French railroad signaling, but in British practice, there are (usually) two signals associated with points: the "protecting signal" which gives the train permission to traverse the points, and the (not always present) signal that indicates which way the points are set.

The protecting signal for a trailing movement (one from a branch of the "Y" intersection to the base) is interlocked so that it shows danger when the points are set incorrectly for the movement, and must be manually set to danger before the points can be moved; someone with a crowbar and knowledge of the switch mechanism can easily defeat the interlocking.

The protecting signal for a facing movement (one from the base of the "Y" to a branch) is interlocked so that it must be set to danger before the points can be moved, but doesn't have any interlocking for which way the points are set.

The direction signal, especially in older mechanical systems, is part of the mechanism that moves the points, and is controlled by the same lever. You'd need someone out there at the signal to get it to show the wrong direction, though if the French system is as you describe (no light for a "through" movement, light for a branch movement), simply disconnecting the signal from the mechanism is sufficient (a fail-safe design that puts the protecting signals to danger if a fault is detected is only likely in an electromechanical system, not a pure mechanical system). --Carnildo (talk) 02:50, 19 April 2013 (UTC)

So, I gather from what you said that there's some additional sabotage required to defeat the signal, but it's quite easily done. Thanks! And BTW, a crowbar would only add about a pound or so to the Maquis' load-out, so no problem there (especially since they only need one for the whole team). 24.23.196.85 (talk) 03:13, 20 April 2013 (UTC)

Oh, and BTW, even an electromechanical or fully electrical system is not entirely fail-safe... 24.23.196.85 (talk) 03:16, 20 April 2013 (UTC)

From nothing

In A Universe from Nothing Krauss states that soething can come from nothing. Is this pure speculation or is this accepted by the scientific community as possible. Pass a Method talk 05:52, 18 April 2013 (UTC)

See Conservation of mass-energy to see why this is utter bullshit. 24.23.196.85 (talk) 05:56, 18 April 2013 (UTC)

The answer lies in the closing statements of the final section of the article you linked to. Plasmic Physics (talk) 05:57, 18 April 2013 (UTC)

To be a little less terse, A Universe from Nothing refers to the quantum vacuum, which "is not truly empty but instead contains fleeting ... particles that pop into and out of existence" (due to the uncertainty principle) for really, really short periods of time (say on the order of Lindsay Lohan's attention span). It's also discussed in more gruesome detail in Virtual particle#Vacuums and Quantum fluctuation. So yes, this is a well-accepted idea in quantum physics. Clarityfiend (talk) 07:27, 18 April 2013 (UTC)

(ec) Based solely on the Wikipedia article, I think Krauss is talking about a vacuum fluctuation triggering cosmic inflation, which is both pure speculation and generally considered plausible given what we know about physics. Energy conservation is not an obstacle to this idea, at least not obviously. However, the vacuum in which this fluctuation happens isn't "nothing", so this really doesn't explain where all of existence came from. At best it could explain where the flat expanding space we see around us came from in a larger universe that was there already.

There have been various ideas about how all of existence could "come from" the philosopher's nothing. Aside from the fact that it seems hopelessly beyond the reach of experiments, this is also considered a reasonable line of speculation, maybe because the alternative doesn't seem to make any more sense. -- BenRG 07:33, 18 April 2013 (UTC)

I find it impossible to consider that the PN can give rise to anything - to consider that it can, is to consider that the PN has properties that allows it to yield something, and to give properties to the PN, is consider the PN as something. As soon as you define the PN, you create a paradox. Thus, a thing can only be yielded by a thing. Plasmic Physics (talk) 07:39, 18 April 2013 (UTC)

As a logical consequence, there is no such thing as the PN. Plasmic Physics (talk) 07:40, 18 April 2013 (UTC)

Futhermore, it is total non-sense to state: "The universe arose from the PN", however, the following is a reasonable statement, whether true or not: "The universe arose from the SN". Plasmic Physics (talk) 07:45, 18 April 2013 (UTC)

It appears i'm getting contradicting answers here. Pass a Method talk 08:05, 18 April 2013 (UTC)

Let me summarise what's been said: "...Something can come from nothing." is a generally true statement, as long as 'something' and 'nothing' is properly defined. However, the specific definitions of those terms as used by Krauss, makes that statement false. Plasmic Physics (talk) 08:14, 18 April 2013 (UTC)

At the very least, that statement is contestable. Plasmic Physics (talk) 08:15, 18 April 2013 (UTC)

