Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

October 12

Image licensing

HI,I AM DOING THIS PROJECT ABOUT NORTH AND SOUTH POLE AND I JUST WANT TO ASK YOU THAT IF I CAN PRINT SOME PICUTER THANKYOU VERY MUCH FROM MEENAKSHI —Preceding unsigned comment added by 68.183.31.96 (talk) 00:18, 12 October 2008 (UTC)

Yes

SpinningSpark 11:23, 12 October 2008 (UTC)

Smallprint for lawyers to read

Almost every photo on Wikipedia is freely licensed. This means that you may re-use or modify the photos (including printed copies). For any specific image, check its license information, which will provide details on what the image owner requires regarding re-use. Also see Wikipedia:Image copyright tags for general information. In general, if you are using these photos for a school project, that would be permissible under most of the image licenses on Wikipedia. Nimur (talk) 00:32, 12 October 2008 (UTC)

I have no idea what cutting pie has to do with the North and South poles....--el Aprel (^facta-_facienda) 00:36, 12 October 2008 (UTC)

Hi! It's OK to print most pictures that are on Wikipedia - but there are a few exceptions. All of the photos at our South pole, Antarctica, North pole and Arctic are OK to copy. You can also go to our sister site "WikiCommons" - and type "North pole" or "South pole" into the search box...you'll find also that there are "categories" of photos: Category:South_Pole and Category:North_Pole. There is also a bunch of photos of the Amundsen-Scott south pole station. All of those photos are OK to print.

If you need to know about other pictures on Wikipedia, what you need to do is to click on the photo you are interested in and when the image's own page pops up, it should look a bit like this one: HERE. Now you need to scroll down and look where it says either: "Licensing" or "Permission (Reusing this image)" - if it says something about "Fair use" then it's not OK.

SteveBaker (talk) 00:47, 12 October 2008 (UTC)

Though honestly if you are using it in an elementary school assignment I don't think anybody cares about the copyright status. --98.217.8.46 (talk) 03:29, 12 October 2008 (UTC)

You mean ANY school project? Who's going to sue you because you used, say, Coca-Cola's logo in a school assignment? That would just make the copyright owner look bad. --M1ss1ontomars2k4 (talk) 04:06, 12 October 2008 (UTC)

Well, I left out "any" because I could imagine some school projects in some scenarios where stuff like that could matter. (A dissertation is a "school project", in a sense, and you have to be mindful of copyrights with those.) But yeah. Really not worth worrying about for run-of-the-mill assignments. Falls under fair use pretty solidly. --98.217.8.46 (talk) 13:25, 12 October 2008 (UTC)

It is important to teach a respect for the copyright law. If kids get the idea that they can copy anything anytime - they are going to get into a lot of trouble in later life. Copyright laws are annoying and a big pain in the butt - but they are laws - and it's important that kids realise that. The idea that copyright holders don't "care" about little things like school projects is likely true - but that's not true of trademark law - where if you don't actively pursue infringements you can lose your ownership of them. Hence, CocaCola may well be forced to pursue even "irrelevant" infringement at the level of a high school project. SteveBaker (talk) 14:58, 12 October 2008 (UTC)

Oh yeah, sorry, I was forgetting about all those CocaCola billboards at the North Pole and the pictures of them in Wikipedia to catch out the unwary. Context! please. SpinningSpark 18:24, 12 October 2008 (UTC)

Large corporations will most certainly sue schools over misues of their trademarks: Disney has done it to day care centers and most other companies will as well. They will also always win, and it isn't only because they have lots of high powered lawyers. Under intellectual property law, there is a concept known as "trademark dilution"; once a trademark (be it a word, logo, or character, basically any symbol of your company) has entered the common lexicon, you can no longer use it as a trademark. Basically, if Disney did NOT aggressively defend its trademark, and was shown to allow, say, a day care center in Florida to use Mickey Mouse in their logos without proper permission, then it would set a precedent for anyone to use it. Disney cannot be selective in allowing infringements of its trademarks; it either has to expressly require that all uses are licenced, or it has to allow all uses by anyone for any purpose. As a result, large corporations can and do pursue these cases... --Jayron32.talk.contribs 18:35, 12 October 2008 (UTC)

Jayron is exactly right. Consider for example a school student project which then becomes entered in the state science fair and wins, subsequent to which prominent newspapers publicize the event c/w pictures. The way copyright law works is that you have to pursue any violations that come to your attention, otherwise you fall foul of the equitable doctrine of laches and your trademark becomes public domain. Aspirin and kleenex are examples of former trademarks that became common names. Companies don't want to pursue daycares, they have to. Franamax (talk) 04:56, 14 October 2008 (UTC)

What colour would you say best describes the upper mandible of a male Eclectus?

Question as topic. A user has suggested that 'candy-corn-coloured' (as stated in the article at present) is less than ideal. I'm inclined to agree.

Any suggestions? I'm thinking 'saffron' - though I'll readily admit that colour naming is not my strong point... --Kurt Shaped Box (talk) 02:52, 12 October 2008 (UTC)

It looks like scarlet (or orange) with a bright yellow tip, though I see what the phrase "candy-corn-coloured" means when I look at the photograph of the parrot. Just "candy corn", without the "coloured", might work for those who have seen candy corn (and for those who haven't, click here [1]) but candy corn has a white tip. ៛ Bielle (talk) 03:09, 12 October 2008 (UTC)

I agree. When writing for Wikipedia, one should strive to keep specific cultural references like "candy-corn" out of articles like that. We are read in dozens of countries around the world - most of whom will never have seen or heard of candy-corn. Most people in the USA know what it is - and what color it typically is - but I doubt whether people from other countries would know. Sure, you can provide a link to the article candy corn - but it would be much better to use a proper description of the color rather than to send people off on hunts for obscure references like that. Better still - just put a nice color picture in there. SteveBaker (talk) 03:26, 12 October 2008 (UTC)

People who don't know candy corn? My God, man! I don't believe it. I won't believe it! Plasticup ^T/C 05:15, 12 October 2008 (UTC)

Well, I've never heard of it. But I wouldn't want to interfere with your deeply held beliefs. Algebraist 09:08, 12 October 2008 (UTC)

Looks orange-yellow to me. [By the way, I have no idea what "candy-corn" is. ;-) ] Axl ¤ [Talk] 11:04, 12 October 2008 (UTC)

Candy corn is little multi-colored globs of sugar, usually served at Halloween in the U.S. I've never had a taste for it... --Jayron32.talk.contribs 13:00, 12 October 2008 (UTC)

Nobody has tasted it. None have been produced since 1934. The entire supply at that time has simply been recycled each year. -- kainaw™ 17:08, 12 October 2008 (UTC)

Yeah, every year the entire supply is melted down to make Circus peanuts. Interestingly, every year the entire suply of Circus peanuts is melted down to make candy corns, resulting in a never ending cycle of recycling inedible "candy". --Jayron32.talk.contribs 18:01, 12 October 2008 (UTC)

I think you've all forgotten that the sole purpose of candy corn is to insert two of them - pointy-end-down - between teeth and upper lip for the purpose of scaring little sisters into thinking you have turned into a vampire on all-hallows evening. Subsequent consumption of these objects can only be accidental. SteveBaker (talk) 19:46, 12 October 2008 (UTC)

I wonder if Eclecti will eat candy corn, if offered? --Kurt Shaped Box (talk) 22:41, 13 October 2008 (UTC)

For what little it's worth, I rather like the stuff. —Tamfang (talk) 01:31, 14 October 2008 (UTC)

I'd never seen, nor heard of 'candy corn' until yesterday. When I saw the term used in the article, I was imagining something like toffee popcorn - or maybe candyfloss. --Kurt Shaped Box (talk) 19:28, 12 October 2008 (UTC)

...which is PRECISELY why we shouldn't use it. SteveBaker (talk) 19:48, 12 October 2008 (UTC)

Be better to pick from shades of yellow and link to the chosen shade. Bazza (talk) 14:21, 13 October 2008 (UTC)

Copper(II) Sulfate Crystal

Hello. Are there any catalysts or fancy methods to make a solution of CuSO₄ • 5H₂O and water crystallize faster, clearer, and with clean cuts? Thanks in advance. --Mayfare (talk) 04:08, 12 October 2008 (UTC)

The problem is that speed and quality are exactly competing factors in crystalization. Any method used to make crystals quickly (such as rapidly dropping solution temperature, or "scratching", or adding seed crystals) will cause LOTS of small, imperfect crystals to form. If you want faster, then create a hot supersaturated solution of CuSO₄, and let it cool to below the precipitation temperature. Drop a small "seed crystal" of CuSO₄ • 5H₂O into the mixture, and viola, you'll get crystals, but they will likely be small and imperfect. If you want high quality crystals, you should aim for making them AS SLOW as possible. You should start with the same hot, supersaturated solution (this is generally made by boiling a saturated solution of CuSO₄ until the volume reduces, but there are ABSOLUTELY NO crystals in the solution) and then place it in some insulation, and let it cool VERY SLOWLY. After several days, crystals should form, and they should be nice and big and well defined. --Jayron32.talk.contribs 11:38, 12 October 2008 (UTC)

1876 Supplement to Harper's Bazar, No.13 and No. 25

I recently discovered two tapestry patterns from 1876 each are double sided on one side clothing patterns on the other side maybe embordry prints/designs. The patterns and instructions are printed on old newspaper and folded in half twice. The paper is very fragile to handle or measure without causing damage. I want to know more about these documents and how to share them? —Preceding unsigned comment added by Yma99 (talk • contribs) 09:35, 12 October 2008 (UTC)

I copied this question from the new users page as how to handle old newspapers is bit beyond a question on how to use Wikipedia. SpinningSpark 09:47, 12 October 2008 (UTC)

Perhaps call a museum in your nearest large city? Or go to the local library and ask? Either of these will have people who can direct you to specialist advice. You might check though whether these are already scanned in a web archive somewhere. Franamax (talk) 04:42, 14 October 2008 (UTC)

photographic chemicals

Up to the 1940's photographers knew various chemical formula for making black & white negatives and prints. Where can I find this chemistry? —Preceding unsigned comment added by 122.111.64.194 (talk) 09:58, 12 October 2008 (UTC)

A good place to start looking is History of photography and follow the links there. Timeline of photography technology may also link to useful articles. SpinningSpark 11:06, 12 October 2008 (UTC)

Which formula do you want? I have books listing many. Edison (talk) 23:21, 12 October 2008 (UTC)

electron configuration of Barium

Hi is the following electron configuration for I have come up with for the element barium correct?

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2. Thanks. —Preceding unsigned comment added by 139.222.240.110 (talk) 12:43, 12 October 2008 (UTC)

Looks right to me. Barium is in period 6, group IIA, which should have the configuration "...6s2" and it doesn't look like you missed any core orbitals either. --Jayron32.talk.contribs 12:57, 12 October 2008 (UTC)

Yeah, that's right. Source: Clicky —Cyclonenim (talk · contribs · email) 13:58, 12 October 2008 (UTC)

thanks :) —Preceding unsigned comment added by 139.222.240.66 (talk) 17:50, 12 October 2008 (UTC)

Using nuclear weapons as a propulsion system for spacecrafts

I'm reading Neal Stephenson's new book Anathem and in it he describes a rather unusual propulsion system for spacetravel (this isn't a big spoiler at all, feel free to read on even if you haven't read the book yet).

The idea is this: a spaceship would have one side on it that is covered by a so-called "pusher plate", which acts as a big shield, capable of withstanding a nuclear blast. A nuclear weapon is deployed on the other side of it and detonated, and thus the spaceship would fly off with enourmous velocity (essentially rocket jumping, but with nuke instead of a rocket and a spaceship instead of a player).

I've thought a little bit about this, and it seems to me that this wouldn't work. The reason a nuclear weapon will blow everything around it to smithereens (like that famous exploding house that we've all seen), is that it has an enourmous shockwave. But space is essentially a vacuum, there's no medium for a shockwave to propagate through. So it wouldn't impart basically any momentum to anything near it. The only thing that would happen (I imagine) is that it releases lots and lots of energy through electromagnetic radiation, which would barbeque any organic material nearby, but it wouldn't actually have a shockwave. I don't know if electromagnetic radiation departs any momentum on the things it hits, but even if it does, it's not all that much, is it?

Look at the sun: the sun is basically a mindnumbingly big nuclear reaction, much much bigger than any nuclear weapon, yet it doesn't "propel" it's satellites to enourmous speeds. The earth isn't flying off into space because of the sun. So why would this system work? 195.58.125.56 (talk) 17:51, 12 October 2008 (UTC)

See Project Orion (nuclear propulsion). Its "performance" section explains how they intended to design special bombs such that they'd maximise the kinetic yield of the nuclear explosive, which they'd then impart to the spacecraft itself by collision. -- Finlay McWalter | Talk 17:56, 12 October 2008 (UTC)

(e/c) Neal stephenson is just one in a long line of science fiction authors who have used the idea proposed by Stanislaw Ulam in or about the late 1950s. See Nuclear pulse propulsion.--Fuhghettaboutit (talk) 17:58, 12 October 2008 (UTC)

Yep - project Orion is famous in Sci.Fi. circles - lots of books have used it. I'd argue that the rather subtle manouvering that's implied would be impossible for such a craft - you've only got an all-or-nothing thrust mechanism. You can't do a "three second orbital injection burn" with a motor that either kicks you up the backside with 20 megatons or does nothing at all. But with such a large craft - you'd need something pretty powerful. SteveBaker (talk) 19:39, 12 October 2008 (UTC)

If I were building such a craft I would include a conventional rocket engine as well for the subtle stuff. Just use the nukes for simple acceleration. You need to be able to get a safe distance from anything you don't want to blow up/irradiate anyway, which requires some kind of propulsion. --Tango (talk) 20:40, 12 October 2008 (UTC)

If you don't mind wasting a bit of ΔV, you can dial down the thrust by delaying the explosions by various amounts, to detonate the bombs further from your ship. --Stephan Schulz (talk) 22:45, 12 October 2008 (UTC)

Nah, you only use nukes for intersteller travel. For manuvering you use conventional muntions. "Three grenades to starboard. Aye, Captain!".  ;-) Dragons flight (talk) 22:49, 12 October 2008 (UTC)

At least that will improve chances for peaceful first contact with the Minbari. --Stephan Schulz (talk) 22:52, 12 October 2008 (UTC)

Just to address the main question in it: it's not the shockwave that pushes the ship. You put in some plastic (basically) and the heat/radiation of the bomb turns it into a very dense plasma which expands/explodes and that pushes things. Basically. --98.217.8.46 (talk) 02:14, 13 October 2008 (UTC)

Also interesting is Nuclear salt-water rocket. Essentially a continuously exploding nuclear pulse propulsion rocket. ScienceApe (talk) 00:13, 13 October 2008 (UTC)

Wow! That's a cool idea. I like it! SteveBaker (talk) 01:37, 13 October 2008 (UTC)

What good an anal probe?

I've just thinking about all those personal accounts of (supposed) abduction and experimentation upon humans by aliens. How much useful data would one actually be able to collect on a human subject by probing its anus? Can anyone think of what it is that the prober might actually be trying to discover about the probee by doing this?

The taking of skin, blood, sperm and tooth samples at least kinda makes sense from a 'research into the species' viewpoint. --Kurt Shaped Box (talk) 19:24, 12 October 2008 (UTC)

It's a particularly unpleasant and degrading experience which elicits sympathy from those the abductee tells about it. --Tango (talk) 19:35, 12 October 2008 (UTC)

Apparently aliens are fascinated by cows (e.g. cattle mutilation). Perhaps they are looking for evidence of beef consumption? Dragons flight (talk) 19:50, 12 October 2008 (UTC)

Temperature and eating habits come to mind. —Cyclonenim (talk · contribs · email) 20:53, 12 October 2008 (UTC)

As does inspiring the fear of invasion. Julia Rossi (talk) 21:44, 12 October 2008 (UTC)

I think they are looking for our brains - they must be in an out-of-the-way place as we only occassionaly use them. SpinningSpark 22:20, 12 October 2008 (UTC)

If this were truly happening - an alien wanting to do a "non-invasive" investigation would of course start off by checking and sampling material from every obvious external orifice. SteveBaker (talk) 22:28, 12 October 2008 (UTC)

Though can cross the galaxy but somehow they haven't invented x-rays, cat scans, or MRIs? Dragons flight (talk) 22:44, 12 October 2008 (UTC)

Sampling...extracting fluids and solids. SteveBaker (talk) 23:50, 12 October 2008 (UTC)

They have. But they have a huge co-pay. - Nunh-huh 22:57, 12 October 2008 (UTC)

You know, I would consider someone sticking something up my rear end to quite invasive... --Tango (talk) 23:01, 12 October 2008 (UTC)

Fair point, Steve - but I don't recall reading many (any?) accounts of oral probing in the abduction accounts. --Kurt Shaped Box (talk) 23:33, 12 October 2008 (UTC)

Observer bias. The people who were asked nicely to say "Ahhhh" and got a lollipop at the end of the probing didn't complain as much as the ones who suffered less dignified forms of testing.  :-) SteveBaker (talk) 23:50, 12 October 2008 (UTC)

I forget the poet and the poem, but it was on the lines of "Aliens came from another planet/and studied humans/and decided they were a means/for the production/of shit". Any outside observer studying our hygiene habits, and the attention paid by humans to the emanations of dogs (picking up in bags and carrying it around fer gawdz sake), would surely conclude that there must be something very important up there and feel the need to investigate. Franamax (talk) 04:35, 14 October 2008 (UTC)

the whole anal probe thing is a front, they only do it to distract the abductee from what they're really doing, and make stories of their experiences sound even more ridiculous when they're returned to Earth. What they really do is something much, much more sinister. --86.135.181.146 (talk) 14:42, 16 October 2008 (UTC)

how much gas?

How much gas would an average human be able to pass in his or her lifetime? ("Would" because normally we don't try to maximize this. I mean if they were to eat a lot of beans all their life -- nothing chemical/artifical). —Preceding unsigned comment added by 82.120.232.170 (talk) 21:41, 12 October 2008 (UTC)

Well, the Mythbusters measured between 3 and 10 'gas passing incidents' per day on a normal diet - with a typical volume of around 13ml per 'incident'. Let's pick 5 per day as an average. Over a 70 year lifespan - that's 70x365x5x13ml = 1600 liters - which you could visualize as being about the volume of a good-sized house. On a 'bean-intensive diet, the Mythbusters registered 22 incidents per day - with a peak volume of 170ml in one hour - so we should say that about five times the 'normal' amount is probably about the maximum. But there are HUGE error bars on those numbers. I'd believe 5 times more or 5 times less than that 1600l number. SteveBaker (talk) 22:46, 12 October 2008 (UTC)

1 cubic meter is exactly 1000 liters, so 1600 liters is 1.6 cubic meters. That's about the volume of a 1.2 m x 1.2 m x 1.2 cube. --99.237.96.81 (talk) 22:56, 12 October 2008 (UTC)

Er - yeah. Sorry - I slipped a zero or three there! Wow...that's *NOTHING*. SteveBaker (talk) 23:52, 12 October 2008 (UTC)

Steve, we're allowed to screw up like that - you're not! ;) hydnjo talk 00:59, 13 October 2008 (UTC)

According to Britannica, a lactase deficient person will produce (or rather, the persons gut bacteria will produce) 500ml to 1000ml of gas from one glass of milk. So if you really wanted to go for it and do record breaking stuff, ten glasses per day would not be too challenging and would yield (for Steve's 70 years) 70x365x10x750ml = 191,625 litres. Which is a bit more house sized. SpinningSpark 23:39, 12 October 2008 (UTC)

October 13

Is our solar system flat ?

In all models and illustrations of our solar system that I have seen, the planets appear to be traveling in one plane. This seems strange to me. Don't the planets actually revolve in different orbital planes, and if so, is there some way that the distance between planets varies with time, maybe to the point of possible collision between two planets? —Preceding unsigned comment added by 58.167.231.238 (talk) 00:11, 13 October 2008 (UTC)

Solar system says: Most large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic. The planets are very close to the ecliptic while comets and Kuiper belt objects are usually at significantly greater angles to it., so yes, they're all basically on the same plane. This came about because the planets all formed from a spinning disk of stuff. As for the second question, no the planets are too far away from each other to ever collide. --Sean 00:18, 13 October 2008 (UTC)

Actually, if you ignore the now disgraced Pluto, they do all revolve in roughly the same orbital plane. Our articles on the solar system are actually some of the best at Wikipedia, most are featured or good articles. See Solar system and Planet for some broad overviews. As far as planetary inclination, which is the term for deviation from the mean orbital plane of the solar system, the largest is Mercury at 7^o off center. All other planets are less than 3.5^o off center. Now, lots of other objects do orbit at distinctly greater angles outside of the orbital plane, but none of the main planets do. See List of spherical astronomical bodies in the Solar System for a full list of planets and their stats. The planets are all in fairly stable orbits, and stand no real chance of coliding with one another (even Pluto and Neptune, which swap place in terms of distance from the Sun, do not actually physically cross orbits, and would never collide). Objects in the Solar System do colide all the time, but this usually occurs because some of the smaller objectes, with more eccentric orbits, will collide with a planet. There is no chance for two planet-sized objects to collide. --Jayron32.talk.contribs 00:25, 13 October 2008 (UTC)

Pluto IS a planet, dammit. 67.184.14.87 (talk) 20:30, 13 October 2008 (UTC)

The distances between planets varies dramatically because they all orbit the sun at different rates. Mars (for example) goes around the Sun once every 1.9 earth-years. So if Earth and Mars were as close together as they ever can be - then about a year later, they'll be on opposite sides of the Sun...and about as far apart as they can ever get. But I presume that you are asking whether the radius of the orbits changes. Well, things are a bit more complicated. The planetary orbits are not circles - but ellipses - so the distance of the each planet from the sun varies slightly through the planetary-year. Those ellipses are also slowly rotating - so each planet's path through the solar system looks a bit like a flowery spyrograph pattern. While this pattern seems very stable and is unlikely to change much in the future, the solar system is an "n-body problem" - which is an unsolved mathematical problem - and is believed to exhibit chaotic properties. That means that we can't reliably predict what will happen over the very long term - and it's possible that some strange combination of conditions could perturb the stability of the solar system. While the planets seem to know where they're going - that's not true of moons. It is known (for example) that our Moon is gradually spiralling away from the Earth and will eventually disappear off into space - it's unclear what the consequences will be when that happens. One of Mars' moons is going to break up in the next million years and form an amazing ring system around that planet. Pluto's orbit is thought to be somewhat unstable. So things are not as stable and clear-cut as they seem. SteveBaker (talk) 01:33, 13 October 2008 (UTC)

The moon is backing away from the Earth because it is increasing its orbital angular momentum by stealing from the Earth's rotational angular momentum via tidal drag. Given a long enough time the Earth rotation would slow to match the orbital period of the Moon, and the system would be doubly tidally locked (like Pluto and Charon are). Once that happens the Moon will no longer recede from the Earth. The mechanisms responsible for its recession don't allow the Moon to escape. A back of the envelope calculation suggests that the orbit of the moon can grow to about 5 times it's present size before the Earth's angular momentum is entirely depleted, so that sets an upper limit on the ultimate size of the orbit. Dragons flight (talk) 07:24, 13 October 2008 (UTC)

Actually, if it expanded to 5 times its current distance I think it would outside the Earth's Hill sphere (our article says the Earth's Hill sphere is about 1.5 million km and the Moon's orbital radius 0.384 million km, and 5*0.384=1.92>1.5), so it would be perturbed by the Sun and would eventually enter a direct solar orbit. --Tango (talk) 11:11, 13 October 2008 (UTC)

squid blood

I was watching a tv show about colossal squid. The narrator said that the squid's blood was blue. I have read through the articals on squid, giant squid and colossal squid but can't find any information as to why the blood is blue. Why is this? Also, are there any other animals that do not have red blood?

Thanks. —Preceding unsigned comment added by 216.154.17.55 (talk) 03:30, 13 October 2008 (UTC)

It's bluish. All your questions are answered in hemolymph and hemocyanin articles. --Dr Dima (talk) 03:46, 13 October 2008 (UTC)

short answer: it uses copper instead of iron to grab the oxygen. rust is red, but copper oxide is green. see articles mentioned above for details.Gzuckier (talk) 00:23, 14 October 2008 (UTC)

to know mechanism

please give me satisfactory mechanism of how blood cells come out from the bone marrow? which mechanism do they follow to come out?

i also want to know that through which respiration method RBC respire?

please send me answers of all this questions. i am a biology teacher.

thanking you. —Preceding unsigned comment added by 117.196.0.122 (talk) 04:59, 13 October 2008 (UTC)

For the record, you sound like a biology student. I'd suggest consulting your teachers manual and colleagues for answers. If you can't find them there, read Red blood cell and Bone marrow. In reponse to your second question in particular, consider the following: What enzymes or cellular machinery does a cell require to perform aerobic or anaerobic metabolism? What do RBCs have/lack? --Shaggorama (talk) 07:28, 13 October 2008 (UTC)

Orthogonal translation

Wikipedia doesn't have an article for this. What is it? --M1ss1ontomars2k4 (talk) 05:50, 13 October 2008 (UTC)

Some context would be useful here. Is this phrase just the "plain-English" sum of its parts, i.e., approximately "Orthogonal translation--motion at a right angle to some other direction"? DMacks (talk) 05:57, 13 October 2008 (UTC)

I agree, context is needed to answer this question properly, but orthogonal transformation might be meant if this is a mathematical concept, and the Maths desk might be able to help more]] SpinningSpark 07:08, 13 October 2008 (UTC)

My bad; I intended this question to be in the biological sense. "Orthogonal translation" is noted in several places in my lecture slides but no definition is given. --M1ss1ontomars2k4 (talk) 16:43, 14 October 2008 (UTC)

Alright, so it's translation (biology), and "orthogonal" meaning "completely different of or independent from each other". Consider doi:10.1038/nchembio789:

"Notably, each module is mutually orthogonal with the other modules such that there is little unintentional cross-talk. For example, the lac repressor acts on promoters containing the lac operator sequence but does not repress transcription from the tet or the cI operator sequence; a similar relation exists among other repressors and promoters."

So you either have orthogonal conrols over translation of a certain gene or different pieces of the transcription machinery that only act on certain pieces of genetic code (instead of a single all-purpose ribosome, for example). DMacks (talk) 13:40, 15 October 2008 (UTC)

quantum mechanics

de broglie predicts that matter is a wave, and hence has a wavelength, right? when my teachers explained this, they usually used a baseball or something to show that the effects were small for large objects. well, let's say that plancks constant was large, like 1 J*second. would the baseball have a discernable wavelength? well, the equations of quantum mechanics say that λ=h/p, and so, since the baseball has momentum, it would have a wavelength. but the baseball is just a myriad of electrons, protons, and neutrons. so wouldn't it be those particles which have the large wavelength, rather than the baseball. this question can also be generalized to other concepts like the uncertainty principle: are analogies with macroscopic objects valid? —Preceding unsigned comment added by 65.92.231.82 (talk) 09:32, 13 October 2008 (UTC)

Both the baseball and each constituent would have a wavelength. An experiment has been done with a very small balls, in fact with buckyballs of 60 atoms (see Quantum Mechanics in that article), and the complete balls produce a diffracton pattern just like electrons. Dmcq (talk) 10:04, 13 October 2008 (UTC)

The de Broglie wavelength of any object is given by the simple equation:

$\lambda ={\frac {h}{p}}$

where h is Planck's constant and p is the object's momentum. Since momentum is directly proportional to mass, then the wavelength is inversely proportional to mass; i.e. the more massive an object is, the shorter the wavelength. For any significantly large object, the wavelength of its DeBroglie wave will be so small as to be meaningless, like wavelengths smaller than the diameter of a proton. --Jayron32.talk.contribs 18:13, 13 October 2008 (UTC)

Clockwise or Anti-Clockwise

I know our solar system travels around the our galaxy the milky way. But I do not know if it travels clockwise around the core of the galaxy or Anti-clockwise. By that I mean if the direction pointed by the north pole of the Earth is defined as up, are we traveling around the core, in a clockwise manner or anti-clockwise manner? 122.107.229.49 (talk) 09:40, 13 October 2008 (UTC)

For that matter, I don't even know if the Earth travels clockwise or anti-clockwise around our Sun. —Preceding unsigned comment added by 122.107.229.49 (talk) 09:42, 13 October 2008 (UTC)

Using the Right-hand rule with north in the direction of the thumb, the earth rotates counterclockwise as can be seen from the sun rising in the east. We go around the sun anticlockwise as well, but that axis is tilted by 23 degrees relative to the north pole. (Warning: Tilting causes seasons)

According to [2] the sun rotates around the galactic centre with an axis that's tilted 117 degrees relative to the earth's north. So we're basically going clockwise around the galaxy. According to the sun article, that's at 220 km/s so it takes the sun 8 days to move a distance equal to the distance between us and the sun. Adding the speed of the milky way with respect to the rest of the universe, we're going at a comfortable 370 km/s.

Sundial shadow

The milky way you can see in the sky are simply stars along the galactic plane, which gives you a bearing on where we are. You can see the 117 degree tilting in that the milky way is never aligned exactly east-west in the sky. (If it had been tilted 90 degrees, it would have run north-south and east-west if by 0 degrees) EverGreg (talk) 10:37, 13 October 2008 (UTC)

As an aside, the shadow on a sundial travels "clockwise" (in the northern hemisphere). Clock hands just copy the motion of the shadow. Saintrain (talk) 16:50, 13 October 2008 (UTC)

FISH

In fluorescent in situ hybridisation, how many fluorescent entities must converge on a point to make it visible? How small a point is it likely to be for a typical probe and its unique recognition sequence?

