Wikipedia:Reference desk/Archives/Science/2008 February 9

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[edit] February 9

[edit] Is it possible to hide somewhere on Earth

or is it all prety much surveilled —Preceding unsigned comment added by 212.51.122.27 (talk) 00:24, 9 February 2008 (UTC)

I'm not entirely sure we are aware of every piece of surveillance technology the governments of the world have at their disposal. My guess would be that, yes it would be possible - There are high profile people currently in hiding who have yet to be found despite our best efforts. The next question is what are the tools we have in our arsenal? Thermo imaging, infrared, satellite etc..etc..Perhaps someone who has more expertise in engineering and physics could field this one. Wisdom89 (talk) 00:36, 9 February 2008 (UTC)
I spent some time in Alaska and know for a fact that it is a very good place to hide, at least in the country. There are no addresses and in some places no good maps to show where things are. And that's in the US! Wrad (talk) 00:40, 9 February 2008 (UTC)
The presence of lack of maps doesn't mean somewhere is easier or harder to hide. All you have to do is meet one person in Alaska who knows who you are and the whole thing is up, even if there is no address. --98.217.18.109 (talk) 00:51, 9 February 2008 (UTC)
Some people have managed (ok, I'm tired of linking) to stay hidden for a long time even with the most technologically advanced nation in the world trying to find and kill them. The earth is a big place; some areas are linked up with heavy technological surveillance, but most are not. Even with those that are, the ability to use disguise, forgery, the help of confederates, etc., make it possible to elude capture for a long time. Is it possible to hide? Obviously yes. The biggest problem is not, I would argue, technological surveillance, but social networks being linked to economic networks and things like that; it's hard to get a job, to open a bank account, to earn money in any real way, etc. without leaving some trace of yourself. --98.217.18.109 (talk) 00:51, 9 February 2008 (UTC)
It is my understanding that countries like the USA have the ability to photograph any spot on the earth above the ground within some time period. However, the presence of electronic surveillance doesn't mean you can't hide. Just because it is possible to photograph you, doesn't mean they can find you - it's a data processing problem. The police need to know which video camera footage to review. --Bmk (talk) 06:25, 9 February 2008 (UTC)
Right, but aerial photography only helps you so much. If you were hiding right now, would aerial photography help find you? Probably not—because you're probably indoors, and from that high up, anyway, most people look pretty much the same anyway. --98.217.18.109 (talk) 17:15, 9 February 2008 (UTC)
Some manage to evade capture for many years. See Victor Manuel Gerena for example.Mr.K. (talk) 06:40, 9 February 2008 (UTC)
Then there is also the man with a US$50 million bounty on his head who we believe is still alive and the US has been (supposedly) very, very actively hunting for the past 6.5 years but is still MIA. BTW, about the satellites, it isn't just a data processing problem. Whether the resolution of current spy satellites is good enough that even a human could recognise a face is unclear, the article suggests it isn't although it's impossible to know what spy satellites are truly capable of. However they may not even be theoretically capable of it if I understand the article correctly. Spy drones are probably a far better bet here. Also it doesn't matter if you can recognise faces if you never actually see the face because it is hidden all the time... Nil Einne (talk) 13:00, 9 February 2008 (UTC)
All we've ascertained from satellite photos is that it's not on the roof! Algebraist 13:27, 9 February 2008 (UTC)

[edit] Do we have a space station orbiting the moon?

Do we have a space station orbiting the moon?

(Just to make sure, my understanding is that we don't have one on the moon, and we don't have one either obiting nor on Mars. Is that right?)

