Wikipedia:Reference desk/Archives/Science/2007 January 18

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January 18

Energy and Radiation

If a hydrogen bomb where to be set off in a tube that could magnetically confine the blast and exit it out behind the tube all except of course the neutrons then how much energy would be needed. Second how much shielding would I need to trap most of the escaping neutrons?67.125.158.217 01:12, 18 January 2007 (UTC)

Note that while a magnetic field will (or can) contain charged particles, it won't stop neutral particles (mostly neutrons) or electromagnetic radiation. In other words, all the gamma rays, x-rays, ultraviolet radiation, visible light, infrared energy, etc. will still come spilling out. This link suggests that for a moderately-sized nuclear weapon detonated in the lower atmosphere, some 35% of the total energy yield of the nuke will show up as heat, light, and soft x-rays; another 5% of the energy will be in the form of hard gamma rays and energetic neutrons. TenOfAllTrades(talk) 02:34, 18 January 2007 (UTC)

Taking that energy and putting it into some kind of shielding,

• for a 100 kiloton bomb;
• there will be 40 kilotons of heat and radiation;
• which is about 1.5·10¹⁴ J;

Which is enough energy to vapourize about 150 tons of lead. Your shielding is going to need to be really durable.... TenOfAllTrades(talk) 02:41, 18 January 2007 (UTC)

So with current materials how durable can I get?

Are you implying you're actually going to set off a hydrogen bomb in a tube? --Wooty Woot? contribs 06:07, 18 January 2007 (UTC)

Make the walls of the tube really, really thick and hope that the thing doesn't shatter under pressure? Ought to make an interesting Youtube video, however it turned out though. --Kurt Shaped Box 06:43, 18 January 2007 (UTC)

It would be more popular if it did blow up. ;-) On a more serious note, this would be a good question for mythbusters, if it wasn't a nuke we're talking about. | AndonicO ^{Talk · Sign Here} 12:13, 18 January 2007 (UTC)

I've always thought this was one of the more-clever jokes in Mars Attacks! -- you know, the scene where the Martian captures the H-bomb inside his gadget, breaths in the result, and then speaks in a very high-piched helium voice Ack. Ack ack ack, ack!. I've always wondered how many people "got" the joke?

Atlant 15:10, 18 January 2007 (UTC)

Escape Velocity

If a craft was launched from the surface of the earth at escape velocity and could travel through the air without burning up how could someone ensure that the travellers inside the craft would not get crushed?

The Escape velocity article states it is a little over 10km/s, (that's 10 thousand meters a second) a human finds acceleration over 3g uncomfortable, that's 30m a second per second, manned rockets are usually limited to that acceleration. Fighter pilots can experience up to 10g for brief periods. Colonel John Paul Stapp survived 46g (still only roughly 460m/s per second) but that's commonly considered fatal in all but minute doses/periods of time. Even at that rate you would need more then 20 seconds and 5km to reach speed. Acceleration is acceleration, you can't negate the force except by slowing down the acceleration. You could make it more then 3g if the occupants were unconscious and maybe suspended in some sort of viscous fluid. What if you had a slingshot type device which accelerated them along the ground first for a while then curved up, only releasing them then at sufficient velocity, that would be more likely to leave the occupants intact. Vespine 02:36, 18 January 2007 (UTC)

Vespine, your previous argument still applies to the centripetal acceleration at the curved part of your slingshot device. The centripetal acceleration will actually exceed its own vertical component, so the situation is not improved. Thus the slingshot device would need to be even taller than the 5km you calculated above, under the same assumptions. --mglg_(talk) 02:45, 18 January 2007 (UTC)

Actually, if air resistance really is ignored, then we don't need to curve up. Just launch the thing horizontally in an obstacle-free direction such as out over the ocean. You still need a multi-km acceleration path, but a horizontal one is less absurd. In reality, air resistance would kill that approach because of the very long time it would take to get out of the atmosphere. --mglg_(talk) 02:54, 18 January 2007 (UTC)

Keep in mind that "escape velocity" is really a very artificial measure; one never needs to attain earth's escape velocity to escape the earth's pull. What you really need is to produce earth's escape energy. 100 miles above the surface the effective "escape velocity" is much lower. So just take your time escaping gravity, and avoid getting crushed :) --bmk

