Wikipedia:Reference desk/Archives/Science/2008 November 30

= November 30 =

Shooting the ISS out of the sky
Just a goofy question I had. What would be the minimum technology necessary to shoot the International Space Station out of the sky? (I've no interest in doing so, personally.) It looks like a rather fragile thing up there, though I suspect its great height and relatively fast speed would mean you'd require some sort of fairly sophisticated anti-satellite weapon to do so. But it is pretty large compared to most satellites, so maybe it would be an easier target? Or maybe you could shoot a missile somewhere into its path that would just shoot out a lot of debris? I'm sure some of you mad scientists out there have even better ideas... --98.217.8.46 (talk) 01:16, 30 November 2008 (UTC)


 * The ISS is in a fairly low orbit, which is why it moves so fast. USA 193 was destroyed at a similar altitude (and therefore similar velocity), so such technology does exist - that's just one example, though, so there's no way to know how reliable it is. The ISS being so big would make it an easier target compared to other satellites in a similar orbit. --Tango (talk) 01:43, 30 November 2008 (UTC)


 * If don't want to develop a real anti-satellite weapon, any ICBM can reach the ISS altitude, and I'd imagine that with a nuclear warhead you'd only have to get close so steering and guidance would matter less. Dragons flight (talk) 04:01, 30 November 2008 (UTC)
 * You would have to get closer than you might expect - without an atmosphere you don't get the same blast wave doing damage over a wide area. --Tango (talk) 13:29, 30 November 2008 (UTC)


 * Though the EMP would fry the ISS's electronics and cause it to drop out of orbit fairly quickly (because there'd be no way of making course corrections - assuming that there's no 'fire booster rockets manually' lever behind a break glass somewhere), wouldn't it? --Kurt Shaped Box (talk) 15:38, 30 November 2008 (UTC)
 * You don't need to make course corrections to stay in orbit, once you're in orbit your momentum keeps you there. You might hit space debris which could do damage, though (I'm not sure how much debris there is that intersects the ISS orbit). Eventually it would de-orbit due to atmospheric drag since the loss of attitude control would make it impossible for craft to dock and use their rockets to boost the orbit (which is done periodically), but that would take months at least, probably years (they boost every few months, but I'm sure they don't leave it to the last minute). They may even be able to use gyroscopes to maintain basic attitude control without electronics, I don't know. --Tango (talk) 16:04, 30 November 2008 (UTC)


 * Well, I was hoping for the most low-tech solution. A nuclear ICBM ain't that! My thought was, what if you had some very primitive sounding rocket, could you get it high enough and have it create some sort of debris field that the ISS would be forced to go through, or something like that. --98.217.8.46 (talk) 16:29, 30 November 2008 (UTC)
 * Our article on sounding rockets says they can easily get high enough, and there's no reason you couldn't put an explosive charge in one to create debris. I'm not sure you would get enough debris to reliably cause an impact, though - it's going to spread out pretty quickly and then fall down (since it isn't in orbit), so you need to get the timing very precise. I'm not sure sounding rockets are that accurate. --Tango (talk) 16:36, 30 November 2008 (UTC)


 * See, that's what I want to hear about. ;-) --98.217.8.46 (talk) 16:51, 30 November 2008 (UTC)


 * What do you mean shoot it "out of the sky"? There was some controversy a while ago when Russia blew up one of their satellites, but the problem was that it was still in the sky, and had created a lot of dangerous debris. — DanielLC 16:54, 30 November 2008 (UTC)


 * Are you sure you're not thinking of 2007 Chinese anti-satellite missile test? While both Russia (well actually the USSR) and the US have blown up their satellites with missiles before it appears to be the most recent case I'm aware of involving a destruction using missiles for demonstration/testing purposes. See Anti-satellite weapon. The only other recent case is USA 193 although officially that was because of the risk the satellite may pose. There was this but if the destruction was intentionally (which we don't know) it was designed to be able to self-destruct and definitely wasn't shot by a missile Nil Einne (talk) 11:35, 1 December 2008 (UTC)

2012
What are the governments saying about it?


 * What governments? What topics?  There are millions of people working for governments around the world and they may be saying billions (if not trillions) of things about 2012.  You must limit your question to something that can be answered within the confines of a reference desk. --  k a i n a w &trade; 01:22, 30 November 2008 (UTC)
 * I assume you're talking about 2012 (film). Those hollywood people love disaster movies, no matter how far-fetched. --  JSBillings  01:37, 30 November 2008 (UTC)

i meant, what is the US gov. saying about 2012 if anything at all...ok i know wikipedia is known for saying 2012 is just hype and paranoia...but guys,... it's scary how all those calendars from dif. cultures coicide on the date and also that strange galactic occurrence... if there is such a hype, why doesn't NASA educate the public? i mean...they don't say anything....thats kinda weird, right? —Preceding unsigned comment added by 75.68.165.235 (talk) 02:25, 30 November 2008 (UTC)