Thank you! —Preceding unsigned comment added by 212.51.122.27 (talk) 00:37, 9 February 2008 (UTC)

We have artificial satellites orbiting the moon, but not since Apollo 17 in 1972 has a human orbited the moon. The next planned human mission to the moon, at least so far as the U.S. is concerned, is Orion 17. It took 8 years to plan and achieve a human landing on the moon with the Apollo program of the 1960's, but with 21st century technology and the lessons learned, it is expected to take 13 years from the 2006 announcement of the program until the first mission tentatively scheduled for 2019. Edison (talk) 00:40, 9 February 2008 (UTC)
Sure it will take longer, but it will also be much more expensive! :) --Sean 16:07, 9 February 2008 (UTC)
Minor nitpick. Orion 15 is planned as a moon landing. APL (talk) 17:03, 9 February 2008 (UTC)
It's actually quite difficult to orbit the moon for long periods due to lunar masscons. — Lomn 01:37, 9 February 2008 (UTC)
(The article is at Mass concentration.) --Allen (talk) 03:06, 9 February 2008 (UTC)
The International space station is the only space station in existance, and its orbits earth, far below the moon.--Dacium (talk) 06:25, 9 February 2008 (UTC)
ok. what is "existance"? —Preceding unsigned comment added by 212.51.122.26 (talk) 13:39, 9 February 2008 (UTC)
A common misspelling of existence. Algebraist 15:12, 9 February 2008 (UTC)
How in the world can we have satellites orbiting the moon and I not have know about them? What satellites? And doesn't the presence of the Earth play hob with an unattended lunar orbit? --Milkbreath (talk) 17:19, 9 February 2008 (UTC)
Not sure who you include in "we", but current satellites in orbit around the Moon include SELENE (Japan) and Chang'e 1 (China). There may be others. Gandalf61 (talk) 18:05, 9 February 2008 (UTC)

[edit] B12 and Folic Acid Masking

If you see someone with Pernicious Anemia which unbeknownst to you is due to a vitamin B12 deficiency, and you give them a folate supplement, their anemia will resolve. Will they still have homocysteinuria?

--142.157.61.48 (talk) 04:39, 9 February 2008 (UTC)

Homocystinuria is usually caused by an inherited genetic disorder in an enzymatic pathway - but yes, if a person does not receive enough B-12, then they can develop an increase in homocysteine in the blood and urine. However, if you give someone folate supplements it will NOT resolve pernicious anemia - as both B12 and folate are required for the synthesis of thymine. Wisdom89 (talk) 05:20, 9 February 2008 (UTC)
Usually the term pernicious anemia refers to a type of (megaloblastic) anemia that results from chronic stomach inflammation with a resulting intrinsic factor deficiency. Since IF deficiency results in B12 deficiency, and since the peripheral manifestations of B12 deficiency resemble those of folate deficiency, people often equate pernicious anemia with megaloblastic anemia secondary to B12/folate deficiency. Anyhow, Wisdom89 is right -- if the B12 deficiency is causing homocysteinuria, then supplying excessive folate will not help. Homocysteinuria involves a pathway of homocysteine metabolism that involves several enzymes, including methionine synthase, cystathionine synthase, and methyltetrahydrofolate reductase. Methionine synthase and cystathionine synthase require methyl-B12 and B6, respectively. Methylation of B12 to form methyl-B12 requires methyl-THF reductase, which depends upon adequate intake of folate (a precursor for tetrahydrofolate, THF). So methionine synthase directly requires B12 and indirectly requires folate. Deficiencies in these vitamins or enzymes, or decreased affinity between enzyme and vitamin can result in a homocysteinuria. An interesting result of this complex system is that homocysteinuria due to B12 deficiency can be ameliorated by B12 but not folate supplementation, while homocysteinuria due to folate deficiency can be treated with either folate or B12 supplementation. (I suppose I could've redirected you to homocysteinuria, but that would've ruined the fun inherent in rambling off useless biochem pathways. :-) --David Iberri (talk) 04:01, 13 February 2008 (UTC)

[edit] Parts of thr skull?

Where is the "orbit and anterior cranial fossa" located? —Preceding unsigned comment added by 207.5.224.47 (talk) 04:56, 9 February 2008 (UTC)

The orbits are the recesses that contain your eyeballs. We have a whole article on the anterior cranial fossa, which lies over the orbits (the bottom of the anterior cranial fossa consists of a bone that is the top of the orbits). - Nunh-huh 07:05, 9 February 2008 (UTC)

[edit] Why is a car moving in a circle at a constant speed said to have accleration?

it's not homework, just something i found in the maargins of my physics textbook. ^^; —Preceding unsigned comment added by 202.156.88.207 (talk) 07:21, 9 February 2008 (UTC)

