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[edit] July 12

[edit] What are these structures?

Can anybody please tell me what these circular structures are? Thanks ItchyHoover (talk) 00:56, 12 July 2009 (UTC)

If you use the Google 'street view' camera - it's obvious that they are Gas holders. Large cylindrical tanks which rise within a circular frame when filled with gas - and whose weight pressing down on that gas ensures that there is sufficient pressure to push it through the local pipework to people's homes and businesses. SteveBaker (talk) 01:14, 12 July 2009 (UTC)

The photo at right is an almost identical Gas holder from West Ham. SteveBaker (talk) 01:40, 12 July 2009 (UTC)

[edit] Life span of the Voyager Golden Record

In the Article on the Voyager Golden Record there is a bit in the Appearances in fiction section that reads:

"In the speculative nonfiction series Life After People it is said that, after a million years of travel in interstellar space, the Voyager probes will be so heavily damaged from micro meteor impacts that the disks will become unreadable."

Because there is no mention of this beyond the fiction section i wanted to know if there was any truth to that statement.--SelfQ (talk) 01:25, 12 July 2009 (UTC)

The probes are so far from the sun now (well outside the Kuiper belt) that the amount of debris is almost zero - the odds are extremely good that these records will last for well over a million years. SteveBaker (talk) 01:54, 12 July 2009 (UTC)

On a related note, how are the disks packaged? It seems to me that the most likely scenario for an alien civilization to get the disks is if the Voyager actually collides with an inhabited planet (therefore, a planet with a breathable atmosphere), with all the consequences that this entails. And you can't very well read a bunch of disks if they've burned up during reentry, can you? 76.21.37.87 (talk) 03:19, 12 July 2009 (UTC)

The discs are packaged in a protective cover, shown here. Micrometeorites would have to penetrate this cover to damage the actual recording medium. Nimur (talk) 03:38, 12 July 2009 (UTC)

It could enter the atmosphere of some alien planet and be burned up. The last meteor to enter the Earth's atmosphere might have been a space probe from some wonderful planet, complete with examples of their music, poetry, and science, that would have enriched our lives. But another scenario is that 100,000 years from now, Voyager is detected by radar and telescopes of another world, and a robot space tug takes it to their scientists for analysis. They play the record, look at the pictures and marvel that there were once such people as us, though we be tribal killer apes who may destroy our race. See also the Star Trek Next Generation episode wherein Picard is the particular target of such a probe from a vanished race and is forever changed as a result. See The Inner Light (Star Trek: The Next Generation) (took some searching to find it). Edison (talk) 03:40, 12 July 2009 (UTC)

Not within the next million years. Neither Voyager probe is aimed towards any particular star - and the odds of just happening to fly close enough to one are astronomically small. There is no possible way they could enter the atmosphere of a planet within that short an amount of time. Also, the Voyager probes will run out of power in about 15 years from now - beyond that, they would pretty much be indistinguishable from a rock as far as alien telescope users would be concerned...but since the closest they're coming to a star in the next 100,000 years is 1.6 lightyears - it's really not likely (and probably outright impossible) for an alien telescope to spot them by chance. The universe is a VERY big place and these are incredibly TINY probes. They'll most likely still be heading off in a more or less straight line without noticable deterioration for a few billion years...they'll probably outlast us, and our planet. SteveBaker (talk) 04:02, 12 July 2009 (UTC)

A more advanced civilization might note its approach. It might cross the path of one of their spaceships. By the way. did you read the article about the Startrek episode, which had the topic of a civilization ending out a probe so someone somewhere would remember them? Edison (talk) 04:52, 12 July 2009 (UTC)

I find it interesting that SteveBaker pretty much rules out the likelyhood of an alien civilization finding either Voyager probe. I never realized that you were that well versed in future alien technologies. ;-) Dismas|^(talk) 05:32, 12 July 2009 (UTC)

You don't have to understand their technologies - you only have to consider the fundamental limitations imposed by the laws of physics and statistics. If you take Dragons Flight's number (below) of 1-10 billion years to get within 60 astronomical units of another star - then consider the likelyhood of detecting something about 2 meters across and weighing 750kg at a distance of 60AU when it's in a totally unexpected (indeed random) position and moving in a random direction. At that kind of distance, the amount of light it would reflect will be truly negligable - it's nuclear power plant will have long ago run down - so it certainly won't be emitting radiation or heat or light or radiowaves of it's own. At 700kg you aren't likely to be able to detect any gravitational disturbance due to it's mass. What conceivable technology could spot it? The extreme limits of our ability to observe objects out that far is to detect Kuiper belt objects down to maybe 100km in diameter! Voyager (at around 2m in diameter) is going to be more than two billion times dimmer! The probability of an alien detector being hit by even one photon reflected by Voyager is quite negligable - so the detector would have to be tracking it for a long time, accumulating these occasional stray photons from it - but since it's coming from a random direction and at a random speed - the probability of the alien detector happening to track it by pure chance is essentially zero. Even if they did happen to pick up some tiny amount of reflected light from it - aside from it's somewhat unusual metallic composition - it's going to be utterly indistinguishable from any other tiny Kuiper-belt type of object - of which there are trillions and trillions to choose from. Why would they bother to investigate this one? Everything says that this craft would be quite impossible to detect with any halfway credible probability. If a similar alien craft entered our solar system - and even if it came close enough to graze our atmosphere - we'd never notice it. If it actually entered out atmosphere - it would burn up before we could tell what it was. There is literally no way for us to detect an alien craft that size. SteveBaker (talk) 15:06, 12 July 2009 (UTC)

A random object travelling through space ought to intersect a star system (within 60 AU) about once every 1-10 billion years. Incidentally, that number suggests the sun may have had a relatively close approach by some other star at some point in its 4.5 Gyr lifespan. It will take Voyager a long time to find another star merely by chance. Dragons flight (talk) 10:34, 12 July 2009 (UTC)

On the other hand, destruction of the disks might not be such a bad thing for us. Consider the inevitable consequences that have occurred on earth every time a culture encounters a vastly more advanced culture, and perhaps the person who characterized that Voyager message as the "single most reckless act in the history of our species" has a point... alteripse (talk) 19:04, 12 July 2009 (UTC)

When we get near-lightspeed spacecraft, we should probably think about going to retrieve it. Googlemeister (talk) 16:35, 13 July 2009 (UTC)

