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January 24

2012

will the earth end in 2012 — Preceding unsigned comment added by Tommy35750 (talk • contribs) 01:12, 24 January 2011 (UTC)

Highly unlikely if you ask me, but see 2012 phenomenon. PrimeHunter (talk) 01:18, 24 January 2011 (UTC)

(EC)We do not engage in speculation on the reference desks. However our article on the subject is at 2012 phenomenon. --Tagishsimon (talk) 01:19, 24 January 2011 (UTC)

There is no accepted scientific reason to think that the Earth might be significantly more likely to end in 2012 than in any other year. That is, there is no accepted scientific reason to think that the Earth has anything greater than almost no chance of ending in 2012. For a scientific viewpoint of Earth ending, skip the 2012 phenomenon article, which is about a sociological phenomenon that has essentially nothing to do with science, and read Risks to civilization, humans and planet Earth. Red Act (talk) 02:03, 24 January 2011 (UTC)

NASA says no at this link. Phew. Comet Tuttle (talk) 18:30, 24 January 2011 (UTC)

Probably not.NASA--Cjc811 (talk) 19:17, 24 January 2011 (UTC)

Look at this site Maybe--Cjc811 (talk) 19:18, 24 January 2011 (UTC)

Don't look at that site, it's just an idiot's ramblings. --Tango (talk) 19:41, 24 January 2011 (UTC)

No reason why it shouldn't except applications of inductive logic as flawed as the optimism of someone who has jumped from a 100 story building and notes that nothing bad has happened after he has fallen 80 stories, 81 stories, 82 stories, ... and who concludes that therefore he might fall without limit, right? The Earth has hosted lifeforms for hundreds of millions of years, so it will continue for hundreds of million or billions more, right? Edison (talk) 02:52, 25 January 2011 (UTC)

This recent article predicting a supernova of Betelgeuse in 2012 is a clear example of the 2012 phenomenon, since those "predictions" of a star emerging from Orion would have been correct should this actually occur. However, even though the diameter of Betelgeuse has shrunk by 15% in the past 15 years, this estimate is highly uncertain due to blurry imaging and differences in development of the technique, though if the estimate is correct, this corresponds to nearly a 40% decrease in volume, although mass has also been decreasing, suggesting the star is shedding its outer layers (spectroscopy of the star may indicate changes); this may represent either an early or a late stage of pre-supernova changes in the star, though periodic changes similar in magnitude also occur in non-near-supernova variable stars, even though those stars too are often red supergiants that are nearing the supernova stage; according to the original article version, a supernova of Betelgeuse may not occur for another million years. Generally, many scientific (and pseudoscientific) predictions imply that "something" of significance may be at an increased likelihood of occurring in 2012, but that it will likely not be the end of the world and may simply represent a self-fulfilling prophecy. ~AH1^(TCU) 23:48, 26 January 2011 (UTC)

Of course if Betelgeuse does go supernova, it will do so some time in the late Middle Ages, and the world did not end then. As far as I know, I wasn't actually here at the time. 148.197.121.205 (talk) 14:30, 28 January 2011 (UTC)

the lower dendrites

in a neuron, there are the upper (receiving) dendrites. and there are the lower and smaller-in-amount (giving) dendrites.

i know this is not the acceptable names for this parts (upper, and lower), so what is the right way to call these so-called "lower dendrites"...?

thanks and blessings. —Preceding unsigned comment added by 109.65.14.202 (talk) 01:35, 24 January 2011 (UTC)

Have you read our Neuron article? Perhaps the word you're looking for is "axon". –Henning Makholm (talk) 01:53, 24 January 2011 (UTC)

Yes, almost certainly "axon". Looie496 (talk) 02:53, 24 January 2011 (UTC)

hey, i have read the article but i understand that the Axon is a fiber which kinda' connect the "upper" dendrite, to the "lower" one... what you guys say is that THE "LOWER" ONE IS THE AXON...

i i understand right,

thanks. —Preceding unsigned comment added by 109.65.14.202 (talk) 12:10, 24 January 2011 (UTC)

There are various neuron structure types, but the most common one taught is the pyramidal neuron: this has a single axon (the signal sender) projecting from one side of the soma (cell body) with a "tree" of many dendrites (signal receivers) projecting from the other side. The axon itself has a number of axon terminals that sort of resemble dendrites, but are structurally different.

So it looks like you are confusing the axon terminals (signal senders) with actual dendrites (receivers) that are on opposite ends of the (pyramidal) neuron. SamuelRiv (talk) 18:32, 24 January 2011 (UTC)

c-1 m/s

If I've understood things correctly, no massive object can be accelerated to the speed of light because, as you approach c, relativistic effects increase the energy required to accelerate ad infinitum.

So, what would happen exactly if I took a 1-kilogram dumbbell moving at c - 1 m/s and exerted a force of one newton on it? At what speed would it be travelling after this?

Thanks. Leptictidium (mt) 07:31, 24 January 2011 (UTC)

Your "1 kg" object has a relativistic mass of over 12,000 kilograms, and will accelerate at less than a tenth of a millimeter per second per second, and become heavier all the while. Someguy1221 (talk) 07:41, 24 January 2011 (UTC)

It's actually worse than that. Assuming that you measure the force in your restframe (i.e. in the frame where the dumbbell moves at (c -1)m/s, then the force relates to momentum and velocity as $F={\frac {d}{dt}}p={\frac {d}{dt}}(\gamma mv)$ (here "m" = 1 kg is the invariant or rest mass, and γ is the Lorentz factor). Doing the derivative gives $F=\gamma ^{3}ma$. If you insist on using relativistic mass (which is ugly because coordinate-dependent), then that is $F=\gamma ^{2}m_{\mathrm {rel} }a$. You forgot to take into account that relativistic mass also changes when the dumbbell is accelerated. At v- (c-1)m/s, $\gamma =12243$, hence a= 5.45⋅10⁻¹³ m/s².--Wrongfilter (talk) 11:10, 24 January 2011 (UTC)

So what if I applied that very same force to an object with relativistic mass = 1 kg? --Leptictidium (mt) 11:17, 24 January 2011 (UTC)

Well, I gave the equation. You've absorbed one factor of γ into your relativistic mass (rest mass is 1/γ kg), hence the acceleration is larger by that factor, i.e. 6.7⋅10⁻⁹. --Wrongfilter (talk) 11:24, 24 January 2011 (UTC)

Then you'd get closer to the speed of light a little quicker, but the energy (AKA weight/mass) you are expending will transfer to your object making it heavier, and the acceleration will slow down. Objects getting heavier as they reach the speed of light isn't from magic. The energy contained in their velocity has mass, and that is what makes them heavier, and since they are heavier, you need even more energy to speed them up, but that extra energy makes then even heavier than before, etc, etc. till you have a runaway effect. Ariel. (talk) 11:30, 24 January 2011 (UTC)

You mean "more massive" not heavier. Cuddlyable3 (talk) 12:03, 24 January 2011 (UTC)

I do, but I will often say heavier so people understand it's not some sort of weird relativity thing, but that it really does weigh more (if you were to bring it near a planet or something). Ariel. (talk) 12:10, 24 January 2011 (UTC)

It is a "weird" relativity thing anyway, isn't it? And even in that pseudo-Newtonian understanding of relativity, it's not weight that matters here, but inertia. --Wrongfilter (talk) 12:22, 24 January 2011 (UTC)

By weird I mean some kind of mathematical thing used for calculations but not "real". And no one has ever found a difference between inertia and weight (aka gravitational mass) - that equivalence is a cornerstone of relativity. Ariel. (talk) 12:32, 24 January 2011 (UTC)

Phenomenologically, they are different effects, even if in general relativity they can be unified. --Wrongfilter (talk) 12:55, 24 January 2011 (UTC)

It doesn't really make any difference if the mass is 1kg or 1/12g (which it would need to be to have a relativistic mass of 1kg), you just multiply or divide the final answer by 12,000. --Tango (talk) 19:46, 24 January 2011 (UTC)

Would it exert gravity as if it weighed 12,000 kg? —Preceding unsigned comment added by 205.193.96.10 (talk) 17:21, 24 January 2011 (UTC)

Tricky. That would seem to make gravity frame-dependent. In a comoving frame, the dumbbell clearly exerts gravity as fits a 1kg rest mass. With the dumbbell zooming past, you would feel a time-dependent gravitational field. Taking into account the required coordinate transformations gravity might be pretty strong for a short time. There certainly is no reference frame where gravity acts like that created by a stationary dumbbell of 12,000 kg. --Wrongfilter (talk) 17:56, 24 January 2011 (UTC)

In its own reference frame, the dumbbell still weighs only 1 kg and exerts only one kg-worth of gravity on its surrounding objects. Also, it is still accelerating at 1 m/s by its own measurements. Only the observer in a different reference frame sees the situation differently. Dbfirs 19:32, 24 January 2011 (UTC)

The force is a vector, so you have to specify in which reference frame the (3-)force is given. That's why I wrote "Assuming that you measure the force in your restframe". If the force is measured in the rest frame of the dumbbell instead of that of the observer, then things are a little different and you get a couple of factors γ in different places. --Wrongfilter (talk) 19:53, 24 January 2011 (UTC)

Also, the 3-force components are three members of the 4-force which also include power as a fourth member which means that the force will have different magnitudes depending on the observer. Dauto (talk) 20:35, 24 January 2011 (UTC)

So, in its own reference frame, the dumbbell has accelerated to c, Dbfirs? Leptictidium (mt) 20:06, 24 January 2011 (UTC)

In its own reference frame the dumbbell is always at rest (duh). Dauto (talk) 20:23, 24 January 2011 (UTC)

Yes, the dumbbell can measure only its speed relative to something else, but in its own reference a measured force of one Newton will produce a continuous acceleration of 1 m/s/s using the length and time of that reference frame. Adding an increase of 1 m/s in speed to a speed of "c-1" in the other direction does not give a speed of "c" by the relativistic addition law of speeds. As others explain, the interpretation in other frames depends on how the observations are taken. Dbfirs 13:05, 25 January 2011 (UTC)

Even in Newtonian mechanics, you need to specify a force and a duration of time to estimate a velocity-change. Special relativity is very nice, because duration of time will also be Lorentz-contracted. So if you exert a 1 newton force for one second, you need to specify in which reference frame you have exerted that force. If you press on the object for 1 second, measured in the "stationary" (laboratory) coordinate frame, the effective force experienced by the moving object will be much more instantaneous; and the momentum transferred will be much smaller. The coordinates all work out using a lorentz transform and you just have to keep your coordinates straight. Convenient, eh? The paradoxes of paradoxical nature of measurements in different coordinate systems, with high velocities relative to each other, have been thoroughly explored: see Ladder paradox for a start. Nimur (talk) 21:10, 24 January 2011 (UTC)

Herpes virus

I was wondering how long the herpes virus stays around outside the body. I had a customer touch her lip and touch some of my book at work she was looking through. Now I am afraid to even touch the books. I can't really spray lysol on the books or clean them. So what else can I do? How long will the virus stay around? —Preceding unsigned comment added by 76.169.33.234 (talk) 08:12, 24 January 2011 (UTC)

Our article on Herpes simplex says "Herpes is contracted through direct contact with an active lesion or body fluid of an infected person." It seems you really need skin to skin contact for transmission. Get back to those books! HiLo48 (talk) 08:34, 24 January 2011 (UTC)

This says that under ideal conditions (temperature and humidity), it can survive a couple of hours. Ariel. (talk) 09:07, 24 January 2011 (UTC)

Inside a mirrored sphere

If you found yourself inside a mirrored sphere with a diameter of twice your eye level height from the ground and a source of light above your head, what would you see around you? How would the view change if you moved around? TheFutureAwaits (talk) 09:18, 24 January 2011 (UTC)

Mostly you would see yourself, but upside down. Your own body will block most of the reflections from other parts of the sphere. Your body will also absorb light, so it won't get constantly brighter and brighter (plus no mirror reflects all light, so some is lost). It looks like Japanese TV actually tried it but someone took down the video. Supposing you had a perfect point source light and a perfect mirror, and you placed the light in the exact center of the sphere, then you would see almost nothing because except for the light reflecting off of the top of your head, all of it would reflect right back into the light and none would reach you. Even if the light was not in the center, all of it would end up focused on one spot, lighting that spot but nothing around it. Just how perfect a mirror and light are we talking about here? Are you making use of reflected light from your clothing? It would be cool to model this with PovRay and it's pretty likely someone already did. Ariel. (talk) 09:47, 24 January 2011 (UTC)

We had a big parabolic mirror at school, over a meter in diameter, and I used to love starting into that thing. It had a tiny spot to mark the very center, if you walked towards the mirror with your eye right in line with the spot eventually, when your eye was right at the focal point, the whole mirror would be a reflection of just your pupil, it was really cool! Obviously even slight imperfections in the mirror make this effect not "flawless" but it was certainly impressive enough for me:) Vespine (talk) 00:52, 25 January 2011 (UTC)

Your eye was twice as far from the mirror as the focal point. 71.101.41.73 (talk) 09:11, 26 January 2011 (UTC)

Yeah good pick up, incorrect assumption on my part. i hadn't actually thought it through completely. Vespine (talk) 01:17, 27 January 2011 (UTC)

Actually, you will only appear upside down (and left/right reversed) if the center of the sphere is in front of your eye. If the center of the sphere is behind your head, you will appear right-side up. And if your pupil is in the exact center of the sphere, all you will see is the blackness reflected from your pupil. Red Act (talk) 00:49, 28 January 2011 (UTC)

Parts of a horses skull

I would like to know and cannot find out the name of the small holes on a horses skull on both sides just above the nasal bone and below the eye socket and what is it's use —Preceding unsigned comment added by 216.218.29.249 (talk) 16:31, 24 January 2011 (UTC)

The word for this type of hole in other animals seems to be "temporal fenestra" [1], but our skull article also says "Mammals, which are synapsids, possess no fenestral openings in the skull". SemanticMantis (talk) 16:44, 24 January 2011 (UTC)

(edit conflict)I believe these are some type of fenestra, See Skull. Mammals characteristicly seem to have these fenestra, located under the eye sockets. You can see small ones on the chimpanzee skull, and they really stand out on the bulldog skull. I am pretty sure that most of the fenestra act as conduits for nerves and blood vessels to get through the skull and other bones that have them, our article on fenestra is woefully weak in this regard, and I am remembering back to the last anatomy class I had, sometime in the fall of 1994. Perhaps someone with more anatomy knowledge can fill in the gaps. Post EC answer after SemanticMantis: I don't think these are temporal fenestra, the article synapsid has a picture which shows the temporal fenestra at the back of the skull, between the postorbital and squamous bones, no where near the nasal bone. If you look at the other skulls of mammals, you can see a fenestra of various sizes in the location described by the OP. This isn't the temporal fenestra. --Jayron32 16:49, 24 January 2011 (UTC)

Correct myself. These are not fenestra, these are foramen, see File:Gray190.png where the human analog to these holes is called the "infraorbital foramen", and according to foramen, serve exactly the purpose I describe above. I knew it was an "f" word, and got my foramens and fenestra confused. --Jayron32 16:53, 24 January 2011 (UTC)

Addendum to the correction: We even have an article titled Infraorbital foramen which describes the exact purpose of those holes. --Jayron32 16:54, 24 January 2011 (UTC)

Also, fenestra is singular; the plural is fenestrae. Not a big deal, but just kind of obvious if you speak Italian, where fenestra is the everyday word for "window". --Trovatore (talk) 00:22, 25 January 2011 (UTC)

(Oh, actually I think it's finestra now that I think about it.) --Trovatore (talk) 00:23, 25 January 2011 (UTC)

Which is of course also the origin of one of my favorite words: Defenestration. Vespine (talk) 00:45, 25 January 2011 (UTC)

Eye bone

What is the name of the bone in the eye of some reptiles? I can't find the article anywhere. Here are some examples: It is a torus shape with radial lines. -Craig Pemberton 17:10, 24 January 2011 (UTC)

• 
• 
• 
• 

Sclerotic ring. LANTZY^TALK 17:20, 24 January 2011 (UTC)

Thank you!-Craig Pemberton 17:34, 24 January 2011 (UTC)

Registering a new rock

My Dad found a rock which he sent to an organization (which I'm trying to find) and they told him it was indeed a newfound rock and should be registered with them. He has died since and I don't know if he registered it or not. What is the organization I go to, and how do I go about it (will ask them if necessary)? Thanks —Preceding unsigned comment added by 4.240.78.111 (talk) 18:22, 24 January 2011 (UTC)

Your IP address geolocates to New Mexico, so the organization could either be the Mineralogical Society of America or the CNMNC (part of the International Mineralogical Association). Physchim62 (talk) 19:08, 24 January 2011 (UTC)

Pure proteins

I'm looking for suggestions for proteins that can be obtained in a relatively pure form (maybe >95%). I'm look for things that I could purchase for research in quantities of about a gram for a reasonable price, say < US$200. I need to identify as many as possible. I'm not asking for specific commercial recommendations or prices, just names of proteins.

So far I've found:

• BSA
• beta-casein
• Lysozyme
• Hemoglobin
• gamma-globulin

Thanks for the suggestions! ike9898 (talk) 20:42, 24 January 2011 (UTC)

Even suggestions on how to search for such things would be helpful. ike9898 (talk) 21:18, 24 January 2011 (UTC)

Pepsin is a cheap enzyme, cheap enough to be used in UK high schools 25 years ago to demonstrate enzyme kinetics. I just checked the price for pharmaceutical grade from a supplier who's known not to be the cheapest, and it's less than €1/g. Physchim62 (talk) 21:29, 24 January 2011 (UTC)

Do you have any requirements other than price, like size, function, species, etc.? I'm not a biochemist so I don't know the specialty-companies in this arena, but one way to search is to pick a chemical/biochemical company and search its catalog. For example, I just poked the Sigma-Aldrich online catalog and found a whole Proteins and Derivatives section. In it are several you did not list. DMacks (talk) 21:34, 24 January 2011 (UTC)

Actually, what I need is variety. I want to study the relationship between various protein characteristics (MW, amino acid composition, secondary structure, ...) and a their activity in a particular practical application I'm interested in. I need them to be soluble under mild, aqueous conditions (keratin and zein won't work). I think ideally I want plain-vanilla proteins, rather than things like glycoproteins, but I'll take what I can get. Thanks! ike9898 (talk) 21:46, 24 January 2011 (UTC)

If you want a big enzyme, then I know you can buy rubisco from spinach. Might you be able to hint at the "particular practical application" that you're interested in? It might help us think of more suitable proteins. SmartSE (talk) 22:26, 24 January 2011 (UTC)

Check over the contact lens cleaning tablets - depending on the store you go to, you might find a variety. Pancreatin and subtilisin are the two most common, I think. Wnt (talk) 20:53, 25 January 2011 (UTC)

Hypothetical question

If all of the illnesses in the world were cure, would human beings still die naturally? --Thanks, Hadseys 22:09, 24 January 2011 (UTC)

It's kind of begging the question. If you define illness as "something that can go wrong with us" then the answer is obviously no. However, these days if you don't die of a specific thing like heat attack or cancer or stroke, then you will still eventually die from the very fact that your chromosomes don't copy perfectly when your cells split. You might find Telomeres interesting. However, you don't actually "die" of this, you die of liver failure (sure you can replace a liver, but not so easy to replace a spine or a brain) or something else which is caused by this, so eventually, excessive telomere shortening might be defined as an illness. Vespine (talk) 23:19, 24 January 2011 (UTC)

Actually our Death by natural causes article also seems to address your question. Vespine (talk) 23:24, 24 January 2011 (UTC)

Even if you somehow could evade death and live forever (assume that the universe will go on forever without a heat death), you would still effectively die, because there are only a finite number of states your brain can be in. You cannot go on to store more and more information in the brain, at some point you have to erase old information to make room for new information. Since you can only be in one of a finite number of states, you will eventually return to some old state you were previously in, meaning that you will have erased all of the information that you had accumulated since you were in that state the last time. Count Iblis (talk) 01:33, 25 January 2011 (UTC)

I'm struggling to reconcile your interpretation with the actual definition of death.. As far as I can tell death has nothing to do with what information is in your brain, i might have forgotten everything that happened to me before the age of 5 but by no rational definition am I "dead". Vespine (talk) 02:35, 25 January 2011 (UTC)

I suppose a philosopher might posit that your 4 year old self is now dead, but that's pretty tortured.

