Wikipedia:Reference desk/Archives/Science/2006 June 10

Ubuntu #2
COPIED

Ok, so what should I do? I previously downloaded the.. uhm.. thing that you can run the system off a cd. I burned it on a cd, but I couldn't figure out how to get it to work. Should I do that? Should I do it the other way? —  The   Mac Davis ] ⌇☢ &#xE0D;&#x19B;. 05:22, 6 June 2006 (UTC)
 * Presumably, you're talking about a Live CD, which can boot the operating system without modifying the hard drive.
 * To get it to work, you need to restart the computer with the CD in the drive. Depending on how your computer is configured, (1) it might say that it has detected a bootable CD and you need to press a key to boot it, or (2) it might go straight to your already-installed operating system (which means you probably need to change the bios - done by pressing delete/F8/etc when the computer starts - to try to boot the CD drive before it tries to boot the hard drive). Raul654 05:29, 6 June 2006 (UTC)
 * Yikes! Change the BIOS! That soudns dangerous. I need to do that. What do I do?— [[Image:Flag_of_the_United_States.svg|17px]]  The   Mac Davis ] ⌇☢ &#xE0D;&#x19B;. 01:36, 10 June 2006 (UTC)

It tells you to press a particular key to access your BIOS settings. Usually, its one of - Del, F1, F2, F4, F8, F10, F11, or F12. It depends on your motherboard. Then look around (probably in the "boot-up settings" if there is one) without changing any settings until you find a boot sequence option. Change it from - "Floppy - HDD - CD ROM" to "CD ROM - Floppy - HDD", then save your settings (often F10) and restart your computer with the CD in the drive... It should now boot from CD. If that doesn't work, tell us the model of the motherboard, and it'll be easy. --Eh-Steve 01:57, 10 June 2006 (UTC)

The Ubuntu Desktop CD includes some Windows programs as well. So to tell if you burned the CD correctly, stick it in a Windows system, and browse the CD-ROM device. If you see the Windows programs (and some documentation) in there, then you've burned the CD correctly, and should be able to boot into Ubuntu if you can convince the BIOS. If you can only see 1 file on the CD, then you burned it incorrectly, and you need to record it as an ISO image, not by copying the ISO file to the CD. This will depend on your CD burning software, but look for something like "record disc from image". --Booch 21:43, 12 June 2006 (UTC)

Compounds
What does H20+CHO+Na+Cl+K make? I know there's saltwater in it, but with everything else what does it make? schyler 01:39, 10 June 2006 (UTC)


 * With the water as a solvent, the ions, Na+, Cl-, and K+ will pretty much just float around, and would form salts if the H20 was removed (NaCl and KCl). I'm not sure what the CHO is doing there, needs clearer notation. Is that an aldehyde carbonyl (a positively charged carbon double bonded to oxygen with a hydrogen connected, which would form Cl-CH=O, an acyl chloride) or an alcohol (COH, where the C would be doubly positively charged, or bonded to 2 other atoms not written)? Essentially, since it seems you are indicating a bunch of ions are floating around in your "seawater", which is istelf an ionic solvent, not much is gonna happen; your ions are mostly just gonna float around as such.Tuckerekcut 02:53, 10 June 2006 (UTC)

Well, I have absolutely no idea what you responded to me with (well, kind of, but not really). I made all C's in chemistry. But it was an extra credit question on my final last week and I had no idea. Thank you though. schyler 02:59, 10 June 2006 (UTC)


 * It looks kinda like one of those cutsey rearrange-the-letters things... would "Water Nacho Clock" mean anything to you? --AySz88^ - ^ 05:37, 10 June 2006 (UTC)

I don't think so :). I think it's actually some kind of food though, because that was the last section we did and we had to do a project that had like 10 compounds we recognized and break it down and tell what made it that and whatnot. I think I got a 47/100 on that one. Thanks. schyler 13:12, 10 June 2006 (UTC)


 * H2O is water, and NaCl is table salt. Perhaps by "CHO" you meant C12H22O11, which is sugar (sucrose). I'm not sure what food you should get from K, which is potassium, a very reactive silvery white metal. You wouldn't want to eat pure potassium. There's KCl, potassium chloride, which can be used as a substitute for table salt by people who want to reduce their sodium intake. Bananas have lots of potassium, but of course there are many, many other things in bananas besides K. Are you sure you gave us the question correctly? —Bkell (talk) 13:31, 10 June 2006 (UTC)

Yah. Pretty sure. My (chemistry-savy) friend said it sounds like what would be in Gatorade. I don't know how she came up with that though. schyler 00:48, 11 June 2006 (UTC)
 * Sounds right (except it would be mighty unpleasant without flavoring). Gatorade is essentially sugar-water with electrolytes (KCl, NaCl) added, meant to replace fluids and electrolytes lost by sweating. - Nunh-huh 01:00, 11 June 2006 (UTC)

Incidentally, the reason sugars (and starch and other sugar-based compounds) are called carbohydrates is that their (empirical) chemical formulas can be written as (CH2O)n, where n is some whole number. That of course tells nothing about how the atoms are bonded together, but back in the days before such details were known, it made sense to refer to them as "hydrates of carbon".

