Wikipedia:Reference desk/Science

Reference Desk

Science Mathematics Computing/IT Humanities Language Entertainment Miscellaneous Archives
How to ask a question Search first. It's quicker, because you can find the answer in our online encyclopedia instead of waiting for a volunteer to respond. Search Wikipedia using the searchbox. A web search could help too. Common questions about Wikipedia itself, such as how to cite Wikipedia and who owns Wikipedia, are answered in Wikipedia:FAQ.
Sign your question. Type ~~~~ at its end. Be specific. Explain your question in detail if necessary, addressing exactly what you'd like answered. For information that changes from country to country (or from state to state), such as legal, fiscal or institutional matters, please specify the jurisdiction you're interested in. Include both a title and a question. The title (top box) should specify the topic of your question. The complete details should be in the bottom box. Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please don't post entire homework questions and expect us to give you the answers. Be patient. Questions are answered by other users, and a user who can answer may not be reading the page immediately. A complete answer to your question may be developed over a period of up to seven days.	Do not include your e-mail address. Questions aren't normally answered by e-mail. Be aware that the content on Wikipedia is extensively copied to many websites; making your e-mail address public here may make it very public throughout the Internet. Edit your question for more discussion. Click the [edit] link on right side of its header line. Please do not start multiple sections about the same topic. Archived questions If you cannot find your question on the reference desks, please see the Archives. Unanswered questions If you find that your question has been archived before being answered, you may copy your question from the Archives into a new section on the reference desk. Do not request medical or legal advice. Ask a doctor or lawyer instead.
After reading the above, you may ask a new question by clicking here. Your question will be added at the bottom of the page.
How to answer a question Be thorough. Please provide as much of the answer as you are able to. Be concise, not terse. Please write in a clear and easily understood manner. Keep your answer within the scope of the question as stated.	Link to articles which may have further information relevant to the question. Be polite to users, especially ones new to Wikipedia. A little fun is fine, but don't be rude. The reference desk is not a soapbox. Please avoid debating about politics, religion, or other sensitive issues.

April 6

Adhesive bonding

I've asked a few questions on Talk:Adhesive without many satisfactory answers. I would like to know, for example, if I glue two pieces of polished steel with cyanoacrylate glue, how much of the bonding is chemical and how much is mechanical. I am inclined to think that it is largely a chemical bond, but if so, what is the bond involved? —Ben FrantzDale 02:59, 6 April 2006 (UTC)

I don't think you could give an exact number for that. I'd think cyanoacrylates would mainly be considered to bond mechanically, polymer glues in general work by filling out the surface area while a liquid and then reacting to form a solid polymer. Chemical compounds in general don't bind very well to metal since the metallic bond is a bit of a different animal from most. It can still bind by chelating to the metal atoms on the surface, probably through either the cyanate or carboxyl groups. However, those bonds would be weaker than in the cases where an adhesive can form hydrogen bonds with the surface. --BluePlatypus 05:13, 6 April 2006 (UTC)

Photographic Memory

Although the eidetic memory page is certainly informative, I'm not quite clear on what answer is arrived at. Is there, or is there not, such a thing as photographic memory as it is commonly portrayed? By that I mean innate, photographic (actually a snapshot, rather than based around important features like 'red shirt' and 'a bit to the left'), essentially effortless, and durable. If not, why is there so much popular certainty that such people exist? Black Carrot 03:28, 6 April 2006 (UTC)

This is from my own incredibly shaky memory, so may not be totally accurate, but from what I recall people actuallt do take in most of the items in a scene, but the linkage between short-term and long-term memory is better in some people than others; also some people are better able to retrieve items from their long term memory. It's not that some people have photographic memory where others don't; it's more that some people are better able ot store and access whatever memories they have received. Because some people can perform very well in such memory tasks, it is popularly assumed that some "super-special" memory is present in some individuals, shich is why the idea of photographic memory is so prevalent. Anyone able to confirm or deny...? My specialy was perception, not cognition :) Grutness...wha? 07:58, 6 April 2006 (UTC)

On the off chance it jogs a memory, the only article I can remember ever reading that mentioned photographic memory existing claimed that, when people with such memory (which they apparently could get hold of enough of to do this test) forgot a picture, which did happen over time, it 'shattered' or 'fragmented' or some such rather than becoming vaguer and less detailed. Anyone recognize this? Black Carrot 04:27, 9 April 2006 (UTC)

The period validity of the patent

The period validity of the patent of the fuel saver by magnet treatment is invalid.Is’nt it ? Wiki? Ngocthuan 06 11:08, 6 April 2006

   U.S. Patent 3,830,621 - Process and Apparatus for Effecting Efficient Combustion.
   U.S. Patent 4,188,296 - Fuel Combustion and Magnetizing Apparatus used therefor.
   U.S. Patent 4,461,262 - Fuel Treating Device.
   U.S. Patent 4,572,145 - Magnetic Fuel Line Device.
   U.S. Patent 5,124,045 - Permanent Magnetic Power Cell System for Treating Fuel Lines for More Efficient Combustion and Less Pollution.
   U.S. Patent 5,331,807 - Air Fuel Magnetizer.
   U.S. Patent 5,664,546 - Fuel Saving Device.
   U.S. Patent 5,671,719 - Fuel Activation Apparatus using Magnetic Body.
   U.S. Patent 5,829,420 - Electromagnetic Device for the Magnetic Treatment of Fuel.

I don't know the dates of these. For great justice. 04:27, 6 April 2006 (UTC) The Inset Fuel Stabilizer [1] appears not to be patented. For great justice. 04:29, 6 April 2006 (UTC)

It seems that we don't have articles on fuel saving gadgets, magnets round the fuel line or in the air flow (Ecoflow, FuelMAX, FuelSaverPro, etc), catalysts in the fuel line or tank (Broquet, Fitch Fuel Catalyst, Prozone, Fuelstar, etc), platinum-based combustion enhancers (PVI, Gasaver, Ctech3000, etc), ignition enhancers (Fuel Saving & Power Push, Fireball Ignition, etc, air bleed into the inlet manifold (Ecotek, Khaos, Powerjet USA, etc), turbulence increasers (Ecotek, Tornado Fuel Saver, Powerjet USA, SpiralMax, etc), devices to "atomise the fuel better" (Ecotek, Tornado, SpiralMax, Vaporate, etc), oil additives (Slick 50, Duralube, etc), fuel additives to enhance combustion (Acetone, PowerPill, BioPerformance, etc), engine "cleaning" products (10k Boost, Powerboost, etc), electrical modifications (grounding straps, voltage stabilisers, etc) or hydrogen generators. Shame. For great justice. 04:35, 6 April 2006 (UTC)

In a slightly less oblique way, For Great Justice is suggesting that patent or no patent, the evidence that any of these devices actually work is extremely thin to nonexistent, particularly the ones related to magnets. See snake oil. --Robert Merkel 04:57, 6 April 2006 (UTC)

Absolutely - although actually, I think an article on these devices wouldn't be a bad idea - explaining the science of why they can't work would be a worthwhile excercise. What would the name of the article be though? Is there a generic word for these? For great justice. 05:06, 6 April 2006 (UTC)

Aside from "junk", I don't think so. To be fair, injector cleaners don't quite belong here, in certain specific circumstances they can actually be useful. Subaru actually recommends the periodic use of one for my Subaru Impreza WRX.

But as to the broader point, how about fuel economy accessories, or something like it? A survey of the devices and their purported mechanisms of action would be quite useful. --Robert Merkel 05:11, 6 April 2006 (UTC)

Fair point on injector cleaners. I still think there's some milage in the phenomenon of snake oil as applied to fuel economy magnets - perhaps only as a section of snake oil though. These aren't really just accessories though - the point is that they are completely spurious... For great justice. 05:18, 6 April 2006 (UTC)

I have been found out the magnet treatment around the fuel pipe from many years ago, but I think that it is the minimium magnetization, because it is very easy for locating the magnet lying perpendicular to another and first and foremost all of the magnets are perpendicularly to the fuel pipe, this thing is the same meaning that they cause the magnetic line perpendicular to the fuel pipe.

   The magnetic Flux = B * S * cos (B,n)
   Here , cos (B, n) =0 ( n : the direction perpendicular to S; i.e: normal line of Surface S)
   For the maximum magnetization , cos (B,n) must be equal to 1

I.e.: the magnetic lines was caused by these magnets which are paralell to the fuel pipe.

   For this raison, we can reduce the volume of the magnets, and follow to their weight shall be reduced noticeable .
   Another raison, many peoples don't like to use word wrap is because the peoples that don't use it like to force a horizontal scroll bar into your web browser. even the powers of wikipedia and firefox combines cannot wrap the text.
  Ngocthuan 06  16:25, 6 April 2006 (Vietnam)

Atmospheric pressure (can someone source this for me?)

An anon added the following to a (featured) page I watch: "Where an atmosphere is less than 0.006 Earth atmospheres water cannot exist in liquid form as the required atmospheric pressure, 4.56 mmHg (608 Pa), does not occur." I didn't see this specific point on the atmospheric pressure page and I don't know an mmHg from a bowling ball. Hoping someone could point to a source. Marskell 08:26, 6 April 2006 (UTC)

It's the pressure at the Triple point of water. --BluePlatypus 08:33, 6 April 2006 (UTC)

red mercuy

Dear Sir is red mecury rs 99.999 can be used in medisence or not

I believe the idea is, that if Red mercury existed (which it doesn't), it could be used in an atomic bomb. --BluePlatypus 08:35, 6 April 2006 (UTC)

I think you are referring to mercurochrome which can be used as a topical antiseptic. - Cybergoth 03:21, 7 April 2006 (UTC)

Ewww, what the hell popped out of that earwig?

Hoping someone knowledgeable in earwig entomology can answer this. I just squished an earwig on the wall with a tissue. While pressing down on it (I had to squish it fast but it took a bit of finger-strength to get it to actually squish) there was a sound not unlike a clicking sound.

I take the tissue off the wall and there's two things -- the earwig's corpse, dead but intact. And then there was something else, it was a dark color and with a shape that an eggplant might be if you were to bend it in the middle 90 degrees. I'm guessing it was either something fecal or was it perhaps an egg it was carrying? Perhaps some inside body part of the earwig? Either way it convinced me that killing an earwig is an ickier experience than merely being in the presence of an earwig, and next time I'll capture one in a jar and let it loose in my neighbor's yard instead.

Just what in the world popped out of that earwig when I squished it? It wasn't even messy, just a solid object with no real "splatter" to it. --209.77.244.12 09:39, 6 April 2006 (UTC)

I heard that earwigs have two penises in case one breaks off during sex. So maybe what you saw was its spare penis. Ah, our article on earwig has that fact as well. You might find some more stuff in that article that might help you. -- Daverocks (talk) 10:21, 6 April 2006 (UTC)

The earwig article doesn't actually have a whole lot on earwig anatomy. Shame. For great justice. 18:00, 6 April 2006 (UTC)

Also. WTF happened? Compact Flash cards are now the new standard for size comparison? Come on! Only on Slashdot, surely - what happened to a ruler, or something?! For great justice. 18:03, 6 April 2006 (UTC)

Nuclear engineering

How is it possible to get highly enriched uranium from a centrifuge?Wont that Uranium possess critical mass and undergo fisson?What initiates criticality accidents?

The uranium first goes through some processing which converts it to uranium hexafluoride. This is a gas, and its density is rather low compared to solid uranium, so criticality isn't so much of an issue here. --HappyCamper 11:16, 6 April 2006 (UTC)

Have a look at Zippe-type centrifuge. The details of the various designs remain a closely-guarded secret. --Robert Merkel 23:17, 6 April 2006 (UTC)

El Nino and La Nina

Hello, I am writing an article for my high school newspaper about El Nino and La Nina because I read somewhere that we are just leaving a La Nina year and entering an El Nino year. Is this true, because the Wikipedia article doesn't say that. Thanks for your help!! Zach 10:42, 6 April 2006 (UTC)

The Australian Bureau of Meteorology's climate page has extensive information about the current state of ENSO. --Robert Merkel 23:20, 6 April 2006 (UTC)

Mermaid

Hi,

Does mermaid exist?--Aju 11:07, 6 April 2006 (UTC)

• Try our article on mermaids. - Mgm|^(talk) 12:40, 6 April 2006 (UTC)

Nope. How old are you? Loomis51 21:52, 6 April 2006 (UTC)

Irrelevant. Misinformation can strike at any age, though generally we learn to guard against it better over time. Tzarius 09:07, 7 April 2006 (UTC)

To a very lonely sailor, a manatee can look like a mermaid. StuRat 08:14, 8 April 2006 (UTC)

Silicon Wafers

I've got a question about the surface of a silicon wafer. Do you get an silicon dioxide layer on the surface? If so, what kind of thickness might you expect? If not, what does the surface of a silicon wafer (outside of the cleanroom environment) look like? 12.106.14.201 14:36, 6 April 2006 (UTC)

It looks pretty much like a (somewhat dark) mirror. Imagine this sliced up. You won't get an oxide layer at room temperature, you have to grow them at high temperature to the desired thickness. Current research involves MOSFET gate oxides with thickness < 10 nm. - mako 02:14, 7 April 2006 (UTC)

APOLOGY

Hello! It’s me Nita .I am going to write an assignment about Feasibility report.I am totally ignorant of this term. I had already sent a question to u n u people replied it too. I confessed that I had committed some mistakes that’s why I am sending you an informal apology .I beg your pardon sir,hope you will ignore my mistake. I admit it that my English is not proper but you people will have to accept the fact that on the face of this earth a lot of nations with different languages are residing and none can snub a person on the plea that he is speaking or writing wrong English .I know four languages .ENGLISH, URDU, HINDI, FRENCH and PERSIAN .I guess its enough for a girl who is just 17 .my purpose of sending u this mail is just to give u this explanation that ; I am sorry for using wrong grammar ,I am sorry for not saying PLEASE .now may you tell me what is feasibility report .I am not asking you to make my whole assignment I am just asking for a little assistance so that I may be able to fulfill my task properly —The preceding unsigned comment was added by 203.99.61.48 (talk • contribs) 14:37, 6 April 2006 (UTC) Thank you.

When touring a strange land, it is best to have a guide, or to learn the local customs. That way, people won't be rude to you. Here, we have the equivalent of a guide at the beginning of this document, and it is best to read it. --Zeizmic 14:47, 6 April 2006 (UTC)

A feasibility report describes whether something can be done or not, how easy or hard it will be to do, etc. Search for the term on google and you will find hundreds of examples of them. Chapuisat 14:52, 6 April 2006 (UTC)

No, I don't think that's true. "Feasible" is different from "possible". For something to be feasible, it has to be something that can be reasonably accomplished within practical constraints, particularly economic ones; it's not enough for it to be possible in theory. That said, there is a minority usage which uses "feasible" synonymously with "possible" (makes my skin crawl, personally; it's as bad as "refute" meaning "deny"). But that usage is unlikely to be the one intended in something called a "feasibility report". --Trovatore 23:04, 6 April 2006 (UTC)

Not sure why you think you're disagreeing with me. That's exactly what I was saying it was. "whether something can be done or not, how easy to hard it will be to do". So a report might come back and say "it can't be done" or it might say "It can be done but it will take 3 years and $400,000 and require extensive paperwork", or maybe "It will cost $0.75 and a trip to the hardware store". Anyways, the best way for the original poster to understand would be to google "feasibility report" and read through some examples. Chapuisat 13:33, 7 April 2006 (UTC)

Huh? Saying it will take 3 years and $400,000 is information about how hard it is to do, not about whether it can be done or not. As far as I can see you're contradicting yourself in the space of two sentences. --Trovatore 19:59, 8 April 2006 (UTC)

Whoops. My eye seems to have interpolated a "not" that wasn't there. I read it as "whether something can be done or not, not how easy or hard it will be to do. --Trovatore 20:22, 8 April 2006 (UTC)

In the case of a feasibility report on an investment, an important indicator of how good the investment would be is the return on investment. This can either be given as a percentage or number of years. For example, if it costs a million dollars to build a bagel factory, and it can make 200,000 dollars in profit a year, that's a 20% ROI or 5 years to pay off the original investment. That would be considered to be a good investment. StuRat 08:09, 8 April 2006 (UTC)

A more general way to evaluate feasibility would be a cost-benefit analysis. The opportunity cost should also be considered. StuRat 22:41, 11 April 2006 (UTC)

Hi Nita, the link to Feasibility report, which was a redirect to Feasibility study has just been fixed. Probably you should ask your teacher what is expected of you though, it's not clear what you want to know. You say "I know four languages .ENGLISH, URDU, HINDI, FRENCH and PERSIAN." That's very impressive. Do you count Urdu and Hindi as one language because they are so close? GangofOne 23:01, 11 April 2006 (UTC)

Software to record data through the sound card

Does anyone know any piece of software to record everything that sounds through the speakers? Something like "redirecting" the data to a file. For MS Windows and GNU/Linux also, if possible. Thanks. --GTubio 14:58, 6 April 2006 (UTC)

I know there's something for the Mac, and I'm sure there is for the PC or Linux, but don't know what it is - would Audacity meet your needs? For great justice. 17:24, 6 April 2006 (UTC)

On windows, double click on the speaker icon, go to Options -> Properties, select the option "Recording" and on that list, enable all checkboxes that has something to do with "out" ("Stereo Out", "Mix Out", "Stereo Mix" or something like that). Click ok. The slide bars will change for recording volumes, and below each one there's a checkbox. Mark one of the outs and just hit record with any program, one of them will work. ☢ Ҡi∊ff⌇↯ 18:45, 6 April 2006 (UTC)

The standard "low-tech" solution is to get a lead with 3.5mm stereo plugs on either end, plug one end into the output from your soundcard, and the other into your input or microphone socket. And then use Audacity to do the actual recording, as others have mentioned. Ojw 19:55, 6 April 2006 (UTC)

Thank you very much to all. --GTubio 08:12, 11 April 2006 (UTC)

Interconnection

If you connect a simple device designed for 240 V/ 50 Hz (like a British hairdryer) with an adapter to 110 V / 60 Hz (like America), will it work? Will the higher frequency damage it? 57.66.51.165 15:24, 6 April 2006 (UTC)

No, it wont work....for a long time atleast.... The fuse will probably burn up..if it has a fuse... otherwise the whole device would blow up... :-D ..... Jayant,17 Years, India • contribs 16:05, 6 April 2006 (UTC)

Well, you can get pretty cheap transformers that will convert the voltage. I have one, but frankly, if you only want a hairdrier, it would be cheaper to buy a small US hairdrier. For great justice. 17:21, 6 April 2006 (UTC)

It won't work, but putting a 240V device in a 120V (the actual US voltage standard) does not, if I recall correctly, cause spectacular failure. The device just doesn't get enough voltage to do anything meaningful. Now, overvolting a 120V device in a 240V outlet... that will cause sparks to fly. As for frequency, damage is unlikely in either direction. — Lomn Talk 17:23, 6 April 2006 (UTC)

If you plug a 60Hz device into a 50Hz socket, if it's got a transformer or coil somewhere in the circuit (most devices except incandescent light bulbs do), the lower frequency can cause the coil to saturate and become effectively a short circuit, quite possibly leading to a fire. --Serie 22:08, 6 April 2006 (UTC)

Having moved around a lot between both sides of the Atlantic, I can confirm most of the above (haven't played much with frequency-sensitive stuff), but wanted to warn about transformers: firstly, they only convert voltage, not frequency, so a 120 -> 240 transformer used in the US will produce 240V 60Hz (not 240V 50Hz, like in Europe) electricity - be warned for frequency-sensitive appliances, they might well go wonky (basically, anything complex). Also, transformers have a maximum wattage rating - a small one might be 50W or 100W, check the label. While this is fine for most small appliances, be warned of anything that produces lots of heat (toaster, hairdryer...) - these use massive amounts of power (a medium-sized hairdryer is often 1000W, check the label), and these will blow your transformer in very short order. I agree with For Great Justice, get yourself one of those 'travel' hairdryers (often sold at airports) which have a voltage selector switch for 120 / 240. — QuantumEleven | (talk) 12:14, 7 April 2006 (UTC)

Orbital feasibility of Counter-Earth

According to the article the orbit of a Counter-Earth (a planet always on the other side of the sun from us) is just feasible. So would somebody please point out what is wrong with this analysis:

Consider the earth at the point where the line joining it to the sun forms an exact right angle with the major axis of its orbit. Counter-earth must be at the opposite side of the sun, at the point where it's line to the sun also forms a right ngle with the elliptical axis.

Now let us advance the earth until it is in the same position on the other side of the sun - i.e. the other point where it's line to the sun forms a right angle with the elliptic axis. In order for counter-earth to still be hidden it must now occupy the position that earth previously occupied. BUT this cannot be the case, because by Kepler's second law the areas swept by the arcs must be identical, and this is obviously not the case (one of the planets must be going round the long side of the ellipse).

So is counter-earth orbitally feasible or not? DJ Clayworth 20:30, 6 April 2006 (UTC)

Well, the counter-earth theory doesn't (or shouldn't) say that counter-earth is always 180° offset from Earth, but rather that it is so nearly so that it is permanently occluded by the sun. There's allowance for wiggle room in the orbit proportional to the apparent size of the sun. However, since counter-earth is effectively debunked by observations of other planets, I'm not going to bother to work out the math on this one. — Lomn Talk 21:04, 6 April 2006 (UTC)

This was my first thought when seeing the problem above, however, as Melchoir pointed out, there is no requirement that Earth2^TM needs to orbit on the same elipse. If the ellipse were rotated 180° for the other planet, then the instataneous velocities of the two would always be opposite and a line could be drawn connecting the planets and sun at each point in the orbit. So Kepler's Laws don't seem to prevent such a situation, but it's really a 3 body problem. The Lagrangian point article mentions L₃ as a possible place for Counter-Earth, but doesn't say whether or not the system would be stable with two approximately equal masses. Maybe the maths reference desk would be able to help out? EricR 22:50, 6 April 2006 (UTC)

I think if the Hand of God were to place 2 perfect earth copies around a single sun, then it might be stable for a few million years. But instabilities, such as solar flares and giant meteors, would soon knock them out of perfect alignment. The formation of a Solar System is horribly unstable, and single planets sweep out their full orbital band. --Zeizmic 21:06, 6 April 2006 (UTC)

Meteors schmeteors. The counter-earth would have to have a moon exactly the same size as ours, and at exactly the same distance from its primary, and at exactly the same point on its orbit as ours at all times, created at exactly the same moment - otherwise the two orbis would get out of synch very quickly. And given that the moon was most likely caused by a chance collision of a proto-planetary body with the earth, the chances of that happening are probably about as good as going down to the beach and finding a grain of sand with your name and address carved on it. Grutness...wha? 00:59, 7 April 2006 (UTC)

And, as a final nail in the coffin, we have several satellites in solar orbit (mostly used for observing the sun), these would have spotted the Earth2^TM already if it was there. — QuantumEleven | (talk) 12:07, 7 April 2006 (UTC)

Ah, yes. It had not occurred to be that there was a different ellipse that might satisfy the conditions. And no, my question was not intended to imply I thought counter-earth might exist. Thanks for your help. DJ Clayworth 15:42, 7 April 2006 (UTC)

Lead and its history

I am doing a research a report about lead and am having trouble finding out about leads history. ANY information would be helpful.