Since this is a theoretical gadget, I would place the passengers in a very very long tube with a viscous damping mechanism, such that the whole assembly was accelerated to escape velocity quickly, but the passengers accelerate more slowly to limit their acceleration to a survivable one of, say, 10 G. From Escape velocity: "On the surface of the Earth, the escape velocity is about 11.2 kilometres per second." (This is 25,000 miles/hour, compared to typical orbital velocity of 17000 mph for a 150 mile altitude.) To go from 0 to 11,200m/s in 1 second would be 1143 G for the total apparatus, from (11200meters/sec)/(9.8 meters/sec). The tube would have to be long enough that the passengers accelerated 1/114 as much as the tube. Like I said, a very, very long theoretical tube. If the launch was 10 seconds for the vessel to reach escape velocity, then it would experience 114 G and the passengers would have to experience about 1/11 as much acceleration, somewhat more plausible. If 114 seconds of launch were allowed, then the passengers would experience 10 G without any special doodads other than a well cushioned seat and perhaps an inflatable suit such as fliers wear for high G maneuvers. Realistically, rocket scientists have claimed that the Jules Verne "Moon gun" projectile, emerging from the barrel at escape velocity, beside squashing the passengers to pulp, would hit such dense air it would lose velocity and fall to the ground. So it is necessary for a ballistic projectile hurled into space to reach its final velocity up where the air is thin. Sci-fi writer long ago speculated about a mass driver built on Mt. Everest, so the projectile would leav it at high speed at 29,000 feet. Is the air there thin enough it could continue into space and retain escape velocity when it left the atmosphere? NASA rockets save their highest acceleration until they are at extreme altitude so they do less work pushing through dense air. Since we are building only theoretical launchers, I could also have a huge dense mass in front of the passengers, whose attraction cancelled the g force due to acceleration. Then the overall apparatus could go from 0 to 11,200 meters/second in .01 seconds, as if fired from a cannon. The G force on the total apparatus would be 1,120,000G. The G force on the passenger would average 0. (Not responsible for any tidal forces which are greater on the passenger's nose than on the back of his head tending to pull him asunder.) The apparatus would work best with flat passengers (the problem did not specify human passengers). Not responsible for any destruction to the Earth from the equal and opposite reaction. Edison 17:15, 18 January 2007 (UTC)

Apollo 11

My little brother is doing some book report on Neil Armstrong, and he claims that the Apollo 11 mission planned a spacewalk (not a moonwalk). My mom also claimed that the video of Neil Armstrong climbing down the ladder is a fake, because there were no cameras that they could use to even record video outside the lander until Armstrong reached the surface. Is there a grain of truth in either of these statements? -- AMP'd 02:14, 18 January 2007 (UTC)

Nope. The Apollo Lunar Module was designed with television in mind, and had a camera mounted on the exterior of the descent stage to capture Armstrong's steps. Our article on the Apollo TV cameras has lots of detail; the camera you're interested in is the first one listed in that article.

Your mother is correct in one regard. Neil Armstrong is NOT the person you see in the famous shot of the man getting off the lunar landing. Often that clip is combined with the audio of Armstrong saying "One small step..." quote. However, the person in the Lunar landing shot is the 2nd astronaut Buzz Aldrin. Aldrin talks at length about the journey in his book (which I highly recommend.) Armstrong had walked across the moon and captured the moment that Aldrin descended. Jeff Carr 03:23, 20 January 2007 (UTC)

The name of the book I was thinking of is "Men from Earth". I had to look it up as it's not on his wikipedia page. Jeff Carr 03:28, 20 January 2007 (UTC)

See also Apollo moon landing hoax for more details about – and explanations for – various 'errors' made by NASA in faking the moon landing. TenOfAllTrades(talk) 02:48, 18 January 2007 (UTC)

Awesome! Now to prove my mom wrong. -- AMP'd 03:17, 18 January 2007 (UTC)

If she's still not convinced, the website [1] has very deeply researched refutations of all the usual hoax claims. Maelin (Talk | Contribs) 04:50, 18 January 2007 (UTC)

Also note that if no cameras were yet set up outside the capsule, they would only need to go out and set them up, then repeat the "first steps" 15 minutes later for the cameras. I suppose this is "fake", in a sense, but it doesn't make much difference to me. StuRat 03:50, 18 January 2007 (UTC)

Note that many famous historic photos are actually ":staged" in this way - most famously, the Iwo Jima flag-raising during WWII. Grutness...wha? 07:23, 18 January 2007 (UTC)

Famously, but incorrectly. The photo of the second Iwo Jima flag raising was not staged. See [2]. - Nunh-huh 07:47, 18 January 2007 (UTC)

Apollo 15, 16 and 17 included "spacewalks" (some only involved sticking head and arms out of the capsule) to retrieve experiments from the outside of the capsule during the flights to and from the moon. I don't believe that the earlier missions ever included these in their plans. Rmhermen 16:08, 18 January 2007 (UTC)

