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October 27

Wikipedia:Reference_desk/Archives/Science/2009 October 27

1. QED
2. Special Relitivity
3. Underdamped Harmonic Oscillator
4. GMO hemp
5. Tsar Bomba
6. spin forbidden versus classically forbidden
7. Black worms with antenna???
8. disaster preparesdness
9. Make up of the Brain
10. destuctive interference
11. Why do most humans grimace when they're straining themselves?
12. Atherothrombotic Cerebral Infarction
13. Triceratops And Their Frills (And Also Stegosaurus)
14. Mad Chicken Disease?
15. code of silence
16. GVO pigmentation
17. chemistry
18. space expands faster than light
19. What sort of medical data is stochastic?
20. Francium in water

October 28

Wikipedia:Reference_desk/Archives/Science/2009 October 28

1. Food safety question
2. Voice differences between blondes and brunettes
3. plz help fft plots
4. Hard drive for archiving video?
5. maximum frequency infinite or not?
6. Maillard Reaction in Pasta Production
7. Why ozone is over antartica?
8. Electron configurations of rhodium and tungsten
9. Spectroscopy
10. Planets shrinking
11. IR spectrum of benzophenone
12. Are we Europeans all Jewish?
13. Maillard reaction creates acrylamide?
14. Icons of Evolution
15. Saturn V versus Ares rocket: Reinventing the wheel.
16. tiredness

October 29

Wikipedia:Reference_desk/Archives/Science/2009 October 29

1. Effect of smokeless tobacco on dental health
2. Human Hearing Range in Nature
3. Counter circuit Photo-Electric Beams
4. Raisin aversion
5. Earth spinning
6. How many buildings 2 story and above are there in the U.S.A.
7. Glycogen Storage in Human Muscle Cells
8. Ladybirds hibernating

October 30

Wikipedia:Reference_desk/Archives/Science/2009 October 30

1. Collar-size of the woolly mammoth
2. Knee injury test
3. Jumping on concrete versus sand
4. The Verity Incident
5. If I were small enough could I observe an atom?
6. Small populations sizes and genetic mutations
7. Flu vs. other diseases
8. Tramadol expiry dates

October 31

Foreign accent syndrome and stroke recovery

I was curious about a case I read about a few years back, regarding a patient who had what, after searching here, I discovered to be foreign accent syndrome. It got me to thinking - if, after a stroke or other brain injury, in rare cases people can speak only in an accent, have rehabilitation workers ever experimented to see if a person who has lost their speech might recover it if taught to speak differently?

I'm aware there might be some flawed biology I'm not catching, but: If a person's neural patterns are such that they can't do the numerous things necessary to form speech, could there still be some mechanism that would let them produce it differently? could those with FAS speak that way because, in essence, they have "relearned to speak," in the same way a child learns to speak in his or her own unique voice? (Since every voice, even without an accent, sounds a bit different.)209.244.187.155 (talk) 00:32, 31 October 2009 (UTC)

Reading your question, I think you've missed that the people aren't really speaking in a foreign accent. It isn't that they've learnt to speak in a different accent, it's that brain damage affects how they pronounce some sounds in a consistent manner. People who hear them interpret this as them speaking in a foreign accent. For example, someone who previously had a rhotic accent might suffer brain damage that affected their ability to pronounce the 'r' in words like 'Arthur'. Their friends and family, who also speak with rhotic accents, perceive this as them speaking a non-rhotic accent (like many British accents). 86.139.237.128 (talk) 02:32, 31 October 2009 (UTC)

Okay, you're right, that's what I was getting confused by; thanks.4.68.248.130 (talk) 09:15, 31 October 2009 (UTC)

Stroke symptoms can be very strange, and it's hard to predict what might or might not be possible. There are, for example, cases of people who have lost the ability to talk but are still able to sing. Looie496 (talk) 04:27, 31 October 2009 (UTC)

I heard from the Media about one Czech turist who had traumatic brain injury after falling from his bike in London. Then, when he woke up in the British hospital he start speaking in fluent English with British accent, something he certainly couldn't done before. So, it seems like the brain could be very flexiable sometimes (but not always). For instance, it seem like the visual cortex of people who lost their sight is being used extensively for the sense of touch -this ability of the brain to gain new functions or to rewire itself isa part of its neural plasticity. But what you asked is more complicated, as we are talking about something more complicated than sensing-language is learning dependent high function and it can't appear out of the blue. So it seem much more similar n to one regression to his/hersecond language, that happened many times during degenerative diseases such as Parkino's disease. That is, one major function is lost, so the brain must use the more preserved areas and the previously dominant brain areas can't longer overpower/inhibit the areas that contain these secondary abilities.--Gilisa (talk) 17:39, 31 October 2009 (UTC)

I am glad he survived. It is sad to see a Czech bounce. Cuddlyable3 (talk) 12:43, 1 November 2009 (UTC)

Increasing the size of the human penis?

Is there any medications available that actually work to permanently increase the size of the penis? —Preceding unsigned comment added by 84.68.36.19 (talk • contribs)

• No. --Jayron32 01:23, 31 October 2009 (UTC)

We have an article on that: Penis enlargement. Red Act (talk) 01:35, 31 October 2009 (UTC)

No. [1] —Preceding unsigned comment added by 79.75.106.210 (talk) 01:50, 31 October 2009 (UTC)

You wouldn't enjoy permanent enlargement this way though there is a popular temporary way. Cuddlyable3 (talk) 14:40, 31 October 2009 (UTC)

I always get e-mails that offer me to buy enlargement kit-all I have to do is to give my address and c. card number and a simple kit will be sent to my post office box. I never tried it, but maybe you want me to give you connection details?--Gilisa (talk) 18:12, 31 October 2009 (UTC)

With all due respect, I hope you're kidding Gilasa. Let me put it this way: if the information is in your spam box, the information fails being trustworthy as soon as your credit card information changes the outcome. Magog the Ogre (talk) 20:12, 1 November 2009 (UTC)

Nifty Propulsion Device

Someone pointed this thing out to me [2] and I don't know enough physics to determine whether it makes sense. Can someone who knows more about it give a ruling? Black Carrot (talk) 04:45, 31 October 2009 (UTC)

This is the EmDrive. As a reactionless drive, it blatantly violates the conservation of momentum and cannot work as claimed. After the magnetron is turned on, the microwaves aren't going to do anything except bounce around and get absorbed with absolutely no effect on the cavity's total momentum. The energy will then be radiated as blackbody photons, though asymmetries in the device's geometry may provide a miniscule force on the "drive". In other words, the "drive" will function much better if the end facing the magnetron is removed, because the photons will then serve as a tiny reaction mass. --Bowlhover (talk) 06:36, 31 October 2009 (UTC)

Someone who knows more about it has given a (rather damning) ruling, and you can see it here: [3]. The basic error Shawyer makes is to assume the impulse imparted on a wall during a particle-wall collision is in an incorrect direction. You can see this yourself by looking at figure 2.4 of [4] (an earlier version of the same document). In the "updated" version, Shawyer removes the section which makes his error obvious. Someone42 (talk) 07:00, 31 October 2009 (UTC)

Roger Shawyer claims[5] to have calculated and measured on a demonstrator engine 16mN thrust from an input power of 850W. Dr. Costella[6] accuses Roger Shawyer of being a charlatan who defrauded a government agency (the UK Department of Trade and Industry). I smell a libel suit where lawyers are bound to earn. Cuddlyable3 (talk) 14:35, 31 October 2009 (UTC)

The only real test will be when someone actually takes his device up into orbit and it moves.When is this going to happen?80.0.98.26 (talk) 11:14, 1 November 2009 (UTC)Trevor Loughlin

Hopefully never, because that would cost a lot of money and I would hope that the people who control such quantities of money would do a bit of investigation before giving it away. Seriously, the guy is a complete idiot (or a con man). He doesn't even claim some hitherto undiscovered law of physics, he claims that his drive works in the framework of standard electrodynamics. But it's a theorem that momentum is conserved in electrodynamics (Noether's theorem), so he's wrong and that's the end of it. The most valuable thing about this fiasco is that it's a lesson in just how far New Scientist's journalistic standards have fallen. It's barely above the level of a supermarket tabloid at this point. The problem isn't so much that it's a terrible magazine—there are lots of those—but that people still trust it as a source of physics news. It's disturbing how often it gets used as a reference in Wikipedia articles. Greg Egan wrote a plea to save New Scientist in the wake of this story, but I think it's too late for that. I would instead plead with people to cancel their subscriptions. -- BenRG (talk) 13:23, 1 November 2009 (UTC)

Dry friction

What actually is dry friction? Can i call viscosity as fluid friction and vice-versa ? —Preceding unsigned comment added by 122.168.213.193 (talk) 11:17, 31 October 2009 (UTC)

Not really. Dry friction is the lateral friction between touching surfaces of solids, and may be classified as either static or dynamic depending on whether the surfaces are stationary or moving relative to one another. Viscosity is the resistance of a fluid to flow, and whilst the name "fluid friction" sounds appropriate, it's ambiguous as the term is already taken to be the friction between two solid surfaces separated by a fluid, or sometimes the friction between layers of a fluid with relative motion to each other. See this.--Leon (talk) 13:55, 31 October 2009 (UTC)

Area dependency of friction

It is stated that frictional force is independent of area of contact then why we fell it harder to ride a bicycle with flat tire (air less) —Preceding unsigned comment added by 122.168.213.193 (talk) 11:26, 31 October 2009 (UTC)

First let me point out (before Steve Baker starts jumping up and down) that that description of the friction force as independent of the area is intended for non-sticking flat hard surfaces. Tires don't meet those criteria. More importantly, though, you are confusing rolling friction (on the bike's tires) with sliding friction (which is the kind of friction this description is intended for). Dauto (talk) 11:34, 31 October 2009 (UTC)

Sliding is not a factor. Squashing and unsquashing the rubber of a flat tyre consumes (i.e. converts to heat) energy, see Rolling resistance, that must be provided by the rider. Cuddlyable3 (talk) 14:11, 31 October 2009 (UTC)

A noise meter to measure outdoor road noise pollution in the UK?

Noise or sound meters are less expensive than I thought, and buying is cheaper than hiring. I want to measure outdoor road noise pollution, in a way that complies with UK standards for doing so - whatever they are. I think this requires using an "A" digital frequency filter, which seems available on many meters. But rather than looking at a fluctuating meter and mentally trying to average the reading, are there any meters that will do this automatically - that will tell you what the average reading was over a minute say? Since I will avoid rainy situations a waterproof meter is not necessary. Thanks 78.144.206.114 (talk) 11:37, 31 October 2009 (UTC)

It sounds (pun) that you want to measure A-weighted long-term average sound level as defined in BS 7445 / ISO 1996. Look for a noise meter that has an analog or digital logging output that you can connect to a PC. If it is analog then you need an A-to-D converter. THe PC can store the data, calculate average(s) and show them on a spreadsheet. A common mistake made by professionals who should know better is to take an average of dB(A) measurements. This is wrong because dB (decibel) is a logarithm of a power measurement. The correct way is to convert from the dB(A) values to power(A) values, take their average, then convert back to dB(A). For the legal background in the UK see [7] the Noise and Statutory Nuisance Act 1993 and the EU Environmental Noise Directive. Cuddlyable3 (talk) 14:05, 31 October 2009 (UTC)

Thanks, although where I want to take the noise readings will be a very long way from my desktop computer. Are there any that can do the "averaging" themselves? Thanks. 78.151.126.29 (talk) 21:35, 31 October 2009 (UTC)

Consider using a portable Laptop or Netbook. Battery time is a limitation. Cuddlyable3 (talk) 22:05, 31 October 2009 (UTC)

Cicely of Oxford Royal Physician

I read somewhere that Cicely of Oxford was Court Physician to either Richard II or England or Edward III of English. Is there any way to confirm this? —Preceding unsigned comment added by 76.200.166.39 (talk) 11:51, 31 October 2009 (UTC)

Both [8] and [9] claim that she was Court Physician to Edward III, although neither look particularly reliable. The whole claim looks rather doubtful, as I cannot find any other references to Cecily or Cicely of Oxford, and historical works which would have been expected to mention a fact so interesting as a fourteenth-century female physician (e.g. this survey of royal physicians in the reign of Edward II and immediately after) don't have anything to say about it. Warofdreams talk 23:06, 31 October 2009 (UTC)

P. C. Doherty is a pretty bad writer of detective stories, but he has strong academic credentials as a 14th century history, so if he claims Cicely of Oxford was physician to Edward III, he probably has a good basis for saying so. Looie496 (talk) 02:49, 1 November 2009 (UTC)

Epidermal growth factor

Hi I'm a little confused about how epidermal growth factor (EGF) is produced in the human body. Are there cells that produce it? The article on EGF says 'sources' are macrophages, platelets, urine, plasma and milk. What does this mean? Do macrophages and platelets produce EGF? I can't imagine urine/milk producing anything, or does it mean ingesting urine/milk would provide a person with a source of EGF? Any clarification would be great, thanks RichYPE (talk) 14:20, 31 October 2009 (UTC)

I think you have to go to the cited source of the information which is Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease. St. Louis, Mo: Elsevier Saunders. ISBN 0-7216-0187-1.Cuddlyable3 (talk) 21:33, 31 October 2009 (UTC)

Epidermal growth factor is a protein, and as such is produced by protein synthesis, which occurs in cells. The megakaryocytes that give rise to platelets, synthesize EGF (see this paper, as do macrophages. When EGF is found outside of cells, it is because it has been secreted from the cells that produced it. --NorwegianBlue ^talk 11:12, 1 November 2009 (UTC)

Hydrocephalus

good evening, I just want to ask about hydrocephalus.. i am a Physiotherapist, and i have a patient who have one, my main concern is that she keeps on crying while the therapy is on going, and im afraid if this is bad or dangerous to her, sometimes she turns cyanotic.. hope you can help me and also I want to know what technique can i improve her trunk control for she will be able to sit and walk independently... waiting for your response": Erlinda M. Mendoza —Preceding unsigned comment added by 120.28.71.159 (talk) 15:46, 31 October 2009 (UTC) —Preceding unsigned comment added by 86.4.186.107 (talk)

Erlinda, I'm sorry but we don't give medical (or physiotherapy) advice on the Reference Desk. Receiving medical advice from strangers for the treatment of a third person is very risky, I'm sure you can understand this. If you are a chartered or qualified physiotherapist you must surely have professional colleague or seniors who can give you advice. Of course we have an article on hydrocephalus, reading this might be helpful. Caesar's Daddy (talk) 16:04, 31 October 2009 (UTC)

Sounds of a Teaspoon in a Mug of Milk?