If you typed "lead" into the search box on the left of this page, you would have found our article on lead. --Robert Merkel 23:24, 6 April 2006 (UTC)

question on animal species

Out of all the animal species in the world, what animals are most abundant? The percentage?--24.147.235.177 21:57, 6 April 2006 (UTC)

You mean the most individual animals or the greatest total mass? —Keenan Pepper 00:19, 7 April 2006 (UTC)

• It would be something small like ants or bacteria (though I can't remember if bacteria are part of the animal kingdom). - Mgm|^(talk) 10:33, 7 April 2006 (UTC)
• if you don't count bacteria as animals, nematode worms are a good candidate Malcolm Farmer 09:39, 11 April 2006 (UTC)

Journal Article

Where can I find the article: " On a supposed proof of a theorem in wave motion" which was written by G.J.Stoney, and published in the Philosophical Magazine in 1897 Vol.5 No.43? I am not sure if I will be able to find the place where your response will be posted, and I don't care if the whole world knows my e-mail address, I get lots of junk mail anyway. So if it's possible, send any information you find,to me at newage@uniserve.com Thank-you Thos

Unfortunately, I can't find an online copy. (JSTOR doesn't have it.) Your only recourse might be to find a substantial university with an old collection. It's actually quite remarkable how many universities have these incredibly interesting historical journals in the open stacks. (Incidentally, be very gentle with the old documents if you do find the paper. Stuff from the turn of the last century may or may not be in good shape, depending on the paper and binding. You might want to ask for assistance from the library staff before you try to photocopy old bound journals—making copies can be very hard on their spines.) TenOfAllTrades(talk) 00:06, 7 April 2006 (UTC)

Yeah, can't find it either. Its too old. -- Mac Davis] ⌇☢ ญƛ. 01:34, 7 April 2006 (UTC)

I presume this is a US journal? If so, a copyright library might be your call of last resort. For great justice. 02:01, 7 April 2006 (UTC)

If the homepage of the journal (here) doesn't have it (which it doesn't), then it's most likely not scanned or available anywhere at all online. Most journals don't have online archives that go back farther than a decade or two. Anyway, what you need to do is check with your local research/university libraries to see if they have it (their catalogs are usually online). If not, you can usually have a photocopy of the article sent to you from a library that does, for a small fee (say $5 or so). --BluePlatypus 04:50, 7 April 2006 (UTC)

I can probably get you a copy of the article early next week, as my university seems to have it available pretty easily for scanning. Let me see what I can do. Also, the title of the magazine from that era was, to be specific, The London, Edinburgh and Dublin philosophical magazine and journal of science. What a mouthful. --Fastfission 12:13, 8 April 2006 (UTC)

Downloading the Yahoo! Toolbar

When I try to download the Yahoo! toolbar, I am led to the MSN Search engine site without my permission, and, of course, no download takes place. This happens no matter how many times I try again.

Here is the sequence of links

1. http://toolbar.yahoo.com/config/slv4_page?.p=featureantispy&.cpdl=net06
2. http://toolbar.yahoo.com/config/slv4_done?.act=3&.dflt=1&.intl=us&.region=us&.partner=none&.guest=&.cpdl=net06&.mf1=as&.xpsp2=1&.data=
3. http://search.msn.com/results.aspx?q=us

Also, under the subject category of Science on the Wikipedia Reference Desk, the word computing looks like a hyperlink while "medicine" and the others don't. When I click on it, I go through the following sequence of links.

1. http://search.globofind.com/search.php?q=computing-service
2. DELETED
3. http://www.google.com/

• Many other links on Wikipedia take me to global find in search of something. I have a Windows XP Media Center Edition. I have scanned my computer with the latest version of Norton Anti-virus and found nothing. I have also updated my Windows operating system. I was going to download the Yahoo! toolbar to use its anti-spyware software, but I can't do it.

Can someone help me? When previewing this page, even words that I haven't created links for on the edit page have links after I click "Show preview."Patchouli 22:07, 6 April 2006 (UTC)

ok it looks like you probably have some sort of spyware? first off, i wouldnt bother with the yahoo toolbar, its not going to help anything. go into start->control panel->add/remove programs. look for anything that might be spyware and get rid of it (get rid of viewpoint media player- your spyware is a bit more malicious than that though, so its gotta be some other stuff). download lavasoft adware, install it, get the latest patch inside the program, and run it, delete what it finds. now go download mozilla firefox for your browser... alot of the spyware that targets internet explorer doesnt affect firefox. if you are still having a lot of spyware problems after these 3 steps, there is a simple solution to it all. backup your desktop, my documents, and any other personal data you have, and reinstall windows. modesty 02:50, 7 April 2006 (UTC)

• I have Ad-aware and have run and deleted everything twice today. Do you think uninstalling Internet Explorer and reinstalling it will help? I can't find IE in the Add/Remove program list.Patchouli 03:10, 7 April 2006 (UTC)

• I obtained a resolution after calling 1-800-HP-INVENT. Here is what I did.

  1. I opened Internet Explorer.
  2. I clicked on the Tools menu.
  3. I chose Internet Options.
  4. I clicked on the Advanced tab.
  5. I removed the check mark next to “Enable third-party browser extensions (requires restart)" under the Browsing section.
  6. Then I clicked OK, closed the browser, disconnected, and restarted my computer.

This was the panacea to all my browsing and file-downloading issues. Patchouli 05:03, 7 April 2006 (UTC)

It sounds as if this turned off some co-operative adware. Nevertheless, the idea of some unsolicited program in my computer fills me with dread. When I had a hint of this the other day, I immediately disconnected the machine from the internet, formatted the hard disk, reinstalled the system and applications, and then restored my personal data (not programs) from last night's backup. I would recommend you do the same. If you aren't willing to, at least never enter any financial data or important password on this machine, ever again. Notinasnaid 12:16, 7 April 2006 (UTC)

i know how you feel but remember if you browse in fear you are letting the terrorists win!!! modesty 16:23, 7 April 2006 (UTC)

It's 8 times easier to catch something with IE than Firefox. The troubles with my kids went down to nothing when I converted everybody. Apparently, even 'good' sites are being hijacked and filled with exploits. --Zeizmic 15:52, 7 April 2006 (UTC)

• The Mozilla browser works well only for some time. If you want to keep it permanently, I believe you have to pay $30 for it.

This is simply not true. Both the Mozilla suite and Mozilla Firefox are free --LarryMac 20:40, 10 April 2006 (UTC)

Dear Gentlepeople:

I herewith assert that visiting every site hosted by blogger.com results in an adware and malfuntions on your computers.

Sincerely,

Patchouli 17:55, 9 April 2006 (UTC)

I sincerely doubt you could visit "every site" hosted by blogger.com; that would take quite a long time. Perhaps you mean visiting "any" site, although that would be wrong. My crap little blog is on blogger and I have never been had any adware trouble. --LarryMac 20:40, 10 April 2006 (UTC)

You are correct, I meant "any site." The asseveration arose due to the fact that after I e-mailed Matt Dattilo with my allegation, I received an answer saying,"This is blatantly false. My site is hosted by blogger.com; thus, if it installs spyware, then every site hosted by blogger does."Patchouli 23:09, 10 April 2006 (UTC)

Webmail

How long has G-mail been an experiment? How long does it take? My university give me this ridiculous 2 Mb inbox limit and delete things without notice if you go over (I've checked, and I can't see how I could possibly over the limit). I'm fed up of it, and since Opera wont let me download IMAP mail (what in the world could make this more difficult than downloading POP email which it allows), I need to find an alternative. Can anyone recommend a service that isn't going to try to charge me to download email or whatever? Another thing that sickens me, is when they say they've "unfortunately" (yeah, right; they "unfortunately" want to extort money out of me) had to reserve the ability to download email or use email clients to paying customers only. Email services should be free, like the sun, the air or the daffodils planted by the council.

Since Google insist on increasing their pledge to users to ludicrously high capacities when they could be opening up 250 Mb accounts to everyone, I pledge to never use their stupid email service as long as I live (or until I forget). --Username132 (talk) 23:50, 6 April 2006 (UTC)

And those "ludicrously high capacity accounts" are open to everyone too. Just find someone with Gmail and ask them to send you an invite. - Mgm|^(talk) 10:35, 7 April 2006 (UTC)

Apart from the privacy issues, Gmail sounds like it could fit your needs, check out Yahoo as well though. BTW, someone pays for those daffodils, most likely through taxes, and someone pays for free email, somehow, sometimes by showing you ads, sometimes by using the info in your emails to better show you ads. You might want to think seriously about what the cost of your 'free' email is. For great justice. 00:17, 7 April 2006 (UTC)

Mozilla Thunderbird (website) can download IMAP mail, if that helps. It's completely free, too, and has a ton of other great features. -- Daverocks (talk) 07:27, 7 April 2006 (UTC)

Note that Gmail are playing a bit of a statistical shell game with their claimed capacity. AIUI, they're working on the principle that the vast majority of people aren't going to use anywhere near as much as they've got available, so they can say that the maximum you can have is very high. Couple this with the fact that they are buying more and more disks all the time and you have the basis of the claim. If everybody suddenly "filled" their Gmail mailbox the servers would collapse in a gibbering heap. (Or, more likely, the allowed capacity would drop very quickly until you'd suddenly met it.) --Bth 11:26, 7 April 2006 (UTC)

If you want to keep your school's "free" email (how much of your tuition money is going towards those 2Mbs?), then I'd go with Daverock's solution and get Thunderbird. A mail client will allow you to use your own hard drive as your email's space, and so you could certainly fit 250 MBs or whatever you need. I'm not sure I understand your anger at Gmail, though. It is indeed open to everybody, they just liked the viral marketing strategy they went with. If you'd like an account, just email me or check out any of the Gmail spoolers that are now chock-full of invitations. But like FGJ pointed out, there's no such thing as a free lunch. — Asbestos | Talk (RFC) 13:52, 7 April 2006 (UTC)

AFAIK the spoolers are all now dead. Henry^Flower 12:29, 9 April 2006 (UTC)

You can sign up to Gmail using your mobile phone, in quite a few countries now. If you're not able to do that, then I'd be glad to send you an invite if you want one. -- Daverocks (talk) 08:54, 11 April 2006 (UTC)

Relative Velocity

Given that a person standing still on earth would nonetheless be moving at several thousand kph due to the earth's rotation, and given that this velocity would only be exponentionally increased by the Earth's revolution around the sun, and given the massive speed at which our solar system revolves around the centre of the milky way, and finally, given the milky way's incomprehensible speed in which it drifts away from the centre of the universe, is it possible to estimate the relative speed at which we're actually moving? If so what is it, and how close is it indeed to the speed of light? Loomis51 23:55, 6 April 2006 (UTC)

There is no "center of the universe," although one can sensibly establish a "universal" reference frame based on the frame in which the surface of last scattering of the cosmic microwave background is stationary. It turns out we're moving at about 0.2% of the speed of light, or about 600 kilometers per second [2], relative to that. -- SCZenz 00:01, 7 April 2006 (UTC)

Wow, interesting. I was about to say the question made no sense but your answer's better. Isn't the surface of last scattering expanding, though? So it's not really stationary in any reference frame, just expanding equally in all directions. —Keenan Pepper 00:07, 7 April 2006 (UTC)

The "surface of last scattering" I believe means the surface at which the CMB last scattered (on average) at the time when it scattered. Thus it's a specifically-defined surface in both space and time. Yes, if you trace the CMB into the present day, obviously it's being spread out in all directions, so you can think of the speed I gave as (in rough terms) our speed measured relative to the average "rest frame" of the CMB near the earth (where the expansion of the universe has little effect). All this was determined based on the measured dipole of the CMB, as is indicated in the reference I added above. -- SCZenz 00:10, 7 April 2006 (UTC)

I also read here that the major source of this movement may be the Local Group of galaxies orbiting the Virgo cluster of galaxies. -- SCZenz 00:13, 7 April 2006 (UTC)

Relative velocity is the velocity of the body, this body interacts to another nearby it , as the earth gravity attracts a man, a man drives round the lake by car, the route of the lake is a curve line.

But all of the surveys of motion always observe based on a nearest object , as a man and earth, and the interaction still exist (i.e.: the gravity extraction). Relative velocity can use to compare something which estimates motionless, when you use the term of relative velocity in this case, it is exactly . But if you can win the gravity extraction, it means you leave the earth into univerve, the relative velocity is not the notion which is applied for discussion. Here, the power is enough to win the earth gravity, it already issues the initial velocity , and from here, when you go slowly, it means your initial velocity is reduced some value which is you must register for your itinerary(or you have to use the formula : v(t)= a v(t)+ v ini ) …

Ngocthuan 06 08:59 2006-04-07 (UTC)

I'm not sure I follow your argument; can you clarify? -- SCZenz 20:25, 7 April 2006 (UTC)

If you are an observer standing motionlessly at a corner of the route, you can see a car going with the speed about 50 km/h. It means you and the observed object which are the same condition:- on the earth and very near together.On the earth, it means you rotate around an earth axis (an axis is thru the north & south pole), although you still stand motionlessly , because the earth turn around itself, and the earth goes progessively in the ellipse orbit around the sun, you also have such progessive motion. And a car is same, it rotates around an earth axis.... and goes with the speed 50 km/h.

But when you observe a car, you have to get the origin for the observation, a car run with 50km/h towards only you (still stand motionlessly at this corner), it is the relative velocity.Ngocthuan 06 2006-04-9 T 11:37 UTC

April 7

Brake Fluid and Clorox

Hi. i was reading an email when it mentioned something about if you mixed Brake Fluid and Clorox it would make smoke.i was wondering if it would make smoke.if not, is there any other household stuff that when mixed will make smoke?(i like pyrotechnic stuff..)

Thanks, --Shannon 00:46, 8 April 2006 (UTC)

I'm not sure about the brake fluid and bleach, but a Google search will yield some results, such as this. In redox reactions like this, there is an oxidizer and a fuel source to be oxidized. There are too many of these chemicals to list them all, but in the example I gave you above, potassium nitrate is the oxidizer and sugar is the fuel.--Chris 01:12, 7 April 2006 (UTC)

Thanks.do u know where exactly i can get potassium nitrate from?

There is no way to get it easily from household items. It must be purchased specifically. I recommend ScienceLab.com. Please be sure to review the MSDS for potassium nitrate before deciding to work with KNO₃. I don't suggest that go ahead with this "experiment" if you do not plan to follow proper safety precautions and have some sense of responsibility. Please follow all directions exactly as they are stated and use your good judgement.--Chris 03:28, 7 April 2006 (UTC)

You might also find it in the local hardware store as 'Stump Remover', where you are supposed to soak the stump in it, let it dry, and then light it. Never worked for me. --Zeizmic 11:56, 7 April 2006 (UTC)

I thought stump remover is straightup black powder, which does have KNO₃ in it, plus charcoal and sulfur. --Chris 22:41, 7 April 2006 (UTC)

Hmmm. i will try to find the chemicals and all safety precautions will be observed. Thanks for helpin me find the answer to it =)

--Shannon 00:45, 8 April 2006 (UTC)

Is sleep deprivation good for anything?

I'm often very tired, and don't have time to get an adequate amount of rest. I'm wondering, is there anything good about sleep deprivation? Flea110 04:22, 7 April 2006 (UTC)

• Well, according to sleep deprivation, it seems that in amongst all the bad things it can do, low sleep levels might help fight depression... temporarily. Seems like the depression usually comes right back after a normal amount of sleep, though. -- Filliam H Muffman 05:10, 7 April 2006 (UTC)
• After 36 hours or so you start hallucinating. GangofOne 07:24, 7 April 2006 (UTC)
  • As this PubMed article suggests, sleep deprivation increases serotonergic activity in the brain, which temporarily relieves psychological disorders such as depression. As a person with social anxiety disorder (which is also linked to low serotonin levels), I can confirm that this is true from experience. You should note, however, that you will only get a noticable effect if you have a chemical imbalance in the first place. Oh, and of course eye candy hallucinations are also encountered with sleep deprivation, although I wouldn't describe them as pleasant. --Aramգուտանգ 08:30, 7 April 2006 (UTC)
  • I agree entirely with aram's comments, and for exactly the same reason. I would add, though, that some artists have used the hallucinations associated with sleep deprivation to good purpose - most famously Salvador Dalí. Grutness...wha? 10:37, 7 April 2006 (UTC)

I doubt that. I've been up for 36-48 hours straight quite a few times, and never ever had a hallucination. You can get flashes in front of your eyes, but I wouldn't call that a "hallucination". A migraine can give you that too. --BluePlatypus 15:15, 7 April 2006 (UTC)

Someone here's an outlier then. I've definitely had hallucinations from that sort of length of sleep deprivation (though mine were auditory -- water in pipes seeming like voices, that sort of thing). --Bth 16:02, 7 April 2006 (UTC)

i heard radiohead frontman thom yorke would use sleep derivation sometimes when writing lyrics modesty 16:20, 7 April 2006 (UTC)

Sleep deprivation helps me get work done, as I get too tired to be anxious, and my anxiety contributes significantly to procrastination. moink 21:26, 7 April 2006 (UTC)

Space-Time Curvature under General Relativity

stereotypical relativity diagram

This is a question about how non-scientific explanations of the Theory of General Relativity are supposed to explain gravitation. Layman explanations of space-time curvature usually have a diagram (apparently always the same one) which shows a two-dimensional surface streched (downwards) into a third dimension at the location of a body having mass. The story goes that a second body going by with no acceleration will follow a curved path because space-time is curved by the first body.

What I don't understand is why this would cause one body to curve towards another rather than away. When I try to figure out what the curved path will actually be (from the diagram), it looks like the it should curve away. Apparently, it is implied that the second body would fall into the 'depression' in the original two-dimensional surface because of.... what? the influence of gravity? It's apparently using gravity to explain gravitation. How is this explanation supposed to work? The Wikipedia article hints it's not a simplistic as the picture, but doesn't seem to go beyond that.

If someone is able to post a complete and thorough reply to this question, please forward it to the Nobel Prize committee. Seriously, though, the curved sheet model just takes advantage of the fact that objects rolling around on a big sheet in a 1 G field happen to move in a way similar to what general relativity predicts for objects moving past planets and the like. It's meant to show you how things move, not why things move. To really understand why things move, you will have to understand nasty things like metric tensors and the Einstein field equations. -- Filliam H Muffman 07:24, 7 April 2006 (UTC)

Well.. I don't quite see why you'd think it would curve away. If you have a downward "dimple" in a tablecloth or similar and roll a ball towards it, moving in a straight line, it will go around the rim in a curved path once it hits the dimple and continue away in a straight line in a different direction, having been deflected somewhat inwards. That analogy is the point of the picture. If the dimple was raised instead of lowered, then it would be deflected in the opposite, outwards, direction. But gravity doesn't act in that direction, which is why you've got a lowered dimple and not a raised one in the picture. --BluePlatypus 07:54, 7 April 2006 (UTC)

The diagram also gives a nice visual analogy for the inverse square law, since the gradiant of the curve is much steeper near the object than far away. But like the others have said, this is a way of visualizing how the objects would move so, not why. — Asbestos | Talk (RFC) 13:36, 7 April 2006 (UTC)

• In other words, it's just a cool picture? It's describing the exactly the same behaviour as Newtonian gravitation. Peter Grey

• Pretty much. It's also meant to give an idea that general relativity deals in spacetime curvature, which, among other things, predicts that light is also affected by gravitation. That makes gravitational lensing possible. Newtonian gravity claimed that light doesn't bend because it's massless. -- Filliam H Muffman 03:03, 10 April 2006 (UTC)

One of the byproducts of Special Relativity has been the famous equation, E= mc², that first stated the fact of mass and energy being only two sides of the same coin, instead of what previous physicists have conceived. While Newton had previously thought light to be massless and thus insupsceptible to gravitation, nonetheless certain details within the mathematical framework he had produced for gravity as a force did predict a certain amount of bending occuring when light approaches gravitational bodies (a third less than what Einstein later proposed), which, although he knew was true, was never able to explain away with his theory. The new definition in modern physics, now, for the word massless, also meant something different. It refers only to those particles with no rest mass, but not necessarily no remaining kinetic energy whatsoever. Due to Einstein's equation, as previously indicated, you may say that light does have mass if you wish to, since its energy could be easily converted to mass via the constant of c². However, the energy of the photon is constantly changing during its flight, so the records for mass you will be able to obtain will never be invariant, thus referred to as the relativistic masss. In modern physics, however, it is no longer considered appropriate to define the particle on terms of its relativistic mass for obvious reasons, and thus it suffices to say that light is massless in the fact that it has no rest mass. Nonetheless, as long as the photon still possessed the kinetic energy/relativistic mass necessary for its existence, then it shall be supsceptible to curvatures in space- time like other particles with rest mass. Luthinya 10:21, 10 April 2006 (UTC)

Erm, where have you got that "third less" from? The Newtonian prediction for the deflection of light around a point mass is half the value given by GR. --Bth 10:34, 10 April 2006 (UTC)

Sorry, got my figures wrong. Thanks for correction. Luthinya 10:45, 10 April 2006 (UTC)

This kind of picture is indeed confusing, but there is another reason for it that hasn't been addressed fully above. The key is the mechanism by which "curved spacetime" affects the motion of objects (particles, satellites, light, whatever). General relativity says that an object moving only under the influence of gravity follows a geodesic in spacetime, which is the analogue of a straight line in Euclidean geometry. Since the spacetime itself is curved, these "straight lines" have properties we do not expect, but they are, in a precise sense, the "least curved" lines you can have within curved spacetime.

Roughly speaking (see below), one of the important properties they share with Euclidean straight lines is that they are the shortest distance between two points. This means you can picture a geodesic in the following way. Take a curved surface, such as the dimpled fabric surrounding the ball in the relativity diagram asked about above, and fix two points, one to be the "pitcher" and one to be the "catcher." We then want to draw the geodesic on the curved surface connecting the two points, representing the path of an object from the pitcher to the catcher. We do this by using a rubber band, stretched taut: this automatically follows the shortest path between the points.

Now suppose we look at the result as viewed from above. If there were no curvature, the rubber band would be a straight line between the two points. Since the ball is there, dimpling the surface downward, the rubber band will not take a path that appears straight as viewed from above, since that path will be rather long due to the dimpling. Instead, the rubber band will curve around the ball slightly, to avoid the trip into the depths of the dimple. When seen from above, it appears that the ball is affecting the path of the object with some "force", when in fact the object is trying to follow the best approximation to a "straight line" that it can in the circumstances.

All that is rather hard to say without additional pictures, hope it comes across. Anyway, very little of that is usually included with the usual picture, which is why it is easy to come to very inaccurate conclusions about what the picture is trying to say. If you want a better version of all this, look at Taylor and Wheeler, Spacetime Physics.