 * What galactic occurrence? Dragons flight (talk) 02:45, 30 November 2008 (UTC)ou her
 * Didn't you hear this? We will be passing through the exact, perfectly defined and perfectly known geometric plane of the milky way on April 1st 2012, exactly at 11:11 (a.m.). --Stephan Schulz (talk) 09:14, 30 November 2008 (UTC)
 * What time zone? --128.97.245.27 (talk) 04:41, 1 December 2008 (UTC)
 * On April 1st, 11:11 occurs simultaneously in all time zones. --Stephan Schulz (talk) 10:04, 1 December 2008 (UTC)
 * There is none, but there certainly are a fair number of conspiracy theories that predict the date 2012 as the end of the world, or Armageddon, or whatever. Their proponents allege various cultures/mavens/seers all agree; you can choose from the Mayans, Edgar Cayce, Native American myth, Our Lady of Fatima, Nostradamus, Medjugorie, etc., etc., etc. Suffice it to say that, to the extent that governments are rational, they have nothing to say about it, and that the question belongs on the pseudoscience desk, not the science desk. I believe the NASA component of the conspiracy alleges they've discovered "Planet X" that is due to collide with Earth in 2012... - Nunh-huh 02:52, 30 November 2008 (UTC)
 * See ZetaTalk on that one. Algebraist 02:55, 30 November 2008 (UTC)


 * It's important to note that there are LITERALLY a million or so distinct belief systems and religions out there; and a significant number of these have specific dates for the end of the world. Every decade or so a new one comes up.  This is just the next one on the docket.  It will pass, like the hundreds of predictions before this, without event, and we will promptly forget it and move on to the next one.  If anyone wants to read more about the end of the world, Eschatology is as good of a Wikipedia article as any on this.  --Jayron32. talk . contribs  03:37, 30 November 2008 (UTC)


 * ZetaTalk lady is, without a doubt, not of sound mind. And I'm not intending that as an insult, it is completely serious. It's actually somewhat sad to hear her on the radio, as well as frightening (not for fear of doomsday, of course). -- Consumed Crustacean (talk) 09:53, 30 November 2008 (UTC)


 * People have been predicting that the world would end in their lifetimes for thousands of years. You might enjoy this list of failed end-of-the-world predictions. (Well, the ones in the past have failed; the ones in the future will fail in a few years.) -- BenRG (talk) 13:36, 30 November 2008 (UTC)


 * And on April 1st no less :) -hydnjo talk 14:47, 30 November 2008 (UTC)

Wouldn't you be MORE worried if your government, which is supposed to be focused on the 10 million ACTUAL problems in the world today, like the totally failing economy, terrorism overseas, multiple wars, genocide, ecological disasters, YOU NAME IT, was instead wasting its time, and YOUR MONEY, looking into whether the coincidence of multiple religions allegedly having similar dates that their calendars loop over was somehow a national security threat? How would they even evaluate that? What would you be expecting them to do? Stock up on shamans? Now take a look at the people who are saying it will be the end of the world. Are they reputable? Are they recognized experts anywhere except for rather crackpot places? Do you really want an acidhead like Daniel Pinchbeck taking government money and directing government policy? (Here's a nice article on him and his ilk if you have the time.]) The government has got limited time and limited money. They use things like "actual science" as a way of determining which of the million potential issues they should be spending it on. Science itself purposefully limits the sorts of things it can worry about to those which have a hope of being reliably determined, because it too has limited attention and limited resources. The 2012 thing, even if you imagine it to be some sort of real thing, is not a great thing for the government to be wasting its limited resources on, especially at a trying time like this. The people who are promoting the idea that there is some sort of disaster are people who all directly profit from people being scared of it. Be wary. --98.217.8.46 (talk) 16:32, 30 November 2008 (UTC)


 * Since you ask: if my government were wasting its time and my money on nonsense like this, then it would have less time and money to spend creating "ACTUAL problems". —Tamfang (talk) 19:51, 4 December 2008 (UTC)

but guys, isn't our solar system supposed (scientifically) to be in a special place and alignment that day? (21, dec.?) i mean...it's not just religions...what do reputable scientistssay about the alignment, pole shift , photon belt and stuff?I read that it's supressed scientific knowledge...


 * Look, let's make a bet. If you lose, come to my birthday party on Dec. 21, 2012 and bring me a gift.  If you win, you would obviously not need to come.
 * Please point out specific claims made by specific authors and the Reference Desk will examine them. For an article on 2012, see http://www.universetoday.com/2008/05/19/no-doomsday-in-2012/.  I suppose you already know that nearly every time the Reference Desk received a question like yours, I linked to all previous questions relating to 2012.
 * Reputable scientists are not likely to waste their time on crackpot theories, so I don't think you'll succeed in finding out their opinions. If you trust the people here, though, many (not including me) have considerable scientific knowledge and are qualified to comment on information you find, as long as you are specific.  --Bowlhover (talk) 19:24, 30 November 2008 (UTC)

thank u guys...u r noble...I used to be a wikipedian...lol, this sounds like a tragic story...I even had a user page and stuff...i should use it again. so...is there NOT going to be a SPECIAL astronomicalevent going on on that date? I mean...doesn't mainstream science basically admit that that is a special date astronomicaly?


 * It's quite possible that something fairly interesting astronomical will happen around then, but not as interesting as the doomsayers are trying to make out. If this is the date I'm thinking of, the "planets will all align and cause massive gravitational effects like tides the size of mountains" is more like "roughly half of the planets will be kind of within a 90° wedge shape while the rest will be fairly randomly scattered, with a gravitational effect less than that of a full jumbo jet flying overhead". Confusing Manifestation (Say hi!) 22:33, 30 November 2008 (UTC)

thank u guys, I luv u and wikipedia! :) --Cosmic girl (talk) 00:22, 1 December 2008 (UTC)
 * Not quite a government, but some within the Republican Party are already considering Sarah Palin as a Presidential candidate for that year's election, so make of that what you will from an apocalyptic standpoint. 69.224.113.5 (talk) 00:46, 1 December 2008 (UTC)