No, the specific terms used by Krauss make the statement undeniably true. The quantum vacuum has fluctuations that can lead to the creation of virtual particles, which don't violate mass-energy conservation because they don't exist for long enough to have a well-defined energy. (Just as there's an uncertainty principle for position and momentum, there's also an analogous principle for energy and time.) The fundamental forces can be described as the exchange of virtual particles--for example, the electromagnetic force is due to the exchange of virtual photons. The Casimir effect is caused either by the zero-point energy of vacuum or the creation of virtual particles from the vacuum, depending on your preferred interpretation. Finally, it's possible for virtual particles to appear "real" in an accelerated reference frame. The most famous example is Hawking radiation, where virtual particle-antiparticle pairs are created near the event horizon: one falls in, the other escapes and is perceived in our reference frame (accelerated relative to the black hole) as a real particle. --140.180.254.78 (talk) 08:37, 18 April 2013 (UTC)

That is one of the terms defined, however, you're missing his definition of 'something'. Both terms need to be correctly defined to make the statement true. Plasmic Physics (talk) 08:48, 18 April 2013 (UTC)

Do you think a proton emitted as Hawking radiation counts as "something"? How about the Casimir force that tries to pull two parallel plates together? How about the photons in a black body, which can "come from nothing" just by increasing the temperature? --140.180.254.78 (talk) 10:53, 18 April 2013 (UTC)

The primary definition, I'm refering to is cosmic inflation, as stated by Ben above. Plasmic Physics (talk) 11:23, 18 April 2013 (UTC)

Not an answer: I've read various pop-sci things about dark energy having negative pressure, causing energy (more dark energy?) to be released as the universe expands, so that it might have had zero energy at the beginning, but I don't pretend to understand them, not sure my sources understood them, not sure they meant anything to begin with. :) Maybe this is a good elaboration of the idea. (oh - that's the same guy the OP mentioned) Wnt (talk) 03:15, 19 April 2013 (UTC)

Mental toll of spying

What are the possible mental/emotional impacts of being deployed as a spy in enemy territory for a long time? I could think of a couple off the top of my head: gradual onset of paranoia from the strain of leading a double life and always being on your guard; fatigue and irritability from the same cause; possible PTSD from a near-capture or from seeing another operative captured... What other possible impacts can you think of? 24.23.196.85 (talk) 05:55, 18 April 2013 (UTC)

One can also think of positives that boost self esteem: Success at changing outcomes, success at a difficult mission; some people thrive on adrenaline. Not all spying has any real life threatening consequences. During the occupation of Germany at the end of World War 2, there was a network of people in the US and British zones reporting on trasnportation traffic back to the Soviet Union. The US and British knew about them but left them alone becasue it suited them to have the Soviets impressed. I doubt that the British spies such Burgess, McLean, etc, felt any stress over what they were doing. They themselves thought they were doing good, and it was alife-long thing for them. Wickwack 58.164.233.93 (talk) 06:13, 18 April 2013 (UTC)

They could end up with something akin to Stockholm syndrome - by watching their subject so much they begin to empathise with them. There's a lot of stories spies that become defectors/traitor by switching sides and I would rationalise that due to having to lead a pretty amoral life where orders are undertaken with limited regard for your own personal moral-compass that some spies could become mercenaries (see Mercenary) who work for the highest bidder. ny156uk (talk) 16:44, 19 April 2013 (UTC)

Do great apes dislike each other?

I read that chimpanzees and gorillas are never caged together, and I do not understand why. Do they hate each other for some reason? --66.190.69.246 (talk) 11:55, 18 April 2013 (UTC)

I can't say I'm surprised if it's not a good idea to mix them. A gorilla is a big strong heavy animal, about 230 to 270 kg (quarter ton), and his personality is that of a quiet peaceful chap. A chimp is a noisy active agressive chap, but only 50 to 70 kg - same as a small human. So, it's likely a gorilla would find a chimp very annoying, but one good blow and that's the end of the chimp. Much the same as why german shepherd dogs can't stand little yappy poodles, and why I can't stand noisy yelling/screaming children or yappy poodles. Wickwack 120.145.164.27 (talk) 12:42, 18 April 2013 (UTC)

Then fortunately there are things like Punt the Pooch. DMacks (talk) 14:47, 18 April 2013 (UTC)

This is just of the top of my head -so don't quote me. Chimpanzees and gorillas probably compete for the same food resources. Both are territorial. Therefore, they would by natural enemies. --Aspro (talk) 18:05, 18 April 2013 (UTC)

This google book (chapter 7) [8] supports the notion that chimps and gorillas are aggressive towards eachother in the wild. I can't figure out how to copy/paste, but it but it describes how, in some places, the can compete strongly for space and resources. SemanticMantis (talk) 19:31, 18 April 2013 (UTC)