Note for experts: in spacetime, with its Lorentz metric, geodesics are actually local maximizers of proper time; but part of the point of the kind of picture we're discussing is to give a Riemannian picture. --Spireguy 20:12, 11 April 2006 (UTC)

Still, for most layemen beginners, it does offer a much more approcheable beginning for the subject, even if much of the important details have been left out. As far as the geodesic problem is concerned, since we as humans possess four dimensions (including Time), and yet space- time may curve in a way that is impossible for us to conceive or imagine- only "talk about", it immediately shows that space- time curves into at least one more dimension than that to which we are accustomed of in our daily life, i.e. the 4D bodies. And just as the 2D figures upon cardboard cannot stand up vertically upon it, since they have no motion or conception of 'depth', we as 4D people cannot cross the barriers of dimension and traverse into the 5th or other higher dimension freely, as we now have the ability to in our 4D world. We therefore have to kind of traverse with the curvatures of the surface of higher- dimensional space- time, which is to us expressed in a 4D fashion like differently laid card boards are to the 2D beings. Thus, for us, the easiest way between two places in space- time may not necessarily be a straight line, but more usually a curved 4D geodesic adapted from the curvatures of space- time from gravity. Luthinya 20:34, 11 April 2006 (UTC)

That's what I'm getting at. Isn't a path curving away from the point mass shorter? What we would need to visualize would be a contraction of space, not a stretching, right? Peter Grey 04:25, 12 April 2006 (UTC)

Bear in mind that we're measuring "shortest" in the coordinate system defined by the grid drawn on the sheet. The deformations of the sheet deform the coordinate system itself -- that's the whole point of the analogy. What looks longer to us from outside the sheet is shorter, when measured in a system where the side of a "square" on the sheet is a constant however stretched it looks to us. --Bth 11:12, 12 April 2006 (UTC)

The shortest path "in the coordinate system" is the straight line. Or is something still missing in the story? Peter Grey 16:13, 12 April 2006 (UTC)

Um, no. In order to walk the "straight line" in which you are depicting, we must abandon the 4th dimensioned (including Time) curvature of the "surface" of the grid (space- time), and seek to traverse into extra dimensions in order to ignore the curved influences of gravitational objects. However as 4D beings this is pratically impossible for us, so instead of this the shortest route for us will have to be the the curved surface of the grid, which at least is 4D and possible to traverse. Therefore, instead of what Newton has previously proposed, the shortest route between two things is not a 'straight line' in the usual sense of the word, but a geodesic varying according to the shape of surrounding space-time influenced by gravitational fields. At least a longer way is shorter than the impossible, so to speak. The thing is that on the diagram you cannot see the grid curving into extra dimensions the way it should, which is what makes the analogy slightly hard to come to mind. Remember the analogy is only a start to understanding; try eventually to draw away from the picture and just let the ideas flow accross your head- aided by some mathematics, you'll find this much easier.

PS May I add that my above language is extremely inaccurate in depiction, especially without the mathematics to compensate for it. Hope it comes through anyway. Luthinya 18:17, 12 April 2006 (UTC)

Sports Science

How can the diet of a body builder be compared to the diet of a jockey?

In many ways. You could compare the number of calories, or the proportion of carbohydrates, or even the sheer weight of the two diets. Grutness...wha? 10:35, 7 April 2006 (UTC)

It's probably a polite fiction that people can significantly bulk up without an Anabolic steroid. Just compare the body builders of yesteryear with the Rambo's of today. --Zeizmic 14:52, 7 April 2006 (UTC)

It's definitely possible. Depends what your goal for bulk is, but with enough protein and exercise, one can add major muscle mass without resorting to drugs. You may not end up looking like the hulk, but rambo is in reach, given the right genes. Night Gyr 17:35, 7 April 2006 (UTC)

Time dilation

What is the easiest way to understand length contraction and time dilation?

Here on Wikipedia, a good starting point might be our Introduction to Special Relativity page, which takes a fairly unusual but (IMO) particularly clear geometrical approach. For more details, try our articles on length contraction and time dilation. Elsewhere online, sites like this and this take the more common playing-ping-pong-on-a-train approach. Do come back here if you have anything you want cleared up. --Bth 11:20, 7 April 2006 (UTC)

Create a super computer by many used computers

I hear that we can create a super computer by many used computer, it means that If I have about 10 pcs of Pentium III Pc, I can create one super computer. The Operating System now is open source.User: Ngocthuan 06 2006-04-7 19:52 UTC

If you had looked at the supercomputer article, you could have probably seen Beowulf (computing), which is the standard model for making a supercomputer cluster. The links and external links in that article will probably tell you most of what you're looking for. — Asbestos | Talk (RFC) 13:19, 7 April 2006 (UTC)

Logical way to finish this Sudoku?

I got annoyed with the Sudoku today because it took me more than 2-3 stops on the T to solve, so now I've decided that it was a bad puzzle (obviously). I solved the puzzle by supposing one box was one number, working through it all and seeing that it didn't lead to any contradictions. My question is: Was there a logical way to finish this sudoku, without starting with "Suppose this box is a ...", and then showing presence or absence of a contradiction? I realize that that is an ok way of finishing a tough sudoku, but I far prefer it when they can be solved more elegantly:

7 2| 6 | 98
5  |928| 71
98 |74 |  2
-----------
6 8|29 | 17
273|156|849
19 | 87|2 6
-----------
3  |872|964
427|639|185
869| 1 |723

Thanks! — Asbestos | Talk (RFC) 13:16, 7 April 2006 (UTC)

Probably not, the puzzle looks like it's been designed with the "pick one of two choices and see if it leads to a contradiction" method in mind. Parts of it can be solved independently, though: for eample, one of the two possible choices for filling the central square leads to a fairly obvious contradiction in the central columns. —Ilmari Karonen (talk) 17:12, 7 April 2006 (UTC)

I'd agree, I can't see a way to do it that doesn't rely on guesswork^W proof by contradiction. As such, it doesn't count as a well-formed sudoku to my way of thinking. --Bth 17:18, 7 April 2006 (UTC)

All solutions depend on proving-by-contradiction. Some of the problems just have more obvious contradictions, making it easier to find the correct one. It's an NP-complete problem, so one solution isn't really much more elgant than the other since they all more or less imply testing all the possibilities. So the perceived elegance is more about whether you can solve it within your mental 'search depth', or whether you have to resort to writing the numbers down. --BluePlatypus 18:23, 7 April 2006 (UTC)

I see what you mean, but solving using the various other "standard" techniques (listed at length in our sudoku article) doesn't feel like guesswork/proof-by-contradiction in the way that having to employ the "what-if" method does. I've never seen a sudoku before that had to be solved by what-if. (OTOH, I've often solved them by that and then used my knowledge of the solution to see what I'd missed in my application of the other techniques.) --Bth 18:54, 7 April 2006 (UTC)

Well, yes and no. Personally I feel that a sudoku should be solvable by deduction in that you should logically be able to deduce simply by examining the puzzle what particular number will go into a space. If you are left with a situation where the only way of finding out is to plug in numbers and see whether the correct solution can be reached you've gone beyond deductive reasoning and into inductive reasoning - a different matter entirely, my dear Watson. Grutness...wha? 03:41, 8 April 2006 (UTC)

Cheating, and using http://sudoku.sourceforge.net/, and adding in all of your available numbers. There is no solution. Sorry! Kilo-Lima|^(talk) 16:54, 10 April 2006 (UTC)

There is indeed a solution according to that site, although it requires a guess. Are you sure you filled it in correctly? --Pidgeot (t) (c) (e) 20:25, 10 April 2006 (UTC)

Desktop & Laptop screen placement

1)In a desktop, the monitor is more or less perpendicular to the desk, and we view that monitor with 3 feet distance. If we use a laptop or a tablet pc whose screen is placed at 45 degrees to the desk/lap, should the same distance of 3 feet be maintained? Or simply, if viewing angle changes, should there be a difference in viewing distance?

2)What is the reccommended viewing distance and reccommended angle for placing laptop screens?

When we place the screen on the laps in a slate tablet PC, the viewing distance is 1 to 1.5 feet. Does that say that viewing distance is related to angle of viewing?

Laptops and tablets are not particularly ergonomic. Get an external keyboard and jack your laptop up on some phone directories when you are using it as a desktop replacement. For great justice. 18:38, 7 April 2006 (UTC)

You can get stands that hold the laptop screen vertically at eye level (the ones we use do so by having a 30° tray to put the laptop base-part on, with the hinge furthest away from you) and plug in an external keyboard and mouse. Ojw 20:36, 8 April 2006 (UTC)

Your screen is probably not at a 45 degree angle; many laptops are barely even capable of bending that far. Night Gyr 06:29, 9 April 2006 (UTC)

Can Envelopes Be Composted?

Paper can be recycled or composted but envelopes cannot be recycled due to the glue. Can envelopes (without plastic windows) be composted? --Username132 (talk) 15:16, 7 April 2006 (UTC)

Theoretically, most things can be, but consult your local recycling company for their facilities / policies on this. For great justice. 18:36, 7 April 2006 (UTC)

I'm sorry - you said composted, not recycled! They will certainly break down if you put them in a composter - the question is, not knowing exactly what chemicals are in it, you might not want to use the compost on vegetables etc you want to eat - otherwise, go for it. For great justice. 22:24, 7 April 2006 (UTC)

The recommended constituents of compost are: 1) vegetable waste (and some miscellaneous kitchen waste like tea bags, eggshells, etc), 2) lawn trimmings or leaves, and 3) shredded newspaper, straw, or wood chips. Bleached paper (normal office paper, including envelopes), cardboard, other paper, cooked food, animal-based waste (except eggshells), fats, etc while capable of decomposition, are NOT recommended for composting.

In the case of office paper (as per your question), it is both the chemicals in the paper and the density of the paper. 'Perfect' compost is alternating layers of dense vegetable matter (kitchen scraps), dry vegetable matter (lawn trimmings or leaves), and cellulose (straw, wood chips or SHREDDED newspaper), not necessarily in that order but definitely including all three. The combination of the three types of elements is ideal for the cultivation of all the different types of organisms that turn waste into soil. If you don't follow the 'formula', your compost will still decompose, but it will be slower, smellier, and grosser.

Newspaper is included for two reasons; one is that it aerates the pile, and it is actually nutritious to worms. White paper is like refined sugar, it has no nutrient value, so worms wouldn't eat it. It's also dense and soaked with chemicals, which would inhibit the movement of the worms and maybe poison them. IF the paper decomposed, it would be a slow process facilitated by bacteria which would be acting on the organic drippings from other parts of the compost that would 'soak in' to the paper. It's waaaaay better to leave it out, most compost experts say leave it out. Recycle your office paper through your city's recycling programme, or send it to the dump to follow its own decompositional path, away from your compost pile.--Anchoress 00:55, 11 April 2006 (UTC)

Thank you - compost without the envelopes it is! :) --Username132 (talk) 04:06, 11 April 2006 (UTC)

No problem. I also forgot to mention that - as far as animal waste is concerned - manure is fine, but not dog, cat or human feces. Also some documentation says cardboard is OK, I think the main thing is unbleached, unpressed paper, and ideally it should be shredded. In my jurisdiction they say only newspaper, no other kinds of paper.--Anchoress 04:34, 11 April 2006 (UTC)

Dr. Keith Black neurosurgeon

Why is there no information on Kieth Black M.D. on wikipedia ?

Because no one has added anything about him yet. I didn't know who you were talking about so I looked him up. He doesn't seem terribly notable to me, but if you feel like adding information about him, go ahead. Be Bold. Chapuisat 16:55, 7 April 2006 (UTC)

He seems sufficiently notable to me to warrant an article (and to displace the drag-racing Keith Black to a disambig link), so I've created a stub for him based on a quick Google search; I'd strongly encourage the questioner to add some info if they have any. More generally, to expand on Chapuisat's point, Wikipedia has gaps and omissions because it's entirely the result of volunteer contributions and constitutes a permanent work in progress. --Bth 17:00, 7 April 2006 (UTC)

• If one added every living and dead physician, lawyer, and dentist, then we would have maybe over 10,000,000 articles on these folks alone. Unless that person made a breakthrough and accomplished something meaningful, I don't think such articles would be needed.Patchouli 23:54, 7 April 2006 (UTC)

Linux

From a Linux tutorial; "Most modern Linux distributions encourage a practice in which each user has a specific directory for the programs he/she personally uses. This directory is called bin and is a subdirectory of your home directory."

Would it not be inefficient for many users to have different copies of the same program? --Username132 (talk) 16:42, 7 April 2006 (UTC)

Well, if it's a big multi-user system, each user probably has a disk quota that they can use to store whatever they want. If the programs they want to run aren't available in /usr/bin or /usr/local/bin or whatever, they can put them in /home/whoever/bin. —Keenan Pepper 17:07, 7 April 2006 (UTC)

And the particular situation of everyone having a local copy of SuperWhizzyUtilityX shouldn't arise if the sysadmin's on the ball. They should be putting anything that several users want into /usr/bin and such places. (Incidentally, if you want to see where the shell searches for executables when interpreting command lines, type "echo $PATH" to see the (colon-separated) list stored in the PATH environment variable.) --Bth 17:15, 7 April 2006 (UTC)

Gold in sea water

I have read somewhere that there is approximately 9 tonnes of gold per km cubed in sea water. --

-Is this true for all seas (apart from where there is large amounts of fresh meltwater)?

-Is the same true for fresh water and what is the amounts?

-Is the gold not worth anything (like industrial diamonds)?

-Is there an efficient/cost effective way of extracting this gold, taking into account; positioning (what sea/ocean), labour, building/machienry etc.

-If you discover anything "good" please don't make it "exceptionately clear" to anyone else and put it on the website. I cant force you to but pretty please do.

Im slightly mad but if it wil work i will be slightly rich....Yipee!!!

                I think im ment to do this: --William Dady 16:58, 7 April 2006 (UTC)

The presence of trace amounts of gold and other precious metals in seawater is not a secret, and it is not economically feasible to extract it because the concentration is so low. 9 tonnes may seem like a lot, but a cubic kilometer is a ridiculous amount of water. See [3] and Fritz Haber, a brilliant chemist who tried and failed. —Keenan Pepper 17:12, 7 April 2006 (UTC)

To put it into perspective, a cubic km of water weighs about a trillion (1,000,000,000,000) kg, or a billion metric tonnes. So you got a concentration in the 9 parts per billion (mass) (by your numbers).

The 1st billion tonnes is the hardest. --GraemeL ^(talk) 23:39, 7 April 2006 (UTC)

Thanks for your query. We figured it out but sorry we're not sharing. alteripse 14:59, 8 April 2006 (UTC)

Finally, there are two metals that might one day be economically viable to extract from seawater - uranium and vanadium. See this abstract. Arthur C. Clarke wrote a short story about the idea decades ago. --Robert Merkel 08:12, 9 April 2006 (UTC)

Centrifugal Force

If a space station were to have a ring with people inside and it was spinning fast enough then it should create artificial gravity. So my question is if a person inside this ring where to jum up would he or she be pulled down to the spot where the jumped up from? Patrick Kreidt

Essentially, yes. You should draw a force diagram of the situation you are talking about. I think you are interested in whether the ring would 'spin' under the person while they were in the air? Sketching out a diagram will show that there are no forces that will do this in the example you mention. For great justice. 18:34, 7 April 2006 (UTC)

I don't think so. Maybe I have not thought this completely out, but here is how I see it. At the time a person jumps 'up' (and 'up' is defined as perpendicular to the surface) a person will be moving forward at a certain speed. Ignoring air friction the person will continue to move forward at the same speed the floor is moveing forward. Since the floor moves in a circle and the person does not, for the person to come down in the same place would require the floor to travel a longer distance in the same time the person requires to land. From this I conclude the person will land in a spot a little ahead of the take-off point.

Why doesn't the person move in a circle? As the ring spins, it emparts momentum to the person at an angle tengental to circle, that means they spin, with the ring, and are pushed away from the center of rotation. If the person jumps towards the center of the ring, they already have momentum emparted by the ring that will carry them 'forward' at the same rate that the ring is spinning. For great justice. 20:49, 7 April 2006 (UTC)

File:Ringgravity.jpg

OK - so take a look at the diagradm - the black arrow shows the force vector of the spinning ring. The red arrow the direction of spin, and the green arrow the arc of the jumping man. Because he has the same forward motion as the ring, the arc he describes, even if he jumps 'up', will put him back where he began. For great justice. 21:06, 7 April 2006 (UTC)

That's roughly true, but remember that the ring moves in a circle, whereas the person's initial velocity (aside from the "jumping speed") is tangential to the circle at the time of the jump. I think you land in roughly the same place, for small jumps, but getting an exact answer requires actually calculating it out. -- SCZenz 21:21, 7 April 2006 (UTC)

Er, I don't think it quite works like that. You have to remember that there's no force 'down' (outward) on the jumping man, just whatever residual momentum he carried when he left the ring.

Picture the following situation. The ring sits in the plane of this webpage, like this: → O

The ring rotates counterclockwise. The top of the ring is moving left (←) and the bottom is moving right (→).

Our hypothetical spaceman is standing on the inner surface of the rotating ring. Assume that we conduct our experiment just as he reaches the bottom of the circle. He, and the ring, are both going to be moving to the right (→) with equal speed.

The spaceman jumps. He retains the original horizontal component of his speed → and adds a modest upward component (↑), assuming he pushes off normal to the ring surface. The path he follows will then be straight along the vector sum of those two components, taking him diagonally up and to the right on our diagram until he smacks into the wall again (er, lands).

So, what happens? Let's follow the spot of ring from which our spaceman started. Its horizontal velocity will be

v_horiz(t) = v_max·cos(ω·t)

where positive velocity is to the right. In other words, its velocity is at a maximum at the bottom of the circle, and decreases as the centrifuge turns.

Our spaceman, on the other hand, retains all of his initial horizontal velocity, so he lands ahead of his starting point. TenOfAllTrades(talk) 21:21, 7 April 2006 (UTC)

Hmmm...looking at that explanation, I think I can cut it down a bit by looking at the problem in a slightly different way.

File:Ringgrav2.jpg

1. The launch point on the ring travels at constant speed along a curved path.
2. The astronaut travels at a constant speed greater than the speed of the ring surface (remember the vector addition of his jump velocity to the ring's velocity) along a straight path.
3. The two paths intersect at some point after the jump.
4. The astronaut gets there first — he followed a straight path at higher speed. Therefore, the astronaut will land at a point on the ring ahead of his departure point. TenOfAllTrades(talk) 21:26, 7 April 2006 (UTC)

So, my diagram is wrong, because the spaceman describes a straight line, not a parabola? For great justice. 21:30, 7 April 2006 (UTC)

Huh. Thanks, that'll teach people to trust anything that they read on the internet! So, why does this not work on earth, which looks like the opposite case? For great justice. 21:27, 7 April 2006 (UTC)

I think it does work on earth, but the difference is so small it can be ignored. Keep in mind, on Earth you will only be jumping maybe 3 feet, on a ball with a 4000 mile radius. I will try to explain, though. Remember that circumferance increases in direct proportion to the radius. This means the arc of a circle with 4000mi radius will be slighty shorter than the same number of degrees of arc of a circle with 4000mi+3feet radius. This means your jumper will have to move a longer distance in the same time the earth does to traverse the same arc.

How about this version? For earth, actually I think the difference is that you do describe an arc, not a line, because gravity is continually acting on you - no? For great justice. 21:34, 7 April 2006 (UTC)

The Earth case is quite a bit more complicated due to gravity, yes. Where you land (ahead or behind your starting point) depends on the size of the centrifuge and speed of rotation (note that it has to be fast enough that you don't fall off when you go over the top....) as well as the impulse you give yourself during your jump. In the special case where you jump while the centrifuge is at the bottom center (as described in my first though experiment above), you'll land ahead of your jumping off point—it comes down to the person maintaining a constant horizontal velocity while the jumping off point is losing the horizontal component of its velocity. I'm too tired to work through the consequences for anywhere else on the centrifuge right now. TenOfAllTrades(talk) 03:41, 8 April 2006 (UTC)

The easiest way to figure out the direction of these effects, and their approximate magnitude, is to pretend the Earth (or other spinning body) is actually at rest, but apply the Coriolis force. --Trovatore 16:40, 8 April 2006 (UTC)

1) There is no such thing as actually at rest.

2) The very fact that you may apply the Coriolis force to a body already implies that it's spinning.

The field of 'artifical gravitation' generated by the spinning ring must be understood as a fairly universal field of 'gravitation', at least certainly one in which the Equivalence Principle may apply, in making this question at all possible. Yet when the astronaut jumps vertically from the ring's frame of reference, the artifical gravitational field acting upon him draws slightly weaker effects due to the longer distance, but the field itself still remains fairly universal for our purposes. However, when the astronaut is jumping up, though he shall still ultimately be drawn to the ring, during his time of suspension he is no longer travelling in the direction of its spin or with its velocity. As we have settled that the field shall be considered universal for our purposes, then it follows that he shall not be drawn to the particular place from which he jumped more than any other. Thus, following the above discussion, it appears plausible that the astronaut shall land in a slightly different place from where he jumped, the exact position determined by other factors and certainly noticeable if the ring was spinning fast enough- and he had not jumped too far away!

Galileo himself actually suffered the same kind of inaccuracy due to the spinning of the Earth from his famous experiment on the Tower of Pisa, however in that case the indescrepancy was too small to mar the ultimate judgment of the experiment. Luthinya 10:38, 9 April 2006 (UTC)

Chemical structure formula in Word?

Does anyone know of any (free) application able to draw chemical structure formulas and save them into the WMF or EMF format, so that they can be inserted in for instance Microsoft Word? --Andreas Rejbrand 18:39, 7 April 2006 (UTC)

You might try ChemSketch.[4] There's a free version, but I'm not sure what file formats it can save in. ChemDraw can save in those file formats, but there aren't any free versions, as far as I know. --Ed (Edgar181) 18:47, 7 April 2006 (UTC)

Thanks; I'll have a look at it. --Andreas Rejbrand 18:49, 7 April 2006 (UTC)

Now I've tested it, and it really looks great. Thank you for informing me, Edgar181. --Andreas Rejbrand 19:12, 7 April 2006 (UTC)

Total human decomposition in Canada

A tall order, I know, but I was wondering how long it would take a human body to totally decompose in a four-season (with a "real" winter, which is to say at least one or two months below zero degrees Celsius) environment.

I've read up on decomposition and eco-cemeteries (the latter being the reason I'm interested in the question), but neither go into enough detail to really tell me how long, pillar to post, it takes before a body is entirely gone. Skeleton included.

I'm aware that there are factors like ground moisture, limestone, etc. involved, but a ballpark-by-decade would be great. 10 years? 20? 60? Thanks! --MattShepherd 20:13, 7 April 2006 (UTC)

I'm no expert but i know the location where you bury the body really matters, they've found human skeletons and even bodies still fully formed (in admitedly extreme conditions) that are hundreds of thousand of years old.

