Wikipedia:Reference desk/Archives/Science/2006 July 29

Humanities Science Mathematics Computing/IT Language Miscellaneous Archives

The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions at one of the pages linked to above.

< July 28 Science desk archive July 30 >

Early jet fighters had the air intake for the engines in the nose of the aircraft, while later aircraft had paired intakes on the sides of the fusilage. Why the difference? --67.185.172.158 00:32, 29 July 2006 (UTC)[reply]

Not all early jet fighters had intakes in the nose. The world's first jet fighter – the Messerschmitt Me 262, flown by the Luftwaffe near the end of World War II – had a pair of engines, one under each wing. The United States' first jet fighter (the P-59 Airacomet) had a pair of intakes along the fuselage. Meanwhile, the British Gloster E.28/39 (Pioneer) had a single nose intake.

Anyway, the reason is pretty prosaic. Both the Me-262 and the P-59 had two jet engines, and one air intake per engine. The Gloster Pioneer, on the other hand, had only a single engine mounted in the middle of the fuselage, dictating the placement of its air intake directly forward in the nose of the aircraft. TenOfAllTrades(talk) 01:59, 29 July 2006 (UTC)[reply]

There are many ways to design an airplane- including how many engines and where they are placed. And around the same time as the jet engine was developed, airborne radar equipment was being developed. The best place for the radar antenna was the nose, which caused the air intakes to move to the sides of the fuselage. Some US fighters used different arrangements. The Republic XF-103 had the intake below the fuselage, similar to the F-16 Fighting Falcon. And the North American F-107 had the intake placed on the top of the fuselage, behind the cockpit.

The nose is useful space for istrumentation and it is also very difficult to arrange the airchannels around the cockpit without interfereing with it, so to simplify it when these problems had been realised, the air intakes were placed behind the cockpit. Philc _T^E_C^I 13:52, 29 July 2006 (UTC)[reply]

N, N'-Methylene-bis-acrylamide FW= 154.2 C7H10N2O2

This chemical is used in Polyacrylamide gels for SDS page with acrylamide.

Refrence: Laemmli, U.K. Cleavage of structural proteins during the assembly og the head of bacteriophage T4. Nature. 277:680-5, 1970.

--129.115.82.89 01:01, 29 July 2006 (UTC) Otis Blanchard[reply]

Check out Sigma Aldrich's web site for a fully drawn structure: product number M7279. Or, a formula that should give you some idea of the structure is (CH₂=CHCONH)₂CH₂. It's used as a crosslinking agent when making polyacrylamide gels. TenOfAllTrades(talk) 02:09, 29 July 2006 (UTC)[reply]

In Gray's Anatomy, what is the meaning of "viz." throughout the book? One instance is, "the remaining constituents of the ovum, viz. it's limiting membrane and the solid spot..." Thanks for any help, Newnam^(talk) 01:25, 29 July 2006 (UTC)[reply]

Our sister project, Wiktionary, can be helpful, viz. wikt:viz.. TenOfAllTrades(talk) 01:46, 29 July 2006 (UTC)[reply]

Thanks! Newnam^(talk) 01:51, 29 July 2006 (UTC)[reply]

But if you are really stuck, ask your uncle, viz. viz --Seejyb 11:57, 29 July 2006 (UTC)[reply]

In electricity, is the amp being pushed from the power supply; or is it pulled from the devise requiring power?

I guess it would be more accurate to say it is being "pushed" from the power supply, but the wording is odd - I would recommend a good read of electricity. --Bmk 04:35, 29 July 2006 (UTC)[reply]

I agree. Purely as a mental picture, I tend to envision that current sources push current, while voltage sources require the load to pull current, and real sources do something in between. This picture may or may not be helpful. Melchoir 07:14, 29 July 2006 (UTC)[reply]

But "current" isn't a substance which can be pulled or pushed. In home plumbing, what thing is flowing inside of the pipes, is it current or is it water? Water flows in pipes, and it is charge which flows in wires. Charge gets pumped through power supplies and through any loads. A current-source is not a source of current, but instead is a source of constant current; it's a producer of constant unchanging charge-flow.