Also, I think the "finite number of states" is a red herring, I wouldn't be surprised if you could survive all the way to the heat death without duplicating states. APL (talk) 04:11, 25 January 2011 (UTC)

lol yes, by adding rational i was attempting to exclude the philosophical "out", maybe I should have said airy fairy ;) Vespine (talk) 05:42, 25 January 2011 (UTC)

Well, the heat death or the big rip would imply mortality, so you have to assume that this doesn't happen and that the universe goes on forever. Then we apply a similar reasoning as in the Poincare recurrence theorem. Count Iblis (talk) 13:44, 25 January 2011 (UTC)

The traditional Four Horsemen of the Apocalypse idea divides up the ways of dying into oppression, war, famine, and pestilence. (I suppose crime, terrorism, ignorance, and suicide or old age also fit roughly into these categories) Curing all diseases (including old age and mental diseases) would cut off one of the exits, but the question is whether the others are always defined by the reader as "natural death". Wnt (talk) 05:14, 25 January 2011 (UTC)

How broadly do you define 'all illnesses' and 'natural causes'? Do accidental deaths count? (Car accidents, falls, drownings, and the like?) The all-ages all-causes rate of accidental deaths in the United States in 1996 was 35 per 100,000 per year: about 0.03%. Assuming that value remains constant, one would have a half-life of about two thousand years. In practice, that risk peaks twice — a bump in late adolescence (ages 15-24) and very sharply in old age (65 and up). So the question is, will our otherwise-immortal humans have the reflexes and durability of early middle age, or will they be frail and fragile geriatric patients? The over-75 risk is actually about four times the average, at 140 per 100,000. (Those numbers also don't include homicides, ranging from the individual crime of passion to the global thermonuclear war.) TenOfAllTrades(talk) 14:34, 25 January 2011 (UTC)

even without diseases, which I'll take as viral, bacterial and parasitic infections for the sake of simplicity, the human body has a certain lifespan. The article on Telomeres explains rather well, but to put it in layman's terms: every time DNA is replicated not all of it can be duplicated, because it is copied at an "angle" (a gross oversimplification of 5' to 3' copying for the sake of a simple explanation). To prevent this there are protective "caps" on the end of chromosomes, these caps become shorter over time, and this is thought to be a reason for biological aging. Lengthening these caps can result in cancer, and all known 'immortal' cell lines are derived from a cancerous growth of some form. 65.29.47.55 (talk) 03:45, 26 January 2011 (UTC)

See biological immortality. Humans do not seem to naturally posess this ability. ~AH1^(TCU) 23:19, 26 January 2011 (UTC)

It is very true that transgenic human beings might well be immortal, however eliminating diseases does not automatically confer biological immortality and experiments with telomere lengthening in animals have usually lead to cancer. It's uncertain if a complex mammalian organism could ever achieve biological immortality without tumor formation. 65.29.47.55 (talk) 09:07, 27 January 2011 (UTC)

Taraxacum

The Taraxacum article says people eat them, but does not say if preparation is required. Can people just eat them raw? 82.44.55.25 (talk) 23:20, 24 January 2011 (UTC)

In fact it does: under 'Classification: Cultivars' it mentions some varieties that are suitable for blanching, and others mild enough (in taste) not to require it, which implies that they can be eaten raw as salad leaves. Further on under 'Properties and Uses: Culinary use' it mentions boiling or eating raw the leaves and buds, and also preparation of the petals for dandelion wine and the roots for dandelion coffee (or tea), with links to more detailed articles on those topics. 87.81.230.195 (talk) 23:47, 24 January 2011 (UTC)

The leaves of the young (pre-flowering) plants are very widely used as a salad green. Once they get more mature, they are too bitter. The flowers are also very bitter. Looie496 (talk) 02:45, 25 January 2011 (UTC)

I eat them every spring, in salad. You pick the leaves early on before the flower blooms or and just make salad with a vinegar and oil dressing, preferably with slices of warm cooked potatoes, because the leaves are somewhat hard and the heat from the potatoes softens them. TomorrowTime (talk) 20:34, 25 January 2011 (UTC)

Just a warning: the flower (yellow type) tastes awful and has no resemblence to the nectar taste. ~AH1^(TCU) 22:47, 26 January 2011 (UTC)

Moon

If you look at pictures such as this or this, you can still see some light on the back of the moon. This light is reflected from Earth, correct? And if not, where from? --T H F S W (T · C · E) 23:59, 24 January 2011 (UTC)

Yes, it's earthlight. HiLo48 (talk) 00:10, 25 January 2011 (UTC)

Starlight would also be a small component of any light reflected by the moon that does not originate from the Sun. WikiDao ☯ 00:15, 25 January 2011 (UTC)

As I have pointed out on this desk in another post a few weeks ago, the image File:Lunar libration with phase2.gif is a synthetic image stitched together from many thousand individual photographs from the Clementine (spacecraft). The photos were stitched into a moon image, and then accurately animated to mimic the time-lapse behavior as if viewed from Earth. Any "earthshine" in those photos should be considered synthetic. The image meta-data even explains: the moon was rendered with an ambient illumination of 1% intensity of the solar illumination - much brighter and more isotropic than actual earthshine. Earthshine is a real phenomenon, though, and you can easily see it tonight, even with the naked eye, if you look beyond the sunlit portion toward the lunar limb. This evening, the lunar sunset will be visible from the Apollo 17 landing site. If you photograph the moon, you can compare it to the synthetic image and see for yourself - the luminosity contrast is much greater than 100 to 1. Our article on Apparent Magnitude lists a full- to new-moon contrast ratio of 10 magnitudes - about 1000x - but apparent magnitude is measured in nonlinear units of luminous intensity, designed to match human perceptions of brightness. If you can manually set exposure on your camera, you can measure the actual luminous intensity difference. Have a look at the exposure chart in this guide to lunar photography. Nimur (talk) 00:16, 25 January 2011 (UTC)

Let's note also that File:Luna Nuova.jpg is no better. Such a view of the moon (no sunlit portion, dark sky) is effectively impossible, as the new moon only occurs when the sun and moon are aligned from Earth. We note that the image is an edit of this one, which displays no earthshine. As such, it's just a darkening of a picture of a full moon. — Lomn 14:09, 25 January 2011 (UTC)

The ballad of Sir Patrick Spens contains the lines (with slight variants in different versions) "Late late yestreen I saw the new moone, / Wi the auld moone in hir arme, / And I feir, I feir, my deir master, / That we will cum to harm." Apparently, "the new moon with the old moon in her arm(s)" was a common idiom referring to a thin (waxing) crescent moon with the rest of the disk dimly visible by earthshine. I've seen it many times myself and only rarely come to harm thereafter. Deor (talk) 04:17, 25 January 2011 (UTC)

You might like to read planetshine which is a little more complete than earthlight, I fancy there may be a case to merge the articles. Richard Avery (talk) 07:23, 25 January 2011 (UTC)

Light also reaches the Moon from Earth during a lunar eclipse, but the light is refracted through Earth's atmosphere rather than reflected. ~AH1^(TCU) 22:44, 26 January 2011 (UTC)

January 25

minerls

How is a mineral inoganic but yet found in natere?♠ — Preceding unsigned comment added by Dwight peru (talk • contribs) 01:52, 25 January 2011 (UTC)

There is no contradiction, maybe your difficulty is in the meanings of the words. Organic in this definition usually means either Organic compound or Organic matter while the definition of Nature can be found there. Vespine (talk) 02:15, 25 January 2011 (UTC)

To be a bit more precise, in the nomenclature of chemistry, "organic" means that it contains carbon as the key element. Inorganic means carbon is not a key component. Thus a "Mineral Acid" (a slightly archaic term) is an acid without carbon as a key component of its stoichiometry. Hydrochloric Acid (HCl) exists in nature but is a mineral acid based on the fact it contains no carbon. 65.29.47.55 (talk) 08:59, 25 January 2011 (UTC)

Furthermore, the "natural" sense of the word "organic" doesn't just mean "found in nature". Uranium is found in nature, after all, but you won't see "with 99.28% natural ²³⁸U!" on your granola bars anytime soon. --Sean 14:16, 25 January 2011 (UTC)

99.28% 238 would be a poor granola bar but an excellent kinetic penetrator for an antitank shell!

Organic food#Meaning and origin of the term states:

In 1939, Lord Northbourne coined the term organic farming in his book Look to the Land (1940), out of his conception of "the farm as organism," to describe a holistic, ecologically-balanced approach to farming—in contrast to what he called chemical farming, which relied on "imported fertility" and "cannot be self-sufficient nor an organic whole." This is different from the scientific use of the term "organic," to refer to a class of molecules that contain carbon, especially those involved in the chemistry of life.

A list of articles related to the various uses of the term organic is at our Organic disambiguation page. -- 119.31.126.68 (talk) 00:31, 26 January 2011 (UTC)

Minerals like calcite, however, can sometimes have an "organic" origin. Any sedimentary rock not considered organic is clastic, though even some new igneous rocks and minerals could have an ultimately organic origin when subducted limestone, coral or the fossil fuel substances return through volcanic activity. ~AH1^(TCU) 22:42, 26 January 2011 (UTC)

Lip cells

Hi. How often do the different layers of lip cells usually replace themselves through cellular division? Is this rate faster or slower than for regular skin epidermis? This is neither homework nor a request for medical/legal advice. Thanks. ~AH1^(TCU) 02:57, 25 January 2011 (UTC)

Epithelial surface cells, in general, will be replaced every 7-10 days. Lips can be divided into keratinized and unkeratinized sections (by the lip wet/dry line) and the unkeratinized (which is contiguous with the lining of the lips and cheeks inside the oral cavity) will be moist, decreasing friction and reducing cell shedding due to mechanical insult. Then again, a quick, sturdy rub of the lips against the teeth will remove cells at a much faster rate than normal -- it's like rubbing a dull knife over your skin. So if you do that 5 times a day every day, which most people do, and then you may bite or pick at the lips, even more cells will be removed. So I'd go for faster rate of superficial layer loss. This is all educated guess-timation, but a derm or dental textbook would likely not take into account the tooth scraping, and it seems as though that should play an overwhelming role. DRosenbach ^{(Talk | Contribs)} 07:00, 25 January 2011 (UTC)

Loss of cabin pressure / oxygen at high altitude flight

I looked at Effects of high altitude on humans, but I have some lingering questions. Obviously losing cabin pressure at high altitude is a problem, but it's my understanding that standard procedure is to descend quickly to a lower altitude. What altitude is that generally? My other question is whether or not this is a substantial problem or not. Obviously it's not beneficial, but humans have been known to survive at 26,000+ feet for hours at a time (mountain climbers of course) and for considerably longer at lesser altitudes. I guess I wonder if emergency oxygen systems are placed out of an abundance of caution, or if there's some other factor that exacerbates the problem when the loss of oxygen is quick... or something similar. Shadowjams (talk) 03:37, 25 January 2011 (UTC)

We have quite good articles on Cabin pressurization and Uncontrolled decompression. Vespine (talk) 03:43, 25 January 2011 (UTC)

Here's a topical answer - "A Qantas airliner carrying 99 passengers from Adelaide to Melbourne was forced rapidly to descend 26,000 feet after a sudden cabin depressurisation this morning... Oxygen masks dropped from the overhead consoles on the Boeing 737-400 as the pilots of flight QF670 announced that they would have to make a rapid descent from a cruising altitude of 36,000 feet to just 10,000 feet." From here. HiLo48 (talk) 03:53, 25 January 2011 (UTC)

Immediately after complete loss of cabin pressure the crew of a civil aircraft will descend quickly to an altitude around 10,000 to 12,000 feet. Trained athletes are capable of considerable exertion at altitudes above 20,000 feet, but the passengers of an airline aircraft are not trained athletes and it must be assumed some of them will be particularly vulnerable to inadequate pressure.

Supplemental oxygen systems are provided in high-flying aircraft to provide support to the passengers during the descent from cruise altitude (typically 30,000 to 45,000 feet) down to below 20,000 feet. Pressurised propeller-driven aircraft, and other aircraft that don't fly higher than 20,000 feet, usually don't have supplemental oxygen systems for the passengers because they can descend to 12,000 feet quickly enough. All aircraft that fly above 10,000 feet have supplemental oxygen systems for the pilots. Dolphin (t) 04:01, 25 January 2011 (UTC)

It's interesting that the article said it took a full 10 minutes to go from 36,000 to 10,000 feet. That's a surprisingly long time. --Sean 14:21, 25 January 2011 (UTC)

Thank you all. I especially found the Time of useful consciousness article helpful, although again, I'm surprised that the TUC limit at Everest style heights is on the order of minutes, when clearly some individuals are able to withstand it for longer. I suppose it only highlights how remarkable a feat that is. Shadowjams (talk) 04:41, 25 January 2011 (UTC)

It does indeed, though it should be added that at such altitudes humans do suffer from effects of altitude, it is common practice for teams making a bid for very high peaks to carry and use oxygen, though at partial pressures not as their only breathing gas. Mishandling of such cylinders due to the effects of oxygen deprivation have been implicated in peak casualties and near-casualties. 65.29.47.55 (talk) 09:03, 25 January 2011 (UTC)

The TUC will be for someone that has not acclimatised. People climbing Everest will do so over several days and will be starting from a pretty high altitude (Everest Base Camp is at around 18,000ft) where they will have spent days, if not weeks, acclimatising before they even start their ascent. That makes a big difference compared with rapid decompression on a malfunctioning aeroplane. The body's abilty to acclimatise to high altitude is pretty remarkable, indeed. --Tango (talk) 23:49, 25 January 2011 (UTC)

As for "surprisingly long time", descending 2600 feet per minute at a forward speed of 800 km/h corresponds to a downwards slope of about 1:19. It appears believable that the 737's lift-to-drag ratio is in about that range, so that would be consistent with the pilots reducing thrust to idle and letting the plane glide downwards at constant speed. Going down faster than this would require some additional drag to avoid exceeding the maximal rated airspeed. It is probably SOP not to deploy spoilers in this situation unless particularly necessary. In the event of sudden trouble (and remember there's a problem of unknown nature unfolding somewhere on the aircraft) it would be preferable not to start dealing with it from a deliberate high-drag/low-lift configuration. –Henning Makholm (talk) 15:35, 25 January 2011 (UTC)

The problem is increasingly difficult to solve as the airplane's cruising altitude increases. The highest-flying airliner is (was) Concorde which cruised around 60,000 feet, almost twice as high as other types of jet airliner of the day. (Time of useful consciousness at 60,000 feet is not long enough for passengers to react and don their supplemental oxygen masks.) The maximum credible cause of sudden decompression was loss of one complete window in the passenger compartment. It was possible for Concorde's engines to supply sufficient compressed air into the cabin to maintain cabin pressure at a survivable level during the deceleration and descent to 10,000 feet, even with one complete passenger window missing and air pouring out the resulting hole. However, it necessitated smaller windows in the passenger cabin than windows in other types of jet airliner of the day. See Concorde#Cabin pressurisation. Dolphin (t) 06:14, 26 January 2011 (UTC)

Exoatmospheric Warefare

Hypothetically, would an airtight bulkhead be of any use when applied to an exoatmospheric vessel intended for warefare? Would the bulkhead be at all effective in minimising the loss of atmosphere due to explosive decompression, like what could result from an explosive ordinance strike?

Conditions:

1. The vessel has a large internal volume, approximately seven million cubic meters.
2. The bulkheads doors are normally in the open position, they take 3 seconds to seal.
3. The doors are approximately 14 square meters in area.

--Plasmic Physics (talk) 10:16, 27 January 2011 (UTC)

Independence Day

Hello.

  I refer to the 1996 film Independence Day, in which during a missile tipped with a nuclear warhead is used to destroy the alien mothership. The alien mothership is said to be 550 kilometers long, with a mass one-quarter that of the Moon; so how can a single nuclear warhead completely destroy such a huge vessel? I'm quite familiar with the scene where anti-ship Harpoon missiles were fired at a 15mi-wide destroyer ship floating in the air, but obliterating a 550km-long mothership with one single nuclear warhead would require new spans of imagination, as I estimate that the equivalent of around 14,600,000,000 tons of TNT would be needed to blow up something that big. Even the world's most powerful nuclear bomb ever made, the Soviet Tsar Bomba, had a maximum yield of 100,000,000 tons. So atleast 146 Tsar Bomba warheads would be needed to obliterate a 550km-long alien mothership. Are my calculations correct?

  Thanks, everyone. Rocketshiporion♫ 03:54, 25 January 2011 (UTC)

Maybe they hit the armory. APL (talk) 04:06, 25 January 2011 (UTC)

Could you share your calculations? Taking your numbers (which sound familiar, so I'll assume they're correct), the gravitational binding energy of the ship (which I further assume, incorrectly, to be spherical) is on the order of 9 x 10³¹ joules, or about 2 x 10¹⁶ megatons of TNT. You could certainly destroy a ship with less, but I'm assuming you're going for the "explodes into a million tiny pieces and leaves no large wreckage" level of destruction that was seen in the movie, which although it leaves Earth being pelted with a considerable amount of debris, is better than being pelted with a moon-sized spaceship. I'm willing to chalk up the epicness of that destruction to secondary explosions - maybe there was antimatter onboard. Someguy1221 (talk) 04:12, 25 January 2011 (UTC)

This really counts as an entertainment question rather than a science question - there's no doubt that such a ship could blow up, if designed in a highly unstable way. In the movie, as I recall, the big saucers over the cities could be blown up with a single 9/11 style attack on their main weapon, and the main ship was attacked with a bomb brought near to a central reactor. Wnt (talk) 04:24, 25 January 2011 (UTC)

I thought the big saucers over the cities were destroyed because the "9/11 style attack" damaged their one and only engine? (Or at least, their one and only glowing bit.) and they fell down onto the city. Not really the best strategy on the part of the saucers. Very intimidating, but it seems like an engines-on hover like that leaves them at their most vulnerable. APL (talk) 06:14, 25 January 2011 (UTC)

gravitational binding energy is not the right way to measure this since no ship would be held together this way. But lets ignore that. The ship massed 1/4 of earth's moon, i.e. 1.836×10^22 kg. The Tsar Bomba has an energy of 420PJ. Put those together and you can accelerate the ship to the amazing velocity of 6.8 mm/s! So yah, a nuclear bomb would do absolutely nothing to it. It would barely be able to move it much less destroy it. Ariel. (talk) 04:37, 25 January 2011 (UTC)

I used GBE not because it was what held the ship together, but because the level of destruction showed that GBE was probably exceeded. Someguy1221 (talk) 04:43, 25 January 2011 (UTC)

The writers and creative directors of Independence Day probably didn't worry too much about the technical merits of the plot. So, suspension of disbelief is called for. But anyway - the energy of explosion is not only from the bomb. Consider another issue: overpressure. The mothership was floating in space; its material construction (or energy beam shielding or whatever) had to keep the air inside in, across a pressure differential with the vacuum of space. A slight increase in the pressure (such as we'd expect, at least locally, when the bomb explodes) would increase the internal pressure, presumably above the yield strength of the ship's walls and superstructure, and boom. All that air - which was not gravitationally bound - serves as an energy reservoir of pressure-volume work. One slight disruption breaks the external containment, and boom. This is one reason why space combat is a very bad idea. You don't need to obliterate a ship - you just have to pop its pressure hull like a balloon. Nimur (talk) 05:31, 25 January 2011 (UTC)

of all the myriad issues with the rigors of science and Independence Day I find the question of how an off-the-shelf apple computer could hack an alien mainframe that might not even use binary logic far more pressing... however it is noted well above and I concur that it has been proven in real-life naval combat that a single blow to a vital section can destroy a ship, assuming an alien energy reactor was poorly designed in such a way it might release energy explosively if tampered with, the real cause of destruction would be the xenos own personal Chernobyl happening in the middle of the ship, not the bomb itself. 65.29.47.55 (talk) 09:07, 25 January 2011 (UTC)

The most unlikely part of that film was the RAF officers saying "Thank God for the Americans" - "It's the Americans - take cover!" is much more likely ;-) Alansplodge (talk) 09:56, 25 January 2011 (UTC)

IMO, destroying a 550km-long spaceship (really more like an artificial moon, given its sheer size and mass) with a single nuclear warhead would be equivalent in scale to blowing up an aircraft-carrier with a single hand-grenade. A well-aimed thermite hand-grenade tossed into one of the jet fuel reserves on an aircraft-carrier would cause the entire ship to explode, but the hull would still mostly be in one piece - there's still be a pretty large wreck. As for my calculations, they are quite crude. Using the Little Boy, which had a blast radius of around 3km, as a yardstick, I calculated as follows.

