Wikipedia:Reference desk/Archives/Science/2013 April 17

= 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...  Bramble  claw  x   01:55, 17 April 2013 (UTC)
 * 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. -- Jayron  32  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.  -- Jayron  32  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:-
 * 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.
 * 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.
 * 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 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 &#124; 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:-
 * Make them archivable - image stable for decades, not years
 * Either make them cheap in large formats or make them built to last
 * 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: .  This rise significantly outpaces inflation, which you can check for yourself using this CPI data from the Bureau of Labor Statistics: .  --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:-
 * 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.
 * 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 . 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?
I would be very grateful. Surtsicna (talk) 19:54, 17 April 2013 (UTC)
 * 1) 16 and 17
 * 2) 18
 * 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)