On a related note, this article postulates that bonobos are less aggressive than chimpanzees because there were no gorillas on the side of the river where the bonobos lived, resulting in less competition for food.--Wikimedes (talk) 20:22, 18 April 2013 (UTC)

"Dislike" is a difficult word to use here. I definitely don't "dislike" tigers or grizzly bears - they are very cool animals and I like them both. But I would feel distinctly nervous if I had to share my apartment with one that had just been captured from the wild! SteveBaker (talk) 12:33, 19 April 2013 (UTC)

Bili ape. --Yoglti (talk) 06:05, 20 April 2013 (UTC)

dredging data

Is there data available on how much sand is dredged from different areas of the ocean floor off the coast of the United States? --149.152.108.90 (talk) 16:13, 18 April 2013 (UTC)

The environmental protection agency might have data regarding it. OsmanRF34 (talk) 18:07, 18 April 2013 (UTC)

OsmanRF34, that URL is incorrect. The Environmental Protection Agency's website is located at http://www.epa.gov and it has an entire website, Dredged Material Management. They also link to the U.S. Army Corps of Engineers Environmental Laboratory, who also maintain a webpage on dredging operations. Nimur (talk) 22:31, 18 April 2013 (UTC)

how much force is required to form m8 thread on aluminium?

how much force is required to form m8 thread on aluminium? — Preceding unsigned comment added by 115.241.59.6 (talk) 18:26, 18 April 2013 (UTC)

That depends on whether you are cutting or rolling a thread, also lubricants, die sharpness and things. Or are you talking about tightening torque? What exactly does your homework question ask? --Aspro (talk) 18:51, 18 April 2013 (UTC)

Infinite well

A particle of mass m is in an infinite well of width L, between x = 0 and x = L. At time t = 0 assume that it is in the following equal superposition of the ground and first excited states: $|\Psi \rangle ={1 \over {\sqrt {2}}}(|E_{1}\rangle +|E_{2}\rangle )$

What is the wavefunction as a function of x and t ($\Psi (x,t)$)? — Preceding unsigned comment added by Bjology (talk • contribs) 19:10, 18 April 2013 (UTC)

If a student starts from point P with x pieces of homework and 0 clues, how soon will they arrive at an F-grade? AlexTiefling (talk) 19:13, 18 April 2013 (UTC)

Is it correct that the wavefunction at t=0 at least is just ${1 \over {\sqrt {L}}}\sin(\pi x/L)+{1 \over {\sqrt {L}}}\sin(2\pi x/L)$? But how do you put in the time dependence. Do you need something like a time-dependent phase adjustment ${1 \over {\sqrt {L}}}\sin(\pi x/L+\phi _{1})+{1 \over {\sqrt {L}}}\sin(2\pi x/L+\phi _{2}t)$ or something else? — Preceding unsigned comment added by Bjology (talk • contribs) 19:18, 18 April 2013 (UTC)

Use the linearity of Schrödinger's equation: solve the problem for the E₁ and E₂ states individually and then add the results. -- BenRG 00:47, 19 April 2013 (UTC)

You're doing fine for t=0. For t>0, you do indeed need a type of time-dependent phase adjustment, but you're not doing that correctly. Red Act (talk) 01:04, 19 April 2013 (UTC)

Orbiting rod

What would happen to the orientation of a rigid, 10-kilometre-long, 1-centimetre-wide rod orbiting high enough above the Earth to avoid significant orbital decay, if it starts out pointing radially away from the Earth? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:14, 18 April 2013 (UTC)

Conserve angular momentum and solve based on initial conditions. Nimur (talk) 19:21, 18 April 2013 (UTC)

Not a HW question. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:28, 18 April 2013 (UTC)

My response never insinuated that your question was homework. My point is, the answer is not merely well-defined, but is trivial to compute, if you specify initial conditions more precisely than you have given. If you write out those initial conditions, you will have your answer. If one of us writes them out for you, chances are good that it will take longer for you to read and cogit the description than it would take for you to independently derive them. If you don't yet have mastery of the required mathematical skills and techniques necessary to understand and describe orbits in terms of momentum and energy, chances are very good that any correct explanation would be lost on you. So, start by reading the articles I linked above; and you can proceed by reading about gravity and orbit; and you can write out the results for yourself. The equations are not difficult. Nimur (talk) 19:34, 18 April 2013 (UTC)

For a not-perfectly-rigid rod, see also Tidal locking. --Dr Dima (talk) 19:27, 18 April 2013 (UTC)