 * And who knows, maybe Canada will have Stef Carse as PM by then. And the name of the President of France will be something easier to spell. Then they can go to war over who controls Montreal Nil Einne (talk) 11:10, 1 December 2008 (UTC)

Piperidine,
wat are the effects of absorbing(smoking,eating,ingecting) Piperidine into the blood? —Preceding unsigned comment added by 76.14.124.175 (talk) 02:29, 30 November 2008 (UTC)


 * Our article on Piperidine does not directly answer this question, but it is VERY well referenced. If you find and read those references, you could find more information.  Alternately, here is an MSDS for Piperidine.  Cheers! --Jayron32. talk . contribs  03:33, 30 November 2008 (UTC)

Why not freeze food twice?
Why aren't you supposed to freeze food twice? Here people argue that bacteria in thawed food procreate faster... which begs the question why that should be so. Shouldn't the cold temperature just after taking the food out of the freezer (and the first minutes after putting it back in) be even colder than regular storage temperature and, if anything, slow bacteria down? --Ibn Battuta (talk) 03:19, 30 November 2008 (UTC)
 * When you freeze food, you break cell walls/cell membranes in the cellular structure of the food. This causes 2 problems:
 * Freezing multiple times increases cellular damage, which produces mushier, less palatable food
 * Cellular membranes are actually pretty good barriers against bacteria. When these are broken, and their contents dumped out, it provides a more nutritious medium for bacterial growth.  Thus, thawed food has a greater potential for bacterial growth than never frozen food.
 * Those are probably the best two reasons NOT to freeze multiple times. Fresh food is of course the best to eat; the closer to "alive" it is, the tastier AND safer it is... --Jayron32. talk . contribs  03:31, 30 November 2008 (UTC)


 * "the closer to 'alive' it is, the tastier AND safer it is..." - So I'm sure you eat all your meats raw and never touch baked goods like pastries and cakes? I find your generic platitude rather unhelpful and oversimplified.  Dragons flight (talk) 03:50, 30 November 2008 (UTC)


 * If you take it to mean the time between the death of the animal or plant and the time to cook, all other things being equal, older food will tend to accumulate more bacteria. Of course, some foods (like Blue Cheese... yummmmmmmm) benefit from a healthy dose of microbes.  But given a simple question of whether a slab of meat or an apple or some other unprocessed whole food is safest to eat, it is always safer to eat said food closest to when it is killed (for the animal) or picked (for the fruit).  Over time, microbes will tend to accumulate on the food and, if uncontrolled, will tend to degrade the quality and safety of the food.  --Jayron32. talk . contribs  20:03, 30 November 2008 (UTC)


 * Many people prefer aged beef, which is purposely allowed to go though some degradation. ike9898 (talk) 02:33, 1 December 2008 (UTC)
 * Other things aren't equal though. Cooking and processing food will kill and remove bacteria, which can dramatically improve food safety and longevity.  For many foods, the result is safer than even if you ate the food as fresh as is possible.  For safety, recently killed is usually far less important than how the food has been handled/preserved/cooked since it was killed.  Dragons flight (talk) 20:59, 30 November 2008 (UTC)


 * You are 100% correct. --Jayron32. talk . contribs  02:18, 1 December 2008 (UTC)


 * There was a Straight Dope with a quite detailed explanation about this a couple of years ago, here's the link. Maelin (Talk | Contribs) 04:37, 30 November 2008 (UTC)

grant for study and visit st buddhist temples are over the world
i am interested to know and visit st buddhist temple,any agencies is ready to give grant to vist st buddhist temples?SAJITH 07:33, 30 November 2008 (UTC)


 * Why would someone give grants for that? --Mr.K. (talk) 18:02, 30 November 2008 (UTC)


 * What are st buddhist temples - it looks to me like you are calling Buddha a Saint. Although, I'm guessing English isn't your first language and you meant to type "visit at" when all you need is "visit."
 * As for grants, nobody's going to give you money just to visit. Are you in college? Perhaps you can devise some reason to study such temples, like for a Masters degree. (Or, even as an undergraduate project in some places. See College of Wooster and their Independent Study program, which gives such grants.) It has to be something that is seemed worthy to study. For instance, the architecture of them. Or, for sociology, peoples' habits upon entering. Things like that.
 * However, be forewarned, visiting "all over the world" will be seen as too broad by most, unless you really want to make it like a PhD. thing. Say, for instance, your professor in SOciology learns you want to study how people approach Buddha in different cultures. He or she will suggest something along the lines of people raised in the Orient versus Westerners who convert. And, he or she will expect you to have some hypothesis that you are trying to prove.
 * So, can you get grants to visit temples? Sure, but you're going to have to put a lot of work into it.Somebody or his brother (talk) 02:54, 1 December 2008 (UTC)

Publicly accessible free scientific lectures?
I saw on iTunes U, that I can download some to my ipod and found a couple of them INCREDIBLY interesting! Is there some free website where I can view/hear lectures by respectable scientists talking about new potential discoveries? Most of the ones on youtube are by fakes. I am interested in physics and biology, and am wondering if there are real lectures anymore? or if there is no real audience for that any more and there won't be any faraday lectures like the 1700s.