Back to the original question. A power supply pumps a little charge out of one wire and into the other. The two wires act as the two plates of a capacitor. This pumping of charge produces a voltage difference across the wires, and when this voltage rises to the same value as the power supply's output voltage, the power supply stops pumping. If we then connect a load across the two wires, this allows charge to flow back where it started, and therefore the voltage across the wires will begin falling towards zero. The power supply sees this and again starts pumping charge from one wire to the other. When things settle down, the load device is constantly discharging the imbalance of charge in the wires, and the power supply is constantly pumping the imbalance back up again. So... does the power supply push the charges, or does the load pull them? The answer is yes!  :) Both things happen: the load device draws a certain amount of charge per second from one wire to the other, and this causes the power supply to pump charges at the same rate in the opposite direction so the voltage-difference is maintained. --Wjbeaty 08:36, 30 July 2006 (UTC)[reply]

I suppose by 'amp' you don't mean 'amplifier' but 'ampere', ie 'current'. A current is caused by a potential difference. Whether one end is pushing or the other pulling depends on what you call 'normal'. If that is 'earth' and you've got a positive charge connected to earth then the electrical current flowing from the charge to earth might be said to push it. But I believe in household electricity there's a negative and a positive side, so you get a push an a pull at the same time. However, which way does the current flow? The electrical current goes in the opposite direction of the electron current, so which side pushes and which side pulls depends on what you are looking at - the flow of electrons or the flow of 'lack of them'. DirkvdM 07:53, 29 July 2006 (UTC)[reply]

2 electrons repel each other because one electron emits a virtual photon (recoils) and the other electron absorbs the photon (more energy, different momentum, changes direction) But WHEN does the electron WHEN to emit the photon? Are they conscious?

AFAIK, electrons are not conscious! My understanding is that electrons repel each other because they have similar charges - not anything to do with photons. -- SGBailey 06:39, 29 July 2006 (UTC)[reply]

Similar charges repel? No, you're talking about distant action theory, an obsolete theory from before the time of Faraday. Since Faraday we know that electrons repel each other because electrons are surrounded by EM fields, and these fields interact with particles to produce attraction or repulsion force. More recently we know that electron repulsion is based on photon exchange, and that EM fields are actually composed of huge numbers of virtual photons.

Regarding the original question: we could also ask whether electrons have some sort of hidden "clockwork" which tells them when to emit a photon. This is called hidden variable theory and is disproved by experiments involving Bell's theorem. So how do electrons do what they do? They just do: it's a law of physics with no deeper mechanism allowed. Also, why do electrons persist, rather than winking out of existence? Why do they have constant charge rather than random variation? Why do they experience a particular force at a particular distance from other charges? They just do. But perhaps you'd want to look at Many Worlds Theory which assumes that during any interaction, the entire universe splits into an infinite number of copies, where the interaction happens slightly differently in each universe. Rather than one electron having to decide when to emit, instead there are many separate universes, and the electron emits a photon at a different time in each universe. --Wjbeaty 08:24, 30 July 2006 (UTC)[reply]

Actually, hidden variables were not disproven, just local ones. Then again, there is nonlocality in the standard QM interpretation too. I think your other explanations aren't quite right either. (Cj67 03:19, 2 August 2006 (UTC))[reply]

Well, the leading Feynman diagram that causes electrons to scatter off each other does involve exchanging a single virtual photon. But that doesn't mean that what physically happens is that one electron emits a single photon, which is absorbed by the other. Instead, the quantum fields at work in some sense figure out the combined result of all possible ways for a photon to be exchanged. Does that make any sense? Melchoir 07:08, 29 July 2006 (UTC)[reply]

And all possible ways result in a repel for this case? Very perplexing!

I think the world of Faraday, but he never heard of an electron and did not write or theorize about them.Edison 20:23, 5 August 2006 (UTC)[reply]

Can anyone explain in layman's terms how electrical signals sent to the brain are converted into mechanical reflexes, resulting in movement? Thanks!