Assuming we would have the faintest clue about where to look for it, which we won't... 76.21.37.87 (talk) 00:58, 14 July 2009 (UTC)

Assuming that the records weren't lost in the meantime, we'd be able to extrapolate its flightpath wouldn't we? Objects travelling in space tend to continue on in a straight line unless influenced by a large gravitational field (which we'd be able to allow for in the calculations), don't they? I think that it's far more likely that Voyager will end up on display in the National Air and Space Museum than in the hands of an alien race... --Kurt Shaped Box (talk) 01:11, 14 July 2009 (UTC)

True, but this assumes that we'd know all the grav fields that the Voyager will encounter along the way, which we don't! 76.21.37.87 (talk) 01:37, 14 July 2009 (UTC)

And besides, if there's two or more grav fields acting on the Voyager at the same time, what we got now is a three-body problem, which is much harder to solve (impossible in some cases). 76.21.37.87 (talk) 01:40, 14 July 2009 (UTC)

And yet another difficulty with extrapolating the flight path: Even for the grav fields that we do know about for certain, in many cases it's almost impossible to obtain an absolutely exact value for their strength, so what we got instead are approximate values with a certain margin of error. Likewise, the Voyager's flight path (therefore its position and direction / velocity) is only known with a certain margin of error (let's say a couple hundred miles for position, a few minutes of arc for direction, and a couple km/s for airspeed). Over time, these errors in flight path will build up (especially since the Voyager's exact flight path influences how close it passes to a given grav field and therefore how much it's deflected), so after a century or two, the uncertainty in the Voyager's position will be so big that we'd have to search a HUGE area! Keeping all this in mind, the search for the Voyager will be MUCH harder even than looking for a tiny airstrip on a tiny desert island in the middle of the South Pacific, especially since islands usually remain in the same place at all times. 76.21.37.87 (talk) 08:01, 14 July 2009 (UTC)

She did not have radar though. We could. On earth, an AEGIS radar can see a small aircraft at 300+ miles, but it is limited by the curvature of the earth. Googlemeister (talk) 19:21, 14 July 2009 (UTC)

You'd still have to get to within 300 miles of the Voyager, which is still harder than looking for an island in the South Pacific.

76.21.37.87 (talk) 01:16, 15 July 2009 (UTC)

So basically, it would be impossible as well for a Message in a bottle to be [read by someone eventually]? If someone wanted a space probe to be found, they could (if their technology were advanced enough) install a very long duration stored energy source and a transponder which would respond to radio signals with a detectable emission, or a beacon which would start operating when it got within plausible detection range of a target starsystem. Edison (talk) 19:24, 14 July 2009 (UTC)

Not the case with Voyager, though, since (as Steve pointed out) it doesn't have such a beacon / transponder. And remember, the only way one can find a message in a bottle is through a chance encounter with a ship (spaceship in this case) or through it washing up on some shore (in the case of the Voyager, that would be a planetary collision, which, as I previously said, would cause it to burn up along with all the disks it carries).

76.21.37.87 (talk) 00:41, 15 July 2009 (UTC)

Watch our ancestors get a ticket for littering. Googlemeister (talk) 19:57, 15 July 2009 (UTC)

Love reading questions like this; the experts theorise of the answer with the best intentions with laws of physics; it is like saying we know how the universe works <TOTAL CRAP> explain the laws of physics for a super massive black hole DOH they dont apply; who is to say the alien networks out there dont have vast nets acting like collectors of information BEEP voyager goes through one o look alien tech lets take a look; who is to say there is a image being portrayed by aliens using sophisticated tech so we think we can see the big bang; <<<<<YES i know amazing but who is to say it isnt truth! if you can imagine it then a civilisation 3 million years older than ours can probs do it just because we cant does not mean they cant; of course with laws of physics and great distances and space is so big it is inconcievable from our prospetive that voyager may bump into a alien race just happened to be sitting on the shoulder of some gas cloud; I like the idea of we are starting to make things like invisability cloaks :) 3 milion year old race wounder what there cloaking technology would be like? wounder if they could be on mars and cloaked sending false images of mars back through our own technology! Yes i guess a bit of a fantasist i am but never rule anything out.Chromagnum (talk) 05:20, 18 July 2009 (UTC)

Hey Chromagnum -- how much $$$ for an "invisability cloak"? I'd love to buy one! LOL! 76.21.37.87 (talk) 05:41, 18 July 2009 (UTC)

[edit] Pain

Congenital insensitivity to pain suggests that the sensation of pain can essentially be isolated from other sensations (with the exceptions of temperature). Does this have any analgesic applications? Is their any method of pain management (obviously one dealing with intense chronic pain) that attempts to "sear" the nerves responsible for pain?

Alfonse Stompanato (talk) 04:00, 12 July 2009 (UTC)

Well, there are many methods that temporarily block the nerves responsible for pain: some of the ones that you're likely to be familiar with are painkiller shots to numb your jaw before a dental procedure such as a dental filling or (if you got really bad teeth) a root canal; or (if you're a woman who's had kids), an epidural block to reduce the pain of childbirth. As for permanently "searing" or deactivating the nerves responsible for pain, I haven't the foggiest. 76.21.37.87 (talk) 04:23, 12 July 2009 (UTC)

Well, there's radio frequency nerve ablation that's been used for chronic pain, but the problem is that nociceptive nerve fibers coexist with those of other perceptions - they don't exist in isolation - so you can lose sensation as well as the pain. - Nunh-huh 04:38, 12 July 2009 (UTC)

[edit] About time dilation

Sorry to ask frequently asked things. But I have two. The first is: I know if two observers start from the same inertial frame, accelerating and decelerating alike in opossite direction, experience the same time of inertial motion, and comes back to where they started, time dilation for both is the same (because everything is symmetrical). But while both are in inertial motion, each observe the other's time delay, and to compensate for that, the time for each (not the other) must delay during acceleration.(I don't think gravitaional time dilation quickens the other's time.) But the other's time does not delay the same amount? If it delays, special relativistic time dilation is not compensated. The second is: In the same situation, but changing only the duration of inertial motion for both, total special relativistic time dilation increases. What compensates for the adittional special relativistic time dilation? Gravitational time dilation has "vertical" distance h in the formula to calculate the gravitational time dilation. I'm not sure, but acceleration at differently distant point (even if the acceleraion is the same) causes different time dilation? And that equals the difference of special relativistic time dilations? Like sushi (talk) 04:38, 12 July 2009 (UTC)