I don't have an answer to your question, but we do have a page on the technique: Fluorescent in situ hybridization (U.S. English spelling) --Scray (talk) 11:01, 13 October 2008 (UTC)

I've created a redirect. --Tango (talk) 11:14, 13 October 2008 (UTC)

I consulted the article before coming here. It was not helpful in this case. :( ----Seans Potato Business 15:25, 13 October 2008 (UTC)

I can't speak to what is typical for the FISH technique, but there is no reason why with the right probe and a sufficiently sensitive sensor that the answer couldn't be one. In general it helps both for visibility and background rejection to have a brighter signal, so FISH may be designed to operate with a greater abundance, but from a technical perspective detecting an isolated fluorescent tag is certainly possible. Dragons flight (talk) 16:52, 13 October 2008 (UTC)

Yup, all you need is one. In FISH, a filter is used on the microscope to exclude all light that isn't within the range emitted by the flourescent tag, so it is an extremely sensitive technique. It is often used to locate individual binding sites on a chromosome, which are tiny! Poke around google for some images. --Shaggorama (talk) 18:13, 13 October 2008 (UTC)

The article is actually a pretty good description of how FISH works. Since the technique is based on hybridization of a unique probe sequence to the target chromosome, only one "fluorescent entity" can be present at a single point on the chromosome. Usually this is a large (50-300 kb) piece of DNA (a bacterial artificial chromosome or fosmid which can be propagated in bacterial culture and purified in large quantities) that is labeled with fluorescent nucleotides so that multiple fluorophores are incorporated into the probe. The size of the probe largely determines the sequence specificity (i.e. whether the probe binds to only one position in the genome), and the sensitivity (brightness) of the fluorescent signal. There will almost always be some background non-specific hybridization that comes from repeated sequences within the probe or low complexity sequences in the genome that are just "sticky", which requires optimization for each given probe. The spatial resolution will depend highly on the conformation of the chromosomes you are using -- the highly condensed mitotic chromosomes will give much lower spatial resolution than interphase ones or the stretched out "fiber FISH" technique (which can supposedly give a resolution of around 1 kb). From a theoretical perspective, one might be able to identify a 16-20 base pair sequence that is present only 1x in the genome of interest, label an oligonucleotide probe and use some fancy tricks to amplify a fluorescent signal so that it could be detected by a highly sensitive microscope. The smallest reported probe is around 50 bp (see this), but from a practical standpoint it isn't done this way very much. —Preceding unsigned comment added by Medical geneticist (talk • contribs) 20:35, 13 October 2008 (UTC)

Questions about massive sqid

1. Is there a theoretical maximum possible size for squid?

2. Would it be possible to capture a giant/colossal squid alive to place on display in an aquarium? —Preceding unsigned comment added by 84.71.115.30 (talk) 12:10, 13 October 2008 (UTC)

Tthere are some theories on how large an animal can get. A predator for instance, may be limited by the size of its prey [3]. But according to Deep-sea gigantism, there may be advantages to being big in the deep ocean. But noone has calculated an exact maximum size. In [4] it is speculated that an unusually large squid had messed-up hormones so in any case there'd always be giant freaks that didn't fit into the theories. As for the second question, it's probably easier to catch a young one and raise it to adulthood in captivity. EverGreg (talk) 12:33, 13 October 2008 (UTC)

Squid belonging to the 'large' species decompress and die if you haul them up from the deep to the surface, don't they? --Kurt Shaped Box (talk) 22:36, 13 October 2008 (UTC)

I get this, ...with the extreme change in pressure, and environment in general, these creatures can't survive for very long, if at all, on the surface. from the article Deep sea creature. Julia Rossi (talk) 09:51, 15 October 2008 (UTC)

composite aircraft

Good Day,I would like to know how many composite (carbonfiber/fiberglass) Federal Aviation Administration certified aircraft were built every year from 1998 to the present.Please if possible list by manufacturer. I would also like to know if any projections are made by the manufacturers or the F.A.A. for the future of composite aircraft.65.15.124.92 (talk) 18:44, 13 October 2008 (UTC)

O-ring and G-ring

I'm confused by the term O-ring; it seems to have one or two additional meanings beside the one found here, referring to metal rings. Is there a 2nd meaning to the term "O-ring" that means the kind of double-looped steel ring that is commonly used as a keyring? I found this meaning e.g. here. My theory is that people don't know how this type of ring is properly called and make an analogy to the related G-ring - "it's like a G-ring but in the shape of an O". Is that right, or is "O-ring" a proper name for this thing? The 3rd possible meaning of the term "O-ring" can be found in items of jewellery such as necklaces and earrings. If my interpretation of the pictures I found via Google is correct, here the term means something like "a bigger decorative circular ring sideways attached" - is that right?--84.155.219.241 (talk) 19:22, 13 October 2008 (UTC)

I have always only heard O-ring to mean a big rubber gasket or washer of some sort. Though it certainly may have other uses. --Jayron32.talk.contribs 19:27, 13 October 2008 (UTC)

Sorry, I need to rephrase the 2nd part of my question. I'm also wondering whether there is a 2nd meaning to the term G-ring, found in items of jewellery such as necklaces and earrings. If my interpretation of the pictures I found via Google is correct, here the term means something like "a bigger decorative circular ring sideways attached" - is that right? 84.155.219.241 (talk) 19:30, 13 October 2008 (UTC)

Sounds to me like in jewellery, an O-ring would be a solid ring such as one found at one end of a necklace; and a G-ring would be an O-ring with that little opener thing (i.e. a clasp) that you pull back to fasten the necklace. By my interpretation, when you pulled open the little clasp-thingie, it would look exactly like a "G". Franamax (talk) 05:07, 16 October 2008 (UTC)

Sounds plausible but does not really correspond to the images that Google finds. 84.155.220.228 (talk) 12:07, 19 October 2008 (UTC)

How does NASA calculate trajectories?

When NASA calculates the trajectory of an interplanetary space probe, do they use Newton's formula's (classical physics) or Einstein's (relativity)? 67.184.14.87 (talk) 23:07, 13 October 2008 (UTC)

Newton is plenty good enough for trajectories. The systems that provide the thrust and measure the position/velocity aren't accurate enough to show the consequences of relativity at the speeds that current spacecraft move. SteveBaker (talk) 23:53, 13 October 2008 (UTC)

It's true that the probe will usually get close enough to its target without relativity, but to take the question literally, "they" (JPL) do actually "use ... relativity" in the detailed calculations. According to this blog, the Messenger's voyage to Mercury requires relativistic corrections. --Heron (talk) 18:14, 14 October 2008 (UTC)

I wonder if that's for all space probes or just Mercury. I've read that Newton's equations don't accurately predict the orbit of Mercury. 67.184.14.87 (talk) 17:12, 15 October 2008 (UTC)

The precession of Mercury's orbit is greater than Newtonian physics would predict and requires GR to get it right. I'm not sure how big a difference that would make over the length of time required for the probe's journey, but it might be enough to warrant including in the calculations. Missions to Mercury will probably require more relativistic corrections that elsewhere in the solar system, since you're closer to the Sun, but I don't know if you just need less for other missions or none at all. --Tango (talk) 17:33, 15 October 2008 (UTC)

The extra 43"/century is about .5 km/day, so significant. Saintrain (talk) 18:33, 15 October 2008 (UTC)

Yes, there are effects like that - but they are negligable compared to the errors due to the inaccuracy of the rocket burn power and duration - and the inability to point the rocket with enough precision. Hence course corrections are needed - and those unpredicatble corrections totally swamp the magnitude of any relativistic effects. In the case of Mercury - you may need relativity to figure out where it will be in 10 years time when your rocket is intended to get there - but the path the rocket takes to get to that point at that time is an entirely Newtonian calculation. The errors due to the speed of the spacecraft causing time & space dilation is nothing compared to the unpredictability of photon pressure from the sun, inaccuracy in your initial launch, etc, etc. It's negligable.

What is the theoretical wavelength upper limit for electro-magnetic waves?

Extremely low frequency waves have a wavelength of ~ 10,000km - 100,000km. Is there an upper limit? The size of the Universe?, or as the Universe is unbounded is the upper limit infinite? Jooler (talk) 23:04, 13 October 2008 (UTC)

There is no natural limit, though the size of the antenna one can operate and other factors do impose many practical limits. Dragons flight (talk) 17:43, 15 October 2008 (UTC)

(ec (who cares about ec's anyway? :-)) It appears that there is no theoretical upper limit to wavelength. From Planck constant (and a little rearranging) $\lambda =hc/E$, where $\lambda$ is wavelength, $h$ is Planck's constant, $c$ is the speed of light and $E$ is the energy of the photon. Since there's no lower limit to E, there's no upper limit to $\lambda$. There is probably a minimum actual energy (steps between electron energy bands, say) that puts a practical limit on the wavelength of a photon that can be emitted. Saintrain (talk) 17:52, 15 October 2008 (UTC)

The expansion of the universe has stretched the wavelength of light in a (so far as we know) continous manner. The microwave background radiation for instance, started out with shorter wavelengths. And if Planck's law is to be taken literally, black-body radiation contain photons of arbitrarily long wavelengths, since the wavelength distribution has no cutoff for large wavelengths. In that case, name a wavelength and it's all around us, though in small amounts.

But with analogy to the quantum well which enforces a maximum wavelength, you can probably find a cutoff invoking the size of the visible universe and inflation theory. If I recall correctly, there's also some low-frequency waves reflected in the upper atmosphere, that have their wavelengths limited and quantized by the circumference of the earth. EverGreg (talk) 08:54, 16 October 2008 (UTC)

What triggers a missile to explode?

What, exactly, is it that causes a missile, specifically a surface-to-air missile, to explode? Does it have guidance built in so that when it reaches a specific point in space, it goes "I have now reached my target; I shall explode now", or does it have sensors to detect that, or a mechanical trigger which goes off on impact? (Could you theoretically grab a missile (gently) out of the air and hold it without setting it off?) What happens if the conditions for exploding are not met and the missile gets lost or starts running out of fuel to keep seeking the target? Does it explode, or become inert/safe? SamSim (talk) 23:11, 13 October 2008 (UTC)

We'd tell you but then, well you know...  ;) hydnjo talk 23:30, 13 October 2008 (UTC)

Well, that scuppers my plans for stealing SAM's and asking on Wikipedia how to set them off. I guess I won't post my question on how to launch them either. Anyone know a good place to sell unused surface-to-air missiles? eBay? Franamax (talk) 04:08, 14 October 2008 (UTC)

Its called a # Fuse_(explosives), If missile goes wrong and is heading back to you, there is a thing called a Break up system that, well, breaks up the missile without detonating the warhead.

--GreenSpigot (talk) 01:04, 14 October 2008 (UTC)

Clearly one could build a missile to explode due to the passage of time, due to altitude, due to impact, or due to proximity to a possible target, as well as due to triggering by the party who launched it. Edison (talk) 05:17, 14 October 2008 (UTC)

For guided missiles, the same system that's doing the guidance is likely to be the trigger. A radar-guided missile (for example) can use the radar returns to set itself off when very close to the target. SteveBaker (talk) 09:43, 14 October 2008 (UTC)

No, sorry. Guidance system and fuzing are completely separate parts of a missile: the fuze is in the warhead. If our articles combine them, they're wrong to do so.--GreenSpigot (talk) 02:44, 15 October 2008 (UTC)

Maybe I'm nuts, but I've always had the impression that most missles were actually designed to physically impact their targets, and hence would generally be expected to have fairly dumb impact driven triggers. That's different from same a cluster bomb or area-effect artillery that simply wants to get close and then detonate in the air. Dragons flight (talk) 10:24, 14 October 2008 (UTC)

For manouvering air targets the chance of a direct impact is relatively small, so relying solely on an impact fuse would not be a wise thing. Also I'm not sure if using the main guidance is generally done. I always thought most *-to-air missiles had a seperate proximity fuze, because the explosion (see continuous-rod warhead) is most effective to the side (where the main guidance system cannot scan, though it could possibly estimate). To answer the second part of your question: the K-13 and Sidewinder articles have a nice paragraph about your theoretical situation. Ever since then, air-to-air missiles self destruct if they miss their target. I'm not sure if it's also true for surface-to-air missiles, but something tells me they do, after all, you don't want your own missile coming down on your troops. - Dammit (talk) 10:44, 14 October 2008 (UTC)

Correct. Physical impact is not required as proximity fuzes of one type or another are almost always used. In fact I think achieving physical contact would be rather difficult in the case of a missile trying to shoot down another missile.--GreenSpigot (talk) 02:44, 15 October 2008 (UTC)

Actually, the Aegis Ballistic Missile Defense System is a direct impact missile to missile system. The impactor is a "kinetic kill vehicle" (see kinetic projectile) and has no explosive at all. This works, in part, because ICBMs are largely unpowered during their sub-orbital arc, and hence don't dodge. Dragons flight (talk) 17:55, 15 October 2008 (UTC)

Why can pulse be normally abnormal?

I'm a little confused, after reading the article on the pulse as it relates to the body. I understand it's not always the same as heart rate - so is that it? Because, I'd been under the assumption one would just check for 10 seconds or so and multiply by 6, or at least 15 and multiply by 4. Does this mean that pulse rate can have a few little skips, and if so, why? Is it slight movements - the hand moving a bit while trying to measure at the wrist? is it the different things that cause the waves in the heart's normal sinus rhythm? Or, what? —Preceding unsigned comment added by 209.244.187.155 (talk) 23:44, 13 October 2008 (UTC)

Pulse rate and heart rate are identical under most circumstances (the exceptions mainly occurring when the heart is pumping abnormally). But neither is as regular as, say, a CPU. It's not a clock. It speeds up, it slows down, based on a variety of variables: exertion, rest, drugs, stress, emotion, vagal nerve stimulation, etc. So 10 seconds is too short a time for a reliable estimate of heart rate. Count for 30 seconds and multiply by 2, or for a full 60 seconds. And you should expect the pulse to fall within the normal range (60-100) rather than to be the same each time you take it. - Nunh-huh 23:57, 13 October 2008 (UTC)

Perhaps the OP is asking about regularly irregular pulse, e.g. second degree AV block. These rhythms are irregular, but beat patterns can be grouped in a way that can be described as regularly irregular. In particular, for these rhythms one should count for a few cycles of the beat group, or about a minute, before estimating the heart rate. --Scray (talk) 02:34, 14 October 2008 (UTC)

To rephrase, they are irregular at regular intervals. They follow a clear pattern, but the pattern is an irregular. --Shaggorama (talk) 16:39, 15 October 2008 (UTC)

October 14

Plutos' core

Is Pluto's core generally hot or cold? From this image, it said the center is made of alloy, iron-nickel, and the mantle is rock and ice. I thouhgt Pluto's core would not be hotter than the surface of Venus, but may still be warm enough for water to become a steam? Since Pluto's atmosp is only 1/1000 of Earth's fraction, the globe colour would be gray perhaps yellow-tan or orange-yellow tinge add to the gray.--Freeway19 00:50, 14 October 2008 (UTC)

Do we have answer to is Pluto's center hot or cold. Some scientist beieve it is made of ieon nickel with alloys stuff. Will It put pluto's center to at least 100 C. I know it is unlikely to be 500 C or 1000 C. --Freeway19 02:30, 14 October 2008 (UTC)

Probably over 1000 C. Hundreds of kilometers of rock and ice is a very good insulator; it holds in heat. If there is a liquid ocean, people think it starts only ~250 km down. [5] Dragons flight (talk) 03:54, 14 October 2008 (UTC)

Except that everything in the solar system is roughly formed at the same time, so roughly exposed to the same conditions. As Pluto is smaller than the moon, and the moon can demonstratably be shown to have a cold center, Pluto is likely to also have a cold center. --Jayron32.talk.contribs 10:38, 14 October 2008 (UTC)

Well, if the moon formed from a collision with the Earth, then it could lack some of the heavier elements and those are often the radioactive ones. That would mean there would be more radioactivity in Pluto's core than the moon's, but I'm not sure it would be enough. --Tango (talk) 10:46, 14 October 2008 (UTC)

The moon's core may be as high as 1400 C [6]. That's "cold" only from the point of view that iron is not molten (needs 1600 C). Dragons flight (talk) 10:51, 14 October 2008 (UTC)

I'd have to do some research to be sure, but my guess would be that Pluto's core is ice cold. How much heat it could have retained from the formation of the solar system is dependant on size and Pluto is tiny, so it likely has very little retained heat. The sun is obviously too weak at that distance to heat it up. There could be some heat from radioactivity, but that's about it (there won't be any tidal heating since it is tidally locked with its only large moon - I doubt Nix and Hydra are large enough or close enough to do much). Radioactivity could keep it warm, but I would guess not to above freezing. If I get a chance, I'll research it later. --Tango (talk) 10:46, 14 October 2008 (UTC)

I already provided a reference to a scientific paper predicting liquid water on Pluto at only 250 km, i.e. 1/5th of Pluto's radius. Dragons flight (talk) 11:03, 14 October 2008 (UTC)

Here's another one [7]. Pluto goes above the freezing point of water at only 180 to 300 km depth. That leaves another 1000 km of temperature rise to get to the core. Radioactive heating is efficient when you are planetary size and can't easily dissipate heat. Dragons flight (talk) 11:14, 14 October 2008 (UTC)

Light Concentration

What exactly is a Light Concentration diagram? I have failed to find one on Google, or anywhere for that matter. And if someone can answer that, could you tell me where I could find one for Lake Baikal (in Russia), or what one would look like?72.65.101.51 (talk) 00:53, 14 October 2008 (UTC)

Could you mean light intensity? A diagram or graph would show the intensity dropping with depth. Graeme Bartlett (talk) 03:07, 14 October 2008 (UTC)

Some mathematical physics expression

$\displaystyle {D_{x}^{I}\rho _{I}V_{I}T_{I}\ {\overline {B_{xy}^{(I\,II)}}}}$
This is an expression I saw in a picture written on a blackboard behind Niels Bohr. Could someone please tell me what it pertains to and means and what articles would have more information about whatever it is? Thanks in advance, Ζρς ι'β' ^¡hábleme! 02:14, 14 October 2008 (UTC)

I don't think you are going to get a definite answer from just that. It might help to know how old Bohr was in the photos since physics evolved a lot in his lifetime. Off hand, I'd guess some form of quantum mechanics expression, with ρ a density, V a volume, T a temperature, D_x a differential operator in x, and the I and II denoting two kinds of material. If you assume he's dropping constants (as theorists often do) then it looks like a derivative operator in x acting on an energy times some interaction function B. What B is, I haven't a clue. Often "B" denotes a magnetic field, but you'd be unlikely to sub and superscript it that way if that were the case.

Also, I could be totally wrong. Dragons flight (talk) 04:53, 14 October 2008 (UTC)

He was older in the photos, perhaps 60-65. Ζρς ι'β' ^¡hábleme! 23:19, 14 October 2008 (UTC)

Looks like Einstein notation to me, but not sure. EverGreg (talk) 09:06, 16 October 2008 (UTC)

Is Heisenburg's Uncertainty Principle really universal?

Perhaps it's just personal, but I find this Principle to be a fraud. Surely, though, I'm not right and everyone else is wrong. It states that by locating a particle you make its momentum uncertain and vice versa. But a Principle of physics should accurately describe matter and the universe, not our ineptitude as observers. For example, if we were omnipotent gods, and could 'see' these particles, Heisenburg's Principle surely would not make sense. If really small aliens possessing intelligence and observational powers were the same size of these particles, surely THEY could determine the position AND momentum for any given unit of time.

I find it like cave men trying to understand tigers, only the tiger eats them when they come near him. They only way they can study him is to throw spears at him until he's dead. Would these perhaps thoughtful cavemen have a Tiger's Uncertainty Principle, and state "Well a living Tiger is just UNKNOWABLE" because they lack the proper tools to analyze the Tiger?

I feel that Heisenburg's Uncertainty should not be presented as a Principle, a 'rule,' or really any part of Physics other than a statement along the lines of "We suck as observers and can only 'detect' these particles by shooting high energy particles AT it, thereby ruining our original setup."

Why is this not presented in this way, or has noone made these objections? Am I missing something?

Ehryk (talk) 05:41, 14 October 2008 (UTC)Ehryk

No the point, and I agree it is spooky, is that a particle cannot have both a precise position and precise location at the same time. It is not simply that they are unknowable, but rather non-existent, even to God, aliens, or whoever else might claim to be able to see them. The double slit experiments, Bell inequalities and related results demonstrate empirically that our conception of matter having fixed position and momentum simply isn't how the universe works on a small scale.

At a fine scale, quantum mechanics tells us that everthing is smeared out in a fuzzy way. Even a single particle doesn't have one precise position but rather a whole distribution of positions, and with them a whole distribution of momentums. Things at the subatomic scale simply don't exist at only one place and time. The more we try to confine them to only a single position, the more they will necessarily widen their range of momentums. Your view that there should be some hidden and singular true position/momentum visible to God is known as local hidden variable theory and the most obvious forms of that have been shown experimentally to be false. Dragons flight (talk) 06:19, 14 October 2008 (UTC)

Heisenburg isn't talking about our ability to measure - he's talking about the fundamental nature of the particles themselves. It is literally true that if you try to limit the momentum of a particle it literally becomes a fuzzier thing so that its position is an increasingly vague thing. If you try to confine it into a small space to nail it's position more accurately - then it's momentum will become more 'blurry'. So you can take the "Us" and "observers" out of the debate here. Even omnipotent gods and teeny-tiny aliens would see the position of a particle as a statistical 'cloud' and its momentum as an indeterminable thing. Quantum mechanics is something that we humans are not equipped to comprehend because at our 'scale' of existence, the effects are generally negligable - but they are strange and oddly beautiful. But without them, the computer you're sitting at right now wouldn't work. The statistical weirdness of the position and momentum of a particle is what makes 'quantum tunneling' work - and without that, you wouldn't have any flash memory for your BIOS, your MP3 player or your memory sticks. So Heisenburg isn't just a means to describe the limits of our abilities - it's describing how the universe operates at a fundamental level. SteveBaker (talk) 09:41, 14 October 2008 (UTC)

As SteveBaker points out, the UP is not just about our limits as observers. Another way to think about it, a more elegant way than the "we move a particle to detect it", is as a wave function. Every complex wave can be considered a series of waves added together. You could, hypothetically, layer more and more wave functions together and they would cancel each other out leaving one big wave in the middle. Now imagine doing that for a very small particle. You'd layer wave after wave after wave, trying to get one little spike in the center. Well, when you get down to the scales where the UP takes effect, it requires an infinite number of waves to make that final tiny wave. Or something along those lines. This formulation of the UP is identical to the more classical ones—except it has nothing to do with measurement. --98.217.8.46 (talk) 11:31, 14 October 2008 (UTC)

The uncertainty principle is a mathematical theorem that holds for any kind of wave, not just quantum mechanical wave functions. If you force a classical light wave (Maxwell's equations) or a classical water wave through a narrow opening it will spread out in all directions on the other side, because by confining its position you've left its momentum very uncertain. Musical notes are subject to a pitch-time uncertainty relation: a note of brief duration has uncertain pitch. Piano tuners listen for beats between a note made by the piano and a reference tone; as the two pitches approach each other the frequency of the beats approaches zero, so it takes arbitrarily long to tune a piano arbitrarily well. That's the uncertainty principle. Waves of any kind behave more and more like particles as the frequency increases. That's why geometric optics works so well for visible light. Classical physics is (in a mathematically precise sense) the geometric-optics version of quantum physics. It works well at ordinary scales because Planck's constant is small. -- BenRG (talk) 11:57, 14 October 2008 (UTC)

The first thing you must know is that Heisenburg's Uncertainty Principle is a mathematical property and NOT a physical property. By that I mean it occur because of mathematics and not because Physicist discovered it in the real world. Human beings are not designed to think in terms of wave like behavior which is why you have such a hard time understanding it. If you imagine taking a picture with a SLR camera, you can increase the sharpness of the picture by reducing the aperture but doing so you would need to increase the shutter time. So you can say the aperture (size) * the shutter time is a constant. The uncertainty principle is just like that. 122.107.229.49 (talk) 13:09, 14 October 2008 (UTC)

Einstein thought that the randomness of the uncertainty principle is a reflection of mankind's ignorance of some fundamental property of reality, leading to Einstein's famous quote, "God does not play dice with the universe".

I read that the Bell test experiments put to rest Einstein's objections although I cannot see how any test can possibly prove this if this test was conducted by a human. To rule out human ignorance, you would need a higher life form.

Scientists have for decades tried to reconcile quantum mechanics and general relativity in a single unified theory, which implies that one or both theories might be wrong or at least incomplete.

I agree with the original poster that the Heisenberg Uncertainty Principle is flawed. According to quantum mechanics, the Moon does not exist unless there is someone to observe it.

Given that everything else in the universe is deterministic - everything from the boiling point of water to the timing of the next solar eclipse, I find it hard to believe that subatomic particles would behave any differently. I still think it is more likely that our inability to make deterministic quantum predictions is due to a lack of understanding than a lack of determinism.

It should be pointed out that scientific consensus can and does change over time. Ptolemy's model of the universe was the consensus for over a thousand years, until it was supplanted by Copernicus' model, which lasted over 300 years until it too was supplanted. Yes, quantum mechanics is the current scientific consensus. But for how long?

Fortunately, science is a self-correcting process. As long as human intelligence is great enough to figure it out, it's only a matter of time before it's disproved.

It would be nice, however, if in my lifetime, this issue is resolved. 12.10.248.51 (talk) 14:06, 14 October 2008 (UTC)

The issue has already been "resolved" - many times over - and to the utter (eventual) satisfaction of great minds like Einstein. The Uncertainty principle is as real as Newtons laws of motion. It is literally true that the computer you are sitting in front of when you read my words would not function if it were not for the truth of the UP at the physical level. This is not something you should be doubting! SteveBaker (talk) 23:04, 14 October 2008 (UTC)

Actually, the HUP says nothing about observations of macroscopic objects like the moon. Your senses and reason are perfectly adequate to make statements of objective reality about objects like the moon, because the act of observing the moon does not change the moon. This is VERY different for fundemental particles. When you look at the moon, you do not need to change it; you can passively observe it. For something like an negatively charged electron, in order to observe it, you need to set up a detector with some sort of charge of its own, and measure the deflection of your detector. The problem is, and this is a basic "classical" mechanics situation, any deflection on your detector will result in an equal and opposite deflection on the electron. Thus, by the very act of observing the electron, you must change it. The HUP is a generalization of this phenomenon, and it patently does NOT apply to large objects whose observation does not depend on changing them in some fundemental way. The moon really is there if no one looks at it. --Jayron32.talk.contribs 16:42, 14 October 2008 (UTC)

Personally, I do believe that the moon exists when no one is looking at it, but that's not what David Mermin, Professor of Theoretical Physics of Cornell University claims:

"Pauli and Einstein were both wrong. The questions with which Einstein attacked the quantum theory do have answers; but they are not the answers Einstein expected them to have. We now know that the moon is demonstrably not there when nobody looks."

http://www.jstor.org/pss/2026482 —Preceding unsigned comment added by 12.10.248.51 (talk) 17:20, 14 October 2008 (UTC)

That's SO bogus. "Looking" is not the same as "observing". Even if the moon were subject to quantum effects (which - for all practical purposes - it's not). What "demonstration" can be done to show that the moon isn't there when you're not "looking"? I can be on the other side of the planet from the moon - and notice that the tide is going in and out. Which is indirect proof that the moon is still there. To have any hope of proving such a patently false hypothesis - you'd have to exclude all kinds of observation. So you'd have to say that the moon isn't there when nobody is looking at it AND nobody is noticing the tides AND nobody is noticing it's effect on the progress of the earth's orbit around the sun AND...so on. Since every atom from here to the next star over is feeling SOME gravitational tug from the moon - how can there ever be a situation when it's not be observed in some sense. This SO bogus. I have two pieces of advice here: (1) Philosophers are a waste of space...unless they are actually IN SPACE - then they're a waste of perfectly useful vacuum. Not one thing they've ever come up with has been worth the effort of reading. (2) If you attempt to learn about quantum theory and what the likes of Einstein and Pauli were REALLY talking about - "The Journal of Philosophy" should not be your first (or last) stop! SteveBaker (talk) 23:04, 14 October 2008 (UTC)

(edit conflict) Err, you really do have to read the whole article to make sense of what he means. He's not talking about the literal moon. He's talking about the EPR paradox and how the Bell tests appear to have resolved it. In a very very simplistic version of the EPR argument: if you know UP means you can't know position/momentum at the same time, what if you do some sort of process which theoretically spits out two identical particles at the identical velocities in exactly opposite directions. Couldn't you measure the momentum of one, jot that down, and at the same time measure the position of the other? Wouldn't that tell you two impossible-to-know things about the particle which you measured the position of? That's basically the EPR argument (except that spin and something else was the entangled property, if I recall)—that UP would limit you physically from measuring things but didn't limit the possibility of measurement of entangled properties. Einstein said, "you can know everything despite UP," Bohr said, "well really you're just wrong", and Pauli said it was just a philosophical debate—like asking about the moon. But decades later a smart dude named Bell came along and actually came up with an experimental setup that could distinguish between the two points of view. That's what the Bell tests are about. They are not that easy to explain (the Mermin article does a pretty good job of it but I was still pretty baffled) but the gist of it is if you do a bunch of statistical tests you'll find that when you "look" at the properties you see different things than if you hadn't looked. Very weird stuff but experimentally it seems to work out. --140.247.11.9 (talk) 23:09, 14 October 2008 (UTC)

You people are talking about Werner Heisenberg, right? I wouldn't trust that Heisenburg guy for a second. Franamax (talk) 08:32, 15 October 2008 (UTC)

If Mermin meant that as a metaphor, then it's not quite that bad, but still wrong. Not being able to measure an electron's position and velocity at the same time is not the same thing as saying that the electron has no position or velocity until it is measured. 67.184.14.87 (talk) 14:49, 15 October 2008 (UTC)

hmm. i'm not satisfied with anybody's answer thus far, so i have to throw in my $.000000002 worth. the uncertainty principle is based on the principle that all particles are actually waves. as such, fooling around with fourier analysis or just a little insight will tell you that a wave of a specific frequency extends infinitely; in order to put boundaries on it, you have to smear the frequencies out a little so that they are finally out of phase where you want the wave to end. in the ultimate opposite case from having a defined frequency with infinite dimensions, you have a pulse with a single defined position; but this requires a mix of an infinite number of frequencies. that's absolutely true for waves, nobody has any disagreements or doubts. well, if all particles are actually waves, then it must be absolutely true for them as well; the more defined they are in "location space", the less defined they are in "frequency space" and vice versa. how it works out in reality, and perception, etc. are all just derived from that basic property. Gzuckier (talk) 15:11, 15 October 2008 (UTC)

Why did bacteria evolved?

What is the need for more complex forms of life above bacteria? Aren't bacteria not fit enough everywhere on Earth? Mr.K. (talk) 09:48, 14 October 2008 (UTC)

Because multi-cellular life didn't die out. One can speculate about what advantages multicellular life might have had (greater mobility, greater ability to regulate intracellular conditions, greater longevity, intelligence, dashing good looks, etc.) but ultimately the only real "reason" behind complex life is that life tried it out and didn't die. Evolution doesn't have some overarching plan or some predesigned number of niches to fill, it is simply the persistent accumulation of whatever genes happened to have worked. Dragons flight (talk) 10:00, 14 October 2008 (UTC)

(Repeating Dragons Flight because this cannot be repeated enough...) Evolution is not intelligent and, therefore, doesn't decide when to evolve and not to evolve. Evolution is a term for a process in which DNA slowly changes over long periods of time. So, you cannot ask "Why did bacteria evolve?" You can ask "How did bacteria evolve?" It evolved by a slow process of DNA mutation, survival of the fittest, and replication of rare qualities until they became common qualities. -- kainaw™ 13:29, 14 October 2008 (UTC)

Of course you can ask why a living organism evolved. The answer would be that some living organisms were not fit for their new environment. That makes specific mutations become stable in a population. The problem with bacteria is that they seem to be the fittest form in any environment on Earth and apparently even outside it. Mr.K. (talk) 15:53, 14 October 2008 (UTC)

Hardly. Archaea are much fitter. --Ayacop (talk) 16:03, 14 October 2008 (UTC)

Well, there's a tautology here, and a valid one, that we are ignoring. When you judge fitness on a set of arbitrary conditions, like "hey, this stuff grows in lots of weird places, so it must be the best form of life EVER", well, that isn't really a measure of fitness. The true measure of fitness is survival. Many organisms are quite fit in their own ways, and if they were somehow less fit than others, the others would have crowded them out by now. --Jayron32.talk.contribs 16:33, 14 October 2008 (UTC)

To Kainaw: Yes, DNA is a big part of the picture, but there's also evolution of the epigenome and siRNA's that are not strictly heritable only through DNA, they seem to be a meta-system inherited with the DNA. In other words, DNA comes with the pre-formed elements that shape the use of the DNA. Just my impression, but it's all quite fascinating. Franamax (talk) 08:24, 15 October 2008 (UTC)

bottom line; there were some environments which bacteria hadn't thoroughly exploited successfully, so there were niches for other organisms to evolve into. (the inside of a refrigerator, for one example....) bear in mind, though, that for billions of years bacteria and their cousins blue green algae were the only critters on earth, so they did a pretty good job. on the other hand, as soon as eukaryotic cells evolved, there has been this burst of complexity in a relatively short time, so that was apparently the area prokaryotes couldn't evolve into. Gzuckier (talk) 15:28, 15 October 2008 (UTC)

A) Blue green algae are bacteria. B) Bacteria shared the early Earth with archaea. C) Prokaryotes did evolve into those niches... by way of becoming eukaryotes. D) Single-celled eukaryotes arose at least 500 million years before they evolved into large complex forms, and perhaps more than 1.5 billion years (i.e. no rush to complexity). Dragons flight (talk) 17:32, 15 October 2008 (UTC)

I see that my knowledge of the evolutionary dates of eukaryotes is sadly out of date. Gzuckier (talk) 21:24, 15 October 2008 (UTC)

Medical condition relating to films

I once heared about a medical condition where the sufferer could not follow films (or tv shows) because if a different camera angle was used in a scene they could not comprehend that it was the same scene. Does anybody know what this condition is? Thanks Mark Model (talk) 11:17, 14 October 2008 (UTC)

This doesn't sound like it's necessarily a medical condition: our capacity to understand the narrative shown to us in filmic media is a trained skill. One common convention we take for granted is the match on action: shot 1 john points to his left, shot 2 we see a car accident. If it we hadn't seen so many movies and TV already, we wouldn't necessarily make the connection that john was pointing at the car accident. I remember hearing that when motion pictures were still young, there was a film that showed a train coming towards the viewer (maybe man with a movie camera?). The audience fled in terror. You may find culture-bound syndrome interesting. If what you describe is a real 'condition,' it may be an agnosia. --Shaggorama (talk) 16:35, 15 October 2008 (UTC)

Some people on 4chan say that their parents get dizzy or sick while watching them play 3d video games. What's this about?Avnas Ishtaroth _{drop me a line} 01:31, 16 October 2008 (UTC)

pwnitis, perhaps. --Shaggorama (talk) 07:33, 16 October 2008 (UTC)

This is the same phenomena as Sim-sickness.