In fact, it turns out that the simple formula is in some ways quite close to the truth: sugars are mainly composed of chained CH2O groups, though not entirely — and it's the "not entirely" that makes sugars behave chemically the way they do. I do hope, by the way, that your Gatorade does not contain plain CH2O — that's formaldehyde. —Ilmari Karonen (talk) 11:52, 11 June 2006 (UTC)

First Springtime Flowers
I have noticed that the the color of the very first flowering bushes in springtime (after winter in colder regions) are almost exclusively yellow. What is the reason for that? --03:04, 10 June 2006 (UTC)
 * What region of the world do you live in? --Ginkgo100 talk · contribs 03:55, 10 June 2006 (UTC)
 * Yellow flowers usually attract bees, as opposed to red, which usually attract birds. I'm not sure exactly how that fits in with springtime. Do bees come out before birds? —Pengo 15:10, 11 June 2006 (UTC)

The Ultimate Speed Limit
The Special Theory of Relativity says no matter or material objects can travel faster that light.But what about things that don't involve the movement of matter, such as gravitational influences?How can it apply and how does it apply to immaterial things?


 * Perhaps even more important than matter, special relativity implies that no information can travel faster than light, because that would be equivalent to sending the information back in time. Things can certainly appear to move faster than light though. For example, take a big laser and shine it on the moon. Now turn the laser quickly so it sweeps across the moon. The spot will travel across the surface of the moon faster than the speed of light, but that's okay because the spot that moves isn't made of matter (it's caused by different photons reflecting off the moon at different times), and because it doesn't carry information from one side of the moon to the other. Of course, because it's going faster than the speed of light, a different observer could see the spot moving in the opposite direction, or a whole swath of the moon illuminated at once. —Keenan Pepper 05:59, 10 June 2006 (UTC)


 * But what if you formed the laser beam spot into a word and repeated the same experiment ? Then information would indeed move faster than the speed of light, wouldn't it ?  Quantum tunneling also seems to violate that restriction, so something about the restriction must be wrong. StuRat 15:24, 10 June 2006 (UTC)


 * It has been theorized, since you mention gravity, that its influence spreads at the speed of light. Experiments seem to be confirming this. Black Carrot 17:01, 10 June 2006 (UTC)


 * Suppose you formed the laser beam into a word. Two people on opposite sides of the moon couldn't use your laser to transmit information between them faster than the speed of light, because for one thing they can't control what the laser says. So when you wave the laser across the moon, you're not transmitting information from one side of the moon to the other; you're transmitting information from Earth to different points on the moon. That information is encoded as a laser beam, so of course it travels at the speed of light, from the Earth to the moon. —Bkell (talk) 19:37, 10 June 2006 (UTC)


 * Skewed logic. You could construct the laser so that it drew out the word instantly across the entire surface of the moon, but that doesn't mean that the information is travelling instantly. The information doesn't travel from the point at where you start drawing the word to the point where you finish, but from the laser source to the target area. freshofftheufo  ΓΛĿЌ  06:01, 12 June 2006 (UTC)

But I'm asking about how can it apply to anything that exists, not just matter.


 * See Is Faster Than Light Travel or Communication Possible? and other questions in the Usenet Physics FAQ. &#x2013; b_jonas 10:29, 11 June 2006 (UTC)

Gravitational influence involves a transfer of energy, and therefore cannot travel faster than light. Some effects can exhibit superluminal velocities though, like the point of contact of a pair of scissors, or a shadow moving across the face of a moon, or the correlation of measurement of entangled particles. These effects convey no energy or information at superluminal speeds. StuRat is mistaken when he claims that quantum tunneling allows superluminal movement. -lethe talk [ +] 05:12, 12 June 2006 (UTC)


 * I don't believe I am mistaken, see this source: . StuRat 04:45, 14 June 2006 (UTC)

Antimatter
This question had me confused for more than a year. I want to know what is antimatter how does it work or happen.
 * Have you read antimatter? Grutness...wha?  03:39, 10 June 2006 (UTC)

Gravity
According to Albert Einstein, gravity curves space. Is this true? If ti is how does this happen.
 * Try General relativity which Curved Space redirects to. Albert Einstein doesn't say gravity curves space, he says that the phenomenon that's known as gravity is caused by inertial motion in a warped spacetime, like a marble rolling around a trampoline with a bowling ball placed in the centre. --ColourBurst 05:01, 10 June 2006 (UTC)


 * Although, it's worth pointing out that using a gravity-based metaphor to describe something that replaces traditional gravity is a bit circular. Black Carrot 16:58, 10 June 2006 (UTC)


 * It is, but it still allows for a nice demonstration. The trampoline thing was shown in Csodák Palotája, an interactive museum for kids in Budapest.  &#x2013; b_jonas 10:14, 11 June 2006 (UTC)