TV cameras had been used on the moon long before Apollo 11. Three unmanned Ranger craft had sent back pictures before they impacted in 1964 and 1965. Five unmanned Surveyor program craft had sent back pictures and tested the soil from 1966 through 1968. No really new or exotic technology was required, and it was very easy to have a camera already on the outside of the lunar lander to televise the first step. It was an obvious thing to put on the mission. Although Apollo 11 was not intended to and did not do a spacewalk or EVA other than walking on the moon, Apollo 11 had about everything needed to do a spacewalk. They could have put on the moon suits, exited from the LEM, and tethered themselves outside with a rope. But the moonsuits had no thrusters for maneuvering, like the little thruster gun Ed White used on the Gemini 4 space walk and used by astronaut Michael Collins on the Gemini 10, or the AMU used on Skylab 3, or the Manned Maneuvering Unit and Safer units used on the Space shuttle. The Apollo 11 astronauts could have stayed outside for hours, and could have improvised ways of moving the spacewalker around by making a long pole out of shovels and tripods, or rigging ropes as handholds if they had to do something to the outside, like remove something stuck to the retrorocket or pulling on something that did not deploy, such as was done on one of the Skylab missions. On a Skylab mission, they also had an astronaut in the Apollo craft reach outside and pull on a solar panel which did not deploy on the Skylab, which is another trick the Apollo 11 could have done: use the Apollo thrusters to manuever the astronaut who is firmly held onto by someone in the craft while he reaches out the open hatch. They were pretty good at improvising, as shown on Apollo 13. Some astronauts have said that if they had been on the crew of the doomed shuttle Columbia and knew there was a fatal hole in the wing, they would have improvised a way to do an EVA and attempted to repair it, or to pack the cavity with a bag of water which would freeze and perhaps prevent the fatal reentry burnup. Edison 17:45, 18 January 2007 (UTC)

synosphere in fly ash

Does the fly ash generated by burning of bitumenous coal in Power plant boilers contents "synosphere" ? What are its characteristics & where is it used ?

"Synosphere" appears on Google only as a manufacturer of a PDA docking station. So if the company stays out of power plant furnaces, they should not show up in the fly ash. Does the word you are interested in have a slightly different spelling?Fly ash has lots of uses as an ingredient in concrete. I do not see anything in the article Fly ash which looks like "synosphere". Why do you expect to find such an ingredient in fly ash? Edison 18:34, 18 January 2007 (UTC)

Fly ash contains a lot of spherical particles, but nothing known to Google as "synospheres". But if you Google for "fly ash" and "spheres" or "microspheres", and you'll find thousands of articles. I'd guess the amount of the spheres produced depends on the non-carbon content of the coal. I recall UK adverts back in the early 1970s about "PFA" (pulverised fuel ash): this was produced by the kiloton by burning powdered coal in power stations, and the producers were keen to sell a waste product for use as a major ingredient in concrete... another thought arises from the name you use, and the possible source you mention: are you thinking perhaps of some kind of fullerene? (in that case, negligable amounts are produced if the coal is burning with sufficient oxygen for complete combution) Malcolm Farmer 00:15, 19 January 2007 (UTC)

Suppose someone were to set off a hydrogen bomb on the surface of the moon...

...what would the explosion and immediate aftermath look like? As there's no atmosphere, there'd be no mushroom cloud, so what exactly would happen to all the flame/ash/debris etc?

(Combining ideas from two different questions here...) --Kurt Shaped Box 06:52, 18 January 2007 (UTC)

High altitude nuclear explosion might give a hint. I'm not really certain, though the article is neat regardless ;) -- Consumed Crustacean (talk) 06:58, 18 January 2007 (UTC)

I suppose the explosion would go on until stopped by gravity, since there in no friction. | AndonicO ^{Talk · Sign Here} 12:20, 18 January 2007 (UTC)

There would still be a cloud - made up of surface material - how impressive would depend on the height of the bomb from the surface - or how far sub-surface. Rmhermen 16:01, 18 January 2007 (UTC)

I would expect that the sudden liberation of energy would look very much like a strike on the surface by a high speed (20 km-30km/sec) rock. It would produce a flash, throw up ejecta, and leave a crater. TNT equivalent says a 1 megaton nuke on the ground creates a 0.5 km crater, tiny compared to many on the moon. This is 4.184 × 10^15 joules according to Tonne of TNT. [3] says the meteor crater in Arizona was created by a 30 meter diameter meteor, the equivalent of a 50 megaton nuke explosion, and it is 1 km in diameter. Coincidentally, this is the size of the Tsar Bomba the largest bomb ever exploded. [4] is a story of a meteor impact on the moon, supposedly observed (photographed) in 1953, which resulted from a 300 meter asteroid and created a 1 to 2 km crater, in an explosion equivalent to a 1/2 megaton explosion. The numbers do not match, perhaps because of different assumed speeds and impact angles, (or because they are wild ass guesses). Edison 18:54, 18 January 2007 (UTC)

Are you saying the Tsar Bomba was dropped in Arizona? :-) |AndonicO ^{Talk · Sign Here} 20:56, 18 January 2007 (UTC)

That would have ben considered an unfriendly act at the time. Edison 06:19, 19 January 2007 (UTC)

It would still be considered so. :-) | AndonicO ^{Talk · Sign Here} 11:54, 19 January 2007 (UTC)

We also know what a high-speed impact with an airless, low-gravity body looks like from the Deep Impact mission - see this image. This impact was not in the megaton range - it was equivalent to just 4.5 tons of TNT, according to the article - but I imagine a megaton explosion would just be bigger and brighter. Gandalf61 12:35, 19 January 2007 (UTC)

Putting a man on Mars

Would they realistically call the manned mission to Mars program anything other than 'Ares'? --81.79.81.144 07:37, 18 January 2007 (UTC)