I certainly get dizzy/sick when watching other people play some kinds of 3D game - and (very rarely) a movie will cause it (the one that comes to mind is Cloverfield). (Which - since my job is writing software for computer games - can be a pain to deal with!) For what it's worth, I can generally pin the problem down to poorly written camera motion software - especially if the field-of-view is set out unrealistically wide (which is almost always the case with 1st person games). When the virtual camera ("eyepoint") is moving at high speeds but not leaning into the corners or being thrown out sideways realistically - then I get sick. The effect is much worse when the frame rate is poor and it's worse when someone else is playing than when I'm playing (but it's still there when I play alone for a large amount of time) - and it's much MUCH worse on large TV's or projection systems. The error between physical reality and what the computer does can be fairly subtle. My "gut feel" (in an all-to-literal-sense!) for bad camera motion has become legendary in some places I've worked. My belief is that when you play the game yourself, your control over the camera gives you some kind of feedback for why it's doing what it's doing. The large screen TV issue is because the more of your visual field is filled by the bad camera action - the more your brain starts to think you're "in the game" rather than "outside the game". The sensation itself is identical to sea-sickness - and drugs like dramamine do help. In the flight simulation world, this is called "Sim-sickness" and an amazing amount of government dollars have been put into fighting it for military flight simulation. SteveBaker (talk) 13:30, 16 October 2008 (UTC)

Cola as a spermicide?

Is this true? Why do so many people still drink it then? Which amounts are they talking about for it to work? --217.227.77.18 (talk) 11:20, 14 October 2008 (UTC)

They mean if you directly immerse your sperm in cola they might swell up and die (2008 Ignobel Prize). This is not generally claimed to be an effective contraceptive under any normal circumstances, and merely drinking lots of cola is not claimed to have any effect at all. Dragons flight (talk) 11:29, 14 October 2008 (UTC)

Yes, although it is probably a weak spermicide. "The Spermicidal Potency of Coca-Cola and Pepsi-Cola," C.Y. Hong, C.C. Shieh, P. Wu, and B.N. Chiang, Human Toxicology, vol. 6, no. 5, September 1987, pp. 395-6. Pubmed. Ingesting a liquid is entirely different than applying the liquid to your sperm. Your digestive system breaks down liquids before they are circulated through the body so it isn't as though pure coke is being pumped into your testes.--droptone (talk) 16:05, 14 October 2008 (UTC)

Just to be absolutely clear, Droptone is not suggesting anyone inject cola into their testes as a contraceptive! ;) My guess is that it would be very effective and very permanent... --Tango (talk) 12:21, 14 October 2008 (UTC)

That sounds like an excellent recipe for a Darwin Award. Dragons flight (talk) 13:21, 14 October 2008 (UTC)

No - it's DEFINITELY not true. The Mythbusters busted this theory. Also Snopes says "No" - and they cite a half dozen impressive scientific studies in reputable journals. SteveBaker (talk) 22:42, 14 October 2008 (UTC)

Actually... the exploration of the "Effect of 'Coke' on sperm motility" (in the NEJM, no less) that showed it was effective, and the followup that refuted the claims were joint winners of a 2008 Ig Nobel Prize! :) — Scientizzle 22:53, 14 October 2008 (UTC)

Wow... with highly scientific and well studied sources who aren't just selecting a few Scientific claims without consideration of Scientific Bias or strict methodology, like those, who needs actual science or to read published papers for themselves? We should just stick to basing our Science on Mythbusters and our Politics on Penn and Teller... then we don't need to think, compare studies or evaluate the experiment's merits in determining whether their conclusions are valid. Seriously though, don't just take everything the TV, or indeed any paper says, on face value, don't question everything for the sake of it either, but come on, you just sound a bit sheep like. - Jimmi Hugh (talk) 23:49, 17 October 2008 (UTC)

Name of Phobia

Is there a name for a phobia of seeing a swarm of the same thing? For instance, I panic and run if I see a swarm of ants. It skeeves me out. But if I see one ant walking around, its fine. Same for worms, bees, ladybugs, etc. And one time, I saw a cartoon of a swarm of catepillars (with happy faces) in a coloring book. I couldn't even look at it without feeling like I was gonna dry heave. Is there a name for this phobia? --Emyn ned (talk) 13:32, 14 October 2008 (UTC)

It may simply be a mild insect/worm/creepy crawly phobia. One is not too much for you to handle, but several at once is too many.CalamusFortis 15:28, 14 October 2008 (UTC)

(ec) Most person-specific phobias aren't medically recognized and named. You could call it swarmophobia if you'd like. -- MacAddct1984 ^{(talk • contribs)} 15:34, 14 October 2008 (UTC)

err..says who? The APA has made a point of classifying every human neurosis and eccentricity imaginable! In fact, I'm of the opinion that they've gone somewhat overboard and are blurring the lines between personality trait and condition in a growing number of instances. --Shaggorama (talk) 17:33, 14 October 2008 (UTC)

See specific phobia (DSM-IV 300.29). The only phobia I can find specifically mentioned is agoraphobia (300.21, 300.22). -- MacAddct1984 ^{(talk • contribs)} 17:47, 14 October 2008 (UTC)

Since it's up for speculation, let's try plethoraphobia because it seems to be a fear of an excess of something, or more precisely, aggregatophobia from aggregare for "herded together" or "a flock". Julia Rossi (talk) 09:46, 15 October 2008 (UTC)

Computer program to visualise biomolecular pathways/interactions

The network of interactions occurring between different proteins in different cellular contexts is terribly confusing. Is there are computer program that aims to help process and visualise the interactions and their effects, using the many databases that exist on the Internet? I'm thinking along the lines of those complicated posters of signalling pathways except that using a computer program, the display could be more simple (not displaying necessary information), dynamic (adding or removing complexity while one studies) and always up-to-date. Does such a program exist?

Such data is manually gathered and presented at http://www.reactome.org

You can't automatize this. Even UniProt has an automatized partition (TrEMBL) and an edited part. --Ayacop (talk) 15:58, 14 October 2008 (UTC)

That website is pretty cool, thanks for sharing! --Shaggorama (talk) 17:22, 14 October 2008 (UTC)

McCain's arm

I have observed that McCain's arm is somehow too stiff. Does he has any known medical condition?Mr.K. (talk) 15:55, 14 October 2008 (UTC)

Yes. Due to injuries sustained while a POW, McCain cannot fully raise his arms. Likely this extends to general stiffness. — Lomn 16:06, 14 October 2008 (UTC)

He's also a septegenarian. Most people to reach his age have some form of arthritis, or stiffening of the joints. Its a general symptom of being old. --Jayron32.talk.contribs 16:28, 14 October 2008 (UTC)

That makes a difference. Is his conditions degenerative? Should we vote for Obama? Mr.K. (talk) 16:37, 14 October 2008 (UTC)

It shouldn't make any difference, we have had very successful presidents who have had crippling mobility issues far worse than McCain has. McCain's arthritis and former injuries should not be a reason to make a decision over his ability to lead. His fitness to lead should be judged on his past actions and on his plans for the country. On those facts alone, we should judge him entirely unfit to lead, but not on any perceived health issues. --Jayron32.talk.contribs 16:46, 14 October 2008 (UTC)

It's worth noting, however, that FDR did die in office. According to our article, his medical condition affected his (and his party's) choice of running mate in the 1944 election—serious consideration was given to the issue of who his successor would be as President if he were to be elected and die. Honestly, John McCain is getting on in years, and it would be foolish to pretend that he isn't. Asking if his running mate capable of running the country in the event of his death is not an unreasonable question.

To be fair, it's a question that should be asked regarding all Presidential tickets. According to our list of United States Presidents who died in office, eight of the United States' 43 Presidents have died on the job (four by assassination), and we've lost at least one other to resignation. Historically, there's a better than one in five chance that the guy elected in November isn't going to make it all the way through his Presidency. TenOfAllTrades(talk) 22:02, 14 October 2008 (UTC)

If not for the incumbent advantage, the relevant question would be how likely he is to get through one term. That would make the odds look better. —Tamfang (talk) 03:26, 15 October 2008 (UTC)

True, but we'd be breaking new statistical ground with McCain. Only three past Presidents first took office after age 65, and none after age 70. (McCain is now 72.) For white males in their mid-seventies in the United States, the average mortality (all causes) is about 3.5% per year—roughly a one in seven shot that McCain wouldn't survive his first four-year term. That doesn't account for the appreciably-better-than-average medical care a President is likely to get, nor does it include the extra stress the Presidency would apply relative to the average 72-year-old's lifestyle. It also doesn't include the risk of an elderly President suffering a non-fatal but incapacitating medical event (most likely a heart attack or stroke) that renders him temporarily or permanently unable to carry out his duties. (Figure the odds of a serious but non-fatal cardiovascular event are going to be another 1% or so per year.)

In the interest of completeness, it should be noted that all of these risks apply to Obama as well, but at age 47 the probabilities are about an order of magnitude smaller. There's also nothing to preclude him being the victim of an assassination attempt, a car accident, or just a bad fall down the stairs. While it is much more likely that McCain's health will fail him in office, voters will certainly want to evaluate both candidates' running mates. TenOfAllTrades(talk) 05:51, 16 October 2008 (UTC)

and none after age 70. Lamentably no longer true. —Tamfang (talk) 04:40, 25 August 2023 (UTC)

@Jayron32 - re: "His fitness to lead should be judged on his past actions and on his plans for the country. On those facts alone, we should judge him entirely unfit to lead, but not on any perceived health issues" - this isn't the place to be advocating for or against any candidate on political questions. It's the Science reference desk. -- JackofOz (talk) 04:04, 15 October 2008 (UTC)

He released his medical records to try and convince people that he was healthy enough for the job and there was nothing in there that suggested it would be a real problem. Of course, at his age new problems can develop quickly. If you think McCain would be a better president that Obama but are worried about his health, you need to decide how bad it would be if did fall ill (based on you opinion of Palin, among other things) and how likely that is to happen and compare that to how bad you think it would be to have Obama as president and vote accordingly. --Tango (talk) 16:59, 14 October 2008 (UTC)

He didn't "release" them, he let a bunch of reporters look through the ~1200 (I've heard 1173) pages for three hours, without taking any copies or such. Among the findings seem to have been four bouts of melanoma, several precancerous colon polyps and a bunch of other worrying things. -- Aeluwas (talk) 17:15, 14 October 2008 (UTC)

And, you must consider the health of Obama, who has not released his medical records. He could easily have extreme hypertension and hypercholesterolemia without showing any outward signs of illness. Then, after a couple stressful months in office, he could have a heart attack. If you are basing your vote on something as silly as possible health risks, why not go for the silliest? If you are simply trying to validate your vote on some silly factor, why not base it on something sillier, such as refusing to vote for anyone who has ever been a pilot? -- kainaw™ 17:19, 14 October 2008 (UTC)

Obama did release a partial medical history that claimed he was in "excellent health".[8] Although the article states that his blood pressure was 90 over 60, which is a bit low for a systolic pressure... -- MacAddct1984 ^{(talk • contribs)} 17:31, 14 October 2008 (UTC)

People never seem to worry about low blood pressure... I'm not sure why not since, as far as I know, it can be just as dangerous as high blood pressure. --Tango (talk) 18:19, 14 October 2008 (UTC)

That depends on how you define "high" and "low" blood pressure. High blood pressure is a modifiable risk factor for cardiovascular disease, and it's more common than low blood pressure. See "Blood pressure". Axl ¤ [Talk] 18:37, 14 October 2008 (UTC)

Oh my! If we are speculating about future ailments, we can toss in a possibility of Addison's disease with a blood pressure as low as 90/60. Can we trust a man with the faint possibility of Addison's to make reliable decisions? -- kainaw™ 18:51, 14 October 2008 (UTC)

You mean like JFK? ;) -- Aeluwas (talk) 18:59, 14 October 2008 (UTC)

Even worse! Now there is historical evidence that electing a President with Addison's leads to an assassination! How many more idiotic reasons can we find to back a superficial preference for one candidate over the other? -- kainaw™ 20:28, 14 October 2008 (UTC)

7812819, give or take 42. --Stephan Schulz (talk) 22:50, 14 October 2008 (UTC)

I plan on voting for whoever is taller. APL (talk) 23:21, 14 October 2008 (UTC)

Au contraire, your the one who is being idiotic. Are you seriously suggesting that it's not valid to consider the health of a candidate or that age and known existing or previous medical conditions are a factor in considering the health of a person; in an election where you are electing that person for a fixed term? Personally, I would say McCains health, while of concern, is probably not enough to warrant people not voting for him solely for that reason. But his health is clearly of far greater concern then it is for Obama. And while if I were an American I would never vote for him anyway, if I was in the position of deciding between the two I would definitely factor his health into the equation and the possibility of Sarah Palin taking over as President I would consider far more likely then Biden. Nil Einne (talk) 08:43, 15 October 2008 (UTC)

I disagree with your premise. Given the nature of the US electoral system, you're basically stuck with the vice-president until 2012 if something were to happen to the president to make him or her unfit for office (including death). Therefore, it's perfectly resonable to consider whether ill-health is likely to make this happen. While obviously this applies to all candidates there is intriscly significantly greater reason to have concern when the candidate is 72 years old with some relatively serious health concerns then there is when the candidate is 47 years olf with no known health concerns. Obviously you can't predict precisely what will happen but this doesn't mean you shouldn't make a decision based on the evidence at hand. After all, for all we know McCain or Obama might go nuts and decide to nuke China and Russia one day because they're bored. In both cases I would say the evidence suggests this is unlikely but clearly if one of the candidates did have a tendency to do reckless things which seriously endanger others when they were bored, d it's perfectly resonable for a person to consider it more likely that this candidate would do something to endanger the security of the US and to let this affect their vote. In other words, just because it's theoretically possible that all candidates would do the same thing or worse doesn't mean it's ludicrious to consider the likelihood of something happening based on the evidence at hand. Nil Einne (talk) 08:31, 15 October 2008 (UTC)

The story now seems to be that his arms were injured when he was tortured as a prisoner of war, but in January 1968 interview with a French reporter [9], he said his arms and a thigh were broken when he ejected from his plane. In the propaganda tape he recorded under duress for the North Vietnamese which was broadcast by Radio Hanoi to U.S. forces in South Vietnam on June 2, 1969, McCain said "“I was a U.S. airman engaged in the crimes against the Vietnamese country and people. I had bombed their cities, towns, and villages and caused more injury even death for the people of Vietnam. After I was captured I was taken from a hospital in (?Da Nang) where I received very good medical treatment. I was given an operation on my leg, which allowed me to walk again, and a cast for my right arm which was badly broken in three rpt three places. The doctors were very good and they knew a great deal about the practice of medicine. I remained in the hospital for some time, I regained much of my health and strength.” In a propaganda interview with a Cuban official 14 days after being shot down, McCain said that when he bailed out he collided with the remains of his plane and fractured both arms, one in three places, and his right leg at the knee. See also [10] which has reports of the McCain interviews while he was a POW and [11]. Edison (talk) 05:01, 15 October 2008 (UTC)

@Jack – so it is! (the science desk). In that case I find Jayron32's comment observational and objective. And personally am enjoying the role of Mccain's arm as punctum.;) Julia Rossi (talk) 09:36, 15 October 2008 (UTC)

Clearly he might have sustained additional injuries "while a POW," as Lomn stated, but his injuries while ejecting from his plane 'before' he was a POW are sufficient to explain his present limited range of motion in his arms. Edison (talk) 14:52, 15 October 2008 (UTC)

what is this plant?

I've been given this plant as a gift, however it has no provided information about species/care instructions etc. I'm fairly sure it's quite a commonly owned house plant but I have no idea what it might be. Here is an image of it: [12] —Preceding unsigned comment added by 86.135.81.194 (talk) 17:53, 14 October 2008 (UTC)

I don't remember what it is called either, but I owned a very similar, if not the same species, of plant. I am fairly certain it is a variety of succulent, but I can't remember anything more specific than that. --Jayron32.talk.contribs 17:57, 14 October 2008 (UTC)

It's either Holiday cactus or some closely related species.CalamusFortis 18:04, 14 October 2008 (UTC)

Thanks, that looks about right :) --86.135.81.194 (talk) 18:09, 14 October 2008 (UTC)

Yes, it is. I've got one. Axl ¤ [Talk] 18:41, 14 October 2008 (UTC)

i have heard the term "Clopathia" applied to similar plants. Edison (talk) 05:37, 15 October 2008 (UTC)

Getting contact lenses in

Hehe, I'm extremely impatient and I can't get the hang of it. Is there any quick tip or something? A putter-inner from eBay for 9.99? --217.227.103.178 (talk) 19:35, 14 October 2008 (UTC)

The first time i got contacts, it took me an hour to get them in by myself. I have now worn contacts for 18+ years. Give it time and practice. Like anything else, you are training your body something new, and it just takes practice. Your body has a natural reflex to prevent bad stuff from getting into your eye. You simply have to retrain your body against this reflex. It's well worth it, I find that my vision is much better with my contacts than with the same prescription of glasses, and once you get used to it, you don't even notice it. --Jayron32.talk.contribs 19:47, 14 October 2008 (UTC)

I'm rather new at it myself. When I have trouble getting them in, I set up a mirror; it helps my aim and also, by giving me something to look at beyond my finger, helps me resist the reflex. —Tamfang (talk) 03:21, 15 October 2008 (UTC)

Frequency guard bands in OFDM

Can anybody explain why the lower and higher frequency subcarriers are left unused in OFDM systems? For example, 802.16 uses a 256-point FFT, however, the 28 lowest subcarriers and the 27 highest are not used. This is also true for the DC subcarrier. What's the reason of this? 85.243.50.175 (talk) 20:42, 14 October 2008 (UTC)

The transmission and reception has to pass through a band pass filter to stop spurious transmission and remove adjacent interference. At the high and low frequency ends there is a roll off in the passband, that will reduce sensitivity and result in noise if signal was used. There is also phase shift in these parts of the passband, so it is best not to use it. The frequency allocations are already overlapped in these sort of systems, so there is no wastage of spectrum. Graeme Bartlett (talk) 21:04, 14 October 2008 (UTC)

Thanks a lot! It has to do with filtering, just as I thought. The frequencies are overlapped indeed, but leaving some slots unused will still make the system sub-optimal. However, that could only be solved by an ideal filter. 85.243.50.175 (talk) 21:37, 14 October 2008 (UTC)

Identify this tree

An unidentified tree, presumably taken near Agumbe.

Same image, retouched to look less foggy.

I recently spotted this image on IfD. I think it could be worth keeping, but it's not very useful if we don't know what it shows. So, can anyone identify the tree with red flowers in this photo? Based on the name and the description page, the picture was presumably taken somewhere near Agumbe, Karnataka, India. In case it helps, I've also uploaded a version I tweaked to make it look somewhat less foggy. Thanks in advance for any help. —Ilmari Karonen (talk) 21:37, 14 October 2008 (UTC)

Royal poinciana or Delonix regia is found in India, or it may be another kind of flame tree. The Indian coral tree is known as Erythrina variegata found throughout southern Asia. Both are suited to tropical areas. Julia Rossi (talk) 09:24, 15 October 2008 (UTC)

Hmm... it does look remarkably like some of our pictures of E. variegata, particularly this image. The timing is a bit suspicious, since all the sources I've found suggest that E. variegata should flower around March, while the Agumbe photo has an Exif timestamp in July, but I suspect the timestamp may simply be bogus — not everyone sets their camera clock correctly. Anyway, thanks! —Ilmari Karonen (talk) 10:36, 15 October 2008 (UTC)

You're welcome, Julia Rossi (talk) 22:20, 15 October 2008 (UTC)

Ethidium Bromide

I was doing PCR analysis today, and touched the ethidium bromide stained agarose gel with my hands when i - instinctively, and without thinking - took it when someone handed it to me. Later i touched the gel again with gloves and then when removing the gloves touched my hand with the glove that i had just used to move the gel. I guess i'm probably not going to die, and after googling i'm almost content in the knowledge that i wont likely be getting cancer any time soon either, but one of my fellow students told me that - if i was concidering it - it would be a bad idea to get pregnant, and that that was a general safety precuation. So for how long should i not be getting pregnant? The next week? Year? Does this mean that my future children will have genetic defects or am i just being paranoid? Thank you 87.60.70.3 (talk) 22:01, 14 October 2008 (UTC)

The Wikipedia Reference Desk is not allowed to give personal medical advice. You are welcome to read Ethidium Bromide (which doesn't really answer your question either), but for concrete advice you should speak to a doctor or poison control specialist. Dragons flight (talk) 22:38, 14 October 2008 (UTC)

(Trying to tiptoe around possibly medical question) I have never personally worked with the stuff, however some background information. MSDS's (JTBaker and Fisher, as well as my LCSS list it only as "possible" teratogen, with more study being needed. I guess it depends on the half-life of it in your system, as teratogens normally only act on a developing fetus. It also depends on how much you came into contact with.

All that said, I'm guessing you are doing this research at a university or school. If you are at all worried, contact your Environmental, Health, and Safety department (or something similar), even to just put your mind at ease. They will possibly have more information, and you are able to give them more information on medical history and under what circumstances it happened, as well as how much and if you followed safety precautions (throughly rinse for 15 minutes or so with water?). It is also likely very confidential. In other words, get information from professionals, not other students.

And being slightly paranoid is good when it comes to your health. This is the only body you get (probably) :) --Bennybp (talk) 22:53, 14 October 2008 (UTC)

[Edit conflict] I don't think that a doctor or poisons service could give you any more helpful information. I searched Pubmed and didn't find any relevant articles. I'll try to look at ToxBase later. From our Wikipedia article, I didn't know that ethidium bromide is used to trypanosomiasis in cattle. Axl ¤ [Talk] 23:01, 14 October 2008 (UTC)

Here is an interesting article, although I can't vouch for the reliability/accuracy of the website. Axl ¤ [Talk] 23:30, 14 October 2008 (UTC)

Also [13] Nil Einne (talk) 07:31, 15 October 2008 (UTC)

That is a SPECTACULAR article Nil. Good find, thanks for sharing. --Shaggorama (talk) 07:45, 15 October 2008 (UTC)

Ironically, it was originally in the Ethidium bromide article until I removed it (it appears to be well written but as the personal blog of an unknown scientist I don't think it can be classified as a reliable source), although I didn't find it from there (I found it from Google). Nil Einne (talk) 09:35, 15 October 2008 (UTC)

It is directly linked from the "bitesizebio" article. Axl ¤ [Talk] 10:27, 15 October 2008 (UTC)

Doesn't help for your question, but I recall talking to a researcher who was complaining about other people who were completely paranoid about any exposure to EtBr, but cavalierly stared into the UV lightbox unprotected. (Ignoring the possibility of getting cataracts or skin cancer from the UV exposure.) My experience has been that most labs have a "bogeyman" which everyone gets irrationally paranoid about, while completely ignoring the 20 other items around them which are as bad or worse. Of course, the MSDS's which recommend full protective gear for water, and labels which claim "this product has not been completely investigated" for compounds which are FDA approved drugs doesn't help things. (Both examples have been seen personally.) Back on point, don't trust medical advise from Wikipedia, but also don't trust medical advise from paranoid labmates. -- 128.104.112.147 (talk) 21:41, 15 October 2008 (UTC)

Tropospheric gas giants

After the tropophere have those gas giants have a surface prior to the fliud interior or not. I know Jupiter and Saturn's sky starts at the upper level to be blue, then at lower level is it the tropos it's sky is like orange, brown, yellow (gold or tan). For Uranus and Neptune the sky must start to be blue as a gatorade, then at lower level it's paler blue. Anyways what part of atmosp layers is tropos on gas giants? And what's beenath the troposhper? Normal people say Jupiter, Saturn Uranus and Neptune contains no surface.--Freeway19 23:06, 14 October 2008 (UTC)

As far as I know, your assertions as to the color of the sky from within whatever planet's atmosphere remain entirely unsourced. I'm not sure why you keep repeating them. Anyway, there's not generally an expectation of a solid surface prior to liquified gases around the core. Per atmosphere of Jupiter, the troposphere's lower boundary is the liquid interior. — Lomn 23:49, 14 October 2008 (UTC)

Image:Structure of Jovian atmosphere.png This image is tough to understand. Jupiter's sky will not be black becasue it have an atmosp perhaps the upper level is blue or blue-purple. About Jupiter's center I know it's 5 to 6 times hotter than surface of sun, is the interior bright and hot or black and hot. Thi s is what the book said, I guess the interior is white-hot.--Freeway19 00:00, 15 October 2008 (UTC)

[14][15] [16] [17] This is the source. The trace above the globe glows tinge of blue on Saturn and Uranus. For Jupiter when Galileo pass t's atmos, I belive is thermo, it's tropo must be orange or orange-scarlet, hoever at upper layer jupiter's sky appears blue or indigo. Lomn, you said no source how you explin those.--Freeway19 01:41, 15 October 2008 (UTC)

I don't mean to be insulting, but you do realize that none of those images are real, right? They're just artwork. APL (talk) 03:54, 15 October 2008 (UTC)

Additionally, the first link (the only one that could be used as an actual reference) doesn't appear to be discussing color. I see no reason to assume that the colors present are anything but a visual aid. — Lomn 13:09, 15 October 2008 (UTC)

Artist interpretations generally make use of artistic license. Plasticup ^T/C 15:54, 15 October 2008 (UTC)

• On those planets I saw the diagram. They don't have a solid surface between. Hydrogen or methane haze will possibly make those sky on stratos blue, but at tropos, is the place of varying cloud layers. At that level the sky may be brown or orange, that's for Jupiter and Saturn, however because of the methan haze of Uranus and Npetune, their sky must start to be deeper blue at top layer, and at lower layer, the sky must be lighter blue. After tropos, it will be liquid interior bound. I wonder will it be light / dark at liquid interior. --Freeway8 22:22, 15 October 2008 (UTC)

  I wouldn't expect any sunlight to penetrate the atmosphere of a gas giant (I haven't researched it, though). It could be hot enough to be radiating in visible light itself, though. I don't know where you're getting all this stuff about colours, it sounds like guess work to me... --Tango (talk) 22:30, 15 October 2008 (UTC)

• Titan's also get very little or no sunlight. it's light is only 1/3000 to Earth, but it's sky appears to be light orange or tangerine colour because of it's haze, Cassini have been able to land on Titan.--Freeway8 00:10, 16 October 2008 (UTC)

• Some source says jupiter, Saturn and Uranus have hazes. hazes is judge to be blue.--Freeway8 01:12, 16 October 2008 (UTC)

  It's pretty dark on Titan due to the distance and thick atmosphere, but yes, there is sunlight on the surface. However, it doesn't have anything like as thick an atmosphere as a gas giant - the thicker the atmosphere the less light can penetrate to the surface. The gas giants certainly have hazes and clouds and their atmospheres will scatter different wavelengths of sunlight differently, so as long as you're not far enough down that sunlight is blocked the sky will have a colour, but I don't know where you are getting these ideas about what that colour would be. Who judges hazes to be blue? --Tango (talk) 15:34, 16 October 2008 (UTC)

• I thouht Uranus is mostly coverwith haze, this is why the sky is blue all the time. Those gas giant's sky stay the same all the time, same as Neptune and Saturn. Saturn is much cover with haze too is thicker than Jupiter and neptune's.For uranus and neptune the sky color should be darker blue on top and get lighter on bottom. At the lowest layer must be light blue. Saturn is also much a blue planet I thouhgt, so it's sky much start out blue on haze, but at lower layer must vary to yellow, brown, and orange. Jupiter's have haze, but the disc is rainbow or opal-like color, so the sky on top is specualte to be blue, but not define. At the tropo level juptier may vary white, orange, brown. For Venus, the sky stay the same much all the time I thought. At the cloud levels, it appears to be yellow, but beenath the cloud could be orange mix, becasue of the terrible greenhouse effect, Venus' sky may look scarlet seen from surface. I am not certain what's the color above the top clouds of Venus, becasue it is on the bound to outer space, so I guess it's black.--Freeway8 20:01, 16 October 2008 (UTC)

October 15

physics

why the electric field inside the conductor is zero?if the electric field inside the conductor is zero then how can current flow through it. —Preceding unsigned comment added by 221.120.210.41 (talk) 06:20, 15 October 2008 (UTC)

• You're totally right. The eletric field inside a conductor in only zero in static situations, i.e., if no current flows. baszoetekouw (talk) 08:54, 15 October 2008 (UTC)
  • But if it is a perfect conductor there is no electric field. Current can still flow, but because there is no resistance there is no electric field. Also the current has to flow on the surface of a perfect conductor, the magnetic field lines cannot penetrate. See superconductor Even in an imperfect conductor such as sea water the magnetic field is slow to penetrate and therefore alternating currents cannot go deep into the sea. see skin depth. Graeme Bartlett (talk) 11:29, 15 October 2008 (UTC)

Practical conductors, even a copper bus bar of 100 sq cm cross section, have resistance and have a measurable and significant voltage drop when carrying rated current. A superconductor may be different story. Edison (talk) 14:55, 15 October 2008 (UTC)

The OP was talking about the electric field inside a conductor (not between its ends) being zero. see this [18]--GreenSpigot (talk) 15:10, 15 October 2008 (UTC)

The "sides" of a conductor and the "ends " of the conductor are all "inside" the conductor. It is relevant to the discussion that in a practical conductor, there is a measurable voltage gradient throughout the substance when it carries substantial current. The OP referred to current flowing, and your example shows a conductor in equilibrium, with no current flowing. Edison (talk) 15:53, 15 October 2008 (UTC)

Baszoetekouw is right. Superconductors have zero resistance at DC, but non-zero reactance and even losses (see here under "Resistance") at AC. This means that a changing E field (e.g. a step function) can penetrate the material and thus set up a current. When the E field stops changing, the current keeps flowing (assuming you have a closed circuit) until you stop it by applying a reverse field. --Heron (talk) 19:00, 15 October 2008 (UTC)

Hückel's rule

I am having difficulties grasping the concept of how the aromaticity of a compound is determined in cases such as that of furan. The oxygen atom has two lone pairs, yet just one of the pairs is counted while counting the no. of pi electrons in the cyclic ring (whereby the no. of pi electrons comes to 6, satisfying the condition for huckel's rule). I read about the relation between the hybridization concept and huckel's rule on the furan article page but could not understand it very well. What exactly is the state of hybridization on the oxygen atom in furan? Additionally, how are we supposed to count the pi electrons in a ring in such cases where multiple lone pairs occur? Leif edling (talk) 06:41, 15 October 2008 (UTC)

It's been awhile but here's how I remember how this one works: 3 of the oxygen's electron pairs are sp2 hybridized, and the third pair is unhybridized in the pi orbital. The pi electrons contribute to to aromaiticity. the sp2 hybridized electrons all lie in the plane of the ring: 2 pairs make up the sigma bonds with the neighboring carbon atoms, and the third electron pair is a lone pair. When counting electrons for huckels rule, use whatever electrons are available to you that are committed to pi orbitals, or in this case CAN BE committed to pi orbitals in the correct plane. The lewis structure shows you 2 pairs of pi bonding electrons already in the ring and 2 more available pairs on the oxygen. One pair contributes to the aromaticity, the other becomes a sp2 hybridized lone pair pointing straight out from the molecule (normally it would be sp3 because there are 4 pairs of electrons associated iwth the oxygen right? BUT we lose one p orbital to that pair of electrons stolen for aromaticity, so instead of sp3 we're downgraded to sp2! It looks just like the hybridzation on the carbon atoms in benzene). The combination of aromaticity and significant resonance causes the lone pair to be very tightly bound: loss of the lone pair would destroy the aromaticity, so the molecule is much 'happier' (more stable/lower energy) with the electrons bound. --Shaggorama (talk) 07:23, 15 October 2008 (UTC)

As far as Huckel's rule or hybridization goes, lone pairs can either be part of the hybridization scheme or part of the pi-system as needed. Because lone-pairs are not "tied up" in a specific location, they are free to "shift" to produce whatever geometry will result in the lowest-energy configuration. All other things being equal, oxygen which is singly bonded (as in, say, dimethyl ether,) will assume an sp3 hybridization. However, in furan, the presence of unhybridized p-orbitals on neighboring atoms makes it so that one of the lone-pairs in the oxygen will assume an unhybridized p-orbital state as well, because of a property called conjugation. Basically, p-orbitals in conjugation (aka "delocalized pi-system) are at a lower energy state than the sp2-sp3-sp2 system which would exist if the singly-bonded oxygen maintained its expected geometry. Again, this is all because the lone pairs on oxygen are "mobile" in a way that bonding pairs are not. Analysis of furan shows that it is, indeed a planar molecule, unlike the similar Cyclopentadiene, where the two hydrogens on the lone sp3 carbon lie out of the plane. --Jayron32.talk.contribs 17:52, 15 October 2008 (UTC)

Gem quality Epidote mineral

I was wondering, and looked everywhere for that matter, the odds of finding gem quality Epidote in the united states. The only things i have read have stated Brazil as the main occurence for gem quality. Also i have read that people buy gem oddities such as this, i was wondering what a gem quality would catch per carat. Thanks to anyone that can find, or knows more information then me. —Preceding unsigned comment added by 216.52.133.15 (talk) 07:43, 15 October 2008 (UTC)

'Landing on Jupiter'

We were discussing in physics class yesterday about the gravitational field strength of Jupiter. We then got onto the subject of what happens if you genuinely do try to land on it. I'd love to know what would happen assuming that whatever we 'land' with is able to cope with the high pressures and the pummelling it'd get on the way down. Can anyone talk me through it? Would there eventually be a rocky, or icy, core because of the high pressure or would it still remain gasous all the way through?

