Wikipedia:Reference desk/Archives/Science/2006 October 23

=October 23=

The "Wholly Grail".....
Let`s talk about the Wholly Grail if we could, for a bit. More specifically, Virtual Particles. You know, those "pesky" electron-positron pairs that are alleged to exist at this level. My understanding of these 'alleged' particles is that they don`t exist long enough to be REAL...i.e. they exist for shorter than a Plank second, therefore, don`t REALLY exist at all. This could bring Hawking Radiation into question. I have, I think, a VERY interesting follow-up to this but I`d like to 'hear' everyones` ideas about these 'alleged' existances first, for fear of sounding a fool. Please, no jokes! TY Dave 205.188.116.74 00:27, 23 October 2006 (UTC)
 * Is your spelling of "Wholly" meant as some sort of pun? If so, I don't get it--64.12.116.74 01:17, 23 October 2006 (UTC)
 * Also, may I suggest, if you want to sign with a name, sign  name , that way the name stands out more than with  name ~ --64.12.116.74 01:22, 23 October 2006 (UTC)
 * I didn`t want to include a spiritual or religious connotaion. You can call it "Holy", if you want, but I`m strictly aiming towards science. There was no pun intended, to answer your question. I have no clue what the person is talking about in regards to "signing", sorry. Please keep to the main subject. Dave 205.188.116.74 01:29, 23 October 2006 (UTC)
 * I too am utterly confused about the title. Since when is wholly an adjective? As for the question itself (which, funnily enough, has no question mark anywhere), who ever said virtual particles were real? I'm sure by Plank second you mean Planck time, but virtual particles can exist much longer than the Planck time (it depends on their rest energy: the more energy they have, the less time they can "get away with it", according to the uncertainty principle for energy and time). Anyway, how does any of this "bring Hawing Radiation into question"? —Keenan Pepper 04:42, 23 October 2006 (UTC)
 * First, will you folks please drop the "Wholly" already? It`s amazing how often you JUMP on someone over a single word, completely forgetting/ignoring the question/comment! Sheesh! Second, who said it was a question?..."Let`s talk..." Third, I DID say, ""MY" understanding of...". Perhaps I was wrong there...forgot about energy/time. Fourth, assuming I was correct, just for an instant, perhaps a Plank second even,(the tiniest piece of Plank Time, thought you`d get that!) if virtual particles didn`t "last" long enough to be 'seen' by Gravity, then that would CERTAINLY put Hawking Radiation into question! I guess I`ll save my VERY interesting follow-up for when I have some more-interested listeners/readers. Any thoughts about Vacuum Genesis? Thanks, Dave 152.163.100.74 05:49, 23 October 2006 (UTC)


 * The Reference Desk is not a soapbox, bulletin board or chat channel. It is meant for asking questions to which you could not find an answer. --Lambiam Talk  10:42, 23 October 2006 (UTC)


 * That question is crackpot physics. Hawking radiation is due to virtual particles. There's nothing 'holy grail'ish about virtual particles - they're a well-understood part of mainstream physics, unlike the question which doesn't seem to have understood any of the terms it's using: Planck time is an unrelated concept to virtual particles. You can have a virtual particle for as long or short time as you want. --83.145.46.141 14:06, 23 October 2006 (UTC)

How gyrocompasses work
After reading the gyrocompass article, I spent a long time trying to figure out how it works. The article describes 2 types of gyrocompasses: the first kind is filled with fluid, while the second kind has weights that pin down its gyroscope.

I pretty much understand how the first kind works. However, according to the article: "This friction force caused by the fluid results in a torque acting on the axis, causing the axis to turn in a direction orthogonal to the torque (that is, to precess) toward true North (to the North star)". Is the torque applied in the direction opposite to the direction the axis is travelling in? If so, how will this torque cause the axis to move toward the north star?

I have no idea how pinning down a gyroscope's axis will cause it to point north. Shouldn't it point east, because that's where the stars rotate around the celestial north pole as much as they do around the celestial south pole? Can someone explain what I'm missing here? --Bowlhover 01:52, 23 October 2006 (UTC)


 * The gyroscope's axis points north, the gyroscope spins around its axis. It points north because it is aligning it self with the earths rotation, the earth also rotates around an axis which points north. This might give you a broader insight: equatorial mount. Vespine 06:40, 23 October 2006 (UTC)


 * I know that, but how does it align itself with Earth's rotation? --Bowlhover 15:37, 23 October 2006 (UTC)


 * Because that is the only orientation where the gyroscope's axis will not experience a change to its angle due to the rotation of the earth. Hold a pencil vertically and then spin around with your arm out, if your friend looks at the pencil, it will look like it is pointing in the same direction while you are spinning. If you hold the pencil on an angle from vertical, the place where the pencil is pointing will change as you turn. You could do this with an actual gyroscope instead of a pencil and feel the actual force involved.Vespine 01:05, 24 October 2006 (UTC)


 * I don't think I've made myself clear enough. So, here is what I do and don't understand:


 * The gyroscope is spinning around its axis. Right now, its axis is pointing toward a certain part of the sky.  Earth is changing its velocity by rotating, but the gyroscope tries to resist this change in velocity (due to Newton's first law of motion).  As the result, the axis will point to the same piece of sky relative to the stars.  This "piece of sky" will rotate around Polaris in a counter-clockwise direction, just like the stars do.


 * Since the gyroscope's axis is rotating around Polaris in a circle, it will rarely point directly north. As a result, torque has to be applied to decrease the size of this circle (i.e. force the axis toward Polaris).  My question is:  how will submerging the axis in a fluid force it toward Polaris?  --Bowlhover 04:29, 24 October 2006 (UTC)

Mercury and Fillings
Can mercury from a 30 to 40-ish year old filling come out and be hazardous to you health? Deltacom1515 02:09, 23 October 2006 (UTC) 02:05, 23 October 2006 (UTC)
 * Current research and the accepted beliefs of dental health organizations hold that dental amalgam fillings do not harm your health. - Dozenist talk  02:10, 23 October 2006 (UTC)


 * Its not done me any haarm yet >Harr, Haa HAAA haarrr!! HHAAAAA!!! HAAAAAr haarrrr!. Where is that hatter? See mercury--Light current 02:13, 23 October 2006 (UTC)

It's believed to not be harmful. Although i'd say most people who've encountered mercury in a chem lab would have doubts about that statement. We actually have an article on this, take a look Dental amalgam controversy -- `/aksha 02:30, 23 October 2006 (UTC)


 * No one is disputing the effects of raw mercury. What is at question is the safety of amalgam in fillings. 8-)--Light current 02:39, 23 October 2006 (UTC)


 * .....amalgam's contain mercury. -- `/aksha 02:56, 23 October 2006 (UTC)


 * Correct.... amalgamated with other metals and therefore not RAW! Read my original post again.--Light current 03:14, 23 October 2006 (UTC)