I don't know; they might even call it Mars, since he was also a god (almost the same as Ares from the Greek side of mythology). | AndonicO ^{Talk · Sign Here} 12:21, 18 January 2007 (UTC)

I'm sure Ares would get a mentioned somewhere (cf. the "Athena Science Payload" on the Mars Exploration Rovers). However - assuming NASA would be the agency who ran the mission - history would suggest a more bombastic mission name would be chosen. Rockpocket 08:08, 19 January 2007 (UTC)

What do you mean by "bombastic"? The moon was Apollo, another greek deity. | AndonicO ^{Talk · Sign Here} 11:56, 19 January 2007 (UTC)

Maybe they should send a woman too, so the trip is less boring. Edison 14:15, 19 January 2007 (UTC)

renewable energy

I can't seem to find a place source that says renewable energy resources are a good idea. They are, aren't they? --24.76.228.161 07:55, 18 January 2007 (UTC)

• Yes, they are. Try it the other way around. I'm positive you can find sources that say it's a bad idea to continue using fossil fuels. - 131.211.210.10 09:24, 18 January 2007 (UTC)

Thanks, fellow IP dude. --24.76.228.161 09:37, 18 January 2007 (UTC)

Hey there well i am currently conducting experimants on my own version of renewable energy it looks very promising now if only i can get enough money for a patent =( but yea there are sources out there that provide that however i wont say what im using till i get a patent =(Maverick423 20:51, 18 January 2007 (UTC)

New inventions in the last 40 years

Someone just asked me if I can think of any new (radical) inventions in the last 40 years. For the life of me I couldn't think of any. Remember that you have to disregard refinements or miniaturizations of existing inventions. For example you can't say "cellphone" as it uses microwave technology and miniaturized chips. Computers are just faster/smaller but all still use von Neumann architecture. I suspect quantum computing would be a new invention but it isn't mainstream yet. Sandman30s 09:08, 18 January 2007 (UTC)

So what? "cellphone" may be using microwave technology and miniaturized chips, but their application is still new as no one thought about using them that way before. Besides, most inventions are based on things we already know. I'd be hard-pressed to find anything that qualifies by your standard. - 131.211.210.10 09:23, 18 January 2007 (UTC)

Exactly, that is my problem too. Unlike true inventions such as the printing press, train (industrial revolution), car, aeroplane and computer (revolution); it seems we are slowing down as far as truly radical inventions go. Not that it's obvious to most. Technology seems to be changing ever faster on the contrary. In truth, technology is just getting more efficient or smaller. When are we going to see the next revolution? Sandman30s 13:41, 18 January 2007 (UTC)

I think the current revolution is in design and smart, eco-friendly engineering. Vranak

I would challenge the definition yet again. Classifying the printing press was a world-changing invention is very similar to classifying the cell-phone as a world-changing invention. There was paper and ink before the printing press was invented, much as there was portable RF communication much before 'modern' cellphones were invented. It's the *use* of existing technology in a novel way that makes for what you would seem to call a 'radical' invention. --66.195.232.121 15:50, 18 January 2007 (UTC)

Not just paper and ink but printing including moveable type existed way before the Guttenberg printing press. The Chinese were doing it since the 11th century Nil Einne 16:26, 18 January 2007 (UTC)

Depends of how you define "invention". A physical device? What about Internet, does that qualify? — Kieff 09:26, 18 January 2007 (UTC)

It would qualify except that it was "invented" over 40 years ago. It originated from arpanet in the 60's. Sandman30s 13:41, 18 January 2007 (UTC)

ARPANET became operational in 69, 38 years ago. :) — Kieff 08:00, 19 January 2007 (UTC)

Packet switching and other arpanet components were invented during the 60's, more than 40 years ago :) Sandman30s 12:39, 19 January 2007 (UTC)

Well, the internet itself is just the network isn't it? What about the World Wide Web/Hypertext on its own? That was invented in c. 1990. --Neo 15:01, 18 January 2007 (UTC)

If you classify http as an invention. I suppose you could define www as a world changing phenomenon. Then again would you class any type of software as inventions? Sandman30s 12:39, 19 January 2007 (UTC)

What about Wikipedia? It is a fairly recent "invention". --V. Szabolcs 21:36, 18 January 2007 (UTC)

It is software. See previous point. Sandman30s 12:39, 19 January 2007 (UTC)

No, it is software + a community! :) And.. what about (other) social "inventions"? Are they not considered inventions? --V. Szabolcs 07:30, 22 January 2007 (UTC)

If you are asking for a new technology invented in the last 40 years, I was going to say optical data storage, but our optical disc article says that the analogue optical disc was patented in 1961. Maybe if you qualify it with digital optical data storage. Our article on disruptive technology might give you some other ideas. Gandalf61 13:50, 18 January 2007 (UTC)

What I am failing to see is why taking a wagon and replacing the steam engine someone added with an internal combustion engine is more of an "invention" than taking a telephone and removing its analog components, its rotary dial, its wired connection and power supply and replacing them with battery power, digital component, wireless connections and touchpads? I don't think I agree with your history of inventiveness any more than your examples. Rmhermen 15:58, 18 January 2007 (UTC)