 3km blast radius - 20kT yield, hence 275km / 3km = 91.6666666667 and 20kT * 91.6666666667^3 = 15,405,092.592kT
 for simplicity (albeit not accuracy) I rounded it off to 20kT * 90^3 ≈ 14,600,000kT

Rocketshiporion♫ 11:31, 25 January 2011 (UTC)

A ship of that size and mass would have a density of about 65 times that of the Moon (and that's assuming the ship is spherical, any other shape would increase the density further). That's denser than the core of the sun! I don't know of any was of constructing a space ship that would give such a high density, so we must assume it is something completely beyond our science. In that case, we cannot predict how it would respond to a nuke. --Tango (talk) 00:07, 26 January 2011 (UTC)

In the very same movie, they use an old Apple Mac to upload a "virus" onto miraculously compatible alien mothership (the very same that was destroyed, I guess US government should review Apple's export activities) when in practice such hypothetical virus would not even be compatible with current Mac OS X. I think you are wasting your time trying to make sense of the logic behind it and maybe you should consider turning on your suspension of disbelief.--110.174.117.185 (talk) 06:33, 28 January 2011 (UTC)

Energy as a measure of damage?

Have there been any studies on how the kinetic energy of a bullet or the thermal energy of an explosive device relates to the number of shots or blasts it takes to kill a person or destroy a vehicle, if accuracy is held constant? NeonMerlin 04:22, 25 January 2011 (UTC)

You'll have to define "destroy". Or even kill. News reports demonstrate a properly aimed Q-tip can kill a man given the right circumstances. Now, as for vehicles, I'm certain you would clasify "hitting a tank so hard the turret comes off" as destroy, but what about simply taking the treads off the wheels? Or what about a weapon that burns a tiny hole through the armor and then incinerates everyone inside? You'd have to not only define destruction, but also hold constant the way the weapon works. Someguy1221 (talk) 04:38, 25 January 2011 (UTC)

You may find Impact depth interesting as it gives a direct relationship. Ariel. (talk) 04:43, 25 January 2011 (UTC)

Possibly the science used to answer this question would be Terminal ballistics. Vespine (talk) 05:37, 25 January 2011 (UTC)

Absolutely yes. Conservation of energy is widely used in the study of weaponry, in both design and operation. If you peruse our various articles on military firearms and heavy artillery, you'll see the term muzzle energy pop up very often. This energy term has huge impact on the stopping power of a handheld firearm, and on the damage of an artillery, cannon, or other heavy weapon; energy can be a more useful parameter than muzzle velocity because it also accounts for the mass of the projectile. Downrange energy is a little harder to be precise about, because it depends on how far down range your projectile ends up; how much air resistance, and the trajectory it took. Have a start at our ballistics article, and our terminal ballistics article, and let us know if you need help finding anything more specific. Nimur (talk) 05:38, 25 January 2011 (UTC)

h (home depot)

does home depot have a basement — Preceding unsigned comment added by Tommy35750 (talk • contribs) 04:27, 25 January 2011 (UTC)

The one near me doesn't. Unless you find a home depot with a second story, it's pretty safe to assume it doesn't have a basement. Why do you ask? Ariel. (talk) 04:41, 25 January 2011 (UTC)

A basement is generally opposed to the idea of a "big box store" (hmmm, that's an American sense - apparently the UK has two story "big box stores", but having to take everything up an elevator is just the sort of labor that an American big box store is trying to cut out), but I would be surprised if they don't have at least some sort of crawlspace for their plumbing, and a "penthouse" on the roof for some of their HVAC equipment. Wnt (talk) 05:46, 25 January 2011 (UTC)

We are lazy, aren't we? My own observation is that the big box stores (not Walmart, but Target and such) have second floors where land is too expensive to have a profitable one-floor outlet. But then high land prices tend to ruin the whole "low low prices" strategy, which is why they're still pretty rare. Someguy1221 (talk) 09:21, 25 January 2011 (UTC)

They put all the plumbing around the sides, and nothing in the middle. It would be too expensive to make a strong elevated floor (the loading levels are much higher than in a residence or office) rather than just placing in on grade. And even if they put something in the middle it would just be a buried pipe without a crawlspace. Ariel. (talk) 07:07, 25 January 2011 (UTC)

Home Depot in Manhattan is the lower levels of a large building. I can't remember if anything except the entrance is as high as ground level--just a small space to get to the escalators/elevators, and I think most of the major actual store floorspace is on the lowest below-ground level (at least among those open to the public). It was built into an existing building IIRC, so this is definitely a large store in a multilevel construction, not "expand exoskeleton to fill the land" as typical "big-box". DMacks (talk) 09:28, 25 January 2011 (UTC)

• I think that everyone has missed the OP's question completely. I think they are trying to ask if the Home Depot runs a bargain basement; which is the term for a store which sells damaged/old/out of style items for a main store. In the past, the "bargain basement" used to literally be in the basement of large, multistory downtown department stores; though they eventually got spun off as independent chains for selling remainders from the main store. In the U.S. northeast, prior to the 1990's department store consolidation, many people will remember Filene's Basement, which was spun off from the higher-end Filene's. I take the OP's question to mean "Does the Home Depot maintain any 'bargain basement' stores for selling its damaged/old/remaindered items." I don't know the answer, per se, but it does give us an extra place to search... --Jayron32 15:47, 25 January 2011 (UTC)

what I wanted no is why A does in the concrete not crack. in my basement there are cracks in flour — Preceding unsigned comment added by Tommy35750 (talk • contribs) 21:58, 25 January 2011 (UTC)

If there are cracks in your foundation, you need to contact a business that repairs them or ameliorates their effects. Look up "foundation repair" to find someone to come out and inspect your situation. If you live in an area with a high water table you may also need to install a sump pump to keep your basement dry. Cracked foundation is generally not a good thing. --Jayron32 04:10, 26 January 2011 (UTC)

The Target store nearest me has two full shopping floors. It has a amusing four-lane escalator. The outer lanes are, as usual, for customers, while the center two are fitted to handle shopping carts. PhGustaf (talk) 22:43, 26 January 2011 (UTC)

Genomic DNA in northern blot

Ummm... is it necessary to remove genomic DNA before performing a northern blotty blot blot? --129.215.47.59 (talk) 10:47, 25 January 2011 (UTC)

According to Northern_blot#Procedure - yes. SmartSE (talk) 10:54, 25 January 2011 (UTC)

You probably should consider a more technical how-to forum like this one (there are many others). In general what you would usually like (though it could be different for specialized situations) is a known amount of polyadenylated RNA in each well, pure as the driven snow. If you have genomic DNA mixed in with your samples, for example, who knows how much you're really loading? And of course there is always the dread of RNAse in less-pure preparations (though then again there's also the dread of contaminating the RNA or letting it get chopped up while you're messing with it).

That said, at least in theory, the emphasis on doing Northerns with poly(A) rather than total RNA does impose a certain bias, because who knows if the RNA you're interested in really follows all the standard rules about how RNA is supposed to be processed in the cell? For all you know, for example, the removal of the last intron is a crucial regulatory step for your gene. Wnt (talk) 20:12, 25 January 2011 (UTC)

What comes after Blu-ray?

There was VHS --> DVD --> HD-DVD --> Blu-ray. What's after? --70.179.181.251 (talk) 14:08, 25 January 2011 (UTC)

Internet TV? I know we already have it, but it does seem as though the time will come when having a physical copy of something will be a bit pointless. If everywhere was to have a high speed broadband connection then you could hire/buy an electronic film in HD and have it streamed to you as and when you want. (Oh and the HD-DVD --> Blu-ray isn't quite accurate as both are the same step, it's just that Blu-ray won the format war, like the VHS over Betamax.) SmartSE (talk) 14:27, 25 January 2011 (UTC)

Blu-ray#Ongoing_development covers some future directions. --Sean 14:29, 25 January 2011 (UTC)

Smartse is probably correct in that the future is fully digital (i.e. physical-copy-less) media. Music is already going that way. Future advances will go towards speeding delivery methods and improving resolution and quality of digital streaming, but given the trends in other media (cloud computing, MP3 and iTunes, etc.) the days of maintaining a hardcopy of anything are fading. In fact, given the trend towards cloud computing, you may not even have a locally stored copy of your media. You simply buy the rights to play a song/movie/video game and then you have the ability to listen/view/play the media anywhere you want, using any of your connected devices. We're already almost there now, there's just the inertia attached to the old media and attitudes. Give it a few decades, and we'll all be wondering why people in past generations felt the need to keep a personal copy of anything... --Jayron32 15:05, 25 January 2011 (UTC)

Your list conflates physical formats with resolution upgrades. You need to split them. I agree that it's likely that the next physical format won't exist, and it will be internet. But a resolution upgrade is certainly possible, and is likely to be 4K resolution, after that comes Ultra High Definition Television (but given how technology works we may skip 4K and go directly to UHDT). Ariel. (talk) 15:16, 25 January 2011 (UTC)

Stereo blu-rays may be "next". They're not a new media, but they're a reason to buy all your movies again if you're into that. It'll be a hard sell, though. 5-10% of the market is stereo blind, (or stereo-blind enough that they don't care about 3d) and the most of rest aren't going to want it until someone invents an auto-stereo TV that can be seen from any angle.

Personally, I'd like to see movies at a higher frame-rate, but I believe that blu-ray disks could handle that as well.

Blu-ray may be the end for a while. Physical collections of movies may become the domain of a small market of enthusiasts and collectors. That's probably not enough of a market to support a new standard every decade. APL (talk) 15:40, 25 January 2011 (UTC)

I stream high definition TV from the internet via Netflix and "Hulu plus" using a Roku wireless connection box. It is a much more satisfying experience than watching Netflix discs or discs from the library or rental place, since most discs which have circulated a few times have scratches causing the program to skip ahead or back, with some bits utterly unwatchable. Only new CDs seem to play reliably without the need to clean the disc and polish out scratches. The only benefit for physical media right now is the larger selection: Netflix still has far more titles on CD than on Internet. I suppose that in the future one might rent or borrow from the library a video program stored on a solid state memory chip. That would get past the problems of a device trying to read a spinning disc optically through jammy thumbprints and deep scratches. Moving media belong in the scrapheap of technology. Edison (talk) 16:33, 25 January 2011 (UTC)

I would like to suggest that your disk player has a problem. Over the years I have rented literally hundreds of disks from Netflix, both DVDs and Blu-rays and I have received exactly two that were damaged in any way that had the slightest impact on my viewing experience. (They were both snapped in half by the postal service.) Not once has a scratch caused even the slightest problem for me. Nor have I ever felt the need to "clean" a disk before putting it in my player, because I know from experience that any number of thumbprints will not effect playback.

On the other hand I find that compression artifacts are very noticeable in Netflix's streaming service, especially since they changed it about two years back. And that's if you have as much bandwidth as Netflix is willing to give you. If your network connection has problems that day (For example, if it's a school snowday and your local cable-provider is over-stressed.) then you'll get even worse quality and the skipping and stuttering you're so afraid of.

(I'll grant that my sensitivity to compression artifacts may be because I watch movies through a projector that lights up my entire wall, and not a small computer screen.)

I'm not complaining, I love both halves of Netflix's service, but for movies that are a "visual feast", there's still no substitute for a blu-ray. Or even a DVD if there's no blu-ray available. APL (talk) 17:14, 25 January 2011 (UTC)

Sadly, the problem is scuffs and scratches on the DVD, (as well as sometimes dirt) since 2 DVD players and a computer DVD drive all have problems with the same DVDs. I would rather have compression artifacts I cannot see rather than have the playback stop, the skip back or forward several minutes. Then I try cleaning the disc, with a soft cloth, which usually does not fix the problem. Then I spend some time cleaning the disc with a device sold for that purpose, if I still want to watch it at that point. Sometimes I try reversing back to as close to the scratched sport as I can, but it always takes out part of some scene I would like to watch without all the fiddling around. You might have a more modern or sophisticated player with more error correction. Edison (talk) 01:00, 26 January 2011 (UTC)

Well, OK, I believe you, but I have rented huge number of Netflix disks (In the three digits) and have honestly never had that problem. I pop the disk into my Playstation3 and it works every single time. I mean that literally. This is not an exaggeration. APL (talk) 03:46, 26 January 2011 (UTC)

Maybe the number of my bad experiences stands out in disproportion to its mathematical exactitude, and the good disc experiences fade into the background. Edison (talk) 18:36, 26 January 2011 (UTC)

I think that the rumors of the death of physical media in the way you are predicting are greatly exaggerated. There will always be people who want to hold physical copies of something, if nothing else, to have possession of it once its DRM authentication server gives up the ghost. Titoxd^{(?!? - cool stuff)} 17:17, 25 January 2011 (UTC)

Based on reports that Blu-ray requires censorship from anyone allowed to mass-produce the disks [2] I would say that it is not actually a storage medium at all, but a publisher with some proprietary format. But it appears that the company is creating some ambiguity on the issue, and I can't say for sure what the full truth is. Wnt (talk) 20:24, 25 January 2011 (UTC)

Note that if you read the linked article carefully, it's only Sony who refused to work with porn. And while Sony may have been a key part of Blu-ray, the Blu-ray group themselves said they would work with anyone. And even before they won the format wars (and everyone else who wasn't part of Blu-ray joined so Sony's influence diminished even more) people were already making Blu-ray porn [3] and there is plenty of porn on Blu-ray porn now [4] (store link, if you are at work and they aren't extremely liberal with what you can do you may want to consider what we're discussing and look at the link name before clicking on it) including of course 3D porn [5] (discussion of a specific title, again think of what we're discussing). On the other hand even while the format wars were ongoing plenty of people mentioned that it didn't really matter much unlike it allegedly was in the Betamax-VHS fight since the porn market was moving on from physical mediums which was what would happen with other movies and shows, and that hasn't died down [6]. Nil Einne (talk) 21:55, 25 January 2011 (UTC)

In fact, the fact the LA porn industry endorsed blu-ray and not HD-DVD was a major deciding factor in the format war. 65.29.47.55 (talk) 01:46, 26 January 2011 (UTC)

I know the Porn-Drives-All-Media has a grain of truth to it, but it can't claim credit this time. Blu-ray's success was almost entirely due to Sony's efforts. Both their strong advertising campaign (Much stronger than the HDDVD one), movies from Sony Pictures were big factors, but most importantly the Playstation3 solved the chicken-egg adoption issue by putting millions of blu-ray players into the homes of people who weren't necessarily looking for a new movie player. APL (talk) 03:58, 26 January 2011 (UTC)

All true I will admit, but the choice by the LA-based porn industry to back blu-ray was a significant coup for the format. If porn decided to back HD-DVD it would have made HD-DVD a potent contender instead of a distant also-ran 65.29.47.55 (talk) 09:10, 27 January 2011 (UTC)

Jupiter," Posibly a furter STAR ?"

I have heard that the core of Jupter is a metalic Hydrygen , posible because of the extreme presure,not posible here on Earth. When our Sun novas and explodes is it posible the core of metalic Hydrgen will ignite and start a new star? ( If you have seen Magneseum burn and the brightness of that, and know the explosive forces of Hydrogen ,with the Sun as a flame or catalist to ignite the metalic hydrogen I wonder if it could become a new Star?" My questioncomes from the artical on Nova posible from Hydogen —Preceding unsigned comment added by 71.190.254.93 (talk) 17:15, 25 January 2011 (UTC)

It already happened in 2010. Staecker (talk) 17:27, 25 January 2011 (UTC)

Most planetary scientists do not believe that the pressures and conditions inside Jupiter are anywhere close to sufficient to sustain nuclear fusion - so the short answer is "no." If you're interested, I recommend this article, Formation of Giant Planets and Brown Dwarfs, written by a leading NASA planetary scientist, that explores the practical observational facts that we have collected on the formation of large planets - there are many similarities and differences from small stars. For the slightly less technical reader, here is a 2002 Nature article, Extrasolar planets, by the same author, that discusses Jupiter structure, comparatively to other celestial observations of stars and star-like objects. That article also states that Jupiter is about 13x too small for deuterium fusion to occur. Nimur (talk) 17:37, 25 January 2011 (UTC)

Stars are not on fire. See fusion. --Sean 18:08, 25 January 2011 (UTC)

Our Jupiter article, in the section "Mass", says that Jupiter might ignite if it were 75 times its current mass. Comet Tuttle (talk) 19:08, 25 January 2011 (UTC)

The chemical reaction of magnesium with oxygen, or hydrogen with oxygen, is completely unrelated to proton-proton fusion. What is more surprising is that fusion is actually a very weak energy source, which our article on the Sun compares to the amount of heat generated by a compost heap! What is difficult to grasp is that the Sun is very, very, very big, and all the heat from the core of the Sun has to come out of the surface. It's as if a "compost pile" the diameter of the Earth were perfectly insulated except for the very top and all the heat just adds up. (See square-cube law if you want a really technical description of that) The funny thing is, hydrogen in the Sun wouldn't even burn with oxygen - in stars that are big enough, just before supernova, the oxygen sinks to the core instead of forming water. That's because the Sun is so hot that it is made up of a "plasma (physics)" where all the electrons are stripped away from the atoms - they're transcended beyond burning. Wnt (talk) 20:35, 25 January 2011 (UTC)

I thought our sun wasn't the right size to even qualify for a supernova death? TomorrowTime (talk) 20:37, 25 January 2011 (UTC)

Sorry about the confusion, I wasn't saying it was - just if it were. Wnt (talk) 20:46, 25 January 2011 (UTC)

This post does pose an interesting question, though: how much matter could Jupiter be expected to capture and accrete while the Sun is shedding its outer layers into a planetary nebula? Titoxd^{(?!? - cool stuff)} 21:13, 25 January 2011 (UTC)

Apply the inverted formula of Jean's Escape to compute a rate of gravitational-capture. The answer depends on the gas temperature. You can estimate an effective "capture cross section" for Jupiter to describe the percentage of gas particles that will pass close enough to Jupiter to be captured (assuming they are ejected from the sun isotropically - a zeroth-order model that you could improve on as you so desire). Over astronomical time-scales, I doubt it even matters which direction or trajectory an individual ejected gas particle follows - eventually, the nebula will reach thermal/gravitational equilibrium; and angular momentum will be conserved. Nimur (talk) 23:15, 25 January 2011 (UTC)

To order of magnitude, if Jupiter captures everything that comes within a few Jupiter radii and the sun ejects matter isotropically then you have a factor that is ((radius of Jupiter) / (orbital distance of Jupiter))^2 = 8×10⁻⁹. Which basically guarantees it won't make a big difference in Jupiter's life cycle. Dragons flight (talk) 23:27, 25 January 2011 (UTC)

The gases that produce a planetary nebula at the end of the Sun's life would be ejected from the outer layers of the red giant sun with enough force to blow away most of Jupiter's atmosphere, leaving perhaps only its metallic core and possibly an outer layer of metallic hydrogen cooling over time despite the core's incredible density. Even to produce a brown dwarf, Jupiter would need to be roughly the same size it is now but at least 13 times more massive, which still is not enough to initiate nuclear fusion. See also formation and evolution of the solar system. ~AH1^(TCU) 22:37, 26 January 2011 (UTC)

I swear we used to have an article on Lucifer project. Vespine (talk) 00:11, 27 January 2011 (UTC)

I think human can do so ...... look that if we add one of jupiters moon mass to it it will be a star , we can send all earth nucleic bombs and explod IO or ganymide or metis then bring it to roche limit and fall on jupiter .then the human will release of that bombs .(INSHALLAH) dont think about that our sun is here for several billion years dont worry

--78.38.28.3 (talk) 16:06, 9 April 2011 (UTC)

  == for more information ==

akbarmohammadzade any interstellar object with mass (Jupiter +moon) will have especial condition and inner pressure and heat for beginning fusion and carbon cycle for nucleic reactivity , my meaning is not that our uranium can case Jupiter to be star , my plan is this (for Imagine only): this is my forecasting of such event 1)first we send nucleic bombs toward one of Jupiter moons (for example Métis or Io) 2)if we bombard it with bombs it will EXPLOD(If all nucleic bombs explode they can explode 5 times earth ) 3)METIS is closer moon to roche limit , and will fall on Jupiter 4)Jupiter mass will Increase (the IO and Ganymede have more mass)with adding it 5)fusion nucleic reaction will began and JUPITER will be a star 6)the magnitude of Jupiter will be first in sky after moon and sun 7) it can create a shadow of objects 8)some nights it will reduce the visibility of other stars and mars in conjunction

9)the radius angle of it remain stable 

10 )it will send poor energy 11)we will see it at day 12)IT can case creating shdow of moon on earth 13)it will send light on unvisible part of moon and we will see it wonder ful 14 )it will has hot winds and storm 16)it will effect on our radio relations --78.38.28.3 (talk) 10:27, 11 April 2011 (UTC) April 2011 (IUST)......