The neuron article should be a good one to read. It's pretty complicated, and very interesting, but i'll give a very general overview. Basically neurons have a cell body, the location of the nucleus and where the regular cellular processes take place, they have dendrites, and axons. Signals come in from the axons of other neurons through the dendrites, crossing the synapse, which is just the tiny gap between an axon terminal and a dendrite. If the total stimulus from the dendrites is high enough, the neuron fires, and sends a signal out to connecting neurons through the axon, propagating the signal along. Once it gets to the brain, the brain does its mysterious thing (brains are basically giant conglomerations of billions of neurons connected in complicated ways), figures out what to do about the stimulus, then sends a signal out through motor neurons, which are similar to regular neurons, except they connect to muscle cells at the axon. This connection between motor neurons and muscles is called the neuromuscular junction. Basically, the signal crosses the junction (see acetylcholine, the neurotransmitter which actually crosses), and causes the muscle cell membrane to depolarize, which in turn triggers the muscle cell to release sodium ions into the muscle, causing the muscle to contract. It's really quite complicated... to give you some clues where to look to find more details, the signal which is transmitted is actually an action potential, which is caused by the movement of ions through ion pumps and ion channels in the neuron membrane - the ions act like people doing "the wave" at a baseball game in the stands. Goodness, this is a huge topic. I'd better stop. I hope that was helpful --Bmk 04:52, 29 July 2006 (UTC)[reply]

Reflexes (such as the patellar reflex) generally don't go to the brain, but are actually automatic responses from the spinal cord. Reflex arc has more information. -- Scientizzle 05:28, 29 July 2006 (UTC)[reply]

I have two questions to ask you:

1.Tell me if the following cities snow (at least one day) in winter or not:

 *Chongqing      *Tokyo           *Oklahoma City  *Barcelona

 *Shanghai       *Seattle         *Raleigh        *Marseilles

 *Seoul          *San Francisco   *Washington, DC *Rome

 *Osaka          *Dallas          *Madrid         *Athens

2.IF most of those cities above do snow in winter, then why?I mean, I live in Sydney in Australia where it never snows in winter.Many of those cities above are on roughly the same latitude and side of a continent as Sydney.So, if snowing is such a normal and common thing in the world and Sydney is not a very warm or hot city, then why doesn't Sydney snow in winter?

60.241.116.24 06:03, 29 July 2006 (UTC)[reply]

• There's a section in snow about occurrence. It doesn't explain outright why, but it appears that snow only falls in extreme latitutes or on high mountains. Since Sydney is at or near sea level, it doesn't get snow. There's a great image (image:Earth-satellite-seasons.gif) that gives a n example of where it commonly snows in the world. There's a noticeable change in winter, but in Summer, the only snow I notice is in South America. But according to this list, it does snow in Australia and other places not usually associated with snowy weather. Hyenaste ^(tell) 06:38, 29 July 2006 (UTC)[reply]
• Latitude is only one of several factors which affect temperature. I live in the far south of New Zealand, and I'm as far from the equator as the Mediterranean coast of France, yet my climate is more like central England's. Ocean and air currents are as important as Latitude, as is the difference between a maritime climate and a continental climate - it is for this latter reason that Chicago - at 42°N gets more snow in one year than Barcelona (also 42°N) would in a couple of decades. Grutness...wha? 07:30, 29 July 2006 (UTC)[reply]

Well it is true that a land mass like a continent causes more severe temperature differences, but the difference between the two sides of the north Atlantic is at least in part also caused by the northern branch of the Gulf Stream that takes warm water to Europe, making it much warmer than it should be. I don't know if this affects snowfall too. Nor do I know if something similar happens in other oceans. DirkvdM 07:59, 29 July 2006 (UTC)[reply]

By the way, cities don't snow. I don't know what does, though. The clouds? It? DirkvdM 08:02, 29 July 2006 (UTC)[reply]

Seattle gets more than one day of snow per winter. We don't get much accumulation of snow compared to other north american cities that get snow. Typically winters here are mild, because most of the airmass is warmer tropical air from the mid Pacific: This warm, moisture-laden air keeps the winter temperature here mild, but brings lots of rain. However, if the jetstream dips far enough south, then we get a lot of very cold, dry air with corresponding low temperatures but no precipitation (either rain or snow). But if conditions are right, and we get a combination of a very cold airmass that also contains moisture then we can get snow. Typically though, the clouds that bring snow also hold in the heat, making the temperature hover right around freezing, and so we get all these "will-it-or-won't-it" forecasts for snow and often when it snows, it immediately warms up and the snow melts away.

Eastern washington is far different though. The same warm moisture-laden airmass from the pacific ocean that gives us rain cools off when it crosses the Cascade mountain range, and dumps tons of snow on Eastern washington.