Take a mug of milk (or milky tea, or milky coffee). Heat it. Take a teaspoon, and tap it on the base of the mug (but from inside the mug, like you're stirring it.) Listen to the sounds, specifically the pitch of the sound. WHAT CAUSES THIS? ASCII image related.

   |
#  |   #
#--|---# Teaspoon in a mug with hot milk,
#  |   # move it up and down, tapping mug base,
#  |   # what the hell are the sounds like that for?
# ( )  #
########

No answers from anyone what has not tried this please. Remember Civility (talk) 19:01, 31 October 2009 (UTC)

Before putting in the milk the mug gave out a tinkle, effectively acting as a bell. As the milk went in the resonant frequency went up because of the smaller part of the mug that can resonate freely, but changed progressively from a tinkle to a dampened knock sound. Then I drank the milk yum-yum. Cuddlyable3 (talk) 21:28, 31 October 2009 (UTC)

That's "Original Research", I'm not sure that's allowed ;-)) Richard Avery (talk) 22:45, 31 October 2009 (UTC)

YOU DIDN'T TRY IT DID YOU? :p Take a full mug of milk. Tap. Listen to that sound. Tap again (not adding or removing any fluid). Listen to that sound. tap - tap - tap - tap - tap - tap - tap - tap, listen to the sounds of the taps. No liquid added or removed. Remember Civility (talk) 22:49, 31 October 2009 (UTC)

I tried it with a heated mug of water (my girlfriend drinks milk, but there's none in the fridge at the moment), and it sounded quite unremarkable. There are a lot of variables here that will affect what is heard with this experiment -- the thickness, shape and material of the mug, how full the mug is, the acoustic properties of the surface the mug is placed on, possibly the thermal properties of the liquid, mug, and surface, since the liquid is heated, etc. Could you please record the sound and upload it, so we can hear whatever it is you're hearing? Decent laptops nowadays have built-in microphones (even if you can't necessarily see where it is), it's easy to record using the Sound Recorder that comes with Windows, and I think it's fairly straight-forward to upload a file using the "Upload file" link under the "toolbox" section of this page. Red Act (talk) 01:34, 1 November 2009 (UTC)

As someone who has heard this noise, I can tell you that what causes this is the same thing that causes any sound. When the spoon hits the mug, the spoon and mug vibrate. The milk in the mug affects the vibrations of the mug and the spoon, and what you hear is a combination of all the vibrations. See sound —Akrabbim^talk 01:04, 1 November 2009 (UTC)

Most of the respondents don't seem to have noticed the phenomenon that I think Remember Civility is referring to: correct me if I'm wrong, RC, but I believe it is that when the mug is tapped, the pitch of successive taps progressively rises for a time. I've noticed and wondered about this when stirring hot tea or coffee: at first I assumed it was due to the rising temperature of the mug (due to heat transfer from the beverage) altering its acoustical properties, but it also seem to happen if one waits long enough before stirring for the beverage and mug temperatures to have stabilised. An alternative conjecture is that tapping (or stirring) releases dissolved gasses in the beverage, altering its density and therefore acoustical properties. I too would really like to know the correct answer to this. 87.81.230.195 (talk) 06:35, 1 November 2009 (UTC)

I haven't tried this (not a tea drinker), but I've certainly noticed something which might be similar. If you fill a glass with hot water from the faucet, and drop some silverware in, it rattles with a sound which I would describe as a knock or a tap. But a few minutes later, if you jiggle the silverware around, the sound is much more tinkly. (And I notice this phenomenon all the time, when I'm soaking the glass and the silverware prior to washing them.)

There's something else I notice. When I first run the hot water into the glass from the faucet, it's cloudy. A few minutes later, when the sound has changed, the appearance has changed, too -- now the water is clear.

You can probably see where I'm going with this, and it's the same suggestion 87.81.230.195 made already. Hot water fresh out of the tap contains a lot of dissolved gases. The dissolved gas seems to quite significantly muffle or deaden sound. It takes a few minutes for the gas to come out of solution, and when it does, both the appearance and the sounds are much clearer. —Steve Summit (talk) 14:35, 1 November 2009 (UTC)

I'm fairly certain the cloudiness is due to temporary hardness (not dissimilar to the limescale in the kettle). Whether this has an effect on the noise, I'm not sure, but it's possible. - Jarry1250 ^{[Humorous? Discuss.]} 15:35, 1 November 2009 (UTC)

editors who've noticed the rising pitch are correct. I didn't want to mention it for fear of "planting" the thought. I've done a bit more search and it is mentioned in an old [i]New Scientist[/i], see this link, and then, 14 years later, they have another, fuller, bit of text. Note that stirring can "reset" the sound back to a lower pitch. Remember Civility (talk) 15:33, 1 November 2009 (UTC)

I just did some original research regarding this question, in a very literal sense of the phrase: I have now tried this three times with pure boiling hot water, and three times with boiling hot water with cocoa powder in it. All three times pure water was used, there was no discernable rise in pitch. All three times cocoa powder was used, there was a rise in pitch.

The third time each way was done simultaneously, and performed identically except for the cocoa powder: I brought identical amounts of water in identical mugs to a boil at the same time in a microwave oven. I moved the two mugs simultaneously from the microwave to adjacent tiles on the same countertop. I poured some cocoa powder into one of them. I stirred both mugs simultaneously with identical teaspoons briefly, and then simultaneously held the two spoons in a bottom corner of their respective mugs briefly, to essentially eliminate the swirling motion of the liquid in each. I then repeatedly tapped the bottom centers of the mugs with the spoons in alternating order. The pitch in the pure water, to the best of my hearing ability, stayed constant. The pitch in the cocoa started off considerably lower than in the pure water, and ended up if anything slightly higher. In neither case did bubbles come to the top of the liquid during the tapping process.

It certainly appears to be quite important that there be a solute in the water. However, it isn't necessary for the solute to be milk, as the OP suggests, since the cocoa powder I used does not contain any milk. The cocoa powder I used was Ghirardelli Sweet Ground Chocolate and Cocoa, which contains sugar, cocoa (processed with alkali), unsweetened chocolate, soy lecithin and vanilla.

The "tiny bubbles" hypothesis put forward by Cecil Adams[10] seems dubious to me, as I could not see any bubbles reaching the surface of the liquids during the tapping process. And the "changing vortex" hypothesis[11] doesn't make sense, either, because the liquid was essentially stationary in both mugs during my final experiment. Red Act (talk) 17:57, 1 November 2009 (UTC)

If stirring the liquid really does "reset" it - then it has to be something to do with the vortices (or lack thereof). Bubbles might be knocked out of solution by stirring - but it's hard to imagine that more could be added - hence stirring couldn't reset things if bubbles were the cause. Stirring won't reset the temperature - so the effect of gradual cooling can't be the cause either. The idea that the liquid has to be moving in some specific manner probably accounts for some of what's going on. Sound waves will get dragged around with the fluid - so you could imagine different resonant pathways in rotating fluid versus stationary. Using a curved spoon to do the tapping will certainly start up some motion of the liquid - and that might easily be "reset" by stirring. Changing the ingredients of the liquid would change viscosity and perhaps the speed of sound - so it should be no surprise that this is a determining factor. SteveBaker (talk) 22:00, 1 November 2009 (UTC)

How about this for a hypothesis: Suppose the liquid is spinning (eg after stirring) in a smooth, circular path with more or less laminar flow. In stationary liquid, the sound from a tap made in the center would travel radially outwards until it hit the side of the cup - but in a spinning liquid, it has to travel around in a spiral. This changes the distance it has to travel thereby altering the resonant frequency - and also alters the angle at which the sound waves hit the side of the cup changing refractive patterns of the sound through to the air outside. Either of those things could change the pitch that you hear. However, because you're using a complicated curved spoon to do the tapping, each movement of the spoon causes turbulant eddies to spin off from it. Progressive taps cause more and more turbulance - and after enough taps, the spinning of the liquid is broken up into much more random motion at small scales and very little laminar flow - resulting in approximately equal travel times for the sound. Stirring the liquid restores the large-scale laminar flow and allows the experiment to be repeated.

Suggested experiments:

1. Try tapping with a thin, cylindrical object (a glass rod would be perfect) - trying to keep the rod in the center of the cup. This ought not to disturb the flow of the liquid so much - so (if my hypothesis is correct) it should take many more taps to mess up the flow rate and get the pitch of the sound to rise.
2. Try messing up the flow of the liquid with random motions of the spoon instead of smoothly stirring it. If the hypothesis is correct, this should immediately "reset" you to the highest sound frequency instead of the lowest.

SteveBaker (talk) 22:11, 1 November 2009 (UTC)

November 1

Numbering of Magicicada broods

Why are the Magicicada broods numbered the way they are? For Brood I (for 17-year cicadas), the year number of emergence leaves a remainder of 6. Why not 1, or 0? —Preceding unsigned comment added by 75.37.158.42 (talk) 04:16, 1 November 2009 (UTC)

They are probably numbered after the first year someone started numbering them. But the numbers are clearly intended to be fairly arbitary because they numbered the 13 year cicadas with the next available numbers after the 17 year variety. I don't think there is anything particular to read into the choice of numbers. SteveBaker (talk) 21:52, 1 November 2009 (UTC)

What specific type of foam is this? (Think tool/bike grips)

Can't find a definitive answer on this anywhere. There are two specific materials I can't identify that I see used in handles/grips of all kinds; ex: tools, fishing rods, bike handlebars, etc..

The first one is in tube form, with an 1/4" wall. It feels squishy and soft (firmer and deforms less than visco-elastic foam) and has a somewhat rubbery feel. The inside of the tube is smooth and shiny like neoprene you'd fnd in a wetsuit or gasket, and the outside has a matte, smooth texture that I assume makes this open cell foam. The second material is similar, except the cell size is much larger, and thus the texture is more 'pebbly' as. It is in a sheet 1/4" thick.

Other than that (admittedly) poor description, all I can add is: the material isn't 'plasticky' feeling like extruded polyurethane tubing for pipe insulation, nor is it low-density like polyurethane foam for upholstery. It's also not so dense that it'd hurt you if someone threw a chunk at you.

Looking around, the likely suspects I've found across were EVA and a PVC variant (may be a trade name) called NPVC. Neoprene also, but I rarely see it in the thicknesses used in these products, or with any texture. So, does anyone know exactly what I'm talking about? Please don't say foam rubber. That much is obvious :) Thanks in advance.