The tricky part is the skeleton, which generally requires salt-water or something rather caustic to break it down. The rest is broken down fairly easily, unless there is some extreme condition in which microbes can not exist. StuRat 07:57, 8 April 2006 (UTC)

• Skeletons can remain for ages in good conditions. Your best bet would be to contact the Body Farm in Tenessee, but you'd better explain why you want to know to them... - Mgm|^(talk) 19:40, 8 April 2006 (UTC)

what if..

if every single human being on the face of the earth decided to jump 1 foot to the right, at the exact same time would it be enough force in one direction to shift the earths orbit? tilt? tidal forces? register on a ricter scale?21:13, 7 April 2006 (UTC)

The Straight Dope answers the question for the specific case of China - seems like not much would happen. [5]. Answerbag has another demonstration of why this is bogus [6]. For great justice. 21:17, 7 April 2006 (UTC)

nah thers no way, but i mean if you do think about it, every particle in your body is exerting gravity on everything... all the time modesty 03:58, 8 April 2006 (UTC)

I think this is an example of the falacy of equivalence of large numbers. The earth is really big, and the number of people on it times their weight is really big. Therefore they are equivalent, and one will automatically effect the other. For great justice. 22:19, 8 April 2006 (UTC)

Why does DNA only replicate in the 5' - 3' direction and not vice versa?

I know this is kind of a homework question and you guys don't like that which is fair enough, but i'm revising for my degree and really have no idea why. I am generally quite interested anyway. Cheers, Mark west 80.42.104.21 22:23, 7 April 2006 (UTC)

I believe it is because the enzyme that catalyses the the replication process can only grip on the "5" end of a strain. Since it can't start at the "3" end, 3-5 replication does not happen. Note that this is from my sketchy memory of biochemistry 5 years ago. SanderJK 23:27, 7 April 2006 (UTC)

WRT homework questions, there's no problem with asking specific factual questions (like yours seems to be, though it's an area I know nothing about). What we object to is when people post an essay topic, or a physics homework problem, or the like, and expect us to do the task for them in its entirety. --Robert Merkel 00:28, 8 April 2006 (UTC)

The reason that synthesis can only occur in the 5'-3' direction is based on the reason these names exist in the first place. If you are an applicant for a degree in molecular biology or something similar, then you know that these names, 5' and 3', refer to the carbon positions in the deoxyribose backbone. Both the 3' and 5' carbons have hydroxyl (alcohol) groups attached, however, wheras the 3' carbon is part of the ring, the 5' carbon is sticking out (read: much more reactive). Therefore, when DNA is split into monomers, deoxyribose molecules with purine or pyrmidine residues, the 5' carbon loses a bond, whereas the 3' carbon is not directly affected (instead the oxygen in the hydroxl loses a bond). Now consider this, since the residue separating the 5' end of one monomer and the 3' end of the next is a phosphate, the electron in the bond between a phosphate (which is completely resonance stabilized) and the sugar monomer is much more likely to go to the phosphate. Thus the positive charge can stick on the 3' oxygen (unlikely) or the 5' carbon (very likely). So wiht all this information, we can explode a diagram of DNA: you have a sugar monomer with a + charge at the exposed 5' carbon and a stable 3' carbon with full bonds and a stable hydroxl; and a phosphate with a - charge. Thus the most likely eventuality is a deoxyribose monomer with a phosphate attached at the 5' carbon. Since the active sight on the polymerase protein is reactive to the hydroxl side, it sits on the 3' end of the DNA chain and waits fot another monomer to come by, then attaches it via the floater's 5' end. Look at this attachment form far a way, and the chain appears to be growing from the 5' to the 3' direction.Tuckerekcut 16:23, 9 April 2006 (UTC)

Awesome answer, that helped a lot, thanks Tuckerekcut.

What is the alloy grade of cast steel which used for cylinder head?

In low speed diesel engine, the cylinder head is Manufactured from cast steel. Please, I need to know the alloy grade of cast steel and the folloing properties: 1- denisty 2- specific heat 3- thermal conductivity

thank you

That's a toughie. You might have to ask a manufacturer of low-speed diesels like MTU to find out - or get a hold of a sample and take it off to the metallurgy lab. If you're interested because you want to set up in competion to them, the latter might be your only option. --Robert Merkel 00:35, 8 April 2006 (UTC)

April 8

Electrical Storms

Why do electrical storms only seem to occur in a rainstorm, but never in a snowstorm? Loomis51 00:19, 8 April 2006 (UTC)

It's possible to see lightning in a snowstorm. I saw it several times in New Hampshire. Brian G. Crawford 01:10, 8 April 2006 (UTC)

See the environmental lapse rate page. A thunderstorm derives some of its energy from air rising in an unstable atmosphere, and moisture condensing as it cools. Warmer air on the bottom can hold more moisture and is more unstable than cooler air. EricR 01:55, 8 April 2006 (UTC)

Also, does lightning strike in the sea, and if so does anything special happen compared to striking land? --Username132 (talk) 01:28, 8 April 2006 (UTC)

Lightning in a snowstorm is referred to as thundersnow, and we had it here this winter. Night Gyr 03:27, 8 April 2006 (UTC)

It depends a lot on other factors, probably - such as the location of the storm, wind currents, etc etc etc. Here in southern New Zealand, for instance, thunderstorms are almost always accompanied by hail rather than rain. And yes, lightning quite often strikes over the sea (where I live I've got a great view over the Pacific), with no obviously spectacular results. Grutness...wha? 04:37, 8 April 2006 (UTC)

Oxidizing Heavy Metals Salts

I would like to know in details about the oxidizing heavy-metal salts as this relates to corrosion of copper and copper alloys. Copper alloys resist many saline solutions, alkaline solutions, and organic chemicals. However, copper is susceptible to more rapid attack in oxidizing acids, oxidizing heavy-metal salts, sulfur, ammonia (NH3), and some sulfur and NH3 compounds.

We have a corrosion problem in one of our gas engines of Caterpillar and the service engineer identified the occurance of oxidizing heavy-metal salts on a engine part made of copper alloy.

I would appreciate your helping me out of this situation by providing details obout oxidizing heavy-metal salts.

Thanks & Regards,

Ahmed Mohiuddin Caltex Oil (Pakistan) Limited A chevron Company

The obvious answer is to replace the copper with something less reactive, like gold or platinum. Another option would be to supply a "sacrificial rod", say made out of aluminum or magnesium, which would react with the heavy metal salts in place of the copper. The rod would need to be replaced as it corrodes, of course. One option might be to place the rod in the oil reservoir. Hopefully, the oil will carry the salts to the rod before they can attack the copper. The rod could be attached to the oil cap, but must be long enough to extend down into the oil in all conditions. Water heaters often use a sacrificial rod. StuRat 07:28, 8 April 2006 (UTC)

You may be looking for the article on sacrificial anode. TenOfAllTrades(talk) 14:28, 8 April 2006 (UTC)

Adobe Photoshop Album Starter Edition 3.0

okay....im really starting to get mad at my Adobe Photoshop Album Starter Edition 3.0 because every time i go to a website any pictures that are on the site are automatically saved to it. Does anyone know how to stop it from doing this?I dont even have to look at the picture specifically...it just automatically saves it....really annoying.

Thanks for any help, Shannon 03:15, 8 April 2006 (UTC)

This is NOT a science question. Ohanian 04:46, 8 April 2006 (UTC)

No, but it's a computer question. I don't know the software, but look for a preferences tab on programs icon bar, failing that, what do you use it for? Why not uninstal it and use a free image editor like The Gimp? For great justice. 06:49, 8 April 2006 (UTC)

Ohanian, please note this text from the main ref desk page, referring to the Science desk: "To ask questions about science, medicine, computing, and technology" --LarryMac 20:17, 10 April 2006 (UTC)

okay ill do that thanks. Shannon 01:14, 9 April 2006 (UTC)

What is hafnium's cosmic history?

What is hafnium's cosmic history? I've looked everywhere I think I could find that information, but I can't seem to get any information that I need. Could you help me find the information I need, please?

What do you mean by "cosmic history"? The only thing I can think of is how it was originally formed, which it shares in common with all the heavier elements, so I don't understand why hafnium has been singled out. You may want to look at our article on nucleosynthesis for more on that. --Bth 07:12, 8 April 2006 (UTC)

Ear ringing

My ears ring when I have earplugs in, I read in the wikipedia article that theres no cure for it, but I was wondering if this was normal, and if there was anything I could do to make them stop ringing, thanks.

Flents

• I have used Flents foam ear plugs which I have learned reduce ringing more than any other type of earplug. However, after wearing earplugs for over six hours every day for some time, I noticed that the ringing sound stayed even after I took the earplugs out of my ears; this is tinnitus. I my case, it ceased after I stopped putting earplugs in my ears for a month. Try to use the earplugs only if it is necessary.Patchouli 09:44, 8 April 2006 (UTC)

The ringing you are experiencing is indeed called [tinnitus], but it is not caused by the earplugs themselves. Most likely your tinnitus is constant throughout the day, however you dont notice it because of the ubiquitous background noise of daily life. Even in the dead of night, the hum of environmental control systems and various electronics in your environment distracts your attention from the ringing sound. However, when you put in earplugs, these sounds are muffled, and the ringing sound, which has been present as a tiny, unwavering signal from your ears to your brain, becomes relatively large compared to the background noise, and you notice it. Unfortunately, tinnitus tends to get worse as we age, mostly from incremental damage to our sensitive ears. Ringing due to acute damage may fade away after a few hours or days, but the underlying chronic tinnitus described here tends to be permanent. Tuckerekcut 15:54, 9 April 2006 (UTC)

Not enough sleep...

having "black lower eyelids" (i don't know its real name) has always been frustrating to many people. i always wonder why they appear when we don't get enough sleep, and perhaps there might be some other reasons?... i would be more than grateful if you could just stop by and answer this question for me. Thx! --219.77.165.58 11:18, 8 April 2006 (UTC)

The skin around the eye (especially directly under it) is extremely thin and has a lot of blood vessels in it. While you are awake, your eyes stay open most of the time and you get a buildup of gunk (wax, dust, salt, etc...) in your eye. Tears help keep it clean, but they work best at night with your eyes closed and with plenty of REM. That buildup does two things - pushes blood vessels closer to the surface of the skin and blocks flow, making the vessels expand slightly. The more visible vessels are what you are seeing when you see shadows (and puffiness) under you eyes. --Kainaw ^(talk) 16:49, 8 April 2006 (UTC)

By the way, the more common term for this is "bags under the eyes". — Asbestos | Talk (RFC) 14:28, 10 April 2006 (UTC)

genius v.s. lunatics

many great mathematitians and well known scientist have the tendency of being nuts, but why is that? Thx :)

A simple answer to your question is that people who are capable of making brilliant new developments (in any field whether it's math, science, philosophy, etc.) tend to be people that think differently than others, that look at problems in a new way, or don't simply accept the traditional point of view. Society tends to think of people with that kind of outlook as nuts (or at least "eccentric" in polite company). --Ed (Edgar181) 11:42, 8 April 2006 (UTC)

I'm also fairly sure that the genius/lunatic thing is incorrect. In my recollection, there is no correlation between true mental illness and intelligence, but the cases in which they do correlate are generally so interesting and noteworthy that we end up letting them dominate our perception of it. --Fastfission 12:07, 8 April 2006 (UTC)

I'd agree with both statements, and would like to add the fact that from my runins with various scientists i would say that many fields tend to attract certain kind of people, and that the studying of some fields can really change your view of the world. Combined with a certain social ineptness that does seem more common among researchers then in most circles, and the relatively often portrail of autistic savant in popular media, and the fact that abnormal people (including scientists) will get more media attention in general, it is easy to understand how such a picture of scientists would become widespread. Most of all, they are just people, perhaps with a little workaholic nature engrained. SanderJK 13:00, 8 April 2006 (UTC)

My cynical hemisphere will bet it's 99% a matter of noticing. Ordinary person has mental illness-- no news. "Brilliant" mathematician (is there any other kind?) or scientist has mental illness, and everybody can feel reassured that they are better off and savor the irony of the smarter guy's misfortune. Eccentricity and poor social skills are usually distinguishable from major mental illness. (what is the dsm-iv for "nuts," anyway?) alteripse 14:56, 8 April 2006 (UTC)

In the case of a "genius", poor social skills and a constant preoccupation are what others call "mental illness". As an example, Einstein has terrible people skills. After his wife died, he became a shut-in. When in public, he either did his obligatory presentation or stayed away from the crowd, preoccupied with other things. Over and over, the genius form of antisocial behaviour has been explained as a disdain for the stupidity of humans in general. Einstein's quote, if I remember correctly, is that "Only two things are infinite, space and human stupidity. I'm not sure about the former." As for the preoccupation, they are working on problems that they find much more interesting than what to have for dinner or which politician do we want to raise our taxes next year. All in all, I see it as an adult trying to fit in with a class of preschool children. The children aren't really stupid, they are normal. The adult isn't mentally ill either. They are just focused on different things. --Kainaw ^(talk) 16:44, 8 April 2006 (UTC)

OTOH, a large part of Einsteins 'genius' status is the fact that he fit so well into the stereotype. I'd say he was a large part of defining it. By comparison, Bertrand Russell for instance, shared a similarily negative view of humanity but was quite social. Given the political activism of both, it's quite obvious that they weren't actually disinterested in humanity itself. All in all, I think the 'insane genius' myth says more about people in general than about the geniuses. First, it displays our need for 'heroes', placing some people on pedestals way above everyone else, even though they're actually just at one end of a continuum. (Einstein was a genius, but was Niels Bohr? Feynman? Gell-Mann? Weinberg? Aage Bohr? Any Nobel-prize winner? Etc) Second, it illustrates a human tendency for 'justice'. People who are very smart must somehow 'pay' for that by having diminished ability in other areas. So geniuses are anti-social. Athletes are stupid. Etc. Sure, there are lots of 'geniuses' who were single-minded and anti-social, but there are those people on any job that doesn't require those skills. And as Alteripse said, there's a big difference between eccentric behaviour and real mental illness. Another factor might be cranks - people might reason along the lines of a crackpot simply being a genius who's wrong or misunderstood. (that's certainly how they see themselves!) A lot of them do seem to have some form of personality disorder, and they also seem to have a rather homogenous set of personality traits. (dogmatism, delusions of grandeur) But those personality traits aren't the ones that make a good scientist in the real-world. --BluePlatypus 20:40, 8 April 2006 (UTC)

As a friend of mine likes to say: "The line between genius and insanity is very thin. In Mexico, we call it the Rio Grande." Grutness...wha? 01:25, 9 April 2006 (UTC)

Someone asked me once whether I suffered from being crazy. I replied that I don't suffer, I love every minute of it. Of course, that was a quote from someone so I can't say I actually made it up, but it demonstrates a distinct lack of feeling by most people towards those who are different. I would never think I suffer from being like I am (ie. a crazy scientist :-) ), but others would instantly think that because they could never like my situation that I mustn't like it myself. Ansell 01:25, 9 April 2006 (UTC)

I think your comment demonstrates a certain lack of feeling towards those who have a genuine mental disorder. Many of them do suffer, profoundly. --BluePlatypus 03:50, 9 April 2006 (UTC)

:-D I was speaking with tongue in cheek of course. Ansell 03:59, 9 April 2006 (UTC)

• Boy, I just don't know where to start with this one. What exactly do you mean by "lunacy" or madness, anyway? I think we have to be careful to distinguish between mere eccentricity and clinical psychopathology. Just because a highly intelligent, academically oriented person has no social skills and little sense of fashion does not mean they are "nuts," although the tabloids would have us believe that was the case. And not all types of madness have been deemed favorable to achievment. The "mad genius" stereotype has been around for a long time, especailly as applied to artists. The art majors on college campuses know that they can get away with all sorts of odd behavior and have it explained away as a manifestation of "artistic genius." Similarly, slovenly, asocial maths geniuses are often excused for their faux pas because such things are somehow a mark of their superiority in the intellectual heirarchy. People like Kay Redfield Jamison have written books about the correlation between bi-polar disorder and certain types of "creative genius." And the media has been playing the "Asperger / Engineer" connection for about 10 years now. Correlation is not cause, however, and it may be that the reason some of these famous "mad" geniuses have been so productive is that, in addition to having psychiatric disorders, they were highly intelligent and highly motivated. This may have enabled them to not simply "work around" their problems but to incorporate some of their supposed problems into a successful combination of skills. For example, many math and music prodigies experience synaesthesia, which gives them a unique perspective and provides an alternate path to understanding their fields. Manic episodes allow some people to work compulsively for days on end until a particular problem or project reaches a satisfactory conclusion. I seem to recall some evidence that in the bi-polar brain, some of the excess neurochemicals that build up in one portion of the brain "spill over" into adjacent areas associated with creative and other activities. And depressives have been found to have an enhance ability to recognize the true consequences of personal and political actions. I'd better stop now. This topic seems to be making me feel a bit crazy. Ande B 09:02, 9 April 2006 (UTC)

The whole problem may be solved on a point of perception. Unless you believe in absolute normality, there really is no single frame of reference from which one may judge sanity. From the scientist's point of view, it may the casual person who is mad. This lunatic behaviour was only caught on the exaggeration of the media and the apparent inpenetrability of many famous scientists/mathematicians. In many cases, misunderstanding and misinformation has always tend to crowd scientists with an air of mystery which others, in failing to understand, classifies as 'eccentricity'. The problem is that scientists are not always interested in making the general public understand themselves, and thus solve the mystery.

Then one must stress that the scientist does not necessarily have a mental illness such as schizophrenia, but his novel ways of perceiving the world, and often autistic moods, sometimes decieves the passer- by into thinking that this is so. In many cases their ways of percieving the world may even be stereotypical enough to be one step from the ideas of a lunatic, save that it is also usually supported by reasoning. The truth is scientists are not always willing to conform themselves in order to undecieve others, and our society does not always enjoy the company of those that do not follow its rules. Luthinya 10:06, 9 April 2006 (UTC)

This discussion is too lengthy to be worth reading. The title thereof implies that every Nobel Prize winner, Fields Medalist, Wolf Prize inner, Shaw Prize winner, Abel Prize winners, etc. + inventor, computer designer, corporate leaders or anyone who didn't watch soap operas, sitcoms, party, and goof off is moron.Patchouli 02:03, 10 April 2006 (UTC)

Unfortunately, this is pretty much how most of our society tends to view especially technological geniuses. Don't get me wrong- I'm often avoided as a nerd for reading maths/physics books all the way through lunchtimes in my high school. Luthinya 10:29, 10 April 2006 (UTC)

dynamic programming

how to implement dynamic programming using 'c' language — Preceding unsigned comment added by 59.92.34.98 (talk • contribs)

Our article on dynamic programming is quite general; the ideas should be readily applicable to C. --Bth 14:27, 8 April 2006 (UTC)

C# Adding Machine

Please can someone give me the code required to make an adding machine in Microsoft Visual Studio C sharp 2005 express edition? Computerjoe's talk 12:53, 8 April 2006 (UTC)

sounds like a homework question. have you tried asking your classmates? Night Gyr 19:18, 8 April 2006 (UTC)

No, it's not a homework question. I'm a good faith editor, and I know this isn't the place to get h/w done. I'm learning C# by myself, and have made an adding machine before; but forgot the code. Computerjoe's talk 21:06, 8 April 2006 (UTC)

Then it should be easier for you to write it the second time. Bubba73 (talk), 01:47, 10 April 2006 (UTC)

wouldn't it just be a matter of creating code for each button, so pushing a key puts a number-symbol onto the end of a string, then when an operation key is pushed the string is converted to a number and the specified operation is performed? it doesn't seem to hard to write if you know how to create button controls. I know java and C/C++, not C#, though, so microsoft may be pulling something different. Night Gyr 05:56, 9 April 2006 (UTC)

Yep. I need to know the code to transform e.g. TextBox1 and TextBox2 into a string. This has float.Parse in I think. Computerjoe's talk 09:02, 9 April 2006 (UTC)

Er, turning the contents of a text box into a string? Should already be a string if it's in a text box. If you're really emulating a calculator (with graphical buttons to provide digits, particularly), you shouldn't be doing any string-parsing anyway. (Just handle the input yourself, forming $10x+d$ or $x+d\times 10^{-n}$ in response to a digit $d$.) Then format floating-point numbers for output only, retaining the number for further computation. In other words, you want to do as few data-conversions as possible. (You also want to be using double precision, probably.) --Tardis 14:58, 10 April 2006 (UTC)

Poincare's radiation paradoxes

Hey folks! I was just reading Olivier Darrigol's paper from the journal Isis on the Einstein-Poincare priority dispute, and I came across the phrase "radiation paradoxes" as an item of importance. What are these radiation paradoxes? I'm a layman, so I was hoping someone could explain it in ordinary english. Thanks in advance! 65.95.139.89 18:49, 8 April 2006 (UTC)

The very short version is that if you try to work out the equations of electromagnetism -- particularly for the propagation of electromagnetic radiation (ie light) -- for different observers travelling at different speeds, but use Galilean relativity (that is, the intuitive idea that the speed of an object moving at $\mathbf {v_{obj}}$ according to one observer is $\mathbf {v_{obj}} +\mathbf {v_{obs}}$ according to another observer in whose reference frame the first observer is moving at $\mathbf {v_{obs}}$) you will get different answers for different observers -- hence "radiation paradoxes". Postulating an invariant speed of light fixes this, but forces you to use a more complicated equation for relative speeds (albeit one that is very close to the Galilean one at low speeds). --Bth 19:26, 8 April 2006 (UTC)

Diseases

How many diseases affect the man most and the woman most? — Preceding unsigned comment added by 70.53.95.183 (talk • contribs)

Red/Green Colorblindness is overwhelmingly male, since it is caused by a recessive gene on the X chromosome, of which women have 2 but man have 1 (They have XY instead of XX). 21:14, 8 April 2006 (UTC)

I'm not sure how to answer this question. Men, for example, are incapable of contracting cervical cancer. And with regards to "how many", you can't really say "six" as an answer. Could you rephrase? Isopropyl

Isopropyl is right; for more examples, see also Sex and illness. Melchoir 22:40, 8 April 2006 (UTC)

Thousands of diseases affect people of different sexes differently statistically for thousands of known and unknown reasons. In other words, it may be more unusual for a disease to have exactly the same sex distribution of the population than to have at least a small sexual association. alteripse 02:07, 10 April 2006 (UTC)

Data compression?

I was wondering, are there any lossy text compression algorithms? he he... it would be a bit like censorship if you think about it.--Frenchman113 21:12, 8 April 2006 (UTC)

Ys, thr prbbl r sm lss txt cmprssn lgrthms. --GraemeL ^(talk) 21:16, 8 April 2006 (UTC)

Pitman shorthand is another one. Four candles, anyone? --Heron 21:31, 8 April 2006 (UTC)

A lossy text compression system wouldn't be very much use, but if you wanted to play, you could run text through an mp3 or jpg compression system, and see what came out - the results would probably show you why there really isn't one in the sense you mean it. For great justice. 22:04, 8 April 2006 (UTC)

you could use abbrev. to repr. words. They lose some data (i.e. gain ambiguity) but as long as context makes up for it, you can save space at min. qual. loss--same prin. as other lossy algos. Night Gyr 06:01, 9 April 2006 (UTC)

• If you have Linux, rm * gives 100% compression. -- Filliam H Muffman 03:55, 11 April 2006 (UTC)
• Another linux option... cat file | tr -d ' ' whichwilleffectivelycutoutallthespaces.thiswillgiveyoumaybea10%sizereduction,butyoucouldprobablystillmakeoutthetextright?