- In regards to the American cities listed above in your first question, approximate average yearly snowfall is: San Francisco - trace amount, Dallas - 4 inches, Raleigh - 8 inches, Oklahoma city - 10 inches, Seattle - 10 inches, Washington D.C. - 18.5 inches. I can also say from experience that I have seen snow flurries in Rome.

Can somebody suggest me a good topic related to electronics? I have to conduct a seminar in my college. The topic must be related to electronics and can also combine electronics with various other fields such as biology, astronomy, geography, military warfare science, communication or anything else but it MUST be related to electrical or electronics. the topic must be interesting. also if u dont mind can u please say in which website I can find manuals or papers related to that topic. PLEASE SOMEBODY HELP ME. I WILL BE VERY GRATEFUL TO YOU. THANK YOU VERY MUCH.

With something like this, it is really best if it is something you already know about and care about, but howabout "the history of computing" from babbage's mechanical devices through relay logic to early valve computers and then transistor and finally IC devices? -- SGBailey 06:35, 29 July 2006 (UTC)[reply]

Definitely, I agree with you SGBailey, you might also talk briefly about Quantum computing as the future of Computing!--219.78.205.155 06:45, 29 July 2006 (UTC)Just Love Science[reply]

History of computing is a great topic and cross-cuts through all of those fields you are talking about. --Fastfission 10:53, 29 July 2006 (UTC)[reply]

I've always found the use of imaginary and complex numbers in electronics to be a fascinating subject. StuRat 07:57, 29 July 2006 (UTC)[reply]

Definitely cellular automata, and AI, although that's more computer science than electronics. --18.239.6.57 11:26, 29 July 2006 (UTC)[reply]

You could talk about Nikola Tesla, he was an amazing and sometime weird inventor. Many of his demoes are famous in the history of electricity. You will have no trouble to find documentation on him all over the internet. --66.11.173.63 10:32, 3 August 2006 (UTC)[reply]

my friend and i once playing table tennis and when we became exhausted i opened the bottle near me and start drinking water.. my friend stopped me from drinking..he said drinking water literally after exercise creates kidney pain...is it true?

Certainly not, this is only for COLD water. If you drink warm water it should be fine. This is because after intensive excercises, your body is still "running" and "agitated". A sudden dose of cold water would contract your organs (only for organs that has contact with the dose of water, wind pipe, throat, stomach etcetera, but the effect compiles on after another, not a sudden phenomenon) based on the fact that "cold contracts, hot expands". So your friend is correct.

I've never experienced this and I find that answer pretty suspect (your internal body temperature does not change that much during exercise, you can raise it a degree or so on a very hot day if you overdo it). If he is talking about developing cramps, that can certainly happen if you mix high water intake with exercise. In my experience though that is only really a problem if you drink a lot of water before exercising (after doesn't seem to affect it). --Fastfission 10:59, 29 July 2006 (UTC)[reply]

And that's really cold water, you know, the kind with ice floating in it and condensation around the bottle.

Hope you can help.

I am seeking any information you may have of Canadian doctors using Fish Oil for health related matters (cardiovascular or other ailments) in the 1930's.

Thank You

Jeff Edgecombe

Fish oil as cod liver oil was used widely throughout Canada, North America, and Europe in the first half of the 20th century as a general tonic for children. alteripse 11:40, 29 July 2006 (UTC)[reply]

Consider this sci-fi scenario:

A group of time travelers from the future (say the 2400s) go back in time to the beginning of human civilization on an expedition and get stranded there. They have a craft that is still usable for some time (for shelter and transportation) but they lost the ability to travel in time. There is no realistic hope of a rescue. They have advanced scientific knowledge and have encyclopedic information about the Earth and the history of technology. What they don't have is the advanced infrastructure of their time that would allow them to repair/re-supply their craft, or to maintain their 25th century lifestyle. These time travelers want to recreate a technology infrastructure from scratch, at a greatly accelerated pace, both for themselves and for their children.

What can they do?