KA - 97.82.253.69 (talk) 04:28, 1 November 2009 (UTC)

NPVC stands for Nitrile PVC. It is pretty much the standard for foam grips. There are many variants of it because it is easy to adjust the formula when producing the grips. -- kainaw™ 04:39, 1 November 2009 (UTC)

I couldn't have asked for a better answer. Many thanks. 97.82.253.69 (talk) 09:29, 1 November 2009 (UTC)

Power vs frequency

Why does the power/torque of an Internal Combustion engine depend on its RPM? —Preceding unsigned comment added by 116.90.224.116 (talk) 07:00, 1 November 2009 (UTC)

You can answer that loads of ways but basically RPM gives the rate at which fuel is burned (RPMxnumber of cylindersxamount of fuel per cylinder) or alternatively the number of explosive pushes by the cylinders which the engine harnesses. So at low RPM power is proportional to RPM but at high RPM the efficiency falls away for several reasons. If you give the approx level of the question it is easier to pitch the answer. --BozMo talk 09:55, 1 November 2009 (UTC)

For the same reason that you have to breathe faster to run faster. Cuddlyable3 (talk) 12:34, 1 November 2009 (UTC)

I'm going to do some simplifying here, but broadly what I'm saying is correct. Torque depends on RPM because the engine isn't equally efficient throughout its rev range. At low revs engines typically do not fill and empty the cylinders efficiently. At high revs it's often the case that the valve openings are too small to allow the combustion gases in and out of the cylinder fully. As a result, maximum torque is often somewhere in the middle of the engine's rev range. Power is given by torque multiplied by revs, so, if the torque was constant over the rev range, power would linearly increase with revs. Since torque drops off at high revs, we find that power will eventually do so as well, but because of the rev multiplier, it's always higher up in the rev range. --Phil Holmes (talk) 18:58, 1 November 2009 (UTC)

lightening shock

if electricity is been harnessed from lightening why does the rain water that flows from the same place conduct? what s the mechanism behind that? —Preceding unsigned comment added by Srividhyaathreya (talk • contribs) 08:02, 1 November 2009 (UTC)

Each little drop of water carries a small static charge. Electricity is not being conducted in the normal sense of electrons flowing in a medium, but though the bulk travel of charged drops. The air only conducts when a high voltages starts to cause a breakdown. Graeme Bartlett (talk) 10:59, 1 November 2009 (UTC)

career

i m an electrical engineer from India. i wish to enter into the field of space science. can i pursue an m.e or m.s. in aerospace engineering. if not what is the apt course to become an astronaut or a space scientist? —Preceding unsigned comment added by Srividhyaathreya (talk • contribs) 08:05, 1 November 2009 (UTC)

I would expect that you may be employed as a support person, however to be an astronaut, you should qualify as an aircraft pilot first. As a space scientist, you had better get a PhD in physics. Graeme Bartlett (talk) 10:56, 1 November 2009 (UTC)

You don't need to be a pilot to be an astronaut. Pilots of spacecraft will generally be pilots, but there are scientists and engineers that become astronauts too. I would expect a PhD is required to do scientific research in space. --Tango (talk) 19:43, 1 November 2009 (UTC)

See Astronaut#Training for NASAs requirements. Other space agencies will be similar. --Tango (talk) 19:45, 1 November 2009 (UTC)

Right, there are lots of different researchers in space, not just physicists, and definitely not just pilots... it is not the 1960s anymore. --Mr.98 (talk) 20:45, 1 November 2009 (UTC)

Inflammatory result of depolarization theory regarding migraines

That title could've been better. But! I've been reading up on your excellent migraine article, and it lists, among other things, depolarization and serotonin levels as resulting in pain. It is the first I am interested in, because browsing through depolarization and action potential, I am hard pressed to understand exactly what it is that causes an inflammatory agent to be released when a depression occurs. I am quite the noob on this field, and so I feel I may have missed something. As I have understood this matter, a depolarization essentially inhibits to a great extent the cells' ability to communicate, suffering from reduced or nonexistant permeability. Under any circumstance, your help is much appreciated! 91.149.2.165 (talk) 10:40, 1 November 2009 (UTC)

Studies in psychoneuroimmunology have shown that during depression proinflammatory neuropeptides (SP) and cytokines (e.g., IL 1 and IL 2) are released as a result of over activation of the sympathetic nervous system and the HPA axis->leading to acute phase response and to the release of Acute-phase proteins. This is only part of the phsyiological effects of different negative emotional situations.--Gilisa (talk) 11:46, 1 November 2009 (UTC)

I am terribly sorry for having used the word "depression", when I in fact meant cortical spreading depression! I understand your answer thus has less validity. :) 91.149.2.165 (talk) 12:19, 1 November 2009 (UTC)

Actually it does have connection after all as cortical spreading depression may lead to the release of SP, but I don't familiar with works on this mechanism and neuroimmunology is not my expertise. I addressed your question to Dr Dima, he may know the answer.--Gilisa (talk) 13:03, 1 November 2009 (UTC)

Absolutely marvellous! Thank you for taking your time on this issue, I certainly hope for a good answer =) 91.149.2.165 (talk) 13:54, 1 November 2009 (UTC)

You welcome! I'm hoping for a good answer myself.--Gilisa (talk) 14:24, 1 November 2009 (UTC)

I will start from the end. When membrane of a neuron is depolarized by injecting electric current into the neuron, such depolarization leads to increased spiking probability. However, membrane depolarization in general does not imply increased spiking (and membrane hyperpolarization in general does not imply depression). When membrane is depolarized due to change in ion concentrations in the cell and around it, or due to change in conductances of particular type(s) of ion channels, such depolarization may be associated with either increased or decreased spiking probability. There is no contradiction, therefore, between depolarization and depression in the cortical spreading depression in a migraine. That being said, I do not know what exact changes in channel conductances and in the ion balance occur in the neurons in the areas affected by the spreading depression. I never worked on migraine or anything closely related. What I do know is that the depolarization is thought to be not produced by serotonin directly. According to the theory I am somewhat familiar with, mutations in a certain subunit of the voltage-gated P/Q-type calcium channel, or possibly other "channelopathies" in the brain stem, result in the over-active vascular response to the increased activity in certain areas of the cortex (see e.g. this article). Change in blood supply affects the activity in the cortex, which affects the blood supply even more, closing the positive feedback loop. Serotonin, it seems, mostly acts on the blood vessels and not on the cortex neurons in this case. However, with serotonin you never know, as most of its effects are modulatory rather than direct; and I am certainly not a migraine expert. I hope this helps in any way. --Dr Dima (talk) 17:46, 3 November 2009 (UTC)

subsequent natural GMO

How likely or what is the probability that a GMO such as corn with a GM to produce an insecticide or a cow designed to give milk with antibodies could undergo subsequent natural GM from a virus or pollutants or electromagnetic radiation resulting in an increase in production of insecticide or antibody which might render the GM product harmful? Biggerbannana (talk) 11:29, 1 November 2009 (UTC)

About the same as ordinary corn or an ordinary cow. We can't predict anything else. Cuddlyable3 (talk) 12:30, 1 November 2009 (UTC)

Perhaps then it depends upon where something grows but I can't find a map anywhere of areas with high numbers of trees that have large cancerous type growths on their trunks although they appear to be in areas near where phosphorus was discovered and is mined in South Florida and in other areas most likely to have phosphorous deposits which has a lot of radioactivity. Biggerbannana (talk) 14:50, 1 November 2009 (UTC)

In "captivity", these products' reproductive cycles are fairly closely tracked - it's unlikely that anything untoward would happen. The issues arise if they escape into the wild. In that case, those transgenic genes would continue to work and to be selected for (or against) and be possible targets for mutation. However, if the genes don't confer any particular benefit to the organism in the wild (for example, a sheep that produces human insulin in her milk) - and since the organism has to expend energy to produce these extra things - the odds are good that they'd be selected out after enough generations. If they DO offer benefits (resistance to certain common insects) - then they might be strongly selected for - and spread out into the wild population. There is evidence that this has happened already with Starlink corn. However, evolution is only going to operate in ways that strictly benefit the organism - which means that there has to be a balance between the cost to the organism to produce whatever this effect is - and the benefits. The fact that wild versions of the organism didn't already evolve this kind of protection suggests that the cost may have been higher than the benefits - but it's really tough to know. Of course it's much less likely that it would be a virus, pollutants or radiation causing the gene to mutate (a relatively rare event) so much as it's likely that mixtures of the transgenic gene with other (relatively rare) genes already out there in the wild population would increase the effectiveness of the transgenic gene in some way (eg by feeding it's chemical pathway with more inputs). So the odds aren't zero that the release of transgenic organisms might cause gradual evolution of novel new features. SteveBaker (talk) 15:25, 1 November 2009 (UTC)

Sounds like what you are saying is that because the two conductor extension cord I found at a local South Korean flea market had blades made of pot metal and 26 gauge copper wires covered by thick insulation attached only by the pressure of the molded plug holding the blades and wires together is okay even though they violate the electrical standard because they will melt quickly and act like a fuse despite the unlikely possibility of not melting quickly and instead heating up slowly resulting in a fire. Biggerbannana (talk) 16:44, 1 November 2009 (UTC)

That is one of the worst rationalizations I've read here - to the point that it is very difficult to assume that you are actually asking a question and not just ranting about GM products based on little (or no) actual knowledge of GM. He stated that evolution works towards the benefit of the organism. If a genetic modification does not benefit the organism, it will not tend to spread. Try - though I know it is very difficult - to relate that to an organism, not an extension cord. -- kainaw™ 20:10, 1 November 2009 (UTC)

The reference being that anyone can produce inferior goods or follow an insufficient regimen to make money without dependence upon repeat buyers. Biggerbannana (talk) 04:37, 2 November 2009 (UTC)

(It's of note, of course, that "benefit of the organism" is not the same thing as "benefit to people." Mutations in viruses that are good for the organism are often quite bad for humans!) --Mr.98 (talk) 22:49, 1 November 2009 (UTC)

I will also add that although what SteveBaker says is correct, it's possible that increased production can be harmful to other creatures (such as humans who eat the cow or corn), although usually indirectly e.g. massively increased production of antibiotics creates promotes resistance in those infectious agents, thereby making the disease harder to cure in humans. ~ Amory (u • t • c) 21:19, 1 November 2009 (UTC)

It may be worth remembering that many plants that we eat already have a number of compounds which are clearly harmful to humans in sufficient quantities. E.g. solanine in potatoes. A far greater concern then any potential (direct) harm to humans is the ecological effects of transgenes. In particular, if the transgene is beneficial to the plant but harmful to something else (e.g. insects or other plants) if the transgene spreads as SB mentioned and spreads widely enough this may have a negative effect on the ecological balance. A key issue is whether and what other wild species the transgene can spread to, as most plants cultivated for food don't survive particularly well in the wild because they're so screwed up, the addition of whatever transgenes is probably not enough to make them into weeds. Note in case it isn't obvious, this doesn't usually doesn't require any mutation. A terminator gene would hopefully nearly eliminate the spread. All this is something that has received plenty of research, so you could easily find many references if you are interested Nil Einne (talk) 22:55, 1 November 2009 (UTC)

Lots of things may have benefited the dinosaurs to our detriment but praise God for the asteroid. Wild or captive anything which might give our molecular adversaries a distinct and overpowering advantage in the long term is still not a good thing even though not present in the short term. Scientists pride themselves on thinking of every possible scenario and that is where the problem lies. Biggerbannana (talk) 04:45, 2 November 2009 (UTC)

I'm not sure "Scientists pride themselves on thinking of every possible scenario" is really the point. I mean, what? Imagine Reason (talk) 19:15, 2 November 2009 (UTC)

The problem comes when scientists fail to live up to their expectations and a few unwelcome scenarios slip passed. In such cases we see reactions from others and unfortunately as a matter of pride a complete effort at dismissal. The Titanic is unsinkable. The seals on the Space Shuttle boosters work great. The American Colonies support Britain. I've probably forgotten a few other better examples. Biggerbannana (talk) 21:06, 2 November 2009 (UTC)

Humans did not coexist with dinosaurs. Please do not use this space to promote a God of some belief system even if you think He willed an asteroid to impact Earth. The Titanic sank because of failed seamanship and inadequate engineering. The seals on the Space Shuttle failed because of failed corporate engineering. The American revolution arose because of failed foreign policy by Britain. No scientists were implicated, least of all any GM biologists who would be relevant to the OP meaning the Original Post not the subsequent debating by the same user. Cuddlyable3 (talk) 22:53, 2 November 2009 (UTC)

PCR for diagnosis of genital warts

Hi the wikipedia article on genital warts says that less than 1% of people infected with the HPV virus develop visible warts. I'm doing some research into how genital warts are diagnosed in the UK. The only diagnostic tests mentioned on the NHS website are: warts being examined by a doctor and colposcopy. However, if the wikipedia article is right, then 99% of people with genital warts will not be diagnosed by these methods! I've also read that PCR can be used to diagnose genital warts, this could be used to diagnose the vast majority of people who are asymptomatic. My question is does the NHS provide PCR tests for genital warts? Thanks to anyone who can help! RichYPE (talk) 14:26, 1 November 2009 (UTC)

If you are unable to find this information online, you could try calling the NHS' telephone health information line, NHS Direct. TenOfAllTrades(talk) 15:00, 1 November 2009 (UTC)