Allergy
I'm allergic to shrimp, which I understand is a common allergen. The only reaction I have ever had is contact dermatitis, whether in my mouth and throat (if I eat it) or on my skin (if I touch it). After reading allergy and other relevant articles, I'm not completely clear what this means, technically. The reaction is fast, within minutes or less, so I think it's Type I (true allergy), but as I mentioned, the only symptom is contact dermatitis (local swelling, hives, itching) -- no runny nose, no anaphylaxis, etc. Rest assured I stopped eating shrimp years ago -- but if I were to eat some, is it reasonable to assume there's a likelihood of anaphylaxis? Or is it some other kind of hypersensitivity? Is there any treatment I could ask my doctor about, or can I never eat shrimp again? --Ginkgo100 talk · contribs 04:15, 10 June 2006 (UTC)
 * Anaphylaxis is a possibility in the future. I too am allergic to crustaceans and prawns (prawn is what shrimp is called in Australia). The reaction I had was an irritated hand, a swollen lip and a swollen eye. After that, I saw an allergist and got an allergy test, which confirmed I was allergic. The only real "treatment"s are things like adrenalin to open up the throat in the case of anaphylaxis, or a steroid like Prednisone to bring down swollen areas quicker. However, these aren't really considered treatment, because they do not "cure" the allergy. The problem is that allergies are a reaction from the Immune system, so treatment of allergies would have to involve suppressing the immune system, but if this was done all the time, you would catch all sorts of diseases pretty quickly due to an inability to fight against them. The quick answer to your question is that no, you should never eat shrimp again. Personally, I don't care about that, since I never really liked shrimp that much, but I still have to watch out for products that contain prawn in them. If you had a nut allergy, I might say different, because it is not uncommon to "grow out" of nut allergies (at the expense of nut allergies in general being more severe). However, crustacean allergies are usually lifelong. Yeah, it might suck, but really, don't ever eat shrimp again. If you are still curious, it would be a good idea to go to your doctor and take his/her advice rather than people on Wikipedia who know no specific details about your condition. -- Daverocks (talk) 08:50, 10 June 2006 (UTC)
 * There are, apparently, six clinics in the UK (e.g. this one) that can "desensitise" you to these conditions. They seem to use conventional medicine. Here is a UK Parliament report describing how difficult it is to find this treatment in the UK.  I have also read that the treatment is much more easily available in France.  Sorry, but I don't know how it works. --Heron 14:45, 10 June 2006 (UTC)
 * See Hyposensitization. --vibo56talk 20:21, 11 June 2006 (UTC)

Allergies come about when our bodies, or more precisely our immunoglobulin, finds a chemical marker that it thinks represents a threat, and mobilizes the immune system's offensive units, most importantly the histamine releasing mast cells. Your Ig cells see a protein specific to shellfish as a major alien threat, but if you were somehow able to sensitize (i use this word ironically, since it is usually used to describe the development of an allergy) your Ig cells to accept that this protein is not a threat, then the allergy would go away. There are clinics that claim to be able to accellerate this resensitization process (it happens naturally over several, usually 7-10, years) and cause patients to lose their allergies. I should note, however, that this might be very dangerous if done outside of strict medical supervision, so don't try it on your own. However, under normal conditions, you can expect your allergic reaction to shellfish to become more severe with each exposure to the causative agent. It is reasonable to assume that a future exposure to shellfish will result in an anaphylactic reaction. By the way, if you are from the US, stay away from both freshwater prawn and saltwater shrimp.Tuckerekcut 16:59, 10 June 2006 (UTC)

Science -Mostly Already Discovered?
Now that we've reached the 21st century, and science and technology has become very advanced, is it true that most of the things and phenomena in science and nature, and all the facts about them, have already been discovered?I mean, is it true that we're reaching an age when there's not much more to discover in science, and not much more to invent?

If there is much more to discover in science, then is there as much to discover in science as to lead to the invention of things such as the time machine,gravity-making machine,teleporter, and warp drive?


 * At the beginning of the 20th century, physicists were pretty content - with Maxwell's equations, and Newton's laws, they thought they had pretty much all of the physical universe figured out. One even went so far as to predict that 'physics as we know it will be over in 6 months'. Then came the ultraviolet catastrophe, which Einstein's and Plank 's work solved, but in the process, they totally demonlished Newton. (The laws based on Einstien's work reduce to Newton's laws at low speeds and low gravity; this is called the corrospondence principle). The laws we have now - relavity (for very large things) and quantum mechanics (for very small things) to a great job of explaining their stuff, but unfortuately the two are provably incompatible - one of them must be wrong. Raul654 08:02, 10 June 2006 (UTC)


 * Raul's claim that at the beginning of the 20th century most physicists thought physics was almost "done" is a commonly repeated and incorrect myth. -lethe talk [ +] 05:08, 12 June 2006 (UTC)


 * It depends what you mean by "discover". It is true that, by some parameters, the rate of technological "invention" has slowed down from the middle to end of the last century (though it doesn't seem that way when i consider that when i went to University just 11 years ago we didn't even have email!). But in terms of scientific understanding, i would argue from a personal perspective, that we are ever advancing in how much we understand and the further we go, they more there is yet to realise. Ask any scientist worth their salt, they will tell you every answer poses 10 more questions. Empirically speaking, that would suggest knowledge space is exponentially large (or at least that we have yet to reach the zenith of knowledge aquisition).