Because the combustion invention was a radical world-changing invention that threw out the steam engine. Sandman30s 12:39, 19 January 2007 (UTC)

I think MRI satisfies your standards. --bmk

Oh, and also Polymerase Chain Reaction --bmk

Actually, by that ridiculous standard of "invention" PCR doesn't really cut it; if I recall it is just a "combination" of certain techniques which had been worked out in the 1960s. I don't have a copy of Rabinows Making PCR on me at the moment but I recall this being central to controversy over authorship (some of the anti-Mullis people claimed that he hadn't really "invented" anything, just put a few new things together in a novel way, which of course counts as an invention under most people's definitions). Also, if you were being contrarian you could say that MRIs just exploit nuclear magnetic resonance, which was discovered many years ago indeed. You'd have a pretty dopey understanding of invention though if you used that sort of standard — turns out nothing was really invented! --140.247.240.75 18:34, 18 January 2007 (UTC)

Arguably, whatever is patented and provides royalties to its inventor is an invention. Other inventions are just given away for the public good. That some of its components or operating principles were preexisting is no different from claiming that fabricated stone tools were not inventions because they were an improvement on rocks found in naturally occurring useful shapes, or the Incandescent light bulb was not an 1870's invention because Volta made a copper wire glow in 1800. Among things I did not see 40 years ago, I find cell phones to be new and amazing inventions, from an era of looking for a pay phone and enough coins to make a call when my office paged me. The pager was an improvement over having to call in periodically to check for messages. The scanner is an amazing invention, as is character recognition, the photo quality home printer, the color plasma tv for homes, the MP3 player, digital cameras, flash memories which can store 128 meg in a thumb drive, digital camcorders, PDAs, videogames, Digital matrix encoded surround sound, gene sequencers, PCR, CAT scans, cloning, MRI, sonograms, digitally guided endoscopic brain surgery, Humalog, Lispro and Humulin insulin, selective serotonin reuptake inhibitors, and above all HeadOn (apply directly to the forehead: the ability to advertise a homeopathic product without making any medical claims whatever, and getting people to buy it.) Edison 19:16, 18 January 2007 (UTC)

All you're doing by defining an invention as something patentable is putting the definition into the hands of the people who write patent laws. This is a rather dubious definition of invention because 1. patent laws allow a lot of things to be called "inventions" that most people would be leery of (business practices, for example), and 2. not all inventions are covered by patents, as trade secrecy is sometimes a better economic alternative. --24.147.86.187 00:35, 19 January 2007 (UTC)

Please reread the part where I said "Other inventions are just given away for the public good" In no way did I say only patented things are inventions. Things kept as trade secrets are indeed another big class of inventions. Edison 06:22, 19 January 2007 (UTC)

Well GOOGLE HAS A LOT TO SAY ON THE TOPIC, and so does Wikipedia, apparently. Anchoress 06:32, 19 January 2007 (UTC)

Ok people my intention was not to start a debate on the definition or standards of inventions. I am stating that I am not impressed with any current technology as it is all an improvement of existing core technology. Electricity was a radical invention that changed the world, as was nuclear energy. I disagree that the combustion engine was not new, it changed the world, as did the Wright Bros flight engine. The invention of antibiotics changed the world. Are we close to a revolutionary invention that will change the world or is man on a "downward" spiral towards the incessant need for economically inspired improvements? Sandman30s 07:30, 19 January 2007 (UTC)

Just wait for the fusion power plant to become operational. It will surely change the world. And if mankind is not able to build it soon enough, it will too change the world into a second medieval age. --V. Szabolcs 08:45, 19 January 2007 (UTC)

Agreed. Add to this quantum technology. Superconducting in mainstream usage. Mainstream nanotechnology could be a moot point. And of course anything that revolutionizes space travel. I wonder when mankind would move on from a type 0 civilization to a type 1? Sandman30s 12:39, 19 January 2007 (UTC)

Here's the problem: you've created a set of conditions that has never existed at any time in human history. Everything is a modified version of something that came before it. Your example of the combustion engine supplanting the steam engine is quite telling. How different do you think they are? Steam engines have cylinders, pistons, and cranks. A modern internal combustion engine operates in essentially the same manner except that the work is done directly ("internally") by the expanding gas, rather than indirectly by the expanding steam. And have steam engines been thrown out? Nah, we just modified them a bit and called the steam turbines.

Part of the problem might simply be perspective - you've seen how modern inventions get tweaked and recalled and modified endlessly, but for 'historical' inventions you've been deceived by lazy teachers who can say "James Watt invented the steam engine" while apparently not knowing that he only modified an existing design that had been modified for decades before him.