 * Yaksha, I certainly do not see mercury in a chem lab ever, but I work with amalgams frequently. To repeat, amalgam fillings are not considered harmful. - Dozenist  talk  03:19, 23 October 2006 (UTC)
 * Salt is not harmful, even though pure chlorine and sodium are extremely harmful. Just because the original subsituents are harmful, does not mean the compound/alloy is. Generally, the more reactive (and therefore, usually the more dangerous) a chemical, the safer the compounds they create. If they release a lot of energy in a reaction, it is not easy to reverse the process. --liquidGhoul 12:09, 23 October 2006 (UTC)
 * The question was about "Can mercury from a 30 to 40-ish year old filling come out". Amalgam isn't meant to be harmful. It's believed the mercury doesn't do anything funny. But if the mercury came out? That's the point. And my comment about the chem lab was meant to be a joke. (Although i can't really imagine why a general chem lab wouldn't have some mercury somewhere, it's not that usual. Even my high school chem labs had it, never worked out why though, it's not like they ever let students near it...) The link to the Dental amalgam controversy was meant to be my answer. The article explains it all. -- `/aksha 14:02, 23 October 2006 (UTC)

Archiving
''This section has been moved to Wikipedia talk:Reference desk. --hydnjo talk 00:20, 24 October 2006 (UTC)

Different roles for insects in a hive/nest
Hi - this might be a silly question, but can someone tell me the entomological term for the different types of members of, say, an ant nest - the soldiers, the workers, the queen - they're not separate species, of course; are they separate subspecies? - phenotypes? - breeds? - what's the correct word here? Thanks Adambrowne666 02:42, 23 October 2006 (UTC)


 * I don't know what they are. But i do know they're not seperate subspecies or breeds. It's not to do with genotype/phenotype either. Insects, especially community insects like bees and ants, commonly have permanent gene loss during development. So your queen and your soldier ant could have almost the same genes, it's just that the soldier ant losses a part of its genome permanently during development. Where as the queen keeps all the genes, obviously...since the queen does the reproducing. I'd assume different 'classes' in a nest are due to different genes lost, since all ants within one nest/community have very similar genetically. -- `/aksha 02:55, 23 October 2006 (UTC)


 * They're called castes. - Nunh-huh 04:02, 23 October 2006 (UTC)


 * Effectively, they're just different genders. In a honeybee colony for example, the queen is female, the workers are infertile females (they have under developed ovaries, and can't mate, being inhibited by the influence of an existing queen) and the drones are males.  The same is true of the ant colony (in this case, queen, worker, soldier respectivally). M a rtinp23 23:03, 23 October 2006 (UTC)


 * In fact that's true for bees, but not for ants. There are female and male soldiers, workers etc., but they are all infertile. --84.166.249.224 14:47, 29 October 2006 (UTC)


 * In case you're interested, there is only one queen in a honeybee colony, and she lays eggs which hatch into workers and drones. The difference between the two eggs is that the worker one is fertilised with sperm from a drone, and the drone egg isn't.  Therefore, interestingly, the males have no father in a honeybee colony.  To produce a queen, an egg is laid fertilised, like that for a worker, and is fed on an enriched diet of Royal Jelly, allowing her ovaries to fully develop.  The queen mates once in her life with around a dozen drones from different colonies (who die after impregnating here) and she stores the sperm for the rest of her life (up to 5 years) within her body.  :) M a rtinp23 23:03, 23 October 2006 (UTC)

Castes! Of course! Thank you very much. Adambrowne666 23:07, 23 October 2006 (UTC)

how may calories are in... me?
To start.... this is NOT A MEDICAL QUESTION. I do not intend to be eaten or eat myself. I am purely curious about this matter.

I am very curious about how many calories there are in me. I am a 5'1" 140lbs woman with a 32% body fat percentage. (I know, I know, I need to lose weight). This means that my "lean body mass" is appx 96 pounds. It would be easy enough to add together the calories of 96 pounds of say, ham, and 44 pounds of pure fat, but there is the issue of bones, hair, brains, teeth, fingernails etc. I am assuming that my organs will not be eaten (although it would be interesting to find out how many calories are in a human kidney or liver). So is there any way to find out what is the weight of my muscle, or non-soft-tissue? All help is appreciated.

PS: Is it legal to eat myself, say, if I am wearing a mask? What about a red mask? ;) 74.117.47.205 03:20, 23 October 2006 (UTC)


 * We have a dog and four cats and they seem to be trying (to eat themselves) on a daily basis and without masks. I don't know about the calorie part as they seem to neither lose nor gain weight. ;-)  --hydnjo talk 04:13, 23 October 2006 (UTC) addendum: If you want to do the math, one pound of fat equals about 3500 - 4000 calories (actually it's kilogram calories or kcals) and one pound of muscle (meat) equals about 1600 - 1900 calories (using the same colloquial term). Water makes up a significant part of your body weight (about 70 pounds in your case) so you'll need to subtract that out. Also, so as to confound your calculations even further, your 32% body fat percentage may include some of the water weight as does the muscle (meat) weight. All in all, your body properly preserved and so on. should provide enough sustenance for one person for several weeks however I would suggest including some vegetables and fruits for a balanced diet.  ;-)  --hydnjo talk 04:50, 23 October 2006 (UTC)


 * I'm not sure what you are trying to get at. If all you care about is the total amount of energy within your body then a calorimeter should be used. Ideally, we put you into the "large" calorimeter and burn you alive and measure the total amount of heat release. Short of that, we use a cadevar in a body similar to yours and burn it instead. 202.168.50.40 04:27, 23 October 2006 (UTC)


 * Do bones have calories? What about hair, cartilage, eyeballs etc? I am not talking about my body as a whole, but rather the parts of my body that a human would consume if he were to eat me. 74.117.47.205 04:34, 23 October 2006 (UTC)

Since you weight 140 lbs, your body mass has about $$5.70735888 \times 10^{18}$$ joules of energy on it (E=mc²), which gives $$1.36409151 \times 10^{15}$$ kcal. Good luck on losing that. :) ☢  Ҡ i∊ ff   ⌇  ↯  04:31, 23 October 2006 (UTC)
 * Umm, don't forget to subtract out the water and bone (hair, nails etc). --hydnjo talk 04:55, 23 October 2006 (UTC)
 * That's if you made her into an atom bomb... --Wirbelwind ヴィルヴェルヴィント (talk) 05:23, 23 October 2006 (UTC)
 * Wow! I sure would like to get the concession rights for that one. Step right up ladies and gentlemen ... --hydnjo talk 05:46, 23 October 2006 (UTC)
 * Atom bombs work by exploiting the mass defect between different atoms to create its energy. Atom bombs are far less potent than the energy amount quoted above. That amount of energy (e=mc2) could only be released if you annihilated every atom (e.g. with an anti-person).Richard B 23:13, 23 October 2006 (UTC)


 * Fat and muscle contain water, I dare say that the kcals figure quoted above includes that water, it isn't kcals of "dehydrated muscle or fat". So I don't think you subtract the water from the calculations.... As far as "edible" goes, most of the body would be and have some sort of nutricius value, as far as eyeballs, cartilage, kidneys, lungs, brains. About the only thing I think isn't digested is teeth and hair, you'd have trouble eating the bones, but you would digest them, if you were to grind them up for example.Vespine 00:42, 24 October 2006 (UTC)

Feral Horses of the World?
Hi, I've been trying to research feral horse populations, but haven't been able to find many, just the well-known ones. I.E. Sweden's Gotland Pony or North Carolina's Corolla "Wild" Horse/"Banker Horse". (The only true wild horse is the Przewalski's Horse.) Can anyone point me to a good site/book that lists feral horses of the world? If not, could I please put in a request for such an article? Thanks in advance:) —The preceding unsigned comment was added by StandardSmiley (talk • contribs).