Orbit

What is the name of the object a satellite orbits around? Our article on Kepler's Laws just uses the phrase "sun", but obviously one would not refer to a planet or a black hole as a "sun". --T H F S W (T · C · E) 20:05, 25 January 2011 (UTC)

Perhaps "focus" (of the orbit) or "barycentre" or "centre of mass"? Dbfirs 20:12, 25 January 2011 (UTC)

Focus_(geometry) seems appropriate, but Barycenter seems incorrect, i.e. the focus around which an object rotates is not the center of mass of the system. From our article on Kepler's laws "The Sun is not in the center but in a focal point". The focal point is the abstract point in space though, not the object. SemanticMantis (talk) 20:18, 25 January 2011 (UTC)

... but the focus of the orbit is the barycentre (and the centre of mass of the two objects). The centre of mass is not at the centre of the ellipse, and the rotation is not around the centre of the ellipse. Dbfirs 00:03, 26 January 2011 (UTC)

I would use primary, although the article says that it has yet to obtain currency for extrasolar orbits. --Tardis (talk) 21:51, 25 January 2011 (UTC)

Yes, that's a better answer to the question, since it does ask for the object, and the focus is not necessarily within the object. Dbfirs 01:09, 26 January 2011 (UTC)

I agree that "primary" is a good term, and another description could be that the satellite orbits the centre of a Hill sphere. ~AH1^(TCU) 22:31, 26 January 2011 (UTC)

Autoclaving a bottle of liquid

Suppose you want to autoclave a bottle of medium, to make it sterile, and suppose the medium actually contains bacteria or bacterial spores at the beginning. If I understand correctly, the autoclave's mode of action is to utilise the latent heat of vapourisation of water to sterilise by subjecting things to steam. However, the liquid medium, whose primary component is water, will not benefit from this because steam will not permeate the liquid - it would be no more sterile than if it were boiled, and if any spores remain after boiling, then they would surely remain after autoclaving? Also, how loose should a lid be? Completely, and just resting on top, or..? --129.215.5.255 (talk) 20:24, 25 January 2011 (UTC)

The heat of vaporization has little to do with it. The main point of autoclaving liquids is that it makes them hotter than boiling them under typical room air pressure. For example, the typical lab autoclave will bring liquids to 121 C instead of 100 C. Now in order to do this, you need to do two things:

• Pressurize the chamber. Because water not under pressure boils at 100C, and it would boil out entirely.
• Saturate the chamber with water. Because if boiling water is not in equilibrium with steam, it still loses volume, and you have things in the chamber a fairly long time. (In practice the volume of solutions coming out of an autoclave still tends to be reduced a little, because the air isn't perfectly flushed out, etc.)

The easiest way to do these two things is with highly pressurized steam.

The lid has to be loose enough that there is no way, despite expansion/contraction, that it can possibly stick and form a tight seal, or else SOMETHING is going to give when the pressure changes. Wnt (talk) 20:43, 25 January 2011 (UTC)

(edit conflict) No, autoclaves usually use high pressure steam. I'm not sure what pressure is typical, but I recall autoclaves that were labeled for 2 atmospheres total pressure. The advantage of the high pressure when autoclaving water-based liquids is that it allows the liquid to be heated above 100 C without boiling away. So the media will reach an elevated temperature (e.g. 120-135 C) that is more effective at killing organisms than boiling (at 100 C) would be. Autoclaves intended for this purpose generally have a "liquid-cycle" that controls the pressure in a way that minimizes boiling during the cool-down phase. One also generally needs to run the cycle longer to ensure the whole volume of the liquid is effectively heated when compared with sterilizing empty containers. A rule of thumb with caps is that if you fill the bottle with water then the cap should be loose enough that the water will flow quickly past it and continue flowing easily even if you press down or pull up on the cap. One way to accomplish this is to simply leave the cap resting on top (and that's pretty common), though it is also common to see caps partially threaded, provided they don't create an effective seal. With liquids most of the heat will be conducted through the walls of the container (rather than through the top), but you need to avoid creating a seal that would lead the container to be at a different pressure than the outside since that could lead the container to explode (or implode). Dragons flight (talk) 20:56, 25 January 2011 (UTC)

The science classic "Microbe Hunters" (1926) says that Lazzaro Spallanzani, in the 18th century, sealed flasks of water or broth and left them in containers of boiling water for hours to kill off microorganisms. How was he able to do that without the flasks exploding? There is no mention of using a pressure cooker, and they were glass flasks of thin enough material he could pull the neck down to a thin tube and flame seal it. I have tried boiling a container full of water in a boiling water bath, and the water in the smaller vessel turned to steam. I have no idea how to calculate the pressure which would have resulted had the small vessel been sealed in an open bath of boiling water, but I expect there could have been an extreme pressure rise. Edison (talk) 00:54, 26 January 2011 (UTC)

I don't understand why there should be an extreme pressure rise in the sealed vessel. Provided that the vessel is surrounded by water at 100 degrees, the very slight pressure rise inside the sealed vessel will increase the boiling point of the water it contains above 100 degrees, so only a limited amount of steam can form and the water in the sealed vessel will stop boiling. Of course, if the sealed vessel contains alcohol or some liquid with a boiling point below that of the surrounding water, then pressure will rise higher. In an autoclave, a sealed vessel will perhaps need to be slightly stronger to withstand pressures both ways during heating and cooling, but, with a small expansion space, I still don't see how there will be extremes of pressure, because, once equilibrium is reached, the pressure (up to two atmospheres?) will be the same inside and out. The best way to test this would be to try it with a sealed aluminium can which will show the deformation either way.Dbfirs 08:24, 26 January 2011 (UTC)

In water bath canning, where the water bath boils at atmospheric pressure, a lid with a rubber ring is screwed onto the jar to be canned, which is filled with any fruit, veg, or juice, some of which would be so watery (low in salt, sugar or other solute as to have about the same boiling point as water. Other recipes would have enough salt or sugar that the boiling point would be elevated a bit. (One could always can distilled water, I suppose, for experiment's sake). Only a small airspace is left. Although the lid is on fairly tight, secured by a screw ring, the steam pressure from within forces out steam, and the water level may drop a cm or two more with normal processing times due to steam production. When the boiling stops, pressure drop inside causes the lid to "pop" downward and stay indented. I have always wondered how high the pressure inside would rise if the lid were very tightly shut, and conjectured that the jar might explode. Would higher pressure inside somehow mean higher temperature inside the jar? There has to be higher pressure for the steam to escape during the processing. Edison (talk) 18:32, 26 January 2011 (UTC)

This mostly has to do with the partial pressure of water vapor. Consider if you have a can of liquid water inside a container of boiling water. You wouldn't expect the water to squirt out of the can, or generate steam, just because you have some of it inside a can. (Excepting minor thermal expansion of liquid water) But when you have a can with an air pocket at the top, the water (which after all is at the boiling point) dissolves into the air pocket. The added vapor exerts extra pressure, and makes the air pocket larger or under more pressure. Wnt (talk) 18:43, 26 January 2011 (UTC)

All that seems clear, but could the pressure rise significantly in a sealed jar in a boiling water bath, if no steam at all could escape, assuming some air space to allow for thermal expansion of the water, like to several atmospheres, or only to a small percentage above atmospheric? (If the water bath boiled away, then a steam explosion would be assured after a bit, so don't try this experiment at home). Edison (talk) 22:24, 26 January 2011 (UTC)

Yes, I'm not sure whether a mixture of gases will exert a higher pressure than either of the gases separately. My intuition says that when the pressure rises just slightly, the water will stop boiling and some of the water vapour will condense back into the water, maintaining equilibrium at marginally above the pressure outside, but I haven't tested this out. It should be easy to test safely with just basic equipment, even in a school lab, using a manometer. Dbfirs 08:39, 27 January 2011 (UTC)

For a sealed jar of water, wouldn't a thermometer provide the same information as a pressure gauge or a mercury manometer? I seem to recall, from "chemical thermodynamics" class, tables of pressure versus temperature for water. Should I conclude that a sealed flask of water at 100C would not go wild producing steam with a large pressure increase, given enough "headspace" to allow for volume expansion of the water at the higher temperature? So that the Spallanzani microbioloigy experiments in the late 1700's are credible? Edison (talk) 05:05, 28 January 2011 (UTC)

Well in the experiment that I was imagining (without the autoclave), the thermometer would always read 100 degrees, since heat cannot flow from a cooler to a hotter region. There seemed to be some claim of increase in pressure from formation of steam, independent of an increase in temperature, hence my suggestion of a (simple water) manometer. I can't imagine that it would happen, but it would be reassuring to confirm my intuition with an experiment because sometimes my intuition is wrong. In the autoclave, a couple of maximum thermometers would subsequently confirm equal pressures inside and out (if we can confirm that boiling temperature and pressure are closely correlated). Dbfirs 08:28, 28 January 2011 (UTC)

January 26

What's the difference between van der Waals forces and London forces?

My chemistry textbook claims that they're different names for the same force, but Wikipedia has separate articles for them. --75.15.161.185 (talk) 00:28, 26 January 2011 (UTC)

Have you read the intros to the respective articles? The London dispersion force is a component of the van der Waals force, which is itself a sum of many forces. We note in the former article that "dispersion forces are usually dominant of the three van der Waals forces", with the other two being orientation and induction forces. Small polar molecules like water are a notable exception to this trend. — Lomn 00:42, 26 January 2011 (UTC)

Forces stronger than London dispersion forces that are also van der Waals include Debye forces, Keesom forces, hydrogen bonds, ionic bonds and induced ion forces; see intermolecular force. The "London forces" are dominant in nonpolar molecules that do not have the stronger forces, as they lack permanent dipoles, and increase in strength given larger molecules and thus more atoms for temporary charge induction. ~AH1^(TCU) 22:27, 26 January 2011 (UTC)

The amount of energy in houshold rubbish

How much energy would a typical household expect to get from burning all their burnable rubbish and using it for heating? Thanks 92.24.182.244 (talk) 02:02, 26 January 2011 (UTC)

More than enough to heat their home, in most locations. But the technology to do it cleanly enough is not feasable on a household scale. And in most developed countries, it would be illegal to try to do this in a crude way yourself. Some cities do this to some of their garbage not just for energy, but to reduce landfills. Some of the remaining matterial (black "nuggets" formed) that doesn't go up in smoke can be collected and used as a raw material (for road pavement is one common application). Roberto75780 (talk) 02:20, 26 January 2011 (UTC)

Well my household does not produce enough rubbish to provide even a twentieth of the heating cost, even with super-efficient combustion, but perhaps some households produce tons of rubbish. Dbfirs 08:18, 26 January 2011 (UTC)

The article Incineration has good information on waste incineration. It says one metric tonne of garbage can produce 0.67 MWh of electricity and 2 MWh of heating. A person produces on average 726 kg garbage per year[7] Taking the average US household size as 2.6[8] that's 1890 kg per household, which will give 1.3 MWh electricity and 3.8 MWh heating.

For comparison, domestic energy consumption is around 100 million BTU or 29 MWh per household [9]. Energy in the United States says 45% of domestic energy is used for heating water, which assuming the figures match would be 13 MWh. Big shortfall. --Colapeninsula (talk) 10:55, 26 January 2011 (UTC)

Energy in the United States actually says "Residential Living quarters for private households: 13% water heating" - not 45%. Living in a mild weather area in the U.S. Midwest which is currently on day 45 of 57 to fail to reach a daily high temperature above 0°C (32°F), 45% of energy just for water heating sounds like optimism. Rmhermen (talk) 14:45, 26 January 2011 (UTC)

For many years I had the job of burning my family's trash in an old 55 gallon drum. It flared up to a high temperature, but burned down quickly, and would have been far too little to heat the home in the winter. For a time, we used coal, so I had a direct comparison of the mass of coal versus the mass of trash, and the heat produced by the coal stove versus the trash fire. There was no trash collection service at that time in that location. Edison (talk) 18:17, 26 January 2011 (UTC)

Methane capture is another method of making energy from trash, and incineration often works best given combustable (ie. organic-based) garbage. ~AH1^(TCU) 22:20, 26 January 2011 (UTC)

Rubbish Island

a) It was a quite frequent trope of 1950s-1970s films set in New York, or elsewhere, to see as a finale the hero ending up on a large barge or 'scow' taking rubbish out to sea. Where did this rubbish in actuality go to? Does this practise still continue?

b) Is there any reason why it would not be a good idea to use rubbish for land reclamation? In Britain the dogger bank is crying out to have an island built on it, and would be a great place to put all the things that nimbys do not like. Thanks 92.15.10.209 (talk) 14:47, 26 January 2011 (UTC)

Fresh Kills Landfill is now closed but the location is used to repackage New York garbage for rail shipment to South Carolina. Also not an island. Rmhermen (talk) 15:03, 26 January 2011 (UTC)

Fresh Kills Landfill is not an island, but it is on an island -- Staten Island. Indeed, it forms a rather large portion of the island. --M@rēino 20:02, 26 January 2011 (UTC)

The trash heaps occupy 2.6% (990 acres) of the 37,400-acre island and the entire site occupies about 6%. Not "a rather large portion". 75.41.110.200 (talk) 21:41, 26 January 2011 (UTC)

I believe your numbers are accurate. I'd still say that's a rather large portion of the island. --M@rēino 17:56, 27 January 2011 (UTC)

The annual volume and mass of NYC garbage must be impressive. How much trash (excluding recycled materials) has to be disposed of from that one city each year? Does SC or other victim states build Mount Trashmores out of it, or what? Edison (talk) 18:10, 26 January 2011 (UTC)

Environmental issues in New York City#Garbage disposal says the city produces 12,000 tons of (landfill) garbage per day (confirmed by this article). This totals more than 4 million tons annually. -- Finlay McWalter ☻ Talk 18:26, 26 January 2011 (UTC)

(edit conflict)New York has shipped its garbage to various places, including Fresh Kills Landfill, Philly, and North Carolina (cf Mobro 4000). Building islands is very expensive; regular garbage, and miscellaneous landfill in general, isn't a stable engineering material. High-value properties like Kansai International Airport have been constructed in shallow water, but it takes a lot of concrete to make something that doesn't just wash away. Moreover, post-consumer waste yields for lots of problems to anyone planning on building, farming, or living on top of it. Firstly it's not compact, so structures built on fill subside - the Japanese airport solution (which I think Changi uses too) is to build structures on jacks, and jack the sagging end of the building up as they subside. Secondly is methane offgassing due to biodegradation in the waste. And third is contamination - the waste stream contains (whether it should or not) all kinds of nasty stuff like paint, motor oil, medical waste, dioxins, asbestos, and heavy metals. So you'd spend a fortune constructing an island that couldn't be used. -- Finlay McWalter ☻ Talk 15:08, 26 January 2011 (UTC)

(edit conflict) The Mobro 4000 article is a very interesting read in this regard. --Jayron32 15:17, 26 January 2011 (UTC)

See also Great_Pacific_Garbage_Patch. Kittybrewster ☎ 15:35, 26 January 2011 (UTC)

I get the impression that some people think the sheer volume of garbage is a problem (see the opening of Wall-E, or of Sex, Lies and Videotape, where I think she's specifically reacting to the Mobro 4000 story). There just isn't that much garbage. Pollutants leaching from garbage into water is a problem, methane from rotting garbage is a problem, but the simple volume occupied by garbage is not a problem. If you want to reduce the environmental impact of garbage, dumping it in the middle of a body of water probably isn't the best idea. Also, if you're upset that Manhattan exports its garbage, remember that it imports the stuff that becomes the garbage. There are advantages to concentrating people in one location and putting the support systems elsewhere -- BenRG (talk) 20:52, 26 January 2011 (UTC)

Some floating islands could be constructed from garbage. ~AH1^(TCU) 22:19, 26 January 2011 (UTC)

The volume isn't a problem, until you run out of convenient places to put it. Some large cities seem to be in this situation.--Srleffler (talk) 02:16, 29 January 2011 (UTC)

Submarine speed

Why do submarines go faster underwater than on the surface? Example: German Type XXIII submarine. When underwater, would they not have more drag and more displacement of water to overcome? Thanks 92.15.10.209 (talk) 14:54, 26 January 2011 (UTC)

Turbulence. Cuddlyable3 (talk) 14:57, 26 January 2011 (UTC)

See diagram. The prop-shafts and therefore thrust is generally in-line with the central axis. If the vessel was to go too fast, the water level behind the vessels would drop further than it does at max surface speed, until the blades of the screws would experience rapid changes in the forces acting upon them as they first left, then re-entered the water. This would lead to early failure. As it is, some screws are only just covered by water when cruising on the surface. Also, and which needs to be mentioned. The deeper a sub goes, the less likely the screw is to experience cavitation but that is a bit secondary to the much faster damage caused by the atmospheric air ventilating the screw.--Aspro (talk) 15:37, 26 January 2011 (UTC)

A significant part of the drag of a surface ship is due to creation of a bow-wave and other signs of disturbance on the surface of the water. See Wave making resistance. A submerged streamlined body, such as a submarine, does not make any disturbance on the surface of the water so this form of drag is avoided.

After a diving entry, competition swimmers remain underwater as long as possible in the hope of maximising their average speed. It seems to work. Dolphin (t) 21:31, 26 January 2011 (UTC)

A Discovery Channel TV documentary I just happened to watch attributed the speed increase to water density. Go deeper, denser water, more stuff for the propeller to push against. 88.112.59.31 (talk) 22:32, 26 January 2011 (UTC)

Untrue! The pressure of water increases with depth but the density is almost constant throughout the ocean. The density of the atmosphere changes significantly with height above the Earth's surface because air is a gas. Water is a liquid and its density does not change (significantly) with changes in pressure. Dolphin (t) 01:41, 27 January 2011 (UTC)

Water does not compress as gasses do, so the density is mostly the same (as the appropriately named Dolphin51 mentioned), and even if it did increased moved mass would be offset by increased density of the medium you were pushing through, to a point. I would also suspect that a significant factor is that submarine hulls are optimized for travel at depth, not surface travel (this is especially true of the modern hull, less so I'd imagine of WWI and II-era hulls that were more closely adapted from surface ships). The article on Teardrop Hulls confirms this. Oddly the article makes no mention of the modern "Albacore" Hull, so named for the ship that first used it, which is the standard more or less today. This hull is strongly optimized for travel sub-surface and highly suboptimal for surface travel. 65.29.47.55 (talk) 09:20, 27 January 2011 (UTC)

First lets dispel the landlubber's myth that submerged vessels do not create bow waves. The sea is a viscous medium and as such, the hydrodynamic force will raise the sea's surface, above the vessel, to a hight over the mean. Although, this hight diminishes with the vessel's depth, its surface area increases. The American Fleet understood bow waves and so by the 1970's had become alarmed to discover the capabilities of synthetic aperture radar satellite technology and its ability to resolve alimentary delta information to millimetre resolutions and thus its possible potential to expose the position of its nuclear launch subs. (Note: and the difference in most cases is only in the order of millimetres.) Quote: The bow wave from submerged submarines could thus show up in radar images of the ocean's surface unquote. Page 97 Therefore, the 'wave making resistance' can not account for the slower surface speed because it exists in both situations. Indeed, if we go here to calculate the approximate displacement hull speed, we find that for this submarine's length it is about 14.3 knots rather than 9.7 or almost half as fast again and this is without the added frictional increases when submerged. Therefore, perhaps a better understanding of the danger of the screw ventilating and the way chosen to prevent it, can be had by looking at photographs of this sub on the surface, both in the article itself and again here. Compare those to the line drawing of this sub and you will see that is surface attitude is trimmed to keep the bow high. The line drawing also shows that if it was to sail without this raised forward pitch, although it would go faster, the trough formed at the rear would quickly allow the screw to suck down air as the speed increases. This would hammer the bearings, fatigue the blades of the screw and create vibrations throughout the vessel. Marine architecture is, like many other engineering structures, an assemblage of compromises. --Aspro (talk) 18:33, 27 January 2011 (UTC)

I'll just note that there have been submarines that ran faster on the surface -- for example, the German types VII, IX, X, and XIV. I think there wasn't much point in optimizing the speed underwater when they couldn't store enough electricity to stay underwater all that long anyway. --Anonymous, 11:22 UTC, January 28, 2011.