If such a rod starts off radial to earth's centre then it will still tend to point at that point in the cosmos that it started off at, as it orbits earth. Its orbit will be around its centre of mass, i.e., 5 km from each end. Disregarding solar winds, it will just stay pointing at the same point in the astral sky. Any atmospheric drag from (say) atomic oxygen, (which would have more effect on its low end) would eventually have it spinning around its centre of mass. How does WWPU keep coming up with these questions? Has he tried decaffeinated coffee ;-)”--Aspro (talk) 19:57, 18 April 2013 (UTC)

Won't the lower end of the rod tend to orbit faster than the upper end? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 22:44, 18 April 2013 (UTC)

It is the centre of mass of the object (this hypothetical rod) that orbits. The fact that the lower end is closer to to the earths centre (at the outset) does not mean that the lower end will orbit faster... it is physically attached to the the rod's centre of mass; just as the the mass higher up at the other end is physically linked. Until solar winds and other influences 'force' the rod to move it will stay pointing where it was left. Out article Space elevator might make this clearer. It is just physics.(ah. say's me, as though I know it all...Chuckle) --Aspro (talk) 23:22, 18 April 2013 (UTC)

If the rod was small enough that the tidal force on the rod could be ignored, then the problem would be as simple as some people above are making it out to be. The rod's center of mass would simply orbit in an ellipse, and the rod would simply maintain a constant angular momentum around its center of mass. However, the tidal force can't be ignored for a 10 km long rod, so the rod's angular momentum can't be cleanly decoupled from its orbit.

It's unclear to me what the intended initial conditions of the rod are, even if I try to fill in the gaps with what seems like the most likely intended assumptions, such as that the initial orbit is circular. In particular, I don't know whether the intended initial angular momentum of the rod around its center of mass is zero, or is the right amount such that the rod remains vertical.

If the rod's initial angular momentum around it's center of mass is such that it remains vertical, then its vertical orientation would be stable, i.e., the rod would be tidal locked. A slight deviation from vertical in either direction would result in the tidal force on the rod producing a torque on the rod that would act as a restoring force. The resulting change in angular velocity around the rod's center would not violate the conservation of angular momentum, because it's only the system's total angular momentum which is conserved, so a small change in angular momentum of the rod about its center of mass can be compensated for by a small change in the rod's altitude.

As always where there is a restoring force around an equilibrium that's proportional to the deviation from the equilibrium, a sufficiently small displacement from the equilibrium (a vertical orientation, in this case) will result in oscillations around the equilibrium. In most dynamical systems there are also dissipative forces that would then dampen those oscillations, but it's unclear to me as to if and how that would happen in this situation, given the specification that the rod is completely rigid.

Also, for some initial conditions for the rod's angular momentum, I presume some form of orbital resonance would occur. Red Act (talk) 04:00, 19 April 2013 (UTC)

Digestion

Do men have a larger digestive system than women? Asking because women have a uterus which most likely limits the size of their digestive organs. Pass a Method talk 19:49, 18 April 2013 (UTC)

Ok, so the uterus take up room but have you noticed they bulge out (sorry ladies curve out) in places you don't ? These differences is what helps to create the female figure. Try taking a woman to an expensive restaurant, then ask yourself if they have a digestive system to match yours. Perhaps that is the point you realize you're both equals... I'm feeling hungry just pondering it.--Aspro (talk) 20:12, 18 April 2013 (UTC)

To be more specific, women have larger pelvises to accommodate the extra room taken up by the uterus, which it should be noted doesn't exist in the same neighborhood as the stomach. Excepting when a large fetus is occupying it, the uterus itself is not that large, about the size of the bladder, and it does not extend farther up than the rectum does; which is to say it only occupies the part of the body that the extreme end of the digestive system does. It is not in the part of the body that contains the bulk of the digestive system, which excepting the rectum, exists entirely above the pelvis. You can confirm this with pictures at Uterus and really any good picture of the human internal anatomy. Pregnant women, especially those in their third trimester, do have impacts on their digestive system, but then again they are carrying around a fairly large object by that point. --Jayron32 22:04, 18 April 2013 (UTC)

Let's put the uterus aside for the moment (but let's not table it, as I have to eat there). Looking strictly at the relative sizes of men and women overall, it would seem reasonable to assume that men's digestive systems are proportionally larger, on average. That is, a 180 pound man ought to have a 50% larger digestive system than a 120 pound woman, more or less. I'm not sure if this means a man's digestive system is longer, or just wider, however (probably a bit of each). Then, for a more scientific approach, we could also compare the flatus volumes produced by each. (Sounds like a fun topic for a Master's thesis.) StuRat (talk) 02:48, 19 April 2013 (UTC)