This question verges on the strict "no medical questions" rule, so I'll answer carefully. Useful search terms would be "genito urinary". The NHS wesites I've seen say that they diagnose by looking, and that only visible warts can be treated. Here's some websites: WARNING: REVOLTING IMAGES http://www.chestersexualhealth.co.uk/genitalwarts.htm - and another link that talks about visual diagnosis http://www.nhsdirect.wales.nhs.uk/encyclopaedia/g/article/genitalwarts/. Remember Civility (talk) 15:58, 1 November 2009 (UTC)

It's a prohibition again medical advice, not medical questions. The OP is clearly not asking for medical advice. --Mr.98 (talk) 16:24, 1 November 2009 (UTC)

thanks for the clarification. I should have been more precise: "Some may think my answer verges on the strict no medical advice rules, but don't worry, I'm being careful". Is that better? Remember Civility (talk) 19:23, 2 November 2009 (UTC)

Also deleting a warning against a known hazard as if it were medical advice is extremely careless. Maybe even culpable. Biggerbannana (talk) 18:59, 1 November 2009 (UTC)

Again, nobody is talking about personal or at-home treatments. (In any case, the treatment plan you mentioned would only be prescribed by a doctor, and would carry copious instructions and warnings and etc. on it anyway.) --Mr.98 (talk) 00:41, 2 November 2009 (UTC)

My understanding is that acetic acid is not prescribed to the patient by the doctor but is used much as a laboratory stain to reveal altered tissue and therefore no warning is called for between doctor and patient but rather between the pharmaceutical company and the doctor. Common sources of acetic acid (vinegar) do not have warnings in regard to its use as a stain or as a cure for wards by its constant or prolonged application to a wart. Ignoring or thwarting the opportunity to provide such warning here does not accomplish the Wikipedia ban of giving medical advice but rather opens the Wikipedia to a potential charge of culpable negligence. Warnings are not medical advice but the responsibility of anyone with knowledge of the danger to convey that knowledge to others. Biggerbannana (talk) 15:47, 2 November 2009 (UTC)

Nobody is talking about treatments, and I've never heard of anybody trying to use vinegar at home (I don't really think you know what you are talking about, regarding what doctors prescribe). You are being ridiculous regarding "potential charge of culpable negligence", because Wikipedia is not recommending anyone do anything, much less anything negligent. You might as well argue that Wikipedia is negligent because every time somebody asks about electricity we don't warn people about the risk of electric shock. If you really have a problem with the medical policy here, just take it to the talk page. You are creating an issue here out of nothing and being silly. --Mr.98 (talk) 23:27, 2 November 2009 (UTC)

I support Mr.98 here. This section is for responses to the OP's question within Ref. Desk policies, not for inventing pseudo-legal accusations. Cuddlyable3 (talk) 11:30, 3 November 2009 (UTC)

chemical induced orgasam

I've heard that electricity has been used to stimulate the genital region but I do not know if it is to the point of orgasm. Is there chemical which can do this? Biggerbannana (talk) 18:55, 1 November 2009 (UTC)

SSRI usage can sometimes result in spontaneous orgasms.[12] Red Act (talk) 19:22, 1 November 2009 (UTC)

Conversely, SSRIs can also prevent orgasm. Mitch Ames (talk) 23:43, 1 November 2009 (UTC)

Clomipramine, which is a TCA, can also cause spontaneous orgasms. Interestingly, these antidepressant-caused orgasms are sometimes triggered by sneezing.[13] Red Act (talk) 20:12, 1 November 2009 (UTC)

Effect of optimism on health

I've often heard it claimed as folk wisdom that "positive thinking has been proven to have a positive effect on recovering from illness" or something similar. My understanding is this is likely based off a few hastily done studies in the seventies which probably found nothing more than the obvious link of heavy stress and it wearing out the body. Additionally, further studies that were done extensively failed to show a link. Do we have an article on this, or anything to back it up? I read this in a magazine, and I would like to probe more in depth; my scientific mind finds it very unlikely that the new age baloney about just having a positive attitude vs. a resigned attitude will have any effect on your illness; short of, of course, extreme stress. Magog the Ogre (talk) 20:16, 1 November 2009 (UTC)

I don't have a lot of knowledge of this topic but I think there is some pretty solid evidence, see PMID 17709956 for example. For your scientific mind, one basic mechanism is that a variety of negative emotions increase the activity of the HPA axis, which leads to increased cortisol secretion, and cortisol has a variety of effects that tend to impair responses to illness, including direct suppression of immune responses. There are currently several whole journals devoted to studying the interactions between the nervous system and the immune system. Looie496 (talk) 21:04, 1 November 2009 (UTC)

I believe the entire institution of placebos may undermine your pessimistic approach towards optomism. Not to mention psychological disorders, in which the mind is essentially the object of the ailment. :) DRosenbach ^{(Talk | Contribs)} 21:06, 1 November 2009 (UTC)

Actually it was found that people who can find attributions for "why me" or to give meaning for live threatening diseases thay were dealing with are more adaptive and have higher survival rates.--Gilisa (talk) 21:40, 1 November 2009 (UTC)

To DRosenbach: the placebo has less to do with actually getting better than how one reports his/her symptoms? I.e., did you feel noticeably better when taking this/that drug? To Gilisa: do you have any sourcing? It's precisely this type of thinking for which the author of the magazine article I was reading was critical. Magog the Ogre (talk) 00:02, 2 November 2009 (UTC)

Did you read the linked article on placebos? The changes are a lot more complicated then simply different reports of symptoms and the article is resonably detailed and sufficiently referenced Nil Einne (talk) 00:32, 2 November 2009 (UTC)

Look at "The Search for Meaning Following a Storke" by S.Z. Thompson (1991) for a review. It's a bit old one but still invariably cited even in recent articles on similar issues. The effects of negative mood on one's health are obvious and were demonstrated using the most rigorous experimental methods and proven to the molecular level. It's a bit harder to make molecular studies on happiness, but at the least-being happy means not being depressed.--Gilisa (talk) 12:52, 2 November 2009 (UTC)

I speculate that optimism and good health could both be the result of having sufficient levels of Vitamin D in the body. People in northern latitudes are thought to be deficient during the winter (see Scientific American article from November 2008), and personally I always find the darkening nights of autumn a depressing time, for example. I have seen a scientific paper that speculated that the health benefits of fish could be as a result of their Vitamin D content - do not know if there is any triuth in that. Note that excessive consumption of Vitamin D is harmful and dangerous. 78.146.167.26 (talk) 15:06, 2 November 2009 (UTC)

How much land is needed to support people?

Hi,

For one average person, or family, in 'the west', lets say Western Europe, how much land in terms of agricultural area is on average needed to support them in terms of food. I know there is no specific amount and the numbers vary widely depending on the habits of countries, eg fish/carbohydrate based diet, and depending on the quality of land in said place but there must be some sort of figure saying something like 'on average one person consumes 1/4 acre of wheat per year' or something like that. Also any figures for other natural resources eg timber, water etc would be useful. Thanks, --86.136.37.191 (talk) 21:47, 1 November 2009 (UTC)

Someone asked a similar question here. People there gave a wide range of answers, I think it really depends on what kind of crop and how much diversity the people eat. Potatoes are famously compact, while any kind of meat is going to require much more overall. Someone at that link said .5Ha per person for a typical Western diet. I would also think it depends heavily on the quality of the land, specifically whether it gets enough water. Sorry, I guess this turned out to be a pretty waffling response ;) TastyCakes (talk) 21:55, 1 November 2009 (UTC)

Oh, also I would imagine if you're in a year round warm climate that gets lots of rain, like much of the equator, each acre is going to be more productive overall and the land needed per capita is going to get smaller. This list gives an idea of this. In Bangladesh, there are apparently 1,946 people per square km of arable land, which is just over .05 hectares per person, and I doubt they are a big net importer of food (although maybe I'm wrong on that). TastyCakes (talk) 22:27, 1 November 2009 (UTC)

Oh, and this page gives some crop yields in tons per hectare. You have to click on the "Table" icons on the left to see them. TastyCakes (talk) 22:30, 1 November 2009 (UTC)

The Tables are likely in tonnes per hectare (t/ha) and not tons per hectare.

Yes, sorry that is likely correct. TastyCakes (talk) 04:04, 2 November 2009 (UTC)

Does phosphorylation occur only with OH / COOH groups?

In order to be phosphorylated, you kind of need to have slight nucleophilicity to begin with right? You can't phosphorylate something if it doesn't have a nucleophilic -OH group to begin with? (The -OH group can be part of a pi system like a carboxylic acid.) John Riemann Soong (talk) 23:08, 1 November 2009 (UTC)

November 2

Hammerhead Sharks

In what part of the world are hammerhead sharks usually found? The article on them didn't give any specific locations.99.251.239.89 (talk) 00:25, 2 November 2009 (UTC)

Hammerhead is a genus name and is pretty broad. Click on the individual species links (e.g. Scalloped hammerhead, Great hammerhead) and you'll see little maps. --Mr.98 (talk) 00:45, 2 November 2009 (UTC)

(edit conflict) That would depend on which shark you wanted. ~ Amory (u • t • c) 00:48, 2 November 2009 (UTC)

Cute. DRosenbach ^{(Talk | Contribs)} 15:52, 2 November 2009 (UTC)

h1n1 vaccine

hey is there blood in the h1n1 vaccine? i cant find any info on whats in it.--Least0190 (talk) 00:28, 2 November 2009 (UTC)

I don't think there is blood (human or otherwise) in any modern vaccine. --Mr.98 (talk) 00:35, 2 November 2009 (UTC)

However, there are chicken egg proteins in it, so if you have any allergies to chicken eggs, you may not be able to take that vaccine. See also 2009 flu pandemic vaccine for the H1N1 (swine flu) vaccine, and Influenza vaccine for flu vaccines in general. --Jayron32 00:40, 2 November 2009 (UTC)

(edit conflict) There most definitely is not. The only people who are injected with any sort of blood are heroine addicts. ~ Amory (u • t • c) 00:40, 2 November 2009 (UTC)

For proof (sort of) you can read Hemagglutinin (influenza). Essentially, flu surface proteins cause blood to clump in vitro, which would make for a very ineffective vaccine. ~ Amory (u • t • c) 00:43, 2 November 2009 (UTC)

{Sidetrack: While I am personally addicted to heroes, I am doubtful about Amory's claim above that heroin addicts are "injected with blood". There may be blood in dirty needles, but there is, as far as I know, no intent to inject blood. ( Blood dopers may inject blood, but that has nothing to do with heroin.) Is there some treatment technique that involves blood injections for addicts?} Bielle (talk) 00:56, 2 November 2009 (UTC)

Not a treatment by any means - Heroin users who want the hit to hit faster and the high to be higher have been known to stick the needle in their arm, draw a little bit of blood up into the syringe, then inject the mixture back in. It's a great way to OD or get bubbles into your bloodstream, and a really, really, really stupid thing to do, but then so is doing heroin. Trainspotting features this technique, iirc. ~ Amory (u • t • c) 01:00, 2 November 2009 (UTC)

I am now better educated. Thank you, Amory. Bielle (talk) 01:04, 2 November 2009 (UTC)

Honestly this doesn't make sense to me. How would this get the heroin to your brain any faster? I had a vague notion that the idea was precisely to prevent bubbles — once your blood was up in the syringe, you knew there was no air in the needle. I don't know whether that makes sense either, but it's more plausible than that it makes you high faster. --Trovatore (talk) 01:43, 2 November 2009 (UTC)

Likely there are 2 good reasons for drawing a little blood, 1. you are sure that you are actually in a vein. 2. you ensure that there isn't too much heroin wasted residually in the needle. Unomi (talk) 01:53, 2 November 2009 (UTC)

Ah right, the vein thing, I think that was it, not the bubbles. --Trovatore (talk) 04:00, 2 November 2009 (UTC)

Well, for one, some people think that mixing powder with water weakens it, so they just put the powder in the syringe, then use the blood to put it in solution. ~ Amory (u • t • c) 06:20, 2 November 2009 (UTC)

Well, there's one pretty blatant error above -- people who get a blood transfusion are certainly injected with blood, obviously. Looie496 (talk) 02:42, 2 November 2009 (UTC)

I left an obnoxious semantic loophole there for myself - transfusions aren't so much injected, per se, as they are dripped. ~ Amory (u • t • c) 06:13, 2 November 2009 (UTC)

ok thanks guys its just that i read that it has pig and horse blood in it, i dont want animals blood in me.--Least0190 (talk) 03:27, 2 November 2009 (UTC)

If you want it, here's a link. You can read through the full contents of each vaccine, and see that none of them contain anything like that. The closest you get, as Jayron said, is the possibility of less than one millionth of a gram of egg proteins. ~ Amory (u • t • c) 06:20, 2 November 2009 (UTC)

May I suggest for you Carl Sagan's The Demon-Haunted World? Imagine Reason (talk) 19:13, 2 November 2009 (UTC)

Is it possible for energy/ information to travel faster than speed of light in the following case

Let we have a straight pipe AB long but greater than 300,000 km in the free space or vacuum. The pipe is full of small balls of perfect shapes from point A to B and each ball is connected to each other just like two circles at their common tangent point. Assume there is no friction between the pipe and balls. For simplicity we can also ignore the pipe.