Endosome/endocytic vesicle

Is there any difference between these two terms? I have read endosome and the Gene Ontology entries [10][11] but I'm still not wiser. Is an endosome an organelle and an endocytic vesicle not (as GO suggests)? But why, both have a lipid bilayer. Can you help? -- Ayacop (talk) 16:45, 26 January 2011 (UTC)

It gets a bit semantic, but the term "endocytic vesicle" tends to be used to describe the structure that pinches off during endocytosis. This vesicle then fuses with an endosome where sorting of different receptors takes place and then allows for trafficking of those consituents to different locations. One way to think of it is that the endocytic vesicle comes directly from the plasma membrane and carries something from outside to inside. The endosomal compartment (not one organelle but a very dynamic collection of membrane-bound structures) is a bit more murky, with different compartments handling flow of materials from inside to outside, outside to inside, into the lysosomes for degradation, etc. --- Medical geneticist (talk) 16:57, 26 January 2011 (UTC)

Ah, thanks. Followup: so a phagosome would be a kind-of endosome (both can mature)? -- Ayacop (talk) 17:01, 26 January 2011 (UTC)

Why the "Coma" Cluster?

The article on the Coma Cluster gives no hint of why it is called that. Was it named after a person or a place? Was it named after the medical condition Coma, or did it somehow look like the galaxies were in a deep sleep? Is it pronounced like the medical condition? Edison (talk) 18:04, 26 January 2011 (UTC)

It's named after the constellation Coma Berenices. Info found on the Coma supercluster article. 90.193.232.5 (talk) 18:26, 26 January 2011 (UTC)

Coma is also a type of optical aberration in telescopes. That could possibly be related to the etymology of the Coma Cluster. On the other hand, coma is also used to refer to any sort of nebulous blurring, whether an artifact of instrumentation or actually due to the characteristics of the astronomical object. The word root is "coma (from the Greek κόμη, "hair")" - not from Ancient Greek κῶμα (kōma, “deep sleep”). See the wikt:coma etymologies. Nimur (talk) 18:28, 26 January 2011 (UTC)

The Latin term "coma", according to the OED, derives from the Greek κόμη, meaning "hair of the head, also applied to foliage, etc., and to the tail of a comet". As the Coma Berenice article points out, in Latin the term means "Berenice's Hair". It's of note that the use of the term "coma" for a comet's tail dates only from the late 18th century, and the use of "coma" to mean aberrations caused by lenses is from the 1860s. So there's the same metaphor here, but it's not that the name of the constellation came from the previous astronomical terms. --Mr.98 (talk) 18:45, 26 January 2011 (UTC)

I've added that piece of information to the article - many nearby clusters are named after the constellation they're in, e.g. Virgo, Fornax etc. --Wrongfilter (talk) 20:52, 26 January 2011 (UTC)

Thanks for the explanation. Someone laughed when I was talking about late 20th century cosmology/astronomy and the importance of the "Coma Cluster" observations, and asked where the name came from, and Wikipedia provided no guidance. In American English, how is this "Coma" pronounced? Like "Coma," or like "comma," or otherwise? The responses above list two differently spelled Greek words, but Wiktionary has one pronunciation. The article Greek alphabet shows the letter ο or Omicron but the one shown above was "ό." The article Omicron says nothing about accents on the letter. Apparently F. Scott Fitzgerald's story Bernice Bobs Her Hair (1920) derives from this ancient Coma Berenices legend of Berenice II cutting her hair off. Edison (talk) 05:09, 27 January 2011 (UTC)

KBOs and TNOs

KBOs, a detached object and the inner Oort Cloud.

Is there any difference between Kuiper belt objects and Trans-Neptunian objects? Or are KBOs a subclass of TNOs? --T H F S W (T · C · E) 20:00, 26 January 2011 (UTC)

Our article Transneptunian object says

"The Kuiper belt, scattered disk, and Oort cloud are three divisions of this volume of space [where TNO reside]."

As I understand this quote, all KBOs are TNOs. But there is a difference between the classes: members of the Oort cloud are TNOs but not KBOs. SemanticMantis (talk) 20:45, 26 January 2011 (UTC)

(edit conflict) Other members of the TNO class that are not KBOs include Scattered disk objects and detached objects. The Oort cloud is thought to lie much farther than the Kuiper Belt and even objects that have great eccentricities in non-parabolic orbits are thought to be unable to reach it, however. Also, the Kuiper Belt seems to cut off almost abruptly at 50 AU. ~AH1^(TCU) 22:15, 26 January 2011 (UTC)

Proton spheres

I have a question which has been left unanswered by our article on photon spheres: are photonic orbits around neutron stars more stable than photonic orbits around black holes? Why/why not? Thank you in advance. --Leptictidium (mt) 22:13, 26 January 2011 (UTC)

No difference because the space around a neutron star has the same metric (space-time shape) as the space around a blackhole. 71.101.41.73 (talk) 02:46, 27 January 2011 (UTC)

Is that totally true? A photonic orbit around a neutron star must be very close to its surface, and so far as I know a neutron star rotates as a solid ball - so matter near its poles moves in a circle that is not an orbit. But a rotating black hole has all its matter stuffed in a ring singularity or the like somewhere far from any orbiting photon. Shouldn't this mean that spacetime is dragged in a different way around a neutron star, and photons should orbit in some weirder way, at least if they aren't on the equator? (Also curious if there would be a difference if the fuzzball theory is true rather than a ring singularity...) Wnt (talk) 19:15, 27 January 2011 (UTC)

It is certainly true for a "spherical cow" non-rotating neutron star -- the Schwarzschild spacetime is the only stationary spherically symmetric vacuum solution to GR where the central body has no electromagnetic field, so it must equally describe the situation outside a black hole and that outside a neutron star.

However, there's no corresponding uniqueness property for spacetimes that are merely rotationally symmetric. (Even with zero angular momentum, surely a long dumbbell-shaped object will have a gravity field that differs from the Schwarzschild/Kerr one).

And real neutron stars can also have strong rotating magnetic fields whose axis need not coincide with their rotational axis (as for pulsars). This situation is forbidden for black holes by the no-hair theorem. Since a magnetic field shows up in the electromagnetic stress-energy tensor and so influences spacetime curvature, that would make the spacetime outside a neutron star different in principle from that outside any black hole. I don't know how that difference affects the stability of photonic orbits, though. –Henning Makholm (talk) 21:10, 27 January 2011 (UTC)

January 27

Best way to dissolve methane in a liquid that mixes with scintillation fluid

Hi,

I'd like to be able to "trap" 14-C methane in some kind of solvent so that I can mix that solvent with scintillation fluid and be able to determine radioactivity. What would be the ideal solvent for this situation? Ideally, I'd like a liquid that can trap all of the methane in the tube but also mixes with the scintillation fluid.

Thanks a lot for your help.

Ccarlst (talk) 03:50, 27 January 2011 (UTC)

Methane isn't going to be soluble to a great extent in any liquid (it is arguably more soluble in a nonpolar solvent like benzene than in water, but only in relative terms. Its not terribly soluble in either). Furthermore, even soluble gases will never completely dissolve in a liquid. Your best option is to react the methane with something, preserving its carbon, but making that carbon now bound to be part of a liquid compound rather than gaseous methane. I'm not sure how feasible it is based on the equipment you have availible, but something like Free radical halogenation would work; the article lists free radical halogenation as a method used most commonly to create chlorinated methanes like dichloromethane (methylene chloride) and trichloromethane (chloroform) both of which are actual liquids. --Jayron32 04:12, 27 January 2011 (UTC)

Try converting the methane to a methanide salt, which is soluble in polar anhydrous solvents. --Plasmic Physics (talk) 09:07, 27 January 2011 (UTC)

Yeah, but methanide salts would be much more difficult to work with than methyl halides. Alkyl salts are metastabile at best, I would expect all of them to be so highly alkaline as to be pyrophoric in air. The nice thing about methylene chloride is that it is fairly easy to work with (it is a low-boiling liquid, so you'd have to work in a cool room, but otherwise is very unreactive). --Jayron32 14:00, 27 January 2011 (UTC)

What's the source of the methane? Does the gas also contain other methane (not containing C-14) and is there anything else that does contain C-14? Google gives lots of literature hits for liquid scintillation of C-14 methane over the past few decades (sample search: 14c methane scintillation). Doesn't necessarily answer your direct question (as others have noted, it's "hard"), trying to figure out solutions to the larger situation. DMacks (talk) 09:36, 27 January 2011 (UTC)

At the moment, the source of the methane is a 1mCi vial I bought from American radiolabeled chemicals- well, at least they say is 1mCi with a specific activity of 50mci/mmol. The reason I am concerned and think that the 1mCi may be off is because according to my calculations, [1mCi X 1mmol/50 mCi X 22.4 ml/1mmol = 0.448 ml] the volume of methane I should have gotten should be around 0.5 ml, when in fact it came in a vial that looks to be about 6-7 ml. They claim there are no other gases there (and they are terrible about answering questions, so I have yet to find out if there is cold methane there too). So, I need a way to test that what they claim is there is actually what is in there. In the future, I was planning to use the 14-C methane in an experiment that is supposed to evolve 14-CO2, which I plan to trap using NaOH and then run in a scintillation counter. Thanks to everyone for your suggestions- it sounds like some of them would work well, but the problem is that it would be hard to do that kind of chemistry in a biology lab..Ccarlst (talk) 01:14, 29 January 2011 (UTC)

Of course, your 22.4 mL/mmol figure presumes the contents of the vial are at atmospheric pressure. It seems to me that if one were going to ship an expensive specialty gas in a small vial, it would be beneficial to have it well below atmospheric pressure so the pressure difference helps maintain the seal. Also, if the vial is supposed to produce a precise amount of radioactivity, they have to have some way to adjust the amount of gas they put in it, so they have to adjust the pressure anyway. Given that, they might as well have low pressure, and adjust the exact pressure when filling the vial, to hit the radioactivity target.--Srleffler (talk) 02:35, 29 January 2011 (UTC)

Geographic center of the world

Hi. I know that the geographic center of the contiguous United States is near Lebanon, Kansas {{coord|39.828175|-98.5795}} Could you, please, tell me the coordinates of the geographic center of the whole world? I searched the internet but couldn't find anything. If you don't know, could a science geek calculate the coordinates using a world map such as File:BlankMap-World6.svg and a good piece of software? --41.178.235.216 (talk) 03:50, 27 January 2011 (UTC)

To my admittedly sometimes muddled mind it seems there is no centre of the surface of a sphere. HiLo48 (talk) 03:54, 27 January 2011 (UTC)

There is, but it's not on the sphere. The center of mass of the earth is located, unsurprisingly, at the center of that sphere, not on its surface. The geographic center is defined as the center of mass of a uniform, two-dimensional cut out of the section of land in question. However, as you correctly note, it makes no sense when dealing with a sphere, only with the (planar approximation) of parts of that sphere does it make sense. --Jayron32 03:57, 27 January 2011 (UTC)

(edit conflict) I mean the center as if the whole world was flat (projected on a surface). It is probably some point in the Middle East but I need the exact coordinates. --41.178.235.216 (talk) 03:59, 27 January 2011 (UTC)

That involves some arbitrary map borders. To make the world appear flat on a map involves choosing edges, which don't actually exist, and flattening curved bits. HiLo48 (talk) 04:02, 27 January 2011 (UTC)

To expand, while a lot of maps do seem to have the Americas on the left, and Asia on the right, this one gives another perspective. HiLo48 (talk) 04:27, 27 January 2011 (UTC)

The proper way to calculate it over the whole globe is to use the (two-dimensional) circular mean. See also land hemisphere, which is nearly synonymous. --Tardis (talk) 05:02, 27 January 2011 (UTC)

For the centre of a conventionally made "flat" map, you're asking for the intersection of the prime meridian and the equator, this article has a story and pictures of a visit there (it's far out at sea off the coast of West Africa). Many world maps show more of the Northern than the Southern hemisphere, for such maps, the centre would be further north. I guess you could also calculate the centre of all the land masses in the world, this is maybe what's described in Tardis' post above. Jørgen (talk) 08:55, 27 January 2011 (UTC)

Further reading at Extreme_points_of_Earth#Center and geographical center.--Shantavira|^{feed me} 09:01, 27 January 2011 (UTC)

Greenwich, Mecca, or Jerusalem have been regarded as being the centre points of the world. At Greenwich you can stand astride the piece of metal the marks the boundry between the eastern and western hemispheres, and its where GMT comes from. 92.24.187.66 (talk) 12:21, 27 January 2011 (UTC)

Surely, the answer is wherever you are at that particular moment? --Dweller (talk) 14:25, 27 January 2011 (UTC)

Actually, the answer is wherever I am at that particular moment! --Stephan Schulz (talk) 17:17, 27 January 2011 (UTC)

I assume DWeller meant where you are. DMacks (talk) 17:25, 27 January 2011 (UTC)

Actually, I suspect it has something to do with the barycenter of the planet. Damn you, chocolate! --Stephan Schulz (talk) 17:33, 27 January 2011 (UTC)

Hmmm, despite the absurdity of it, this question is theoretically answerable. Imagine you make a globe where all the world's land surface is accurately represented by a homogeneous layer of material. Wrap it in a much lighter layer over the whole sphere to hold it together. Now put it on a smooth floor and let it roll to a stop. The point on the bottom should be "the center point of all land on earth", and the point on top should be "the center of all Earth's oceans". An industrious person could probably do this on a computer in a jiffy, but alas... Wnt (talk) 18:01, 27 January 2011 (UTC)

I think that method would find a centre very close to (but not exactly at) the centre of the land hemisphere mentioned above by Tardis. --Tango (talk) 22:12, 27 January 2011 (UTC)

According to this web page, "If you've ever wondered where the geographic center of the world's land area is, the coordinates are latitude 34 deg 26 min North and longitude 27 deg 19 min East. This puts it in the eastern Mediterranean Sea about halfway between Athens and Alexandria.".Looie496 (talk) 01:01, 28 January 2011 (UTC)

I wonder if what they mean by that is "the point at which the sum of the distance (along the surface) from there to the center of every 10 arc-minute² area of land (maybe defined as just "not-ocean"?) is minimized." WikiDao ☯ 01:32, 28 January 2011 (UTC)

If we define the problem as:

${\vec {x}}_{center}=\int _{-\pi /2}^{\pi /2}\int _{0}^{2\pi }{\vec {x}}(\theta ,\phi )\delta _{land}(\theta ,\phi )\,sin(\phi )d\theta d\phi$

Where $\delta _{land}(\theta ,\phi )$ equal 1 over land and zero otherwise, and then take the ray extending from the origin through ${\vec {x}}_{center}$, I get that it intersects the surface at 43.5222 N and 28.5470 E. That happens to be in Bulgaria at the edge of the Black Sea. That's a well-defined, non-trivial answer, though admittedly it is about as arbitrary and useless as any other answer. Dragons flight (talk) 05:04, 28 January 2011 (UTC)

That's actually the same definition that I had in mind above, though I had a well justified fear that I might foul up with three-dimensional polar coordinates, and I don't know where you found the delta(land) database.

To recap, the definitions so far cover:

• The center (barycenter) of the Earth
• The center of the land hemisphere drawn to contain the most land and least sea
• The location where you could site a "Transcontinental Congress" so that the total travel miles of delegates from evenly sized small districts throughout all the land on Earth (via great circle route) would be minimized
• The location directly above the spot deep inside the Earth where you could site the Transcontinental Congress so that the total teleportation miles of all delegates (via straight lines) would be minimized

To this I can imagine adding at least one more:

• The location directly above the spot where the barycenter of the Earth would be, if all volatiles (water, air, ice, maybe fossil carbon) were stripped away from the planet, as projected from the current barycenter.

This last one, in essence, is a way to average where the center of all the Earth's water is taking into account how deep the oceans are at each point, or where the center of all the Earth's land is taking into account how high the mountains are.

All these methods, except for the trivial answer of the barycenter, imply a dipole in the Earth between land and sea, with one centered at one spot and the other centered at the diametric opposite point.

What seems extra surprising to me is that there seems to be a close analogy between this and the philosophical issues of act utilitarianism (the "transcontinental congress" methods) and rule utilitarianism (the land hemisphere method); there are different ways of trying to decide on the "true" center depending on exactly how the "greater good" is defined. Wnt (talk) 06:11, 28 January 2011 (UTC)

For practical reasons I would add

• The location directly above the spot deep inside the Earth where you could site the Transcontinental Congress such that the sum of each delegate's squared teleportation miles would be minimized.

Least squares is a lot easier to compute, because it's just the arithmetic mean of all the land points in Cartesian coordiantes. To minimize the sum of absolute distances you'd probably need some kind of iterative approximation, and are we even sure that a local minimum would also be global? –Henning Makholm (talk) 06:37, 28 January 2011 (UTC)

Hmmm... I didn't think about that. I assumed that the "teleportation miles" (4th definition above) would work out to be the same as the average of all land areas as calculated by Dragons flight above, but is that true for the summed distance, or the summed squares of the distances, or...? Wnt (talk) 16:02, 28 January 2011 (UTC)

In one dimension it is easy to see that least squares gives the arithmetic mean, and least absolute distances gives the median. It is still the mean for least squares in higher dimension, but it is not clear to me that the median has a similarly nice generalization. –Henning Makholm (talk) 11:10, 29 January 2011 (UTC)

ORME Orbitally Rearranged Monoatomic Elements

There is some ideas on the web, but what is actually "Orbitally Rearranged Monoatomic Elements (ORME)"?, there is no information on english Wikipedia, usually it the best place to serch, would you explain please?Ghrmsn (talk) 06:23, 27 January 2011 (UTC)

It looks like it's not something real. One user attempted to write an article about it: User:Sloth_monkey/ORMEs and was deleted : Wikipedia:Articles_for_deletion/ORMEs and Wikipedia:Articles for deletion/Monatomic elements. Maybe you can glean some information from the deletion comments and the article draft. Ariel. (talk) 08:59, 27 January 2011 (UTC)

Actually it is true, there is information un many languages, although, I don't know why Wikipedia is not accepting this info. There is many more things less important or ridiculus, but not this, it is for real, probably some kind of goberment complot, trying to hide information.Ghrmsn (talk) 16:34, 28 January 2011 (UTC)

See WP:FRINGE and WP:RS for starters. DMacks (talk) 17:17, 28 January 2011 (UTC)

Mean distance in a square

Maths have always been my Achilles' heel, so I'm having trouble trying to figure out a problem with a square.

Let's imagine a big 100 sq. ft box divided into one hundred 1 sq. ft boxes. In the centre of each small box there is a candle. If I were to calculate the average distance from each candle to all other candles, would I get the same result for all the candles, or would there be a divergence depending on the location of the candles within the big box? Intuitively, I think candles located along the edges would have a greater average distance to all other candles, but I can't find a way to prove it mathematically.