Stu, your estimate that the male digestive system is "50% larger" is literally naive. First, Wolfram alpha gives data (and sources) for mean weight of males and females, 166 lbs and 144 lbs, respectively, so your male/female ratio is far off base. Secondly, your assumption of linear scaling ignores the important aspect of allometric scaling. By your logic, a 6' tall human would have a head that is roughly 2 feet tall and weighs ~50 lbs. That's just 3X the size of a 2' child, right? [9]. I'm no expert here, and I don't know the true answer. I think Jayron's answer makes a lot more sense. Your claims here and "evidence" are not convincing. SemanticMantis (talk) 03:19, 19 April 2013 (UTC)

Your comparison of children to adults is a red herring, as obviously size ratios vary there. And I never claimed that men are 50% larger than women. I just said that, if a man was 50% larger than a woman, I'd expect their digestive system to be roughly 50% larger, as well. If you claim that their digestive systems are the same sizes, then you need to explain why. What, does someone 50% larger have lungs twice the size, in order to take up the space which otherwise would be taken by a scaled-up the digestive system ?

Here's a source: Landois, Leonard, & William Stirling: Textbook of Human Physiology: "The human intestine is ten times longer than the length of the body,... It's minimum length is 507, its maximum length 1194 centimeters (17 to 35 feet);...": [10]. I'm also going to assume that the diameter increases proportionately, meaning the volume would, as well. StuRat (talk) 05:08, 19 April 2013 (UTC)

I looked for this but somehow missed it. I'd think there must be a standard reference pathology textbook/manual somewhere that gives the normal range for stomach weight on autopsy. Noting that obese individuals don't actually have stomachs much if at all larger than others, I don't know if a sex difference can be expected; like everything in biology you need an empirical result. Wnt (talk) 04:54, 19 April 2013 (UTC)

The relavant article here would be Human sexual dimorphism, I can't see any mention there of digestion, intestine, stomach. My guess is no, the uterus does not "limit" the size of the female digestige system... Vespine (talk) 04:56, 19 April 2013 (UTC)

BTW, the OP is clearly NOT talking about a man which is 50% larger then a woman. Forget your quibbling, it's completely missing the point, the same arguments could be made about a woman which is 50% larger then a man. Vespine (talk) 05:31, 19 April 2013 (UTC)

This is a horribly difficult question to answer - not because we can't find the answers - but because it's just too vaguely couched.

It seems like we need to tighten the wording of the question. If the question is "Does an average man have a larger digestive system than an average woman?" - then because men are (on average) around 15% larger than women - we'd expect the answer to be "Yes". But if the question is "Does a 30 year old, 5'8", 150lb man have a larger digestive system than a 30 year old, 5'8", 150lb woman?" - then it's a tougher call. Aside from any sexual dimorphism, a 150lb man would be a smaller-than-average man - and a 150lb woman would be larger-than-average. If the woman is overweight and the man isn't - then you get one answer - but if the woman has a naturally chunkier build then the answer might be different. The answer in this case is highly unclear...but from what people have already said here - I strongly suspect that the answer is "No"...or at least "Not by much"...or "typically not".

More complicated is what we mean by "a larger digestive system"? Does our OP mean to ask "Can a woman eat more than a man at one sitting?" - or do we mean the total length of the digestive tract - the total volume - the maximum rate of material flow through it? These are all liable to produce very different answers - and may or may not answer what the OP *really* wants to know.

Worse still - the digestive tract is not a rigid container - it's flexible...I bet that (as with several other organs), that flexibility varies between individuals and decreases with age. It's very possible (without evidence) that an older and a younger man with identical "relaxed" stomach sizes would differ in the amount they can eat because the older man's stomach is less flexible and can't stretch out as much. That's certainly true for bladder capacities.

So, I think the disputes here relate more to the vagueness of the question.