The only lectures so far which are plentiful and meet this criteria is global warming lectures, but I don't get enjoyment about hearing my 10th lecture on it. I like physics and biology personally, and no disrespect to climate scientists. 65.41.148.101 (talk) 07:53, 30 November 2008 (UTC)


 * Addendum I already know about OCW, and I love it! I am looking for an OCW style (in terms of quality and accuracy and no side-goal of trying to push a POV, but the only goal to educate), geared towards bright inquisitive minds who are temporarily under a 48 hour WoW ban, or similar. 65.41.148.101 (talk) 07:55, 30 November 2008 (UTC)


 * Here you can find some excellent neurobiology lectures. Lova Falk (talk) 12:30, 30 November 2008 (UTC)


 * Ok, these aren't new but you might find these lectures by Richard Feynmann interesting: http://vega.org.uk/video/subseries/8 Jdrewitt (talk) 13:08, 30 November 2008 (UTC)

MIT offers many free online lectures from their courses in a wide variety of departments. Take a look: http://ocw.mit.edu/OcwWeb/web/courses/av/ – ClockworkSoul 07:51, 1 December 2008 (UTC)


 * Also CalTech and JPL have some very good streaming lectures but they don't look podable. Saintrain (talk) 00:05, 2 December 2008 (UTC)


 * I don't see why not. Just save the stream (both VLC and mplayer should be able to handle that although VLC at least won't be able to play the file, and also many more general purpose downloaders that support RTSP) and then convert it (you'd need something capableof support the RV40 codec obviously) to a format the iPod will accept (like MPEG-4 AAC). If the country you live doesn't allow format shifting this may be a violation of JPLs copyrights if they don't allow the practice but that's a different matter. Indeed for audio at least as far as I'm aware if your talking about portable level audio quality there's really no current way you can be stopped from format shifting becausde you can get decent enough quality by using the analog hole. With nearly all computers, this would simply be plugging the analog speaker out into the line in so the loss of quality is not likely to be noticable on a portable device except perhaps to someone with excellent hearing and ear phones. And indeed the vast majority of digital audio formats even those infested with DRM can usually be loselessly converted to an uncompressed wave with the right tools even I think on something like Vista Nil Einne (talk) 10:30, 2 December 2008 (UTC)

Water pressure
Why does water pressure increase with depth. I have the general idea: there's water above pressing down, an analogy with pressing on jello shows why there would be an increase in lateral pressure with depth. But where's the origin of the water pressure that's pushing up on an object in water?


 * See bouyancy. If that article doesn't float your boat, come back and ask a follow-up Q. StuRat (talk) 17:59, 30 November 2008 (UTC)


 * Well, I've read through the article, and I haven't seen anything that really answers my question. I know that bouyancy is caused by this pressure difference, and I know that this is in turn caused by the difference in the weight of water above a point, but I don't get why water pushing down on an object will cause an upward force.


 * At a lower depth, there is more water on top, pushing down. This causes pressure from the top, which in turn squishes the water molecules together, causing the water to be denser. Since the water is denser, it has more bouyancy ability, and thus it is able to float denser objects, as well as cause the water pressure to push on them from all sides, thus squishing them and causing it not to float. ~ A H  1 (TCU) 23:43, 30 November 2008 (UTC)


 * No. Water density doesn't change significantly with depth. You're thinking of a gas.


 * Try this: (as a thought experiment: don't actually do it.) line down on a partially-filled waterbed in its frame, place an empty waterbed mattress on top of yourself, well spread out. Now fill the top mattress with water to a depth of 10cm. do you think you will feel pressure? Why? how much? Why is this different than when the two mattresses contain air? Is the pressure different that what you would feel if you wer wrapped in a dry suit and held 10cm beneath the water surface? -Arch dude (talk) 01:14, 1 December 2008 (UTC)


 * As for why water pressure can push upwards, water resists the compression force exerted by the water above it, just as the ground exerts a normal force that prevents gravity from pulling objects through. The downwards force of gravity equals the upwards force because the water isn't moving; it is in mechanical equilibrium.  --Bowlhover (talk) 04:50, 1 December 2008 (UTC)


 * I think I get it...now for a related question. If I were to construct a hut at the bottom of the ocean, would the water pressure in this hut be the same as the surrounding? Intuition says yes, but wouldn't there not be the weight of the water above pushing on it?


 * If the water can flow through it, then the pressure would be about the same throughout it. However, it would be slightly higher at the bottom of the hut than the top. StuRat (talk) 09:13, 1 December 2008 (UTC)


 * I'm saything that water can't flow through it.


 * OK, if you have a tank at the bottom of the ocean, which has been sealed since it was moved there from the surface, one of three things will happen:


 * 1) The much greater pressure outside will cause the tank to collapse until the pressure is equalized.


 * 2) The tank will collapse somewhat, and subsequently the pressure will increase a bit.


 * 3) The tank is strong enough to resist any significant collapse. This would be easiest with thick metal and a spherical shape that distributes the forces evenly.  In this case the pressure inside would be approximately the same as on the surface.


 * If you had constructed the tank at the bottom of the ocean, then the pressure inside would be the same as the outside, unless you pumped out some of the water inside to reduce the pressure. StuRat (talk) 13:59, 1 December 2008 (UTC)


 * If you constructed the tank at the bottom of the ocean, why would the pressure inside be the same as the pressure outside? Afterall, the weight of the water above no longer has an effect on the water inside the tank.