(To make the exercise more interesting, consider this: these time travelers know where the natural resources are, and can fool the humans of the time into believing that they are gods and thereby obtain their cooperation.) --71.246.1.25 11:54, 29 July 2006 (UTC)[reply]

This theme has been dealt with many times by science fiction writers. I seem to remember one in which the protagonist made a fortune by devising a paper clip or something like that. These scenarios tend to skip over several big problems. First, you don't jump from primitive to advanced technology in a single leap just because you have the knowledge. Advanced technological products require both social and industrial infrastructure, which develops over centures or can be transferred in decades. So what if they settle for only slightly advanced technology? The problem then is the farther ahead you are, the less you are likely to understand primitive forms of your own technology. I'll bet more people can use a GPS system than a sextant-- so as soon as the batteries on the time travellers' GPS system wears out, they are worse off than the locals at exploring and finding things. Just because you can drive a car or use a computer doesn't mean you can build one. So the ideal time traveller might be a historian of technology who has studied the evolution of technology and take whatever exists a few steps ahead faster. Third, the business of being perceived as a god has some inherent flaws. If you think about human history, what happens to "gods" and great prophets? They get co-opted or swept up or crushed by local political forces, or they become a successful political movement, all within a few years. The story of a time traveller successfully leading the local people would be the story of a time traveller converting them into a militarily aggressive and successful society by providing one or two slightly advanced weapons and tactics (i.e., an iron knife instead of a flint one), not someone who pushes them from the stone age to the industrial age in a generation. If successful, he would transformed from an astronaut/explorer/engineer type into an emperor or god/king type for a few years before he met his violent death. Maybe that's the more interesting story. alteripse 12:15, 29 July 2006 (UTC)[reply]

Yeah, they'd have a very hard time if they are really at the beginning of civilization. They have no real way to generate electricity, most likely, and without that modern technology is totally screwed. Without the ability to set up extensive mines, you're not going to have the raw metals needed to build even the most rudimentary technologies. Infrastructure takes a long time to build from scratch, especially if you are doing it to build something that nobody else understands the purpose for (and unless you have a lot of barterable currency you're going to have a hard time convincing anyone to do anything for you). --Fastfission 12:27, 29 July 2006 (UTC)[reply]

Without electrical generators they'd be pushed all the way back to the 1910 era. Don't forget that the industrial revolution happened before electric energy systems and was based on cast iron. --Wjbeaty 07:59, 30 July 2006 (UTC)[reply]

They would probably set up a paradox resulting in the destruction of the universe. Not great for their children. Philc _T^E_C^I 13:48, 29 July 2006 (UTC)[reply]

Conceptually similar, albeit less dramatic, scenarios have enfolded time and time again throughout history. European's travelled through technologically evolved "time" when colonising Africa, South America and the Pacific Rim. More often than not, especially when the numbers are small, a significant number of the the technologically advanced colonising party meet a violent death. The indigenous parties usually suffer greatly as they are exposed to technology - and the vices and dangers that accompany them - far too quickly, eventually a strange equilibrium emerges between so-called advanced culture and tribal customs. This type of culture-clash be seen even today in regions of Africa and South America. In other words, empirical evidence would suggest that your time travellers would most likely settle into a lifestyle somewhere between theirs and their hosts. Rockpocket 19:04, 29 July 2006 (UTC)[reply]

This was a plot point in A Fire Upon the Deep and A Deepness in the Sky. Planetary civilizations would crash for various reasons, and traders who'd spent a lot of time and resources getting there, and who planned to stay for a decade or two. They had a variety of discovery trees, showing how to get from the Iron Age up to the local limit of technology. Pretty much the sort of thing you're describing. grendel|khan 23:55, 29 July 2006 (UTC)[reply]

These time travellers, perhaps they started from a tropic port, aboard a tiny ship? --Wjbeaty 07:59, 30 July 2006 (UTC)[reply]

Their time machine was set for 'a three hour tour'...