--Jmeden2000 15:17, 12 April 2006 (UTC)

Another question

Hate to be a nuisance, but how can I force WMP to save video that's being streamed from the web? I'm totally missing something here...--Frenchman113 22:31, 8 April 2006 (UTC)

Try asfrecorder, http://sourceforge.net/projects/asfrecorder/ 202.58.62.4 00:27, 9 April 2006 (UTC)

Projectile, Missile, and Rocket

What is the difference among these?Patchouli 23:15, 8 April 2006 (UTC)

A projectile is any object launched into the air by any given power source (includes asteroids, arrows, cannoballs, meteors, etc). A missile is a projectile launched by a human (in the modern sense, usually an explosive-bearing rocket). A rocket is a device powered by Newton's third law of motion (exhaust=action, rocket movement=reaction). Hope that helps.--Frenchman113 00:02, 9 April 2006 (UTC)

In a general sense, a missile is a general term encompassing all human-launched projectiles, including stones flung from slings and shells from battleship cannons, but in a modern military context, it's the subset of rockets that have their own guidance systems, i.e. guided missiles. Night Gyr 06:04, 9 April 2006 (UTC)

Thank you.Patchouli 10:58, 9 April 2006 (UTC)

Many people disambiguate rocket and, say, jet engines, by the idea that rockets carry their own fuel and reaction mass. -Fangz

April 9

latex in xfig diagrams

I'm trying to make a diagram in xfig which includes some LaTeX formatted text. I'm following the instructions here.

Here's what I do:

1. draw my diagram
2. make a text box with text "$\int f(x)\, dx$"
3. set the "special" flag to "special" of the text box
4. choose export, then select "combined PDF/Latex both parts", then export, resulting in two files intbox_t and intbox
5. change the filename of intbox to intbox.pdf; my system won't work without the extension
6. change the line "\includegraphics{intbox}%" to "\includegraphics{intbox.pdf}%", so account for the change in filename above
7. in my tex source file, I include the header "\usepackage{graphicx}"
8. I input the file with "\input intbox3.pdftex_t"
9. then I tell latex to do its work. It seems to find the file and import the pdf, but then it barfs with:

loading : Context Support Macros / PDF (2004.03.26)
) (./intbox3.pdftex_t <intbox3.pdf, id=1, 258.9675pt x 177.66376pt>
<use intbox3.pdf>
! Undefined control sequence.
\color ...vevmode \csname fi\endcsname }\@ldc@l@r 
                                                  
l.14 }}}}
         
? 

I'm using an OSX system, using TeXshop frontend to pdflatex.

I'm a hair away from giving up. This is for a wikipedia article, so if you can straighten this out for me, you're helping grow an article. -lethe ^{talk +} 00:23, 9 April 2006 (UTC)

Are you using \input{intbox3.pdftex_t}? If you want to email me the sources I could have a look. I use TeTeX under Linux but it doesn't seem to be an operating system problem. Ansell 00:54, 9 April 2006 (UTC)

OK, I've sent an email. Thanks for taking a look. -lethe ^{talk +} 17:55, 9 April 2006 (UTC)

Another solution is to export the xfig doc in "LaTeX picture + epic macros" (or "eepic macros" if you need them). Then you have to \usepackage{epic} (or eepic), but everything is in LaTeX format from the start. So for the text you just put placeholders in the xfig doc, and then go into the exported source and hack the text in by hand. The biggest downside is that if you need eepic, it won't work with PDFLaTeX and you'll have to do the two-step process to get a pdf file, which may not have hyperlinks. --Trovatore 18:47, 9 April 2006 (UTC)

LASIK and losing vision

I overheard someone saying that you lose part of your vision or something like that when you have LASIK surgery, is this true?

Our article on LASIK might be helpful to you, in particular the Complications section. -- Daverocks (talk) 02:53, 9 April 2006 (UTC)

BMW Bluetooth

I have a BMW with bluetooth, and I had the code but I lost it. BMW says they dont have it and want $120 to retreive it from my car, is there any other way to get it? I used to use a motorola v600 and the code is in the phone, I just cant retreive it (I dont know how), how can I get the code?

Fortune cookie say: He who can afford BMW, can afford to get it fixed. --Zeizmic 15:19, 9 April 2006 (UTC)

Heh. But anyway, if you can get the code without paying, then so can anybody else. OMG CAR HAX!!!!1 Tzarius 09:40, 10 April 2006 (UTC)

Cloning

Is it possible at this time to produce a clone of someone?

I think so, yes. According to the article on human cloning, ACT was the first to sucessfully clone a human embryo. There are many claims of success beyond the embryo stage, but none of them have been verified. --Bowlhover 04:54, 9 April 2006 (UTC)

No, not quite, but we are getting close. Part of the problem lies in defining "clone" in a consistent way, and the media has failed to do this. But I assume you mean "Is it possible to make a human being who would have the exact DNA as another." In a somewhat trivial sense, the answer to that is yes. We have long had the ability to perform artificial insemination in a culture dish. And one of the most frequent reasons to do this is to avoid conceiving children with an inheritable disease. By removing a single cell from the early zygote, and allowing that cell to grow for a while before (destructively) analyzing its DNA, we have created a clone of the original zygote. Many such clones can be made from these early embryonic cells and each of them has the potential of growing into a healthy human who would have DNA identical to the other humans who were derived from that same original zygote. But making a human clone from an adult does not yet seem possible with current techniques and understanding. Just convincing the early cell to make the initial divisions has been problematic. Developmental biology is not a simple field. In fact, it's in its infancy. Until we understand the numerous developmental hurdles and chemical cascades that determine human development, we wont be able to undertake this task without high risk. Once we do reach that stage of technological capability, the entire process will likely seem so incredibly obvious we'll be baffled at why it took us so long. Ande B 09:18, 9 April 2006 (UTC)

Yes, but I have a feeling that it's going to take us a very long time to reach that stage, certainly much longer than needed. The world's most advanced nation, the U.S., has prohibited federal funding for human cloning research. Some U.S. states have even banned all forms of human cloning. Religion got into the way of scientific research, just as it did in the past. --Bowlhover 17:35, 9 April 2006 (UTC)

The world's most advanced nation, the U.S.

(much coughing and spluttering and muttering about damn Yankees) ;) — QuantumEleven | (talk) 09:31, 10 April 2006 (UTC)

How accurate are the Heavens Above predictions?

In terms of time, how accurate are the Iridium flare predictions? I know my latitude, longitude, and elevation to within 30 m, so the errors in my position shouldn't affect the results too much.

I'm curious about this because I plan on photographing tomorrow night's magnitude -2 flare, using a 15-second exposure time. I'm going to use an accurate clock to tell me when to press the shutter button--there needs to be 7.5 seconds of exposure before maximum brightness, and 7.5 seconds after. --Bowlhover 04:42, 9 April 2006 (UTC)

I successfully photographed the iridium flare whose maximum brightness was at 21:17:08 (according to the Heavens Above prediction). Here is the 4.1-megabyte photograph--the flare is the streak of light in Cepheus, and to the left of the photo is Cassiopeia. I pressed the shutter button at 21:17:00, so the shutter opened at 21:17:02 due to the 2-second self-timer. It closed at 21:17:17. As you can see from the photograph, the flare was already very near its maximum brightness when the shutter opened. So the prediction was off by about 5 seconds. --Bowlhover 02:22, 10 April 2006 (UTC)

Nice work! Ande B 21:14, 11 April 2006 (UTC)

Tinted CD-Rs

I saw and purchased some tinted CD-Rs yesterday in Taipei. The writing surface of these discs is in bright orange or bright green (they are colored like highlighter marker pens) and they cost NTD6 each (less than US$0.20 cheap). Do they employ newer dyes? Or are they just ordinary CD-Rs with tinted polycarbonate plastics? -- Toytoy 07:15, 9 April 2006 (UTC)

I actually just saw one of those the other day for the first time. As you guessed, it's just tinted polycarbonate. Chapuisat 15:08, 11 April 2006 (UTC)

Open University Recommendation

Can anyone help in recommending a free Open University that allows under- 18 pupils to enjoy the studies of Mathematical Modelling and Theoretical Physics? I shall be deeply grateful for any suggestions. Luthinya 10:10, 9 April 2006 (UTC)

If you want an Open University, you're probably in the UK, but MIT has a lovely site over at OpenCourseWare, where lecture notes and readings and other materials are posted. Isopropyl 15:38, 9 April 2006 (UTC)

Angular Momentum

In a book I have read recently concerning the spin of subatomic particles, I have heard Max Born say that though particles do not actually have spin in the usualy sense of the word, yet they still behave as if they have angular momentum. I am afraid I have not been able to decipher this remark, and shall be grateful if anyone may help in understanding it. Luthinya 10:15, 9 April 2006 (UTC)

Subatomic particles do have angular momentum. They can rotate about a linear axis in three dimensions, with such rotation obeying conservation of momentum, affecting collisions (although not always the same as for molecules and solids; baryons and fermions are very different in this respect because of their different properties) and wobbling with gyroscopic effects including when rotation interacts with field effects such as electromagnitism. Particles also have quantum spin which is a quantum number which is completely disjoint from angular momentum. "Spin" was named after experiments with polarization suggested that the quantum number was similar to angular momentum. As a quantum number, spin has conservation laws based strictly on small or simple fractional multiples of integers. Note that the angular momentum of a low-mass electron is unlikely to ever have much of an affect on its behavior when compared to electrostatic forces. For nuclons, though, angualr momentum can be very significant. See, for example, Cold fusion#Current understanding of nuclear processes. --James S. 11:30, 9 April 2006 (UTC) This is a bad explanation for several reasons. Please see Spin (physics), Spin quantum number, and Angular momentum. --James S. 13:15, 9 April 2006 (UTC)

• Ok, well.. There are a lot of levels of explaination that could be given here. The simplest, most common one is to describe spin as 'intrinsic angular momentum'. That is, an amount of angular momentum that is built-in to the particle, so to speak. So spin does work 'as if they have angular momentum', but it's a different property. (they can, however, interact. (Spin-orbit coupling) --BluePlatypus 01:49, 10 April 2006 (UTC)

Sheep

Can a human physically make a sheep pregnant by sexual intercourse?

No, in general, different species can not interbreed. (But he can try.) --James S. 11:17, 9 April 2006 (UTC)

But, but I can make it happen. It's actually doable.

Give me some sexually matured male sheep and female sheep. I can physically force the female ones to pregnant. In fact, they may just go pregnant with or without my efforts. -- Toytoy 14:30, 9 April 2006 (UTC)

See Hybrid and Horizontal gene transfer and HeLa (a single cell species created by humans from a human) for interesting examples of what is possible, and Category:Mythological hybrids for what people used to think was possible. WAS 4.250 14:44, 9 April 2006 (UTC)

Chimera (genetics) is also an interesting read. Isopropyl 15:36, 9 April 2006 (UTC)

Do I detect a sense of urgency in this question? I hope not. Phileas 06:19, 10 April 2006 (UTC)

astronomy - colour correction

In colour images taken of the night sky, do astronomers ever attempt to correct the colours to allow for redshift? Obviously this would be tedious, difficult and probably impossible where the redshift of objects is not known. However for something as large as the Orion Nebula, is this ever done? --Paul venter 14:34, 9 April 2006 (UTC)

• The Orion Nebula is in our own galaxy, and therefore can be expected to have a negligible redshift. In general, quite a bit of processing is done on most astronomical images, and correcting for redshift would be relatively easy. See this link for information about how the Hubble Space Telescope does it. In any case, computing an object's redshift is relatively easy; if you have a spectrograph, you're most of the way there. -- Filliam H Muffman 03:14, 10 April 2006 (UTC)

You don't even need (expensive and time-consuming) spectroscopy; if you have good photometry at multiple wavelengths you can get a reasonable estimate from photometric redshifts. (We should have an article on them; maybe I'll add it to my to do list.) --Bth 07:17, 10 April 2006 (UTC)

Can we defeat radiocarbon dating?

Can we defeat radiocarbon dating? I think it is very possible.

• Build a totally enclosed greenhouse similar to the Biosphere 2 (with positive pressure).
• Buy lots of coal.
• Grow Cyperus papyrus in the greenhouse using hydroponics equipments.
• Burn the coal to provide ¹²C-rich CO₂.
• If you need other organic fertilizers, grow alfalfa at first and use it as the fertilizer.
• Make your papyrus with your ¹⁴C-poor Cyperus papyrus.
• Let an expert create the forgery.
• Hire an antique dealer to inform scholars.
• Let them see the v1.0 fake which may not be good enough.
• Let the antique dealer to ruin the deal.
• Let the forged item sit in a bank safe for years.
• Take your time to create and age your v2.0 fake to the desired status of corruption.
• Let the scholars buy it.

I think you can always find cheap and aboundant materials that are not polluted by post-WW II radioactive fallout (e.g. antartic ice to provide water). Scientists can only conduct destructive tests on unwritten parts of the speciment. I guess you don't even need to make ¹⁴C-poor ink. I think it is possible to make something to defeat ¹²C and most other scientific dating techniques. You can mass-produce multiple copies of the forged document (each created and aged a little differently) and test them with all the tools available. The copy that can fool all tests will be released to the scholars. Maybe you can breed your own "ancient" Cyperus using DNA fragments extracted from real antiques. - Toytoy 16:09, 9 April 2006 (UTC)

I like it! Seems like it would be possible, but with your method the forgery would be just as old as the coal you bought (by C-14 dating). I'd add another step about regulating the C-14 concentration by adding outside CO2 to get just the right date you want for your papyrus to have died. -Snpoj

Yes, you're right. I'll build a window. It's easy to regulate the amount of ¹⁴C. You can build a window or buy some charcoal. You may also want to filter your coal burner because unfiltered smoke may contain too much sulfur. Anyway, I think it is very possible to cheat scientists. All you need is a great expert of ancient literature. You can open the window and harvest your Cyperus every 12 hours. Sooner or later, you'll get a batch of Cyperus that's dated to the desired time period. These grasses are growing fast! Maybe you can sell the unused but dated portions to other law breakers! :) -- Toytoy 16:37, 9 April 2006 (UTC)

But why fool scientists now if you can fool them thousands of years in the future? Why rewrite the past when you rewrite the future!? Using a mass spectrometer, isolate C-14, burn it and infuse it into the atmosphere of the dome. Now when the papyrus dies it will have a healthy stock of C-14 with which to pass the time. Eventually, in the year xxxx so much C-14 will have degraded as to appear that our Cyperus died just last year in xxxx-1! Now in the year yyyy documents written by us on the Cyperus back in 2006 will be found. The unsuspecting scientists will believe they must rewrite the history of xxxx with our falsification and we'll be laughing in our forgotten graves! -Snpoj 03:48, 10 April 2006 (UTC)

I don't think anyone claimed it to be impossible, either. But you leave out the problems with aging. There are no doubt chemical markers (e.g. various decomposition products) which can be used to distingush something which has aged normally and something which has been bleached or similar. Then there are of course all the other usual methods of detecting a forgery. I don't think radiocarbon dating is terribly important for dating documents either - from what I understand from reading bibliophile literature, old paper is in relatively good supply. --BluePlatypus 18:00, 9 April 2006 (UTC)

Unfortunately the problem you have is that C-14 is created from C-12 by solar raditation.

http://www.ndt-ed.org/EducationResources/CommunityCollege/Radiography/Physics/carbondating.htm Thus the ration of C-14 in your papyrus would still have the correct C-14. Now add to the fact that your Ancient language experts are few and far between. Most of them are scholars, and they all know each other. -Tollwutig 14:56, 10 April 2006 (UTC)

If you build a greenhouse at near sea level, and you burn fresh coal to produce fresh ¹⁴C-poor CO₂, solar radiation can do nothing. To create ¹⁴C, you need high energy cosmic ray that's only available very very high above.

You can always obtain genuine unused ancient papyrus or Chinese paper from antique dealers. In fact, many high-end Chinese art counterfeiter have their personal stockpiles of unused paper aged for at least a couple hundred years. However, if you have an endless supply of ¹⁴C-poor papyrus, you can mass-manufacture history-making documents and age them by a trial and error approach. If you take time and money to do it, you will have some really great speciments in a few decades that can fool almost everyone on Earth.

This method is surely difficult. An ordinary counterfeiter will not do it, but a determined government or religious group may have the will, expertise, time and resources to create something to support its own position (we own this land, we are better than you, our god was ...). -- Toytoy 15:41, 10 April 2006 (UTC)

• I have an even better idea, I could just use my time mahcine to go back to 1192, and drop off a reem of printer paper in an easy to find location, then travel back to the future, and pick it up there after it's had a few thousand years to age, then write whatever the heck i want to on it — Preceding unsigned comment added by 64.12.116.74 (talk • contribs)

With your specifics I take you are discussing the recent Gospel of Judas release by National Geographic? If so you'll have a hard time finding someone who knows Coptic, there are what 5 people who can readily translate it?--Tollwutig 19:50, 10 April 2006 (UTC)

You're damn right. I am very skeptical to the NG's Gospel of Judas TV show. I think it is difficult to create such a scholar bait but that's not totally impossible. In my opinion, NG failed miserably by creating a two-hour-long show that does not interview reasonable skeptics. I mean they jump to the conclusion too soon or they want the audience to buy the theory that the Passion could be simply wrong.

Logically, you may also say the Gnostics had build a myth to counter other Christian sects or you may even say both sides lied when they talked about the death of Jesus. NG failed to present a more neutral POV with their dog and pony show. It didn't even say Jesus could turn himself to the Romans rather than asking Judas to betray him. The NG is telling a lousy detective story.

As to the "only five people on Earth could write ancient Coptics" statement, I really cannot disprove it. However, I am very skeptical. Let's say the text was created by a counterfeiter. If you put it down in ancient Greek, the expert pool will be much more larger and there will be more skeptical eyes to review your text. And by the way, I don't think ancient Coptics is some sort of regulated language. You don't need a license to learn it. You just don't see many college job offers. A determined person previously trained in related languages may learn the language from various sources. Logically, you may also say some Evil Theologist discovered a Medieval Coptic text that tells such a story. He hired an Evil Linguist and an Evil Scientist to rewrite the text to match 3rd century grammer and put it on a piece of 3rd century papyrus to make the text closer to truth. Did I ever mention the Black Helicopter?

Personally, I have only seen statements such as: GoJ said Judas was not a bad guy. The existence of the GoJ was proven by ... . I did not see them to advertise other previously unknown findings from the GoJ. If you unearth a document like this, I expect to learn some unknown things that are trivial in scope such as "The Apostle Peter had ulcer." or things like this. I don't think all genuine documents shall carry such information, but a forger may invent a story with all known facts and insert just one think to prove his point. After all, I think NG failed to take a more neutral stand in this case. It only took me minutes to devise a way to counter ¹⁴C dating. To a determined expert with money to burn, it could be even easier. The NG shall be more careful and skeptical with their discovery. -- Toytoy 00:31, 11 April 2006 (UTC)

• Frankly, you seem to have a little bit of a chip on your shoulder about this, Toytoy. If it makes you feel any better, just because the document is authentic doesn't mean you have to believe what it says. Why not just say "this is what the Cainites believed but they were full of crap", instead of camping out on the grassy knoll? --Trovatore 00:46, 11 April 2006 (UTC)

I believe some questions can never be fully answered even if we travel back in time with all kinds of evidence collection tricks and tools. If we cannot fully answer today's questions, how can we be so sure about yesterday's unsolved mysteries?

However, I think some scholars are extremely gullible. I have first hand experience with an easily debunkable pre-Columbus historical discovery. Some scholars, I mean some of them, are just too eager to believe.

Based on what I have seen, I believe the QC Dept. of the National Geography Society failed to do their job. Instead of showing us non-experts a less loaded version of the story, they made the show as if it was almost the truth. It didn't answer some trivial questions. I think it is natural for some earlier sects to pro Judas and some others to bash Judas. A skeptic may require more solid evidence before jumping on the band wagon. Too willingly to accept can lead to miserable mistakes. Do I have to make up a text that says "All apostles other than Judas betrayed Jesus. They took the money and framed Judas"? If you're willing to believe, someone somewhere may be willing to cook you some tasty truth.

If the text was genuine, it would be more insightful to study the societal structure of the writers rather than to ship us another version of the truth. I mean the original Gospels were created by the 1st generation followers. By the time the stories travelled to Egypt, it must had been modified a little bit here and there to please local Christians. It's like making locally adapted versions of Hamlet for 17th century Japanese or 18th century Persian viewers. -- Toytoy 07:02, 11 April 2006 (UTC)

Popular presentations of academic subjects, particularly on TV, tend to be slanted towards providing some sort of "narrative" (often, as in this case, "everything you thought you knew is (probably) wrong", though "person X's wild speculation is vindicated centuries later because it happens to sound a bit like what we now understand" is also popular), and have been for decades now. All that's happened is that you've seen one that touched on a subject that you have some knowledge of, or at least strong feelings about. Almost every show like this makes people who know the field feel the way you do right now. You should probably bear that in mind next time you watch one.

On the other hand, I'm fairly sure I was aware of these ideas about Judas having been around in some of the now-extinct branches of Christianity well before this flap, so I'm not sure there isn't something in it. --Bth 07:20, 11 April 2006 (UTC)

Inductance

How to make 1 henery inductance coil?

Did you check induction coil? I don't know what a Henry or Henery induction coil is. -- Mac Davis] ⌇☢ ญƛ. 12:46, 10 April 2006 (UTC)

The henry is the SI unit of inductance. --Bth 13:25, 10 April 2006 (UTC)

Here's a site which discusses design and construction of coils. EricR 14:02, 10 April 2006 (UTC)

Self of Solenoid

L= (m0mr S N*N) / l An above Equation can use to calculate a self of a coil with the defined length and l>> D( D : is a diameter of the coil, S: Surface of coil ; S= (1/4)*4*3.14 D*D) m0= 4*3.14*10-7 ( here mr=1, a core is air ) Supposed: S=4cm2 = 4*10-4 m2 N= number of turn ( round) l= length of coil= 10cm=0.1 m For L =1 H , we must have N= 4461 rounds --User:Ngocthuan 06 18:25, 10 April 2006 (UTC)

electrical potential of the sun

My question is based on the following, which is from "Beyond Velikovsky", by Henry Bauer, page 59. He says that Velikovsky attributed some things to electromagnetic forces between astronomical bodies. In particular, in 1952 astronomer Donald Menzel calculated that the potential of the sun would have to be 10^19 volts to account for some of Velikovsky's claims (also in Worlds in Collision), which Menzel said is impossible. In 1960 physicist V. A. Bailey (unaware of Velikovsky's work and Menzel's calculations) proposed a theory that had (as a consequence) a potential of 10^19 volts for the sun. Bailey found a mathematical error in Menzel's calculations.