Thanks to whoever can help. Leptictidium (mt) 08:55, 27 January 2011 (UTC)

When you have a problem like this simplify it. Imagine a line with just 3 squares in it, and calculate the average distance for each of those 3 candles. Ariel. (talk) 09:04, 27 January 2011 (UTC)

It would be ideal for a simple Basic program, such as SmallBasic. 92.24.187.66 (talk) 12:54, 27 January 2011 (UTC)

It's not clear from your phrasing what geometry you mean, but you will get different answers for a 1X100 rectangle of boxes compared to 10X10. The issue at play here is the perimeter to area ratio, and more generally the notion of boundary_(topology). For instance, if you put the small boxes on the surface of a sphere (and measure distance along the same surface), then all candles would share the same mean distance to the others. SemanticMantis (talk) 15:06, 27 January 2011 (UTC)

First, it has been noted that there are 100x100 10x10 1 square foot boxes in a 100 square foot box. Regardless, this is a very simple program to write. The output for a 5x5 box is:

3.31  2.83  2.67  2.83  3.31 
2.83  2.31  2.14  2.31  2.83 
2.67  2.14  1.95  2.14  2.67 
2.83  2.31  2.14  2.31  2.83 
3.31  2.83  2.67  2.83  3.31

As you can see, the mean distance to all other candles is not constant. -- kainaw™ 15:19, 27 January 2011 (UTC)

It is interesting to see the calculations, thanks. Also, I think you mean 10X10 1 square foot boxes in a 100 square foot box :-) SemanticMantis (talk) 18:29, 27 January 2011 (UTC)

And in the limit (as you use smaller candles and pack more of them) the average distance from a corner is exactly twice the average distance from the center. This is because to compute the average distance from the center, you can cut the square into 4 smaller squares, and only consider one of them by symmetry. So the average distance from the center is the same as the average distance from the corner of a square with half sides. 98.248.42.252 (talk) 18:57, 29 January 2011 (UTC)

Religion, mental health and education

Is religion correlated more positively with mental health in people with higher education? I ask this because it would test my hypothesis that approaching the ultimate nature of humanity or the universe is hazardous to a person's mental health, and that religion is a way of defending against that hazard. (I agree with Richard Dawkins' assertion that religion itself is a mental illness, but I'm not sure I agree that it's a more severe mental illness than the alternative.) NeonMerlin 11:05, 27 January 2011 (UTC)

Who's to say what the "ultimate nature of humanity or the universe" is? I don't think physicists are more crazy than other people, except in cartoons. 92.24.187.66 (talk) 12:56, 27 January 2011 (UTC)

Is this the religious version of "You can't handle the truth"? HiLo48 (talk) 14:03, 27 January 2011 (UTC)

I read an article about this in the last few weeks; the author claimed that religion (particularly the fervent, born-again type) is measurably more popular among undergraduates at Britain's most prestigious universities than at other, less rarefied institutions. His interpretation was that unusually bright people under intellectual stress are more likely to turn to religion. Anecdotal and unscientific, but it did strike a chord. It could have been in The Guardian or maybe the Financial Times; I can't find anything online ATM but I'll try to dig up a reference for you. Karenjc 16:04, 27 January 2011 (UTC)

Sorry, tried hard but couldn't find the original article - my post-Christmas recycling binge seems to have claimed it. Karenjc 10:07, 28 January 2011 (UTC)

Interesting comments regarding "unusually bright" students turning more to religion. From what I've seen, most studies show a strong negative correlation between "intelligence" (as measured by IQ) and religious faith. -- Mesoderm (talk) 16:16, 27 January 2011 (UTC)

Yes, given the strong negative correlation between religiousness and intelligence, it presumably isn't those students' intelligence that's causing them to turn to religion, so much as their highly competitive, high-stress environment. And a high-stress environment does increase a person's risk for developing other forms of mental illness (see Causes of mental disorders), so a stress/religiousness correlation would seem to fit Dawkins' religion-as-mental-illness paradigm in at least that regard. Red Act (talk) 17:36, 27 January 2011 (UTC)

Were I to try and identify a confounding variable in the relationship between university status and proportion of students who are religious believers, I would look at the number of international students. High status universities in the UK attract international students from all over the world, including countries with much higher religious observance rates than the UK. Itsmejudith (talk) 15:50, 28 January 2011 (UTC)

Correlation is not causation (Propter hoc fallacy), and doubly so when dealing in false syllogisms. If I say "I love you, and I love cheese, therefore you are cheese" you can see the rediculous leaps of logic needed to reach that conclusion. However, I have no idea why, replacing random nouns and verbs in that statement, it suddenly becomes a reasonable proposition. Lets try it "Stress causes religiousity, and stress causes mental illness, therefore religiousity is mental illness." Nope, its still a patently stupid conclusion to reach. --Jayron32 18:05, 27 January 2011 (UTC)

I did not use that syllogism. You incorrectly extrapolated what you thought I meant from what I said. I will explain what I meant more clearly.

Biological contributions to the etiology of mental illnesses are of course very important, but to make the logical content of the following clearer, pretend that stress is the only cause of mental illness. Then if you take Dawkins' paradigm as being valid, you can use the syllogism "the cause of mental illness is stress, religiosity is a mental illness, therefore the cause of religiosity is stress" to predict that there is a positive correlation between stress and religiosity. So if a study shows that there really is a positive correlation between stress and religiosity, that suggests that the model of religiosity as a mental illness may have some predictive value, in that it could have enabled you to predict the positive stress/religiosity correlation ahead of time, from just knowing the cause of mental illness. This alone isn't enough to conclude that it's useful to model religiosity as a mental illness, since it may be purely coincidental that the religion-as-mental-illness paradigm led to the correct prediction that there is a positive stress/religiosity correlation. That's especially true because mental illness in reality has multiple causes, so one has to deal with messy correlations instead of clean Boolean logic as in the syllogism above. But this could validly be used as one element of a set of information used in determining how valuable it is to model religiosity as a mental illness. Red Act (talk) 21:13, 27 January 2011 (UTC)

There is a strong correlation between citing studies linking low IQ to a group of people 'and' your personal dislike of these groups. Quest09 (talk) 18:10, 27 January 2011 (UTC)

Red Act (talk) 21:15, 27 January 2011 (UTC)

This isn't quite what you asked for, but I did stumble across this study that attempted to measure the effect of religion on physical (rather than mental) health while also controlling for the effects of age, income, education, etc. They found that religious practice had a positive and statistically significant association with health even after controlling for other variables. (Probably not surprising.) However, they also found that those holding self-reported "conservative" ideologies were on average less healthy than those with moderate / liberal religious beliefs, even after controlling for other variables. They speculated that religious conservatives may be more reluctant to seek out medical treatment when problems arise. They also found that people with higher levels of education where more likely to engage in regular religious practices (e.g. praying, going to services, etc.), but paradoxically less likely to report feeling "closeness to God". Dragons flight (talk) 18:16, 27 January 2011 (UTC)

The elephant in the room here is, how do you define "mental health". I mean, Jesus and his followers undertook many actions that they pretty well could guess were going to get them nailed to a cross waiting for a cold, cruel end. Any competent mental health professional could argue that that made them "a threat to themselves or others", right? But it was about more than physical survival. Now a person can look at a far-gone mental patient and say that there the pattern of actions is totally pathological, not productive, not for some grand and noble purpose, but how can anyone accurately draw a precise line between what behavior is less than human and what is more than human? Wnt (talk) 06:23, 28 January 2011 (UTC)

Though the behavior of Jesus and the apostles is not really germane for talking about modern religion. Most practitioners are not founders. Practically zero Christians actually behave like Christ is supposed to have. --Mr.98 (talk) 20:16, 29 January 2011 (UTC)

Anal sex in the 1800s

I watched Total Eclipse (film) the other day and was confused about something. When Verlaine is in court and a doctor tests whether he was having anal sex, the doctor says there was proof that he was having both active and passive sex. I understand how the doctor could tell that Verlaine was having passive sex, but how could he ever know that Verlaine was also having active sex? Or were they just saying that to further incriminate him...? Thanks, this has been bothering me for some time! 129.3.178.228 (talk) 14:06, 27 January 2011 (UTC)

Was something like syphilis involved? (Which was common enough at the time) Wnt (talk) 18:11, 27 January 2011 (UTC)

I can't find anything saying he ever had syphilis, no. 129.3.151.117 (talk) 18:45, 27 January 2011 (UTC)

According to the article on Verlaine at French Wikipedia he did have syphilis. --Antiquary (talk) 23:39, 27 January 2011 (UTC)

I've heard first hand accounts about how doctors belonging to certain religious groups would tell adolescent males (from families that also belonged to that group) that they had "symptoms" of having masturbated so they should cut it out. Obviously, chances are the majority of males by a certain age have at least tried masturbation so the doctor wasn't really taking a wild guess. Maybe this was a similar case where they were just making a broad assumption, obviously chances were probably less but that doesn't change much. Vespine (talk) 00:12, 28 January 2011 (UTC)

Medical textbooks of that age did actually sometimes give lists of symptoms, as here. ("...circulatory disturbances of both motor and sensory nature; irritability; insubordination and outbursts of inexplicable anger... a decided bashfulness and reserve in society; averted gaze; and lack of manly bearing... a tendency to avoid company or the joining in youthful sports, but rather to retire alone or with a single companion, upon whom the suspicion of being an accomplice should rest; in study hours there is dullness, drowsiness, preoccupation, faraway gaze, and lack of application, with often pronounced weakness of memory and absent-mindedness..." and it goes on.) Marnanel (talk) 00:46, 28 January 2011 (UTC)

The doctor was talking bullshit obviously, he could not know that. --Lgriot (talk) 13:12, 28 January 2011 (UTC)

How long after the sex act did they perform the "test". I don't want to be gross, but bathing wasn't exactly a big thing in 19th century Paris, right? Matt Deres (talk) 22:39, 28 January 2011 (UTC)

Sky photography

I stumbled upon this image during one of my Wikipedia strolls, and I was surprised to learn that it was a photograph. It looked like a negative or even a diagram to me. To what purpose would an astronomer use such a picture as opposed to a more usual (to my lay eyes) photograph such as this one ? What are those "negative" images useful for ? Thank you, have a nice day. 130.79.160.112 (talk) 15:33, 27 January 2011 (UTC)

Many astronomers would find it simpler to pick faint black specks out of a white background than vice versa, particularly if you're working by hand rather than with digital photo processing equipment. — Lomn 15:47, 27 January 2011 (UTC)

Technically, it is the negative (or a print of a photograph of the original plate); the 'raw' image collected on film at the telescope would look exactly like that, as bright stars would create dark spots. From the standpoint of working with the image, it's usually easier to pick out a small dark spot on a white (or clear, on the original film/plate) background than it is to pick out a slightly-less-dark spot on a black background. (This applies both to manual examination and to automated discrimination.) When printed non-photographically, the negative version uses less toner (or ink), and is more forgiving of printing flaws. When annotating the image, it's much easier to add dark text and symbols to the clear background (particularly when dealing with physical copies of the image) than it would be with a positive image. TenOfAllTrades(talk) 16:32, 27 January 2011 (UTC)

When I was measuring faint structures in deformed minerals on electron micrographs (more decades ago than I care to remember) I always used the negatives directly - you always lose some information when you print. Mikenorton (talk) 18:11, 27 January 2011 (UTC)

(Edit Conflict) In addition to the previous answers, an important factor is that every time a non-digital image is processed (such as when making a positive print from an original negative) degredation of the image occurs. Similarly, every extra lens that an image has to pass through will reduce the inherent quality of the image. For these reasons, professional astronomers from the earliest use of telescopes and of astrophotography generally did not add an extra lens into their eyepieces usually necessary to convert the inverted image into an upright one, and worked with original negative plates (film tended to distort more so was not used for astrometry). Thus astronomers have always been used to dealing with such images, which also have the advantages previously described. 87.81.230.195 (talk) 18:16, 27 January 2011 (UTC)

Even just on my computer screen, I find it a lot easier to see faint spots when it is black-on-white than it is when it is white-on-black. I suspect the human eye is measurably better at the former than the latter. --Mr.98 (talk) 20:37, 27 January 2011 (UTC)

I asked a similar question while studying for my (astrophysics) degree. Yes, it is easier to pick out faint detail (pale grey wisps) against a light background. Also, you get less distortion/artifacts during measurements, if using the original (negative) photographic plate. Astronaut (talk) 16:06, 29 January 2011 (UTC)

incipient fusion

A google search suggests that in geology or materials science or something like that, there is a concept called "incipient fusion". But Wikipedia has no article with that title. Can someone say what it is?

There is a joke I heard many years ago, in which a school principal visits a class and tries to ascertain what they're learning. He asks the pupils what they would expect to find if they dug down to 4000 miles below the ground. Nobody could say anything. Then the teacher assisted. He asked them:

"What is the state of the center of the earth?"

They all responded in perfect unison:

"The center of the earth is in a state of incipient fusion."

Michael Hardy (talk) 19:10, 27 January 2011 (UTC)

I don't think that's a joke, it's just an incorrect fact. You can read the definition of "incipient" at Wiktionary. "Incipient" means that something is just starting. The material at the center of the Earth is part of the inner core, and is a solid (or solid-like) mass of mostly iron and nickel. Some scientists have speculated that radioactive or nuclear processes deep inside the Earth may contribute to the net planetary heat flux; but I have never heard a reasonable geologist pass off fusion as a plausible nuclear reaction occurring inside the Earth. Nimur (talk) 19:22, 27 January 2011 (UTC)

It is a joke, but it's true: It sometimes (often) happens that students learn to recite memorized answers to memorized questions, without understanding them. This is just parodying that phenomenon. Michael Hardy (talk) 19:35, 27 January 2011 (UTC)

And, "Nimur", you're missing the point. Nuclear fusion is obviously not what the word "fusion" refers to in this case, as you'll see if you google "incipient fusion" in quotes. It's about a different kind of fusion. "Fusion" generally means joining together. That can refer to lots of different things. Michael Hardy (talk) 19:36, 27 January 2011 (UTC)

I never heard this one, but it ties in with the question about Jupiter that was asked last week or so - as very large gas giants approach brown dwarf status during their initial formation, one might say one expected "incipient fusion" near their centers? (Whereas Earth, with a big iron core, is not fusing anything, no matter what) My feeling on reading this is that the joke implies their teacher has drilled something into the kids which is just plainly wrong. Wnt (talk) 19:20, 27 January 2011 (UTC)

For earth-specific geological-scale nuclear reactions, see geothermal gradient - heat sources. Most of the (nuclear-related) heat is simple radioisotope decay - more like an RTG than a reactor. A few scientists speculate that there may be fission in the deep mantle, and many scientists believe isolated patches of Earth's crust have experienced natural nuclear fission. Nimur (talk) 19:25, 27 January 2011 (UTC)

I think this thread of discussion is going away from the OP's question. From the brief google search I did, incipient fusion seems to be to do with materials joining together, not with energy release as a result of nuclear fusion. --Tagishsimon (talk) 19:31, 27 January 2011 (UTC)

From an article on brick making "incipient fusion, when the clay particles become sufficiently soft to stick together in a mass when cooled" [12] --Tagishsimon (talk) 20:43, 27 January 2011 (UTC)

Thank you, Tagishsimon. (Amazing how Nimur and others missed the point so clumsily. I wonder if they know that nuclear fusion has only been known for less than a century but the word "fusion" is (obviously) much older than that.) Michael Hardy (talk) 00:50, 28 January 2011 (UTC)

Irrelevant here, I guess, but it might be worth pointing out that yet another meaning of "fusion" is simply melting, as seen in the term heat of fusion. --Anonymous, 11:27 UTC, January 28, 2011.

this reminds me of one of the messages in Richard Feynman's “Surely You’re Joking Mr. Feynman!”, which was that students should be taught to understand and not only to memorise. The OPs 'joke' is an example of what happens when taught only to memorise. see http://www.hpcnet.org/cgi-bin/global/a_bus_card.cgi?SiteID=305793 —Preceding unsigned comment added by 80.168.88.74 (talk) 13:47, 28 January 2011 (UTC)

Practicality of experimental procedure for measuring microwave wattage

Is there anything about the following procedure that in actual practice would make its results significantly inaccurate? Thanks in advance.

Procedure for finding the wattage of a microwave with no labeling whatsoever:

1) Place 0.1 kg (100 mL) of water in a beaker and measure the initial temperature T1.

2) Heat water in the microwave for 10 s.

3) Quickly measure temperature of water T2 and find dT = T2 - T1.

4) Calculate energy transferred to water Q = m*c*dT using c = 4.187e+3 J/kgK.

5) Divide Q by 10 to get wattage (J/s).

76.27.175.80 (talk) 19:15, 27 January 2011 (UTC)

It sounds plausible, but it will need experimental checking. For example, this is a net measurement of the wattage absorbed by the water, but the microwave packaging probably gives a gross wattage to make it sound bigger, and so as not to overly dwell on whatever losses occur in the walls of the oven, etc. Packaging for food probably follows the manufacturer's packaging.

And of course, be sure to stir the water thoroughly. Wnt (talk) 19:24, 27 January 2011 (UTC)

100 mL of water beaker might not be enough to get average energy (assuming a standard kitchen-sized microwave oven, with a cavity of a few 10s of cm in each dimension). One of the reasons ovens now have carousels and other waveguide tricks is because the microwaves are not evenly distributed in the cavity (and these tricks only partially compensate). The plausible values for a household model do not cover that large a range, so you need to make sure you are not sitting in a particularly high-energy or low-energy region (being in a cool spot could create noticeable experimental error). How does your approximately 4x4x6 cm sample compare to the wavelength of microwaves, and are you likely have Nyquist–Shannon sampling theorem problems? DMacks (talk) 19:47, 27 January 2011 (UTC)

You want as big a ΔT as possible without errors from evaporation. So you need to do some preliminary experiments to see how fast the water heats up. A big hint: you don't really want the water to go above 60 °C (140 °F), or you'll have all sorts of practical problems in the measurements, not to mention safety issues if you're doing this as a class experiment. But don't restrict yourself to 10 seconds heating, you might get better results from a longer time. Physchim62 (talk) 19:59, 27 January 2011 (UTC)

In addition to any experimental error in finding the average power delivered to the food, you must also consider what the power will be used for. Naturally the oven will not be 100% efficient, so the power delivered to the food is less than the power drawn from the electrical mains. If you are trying to determine whether the circuit breaker supplying the oven is adequate, this must be allowed for. Also, recipies that mention the power of the oven might refer to the actual power delivered to food, or to the power drawn from the mains; you will have to figure out which meaning the recipie uses before deciding upon any modification to the recipie. Jc3s5h (talk) 20:04, 27 January 2011 (UTC)

It would be interesting to correlate the calculated absorbed energy with the actual calculated electrical draw (an ammeter on the mains line and its voltage). I don't know the typical efficiency of a consumer-grade magnetron, but that sounds like something one could find in a library or online reference (maybe even the spec sheet of an actual device?). And then consider that there are one or more motors and lights being powered in addition to the microwave source itself. Gauge the overall efficiency of the oven as a food-heating device. DMacks (talk) 20:15, 27 January 2011 (UTC)

I checked an old microwave cookbook I've got lying around, and the test there is:

1. Place two cups (500 ml) of room-temperature water in the microwave.
2. Set the microwave for a long period of time (ten minutes or more).
3. Measure the time until the water starts boiling.
4. Find the nearest time in the cookbook's chart. This gives the approximate wattage of the microwave.

Unfortunately, the page containing the chart is missing.

This procedure has some practical advantages over yours: the greater quantity of water increases absorbtion of microwaves, while the greater heating time makes for a more accurate measure of temperature (and the use of "boiling point" means you don't need a thermometer, but does introduce errors from evaporation). --Carnildo (talk) 00:49, 28 January 2011 (UTC)

Thanks all for the responses. I tried out the experiment as I described it, but with 500 mL (0.5 kg)and for 90 s. The rotating carousel carried the pyrex pitcher over a good volume of the space in the microwave continuously, so I assume I got a good sampling of whatever "hot" and "dead" zones there were in the microwave. The initial temp was 15.6 C and the final was 48.9 C for a dT of 33.3 K. So the total energy was 69.7e+3 J which over 90 s comes to about 774.6 W. I found the documentation for the microwave, which claims it's an 1100 W microwave, which, if it's true, means that it was about 70.4% efficient at putting its energy into my water. ~70% seems realistic to me, and not knowing what kind of stuff people will be putting into their microwaves, it seems logical for the manufacturer to advertise the wattage made available instead of any estimated final wattage absorbed by the food. 76.27.175.80 (talk) 17:51, 28 January 2011 (UTC)

For maximum power transfer from the waveguide to the water, the water in the cavity (oven space) must present a matched load to the waveguide. In this case, the same energy will be dissipated in the water load as in the anode of the magnetron. Im not sure how microwave ovens powers are specified: Is it the maximum power that can be transferred into a matched load?--92.25.98.49 (talk) 23:05, 28 January 2011 (UTC)

Marketing can usually be counted on to trumpet the best case scenario. 76.27.175.80 (talk) 20:26, 29 January 2011 (UTC)

Safe to store water in garage?