Don't forget to read "A Connecticut Yankee in King Arthur's Court" wherein the hero did not go back quite so far, but encountered some problems our fearless crew would doubtless have. The King thought the hero was a fine fellow, but the religious establishment resented change. Also Andre Norton wrote about "time traders." Heinlein wrote "Farnum's Freehold" (sp?) No need to worry about time travel paradoxes, because there are an infinite number of alternative universes. "Civilization" might be a term applied to the earliest time when some people appointed themselves the bosses of others, the warrior/cheiftain/priesthood, on religious/military grounds. Before that the people weren't well enough organized for mass warfare and exploitation. So our chrononauts would find rulers who wanted to retain and increase their power, and workers who perhaps wanted to be left alone or to rule in their stead. So one avenue of prosperity is trade: to offer either or both sides slightly better weapons. Hope they have everything from Wikipedia, project Gutenberg, and a lot of industrial handbooks along with some programmable robotic machine tools. Perhaps hire workers extract copper (acheived by 8700 BCE) from the ores whose location you already know, and introduce copper knives, arrows, and plows. Now you can make copper wire, and you're part way to modern industrialization. Extract tin (achieved by 3500 BC) and your customers will want the new improved bronze tools and weapons. Now they are used to mining and metallurgy, so get them extracting zinc (achieved by 1300 BCE). You are all set to make miles of copper wire, and to get power from copper-zinc galvanic batteries. Your workers should be able to make iron, so you can build steam engines, generators and motors, not to mention pistols, rifles and artillery. Those new steel drillbits will help your guys drill for petroleum and refine it in stills. Electronics and computers should be doable, so why not space travel and time travel? How many years would it take to advance technology by say 8000 years? What happens when technology develops in advance of religious and moral philosophy? Vicious amoral tribal chieftains with weapons of mass destruction? Oh wait: that is today's world situation. Never mind!Edison 20:55, 5 August 2006 (UTC)[reply]

hi would it be possile for you to tell explain to me the way in which alterstions of the CNS neurotransmission may account for psychiatric disorders using the xample of clinical depression. I have looked at your information about clinical depression but it appears that you do not discuss this aspect, thanks for you time and i eagerly wait for you reply. from laura

Short answer: the cause of depression isn't really known at the neuronal level. But since you asked about neurotransmission, I'd suggest taking a look at serotonin (a neuromodulator, not a neurotransmitter), which is implicated in depression. Dopamine too, to some degree, although it's most associated with Parkinson's disease. Digfarenough 12:49, 29 July 2006 (UTC)[reply]

We have indirect evidence that in severe depression there are lower levels of at least one neurotransmitter, serotonin, and perhaps others such as norepinephrine. The strongest evidence is that the most effective antidepressant drugs (SSRIs) seem to work by increasing the amounts of serotonin in the neuronal synapses. That is the short answer. A full answer is more complex and beyond my power to make something complicated intelligibly simple. There is some additional detail in our clinical depression article, which looks like a reasonably good overview, and if it hasn't changed recently, I recall we have a detailed article on psychopharmacology. alteripse 12:54, 29 July 2006 (UTC)[reply]

You might also wish to read the biological psychiatry article for an overview of the theory and practice of understanding mental disorder in terms of biology. Note that this explanation for psychiatric disorder is notwithout its critics, see Biopsychiatry controversy. Rockpocket 18:39, 29 July 2006 (UTC)[reply]

Can somebody suggest me a good topic related to electronics? I have to conduct a seminar in my college. The topic must be related to electronics and can also combine electronics with various other fields such as biology, astronomy, geography, military warfare science, communication or anything else but it MUST be related to electrical or electronics. the topic must be interesting. also if u dont mind can u please say in which website I can find manuals or papers related to that topic. PLEASE REMEBER THAT IT HAS GOT TO BE SOMETHING NEW AND INTERESTING. TOPICS SUCH AS "THE HISTORY OF ELECTRONICS" WON'T DO. I NEED TO EXPLAIN IN SCIENTIFIC AND MATHEMATICAL TERMS ABOUT SOME NEW INVENTION OR TECHNOLOGY OR CONCEPT OR ANYTHING INTERESTING. MUST BE RELATED TO ELECTRICAL OR ELECTRONICS.PLEASE SOMEBODY HELP ME. I WILL BE VERY GRATEFUL TO YOU. THANK YOU VERY MUCH.

You got 5 interesting topic suggestions above. Now you need someone to write it for you? You can YELL at us all you want but you are in the wrong field if nothing yet has interested you enough to be able to teach people about it. Drop your course, learn to repair computers or something and stop bothering us. Harsh, I know, but there are limits to the "do my homework" pleas. Next week someone will ask us for a PhD thesis suggestion, and then the website where they can find the already-done research. alteripse 15:06, 29 July 2006 (UTC)[reply]

What about smart cards? BenC7 09:44, 31 July 2006 (UTC)[reply]

Does anyone know if the following levels of the following vitamins are dangerous? Their respective articles don't tell. I do heavy lifting 4-5 times a week if that has any impact... I'll leave that for ye wise to determine...