 * The horse section of feral suggests that there are hardly any real wild horses, so any horses in the wild are likely to be feral. Confusingly, the wild horse article uses the term 'equus ferus'. But I don't really know anything about the subject. I'm just doing your work for you, looking it up in Wikipedia. Note, btw, that feral horse simply redirects to 'horse'. As for requesting an article, you can do that at Requested articles. I have never done that, so I don't know how successfull such a request might be. DirkvdM 08:21, 23 October 2006 (UTC)
 * The confusing thing is that a Latin word meaning "wild beast" has been given a rather more specialized meaning when applied to animals; specifically: domesticated animals having reverted to a "non-domestic lifestyle". Equus ferus is simply classical Latin for "wild horse". When your compatriot Pieter Boddaert introduced the scientific binomial name, the word in English just meant "wild", "savage". --Lambiam Talk  09:29, 23 October 2006 (UTC)

Chlorinated water and eye damage.
Would my eyes be damaged from exposure to chlorinated water for 20-30 minutes a day? I often swim with my eyes open, and haven't noticed any damage to my sight in the six months I've been swimming, but wanted to make sure. —The preceding unsigned comment was added by 202.10.86.63 (talk • contribs).


 * I assume you've read the medical disclaimer, so I'll skip the lecture. Swimming pools are "chlorinated" with hypochlorite salts like sodium hypochlorite (a.k.a. chlorine bleach). A quick search on Google Scholar for cornea hypochlorite damage doesn't turn up anything worrying. It causes "irritation" (duh), but I don't see any mention of long-term damage. —Keenan Pepper 05:03, 23 October 2006 (UTC)


 * No your eyes will not be damaged. Mine were not and I swam in chlorinated water for dozens of hours each week every summer for a few decades. Eyes open. I loved swimming underwater. Don't do it much anymore, tho. WAS 4.250 16:11, 28 October 2006 (UTC)

Fissile material
After obtaining enough fissile material, what would one need to do to create a crude nuclear bomb (assuming one also had trained nuclear technicians to do so)? Like, what kind of steps would ahve to be taken? For the record, I'm not a terrorist, I'm just writing a thriller for NaNoWriMo. —The preceding unsigned comment was added by 58.7.219.86 (talk • contribs). 01:17, 23 October 2006 (UTC)
 * It's not just obtaining the fissile material - it's seperating it from non-fissile material. Fissile uranium and plutonium make up less than 1% of all teh uranium and plutonium in all of nature. So, you have to run it through very long pipes (3 miles or more); the lighter (fissile) material comes out first, and that's what you put in your bomb. The problem is that in order to make it run through the pipes, you have to bond it with flurine to make it Uranium hexafluoride gas. However, Uranium hexafloride is *extremely* corrosive. In early WWII test, it ate through a 3 inch think glass pipe in 10 minutes; and a 3-inch steel pipe in two hours. The next trick: coat the inside of the pipe with Telfon and your corrosion problem is solved (This is why Teflon was a major war secret). After that, it's relatevely easy to build a uranium bomb. A plutonium bomb requires a lot mroe work though. Raul654 06:04, 23 October 2006 (UTC)
 * That's only if you are trying to enrich the material yourself. No terrorist has the facilities to enrich their own material; they'd either try to buy it or steal it. Both would be somewhat difficult; I'm inclined to think stealing it would be slightly easier though not much (buying it already requires somebody to have access to it and be willing to stake their own life on it, and you also have a high chance of either ripped off by the seller or by accidentally trying to buy it from a CIA agent). --Fastfission 00:36, 24 October 2006 (UTC)


 * Read the Nuclear weapon article. I'm afraid that's all the help we can provide right now (and it's substantial). I usually don't speak for other users but in this case I'll make an exception; none of us are terrorists. Perhaps you could add your manuscript to Wikibooks as a token of thanks for our research.  --hydnjo talk 06:04, 23 October 2006 (UTC)


 * Yep, and nuclear weapon design. If you've got enough highly enriched uranium, the task is conceptually simple - just slam two bits of it together at a reasonably high speed - the easy way to do this is essentially whack one bit of uranium in a custom-built cannon and have the other bit at the end of the barrel.  With a bit of experimentation, I reckon I and the local blokes down at the local welding shop would be able to do that.  By contrast, if you're trying to use plutonium, it's a much, much harder task.  You need to   create a set of explosives that can "pinch" a sphere of plutonium into a super-compressed state, and then just as the compression reaches its maximum release a supply of neutrons that starts the reaction going - if you get the timing of the explosives or the neutrons wrong, you may get no bang at all, or a much smaller one.  From the information to hand, it seems like North Korea's nuclear test was just such a "fizzle".  --Robert Merkel 06:30, 23 October 2006 (UTC)


 * In The Fourth Protocol (film), you can see Pierce Brosnan assemble a nuclear bomb. Not too much detail, but it's a good film, so if you might ever want to watch it, now would be a good time. Btw, I like your disclaimer. I wonder what answers you would have gotten if you would have said you were a terrorist, since that would obviously have meant you weren't. Or would it? Let the double guessing begin. :) DirkvdM 08:05, 23 October 2006 (UTC)

Uranium bombs are easier to build - you just fire two sub-criticle masses at eachother, when they are close enough to make a criticle mass they explode, assuming enough neutrons are floating around in the environment. The WWII bomb had a 10% chance (if memory serves) of not working due to a lack of available neutrons.