You seem confused. There is no need to include gravitational effects in any of your examples since there is no gravity present. Acceleration is equivalent to a gravitational field only locally which is not the case here since there are two observers with an arbitrarily long space-like distance between them in your examples. When your observer accelerates it jumps from one reference frame into a different reference frame with a different set of simultaneaties. It is even possible that a distant event that was considered already past before the accelaration becomes a future distant event after the accelaration. No gravitational doppler shift (a better term than time dilation) can do that. Dauto (talk) 05:11, 12 July 2009 (UTC)

"Acceleration is equivalent to a gravitational field only locally" and we are dealing with "observers with an arbitrarily long space-like distance"? But if the motion of both are symmetrical,they would return to the point they started, and at the time they have just returned to the point they started and to the same reference frame, the traces of both are fully in the light cone of both. So everything is not "spacelike" at the time?

Like sushi (talk) 06:18, 12 July 2009 (UTC)

You are saying that the other is out of the light cone when the acceleration takes place? That is impossible (at least for an observer to see, because the skirt of light cone expands faster than the speed "the other" is observed to recede).

Like sushi (talk) 06:48, 12 July 2009 (UTC)

Or you are saying that the observer can not see the other's acceleration?

Like sushi (talk) 06:52, 12 July 2009 (UTC)

I forgot to write this, I am assuming that the two observers start from the same point.

Like sushi (talk) 07:25, 12 July 2009 (UTC)

I think what you're saying is this: if two people travel in a perfectly symmetrical way then when they meet again the elapsed time must have been the same for both (by symmetry). But that's inconsistent with each one seeing the other's clock run slower. The answer is that they don't see the other's clock run slower, they see it run sometimes slower and sometimes faster, with the average speed over the whole trip being the same as their own. The observed speed of the clock is determined by the Doppler shift factor, $\sqrt{\tfrac{1+v/c}{1-v/c}}$ , not by the time dilation factor, $\tfrac{1}{\sqrt{1-(v/c)^2}}$ . The latter is rarely relevant in physically meaningful situations. -- BenRG (talk) 08:59, 12 July 2009 (UTC)

Thank you. The formula you wrote is a variant of one in Velocity-addition formula#Doppler Shift##Relativistic Doppler Shift? I haven't known that. The observers do not always see time to delay. Thank you again!

Like sushi (talk) 10:18, 12 July 2009 (UTC)

Well, I have thought about it, and using the formula $\sqrt{\tfrac{1+v/c}{1-v/c}}$ , there is still time dilation observed in the case each recedes and approaches with the same speed, because observed time dilations are reciprocal to each other, adding them does not (at least always) result in no dilation.

Like sushi (talk) 10:42, 12 July 2009 (UTC)

No, this is not time dilation, time dilation and time hastening (should I say?) both occur and total time in this case is hastened.

Like sushi (talk) 11:32, 12 July 2009 (UTC)

This isn't usually called time dilation (or time hastening). The effect actually called time dilation is something more abstract involving distributed networks of synchronized clocks. The total time (i.e. number of ticks) is not hastened, it's identical for both travelers (both in reality and "as observed" by each one). It's complicated to work this out explicitly. For one thing, the Doppler shift formula depends on the velocity of the emitter when the light is emitted relative to the velocity of the receiver when the light is received. Since those times are different for light going in the opposite direction, there's no simple relationship between the Doppler shifts seen by the two travelers.

Look at relativistic Doppler shift for the formula. The one I gave, $\sqrt{\tfrac{1+v/c}{1-v/c}}$ , is only for motion in a straight line. For the general case it's more complicated. -- BenRG (talk) 11:29, 13 July 2009 (UTC)

Thak you. I don't know if I understand it, but I am taking it this way. Ignoring acceleration, the trace of both observers are a rhombus, and thinking about "the velocity of the emitter when the light is emitted relative to the velocity of the receiver when the light is received", the time during which one observes the other receding is full one way, but because there is time during which one observes the other to move in the same direction, the time during which one observes the other approaching is less than full one way. While receding, the other's time is observed to run slower, and while approaching, the other's time is observed to run faster, but because "the time during which the other's time run slower" is more than "the time during which the other's time run slower", both multipied is the same?

Like sushi (talk) 02:13, 14 July 2009 (UTC)

I tried calculation.

When the distance at which both swicth from receding to approaching is l, the time observed to pass during recesion and aproach seem to be both

$\frac{l}{2v} \sqrt{\frac{c-v}{c+v}}$

and the time during which one observe the other to recede and approach added seems to be

$\frac{l}{v} \sqrt{\frac{1}{1+\frac{v}{c}}}$

$\frac{former*2}{latter}$ = $\sqrt{1-\frac{v^2}{c^2}}$

Am I doing wrong?

Like sushi (talk) 04:42, 14 July 2009 (UTC)

Something to keep in mind is that observations can't happen instantaneously. Information is limited by the speed of light. So when A observes B, A is not seeing what B is doing right now. There is a delay of t = d/c where d is the distance between them.

In the case of the rhombus, from A's reference frame in the first part of the trip: A is stationary for a length of time t. Before B turns, B is moving away at speed v, and is experiencing time at a slower rate due to time dilation, so B travels for $t' = t/ \sqrt{1 - (v/c)^2}$ time before turning and goes a distance of vt' away from A. After B turns, B is stationary and sits for time t. After A turns, A is moving toward B at speed v and experiences time at a slower rate, therefore traveling for a time t' before meeting B. In this reference frame the point where B turns is after the point where A turns. When A turns and assumes a new reference frame, there is a Lorentz transformation of space time, and so the point where B turns moves. In A's new frame for the second part of the trip: A was moving away from B for a time of t' until turning and is now stationary for a length of time t. B was stationary for time t until turning, and after turning B moves toward A at a speed of v, and experiences time at a slower rate due to time dilation. B again travels for t' time and then reaches A. In this reference frame, B turned before A did. This is what Dauto was talking about. Immediately before A turns, the point where B turns is in the future, but immediately after A turns, the same point has shifted into the past. You can check yourself that the Lorentz transformation for increasing velocity by v in the x direction shifts the point (t'-t, vt', 0, 0) to (t-t', vt', 0, 0). B has the exactly symmetric experience. This is how both people can experience time at a faster rate in their own reference frame and still meet up after traveling for what they each perceive to be the same amount of time. This is different from what person A observes B doing, since observations of B are facilitated by light traveling from B to A, which is I think what BenRG is talking about. Rckrone (talk) 21:10, 15 July 2009 (UTC)

Thank you. I drew pictures and I think I understand what you say. So for an observer, not only the other's time delays, but also the time of himself during different inertial motion is different, and the time of the other once was delaying becomes not delayed when he assumes the same velocity as of the other at the time.