Acceleration is a change in velocity, which is both a speed and a direction. So if the car is changing direction, it is accelerating, if not in the non-scientific sense. You may be interested in centripetal force. Someguy1221 (talk) 07:48, 9 February 2008 (UTC)
Also vectors Nil Einne (talk) 13:15, 9 February 2008 (UTC)

[edit] The natural world: snails

What are snail offspring called?Issi5690 (talk) 10:09, 9 February 2008 (UTC)

Snail life cycles vary from species to species, but it's typically egg, hatchling/larva, tiny snail (uh, not a scientific term ;-) ), adult snail. Sea snails have the additional stages trochophore and veliger (both actually considered types of larva) before adulthood. Someguy1221 (talk) 10:15, 9 February 2008 (UTC)
These are termed as trocophore larvas.--Mike robert (talk) 17:06, 9 February 2008 (UTC)

Bob, Jemima, or, more famously, Brian, but really, pretty much any name the parents like. Except, I hear that modern snail parents have an irrational aversion to calling their offspring "Snoop Doggy Dogg" on the basis that it's too silly (although Snoop Dogg is apparently acceptable). --Dweller (talk) 12:45, 12 February 2008 (UTC)

[edit] thermoacoustic refrigerator

hi friends,

i m trying to model the thermoacoustic refrigerator as given in the link:

www.kettering.edu/~drussell/Publications/ThermoDemo.pdf

in this article it is given that a fundamental harmonic is to be established in the resonator(quarter wave) tube and then the power of the speaker is to be increased to such an extent that a second harmonic is barely audible.i m unable to recognize that a second harmonic is heard.rather the incident sound is so high that it is impossible to hear any other sound.any friend with some knowledge on waves.help me.

regards, sam. Reveal.mystery (talk) —Preceding unsigned comment added by Reveal.mystery (talk • contribs) 10:32, 9 February 2008 (UTC)

The article you point to gives 385Hz as the fundamental, right? So the second harmonic will be at 770Hz. This is slap bang in the centre of the human hearing range so you should have no trouble hearing it unless you are stone deaf. I suspect that the problem is more likely that you are not used to picking out harmonics from a composite sound. This can be quite difficult for many people. If you know any piano tuners, ask them to listen, they will be able to do this exercise with ease. If you can't find anyone from the music world to help, you will have to solve the problem with expensive technology; audio spectrum analyser is the instrument you need.
By the way, 100W speakers can generate high sound pressure levels. You would be advised to use ear protection while doing this. SpinningSpark 18:26, 9 February 2008 (UTC)


sir, thank you very much for your answer.if you went through the article .you must have read that there is a need of a thermocouple in it.i live in a remote place,so no thermocouples with me. i m trying to measure the temperature with a metal pin inserted in the resonator such that it touches the stack at a point which is expected to get colder.and then a labrotory thermometer touching it.i am not sure about its working can any one help.

regards sam Reveal.mystery (talk) —Preceding comment was added at 05:10, 10 February 2008 (UTC)

[edit] Books on science history

Hi! When I was little I read a set of volumes of books called "Stories of Science" (it was a Hindi translation actually). It gave detailed and fascinating historical accounts of how various discoveries and inventions of science were made and what the people involved went through, and the even the politics involved. I don't have those books any more. Can anyone suggest a similar book(s) that gives an interesting, historical account of the stories of science? Thanks a zillion :) ReluctantPhilosopher (talk) 15:35, 9 February 2008 (UTC)