Plutonium bombs need an initiator to supply a burst of neutrons at the right time to start the reaction (during implosion). The WWII bomb used a Berillium based initiator that is still classified (as of twenty years ago). Modern plutonium bombs use a minuture linear accelerator and target material for the initial neutron burst. Dallas67 10:25, 23 October 2006 (UTC)


 * The Little Boy gun-device also had neutron initiators. They wouldn't have left anything to such a high chance as 10%. --Fastfission 00:36, 24 October 2006 (UTC)
 * If you obtain enough fissile material you've gone 90% of the way to making a very crude nuclear weapon — fissile material will be the biggest and most difficult step for any non-state entity. You could create a pretty nasty explosion just by throwing a critical mass together any which way. It might not be on par with a kiloton-range weapon but it would be pretty impressive on a human scale. It really depends what you, the hypothetical user, are going for. If it is just a scary and deadly explosion you can get that without it being elegant from an engineering standpoint. The fancy implosions and all of that are for when you really want to get a VERY big explosion out of it; if you are content with something which is less than a kiloton in yield (which is still very large from a human point of view; the Oklahoma City bombing explosion was only .002 kt in yield) and radiologically messy you can cut a lot of complicated engineering corners. --Fastfission 00:36, 24 October 2006 (UTC)


 * On a related note: I've heard whispers of the theoretical possibility of a fustion bomb without a fission trigger, relying on super accurate implosion techniques. Does anyone have any information on this? Dallas67 02:11, 24 October 2006 (UTC)
 * That possiblity is discussed in Induced gamma emission and Sam Cohen and the book Imaginary Weapons. (Hafnium bomb) Current consensus says it doesn't work. --GangofOne 05:16, 24 October 2006 (UTC)


 * Might I point out that it violates the rules of NaNo to begin research before November starts? :(

Your uranium separation comments suggest that you are talking about the gaseous diffusion method of separating the 235 from 238. That takes a lot of space, money and time. Only nation states have those resources. Terrorists will either 'steal' the 235 or they will buy a flow forming machine and make thier own centrifuges. The centrifuge method of isotope separation is by far the cheapest and most space efficient way to do enrichment. The space aspect is important if you are trying to conceal the fact that you are doing it. The total number of centrifuges needed in a cascade system is dependent on the speed you can obtain with your centrifuges. Really good designers use magnetically levitated cans. Yes, there are tricks but then you would not need to show those on a movie. What you need to concentrate on showing is the fact that the centrifuge method of enrichment has changed the game totally and made terrorist nukes a very real PROBABILITY. They are cheap to build and easy to hide. That is scary! Forget calutrons and gaseous difussion. Today, that would me like using vacuume tubes to build a laptop.

Genetic tendancy towards AIDS amongst Black people?
It seems all statistics show that black people have a greater chance (up to 15 times!) more to get AIDS then a white person of European decent. Is this a genetic tendancy or some other reason? Has there been any scientific studies? —Preceding unsigned comment added by 68.235.225.150 (talk • contribs)


 * The question is flawed. There is absolutely no genetic basis for AIDS. Raul654 05:59, 23 October 2006 (UTC)


 * I believe Africans have a high rate of AIDs, did you mean that? See AIDS and the graph there, for example. But no, AIDS isn't a genetic thing; it has to do with behavior, which might be impacted by upbringing, family, where someone grew up, etc. --Wirbelwind ヴィルヴェルヴィント (talk) 06:09, 23 October 2006 (UTC)


 * I am seeing different responces from different people. It seems most black professors who have studied the subject claim that AIDS is in fact a genetic disease, while white scientists claim that it is not. I haven't been able to find any scientific studies. 68.235.225.150 06:25, 23 October 2006 (UTC)


 * Indeed. It is probably due to behavior. --Proficient 06:27, 23 October 2006 (UTC)

Okay... just like any disease, there is a genetic component to HIV infection, at least with regards to susceptibility, meaning that there is likely some degree of variation; I recall reading a paper about a number of African women appear to be entirely immune to the disease, probably because they carry a mutation in a gene that affects the expression of the glycoproteins that HIV attaches to. I cannot say whether any particular population is more or less susceptible to HIV infection, (and I have no doubt that the answer is complicated by the fact that the strains of HIV that are prevalent in Africa are not the strains more common to Europe and the Americas) but I would think that someone, somewhere, managed to get grant money for such a study. If you find an answer, let me know. – ClockworkSoul 06:38, 23 October 2006 (UTC)


 * For a start, i believe the question you're really asking is whether Black people are more suspectible to HIV, the virus which results in the syndrom called "AIDS".


 * The answer is, yes, black people more commonly get HIV and are more 'suspectible' to AIDS. But it has nothing to do with genes.


 * Let's start with HIV.


 * HIV originated in poor parts of asia/africa area, and didn't enter western society for quite some years. Not surprisingly since people from those poorer parts don't often immigrate to the western world. In other words, HIV has had far longer to spread in africa, where it's all black people.


 * no one knew what HIV was at first. When it hit the western world - the western world keeps medical records, has medical databases, has hospitals and doctors and the facilities. When people noticed a how bunch of gay guys suffering from immuno-deficient disorders, they had the resources to investigate. They worked out what it was, what caused it, and how it spread. I'm afraid africa doesn't have those luxuries. Since AIDS is a slow disease (you don't get sick and die immediately from contracting it), AIDS probably existed and had time to spread for ages in africa before it hit the western world and got identified. In africa, HIV has had the chance to integrate into the population so much that children are often born carrying the virus these days (because their mothers do), which further increases the rate of HIV in those countries.


 * HIV is spread primarily as a sexually transmitted disease. Condoms are rare in african countries, people do not have a culture of using them. Rape is also common. It's also common for men to have many wives. All these things means VERY easy transmission of HIV. In the western world, people are on average more monogamous (sticking to one sexual partner), condoms are readily avaiable and used.


 * HIV is not acute - you get it and have no symptons for ages. In africa, many people probably don't realize it when they contract HIV. In the western world, people can access a doctor very easily. If they just get a little sick, they go see a doctor. Blood tests are easy to do, and experienced doctors will notice the symptons and diagonose quicky. People can then take measures to not spread it. In Africa, people get sick a lot more often, and don't have access to doctors so easily.


 * Even in western society, black people are more likely to get HIV. This is because black people tend to be of the poorer, low social-economic class. Poorer means less access to medical facilities. Low social economic class means less education about health, disease, spread of disease, and safe sex in terms of sexually transmitted diseases. Poorer also means living in areas of higher crime, basically meaning more cases of rape and so on. You'll find that black people iin general tend to have more health problems, because they're poor and of low social-economic groups. HIV is not an exception, it's pretty much the norm.