SteveBaker (talk) 12:28, 19 April 2013 (UTC)

April 19

Unknown salt water animal

Does anybody know of a salt water creature that is about the size of a coffee bean, is coloured red and black, has fins and lives in the Arctic. I'm not sure how widespread this is but it has been observed on the south coast of Victoria Island (Canada). I've never seen one so I can't really expand on the description. CambridgeBayWeather (talk) 07:12, 19 April 2013 (UTC)

It turns out I missed part of the description. It isn't red and black but clear like a jellyfish. The colouration is inside and the red is what appears to be blood and there is a black spot. Apparently asking a local man who has spent most of his life hunting and fishing was no help as he had never heard of them either. CambridgeBayWeather (talk) 08:00, 19 April 2013 (UTC)

That's not much to go on. Maybe some sort of marine cladoceran? (See the picture of Evadne spinifera in the article. It's too small [1–1.35 mm] to match your description; but there are larger species, though most of the order's species live in fresh water.) Or some type of copepod, many of which live in arctic climes? Deor (talk) 11:35, 19 April 2013 (UTC)

Thanks. I realise that it is unlikely I'm going to get an answer but I thought it worth a try. I did get a bit more information. It turns out there was a range of sizes with the coffee bean being an average but some were as big as 2-3 cm while others were smaller. The fins resembled those of Batoidea. I'm now wondering if it may have been a juvenile fish of some sort given the rage of sizes. CambridgeBayWeather (talk) 16:17, 19 April 2013 (UTC)

Yes, I was going to suggest a juvenile stage, too. They often lack pigment, except for red blood and a black spot. For example, here's a tadpole that roughly matches what you described, although it's starting to get some body pigment: [11]. (I'm not suggesting that what you describe actually is a tadpole, just using this as a juvenile example.) StuRat (talk) 17:27, 19 April 2013 (UTC)

Saltwater tadpoles are called larvaceans. μηδείς (talk) 17:35, 19 April 2013 (UTC)

Clione limacina? Oda Mari (talk) 19:43, 19 April 2013 (UTC)

And that's what it was. Thanks very much. Strange that I've never seen them before or that they only seem to occur in a small area. CambridgeBayWeather (talk) 02:41, 20 April 2013 (UTC)

Resolved

recognizing a flower

anyone can identify me?

Hi, I took this picture in East Talpiot, Jerusalem. Does anyone know which flower it is? --SuperJew (talk) 09:17, 19 April 2013 (UTC)

Without a doubt this is an aloe, but there are many species of aloes and some time will be needed in sifting through the long list to find the identity. Richard Avery (talk) 09:41, 19 April 2013 (UTC)

could it be Aloe vera? --SuperJew (talk) 11:22, 19 April 2013 (UTC)

Jerusalem Tulipusis?165.212.189.187 (talk) 14:29, 19 April 2013 (UTC)

• Looks like Aloe brevifolia, see this picture. μηδείς (talk) 17:32, 19 April 2013 (UTC)

• Hmm, good match on the flower, not so sure on the leaves. Richard Avery (talk) 19:27, 19 April 2013 (UTC)

growing a hair in a petri dish

if you could remove a human hair complete with hair follicle, could you then grow the hair in a petri dish? Horatio Snickers (talk) 10:56, 19 April 2013 (UTC)

Yes - according to our Hair follicle article, people have been doing this since the 1980's. Evidently, some researchers have gone even one step beyond that - according to THIS, scientists at Berlin Technical University in Germany have grown artificial hair follicles from stem cells. If they can keep those alive in-vitro, then I would expect there to be no problems in doing it with follicles taken from a human scalp. There are a lot of links relating to this subject - I suggest you google for "grow hair in-vitro". There is more information in Hair_follicle#Hair_follicles_in_hair_restoration. SteveBaker (talk) 12:12, 19 April 2013 (UTC)

What is the optimal x-ray balance for sterilization?

How does one figure out the optimal balance between x-ray voltage (kV) and current (mA) to sterilize an object like a shoe ? the radiation has to penetrate leather, it has to have enough high probability to hit the virus, and then to actually kill it. Electron9 (talk) 12:23, 19 April 2013 (UTC)

I don't know how this is really calculated (or experimentally determined) - but one way to do it would be to put a sheet of photographic material beneath the shoe - then adjust the X-ray parameters until "sufficient" radiation to kill whatever it is shows up on the sheet beneath it. Food_irradiation#Dosimetry seems to suggest that this is (essentially) what is done when irradiating food - they use dosimeters to sample the amount of radiation at key points in a load of food.

Incidentally, current and voltage aren't the only parameters - time is another. A short burst of X-rays would be less likely to sterilize something than a long burst. It would also matter whether the shoe could be rotated slowly as it passes through the X-ray beam...shoes sometimes have metal components that would effectively block the X-rays giving organisms a place to hide even from very large doses. In many cases (eg in food sterilization), it may not be necessary to kill 100% of organisms - merely enough to prevent a dangerous level of them from building up before the desired "Sell by" date.

Also, from what I can see, X-rays are used to kill bacteria and mold spores - but not viruses. I could be wrong about that - but viruses don't seem to be mentioned in any studies I looked at.