Would the last ball at point B be move out if we add a ball to point A of the pipe in less than a second, if not why?

I know nothing can travel greater than speed of light but I'm just asking if it might possible. Thanks 68.147.38.24 (talk) 01:34, 2 November 2009 (UTC) khattak

Nothing can be perfectly rigid. The balls are made up of atoms. When you push on the first ball, what happens? Its atoms get pushed closer together. They don't want to be closer together, so they start pushing on other atoms behind them, which move farther away. This generates a compression wave down the pipe, which moves quite fast, but slower than light. (It probably moves at about the speed of sound in whatever the balls are made of.) --Trovatore (talk) 01:38, 2 November 2009 (UTC)

Thank you for your swift reply but sorry to ask you again. Would your answer be the same if two persons commune each other by pushing the same whole pipe or rod in dark space against one another? Because there is diference between the pushing speed of atoms and the pushing speed of the whole pipe/ rod 68.147.38.24 (talk) 03:42, 2 November 2009 (UTC)khattak

"The whole pipe/rod" is an object composed of atoms. It is no more solid and no more rigid than its full packing of balls. DMacks (talk) 03:48, 2 November 2009 (UTC)

Trovatore and DMacks are correct. See "Faster-than-light#FTL_phenomena" for some interesting findings. Axl ¤ [Talk] 07:10, 2 November 2009 (UTC)

Supposing the rod was made of quark matter?80.2.195.180 (talk) 12:30, 2 November 2009 (UTC)Trevor Loughlin

Ho hum, I asked this question a while back - revisiting the archive, I see I forgot to respond, so here's a belated thanks to everyone who answered me. Here is that discussion. Vimescarrot (talk) 13:38, 2 November 2009 (UTC)

This question is asked so often that it has made me wonder if we have a template for the constant answer that keeps getting rehashed over and over. -- kainaw™ 15:09, 2 November 2009 (UTC)

Hmmm... I just thought that if I have time today, I will trek through the archives and get a list of links to the previous questions. There should be at least 100 of them. Then I can make a template that says: "Your question has been asked and answered here and here and here and here and here and here and here...." -- kainaw™ 15:10, 2 November 2009 (UTC)

Hmm... seems like more work than just answering it again, in most cases (or, putting it another way—it is probably easier for four people to recapitulate parts of an answer than it is for one person to look up all of the previous answers. Also more fun, for the four people). This one is common enough in general that we could have just provided Google links—[14]. --Mr.98 (talk) 16:10, 2 November 2009 (UTC)

That information cannot travel faster than the speed of light (locally, at least) is a fundamental principle of special and general relativity. Those theories have been very successful at making predictions we have experimentally verified, so we assume that principle is correct. That means that there is a fundamental limit on the rigidity of any object, whatever its composition, since it the speed of sound in it (which is what we are talking about, really) must be slower than the speed of light. --Tango (talk) 18:34, 2 November 2009 (UTC)

Short answer: in order to change what is happening, you need to apply a force. Either you force something directly, or apply a force to something which applies a force to something else ... We only have four forces - electromagnetism, gravity, strong, and weak, and all four are transmitted (over long distances) at the speed of light. No force travels faster than light, so your effect can't be transmitted faster than light. -- 128.104.112.149 (talk) 22:15, 2 November 2009 (UTC)

What about Quantum entanglement? From the dictionary: a quantum mechanical phenomenon in which the quantum states of two or more objects have at all times to be described with reference to each other, each instantaneously tracking changes to the other, however large the spatial separation of the objects. Instantaneously, no matter what the distance. That's faster than the speed of light. 20.137.18.50 (talk) 17:51, 3 November 2009 (UTC)

It's only in a very limited way that quantum entanglement can violate locality. Regardless of quantum entanglement, information can't travel faster than the speed of light, which applies in the case of pushing a long rod. See no-communication theorem. Red Act (talk) 18:42, 3 November 2009 (UTC)

In short - the quantum states being transmitted are random, so you can't use them to communicate anything other than random values. I did see a proposal that they could be used to communicate a random key for encryption. The encrypted information would then be transmitted by conventional means. --Tango (talk) 18:47, 3 November 2009 (UTC)

I got rid of the wrong definition at Wiktionary. The original entry, created on August 10, 2005, was okay, if not very edifying. Five days later it was replaced with the incorrect one, which survived for more than four years. Sigh. -- BenRG (talk) 19:49, 3 November 2009 (UTC)

hox and homeotic transformation

"I have a question/challenge on the homeotic gene page. Are HOX actually homeotic? They definitely are in their ability to regulate A/P development (with anteriorization if a paralogous cluster is knocked out), but there are not homeotic transformations of the limbs in knockouts (HOX 10 and HOX 11 Genes are Required to Globally Pattern the Mammalian Skeleton, Capecchi, et al., 2003, Science Vol 301, p363) From this article, while there are gross limb defects, there is not the reassignment of stylopod to zeugopod, or anything along those lines, making me think that these genes are not completely homeotic in nature. Thoughts? Thanks for maintaining this extremely important page." —Preceding unsigned comment added by Terragamo (talk • contribs) 05:06, 2 November 2009 (UTC)

I believe the HOX genes are unusual in that respect due to the nature of their distinction in limb development. The differential expression of the HOX genes is established during the limb bud stage, when the future limb is at only a small fraction of its final length, barely extended from the imaginal disc. It'll be a day before I can get back to my old developmental textbook, though, so I should note that that's simply my idea. Someguy1221 (talk) 05:12, 2 November 2009 (UTC)

carbon monoxide

Plants metabolize carbon dioxide. What about carbon monoxide? 71.100.8.110 (talk) 06:20, 2 November 2009 (UTC)

They're capable of metabolizing carbon monoxide, but the experiments that showed this exposed the plants to carbon dioxide free atmosphere, so I'm not sure how physiologically significant the effect is. One paper describing this: [15] Someguy1221 (talk) 06:26, 2 November 2009 (UTC)

What happens if a non-depressed person takes anti-depressants?

Not a request for medical advice as I'm just curious about what would happen. Assuming they took them regularly for some time. Would they feel happier, drunk, manic, lose their rational judgment, what? It seems like a scenario for a dystopian science-fiction novel. 78.146.167.26 (talk) 14:58, 2 November 2009 (UTC)

The answer is going to depend on which specific anit-depressant drug is taken. Googlemeister (talk) 15:39, 2 November 2009 (UTC)

And the dose. --Mr.98 (talk) 16:13, 2 November 2009 (UTC)

Don't those drugs sometimes have nasty side-effects? RJFJR (talk) 15:47, 2 November 2009 (UTC)

Drug abuse and antidepressant might be a good starting point... TastyCakes (talk) 16:25, 2 November 2009 (UTC)

Terrible withdrawals as well if you forget a dose. Readro (talk) 16:56, 2 November 2009 (UTC)

Not really. They take several days to begin to take effect. Withdrawal happens after a week or so.--Drknkn (talk) 17:30, 2 November 2009 (UTC)

That really depends on the drug (and its half-life). Effexor can cause withdrawal with a single missed dose, the same day you missed it. -- Aeluwas (talk) 18:38, 2 November 2009 (UTC)

I was speaking from personal experience, and you managed to guess my brand of pills in one! Congratulations :) Readro (talk) 20:53, 2 November 2009 (UTC)

I didn't know about that drug. I've used Paxil, Prozac, and Zoloft. They work slowly.--Drknkn (talk) 21:15, 2 November 2009 (UTC)

The vast majority of real-world side effects are mental. Lethargy (laziness), and apathy are common, especially with Zoloft. Anti-depressants do more to curb caring in general than depression. So, you don't feel over-joyed or anything. You'd need a stimulant (like, say, ritalin) for that. If you're already happy, and you take a stimulant, then you'd feel ecstatic. But if you're anxious and you take a stimulant, then the results could be catastrophic.--Drknkn (talk) 17:29, 2 November 2009 (UTC)

. Comet Tuttle (talk) 18:04, 2 November 2009 (UTC)

This article suggests that some non-depressed people have become habitual users of anti-depressants for "lifestyle" reasons, perhaps after first being prescribed them for reasons other than depression. The user cited in the article does indeed claim that his daily SSRI makes him feel happier, although it is made clear that the effects of using these drugs in this way are unknown and potentially dangerous. Karenjc 18:40, 2 November 2009 (UTC)

I don't think it's that simple. Depressants like alcohol, for unknown reasons, make people feel good, while stimulants often dampen their enthusiasm. Imagine Reason (talk) 19:10, 2 November 2009 (UTC)

Right. I guess it depends on your personality. I've used Paxil, Prozac, and Zoloft over the years. They all make me lethargic and apathetic. Alcohol makes me depressed, but other people get happy when they're drunk, so YMMV.--Drknkn (talk) 21:15, 2 November 2009 (UTC)

There are different types of anti-depressants. "Tri-cyclics", "MAOI", "SSRI", and then a bunch which are a bit like SSRIs but have different acronyms, such as NASAs, etc. Ann and Bob might have very different experiences even of the same dose of the same medication. There's something called "seretonin syndrome" which can affect people who overdose on soem types of anti-depressant meds. One way to answer the question would be to look at the side-effects of the medications, and the frequency of those side effects, to see what might happen. Don't forget the important Placebo Effect either. Remember Civility (talk) 19:33, 2 November 2009 (UTC)

Some antidepressants are routinely prescribed for their side-effects, not their anti-depressant effect. See Amitryptiline. I've just come off this drug after 15 years on it for nerve pain: apparently it is the treatment of choice for such pain. I didn't notice a particular anti-depressant effect while I was on it. --TammyMoet (talk) 20:33, 2 November 2009 (UTC)

the form of energy as matter

Harmonic analysis/synthesis reveals that a combination of sinusoidal frequencies can generate an approximate square wave of any amplitude with a virtually infinite wavelength or zero frequency (assuming that in the case of the expression of energy that the reason absolute zero can not be obtained is the same reason absolute zero frequency can not be obtained). Is it possible that this state of combined frequencies is the state of energy we call energy or matter in the form of a particle? Biggerbannana (talk) 15:25, 2 November 2009 (UTC)

I'm not really sure what you mean. What are you measuring the frequency of exactly?

The wave function of a particle has a non-zero frequency. See matter wave. Rckrone (talk) 17:23, 2 November 2009 (UTC)

The idea I am referring to is that of matter or energy being created in a star say by fusion when two atoms of hydrogen becomes one atom of helium. While hydrogen and helium are both matter the energy difference is not expressed in the form of matter but in the form of electromagnetic radiation. The amount of this electromagnetic radiation is known. However, the radiation contains both light and heat and x-rays and Gamma rays and more. However, if you only measure the visible light energy then you come up short and the same for all of the other wavelengths as well but not if you add them all together. When you do add them all together and plot a graph you should get approximately a square wave which itself may have a wavelength near one half the half life of Helium. What I am asking is has anyone else explored this idea and if so have they written a paper? Biggerbannana (talk) 20:52, 2 November 2009 (UTC)

Animation of the additive synthesis of a square wave with an increasing number of harmonics

A square wave is the sum of an infinite series of sinusoidal waves. Conversely a square wave can be generated by adding together the same series of sinusoidal waves. The frequency of the square wave is that of the lowest frequency sinusoidal wave, so this is not a way to generate a lower frequency wave than one already has. The amplitude of the square wave is less than the amplitude of the lowest frequency sinusoidal wave, shown by the animation. Cuddlyable3 (talk) 22:25, 2 November 2009 (UTC)

What would say is the lowest electromagnetic frequency produced by the fusion reaction and its amplitude? For that matter how about the amplitude of each frequency produced? 71.100.8.110 (talk) 02:12, 3 November 2009 (UTC)

A single fusion reaction doesn't create a wide spectrum of EM radiation. The energy released is in the form of just one or a few high energy photons and some kinetic energy. Rckrone (talk) 00:09, 3 November 2009 (UTC)

Yes and the amplitude and frequency of each...? Have any been measured and added? Biggerbannana (talk) 02:27, 3 November 2009 (UTC)

They certainly have been measured, but it depends on what reaction it is and on your reference frame. The point I was making is that the Fourier series of a square wave has countably infinite non-zero terms. You can't build it out of 1 or 3 or even 100 frequencies. Rckrone (talk) 06:09, 3 November 2009 (UTC)