Then what happens if the receding and approaching speeds are different? (I think symmetry is still preserved)

Like sushi (talk) 05:44, 16 July 2009 (UTC)

Yeah, that's right.

Instead of thinking of events in space and time and using time dilation and length contraction to figure out how things change when we switch to a different reference frame and making sure that everything works out, I find it's a lot easier to think of events as points in Minkowski space M. In a particular reference frame, our usual space and time coordinates form a basis of M that's orthonormal according to the Minkowski inner product, but there are many orthonormal bases that we can use, each corresponding to a different inertial reference frame. The Lorentz transformations are exactly the transformations between different orthonormal bases, in other words they're the trasformations that preserve the inner product (modding out by the transformations that reverse time or flip space). This can be checked. Time dilation and length contraction (as well as relativistic energy and momentum, and the relationship between EM forces) follow naturally from this construction. Minkowski space, Lorentz transformation and related articles helped me understand special relativity much better than I did when it was just a bunch of mysterious formulas that miraculously worked out, so I highly recommend them. Rckrone (talk) 19:00, 16 July 2009 (UTC)

Thank you. I will try it.

Like sushi (talk) 10:23, 17 July 2009 (UTC)

[edit] Dumb sheep

What is Natalie Angier talking about 44 minutes into this 1995 Charlie Rose interview when she apparently states that the encephalaization quotient for sheep is the "highest of any mammal"? http://video.google.com/videoplay?docid=946792731875962671&ei=QKVZStmnCIPslQeU3sWoDg&q=natalie+angier&hl=en There is NO WAYYY we didn't know the EQ of sheep in the mid 90's, which, so far as I can see is nowhere near the largest of any mammal. So what is she talking about? —Preceding unsigned comment added by 67.240.160.115 (talk) 09:29, 12 July 2009 (UTC)

Well there is a lot of bullshit out there. However, I listened from 41:00 to 47:00 and she didn't come anywhere close to mentioning sheep or encephalization quotient.--Shantavira|^{feed me} 10:59, 12 July 2009 (UTC)

Oops sorry here's the right link: http://video.google.com/videoplay?docid=-8169749641559849989&ei=PbZaSumdLaXqrAL4za3JDw&q=natalie+angier&hl=en&emb=1 ......anyone? —Preceding unsigned comment added by 67.240.160.115 (talk) 04:30, 13 July 2009 (UTC)

Well, she also says that without dung beetles "we wouldn't have a planet", so I'd take her pronouncements with a grain of salt. Anyway, page 243 of Macphail, E. "Brain and Intelligence in Vertebrates". Clarendon Press, 1982 lists the following EQs:

Man           7.44
Dolphin       5.31
Chimpanzee    2.49
Rhesus-Monkey 2.09
Elephant      1.87
Whale         1.76
Dog           1.17
Cat           1.00
Horse         0.86
Sheep         0.81
Mouse         0.50
Rat           0.40
Rabbit        0.40

I looked in the book she was hawking and saw the sheep EQ assertion, but there wasn't any citation for it, or even a notes section. --Sean 15:05, 13 July 2009 (UTC)

It's of note, in that list, that the sheep certainly is the dumbest of the large mammals listed. (Obviously "large" is somewhat subjective but mouse/rat/rabbit aren't large by any definition.) That being said, being just slightly "dumber" than a horse ain't too bad. Not like being as dumb as a rabbit, which even in causal acquaintances are pretty dumb. --98.217.14.211 (talk) 20:51, 13 July 2009 (UTC)

[edit] Trading agro products

Is there a Board of Trading where all agro products are traded? So far, I only found the more important like coffee, rice and such stuff. --Quest09 (talk) 11:08, 12 July 2009 (UTC)

OR Some (most?) vegetables don't get traded by boards of trading because they are grown on contract. I.e. depending on company rules/contract terms, a company like Green Giant will give the farmer the seeds, the fertilizer and if required pesticides (or issue rules for "organic" produce) and will come pick up the harvest with their trucks right from the field. They'll process and package the produce in their facilities and deliver to their distributors. Smaller non-contract producers will sometimes make contracts directly with local supermarkets. Restaurants and small markets pick up produce at local Farmer's markets sometimes.71.236.26.74 (talk) 20:48, 12 July 2009 (UTC)

Check out List of traded commodities which has a list of commodities and the location where they are traded.--SPhilbrick T 23:00, 12 July 2009 (UTC)

This is list is clearly incomplete. Frozen orange is not there, frozen butter is not there. The question still remains: are there other products like dried garlic, apple juice or the two in the last sentence so uncommon that no trading board would trade them? I understand that lettuce, strawberries or even tuna can not be easily traded by a board, but many other precisely defined product should be traded in a trading board. Just compare it with the small caps that are traded at stock markets. How small must a market be to be excluded from a trading board? --Quest09 (talk) 10:19, 13 July 2009 (UTC)

Plse. feel free to expand the article with well sourced material. Your question wasn't really a Science question to begin with and you might have had more luck on the Humanities desk. (There's some discussion on creating a business desk because "humanities" don't really come to mind there.) I don't really see a necessity for things to be traded by a board. FWIW the following links might help Onion Futures Act, [1], [2], [3], [4] probably not a good article reference, but for information check out commodities trading sites e.g. [5] -- 71.236.26.74 (talk) 17:10, 13 July 2009 (UTC)

I can't really comment on the reasons, but I think organized market trading is more of the exception than the rule for ag products. Feedstuffs, for example, seem to be bought and sold through individual contracts, even through they are fairly standard and traded in large quantities. (I'm not 100% sure about this. I know it is the case for animal byproducts, but not as sure about others). ike9898 (talk) 19:23, 13 July 2009 (UTC)

[edit] Why do men and women exist? (evolutionary biology)