James Burke did an excellent series thirty years ago called "Connections" that examined this error in thinking in depth. It's available on DVD these days and well worth the watch even today. Matt Deres 00:35, 23 January 2007 (UTC)

• Blue laser technology. Combat UAVs like the armed Predator. Mieciu K 14:04, 24 January 2007 (UTC)

Tonsilitis and the common cold

Is there a connection between cold and tonsilitis? It often seems that people with colds develop tonsilitis. Could it be an opportunisitic infection, or is it the cold virus itself which causes symptoms similar to tonsilitis? —LestatdeLioncourt 13:51, 18 January 2007 (UTC)

Here's one possible explanation. The palatine tonsils are part of the surveillance arm of the immune system. Just like lymph nodes, they tend to swell when responding to infection (mostly due to B cell proliferation). --David Iberri (talk) 16:20, 18 January 2007 (UTC)

Makes sense. But I believe it's the T cells that are more active in the immune response against viral infections. —LestatdeLioncourt 17:12, 18 January 2007 (UTC)

Of course I totally overlooked the "common cold" part of your question. :-) --David Iberri (talk) 17:21, 18 January 2007 (UTC)

If you want to read some incorrect, speculative 'original research' on the issue, check out the Reference Desk talk page. Vranak

Someone please apply that darned medical advice template. But from longtime personal experience, a viral infection (cold, flu) which persists seems to irritate the mucosa and the drainage seems to irritate the tonsils, perhaps making them more subject to bacterial infection. Repeatedly I have had colds which went on and on, were replaced by bacterial sinus infections or tonsillitus, and finally I developed a strep infection which was cured with antibiotics. Coincidencce? I don't THINK so!Edison 19:21, 18 January 2007 (UTC)

Please don't apply the medical advice template. None was asked for, and none was supplied. - Nunh-huh 19:27, 18 January 2007 (UTC)

Asking questions regarding pathology is not asking for medical advice. The difference is vast. —LestatdeLioncourt 19:46, 18 January 2007 (UTC)

Mine swell up terribly everytime I am sick and are "very large" according to one doctor I had seen about it. X [Mac Davis] (DESK|How's my driving?) 21:38, 18 January 2007 (UTC)

Acetylcholine

While researching the effects of nicotine on small cell carcinoma, I found a reference to acetylcholine, which was identified as "a neurotransmitter" that may also stimulate cell growth in tumors. I could not find anything further on acetylcholine's function in the nervous system. Could someone please add this? Hcbowman 15:41, 18 January 2007 (UTC)

Acetylcholine is the major neurotransmitter at the neuromuscular junction and a couple other sites in the brain (eg, basal forebrain). Acetylcholine should already contain this. --David Iberri (talk) 16:12, 18 January 2007 (UTC)

Mea culpa. Typo when I searched. Thanks! Hcbowman 18:50, 18 January 2007 (UTC)

Blue moon in February?

When would be the next year that there would be a full moon on the evening of January 31st and a full moon on the evening of February 29th (or is that even possible)?

Time

I don't see any reason why it would be impossible which suggests it will occur Nil Einne 16:33, 18 January 2007 (UTC)

On 31 January 2048 there is a full moon at 0:16 ET and another on 29 Feburary at 14:39 ET. That doesn't quite meet your criteria, but I suspect that is about the nearest you will get to a blue moon in February. (I have given ET rather than UT as we do not know the value of delta T so far in advance.)--Shantavira 16:47, 18 January 2007 (UTC)

I take it then that by ET you mean ET rather than, say, ET. Note that the original poster did not specify a time zone and might be assuming his/her local time zone, which we weren't given. --Anonymous, January 18, 2007, 18:26 (UTC).

Why does cuticle skin come off so easily?

That is, the skin on the sides of the nail, not on the top. I almost always have cuticle issues. Much help appreciated ! Xhin 18:23, 18 January 2007 (UTC)

See Nail biting. I believe they make bitter tasting products to be placed on the cuticles to remind one not to bite them, if that is the issue. Picking at them with the other fingernails may just be a nervous habit of self stimulation. Edison 19:26, 18 January 2007 (UTC)

Skin is made up of layers of cells covered with a (relatively) thick, horny layer of keratin. This keratin protects against abrasion, but does slough off rather easily. On most of the skin, the keratin is constantly falling off and being replaced. The nail itself is also made of keratin, but this keratin is thicker and has a high sulfur content, making it harder. Once the nail desiccates, it becomes clear and resists tearing. The part of the nail usually referred to as the cuticle, the eponychium, is made up of the same, high-sulfur keratin as the nail itself, however, since this layer is very thin, it is much more fragile. For most people, this "cuticle" never fully desiccates, and is easily torn. When the eponychium fully dries, it becomes brittle and flakes of easily. Tuckerekcut 00:53, 19 January 2007 (UTC)

Depending on your sex and style this may not be a viable option for you, but I find that - for some reason - keeping my nails coated with nail polish makes my cuticles more manageable and less likely to develop pickable ridges. Anchoress 00:56, 19 January 2007 (UTC)

I went through a period of horrible hangnails, but after drastically improving my diet, my cuticles are now beautiful and healthy. Vranak

Group and phase velocities...