 * now moving on to aids. HIV can stay in the body for a period of time without causing any harm. Up to about 10 years without medical help. At some point, no one knows what the trigger is, HIV activates and the body starts showing the symptons. These symptons are what's called the "Acquired Immune Deficiency Syndrome" (acquired refering to how AIDS is aquired from the virus HIV). -- `/aksha 03:42, 24 October 2006 (UTC)


 * One tiny point: AIDS is called "acquired" because it's acquired from other people (it's contagious), rather than being genetic. --Tardis 19:13, 23 October 2006 (UTC)


 * Uhh...isn't it "acquired" as oppossed to cognetial? ...uh...however you spell that word. The one which means you're born with something. -- `/aksha 03:42, 24 October 2006 (UTC)


 * Congenital means, literally, present at birth. Babies with AIDS still "acquired" it; they just did so rather early in life.  The opposite here is really genetic, because then it's just that your immune system is inherently broken.  Or perhaps it was simply not known that AIDS could be congenital when it was named, since "acquired" and "congenital" usually are opposites in medicine.  --Tardis 23:25, 24 October 2006 (UTC)


 * Once aids starts to show, people are more or less doomed to die soon. There are drugs to slow this process down, so HIV can lie dormant in the body for a long time and the person will not start to suffer from AIDS. These drugs are expensive - not the kind of thing that's regularly found in Africa. The drugs are also most effective if the person starts taking them as soon as they get HIV. Once again, black people who are of the poor social-economic groups tend not to do this. Some don't realize they have HIV. Others can't afford the drugs. Others simply can't be bothered. Hence the HIV infected black people develope AIDS much more quickly.


 * "I recall reading a paper about a number of African women appear to be entirely immune to the disease" they're not actually immune. There were reports of people in Africa who seemed to be infected with HIV and just carried it with them all their lives without realizing it. In other words, they lived long (long as in normal age for healthy people in their society) and normal lives despite having the virus. So for whatever unknown reason, despite being infected with HIV, the HIV never really activates in their body. So not exactly immune...more like being sick but just not dying. Which i guess is 'immunity' in one sense of the world. -- `/aksha 13:54, 23 October 2006 (UTC)


 * The term for that is a carrier, with Typhoid Mary being perhaps the most infamous example. Another problem in Africa is the persistent myth that having sex with a virginal woman will cure the man of AIDS, while, in reality, it only spreads AIDS to the woman.  Also, women in Africa are so dependent on men for survival that they must do whatever they are told, including having sex without a condom, even knowing that their man sleeps around.   StuRat 19:20, 23 October 2006 (UTC)

Um, no there is a genetic component to susceptibility to AIDS. The HIV virus requires several proteins in order to attach to and infect a cell. One of these is the chemokine protein CCR-5. Patients who lack CCR-5 are relatively immune to infection by HIV!


 * why do i have a feeling that the only way someone can lack CCR-5 is if they don't have a functioning gene for it? -- `/aksha  03:42, 24 October 2006 (UTC)


 * Does the CCR-5 gene do anything useful ? If not, we could wipe out AIDS by creating a virus that destroys that gene, then let the virus go free. StuRat 16:57, 24 October 2006 (UTC)


 * CCR5 discusses this in come detail. – ClockworkSoul 13:49, 25 October 2006 (UTC)


 * Come again ? Are those details about how HIV is spread ? :-) StuRat 22:34, 25 October 2006 (UTC)

Gamma rays
Why gamma ray is not a particle but a ray only? It is told that waves also behave as a particle, then why is it not true with gamma ray?
 * It's not... Although the name is a bit confusing, gamma rays are simply the highest-energy example of electromagnetic radiation. Their particle is the photon. – ClockworkSoul 07:21, 23 October 2006 (UTC)


 * Make that the highest-energy range of EM. Just like visible light is an EM range, ranging from red to violet. Gamma rays, however, are not defined to have an upper limit. Something tells me that in reality there is a limit, but the article doesn't seem to say. DirkvdM 07:57, 23 October 2006 (UTC)


 * Cosmic Rays are supposed to have an even shorter wavelength.
 * But Cosmic rays are particles. ☢  Ҡ i∊ ff   ⌇  ↯  15:14, 23 October 2006 (UTC)


 * At shorter and shorter wavelengths, dont these things appear more like high energy particles. All particles can be considered as waves and vice versa.--Light current 16:08, 23 October 2006 (UTC)


 * As Feynman said, they're particles, because you can hear the individual clicks they make in a Geiger counter. There's no such thing as half a gamma ray. —Keenan Pepper 19:36, 23 October 2006 (UTC)
 * But again, there's no such thing as a "particle" when one looks at the proper scale - gamma rays are just very high frequency/short wavelength light (with the attendent wave/particle duality involved). Virogtheconq 04:10, 24 October 2006 (UTC)

Application of Nature Cure for treatment psoriasis
Can you kindly explain whether Naturopathy can be successfully applied in the treatment of psoriasis of skin, where treatment by allopathy, siddhavaidya etc., have not yielded satisfactory results. If so. what are the sources (hospitals etc.,) available in Hyderabad? Regards Chandru —Preceding unsigned comment added by 59.144.66.3 (talk • contribs)


 * A very natural treatment is by doctor fish. I'm afraid this may not yet be available in Hyderabad. --Lambiam Talk  08:50, 23 October 2006 (UTC)


 * Some people have suggested that a change in diet can be helpful. Also, some preliminary evidence exists for positive results from topical application of some botanicals. --JWSchmidt 13:56, 23 October 2006 (UTC)


 * You are likely to get two very different kinds of answer to a question about naturopathy here, depending on whether the poster believes that naturopathy has any efficacy at all. I suspect that the majority of posters to this reference desk are in the latter group, but I may be wrong. I would not recommend wasting time on it myself. --ColinFine 15:09, 28 October 2006 (UTC)

alluvial sedimentary rock
what is an alluvial sedimentary rock? —Preceding unsigned comment added by Ali khoobani (talk • contribs)


 * Here "rock" is a mass noun. Alluvial sedimentary rock is an alluvial deposit consisting of rock. --Lambiam Talk  08:40, 23 October 2006 (UTC)

And I'll say it's a rock composed originally of alluvial deposits. :) --Zeizmic 12:43, 23 October 2006 (UTC)

heat
what generates the heat to melt the rock in the earth core? —Preceding unsigned comment added by Ali khoobani (talk • contribs)


 * According to the prevailing theory of planetary formation, planets are formed by dust and gas clustering together in increasingly larger clumps, finally collapsing together to form a planet-sized body. The heat generated by the kinetic energy lost in the impacts made the Earth melt. Since then it has only been cooling down. The generally accepted explanation is that the heat is simply left over from the Earth's initial formation; see Structure of the Earth. --Lambiam Talk  08:33, 23 October 2006 (UTC)

I sure wish I had cared more about global geophysics. Our article seems wrong about the source of heat for the earth. This is more in line with what I understand. --Zeizmic 12:40, 23 October 2006 (UTC)
 * I agree, the primary source of heat in the earth is radioactive decay. If the earth had no internal heat source it would have cooled down a lot more already. Wikipedia does have some articles that mention this - see Geothermal power, Age of the Earth and Uranium. JMiall 12:57, 23 October 2006 (UTC)