 * During the construction process the tank would be open, and the high pressure water would flow in. You would then need to remove most of it to lower the pressure to that at the surface. StuRat (talk) 00:45, 2 December 2008 (UTC)


 * (deindent) As StuRat said, the water is exerting significant pressure at any depth beyond a few feet. In fact, as all SCUBA divers learn, every 33 feet you end adding 1 more atmosphere's worth of pressure - 14.7psi.  Lets say our hypothetical structure is at 66 feet under water.  At this point the water is pressing in with 44 psi (2 atmospheres worth of water + 1 at sea level).  If the internal pressure is equivalent to sea level then the net pressure is 29.4psi.  You could deal with that pressure one of two ways - 1, increase your internal pressure until the net difference is 0 or 2, build your structure to handle that force. 29 pounds might not sound too bad, but that ends up being over two tons per square foot.  It really is a huge amount of pressure.  It can be done, (subs, for instance) but it has it's disadvantages.  So why not increase the internal pressure? Well, that can be done but you end up introducing concerns with nitrogen narcosis and decompression sickness. Both can be dealt with ( see underwater welding. ) ---J.S  (T/C/WRE) 22:01, 1 December 2008 (UTC)
 * See Caisson (engineering) - example of a pressurized underwater structure. -J.S (T/C/WRE) 22:46, 1 December 2008 (UTC)

Thoughts, feelings and reality.
I'm not completely sure if this belongs in the science section, but nonetheless I'm looking for a scientific answer. I was just wondering, can thoughts influence or alter reality? For instance, let's say I'm going to do an exam and I think I will fail, will the probabilities of approving the exam change? Similarly, can feelings influence or alter reality? Note that I'm talking about reality, not the perception of reality. Thanks in advance. ― Ann ( user 12:09, 30 November 2008 (UTC)
 * Would self-fulfilling prophecy be an answer? And for an answer from me personally: yes, absolutely. Thinking you will fail an exam, can cause stress which leads to certain reactions in your body (and already on this level, thinking has changed reality, because the body now shows a number of physical reactions, such as a higher heart rate, muscular tension, faster respiration etc), which can influence how you perform on your exam. One of the results of stress mentioned in the article on stress is an inability to concentrate, and that would make it less probable that you pass the exam. Lova Falk (talk) 12:24, 30 November 2008 (UTC)
 * Thinking you will fail an exam can also cause learned helplessness, which in turn may lower the amount of effort you put into it. --82.21.25.219 (talk) 12:26, 30 November 2008 (UTC)
 * I see your point. Homever, those are reactions caused by the thoughts, not the thoughts themselves. Perhaps I phrased my question poorly, but I'm specifically asking about the thoughts. Let's suppose that I think I will fail such exam, but I don't feel stressed, my heart rate is fine, my respiration is normal, etc. Could reality be influenced or altered simply by mere thoughts? ― Ann ( user 13:59, 30 November 2008 (UTC)
 * In the sense that you're asking, no, science has no evidence to support telekinesis or other mind-alters-world phenomena. Absence of evidence is not evidence of absence and all that, but there have been plenty of opportunities to validate such claims and they've all struck out. &mdash; Lomn 14:21, 30 November 2008 (UTC)
 * Surely absence of evidence is evidence of absence. Maelin (Talk | Contribs) 14:30, 30 November 2008 (UTC)
 * No, it's not. We have an absence of evidence that there is extraterrestrial life elsewhere in the universe, but that's more a statement about the difficulties of collecting such evidence than it is that there isn't any out there. --98.217.8.46 (talk) 17:46, 30 November 2008 (UTC)
 * If you have an absense of evidence, then you have evidence of absense existing ;) —Cyclonenim (talk · contribs · email) 19:43, 30 November 2008 (UTC)
 * If you're referring to thoughts effecting anything other than the person with those thoughts, and not indirectly through said person, it's technically possible thanks to the butterfly effect, but what actually happens has no relation to what you were thinking. It will tend to be something equally unsurprising as what would have happened. By the way, conspicuous absence of evidence (i.e. absence of evidence when evidence would be expected) is evidence of absence. — DanielLC 16:43, 30 November 2008 (UTC)
 * This seems like an interesting answer. Now you have my curiosity sparked. Could you please explain this a little further, particularly regarding how it would work? ― Ann ( user 17:09, 30 November 2008 (UTC)
 * Also, if a tree falls in a forest... ~ A H  1 (TCU) 23:39, 30 November 2008 (UTC)

To me it seems confusing to separate thoughts and reality. Thoughts are real and have influences, causing an "alternate" reality compared to not having those particular thoughts. Exactly what effect they have is another question, and depends on many factors. But as to whether thoughts have an effect on reality--of course they do, they are part of reality. The question strikes me as a bit odd--doesn't reality include your thoughts, feelings, perceptions, and so on? Don't these influence your actions? Don't your actions influence the world around you? In short I don't understand the difference between the question "can thoughts influence or alter reality?" and the statement that some things, like stress, are reactions "caused by the thoughts, not the thoughts themselves." It sounds like you are asking whether thoughts can alter reality without causing any reaction to happen. How can there be an effect without a cause? Pfly (talk) 07:36, 1 December 2008 (UTC)

Instituto Conmemorativo Gorgas
How could I link Instituto Conmemorativo Gorgas to other pages like the one on William Crawford Gorgas and pages related to infectious diseases of the tropics, publica health and history of medicine?