This might seem like a simple question, but I still can't figure out the answer. Evolution of sexual reproduction gives some plausible reasons for the development of sexual reproduction, in the sense of reproduction requiring more than one individual. But why are we and many other species not hermaphrodites (like Earthworms and plants)? After all, this seems like an advantage to me: a hermaphrodite can reproduce both as a male and as a female, thus increasing its reproduction chances. --filip (talk) 11:21, 12 July 2009 (UTC)

An earthworm has been around for a long time. It hasn't evolved much. This is one of the reasons for it. Having two sexes increases the chances for evolution and diversity. Rkr1991 (talk) 11:33, 12 July 2009 (UTC)

Expanding a little on Rkr1991, some creatures (eg aphids) will even reproduce by parthenogenesis at times when food is plentiful, making an immediate supply of identical creatures to consume the food. Later they will reproduce sexually to increase their diversity. Hermaphrodites will turn into female to take advantage of good conditions, as one male is enough to impregnate many females. This type of arrangement is suitable where quantity of population is needed for species survival. I all these cases the young are produced and left to their own devices.

In higher animals, much of survival depends on the (few) young being well cared for and educated, over long periods of time. This makes a variably large number of females a disadvantage, over a fixed smaller number having the permanently female characteristics needed for the nurturing of the young. In other words, we don't come in two sexes to be able to conceive more young, but to be able to nurture to maturity the few young that we do conceive. - KoolerStill (talk) 12:19, 12 July 2009 (UTC)

The benefit of not being hermaphrodites is that there are adaptations in the two sexes that make child rearing more efficient. For example, if we were hermaphrodites, we'd all have to have all of the baby-making apparatus - mammaries, womb, fallopian tubes, extra-large hips, monthly periods, etc. Since human children cannot be abandoned to fend for themselves at birth (as is the case with the offspring of hermaphroditic species) - it takes a minimum of two individuals to care for the child - one to stay home and look after it - the other to hunt the mammoth for supper. The one who is hunting the mammoth is more a more efficient hunter because he doesn't have to carry around all of that baby-rearing stuff. Of course, in reality - the split came a very long time ago when some hermaphroditic ancestor of all non-hermaphroditic animals evolved to have two different sexual morphologies - we would really have to ask the question as to why the change was most beneficial for THAT creature - which is tricky because it's unlikely that we know precisely when that happened and why. SteveBaker (talk) 14:31, 12 July 2009 (UTC)

Steve, that explanation applies to very few species, so clearly is not the explanation. It also smacks of 'Man, the mighty hunter' anthropology, which surely was discredited years ago because it doesn't really make sense? 86.140.144.220 (talk) 18:28, 12 July 2009 (UTC)

Agreed. Steves explanation, especially the part about having a womb and boobs making someone a less efficient hunter is a pile of steaming bs.

bs or not (ok bs) - 2 sexual organisms tend to be(are) higher up the food chain - thus a grain of truth

There is some sort of link here - 83.100.250.79 (talk) 21:35, 12 July 2009 (UTC)

The latest explanation, for which there is some recent experimental evidence involving sexy & unsexy snails (actually sexually and asexually reproducing) is that the main benefit of sexual reproduction is parasite protection because a greater genetic variety of individuals is generated with each generation. Far more individual variation is provided by recombination of chromosomes than by single codon mutations. alteripse (talk) 18:58, 12 July 2009 (UTC)

That explains the point of sexual reproduction, which the OP already said he understands, but I don't see how it relates to the actual question: what's the point of some snails (or humans) having only male reproductive organs and some having only female reproductive organs? —JAO • T • C 19:33, 12 July 2009 (UTC)

You are correct, I misunderstood the question. I suspect it has to do with the expense of maintaining parallel or bipotential reproductive systems not being worth it. There are a few vertebrates, like the wrasse that have capability to change sex if environmental circumstances make it advantageous. alteripse (talk) 20:17, 12 July 2009 (UTC)

Men and women exist because the far more primitive organism(s) from which we evolved found pressures to reproduce sexually. It was advantageous for some earlier link in the chain of life forms that led to us to reproduce sexually. It doesn't make sense to ask why we didn't switch back to asexual reproduction. (I realize the OP didn't ask this question.) The possibilities of the configurations both physical and behavioral of life-forms is bewildering. Why don't we have antennae? Why don't we possess the ability for echolocation? Bus stop (talk) 20:44, 12 July 2009 (UTC)

The primary function of sexual reproduction is to generate new combinations of alleles of the genes of two organisms. In hermaphroditically generated offspring, all the genes come from the same animal, so you don't get novel combinations. Looie496 (talk) 21:56, 12 July 2009 (UTC)

No. Hermaphrodites, even those that are technically able to, avoid copulating with themselves, so generally the genes will still come from two different animals. Again, this question was specifically not about sexual vs. asexual reproduction. —JAO • T • C 11:57, 13 July 2009 (UTC)

Because it takes a long time to rear the young, there is no point having 99% of the population being able to turn female and HAVE young all at once. They will then have to remain female for the ages it takes to rear the young, including the ability to feed them, which is a substantially bigger change than just changing the reproductive organs short-term. Food supply for the large number of young (and supporting mothers) would become a big problem, with very few food providers not engaged in rearing offspring. All the hermaphrodites just produce some eggs and go their merry way as whatever sex they then turn into. Having the majority of the population do this in good times increases the numbers, and therefore their survival chances as a species while lowering the chances as individuals -- which you can't afford with young that have years of work invested in their nurturing. Higher animals go for quality rather than quantity. - KoolerStill (talk) 18:33, 13 July 2009 (UTC)

But many, many, many animals that do not rear their young have roughly 50/50 male/female ratios, without being hermaphrodites. Again, you are offering (some)higher-animal-specific explanations for something that evolved much earlier, and neglect the species (for example, some garden birds) in which both parents share the child-rearing and feeding, and... it just really doesn't answer the question. It's just the usual 60's explanation of why contemporary gender roles were natural and part of our basic nature. It assumes that the usual situation in 'primitive' cultures and higher animals is for the male to provide most of the food for the children and female. 86.140.144.220 (talk) 21:50, 13 July 2009 (UTC)