This played an interesting role in the history of science. Before radioactivity was understood, people such as Kelvin claimed that their physical science theories for rates of cooling of the Earth and rate of chemical fuel depletion in the Sun showed there had not been enough time for biological evolution to take place on Earth. A good example of why scientific claims should always begin with, "If my assumptions are correct...." --JWSchmidt 13:39, 23 October 2006 (UTC)

What about all the pressure on the earth's core? That's what I always assumed made the nickle and iron in the core liquid. - AMP&#39;d 14:09, 23 October 2006 (UTC)


 * No, high pressure forces most materials to become solids. This is why the very core of the Earth is thought to be solid, even though the mantle is molten, and the core is even hotter. StuRat 19:01, 23 October 2006 (UTC)


 * So I had it backwards? - AMP&#39;d 02:20, 24 October 2006 (UTC)


 * In general, yes, although there are exceptions, as some materials, like water, are actually less dense as a solid. StuRat 16:53, 24 October 2006 (UTC)


 * Radioactive decay is what generates the heat. since nothing can burn in the conventional sense, this is the only possible answer (I think).--Light current 14:53, 23 October 2006 (UTC)


 * Also, tidal forces from the Moon and Sun generate some heat in the interior, but likely far less than radioactivity. StuRat 18:57, 23 October 2006 (UTC)


 * Current researches about earth core neutrinos try to tell the percentage of heat caused by radioactivity. It could be only 30-40%. -- DLL .. T 18:59, 23 October 2006 (UTC)


 * So what causes the other 60 -70 %?--Light current 00:21, 25 October 2006 (UTC)

I just saw a TV program on the Earth's magnetic field, which claimed the Earth's core is cooling at a rate of about 100 degrees (they didn't specify units) per billion years. How fast the initial heat (created by planet formation) would dissipate without radioactivity and gravitational tides was not exactly clear. When the mantle does solidify, in a few billion years, this will cause the magnetic field to cease, which, in turn, will cause the atmosphere and oceans to be driven off by the solar wind. StuRat 22:31, 25 October 2006 (UTC)

Unidentified Mushrooms
What mushrooms are in this image? It's a very good image, and I would like to put it in the appropriate area, but I don't know what kind of mushroom it is. Chanterelle, maybe? Nautica Shad e  s  07:49, 23 October 2006 (UTC)


 * They certainly look like it. I wouldn't eat them, though, unless they are printed on edible paper. Did you think of asking the photographer and uploader André Karwath aka Aka? --Lambiam Talk  08:16, 23 October 2006 (UTC)
 * Oh man, so many witticisms in one reply, I think I'm going into repartory arrest! Anchoress 09:47, 23 October 2006 (UTC)
 * Google has 280,000 hits for "repertory arrest", and it is my sad duty to report that a lot of them seem to be talking about cessation of breathing, eg. respiratory arrest. JackofOz 09:56, 23 October 2006 (UTC)
 * Dood, you need to bone up on your ironical vocab. I meant repArtory as a mangling of 'repartee'. I assure you that clever word play is not sufficient to induce respiratory arrest, in me anyway. ;-) Anchoress 10:19, 23 October 2006 (UTC)
 * Oh, I detected the irony and the humour alright, although I admit I thought it was a mangling of "repErtory" rather than of "repartee". What's it called when you laugh at a joke for completely the wrong reason?  Dorkness, maybe?  But I don't think it matters as long as you're having jolly fun with your chums.  Anyway, we've discovered a further reason to be cautious when a doctor uses big words.  :-) JackofOz 19:58, 23 October 2006 (UTC)

I love collecting edible mushrooms, but that looks like a pile of several types. --Zeizmic 12:25, 23 October 2006 (UTC)


 * Looks like chanterelles to me. I wouldn't worry too much about eating them myself. I've heard more than one mycologist say that chanterelles don't resemble any poisonous fungi. (And are therefore recommended to inexperienced mushroom-pickers). --83.145.46.141 13:53, 23 October 2006 (UTC)
 * Um, ah, well, it all depends where you live. If you happen to live somewhere that the Jack o'lantern mushroom grows (and glows), you can make yourself sick as hell if you confuse the two pretty orange mushrooms. We really oughta give the same disclaimer for mycology here that we do for medical and legal advice... --jpgordon&#8711;&#8710;&#8711;&#8710; 17:17, 23 October 2006 (UTC)

They do look a lot like chanterelles, and the fact that someone bothered to pick and dry a whole pile of them does suggest that they might be an edible species. Of course, I'm saying this safe in the knowledge that I won't be eating those particular mushrooms. Still, I'd find the identification sufficiently plausible for adding something suitably equivocal, like "probably chanterelles", to the image description, especially since correctly identifying dried mushrooms by sight is generally much less safety-critical than identifying fresh ones — dried fungi, if you didn't dry them yourself, usually tend to come pre-labelled. (And yes, jpgordon's point is important — just because a particular edible species looks like nothing else that grows near you doesn't mean there isn't a poisonous look-alike growing in some other part of the world.)  —Ilmari Karonen (talk) 14:56, 27 October 2006 (UTC)

Chemistry/ Heat curves
How much energy (kj) is required to convert a 15.5 g ice cube at -5.0 to water vapor at 180 degrees Celsius?


 * Yeah, I had those questions in school too. You'll want to divide the problem into a few steps:
 * Heating the ice to the temperature where it can melt
 * Melting the ice
 * Heating the water to the temperature where it can evaporate
 * Vaporising the water
 * Heating the vapour to the final temperature
 * —Bromskloss 13:15, 23 October 2006 (UTC)

Sodium Dodecyl Sulfate
I did a Chemical Engineering lab last week to investigate the surface tensions of various concentrations of solutions of sodium dodecyl sulfate, also known as sodium lauryl sulfate. One of the aims was to discover the maximum surface concentration at the liquid/gas interface, and the minimal area of a molecule of said compound. This was done using the maximum slope of a plot of surface tension against log of concentration. Does anybody know the correct value for either of these, so I can analyse the accuracy of my results in my lab report? I only need one correct value because there is a simple relationship between the two. I already tried to google it but no luck, and I can't access the library at the moment.

Thanks! 7Munkys 13:07, 23 October 2006 (UTC)

Bad horror-movie bacteria!
How the hell do you kill these things??? Just reading the article is personally scaring the crap out of me! I mean, it can take heat, cold, vacuum, radiation, dehydration, even acid! Do you lock them up in jar and watch them starve them over three years? Do you try to poke it with a sharp stick? What? I really want to know! I need to be able to sleep at night! 83.250.208.83 14:57, 23 October 2006 (UTC)


 * Just put it in the oven and bake it for a few hours at 300 degrees Celsius. I'm sure it can't take that much heat.  --Bowlhover 15:34, 23 October 2006 (UTC)

I'd prefer a plasma arc, if in fact, those things actually exist! --Zeizmic 15:46, 23 October 2006 (UTC)

One should consider whether it is, in fact, pathogenic before getting worried about them. Also, just because it is an extremophile doesn't mean it will flourish in normal environmental conditions, given that it is suddenly confronted with both competition and predators. —The preceding unsigned comment was added by 192.91.171.42 (talk • contribs).