 * In the field of molecular biology, for example, there were some who believed the discovery of the structure of DNA in the 1950s was the key step in understanding "life". It was certainly important as a milestone, but it revealed further levels of complexity that we set out to understand. The sequencing the entire human genome about 50 years later led some to believe this would be the key step in understanding "life". Instead what happened was the the scientists realised a further level of complexity (alternative splicing) must be understood before we can claim to fully understand the basis of "life". I expect, at some point in the next 10 years or so, we will have a handle on the entire transcriptosome only to find yet another mechanism through which complexity is generated, and so on... So will we ever reach a level where there is nothing left to learn? Perhaps, but i doubt it. If only on a philosophical level, will anyone ever really be able to answer the question: Who am i and why am i here?. Though it seems to me that we will never know the answer to your question, as the rate of self destruction may well be advancing faster that of human knowledge, so i expect our extinction will beat us to any definative answer.  Rockpock e  t  08:37, 10 June 2006 (UTC)


 * To wonder how close we are to discovering all there is to know is to assume a finite amount of knowledge, but there's no evidence to support that assumption. Humans have been discovering new things since Neanderthal times. They have a funny way of asking tricky questions that nobody else ever thought of, and these lead to further enquiries, that lead on to further discoveries.  If anything, the pattern suggests we will just go on forever, questioning and discovering.  History is replete with examples of people who considered that the level of knowledge at their time was pretty much all there was to know, and anything else was just unimportant trivia.  How wrong they were.  One of my favourite anti-quotes is by Max Beerbohm: "Anything that is worth doing has been done frequently. Things hitherto undone should be given, I suspect, a wide berth" - I think this can be applied to discovery of things hitherto unsuspected.   JackofOz 09:04, 10 June 2006 (UTC)


 * I don't think we're done with science until I can buy a pocket-sized wormhole-generator for less than $10. -- SCZenz 10:42, 10 June 2006 (UTC)


 * Ah of course the iHole, Apple's ultra-stylish solution to 21st Century consumer apathy. 10,000 parallel universes in your pocket (battery life 4 hours). --The Gold Miner 12:36, 10 June 2006 (UTC)


 * But who has the time to figure out which 10,000 alternate universes to load into their iHole ? :-) StuRat 15:16, 10 June 2006 (UTC)


 * I don't know about you, but I just subscribe to several popular Holecasts. Of course, you can always download collections of alternate universes from The Pirate Bay, since they've relocated their servers to the Tannhauser Gate, and the MPAA/RIAA attack fleet won't be there for another three parsecs. --ByeByeBaby 17:16, 10 June 2006 (UTC)

I agree that knowledge is infinite (although perhaps finite in life sciences, since I doubt if anything biological happens below the atomic level). However, we do indeed appear to have reached a plateau, where everything "new" is just a slight tweak on old technologies (cell phones from land lines, Internet from DARPA-net, laptop computers from mainframes, etc.). I suspect a new scientific discovery, equivalent to Relativity or Quantum Mechanics, is needed to spur on a round of truly new inventions. StuRat 15:16, 10 June 2006 (UTC)


 * Think you so? I would have thought there were more than enough natural laws to keep us inventing for quite some time. And no, we probably aren't anywhere near understanding everything there is to understand. And there's no way to predict, at this point, whether things like time travel will ever be possible or not. Black Carrot 16:56, 10 June 2006 (UTC)


 * Amazing that you consider cell phones a "slight tweak" from landlines and laptops a "slight tweak" from mainframes. I think it goes to show how entirely subjective something like technological change is. I consider both of those examples to be evidence of how radically technology can change in a brief period of time. Sure, the basic concepts are related, but the implementation required major jumps in a wide variety of technological and scientific areas. I imagine you also think that rDNA technology is just a "slight tweak" on classical breeding. ;-) --Fastfission 19:39, 10 June 2006 (UTC)


 * Compare the changes taking place around 1900 with those around 2000... Don't you consider the change from horses and buggies to automobiles a greater change than from land lines to cell phones, for example ?  Or from hot air balloons to airplanes versus from mainframes to laptops ?  And don't you consider the change from photographs to movies a greater change than from analog TV to digital TV ?  How about the change from gas lights to electric lights versus from incandescent lights to high intensity LEDs ? StuRat 05:04, 14 June 2006 (UTC)


 * I'd say about 90% of modern day science is accepted theory and not proven, therefore, is a way, we haven't "discovered" much yet, we have only guessed what it is. So really, we have just about everything to discover. Philc TECI 16:59, 10 June 2006 (UTC)


 * Be careful that you don't fall into the trap of thinking "scientific theory" means "guess that hasn't been proven". The word theory in science does not mean a guess or a hypothesis, as the word is often used in casual conversation. —Bkell (talk) 19:34, 10 June 2006 (UTC)


 * Oh, I know it's much more than a guess, and there is lots of evidence for these theories, but for example tectonic plates, all the evidence points to it being true, and their is no feasible alternative explanation, but it still can't be categorically proven, so it may be wrong. Though, admittadly it is unlikely. Philc TECI 19:52, 10 June 2006 (UTC)


 * Out of curiosity, what's the 10% of science that you think has been "proven", and how is this different from the other 90%, other than just having more evidence? —Bkell (talk) 20:25, 10 June 2006 (UTC)