Jorge Motta, MD, MPH


 * Like this: William C. Gorgas. --Cookatoo.ergo.ZooM (talk) 18:46, 30 November 2008 (UTC)


 * You need to go into "edit" to see what was done there, which is this:, double square brackets surrounding the article name.  Sp in ni  ng  Spark  18:56, 30 November 2008 (UTC)

Is it correct to say this (see below)?
Let's say that I want to know how to determine the gravitational force on the Earth due to another massive body. Isn't it then correct to say, "To weigh the earth, the gravitational force experienced by the Earth due to another massive body is measured"? 203.217.34.128 (talk) 16:28, 30 November 2008 (UTC)


 * To strictly describe the force attracting the Earth to the other body, yes. However, you would also want to determine the force attracting the other body to Earth, in order to determine the acceleration of the two bodies toward each each. StuRat (talk) 17:55, 30 November 2008 (UTC)


 * 1) Newton's third law says the force attracting the other body to Earth is equal in magnitude and opposite in direction to the force attracting the Earth to the other body.
 * 2) If you use the term "weight" to describe the attraction between the Earth and, for example, the Sun or the Moon, then I would say there is scope for much confusion here, as the Earth simultaneously has many different "weights". "Gravitational force" or "gravitational attraction" would be better terminology. Gandalf61 (talk) 19:58, 30 November 2008 (UTC)

Leaking batteries
What is the white crystalline stuff that leaking AA batteries sometimes leave behind and what is the best way to remove it from the appliance, e.g. is it okay to use a mild solvent?--Shantavira|feed me 16:53, 30 November 2008 (UTC)


 * If it is regular alkaline batteries you are using, the electrolyte is potassium hydroxide and the white crystals are compounds that this alkaline chemical is forming with the metals (often copper) that it is attacking. I would recommend chipping off the larger pieces with a small screwdiriver or other tool and then polishing the battery contacts with a fine abrasive, I use a fibreglass pencil.  You can use an electronics solvent such as Electrolube's ECSP to clean up any electrolyte on the circuit boards.  If it is a bad attack there is a good chance that the corroded battery contacts disintegrate or break off while you are cleaning them and you will have to replace them.  It is likely in any case that the protective plating on the contacts has been corroded away and they are more likely to oxidize and give you problems in the future (you will have to clean them now and then).  A lot of Q&A sites, such as this one from Hewlett Packard recommend a 50:50 solution of water/white vinegar.  This makes sense chemically as the acetic acid in the vinegar will tend to counter the alkaline electrolyte but I would not recommend it.  Anything acidic being splashed around inside electronics is likely ot result in further damage if you do not take extreme care.  Sp in ni  ng  Spark  18:38, 30 November 2008 (UTC)


 * Interesting. Thank you.--Shantavira|feed me 08:57, 1 December 2008 (UTC)

Medical opinion (but not advice)
After seeing the picture below on the local news (in Spanish) about the burns of an Afghan girl, I was wondering: are this injuries recent or is the picture after a ´healing´? Is there any chance that this girl will have a somehow normal skin? (link: here, disturbing image!)--Mr.K. (talk) 18:23, 30 November 2008 (UTC)


 * I'd say those pics are after healing. It may be possible to restore an approximately normal appearance with a series of skin transplants, but this is well beyond the scope of what the average Afghan family can afford. StuRat (talk) 19:42, 30 November 2008 (UTC)
 * I'd say they're in the late stages of healing, judging by the fact there are still some scabs there. However, some of what appears to be scabbing may actually be an infection, hard to tell from the image. Anyway, StuRat has it about right. Skin grafts could reduce the image and help restore a normal look but it'd be difficult to make it anywhere near perfect, and Afghans cannot usually afford such operations. —Cyclonenim (talk · contribs · email) 20:19, 30 November 2008 (UTC)

Telling sunrise from sunset
Let's say I have a color photo where the sun is on or near the horizon, and I don't know anything about the time it was taken or the surrounding terrain which would allow me to tell if this is a sunrise or a sunset. Is there a way to discern which it is from the lighting or color of the sky alone? 69.224.113.5 (talk) 18:24, 30 November 2008 (UTC)


 * If all the people in the picture are still drinking then it is sunset. If they are laying unconcious on the beach or look like they have a hangover, then it is sunrise.  For a serious answer, there is a daily change in the F layer but the change is only visible at radio wavelengths, as far as I know there is no effect on the visible spectrum.  There might possibly be meteorological clues, but I leave that to a met expert to answer.   Sp in ni  ng  Spark  18:53, 30 November 2008 (UTC)


 * According to sunset:
 * "The sunset is often more brightly colored than the sunrise,[citation needed] with the shades of red and orange being more vibrant. The atmosphere responds in a number of ways to exposure to the sun. In particular, there tends to be more dust in the lower atmosphere at the end of the day than at the beginning. During the day, the sun heats the surface of the Earth, lowering the relative humidity and increasing wind speed and turbulence, which serves to lift dust into the air. However, differences between sunrise and sunset may in some cases depend more on the particular geographical features of the location from which they are viewed. For example, on a west-facing coastline, sunset occurs over water while sunrise occurs over land."
 * Also see the previous discussions at and .  Ignore the last answer in the first link; even the rising or setting Sun can completely overwhelm light pollution.

On a completely irrelevant answer, ignoring the color of the sky, if you used a digital camera to EXIF data can probably give you a 'time taken'. —Cyclonenim (talk · contribs · email) 20:16, 30 November 2008 (UTC)

One more difference: mirages of the Sun occur more frequently during sunrise than during sunset because they can only exist when the layer of air above the surface is hotter than the overlaying air. --Bowlhover (talk) 20:02, 30 November 2008 (UTC)

A similar question was once asked on Talk:Sunrise, but I'm not sure the responses there are much help. -- Coneslayer (talk) 17:10, 1 December 2008 (UTC)


 * If you can upload the picture somewhere we can take a look. Might be other clues in the picture. -J.S (T/C/WRE) 21:02, 1 December 2008 (UTC)