Thanks, —Cyclonenim (talk · contribs · email) 07:51, 15 October 2008 (UTC)

• See Jupiter#Internal_structure baszoetekouw (talk) 08:52, 15 October 2008 (UTC)

• Also note that it's been done, insofar as it's possible. --Sean 13:15, 15 October 2008 (UTC)

It sounds like at some level of the Jovian atmosphere conditions are such as to allow a balloon, or a more solid probe with a degree of bouyancy, to float for an extended period. The article about the Galileo probe indicates that it lasted down to a pressure of 23 atmospheres and 150 Celsius, but a probe with a gas bag or a bouyancy chamber filled with gas or liquid could be deployed to float at a higher and cooler level of the atmosphere, or it could ascend or descend like a submarine. Like the bathyscaphe, it could have a large flotation chamber which was not shielded from ambient pressure and a small instrument chamber which was braced to keep lower pressure inside. It could also have a cooling system to keep the instrument chamber cooler than the ambient temperature, with a refrigerant system which transferred heat from the instrument chamber to the flotation fluid or gas in its larger chamber, which would in turn reject heat to the atmosphere. The pressure of 23 atmospheres was not all that high. The manned Bathyscaphe in 1960 descended deeper than 10,000 meters in the Challenger Deep on Earth, where the pressure should have been about 1000 atmospheres, 43 times the pressure the probe was able to endure. Modern submarines are tested to a depth equivalent to 50 atmospheres, and are estimated to be able to survive over 70 atmospheres. Edison (talk) 15:18, 15 October 2008 (UTC)

Have you seen Floating city (science fiction)? It's a similar idea, although not going so deep. --Tango (talk) 16:01, 15 October 2008 (UTC)

You really sould be thinking about a balloon, not a submarine. 50 atmospheres of gas still only has about 5% of the density of water, and hence only ~5% the bouyant force. I don't think anything that looked like submarine could sustain high pressures with so little mass. You could probably design a balloon-like system to be bouyant at a few atmospheres of pressure though. Dragons flight (talk) 16:39, 15 October 2008 (UTC)

You might be interested in the article Comet Shoemaker-Levy 9. --Shaggorama (talk) 16:09, 15 October 2008 (UTC)

The density question was not clearly adressed in the article about the Jupiter probe of a few years ago. I recall a sci-fi story of many years ago about a metal craft which dropped down into the Jovian atmosphere until it reached the layer where its density allowed it to float. With today's technology a Blimp might be a better model than a bathyscaphe, to stay at a higher and cooler level. Lightning and tumultuous wind would be a challenge. I wonder how far down into the atmosphere sunlight penetrates before it is as dark as a cloudy moonless night on earth? Edison (talk) 22:39, 15 October 2008 (UTC)

It seems like it depends on wavelength - see the image caption on the right hand side here. --Tango (talk) 22:54, 15 October 2008 (UTC)

Another interesting feature is that Jupiter's clouds are generally thought to give way to an essentially transparent Hydrogen/Helium sky within 100km or so. So if you could float a blimp there, you could get to look up at the swirling clouds from below. Dragons flight (talk) 01:11, 16 October 2008 (UTC)

Arthur C. Clarke wrote about balloon travel in the atmosphere of Jupiter in his 1971 novella A Meeting with Medusa. Gandalf61 (talk) 13:30, 16 October 2008 (UTC)

orchestra

why doesn't the sound emitted by the instruments of an orchestra interefere with each other? on an unrelated note, are the different instruments arranged in any particular order? thanks —Preceding unsigned comment added by 65.92.231.82 (talk) 08:25, 15 October 2008 (UTC)

Q.2. Yes, they are usually, although various conductors have experimented with alternative layouts. I'm surprised we don't seem to have an article with the traditional orchestral seating plan. Anyone? -- JackofOz (talk) 08:42, 15 October 2008 (UTC)

This is the usual arrangement. -- JackofOz (talk) 21:15, 15 October 2008 (UTC)

Q.1: They do; however, most composers work to make that interference pleasant to the listener. The concept of acoustic beats may also be of interest (tuning the orchestra is used to prevent this) — Lomn 13:05, 15 October 2008 (UTC)

A band or orchestra has the sounds of the instruments combine in various harmonies and dissonances, intended or unintended. "Tuning" is an exercise musical ensembles go through to get all instruments on the same pitch, and if two or more are not tuned exactly the same, audible "beats" are heard, which sound like the volume increasing and decreasing by a number of times per second equal to the difference in the frequencies of the two instruments. String tensions are adjusted, brass instrument tuning slides are pushed in or out, and woodwind mouthpieces are pushed in or out to alter the physical characteristics of the instrument. Edison (talk) 15:24, 15 October 2008 (UTC)

As the preceding responders have stated, the sounds certainly interfere with each other. Each instrument produces a complex wave, and the waves from each instrument add up, producing a very complex signal indeed. The amazing thing is that your brain more often than not is capable of doing the reverse transformation, i.e. to decompose the composite wave into its constituent parts, to allow you to distinguish the oboe from the violin. The article psychoacoustics might be of interest to you, as well as some of the articles it links to, notably missing fundamental and auditory masking. --NorwegianBlue ^talk 21:21, 15 October 2008 (UTC)

Just to make sure i understood what was said, when the orchestra is 'practicing', they're also making sure that there isn't much unwanted interference? Also, for my second question, yes I do know that the orchestra has a certain, fixed arrangement. I was wondering if there was any reason (acoustically) for, say, the violin's being closer to the centre than the cello's etc. THanks

This is one of those ikky things where pure, simple Physics-101 doesn't really cover the bases.

When we think of interference, we're thinking of nice, simple sine-waves that go on for a long time so that when two waves are mixed together, they add together to produce extra large peaks and troughs when the peaks and troughs of the two waves happen to line up - and they cancel out when the peaks of one wave line up with the troughs of another. This is all very wonderful - and you can have it happen before your very eyes in a wave tank or with electronic systems that produce perfectly pure sine wave audio.

But in reality, the waveform produced by a musical instrument is a mixture of an insane number of sine waves - all of different frequencies. Each part of the instrument is vibrating and resonating - each part producing different harmonics and noise. Each sine wave is starting and ending - or changing amplitude or frequency as the note progresses. Look at almost any instrument on an oscilloscope or a spectrum analyser and it's a total mess to look at. The waves within a single instrument are continually interfering with each other for short periods - those effects shift around millisecond by millisecond as the note builds up and dies away.

When you add more instruments, it just gets more and more complicated. Certainly the instruments are interfering with each other periodically. But consider why two seemingly identically tuned violins playing the same note at the same time sound completely different from one violin played at twice the volume. The two violins will never completely cancel each other out and never completely add together because they are subtly different - their dimensions are not the same, the wood they are made from has different thickness and flexibility because they have aged differently and have different amounts of humidity inside and varnish on the surface. The wood grain density is a little different. The bows have different amounts of rosin on them - and the horse-hair the bows are made from came from horses of different genetic makeup giving them different frictional characteristics. The two musicians are applying different amounts of force to bow and string for different durations throughout the note. The instruments are not identically or perfectly in tune and the position of the musician's fingers on the fingerboard are not identical. The distance of each violin from the walls and ceiling of the room are different - and since the musicians are not perfectly still (compared to a wavelength of sound at least), that distance is changing throughout the note. The audience has variable refractive indices depending on how they are dressed - this bends the sound around in yet more complex ways.

The result is that even with two seemingly identical instruments, those interference patterns are totally chaotic - changing so fast throughout the note that it would be utterly impossible for the two instruments to perfectly add or perfectly cancel each other out for more than a tiny fraction of the time. The result (to our ears) is that we hear two separate instruments...which is an amazing feat of calculation in our brains!

Two perfectly tuned electronic music synthesizers - playing the same, simple waveform through really high quality amplifiers and speakers in a large anechoic room WOULD interfere...but we are never in that situation with a real source of live music.

SteveBaker (talk) 13:14, 16 October 2008 (UTC)

OK that's it now. I'm going to start collecting these q's and responses to publish in my Book of SteveBaker. It will sell a million copies and I will get all the money, thank you very much GFDL. :) Franamax (talk) 06:30, 17 October 2008 (UTC)

My understanding on some of these issues-- the ways violins are held tends to make them tilt to the right, which means by putting them on stage right the instruments mainly point their fronts toward the audience. Violins being so important to an orchestra this is more important than for say, violas. Also given the importance of the strings, it makes sense to place them toward the front of the stage. The woodwinds make sense being more in the center, but in front of the louder brass and percussion.

Also on the ability of our brains to hear separate instruments within a mass of sounds-- this isn't so much the case with masses instruments of the same type. For example, while a solo violin has a somewhat biting and piercing sound, a mass of violins, as you get in an orchestra, sounds less like 20-30 individual instruments and more like a single sound, but one notably different from a single violin. Massed violins (or clarinets for that matter) tend to sound smoother, less piercing, richer, etc. Pfly (talk) 05:36, 17 October 2008 (UTC)

Doesn't that depend somewhat on the skill level of the players? The difference between massed violins and clarinets on the one hand, and bassoons on the other hand, is that the clarinets and violins are easier to light, but the bassoons burn longer. (Classic joke from brass players) Edison (talk) 02:45, 18 October 2008 (UTC)

Molecular Formula of Gasoline

What is the molecular formula of gasoline(petrol)? —Preceding unsigned comment added by PunarvasuOMEGA (talk • contribs) 08:26, 15 October 2008 (UTC)

Gasoline is not a pure substance, so it doesn't have a single molecular formula; it is a mixture of different hydrocarbons. Our article says "typical gasoline consists of hydrocarbons with between 5 and 12 carbon atoms per molecule ... benzene (up to 5% by volume), toluene (up to 35% by volume), naphthalene (up to 1% by volume), trimethylbenzene (up to 7% by volume), MTBE (up to 18% by volume) and about ten others". Gandalf61 (talk) 09:34, 15 October 2008 (UTC)

Would a car run well on a single carefully selected hydrocarbon, for instance if someone found a way to add hydrogen molecules to carbon dioxide with the addition of energy from solar or nuclear to create a synfuel? In other words would some single compound like octane serve as auto fuel, or is a blend necessary to achieve proper combustion? Edison (talk) 15:45, 15 October 2008 (UTC)

Propane is used as a fuel, and so is natural gas which is mostly methane so I don't think a blend is necessary. I believe gasoline is a blend because the energy it would take to separate it doesn't actually give you a benefit.-- Mad031683 (talk) 16:23, 15 October 2008 (UTC)

I suspect one could almost certainly find pure substances that a normal car would happily run on. It's less obvious whether a pure substance would outperform a mixture when it comes to variables like efficiency of combustion and pollution control. Some of the things in gasoline are explicitly added to improve performance, and I suspect that even synfuels are likely to be blended for best performance. Dragons flight (talk) 16:28, 15 October 2008 (UTC)

(ec) With minimal modifications, most cars today can be easily adapted to run on pure propane and natural gas (primarily methane). Brazilian flex-fuel vehicles can run on pure ethanol, while flex-fuel vehicles in other jurisdictions are often able to handle up to 85% ethanol (E85 gasoline). I would expect that an unmodified car today could run quite comfortably on pure iso-octane (2,2,4-trimethylpentane), as such a fuel would by definition have an octane rating of 100. TenOfAllTrades(talk) 16:31, 15 October 2008 (UTC)

Orthogonality in OFDM

Why does the fact that the subcarriers used in a OFDM system are equally spaced mean that they are orthogonal? Can anyone provide a clear and simple demonstration of the subcarriers' orthogonality in OFDM? 85.243.50.175 (talk) 15:32, 15 October 2008 (UTC)

Have you read Orthogonality#Radio_communications? --Shaggorama (talk) 16:12, 15 October 2008 (UTC)

Yes, sure. I'm just looking for a couple of explanations from other people in order to formulate a more comprehensive view on the issue. —Preceding unsigned comment added by 85.243.50.175 (talk) 16:33, 15 October 2008 (UTC)

If you build a perfect coherent detector for any one of those carriers it will not respond to any of the other carriers. To demonstrate this integrate over one symbol time the product of one carrier, with another one. When you multiply sine functions you will get a sum frequency and a difference frequency. If this difference frequency is the same as the symbol rate, the integral will be zero. Graeme Bartlett (talk) 20:41, 15 October 2008 (UTC)

Mining collapse question?

What is it called when the surface ground (way above where mining took place) suddenly sinks a few metres because of shifting of the earth or collapsing in mines underground? Or if a deep hole/shaft suddenly opens up like a pothole on the surface due to collapsing hollowness and mining underneath? Are there terms for these changes to the surface's geology?--Sonjaaa (talk) 17:55, 15 October 2008 (UTC)

"Subsidence". Axl ¤ [Talk] 18:15, 15 October 2008 (UTC)

"Subsidence" refers to the process, but does not necessarily imply that it reaches the surface; it could be entirely underground. If a hole forms in the surface, it is called a sinkhole. But both terms could apply to wholly natural effects as well as the consequences of mining. You need to use additional words if you want to limit it to that cause, I think. --Anonymous, 21:40 UTC, October 15, 2008.

"Sinkhole" explicitly refers to subsidence caused by the action of water. It is not a consequence of mining, but may be due to artificial alteration of water courses. Axl ¤ [Talk] 22:14, 15 October 2008 (UTC)

Well, the "sinkhole" article says "Sinkholes also form from human activity, such as the ... collapse of abandoned mines..."; perhaps there are conflicting definitions in use. --Anon, 04:05 UTC, October 16, 2008.

From Sinkholes: "Many ground collapses are labelled sinkholes when they actually belong to a more general category: subsidence." Axl ¤ [Talk] 09:09, 16 October 2008 (UTC)

Acorn

Are all varieties of Acorns edible?--76.28.73.16 (talk) 20:18, 15 October 2008 (UTC)

According to our article Acorn all are, with the exception of toxicity to horses. Some have higher tannin content which takes some processes to deal with whether you're a wildlife creature or a human. Is all there under "Nutrition". Cheers, Julia Rossi (talk) 22:24, 15 October 2008 (UTC)

Other sources say acorns are poisonous, unless specially treated:[19] , [20] , [21] . Edison (talk) 22:33, 15 October 2008 (UTC)

Koreans eat them as a jelly called Dotorimuk. Acorns are poisonous only to the extent that they contain a lot of tannins from some species of oaks, as such if you eat them straight you may get all sorts of nasty stomach problems or nutritional deficiencies. Sjschen (talk) 16:20, 20 October 2008 (UTC)

October 16

Manhole question

why is that a person going in a manhole had met with accident and blood came out of his body —Preceding unsigned comment added by 117.197.116.74 (talk) 05:04, 16 October 2008 (UTC)

Why did they go into the manhole? To chase an alligator, perhaps? If so, that would be a clue. --Scray (talk) 05:35, 16 October 2008 (UTC)

Are you sure it's not a hole in a man, that would leak blood. Graeme Bartlett (talk) 05:39, 16 October 2008 (UTC)

Didn't you two read the question? It's not how the person met with a bloody accident, it's why. If you are a religious fundmentalist, the answer is probably because he/she pissed off God. If you are an atheist, it's because he/she was not fit for going into manholes due to genetics. :-P

Right. For the latter, the genetic non-fitness was that he was too stupid to stop traffic before working in a manhole in the middle of the highway:) DMacks (talk) 18:25, 16 October 2008 (UTC)

Who knows? Maybe the person took a printed copy of the wikipedia reference desk and was squinting to look at one of the answers and collided with a wall... Clearly a strong Darwin award candidite, if the person then falls into the sewer water, gets a deadly infection and dies.Nil Einne (talk) 09:35, 17 October 2008 (UTC)

If he was working in an electrical vault, it could have been due to the arcing of 480 volt conductors. That has been known to cause bleeding, third degree burns, and death. Edison (talk) 02:42, 18 October 2008 (UTC)

Thank you to the contributors

Hi everyone. I used to contribute to this reference desk occasionally, but that has fallen off. Nonetheless, I wanted to start a section to thank the contributors of the Science Reference Desk. Not only do you help people everyday in their pursuit of knowledge, you make for some darn good reading. I could put this on the talk page, but you all deserve a slightly more public recognition. Cheers! Eric (EWS23) 09:59, 16 October 2008 (UTC)

I too would like to thank everyone for their contributions. Some of the discussions going on here are quite interesting and often shed a lot of light on subjects that the Wikipedia articles themselves fail to do. 12.10.248.51 (talk) 13:13, 16 October 2008 (UTC)

I agree. One of the often unrecognized goods i asociate with the rd is that a lot of article improvement and expansion is generated here. --Shaggorama (talk) 10:06, 17 October 2008 (UTC)

Heat effects

You know sometimes you get sun shining through a window onto a wall, and if it is a hot day you get sort of wavy shadows in the sunlight hitting the wall? What is this called, and is it linked to the effect you get when heated air distorts what is behind it. What is this effect called as well? I'm sure I have the word somewhere in my head but I can't recall it right now. 88.211.96.3 (talk) 10:45, 16 October 2008 (UTC)

Heat wave? The shadow is simply the same thing as the shadow is just cause by light. 194.221.133.226 (talk) 11:00, 16 October 2008 (UTC)

No that doesn't look right, that seems to be an article about exceptional large area high temperatures. 88.211.96.3 (talk) 11:44, 16 October 2008 (UTC)

It's hard to guess the word you are thinking of - so let's toss in some gratuitous explanation and maybe we'll hit the right word by luck!

So the effect you are thinking of is caused by the air temperature variations causing subtle shifts in refractive index. Glass is a better conductor of heat than air - so the air nearest to the window is likely to be at a different temperature than the air in the remainder of the room. As convection causes warmer air to rise and cooler air to sink, there is likely to be a certain amount of turbulence - although laminar flow is also possible, this would not cause the effect you are seeing. A bubble of turbulent air that is at a different temperature to its surroundings (and hence has a different refractive index) acts like a lens - focussing or dispersing the sunlight that is cast onto the wall - increasing the light intensity in some areas at the cost of decreasing it in others. The areas of decreased light intensity look like shadows and the turbulence makes tham wave around. Hence "wavy shadows".

Words to describe this phenomena would be "heat haze" (a term I've never been very happy with), or perhaps "shimmer". It's possible that you are also thinking of a mirage. But that's a different effect - although it's also caused by temperature variations in the air and consequent changes in refractive index. A shimmer due to turbulance will be more obvious in the case of a mirage. You might also be thinking of the scintillation of stars (more commonly called "twinkling") - or perhaps the word you are after is "dispersion". The pattern of light on the wall might also be called a "caustic" - although that term is more commonly used for things like the pattern of light on the bottom of a swimming pool. The root cause of caustics in a swimming pool is the same as with the shimmering air though - regions of different refractive index (hot and cold air - or air and water) are moving relative to each other and focussing the light in peculiar ways. A plot of the light concentrations in an idealised caustic takes the form of a nephroid.

SteveBaker (talk) 12:31, 16 October 2008 (UTC)

Thanks! I still wonder if wikipedia has an article on the effect. I just thought of another example of what I am (well was, it is raining now, bloody weather) seeing. You know when you have a large fire, and you get distortion. I am sure this is the same effect as what causes the shadows on the wall, and what you describe, but surely it has an actual name? I'd call it heat distortion or something. 88.211.96.3 (talk) 12:46, 16 October 2008 (UTC)

It's the same thing - the heat from the fire is now the source of the temperature variation - and the convection and refractive index changes that result from that are exactly the same as in the case of the window. SteveBaker (talk) 12:49, 16 October 2008 (UTC)

Yes but does it have a name? If it does someone should maybe write a wikipedia article on it, and I may even have a pop at it. 88.211.96.3 (talk) 12:52, 16 October 2008 (UTC)

Schlieren effect. DMacks (talk) 15:01, 16 October 2008 (UTC)

Recommended book reading if you're interested in the many effects that air and moisture can have on light: "The Nature of Light and Color in the Open Air", also known by other title variations such as "Light and Color in the Outdoors", by Marcel Minnaert. --Anonymous, 21:36 UTC, October 17, 2008.

Stability of carbon

I came across the following passage: "The rarest carbon isotope is carbon-14, with eight neutrons. Unlike the other two isotopes, carbon-14 is unsta- ble". Is ¹³C stable? Why is C-14 unstable?Mr.K. (talk) 12:17, 16 October 2008 (UTC)

For smaller elements, the general trend is that elements that deviate greatly from a 1:1 proton-to-neutron ratio are generally less stable. The "stability line" generally trends more towards the neutron side as elements get larger; the actual stability line has a somewhat parabolic character. There are also some trends over the stability of "even-even" proton-neutron nuclei as well. See Isotope#Nuclear properties and stability and Stable isotope for more information on this. The general understanding is that the balance between the three forces which work to hold the nucleus together, which are the nuclear force, strong interactions, and weak interactions, require a certain balance of neutrons to protons (this relationship is not necessarily linear, however). Carbon-14 is "out of balance" with regard to this relationship, and so is unstable. The other two carbon isotopes, C-13 and C-12 are stable. --Jayron32.talk.contribs 12:29, 16 October 2008 (UTC)

The nuclear force is the same thing as the strong interaction. The relevant forces are electromagnetism and the strong nuclear force (the weak force may be involved as well, but as the name suggests, it quite weak!). --Tango (talk) 18:33, 16 October 2008 (UTC)

Actually, the nuclear force is not the same as the strong interaction. Read the articles for more on this. What we call the nuclear force used to be called the strong force, however under Quantum Chromodynamics, the strong interaction (as carried by "gluons") is restricted to cover internal forces inside the neutron and proton holding the quarks together. The nuclear force (as carried by pions) is what holds the nucleons to each other. It is generally assumed that the pions contributed by the neutrons are necessary to overcome the force of electrostatic repulsion to be felt by neighboring protons. Pions themselves are made of quarks, so the strong force holds their internal structure together as well. --Jayron32.talk.contribs 21:00, 16 October 2008 (UTC)

It looks like I'm just not familiar with the terminology (it's not a subject I've studied in depth). They are manifestations of the same fundamental force, aren't they? --Tango (talk) 22:28, 16 October 2008 (UTC)

Yes; the simple answer is that the force between nucleons is a residue of the force between the quarks that, unlike the "real thing", can act on things (nucleons) that have no color charge, much as the van der Waals force is a residue of the electromagnetic force in atoms/molecules and can act on things (atoms/molecules) that have no electric charge. --Tardis (talk) 01:06, 17 October 2008 (UTC)

HIV and hemodialysis

Could a HIV virus load be removed through some sort of hemodialysis ? Mr.K. (talk) 12:23, 16 October 2008 (UTC)

No - dialysis is able to remove certain undesirable substances from the blood by physical and chemical means - but these are typically simple chemical byproducts. The complex biochemistry of a virus makes it hard or perhaps impossible to distinguish and remove by such a simple process. Being a virus also means that HIV has insinuated itself inside the cells of the host's body. Some of those (white blood cells, for example) could perhaps be removed by some hypothetical dialysis process - but there is a limit to the number of white blood cells you can remove and still remain protected against all of the other infectious agents in the environment. But HIV invades all sorts of other cells that are not a part of your blood - so even in theory, with some amazingly high-tech science-fiction blood cleaning machine, you couldn't remove more than some percentage of the HIV load. Viruses (not just HIV - but viruses in general) invade the inside of functioning cells and actually insert their DNA into your DNA. This makes them very hard to eradicate. Viruses replicate by having your own body make new copies - and even if you remove every single independent "virus" from your body - their DNA will still be tucked away inside your DNA waiting for your own cells to produce new viruses the next time the cell replicates. SteveBaker (talk) 12:48, 16 October 2008 (UTC)

Steve is (as always) right on the money - just thought I'd add a fascinating reference to a study of plasmapheresis for HIV and Hepatitis C virus: [[22]]. As Steve said, even removing a large percentage of a virus from the blood still leaves more than enough inside and outside the cells to maintain the infection. --Scray (talk) 12:58, 16 October 2008 (UTC)

Steve's answer is a good one, but a minor clarification would be good here. While many types of virus will make use of some of their host's DNA/RNA processing equipment, most viruses don't insert their DNA into the genomic DNA of the host. Group VI reverse transcribing viruses – including HIV – are the key ones that do; in addition to AIDS, these viruses can also be responsible for an assortment of other unpleasant diseases, including some cancers.

Interestingly, some of these viruses have become permanently incorporated into our genome, and may serve a host of useful purposes. See endogenous retrovirus for more details. TenOfAllTrades(talk) 14:29, 16 October 2008 (UTC)

Note however that even if a virus doesn't incorporate into the human genome, it may still remain latent in the body via episomal latency. See virus latency for some information. For example the Varicella zoster virus, as with other herpes viruses, establishes episomal latency in neurons. After chickenpox resulting from the primary infection it can re-active sometime later in life and result in shingles (something I've personally experienced). Nil Einne (talk) 09:30, 17 October 2008 (UTC)

Fair enough, though I'm not aware of a true RNA virus that has been shown to have a latent form (not talking about clinical latency). --Scray (talk) 01:51, 18 October 2008 (UTC)

Effects of masturbation

I am too embarrassed to ask anyone this question face to face, so I thought this might be a good place find an answer. I just wanted to know what the effects of masturbation are in teenage boys. --203.81.223.178 (talk) 15:41, 16 October 2008 (UTC)

Ejaculation, usually. A feeling of guilt maybe, if you grew up in a culture that still treats masturbation as some vile evil practice that makes your hair fall out. Certainly there are no serious negative health effetcs -- Ferkelparade π 15:47, 16 October 2008 (UTC)

...unless you do it often enough to get raw ;-). Seriously, it's good exercise, may decrease the risk of getting prostate cancer, will have no obvious side-effects, and everybody does it. --Stephan Schulz (talk) 15:55, 16 October 2008 (UTC)

Indeed - the general advice "if it hurts, stop" applies to masturbation just as to anything else. If you're doing it right, it won't hurt! --Tango (talk) 16:00, 16 October 2008 (UTC)

In fact there are possibly some benefits. It won't give you hairy palms, you can rest assured there. If you want more detailed advice, however, you really do need to speak to a doctor (don't be embarrassed, it's a perfectly normal thing to be curious about and doctors will keep your question entirely confidential, you can generally ask specifically to see a male doctor if that would make you more comfortable), we can't give medical advice. I'll give you some general advice, though: People in the playground generally don't have the faintest idea what they're talking about! Ignore any advice you get from a unreliable source, it's probably worse than useless. --Tango (talk) 16:00, 16 October 2008 (UTC)

There is an addiction side-effect. Addiction is often overlooked as a health problem, but it is a problem. Just noticed that orgasm makes no reference of any kind to endorphin. I was going to point out that becoming addicted to an opioid compound is not difficult. -- kainaw™ 16:01, 16 October 2008 (UTC)

Now, be careful. See Chuck Negron. While our article (perhaps rightfully) doesn't cover it, Mr. Negron's penis exploded due to massive overuse of said organ. [23] He reports the incident in gory detail in his own autobiography Three Dog Nightmare (the phrase "split open like a hot dog" appears in the book). He had been warned by his doctor that his level of sexual activity was damaging his L'il Chuck, but he unwisely ignored the advise of medical professionals, and continued to have sex like if he stopped for 10 minutes he might die. He reports an incident that led him to an Emergency Room in Oklahoma; the incident involved an audible tearing sound, lots of blood, and a groupie who will likely be in serious, intensive therapy for the rest of her life. Gives new meaning to the song Mama Told Me Not to Come, now don't it? Moderate levels of any sexual activity is perfectly safe (and some medical studies indicate that a regularly emptied scrotum is vital to helping prevent prostate cancer: [24]), but as with anything, you CAN overdo it. The above does not constitute medical advice in any way. --Jayron32.talk.contribs 16:03, 16 October 2008 (UTC)

Maybe Mr. Negron unwillingly pressed some Tsubo spot, like in the Hokuto Shinken martial art. Seriously, nobody hurted himself using hands. Some people are injured because they tried drugs or dangerous tools. But if you are worried, talk to a doctor. PMajer (talk) 10:12, 17 October 2008 (UTC)

ON the contrary, as mentioned by other above, the general friction, even lubricated, of overubbing can cause inflamation and discomfort or injury... Rub the same spot on your arm for hours on end, day after day, and you are likely to wear a sore into your arm. Now, apply that same test to your penis... SOund like fun? The general cautionary tale is that regular masturbation isn't harmful, but obsessive masturbation can be. --Jayron32.talk.contribs 12:13, 17 October 2008 (UTC)

Sorry but this analogy with rubbing one's hand is not convincing... The mechanics is totally different, in particular there is no friction at all on the skin in masturbation. Among all activities of a teenager, I would say this is the less dangerous (and let's add that normally it is the penis itself who decides when it is enough, and just goes to sleep). Of course too much is bad, but mainly because one misses other important things (reading, studying, socializing, making sport etc). An excessive masturbation activity is often due to a situation of stress, this is the point. Should one understand that his son is doing it too much, I would suggest to check if he is under stress, and why. Just repression would only add other stress. PMajer (talk) 16:45, 17 October 2008 (UTC)

there is no friction at all on the skin in masturbation - you are clearly basing that view on your own experience, PMajer. I can personally attest to the contrary. If the skin of the palm and penis is totally dry, there's no problem. And if it's well lubricated, there's no problem. But if there's only a small amount of moisture present, that does present a friction problem, and can lead to inflammation. -- JackofOz (talk) 22:38, 17 October 2008 (UTC)

Then I agree. In particular, it should be recommended not to handle chili peppers before. This is also based on one ancient personal experience :( --PMajer (talk) 19:25, 18 October 2008 (UTC)

Is it just me or "masturbation in teenage boys" is ambiguous? Indeed, it can be quite destructive to the personality of teenage boys. Mr.K. (talk) 16:11, 16 October 2008 (UTC)

I don't see an ambiguity and it's only likely to destroy someone's personality if they become addicted, which is unlikely. --Tango (talk) 16:38, 16 October 2008 (UTC)

I think Mr K. is playing on the word in there. As in, "The sixty year old felon who performs masturbation in teenage boys...". Personally, I think the terms masturbation and teenage boys are pretty much redundant. Matt Deres (talk) 17:33, 16 October 2008 (UTC)

Are you suggesting that adults and girls don't masturbate? I think the statistics would disagree with you there... --Tango (talk) 17:38, 16 October 2008 (UTC)

It's a superset/subset, not equivalency. He didn't say which term is redundant (and could be omitted without changing meaning) vs which term is the more limited in scope. Given "a hot fire", consider "a fire" vs "something hot" (assuming you have more experience with flames than with chicken-chokin' and...whatever the comparable female slang would be:). DMacks (talk) 18:16, 16 October 2008 (UTC)

Ok, I suppose that makes sense - since said both were redundant I assumed he meant they were mutually redundant (ie. equivalent), it makes more sense if he only meant one of them was redundant given the other. --Tango (talk) 18:27, 16 October 2008 (UTC)

Saying that teenage boys masturbate and other people masturbate too is like saying bullets are dangerous when fired from a machine gun and also when thrown freehand. Matt Deres (talk) 13:28, 17 October 2008 (UTC)

You should maybe redirect your question to the Reference desk/Masturbation in order to get an expert opinion. PMajer (talk) 13:12, 17 October 2008 (UTC)

The expert? DMacks (talk) 20:30, 17 October 2008 (UTC)

Why does pressure increase with depth

If pressure is caused by experiencing the sum total of elastic collisions of fluid molecules against an arbitrary plane (my words as I'm writing them)...

but given my current definition for studying fluid mechanics, this doesn't explain why the collisions are "stronger" at deeper depths because the density is the same and the temperature is the same.