Could someone explain the difference between the two, for a beat wave produced by two waves of similar frequency? I've read the articles, but to me, the definitions didn't shed any light. Which one is the velocity of the "larger" amplitude, which moves along the whole group (some might say :P) of waves (I'm tempted to pick this as group velocity because of the name, but I'm unsure), and which is the velocity of the individual waves inside this envelope?

Thanks, Icthyos 18:59, 18 January 2007 (UTC)

See Dispersion (optics) which has a somewhat understandable explanation, in addition to Phase velocity and Group velocity. The graphic demo at [5] may help. I wish it had been around when I took the engineering course in fields and waves. Edison 19:35, 18 January 2007 (UTC)

We've had this question a few times! It is difficult to understand. Here's a good one we had in August 2006.[6] X [Mac Davis] (DESK|How's my driving?) 21:35, 18 January 2007 (UTC)

So, the group velocity is the velocity of the wave that I mentally "sketch" onto what is caused by the varying amplitudes of the higher frequency waves? And the phase velocity is that of the "component" waves that make up the envelope? With the analogy of the AM radio transmission: the phase velocity is the speed of sound, since it is the wavelength of the light wave that is being modulated, and the group velocity is the speed of sound?

Thanks, that was a great help. (...unless what I just posted was wrong. Then I'll entirely reverse my thinking!) Icthyos 23:31, 18 January 2007 (UTC)

request information on radiation posion

Hey guys

well basicly I want to make a request on radiation Poison

i have read the articles however there is one problem yes the symptoms are stated and all but does anyone know how it FEELS to be in the proximity of radiation or to touch something radio active. in other words do you feel heat from something radio active? do you feel a weird nausia feeling while you are reciving a radio active dose (regardless of its potency) what does a person feel before the symptoms arise and when you are acctually reciveing the dose is what i want to knowMaverick423 19:06, 18 January 2007 (UTC)

See our article on radiation poisoning for a discussion of symptoms associated with various doses. Note that even for lethal doses, symptoms can take minutes or hours to appear. (Very high doses will be followed by nausea within a few minutes.) You have to get up to about a hundred times the lethal dose of ionizing radiation to 'feel' the damage as it occurs (immediate disorientation followed by coma).

Radioactive materials may be warm to the touch, but what you feel is simply heat produced by radioactive decay, rather than the ionizing radiation itself. TenOfAllTrades(talk) 19:35, 18 January 2007 (UTC)

OMG thank you so much this is exactly the kind of information i was looking for! someone should add this to the article for future refrence. i mean yea the article says this and that about the effects (after) you come in contact but they dont mention anything about the time during your inital contact! thanks again TenOfAllTrades Maverick423 20:30, 18 January 2007 (UTC)

one more question

hey its me again well basicly i want to know (that i dont belive i saw in the article) what is the range of radiation? is it always imminate close or touching distance or can you be like a mile away from it and still get posioned (not including the mention of nuclear bombs i know that one already) but just basicly the radation itself with no propellents to move it far away just the range of the most / or a highly radioactive material sitting on a table with out nothing stopping the radiation from spreading. how far can that radiation reach? Maverick423 20:46, 18 January 2007 (UTC)

Different types of radiation have different ranges. alpha rays are stopped in a very short distance by air. gamma rays OTOH can go much farther. Theresa Knott | Taste the Korn 20:54, 18 January 2007 (UTC)

are we talking in terms of miles for gamma rays or feet meters?. Maverick423 20:56, 18 January 2007 (UTC)

They are blocked by meters of concrete and several centimeters of lead. They certainly will be stopped by air. This is why we didn't detect gamma ray bursts until we had satellites. But I don't know how much air is needed. Theresa Knott | Taste the Korn 21:22, 18 January 2007 (UTC)

Alpha particles are helium nuclei and can be stopped by a piece of paper, beta particles are electrons/positrons and can be stopped by a piece of aluminum foil, gamma rays are photons in the gamma range, and takes 6 inches of concrete to decrease their intensity by 50%. Alpha radiation is unharmful to the outside of a person since it is absorbed within micrometers of the skin. In order of potency the list goes: alpha, beta, gamma. X [Mac Davis] (DESK|How's my driving?) 21:29, 18 January 2007 (UTC)

Thanks much for the information guys you are all great!! Maverick423 21:40, 18 January 2007 (UTC)

oh and dont worry these arnt work related or anything after all i finished school 2 years ago they are just questions burning in my mind. when u see movies where radiation is involved you see people trying to get as far away from the radiation as possable or they look like they get hit by something sometimes when they see a radio active substance come into contact with their hands or jus from simply looking at the matiral . this is what got me asking these two questions and i am thankful that you all anwsered them =) thanks again!Maverick423 21:43, 18 January 2007 (UTC)

Not mentioned above is that even when radiation is not being stopped by something, its intensity diminishes in proportion to the square of the distance, so if you are initially 1 foot from a gamma source and you move out to 50 feet away, that is 50 times farther and 50 squared is 2500, so the radiation is 1/2500 of what it was. This is just for geometric reasons -- the same amount of radiation is spread out over a spherical region with 2500 times the area -- and also applies to things like light and sound. --Anonymous, January 18, 2007, 22:58 (UTC).