We have some blue 55-gallon water barrels to store water for an emergency. I have heard that you should not store these in the garage because of gasoline fumes (assuming your car is in the garage). Are there some authoritative sources that state that water barrels should not be in the garage? I cannot find any. All I can find is to make sure the barrels are not sitting directly on concrete. Thanks, Alanraywiki (talk) 20:05, 27 January 2011 (UTC)

Don't both your drinking water barrels, and any gas cans you have laying around, have lids that seal? APL (talk) 20:27, 27 January 2011 (UTC)

Yes, the water barrels are well sealed. The plastic on the barrels is thick. I think the permeability of the plastic may be the concern. But, I can't find any sources to corroborate. Alanraywiki (talk) 20:39, 27 January 2011 (UTC)

The LD50 of gasoline would require a 75 kilo person to drink about 1.5 liters of it to have a 50% chance of dying. That's a lot of gas to seep through thick plastic to even get in the ballpark. Like using non-food-grade barrels for this kind of thing, it seems like a minor concern if you change the water now and then and don't make a habit of undergoing emergencies. --Sean 20:55, 27 January 2011 (UTC)

The LD/50 isn't the only issue with gasoline toxicity, I'm pretty certain people have been seriously injured by less due to chemical burning of the esophagus and stomach. The listed symptoms at drugs.com seem to confirm this: abdominal pain, bloody stool, vomiting (with possible hematoemesis), throat swelling, difficulty breathing, ect. It also says expected treatment will probably include an endoscopy to check for burns. That said, to the original question, with that much water in an impermeable container I wouldn't worry personally, the only problem if a small amount of vapor did seep in would be one of taste. Keep in mind that garages typically aren't innundated with fumes and are far from airtight. 65.29.47.55 (talk) 21:40, 27 January 2011 (UTC)

I cannot see the logic of the alleged problem. Gasoline isn't that sneaky. HiLo48 (talk) 21:04, 27 January 2011 (UTC)

Maybe they mean the exhaust fumes? And maybe it's not a "it will kill you" but a "it will taste really unpleasant" thing. Just guesses. Vespine (talk) 21:31, 27 January 2011 (UTC)

With small amounts of gasoline, I'd be more worried about carcinogenicity than acute toxicity. Gas contains significant amount of benzene.

The scary thing about carcinogens is that you can never be sure whether they've hurt you or not. With a lot the standard acute poisons, say cyanide or strychnine or carbon monoxide, if you live 48 hours, you're probably over the hump (not a guarantee, I suppose, but the major concern is over). With benzene, who knows? It could come back to haunt you years later.

(That's not to say that the acute poisons are actually better. In an emergency situation where I had to drink contaminated water to live, I'd probably pick the one with gas in it over the one with cyanide.) --Trovatore (talk) 06:36, 28 January 2011 (UTC)

If you're in the sort of emergency where you need hundreds of gallons of fresh water that you can't get any other way, minor contamination from exhaust fumes would be the least of your worries! Physchim62 (talk) 10:52, 28 January 2011 (UTC)

Why can't the barrels be placed on concrete? If water is in a closed, non-permeable container (which all water barrels should be, at least here in Finland), the placement shouldn't matter at all. Of course you do'nt want them to freeze or get a funny taste from sitting in direct sunlight. --Albval (talk) 10:29, 28 January 2011 (UTC)

Smallest meaningful length

Hello. The Planck length is the length scale at which the structure of spacetime becomes dominated by quantum effects. But, unlike the Planck time, it is not seen as the smallest unit which can exist. What is the smallest possible distance which can exist? Thank you. Leptictidium (mt) 20:42, 27 January 2011 (UTC)

Sorry to be pedantic, but you'll have to qualify the meaning of 'exist' in this context. For example, operating under mathematical realism, the so-called 'real numbers' are actual real entities, and there is no such thing as a smallest distance, i.e. there is no smallest positive real number. You may be interested in exotic types of math where true infinitesimals exist.SemanticMantis (talk) 21:28, 27 January 2011 (UTC)

As is touched on in the last paragraph of Planck time#Physical significance, and the first paragraph of Planck length#Physical significance, the physical significance, if any, of either one of those quantities is debatable. There are various theories that predict various things, but physicists really do not yet have a solid understanding of what goes on at that scale or smaller. Red Act (talk) 21:38, 27 January 2011 (UTC)

Possibly, a smaller distance than the planck length cannot be measured due to quantumn effects. To discuss smaller distances would not make sense, as it is impossible to distinguish fractions of this distance from each other. Like quantumn super position, you can't measure it, but it does exist; smaller distances cannot be measured with any certainty, but they do exist, for different reasons of course.

Statistics play a major role, you're simply cannot be certain of the absolute length, if it is smaller than the planck length.

If the planck length is the smallest quantisisable distance, then would that put a cap on the maximum energy of a photon which can be quantisised? --Plasmic Physics (talk) 22:26, 27 January 2011 (UTC)

Yes, there's an energy limit. The nature of a photon as we currently understand it wouldn't make sense at energies above the Planck scale. Red Act (talk) 22:56, 27 January 2011 (UTC)

Isn't the photon-as-we-know it supposed to last only up to the electroweak scale (far below Planck)? –Henning Makholm (talk) 00:46, 28 January 2011 (UTC)

I'm way out of my depth here, but after reading electroweak interaction and electroweak epoch, and noting that the expected mass of the Higgs boson is around that of the electroweak scale (so that energies higher than that can't necessarily be made to "disappear" by just doing a Lorentz boost), and reading that in theories with extra dimensions, the fundamental scale of gravity is lowered from the Planck scale to the electroweak scale[13] (again making it impossible to make higher energies "disappear" with a simple Lorentz boost), I'm thinking you're probably right. Red Act (talk) 01:47, 28 January 2011 (UTC)

What you said about energies higher than the electroweak scale not being boostable is not correct. I don't understand how you got to that conclusion but I know it is not correct. 71.101.41.73 (talk) 04:46, 28 January 2011 (UTC)

The link above says that in theories involving extra dimensions, the fundamental scale of gravity is lowered from the Planck scale to the electroweak scale. My thinking was that whenever you get to a scale where you need to take gravity into account in any way, you can't simply apply a boost to the description of a high-energy photon such that in the new frame of reference, the high-energy photon simply looks like a normal low-energy photon. The point being that gravity isn't something that takes place within a simple Minkowski space (although linearized gravity can be treated that way), so expecting to be able to apply an arbitrary Lorentz transformation at that scale and have the physics look the same would seem iffy at best. But like I said above, I'm way out of my depth here. I think I've got a decent grasp of general relativity and non-relativistic quantum mechanics, but I don't even really understand quantum field theory, much less physics beyond the standard model, so if I'm full of shit on this one, I'm completely unsurprised. Red Act (talk) 06:32, 28 January 2011 (UTC)

My ignorance is of about the same order as yours, but what I think I understand is that the problem is not with the photon humming along all by itself through the vacuum, but what happens when it interacts with something else. In the latter case it is meaningful to ask about the energy in the center-of-mass frame. I think the electroweak interaction article says that when this energy is high enough, pertubation-based QED loses validity, and you need to treat the photon as a superposition of W° and B° bosons, which have different interactions. But my grasp of spontaneous symmetry breaking is infinitely fuzzy and heuristic, so don't take any of that as gospel. –Henning Makholm (talk) 07:18, 28 January 2011 (UTC)

It's far from clear that "smaller distances cannot be measured…but they do exist". String theory postulates additional dimensions that might come into play at distances around the Planck length (nobody really knows), and at least most if not all of the extra dimensions are probably compactified, although I think one or more additional large dimension(s) haven't quite been conclusively ruled out, and even the standard four dimensions of spacetime use a metric tensor that isn't even positive definite. So our whole intuitive Euclidean notion of "distance" may well work very poorly at that scale. Red Act (talk) 23:47, 27 January 2011 (UTC)

January 28

Artemisia absinthium

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

I'm not going to argue this one, because my feeling was that we couldn't have answered it anyway. For most uncommon herbal remedies too little research has been done to tell whether the herb itself is safe or effective, let alone in combination with specific pharmaceuticals. Wnt (talk) 06:27, 28 January 2011 (UTC)

Chemistry and Calculus

Hello. I am in intermediate chemistry at my high school right now. Unlike most of my peers, however, I have already got a solid grasp of calculus. What is a good book for understanding chemistry with the involved calculus (for example, in entropy or enthalpy)? I would like a book to cover chemistry from the very basics (down to Lewis theory even) up because I am only in intermediate chemistry right now. I have had some physics but also not from a calculus perspective. Thanks. 24.92.70.160 (talk) 02:35, 28 January 2011 (UTC)

Sounds like what you need is a thermodynamics textbook. The one I used in college for chemical engineering was by Smith, Van Ness, and Abbott. --shoy (reactions) 03:52, 28 January 2011 (UTC)

Any college-level physical chemistry book should be chock-full-o-calculus. Find the nearest used college book store, or look online for a used book; you can get one on the cheap. --Jayron32 04:16, 28 January 2011 (UTC)

Hadron collisions

Would the collisions be the same (or show the same information)if, instead of TWO atoms colliding AT each other linearly, there were four or eight atoms colliding in the same symmetrical way? —Preceding unsigned comment added by 98.221.254.154 (talk) 05:30, 28 January 2011 (UTC)

In theory it would be the same, as long as you had balanced collisions so there was no leftover momentum. But in practice the messier the collision the harder it is to extract good data from the experiment. Plus it would be nearly impossible to get the timing exactly right. Ariel. (talk) 06:58, 28 January 2011 (UTC)

Does having one linear collision as opposed to a "multi-atomic implosion" also limit the data you can gather? —Preceding unsigned comment added by 165.212.189.187 (talk) 14:41, 28 January 2011 (UTC)

Firing a gun underwater

What factors determine whether a gun (pistol, assault rifle, whatever) can be successfully fired underwater, or will simply explode as soon as the trigger is pulled? --Kurt Shaped Box (talk) 10:04, 28 January 2011 (UTC)

Mythbusters episode 51 tested four modern firearms. "The entire gun had to be completely submerged in water—all pockets of air must be removed—in order to prevent a possible explosion when fired." No gulls were harmed in the testing of this myth. Clarityfiend (talk) 10:22, 28 January 2011 (UTC)

I have been told that a firearm will explode (burst the barrel or the breach, with danger to the shooter) if anything but air is in the barrel: a bullet which did not leave the barrel due to poor discharge of powder, snow, mud, someone's finger. Mythbusters "disproved" this for a shotgun they tested, but rifles and pistols are not modern shotguns, and older weapons may not have been made to the same standard. WW2 veterans have told me that keeping barrels clean was highly emphasized, to prevent the barrel bursting. Water is so much denser than air that when a bullet traveling 1000 feet per second strikes it it would seem to be as immoveable as concrete. So it is surprising that the bullet somehow instantly pushed the water out of the way without a pressure buildup which bursts the barrel, if the other plugs mentioned would cause the barrel to burst on some firearms. Rifles and pistils sometimes blow up for no known reason, so water filling the barrel would push a marginal barrel over the edge. Edison (talk) 17:07, 28 January 2011 (UTC)

From looking on YouTube (of course there are going to be videos of guys firing guns underwater on there!), various Glocks seem to manage just fine, as does the AR-15 and the Ruger LCP - though the bullet's range is something like 4 feet, or less. The Mythbusters ep (also on YouTube) proved that being shot underwater at this range would probably still be lethal (I guess that you'd have to go for a contact shot, or close to it to be certain). Heh, wonder if SpecOps ever do this? --Kurt Shaped Box (talk) 17:35, 28 January 2011 (UTC)

Naturally there is an article APS_amphibious_rifle --80.176.225.249 (talk) 18:27, 28 January 2011 (UTC)

It is perfectly possible (if not especially advisable) to fire a well-made gun underwater without an explosion, as is stated above. Firing a gun that is only PARTIALLY filled with water might be more of an issue. On the other hand, even the mythbusters tests didn't use frangible rounds: many (if not most) civillian bullets are meant to expand when they hit flesh. Flesh being very similar in density to water, I'd suspect a hollowpoint or JHP round might start to mushroom in the barrel underwater. 65.29.47.55 (talk) 00:55, 29 January 2011 (UTC)

Full name for invertebrate zoologist "von Linstow" active late C19, early C20?

Resolved

Hi all,
Have I mentioned that my pet peeve is binomial authorities without corresponding biographies? OK. So, "von Linstow" is the binomial authority for Telosentis exiguus. He also appears to be the binomial authority for nematodes hosted in "Salties" Crocodylus johnstoni and Crocodylus porosus.
All that said, who is this "von Linstow" guy? --Shirt58 (talk) 11:57, 28 January 2011 (UTC)

According to this book, his initials are OFB. Hope it helps. --Albval (talk) 12:03, 28 January 2011 (UTC)

And after some more google-searching the guy should be this Otto Friedrich Bernhard Von Linstow (page in Finnish) --Albval (talk) 12:09, 28 January 2011 (UTC)

The above link is to a Finish book shop, for ISBN 9781103982332. Both the Finish bookshop and Amazon indicate that the book is in English, however, the title and front-cover are in a Germanic language. CS Miller (talk) 12:57, 28 January 2011 (UTC)

The book is about helminths, which would agree with Shirt58's original request. CS Miller (talk) 13:02, 28 January 2011 (UTC)

(EC)This gives his dates and the dates of publication of his main work Compendium Der Helminthologie: Ein Verzeichniss Der Bekannten Helminthen, Die Frei Oder in Thierisch. Mikenorton (talk) 13:06, 28 January 2011 (UTC)

His book is on Archive.org, oddly enough. He is listed as a "Stabsarzt," which I believe is an Army medical officer. Seems like an obscure guy who happened to write one of these obscure compendiums that named a few new species? --Mr.98 (talk) 13:43, 28 January 2011 (UTC)

I think so too; he was probably an army doctor with an interest in helminths. Here are some more publications of his; he wrote more than that one book. Ucucha 14:15, 28 January 2011 (UTC)

Wikispecies have what looks to be a very comprehensive list of taxon authorities and a tiny stub on him. (I wish I had known about this last time you asked!) SmartSE (talk) 18:51, 28 January 2011 (UTC)

A biography says that he was born 17. October 1842 in Itzehoe received his medical phD 1864 in Kiel and worked as military doctor in Hameln later in Göttingen he published his book Compendium der Helminthology in 1878 in Hannover and died 3. May 1816 in Göttingen.--Stone (talk) 21:16, 28 January 2011 (UTC)

Oh we have an article Otto Friedrich Bernhard Von Linstow.--Stone (talk) 22:06, 28 January 2011 (UTC)

Resolved. Now, if we can turn our attention to the species H. finlandicus, endemic to Albval's Finland... :-) --Shirt58 (talk) 12:19, 29 January 2011 (UTC)

Fuel efficiency

I know that natural gas and propane both burn cleaner than gasoline but are they as "fuel efficient" as gasoline (i.e. all things being equal, will one get the same "MPG" with NG and Propane as one would with gasoline)? 74.198.17.84 (talk) 14:34, 28 January 2011 (UTC)

There is no way for all things to be equal. Which is why we have MPGe. Rmhermen (talk) 15:41, 28 January 2011 (UTC)

The most similar fuel commonly used to power cars is Liquefied Petroleum Gas, which contains mostly butane or propane: efficiency is around 25% worse with LPG compared to gasoline.[14] --Colapeninsula (talk) 15:56, 28 January 2011 (UTC)

If we're strictly talking propane and natural gas, and comparing "miles per gallon" (really, "energy per volume"), then the comparison is a no-contest win for Gasoline. Have a look at energy density - there are many ways to measure energy "per ___": energy per mass, per volume, per dollar, and so on. This chart of energy density in materials can be sorted by mass- and volume- density. Nimur (talk) 18:14, 28 January 2011 (UTC)

LPG is as the poster above says around 25% less efficient, but in the UK it's compensated for (at least financially) by being about half the price of petrol (gasoline) so you still come out ahead in terms of cost per mile. Downside of course is the installation cost and the loss of space for a spare wheel or in the boot. Exxolon (talk) 16:42, 29 January 2011 (UTC)

Can vets determine the cause of death in a hamster?

Topic says it all. ScienceApe (talk) 15:27, 28 January 2011 (UTC)

In principle, a veterinarian can conduct or order virtually all of the same diagnostic tests during a hamster necrospy that a pathologist would perform as part of a human autopsy. With a certain number of caveats, there is a lot of common ground among most mammals from the level of biochemistry right up to tissue structure.

In practice, there are limitations caused by the smaller size of the animal (it is more difficult to examine and conclusively describe fractures of the smaller bones, less blood and other tissue is available for destructive tests, etc.); the vet may have less access to certain items of specialized equipment, and the resources available for conducting animal necropsies may be limited; and the body of literature and reference materials for diagnosing cause of death may be more limited in animal forensics than it is for humans. As with humans, some causes of death in animals are easier to conclusively diagnose than others. TenOfAllTrades(talk) 15:53, 28 January 2011 (UTC)

Pragmatically, hamsters are fairly disposable as pets. At the outside, they live maybe 3 years. A hamster that lived into his fifth year would be positively Methusalah-like on a Hamster scale. While that does nothing to lessen the emotional loss for someone that suffers the loss of a pet, it does explain why, even if technically feasible, it probably doesn't happen with any regularity that one would autopsy a dead pet which, if it was older than a year and a half, was already beating the average... --Jayron32 17:51, 28 January 2011 (UTC)

In vaguely the same ballpark, my dad had his dead rabbit necropsied. He was very close to her (nursed her back from cancer and an op that involved basically lifting all her innards out, cutting out/off the bad bits, then putting them back in - she lived for another three years after) and he wanted to know what had happened. He just asked the vet to do it. Heart attack, as it turned out. --Kurt Shaped Box (talk) 18:01, 28 January 2011 (UTC)

Yes, they can, if you want to pay a lot of money. Small mammals have been dissected and studied micropically for a long time. Robert Koch in the 1870's would give mice anthrax, then dissect them and examine the liver, lungs, etc microscopically to determine the cause of death. Today medical researchers use mice, hamsters, guinea pigs, etc to study all sorts of infections, cancer, and other ailments, and routinely dissect them postmortem and study sections microscopically and in comparable ways to what a human autopsy involves. It is just not done that often for dead pets, due to the cost. Edison (talk) 21:08, 28 January 2011 (UTC)

Though if you're a hamster breeder, or have a large collection of fancy hamsters, it may be worthwhile to order (and pay for) a necropsy if your beasties start dropping dead inexplicably at a young age. --Kurt Shaped Box (talk) 00:40, 29 January 2011 (UTC)

If the gas pressure decreases what happens with temperature?

What happens with the temperature when the pressure of a gas decreases? I'd like to know this for my job, but it doesn't make sense for me. For example if we have steam at 1.3 MPa and 192 Celsius (just above saturation), according to WolframAlpha, its enthalpy is 2788 kJ/kg (http://www.wolframalpha.com/input/?i=enthalpy+water+at+1.3+MPa+and+192+Celsius). If the pressure would decrease, and I assume the temperature is constant, to 1.0 MPa its enthalpy would be 2809 kJ/kg (http://www.wolframalpha.com/input/?i=enthalpy+water+at+1.0+MPa+and+192+Celsius). So the energy increases which seems strange to me. I thought the energy would decrease when the gas loses pressure. Will the gas temperature actually drop for the energy to be constant or decrease? In my example it is steam in a power plant that passes through a valve and there the pressure drops. Assuming no loss of heat to the surroundings. Wikifantast (talk) 15:36, 28 January 2011 (UTC)

See Ideal gas law. Looie496 (talk) 18:44, 28 January 2011 (UTC)

An assumption is wrong; unless the valve does work on the steam, the energy in the steam can't increase. So, either the steam is no longer at 192 celsius, or work was performed on it (in the form of heat transfer, or some other method). If exactly zero energy was transferred, and there was absolutely no change in volume, the temperature will change (per the pressure-temperature law; with that temperature, you should find an exactly equal enthalpy on both sides of the valve. In reality, energy should be lost: work was performed by the steam as it passes through the valve: some percentage of steam cavitated, liquified, condensed, changed volume, and lost heat to the walls of the valve and pipe. So energy was lost through that process. We should expect a temperature change to account for both the adiabatic- (ideal gas law) and non-conservative work (energy loss to surroundings). Why do you believe the temperature would be constant on both sides of the valve? Have you instrumented the steam-temperature on both sides? Nimur (talk) 19:27, 28 January 2011 (UTC)

Thank you. I think then that both the volume and temperature will change too. At 184 Celsius Wolfram Alpha says the energy is the same[15]. I have no data of the temperature on both sides. But intuitively it seemed to me that the temperature could stay constant although the pressure dropped through the valve; pV/T could still be constant if the volume increased (density decreased). Wolfram Alpha also calculates the density.