If water molecules are crashing into the vertical wall of a dam then why should forces coming from above affect the frequency or impulse of collisions? If the impulse was greater, that would imply greater kinetic energy in the fluid molecules, which means they have more energy.

Take a 100 meter high dam, the horizontal collisions near the bottom should not depend on molecules above them, which act in a perpendicular direction, right? Water has the same density, and lets stipulate that the fluid is iso-thermic

How does defining pressure this way not explain why at greater depths, pressure is higher? I think it is because pressure exists in all directions right? So the upward force = the horizontal force. Right? So does that mean that the collision frequency is higher? or that the impulse per collision, greater? Or am I just completely wrong. Sentriclecub (talk) 17:49, 16 October 2008 (UTC)

I'll take a stab at it (though admitedly by stat-mech/thermo is a bit rusty… Pressure really does exert "in all directions" as you suggest. Molecules don't just bounce "up and down or side to side", but at all other angles as well. So vertical pressure (weight of what's above, or the effect of vertical collisions each pushing down upon the next) can exert a non-vertical force if any molecule has a non-zero horizontal component to its motion. DMacks (talk) 18:08, 16 October 2008 (UTC)

Additionally, I've spent 5 days studying the topic, and know it can be explained by Pascal's law, but I want to know why it can't be explained or deduced from the method of looking at pressure as ultimately a result of elastic collisions on an arbitrary surface. There's only two ways to increase the average force of a series of impulses... either increase the frequency, or increase the impulse per collision. How does the random translational motion increase with depth, if density and thermal energy and temperature stay the same? I've already asked on yahoo answers, and got a starred question award, and 2 wrongs answers ("because density increases") and the other answers are not helpful, and they use weasel words "well could be..." Sentriclecub (talk) 18:13, 16 October 2008 (UTC)

DMACKs, Yes I understand they exert a force downward onto other molecules, but the bottom line is that somehow there is a resultant increase in collision frequency or an increase in impulse magnitude. I fully understand Pascal's law, but my book doesn't answer my specific question, nor the related wikipedia articles. Sentriclecub (talk) 18:18, 16 October 2008 (UTC)

So far the best answer from the other website is...You asked a very good question. You can't quite compare gas and fluid but for simplicity, I will. Water is NOT incompressible. As you go deeper, its density increases with pressure. Before you go down, there is very little room between the molecules. But you go down 30 m, there is now even less room. This means that the number of collisions will go up dramatically. So the pressure increases. The water, however, keeps the same kinetic energy and temperature. BTW: The reality is a little different. The water molecules vibibrate against each other, but they also impinge on each other's electron clouds. Kinda of a spring effect, so it is not quite so straight-forward.

My next guess is through statistics and a normal distribution. Maybe if the layer of water molecules on the bottom of the fluid can only bounce between 0 and 180 degrees, then the second layer has an extremely small chance of colliding straight down because of the concentrated upward range of the the molecules directly below it. In other words, near the bottom, the statistical distribution of all possible collisions that can occur in 3d space isn't equally probable. Molecules on the bottom have zero probability of being able to return from a collision against the ground with a downward momentum. That is a majority of molecules near the very bottom can only have an upward momentum at any given time. This "fact" must be balanced by the second layer of water molecules who must pass the "fact" along, and give this problem to the layer higher up, who must eventually "resolve" the fact, by being basically free to have zero net momentum as observed in the top layer. This is just a educated guess, based on creativity, not science. Sentriclecub (talk) 18:46, 16 October 2008 (UTC)

To put in better terms, 100% of molecules on the bottom layer must have a upward momentum immediately after a collision. 50% of molecules on the bottom layer have an upward momentum before a collision. Thus the net momentum of the bottom layer is 75% upward, if a reasonable assumption is that all the bottom layer fluid molecules are returning from a collision, and fixing to collide again. A net downward force would need to act on the bottom layer to counteract the upward momentum as suggested by the 50%/100% theory. Still this is all a guess, but I have been unable to finish writing my notes because I hate the feeling of a lingering doubt on pressure. Sentriclecub (talk) 18:52, 16 October 2008 (UTC)

Just a teaser, and I plan to write a long response this afternoon when I get a chance. However, some of the confusion stems from drawing a false analogy between pressure in gases (mediated primarily by kinetic energy) and pressure in liquids/solids (mediated primarily by bond energy). Dragons flight (talk) 18:58, 16 October 2008 (UTC)

I think I'll take a wild guess. How about gravity? Looking at a free water particle outside of a gravitational field, any of the 360 degrees are equally possible. Within Earth's gravity, however, it becomes more probable that the particle has some "downward" component to its velocity vector. These add up the deeper you go, resulting in higher pressure. The interesting question would be: If you had a jug of water (maybe a large pool-sized jug) in space, would the pressure change the "deeper" (more towards the center) you go? I don't really have an answer to that. --Bennybp (talk) 19:50, 16 October 2008 (UTC)

Actually I didn't really answer the question (why it would be omni-directional, and not just downwards). It's probably a pretty flimsy theory, but - Due to the pressure from the molecules coming from the top, the molecules at the bottom would be given more side-to-side velocity, since 1.) They have the same average speed (same temperature), and 2.) There's a limit on their direction of motion ("up" is no longer available, so all others become more probable). Man, I think I'm just digging myself a nice hole. I eagerly await Dragons' answer :) --Bennybp (talk) 20:03, 16 October 2008 (UTC)

The false analogy here is that the treatment of "pressure" for the gas phase is the same as for "condensed" phases. It isn't. For gases, there is roughly a linear relationship between pressure and density; double the pressure, double the density (I say roughly; its exact under the Ideal gas law; the Van der Waals corrections alter this slightly). That is because, for gases, the intermolecular distance is roughly 1000x greater than the molecular radii, meaning that gases are compressable (you can simply "push" the gases molecules together). The entire question by the OP assumes this compressable model of pressure; it works fairly well for gases. However, liquids and solids are condensed phases; for all intents and purposes the intermolecular distance between them is essentially nil. (they can be compressed slightly; water at 100 m below the surface is slightly more dense than the water at the surface). In the case of condensed phases, pressure is determined by weight of the bulk material above you. That's it. Pressure is only force per unit area, and weight is only a force. With a gas, the force is primarily determined by collisions, since the gas molecules don't remain in contact with the surface for any meaningful length of time. With condensed phases, the surface is essentially in constant contact with the molecules (and for a liquid, the exact molecules shift places because it is a fluid, but in bulk, essentially the entire surface where the pressure is measured is totally covered with the molecules). Consider two thought experiments:

1. Imagine burying someone under a 100 m tall pile of sand. What happens? We say they are crushed to death because of the weight of the sand on top of them But this is merely convention. The weight is a force, and it crushes them by pressing in on the surface of their body? What is a force distributed over a surface? Pressure... Now, replace "pile of sand" with "depth of water". Its the exact same problem.
2. Imagine the same person, with appropriate breathing apparatus, encased in a cube of water 100 m on a side, but the person and the water are in a zero-g situation, like floating in space. What happens? Nothing. They survive fine, because the water doesn't press them because there is no gravity to force the water in any one direction. Even if they swim to one side or the other of the cube, there is no net pressure effect, because there is no gravitational force. No force equals no pressure.

Does that make sense to everyone, the OP's question is in error because it makes assumptions about pressure which are incorrect to the situation; liquids are fundementally different than gases WRT molecular organization, and that fundemental difference affects the way that the molecules exert a "force" on their surroundings. --Jayron32.talk.contribs 20:26, 16 October 2008 (UTC)

Hooray for that answer (well, for the first part - the second part is muddled ;-). People are (mostly) water, so with "appropriate breathing apparatus", we survive fine under a hundred meters of water, even under gravity. See SCUBA. We are crushed only if the pressure does not come from all sides equally, or of there are unequalized air spaces in the body. --Stephan Schulz (talk) 20:43, 16 October 2008 (UTC)

I think you are mostly correct. There's still a little bit of explaining to do as far as it acting on all sides at once, with equal pressure. Consider a perfect structurally-sound sphere. In my mind, under 100m of sand (with plenty on the sides, too), it would be crushed flat. The pressure is not equal all around. In water, in my mind, it would implode - the pressure being equal on all sides. This would be due to the fact that water cannot be treated completely as a bulk material - there still is plenty of molecular motion to account for - sand is held in place with friction. If the sand were frictionless, it would be just like macroscopic water (ignoring hydrogen-bonding, van der Waals forces, etc.)

I believe modeling water as a pseudo-gas is correct. The amount of material above you does cause the increase in pressure - for condensed phases and the gas phase as well. On Earth, our air pressure is omnidirectional - we are under a bunch of atmosphere. Same with water at the bottom of the ocean. Where does the "sideways" pressure come from? I guessed at that above. (I say authoritatively, but I might run to my p-chem book to find some equations) --Bennybp (talk) 20:57, 16 October 2008 (UTC)

In answer to Bennybp's question about water in zero-g, the water will attempt to form a sphere since that's the least energy configuration (because of surface tension, I believe - a sphere has the least surface area for a given volume). The pressure will increase as you move towards the centre because of the gravity of the water itself, however for a swimming pool sized amount of water that gravity (and therefore the pressure) would be minimal (in fact, it may not even be enough to keep the water together depending on initial conditions and outside influences - the water may break up into lots of smaller spheres). For a planet sized amount of water, the pressure at the centre will be very great. --Tango (talk) 20:40, 16 October 2008 (UTC)

Thanks Tango. I feel I knew that at one time. The more I read the answers above and below the more I realize I think I have the right answer but to the wrong question. Ah well, better luck next time :) --Bennybp (talk) 15:38, 17 October 2008 (UTC)

DF answer

Sentriclecub, your problem is mostly one of a false analogy. In gases, particles act more or less independently. In that case, pressure is primarily the result of elastic collisions and is proportional to density times temperature/kinetic energy. Hence increasing pressure implies increasing either the density or the energy per particle.

However, liquids and solids are not gases. Pressure is mediated not by kinetic energy but rather primarily by changes in the intermolecular potential energy. To see how this works, let's consider the other extreme: solids. A typical solid at fixed tempertaure can resist very large pressures with very little appreciable deformation (i.e. very little change in density. It does this because the bonds between atoms resist being compressed, and hence provide a spring-like quality to the matrix of the solid. It is that springness, essentially a result of potential energy stored in compressed bonds, that provides the force to resist compression.

Now consider what happens at the interface. For a gas, the force it applies to a wall is caused by particle bouncing off. For a solid, the force is more direct than that. It is caused by the electrostatic repulsion of the electrons in the solid interacting with atoms in the wall at the point of contact. That is a direct steady-state impact, that occurs independently of how rapidly the molecules might be moving.

Like solids, the pressure in liquids is also dominated by the effects of intermolecular "bonding", though it is harder to understand because such bonding in liquids is transitory and mutable. Molecules in a liquid can slide past each other and be rearranged, but nonetheless they try to maintain a roughly constant distance from each other due to the electrostatic interactions between molecules. It is that constant interaction with their nearest neighbors that allows liquids to resist compression and have a preferred density.

So that answers part of your question. Rather than being related to molecules bouncing off of the wall (as in a gas), the pressure the water exerts is caused by the compressed intermolecular interactions within the water and in continuous contact with the wall.

You also ask why is the pressure the same in all directions. Again I am going to start with solids and work my way over to liquids.

In a solid there is a stiff arrangement of atoms that can thought of like masses seperated by little springs. For the sake of discussion let's start with a 1-D set of mass and springs:

 O -vv- O -vv- O

If you apply a force along it's length, you compress it:

 O -w- O -w- O

As long as that is held perfectly linear, the forces balance and cancel. But the real world is not linear. We have vibrations and other imperfections, and given the opportunity, the middle mass would like to relieve the tension in the springs by skewing out of the line.

    |- O -|
 O -|     |- O

For a solid, linear compression creates a relatively small sideways force because other atoms in all the other directions are approximately fixed and restrain this sideways skew. If you kept applying force though, the solid would bulge out sideways and eventually break.

So how does that apply to a liquid. Well like a solid, if you apply a linear force, that tends to squeeze things in the middle. However, unlike with a solid, the individual atoms are free to move. So if you try to squeeze water it will squirt out sideways immediately. The only way to stop it from doing so is also apply an additional sideways force to restrain it. It may not be obvious, but the amount of lateral restraining force ends up being exactly the same as the amount of compression force being applied. Or, more simply, the amount of force in all directions must be the same in order to keep the liquid stationary. And, as if by magic, we arrive at the concept of pressure, i.e. a force acting equally in all directions. Dragons flight (talk) 22:10, 16 October 2008 (UTC)

Perfect explanation. This whole time I was thinking that pressure is just a corollary from the concept of force. This is exactly like the time I sought a relationship between impulse and work, because I just knew there was some deep intuitive relationship, and after several days and dead-ends I finally saw that they are related by average velocity. This explanation through the analysis of force, is exactly the way my brain needed to understand it. It makes sense that if the additional sideways force wasn't as large as the linear force, then a very slight disturbance to the unstable equilibrium would further propel that unequilibrium in that continuing direction.

In my own notes on Pascal's principle, I wrote: An enclosed liquid is extremely inefficient at resisting pressure. If force is applied at one point, the fluid responds everywhere as an equal & opposite reaction, as if the pressure was thought to be coming from everywhere. because this is intuitive and explains how a tall narrow straw filled with water could add several billion newtons of pressure to an enclosed liquid in a multi million gallon rigid tank, according to an ideal fluid. Your answer meshes perfectly with my notes from yesterday, and now I can expand on my notes using the same analysis method proving everything through force. What a swell day! In order to maintain the 3-d matrix, the force must exist everywhere continuously, and varies with respect to height, in order to "balance all the equations" and not violate any force laws which stipulate that an imbalance would cause an acceleration to some part of the system.

The combined answers today are definitely the best help I've had from the ref desk. I don't have a professor or t.a., just a physics book, and youtube[25], and the ref desk. My passion for learning is fueled by making connections between concepts allowing such insights into nature that I feel fortunate for being invited to see. Just as chess grandmasters have their priceless insights into chess, I cherish mine into nature(though I'm still a noob), as nature reveals herself through physics and everything else. Sentriclecub (talk) 22:38, 16 October 2008 (UTC)

Hi. Going back to the OP and the issue of a molecular explanation for pressure in liquids, the stiffened equation of state section of equation of state might be useful for understanding the compressibility of water. Water is "like air that is already under 20000 atmospheres of pressure" which explains why it is essentially incompressible under daily life (taking water from 1 to 2 atmospheres is like taking air from 20001 to 20002 atmospheres). HTH, Robinh 07:12, 17 October 2008 (UTC)

bladder TCC insitu with bone mets

a patient has been diagnosed bladder TCC insitu for many years, is recently found metastasis to bone. is it possible that a bladder TCC insitu patient has a bone mets?

Thanks,

George —Preceding unsigned comment added by Gxu (talk • contribs) 21:22, 16 October 2008 (UTC)

Sorry, no medical advice allowed here (see top of page). --Scray (talk) 22:53, 16 October 2008 (UTC)

Sounds like home work. We do not do homework either. Look up your text book.--GreenSpigot (talk) 00:29, 17 October 2008 (UTC)

Both the above comments are unnecessary. No medical advice was asked for: medical information was ("Can in situ carcinoma (as opposed to invasive carcinoma) metastasize to bone?"). And it's clearly not homework, nor would it need comment, especially one like "look up your text book", if it were. - Nunh-huh 00:53, 17 October 2008 (UTC)

Actually it could be homework. Cancers preferentially metastasize to certain other tissues - that would be a valid "homework" question, although someone at that stage of education would hopefully not be checking Wikipedia (though I know a doctor who regularly checks eMedicine for more reliable, but still background, info). And it could also be a request for "advice", as it's a pretty specific question. If we answer anything other than "maybe, ask your doctor", we are providing specific information - but we don't get to see the biopsy results, X-rays, MRI's, diagnostics from the bloodstream, nothing. So - maybe, see your doctor. Franamax (talk) 06:09, 17 October 2008 (UTC)

I've been through every course it could conceivably be "homework" for, and such classes don't assign that kind of "homework". Clearly not a homework question, and - even if it were - the original questioner will not be in any way enlightened by learning that it "sounds like homework" to a Wikipedia user. And no, a request for information, no matter how specific, is not a request for advice. - Nunh-huh 17:11, 17 October 2008 (UTC)

This statement: I've been through every course it could conceivably be "homework" for, and such classes don't assign that kind of "homework" is remarkable, considering the number of professions (medical, nursing, graduate programs...), cultures, etc that are "conceivable". Wow. --Scray (talk) 01:21, 18 October 2008 (UTC)

No matter the profession, the class would be "clinical pathology (human)", "oncology", or some variant thereof. Wow indeed. - Nunh-huh 01:42, 18 October 2008 (UTC)

Try Metastasis for the mechanics of it. Julia Rossi (talk) 07:21, 17 October 2008 (UTC)

Yes. See this article. Axl ¤ [Talk] 08:26, 17 October 2008 (UTC)

Thanks, I didn't want to post the answer without a reference. Great work! - Nunh-huh 17:11, 17 October 2008 (UTC)

October 17

Uvula

Hi - I think somethings wrong with my uvula. Do you have any recommended sites to help me self- diagnose what could be wrong with my uvula.

Thanks, April 67.182.219.78 (talk) 02:52, 17 October 2008 (UTC) —Preceding unsigned comment added by 67.182.219.78 (talk) 02:51, 17 October 2008 (UTC)

Once again, we cannot legally offer medical advice. See a doctor if you feel that you have a problem.CalamusFortis 03:01, 17 October 2008 (UTC)

There is a site called WebMD. I've never used it, but I'm certain it's not as good as seeing a real doctor. AlmostReadytoFly (talk) 07:57, 17 October 2008 (UTC)

There;s also the article Palatine uvula with pix and pathology. Julia Rossi (talk) 08:35, 17 October 2008 (UTC)

I've tried the symptom checker, and for any given set of symptoms, it'll typically give you two dozen causes, with treatments ranging from "ignore it" to "get to an emergency room yesterday". --Carnildo (talk) 20:32, 17 October 2008 (UTC)

You know, I've heard of these people called "doctors" that have experience with this sort of thing. Maybe you could try one of those?CalamusFortis 03:42, 18 October 2008 (UTC)

Need Genetic Analysis of Japanese people

Historically, various non-Chinese groups like the Central Asian Turks, Iranians and Uyghurs have moved to Central China and were sinified in successive waves and together affecting the ancestry of the Chinese, thereby the Han Chinese are not very pure mongoloids. Similarly, the southeast asians may look mongoloid but they have mixed with arabs and east indians in ancient times. However, the Japanese had not mixed with many various non-mongoloids like what the Chinese and southeast asians had done and therefore they kept their race pure by living in remote, islolated islands for thousands of years.

I need a genetic analysis comparision between the Japanese people and other asians (Chinese and southeast asians) and the analysis explains that the Japanese are more pure mongoloid. Can anyone please provide me with a website that has a genetic analysis comparision between the Japanese and other asians? 72.136.111.205 (talk) 03:11, 17 October 2008 (UTC)

I think you'll have a hard time finding what you're looking for, because most geneticists reject these old conceptions of race. For example, see Mongoloid race and Historical definitions of race. --Allen (talk) 03:55, 17 October 2008 (UTC)

I's also suggest Japanese people. Though if you are trying to prove the superiority of a culturally and genetically isolated people, you'll probably be disappointed. Minorites like the historically repressed Ainu are probably a better approximation of the genetic heritage of the original occupants of Japan than is the current dominant ethnic group, which is itself probably a mixture of the original Japanese with Korean and Han lineages. Dragons flight (talk) 04:31, 17 October 2008 (UTC)

Your question isn't very scientific. You start off with a premise, that may or may not be correct which is fine. But then despite the fact your premise is unproven, you asked for evidence to support your premise rather then simply asking for what evidence there is out there and whether it supports your premise Nil Einne (talk) 09:12, 17 October 2008 (UTC)

If you don't readily see nil einne's point, we have a decent article on the phenomenon. SeeConfirmation bias. --Shaggorama (talk) 09:54, 17 October 2008 (UTC)

Sites of interest: the International HapMap Project [26] (genetic mapping of SNP's); the Yanhuang project (mapping genomes of 100 Chinese individuals); the 1000 genomes project (mapping genomes of 1000 individuals worldwide, including HapMap participants); overview of these projects in Nature [27].

And to the comments above imputing racist motivations for the question: it is actually quite likely that Japan, as a more closed society over the last thousand years or so, will have a more "pure" genetic background similar to that of Iceland, which deCODE genetics, Inc. sought to exploit. The exact meaning of "pure" is of course wide open to interpretation - but the projects I've cited are a scientific attempt to quantify those differences and similarities. Franamax (talk) 22:58, 17 October 2008 (UTC)

Franamax, I don't have access to those sites. I don't care about Ainu and the HapMap. Let's get to the real point. A certain group that live isolated for a long time, is generally more "pure". I simply want a genetic analysis that compares the Japanese people and other asians and to explain that the Japanese people are more pure oriental. 72.136.111.205 (talk) 23:42, 17 October 2008 (UTC)

It's too bad that you don't have such access or you would see that the premise "a certain group that live isolated for a long time" is fatally flawed. Japan and surrounding areas is part of at least three major migration routes: Southern Asian coastal and overland; and mid-Asian overland. mDNA evidence makes this clear. It's important to start with evidence then draw conclusions instead of vice-versa. Saintrain (talk) 00:23, 18 October 2008 (UTC)

And thanks for revealing your true colours in the face of my good faith efforts. The first three of my links are open to all. Those links are where you can watch the efforts and begin to construct your theory of racial purity. The world being what it is, I doubt such evidence will turn up, but watch the science and maybe you can twist it somehow. As to your "simple analysis" to explain Japanese people being "more pure oriental" - I don't know of one existing and I don't know of any scientific group particularly interested in pursuing such a ridiculous notion (since e.g. they would first have to genetically define "oriental", which is an exercise in futility). The concepts are much more complex than you seem to think. Franamax (talk) 00:45, 18 October 2008 (UTC)

Further proof you just don't get it: haplotype maps are the way to identify genetic "purity", through persistent SNP linkage patterns among homogeneous populations. Franamax (talk) 00:51, 18 October 2008 (UTC)

The other question is, what do you mean by 'oriental'? As others have point out, the idea of a Mongoloid race is now not particularly well supported. Furthermore the idea of an 'ideal' specimen of any race is even less supported. You can perhaps say members of race 'X' tend to have features A, B and C but to say an ideal specimen of race 'X' should have features A, B and C is quite a different thing and doesn't make much sense based on out modern understanding of genetics and evolution. So back to the question, what do you mean by 'oriental'? If you define 'oriental' to mean 'like-modern Japanese' then yes you can say modern Japanese are the 'race' most 'pure oriental'. But that's not surprising since basically what you've said is modern Japanese are the 'race' most 'like modern Japanese'. You don't really need any link to tell you that the modern Japanese are more like modern Japanese then modern Han Chinese are like modern Japanese. Of course you may find that modern Japanese are often more different from one another then some modern Koreans or modern Han Chinese are from some modern Japanese. Nil Einne (talk) 05:16, 18 October 2008 (UTC)

As an interesting footnote to this point, I strongly suspect that if one were to define "oriental" as something like a collection of those alleles having the highest frequency in the peoples of East and Southeast Asia, then Japan would probably be less "oriental" than China. By virtue of being somewhat more isolated and less numerous than mainland populations, I'm sure they do a poorer job of reflecting the median phenotype. For example, O is the common blood type among Chinese (~40% of the population), but only 25% of Japanese have that type, with A being most common (~35%). Similarly, there is a "Japan type" Y-linked DNA marker that is more prevalent on the islands than anywhere else and probably originated there. The flip-side of isolation is that a population also has the opportunity to evolve independently of the larger parent group. Dragons flight (talk) 15:25, 18 October 2008 (UTC)

Oriental means mongoloid. You can't find what I want which is okay. 72.136.111.205 (talk) 22:13, 18 October 2008 (UTC)

"Mongoloid" is a historical term pre-dating genetics by nearly a century and doesn't have any widely accepted genetic meaning, hence asking for a genetic analysis of "oriental" or "mongoloid" traits isn't a meaningful question unless you also provide a means of specifying precisely which genetic traits you really mean. Dragons flight (talk) 22:56, 18 October 2008 (UTC)

Mongoloid and oriental in common use simply means something like "people who look like the average individual that one will find in the 'orient' ", and it's a pretty crappy meaning if you look at it from a scientific standpoint. Looks are deceiving and the "looks Oriental/mongoloid = genetically 'Asian' " correlates very poorly with any genetic traits other then the ones that express the phenotype of the "looks". And sometimes not even. If you are simply interested to know the genealogy of the Asian cultures maybe Genealogical DNA test can be a good place to start the learning process. Sjschen (talk) 03:26, 19 October 2008 (UTC)

Movie sound

There's a stereotypical background animal sound that always turns up in jungle movies. It goes something like ooh, ooh, ooh, ooh, aah, aah, aah, aah (you know the one). Is there really some critter that makes this sound, and if so, what is it? Clarityfiend (talk) 05:27, 17 October 2008 (UTC)

I think it's a chimpanzee call you're thinking of. [28]. --Allen (talk) 06:44, 17 October 2008 (UTC)

Or kookaburra?[29] --Rallette (talk) 07:31, 17 October 2008 (UTC)

This could be several types of apes. You may want to listen in at [30] for some samplings of very jungle-like sounds of gibbons —Preceding unsigned comment added by EverGreg (talk • contribs) 12:56, 17 October 2008 (UTC)

I'd say it's certainly the kookaburra. Probably soon to be followed by the Wilhelm scream. --Sean 13:38, 17 October 2008 (UTC)

I was going to say that "there's only one problem with the kookaburra: it's found only in Australia and New Guinea. We do have lots of tropical jungles and rainforests, but not many movies have been made in those locations to my knowledge". But then I was shocked to read that "Although the kookaburras are restricted to a relatively small part of the world, the distinctive sound they make has found its way onto many "jungle sound" soundtracks, used in movies and television as well as certain Disney park attractions no matter where in the world the action is set". This cultural phenomenon must also explain why I blithely assumed for many years that tigers were native to Africa - I saw them in lots of African-set movies as a child. -- JackofOz (talk) 22:19, 17 October 2008 (UTC)

In Ramar of the Jungle this sound was constantly heard, and it sounded like a bird. "Hoo! hoo! hoo! haa! haa! haa!" Either that or a very crazy ape or human.Edison (talk) 02:39, 18 October 2008 (UTC)

The belief that there are penguins in the Arctic seems to be a fairly widespread one. That probably originates from Saturday morning cartoons. Heh, I used to think that dinosaurs lived alongside humans because of cartoons I watched when I was a kid. --Kurt Shaped Box (talk) 23:08, 17 October 2008 (UTC)

Tooky-tooky bird (Tookarus birdoozi). Characteristic call is "Ah ah ee ee tooky tooky". Hope that helps. Saintrain (talk) 00:29, 18 October 2008 (UTC)

Thank you ou ou ou, aah aah aah aah. Clarityfiend (talk) 03:53, 18 October 2008 (UTC)

Distance from nucleus: d or s orbitals

(moved from RefMisc by Franamax (talk) 05:56, 17 October 2008 (UTC))

Yo, just some basic high school chemistry here: Say we take a transition metal in Period 4; the 4s suborbitals fill up before the 3d orbitals right? Yet, the 4d orbital electrons are lost first before the 3d ones in a reaction? So which one is the valence electrons? The ones in the 3d or 4s orbitals? Also, which of these suborbitals is farthest away from the nucleus. ie the greatest radius away? I'm guessing 4s because transition metals are dense because the 3d orbitals increase the atomic mass, without increasing radius. If this is the case, why is the 3d orbital considered a "higher energy" orbital than the 4s?

Peace guys, Hustle (talk) 01:20, 17 October 2008 (UTC)

See Electron configuration#Ionization of the transition metals. That subsection of the article on configurations explains the transition metal paradox, that the filling order does not match the removal order. The assumption that all iso-electronic ions have the same configuration is faulty; the different Z_eff between, say, Fe⁺² and Cr shows that the two systems are not in the same general electric field, so the two systems do not behave identically WRT electron organization. Also, it is helpful to remember that the idea of electron configuration is more descriptive that predictive. We have a limited number of samples, 100 and change, with which to make understandings of the system. Describing the trends in the system is easier than explaining why those trends occur. The common explanation for any deviation from expected norms in chemistry is "Well, that is a more stable state" or "Well, that is a lower-energy state", both of which mean, essentially, "Well, that's just what it does". Its also helpful to remember that all atomic models, even rather complex and detailed models such as quantum mechanics, are models, and by necessity, are incomplete in explaining all aspects of the real system. Nature does what it does, and our models can be adapted if they don't completely fit; however it may be impossible, from a philosophical point of view, to ever create a model which fits nature 100%. --Jayron32.talk.contribs 11:57, 17 October 2008 (UTC)

Alpha Centauri system seen from Saturn

In this image: [31], Cassini took a picture of the Alpha Centauri system just over the limb of Saturns rings. You can clearly see that it is a binary star in the image, but why is this? α Centauri Appears as a single star from Earth and Satrun isn't that much closer (relatively!) to α Centauri, so why is it so much larger? How much magnification is necessary to see that α Centauri is a binary? Did Cassini magnify the image? 63.245.144.77 (talk) 08:44, 17 October 2008 (UTC)

Gravitational lens? PMajer (talk) 09:43, 17 October 2008 (UTC)

It's the nearest star to us, what could get inbetween to create a lens? --Tango (talk) 13:35, 17 October 2008 (UTC)

Our article on Alpha Centauri says that the angular separation of the two brightest stars in the Alpha Centauri system varies between 2 and 22 arc seconds. Let's take a value of, say, 10 arc seconds. Our visual acuity article says that a person with standard visual acuity can distinguish a pair of objects with a separation of 1 arc minute. So a magnification of about 6 is required to visually separate the Alpha Centauri binary pair. Couldn't find any detailed information about Cassini's visual imaging systems, but the flatness of Saturn's rings in that image suggests a considerable amount of magnification, either in the original image or in subsequent processing. Gandalf61 (talk) 10:19, 17 October 2008 (UTC)

And indeed, you can separate Alpha Centauri with a small backyard telescope, or even a pair of decent binoculars. The Cassini Narrow Angle Camera is a 2 m f/10.5 reflector[32]. I know little about optics, but this provides more magnification than a pair of binoculars ;-) . --Stephan Schulz (talk) 11:31, 17 October 2008 (UTC)

The image's filename is Alpha_Centauri_AB_over_limb_of_Saturn_PIA10406.jpg. It appears to me that we're looking at the limb of Saturn itself, with atmosphere – not the rings. In the foreground we see the rings' shadow (fuzzier than we usually see the rings, because the shadow falls on clouds). What does this say about the flatness? —Tamfang (talk) 03:01, 18 October 2008 (UTC)

I really can't see how bright band across the image can be the limb of the planet itself - more likely, as the OP says, the star is appearing over the limb or edge of Saturn's rings. Maybe the filename of the uploaded file is inaccurate or incomplete. But this is all speculation. If we knew the original source of the image, it might have more details of context, exposure time, magnification etc. Gandalf61 (talk) 11:10, 18 October 2008 (UTC)

But the outer edge of the rings doesn't look like that! —Tamfang (talk) 16:40, 18 October 2008 (UTC)

Makes me wish I lived in the Southern Hemisphere so I could look at Alpha Centauri with binoculars. :( Are there binary stars in the Northern Hemisphere that you can tell are binary systems using only binoculars? 63.245.144.77 (talk) 17:58, 18 October 2008 (UTC)

Alpha Centauri is interesting to watch because the two components have very obviously different colours. This search returns info on some Northern hemisphere double stars that can be observed with binoculars. Albireo (β Cygni) is described as quite beautiful. --Stephan Schulz (talk) 19:38, 18 October 2008 (UTC)

Thanks a lot! I'll have to look at some of these objects. Ob the search, one of the first things that shows up is the Moon, and I look at the Moon with binoculars nearly every night it's out, but these other objects look like a lot of fun too. Thank you. 63.245.144.77 (talk) 06:55, 19 October 2008 (UTC)

Frequency of different forms of cancer

Why are some forms of cancer much common than others? For example, why is heart cancer so uncommon?Mr.K. (talk) 09:32, 17 October 2008 (UTC)

See "Carcinogenesis". In cancer, there is a mutation in a cell line that leads to uncontrolled cell division. Certain cell populations already have high rates of natural cell division, notably epithelium and bone marrow. Other tissues, especially connective tissue and muscle, have low natural rates of cell turnover. High turnover tissues require less exposure to carcinogens in order to transform. Also, epithelial surfaces have more contact with the outside world, so have greater exposure. Axl ¤ [Talk] 10:52, 17 October 2008 (UTC)

Length of electric power transmission lines

From out article on Electricity_transmission#Losses: "As of 1980, the longest cost-effective distance for electricity was 4,000 miles (7,000 km), although all present transmission lines are considerably shorter."