 * Exactly. They're probably harmless to humans. And Strain 121 can kick their asses anyway. =P —Keenan Pepper 19:45, 23 October 2006 (UTC)


 * Don't waste time; break out the phasers and photon torpedoes. B00P 20:38, 23 October 2006 (UTC)


 * Being extremophilic, I doubt they've had much experience of antibiotics, so a good dose of those could probably kill it. La  ï  ka  21:37, 23 October 2006 (UTC)


 * If you're afraid of foreign creatures which can stand high temperatures, does that make you an xenophobic in regards to extremophilics? --Fastfission 00:23, 24 October 2006 (UTC)


 * Very cool - are there other bacteria like these two? Aaadddaaammm 03:38, 24 October 2006 (UTC)


 * Lots of weird extremophiles are being discovered . Also, do you know the Archaea story?  In 1977, biologist Carl Woese was working with bacterial cultures from deep underground when he discovered that they were not bacteria, with the result that today we say there are three types of life forms: prokaryotes (bacteria,) eukaryotes (protists, plants, animals,) and Carl Woese's archaea.   Here's another: biologist Lynn Margulis proposes that all natural deposits of mineral ore are actually created by chemosynthetic deep-rock bacteria/archaea where different species metabolize each dissolved mineral from ground water while depositing the insoluable ore.  Ever wonder why are there mines?  It's because the Earth is like blue cheese!  More like copper cheese, molybdenum cheese, etc. (Does this mean that we could pump seawater through bacterially-contaminated hot wet sand and later extract gold or platinum?  Or how about Uranium?) --Wjbeaty 02:11, 25 October 2006 (UTC)


 * That's some pretty cool bacteria. --Proficient 02:30, 26 October 2006 (UTC)

Reishi and Birth Control Pills
Dear Wikipedia:

Good Day! My wife is taking some birth control pills but she's also taking some reishi mushroom for her health. Does reishi can hinder the effect of pills?

Thanks> Gerry


 * Please read the rules. "If requesting medical or legal advice, please consider asking a doctor or lawyer instead.--Russoc4 16:21, 23 October 2006 (UTC)


 * You could also ask your pharmacist. Make sure you can specify the specific pills used. --Lambiam Talk  16:25, 23 October 2006 (UTC)


 * The pill can be made ineffective if you experience vomiting or diarrhoea and this mushroom seems to have symptoms of gut clearing, so I would definitely check with a professional. Vespine 23:07, 23 October 2006 (UTC)

watershed management
how can watershed management be done? can you give an example of a place where this is being implemented?61.246.87.148 16:51, 23 October 2006 (UTC)abcd


 * I'm not sure what you mean. Do you mean management to prevent floods, to limit soil run-off, prevent water pollution, reserviors for irrigation and human consumption, sewage treatment, hydroelectric generation, etc. ? :-) StuRat 18:41, 23 October 2006 (UTC)


 * ...or trying to get your kids to bed by 9pm?--Shantavira 08:48, 24 October 2006 (UTC)


 * Make sure they pee before turning in, or the bed could become a water shed. :-) StuRat 20:00, 24 October 2006 (UTC)

Alpha Helix
I am trying to do a quesstion for an university assignement and after looking through 3 text books, I am still puzzled. The question is as follows:

"The peptide chain below folds into an alpha helix. /an alpha helix is 0.54 nm long (5.4 Angstrom units) for every complete turn, and there are 3.6 amino acid residues per turn of the helix.

Lys pro val leu gly ala Ile ala asp leu val val gly leu glu ile leu ala val ala gly tyr ser"

I know this is kidna a homework question but I am officially stumped.

I am also to describe the nature of the protein (i.e. polar, non-polar, predominantly charged)

and finally,

If the hydrocarbon core of biological membranes is approximately 30 Angstroms, suggest a plausable function for the peptide.


 * Was there supposed to be a question already before you came to "I am also to"? If so, I couldn't find it! —Bromskloss 18:33, 23 October 2006 (UTC)


 * I apologise, it says I am to calculate the length of the helix. I got 3.45 nm.


 * You might find it useful to read this article. It has more detail than do Wikipedia articles such as this one about how to make guesses about the functions of alpha helical domains.--JWSchmidt 22:14, 23 October 2006 (UTC)


 * You might want to visit the amino acid article and take a look at each individual amino acid in the peptide. Make a list of the charge and polar nature of each residue. For instance, the first residue is charged and polar. Look at the second residue very closely, as it will do something weird to the helix. Also, you basically answered one of your questions yourself: put the membrane thickness and helix length into the same units, and you might see a similarity.Tuckerekcut 23:07, 23 October 2006 (UTC)

Black Engineers
Hello. I was wondering, where could I find an article or a list of African American Mechanical Engineers? I searched this topic 3-4 times before, but couldn't find anything specific. Thank you for your time.

Thank you, A Troubled User

See Category:African American inventors. StuRat 21:12, 23 October 2006 (UTC)

Crucell
Hie I am a wondering if you could possibly put up the Crucell's profile on wikipedia. Crucell is a leading Dutch Biotech company based in the city of Leiden. I am a press officer at Crucell so should you need some help compiling the profile, please feel to contact me on email removed

Thanks for the good work

Best regards

Bruce
 * We want money! --Zeizmic 21:20, 23 October 2006 (UTC)         :)
 * Of course, Wikipedia does not change editorial standards for pay. A good spot to list this would be Requested articles.  Standards for the inclusion of a corporation are noted at WP:CORP.  Cheers, --TeaDrinker 23:12, 23 October 2006 (UTC)


 * a) That sounds like advertising, b) This isn't the request section, and c) I removed your email as per policy at the help desk. --Wirbelwind ヴィルヴェルヴィント (talk) 23:14, 23 October 2006 (UTC)

C'mon, guys! That was unnecessarily rude and in bad faith. A simple Google search in Wikipedia shows that we already have 20 references to this company - among them the fact that they're part of the AMX index. So they clearly meet our WP:CORP criterium. &mdash; Sebastian (talk) 20:48, 25 October 2006 (UTC)

OK, I created the article: Crucell. &mdash; Sebastian (talk) 23:37, 25 October 2006 (UTC)

Algorithms
Just as articles need to be factual and accurate and subject to correction so do algorithms. So as not to break with the tradition of making encyclopedic articles as esoteric as possible is there an alternate place to post scientific and mathematical algorithms within the Wikipedia? Adaptron 21:38, 23 October 2006 (UTC)


 * Try Wikibooks. --JWSchmidt 22:19, 23 October 2006 (UTC)

Some can be posted here, like common sort algorithms. What does your do ? StuRat 23:13, 23 October 2006 (UTC)


 * I have many algorithms I am interested in posting but the current one involves the computation of sunset and sunrise from latitude and longitude. Except for one freely available from an online magazine I have yet to find any that are complete and error free. With a place set aside in the Wikipedia for publishing such algorithms I would hope such incompleteness or error would soon be eliminated. Adaptron 23:18, 23 October 2006 (UTC)


 * You've got a good idea for a new wiki there (WikiCode ?). I could post a few myself.  What does everyone else think ? StuRat 23:39, 23 October 2006 (UTC)


 * If it doesn't belong in either WikiBooks or WikiSource, I would definitely be behind such an idea. It's a pity the Wikimedia Wiki-creation process is in a state of flux, or I'd suggest putting a proposal up right away. Confusing Manifestation 02:10, 24 October 2006 (UTC)

Here is a sunup/sundown computational algorithm in need of new wheels and a fresh coat of paint which it might acquire if left in a wiki instead of parked on the street.