I have two questions: (1) what became of Bailey's theory? (2) What is the electrical potential of the sun (if it is known)? Bubba73 (talk), 01:42, 10 April 2006 (UTC)

Take a look at Electric Universe. ☢ Ҡi∊ff⌇↯ 02:10, 10 April 2006 (UTC)

I can't find any mention of Bailey's theory there, or the Sun's potential. Is Bailey's theory part of the Electric Universe theory? Bubba73 (talk), 02:18, 10 April 2006 (UTC)

"[The "electric star" model proposed by Ralph Juergens in 1970s (in Pensee II, IX & X, SIS Review, & Kronos) and revived by Wallace Thornhill in The Electric Universe (1998), part of his "holoscience" project, (in which the Sun is a non-convecting, isothermal ball of plasma powered by infalling galactic electrons and many craters in the Solar System are the result of gigantic electric discharges, etc.) [as deus ex machina] cannot rescue the "polar configuration" from its fatal flaws because the model is a non-starter. It is disproved by practically everything known about the actual behavior of the Sun and heliosphere. This was first explained by this writer in Kronos X:3, 1985, pp. 15-23, and recently in more depth on e-mail list-serves by Robert Grumbine, Karl Hahn, Burch Seymour, Tim Thompson, and Wayne Throop. Thornhill either ignores or dismisses all the negative evidence such as (i) the absence of x-rays in coronal holes (which should be produced by infalling electrons for which no evidence exists beyond the wishful thinking of Thornhill and star-struck acolytes such as Amy & Mel Acheson writing for Thoth and Atlantis Rising, and Don Scott, an electrical engineer, who in parroting Ralph Juergens in Kronos IV:4, 1979, also fails to understand the importance of the Reynolds Number in defining turbulence in photospheric granulation.), (ii) the proof that granulation in the Sun's photosphere is an expression of convection, (iii) the mere existence of the solar wind in which no inflowing electrons have been detected, (iv) the absence of characteristic particles from the nuclear fusion claimed to occur in the photosphere, etc., etc. The model lacks rigorous mathematical support. No one has ever shown that the electric charge required to produce the cited craters, e.g., Aristarchus on the Moon, is feasible, while rigorous mathematical modelling to explain the high temperature in the Sun's corona, a favorite anomaly cited against standard theory, in conventional terms is progressing steadily. The simplistic analogies to plasma and electrical discharge phenomena that are invoked to support the model [as in Talbott & Thornhill's Thunderbolts of the Gods (2002)] cannot nullify the verdict of the overwhelming negative evidence and serve only as an example of invincible ignorance, showing the proponents do not know, for example, the difference between a plasmoid and a pair of opposed lotus blossoms used by the Greeks to represent the thunderbolt held by Zeus. Other examples of so-called electric discharge effects on planets, asteroids, and satellites (such as Europa) can be explained by conventional means without invoking cosmic electricity.]" from AN ANTIDOTE TO VELIKOVSKIAN DELUSIONS WAS 4.250 12:46, 10 April 2006 (UTC)

http://www.asap.unimelb.edu.au/bsparcs/physics/P000031p.htm doesn't seem to identify this theory with BAILEY, Victor Albert although it seems to be a list of all his papers. WAS 4.250 12:46, 10 April 2006 (UTC)

This page of notes for a Velikovskyite essay references a Nature paper by Bailey from 1960 which isn't on that list: vol 186, p508. Not in any online archives that I can see, annoyingly. But it's probably the paper in question here, if anyone can get to a good library. --Bth 13:16, 10 April 2006 (UTC)

Science. RF Power Measurement.

Dear Sir/Madam,

I wish to know in detail the method of RF power measurement in different modes such as a. Timeslot Mode b. Continuous Average Mode c. Buffered Continuous Average Mode d. Burst Mode & e. Scope Mode

Kindly help.

Regards Pavan

Our article on Radio frequency might be of interest to you, as well as this page about measuring RF power. -- Daverocks (talk) 09:02, 11 April 2006 (UTC)

Website Hosting

Is it possible to host your own website on your own computer? Would this require a fixed IP address? Is it possible to demand a fixed IP address from your ISP? --Username132 (talk) 05:22, 10 April 2006 (UTC)

To answer my own questions, yes it is possible and a fixed IP is not necessarily necessary. http://www.no-ip.com for example, offers ways around dynamic IPs, although I don't really understand how it works (anyone else?). Some ISPs offer a fixed IP as standard or for an extra fee, or even not at all, but some users report that they have had the same IP for up to two years even with switching equipment on and off multiple times. What is it that dictates when a persons IP is changed?

Would an admin on this website be able to compare the IPs used to make my first ever edit and this edit I'm typing now, for me? There may be other IPs inbetween due to editting done at university accomodation. Thanks :) --Username132 (talk) 06:31, 10 April 2006 (UTC)

I've used http://www.dyndns.org which gave me a domain name that I could attach to my (current) IP. I also had a program running on my computer that constantly updated the information about my current IP to dyndns, keeping the domain name attached to my computer. I would assume no-ip works like this, too. My current hardware firewall is also capable of updating its IP to dyndns by itself. –Mysid 06:40, 10 April 2006 (UTC)

Thanks. I have the option of

a) hosting through the WinXP machine my mum uses; or

b) hosting through a Proliant 3000 server with Fedora Core 4 installed which would then have to relay internet access to mum's computer as required.

Is setting up a web server difficult? I'd like to be able to receive email to my domain name aswell. --Username132 (talk) 07:24, 10 April 2006 (UTC)

Setting up a web server is not trivial - especially as you want to configure it so that it's secure against attacks - but with a bit of knowledge and lots of reading of help documents, it should be doable. Check out Apache HTTP Server, the most popular (and free!) webserver available. If you want to receive e-mail through your domain, you need to also run (at the same time) an e-mail server on your computer.

A more general note - is there a reason why you want to set up your own server? There are plenty of hosting sites which offer you ample web space, already set up, for a modest monthly fee - most of these have e-mail facilities, too. Obviously, it's up to you, I'm just wondering if you're not going to more hassle than you need to. Also, you need to make sure your server is on 24/7, and that your internet connection can handle the outgoing traffic. For instance, an ADSL connection can only handle very limited outgoing traffic, you can easily saturate your link if you are serving large files or many users. Just something to think about. — QuantumEleven | (talk) 09:28, 10 April 2006 (UTC)

Admins can't see your IP, only developers and those with checkuser access can. If you want to see what your public IP is, go to DNSstuff.com. -- Finlay McWalter | Talk 14:39, 10 April 2006 (UTC)

I see. I wanted to know what my IP was a few months ago and I don't think there's anyway to do that except contact a forum where I posted. I'll try somewhere else. --Username132 (talk) 16:42, 10 April 2006 (UTC)

To see your IP address as the Wikipedia servers see it, click here and wait ten seconds. Note that this logs you out of Wikipedia, so you'll have to log back in afterwards. —Ilmari Karonen (talk) 12:14, 11 April 2006 (UTC)

Some questions about C programming.

Well here are some of my doubts about some basic concepts of C programming. I have divided them in different queries.

QUERY 1)

---

i have two programs prg1 and prg2 as follows

//prg1 main() { int i,j,k; }

//prg2 main() { int i; }

First i compile (not run) prg1, then i compile prg2. Now, after the compilation of prg2 is over, what happens to the space which was reserved by variables like j and k? As we have not used memory allocation functions, does that memory get freed on its own?

If you don't run either of these programs, the memory used by them isn't relevant. The compiler certainly allocated some memory to deal with your source code, and probably had the names "i", "j", and "k" written down somewhere (except not "j" and "k" for prg2, of course!). But once you've compiled them, the compiler has exited and all that memory has been long since released to the operating system. --Tardis 18:30, 10 April 2006 (UTC)

A second question about this same query, in any of the above programs, when i would print the values of any variable i,j or k, a random or garbage value would be printed. But wat is the basis of that random value? I mean some logic would have been built up in the writing of the code for the functions like rand() srand(), etc. So wats the logic there and also here?

Garbage values and random values are totally different. Random numbers are supposed to be evenly distributed and to have no pattern. Garbage probably will have a pattern, but not a dependable or useful one because it's just what happened to be left over from the last program to use that memory. —Keenan Pepper 16:46, 10 April 2006 (UTC)

Variable declarations in C literally assign a name to a chunk of memory. That physical memory already existed (as in silicon), and had something stored in it: possibly all 0s, or maybe the hex pattern 0xDEADBEEF, or part of the Wikipedia logo. The point is, you have no control over it, so you shouldn't assume anything about it. --Tardis 18:30, 10 April 2006 (UTC)

QUERY 2)

---

Now this one is about arrays. consider the following statement,

int a[x]; //x is a valid no., i.e non-negative, etc. etc.

now wat is the limit of "x", wat is the maximum value of "x" which i can use? Or does it not have any limits?

First, note that in standards-conforming C, x must be a compile-time constant; not even

const int x=10;

will work. But assuming you didn't mean a variable "x" but just some quantity, Keenan's prior comment below is (mostly) right. --Tardis 18:30, 10 April 2006 (UTC)

Secondly, if "x" has a limit, on what does it depend? Does it depend on the type of array, like here its an integer array, so does it depend on the type of the variable defined?

It depends on how much memory is in the computer you run it on. If it's too big, it will compile, but when you run it the memory allocation will fail and your program will crash. —Keenan Pepper 16:48, 10 April 2006 (UTC)

It only depends on the type of the array in that 5 doubles may take up more space than 5 shorts. Also, if it's initialized, or if the operating system/executable file format require it, the memory may become part of the executable file, and perhaps may be part of the compiler's memory space. Then it would fail to compile, or it might fail to be written to disk for disk space reasons. Beyond that, it's restricted by the data type of array indices. In Java this is int, but in C it might be size_t instead (check a book). --Tardis 18:30, 10 April 2006 (UTC)

Explore your system. Make files a10000.c, etc:

a10000.c is void main(){int a[10000];printf("10000\n");}
a100000.c   void main(){int a[100000];printf("100000\n");}
a1000000.c  void main(){int a[1000000];printf("1000000\n");}
a10000000.c void main(){int a[10000000];printf("10000000\n");}

Run. On MY system:

 -> ./a10000
10000
 -> ./a100000
100000
 -> ./a1000000
1000000
 -> ./a10000000
Segmentation Fault (core dumped)

On unix, now see the ulimit command. Explore variations on the theme, try long instead of int, etc. Contemplate the implications for portable programming. GangofOne 22:08, 10 April 2006 (UTC)

main() should return int, not void. —Keenan Pepper 00:03, 11 April 2006 (UTC)

QUERY 3)

---

This one is about memory addresses and pointers.

Consider following:

int i; printf("%u",&i);

Now, whenever the address of "i" is printed, its always less than 65524 (or some value near that). Why is it so? even if many variables are created, each variable's address value would be less than 65524. Why is it so? Is it because of the reason, that the disk segments are always divided in sizes of 65524 units?

First, pointers are properly printed with the '%p' conversion specifier. It has nothing to do with disk organization at all; perhaps the best answer is "don't print pointers because they won't mean anything". Pointer values will differ between different systems, will differ because of compiler choice or different compiler options, may differ between different runs of the same program (simultaneously or in sequence), and don't have a well-defined association with any particular point in physical memory (see virtual memory for more on that). As a stab at answering your question, 65524 is very close to $2^{16}=65536$, automatic variables are typically located on the call stack, and such stacks often grow downwards in memory; perhaps you have a 64K stack, and your pointer is (for any of a variety of reasons) relative to the bottom of that stack's memory area. --Tardis 18:30, 10 April 2006 (UTC)

Explore your sytem. while(i<1000000}{printf("%p ",&(i++));) This will generate another question in your mind. Write a program to answer it. This will generate another question... Repeat until (2038 AD). GangofOne 22:08, 10 April 2006 (UTC)

the structure of a dimerized pair of thymine molecules in a chain of DNA

could you please draw me this structure?

Can you use Google Image search? --Tardis 18:35, 10 April 2006 (UTC)

car audio - necessity of a capacitor

i was considering getting a small subwoofer for my girlfriends car to improve the sound quality. we listen to the music loud sometimes, but i mean it doesnt have to be ridiculously loud, just sound a little clearer when the volumes up and hear the bass tones a little better. anyway i talked to my dad about this because his neighbor runs a car audio store, but its a 'pimp my ride' kind of place (hes from romania). my dad said that it will need an amp and a capacitor. i know ill need an amp but do i really need a capacitor for a small subwoofer? i feel like i cant trust his opinion because his last car had a tv that slid out of the dash, this ridiculous sound system (my dad doesnt even listen to music) that soudned terrible when it would be put up loud to impress you, and vertical doors (he now admits the vertical doors were a mistake) anyway im sure ive seen many cars with subwoofers and no capacitors. my question is at want point do you have to install a capacitor, and for a small single amp will i need one? modesty 22:02, 10 April 2006 (UTC)

The purpose of a Cap is, like in any load circuit, to buffer power between a source and a load. A cap allows the voltage drops from the battery or alternator to be filtered out, which is important if you are running a lot of power. If the amp is running only 200-300W RMS (likely for a single sub 10-12") then there is generally enough capacity in the battery and alternator, so a big external cap is superfluous. Once you get past 500 WRMS is when you see issues with voltage drop along the wiring, and overloading of alternators and batteries (to the point of destruction) so extra provisions (a cap is among them, but shouldn't be the first) may be needed. --Jmeden2000 15:36, 11 April 2006 (UTC)

thank you --modesty 19:11, 11 April 2006 (UTC)

"The Critter"

I was reading a book about the Vietnam War the other day and a section of the book referred to the portion of the war in Laos. The author of the book referenced a certain animal that one of the other Americans had as a pet. For a long time nobody knew what the animal was called until one of the people stationed there happened to see the animal "Critter" on a Laotian postage stamp with the name "Panis Auritas". I can find no information on this animal.....I did find a picture of the postage stamp but no "Critter". Can anyone help with this information search.--67.98.38.212 22:53, 10 April 2006 (UTC)Benny

so what was on the postage stamp? alteripse 22:56, 10 April 2006 (UTC)

It looks a lot like a Pangolin to me -84.9.46.44 23:14, 10 April 2006 (UTC)

...which is genus Manis. I suspect a typo somewhere down the line. There is such a thing as a golden pangolin (though I note it's not listed in the Pangolin article), which might well have something like Manis Auritas as its taxonomic name. Grutness...wha? 02:31, 11 April 2006 (UTC)

April 11

Electromagnetism and force?

I have read in some places and seen some examples that electro-magnetism , specifically ionised air and static electric fields can move objects of any kind of matter. and also is the radiation pressure of light [which i know can move matter as have read article in scientific american on it] electromagnetic. How does it work if it does. I think it does as have read an interesting article on it. Am looking into it as a skeptical answer to poltergeist phenomena. this is the interesting article. it is about an electrostatic wall

".7 CASE STUDY - LARGE PLASTIC WEB ELECTROSTATIC PROBLEMS, RESULTS AND CURE, D. Swenson, 3M Company Tremendous static charge generation on a plastic web causes unique physical phenomena and special problems. Solution was simple and cost effective.

---

David Swenson of 3M Corporation describes an anomaly where workers encountered a strange "invisible wall" in the area under a fast-moving sheet of electrically charged polypropelene film in a factory. This "invisible wall" was strong enough to prevent humans from passing through. A person near this "wall" was unable to turn, and so had to walk backwards to retreat from it.

This occurred in late summer in South Carolina, in extremely high humidity. Polypropelene (PP) film on 50K ft. rolls 20ft wide was being slit and transferred to multiple smaller spools. The film was taken off the main roll at high speed, flowed upwards 20ft to overhead rollers, passed horizontally 20ft and then downwards to the slitting device, where it was spooled onto shorter rolls. The whole operation formed a cubical shaped tent, with two walls and a ceiling approximately 20ft square. The spools ran at 1000ft/min, or about 10MPH. The PP film had been manufactured with dissimilar surface structure on opposing faces. Contact electrification can occur even in similar materials if the surface textures or micro-structures are significantly different. The generation of a large imbalance of electrical surface-charge during unspooling was therefor not unexpected, and is a common problem in this industry. "Static cling" in the megavolt range!

On entering the factory floor and far from the equipment, Mr. Swenson's 200KV/ft handheld electrometer was found to slam to full scale. When he attempted to walk through the corridor formed by the moving film, he was stopped about half way through by an "invisible wall." He could lean all his weight forward but was unable to pass. He observed a fly get pulled into the charged, moving plastic, and speculates that the e-fields might have been strong enough to suck in birds!

The production manager did not believe Mr. Swenson's report of the strange phenomena. When they both returned to the factory floor, they found that the "wall" was no longer there. But the production workers had noticed the effect as occurring early in the morning when humidity was lower, so they agreed to try again another day. The second attempt was successful, and early in the morning the field underneath the "tent" was strong enough to raise even the short, curly hair of the production manager. The "invisible wall" effect had returned. He commented that he "didn't know whether to fix it or sell tickets."

- Bill Beaty

It later claims that this could be ionized air? how would this work? Robin

The story was made up. -- Mac Davis] ⌇☢ ญƛ. 01:21, 11 April 2006 (UTC)

Here's the origianl onlien, it was easy to google. http://www.amasci.com/weird/unusual/e-wall.html which references http://www.esdjournal.com/articles/final/final.htm , with pictures. GangofOne 02:14, 11 April 2006 (UTC)

FYI amasci.com is the site of User:wjbeaty, mentioned above.

Uuuuuum so now we have established that i didnt make the story up and its from a competant source, exactly how would it work? or am i just gona get accused of fraud again instead of getting the answer i asked for? I thought thats what this part of the site was for. Robin

Actually, you are going to be accused of being unable to properly respond. I moved your comment from the bottom of the page to this section. --Kainaw ^(talk) 15:38, 11 April 2006 (UTC)

Those aren't authoriative sources. This Beaty character seems to be a crackpot as well. His page is linked to by crank.net. What else need I say? --BluePlatypus 16:56, 11 April 2006 (UTC)

That's interesting. I know Bill Beaty's site, and I wonder whether crank.net listed him as an "anticrank" or a "crank". Could you give me the context for the link that you found on crank.net, please? I tried the obvious Google searches like "beaty site:crank.net", but without success. I spend a lot of time battling real cranks on Wikipedia, and IMO Bill isn't one of them. --Heron 19:23, 11 April 2006 (UTC)

The answer Robin is looking for can be found in human psychology, not physics. Humans mispercieve things all the time. Humans misreport things all the time. "How would it work?" It doesn't. It can't. Wouldn't it be cool, useful, and a source of immense profit if it existed? Of course it would. The actual profit here lies in selling books and ads on sensationalistic sites. Always follow the money. WAS 4.250 17:37, 11 April 2006 (UTC)

Thank you for a civil reply. Actually if you study the evidence, and arthur c clarke did in his book "world of mysterious powers" not all poltergeists can be put down to misunderstanding, illusion and fraud. Secondly their seems to be many effects that can do things described in some poltergeist cases. I have been told electromagnetic fields, ultra and infra-sound, ionizing radiation,radiation pressure and static charging can shoot things about. But the complete expulsion of the case i mentioned as fraud without a proper incquiry bugs me. It seems like a genuine case. and remember ball lightning was thought to be non-existant by scientists at first but lo and behold http://physicsweb.org/articles/news/10/2/6 , http://www.newscientist.com/article/dn1720.html in fact one of these thinks that poltergeists and them may be completly related natural phenomena. not paranormal or magical or spiritual, just misunderstood. And the only bill beaty articles i can find on crank .net are critisms of over skeptical science, no listing of his site on either science, paranormal, electromagnetism, or antigravity pages which he should be listed under. Robin 22:45 april 11th

I toss this out as speculation. Since the fields where so high and the 2nd guy felt crackling over his skin, maybe the effect was physiological. Maybe the fields where so high they were interfering with the action potentials of his nerve-muscle synapses. He said he couldn't turn around , he had to back out. Lost control of some muscle groups. This could be new information for the biophysics journals, if it were followed up with more testing. --GangofOne 23:30, 12 April 2006 (UTC)

Eusing Free Registry Cleaner

Does anybody have experience of using Eusing Registry Cleaner? My registry must be in need of serious cleaning out but I know that tinkering with one's registry is a dangerous activity, so I'd really want to know I can rely on any software that's going to effect it. Casual reviews much appreciated. --bodnotbod 01:25, 11 April 2006 (UTC)

If in doubt, always make a full backup first (open regedit, File -> Export, and make sure to select "All" as "Export range"). Then make small, incremental changes, restarting your computer between changes to ensure it still works. I have no familiarity with the program you mention, but check if it has a backup or undo option - most registry editors do. But, in any and all cases, make backups! :) — QuantumEleven | (talk) 06:16, 11 April 2006 (UTC)

This one looks OK (softpedia give it a clean rating though like Quantum I have no direct experience of it), but you're right to be cautious; the whole malware arms race has led to increasing amounts of malware masquerading as anti-malware tools. --Bth 10:12, 11 April 2006 (UTC)

The software claims to back up for you (or offer a restore point), but I shall follow your backup idea as best practice, thank you. Anyone with direct use of it? Oooh! ALternatively, can anyone recommend a highly regarded open source app for the same sorts of things? --bodnotbod 13:03, 11 April 2006 (UTC)

Constructivist learning theories

Does anyone know of exmaples of cognitive and social constructivist learning theories? i understand the concepts but need to exmaples to understand them clearly.

There is a very large selection of pedagogies (approached to teaching) that trace their origin to constructivist learning theories. At the base level an approach that uses hands on, discovery learning, can be considered constructivist in origin (students being the architects of their knowledge). There are many sophisticated examples (try doing a google search for constructivist pedagogy). One example I am familiar with is Covis. -Fermion 02:17, 11 April 2006 (UTC)

Yahoo! and computing services

The first page of the Yahoo! article states that Yahoo! is a "computing services" company. However, the provided link, computing services, seems to be a redirect to outsourcing. I was hoping to learn from the article what Yahoo! does, since I'm under the impression that they "run a website". I assume that the outsourcing link is inaccurate? -- Creidieki 02:29, 11 April 2006 (UTC)

The outsourcing link is accurate. Yahoo! hosts and maintains one of the e-commerce web sites for one of the companies that I work for. So we outsource the work to them. They do this for lots of companies. I'm not real familiar with the company and its services but they do perform at least some outsourcing. Here's the address for that service: http://smallbusiness.yahoo.com/merchant/ Dismas|^(talk) 04:17, 11 April 2006 (UTC)

I believe Yahoo! is also an internet service provider and provides it's own search engine. StuRat 22:29, 11 April 2006 (UTC)

Could you contain the current from a lightning strike

If you ionized the clouds (somehow), would it be possible to store the current from an lightning stike, given the amount of power discharged by them?