...in a vacuum. Even in low pressure that doesn't hold close. X [Mac Davis] (DESK|How's my driving?) 23:18, 18 January 2007 (UTC)

Yes but it will always drop off at least by that much. Theresa Knott | Taste the Korn 23:43, 18 January 2007 (UTC)

Some radiation can go very far distances indeed. Cosmic rays can travel millions of miles (most of which in a vacuum, though) and still be very highly energetic. --24.147.86.187 01:40, 19 January 2007 (UTC)

This may seem picky, but the distinction is the basis of 20th century physics - cosmic rays do not lose 'energy' as they travel through the vacuum, although they do lose 'intensity' as ${\frac {1}{r^{2}}}$. --18.214.1.72 02:02, 19 January 2007 (UTC)

After an atomic blast, the radiation carried in fallout particles (formerly the ground, houses, people, trees, etc near the blast) can travel hundreds of miles downwind in a deadly plume. The radiation from such a particle may fall off as described by the inverse square law, but that law does not describe bomb fallout or particles released from a nuke accident such as Chernobyl. Edison 06:27, 19 January 2007 (UTC)

Great info guys thanks a ton. if only wikipedia was available when i acctually had homework to do lol that would of been great. in anyways thanks alot you all!! Maverick423 17:08, 19 January 2007 (UTC)

Time and thought

One thought that occurred to me today was that our psychological perception of time must be dependent on how "fast" we think, so to speak. Now I know that there are objective ways of defining time intervals (e.g. the second and the oscillations of Cesium's electrons), but in the end isn't what really gives meaning to the flow of time how fast we perceive it (à la relative motion)? If we thought slower, would events unfold at a slower rate according to our perception? Conversly, would we experience a "faster" flow of time if we had superior mental processing abilities? —LestatdeLioncourt 21:26, 18 January 2007 (UTC)

Just want to fix a bit of your reasoing here: if we thought slower, we'd perceive events and time as faster, and not slower. You wouldn't keep up with external time. — Kieff 23:54, 18 January 2007 (UTC)

You're right. It should be the other way around. My mistake. —LestatdeLioncourt 09:26, 19 January 2007 (UTC)

You may find our article on Time#Psychology informative and useful in finding other sources. Hipocrite - «Talk» 21:34, 18 January 2007 (UTC)

I have heard that outstanding athletes (e.g. Wayne Gretzky), who presumably have superior mental abilities (at least with regards to their particular sport) actually experience crucial events in a game at a lower speed than usual. Vranak

This concept is explored in a number of fiction works, usually by means of explicitly "speed-up" drugs or special abilities. I always wondered if it's possible to artificially speed up our thoughts (without other effects), and what problems that could bring us. — Kieff 23:54, 18 January 2007 (UTC)

Totally relevant. Vitriol 01:26, 19 January 2007 (UTC)

Somewhere in the Lensman series there is a description of the "speed of thought" being faster than the speed of light! In fact, human thought processes are slower than we tend to notice. Books such as The Astonishing Hypothesis discuss experiments that have measured how long it takes for people to respond to sensory stimuli and become consciously aware of them. Ultimately, the "speed of thought" depends on how quickly metal ions can diffuse through water at body temperature and the overall size of the brain. The electrical signals that carry information in the brain depend on the diffusion of charged ions through pores in the membranes of neurons. --JWSchmidt 02:28, 19 January 2007 (UTC)

Elderly relatives have insisted to me that the older they get, the faster time sems to pass. When they were young, a year lasted a long time. When they are elderly, the years go by zip zip zip. A baby seems to grow up quicker than when the observer was young. If their thought process slowed down, that could account for time seeming to go faster per the above. Edison 06:31, 19 January 2007 (UTC)

I've noticed this same phenomenon, but my garden theory is that we perceive life "ratiometrically". When we were little, the eleven months between now and Christmas represented, say, 25% of our life and so seemed like a long, long time. Now, it represents less than 2% of my life, so it seems rather quicker. Plus, I spend so much time on Wiki that it all passes like a blur anyway... Atlant 12:42, 19 January 2007 (UTC)

A lot of our senses are logarithmically scaled. We notice change, not absolute value. If you double the intensity of a light, you'll feel a certain increase. Once you're accustomed with that intensity, a second doubling (so now it's 4x) gives the same perceptual increase of intensity. So perhaps that's exactly how it goes with time: we just need more passed time to feel the same way than we did before. Life is logarithmic. That phrase has a nice ring to it, doesn't it? — Kieff 13:50, 19 January 2007 (UTC)

Here is an experiment you can conduct. I have done it many times and it works great for me. Get a quartz watch, digital of with hands, does not matter. make sure if it's digital that it reads out the seconds. Stare at the watch looking at the seconds going by and concentrate trying to speed up your "internal thoughts". This may take some practice but one can learn to do it. While one is speeding up ones thoughts, one can actually "observe" the speed up the seconds ticking by changing. It really works. Zeno333 08:17, 20 January 2007 (UTC)