Thiamine (B1) - 15mg Riboflavin (B2) - 10mg Pantothenic acid (B5) - 25mg Pyridoxin (B6) - 11.8mg (of which 10.5mg is pyridoxal-5-phosphate) Biotin (B7) - 100mcg Folic acid (B9) - 500mcg Cyanocobalamin (B12) - 100mcg

You see all, I'm considering a new multivitamin and this new one contains significantly higher levels of the above vitamins than my current one does. Don't wanna poison myself, or waste my money for that matter. Jack Daw 15:17, 29 July 2006 (UTC)[reply]

Nothing you've listed is even close to toxic levels (I'm assuming a once-a-day dose). Toxicity is mostly a problem with fat soluble vitamins, not water soluble ones. - Nunh-huh 15:56, 29 July 2006 (UTC)[reply]

Over the months I've noticed that the Hovercraft article has been gradually edited to make it appear that the role of Christopher Cockerell in inventing the hovercraft was only that of doing some minor tinkering to produce a working hovercraft (that travelled across the english channel in the 1950's).

By this logic, couldnt it be equally claimed that the British invented powered flight and that the Wright Brothers only did a bit of tinkering?

Oooh, after writing the above I re-read the Hovercraft article, and saw the article has now been re-written to give CC more credit. There has also been a considerable battle on the discussion page http://en.wikipedia.org/wiki/Talk:Hovercraft about this which I had not seen.—Preceding unsigned comment added by 81.104.12.22 (talk • contribs)

Yes, the talk page is the best place to discuss this. If you still have problems, try asking at Wikipedia:Peer review.--Shantavira 17:50, 29 July 2006 (UTC)[reply]

I was not being sarcastic - it is a serious question. Thanks.

No, no, some German guy was the first to fly. He just didn't get the media attention, so he has almost been forgotten. Can't remember his name, though. I'll look into that tomorrow. DirkvdM 19:11, 29 July 2006 (UTC)[reply]

Mmm. it wasn't Richard Pearse, because he was a New Zealander (and he also flew before the Wright brothers). Otto Lilienthal, perhaps? Or maybe Karl Jatho (although he was also after Pearse). Grutness...wha? 01:50, 30 July 2006 (UTC)[reply]

These article illustrate how silly the question really is. Times were right for human flight to take off (pun :) ). So it happened all over the world in a very short time span. I suppose the ones who were most into publicity won the popular title. It's like with evolution. The theory was well known. Charles Darwin, however, wrote it down in a book, so he got the title. Lilienthal didn't use a motorised plane, Jatho's may not have been a controlled flight, Cockerell didn't fly very high and Pearse forgot to photograph his achievement (the publicity bit). What is flight? How high and how far do you have to fly (does a hovercraft count?) Are you allowed to crash-land? And does it have to be repeatable, to the extent that almost every flight is successful? (When was that achieved anyway? A more important issue, I'd say.) So who was first? They all were. The Wright brothers included. DirkvdM 09:48, 30 July 2006 (UTC)[reply]

Watching TV footage from Beirut (and in most other similar cases where an explosion is filmed from afar) the sound recording of the explosion is superimposed onto the video footage such that there appears to be no delay - as if the cameraman was actually at the scene of the explosion. Who are they fooling? Is it just to make "better" TV, or is it done so that we, the viewers, cannot work out how far the cameraman is from the explosion?--G N Frykman 18:10, 29 July 2006 (UTC)[reply]

I have always assumed the audio and video was recorded independently in such situations. Thus, in the editing suite, the are combined, and the editor simply cues up the sound precisely with the explosion, rather than try and gauge the delay. Can any foreign correspondents shed light on this? Rockpocket 18:32, 29 July 2006 (UTC)[reply]

How many roads must a man walk down Before you call him a man?

4.20x10¹ Black Carrot 20:26, 29 July 2006 (UTC)[reply]

None, being able to walk down roads is not correlated with being a man.-gadfium 00:02, 30 July 2006 (UTC)[reply]

Given the number of infants who neither walk at all nor claim to be men, I would expect a slight correlation. Melchoir 00:12, 30 July 2006 (UTC)[reply]

Don't forget the women.