SteveBaker (talk) 12:52, 19 April 2013 (UTC)

Probably it's not mentioned because it doesn't matter -- viruses can only reproduce in living cells, and their spores generally don't last very long in nonliving matter either. Ionizing radiation should certainly be capable of disrupting the DNA of viruses. Looie496 (talk) 17:11, 19 April 2013 (UTC)

Suppose one powers a rectifier tube like 1B3GT that can sustain 33 kV and 1.1 mA (36.3 W) and most food irradiation seems to be specified to 10 kGy. The aperture is also something to take into account. So how long does it need to be on in order to irradiate sufficiently? Electron9 (talk) 19:12, 19 April 2013 (UTC)

I wouldn't be comfortable giving advice here, even if I knew the answer. Do-it-yourself projects with X-rays are potentially quite dangerous, and a person who would do something as ludicrous as sterilizing shoes with X-rays is not to be trusted to behave sensibly (if you'll excuse me for putting it bluntly). Looie496 (talk) 21:09, 19 April 2013 (UTC)

I had mouse poo on them and leather is sensitive. Protection can be done with bricks and concrete after penetration depth analysis has been done. Electron9 (talk) 23:05, 19 April 2013 (UTC)

Oh good grief. Mouse poo can be shaken off - possibly the affected area of the shoe might be wiped with some antibacterial goop...but setting up a home X-ray system is...um...LUNACY. Yeah...completely nuts! Messing around with a home-made X-ray irradiator is about a million times more likely to harm you than a microscopic quantity of mouse pooh on your shoe! You walk on the sidewalk in your shoes...probably across grass...those surfaces are likely to be at least as bacteria-laden as mouse poop! SteveBaker (talk) 23:58, 19 April 2013 (UTC)

What are we doing when we compose?

Possibly a weird question, but I'm sure a couple of people here know where to look. What I'm looking for is recommended reading that will help me understand this idea.

What are we actually doing, or what is our brain actually doing, when we compose music? I can sort of see, when we compose songs, that we start with the rhythm and tones of the spoken word, and then play with those in a way that we call music. And I can sort of see, when we replicate sounds we've heard such as bird song or mechanical noise and play with those, what we're doing there. But when we get an original bit of music just sort of appear in our heads, and can continue to play with that to express mood (for example) or just to expand it and make it interesting, what are we actually doing? Or when we want to compose a fresh piece of music, not based on words, but based on emotion or an idea, what are we actually doing? 86.161.209.128 (talk) 12:40, 19 April 2013 (UTC)

Our Musical composition article talks about this at length - and links to many more articles that contain relevant material. SteveBaker (talk) 12:55, 19 April 2013 (UTC)

Hey mon! We be jammin'! See jam_session 196.214.78.114 (talk) 13:13, 19 April 2013 (UTC)

I wrote a toy algorithm a few years ago, implemented in Java, to compose music. I pre-programmed several chords and preprogrammed several chord-transitions, so the algorithm had a lot of prior knowledge of music (or at least, of western tonal-scale music and conventional chord transitions). I used a random-number generator to provide pseudorandom beats for the melody for syncopation; and a non-random sequence to play chords for the harmony. (This algorithm was an experiment in an extremist interpretation of structure in music theory). I had hoped that my toy program would be able to jam with me, and by tuning or postprocessing the random number sequences, that I could teach it to play jazz improv; but it always created very pleasant, simple ambient music in the style of a carousel or music-box. You can probably find better incarnations of melody synthesis algorithms with additional tunable parameters; these are computer programs intended to mimic human creativity. While my program didn't create anything very spectacularly symphonic, it gave me a lot of insights into the ways that musical parameterization affects the final "experience." And it gave me a lot of insight into the degree to which the final product was limited or defined by the note and chord structures that I had built into the algorithm.

I'll take a look through my bookshelf, because I'm sure I have some music theory books that explain "structure" in a more structured way... if your interest is in the actual sounds and waveforms, rather than in song composition, Physical and Audio Sgnal Processing talks about the theory and practice of synthesizing realistic-sounding musical instruments.

Here are some course-notes on symbolic analysis of music: Computational Music Analysis. Nimur (talk) 13:30, 19 April 2013 (UTC)

Certainly there are plenty of computer-based composition systems that can produce acceptable and original music. I've also played around with Markov-chain systems - fairly simple C++ programs that can be fed large bodies of music (in MIDI-file format in my case) and which can then generate unending quantities of entirely new music in that style. My experience (like yours) is that they fail to produce anything very memorable or moving - but it's pleasant enough for background music.

But I've never found myself humming any of their compositions to myself.