I disagree. Although not a perfect square wave only a few frequencies are necessary to produce a reasonable one with less that maximum amplitude but sufficient duration to trigger a programmable voltage sensor for instance. Biggerbannana (talk) 13:26, 3 November 2009 (UTC)

But they don't make anything that looks like that. If you have a reaction that sends off one gamma ray, there's no way to argue that's something like a square wave, and the frequency is somewhere on the order of 10¹⁹ Hz, which is a bit off from the theorized half life of a proton which would be less than 10^-41 Hz. Rckrone (talk) 17:51, 3 November 2009 (UTC)

Also not sure how you would measure the amplitudes of each of these components. The Fourier coefficients have to go to zero as the frequency go to infinity, but the energy of a photon grows. Rckrone (talk) 06:45, 3 November 2009 (UTC)

BTW -thanks for whomever provided the graph... 71.100.8.110 (talk) 02:14, 3 November 2009 (UTC)

YW. User Kief on Commons made the animation and I posted it. Cuddlyable3 (talk) 11:16, 3 November 2009 (UTC)

Much thanks or hugs and kisses if you are female. ;) Biggerbannana (talk) 13:28, 3 November 2009 (UTC)

Definition of species

The most common definition of species that I've seen is that a species is a group of organisms that can breed with one another to produce fertile offspring. How are species defined for bacteria and other organisms that reproduce asexually? ----J4\/4 <talk> 18:15, 2 November 2009 (UTC)

Species#Definitions of species discusses this issue. Basically, the answer is that there is no good answer. --Tango (talk) 18:30, 2 November 2009 (UTC)

It's a controversial area. See "Species" and "Species problem". There are many species that have been renamed/reclassified: Helicobacter pylori (previously Campylobacter/campylobacter-like organism), Moraxella catarrhalis (previously Branhamella), Pneumocystis jiroveci (previously Pneumocystis carinii), etc.. Axl ¤ [Talk] 18:35, 2 November 2009 (UTC)

Centrifugal force in Earth's orbit

Are there any observable effects of the centrifugal force experienced on the Earth as a result of its orbit around the sun? (Not the centrifugal force resulting from the spinning of the earth on its axis.) For instance, the weight of an object should be slightly greater when it is between the earth and the sun (i.e. daytime) versus when the earth is between it and the sun (i.e. nighttime). I assume that this weight discrepancy would be too small to measure, but is there any such effect that can be measured? Or perhaps I'm thinking wrong about the whole thing? Thanks- Staecker (talk) 19:56, 2 November 2009 (UTC)

There is a tidal force on the Earth due to the sun that causes a noticeable effect. The tidal force on the Earth due to the moon is about twice as big, though. The tidal forces on the Earth from the moon and to a lesser extent the sun are what causes tides. Red Act (talk) 20:18, 2 November 2009 (UTC)

Indeed. That tidal force is what the OP is describing - the centrifugal force is equal to the gravitational force (in an inertial frame of reference the gravitational force is a centripetal force and there is no centrifugal force, but if the Earth's frame there is). The difference between the gravitational force between two points on the Earth is called a tidal force. --Tango (talk) 20:27, 2 November 2009 (UTC)

I'd just add that sometimes the Sun tide and Moon tide reinforce one another (the so-called spring tide), and sometimes partially cancel out (neap tide). This effect has presumably been observed for as long as Man has gone to sea, so yes, the effect is very observable, even if it took a while to figure out the reason. --Trovatore (talk) 20:29, 2 November 2009 (UTC)

• Tides have nothing to do with centrifugal force. Tides are due to gravity gradient, i.e. the fact that gravity diminishes with distance. Centrifugal force is due to being in a rotating frame of reference, i.e. in orbit. If the Earth was falling directly into the Sun instead of orbiting, there would by no centrifugal force due to its orbit, but there would still be a tide. Conversely, if the Earth was in a circular orbit but gravity was constant regardless of distance instead of diminishing as 1/r², there would be centrifugal force but no tides. --Anonymous, 06:50 UTC, November 3, 2009.

No, that's not so. The centrifugal force is larger on the midnight side than on the noon side. That still gives you tides. --Trovatore (talk) 06:53, 3 November 2009 (UTC)

Okay, that's a force gradient effect, but it's not a gravitational force gradient effect, therefore not a tide. --Anon, 22:49 UTC, November 3, 2009.

Well, it'll make the oceans swell up, so whatever you wanna call it, I guess. From the point of view of Mach's principle it should be the same.

A back-of-the-eyelids calculation last night while I was driving home suggests that the centrifugal force gradient should be responsible for one third of the observed tidal effect, not considering the Earth's rotation, which is an approximation I don't know whether you can make or not. Wouldn't stake my life on that being right, but it made sense while driving, anyway. --Trovatore (talk) 23:00, 3 November 2009 (UTC)

It must be 100% of it, otherwise where does the rest come from in that rotating reference frame? There is no gravitational force in that frame. Wait, that's not true. There is no resultant force in that frame. The centrifugal force must therefore equal the gravitational force, so presumably they each account for half the tides. --Tango (talk) 23:09, 3 November 2009 (UTC)

Centrifugal force is the same as centripetal force, just in a different frame of reference (and in the opposite direction). With constant gravity you would have centrifugal force because you have centripetal force (the gravity). The centripetal force would be constant, therefore the centrifugal force would the constant, therefore there would be no force gradient effects from either force. You can only have tides due to varying centrifugal force if you have a varying centripetal force and it is distinguished from tides only by the frame of reference, so they are as equivalent as gravity and acceleration. You can consider a radial free-fall situation in a rotating reference frame and the centrifugal force will still be there, so if you really wanted to I expect you could reformulate the tides in that situation in terms of a varying centrifugal force (I haven't actually tried, though). --Tango (talk) 23:09, 3 November 2009 (UTC)

The Effective potential is a way to rewrite the mechanical equations of motion to make it appear that earth's orbit is due to an "effective" force (centrifugal force) - but all that is really happening is that energy and momentum are being conserved. You can interpret the orbit as a "measurable effect" of centrifugal force in this treatment - but you should be aware of the assumptions made by such a formulation. Our effective potential article has a good overview of this topic. Nimur (talk) 20:33, 2 November 2009 (UTC)

The centrifugal force you're thinking of doesn't exist here. If the Earth were being swung around on the end of a rope, you would feel yourself pressed toward the Earth if you were on the inner side and pushed away from it if you were on the outer side, and that difference would show up on a scale. But the Sun's gravity accelerates you along with the Earth, so there's no such effect. There is a much smaller effect due to the change of the gravitational field with distance (the tidal force already mentioned), but it's not the same thing. For one thing it's symmetrical—on the near side you're pulled away from the Earth because you're closer to the Sun, on the far side you're pulled away from the Earth because it's closer to the Sun. For another thing the tidal force drops off with distance from the Sun, while a centrifugal force would increase with distance. -- BenRG (talk) 20:46, 2 November 2009 (UTC)

Oh please, not this silly quibble again. http://xkcd.com/123 . Oops, sorry, you were making a different point; I hadn't read carefully enough. --Trovatore (talk) 20:48, 2 November 2009 (UTC)

The weight will be greatest when the body is at right angles to the sun or moon, ie at dawn or dusk for the sun. Dmcq (talk) 20:49, 2 November 2009 (UTC)

I think BenRG has the right response. I'm pretty sure that what I'm trying to talk about is different from the tidal force, which I know and understand perfectly well. My alleged force would have different properties than the tidal force (read my original description), but if I understand BenRG correctly this effect is cancelled by the sun's gravity. Staecker (talk) 20:54, 2 November 2009 (UTC)

One way to think of it is that the Sun's gravity cancels the centrifugal force at the Earth's center. On the noon side of the Earth, the Sun's gravity is greater (because you're closer to the Sun) but the centrifugal force is smaller (because the angular velocity is the same, but the radius is smaller), so you're pulled towards the Sun. On the midnight side, the Sun's gravity is diminished, but the centrifugal force is larger, and pulls you out. --Trovatore (talk) 21:05, 2 November 2009 (UTC)

... of course this ignores the Earth's own rotation. The angular velocity on the noon side is not exactly the same as the angular velocity on the midnight side, because the Earth is spinning. I haven't worked out how much difference this makes. --Trovatore (talk) 21:44, 2 November 2009 (UTC)

Mass spec

If I wanted to conduct an analysis of a suite of polycyclic aromatic hydrocarbons in a solvent extract of soil using mass spectrometry in order to obtain information on the molecular masses of the constituents what sort of ionisation and insertion techniques should be used? Thanks 188.221.55.165 (talk) 20:01, 2 November 2009 (UTC)

I'm no analytic chemist, but it sounds like you're talking about GC-MS. Seems that's the way people are measuring soil contaminants these days (refs here: [16],[17],[18] will probably have more detail than WP:RD could provide). --- Medical geneticist (talk) 20:32, 2 November 2009 (UTC)

Banging your fists from a different perspective

The act of banging your fists on a table, a relatively common gesture, is usually displayed when someone wants to give their speech a firm and absolute meaning, or when that person is angry. What purpose does this gesture serve from an evolutionary perspective, that is, it obviously serves a purpose nowadays to humans, but is this gesture seen in other primates, and how does this gesture in particular serve us for a certain purpose, instead of using a different gesture. Any thoughts? —Preceding unsigned comment added by 201.21.180.57 (talk) 20:43, 2 November 2009 (UTC)

As a layman, I'd suggest that banging one's fist on the table is no more "innate" than rolling one's eyes; our article Gesture is woefully short but has some interesting-looking references. Comet Tuttle (talk) 20:47, 2 November 2009 (UTC)

Why make the assumption that this gesture must have an evolutionary "purpose" different than any other gesture? Fist thumping is a useful, easily interpreted gesture. Various primates (including humans) pound their fists on their chests... probably something having to do with trying to establish dominance or display aggression, etc. --- Medical geneticist (talk) 21:53, 2 November 2009 (UTC)

I'm not sure how biologically relevant it is (I can't find a WP article), but stereotypically male gorillas are thought to pound their chests with their fists in a gesture of physical dominance. Pounding the table could be a related gesture used to connote power and authority. -- 128.104.112.149 (talk) 22:06, 2 November 2009 (UTC)

Pounding with clenched fist an object such as a table is expressing an urge to Violence that is in conflict with one's unwillingness to hurt a person. Cuddlyable3 (talk) 22:10, 2 November 2009 (UTC)

. Comet Tuttle (talk) 22:31, 2 November 2009 (UTC)

Can the Yarkovsky effect be used for space propulsion?

Say you build a probe that heats only part of its exterior using an internal radioactive source. Would you be able to get a net thrust out of this system because of the Yarkovsky effect? I looked around the net for things about such a mechanism but didn't really find anything. 189.15.218.71 (talk) 23:29, 2 November 2009 (UTC)

Heating only part of the probe would be hard. You would be better off heating all of it and painting different sides different colours so they emit differently (white on one side so it doesn't emit much, black on the other so it does). That kind of thing has been proposed for giving asteroids a slight nudge over a long period of time so they don't crash into the Earth. I've never seen it proposed for spacecraft propulsion. I guess it would work, but it would be really slow - there are better ways. --Tango (talk) 23:42, 2 November 2009 (UTC)

The problem is that radiation pressure at any reasonable temperature (i.e., a temperature low enough to not melt the propulsion system) is very small, generally measured in micropascals. So plenty of energy may be available from the radioactive source, but you're limited as to how fast you can use that energy, i.e., how much power the propulsion system can provide. That's why nuclear electric rocket designs instead use some kind of electric propulsion system such as an ion thruster, that uses some kind of reaction mass. Red Act (talk) 00:48, 3 November 2009 (UTC)

November 3

Mil vs Micron

Hi guys, Mil and Microns are measurements used to represent the thickness of plastic. Does any body knows how many microns are equal to 0.55 Mil? —Preceding unsigned comment added by Ferchyn (talk • contribs) 01:14, 3 November 2009 (UTC)

I would guess "Mil" is short for "millimetre" (one thousandth of a metre). A micron is an alternative name for a micrometre (one millionth of a metre). So there are 1000 microns in a mill. That means 0.55 Mil is 550 microns. And I would guess wrong - it's short for milli-inch. So the actual answer is 0.55 Mil is 13.97 microns. --Tango (talk) 01:25, 3 November 2009 (UTC)

(edit conflict) I was going to correct Tango, but now I don't need to. Our article is at Thou (length). Deor (talk) 01:33, 3 November 2009 (UTC)

Hmm, in my experience mil is much more common. Probably the article should be moved. --Trovatore (talk) 03:07, 3 November 2009 (UTC)

I agree, I've never even heard of thou. I'm sure mil is much more common. Red Act (talk) 03:13, 3 November 2009 (UTC)

Thou is more common in my experience. Perhaps it is a British vs American English thing (me being British)? --Tango (talk) 03:19, 3 November 2009 (UTC)

e/c Try this Mil to Micron conversion calculator. hydnjo (talk) 01:32, 3 November 2009 (UTC)