How long is the longest line? How long are common lines? Mr.K. (talk) 12:53, 17 October 2008 (UTC)

From the same article: "Longest power line: Inga-Shaba (length: 1,700 kilometres (1,056 mi))", and it also states that intermediate length lines are about 100km. Capuchin (talk) 14:45, 17 October 2008 (UTC)

Interesting note: long power lines are vulnerable to coupling to the weather in space. Franamax (talk) 22:32, 17 October 2008 (UTC)

Solar phenomena can cause substantial DC voltage gradients on earth. These can be controlled by the proper placement of capacitors in neutral connections. Common lines go from substation to substation which can be tens to hundreds of miles.The referenced article says "Longest power line: Inga-Shaba (length: 1,700 kilometres (1,056 mi))" In more highly developed countries, lines would not be that long because of generating stations or load centers being more closely spaced. ("Hey! Gimme access to that power line!") In more war-torn regions, it would be easy to keep the line shut down by obvious means. Since it is high voltage DC, it would be expensive to tap into it to promote local industry along the route, due to the high cost of valve halls and switching yards. Edison (talk) 02:27, 18 October 2008 (UTC)

helicopter lift control

I have been working on creating a model helicopter with some automatic hover control. But I would like to know that what is it: torque or rpm of the motors that would determine the lift? Any shortcut method of creating the driving circuitry of brushless dc motor would be highly appreciated. 218.248.70.235 (talk) 14:52, 17 October 2008 (UTC)

Lift in a helicopter depends on both rpm and collective pitch. Our radio-controlled helicopter article has a section on typical model controls - sounds quite complex. Gandalf61 (talk) 15:10, 17 October 2008 (UTC)

Does your model helicopter have pitch control? If so, it is likely going to be much easier to adjust pitch than to constantly increase/decrease RPM. I would expect it to increase the lifespan of your main rotor motor as well. -- kainaw™ 15:49, 17 October 2008 (UTC)

Remember - that changing the motor rpm (which requires you to change the torque - they aren't independent variables!) also changes the tail rotor rpm (the two are connected via a driveshaft and gearbox). In theory, you have the two nicely balanced by the pitch of the tail rotor blades - but that's rarely a perfect thing - so expect the helicopter to yaw around as you control the lift. When you change the collective - you increase the drag on the main rotor so it will tend to slow down. When hovering (particularly) you get all manner of interactions from 'ground-effect' at low altitude - and if you are hovering in a confined space (eg close to a building or something) then there are lateral forces due to that same effect. If the helicopter does start to move laterally or forwards/backwards, the amount of airflow over the forward-moving rotor is more than that on the backward-going blade - so the helicopter will want to roll or pitch because of increased lift on the faster-moving blade. Even as you attempt to cancel out the original motion, you need to compensate for the induced roll using the cyclic pitch control...but that too increases drag and that changes the required engine torque which cuts rpms which... Well, let's just say that the take-away lesson with helicopters is that no matter what parameter you change - at least two others will change as a consequence of that. Good luck with your project - it sounds fascinating! SteveBaker (talk) 00:35, 18 October 2008 (UTC)

Eskimos

Why do eskimos live in such inhospitable locations? If they settled there when it was inhospitable, why? If it became inhospitable after they settled, why didn't they migrate somewhere else? I suppose they have enough food and other resources, but why didn't they seek out somewhere easier to live? MikeInABox (talk) 15:21, 17 October 2008 (UTC)

Probably because there were already people living in the more hospitable places. It was easier to live in the inhospitable place than to fight for resources elsewhere. --Tango (talk) 15:43, 17 October 2008 (UTC)

Or maybe they didn't know anywhere else was actually more hospitalable? But Tango's response is more convincing :) —Cyclonenim (talk · contribs · email) 15:46, 17 October 2008 (UTC)

That still leaves the question why they do not migrate now.--Radh (talk) 15:56, 17 October 2008 (UTC)

It's what they've always known, it's their cultural tradition. People often choose to stick with what they're familiar with rather than change to something better. --Tango (talk) 16:42, 17 October 2008 (UTC)

Not really. They are perfectly well adapted, culturally speaking, to their environment. They have no reason to leave, and indeed why would they or anyone else want them to. If we judge them from our perspective in our environment (like "I would never want to live there"), then we do the Eskimo culture a disservice. They probably look at modern city life and make the same statement. --Jayron32.talk.contribs 16:41, 17 October 2008 (UTC)

Indeed. Why don't we all move to Tahiti? --Stephan Schulz (talk) 16:48, 17 October 2008 (UTC)

Because we don't really have a better chance of survival there. I am not at greater risk living in Cardiff than Tahiti. I understand they may have a preference for one area over another, but surely they would move to increase their chances of survival. MikeInABox (talk) 16:51, 17 October 2008 (UTC)

I'm sure your quite mistake. Cardiff is rather cold in the winter. It may not be as cold as a number of other places but it still requires adequate heating or good insulating clothes. I don't know if Tahiti is the best example, a place which is too hot or has too much sunlight is not necessarily great either (although it's worth remembering that while nowadays we may spend a lot of our time outdoors in uncovered areas, historically in the hunter-gather era people would have spent a lot of their time in their shelters or under the cover of trees) but there are definitely places that emperically are more habitable. Definitely humans live in a lot of places that, while not as bad as Alaska have extremely cold winters (sub zero) and with regular snow. Are you really trying to convince me that climatically, such places are not more difficult for humans (being without any great level of fur and without hibernation) then a place with a mild 15-25 degrees year round temperature? Sure the temperature is not a great problem for us now because we have homes with good insulation, electricity etc. The key point is that humans are really adaptable which is why we are able to live fine in Tahiti, Cardiff or Alaska. Nil Einne (talk) 04:45, 18 October 2008 (UTC)

I can understand that they might not want to live in a city or leaves their groups/culture, but it is more a question that people (and animals) generally migrate to more hospitable environments where the effort to get a given amount of resources is easier. Not to be lazy, but just to increase their survival chances. If food does become scarce living in a cold environment must significantly reduce you chance of survival. MikeInABox (talk) 16:49, 17 October 2008 (UTC)

Do modern Eskimos often die for reasons they wouldn't have died of in a city? I see no reason why they would. The chance of getting hit by a car in a city is probably higher than the chance of an Eskimo getting frostbite. --Tango (talk) 17:11, 17 October 2008 (UTC)

But wouldn't they still seek out somewhere better and keep looking until they found a better place where there was less competition? If they found a place that was more hospitable but with competition, they would know that there were at least more hospitable places. Also, why didn't they move when they knew there were better places (following contact with people with knowledge of other areas), but before technology (medicine/machinery etc) made life easier for them? MikeInABox (talk) 16:49, 17 October 2008 (UTC)

Live wasn't particularly hard for the Innuit. Why would it be? They are hunters and gatherers, and these, at least on pre-industrial times, have much better quality of life than peasants. The arctic sea is very productive, with lots of fish, birds, and sea mammals. --Stephan Schulz (talk) 16:53, 17 October 2008 (UTC)

This is purely speculation on my part, but the angle of the Earth's axis does change over time. It's possible that when the Eskimos migrated, it wasn't as cold. 12.10.248.51 (talk) 17:01, 17 October 2008 (UTC)

The Innuit arrived in Greenland at about the same time as the Norse. There is some debate about exactly how much colder or warmer than today it was back then, but in any case it was very cold by our middle latitude standards. They simply were well-adapted and knew how to live a good life there. --Stephan Schulz (talk) 17:05, 17 October 2008 (UTC)

While the climate may well have changed, it wouldn't be due to shifts in the Earth's axis over such a short timescale (by geological standards). Also, it would have likely been colder, not warmer. Theories put migration to North America between around 10,000 and 30,000 years ago, which would be during the last glacial period or the very beginning of the current interglacial period, so presumably much colder than currently. --Tango (talk) 17:11, 17 October 2008 (UTC)

Moving around is far harder than staying still, they would need a good reason to move their whole group somewhere else. They wouldn't necessarily know of anywhere that wasn't already populated (if there even was such a place), so they would be walking around randomly constantly running into people that didn't like them using their resources. --Tango (talk) 17:11, 17 October 2008 (UTC)

And if you're perfectly well adapted to a place, know every inch of its geography, know exactly how to survive, and know there won't be other people showing up regularly to take your stuff - why move? Lots of people live today in cold climates (ahem, Canadian talking here :), yes you could die if you get caught in a storm, but you prepare and you harvest the bounty around you while you can. Franamax (talk) 22:15, 17 October 2008 (UTC)

Cultural note: while I personally associate the term "Eskimo" with a people having incredible survival skills and intimate knowledge of the environment, as well as an admirable society, the term is one given by "Indians" (people living where the trees were) and I believe means "eat raw meat", was derogatory, and was indicative of the Indians willingness to kill any and all Eskimos they encountered. The peoples name for themselves is generally Inuit (although there are sub-names which more closely identify those who lived in certain areas). Because of the derivation of the term Eskimo, Inuit is much preferred. Franamax (talk) 22:09, 17 October 2008 (UTC)

As I understand it, Inuit refers only to a subset of Eskimos. See Eskimo#Nomenclature, it would appear you are under a common misconception. --Tango (talk) 22:26, 17 October 2008 (UTC)

My information comes from a professional with intimate knowledge of Inuit people and culture and adoptive mother of an Inuit child. Perhaps the misconception is also shared by the Inuit people themselves? Following the argument that a term is of uncertain etymology and thus not derogatory means that nigger and kike are also perfectly acceptable. As I noted, sub-populations have individual names, but from the link you give above "defines Inuit...as including the Inupiat, Yupik (Alaska), Inuit, Inuvialuit (Canada), Kalaallit (Greenland) and Yupik (Russia) [people]". It's usually better to consult the actual people, for instance to decide how to pronounce your name, I would ask you for advice (and possibly your mother as the ultimate authority :). Franamax (talk) 00:36, 18 October 2008 (UTC)

Or you could actually read the article Eskimo, which says "There are two main groups referred to as Eskimo: Yupik and Inuit. A third group, the Aleut, is related" and leave out mention of other editors' mothers. Edison (talk) 02:22, 18 October 2008 (UTC)

Let me clarify then: in order to discover Tango's name, I would directly ask Tango rather than consult a third party to see what their opinion was. Failing that, I would ask a related party, in this case Tango's parent, who would surely be authoritative on the matter. Sorry if my colloquialism has caused you confusion. And I evidently have read the article, since I quote from it directly in mentioning the preferred naming. I quite understand that Eskimo is a term for North American native peoples generally living north of the treeline. The older of those people are comfortable with the term, the younger are less so. The members of the Inuit Circumpolar Council seem comfortable with the overall term Inuit, although as I said, they will preferentially use their own regional name for themselves. "Eskimo" is an exonym and there is no particular reason to use it. Was there anything else? Franamax (talk) 09:19, 18 October 2008 (UTC)

As to the OP's question: lots of Eskimos have moved far from home, although such a thing is hardly limited to Eskimos. Perhaps the question would be better worded "why don't the Eskimos move en masse, completely abandoning their homelands?" I think it is reasonable to say that that kind of mass migration is quite uncommon. Why hasn't North Dakota been completely abandoned? It's hardly Tahiti. Pfly (talk) 06:47, 18 October 2008 (UTC)

The question begins from a misapprehension - that the arctic is inhospitable. It sure would seem so to me, just as a Floridian would find my Ontario inhospitable, but it's all a question of what you're used to. To them (personal communication) our (Ontario) climate is ridiculous - rain all spring and fall and stinking humidity in the summer. Matt Deres (talk) 14:10, 19 October 2008 (UTC)

Apollo Landing Hoax

I asked this on the Apollo Landing Hoax discussion page and nobody there could come up with a satisfying answer. Watch the following video all the way through. The video begins with the flag at complete stop. At about 37 seconds into the video, an astronaut walks by. The flag begins to wave as if the astronaut's movement created a breeze. Obviously, NASA didn't fake the Apollo lunar landing, but I haven't been able to come up with a definitive explanation. I have a number of possible explanations:

1) The astronaut's bouncing on the ground caused the flag to move. But earlier in the video, an astronaut walks away from the flag and the flag doesn't move. 2) The astronaut's shoulder brushed against the flag. But he looks like he's too far away to make contact. 3) When the astronaut starts moving, he kicks a rock which hits the flag pole. 4) It's caused by static electricity 5) Gas emission from space suit but I have no idea if space suits actually have gas emissions.

Space suits both the material and the air inside both have small gas emisssions. ( usually from oil contaniments ). Even though the suits are tested, cleaned and packed with the *utmost* care. Still some still get finger-prints on them. A finger print is enough to cause a flag to wave. ( I have seen it in a vacuum chamber ).

Btw, this is a really good question. But you seem to have missed:

6) The astronaught bouncing by the flag, jars the ground. ( the lunar surface, aside from the dust is volcanic flows, i.e. its structure allows for the translation of movement rather easily, and since the air is NOT there to absorb any of the sound, likely it all gets translated into the ground. ( and note that the likely vector for the movment is perpendicular to the camera, so you dont see the flag pole wave, but as a result of the flag pole waving, the flag waves ).

Also, just so you know, The Flag was made of nylon.

[33] Information on the flag. —Preceding unsigned comment added by 99.185.0.29 (talk) 14:14, 18 October 2008 (UTC)

Actually, that was #1. 67.184.14.87 (talk) 08:49, 19 October 2008 (UTC)

http://www.youtube.com/watch?v=DWajUJ_NnHs

Does anyone have a definitive answer?12.10.248.51 (talk) 16:10, 17 October 2008 (UTC)

My answer is #2. Lenses on cameras can certainly give false senses of perspective, I see nothing in the video to show that he didn't physically touch the flag. My best interpretation is that he physically brushed the flag when he went by. For an example of the tricks that cameras can play on perspective, see this one: [34] showing Theodore Roosevelt, Jr. and George Patton. Teddy Jr. wasn't a midget, and Patton wasn't a giant; the illusory perspective what causes us to make it look that way. --Jayron32.talk.contribs 16:39, 17 October 2008 (UTC)

I vote for #2 as well. The flag looks like it's pointing towards the camera, so the tip of the flag would have nearer the astronaut than the pole, probably near enough for him to brush it - remember a spacesuit is quite big and bulky and it would only take the slightest contact to set it moving with no atmosphere to damp it. --Tango (talk) 16:55, 17 October 2008 (UTC)

You know, now that I think about it, I recall someone on the YouTube page saying that the flag first moves towards the astronaut. To me, it the video moves too fast for me to tell, but he/she advocated the static electricity hypothesis. 12.10.248.51 (talk) 17:06, 17 October 2008 (UTC)

It moves far too fast to tell without slowing it down and analysing it properly. I'm not sure you could tell even with that, isn't the astronaut in front of the flag, blocking it from view, when it starts moving? --Tango (talk) 17:13, 17 October 2008 (UTC)

No, according to the static electricity proponent, the flag starts moving before the astronaut gets there. If this is true, it would invalidate hypothesis 2 and 5. Maybe if I get time, I'll see if I can analyze the video. 12.10.248.51 (talk) 17:34, 17 October 2008 (UTC)

I'd go with either #1 or #2. When the astronaut walks away from the flag, he's taking baby hops (or the wires are lifting him less, take yer pick), when he moves in front he looks to be taking bigger jumps, although perspective enters the equation there. And there's no way of knowing the soil structure, which might not be uniform around the flag and he hit the bouncy part moving in front. That would explain any movement before the guy gets to the flag. #2 is much the most probable, those spacesuits were pretty bulky. It is of course possible that NASA hired a really lousy continuity clerk and they totally missed that little detail. Anyway, I thought we could already tell by the shadows of the moon lander that they faked the whole thing by filming it in a location with two suns. Franamax (talk) 21:59, 17 October 2008 (UTC)

Is the video real? Anyway, it's possible he brushed against the flag, but consider what is holding the flag up in the first place? I think it's either held up by a string/tether or there's a machine that blows air onto the flag. ~AH1^(TCU) 22:09, 17 October 2008 (UTC)

R u kidding? It's a metallic flag with pre-formed ripples made to look like a US flag waving on the moon - but it is the flag they used. And they wouldn't need a machine more complex than a valve cracked open on an air tank to make it move back and forth, but they didn't do that. Real video - crackpot interpretations to "expose the hoax". Franamax (talk) 00:06, 18 October 2008 (UTC)

I think the flag is normal cloth, but there is a telescopic rod at the top to hold it out. I've read that the ripples are due to the rod on Apollo 11's flag getting stuck and not opening fully and the astronauts on the later missions thinking that looked good so intentionally not opening it fully. --Tango (talk) 16:35, 18 October 2008 (UTC)

You're right. [35] Shows what I remember from my distant youth :) Franamax (talk) 21:05, 19 October 2008 (UTC)

You really can't tell - I stepped through it one frame at a time and whatever happens - it happens when the astronaut is blocking the view of the camera. I'd say this though...depth perception on the moon is seriously screwed up - and so is lighting - and that's the source of almost all of the conspiracy theorist's misconceptions. That pole is only about a meter tall - roughly half as tall as the astronaut. To me, it seems bigger - and further away - and I think that's the problem here. In truth it's close enough that he either just caught the corner of it on his spacesuit - or perhaps he was so close that vibration did the job. One thing that's seems strange about flags on the Moon is that in a vacuum, flags keep swinging for MUCH longer than they do here on earth - the internal stiffness of the cloth damps down the motion very slowly on the moon - but here on earth the lightweight cloth and the denseness of the air conspire to kill that kind of motion very rapidly. Hence, even a small vibration

would have been enough to start it moving - and once started, it would swing more impressively than we'd expect by our normal experience of cloth flapping here on earth. The pole that the flag was hooked onto was also engineered to be as lightweight as possible (easier in 1/6th gravity) - so it would more easily transmit any vibration to the flag than a pole strong enough to keep the flag flying here on earth would manage. Vibrations through the ground also depend on the force of the impact from the astronaut hitting the ground. While gravity is weaker on the moon, momentum depends on the MASS of the astronaut - not on his WEIGHT - so that "high mass" (but not "heavy") suit would have been able to transmit pretty large impacts onto the lunar surface. Astronaut plus space suit weigh about 480lbs - so the momentum transferred to the moon rock would have been pretty high. SteveBaker (talk) 00:21, 18 October 2008 (UTC)

An astronaut adjusts the camera, then moves between the camera and the flag, and the flag moves. There is not basis for assuming that he did not brush against the flag. Occam's Razor. If it were a 20 billion dollar hoax, they could have paid Disney Studios to do a letter-perfect fake. The hoaxologists seem like a jealous bunch who don't want to believe that capable and hard-working scientists and engineers could achieve something they never could. Edison (talk) 02:14, 18 October 2008 (UTC)

Of course I'm not saying that there was a hoax, but it's better to avoid arguments against it that are flawed. "They could have paid to have it faked perfectly" is not a hypothesis that's obviously correct. Study the IMDB goofs sections for big-budget movies and you'll see that they always have slip-ups... not only in movies that are light entertainment but also in the kind that try to meticulously re-create a historical incident. It almost seems as though the more effort and money they put into getting things right, the more goofs people find. Look at the IMDB goofs lists for the movies Apollo 13 and Titanic, for example. --Anonymous, 23:54 UTC, October 18, 2008.

Obviously this and this are involved ;) -hydnjo talk 23:08, 18 October 2008 (UTC)

Well, I watched it a few more times and at least to me, the flag appears ti move away from the astronaut, not towards him. BTW, when Mythbusters tested waving a flag in a vacuum, it waves more due to the lack of air resistence. 67.184.14.87 (talk) 08:53, 19 October 2008 (UTC)

There's another version of the video at http://www.youtube.com/watch?v=mJGZte-k4G0&feature=related. Unlike the previous video, this one allows comments. I'm going to skim through them to see if anyone has a good explanation. 67.184.14.87 (talk) 09:13, 19 October 2008 (UTC)

Highly Evolved Dinosaurs

What are some of the arguments against the theory that dinosuars evolved to higher thinking, more so than human beings today, and developed superior technology and left Earth? I have a friend that believes that this is very possible and that these very same beings are visiting Earth today. His argument is that dinosaurs have been around a lot longer than any humaniods thus had the time to develop into highly evolved dinosaurs. He states that there is no evidence of this because it could have happened so long ago, that the evidence got destroyed or buried beneath tectonic plates.--Emyn ned (talk) 17:54, 17 October 2008 (UTC)

We have fossils of non-highly evolved dinosaurs (size of the scull, lack of opposable thumbs or other means of fine manipulations, etc. show they probably weren't capable of developing space travel). If there were later dinosaurs that were more advanced, their fossils would be easier to find (unless they cremated all their dead, but there should still be something inbetween what we have and something advanced enough to have burial rites). While it is not entirely impossible, there is no evidence of such a thing. There is certainly no evidence of them visiting us today. --Tango (talk) 18:12, 17 October 2008 (UTC)

Extraordinary claims require extraordinary evidence. Lack of evidence can not be used as proof. As Tango said, the theories that we have are derived from the current and best evidence available. -- MacAddct1984 ^{(talk • contribs)} 18:45, 17 October 2008 (UTC)

"Lack of evidence can not be used as proof." Ah, c'mon! Why not? 206.66.66.1 (talk) 19:46, 17 October 2008 (UTC)

'cos. --Tango (talk) 20:20, 17 October 2008 (UTC)

A slightly more sophisticated response is that absence of evidence is not evidence of absence. -- JackofOz (talk) 02:23, 18 October 2008 (UTC)

Your friend should also perhaps be introduced to Occam's Razor. Given the choice of supposing that the dinosaurs died versus evolved to intelligence, created space flight, left Earth, deliberately wiped out all traces of existence, but stuck around close enough to revisit and play pranks on those silly mammals millions of years down the road... well, one clearly requires fewer ridiculous assumptions. — Lomn 19:18, 17 October 2008 (UTC)

Occam's Razor can be used to disprove the existance of the universe. After all, nothing is simpler than something. 206.66.66.1 (talk) 19:46, 17 October 2008 (UTC)

Occam's Razor says we should choose the simplest theory which satisfies our observations. We observe the universe to exist, so a theory that says it doesn't can be rejected long before we need to invoke Occam. --Tango (talk) 20:20, 17 October 2008 (UTC)

1) Occam's Razor does not prove anything. It is a problem solving technique, anyone who 'proves' something with Occam's Razor does not understand what it is. 2) Occam's Razor is not about "Simple" it's about "needlessly multiplying entities". ie: Making stuff up that there's no evidence for. (example: "I lost my keys." verses "Pixies stole my keys". Both possible. One involves making stuff up.) 3) "The universe doesn't exist" does not satisfy observed evidence (I can see stuff.) therefore it is not suggested by Occam's Razor.

You guys do realize I was joking, right? 67.184.14.87 (talk) 21:51, 17 October 2008 (UTC)

This is the internet. All attempts at humor or sarcasm must be accompanied by at least one emoticon to show you aren't serious.  :-) Dragons flight (talk) 21:57, 17 October 2008 (UTC)

Which one was you? —Tamfang (talk) 02:43, 18 October 2008 (UTC)

Sorry, I am 12.10.248.51, 67.184.14.87 and 206.66.66.1. 67.184.14.87 (talk) 08:55, 19 October 2008 (UTC)

The problem with things that fail the Occam's razor test is that there are an essentially infinite number of them - and without evidence, there are just too many to believe or even investigate. Sure, there might have been intelligent dinosaurs who did amazing things - but there might have been intelligent sharks/elephants/sea-sponges/penguins/octupii/dogs/herring who did something similar. It's only taken humans maybe 10,000 years to go from an animal-like existance to civilisation-as-we-know-it-today. There has been plenty of time in past history for any of those other species to go through the same cycle we've been through. You don't need to look all the way back to the dinosaurs to make those hypotheses. But why worry about the possibility of there being something for which absolutely zero evidence exists? There is no need to form any of those theories in order to explain some profound thing that we don't already understand. This is why Occam's razor is appropriate under these circumstances. SteveBaker (talk) 23:55, 17 October 2008 (UTC)

Rather than Occam's razor, I thought first of Russell's teapot. —Tamfang (talk) 02:43, 18 October 2008 (UTC)

HAHAHA!! Too funny! THAT'S what I am going to tell my friend. Thanks, Lomn!

The friend (or anybody) might enjoy reading the novels in the Anonymous Rex series by Eric Garcia. --LarryMac | Talk 20:53, 17 October 2008 (UTC)

Ok, that Sarah Palin bit in the Anonymous Rex article is vandalism, right? 84.239.160.166 (talk) 10:14, 18 October 2008 (UTC)

Or in a more serious vein, try Toolmaker Koan, a 1988 novel by John McLoughlin. (Neither the book nor the author has a Wikipedia article currently, although some other people with the same name as the author do.) --Anonymous (although definitely not Rex), 21:55 UTC, October 17, 2008.

One way to think about it is that any civilization on Earth with sufficient resources to eventually leave Earth would have had to consume a lot of resources in the process. Some of these resources would replenish over very long periods of time (like biomatter and all of its derived products like fossil fuels) but many, like heavy metals, would not. There is no evidence that I know of that there were less iron, copper, or uranium reserves, for example, when humans began to use them in quantity than one would have expected there to be. If humans suddenly disappeared today and no evidence was left of them in a million years, I imagine a civilization of the future would still be able to tell that civilized life was here by the relative lack of heavy metals in the soil compared to a null hypothesis. But maybe I'm wrong on that. --98.217.8.46 (talk) 21:18, 17 October 2008 (UTC)

But all the heavy metals are still here (except the very few we've fired off into non-Earth trajectories). All we've done is move them around. Franamax (talk) 21:44, 17 October 2008 (UTC)

Ore deposits are also replenished over time. Ores are formed by various igneous and geologic processes that happen to concentrate certain elements in one location. The metals we mine are only a tiny fraction of those that exist in the Earth, but in general we focus on the fraction that has been naturally concentrated in easy to get at deposits. Given ridiculously long periods of time, like 100 Myr, we can expect that new ore deposits will also be formed. Not to mention that natural erosion can dig down kilometers in that time and expose deposits to the surface that wouldn't be accessible previously. Dragons flight (talk) 21:55, 17 October 2008 (UTC)

This has been covered in science fiction, where the highly evolved dinosaurs left earth due to some climate crisis and came back after eons to find that squirrel-like creatures they remembered as "tree-jontyles,(sp?) quite delicious" had evolved into humans. The dino descendants looked at our society and decided to leave for additional millenia, since we clearly were about to exterminate ourselves with nuclear or biological weapons, so they did not need to exterminate an arguably intelligent species o reclaim their homeworld. And the name of the story is? Edison (talk) 02:10, 18 October 2008 (UTC)

Could it be one of the Astrosaurs series? SpinningSpark 14:34, 18 October 2008 (UTC). Doh, we have an article of course. SpinningSpark 14:39, 18 October 2008 (UTC)

I liked a story about a research group who create alternate timelines to study the effect of, say, reintroducing horses to Kansas a few hundred years before Columbus. Their grandest experiment was to divert the Chicxulub impactor. Shortly after they came home from doing so, there appeared another tardis from which a reptile emerged, saying, "We saw you divert a rock in our past. So we un-diverted it to see what would happen, and here you are!" —Tamfang (talk) 02:43, 18 October 2008 (UTC)

do cleaners age your skin?

if you use cleaners (stuff to clean) without gloves, then does it age your skin faster? If for ten years you cleaned regularly (several times a day) with strong chemical cleaners, just washing your hands afterwards, would your hands end up aged more? Why? —Preceding unsigned comment added by 94.27.166.235 (talk) 22:12, 17 October 2008 (UTC)

I'm not sure there is really a strict definition of "age" in that context. Using strong chemicals without gloves can harm your skin, certainly, and that harm could well be cumulative over a long time. Whether you consider that harm to be ageing or not is up to you, I guess. For advice on what to do to prevent such harm or heal it, see a dermatologist (or your GP, who can refer you). --Tango (talk) 22:39, 17 October 2008 (UTC)

Ceramic Insulation : Cenospheres

Those old Ceramic Insulators that people collect as antiques, glass as well, seen on ebay--do those actually still work in your home? If lets say you lived close to High-Level Power Lines.

Or Cenospheres, The microscopic ceramic beads (balls) have a technical name: Cenospheres, or sometimes called micro-spheres, or nano-spheres for the smallest size. Could you use like a shaman/indian/hippie medicine bag, and put these cenospheres in them to guard yourself from high voltage? Or am I on the road to myth making and Neo-Wives Tales?

Cheers, --i am the kwisatz haderach (talk) 23:20, 17 October 2008 (UTC)

The insulators I have seen people collect are from telegraph wires on railroads, and are not at all suitable for high voltage. Insulators for increasingly high voltages are thicker and have more convolutions or "petticoats." You are talking hundreds of volts rather than thousands of volts. Interestingly, the earliest telegraph insulators were literally glass knobs intended to go on furniture drawers. Edison (talk) 02:03, 18 October 2008 (UTC)

October 18

How large can a Trojan planet be?