Starting with the number of days since Nov. 17, 1858 or a modified Julian date of

JD = 2454032.24616, a computed event (sun up or down) set to UT = 0 or noon and an

estimated event set to UTO = 6 an iteneration is begun to compute the actual value

of UT.

(Note: addition of functions to convert degrees to radians may be necessary)

'initial values

Lat = latitude

lon = longitude

PI = 4 * Atn(1)

HORIZON = -50 / 60

while (abs(UT-UTO) > .0008

'compute the number of centuries since the epoch of Jan. 0, 2000.

T = (JD + UT / 24 - 2451545#) / 36525#

'compute the solar mean longitude

l = 280.46 + 36000.77 * T

'Compute the solar mean anomaly in degrees.

G = 357.528 + 35999.05 * T

'Compute the ecliptic longitude in degrees.

M = l + 1.915 * Sin(G) + 0.02 * Sin(2 * G)

'Compute the obliquity of the ecliptic in degrees.

E = 23.4393 - 0.013 * T

'Compute the equation of time.

ET = -1.915 * Sin(G) - 0.02 * Sin(2 * G) + 2.455 * Sin(2 * M) - 0.053 * Sin(4 * M)

'Compute the Greenwich Hour Angle in degrees.

GHA = 15 * UT - 180 + ET

'Compute the sun's declination in degrees.

DEC = arcsin(-Sin(E) * Sin(M))

'Compute the hour-angle at UT (the current estimate)

HA = arccos((Sin(HORIZON) - (Sin(Lat) * Sin(DEC)) / (Cos(Lat) * Cos(DEC))))

'Compute the time of sunrise, sunset, or twilight.

'RISESET is +1.0 for morning (rising) and -1.0 for evening (setting).

RISESET = 1#

UT = UT0 - (GHA + lon + (RISESET * HA)) / 15#

'The result is in hours.

'Continue until the UT and UT0 estimates are close together.

Wend

'print the computed event time.

print UT

Adaptron 08:42, 24 October 2006 (UTC)

Rate of lunar transit
What is the calculation or rate at which the moon 'crosses' the night sky? In other words, if you were watching a shadow on the ground cast purely by the moon's reflection, is there a calculable rate to ascertain how long it would take to travel an inch, or a foot?


 * The moon or a shadow cast by it is easier to imagine travelling in degrees, not feet or inches. Imagine a big tree and a little fence post, in one night the tree's shadow may travel dozens of feet while the fence post's only looks like it moves a couple of feet, the commonality is that both shadows travel the same number of degrees. The shadows turn, like the hands of a clock.


 * Obviously the 'turning' is caused by the earth spinning on its axis. The earth spins fully around once every 24 hours, meaning the moon looks like it is travelling 360 degrees every 24 hours, or 15 degrees an hour, (ignoring the much longer monthly period of the moon). If you do include the monthly revolution of the moon around the earth, it actually adds up, the moon travels forward by an extra 28th of a full revolution every day, or about 13 degrees, which is almost one hour, so every day the moon is almost an hour earlier.Vespine 22:47, 23 October 2006 (UTC)

Dear Vespine: Dynamite answer, in every fashion -- I'm very grateful for your help. Wolfgangus 01:17, 24 October 2006 (UTC)


 * I think the Moon lags behind the Sun; while it apparently travels from East to West like the Sun, it does so more slowly. See the picture at Lunar phase. This also explains why the path of the Moon's shadow during a solar eclipse travels West to East; see e.g. the animation at Solar eclipse of 2006 March 29. So "Moon rise" is a bit later each day. Using the value of 29.5 days for the synodic month, so that we have on the average 29.5−1 = 28.5 Moon rises in that period, the time from Moon rise to Moon rise is (29.5/28.5) × 24 hrs = 24.8 hrs = 24 hrs 50 mins. The overhead Moon traces out 360° in that period, which amounts to about 14°/hr = 0.25 rad/hr. --Lambiam Talk  06:49, 24 October 2006 (UTC)

Dear Lambiam: Thank you so much for the valued additional input. Now, if I may ask a question that perhaps begs the obvious: with all this in mind, does the Moon have a verified annual apsis and periapsis with the Earth? If so, how is it calculated?Wolfgangus 09:18, 24 October 2006 (UTC)


 * It has a perigee and apogee. I imagine this will be calculated assuming the Moon's orbit is a perturbed ellipse. Typical values for perigee is ~363000 km, and for apogee ~406000 km. Richard B 11:31, 24 October 2006 (UTC)


 * After edit conflict:
 * Stuff like this can even affect politics. After the Venezuelan coup attempt of 2002, there was controversy over when certain footage was shot. The Revolution Will Not Be Televised (documentary) had the shadows cast differently from another shot, so the argument was used that they were shot during different parts of the day. But how far apart those images were in time depends on the size of the building that cast the shadow. If cast by a tall building, the shadow would move very fast. DirkvdM 09:22, 24 October 2006 (UTC)

Sometimes I have my doubts about the relative 'greatness' of the internet, but this brief forum alone merits its tremendous caliber. Thanks so much to everyone for your help.Wolfgangus 22:47, 24 October 2006 (UTC)

Abnormal waves and tides
Is tidal [and waves] data from ocean buoys available for download online? Adaptron 22:02, 23 October 2006 (UTC)
 * I don't think marine buoys are an effective means of measuring tide (which is an interaction with the shore). Other bouy data (NOAA data) can be obtained from the National Buoy Data Center.  For tide information, you might try tides online (another NOAA service).  --TeaDrinker 23:07, 23 October 2006 (UTC)


 * Sorry I meant ocean height (to include wave action) which includes changes caused by tides whether at the shore line or offshore. What I am ultimately after are the Fourier coefficients for all locations of measurement, either offshore or at the shoreline. Adaptron 23:28, 23 October 2006 (UTC)


 * Found it at harmonic_cons_defs Adaptron 23:42, 23 October 2006 (UTC)