Worth noting is that Google supports unit conversions in their search field: Check it out. TenOfAllTrades(talk) 03:03, 3 November 2009 (UTC)

If thou is a British thing, then why don't we have the article at Mil (length), since the British use the metric system? —Akrabbim^talk 04:28, 3 November 2009 (UTC)

Should be, "if thou art a British thing". HTH. --Trovatore (talk) 04:30, 3 November 2009 (UTC)

Brits use a mixture of metric and imperial. If I need to gap a spark plug I know it's 25 thou, and I always used to gap distributor points to 15 thou. I wouldn't know (although could calculate or look up) the metric equivalent. We mostly inflate tyres to PSI and we always drive miles at MPH. Not very metric, really. --Phil Holmes (talk) 10:47, 3 November 2009 (UTC)

Oh, I didn't know that. Here in America, all the sciencey people that like metric spin the US as the last barbaric nation to still hold on to feet, pounds, and gallons. —Akrabbim^talk 12:10, 3 November 2009 (UTC)

No, there are 2 barbaric nations left ;-) Fribbler (talk) 13:19, 3 November 2009 (UTC)

Quite recently I was remarking to my wife how I have to mix units to understand the sizes of things without lots of consciuos thought. I only really know my weight in stones and pounds (which, I know, won't help in the US). I run a weather site and follow rain in mm and temperature in Celsius. I'm equally at home with metres or feet or yards. I can only think of fuel consumption in miles per gallon. I used to work on Integrated circuits and couldn't conceive of specifying them in anything other that microns - oh - except their diameter, which is inches. Such is life :-) --Phil Holmes (talk) 17:21, 3 November 2009 (UTC)

Hmm, you did do your silicon work a while ago, eh? The micron is still used (in the sense that no one says micrometer) but it's kind of too big to be a very useful unit. Sometimes comes up when talking about regions of a chip and stuff like that. --Trovatore (talk) 19:11, 3 November 2009 (UTC)

Best time to buy new houseplants?

I'm a beginning apartment gardener who's ready to move beyond philodendron and spiderplants. I've purchased and read a number of guides and feel ready to buy some new species specimens. I'd like to know if there are guidelines as to the best time to purchase new plants? None of my books have mentioned this, other than notes about protecting plants from cold/heat damage during transit from your nursery to your home. For example, I was wondering if buying plants in spring, when they're waking up and preparing for new growth, makes them more able to adapt to the climate difference in their new location? I'd rather not buy a nice selection of new plants now only to find that they've been too weak to successfully acclimate to their new home... I have an underfloor heated apartment in a climate roughly equivalent to Ohio. Thank you! 218.25.32.210 (talk) 01:29, 3 November 2009 (UTC)

Your indoor plants are going to have survive dry air conditions. It probably does not matter much when you buy them, but you may get a better price in the autumn when nurseries try to get rid of plants before frost kills them. Graeme Bartlett (talk) 08:29, 3 November 2009 (UTC)

You'll get a better answer if you just tell us the species you want to grow indoors. One thing you might consider is setting up a heated propagation area (using a heat mat, plastic hoods or vivarium-like enclosures) and instead of buying plants, just grow some from seed, choose the best one as a mother plant, and clone the rest with cuttings. You can do this with several different species, and this will allow you to have some redundancy; If one plant dies, you'll still have the others to work with. Viriditas (talk) 11:05, 3 November 2009 (UTC)

I actually find it better to buy the plants that are in flower when they are in flower, so I can see whether I like them or not! In the UK, houseplants in garden centres are generally on sale in heated greenhouses or similar environments, so they shouldn't need to acclimatise. --TammyMoet (talk) 11:30, 3 November 2009 (UTC)

Elements formed by a hydrogen bomb detonation

I've looked on many articles relating to nuclear processes but I haven't found anything particularly straight-forward on the elements created by an atomic explosion, especially hydrogen bombs, which produce high atomic mass elements. Could someone help find/add these elements and add them to an existing article? Much appreciated! Letter ⁷ _{it's the best letter :)} 01:55, 3 November 2009 (UTC)

I think the high atomic mass elements will be from the fission part of the bomb (ie. the bit that doesn't involve hydrogen). Nuclear fission product should contain the information you want, but note there aren't specific elements produced - there will be a mixture. --Tango (talk) 02:01, 3 November 2009 (UTC)

Much obliged! In my rush I didn't see that page, thanks again! Letter ⁷ _{it's the best letter :)} 02:09, 3 November 2009 (UTC)

Note that there are some elements that are formed by nuclear reactions other than fission in a bomb. See, e.g., Einsteinium, which is formed by the capture of 15 neutrons by U-238 (which is the sort of thing that you'll only find in a very high neutron economy, of course—like the inside of a bomb, or a particle accelerator). --Mr.98 (talk) 04:41, 3 November 2009 (UTC)

composite spectral waveform of each element

Have the composite waveforms (harmonic synthesis) of the frequencies and amplitude of the spectral lines for each element been published? Biggerbannana (talk) 05:41, 3 November 2009 (UTC)

What spectral line are you referring to ? If you mean the emission spectrum, you can find such data at (say) this NIST website. Abecedare (talk) 05:59, 3 November 2009 (UTC)

Yes, this page seems to point to the spectral data but without graphs and in particular the waveform of the composite emission spectrum for each element. Biggerbannana (talk) 06:18, 3 November 2009 (UTC)

The wavelength of the composite waveform is the Least common multiple of its component wavelengths and likely to be extremely long i.e. of low frequency. Cuddlyable3 (talk) 11:05, 3 November 2009 (UTC)

DIY amatuer water quality testing for real nasties like mercury, et al ?

Is it possible for someone without a mass spectrometer // well-equipped laboratory to test water quality for things beyond pH and dissolved oxygen levels? Are there kits one can buy that would reliably identify the presence of heavy metals and such? Or is the only recourse to send a sample to a lab? 218.25.32.210 (talk) 05:48, 3 November 2009 (UTC)

I've seen at home test kits for mercury, lead, and nitrates. Also things like water hardness and sodium content, but those have less to do with whether the water is potentially harmful. Dragons flight (talk) 06:02, 3 November 2009 (UTC)

Yes. Aquarium hobbyists measure a range of variables in the aquarium water. These are either test-strips or fluids you mix with water samples and they change colour depending on the concentration of various chemicals. These are available from websites and pet stores. Checking the website of JBL I find test sets for: Iron, copper, ammonium, phosphate, Nitrite, Nitrate, silicic acid, CO2 concentration and Gh and Kh measures of hardness, plus separate calcium measures and a magnesium calcium indicator.

I also know that in parts of india, the groundwater is tested for arsenic with similar and supposedly inexpensive equipment. EverGreg (talk) 09:49, 3 November 2009 (UTC)

Mass spec isn't usually used for testing heavy metals in water. Inductively coupled plasma spectroscopy is more common. Rmhermen (talk) 15:26, 3 November 2009 (UTC)

aluminum-zinc alloys

Help! I'm trying to find a phase diagram for this system and am getting confused. In the first google images hit I find, I get alpha and alpha prime being in the same phase region?! Help?! John Riemann Soong (talk) 06:16, 3 November 2009 (UTC)

Information on shoulder/chest area anatomy (Medical Science)

Hi, I am writing a novel and I'm trying to make it as realistic as possible (sometimes to a brutal extent). I've come to a point where I need in depth medical information and my local doctor is indisposed. It's also tough to gleam the information I need from several (incomplete) diagrams. So here we are.

Be forewarned, the information I need is for a particularly descriptive(/brutal/violent) fighting scene.

I need to know if there is a name for the area between the shoulder and neck, that is to say, between the Clavicle and Scapula, as this is the point of entry of the character in question's sword. That would be the first part of my question. The second being: I also need a listing of tendons, muscles and organs that a 50cm sword would puncture/cut, if such an action was possible (Not obstructed by bones, etc). Or a source where I can get this. It may carry more relevance than simply determining whether the heart will be among this list, so I will include that it is on the right side of the individual. If the lungs are among this list (Which I believe it will be), am I correct in assuming the individual will cough or gurgle blood in his final moments?

Thank you in advance (In case this question isn't appropriate on this format, I do apologize. I must admit it was rather unclear to me at the time of this posting.) —Preceding unsigned comment added by RyuGenkai (talk • contribs) 09:52, 3 November 2009 (UTC)

Well, that's a nearly 20 inch sword. You can cut anything within 20 inches of where you stab, by aiming at it. Straight down, on the right, you'd hit the apex of the lung, the lung, the diaphragm and probably reach also have the liver en brochette. On the left, the apex of the lung, the pericardium, the heart, the diaphragm and the stomach. Should you decide to go sideways, you could probably get a lung-heart-lung shishkabob. You could cause bilateral pneumothorax and cause death by suffocation without any coughing or gurgling of blood, or if it make for a more dramatic scene you could have blood coughed everywhere. You could transect the carotid and have blood spurting out of the neck, or for a more subdued and dignified death, transect the aorta within the chest cavity and have the victim bleed to death internally with no mess on the carpet. Which is to say: big murder weapon can cause about anything entering about anywhere. Anyway, you should have a look at apex of the lung, which is the area you're entering, and you may get some idea of the anatomy of the area by looking at sternocleidomastoid muscle, scalene muscles, and File:Musculi_coli_base.svg. - Nunh-huh 10:15, 3 November 2009 (UTC)

If I recall correctly, in Rome (TV series) Marcus Tullius Cicero was assassinated "execution style" by veteran soldier Titus Pullo (Rome character), who killed him with a downward sword thrust similar to the one you describe, as if it were a standard way of killing. In actual history, this is not documented. Edison (talk) 14:32, 3 November 2009 (UTC)

Thanks folks. Yes, I did mean straight down, don't know why I omitted that. I did say 50cm, but I'm assuming even with the momentum the character has (He's jumping down from above his victim) he won't bury it up to the hilt. At least not with the (limited) knowledge I have of Physiology. I've always had the opinion that humans are a lot more resilient than books and movies make them out to be. I am liking the pneumothorax idea - it opens up new options. I must admit I also have never heard of a historical case of killing in this way, but then again, my character isn't much for history. Nor is he very experienced in the killing business, shall we say. This is the best method he could come up with when presented with a drop from elevation onto the target. RyuGenkai (talk) 16:14, 3 November 2009 (UTC)

What sort of author capitalizes common nouns like 'physiology,' 'clavicle' and 'scapula.' DRosenbach ^{(Talk | Contribs)} 20:43, 3 November 2009 (UTC)

The film Torn Curtain is notable for a murder scene "that Hitchcock made specifically to show the audience how difficult it is to kill a man". 81.131.65.113 (talk) 21:38, 3 November 2009 (UTC)

melanin benefit vs cancer risk

Melanin seems to prevent damage to DNA by keeping free radical generation at a minimum. Its deficiency appears to be associated with genetic abnormalities. Is there a "Goldy Locks" level (not too hot and not too cold) of melanocytes to maximize benefit and minimize risk tht can be achieved through selective breeding? Biggerbannana (talk) 13:18, 3 November 2009 (UTC)

I assume that would vary by the exposure in question, right? That's why melanin content varies in human populations by latitude. The averages of human skin pigments of historic populations at given latitudes is probably close to an ideal "level" for that given latitude, with evolution having found the sweet spot for that level of exposure. --Mr.98 (talk) 13:41, 3 November 2009 (UTC)

Actually I mean amount of melanocyte cells rather than melanin assuming more cells produce more melanin in total. Biggerbannana (talk) 13:49, 3 November 2009 (UTC)

Our articles on melanin and melanocyte don't appear to mention any association with genetic abnormalities. Do you have some source for that could be used to improve the articles? 75.41.110.200 (talk) 15:16, 3 November 2009 (UTC)

The very article you linked to says "The difference in skin color between fair people and dark people is due not to the number (quantity) of melanocytes in their skin, but to the melanocytes' level of activity (quantity and relative amounts of eumelanin and pheomelanin). This process is under hormonal control, including the MSH and ACTH peptides that are produced from the precursor proopiomelanocortin." I didn't know this for sure before I read the article but expected it would be very likely for there to be a big difference in the regulation outside the number of cells as many/most? human systems have rather complex regulation. Nil Einne (talk) 16:20, 3 November 2009 (UTC)

Has now been by blocked User:TenOfAllTrades, check WT:RD for more. Nil Einne (talk) 16:26, 3 November 2009 (UTC)

How is heat transfered from one body to another?

and no not a homework question, I assumed it was by the vibrating or moving particles in the hotter substance banging off the particles in the cooler substance/the air in between and causing them to vibrate or move as well. Is that true? —Preceding unsigned comment added by 92.251.255.16 (talk) 17:04, 3 November 2009 (UTC)

Start with our heat transfer article. DMacks (talk) 17:07, 3 November 2009 (UTC)

The OP describes heat conduction. The other two ways of heat transfer are radiation and convection. Cuddlyable3 (talk) 20:05, 3 November 2009 (UTC)

What species is the mushroom in this photo?