I'm trying to get a rough, seat-of-the-pants idea of how large a Trojan Planet or Trojan Moon could be relative the closer of the two bodies creating its L4 or L5 Lagrangian points. The Lagrangian point article only says "it needs not be negligible mass." How large of a Trojan Moon could Jupiter-Sun L4/L5 support, for instance? How massive a space station could Earth-Sun L4/L5 support? I anticipate that the main problem has to do with planet formation, and that the fuzzy nature of a Lagrange point causes formation-by-accretion to be unlikely. What I'm wondering is how large a planet could be held-onto in the unlikely event of capture. Thanks in advance for anything anyone has to say. DeepSkyFrontier (talk) 03:49, 18 October 2008 (UTC)

Theia (planet) mentions this issue, although it doesn't give any exact numbers. From that article, it would seem that a planet larger than Mars would not be stable at the Sun-Earth L4 or L5 points, but it doesn't say how much less than that it needs to be to be stable (it was about Mars sized when it is presumed to have hit the Earth, but that could well have been some time after it lost stability so it could have kept growing for a time). --Tango (talk) 12:27, 18 October 2008 (UTC)

Giant impact hypothesis says it was about Mars sized when it lost stability. --Tango (talk) 12:30, 18 October 2008 (UTC)

orchic

Is orchic supplement bennificial ? —Preceding unsigned comment added by 68.221.224.43 (talk) 05:05, 18 October 2008 (UTC)

I don't see how. "Orchic supplements" (bovine testicular extracts) are broken down by the digestive tract, meaning they cannot be pharmacologically effective. They may exert a placebo effect, but other than that....they're pure bollocks ;-) Fribbler (talk) 11:58, 18 October 2008 (UTC)

I couldn't find any reliable sources about this. However Fribbler's second comment: "Orchic supplements are broken down by the digestive tract, meaning they cannot be pharmacologically effective" is not necessarily correct. Prescribed oral medications do have pharmacological activity, despite digestion. There are many plant extracts (medicinal herbs) that do have pharmacological effect: opium, belladonna, digitalis, etc.. Axl ¤ [Talk] 13:24, 18 October 2008 (UTC)

Of course oral medications are pharmacologically active. I should have been more clear. Testosterone, the "active ingredient" of Orchic Supplements, is heavily affected by digestion. Here is a link: [36]. This is why testosterone used in the treatment of hypogonadism is given either intramuscularly or transdermally: [37] Fribbler (talk) 16:12, 18 October 2008 (UTC)

Sure, testosterone would not be absorbed when eaten. However this might not be the only "active" component of orchic. I couldn't find any reliable evidence of appropriate testing of orchic. Axl ¤ [Talk] 16:39, 18 October 2008 (UTC)

Me neither. A red flag in my book. The medical community appear to be uninterested in this supplement. Fribbler (talk) 15:35, 19 October 2008 (UTC)

sex without condom

What are the most probable infections for a person who practices sex without condom?Mr.K. (talk) 09:32, 18 October 2008 (UTC)

Try reading the article Sexually transmitted disease. Jdrewitt (talk) 09:40, 18 October 2008 (UTC)

Note that I think you are implicitly meaning "with multiple partners" here. --98.217.8.46 (talk) 09:44, 18 October 2008 (UTC)

There are, in fact, two separate questions. One is how likely it is to become infected from an infected partner, the second is closely related to the statistical distribution of STDs in the population. Actually, a third interpretation would lead to an answer like Herpes simplex (infection rates of close to 90%), athletes foot or common cold ;-). --Stephan Schulz (talk) 11:33, 18 October 2008 (UTC)

Genital Herpies is pretty easily the most common STD, and it can infect you ( its a virus ) with a comdom, so condom or hot, the most probible infection is going to be the most common STD. $--~~~~$ —Preceding unsigned comment added by 99.185.0.29 (talk) 13:56, 18 October 2008 (UTC)

While HSV is exceedingly common, it is cumulative and most people don't have constant heavy shedding. This illustrates why you should not use prevalence to estimate incidence. Chlamydia may have higher incidence in some populations. Stephen Schulz was right in saying that it depends on specific factors (including locale, ages of involved persons, and what sexual practices are involved). --Scray (talk) 14:25, 18 October 2008 (UTC)

I was actually surprised a while back reading our article on HIV that vaginal unprotected sexual intercourse only gets you a 5 to 10 in 10,000 chance of receiving the virus, I had thought it was much much higher. (Not that it's worth even that risk!) -- MacAddct1984 ^{(talk • contribs)} 19:56, 18 October 2008 (UTC)

Those estimates are averages from multi-year follow-up of couples in whom coital frequencies have been recorded. This type of research involves finding discordant couples, i.e. couples with one person who has HIV and another who does not, then following them for years to determine risk. If you ask them on a regular basis how often they are having sex, and what they do when they have sex, then you can get an estimate per act. The problem with this approach is that these couples may not represent the setting in which HIV is usually spread.

It's known that there is an early phase of HIV infection when the individual tends to have very high levels of HIV in blood and body fluids. People are more susceptible to getting infected if they have ulcerating STDs, and they may be promiscuous. Thus, susceptibility to infection might occur in peaks and valleys, and when someone is at their peak of susceptibility they may also then be most infectious - with a high level of virus in body fluids, ulcers, and promiscuity - sort of super-transmitters. This would explain observations of rapid spread within mini-epidemics, and is supported by what's known about transmission mechanisms. It's likely to be very hard to find these people, in part because it's a transient state.

Adding to the confusion is that the same person could be highly infectious for a few weeks or months, then a year or two later might be different in many ways, with lower HIV level (their viral load "set point"), ulcers healed, and in a stable relationship. --Scray (talk) 00:42, 19 October 2008 (UTC)

STDs have different prevalences in different populations, so it depends on where you are, but really it only depends on who you are sleeping with. If your partner is clean, then the only STD you really have to worry about is pregnancy. --71.178.135.144 (talk) 06:41, 20 October 2008 (UTC)

size of a lysosome?

Hi could anyone give me an estimate of the length of a lysosome? The article on lysosomes does not give a value. Presumably we're talking nm here. I realise sizes will vary from cell to cell but a rough estimate would be good. Thanks in advance. —Preceding unsigned comment added by 139.222.240.110 (talk) 15:39, 18 October 2008 (UTC)

On a similar topic, does anyone have some kind of semi-visual (the parts that are possible) to compare sizes between things such as cells, mitochondria, chromosomes, genes, neurons... and then atoms, certain proteins/amino acids, you get the idea. I'm well aware that a cell has an insane amount of atoms, which is why I said semi-visual. :) -- Aeluwas (talk) 15:54, 18 October 2008 (UTC)

From "Cytology & Histology" by Wolfgang Kuehnel, p. 34: "Their sizes are 0.1 – 1.2 μm." Axl ¤ [Talk] 17:31, 18 October 2008 (UTC)

...With the caveat that they can get much larger in the lysosomal storage disorders. TenOfAllTrades(talk) 18:49, 18 October 2008 (UTC)

Thanks —Preceding unsigned comment added by 139.222.241.15 (talk) 11:36, 20 October 2008 (UTC)

where does the air in hypercaviation come from?

the supercavitation article says "drag is normally about 1,000 times greater in water than in air."

However, isn't the gas water vapor (h2o in gas form) NOT air (homogenous mixture, largely nitrogen, o2, etc)...? If it is indeed "air", where would it come from? —Preceding unsigned comment added by 79.122.55.76 (talk) 17:35, 18 October 2008 (UTC)

Yes, it's water vapour. The supercavitation article says "The pressure of the fluid can drop due to its high speed (Bernoulli's principle) and when the pressure drops below the vapor pressure of the water or the temperature increases thus vapor pressure increases reaching water pressure, it vaporizes — typically forming small bubbles of water vapour (water in its gas phase)." -- Finlay McWalter | Talk 17:42, 18 October 2008 (UTC)

Defrosting beef

Is it possible to defrost minced beef by putting it in the oven at a low temperature (about 50 degrees centigrade)? —Preceding unsigned comment added by The Defroster (talk • contribs) 18:21, 18 October 2008 (UTC)

Of course it is possible, but the outer part will tend to cook before the center is melted. Externally-applied heat will maximize the temperature gradient between center and exterior meat. If you were to slice the minced beef thinly, this effect won't be much of a problem. I don't see a WP article right off, but here's a link: [[38]] --Scray (talk) 18:36, 18 October 2008 (UTC)

It's worth noting that prolonged incubation at 50C could encourage bacterial growth in the interior of the meat. This is another reason to thaw at refrigeration temperature, or warm using more rapid or uniform heating methods (see the link previously provided). —Preceding unsigned comment added by Scray (talk • contribs) 18:46, 18 October 2008 (UTC)

In the case of minced beef, I generally find that it works fine to just start cooking it as you normally would - if you're frying it it defrosts pretty quickly as you do it as it has such a high surface area. ~ mazca ^t|c 19:03, 18 October 2008 (UTC)

I agree. If frying it, I usually (more or less) take it out of the freezer. Microwaving it for a while helps, and that's what I would do if I needed it thawed (to make meatballs, for instance). -- Aeluwas (talk) 19:11, 18 October 2008 (UTC)

Are you referring to Ground beef? Edison (talk) 19:19, 18 October 2008 (UTC)

I assumed he was... what else does the phrase "minced beef" refer to that could be confused? ~ mazca ^t|c 23:58, 18 October 2008 (UTC)

Mince means "cut into small pieces," which sort of fits ground beef, but it also means "to pronounce in an affected way," like saying "boeuf" for "beef" in English speaking countries, or it means to "walk with short steps or exaggerated primness," which would be atypical behavior for cattle. Edison (talk) 01:14, 19 October 2008 (UTC)

It depends on the person you ask, but to me ground meat is produced using a meat grinder and usually passed through the machine one ore twice. Mince beef, on the other hand is cut finely by hand and usually has a meatier and less "floury" texture when compare dot ground beef.Sjschen (talk) 02:47, 19 October 2008 (UTC)

If a recipe told me to prepare a quantity of "minced beef" I would slice and dice it as finely as possible with a sharp knife on a cutting board. As Sjschen said, to make "ground beef" I would run it twice through a grinder. "Two great nations divided by a common language." Edison (talk) 04:13, 19 October 2008 (UTC)

...and don't confuse your minced meat with your mincemeat. Gandalf61 (talk) 08:49, 19 October 2008 (UTC)

I have no problem understanding what someone means when they say mince beef or ground beef (even if the second is not something I'd use in conversation/writing) as I expect many kiwis and I expect Brits and Australians. It's only other people who have funny ideas about what mince beef is... Perhaps it's only one great nation that is at fault? :-P P.S. Before you argue it's my fault for not understanding your meaning for mince beef, I should ask, how often do you use or encounter 'mince beef'? Surely the more common use of the term should be given preference of one used rarely... ;-) Nil Einne (talk) 09:41, 19 October 2008 (UTC)

Heh, I was unaware of the extent of the American use of "grind" for where I (as a Brit) would use "mince". An American apparently uses a "meat grinder" to produce "ground beef" while I would use a "mincer" to produce "minced beef", with both the equipment and the final product being exactly the same. While to an American "mince" may instead mean "chop finely", to me "grind" implies reducing the meat to a horrible homogenous paste. ~ mazca ^t|c 11:54, 19 October 2008 (UTC)

Same here in Oz but being so far away from birth of the terms, we can mix them too, getting mince from a grinder. The current answer to an otherwise homogenous paste is to pack it with wavy grooves resembling nothing I can think of. ~:\ Julia Rossi (talk) 13:27, 19 October 2008 (UTC)

Don't forget spraying red dye on the outside of the lump to make it look fresh-killed. At least, that's how they do it here in Canadian supermarkets (another country where we (or at least I) can assimilate the concept of ground and minced being the same). Franamax (talk) 20:45, 19 October 2008 (UTC)

I don't think that's red dye, at least not in the U.S.A. It's a tiny amount of carbon monoxide gas placed in the package just before sealing, considered safe and simply cosmetic by the FDA and meat-packing industry. Seems people won't buy brown meat generally, and I would guess that's true. --Scray (talk) 01:30, 20 October 2008 (UTC)

To defrost something quickly and safely, place it in your sink with a small amount of water. Turn your tap on so that barely a trickle of cold water comes out. You want a stream, not drops. The purpose is to keep the piece immersed in moving cold water; the coldness of the water delays the proliferation of bacteria, the movement facilitates the contact of fresh water with the frozen product. Before long, the piece will assume the temperature of the surrounding water (i.e. defrost). Because of water's thermal properties, the meat will defrost faster than it would on the counter. And much more safely. Matt Deres (talk) 14:24, 19 October 2008 (UTC)

Yes, this is what was recommended in the link at the end of my original answer to the post. --Scray (talk) 15:42, 19 October 2008 (UTC)

Toaster in the ocean.

What would happend if you threw a toaster with a very long extension into the ocean?Bastard Soap (talk) 19:50, 18 October 2008 (UTC)

Lots of sparks around the toaster, then shortly a wire will burn through, breaking the circuit. Charge density will tend to disipate with the square of distance from the charge source, so anyone or anything near the toaster is likely to get a nasty shock; anyone a considerable distance away will notice nothing. --Jayron32.talk.contribs 20:18, 18 October 2008 (UTC)

If you threw a whole toaster in the ocean there is no obvious reason that melting would kill the circuit. A) the water will cool the wires, and B) conductive salt water will continue to carry current around the break even if some wires melt. Obviously a circuit breaker/GFI could stop the thing, and I suppose one might also melt part of the extension cord above the water, but if neither of those things happened I don't see any obvious reason for the circuit to ever shut down on its own. Dragons flight (talk) 00:15, 19 October 2008 (UTC)

It would get wet. Hopefully you unplugged the cord first for safety. If still plugged in the element would heat up the water and put some hazardous currents in the sea water. Hopefully a fuse would blow before the wires melt or ELP would disconnect it. Graeme Bartlett (talk) 20:38, 18 October 2008 (UTC)

Who is ELP? —Preceding unsigned comment added by Seans Potato Business (talk • contribs) 22:22, 18 October 2008

Most likely Earth Leakage Protection. -hydnjo talk 22:50, 18 October 2008 (UTC)

If you were smart/lucky enough to have plugged the extension cord into a GFI protected outlet then the stupid act of tossing a plugged-in toaster into the ocean would cause little harm except to the toaster. I suppose you could pull it back by the extension cord and try and try again but the tripped safety device would remain tripped and you would have no clue as to what was going on. How about making some toast instead? -hydnjo talk 22:34, 18 October 2008 (UTC)

For the sake of clarity: ELP and GFI (or GFCI) are the same thing. This form of protection has a large number of different names and the best-known ones vary from one country to another. Another one I remember seeing is RCCB. --Anonymous, 23:56 UTC, October 18, 2008.

Oh, and besides the usual "don't try this at home" admonishment regarding this dangerous stunt you'll probably not know how to properly secure the toaster cord to the extension cord so forget about pulling it back, it'll be sleeping with the the fishes. -hydnjo talk 00:18, 19 October 2008 (UTC)

I would not expect sparks, despite the drama shown in movies when electrical appliances encounter water. I have seen flooded electrical vaults where the water simply boils without great drama due to submerged 120/208 volt bus bars. Saltwater is not as conductive as some think. Current would flow through the salt water from the phase to the neutral connected wires near the entry point of the power cord, where the switch is, but only a small area of conductor is exposed with full phase to neutral voltage between the conductors. The heating element would continue to carry the current it carried in normal use (neglecting the slightly lower voltage due to the additional drop in the extension cord). More current would likely flow through the heating element than directly through the water. The heating element would not get red hot due to the cooling effect of the water. Current would also flow from the heating element directly to the ground connection afforded by the ocean, so that if it were connected to a Ground fault interrupter it would trip offline in milliseconds. Any bread in the toaster might cook, but it would never toast satisfactorily.There would be bubbles of hydrogen and oxygen liberated due to Electrolysis. Anyone attempting the experiment runs a serious risk of death from electrocution, and anyone in the water near the toaster might be electrocuted. Edison (talk) 00:51, 19 October 2008 (UTC)

Thanks Edison for your serious and comprehensive response to an inquiry that some of took as frivolous. -hydnjo talk 01:37, 19 October 2008 (UTC)

Bah! Cut the praise. I don't like Edison's answer. Specifically, the claims that "The heating element would continue to carry the current it carried in normal use" - and that "Saltwater is not as conductive as some think" are entirely misleading. We need to look at the numbers here...(So many of my answers start that way!)

The current has to follow the lowest resistance path - so we need to look at the resistances involved here. Since this is the science desk rather than the guessing desk - I just performed the simple experiment of measuring the resistance of the heating element in my toaster with a meter. I used the cold resistance on the assumption that the ocean water will prevent it from heating up so much (and because I didn't want to plug my toaster in while it was in pieces on my bench!)...and it measures 6,000 ohms. The hot resistance is going to be different - but (as we'll see) - it's not going to matter a damn. The resistance of sea water is just 0.2 ohms per meter. Is this "not as conductive as some think"? It's hard to tell.

So will the current flow through the sea-water between the two exposed metal contacts inside the switch of the toaster (less than 1cm apart in my toaster) or will it flow through the 6kohm heating element? Well, let's approximate this as a simple parallel circuit comprising one 6kohm resistor (the heating element) and one 0.002 ohm resistor (1cm of salt water). In a parallel circuit, the current splits by the reciprocal of the resistance - so the current that flows through the heating element is 0.002/6000 times less than flows through the water. Yes, TECHNICALLY, some electricity will still flow through the element - but unless the extension cord can carry 6 megawatts (the output of a small powerstation) - the heating element WON'T carry more than an utterly negligable much of the available current and it certainly won't get even slightly warm. In fact, it doesn't matter a damn whether it's a toaster or just the exposed end of an extension cord that we toss into the ocean - the result will be the exactly same.

If we assume that any protection device inside the toaster gets wet also - then it will get shorted out by the water on the 'hot' side of the circuit and since almost zero current will flow through it, it will utterly fail to operate. So a lot of current will flow through the water - at 110volts, ohms law says: I = V/R = 110/0.002 = 55,000amps. At 110 volts - that's 6,000,000 watts. That's a LOT of current. If the other end of the extension cord is plugged into any kind of protection device (a simple fuze, an ELCB, GFI or whatever) - it's obviously going to trip with that much current flowing. But if we hypothesise that there is no protection of any kind - then the next question is whether the copper in the cord will melt before the water boils. Certainly there is no extension cord in existence that can carry six megawatts - so clearly it'll break somewhere if it has to carry anything like that much current.

But it's a bit more subtle than that. If the water does boil - then you're concerned with the electrical resistance of steam - which is in the many-mega-ohms per meter range (a lot depends on temperature and pressure). But once the water boils, the circuit is broken and hardly any current flows until the bubble rises and is replaced by more sea water - so the average current flow will be vastly less than 6 megawatts - and perhaps the cable can survive. If so, then the system can keep that up until the ocean boils dry. Over one second, 6 million watts will produce 6 million Joules of heat energy. The Latent heat of water is 2.5MJ/kg - so one second of 6 million watts is enough to flash-boil more than two liters of water and the little bit of water between the the two wires might only represent a couple of cc's - so it's going to boil in a fraction of a millisecond. Since this is actually AC current - the current flowing as the voltage reaches some small fraction of a volt will be enough to create a bubble of steam and cut the current for a while. Since there is some capacitance in the system, when the connection re-establishes as the bubble moves out of the way, the voltage will build up slowly until enough current flows to boil another bubble. The voltage will never reach 110v and the current will be limited by the amount required to boil water at whatever rate it flows in as bubbles move out of the way. As soon as a continuous wet-path between the contacts forms, it'll immediately boil out of the way and cut the circuit again.

It's harder to figure the melting of the copper because too much depends on how well cooled it is by the sea water and on whether there are weak points in the cable (eg at the connections at either end. However, because the mechanism of bubble formation moderates the current flow to that required to boil fairly small amounts of water - I strongly suspect that the formation of bubbles at the end of the cable in the water will moderate the average current flow to the extent that the copper would not melt.

Conclusion. If there is any kind of protection device present in the circuit - it'll trip and end the experiment. If there is no protection whatever - then almost certainly the water near the end of the cable will boil and not much else will happen.

SteveBaker (talk) 15:30, 19 October 2008 (UTC)

This question should be graced by the answer "A wet salty toaster" ;) Sjschen (talk) 02:44, 19 October 2008 (UTC)

My answer would have been "wet toast", but I think that Steve's (usually great) answers have gone a little off track on this one. First of all, the units of resistivity are ohm-metres, not ohms per metre. The resistance of a 1 cm cube is not the resistance of a 1 metre cube divided by 100. The 1 cm cube is x100x less because of the decrease in length but x100² more because of the decrease in csa, making a net x100 increase in resistance. If a metre cube of material has a resistance of 0.2Ω then a 1 cm cube of the same material will have a resistance of 20Ω. Secondly, you will only get that resistance if the field is linearly distributed throughout the cube. This can be achieved by metallising the ends of the sample cube with a near perfect conductor (copper is good enough for most materials). The field from a point contact, eg your meter probes or the ends of the cable chucked into the sea will give you a completely different (much higher) result which needs some more than simple maths to calculate. So being a simple person, I have just put the probes of my meter in a half-pint glass of warm water saturated with salt. At a distance apart of 1 cm my meter measures around 100kΩ betwen the points of the probes and 55-60kΩ if I immerse them in the liquid. more than most peaple think . . it is cetainly more than I was expecting. I don't think you are going to get 55,000 amps going through that very easily. By the way, I have come across the use of a jar of water as a makeshift fuse while testing high current machinery. Too much current causes the water to boil away and break the circuit. SpinningSpark 18:08, 19 October 2008 (UTC)

MRI history

When, where and which manufacturer installed the first commercially-available clinical MRI? —Preceding unsigned comment added by Henpecked (talk • contribs) 20:12, 18 October 2008 (UTC)

Not sure on commercial availibilty, but there is considerable controversy over the first workable NMR machine. There are dueling claims from both Raymond Vahan Damadian, who holds the first patent on what would later be called MRI, while Paul Lauterbur and Peter Mansfield won the Nobel Prize for producing theraputically viable MRI. No one disputes Damadian's contributions as coming first; there is however considerable debate over how much Lauterbur and Mansfield contributed to the field. Some say that Damadian's initial discoveries were the most important discovery; others claim that it was Lauterbur and Mansfield's work that made it a viable technology in the medical field. Click the links to get more info on all of these topics. I hope that helps some! --Jayron32.talk.contribs 20:22, 18 October 2008 (UTC)

As for where the first clinical MRI scanner was installed, I believe it was in my home town of Nottingham in the Queen's Medical Centre. —Cyclonenim (talk · contribs · email) 22:42, 18 October 2008 (UTC)

Quick eye shift breaking white into RGB

I was watching a movie which was being projected via one of those projectors which I suppose was fairly cheap and marketed to domestic users (not sure if the cost is relevant). When I looked at the screen and then shifted my eyes quickly, I noticed that the white areas of the screen appeared to break down into red, green and blue components. What's going on there? I've noticed it before, very occasionally, but it doesn't happen for example, with my PC monitor.

Cool! I wonder if it was a technology with sequential presentation of the three images and a fairly slow scan rate? Edison (talk) 01:00, 19 October 2008 (UTC)

Assuming you have a DLP projection system, see the DLP "rainbow effect" in single-chip systems. -- Tcncv (talk) 01:15, 19 October 2008 (UTC)

Yep. Normal TV's and computer monitors show the red, green and blue images simultaneously. In a single-chip projector, there is a monochrome image and a rapidly spinning three-color wheel in front of it that allows the system to display first all of the red, then all of the green and finally, all of the blue. There are three images displayed over every 1/60th of a second - so each image is there for 1/180'th second - but persistance of vision merges all three together visually into a single image. If you blink, you miss one or two of the colors so you get a brief flash of a magenta, yellow, cyan, red, green or blue image. (I find this effect particularly disturbing) But if some small object moves quickly across the screen there is something more complex going on. Because the three images are displayed separately - they appear at different times. Yet all three images are of the object have it in the same place on the screen - we get a rather peculiar effect. Imagine you plotted a graph of position on the screen versus time. The graph would look like this:

  ^   |                           . . .
  |   |                    . . . 
Posi- |              . . .
tion  |       . . .
      | . . .
      +------------------------------------
            Time ==>

(each dot being a red, green or blue 'rendering' of the object)

...instead of a nice straight line, we have a staircase. What our brains do with this ought to be something like seeing a jerky motion instead of smooth motion - but at these kinds of frame rates, what we actually "see" is three objects moving on a set of parallel paths across the screen. Since each one is a different color, we see a red object, a green object and a blue object moving close to each other - separated by one third of the distance the object moves in a single 1/60th second frame. For slow objects, this isn't noticable - for faster objects, you see a rainbow fringing effect and for very fast objects, you see three separate things tracking across the screen.

When you move your eye rapidly across the screen - it's just like the entire scene is moving rapidly in the opposite direction - and the result is the same as if the entire picture were moving quickly - so the fringing happens all over the screen instead of in just one place. That's why the effect is most noticable when you do that.

More modern projectors (or at least, more expensive ones) have three separate projectors inside - so it can display red, green and blue at the same time - which completely eliminates all three problems (fast eye motion, fast object motion AND blinking). Some intermediate price systems display at even higher than 180 frames per second (eg 360 frames per second) and they show red,green,blue,green,red,blue in every 1/60th second frame. This helps by confusing the eye and making it harder for the eye to misinterpret what you're seeing. That helps the blink problem a lot (because you can't blink and miss (for example) both green presentations and end up seeing a magenta image. The color fringing is also somewhat disguised.

SteveBaker (talk) 13:29, 20 October 2008 (UTC)

Weight of bones

A bird skeleton equals only about 5% of its mass. How does this compare with mammals? —Preceding unsigned comment added by 66.121.22.163 (talk) 22:27, 18 October 2008 (UTC)

According to our article on the Human skeleton, it accounts for about 20% of a human's body mass. I am not sure how representative we are for all mammals, but there you go... --Jayron32.talk.contribs 22:32, 18 October 2008 (UTC)

Heavier animals devote a larger percentage of their body mass to their skeleton than do lighter animals. Small mammals (e.g. mice and things) are generally also in the several percent range. [39] Dragons flight (talk) 23:07, 18 October 2008 (UTC)

• For the reason this is true, see square-cube law and particularly the "Biomechanics" section. --Anonymous, 23:59 UTC, October 18, 2008.

According to the Natural History Museum of Los Angeles Co., the weights of a bird's skeleton and that of a mammal of equal size are comparable, noting Dragons flight's observation that the larger the animal the heavier the bones. - Nunh-huh 23:11, 18 October 2008 (UTC)

October 19

nigilism

a foreign friend referred in passing to 'nigilism' - what could she have meant? —Preceding unsigned comment added by 79.122.55.76 (talk) 00:45, 19 October 2008 (UTC)

or niginism or something similar. I first thought she was trying to say "nihilism" but no... —Preceding unsigned comment added by 79.122.55.76 (talk) 00:47, 19 October 2008 (UTC)

COuld you provide more context to the conversation? If we knew what she or you were discussing at the time, it might help figure out what she was trying to say... --Jayron32.talk.contribs 00:54, 19 October 2008 (UTC)

Google book search for "nigilism" produced 25 hits:[40]. Seems to come from Russian literature, in the character of Bazarof introduced in 1861 by Turgenief. Too turgid for me to follow: [41]. Some of the hits are bad optical character reading of "nihilism" and it seems to be nothing more than a quirky Russian spelling of same, per [42], which says nigilism=nihilism " g in Russian doing service for h." Edison (talk) 01:07, 19 October 2008 (UTC)

I think you're right on. In Russian Cyrillic the concept is spelled "Нигилизм" which can be romanized to "Nigilizm" 02:40, 19 October 2008 (UTC)

Weren't inhabitants of parts of the Soviet Union in WW2 under the impression that they were being persecuted and killed by "Gitler?" See "Re: Gooray for Gollywood"[43]. AGoogle search shows that a number of persons apparently from non-English speaking backgrounds spell the name in English "Adolf Gitler."Edison (talk) 04:08, 19 October 2008 (UTC)

'h' in loanwords often becomes 'g' in Russian; I guess this is because some other Slavic languages regularly have /h/ where Russian has /g/ – see e.g. Ukrainian city-names with –hrad vs Russian –grad. —Tamfang (talk) 20:39, 19 October 2008 (UTC)

My brain is niggling at me, and has asked me to mention that it's surprised the Russians didn't have a word such as ничевизм (nichevizm), from ничего (pron. nichevó, meaning "nothing"). -- JackofOz (talk) 07:03, 20 October 2008 (UTC)

Just as another example, there's Ibraham Petrovich Gannibal, the "black slave" of Peter the Great. Gannibal/Hannibal was an ancestor of Pushkin. - Nunh-huh 07:44, 20 October 2008 (UTC)

Skin condition photos

I added some old photos to Erythema multiforme. However, this photo shows what is meant by Erythema multiforme target lesion, and the target lesion do not appear to be in either photo set in the Erythema multiforme article. If you have a chance, would you take a stab at identifying the skin conditions in the photos in the Erythema multiforme article so that the photos can be placed in the correct skin condition article. Thanks. -- Suntag ☼ 01:37, 19 October 2008 (UTC)

This seems closer for the first set having three photos. -- Suntag ☼ 01:56, 19 October 2008 (UTC)

Dream On! Dream On! Dream until your dreams come ... on a small video monitor?

• http://www.telegraph.co.uk/earth/main.jhtml?view=DETAILS&grid=&xml=/earth/2008/10/17/scidream117.xml

Black and white TV generation have monochrome dreams

By Richard Alleyne, Science Correspondent

Last Updated: 5:01pm BST 17/10/2008

While almost all under 25s dream in colour, thousands of over 55s, all of whom were brought up with black and white sets, often dream in monchrome - even now. ...

This is funny, however, ...

• why wouldn't people have commercials inserted in their dreams?
• why don't people dream in flat-colored pencil outlines thanks to all the animations they have seen during childhood?
• why don't people have silent movie dreams, i.e., scratched frames, exaggerated moves, flash cards ...?
• why don't people have radio drama dreams?
• why don't people have "pulp fiction dreams," i.e., a text-based dream printed on cheap and lousy paper?

Tell you the truth. I have had a dream with a commercial in it. I could not recall the dream itself. While I was dreaming, a man interrupted my dream with a book commercial. I returned to the dream after the sponsor of my dream has done his spamming. I woke up feeling really bad about it. My dream has a commercial in it but I could not get any money. It was the only time some greedy book seller in the Twilight Zone stole air time from me. -- Toytoy (talk) 01:50, 19 October 2008 (UTC)

Wouldn't this mean that before TV humans didn't have dreams?203.59.155.251 (talk) 03:16, 19 October 2008 (UTC)

More likely that TV sometimes influences our dreams now, whereas before TV people sometimes dreamed about what they heard on the radio, or the Sheriff of Nottingham, or the sabretooth tiger they killed the day before. Astronaut (talk) 07:16, 19 October 2008 (UTC)

I expect that before the existence of telly, radio, printing or gossip, that we all dreamt in cave paintings. SpinningSpark 14:09, 19 October 2008 (UTC)

I've dreamt a dream was a book I was reading, and that it was a film I was watching. I've dreamt I was in a Philip K. Dick short story. I think all those types of dream are possible. I even had sepia dreams when I was small and reading a lot of old picture books. 79.66.121.198 (talk) 15:25, 19 October 2008 (UTC)

When my bed faced a window, I once woke up from/through a dream in which the window (a pale rectangle) was a website. —Tamfang (talk) 20:31, 19 October 2008 (UTC)

I suspect observer bias. Let's suppose that we have always had some dreams in color and some in monochrome. It's possible that before the era of television and film, nobody thought very much about whether there was color or not. Things naturally tend to look monochromatic in dim light because the 'cone' cells in our eyes that detect color don't work well in low light levels and our 'rod' cells - that work well in low light levels - don't produce color information. This is so ingrained into us that very few people even realise that it's happening. So it's possible that before we saw monochromatic-in-full-daylight scenes in the movies and early model TV's - we'd have simply interpreted monochromatic dreams as happening in low light conditions. When monochrome TV's appeared, we had this other interpretation thrust upon us - resulting in reports of seeing dreams in monochrome - then when that period went away and we all started seeing monochrome only in dim light again - that we'd go back to reporting monochromatic dreams as not being unusual - just like we don't report dim-light vision as being unusual.

SteveBaker (talk) 13:11, 20 October 2008 (UTC)

Is there evidence to suggest that the Black and White ness isn't age correlated? That would seem to be the simplest assumption to make, 137.108.145.10 (talk) 13:43, 20 October 2008 (UTC)

Genetic mutation- Double tail gourami

I was at the pet store today looking at the fish for sale. I noticed in one of the tanks a dwarf gourami with a true split tail (double tail). It looks like a split tail betta splendens. Ive looked online for some information on genetic mutations of the gourami but havent found anything. I was curious what causes this and if there is any information available to breeding true split tail gourami.

http://en.wikipedia.org/wiki/Gourami —Preceding unsigned comment added by 69.45.184.77 (talk) 06:34, 19 October 2008 (UTC)

This[44] finds double tail betta females and possibly others. If it's what you're looking for, specialised aquariums might be able to help. Julia Rossi (talk) 22:20, 19 October 2008 (UTC)

Ultimate fate of the universe

I tried pointing this out at Talk:Ultimate fate of the universe, but I received no response, so I'll repeat it here.