Your terminology "store the current" isn't what I think you mean. I think you mean "store the charge". While you could store some charge from a lightning strike, it would be very little of the overall charge. To date, devices that store charge require time to store up a charge. Lightning happens so quickly that there is no time to store much of the charge. However, it may be possible to steal a little charge from the clouds over time. There is a clear difference in charge between the top of tall buildings and the bottom. It isn't a huge amount, but it may be enough to trickle charge a battery. I've often considered doing an experiment with a lead on top of my offfice (13 floors) and a lead on the ground. The problem is that I don't have easy access to the roof and I'm sure someone would get upset if I hung a cable from the roof to the ground. But, you are free to try it. You may be able to do the same with a kite, using insulated wire for the 'string'. --Kainaw ^(talk) 13:37, 11 April 2006 (UTC)

Sorry, I must object. Flying a kite where there is possibility of lightning strike is potentially lethal. We all know Benjamin Franklin did it and became famous for it, but he was lucky. He was smart enough to know to use a silk thread (a nonconductor) for a distance to the cotton thread that went to the kite. The cotton , when wet, was a conductor, was connected to the famous key. He did NOT hold the cotton thread. He held the silk thread that was tied to the cotton thread, according to what I understand. I recommend some library research before messing with lightning. Trying to store the charge of lightening has been tried and done, by Franklin, but it is not practical. Read all about it first. No point in dying redoing 18th century science experiments. GangofOne 23:35, 11 April 2006 (UTC)

Thanks...and no I won't fry myself.

I did not say "fly a kite in a thunderstorm". I suggested that a kite be used to get an electrical lead off the ground to see if there is enough potential between high altitude and the ground to charge a battery ... when lightning is not present. As for storing the charge, there is much doubt that Franklin performed such an experiment. He flew a kite in the rain (after Thomas d'Alibard did a nearly identical experment with a tall iron rod). Then, there were many failed experiments around the world with lightning rods and jars of various substances. Many house fires followed. --Kainaw ^(talk) 23:46, 11 April 2006 (UTC)

Linux system keeps setting clock time wrong

I am running a Fedora Core 3 Linux system with Gnome 2.8. Every time I power up the system, its clock is at the wrong time, it's usually about 40 minutes in the past. I've tried setting the correct time with both date and hwclock but that only helps for the current session, when I reboot the computer the clock is at the wrong time again. Is it some weird service I'm running or is it a bug? I usually have fairly long uptimes, up to over a month, might this have something to do with it? How would I go about diagnosing it? JIP | Talk 06:42, 11 April 2006 (UTC)

Fedora might be synchronising the clock with an NTP time server every bootup. I haven't used Fedora on a day-to-day basis, but quite a few distros seem to do that. Check the ntpd service and if it's starting on bootup. -- Daverocks (talk) 09:07, 11 April 2006 (UTC)

Maybe try the BIOS? - mako 09:14, 11 April 2006 (UTC)

I've had (acutally, have) the same problem. It is caused by hwclock (see man hwclock). On my previous install I fixed it by rm /etc/adjtime, but I think that removing the --adjust parameters when hwclock is loaded should fix it as well. —Ruud 11:01, 11 April 2006 (UTC)

Another possibility is that the hardware clock is bad. They don't last forever. StuRat 22:16, 11 April 2006 (UTC)

But this is a fairly new system. I only bought it fresh from the store, assembled from off-the-shelf parts (new, not used) a year ago. JIP | Talk 15:36, 12 April 2006 (UTC)

The next step in diagnosis is to note exactly in what way it is bad. Is it always shifted by a fixed amount from the correct time? Is it always a particular date, like January 1970? Is there some other pattern? Notinasnaid 18:38, 12 April 2006 (UTC)

Timing Diagram

Hello,

I would like to write an article on Digital Electronics Timing Diagrams.

I have found a stub: wiki/Timing_diagram, but this relates to the new UML 2.0 Timing Diagram.

Where should I start my article.

Regards,

Mark

If there are two clearly different subjects that could fit into a title it can be handled using the diambiguation guidelines. Basically with two articles, you put links up the top of each page, explaining its context, and directing people looking for the other context, to the other page. A likely target for starting your article could be Timing diagram (electronics), as a suggestion. Ansell 09:01, 11 April 2006 (UTC)

UML Aggregation and SQL

I've been set the task of implementing a database schema given in UML as a MySQL database. In terms of design, what does the composition/aggregation relationship on the UML diagram translate to in terms of the tables required? The specific problem is the classic "library" system - there is a table Book which has the book details, then a relationship to an entity BookCopy, which has only one field listed. Is this extension, or inheritance, or neither? - does the arrow imply a foreign key? There is then another entity with the aggregation symbol - LoanedCopy. Could anyone give any advice on the structure of this, or a pointer to somewhere which has a decent tutorial covering UML -> SQL.

Cheers. QmunkE 12:54, 11 April 2006 (UTC)

It sounds like there would be a one-to-many relationship from the Book table to the BookCopy table. Perhaps each copy has a unique serial number ? In that case that would be the primary key to the BookCopy table. The ISDN would be the primary key in the Book table and also a foreign key column in the BookCopy table. The LoanedCopy table would be similar to the BookCopy table, but would also have info on who checked out the books, when they checked them out, when they returned them, etc. StuRat 22:09, 11 April 2006 (UTC)

Spacetime

Could anybody popularly explain the concept of four dimensional spacetime?

Time is just a dimension - like depth, width, and height. The best explanation I've heard is the "flatworld" example. Get a piece of paper. Put a penny (or something flat) on it. That is your flat man. He cannot see up and over anything because his world is completely flat. Draw a line on the paper. He can't see over it. It is a wall to him. You can make a box with an opening for a door and call it his house. When he is in his house, he thinke he is boxed in on all sides. But, you know different because you see in three dimensions. You know that you can pick him up and put him outside his house. The little flat man's point of view (lack of being able to see up) is similar to our point of view (inability to see forwards and backwards in time). --Kainaw ^(talk) 16:14, 11 April 2006 (UTC)

Spacetime GangofOne 23:20, 11 April 2006 (UTC)

Kainaw's example is greatly explored in the book Flatland by Edwin A. Abbott, a book I'd certainly recommend. EWS23 | (Leave me a message!) 01:10, 12 April 2006 (UTC)

Or The Planiverse for a more detailed and mind-blowing view of what life would really be like in 2D space. —Keenan Pepper 04:06, 12 April 2006 (UTC)

The allies of space and time was first perceived by the German mathematician Hermann Minkowski, when he studied his former pupil Einstein's Special Theory of Relativity and realized that their unique connection in behaviour due to the states of motion of the observed objects must be that they are ultimately one thing altogether- space- time, neither one nor the other. This idea was so radical and useful that Einstein incorporated it himself later for inclusion in General Relativity, ten years later. For a better mathematical understanding of the subject, please consult the special introductory page on the Special Relativity page and spacetime. Luthinya 18:32, 12 April 2006 (UTC)

Size exclusion chromatography - De-salting a protein solution

I am trying to desalt a protein solution using a column of Sephadex G-25. Is there a rule of thumb for how concentrated this protein solution can be? (I know that if the solution is too concentrated, it causes problems) ike9898 17:08, 11 April 2006 (UTC)

Salt concentration or protein concentration? --BluePlatypus 18:29, 11 April 2006 (UTC)

Protein concentration. ike9898 20:51, 11 April 2006 (UTC)

Well, it all depends on the flow, eluent, the protein itself, etc. But 25 mg/ml seems to be the maximum recommended[7]. --BluePlatypus 21:42, 11 April 2006 (UTC)

If you have a concentrated, salty protein solution the best desalting choice might be dialysis. Simply put the solution inside some moistened dialysis tubing and place the whole thing into a low salt buffer, which you can replenish as necessary. You can leave it overnight or longer. The dialysis membrane traps the protein inside while the tiny salt ions will diffuse through the membrane into the low salt solution by osmosis. This is a routine technique in protein prep.

Another option may be using a centrifugation based device. This allows you to desalt and concentrate the protein in a single step. Refer to the manufacturer for more details (e.g. Centricon).

Size exclusion chromatography is a good technique for purifying one protein from a mixture of proteins and is seperates based on molecular weight. As in all chromatography, the amount you load on this column depends on how big the column is. The bigger the column, the more you can load. Refer to the manufacturer's instructions for your particular brand of packing for the recommended loading amount.

I'm desalting a protease and I get autolysis if I dialyse. SEC is very quick, and easy to set up in a cold room. But, my protein peak is spreading WAY too much. I thought it might be due to too high a protein conc (increasing viscosity). This technique should be routine, but it is new to me and it's giving me a royal pain! ike9898 17:55, 12 April 2006 (UTC)

LG L1515S monitor

I use a LG LCD monitor LG L1515S. Is it a low end, low quality monitor? This is the cheapest LCD monitor which I saw and I thought it does not matter to buy the cheapest monitor? Is there any problem buying cheap LCD? whats the problem? Comparing cheapest LCDs and mid/high quality CRTs, which is better?

LCDs tend to be dim, only give a good quality pic when viewed straight on (not at an angle), and occasionally have a few pixels which are some random color. CRTs don't have these probs, but might be harmful to your eyes, can be blurry, tend to be rather heavy, and may not last as long. A plasma screen display is the best of all, but most expensive, too. You should look at the max resolution (1280x1024, for example), screen size (15 inches, for example), and the refresh rate (60Hz, for example) to evaluate a monitor. Ideally, they should all be as high as possible. Note that the refresh rate often varies with the current resolution setting. A low refresh rate will make the screen appear to flicker, especially when a white screen is displayed. A low resolution will make it difficult to display much on the screen at once and a small screen will make you need to squint to see anything. StuRat 21:50, 11 April 2006 (UTC)

Call termination charge in USA

Is there call termination charge in USA? In India, telecom companies from which calls originate pay a call termination charge of Rs.0.30 to the network in which the call terminates. Is there any call termination charge in USA? If yes, what is the call temination rates? How come companies offer unlimited calling to other companies's phones when there is a termination charge which metres by the minute?

The US telecom industry places all sorts of goofy charges and surcharges on telephone calls. While our article doesn't enumerate many, the FCC has a sample phone bill complete with charges and explanations for a typical US monthly phone bill. As for termination charges specifically, I think that varies by plan. As I recall, such charges may exist but are frequently handled by a long-distance provider who then provides the end-user with a flat per-minute rate. — Lomn Talk 19:46, 11 April 2006 (UTC)

Difference between Google news & topix.net

What is the difference between topix.net and Google news? Both seem to aggregate news. But topix.net serves ads and no one minds while there has been lawsuits against Google news and it is not able to serve ads. Whats the reason and whats the difference between these two?

First, money. Google is a cash cow for lawyers to sue. Second, methodology. Google searches anyone they like and they post results of their search. News sites have to partner with Topix (see their 'about us' page for info on the types of partnerships they have). --Kainaw ^(talk) 23:58, 11 April 2006 (UTC)

A medical query?

Taking my place at the urinal this afternoon, I was joined by my newest coworker setting up shop at the adjacent recepticle. Somewhat contrary to my own restroom M.O., he asked how I was doing, and out of politeness I returned the question. However, despite the divider between the urinals (which really ought to be law), I was struck by that phenomenon commonly known as "stage fright." That is, even though I had a full bladder on (in) my hands, I was incapable of micturating until immediately after he left. Why/how does this occur?

The bladder is controlled by the autonomic nervous system. Parasympathetic neurons innervate the wall of the bladder (the detrusor muscle, trigone and sphincter). Parasympathetic stimulation results in contraction of the bladder muscle and relaxation of the urinary sphincter resulting in urination. This is opposed by the sympathetic division of the autonomic nervous system.

Anxiety or fear, including social anxiety, results in decreased parasympathetic stimulation and increased sympathetic stimulation of the bladder, resulting in relaxation of the bladder proper and tightening of the urinary sphincter, making it more difficult to pee. There's always the stall. - Nunh-huh 18:47, 11 April 2006 (UTC)

There is an article covering this: Paruresis --Ed (Edgar181) 20:34, 11 April 2006 (UTC)

I believe this is an evolutionary adaptation. That is, urinating or defecating in the presence of a stranger (or someone you don't fully trust) is a bad idea, as it leaves you vulnerable to attack. Thus, humans (and other animals) tend to delay elimination until they feel safe to do so. I suggest you use a stall, instead. StuRat 21:37, 11 April 2006 (UTC)

Indeed this phenomenon is contrary to the popular train of thought: that fright causes urination. As noted above, in humans, a sympathetic response to a stimulus will basically keep you from urinating, it is when you get to a safe place and the sympathetic stimulus stops that you will urinate (in a situation where your body decides you are safe again, although you still may be "scared") often uncontrollably. This reaction is actually a situation rather specific to humans: in canines, for example, sympathetic stimulation will usually cause urination when the bladder is anything but empty. Tuckerekcut 01:20, 12 April 2006 (UTC)

I believe in dogs, urinating on themselves is used as a sign of submission. StuRat 03:49, 12 April 2006 (UTC)

benefits of organic foods for immunno-compromised individuals...

I would like to know what the benefits are, if any, of organic foods are for immuno-compromised individuals, those with HIV/Hep C in particular. Thank you.

---BR.

I'm not sure that they are. You may want to check out our article on organic food. The crux of your question revolves around how organic foods differ from ordinary foods, which itself is the center of a firestorm of debate. However, the article does mention that organic foods grown in manure actually increase the risk of contamination with E. coli and other bacteria, which is not a benefit at all. Isopropyl 19:29, 11 April 2006 (UTC)

No body knows. No rigorous research has been done on this. Some doctors believe that there may be benfits, but it's highly controversial. For great justice. 01:23, 13 April 2006 (UTC)

computer repair?

what is the best way to fix up an old computer?Cooliabeanias 19:26, 11 April 2006 (UTC)

Using old computers to run Linux is always a good choice. It runs well even with limited resources, and you can learn to use it on an expendable machine. Isopropyl 19:29, 11 April 2006 (UTC)

If you are technical enough to figure out what type of power supply and memory you have, you can look into getting an upgraded motherboard and CPU that will use the same power supply and memory. You'll benefit from extra CPU speed with little investment. The common mistake is to buy the motherboard first - then finding out that you need to buy a new power supply and new memory because the old stuff is incompatable. Then, the cost is so much that you could have bought a new computer. --Kainaw ^(talk) 19:53, 11 April 2006 (UTC)

Many "old" but workable computers get put out with the trash. It is possible to get quite usable parts from such machines. Power supplies, drives, cases, sound cards. Sometimes the machine works perfectly, just is old. This is a wasted opportunity, when so many people, mostly kids, could learn a lot from having such a machine. Out of date for the lastest stuff perhaps, but plenty good for learning. If you can put together such machines, you can just give them away, if nothing else. GangofOne 23:15, 11 April 2006 (UTC)

I've tried to give away old "refurbished" computers for email/web browsing. It is difficult. Beggers quickly become choosers. I set up four computers at the homeless shelter with a 5th providing a shared dial-up connection. The problem was that the shelter didn't want to provide a line for dial-up. So, they just became machines for playing solitaire (which was easier to do with the many decks of free cards laying around). Also - on a distantly related topic - I was with a professor doing a talk on Beowulf Clusters. A reporter at the conference asked if these clusters will make use of all the old computers out ther. The professor's response was memorable: "Sure, if you want a huge power hungry heat box with nearly as much processing speed as a standard home PC." --Kainaw ^(talk) 23:38, 11 April 2006 (UTC)

Chemicals

how do chemicals reacted in diffrent ways when mixed together thanks alot tomas

They react in a predictable fashion depending upon their chemical properties, hope this helps.

• There are several good articles where you could start looking to find what you need: chemical reaction, list of reactions or the category Category:Chemical reactions. --Ed (Edgar181) 20:30, 11 April 2006 (UTC)

Well, if there was an easy answer to that question, there wouldn't be much need for chemists, would there? :) --BluePlatypus 21:31, 11 April 2006 (UTC)

Library Classification of books

I have the responsibility of classifying our monastery library. I have been able to find a conversion of Library of Congress numbers with the Dewey Decimal numbers for an annual fee of over $300. Out of the question for such a small library. Is there a conversion table or some kind of rule of thumb that would help quicken the process? I have not been too successful wiht an internet search.--216.129.236.59 19:44, 11 April 2006 (UTC)

Is the Poor Clares Monastery in Great Falls? How large a library do you have? Does the existing library have Dewey call numbers, and you want to switch over to Library of Congress? If so, and if the library is not too large, would it be useful to use the LOC website to look up the books and obtain the LOC call number? Some of the external references in the linked articles may help. - Nunh-huh 20:18, 11 April 2006 (UTC) You may also want to consider joining the "Project:Wombat" mailing list, where a lot of librarians hang out, and ask this question there. - Nunh-huh 00:31, 12 April 2006 (UTC)

I have an old book called Dewey Decimal Classification and Relative Index - published by Forest Press Inc, Lake Placid, NY. My copy is dated 1959, so whether it's still being printed or not I have no idea. Unfortunately, given its age, it has no ISBN (ironically it has a LoC Call number - 59-11569). It is designed for libraries and provides a list of all the dewey classifications both alphabetically by subject and numerically by code. Understandably, given its age, it has certainly been considerably revised since then (where would you file books on DVD recording, OCR, or even digital watches?), but if it's still out there it might be exactly what you need. Grutness...wha? 02:36, 12 April 2006 (UTC) uhh. skip that - I misread the question. Grutness...wha? 02:42, 12 April 2006 (UTC)

I am familiar with the Forest Press book. I used it in school eons ago. I don't need a detailed list as we are going with a modified Dewey Decimal classification. And, good heavens, Nunh-huh, why would you come up with Great Falls Montana and specifically a Poor Clare Monastery at that? Isn't that a little obscure and wild? Our books are unclassified at this point. So I am starting from scratch. 12:22, 12 April 2006 (UTC)

Your IP address (216.129.236.59) is listed as being in Great Falls, MT. --Kainaw ^(talk) 13:24, 12 April 2006 (UTC)

I found this site which gives the Dewey classification if you enter the ISBN. If you can get your hands on a bar-code scanner (maybe an old CueCat somewhere?), there seem to be several free utilities around to help in creating a catalog. --LarryMac 15:09, 12 April 2006 (UTC)

Not much help for any book published before 1970, though... Shimgray | talk | 15:29, 12 April 2006 (UTC)

Speaking as a cataloguer for a small-medium library, we use DDC20 at work - it's two decades old, but as long as you're willing to be creative with some sections (we have a heading which technically parses as "21st century history of the Soviet Union"!) that's not much of a problem. Anyway, the point there is that older editions of Dewey work fine, and if you try asking around it's quite possible a larger library (or library school) still has the old cataloguing manuals gathering dust on a shelf somewhere after they went to a more modern version - they're not much use after you've changed, except for training purposes, so asking nicely might well just get them as a donation.

Of course, real classifying might be more effort than you want... if all you need is a very simple "high-level" classification, OCLC do publish a list of the "thousand sections", the top-level sections of Dewey (PDF), which should give you a baseline to be going on with. For individual books, you could try running them through the Library of Congress online catalogue - they have Dewey numbers listed for most of their stock - but it's probably just as quick to give them a general classification yourself once you have the hang of it. Shimgray | talk | 15:28, 12 April 2006 (UTC)

Thank you, for all your help. With the information provided I was able to find just what I needed. Shimgray's link to OCLC.org I was able to find the summary. Now I will be able to keep our classification consistant and heave others help me do the cataloging. We want the library to be extra user friendly and so we are using a modified DDC. I checked with all our PC monasteries on-line and culled the best possible classification system for our smaller libraries whcih ae also over loaded in the 200's. And, yes, I am at the Poor Clare Monastery in Great Falls, Nunh-huh. I would like to go back and do some adding to the Poor Ladies entry as it is bare bones information. It will have to wait a while as I have my hand full right now.Judith 20:26, 12 April 2006 (UTC)

Sounds good, and glad you got to a solution. Have a good time organizing, and we await any contributions to the Poor Clare article with patient antici-----pation! (It really is a little pitiful!) - Nunh-huh 23:34, 12 April 2006 (UTC)

Gasoline and styrofoam

I've always been told that styrofoam will dissolve in gasoline and therefore you shouldn't store one in the other. Does this happen? And if so, why? Dismas|^(talk) 22:17, 11 April 2006 (UTC)

Yes, gasoline does dissolve styrofoam; I know because I once tried to fashon a funnel from a styrofoam cup, to help get gas into my moped. Gasoline is a non-polar solvent, and it is good at dissolving other non-polar materials, including stryofoam. Some synthetic polymers are much more resistant to this than others. ike9898 22:21, 11 April 2006 (UTC)

Gasoline is a good solvent. Some idiots apparently use it in the washing machine to clean grease off their clothes, and then get a nice explosion when they put the clothes in the dryer. (The clothes may not have any oil stains, but you will need to pick them out of the debris to find out.) StuRat 22:34, 11 April 2006 (UTC)

Styrofoam melts easily in any number of solvents, including gasoline, turpentine, paint thinners, etc.. It can also sometimes melt from lemon juice. Ande B 00:48, 12 April 2006 (UTC)

Dissolving styrofoam and soap in gasoline is a good cheap way to jellify it, creating a napalm. :) -- Mac Davis] ⌇☢ ญƛ. 04:29, 12 April 2006 (UTC)

Thanks for the replies, everyone. I'm sure the gasoline that those people use in their washing machines does wonders for their septic systems if they happen to be on one.  :-) Dismas|^(talk) 10:29, 12 April 2006 (UTC)

Coyote/dog hybrids

I overheard a man at the pet store the other day say that his dog is half coyote. Are Dog/Coyote hybrids fertile? User:Zoe|^(talk) 23:01, 11 April 2006 (UTC)

I guess Coydog answers my question. User:Zoe|^(talk) 23:04, 11 April 2006 (UTC)

April 12

Gettin' burnt...

i accidentally burnt my finger yesterday with an iron, and little watery poxes appear on my finger, why's that? Thx --203.218.93.206 01:08, 12 April 2006 (UTC)

I'll take blisters for $400, Alex. - Nunh-huh 01:09, 12 April 2006 (UTC)

You can check out Burn (injury) as well for more information about burns. Ansell 01:11, 12 April 2006 (UTC)

Need Help on an Article

Can I get some help with checking the information on the Boiling Constants page and also setting up the data into tables? Ctifumdope 01:33, 12 April 2006 (UTC)

One comment, the Wikipedia naming convention is to only capitalize the first word in an article name, and make it singular, so you should rename the article accordingly to Boiling constant. StuRat 03:43, 12 April 2006 (UTC)

Help:Table is a good page that can help you with formatting your information into tables. -- Daverocks (talk) 04:35, 12 April 2006 (UTC)

I moved the page to List of boiling constants of solvents. -- Mac Davis] ⌇☢ ญƛ. 05:40, 12 April 2006 (UTC)

Sound and Balloons.

hi, i would like to know why and how does a exploding balloon produce sound? thankyou — Preceding unsigned comment added by 202.138.102.141 (talk • contribs)

Sound waves in air are composed of alternating pressure differences. The pressure inside a balloon is higher than outside (or it wouldn't be inflated in the first place). When you prick it, the pressure equalises; because the speed of propagation of pressure differences isn't infinite (it is, of course, the speed of sound), this doesn't happen instantaneously -- an expanding sphere of high pressure radiates out from the balloon, which you hear as a bang when it reaches your ear. --Bth 09:46, 12 April 2006 (UTC)

I was interested in this question, since the process is somewhat identical to earthquakes. Here is a good reference: [[8]] It has nothing to do with the air, but the speed of the fracture propagation, and the whip of the fragmented ends. These form mini sonic booms. You can experiment by interferring with the latex (tape) and showing how it muffles the sound. You can do different things to get a really loud pop. --Zeizmic 14:30, 12 April 2006 (UTC)

ElectroMagnetic Disturbance

How is it that a nuclear explosion creates an elecromagnetic pulse?How does this harm modern IC's only when they are in use?