 * The proven things are generally the things that recquire a short timescale (i.e. shorter than a human lifetime) to enact. Like a lot of biology and some chemistry, but almost no physics (if any). For example, alot the organ systems are well understood, and chemical reactions, the conservation of mass in chemical reactions, and things like that. Philc TECI 22:46, 11 June 2006 (UTC)
 * Now that we have GPS, plate tectonics can be "proven". See the results from this experiment, for example.  --Bowlhover 03:11, 12 June 2006 (UTC)
 * I'm sure a sceptic could come up with some reason why this isn't undeniable proof. Philc TECI 19:46, 12 June 2006 (UTC)
 * Two things sit at the bottom of your question: 1. is it possible to have a perfect description of reality?, and 2. is it possible to know how close our current descriptions are to that? The first case is not just a question of "is reality out there?" but a more complicated and nuanced question about what it means to describe reality (a big, long-standing philosophical question). The second case is not just a case of knowing "what is true?" but being able to take into account our current state of knowledge in comparison with the potentiality of perfect knowledge. Since we don't know the latter, though, it's hard to judge the former. I'm personally of the persuasion that judging scientific knowledge as a state of completeness (i.e., "we are 50% to perfect knowledge") is a misleading and ultimately useless metaphor. --Fastfission 19:39, 10 June 2006 (UTC)


 * You took the words out of my keyboard. Black Carrot 20:29, 10 June 2006 (UTC)


 * "Sometimes I really regret that I did not live in those times when there was still so much that was new; to be sure enough much is yet unknown, but I do not think that it will be possible to discover anything easily nowadays that would lead us to revise our entire outlook as radically as was possible in the days when telescopes and microscopes were still new." - Heinrich Hertz as a physics student, 1875.   A bit more here: |The End of Science?


 * Also, there are several places in science history where the Next Big Thing had already been discovered, but it was being disbelieved and ridiculed by the science community at the time. This isn't common, but it's also not that rare.  The seeds of the Next Big Thing may already be sitting around ignored.  But only someone from fifty years in the future could tell us which "crazy worthless" new ideas are important, and which ones are genuinely worthless.  --Wjbeaty 05:14, 11 June 2006 (UTC)


 * Obviously no. As a practical counterexample, we can't prove AIDS yet.  &#x2013; b_jonas 10:11, 11 June 2006 (UTC)
 * There are many unsolved problems in physics. Conscious 15:44, 11 June 2006 (UTC)
 * Huh? Of course we have.  Just because there are some lunatics out there with conspiracy theories to the contrary doesn't mean that mainstream science hasn't figured it out.  Ditto for evolution, only the dissenters aren't conspiracy theorists, they're religious loons ... still with no more understanding of science, though.  -- Cyde↔Weys  15:50, 11 June 2006 (UTC)

From a practical point of view (not a philoscophical one), science is progressing more rapidly now on more fronts, than ever before. I don't know how many scientific journals are published a month, but it is a lot (>10,000). Certain specific areas seem to get exhausted and people lose interest in them, on balance, more new areas of inquiry open up than shut down.

Also, I think sometimes in this conversation 'technology' and 'science' have been used as if they are interchangable. I don't believe they are. I think that the development of a technology can reach a practicle endpoint. The nail is an important piece of technology, but now, new developments in nails are pretty far between. I suppose 20 years from now, cell phones will be much the same. ike9898 17:13, 12 June 2006 (UTC)


 * You say that 20 years from now cell phones will be much the same as they are now? I'll take you up on that bet. —Bkell (talk) 21:03, 12 June 2006 (UTC)
 * Oh, that's not actually what I meant. I meant to say that in 20 years cells phones will reach a point in their development where they aren't changing much anymore. I realize they are rapidly changing right now. ike9898 18:08, 13 June 2006 (UTC)

Neural Networks and Parallel-Processing Computers
In computer science, what's the difference between a neural network and a parallel-processing computer?


 * Have you already checked artificial neural network and parallel computing? –Mysid(t) 08:18, 10 June 2006 (UTC)


 * A parallel computer is a computer capable of working on two or more problems (or parts of the same problem) at the same time. A neural network is a mathematical construct - a way of associating data (much like a graph, or a venn diagram, or an excel spread sheet). They are two very different things. Raul654 09:44, 10 June 2006 (UTC)


 * However, there is a link in that a parallel processing computer might be the best way to simulate a neural network. StuRat 15:03, 10 June 2006 (UTC)


 * By what definition would that be "best"? Parallel computation and serial computation are both Turing-equivalent, so the only real difference is speed. It should be mentioned that a neural network embodied in, e.g., a silicon substrate is basically a parallel computer. It has been shown that neural networks are also Turing-equivalent (well, for specific sorts of neural networks). 128.197.81.181 23:26, 10 June 2006 (UTC)


 * So, given that all such computers are operationally equivalent, how would the fastest one not be the "best"? What, specifically, are you nitpicking at? Black Carrot 16:53, 11 June 2006 (UTC)


 * "Best" is a relative term. It really depends on the work you're having the computer do.


 * For example, a neural network is very fast at pattern recognition, but slow at mathematics. A traditional digital logic computer is very fast at mathematics, but slow at pattern recognition.  A massively-parallel supercomputer is fast at numerical simulation, but slow at logic-based computing.  Each of these computers can do all of the same tasks, but at different speeds. --Serie 21:30, 12 June 2006 (UTC)

The Reaction Between Silver Chloride and Concentrated Hydrochloric Acid
Background: My chemisty teacher and I saw a question on a practice test in which AgCl was added to HCl(conc), and a reaction was supposed to occur. We debated on what could possibly happen, or if the test made a typo. I looked on the page Silver Chloride and found out that a complex was supposed to form, AgCl2-. When my teacher and I performed the experiment, we were not too surprised to see no reaction had occurred. When we wafted the test tube we found that Chlorine gas was being released. After we added NaCl, the solution turned a pale green, the color of chlorine gas. The experiment was cut short, but we still noticed that the AgCl had disolved and the NaCl was left behind.