 * There are a numer of ways that you may be able to discern north and hence use the fact that sun rises in the east and sets in the west. Firstly stars, if you can see an identifiable constellation.  Prevailing winds have characteristic directions, which may provide other clues.  Similarly, you can often discern the north side of hills (in the northern hemisphere) because they have more snow and/or less vegetation.  Buildings are sometimes oriented south or north (to gather/avoid sun) depending on the location.  If you know the date, you may also be able to use the presence of Venus or the moon in the sky near the sun and calculate its expected position, though I'm not sure about the mathematics.  There are also other clues for time, e.g. plants which flower at particular times of day, signs of human activity, maybe animal behaviour.  Individually, these may be comparatively rare things to see in photos, but I'm sure people can thing of other factors. --Maltelauridsbrigge (talk) 16:16, 2 December 2008 (UTC)

Where does today end and tonight begin ?
Weatherforecastwise, that is. 6 PM ? StuRat (talk) 20:43, 30 November 2008 (UTC)
 * I don't think there is a rule for this. 6pm is plasuible. Dusk is another good choice. I think it is just casual expression. -- SGBailey (talk) 22:35, 30 November 2008 (UTC)


 * Sunset would be a good guideline. Add 30 min fudge factor either way and you should be a-ok. -J.S  (T/C/WRE) 02:00, 1 December 2008 (UTC)


 * This is an unsupported personal understanding, but I always assumed that morning was 6:00 AM - 12:00 Noon; afternoon was 12:00 Noon - 6:00 PM, evening was 6:00 PM - 12:00 midnight, and overnight was 12:00 midnight - 6:00 AM. Day(morning + afternoon) is thus 6:00 AM - 6:00 PM and night(evening + overnight) is 6:00 PM - 6:00 AM.  --Jayron32. talk . contribs  02:17, 1 December 2008 (UTC)


 * I have found myself saying "good evening" when at the start of an evening activity, even if it starts in what would be afternoon normally. (Say, a church service starting at 5 PM, saying it a few minutes before.) However, I think that's because it is unusual, to me at least, to say "good afternoon."


 * However, if you are looking at a technical definition, I would say dusk is the most likely, because unlike the definite AM and PM, evening is more of a state of mind. And, in the witner, at least to me, if it's 6:30 PM it can feel like 10:00 at night. Like Yogi Berra said once, "It gets late early out there." Just like, psychologicall, if a person has been up all night studying, there doesn't feel like there's been a break between night and the next day; they might say "good evening" to the guy delivering pizza at 1 AM even though, technically, it's "good morning."Somebody or his brother (talk) 02:45, 1 December 2008 (UTC)


 * I don't think I would usually describe 6pm as night unless it's rather dark. Perhaps it's because I grew up in Peninsular Malaysia which is in the UTC+7 timezone but uses UTC+8 so it isn't even close to being dark at 6pm and here in Auckland it seems to be getting dark way to early during winter. Agree dusk or around sunset time is a more likely definition although I guess that's somewhat problematic near to the poles where I think people would still consider there to be a night time and a day time even if it doesn't get dark or is forever dark Nil Einne (talk) 10:51, 1 December 2008 (UTC)


 * In calculations for working out the Jewish calendar, the day begins at 6.00 p.m. Simonschaim (talk) 09:26, 1 December 2008 (UTC)


 * Not sunset?? —Tamfang (talk) 19:34, 4 December 2008 (UTC)


 * In the UK all the newspapers used to publish daily "lighting up times", this used to be shown in calendars too. No one seems to bother any more but the Royal Observatory website still shows the details, basically half hour after sunset.  Sp in ni  ng  Spark  11:44, 1 December 2008 (UTC)


 * There is also the definition of three different versions of twilight at the bottom of that page.  Sp in ni ng  Spark  11:47, 1 December 2008 (UTC)


 * Why would the general public need to know when streetlights come on each day? Was each streetlight formerly a responsibility of the nearest resident or shopkeeper? —Tamfang (talk) 19:38, 4 December 2008 (UTC)


 * I work at a television station in the US. When promoting our own programs, we use "today" for programs starting up to and including 5:30pm and "tonight" for those starting at 6:00pm or later. Thomprod (talk) 17:55, 2 December 2008 (UTC)


 * @Tamfang: 'lighting-up time' refers to lights on vehicles. --ColinFine (talk) 23:32, 5 December 2008 (UTC)


 * I'll bet it had an entirely different meaning at Woodstock. StuRat (talk) 01:38, 7 December 2008 (UTC)

Distortions of sunrays and starlight by atmosphere: what can we conclude?
If Earth did not have an atmosphere surrounding it, the photons from the sun ("sunrays") and the stars could hit the ground unobstructed, traveling in a straight line from celestial light sources to Earth. However, the atmosphere is a mix of gases (oxygen, nitrogen, etc.). If I picture the atmosphere's molecules as tiny billard balls floating about in space and the photons as bullets mostly whizzing past the billard balls but sometimes getting absorbed by or ricocheting off them... what can I conclude about the density of the atmosphere. Most photons must be getting through unobstructed otherwise a glance at the sky would seem like seeing underwater with your eyes open or seeing nothing at all.