Why not hermaphrodism instead of gonochorism? Both strategies can work, but in many instances hermaphrodism is subject to specialization by individuals, leading to gonochorism. Suppose there are many available partners around, and an individual happened to fail to develop the eggs it was carrying but instead used the energy of egg development and nurturing for inseminating others. In many cases it could be much more successful in spreading its genes into the next generation than the typical hermaphroditic individual, who would inseminate fewer times due to the higher resources needed to develop eggs, lay them, and perhaps care for young. In such situations, it would be common for insemination specialists to evolve, and from this the species could easily establish them as a requisite male sex distinct from the egg carrying individuals. -R. S. Shaw (talk) 04:00, 14 July 2009 (UTC)

And keep in mind that this works both ways: the individual that develops the eggs would not have to spend energy for insemination of other individuals, so would be more successful in bringing forth her progeny. FWiW 76.21.37.87 (talk) 08:09, 14 July 2009 (UTC)

[edit] Plz help me quickly(some science related questions)

1>Which Filter is used for passing ONLY HIGH frequency a: LADDER B. crystal

2>If water is heated from 0degree to 10 degree effect on volume a: increase steadily b: remain same c: decrease steadily

3>if we dig EARTH FROM North to South pole and a stone is dropped in it then efffect on its velocity a :increase continously b: First increase and become Zero in center c. It Will Start Oscillate

4>Radiation pattern of loop antenna a: cardioid b. semicircular c. circle d. none

5>plural of "DIBIYA"IN HINDI ?

6>RADDISH is a a: modified root b: bulb c; stem —Preceding unsigned comment added by Swapnendu (talk • contribs) 11:36, 12 July 2009 (UTC)

Pardon me if I am mistaken, but this looks like homework. The Reference Desk does not do your homework. You can try reading the relevant articles or consult your textbooks. If you still have doubts in understanding any particular concept, we would be happy to help. Cheers. Rkr1991 (talk) 12:01, 12 July 2009 (UTC)

I also thought "homework" but I wonder what sort of class would ask questions that diverse. Anyway, coincidentally if there was a hole from north pole to south, or any other line through the centre of the Earth, and all air was evacuated from the hole, it would take 42 minutes to traverse the passage (42, of course, being the meaning of life, the universe and everything). Anyway, velocity of a falling object is due to acceleration due to gravity. At the start of the drop the stone would have the whole world ahead of it - the whole world has quite a bit of gravity. By half way, it'd have half the world ahead and half behind - so would be pulled equally in both directions. As it approached the other end of the tunnel, it would have more and more of the world behind it, pulling it back. Repeat. --203.129.49.222 (talk) 12:10, 12 July 2009 (UTC)

oh and...

1. A high pass filter passes high frequencies. <- If it's homework, check your text book. Radio filters can be made with crystals, but also look a little like a ladder.

2. Hotter gasses or liquids have greater volume. Water is a liquid.

4. See loop antenna

5. Sorry, try the language ref desk.

6. See Raddish, root, bulb and stem

--203.129.49.222 (talk) 12:15, 12 July 2009 (UTC)

Actually for number 2, the volume would increase, then decrease. Water reaches its maximum density at 4°C, which is why water expands when frozen. Chaosandwalls (talk) 13:49, 12 July 2009 (UTC)

This does sound an awful lot like homework - but much nicer answer to Q3 (which is a very complicated question unless there are a LOT of caveats) is that the air pressure in the hole increases the deeper you go - and quite a long time before you reach the center of the earth, the pressure would be sufficiently high to liquify the air - hence your rock will fall for a very long time (because it'll reach terminal velocity quite quickly) then make a very, very distant "splash" sound and then slowly sink to the center of the earth. If there is a vacuum throughout your tunnel then 203's answer above is good enough. For 203's benefit, the reason the hole has to go from North pole to South pole is because coriolis forces on the rock would cause it to hit the sides of the tunnel on the way down if it were drilled in any other direction...so it's NOT true that just any old hole would do! SteveBaker (talk) 14:21, 12 July 2009 (UTC)

I believe 42 is the answer to a couple of other interesting questions as well, which I vaguely seem to remember. I think it is half the time period of an infinitely ling pendulum, and something to do with waves which I can't remember.. And Steve, don't forget that these are just ideal imaginary textbook problems, so we should approach it without thinking too broadly...Rkr1991 (talk) 15:18, 12 July 2009 (UTC)

Perhaps you are thinking of the angle of the bow waves formed by a ship - irrespective of shape or speed through the water - which is 42 degrees. SteveBaker (talk) 16:13, 12 July 2009 (UTC)

If you have a source for that, you may want to add it to 42 (number). Deor (talk) 16:16, 12 July 2009 (UTC)

also number of faces on a ~~football~~ Truncated rhombic triacontahedron - thus football is not the meaning of life...83.100.250.79 (talk) 19:50, 12 July 2009 (UTC)

#2: water DEcreases in volume from 0C->4C then increases;

#3: time-of-passage through a straight tunnel from ANY 2 points through the (spherical, homogeneous, frictionless, etc.) Earth is the same! How cool is that?

Saintrain (talk) 01:39, 17 July 2009 (UTC)

[edit] General all-over soreness and tenderness when ill

I appear to be coming down with some nasty virus, and it has me curious. Nearly every time I get sick, I always get a very unpleasant feeling of general weakness, tenderness and soreness all over my body. It makes me want to curl up in bed and not move. Every tactile sensation, particularly unexpected ones, has a note of unpleasantness that it doesn't normally have. What is the cause of this general "unwellness" symptom? Note: I don't want a diagnosis, that's what I'll go to the doctor for. I'm just curious about the actual mechanism behind the symptom. Maelin (Talk | Contribs) 11:46, 12 July 2009 (UTC)

I have the idea that it comes from interferons and other cytokines. Exactly how they do it I have no idea. I seem to recall that this is considered to be adaptive because it keeps you from running off after mammoths while you're sick. --Trovatore (talk) 11:55, 12 July 2009 (UTC)

Our most relevant articles seem to be Malaise and Sickness behavior, which may lead you to more information. Trovatore's response appears to be borne out by Hyperalgesia#Causes. Deor (talk) 14:37, 12 July 2009 (UTC)

Malaise is my favorite symptom ever; it sounds like some sort of jungle fever. If you call up your boss and tell him your doctor says you have malaise, I can bet that boss is going to let you stay home. :-D -RunningOnBrains^{(talk page)} 22:45, 12 July 2009 (UTC)

[edit] What mechanisms trigger vasodilation?