Wow - historical accounts of the stores of science - the only problem here is where to start. In no particular order:
Gandalf61 (talk) 16:06, 9 February 2008 (UTC)
I second the Double Helix suggestion, as it shows how vital beer is to the scientific enterprise. The Making of the Atomic Bomb gives a lot of good social/historical background to early nuclear physics work. --Sean 16:09, 9 February 2008 (UTC)
Alright, thanks a lot :) ReluctantPhilosopher (talk) 17:09, 9 February 2008 (UTC)
OK I'll read that, thanks :) ReluctantPhilosopher (talk) 17:17, 9 February 2008 (UTC)
More suggestions:
  • The World of Gerard Mercator by Andrew Taylor.
  • Brunelleschi's Dome by Ross King.
  • Chasing the Molecule by John Buckingham - the origins of organic chemistry.
  • The Book Nobody Read by Owen Gingerich - fascinating account of tracking down the remaining copies of Copernicus' De revolutionibus orbium coelestium; an unusual angle on a slice of the history of astronomy.
  • For accounts of contemporary science, try Sequence: Inside the Race for the Human Genome by Kevin Davies and Roving Mars, the story of the Mars rovers Spirit and Opportunity, by Steve Squyres.
Gandalf61 (talk) 17:54, 9 February 2008 (UTC)
The Day the Universe Changed by James Burke (also a TV documentary). --Milkbreath (talk) 18:17, 9 February 2008 (UTC)
Thanks, fellas. ReluctantPhilosopher (talk) 17:53, 10 February 2008 (UTC)

[edit] Difference between a penny and a penny.

What is the difference between a penny and a penny? Thank you! —Preceding unsigned comment added by 79.122.70.107 (talk) 16:16, 9 February 2008 (UTC)

It is 0d in old money, 0p in new money and 0¢ in American money. SpinningSpark 16:23, 9 February 2008 (UTC)

This question doesn't make any cents. —Nricardo (talk) 16:34, 9 February 2008 (UTC)
ROFL XD ReluctantPhilosopher (talk) 17:08, 9 February 2008 (UTC)
No, really. It doesn't. Are we missing something? Wisdom89 (talk) 17:58, 9 February 2008 (UTC)
Penny, a penny is a unit of currency in several different countries. There are a number of online currency conversion tools that can compare the various values of different pennies. IF that's what you're asking.--VectorPotentialTalk 18:44, 9 February 2008 (UTC)
This one seems to have everyone foxed and the OP has gone away but I think this may have been the question and it does actually get a mention in our article Cent (United States coin). SpinningSpark 21:37, 9 February 2008 (UTC)

Uh, there is no difference between a penny

ok, I'm the OP -- I was just interested in what kind of answers you would give. In fact, you have given answers in terms of a pun, materials science, and finance (currency). But not mathematics (the difference [ie if you subtract the latter from the former] is "zero") or Grammar (the word's place in the sentence - as the first or second object of the preposition "between", perhaps inflection falls at the end of a sentence too...). Surprisingly, no one gave the answer that I was expecting people to give: "Nothing" -- there is no difference between a penny and a penny. —Preceding unsigned comment added by 79.122.91.85 (talk) 23:37, 9 February 2008 (UTC)

Identity_(philosophy) is interesting. --Allen (talk) 23:48, 9 February 2008 (UTC)
Isn't the answer "One of its legs is both the same"? AlmostReadytoFly (talk) 01:03, 10 February 2008 (UTC)
Because vests don't have sleeves. 82.44.115.41 (talk) 22:38, 11 February 2008 (UTC)

[edit] trivial querry...

Please tell me why High Tension electric cables(overhead) buzz?? A conspicuous very much audible buzz is found below such a cable..
LONGBOW001 (talk) 17:21, 9 February 2008 (UTC)

It is the magnetic field generated by the current in the cables causing either other cables, or nearby metal parts (in the pylons etc) to vibrate. The note will be twice the frequency of the ac power system. As this is 60Hz in the US and 50Hz in Europe, the audible note will be 120Hz or 100Hz respectively. You might also hear the noise of arcing in damp weather when there is tracking across the high tension insulators. SpinningSpark 17:54, 9 February 2008 (UTC)
See Mains hum. —Keenan Pepper 19:32, 9 February 2008 (UTC)
Corona discharge is a strong component of the buzzing noise. It is not really arcing, but rather the ionization and breakdown of the air around conductors, especially at transmission voltages and particularly around sharp points or sharp edges, where the potential gradient is the greatest. Edison (talk) 20:37, 9 February 2008 (UTC)

[edit] Odd-looking moon tonight...