Does the degree of visual acuity, or lack of it, permit an extrapolation of the number of molecules in a given volume of air? Would that be easier to do in the daytime or at night, gauging the blurriness of stars? What data does one need to do the extrapolation -- for an example, is there such a thing as a cross-section of an O2 molecule? Is it possible to conclude that out of 3x106 photons, 2x106 (grabbing a number out of thin air -- sorry for pun) will get through to my retina unimpeded?--Goodmorningworld (talk) 23:20, 30 November 2008 (UTC)


 * There are really two factors at play: Rayleigh scattering and astronomical seeing. The first covers most of what you are discussing and addresses in general the ability of molecules to scatter light.  For example you could measure the ability of the atmosphere to scatter light by comparing the intensity of direct sunlight to the intensity of blue sky.  That, plus some other assumptions could get you a density estimate.  However that bulk scattering is not the principle source of the blur or twinkling in stars which arises mainly due to atmospheric turbulence.  Dragons flight (talk) 00:22, 1 December 2008 (UTC)


 * Indeed there is an entire field, called aeronomy, which is the study of the atmosphere (and sometimes, the ionosphere, by proxy). The typical methods involve passive observation or active stimulation of the various layers of atmosphere (see ionosonde, LIDAR), seeking specific physical or chemical indications for various processes at a given layer of atmosphere.  Not only can the density be calculated, but species can be determined (i.e. "How much Oxygen?  How much O+ ion?  How much Ozone?").  The standard techniques rely heavily on absorption spectrometry but the field is fairly mature and a lot of specific techniques have been explored.  Nimur (talk) 21:34, 1 December 2008 (UTC)
 * Thank you, both of the respondents above, for the useful links. Is it possible for you to give me a ballpark figure as to what percentage of photons coming from the Sun travel in a straight line until they hit the ground (or my retina), conversely, what percentage get absorbed or refracted by the atmosphere?--Goodmorningworld (talk) 12:34, 2 December 2008 (UTC)

Cough-induced abdomenal reflex
During medical examinations, in addition to testing for the knee jerk reflex, sometimes they test for this thing where they ask you to cough, and listen with the stethoscope for some kind of reflex in your abdomen at the places where I imagine your ovaries would be (except I'm male, so I don't have any ovaries). What's this phenomenon called? Is there an article on it? Cough reflex doesn't talk about it; and none of the other ones on the list of reflexes seem to be relevant. Also, what is the place they are listening to called? --71.106.183.17 (talk) 22:46, 30 November 2008 (UTC)


 * I don't know of an exact match for what you describe. In examining a man for evidence of inguinal hernia, one can insert a digit into the inguinal canal and ask the patient to cough (or bear down - the goal is to increase intra-abdominal pressure).  If one feels pressure at the fingertip, then a defect in the abdominal fascia may be suspected.  If scrotal contents are enlarged and inguinal hernia is suspected, one may listen over the scrotum for bowel sounds (which should normally be absent).
 * Alternatively (no coughing involved in these) when renovascular hypertension, aka renal hypertension is suspected one may listen over the renal arteries for a vascular sound or bruit that would suggest renal artery stenosis (can you believe what a wiki-mess this is?). Similarly, one can listen for bruit over the inguinal ligaments when vascular disease of the iliac or femoral artery is suspected. --Scray (talk) 23:03, 30 November 2008 (UTC)


 * The inguinal canal seems to be totally internal to the body. How can you "insert a digit into the inguinal canal'? Or is "pressing on the skin near the inguinal canal" what is meant?


 * What diameter approximately is the inguinal canal?


 * Are new internal body parts still being discovered? When I went to school, there were heart, lungs, liver, kidneys, stomach, gall bladder, appendix, and tonsils. Some people had "intestines", but that was a lower class thing.  And that was it.  Now practically every time I read this Reference Desk, some other internal body part crops up.  It's getting out of hand.


 * CBHA (talk) 06:46, 1 December 2008 (UTC)


 * (regarding the inguinal canal) In men, the scrotum provides loose skin and a path for a finger to reach the inguinal canal. The diameter is between 1 and 2 cm.
 * (regarding body parts) Just about everyone has intestines - even upper-class people. --Scray (talk) 12:21, 1 December 2008 (UTC)
 * Inserting a finger into the inguinal canal would be rather painful (for the recipient, and a rather tight squeeze for the probing finger). Axl  ¤  [Talk]  10:46, 2 December 2008 (UTC)
 * It is not usually painful when done by a doctor, but can be uncomfortable. --Scray (talk) 12:21, 2 December 2008 (UTC)
 * The doctor does not insert his finger into the canal. He places his fingers over the superficial inguinal ring in order to feel pulsation from a hernia. Axl  ¤  [Talk]  19:48, 2 December 2008 (UTC)
 * About which doctor are you speaking? All doctors?  Take a look at point III.C. here: . Perhaps you should not be so dogmatic. --Scray (talk) 05:02, 3 December 2008 (UTC)
 * The (normal) external inguinal ring is relatively narrow and contains structures that don't easily compress or move out of the way. It is not possible to push a finger through the ring. It would require a lot of force, be painful for the patient, and damage the ring itself. FPNotebook states: "Gently insert finger into canal along spermatic cord". This is misleading, because it is not possible to insert a finger into the inguinal canal. The diagram here shows what happens when the doctor tries to push into the inguinal canal: the whole ring is pushed up towards the abdomen, and this is particularly uncomfortable if not painful. Macleod's Clinical Examination (11th edition, p. 175) states "Palpate the external inguinal ring and posterior wall of the inguinal canal for possible muscle defects. Ask the patient to cough and feel for any impulse. Ask the patient to lie down and see if the hernia reduces spontaneously. If so, press with two fingers over the internal inguinal ring at the mid-inguinal point and ask the patient to cough or stand up while you continue to press over the internal inguinal ring and see if the hernia reappears." Hutchison's Clinical Methods (22nd edition, p.133) states "Push gently upwards from beneath the neck of the scrotum with the index finger, but do not invaginate the neck of the scrotum as this is painful." Both of these textbooks as classic medical student texts in the UK. Axl  ¤  [Talk]  09:40, 4 December 2008 (UTC)