My Question: What accounts for the reactions we witnessed? Any help would be appreciated, it has us both somewhat confused. M@$+ @  <font color="#000000">Ju  ~ <font color="#000000">♠  13:40, 10 June 2006 (UTC)
 * Sorry to but in here but Silver cloride (AgCl) will decompose (quite rapidly) in the presence of light - giving elemental chlorine and very small particles of silver. Also if you made the AgCl from AgNO3 and NaCl (by precipitation) if the precipitate was not properly washed then contamination with nitrates would be a possibilty - on acidification a certain amount of nitric acid would be formed which would easily oxidise any chloride ions to chlorine. So if there was some nitrate left from the precipitation left then that would explain a lot. Also oxidation with nitric acid often results in the formation of NO2 which is yellowish and could easily be mistaken for chlorine (similar smell). Also chlorine gas in aqueous solution can give a (pale) greenisj colour.HappyVR 23:32, 16 June 2006 (UTC)
 * Was silver metal formed? If so, the $$ Cl^- $$ was apparently oxidised by $$ Ag^+ $$, which makes even less sense because the E std. value for this redox reaction is (0.8 - 1.36 = -0.56V), so the reaction is not feasible, and should never happen... but thats seems like the most likely way that $$ Cl_2 $$ is formed. Unless it was just HCl fumes...--Eh-Steve 15:07, 10 June 2006 (UTC)


 * Tap water already has some chlorine gas which can be released if you just wait. &#x2013; b_jonas 10:40, 11 June 2006 (UTC)


 * Well Silver metal was not formed in any significant amount (if at all). My teacher said that it smelled like Chlorine gas and not just the fumes of Hydrochloric Acid.  As for waiting around for the gas to be released, that didn't happen because we were involved in an experiment that lasted 2 minutes at most.  When the whole mixture turned pale green, was that dissolved Chlorine gas? <font color="#000000">M@$+  @  <font color="#000000">Ju  ~ <font color="#000000">♠  21:17, 12 June 2006 (UTC)


 * Probably not — a bit of googling confirms my recollection that Cl2(aq) is pretty much colorless. I'll try to find my inorganic chemistry lab notes and see if I can figure out what was going on.  However, I can't really think of any way to get a green tint from a solution of Ag+, Na+ and Cl- in pure water, so I suspect some impurities were involved.  —Ilmari Karonen (talk) 11:40, 13 June 2006 (UTC)


 * Strange that there would be impurities in a stock solution of HCl and distilled water, but my teacher had to make the AgCl from the reaction of AgNO3 and NaCl, or some similar mixture, so it is possible. <font color="#000000">M@$+  @  <font color="#000000">Ju  ~ <font color="#000000">♠  20:57, 13 June 2006 (UTC)

Revision IDs
I realise that this is a question about Wikipedia, but it didn't seem right for the helpdesk, as it is more about trivia. Are the revision ids (like this one: ) just given out at random? The lowest one I can find is 5, which is an edit to User:Magnus Manske, but it doesn't appear to be the oldest. What do the numbers mean? <font style="color:#BBBB00">smurrayinch <font style="color:green">e <font style="color:#BBBB00">ster(User), (Talk) 16:02, 10 June 2006 (UTC)


 * If this question doesn't get answered here, you might try the Village pump (technical). —Bkell (talk) 19:45, 10 June 2006 (UTC)


 * I think they're given out in order. Try going to Special:Recentchanges and opening the first few diffs. You'll find that the revision IDs are consecutive. --Cadaeib <font color="#707070">(talk) 22:24, 10 June 2006 (UTC)
 * A also think so. At ru:, revision 1 is a test page. Conscious 15:41, 11 June 2006 (UTC)

What (human) bodily fluids can disslove gum?
There was this time that i chew gum for a short while until it mysterously dissloved in my mouth. Can anyone find an explaination for that?


 * High Acidic content from bacteria in your mouth respiring using sugars left from eating. Do you brush your teeth more now that you can't do it? <font color="Green">Philc TECI 16:54, 10 June 2006 (UTC)


 * Black Carrot 20:23, 10 June 2006 (UTC)


 * What also sometimes happens after a few years of marriage is that the partners experience diss-love for each other, so they decide to dissolve the marriage. :--) JackofOz 22:37, 10 June 2006 (UTC)


 * Was it altoids gum? If so, anybody can make that kind dissolve in their mouth. — [[Image:Flag_of_the_United_States.svg|17px]] <tt> The </tt>  <font color=#006600>Mac Davis ] ⌇☢ &#xE0D;&#x19B;. 23:23, 10 June 2006 (UTC)