What I take from this is that the actual mechanics of composing music is something that can be substantially rule-based (although the composer may be unaware of the rules and has somehow subconsciously deduced them - much as a two year old child learns how to form grammatically correct sentences just by listening to their parents talking). However, producing memorable, moving, emotional music seems to require a human spark that's not easy to capture or teach. That is clearly something that cannot be taught - or else there wouldn't be just a few handfuls of composers who are thought to be so much better than the rest of us.

The analogy with spoken language is probably no accident. Our brains are wired to do this amazing trick of learning to understand and produce spoken language with absolutely no formal training and no input other than odd snippets of language we can pick up as a child.

It seems highly likely that this same mechanism is what allows us to understand and compose music just by listening to music we hear.

However, not every person who learns to converse fluidly in their native language ever becomes a poet or a novelist - or an empassioned public speaker...which probably explains while everyone can probably be trained to compose music, it likely takes someone with more specific skills to produce music that's memorable and moving.

SteveBaker (talk) 14:02, 19 April 2013 (UTC)

Where I can find these programs that can compose music? 190.60.93.218 (talk) 16:48, 19 April 2013 (UTC)

See Algorithmic composition. Red Act (talk) 17:26, 19 April 2013 (UTC)

Thanks for all this, but I don't think I can have been clear enough (because I didn't fully understand what I was asking for), but I think I'm looking for more of a neuroscience answer? Although I think the algorithm answers are probably also useful, if I can understand them properly. 86.161.209.128 (talk) 19:49, 19 April 2013 (UTC)

We have quite a lengthy article on the cognitive neuroscience of music, and several other related articles. I'm not sure how much they'll tell you, though -- we really don't understand brain activity on the level of composition algorithms. The book Musicophilia, by Oliver Sacks, might also interest you, although it is mainly a collection of anecdotes. Looie496 (talk) 21:01, 19 April 2013 (UTC)

What is (or was) the neutretto?

In various outdated popular books and articles, one finds references to a sub-atomic article called the neutretto. According to Wikipedia, the neutretto is a historical name for the muon neutrino. According to this book, the neutretto is an older name for the neutral pion. Yet a third neutretto, apparently, is that mentioned in several newspaper articles from 1948, as having being ruled out after being hypothesized in 1947 to explain a mass defect in heavy meson (i. e. pion) decays.

What was the original "neutretto hypothesis"? Was it conclusively ruled out, or was the 1948 "exclusion" premature, and the neutretto lives on as either the muon-neutrino or the neutral pion?

הסרפד (call me Hasirpad) (formerly R——bo) 18:49, 19 April 2013 (UTC)

The neutretto, as far as I can tell, was a hypothetical particle with neutral charge and substantial mass, proposed in 1938 in this paper in order to explain the mutual attraction between protons (see p. 170). It is now believed that the strong force is responsible for that attraction, and that no such particle as the neutretto exists. The term was frequently used in the following years, though, and perhaps not always with exactly the same meaning. It always meant a neutral particle with nonzero rest mass, but other properties may have varied. Looie496 (talk) 20:56, 19 April 2013 (UTC)

The "heavy electrons" and "neutrettos" in that paper are bosons that are supposed to mediate the nuclear force, which makes them clear precursors to the charged and neutral pions. Here's a paper (surprisingly recent) that unambiguously uses "neutretto" to refer to muon neutrinos -- BenRG 01:24, 20 April 2013 (UTC)

Balloon Framing

What is the citation for the line drawing image of balloon framing at http://en.wikipedia.org/wiki/Balloon_framing#Balloon_framing? Is it in the public domain? Thanks. — Preceding unsigned comment added by Abqwriter (talk • contribs) 20:23, 19 April 2013 (UTC)

Just click on the drawing and you'll find out -- you're taken to the page for that file, which contains information about its copyright status. Looie496 (talk) 21:03, 19 April 2013 (UTC)

Dam seepage

Does more water discharge/seepage under a dam effect its stability? — Preceding unsigned comment added by 99.146.124.35 (talk) 23:06, 19 April 2013 (UTC)

Yes, seepage tends to cause erosion and thus undermine a dam. This can happen quite quickly with an unreinforced earthen dam (note that our article is about reinforced earthen dams), and much more slowly in a concrete dam. StuRat (talk) 23:19, 19 April 2013 (UTC)

The St. Francis Dam disaster was caused by the dam being undermined by seepage. It was a concrete dam. --Jayron32 00:36, 20 April 2013 (UTC)

Also the Malpasset Dam. 24.23.196.85 (talk) 03:07, 20 April 2013 (UTC)