In reality of course there will always be heat loss to the ambient (non-conservative work) but I guess you can assume it is zero. Wikifantast (talk) 21:37, 28 January 2011 (UTC)

please explain binary stars in simpler language than the article

I am trying to understand how binary star systems work with planets. 1. how close are the two binary stars? would it be like the sun and jupiter, or the sun and pluto, or the sun and alpha centori? 2. would the planets orbit both stars or just one? 3. in stars wars on luke's planet there are two suns in the sky of the same size not too far from each other. does this mean the stars are very close or one is a lot bigger than the other? would luke's planet be orbiting one or both of them? 4. if you are on a planet orbiting just one of the stars, and the other one is far away, does it look like another star in the sky? is there a way you could tell it is your binary sun? for example, i know you can tell other planets from stars because they sometimes move backwards in the sky. would the sun you are not orbiting do the same? Many thanks. —Preceding unsigned comment added by 74.14.13.241 (talk) 15:43, 28 January 2011 (UTC)

Let's simplify the problem first. 1) Any two objects orbit the Barycenter of the two objects. The barycenter is the center of mass of the two object system. For the earth-sun system, the barycenter is NOT the center of the sun. It is inside the sun, but off-center by a small amount. So it is technically incorrect to say that any one object orbits another; the two objects oribit around a point on a line between their individual centers of mass, which is located relative to their relative masses. The effect is really obvious when the objects are close enough in mass so that the barycenter lies outside of either object; this happens in the Pluto - Charon system. This works exactly the same regardless of the composition of the two objects; so two chunks of rock (like Pluto-Charon or Earth-Moon), a planet-star system (like Earth-Sun) or a binary star system. The way the two objects move is the same. 2) The major problem with adding a planet to the system is that you create an n-body problem, which is not stable; that is there is no way to predict the relative motion of all three bodies in the long term, even given their initial locations and velocities. --Jayron32 16:14, 28 January 2011 (UTC)

(e/c) Binary systems vary a lot in terms of the size of stars and the distance between them. This page discusses a stable system similar to that around Tatooine where stars are on average 23 AU apart, which is slightly more than the distance from Earth to Uranus.

The Wikipedia page on binary stars says it is possible for a planet to either orbit a single sun or to orbit both, depending on how close the stars and planet are. The example I mention above assumes the planet orbits only one star, at a distance of less than 3 AU (a bit more than the distance between the sun and Mars). Orbitting a single star would probably be a bit more hospitable for human life.

The distance from the planet to the farther star would be far less than between the sun and the next nearest star (our sun is 250,000 AU from the next-nearest star), so assuming the farther-away star was a similar size to the sun, it would look much brighter than any star but much smaller and dimmer than our sun. --Colapeninsula (talk) 16:23, 28 January 2011 (UTC)

Thank you and thank you. that helps to visulize it. Jayron do you mean that a planet like tattoone is not possible because it would keep moving a different distance from the suns and get too hot or cold for life? Because colapeninsula says it can be stable? That is interesting you would always be able to tell you are in a binary system because there are two things brighter than the stars. --74.14.13.241 —Preceding unsigned comment added by 74.14.13.241 (talk) 17:39, 28 January 2011 (UTC)

You can carefully construct 3-body problems like Tatooine so that they can be stable over fairly long periods; so yes, it is technically possible to do so. It would be rare, but of course not impossible, that such an arrangement could arise naturally. --Jayron32 17:47, 28 January 2011 (UTC)

Sorry, I just read colapeninsula's link that says the planet like tattoine would have billions of years before it moved enough to make it unhabatable. thanks again for the help. (talk) —Preceding undated comment added 17:43, 28 January 2011 (UTC).

Can we keep Tatooine from getting too close to a star by putting it in a Lagrangian point? I guess if you want to see both suns in the sky at the same time it would have to be points L4 or L5, unless it's possible to orbit around the L2 point (the article implies that it's possible). —Preceding unsigned comment added by 205.193.96.10 (talk) 21:03, 28 January 2011 (UTC)

You might find HD 188753 interesting. Astronaut (talk) 16:23, 29 January 2011 (UTC)

ear piercing

When you pierce your ears is anything dying or is it just being pushe to a new location?Accdude92 (talk) 16:35, 28 January 2011 (UTC)

Surely at least some cells are ruptured by the act of piercing, though that article doesn't discuss piercing trauma very much at all. Comet Tuttle (talk) 17:46, 28 January 2011 (UTC)

Agree. In addition to the many types of skin and subcutaneous tissue cells that would be directly crushed during piercing, trauma to blood vessels will result in some bleeding, and the cells leaking from the laceration will die quickly. -- Scray (talk) 19:25, 28 January 2011 (UTC)

Hmmm. Why is it that ear piercings done with a piercing gun don't tend to bleed (or if they do, in such a tiny volume as to be unnoticeable)? This is my experience, as well as that of others I've discussed it with. --Kurt Shaped Box (talk) 19:29, 28 January 2011 (UTC)

I would guess that they are designed to apply pressure on both sides of the puncture, in a standardized way. The challenge has been to do so with an instrument that can be cleaned properly between victimscustomers. -- Scray (talk) 23:50, 28 January 2011 (UTC)

Personally, I'd recommend that anyone who fancies a piercing goes to an *experienced*, *competent* (shop around, ask questions - they're pros, they don't mind) piercer who uses a needle and an autoclave. I know it's a highly politicized subject (some piercers basically consider those guns to be the devil's spunk and seem genuinely furious that they exist) - but I'm simply stating this from my own personal experience with ear and eyebrow piercings (been considering a bridge piercing on and off for a couple of years) - and the healing thereof. Plus, you're not restricted to a stud for your first piece of metal. --Kurt Shaped Box (talk) 00:58, 29 January 2011 (UTC)

Physics, conservation of linear momentum-collisions

2 bodies make elastic head-on collision on smooth horizontal table kept in car. Do u expect change in result, if the car is accelerated on a horizontal road because of the non-inertial character of the frame? Does the equation " Velocity of separation = velocity of approach" remains valid in accelerating car? Does the equation " Final momentum = initial momentum " remain valid in the accelerating car?

.....with proper reasons.

—Preceding unsigned comment added by 122.169.145.208 (talk) 17:20, 28 January 2011 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. DMacks (talk) 17:29, 28 January 2011 (UTC)

Aside the obvious answer

How can I find out if a sheet of glass is toughened (without actually breaking it)? --BozMo talk 17:31, 28 January 2011 (UTC)

A polarizing filter will help you see if there are strains in the glass. Here's a reference, The Identification of Toughened Glass using Polarized Light (1973). You can also use a web-search for comparative images: here's a sample Google query. Nimur (talk) 18:00, 28 January 2011 (UTC)

(EC) As per Toughened glass#Properties, the strain pattern resulting from tempering can be observed with polarized light or by using a pair of polarizing sun glasses. Red Act (talk) 18:05, 28 January 2011 (UTC)

In case anyone doesn't have access to the article I linked, here's a summary of the "methods" section: place the glass-under-test between two crossed polarizer filters, and illuminate from behind with white light. Rotate the polarizer filters. If you see an iridescent color-behavior that has a periodicity with each 90-degree rotation of the polarizer-filter, you have toughened glass; if you simply see a variation in light intensity, you have annealed glass. A few caveats exist, related to whether your glass has any fracture surfaces, that are described in detail in the paper I just linked and elsewhere on the web. Nimur (talk) 18:08, 28 January 2011 (UTC)

A hydrogen bomb in an undersea volcano= add new land?

If a fusion bomb was placed in an undersea volcano, would it induce an eruption so massive that this volcano will spew out enough lava to permanently break the sea level and become an island?

Surtsey happened naturally, and Japan and Taiwan is in an epic land crunch for real estate so this would be an instantaneous way to reclaim more real-estate from the sea, wouldn't it?

By the way, I think the results might be better if the bomb was made to explode upside-down. Instead of a mushroom cloud, how about a mushroom laccolith under the volcano's base? Therefore, how can a bomb be made to explode a mushroom cloud into the earth instead of up in the sky? --129.130.32.220 (talk) 20:07, 28 January 2011 (UTC)

I'll add that to the list of crazy ideas I've seen on those pages over the years. BTW, there is no such thing as an upside down explosion. The mushroom goes up because hot air rises. 71.101.41.73 (talk) 20:37, 28 January 2011 (UTC)

Yes, the idea of an upside-down explosion is just confused. The explosion of a nuclear blast is just a sphere of fire and blast. It rises because it is hot.

You could shape the blast, probably, to fire more energy in one direction than another, though. These sorts of schemes were considered in developing Project Orion. It strikes me as probably doable, though whether that would hep or not, I don't know.

As for the geology of it, I have no clue. There were worries in the 1980s that sufficiently large underground nuclear tests could induce seismic and possibly volcanic activity (see, e.g. Amchitka). But this didn't happen. But it wasn't meant to happen, either — it's not clear to me that you couldn't do it on purpose. It should be noted, though, that Japan is probably the last place on Earth that would ever embrace Plowshares-like projects. Their disinclination to mess with nukes goes pretty deep!

There is nothing on this topic in The constructive uses of nuclear explosives (1968), which is sort of a catch-all book of proposals for "fun" and "peaceful" things you could do with nukes. --Mr.98 (talk) 20:55, 28 January 2011 (UTC)

How could one prevent the bomb from melting or being disrupted by the heat while placing it "in a volcano?" Place it in a shell of Unobtanium? Edison (talk) 21:01, 28 January 2011 (UTC)

Heh, heh, Edison, Tungsten has a higher melting point than the temperature of lava, IIRC. We just have to get it thrown in there deep enough (by a tungsten drill, maybe?) and have it detonate by a timer or a switch. --70.179.181.251 (talk) 06:03, 29 January 2011 (UTC)

Presumably you wouldn't put it in the lava itself, but near it. E.g. to the right of the label "3" in this diagram, or something like that. But I am not a geologist. --Mr.98 (talk) 21:05, 28 January 2011 (UTC)

For perspective, consider reading about human-induced seismicity. Most induced seismic response is the result of many years of continuous changes in the overburden or fluid-pressure, due to extraction of solid or liquid material during mining, water-well extraction, or fossil-fuel extraction. Nimur (talk) 21:04, 28 January 2011 (UTC)

Even if it could work (I am pretty sure it couldn't, but lets play a game and pretend that it could), what would be the point? I am pretty sure that the lava would become impregnated with lots of highly radioactive fallout from the bomb you just set off; great, so you have new land but its so radioactive to be unlivable. What good is that? That of course ignore the point that even the most powerful thermonuclear devices pale in comparison to the power of geologic events. A single volcanic eruption or earthquake packs many times the wallop of an H-bomb. I'm pretty sure if you put the entire world's nuclear arsenal in one place and set it off all at once, it wouldn't even be as big as the 1980 eruption of Mount St. Helens, which while impressive was not uncommonly so, at least on a geologic scale. The main blast which caused the collapse of the north face of the mountain moved about 1/20th of a cubic mile of earth, an unimaginably large chunk of solid rock to be pulverized to dust. I just can't see a bomb doing that kind of work. --Jayron32 21:14, 28 January 2011 (UTC)

To be fair, nobody is saying that the bomb would have the force of a volcano, just that it could be used to trigger one. I'm not sure that's not impossible. The trick about energy release is that it matters how much is released in how small a volume. An earthquake releases a huge amount of energy but over long distances. The sun releases an unfathomable amount of energy but it does so over such a diffuse distance and time scale that we perceive it as a warm bath, not a searing flame. I think there are probably geological situations where a properly placed, sufficiently large thermonuclear detonation could act as a catalyst for a much larger volcanic eruption. It's not necessarily the case that fallout would be mixed into the magma itself — there might be clever ways to make the eruption contain the bomb blast (e.g. bury it even while it erupts upwards). But I don't know much about volcanos, to be sure. --Mr.98 (talk) 21:27, 28 January 2011 (UTC)

Actually Mount St. Helens released "only" about 24 Megatons of energy which is somewhat less than the largest hydrogen bomb ever detonated. The Krakatoa eruption, one of the largest eruptions in recorded history, was about 200 Megatons of energy. So, volcanoes are somewhat larger than but on the same order as hydrogen bombs. Of course the energy is released in very different ways, which does make a significant difference with respect to the impacts it has. Dragons flight (talk) 21:36, 28 January 2011 (UTC)

It's worth noting that Krakatoa's explosion left less land above the sea than before. And Mt St Helens got smaller when it exploded. Guaranteeing more land would be a challenge. HiLo48 (talk) 21:58, 28 January 2011 (UTC)

True to a point, but keep in mind that the goal would be to take the internal parts of the mountain and spread them out in order to create a structure with more surface area and less height. Still, Mt. St. Helens is a good example in many ways. Even if it had been surrounded by water, and somehow did end up with water above sea level, mixed ash is not really an ideal building material. And it strikes me that for all of the effort, the amount of land is still not going to be that useful by human standards. (And again, I'm wary about comparing nukes to volcanos in terms of explosive force, anyway, because the time scales are usually quite different, and the effects that correspond are quite different.) --Mr.98 (talk) 20:12, 29 January 2011 (UTC)

I'm not certain that the demand for new land in Japan is any higher than it is in New York. Though they have enormously high population densities in the biggest cities, due to most of the land being unusably steep (Japan#Geography), they also have a falling population size, and 6,852 little islands that already exist. The most significant reason for the high population of cities is that a large number of people want to live close together. Is Izu Ōshima so crowded that they need a second one? Land reclamation does say that 20% of Tokyo Bay has been reclaimed, but land that's contiguous with Tokyo must be worth a lot more than land which is offshore and radioactive. 81.131.22.166 (talk) 23:25, 28 January 2011 (UTC)

January 29

Sweet crude oil

I was in class and my prof mentioned that there is a type of crude oil called Sweet crude oil, and he said that workers would actually taste the oil. Isn't oil toxic? Wouldn't tasting it be detrimental to their health? ScienceApe (talk) 02:34, 29 January 2011 (UTC)

According to this document from the Oil Spill Academic Task Force of the State of Florida, "In the 19th century, oil workers would taste and smell small amount [sic] of oil to determine its quality." Clarityfiend (talk) 02:56, 29 January 2011 (UTC)

Many geologists are rather partial to having the occasional lick of anything that looks (or smells) interesting. DuncanHill (talk) 03:07, 29 January 2011 (UTC)

It looks like geologists like to put dirt in their mouth for several purposes, also to evaluate a sample's texture. See, for example, siltstone or, regarding oil, old formation evaluation tools to detect oil and gas by grounding the well cuttings between their teeth. They "tasted to see if crude oil was present", according to that article, unreferenced. Other sources seem to suggest it was for detecting texture, not taste. ---Sluzzelin talk 05:06, 29 January 2011 (UTC)

Tasting this oil is not detrimental to the health? ScienceApe (talk) 16:25, 29 January 2011 (UTC)

No one is claiming that! This (commercial) site lists some figures and hazards, toxicity in case of ingestion or skin contact included. The data are referenced. They don't directly answer your question, but it's pretty clear this isn't something you want to try at home, and certainly not repeatedly. Some of the long-term hazards from doing this repeatedly, such as carcinogenicity, probably couldn't have been detected soon enough to make a connection, at the time. (I wanted to point you to an article on the history of occupational health and safety, but, judging from the few articles that link to Bernardino Ramazzini, we have no such article, nor is it well-covered in any of the history sections). ---Sluzzelin talk 16:53, 29 January 2011 (UTC)

giving m₂=0 for newton formula

what happens for field when we give m₂=0 for newton gravity formula.(G) a. mohammadzade —Preceding unsigned comment added by 78.38.28.3 (talk) 11:26, 29 January 2011 (UTC)

See the article about Newton's law of universal gravitation which is expressed by the equation

$F=G{\frac {m_{1}m_{2}}{r^{2}}}\$

Any real physical object has mass, but if a hypothetical object had zero mass it would have no gravitational attraction to any other object. Cuddlyable3 (talk) 15:23, 29 January 2011 (UTC)

Well, there would at least be zero gravitational force acting on the zero mass object. But from F=ma (Newton's second law), calculating what acceleration results when an object with zero mass is acted upon by a zero force results in the indeterminate form a=0/0, so you can't conclude that the zero-mass object experiences no acceleration. What works better in this case is to combine Newton's two equations to give

$a_{2}=G{\frac {m_{1}}{r^{2}}}\$,

where a₂ is the acceleration of the object you're calculating the acceleration of, and m₁ is the mass of the other object. That combined equation avoids the indeterminate form when m₂=0, and helps lead toward the more appropriate understanding of gravity as involving a coordinate acceleration as is produced by a fictitious force, rather than being a real force, as per Einstein's equivalence principle. As per that combined equation, a theoretical zero-mass object will still experience the same acceleration due to gravity as an object with nonzero mass, even though there is no force acting on it. Red Act (talk) 18:06, 29 January 2011 (UTC)

Anal orgasm

Is it possible for woman to have orgasm from anal stimulation alone, and how is it distinct from vaginal orgasm? --78.150.235.125 (talk) 11:43, 29 January 2011 (UTC)

Orgasm#Anal_stimulation provides some referenced information for this and this Slate article may also be useful. SmartSE (talk) 12:34, 29 January 2011 (UTC)

Balloons

How much force upward does a balloon exert? I recently saw Up, and I know getting a house airborne would be impossible, but I am curious as to how much helium would be needed to lift a person or a basket. And how about hydrogen balloons? What is hydrogen and helium's lifting power per square inch? --T H F S W (T · C · E) 18:15, 29 January 2011 (UTC)

Per square inch it's zero ;-). The molecular weight of Hydrogen (H_{2) is 2 g/mol, the molecular weight of Helium (He) is 4 g/mol, and the average molecular weight of air is 80%*28+20%*32 (for Nitrogen and Oxygen, both diatomic gases), or just shy of 29g/mol. So one mol of Hydrogen can lift 27g, one mol of helium can lift 25g. One mol of gas under standard condition occupies 22.4l, so the lifting power of either gas is about 1g/l or 1 kg/m³. Of course, that is the gross lift - for the net lifting capacity, you need to subtract the weight of the balloon. If you need more exact numbers, apply a calculator ;-) --Stephan Schulz (talk) 18:27, 29 January 2011 (UTC)}

There was the interesting case of Lawnchair Larry, who dared in 1982 to try this experiement "at home". He attached 45 helium-filled weather balloons to a lawn chair in his back yard and flew to an altitude of over 15,000 ft! (Asked why he did it, he replied, "[Because] a man can't just sit around.";) WikiDao ☯ 18:28, 29 January 2011 (UTC)

OK, thanks, I'll start collecting weather balloons! Joke - for now.--T H F S W (T · C · E) 18:48, 29 January 2011 (UTC)

N.B. his "honorable mention" at the Darwin Awards...;) WikiDao ☯ 19:36, 29 January 2011 (UTC)

Anyone know the area of a normal party balloon? And @Stephen, yeah, I meant a cubic inch. Heh heh. --T H F S W (T · C · E) 19:58, 29 January 2011 (UTC)

Graphite

In graphite, are the layers stacked so that the carbon atoms in one layer are directly on top of the carbon atoms in the lower layer, or are they over the centers of the other layer's hexagonal holes? --75.15.161.185 (talk) 19:39, 29 January 2011 (UTC)

The latter. See: graphite. Dragons flight (talk) 19:41, 29 January 2011 (UTC)

Converting ohm to siemens

I'm doing a science project on the electrical conductivity of different materials. I have an ohmmeter and know how to convert ohms to siemens. The problem is, I'm testing piece of rubber and the reading just shows up as 1 on the 2M setting. How would I convert this value? Writing down 1 [S/m] doesn't seem correct. —Preceding unsigned comment added by 68.230.183.227 (talk) 19:49, 29 January 2011 (UTC)