Looking out of my window as I drew the curtains this evening, I noticed the crescent moon in the sky. I don't normally spend a lot of time looking at the moon, but tonight's moon is strange. Despite it being a crescent moon, I can still see the entirety of its face. The proportion of it which should be fully in shadow is actually slightly brighter than the surrounding sky and shows up clearly against it - dark grey on black, to put it simply (I know the sky isn't *really* black - but near as dammit). I live in Northern England, if anyone from my part of the world wants to have a look out at what I'm talking about (it's still doing it now as I type this)...

What's going on? I can't recall ever seeing a moon like this. Unless I just haven't been paying attention (taking the moon for granted?) for all these years. --Kurt Shaped Box (talk) 18:44, 9 February 2008 (UTC)

You can see the "dark" part of the moon in reflected earthlight. This effect is not very noticeable in this country but increases towards the equator. When I was in Oman, this effect was very obvious in the clear desert air. SpinningSpark 18:55, 9 February 2008 (UTC)
Ah, hear we go, I knew there had to be an article on this, I just couldn't find it for the first post - Planetshine SpinningSpark 19:08, 9 February 2008 (UTC)
Hi. Isn't it Earthshine? Thanks. ~AH1(TCU) 19:09, 9 February 2008 (UTC)
If you look carefully, you will see that Earthshine is a redirect to Planetshine and doesn't have an article of its own. SpinningSpark 19:13, 9 February 2008 (UTC)
Yeah, that's precisely what I'm seeing! Thanks very much, guys. So, is this a particularly common phenomenon? As I said, I don't recall ever noticing it before (the article is nonspecific). --Kurt Shaped Box (talk) 19:18, 9 February 2008 (UTC)
(edit conflict)Oh. Well then, just out of curiosity, could Light pollution sometimes be intense enough to radiate to the moon and be reflected back to Earth at detectable levels? Thanks. ~AH1(TCU) 19:20, 9 February 2008 (UTC)
The effect is there all the time, um, correction, it is there all the time near the New Moon. On the other half of the moon phase cycle the Full Moon is facing the night side of the earth and therefore gets no reflected sunlight. The reasons we don't often notice it are 1)our weather, 2) relatively high latitude and 3) light pollution. And no, light pollution cannot cause the effect, it is many stellar magnitude (can't be bothered to actually calculate anything) below the reflected sunlight. SpinningSpark 19:27, 9 February 2008

Another and more picturesque name for the phemomenon is Old moon in the new moon's arms (that's also a redirect to Planetshine). It is very common for it to be visible when the moon is a thin crescent, but only when the sky is also dark, and when it's a thin crescent it's mostly in the day sky, not the night sky. --Anonymous, 01:08 UTC, February 10, 2008.

Earthshine is more apparent when the Moon is a crescent because night vision is better preserved. With a nearly-full moon, the eyes do not become more sensitive over time because there is no need to do so. --Bowlhover (talk) 02:31, 10 February 2008 (UTC)

[edit] colour of sky

Hi. I'm just wondering, what is the colour of the average clear sky on Earth during the middle of the daytime excluding the colour of the sun and clouds and moon and dark areas and haze and terrestrial objects and aircraft and contrails and lightning and halos and all other objects' colours in the sky other than the average colour of the daytime sky itself, in HTML? Thanks. ~AH1(TCU) 19:07, 9 February 2008 (UTC)

There is a HTML colour named "SkyBlue" which looks like this but I don't know whether that corresponds to the actual colour of the sky. The HTML code is 87 CE EB. SpinningSpark 19:19, 9 February 2008 (UTC)
The sky is blue, but the exact shade varies enormously with the time of day and the angular distance from the sun. The blue is deepest at 90 degrees from the sun on a line drawn through the zenith. There is more information at Rayleigh scattering and diffuse sky radiation and the links from that page.--Shantavira|feed me 19:23, 9 February 2008 (UTC)
What Shantavira said; and also note that when you ask for the color "in HTML", you're really asking for its representation in the sRGB color space. —Keenan Pepper 19:28, 9 February 2008 (UTC)
By the way, you get the prize for todays' most difficult to parse sentence. SpinningSpark 19:40, 9 February 2008 (UTC)
I think this belongs to the Computing Desk. Visit me at Ftbhrygvn (Talk | Contribs | Log) 15:31, 10 February 2008 (UTC)