Light going though matter
Say that you have a concrete wall. Gamma rays, X-rays, radio waves can all pass though it. But why does it block visible light?Yanwen 02:52, 11 June 2006 (UTC)
 * When electromagnetic radiation (in the form of photons) passes through a material, its intensity decreases exponentially (attenuation). The decrease in intensity depends on the energy of the photons, the thickness of the material and the absorption coefficient of the material. A dense material like concrete will have a high absorption coefficient. The energy of the photons varies with frequency according to Planck's law. Gamma rays and x-rays have a high frequency (and therefore higher energy) in comparison with visible light, and are hence more likely to pass through the concrete wall. However, their intensity will still decrease. Radio waves have a lower energy than visible light and would not pass through the concrete wall - notice how you lose reception on a car radio if you go through a tunnel. Oldelpaso 18:29, 10 June 2006 (UTC)


 * Yes, concrete has a high absorption coefficient, but that does not answer the question. The bit about high-energy photons passing more easily through materials is also not entirely true.  Low-energy photons can also pass through materials, as ELF radio waves do when they penetrate the oceans.


 * The answer is that materials absorb different wavelengths by different amounts according to their atomic structures. At different wavelengths, different absorption mechanisms are at work.  The Permittivity section has a nice graph that shows these different mechanisms.  (Complex permittivity is a fancy name for the absorption coefficient.) You can see that the transmission of visible light is governed by electronic absorption: when the energy of a photon coincides with a difference in allowed electron orbits, the photon is absorbed, so the substance is opaque at that wavelength.  Radio waves have longer wavelengths than visible light and are blocked only by electrically conductive materials, which concrete is not.  Reinforced concrete, on the other hand, contains conductive steel bars which do block most radio wavelengths. Tunnels also tend to be built in soil or damp rocks, which are also electrically conductive and block radio waves for the same reason.  Gamma rays and X-rays are different: they have extremely short wavelengths which are beyond the main electronic resonances of atoms, so they pass straight through most materials. --Heron 19:39, 10 June 2006 (UTC)


 * There is a part of the complete answer that nobody wants to hear: Light doesn't pass through walls because if light did pass through them we wouldn't use that material to make walls out of. We'd use it for windows.  If our eyes saw radio waves instead of visible light, well, first off we'd be calling radio waves "visible light".  Then, we'd be using some other material for our walls. --Kainaw (talk) 21:39, 10 June 2006 (UTC)


 * I like that answer. The anthropic principle in materials science!  moink 23:49, 10 June 2006 (UTC)


 * Ha! I agree with Kainaw. — Knowledge Seeker দ 02:42, 11 June 2006 (UTC)


 * I was assuming that visible light describes the section of the electromagnetic spectrum that we, humans, can see.Yanwen 02:50, 11 June 2006 (UTC)


 * Absorbtion isn't the only thing. Light also has trouble with white pigments (thin white paint) even though the ground-up pigment is transparent.  The paint essentially acts as a mirror: any light going into the paint will hit a particle and be scattered, with almost all of the light ending up being reflected.  But of the pigment particles were much smaller, the paint would be translucent like ice cubes in water.  Or if the pigment particles were much smaller, the paint would also be transparent, like dissolved sugar molecules.  If the transparent pigment particles are about the same size as light wavelength, then the paint becomes VERY white and VERY opaque.  --Wjbeaty 05:01, 11 June 2006 (UTC)

Neural network
Hello! I'm at loss to explain he difference between an artificial neural network and an ant colony, to find an analogy with this encyclopedia building (I am for the ants).

Basic needs and skills, and collaborative tasks, help ants build houses and domesticize other insects or mushrooms without any more learning. An ANN may seem to learn but through controlled input done by man. In both case, the results are surprizing and/or helpful to man. Also, which is closer to WP building process ? Any ideas ? Thanks. --DLL 19:44, 10 June 2006 (UTC)


 * Probably an ant colony is a better metaphor for Wikipedia than a neural network. In a neural network, individual neurons don't have the slightest idea of what the big picture is; their output is simply a response to the input they receive from neighboring neurons, so their "knowledge" of the system is highly localized. Also, when a neural network is used to accomplish a task, it doesn't really split up the job into smaller pieces and assign the pieces to the individual neurons, because an individual neuron can't do anything. Instead it's the interaction of the neurons that causes the entire task to get done. So in some ways there are similarities between neural networks and Wikipedia, but I would go with the ant colony metaphor because the neurons in a neural network are a lot dumber than the network as a whole, whereas in an ant colony and in Wikipedia individual members can do a lot on their own. —Bkell (talk) 20:22, 10 June 2006 (UTC)


 * I concur. Black Carrot 20:34, 10 June 2006 (UTC)


 * Thank you, We'll try to stick to that : individual members can do a lot. But do you think they knew what would be built when they started some years ago ? --DLL 21:14, 10 June 2006 (UTC)


 * I imagine so. The results have stayed pretty true, at least, to the grand visions that people claim they started out with- huge encyclopedia that anyone can edit, on every topic under the sun. Black Carrot 21:59, 10 June 2006 (UTC)

multiplexers
What are the advantages of Frequency Division Multiplexing over Time division Multiplexing?