• 

The graph from the section "Role of the shape of the universe" shows the accelerating universe as a sinusoidal curve, with "Now" on the inflection point. In my opinion, it seems more likely that an accelerating universe would be concave all the way along, with a constantly rising gradient. Axl ¤ [Talk] 09:01, 19 October 2008 (UTC)

I don't think the shape of the curve is quite right, but the inflection is. If you assume a cosmological constant version of dark energy then the curve should decelleration due to gravity initially until dark energy starts to dominate and only then does it start to accelerate. As I recall, that transition was a few billion years ago more or less. Dragons flight (talk) 09:25, 19 October 2008 (UTC)

The correct ΛCDM curve is roughly $a(t)\propto (\sinh(t/{\mbox{11 Gyr}}))^{2/3}$. The curve in that diagram has the right general shape, but it's not drawn very accurately. -- BenRG (talk) 14:14, 19 October 2008 (UTC)

Gibbs free energy

ΔG⁰=RTlog_eK

The K used here is the equilibrium constant. But there is a problem in knowing that is it K_p or K_c

If we use either of the constants the values come out to be different. Please Explain. —Preceding unsigned comment added by 122.173.65.66 (talk) 14:41, 19 October 2008 (UTC)

You will have to refresh my memory as to what the "p" and "c" subscripts mean (constant pressure and ??), but I believe the real equation is ΔG=RTln(Q), which takes into account concentrations of the reactants and products. Under standard conditions (superscript °), then that would mean various things (concentrations of reactants are 1 molar, STP). This calculation of ΔG is for the instant at the beginning of the reaction. Once the reaction starts to proceed, ΔG will change (due to mass action and Le Chatelier's principle) until it reaches zero - equilibrium. --Bennybp (talk) 20:05, 19 October 2008 (UTC)

K_c is the constant for concentration. —Cyclonenim (talk · contribs · email) 22:17, 19 October 2008 (UTC)

ΔG⁰ is the instantaneous free energy change at the start of a reaction, at standard conditions (273K, 1 atm, 1 molar concentrations) and constant pressure, whose equilibrium constant is K. K is generally assumed to be unitless and calculated from the "activity" of the compounds involved. Since actvity is not directly measureable, a "surrogate" which can be measured is often used. K_c is the equilibrium constant as calculated from molar concentrations (aqueous solutions or gasses) and K_p is the same constant as calculated from pressures. For gases, K_c = K_p divided by (RT)^Δn, where Δn is teh number of moles of gas that changes in the balnced reaction. --Jayron32.talk.contribs 22:38, 19 October 2008 (UTC)

The shape of the orbit of the Moon over the Earth

Imagine a line from the centre of the moon to the centre of the earth. At the surface of the earth, this line forms a dot which moves with the rotating orbit of the moon, and the rotation of the earth. If this moving dot was plotted on a stationary globe, what shape would it make? Some sort of spiral? Thanks 78.149.192.49 (talk) 17:40, 19 October 2008 (UTC)

Hm. This may be a start for you: Orbit of the Moon. From that, it appears that there are some rather complex motions to consider. If you picture the moon's orbit as a big coin, the coin is at an angle to the earth's equator (called inclination) and that coin is itself "wobbling" (called precession). The wobbling is in two different planes (parallel to and perpendicular to the ecliptic). The periods of these two precessions is quite short, 8.5 years for one and 18.6 years for the other. Not sure what this means for the overall pattern you are looking for, but if you can wrap your head around all of that (the article is more detailed) then there ya go. --Jayron32.talk.contribs 18:19, 19 October 2008 (UTC)

If you unwrap the earth into a typical rectangular Mercator projection map - the path of the moon would be (more or less) a series of overlapping sine-waves. SteveBaker (talk) 12:56, 20 October 2008 (UTC)

Similar to the map that is always in the background during film scenes set in mission control. That was my first thought, but I'm a little unsure how the fact that the Earth's rotation is orders of magnitude faster than the orbit (with an artificial satellite it's usually the other way around) would affect that. I think that it would still, technically, be overlapping sine-waves, but the wavelength would be extremely long so the wave goes all the way round the Earth 28 days per period (ish, I'm not sure exactly which definition of lunar month we need). Therefore what you would actually see is basically a series of straight lines across the surface of the Earth (well, straight as in constant latitude, whether they are actually straight lines depends on the choice of projection). --Tango (talk) 13:12, 20 October 2008 (UTC)

Actually, it probably wouldn't be all that different. The absolute motion of the moon around the center-of-mass of the earth (the Month) is not what is relevent here, its the relative motion of the moon to the earth's surface, which is still about a 24 hour period. The question is kinda vague, since the picture is different whether one wants to know what the pattern would look like projected on the real map of the earth OR a theoretically static earth. The two wavepatterns would look very different, since one takes into account the earth's day-rotation, while the other only takes into account the moon's month-revolution. --Jayron32.talk.contribs 13:54, 20 October 2008 (UTC)

While the longitude of the point goes in a roughly daily cycle, the latitude will go in a monthly cycle since the Earth's rotation doesn't affect where the moon is in relation to the plane of the Earth's equator. I think the OP's question was quite clear, since it specifically mentioned the rotation of the Earth, so the reference to a static Earth refers to a co-rotating frame of reference rather than actually stopping the Earth moving. --Tango (talk) 14:49, 20 October 2008 (UTC)

Thanks. So how far north or south from the equator would the dot go? I assume that at the poles, the moon is never directly overhead. 78.149.175.26 (talk) 14:11, 20 October 2008 (UTC)

The Moon's orbital inclination relative to the Earth's equator is (according to the infobox on Moon) "between 18.29° and 28.58°". That means the dot will never go north of 28.58°N or south of 28.58°S (and will rarely get even that far from the equator, I'm not sure precisely what determines the inclination at any given time, but the difference is almost exactly twice the inclination from the ecliptic which suggests to me that it's probably an annual cycle). --Tango (talk) 14:49, 20 October 2008 (UTC)

Thanks again. What prompted these questions - and what really interests me - is the track of the moon in the sky over time. Where I habitually sit, I see the moon through the window pass in an arc across the night sky during the evening. I think the centre of the curve of the arc is to the south. As the nights go by, this arc gets lower and lower in the sky. I can only see a small part of the sky through the window. I'm wondering what the track of the position of the moon would look like overall. A few nights ago I went out of the house and was surprised to see the moon in the north-east or east of the sky, I think. I'm also wondering if the moon is capable of being in any part of the sky (from my point of view) or in just some of it. If in just some of it, then how does the moon get into position to draw the arcs I have described? 78.147.35.151 (talk) 21:39, 20 October 2008 (UTC)

The track of the moon in the sky from a fixed point on Earth is quite a different matter to the track on Earth of the point below the moon. The moon will follow a similar path along the sky as the Sun, rising in the east and setting in the west once a day. It will never stray more than about 5 degrees from the ecliptic (the path travelled by the Sun, where that is depends on the time of year and your latitude). I suppose you are in the northern hemisphere, so the moon is getting lower and lower in the sky for the same reason the sun is - it's getting into winter. That's caused by the Earth's axis being tilted with respect to the Sun's/Moon's orbit (the sun's and moon's orbits are at pretty much the same angle (only 5 degs different), so the tilt is pretty similar). --Tango (talk) 22:02, 20 October 2008 (UTC)

Thanks, but I have to disagree with the moon getting lower in the sky with the seasons - it seems to happen about every month, not every year. And in the small part of the sky I see out of the window, the moon is more or less full. I wish there was some nice freeware software somewhere that could show what I have described. 78.151.133.172 (talk) 22:55, 20 October 2008 (UTC)

Helicopter under a bridge?

This question has one foot in the Entertainment Desk, but it's the science side I'm asking about.

Last night I watched Terminator 2 (a documentary that hasn't been made yet:) and in one scene a helicopter flies under a fair-sized road bridge, six-lane overpass type. Now I know they built a real polyalloy cyborg for the movie, but is the helicopter shot faked? Helicopters generate downwash, so the air has to come from somewhere, seems to me having a bridge deck just over the rotor would seriously disrupt the aerodynamics - lifting the 'copter as it ate away the air above it and causing it to hit the bridge deck above.

Is it actually possible to fly a 'copter under a bridge, let's say an 80-foot span-breadth with 30-foot clearance? Thanks! Franamax (talk) 20:30, 19 October 2008 (UTC)

I know that they regularly fly helicopters under the Golden Gate Bridge, but that is several hundred feet high. I don't know what the lower limit would be. --71.106.183.17 (talk) 20:38, 19 October 2008 (UTC)

Even if the scene in the movie is possible, I cannot imagine it would be legal in the US. So the filmmakers would certainly have used special effects to simulate it. At least it's not as obviously impossible as the helicopter scene in the 1996 "Mission: Impossible" movie. --Anonymous, 22:12 UTC, October 19, 2008.

I don't remember that scene in the movie. Is it particularly spectacular? Is a big deal made of the fact that they flew a 'copter under a bridge? If not, they probably wouldn't have wasted special effects on it. Anyway, I think pretty much anything is legal if you get it approved for movie-making purposes. --Masamage ♫ 03:59, 20 October 2008 (UTC)

Mission Impossible scene - helicopter flies into Channel Tunnel in pursuit of high speed train to which it has rather carelessly become tethered. Gandalf61 (talk) 09:30, 20 October 2008 (UTC)

Sorry, I meant the Terminator scene. --Masamage ♫ 21:23, 20 October 2008 (UTC)

It's not obvious to me that this would be illegal, for the same reason I doubt there is any law that says don't use a bullwhip on high voltage electrical wires. It is so incredibly dumb and unusual that quite possibly no one has wasted the time required to write a law addressing it. Dragons flight (talk) 09:36, 20 October 2008 (UTC)

I'm assuming in any case that the stunt would be legal. They presumably got the highway below blocked off to film, and (almost) anything is possible in movie-shoot areas (punch buggy alert, but watch the chase scene in Bullit). I'm asking physics-wise two cases: could you fly a helicopter at speed under a bridge with the parameters I described (confined space longer than it is high, 100'L x 50'W x 30'H)? And could you even edge a helicopter into that space and traverse it? We're talking a light 'copter like the ones they rent to movie companies or use for traffic reports, and no, it wasn't that spectacular of a scene. Similar to flying into the Chunnel (although that's much less likely, how would they get it back out?) - is it physically possible to perform such a maneuver? Franamax (talk) 10:50, 20 October 2008 (UTC)

There are probably laws about how close you can fly to solid objects, but there's no reason they couldn't have gotten permission from the relevant authorities. --Tango (talk) 10:56, 20 October 2008 (UTC)

The Wikipedia page Stunt seems to suggest this is genuine, but it's very vague. The page says "The killer robot T-1000 flies a helicopter in a freeway chase after a S.W.A.T. van driven by The Terminator and at one point flies under an overpass. As if to prove the stunt was done for real, the pilot attempts a second underpass, but flies away at the last second." There is no cite for this claim. --Maltelauridsbrigge (talk) 11:50, 20 October 2008 (UTC)

I'd also mention "The Italian Job" (the recent remake - not the 1960's original) where there is a helicopter inside a warehouse chopping up a poor-defenseless MINI Cooper.

The problem is that the rotors are sucking air from above the helicopter and pushing it downwards to support it's weight. When you get close up to the underside of a bridge or other enclosed structure, that sucking causes an increase in lift - which forces the helicopter closer to the bridge and that in turn causes an even more powerful upward force. This positive feedback effect makes flying under covered areas quite hazardous. Flying quickly under a narrow structure like a bridge is reasonably OK because you aren't under the bridge for more than a couple of seconds - but hovering under a bridge, or inside a building or (god forbid) inside a railway tunnel - would be very hazardous indeed.

We can get an estimate of "how close is close?" by noting that the ground effect occurs at about one to one-and-a-half times the rotor disk diameter. Below this height, the extra pressure caused by the ground interacting with the downward-moving air column dramatically increases the efficiency of the rotors. So when a helicopter comes in to land, it's like it hits this soft cushion at about one rotor-diameter above the ground. That's really convenient - and the lower you go, the stronger the effect. So I would guess that if you flew under a structure at a low enough height that there was at least (say) two rotor diameters of air between the top of the helicopter and the underside of the structure - then you'd barely notice that there was a problem. But if you got within (say) one rotor diameter of the structure, it would go badly wrong quite quickly. If the pilot was expecting this to happen, he could probably throttle back or reduce the collective pitch to cut the helicopter's lift - but unlike coming in to land where the negative feedback gives you a gentle cushioning effect that makes landing easy - the positive feedback sucking you upwards would be like a magnet pulling you where the closer you get, the more pull there would be. Flying the helicopter accurately under those circumstances would be exceedingly difficult.

So flying 100' below the golden gate bridge with a 30' diameter helicopter is no problem whatever - but the flying-though-the-rail-tunnel thing in Mission Impossible is...Impossible.

SteveBaker (talk) 12:50, 20 October 2008 (UTC)

It says above that helicopters are regularly flown under the Golden Gate Bridge. Is this legal?

(I do not consider that I'm asking for legal advice here. I'm just seeking factual information about the law. Also, for the record, I'm not planning to make any such flight.)

If it is legal, do the applicable laws cover what size of helicopters may be used? After all, there are helicopters and then there are HELICOPTERS.

Similar question for fixed wing aircraft. Piper Cubs good? Concordes not good? Where is the line drawn? Thanks, Wanderer57 (talk) 17:36, 20 October 2008 (UTC)

Carbon-neutrality of paper waste

Does paper waste contribute to global warming, or is it an offsetting factor? Most paper waste is put in landfills and does not biodegrade over the short term. This would suggest that paper waste reduces the amount of carbon in the atmosphere, and thus offsets global warming. On the other hand, energy must be consumed in order to convert the wood into paper and to transport the timber, paper products, and waste paper. What is the net effect? John M Baker (talk) 20:55, 19 October 2008 (UTC)

Assuming the paper is produced from wood produced in sustainable forestry, the carbon content in the paper itself will be neutral, since new trees are absorbing carbon where the old trees were cut down. To the extent that the waste paper conributes to production of methane in the landfill (where the methane is not captured from the dump), the paper will contribute in the short term (10-20 years) to global warming since methane is a much more potent heat-trapping gas than CO2. And to the extent that the waste paper could have been diverted to a recycling stream, it will also contribute to global warming, since more energy is required to make paper from virgin wood than from recycled, and the net effect will generally be to cause increased consumption of fossil fuels. Franamax (talk) 21:23, 19 October 2008 (UTC)

Are we sure that most waste paper is sent to landfill? Collection and recycling of waste paper is advanced compared to many other forms of recycling. Note that one of the uses of recycled paper is cellulose fibre insulation for buildings - environmentally benign. Itsmejudith (talk) 21:29, 19 October 2008 (UTC)

Responses to the points made so far:

• As to the sustainable forestry point: Yes, cutting the tree down is itself a carbon-neutral act, since a new tree will be planted in its place. It's after the tree is cut down that carbon is affected.
• Waste paper in landfills generally does not produce methane over short periods of time, perhaps not for millennia. Newspapers from landfills a half century ago remain readable. My source is Rathje & Murphy, Rubbish!: The Archaeology of Garbage (which I recommend as an excellent read, as well as being enormously informative).
• My question really asks about carbon-neutrality in absolute terms, and not in comparison to some other, perhaps superior, method of disposal, such as recycling. That said, I am intrigued by the comparison to a recycling stream. Are the incremental carbon savings from recycling greater than the amount of carbon removed from the atmosphere by burial in a landfill? That seems intuitively unlikely, but I'm prepared to be influenced by actual facts. Of course, there are reasons other than global warming to favor recycling.
• I don't have statistics on disposition of waste paper, but I think most is sent to landfills. Recycling would also have favorable carbon effects, while other methods of disposition, such as incineration, generally would have unfavorable effects. I don't know which of these effects predominates. John M Baker (talk) 22:04, 19 October 2008 (UTC)

Hmm, those are some cogent points. To a certain extent, you are suggesting cutting down whole trees and burying them to sequester their carbon (not that you're saying that, but extend the argument that way...). I have no statistics on buried paper conversion by bacteria, you're right about reading old newspapers, whether that applies to non-chlorine-bleached vegetable-ink modern newsprint, I dunno. Certainly in my area, the majority of paper goes to the blue-boxes, either newsprint or cardboard/fine-paper. Of course by observation, people aren't able to recognize the pictures and words asking them not to throw in their waxed-paper milk cartons (or pizza boxes with the pizza still in them, or their old VCR in the paper bin) - so I can't estimate how much "recycled paper" gets rejected at the plant and sent to landfill. We would need to look at the energy balance - new paper vs recycled. We will always be using more new pieces of paper, how much (presumably carbon-intensive) energy do we expend to produce virgin vs. recycled material? How does that balance with the putative benefit of burying carbon for some millenia? I've got no good numbers on that and it's an interesting question. For comparison though, why don't we just cut down trees and bury them? Franamax (talk) 00:57, 20 October 2008 (UTC)

One minor point. I would wager that household use of paper probably pales to office/commercial use of paper. My experience in that field suggests that office workers do a very poor job of separating their recyclables leading to a great deal of supposedly recyclable goods getting dumpstered. Matt Deres (talk) 13:42, 20 October 2008 (UTC)

And dang, I missed a point - incineration works out, give or take 10-100 years, to be not that bad. In the case of clean incineration and efficient use of the energy, as in combined cycles of incineration to produce steam for power generation combined with district heating schemes (I'm thinking Sweden and Denmark especially), again fossil fuel use is reduced in proportion. Given a sustainable forestry scheme, the carbon is directly recycled - again, need to consider here the energy balance between producing the finished good and incinerating it (and having enough burnable material to sustain an incineration scheme). Franamax (talk) 01:06, 20 October 2008 (UTC)

Burying paper cut from a managed forest should be a net carbon win. Burying trees would also be a win - providing the energy you consume in doing so is small enough. Of course nature has been solving the carbon problem by burying trees for a very long time - and that's been working out pretty well, right up to the point where humans started digging them up again (as coal) and burning them. I very much doubt that deliberately cutting down trees in order to bury them is a good idea - it's probably better to simply leave the forest alone and let it bury its own trees - thereby saving all of the fuel and manpower needed to cut and bury. Using wood to build houses is a net carbon win - but only so long as the total number of houses increases over time. As soon as you reach some kind of market saturation where old houses are demolished in order to make new ones, the question becomes one of what you do with the refuse coming from the demolition of old houses. If you bury it - then you're still winning the carbon battle - but if you burn them it's a break-even thing.

The underlying problem is that for the earth to reach equilibrium, we have to bury carbon at a rate equal to the rate that we dig it up and burn it. Since coal is essentially dead trees with all of the non-carbon squeezed out of them - it would take many tons of modern tree burial to cover every ton of coal dug. When you look at the numbers - a typical mid-sized power station consumes 10,000 tons of coal per day - and consider the number of acres of trees that would represent...[45] says that around 50% of the mass of a tree is carbon. [46] says that around 500 trees per acre is typical for a managed forest and that turns out to be about 8 tons per acre. So to compensate for the carbon created by just one medium-sized coal fired power station, you need to chop down, bury and replant 1250 acres of managed forest every single day. The fastest growing trees can be cut and replanted every 10 years - the slowest, every 60 years - so to sustainably cover the carbon from one powerstation requires at the very least, 1250x356x10 or about 4 million acres of managed forest - and at the worst 1250x356x60 or about 24 million acres. In the whole of the USA, there are about 600,000,000 acres of managed forest - which (if you buried every single tree they grew) would cancel out the carbon emissions from between 25 and 150 medium sized power plants. Sadly, there are over 600 of those plants in the USA - so even if you eventually buried every single piece of wood and paper we ever used - you'd only be saving between a 4% and 25% of the carbon we're producing from coal power plants alone.

However, there are faster-growing plants than trees. So if we were serious about this, we could grow (for example) saw-grass - and perhaps reach the break-even point that way. But the idea of turning over all of the managed forests in the USA for the entirely non-productive growing and burying of plants seems like an economic non-starter. Replacing the coal fired power stations with nuclear power and using just a few of those 600 million acres for the intensive storage of nuclear waste seems like a much simpler proposition. SteveBaker (talk) 12:32, 20 October 2008 (UTC)

Yes, it's true that cutting and burying trees is a form of carbon sequestration, and one that is being taken seriously; Dyson, for example, has written about genetically engineered carbon-eating trees. My question, however, is about paper waste that would be generated in any case. John M Baker (talk) 14:51, 20 October 2008 (UTC)

Going by this, pulping waste paper saves 5-7GJ/ton compared to virgin pulp. Using 57 lb carbon/MBTU for coal energy [47] and a very ragged envelope back gives me 342 lb. carbon saved by recycling one ton of paper, versus 1000 lb. sequestered by burial (using Steve's 50% ratio). This would look like an argument for throwing the paper away. However I'm not sure on the energy intensity for coal, i.e. the conversion efficiency from primary energy to usable energy. If the efficiency is 30%, it's a wash. If it's 50%, you could feel good about throwing paper into the trash. Additionally, this depends on the assumption that all the carbon in the paper will in fact be sequestered, and this suggests that it actually supports methane production, so you're going to get a lot of it back out again over a period of 30 or so years [48]. Maybe Steve has a better calculator than me. Franamax (talk) 22:39, 20 October 2008 (UTC)

Stuffy noses -- one side is blocked, then the other, then both.

During a cold or the flu, how does one nostril become completely blocked? Sometimes they both are, sometimes none. And it seems to change sides for no apparent reason. What's going on inside my head? --64.123.119.182 (talk) 01:56, 20 October 2008 (UTC)

We cannot offer medical advice. Please see the medical disclaimer. Contact your General Practitioner. Paragon¹²³²¹ 03:07, 20 October 2008 (UTC)

Good thing no one asked for advice then, isn't it? - Nunh-huh 03:08, 20 October 2008 (UTC)

Definitely not a medical advice question; anatomical curiosities are different. Unfortunately, I have no idea what the answer is. Something to do with sinus pressure. --Masamage ♫ 03:57, 20 October 2008 (UTC)

Since it's your face and not mine, I can't speak directly to your experience. Here's mine: I've had ear nose and throat problems all my life, especially terrbile sinus headaches (took me a decade of living with a cat to figure out I was allergic to it). I almost always get them on the same side of my head, which puzzled me until I realized: it was the side I slept on. Mucus is a fluid, albeit an especially goopy one, and if you preferentially sleep on one side more often than on the other, I wouldn't be surprised if that's also the nostril that's getting stuffed first. --Shaggorama (talk) 04:49, 20 October 2008 (UTC)

It's also not simply that "nostril that feels clogged" = "nostril that's obstructed by mucus". Congestion consists of swelling of the nasal mucosa; it's as likely to be this swelling as it is actual mucus obstructing air passage. In a paper discussing a system to measure differential air flow in the left and right nares, , there's a statement of some things that can change the sensation of which nostril is obstructed:"left naris becomes less congested ", " patient changes head position that affects air flow or swelling").[49]. The side you sleep on is also the side that's more "dependent" and could be more congested as well as more blocked by mucus. - Nunh-huh 06:31, 20 October 2008 (UTC)

One would also have to take into account the state of the nose before it became infected. It is possible that your nose has been injured at some time and the airway somewhat reduced during the healing process or you may have a small nasal polyp that is affecting one side of the nose, but only causing a blocked sensation when the mucosa is inflamed and swollen. Richard Avery (talk) 13:44, 20 October 2008 (UTC)

I did read/hear that it's normal to breathe predominantly through one nostril, with the nostril used alternating every couple of hours. Unfortunately I can't remember where or cite a reliable source, as it's just one of those factoids you pick up. AlmostReadytoFly (talk) 15:13, 20 October 2008 (UTC)

Gravity waves

See Gravity wave. Anyone know what shape the wave is? It obviously isn't a sine wave. -- SGBailey (talk) 16:46, 20 October 2008 (UTC)

Do you mean the waves that that article are talking about (waves on the ocean, for example) or the waves in general relativity? The former are probably sine waves (if they're periodic at all, a tsunami is a gravity wave, but is just a single wave). The latter will depend on the source, two objects in a circular orbit around their centre of mass will probably give off sine waves (a GR expert may come along and say I'm wrong in a minute, I'm just guessing based on the animations in our article, gravitional waves, they look to me like they are oscillating as a sine wave). A more complicated system will give off something more complicated. --Tango (talk) 18:33, 20 October 2008 (UTC)

The shape of a gravity wave is too complex to have a simple name, it seems. See Airy wave theory for the simple, sinusoidal approximation. That article links to the more complex, nonlinear models. One of them is the trochoid, a shape that resembles simple nonlinear waves reasonably well. --Heron (talk) 21:14, 20 October 2008 (UTC)

I suppose I meant what shape is the animation of a surface gravity wave shown. What reason did the author have for making it the shape he has? -- SGBailey (talk) 21:39, 20 October 2008 (UTC)

Ah, I get you. Sorry. It's pretty close to a sine wave, but I agree it doesn't look exactly like one. I no idea why the creator chose that particularly wave, but they are still active so you could always ask! --Tango (talk) 22:07, 20 October 2008 (UTC)

Vaccine versus Control group testing

In the information sheet for an oral vaccine against travellers' diarrhea and cholera, there is a table comparing "adverse events reported".

The two most commonly reported "events" are:

• abdominal pain, reported by 16% of those who received the vaccine and 14% of the control group, and

• diarrhea, reported by 12% of those who received the vaccine and 11% of the control group.

My question is about the methodology of such a comparision. I assume that people in the two groups are given the same information. What information are they likely given about what they are receiving?

Speaking personally, I think I would be likely to react differently if I were told:

"Please drink this. It contains one hundred billion inactivated cholera bacteria."

than if I were told:

"Please drink this. It will stop you from getting diarrhea."

- - -

Aside from the specific question of what the people in this test were told, in general what is the proper approach as to what people in such tests SHOULD be told? Wanderer57 (talk) 17:14, 20 October 2008 (UTC)

See double-blind study for more information on the generally accepted means of doing medical research of this nature.--Jayron32.talk.contribs 17:29, 20 October 2008 (UTC)

That article says: "Single blind describes experiments wherein information that could introduce bias or otherwise skew the result is withheld from the participants." I suppose either of my suggested wordings would introduce bias and thus could not be used. But it seems to me the participants have to be told "something". What can they be told? The article doesn't cover this. Wanderer57 (talk) 18:00, 20 October 2008 (UTC)

They'll be told something along the lines of: "Please drink this, it is either a vaccine against diarrhoea or a placebo." Everyone will be told the same thing and the person saying it doesn't know which one each person is getting (that's the "double" bit of "double blind"). --Tango (talk) 18:36, 20 October 2008 (UTC)

Bouncing off the atmosphere

You often hear people using the expression "bouncing off the atmosphere" to describe what happens if a spacecraft re-enters the atmosphere at too shallow an angle. This makes it sound as if the atmosphere is an elastic substance that can absorb the kinetic energy and return it - that can't be right, can it?

I think that the spacecraft would experience a force directly opposite to its direction of travel, and that this would slow it down. If the deceleration was inadequate, the spacecraft would return to space, but with reduced kinetic energy.

I remember when young reading about this affecting the height of the apogee, and I think I now know why. If the craft was in an elliptical orbit, the loss of kinetic energy at the perigee would reduce the potential energy of the apogee, due to the exchange between the two energy types as the craft orbits. This would progressively reduce the apogee until the orbit was near circular, when it would re-enter properly and land, crash or burn up.

If the craft was in a hyperbolic orbit it would still lose energy, possibly enough to be captured by the earth.

Is this what actually happens, or have I got this wrong? If correct, why "bouncing off"?

--J987 (talk) 19:56, 20 October 2008 (UTC)

I don't think the force is directly opposite the direction of travel - there will be lift as well as drag. I'm not quite sure how all that works, though, so I'll leave that to someone else. You are right about air resistance circularising an orbit, although it would probably re-enter some time before the orbit became circular. As the apogee drops, the object spends more and more time in the thicker part of the atmosphere and the apogee drops faster and faster, the final drop from being above significantly atmosphere to being on the ground would probably happen in less than one orbit. A hyperbolic orbit will certainly lose energy if it goes through an atmosphere, whether that could lead to capture or not, I don't know, it's certainly plausible. When probes to Mars, and similar, enter Martian orbit they sometimes (maybe always, I don't know) use their rockets to enter a higher elliptical orbit and then use atmospheric breaking near periapsis to circularise the orbit - they have rockets to prevent it going beyond circular and crashing, of course (I believe they keep the periapsis above the significant atmosphere and use rockets to periodically dip down into it, lose some energy, and then use the rockets to lift them back to safety). --Tango (talk) 20:16, 20 October 2008 (UTC)

4D

I've read part of Flatland and a sequel to it, and I've read The Planiverse, and I've run across a few other stories that ponder life in two or fewer dimensions. What about more dimensions? It seems like there would be even more technical problems to overcome in building a sensible lifeform and an environment for it to live in, but it shouldn't be impossible. Obviously the musculature would have to be as different from ours as ours is from that of an Ardean, since it has four dimensions to grow in and probably more complicated shapes to move around, and naturally ratios like height-to-weight would have to be rethought, but there's no reason it shouldn't work. Anyone run into anything like that? Black Carrot (talk) 20:24, 20 October 2008 (UTC)

I'm pretty sure people have considered life in 4D, although I can't find anything explicitly about it. I remember hearing somewhere that the extra dimension means particles are less likely to meet eachother (more ways to miss, I guess) which slows down reactions so life might not be possible (or would at least be less likely) - that was as part of an attempt to explain why our universe has 3 dimensions using the anthropic principle (in 2 dimensions you have problems with things like a body falling apart if you try and have a tube going all the way through to make a digestive system which causes lots of restrictions on how life could work, and in 1 dimension you can't change the order of particles from their initial conditions which restricts pretty much everything, so 3 dimensions turns out to be the optimal number for life to evolve). --Tango (talk) 22:14, 20 October 2008 (UTC)

Hi. Wouldn't the fourth dimension be time (and 5-11 branes)? Thanks. ~AH1^(TCU) 22:49, 20 October 2008 (UTC)

Possible non-conventional ways to counter global warming?

Hi. First of all, this is neither homework nor legal/medical advice, and I'm not exactly probing for oponions, I just want to know about the plausibility of these scenarios.

• Jumping simutaneously

This occured to me after remembering a joke on an April Fools' day, but I thought it might have a bit of plausibility. Consider people around the world simutaneously jumping at diffent times of each 24-hour period, say during the local early afternoon. People would jump at timed intervals around the world at a set local time, so that about 3 billion jumps would occur in one 24-hour period, daily, more so in the summertime than in the winter. I don't know if this would violate conservation of momentum or something, but if people simutaneously jump when their heads are facing closer to the sun, their downward forces would be pushed into the ground, and their upward forces into their bodies and thus not into the Earth. Would that be able to, over a long period of time, propel Earth into a very slightly farther (and more eccentric) orbit? Or, would it cause more problems than it would solve (they're saying that river dams and strong cyclones could cause earthquakes on stressed fault line zones)?

• Due to conservation of mementum this does not work.

• Painting albedo:

This idea is to paint urban items such as buildings, roofs, roads, etc, white, as long as it doesn't use much more oil, such as painting a roof white instead of a different colour. After all, there is the "urban heat island" effect, so this would cool down the city and also reflect more heat into space.

• could assist

• Firing gravitons

Yeah, I know, gravitons aren't even proven to exist. However, if they do exist, and we can find out the mechanism for their creation, then maybe we could place graviton-generating stations around the world, and when it's dark at night, the machines could either point toward the Earth and switch on, and pull the Earth toward the machine, or they could point toward space, and the stream of gravitons could pull the Earth away from the sun, and they wouldn't propel the Earth toward the sun because they have no mass. Or, is this technicly not plausible, or would have too little effect even if we did somehow succesfully make one?

• Complete sequestration

I know, you've all heard of carbon sequestration, but this time without storing the carbon dioxide somewhere. Some sort of catacystic converter would separate the CO2 into oxygen and pure carbon, which would then be made into diamonds.

• would require too much energy to do, and burning coal to carbon dioside and then forming pure carbon produces no energy,

• Methane removal

Instead of burning methane in oxygen, store them with tubes, whether it be animal gas or garbage gas or clathrate gas or permafrost gas, and burn them in an oxygen-free environment, under high pressure. The hydrogen would float off into space, and the carbon would again be made into diamonds.

• Filling in of sea water

It's impossible to tell by looking at the title, but there are small spaces left in the Earth's layers when oil and gas are drilled, correct? Why not direct some of the sea water into a tunnel system that works like a piston, so that the water can go down, and heat cannot go up. Next, the water would be channeled into those gaps in the Earth's layers. This, if plausible, would allow for less sea level rise.

• Ocean water supply

If the freshwater resources in the future are too small, and sea level rise has risen a lot, then could it be possible to get water from a bit below the surface of the sea especially near polar countries, to avoid the oil slicks and also avoid the lower salty layer, so you'd have almost fresh but slightly brackish water that would take less energy to convert?

Is any of this plausible? Again, I'm not asking for opinions, just for if this might be plausible, which is a factual query. Thanks. ~AH1^(TCU) 22:46, 20 October 2008 (UTC)