Ah, you mean because the average trip from the bedroom to the kitchen is insufficient training for walking down an entire road? Tsk tsk, what a terrible thing to say. Melchoir 04:56, 30 July 2006 (UTC)[reply]

If you estimate an average walking speed of about 4 mph and estimate that most children can walk around the time of their first birthday, then you can say that after walking down around 37,000 miles worth of roads you should legally be an adult in the United States. In reality the number would be far less than that, since you'd have to take breaks to eat, rest, attend school, etc. If you divided this by the average road length, though, you'd have an idea of how many roads you'd have to walk down, if you were continuously walking from around age 1, to become 18 years old, as a factor of time. --Fastfission 02:54, 30 July 2006 (UTC)[reply]

The answer, my friend, is blowin' in the wind. User:Zoe|^(talk) 03:30, 30 July 2006 (UTC)[reply]

You beat me to that one, but let me point out that the question states "how many roads", not "what distance". DirkvdM 08:55, 30 July 2006 (UTC)[reply]

follow up scientific question!!

Yes, 'n' how many seas must a white dove sail Before she sleeps in the sand? Exact scientific answers only please--172.163.144.21 20:03, 29 July 2006 (UTC)[reply]

White doves are not asexual.

White doves can no doubt be convinced to sleep in the sand if there are no other options, so you can probably get them to do that without sailing any seas. --Fastfission 02:54, 30 July 2006 (UTC)[reply]

White doves don't sail, afaik. so this is sort of like dividing by zero. So there is no answer. In other words, it's still blowing in the wind (ha! I'm the first one this time). DirkvdM 08:55, 30 July 2006 (UTC)[reply]

If you use the verb "sail" to mean, "travel on boats", there was at least one (and probably two) on Noah's Ark. User:Zoe|^(talk) 21:12, 30 July 2006 (UTC)[reply]

Ah, and (assuming the correctness of the story for the sake of the argument) if all land were covered by water then there was just one sea, so the answer is one. Which leaves the question why the dove was so stupid to return to the boat after it found some sand to sleep in after its long flight. DirkvdM 09:03, 31 July 2006 (UTC)[reply]

Maybe it was a homing pigeon.  :) User:Zoe|(talk) 03:13, 1 August 2006 (UTC)[reply]

i m required 2 submit a science project innovative in nature....i have an idea AN ELECTROMAGNETIC GUN..using an copper coil and a iron bullet ...indeed high voltage is required...that can b taken from ny T.V set...(circuit that powers the picture tube).range and firing force could b elecronically adjusted...could b upgraded by connecting with a computer..plz comment and lemme kno about its various features that i must not have came into my mind..

It's already been invented - check out gauss gun for info. --Kurt Shaped Box 22:43, 29 July 2006 (UTC)[reply]

Note, it is highly dangerous to experiment with high voltages and ampereages, you really need to know what you're doing if you want to try to make a coilgun. And if you do, please add pictures to the coilgun page--we don't have any Thanks,

AFAIK, you'd have to make it pretty long in order to accelerate the bullet to a decent speed (i.e. enough to kill your hypothetical target). It would require a rather large amount of electricity too (fancy lugging around a large battery pack strapped to your back?). Abandon all thoughts of your own gauss pistol... ;) --Kurt Shaped Box 01:03, 30 July 2006 (UTC)[reply]

It's a school project. I don't suppose the goal is to kill any targets (hypothetical or not). It'll more likely be measuring speeds against voltages and such. But apart from the high voltages, bullets flying around is indeed a safety concern. DirkvdM 09:02, 30 July 2006 (UTC)[reply]

Not only that, but if you bring any form of a gun anywhere near a school you will likely be expelled, no matter what the reason, at least in the US. Time to pick another project. StuRat 04:55, 31 July 2006 (UTC)[reply]

Good. Now if only they can apply that exclusion zone to all other humans, all buildings and other structures, all animals, all forms of transportation, all geographical features, water, air, any form of matter whatsoever .... JackofOz 06:29, 31 July 2006 (UTC)[reply]

Moved to Computer/IT RD--207.75.179.117 22:29, 29 July 2006 (UTC)[reply]