 * For one thing, with frequency-division multiplexing, whenever a station has data to send it can begin transmission immediately. With time-division multiplexing, it must wait for its time slot. It might be cheaper to build equipment that can transmit with frequency-division multiplexing, because all you need is a simple transmitter that is set to transmit on a particular frequency; with time-division multiplexing, you have to have a transmitter that can sense when its time slot has arrived, and can transmit in bursts. But I only took a couple of electrical engineering courses, so I don't know what the circuits would be like. You might find more information in the multiplexing article. —Bkell (talk) 20:15, 10 June 2006 (UTC)


 * Time division works very well if there is a single source (e.g. sending 1000 phone calls from exchange A to exchange B) and/or a relatively small ammount of availible bandwidth, frequency division is much simpler for multi-source systems (no need for turn waiting) and in a high bandwidth environment keeps the ammount of high frequency stuff down (in the ultimate the final frequency may never be treated electronically at all, see wave division multiplexing). Delays are a complex one, in FDM the source can transmit at any time BUT you need filters and the better you make a filter the more delay it has. In TDM each channel has to wait its turn to transmit but if the channel is viable down to near DC then the recieved information can be decoded almost immediately. Often both techniques are combined (e.g. multiple OC-192 lines wave division multiplexed onto a single fiber) Plugwash 19:45, 16 June 2006 (UTC)

Chemeleon Frog
I saw a frog yesterday that seemed to be trying to blend into its environment. It was sitting on some metal (silverish), and most of its body had turned a whitish grey color, and its skin looked kind of wrinkled up. There was just a patch on its back that was still green and smooth. I thought only certain reptiles could do that. Black Carrot 20:32, 10 June 2006 (UTC)


 * I do concur, carrots can't. --DLL 21:15, 10 June 2006 (UTC)


 * There are multiple species of frogs that can change color. Greem tree frogs normally change from green to yellow-brown.  There's an african frog that can turn from green to white and another that can turn from white to brown.  All in all, color change is not unique to reptiles. --Kainaw (talk) 21:36, 10 June 2006 (UTC)


 * Cool. Can anyone identify which one this is? [[Image:Chameleon_Frog.jpg|thumbnail|Froggy]] In case it helps, I live in southeast Texas. Black Carrot 21:56, 10 June 2006 (UTC)


 * The article chromatophore explains how pretty much all poikilotherms can change colour to some extent.  Rockpock e  t  23:07, 10 June 2006 (UTC)

Biology vaccinations
In what ways do vaccinations prevent infection???


 * Using the 'search' box on the left side of the page, you can find our articles on vaccine and vaccination. TenOfAllTrades(talk) 22:49, 10 June 2006 (UTC)

Crabs - what do they eat?
Walking the seashore with my grandson (7) he asked "what do crabs eat?" at the same time showing me two in his hands. I told him I thought they ate small fish and insects but I wasn't sure. He told me a friend had suggested that they ate seaweed. Maybe it's both, can you help please? I have looked at Crab and it didn't help. Abtract 23:25, 10 June 2006 (UTC).


 * Don't be silly. They eat Purina Crab Chow! In the wild, hermit crabs eat fallen fruit, decaying wood, leaf litter, plants and grasses and almost anything that washes up on shore. Some carnivorous crabs (Telmessus acutidens and Charybdis japonica) eat mussels. Horseshoe crabs (which are apparently not "real" crabs) like worms, molluscs, and dead fish. In short, it seems crabs are not fussy eaters at all, and their preferred food depends on ths specific species you're considering... - Nunh-huh 23:41, 10 June 2006 (UTC)


 * Crabs mostly fall into the decomposer category. — [[Image:Flag_of_the_United_States.svg|17px]] <tt> The </tt>  <font color=#006600>Mac Davis ] ⌇☢ &#xE0D;&#x19B;. 03:44, 11 June 2006 (UTC)

Crabs occupy several niches. Some filter organic material (microbes, algae, fungi etc) from sand and mud, e.g. fiddler crabs and sand bubbler crabs. Some hunt insects (e.g. ghost crabs); the coconut crab eats coconuts. Many are bottom-feeding scavengers. Gdr 09:49, 12 June 2006 (UTC)

What connector???
I want to connect my dvd player which has a scart, a composite and s-video,connectors to my 17 inch crt computer screen which has a vga in connector as usual on crt screens. How can I do that? Is there any adapter or connector, but not like the special external boxes which include tuners and so on. I only want this converter.. Thanx!!!!!!!!!!!!!!!!


 * The difficult thing with converting TV signals to VGA is that TV signals do have their own format, usually NTSC or PAL, and they do need to be converted. That's why most of the converters need a big external box to tune and convert, like this one. However, going the other way around, that is, connecting a VGA-out to a TV to display a computer screen on a TV is a lot simpler and can be done with a regular cable, like this. Searching Froogle will probably give you more products. -- Daverocks (talk) 01:43, 11 June 2006 (UTC)


 * If your computer has a video card that accepts S-video in, you should be able to get it to display on the monitor as long as both the DVD player and the monitor are hooked up to the computer.--inksT 03:58, 11 June 2006 (UTC)


 * SCART connectors usually include RGB signals, which are closer to what a computer monitor expects than either composite or s-video. Searching google for 'scart vga' finds many products, for example this one or this one.   The CRT manual (if you've thrown yours away, you can usually find something online) will tell if the monitor supports TV frequencies, which is not necessarily the case.  Be warned that if you're sensitive to flicker, you may not be happy with a TV quality signal on a computer screen, since computer CRT displays are designed for higher refresh rates.  84.239.128.9 08:03, 11 June 2006 (UTC)