I've been researching a minor affliction I suffer from which I think is cholinergic pruritus (but note that this is not a request for medical advice!). Assuming it is that, is the following an accurate description?:

I get too hot (or embarassed etc.) > ... > ... > Histamine is released as a vasodilator > This also makes C fibers fire which causes the itch sensation (H1 antagonists such as Loratadine are very effective preventatives.)

So, firstly, is that right? Secondly, what happens in the dotted sections? How does thermoregulation work? What detects elevated temperature, what releases histamine (mast cells?) and how are signals sent between the two? Thirdly, what is it that makes me different from most people? Is it how much histamine is released, or how sensitive the nerves are to it, or something else?

My curiosity yearns for further insight so thank you very much for any information you can give on these mechanisms. ASmartKid (talk) 14:14, 12 July 2009 (UTC)

[From Terry0051] May I suggest some preliminaries -- like first taking a step back and having another look. Look at as many alternative explanations as you can find. It might not be the complicated thing you suspect. Common things happen most commonly. Skin is a temperamental and individual tissue/organ. For an otherwise healthy young person, traditional homespun measures to get you comfortable can often be all that is needed. Try various simple and safe measures. Beware of pharmaceutical (over)use. If still uncomfortable, get yourself along to a physician. Good luck. Terry0051 (talk) 21:07, 12 July 2009 (UTC)

Thanks for your concern but I'd love some info on the mechanisms, regardless of what I have. ASmartKid (talk) 16:33, 13 July 2009 (UTC)

Don't know, but the following articles might help Thermoregulation, Human homeostasis (stub), Homeostasis, Vasodilation. 71.236.26.74 (talk) 17:24, 13 July 2009 (UTC)

[edit] Abdominal muscles

I have a feeling this question may well be rejected as medical advice but if it is, it was still worth trying. I'm currently working on my abs in hope of getting a sixpack and, after looking around online, the bicycle crunch seems to be the exercise of choice. Now I've been doing this for a while and have noticed it's getting easier and am looking for a way to make it more challenging, in the hope of causing more muscle development. Is there any suggested way of altering it? I've tried making my elbows meet my leg closer to the hip, rather than meeting at the knee as suggested, and this has definitely been tougher. I'm open to any suggested or even suggestions of different exercises to try. Thanks 92.2.120.88 (talk) 15:19, 12 July 2009 (UTC)

According to the crunch article, “the difficulty of the crunch can be increased by lying on a declined bench and/or holding a weight on the chest or behind the head.” Red Act (talk) 16:11, 12 July 2009 (UTC)

Or attaching weights to your legs. Anyway, you'll only get a six pack if your fat is low enough.--Quest09 (talk) 18:57, 12 July 2009 (UTC)

Who needs a six-pack when you can have a whole keg... ;)--Jayron32.talk.say no to drama 04:56, 13 July 2009 (UTC)

I'd imagine it's unlikely that the average person which achieve a six-pack merely through abdominal crunches. As mentioned above, you need to have sufficiently little fat for it to show. I got lucky in that I'm pretty skinny anyway, so exercises tend to work and I got one pretty easy (and as an unexpected byproduct of exercise). I recommend you just keep trying like you are, and if it doesn't work, combine it with another form of exercise which is more efficient at burning away fat (for example, running). As for altering it, or making it harder, the best way is to have weight added as suggested above. Remember though that the key point is reducing the fat levels around your stomach area sufficiently for a six-pack to show as it's pretty easy for fat to cover up the strongest of muscles. Regards, --—Cyclonenim | Chat 19:34, 12 July 2009 (UTC)

[edit] Video... thing to I.D

Not for the squeamish. Link. Online guesses include slime mould and tubifex worms. Neither seems quite right. To me, there's something wrong with the supposed scale in the vid; given the size of the supposed tunnel, you'd have to guess the large one here is about a foot high or thereabouts, but the water doesn't look right to me. Water doesn't miniaturize properly and the way this water behaves makes me think there's some trickery involved, like the tunnel is more like six inches high instead of six feet. Gross, anyway. Matt Deres (talk) 16:28, 12 July 2009 (UTC)

I agree it's probably a 6" sewer - with one of those remote cameras 'they' have (ie they = CIA hopefully.. help) 83.100.250.79 (talk) 17:19, 12 July 2009 (UTC)

Apparently 6"CP = 6 inch clay pipe. (or concrete or cement )

also see http://www.cassiopaea.org/forum/index.php?action=printpage;topic=12820.0 83.100.250.79 (talk) 17:28, 12 July 2009 (UTC)

or http://www.news14.com/content/local_news/triangle/611427/raleigh--sewer-creature--surprises-city-officials/Default.aspx 83.100.250.79 (talk) 17:31, 12 July 2009 (UTC)

http://www.villageoffruitport.com/bryozoan.htm 83.100.250.79 (talk) 17:34, 12 July 2009 (UTC)

Actually, it looks very much like a slime mold. I would be surprised if it were not one. There are hundreds of varieties of slime mould. This one seems likely to be a Dictyostelid or something similar. --Jayron32.talk.say no to drama 17:50, 12 July 2009 (UTC)

I'm not disagreeing - but the thing is red - can a slime mold be red? also the things move quickly and appear to be 1" long - I wonder if there's a mixture of different things in there? 83.100.250.79 (talk) 21:09, 12 July 2009 (UTC)

See also this discussion from a few days ago. 62.78.198.48 (talk) 18:04, 12 July 2009 (UTC)

offtopic someone should tell the Church_of_the_Flying_Spaghetti_Monster - if they didn't already know... mmh I wonder [6] 83.100.250.79 (talk) 19:07, 12 July 2009 (UTC)

Definitly a small pipe. Nowhere near 6 feet. But the...thing, appears to be sensitive to light, as it begins to squirm each time the camera (and consequently light) passess over them. It seems very much like a slime mould, but not exactly like any particular slime mould I've ever read about. Drew Smith What I've done 04:38, 18 July 2009 (UTC)

[edit] Cartanium?