See electromagnetic bomb for the processes involved and how they interfere with electronics. But where do you get the idea that ICs are only vulnerable when in use? Unless they're shielded (by being put in some sort of Faraday cage) they're going to be vulnerable on or off. --Bth 10:56, 12 April 2006 (UTC)

Computing Data Storage DVD

What is the difference between a DVD-RW DVD-R and DVD+RW DVD+r?

"R"s can be written to once, then the data's fixed; "RW"s are rewritable (with full erasure first for the -, random access for the +). The +/- thing is a standards mismatch between different manufacturers (like VHS/Betamax for video formats, except that we're still at the stage where the marketplace hasn't chosen a standard). Various arguments are advanced in favour of the two; you can read more at the articles in question. --Bth 10:45, 12 April 2006 (UTC)

Altitude and temperature

Why does it become cooler as we go higher?As we are nearing sun i suppose it should get hotter.-explain

Erm, no. For one thing, the heat from the Sun reaches the Earth as radiation, much of which passes through the atmosphere and heats up the ground, but the overall siutation is complicated --there are layers where temperature increases with altitude, but the processes involved are more involved than just "it's nearer the sun". See Earth's atmosphere for more. --Bth 10:35, 12 April 2006 (UTC)

The higher you go the thinner the atmosphere is, which means fewer particles to transfer the sun's radiation (or heat absorbed from surroundings) to you. Also with more room to move the particles are less energetic. Higher pressure = hotter. Lower pressure = cooler.--Anchoress 11:08, 12 April 2006 (UTC)

However, in the thermosphere the temperature is controlled by the absorption of solar radiation and the temperatures can get as high as 2000^oC. So there the questioner's original assumptions do sort of hold. --Bth 11:11, 12 April 2006 (UTC)

It's still entirely irrelevant that you're closer to the sun. The difference in solar radiation intensity between the ground and the top of the thermosphere (using 690km) is $9.2\times 10^{-6}$, which is hardly important. It is true that some high-energy radiation is available there for heating that isn't available on the ground, but it's more like the rest of the atmosphere is in the thermosphere's shadow, rather than that the thermosphere is appreciably physically closer to anything. --Tardis 17:11, 12 April 2006 (UTC)

Unfortunately your idea happens to be the common misconception. It is totally irrelevant here, as Tardis has said, whether you are close to the sun or not. The fact is that as you go up higher, the atmospheric pressure drops considerably, and with fewer air particles to transmit the sun's radiation or generate energy between themselves by bumping into each other, naturally the air temperature drops. I suppose your closer distance does mean that you would expect to feel the heat of its radiation more strongly, but even without the effects of the atmospheric pressure as I have described, considering the vast cosmic distances between the sun and the earth, even a mountaineer standing at the top of Everest will not be able to feel all that much difference to when he was upon sea- level itself. Luthinya 18:39, 12 April 2006 (UTC)

Vectors in EMW

Is there an easier practical illustration of the common terms we use in Electromagnetic Theory like Gradient,Curl,Divergence?

Which illustrations are you already familiar with? In general, they're slightly fiddly to get across in non-mathematical form, hence the amount of handwaving that generally goes on, but they work wonderfully once you get your head round the del operator.

Having said which, Feynman probably handles them wonderfully in Volume II of the Lectures on Physics; I'll look it up tonight when I get home. --Bth 10:40, 12 April 2006 (UTC)

Marine Engineering

How is it possible to maintain a watertight seal between the rotating propeller shaft and the hull in a submarine or ship keeping in mind the intense water pressures the submarine will face when submerged?

I'm sure this question's been asked before, but I can't find it ... --Bth 11:08, 12 April 2006 (UTC)

Stuffing box --Zeizmic 11:45, 12 April 2006 (UTC)

calcium / sugar

Is it oxalic acid, made from calcium?, that the body uses to digest sugar?? not sure if i spelling right.

m

Oxalic acid is two COOH groups bolted onto each other; it contains no calcium. Enzymes are what break foods down in digestion -- for the specifics of the digestion of sugar, see glycolysis and for what happens after that, Krebs cycle. Calcium is important in the body as a constituent of bones and teeth. --Bth 12:48, 12 April 2006 (UTC)

As a note Calcium is involved in Muscle contraction and is involved in carrying the eletrical charge down a Neuron in the Electrical synapse. Wish I had better sources for the neuron thing as it's been 9 years since my animal physiology course.--Tollwutig 13:30, 12 April 2006 (UTC)

Oxaloacetic acid is an intermediate in the breakdown of most sugars, yes. Neuronal transmission is mostly the affair of sodium and potassium. Physchim62 (talk) 13:41, 12 April 2006 (UTC)

Though calcium is involved in transmission across chemical synapses, by triggering the release of neurotransmitter vesicles. I'm guessing calcium has only a small role in typical electrical synapses because the intracellular concentration of calcium is so low in most cells. --David Iberri (talk) 22:03, 12 April 2006 (UTC)

And, yet, if the concentration of calcium ions in the extracellular fluid drops, it produces excessive and painful muscle contractions called hypocalcemic tetany. The concentration may be low, but Ca is certainly not unimportant to neurmuscular transmission. alteripse 00:43, 13 April 2006 (UTC)

MIME

Can you please explain what a "MIME TYPE" is?and can you list a few MIME types?

We have a good article on MIME. MIME helps identify what the type of content that is being sent is. Some examples are: text/plain, text/html, image/jpg (I think). -- Daverocks (talk) 12:42, 12 April 2006 (UTC)

IIRC the last one should be image/jpeg. --cesarb 19:18, 12 April 2006 (UTC)

Time series analysis

The linear regression model can be used to estimate expected value. When applied to a time series, linear regression may not be useful because it is time-neutral. If I have a scatter chart of a time series, what kind of statistics tool should I use, if I want to:

• Estimate a rope's possibility of breaking over time. The rope is under a significant load, the fibers of the rope could break any minute. So the strength of the rope may suddently decrease over time. To estimate the possibility of breaking at t₀, we may forget about past values. Let's say we have a lab and 1000 such ropes and loads.

• Estimate a rich person's tendency to buy gifts over time. Suppose the man is influenced by his ever-changing mood. If he's very happy, he can be buying gifts all the time. We don't know if he's happy at any given moment, but we can increase the weight of t₀±Δ to emphasize the influence of his mood.

• Estimate a person's tendency to invest over time. Suppose all that person has is a stock ticker. At the time of decision making, he/she only has past performance. -- Toytoy 12:40, 12 April 2006 (UTC)

Did you come up with those examples yourself? 'Cos they sound awfully like homework ... --Bth 13:02, 12 April 2006 (UTC)

Yes, that's homework. And I am my own teacher. @#$% I should have taken some statistics while I was in college but I did not. -- Toytoy 13:13, 12 April 2006 (UTC)

I'm not sure how a linear regression is relevant here. In the rope example, it sounds like you're trying to statistically describe the lifetimes of ropes under stress. That's just one-dimensional data: a vector of times. You'd just be using standard things like mean, variance, and [[skewness|]] to analyze that. The other two examples don't have a clear goal to me... if you have data like "on December 11, Roger bought 2 gifts" and "on December 12, Roger bought 0 gifts", all you can usefully do is find times that seem interesting and posit that important events happened then. If you additionally had "on the evening of December 11, Roger's pet mouse caught the flu", then you might want to compute some sort of correlation between the two sets of data. With appropriate quantification of everything and some luck, you might be able to come up with a reasonable model ($d^{2}{\mbox{gifts}}/dt^{2}=k({\mbox{good news density}})$ or something), and then you could do predictions of one variable (gifts or good news) from the other. But when, say, you were trying to calibrate $k$, you'll just want to use regular statistics, since your model exists outside of time and does not need to be causal. If you do do past-only analysis, it's typically as simple as truncating your data to whatever point in time, fitting some sort of curve to it in the usual ways, then extrapolating beyond it. --Tardis 17:24, 12 April 2006 (UTC)

A problem about Live Linux CD.

Hi, just recently i got a softwares dvd, in which Tablix Live Linux CD's ".iso" file was supposed to be there. but actually it was a ".rar" file. so i extracted the whole "rar" file, and then "burned" all the extracted files onto a CD. i am using windowsXP. then i tried to run "tablix" from that cd by making default boot from cd drive, but it didnt work. after that i ran the cd on winXP, even then it didnt start, actually a ".html" file about "tablix" from the cd did start on autorunning, but the OS wouldnt start. now how to do it? even on their website they have not mentioned how to install and use it for windows user. Similarly, on the same DVD, there is an "image" of Cluster Knoppix, but when i see that file's properties, it doesnt show it to be an "iso" file. i tried to burn that knoppix image on to a cd, by using nero 7, but it showed the message that unrecongnisable format, and so i didnt go further. so wats all this going on ? i am a windows user, and if a normal user like me has to go through so much hassles for just trying Linux, is it serving good to the open source community? not at all. so could you please recommend some Live CD OS which can work directly without such hassles. Also , can u tell me any website or organisation , which could send me these Live Linux CD's or other free Linux CD stuff to me. i am from india, and internet speed at my home is not too great, and also too expensive for me to download the ".iso" files of around 600mb size. so if u could recommend some sites which would do so and send me the CD's in india at my place? thank you.

If you have WinRAR installed on Windows, it makes itself the default application to open ".iso" files. This could possibly be why you think it's a rar file, because WinRAR likes to open iso images. If you're right, though, and the images are really ".rar" files, it would probably be better to put all the extracted files into an iso of its own, rather than burning all the files manually. Also, when you say you tried to run Tablix and it "didn't work", does that mean that Windows started booting and the CD didn't? More details would be appreciated. Also, if you tried to get Nero 7 to burn an image file and it said "unrecognisable format", then what you're trying to burn definitely isn't an ISO. What format is that image in? -- Daverocks (talk) 12:51, 12 April 2006 (UTC)

More generally, you could try Linux India (that's the WP article, this is their site) or one of their affilliated LUGs (Linux User Groups) for help getting started with Linux -- it seems to be a large part of their mission to help newbies. And if you don't manage to solve your problems, apparently thanks to LI's activities, sites like this one now sell distros on cheap CD to India. --Bth 13:01, 12 April 2006 (UTC)

I think Ubuntu linux will still mail you free cd's. They send a live CD and an installation CD. And your problems seem to have to do with the configuration of your Windows system, not the linux distrobutions themselves. But I agree getting in touch with the local linux groups would be good, as you'll have lots of things that will be much easier if you have someone to help you with. - Taxman ^Talk 17:48, 12 April 2006 (UTC)

Have you set your bios to boot from cd? For great justice. 01:15, 13 April 2006 (UTC)

Why are adults less able than children to tolerate dizziness?

Most kids could spin in circles for a minute or more with only mild nausea that quickly passes. Many or most adults would feel ill to the point of vomiting from such motion, and are probably more likely to get nauseous from a simple thing like swinging. Why are children generally better able to handle getting dizzy? --Jonathan Kovaciny 12:49, 12 April 2006 (UTC)

Your assumption does not sound correct to me. People that are highly active can handle motion better than people who rarely move. Children spin, tumble, and run around more than adults. So, a higher percentage of children have a tolerance for that action. Adults who continue to spin, tumble, and run around maintain the tolerance. Also, children who spend all their time sitting in front of the tv do not have a tolerance for motion. --Kainaw ^(talk) 13:11, 12 April 2006 (UTC)

Need to buy a 'surge protector'

1:24 PM 4/12/2006 DST Need to buy a 'surge protector'

Hi all, I need to buy a 'surge protector' or I think an 'automatic voltage stabilizer' for my home computer as power cuts are becoming more

frequent. The budget is low and i don't think I need anything as fancy as a Uninterruptible Power Supply; just a Plain Old stabilizer is sufficient? I

don't know much about the impact of a hot boot on the devices in my Willamette processor or the 1.5 GHz board. All I know is there might be some

damage to the hard disk with repeated incidents of power failures. Is there anything I am missing? Thanks for your care and dedication. I have been reading this page for quite some time now and I CTRL+D ed it on my firefox. Yours truly, -- Kushal one 17:38, 12 April 2006 (UTC)

A surge protector is no use at all in a power cut. It is designed to protect against sudden increases in power ("surges"). In a power cut, the computer switches off, unless you have an Uninterruptible Power Supply. Notinasnaid 18:34, 12 April 2006 (UTC)

Don't know what a stabilizer is, but you need some form of Uninterruptible power supply --Zeizmic 19:55, 12 April 2006 (UTC)

A UPS can act as a stabilizer, in that it will maintain a steady voltage in the event of power sags or power surges. A surge protector alone might help in eliminating any surge that occurs as power is restored after a power cut. --205.143.37.68 21:25, 12 April 2006 (UTC)

I think there is a difference between a 'surge' protector and a 'spike' protector. I am not sure if that is relevant to what is being discussed here, but here goes what I think is the difference. A 'surge' protector is for things like electric motors which will overheat if too much current is pushed through them, often they have circuit breakers to protect against that. A 'spike' protector protects against brief overvoltages which often occur when powerlines are near a lightning strike, these are very hard on electronics and can cause progrsssive failure because each spike does some damage to the components.

Yes. If you are living somewhere with frequent power cuts, you likely have spikes and surges too. Get a UPS. If you can't afford one, a surge protector will help reduce damage from too much electricity, but won't help with not enough. For great justice. 01:08, 13 April 2006 (UTC)

The colour of water

I recall reading once a upon a time that the colour white corresponds to the highest frequency point on the Sun's black body curve (somewhere around 6000K). This is not coincidence, but an evolutionary adaptation. Rather than saying "sunlight is white at its brightest" it is probably more accurate to say "our manner of perceiving white has been conditioned by the sun." An animal around a red dwarf might perceive our red as white and our white perhaps might be invisible in the manner of x-rays etc. OK, if that's utterly out to lunch somebody tell me.

So this got me thinking about water the other day. Again, it's obviously not coincidence that our main biotic solvent happens to be transparent. Would it be fair to say "our manner of perceiving transparency has been conditioned by water"? Another hypothetical alien basking in liquid ammonia might view H2O as an opaque poison? Any formula that describes this sort of thing? I suppose the evolutionary mechanism would be "the clearer the water the safer the drinking." Marskell 17:50, 12 April 2006 (UTC)

As I understand (part of) your question, you are asking if, given different conditions during our evolution, we could ahve evolved in a way that water was not transparent to us, but something else (that is opaque to us) might be transparent to these alterative people. Water is transparent becuase it absorbs little radiation from the 'visible' portion of the spectrum. The radiation absorbed by water wouldn't change, but we could have evolved so that our eyes were attuned to a different part of the spectrum. I believe water is fairly opaque in the UV, so if our eyes saw UV, water would indeed be opaque as well. As to whether there is some solvent that is opaque in the visible but transparent on UV or infrared, there probably is, msaybe someone could provide an example? Chapuisat 18:41, 12 April 2006 (UTC)

"the colour white corresponds to the highest frequency point on the Sun's black body curve", better to say, not highest frequency, but rather , most abundant. Which is maybe what you mean. Yes, it is natural that we are sensitive to the light frequencies that are most copious in penetrating the atmosphere. To be otherwise would be a missed opportunity. But it doesn't apply to transparency. What is transparent to light is physically determined couldn't be changed subjectively in the viewer. Anyway, why would it matter if water where opaque? What if water were silvery like mercury, why would that matter? Except for minor adjustments, like not diving into water without testing depth etc? I don't see why life couldn't evolve if that where the case. (Water in the eyes, would be a problem; probably a workaround) GangofOne 23:08, 12 April 2006 (UTC)

Transparency could be changed if we are talking about seeing with a radically different spectrum of "visible light". For example, if infrared was all we could see, we would perceive some things as being transparent which are not transparent to the radiation we call "visible light", and we would perceive some things as opaque which are currently transparent. Transparency is not quite the same sort of thing as color perception but it is not radically far off. But the "color of water" bit is misleading in this regard, I think. --Fastfission 00:02, 13 April 2006 (UTC)

A problem about GIMP

Hi, just recently i downloaded GIMP (latest version) from sourceforge.net, and all the help files and also animation package along with the necessary GTK. it was working fine on my laptop, but when i tried to install it on my personal computer, running winXP, during installation it said that some files were already present , so it gave me option of "renaming" them. but i decided not to rename them. so it got installed with no problem.but now whenever i try to run it, a msg appears that "an error has occured and GIMP will shut down". this error just wouldnt go. i re-installed it several times, but it didnt work, now what should i do? GIMP is great , but these problems just make open source a headache. could u help me?

Why is this an open source problem? As for Gimp, did you remove it first before reinstalling it? --Kainaw ^(talk) 18:38, 12 April 2006 (UTC)

yes i did uninstall it before installing it.

For more specific help here, you'll need to be a bit more specific about the errors during installation, and whether you get the same errors each time. Also, have you tried that project's help forum? --Tardis 20:15, 12 April 2006 (UTC)

Skew Universe

What exactly are the implications of a skew universe, and what are the possiblities that we may live in one ourselves? Luthinya 18:41, 12 April 2006 (UTC)

You'll have to give a rigorous definition of "skew universe" first. It doesn't seem to be a well-established scientific term. Perhaps you'd be interested in brane cosmology? Also, skew in other fields is typically a relative description; it means nothing if you only consider one object. If that's the case here, then the question "do we live in a skew universe?" is meaningless, and the "implications of a skew universe" are null. Now, if we somehow found another universe and it was skew to ours... --Tardis 20:34, 12 April 2006 (UTC)

I think this is a follow up to the question about the perpendicular universe theory that was asked a while back--172.129.106.218 00:10, 13 April 2006 (UTC)

Unless its the same person, I think he is just asking about parallel universes. Check it out. -- Mac Davis] ⌇☢ ญƛ. 01:18, 13 April 2006 (UTC)

radiology

What is the flow of electrons in an x-ray tube?

See X-ray; in particular, the history section. --Tardis 20:47, 12 April 2006 (UTC)

cells

Why do lysosomes function best in acidic environments?

Maybe you should look up lysosome? I'm sure that has the answer to your homework question. --Tardis 20:56, 12 April 2006 (UTC)

This isn't sufficiently answered on Lysosome. --David Iberri (talk) 21:17, 12 April 2006 (UTC)

(After an edit conflict, and noting that this didn't immediately strike me as a homework question...)

It's really the digestive enzymes within the lysosomes that function better in acidic environments. Each of these enzymes (like all enzymes) is a protein whose ability to function is dependent on its ability to assume the proper shape. If the enzyme is in the wrong shape, it won't be able to act efficiently on its substrate. For lysosomal enzymes, having the wrong shape means not being able to perform enzymatic digestion optimally. A protein's shape is governed by its tertiary structure, which is maintained in large part by hydrogen bonds between the protein's amino acids. And hydrogen bonds are exquisitely sensitive to pH. Change the pH enough and the hydrogen bonds will be disrupted, forcing the protein to assume an improper shape (called denaturation) and therefore become less active.

This provides some measure of protection to the cell. Consider a case in which the lysosome bursts, spilling digestive enzymes into the cytoplasm. The higher pH (less acid) of the cytoplasm would render the lysosomal enzymes less active, protecting the cell from digesting itself. Hope that helps, David Iberri (talk) 21:17, 12 April 2006 (UTC)

Relativity and the speed of light

My friend posed the following scenario to me earlier: Assume that you have a highly efficient solar sail attached to a ship, and that you set the ship and sail in motion in space. Assuming the ship does not pass near enough to any highly massive objects to greatly affect its speed, and that it receives a steady supply of solar energy, will the ship ever exceed or match the speed of light?

I say no. Mass increase tells us that, even given a steady source of energy, the ship's mass would increase without bound as its velocity increases, and the ship would require infinite energy to meet the speed of light.

However, my friend tells me that, given Newton's F=MA, sufficient energy would allow the sail and ship to meet and exceed the speed of light.

I am quite confident of my own thoughts on the matter. However, I would like concrete mathematical or physical evidence to show my friend the error of his ways.

--Doubleplusungood 22:46, 12 April 2006 (UTC)

You're entirely correct; in fact, it requires an infinite energy (and hence infinite time) to accelerate an object with non-0 mass to c , which will, of course, never happen. The kinetic energy of the spacecratft would be $E_{k}=mc^{2}({\frac {1}{\sqrt {1-(v/c)^{2}}}}-1)\!$ (see Kinetic_energy#In_relativistic_mechanics). As v approaches c, this number approaches infinity. Recommend a good book on relativity to your friend. --Borbrav 00:26, 13 April 2006 (UTC)

He's kind of right - sufficient energy will accelerate the ship to the speed of light. It's just that sufficient energy doesn't exist in the universe... For great justice. 01:05, 13 April 2006 (UTC)

Excretion and body temperature

Is it possible to lower one's body temperature by urinating or defecating? The answer is probably a resounding no, but I want to know for sure. Bhumiya (said/done) 22:47, 12 April 2006 (UTC)

No. Poop and pee are the same temperature as the human body as long as they're in the human body. So there's no chilling or warming effect by getting rid of either of them. - Nunh-huh 23:30, 12 April 2006 (UTC)

Not by urinating or defecation but by eating and drinking it is possible because all of that food/water has to be heated. Just look at the energy balance. Assume you take in all food and water at room temp. (25 C) for one day. Assume it comes out of your body at 98.6 F (37 C). Then, 12 C or 12 K is the difference. Now find the specific heat of the composition of urine, probably around water, which is about 4.18 J/(g*C). Approximate urine as water again and at 1 g urine / 1 mL urine

..then for every 1 mL of water you consume at room temp you're burning 50 J which is .012 food Calories (kcal). I think this is negligible. Even if you drank 10 liters of water a day that'd only be 120 Calories of heat exiting your body. That's nothing.

Because I don't have an approximation of the specific heat of feces I don't know how much energy it takes to heat it, but you can bet that based on our water approximation that the energy spent to heat up the food you take in is nothing compared to the Calories in the food (or even if the food has no Calories it would still be so small as to be negligible).

So no, I don't think it's physically possible to intake so much food and water as to decrease your body temp.

-Snpoj 02:13, 13 April 2006 (UTC)

April 13

Perfect Secrecy in a Cryptographic System

According to Claude Shannon's paper, perfect secrecy is obtained when |P|=|C|=|K|. Is it admissable to have |C|=|P|<|K|? i.e. if I have a cipher where Pr(y|x) = Pr(x) does the size of the key matter as long as it isn't smaller than the C or P space? This is all assuming that the keys are equally possible and unique. Any help would be greatfully appreciated, C.Meyers

Cheese!

I assume individually packaged cheese slices solved two problems:

1. consumer demand for pre-cut cheese (i.e. not having to cut out a slice from a big block, just like sliced/unsliced bread)

2. consumer demand for cheese with a longer expiration date. Individually wrapped cheese will last much longer than cheese in a block which supposedly goes bad after about 5 days because once you open it, you've opened an manufactured air-tight seal.

Question: is assumption 2 correct? (how bout 1?)

-Snpoj 02:25, 13 April 2006 (UTC)