I have taken a set of five photos of some mushroom I found in the coastal forest of Poland in October 2009. I think the images have high value but I do not know the type of mushroom in the photos. I have five images in the total set. Here is one of them File:Unidentified_red_mushroom_in_Poland_in_October_2009.jpg and I can post more if need to help identify it. Jason Quinn (talk) 18:00, 3 November 2009 (UTC)

Amanita muscaria or fly agaric --Tagishsimon (talk) 18:07, 3 November 2009 (UTC)

That was the first species I found but I don't think it is correct. The mushrooms in my photos (there are the two you see in this photo and a third one in pictures I haven't posted yet) are flatter and less bell-shaped. Jason Quinn (talk) 18:10, 3 November 2009 (UTC)

Actually, maybe you are correct. Some of the other pictures of them show them to flatter sometimes. I'll wait for more opinions. Thank you. Jason Quinn (talk) 18:12, 3 November 2009 (UTC)

If you Google image amanita muscaria there is a surprising number of forms displayed. I can't believe that the labelling is so bad. The other point to note is that the cap changes shape as it ages.It opens from an egg shape and will flatten as it matures, some even curling up at the edge, in the final stages before they decompose. Richard Avery (talk) 18:22, 3 November 2009 (UTC)

Noon in the tropics

Would the variation of the position of the sun, at noon, in the tropics be noticeable. Presumably at some times of the year it is due north, and at others due south. Would it be noticeable? Stanstaple (talk) 18:26, 3 November 2009 (UTC)

Yes. My Dad used to live in Kuala Lumpur (latitude 3 degrees north) and his condominium had a swimming pool. The temperature of that pool varied widely at different times of the year because the sun would go one side of the building at one time of year and the other side 6 months later. That means that during dry season the swimming pool spent quite a long time in the shadow of the building and during wet season it was in the sun almost the whole time, so was much warmer during the wet season. --Tango (talk) 18:51, 3 November 2009 (UTC)

Just as in other places, the position of the sun in the sky at the same time of day has range of about 47° (twice the tilt of the Earth's axis) depending on the time of year. Rckrone (talk) 20:14, 3 November 2009 (UTC)

47 degrees doesn't really mean anything to me viscerally- i very much notice that the day is shortening dramatically at my latitude- the day goes from bright from four till eleven to eight till four- i just wanted to compare Stanstaple (talk) 21:58, 3 November 2009 (UTC)

The length of the day doesn't change considerably in the tropics because the Sun goes from 23.5 degrees one side of directly overhead to 23.5 degrees the other side. --Tango (talk) 22:45, 3 November 2009 (UTC)

ptsd

if you had ptsd how long does it last —Preceding unsigned comment added by 24.98.148.83 (talk) 19:43, 3 November 2009 (UTC)

You mean Posttraumatic stress disorder? According to Posttraumatic stress disorder#Diagnosis, it has to last more than a month to count as PTSD. I think it can last the rest of someone's life in some cases. --Tango (talk) 19:49, 3 November 2009 (UTC)

Glitch in thermochemistry calculation

Okay, so I have this little problem:

A 100-gram rod of copper (specific heat 0.385 J/g) at 100ºC is immersed in 50 grams of water (specific heat 4.18 J/g) at 26.5ºC. What will the temperature be when both components achieve thermal equilibrium?

And I have tried to solve it as follows:

• From the information given, we can calculate that when copper cools by 1ºC, it releases 38.5 joules. On the other side, water needs 209 joules to gain 1ºC.
• Therefore, we can produce the following equations:

$100-x/38.5=y$ and $26.5 x/209=y$

where x represents the amount of joules gained/lost by the component, and y represents the temperature of the component.

• To know where the equations intersect, we make them equivalent:

$100-x/38.5=26.5 x/209$

• We simplify:

$x=2,371$

• Now that we know that each component has gained/lost 2,371 joules, we can use that in the original equation to find out the gain/loss of temperature. Let's do it for copper:

$100*0.385x=-2,371$

$x=-2,371/38.5$

$x=-61.59$

• Therefore, that means that copper has lost 61.59ºC, i.e. its temperature at equilibrium is 38.41ºC. Nevertheless, my textbook gives a value of 37.9ºC. Did I make a mistake, or is this small deviation due to differences in rounding up/down numbers? Thank you. Leptictidium (mt) 19:52, 3 November 2009 (UTC)

I think you made an error simplifying - I get x=2389.566667, albeit on the back of an envelope and as yet unchecked.

$100-x/38.5=26.5 x/209$

$73.5-x/38.5=x/209$

$73.5=x/209 x/38.5$

$8046.5*73.5=38.5x 209x$

$8046.5*73.5=247.5x$

$2389.566667=x$

$100*0.385x=-2389.57$

$x=-2389.57/38.5$

$x=-62.06675325$

$100-62.06675325$

$37.93324675$

$37.9$

--Tagishsimon (talk) 20:17, 3 November 2009 (UTC)

I'm sorry for asking what is probably a very stupid question, but where does the 8046.5 come from? Leptictidium (mt) 20:48, 3 November 2009 (UTC)

It's 38.5*209 ... just some convenient figure allowing me to get rid of both fractions. --Tagishsimon (talk) 20:51, 3 November 2009 (UTC)

looking at yellow or bright purple stuff for a long time

From my personal observence, okay I wear yellow goggles at night when I sleep. When I wake up when I take off the yellow goggle I still see white stuff for white. If humans look at yellow or purple stuff for a long time I thought white stuff will stay white, and it will not look blue or lime green. Since when I took off the yellow goggle I didn't see white as blue. Will yellow and purple just look less vivid? --209.129.85.4 (talk) 20:22, 3 November 2009 (UTC)

The human brain compensates for ambient light (wearing yellow goggles would be the same as having the room illuminated by a yellow light). You know what things ought to be white and your brain works out what the ambient light must be and then compensates for it so you see things the colours they would be under white light. If you were in unfamiliar surroundings and didn't know what colours things should be, then your brain might get it wrong or it may take some time to work it out. --Tango (talk) 20:34, 3 November 2009 (UTC)

Why do you wear yellow goggles when you sleep? Looie496 (talk) 20:39, 3 November 2009 (UTC)

Corneal transplant--209.129.85.4 (talk) 20:55, 3 November 2009 (UTC)

UFO identification

I snapped these beautiful critters on Sunday at the Kirstenbosch National Botanical Garden. Can anyone please help identify them? Also, please advise if these pics are the best of their type and pick the best ones between the duplicates. I'm loathe to upload the full res versions if we already have better pictures in our articles. Also, anyone with a good eye for composition feel free to crop these photos (or even just draw borders on the existing) as you see fit. The full res pics are 8MP so I should be able to throw away plenty of pixels and still have something usable.

Photographic critique would be greatly appreciated. Also what's the best way to go about editing these? They are taken with a Canon EOS 350D in Adobe RGB color space, will The GIMP handle it properly? (The low-res versions have been created with Windows Image Resizer PowerToy, causing some colour "bleeding" which I put down to it not playing nice with Adobe RGB.) Or should I just upload the originals and request our WP:Graphic Lab to do the touching up? Regards. Zunaid 20:37, 3 November 2009 (UTC)

• 
  Identify me. Slightly clipped on top but in focus.
• 
  Same bee. Not clipped off but slightly out-of-focus. which one to choose?
• 
  Same butterfly, which pic is best?
• 
  Identify me and the flower. Crop needed?

I don't know the answer, but I put them in a gallery for you so I thought I'd leave a message to let you know. They're beautiful, but I don't see much photography. Vimescarrot (talk) 21:08, 3 November 2009 (UTC)

Thanks. I've edited some captions. Check out the pics in our bee article for some REALLY superb photography. This is rather second-rate in comparison. Zunaid 21:26, 3 November 2009 (UTC)

The first one is a carpenter bee, Xylocopa sp.. The last one is Oxythyrea sp. (I'm going to write a stub article for that one soon). The butterfly species name eludes me for a moment, but it will come back to me in a minute or two. --Dr Dima (talk) 23:14, 3 November 2009 (UTC)

The before-last one (middle one in the lower row) is also a chafer beetle, family Scarabaeidae; there is not enough resolution to make a more accurate identification. --Dr Dima (talk) 23:47, 3 November 2009 (UTC)

vision acuity over 20/400

Is this possible to have vision over 20/400. Do anybody have like 20/1000 or 20/700. From corneal scar I have had my vision was 20/400--209.129.85.4 (talk) 20:56, 3 November 2009 (UTC)

This article [19] implies that such Snellen fractions do exist. --Cookatoo.ergo.ZooM (talk) 21:14, 3 November 2009 (UTC)

Well, only being able to detect light and dark as if your eyes were closed could be described as 20/infinity. --Tango (talk) 22:15, 3 November 2009 (UTC)

Human - 23 chromosome pairs

What happens when one is born with more or less than 23 pairs? --Reticuli88 (talk) 21:39, 3 November 2009 (UTC)

It will cause one or another disease. There are many, depending on which chromosome was duplicated/deleted. See Aneuploidy. Someguy1221 (talk) 21:43, 3 November 2009 (UTC)

Well, technically it will "kill" the potential life (well before birth approaches), and the (semi-)survivable diseases caused by the monosomy and trisomy Someguy refers to are the rare exceptions. ~ Amory (u • t • c) 22:34, 3 November 2009 (UTC)

Indeed. Miscarriage is often caused by a fault in the genes. --Tango (talk) 22:42, 3 November 2009 (UTC)

Biological distinction between Sickness and Contagiousness in Contagious diseases.

I understand that people can be contagious but not ill during the incubation stage of a disease. The opposite, being ill but not contagious, is commonly said to exist at the tail end of a disease. What is going on biologically during both of these periods? I'm starting to think that latter is a bit of folk science invented by ill people who are feeling cooped up and better enough to want to rejoin the world. -Craig Pemberton (talk) 23:12, 3 November 2009 (UTC)

If "Big bang" is accurate...

If the universe's big bang beginning is accurate, then at that time all matter was together. We are also told that the light from distant galaxies hasn't made it all the way across the universe yet. I imagine that there is lots of relativity and stuff involved, but surely for both statements to be true some matter needs to have moved at faster than the speed of light. What am I misunderstanding? -- SGBailey (talk) 23:36, 3 November 2009 (UTC)

Actually, we can see almost all the way to the big bang itself. Just a short while after the big bang, the universe became clear and light could start traveling. We can see back to this wall and it is called the cosmic microwave background radiation. But events which happened too recently for light from them to reach you, you cannot see yet. Even when you pour yourself a cup of coffee you can't observe it for a time = armlength/C. -Craig Pemberton (talk) 23:46, 3 November 2009 (UTC)

It's generally assumed that everything in the universe came from one place, because it's hard to see how it could be so homogeneous otherwise. So it's all in our past light cone. But we can't see everything. The picture is something like this:

                           * /\           ^
                      @     /  \          |
                           /    \         |
                     ##################  time

We're at the top center and #### is the primordial fireball (the source of the cosmic microwave background). We can't see the event marked *, but we can see the matter that later does *. We can't see the event marked @ and we also can't see the matter that later does @, because the universe is opaque below the ####. But in principle if you extend the diagonal lines through the fireball they encompass the whole universe. The "edge of the visible universe" is defined by where the light cone hits the fireball. -- BenRG (talk) 00:51, 4 November 2009 (UTC)

We need to be careful with our terminology. You are using "universe" to mean "observable universe" (which means everything that can be theoretically observed, not just things that can be observed using EM radiation). Anything outside the observable universe can't have any impact on us, so in a sense we can just say it doesn't exist (which is why people do often abbreviate the observable universe to just "universe"), but in another sense it is very likely that it does (the size of the universe happening to exactly correspond with the size of the observable universe would be a massive coincidence unless there is something going on that we don't know about - alternatively, the universe could be smaller than the observable universe, in which case we should be able to see the same objects multiple times as the light goes all the way around the universe). --Tango (talk) 01:00, 4 November 2009 (UTC)

The expansion of the universe isn't matter moving outwards through space, it is the space itself expanding. There is no speed of light limit on the expansion of space, just on matter moving through space. See Metric expansion of space. The standard analogy is blowing up a balloon with dots on it. The dots are stationary compared to the bit of balloon they are on, but they move apart from each other as the balloon expands. The further apart they are, the faster they move apart. For objects far enough away from us, they are moving away from us (or, rather, the distance between them and us in increasing - they aren't actually moving, that's the point) faster than the speed of light. At the moment, the relevant distance is about 45 billion light years, I believe. --Tango (talk) 00:07, 4 November 2009 (UTC)