Watching Top Gear, they mentioned a new Zonda car which is made of something like Cartanium or some other made up name, a combination of carbon fiber and titanium. The first mention of titanium and carbon makes me think of titanium carbide, which if my memory serves me correctly, is brittle and thus a big reason we don't extract titanium through the blast furnace. Anyone heard about this cartanium or similar name, and why it's so different to titanium carbide? Regards, --—Cyclonenim | Chat 19:26, 12 July 2009 (UTC)

titanium carbide could like any other brittle material be made in to fibes eg glass fibres, basalt fibres

Cartanium i suspect is a joke - ie car-tanium eg indestruc-tanium [7] , category:fictional materials etc.83.100.250.79 (talk) 19:38, 12 July 2009 (UTC)

Just a mention at Pagani Zonda#Zonda Cinque. I haven't found any clear description on the Web, but that's not surprising; I suppose Pagani wants to keep the details secret. Deor (talk) 20:01, 12 July 2009 (UTC)

I've no idea what exactly they do, though I wouldn't be suprised if it were something like this [8], though it could equally as likely be something else involving titanium and carbon... (I'd imagine that the price of a relatively new material would be just as effective as preventing copying as secrecy - I doubt they were trying to cut costs on the design :) 83.100.250.79 (talk) 20:52, 12 July 2009 (UTC)

If it is TiC coated then the aim is to protect the fibre, - it seems that other strong metals are not as good see [9] 83.100.250.79 (talk) 20:57, 12 July 2009 (UTC)

It would be easier to guess if it was known what part of the car was being made - other options exist - such as titanium metal with carbon, or titanium carbide fibre reinforcement, and carbon fibre with titanium carbide inside it eg [10] mentions brake discs. 83.100.250.79 (talk) 21:03, 12 July 2009 (UTC)

If anyone is curious, the actual term used was "carbotanium". --Mark PEA (talk) 11:46, 13 July 2009 (UTC)

Ahh that's the one, thanks! Regards, --—Cyclonenim | Chat 14:34, 13 July 2009 (UTC)

[edit] Primate Relatedness

I know that the apes are the closest relatives to humans, with the Chimpanzee/Bonobo being the closest to humans out of the apes. I also know that Old World Monkeys are then the next closest in relatedness to humans after the apes, but which living species of Old World Monkey is closest in relatedness to apes, and thus humans? Hot floppy bread (talk) 21:00, 12 July 2009 (UTC)

Remember that the evolutionary tree spreads (sideways), and is not purely linear - so that the old world monkey closest to apes is not necessarily the closest to humans. (Though it probably will be having said all that)83.100.250.79 (talk) 21:07, 12 July 2009 (UTC)

Indeed that is something I should have taken into consideration. If there are two different species for ape/humans I suppose I'd be interested in what both of them are. I was thinking it may possibly be a species of Macaque seeing as some of them have not much of a tail, although I suppose that it is far more likely a result of paralell evolution between the macaques and apes rather than a direct linear evolution from macaque to ape.

It seems that the prevailing opinion is that the old world monkeys are a monophyletic group, that is, they all derive from a single common ancestor species. This would mean that they are all equidistant from humans in evolutionary terms. Looie496 (talk) 21:39, 12 July 2009 (UTC)

Interesting, thanks. So that obviously explains the relatedness in evolutionary terms, but presumably the genetic relatedness to humans would differ within the old world monkeys, considering the wealth of diversity found within the family? If this is the case, which species would genetically be the closest (if this is even known at all)? Hot floppy bread (talk) 21:53, 12 July 2009 (UTC)

Even if the genes of all were known I think you would be looking at different species sharing and lacking matching dna (with humans) to varying extents (not necessarily the same sets of genes) - possibly with no clear winner. eg which of "1235" and "1245" is closest to "12345". Maybe it would be best to ask in terms of characteristics. 83.100.250.79 (talk) 22:05, 12 July 2009 (UTC)

Looking at characteristics leads to endless disputes with no principle way of resolving them. If you look at genes, and if you buy into the prevailing dogma that average rates of genetic change are constant over time, then the Law of large numbers applies: with thousands of genes to take into account, the differences between various species of monkeys and humans should all be the same to within a few percent. Looie496 (talk) 00:22, 13 July 2009 (UTC)

"The prevailing dogma that average rates of genetic change are constant over time" is neither a dogma, nor an assumption, nor true. It seems to be approximately true for certain types of non-coding DNA among closely related animals with similar generation lengths. --Stephan Schulz (talk) 12:05, 13 July 2009 (UTC)

[edit] Gametogenesis in Hermaphrodites (earthworms)

I understand earthworms, nematodes, and several other species reproduce sexually with both sperm and egg production. Since they are hermaphrodites, and they perform both oogenesis and spermatogenesis, I wonder how they split their chromosomes during meiosis. Do they have an X and a Y, or do they have some type of sex determining chromosome?

And how exactly do they form sperm and egg? I know during meiosis in humans, it is supposed to be only sperm or only egg, and the determining chromosome, the Y in males, is what leads to the formation of male sex organs. Do earthworms have specific karyotypes for male or female? XX or XY?

And how are male earthworms made? (A small percentage apparently have only male sex organs).

I ask this because I have learned about the XX and XY chromosomes, but I can't understand the concept of meiosis in hermaphrodites.

Any biologists please help.

--Screwball23 talk 22:11, 12 July 2009 (UTC)

The Sex-determination system article is a good place to start. It addresses some of your questions directly, and provides links for further reading. --Dr Dima (talk) 23:08, 12 July 2009 (UTC)

[edit] July 13

[edit] Tornado Hypothesis

Hi all,

I would like to open a discussion about a thunderstorm and tornado hypothesis I have developed. Where in Wiki would be the best place to present the theory and data I have compiled as it is to long to be placed here? Thanks

Original research doesn't belong anywhere on Wikipedia. There are lots of places where you can start a blog; that's what you need. Looie496 (talk) 05:53, 13 July 2009 (UTC)

Yeah, see Wikipedia's no original research policy. Blogger is one very popular place to start a blog. It’s what my girlfriend uses for her dog agility blog. The blog article would be a good place to start to find other possible places to host a blog. Red Act (talk) 06:20, 13 July 2009 (UTC)

http://weather.wikia.com might be suitable (I don't know their policies, you'd have to ask there), or you could search for a meteorology discussion board. AlmostReadytoFly (talk) 08:55, 13 July 2009 (UTC)

I'm thinking that [11] looks like an OK forum and on [12] there's even a discussion on tornadoes. These are good places to discuss your hypothesis. As other stated, wikipedia would have been the wrong place :-) EverGreg (talk) 09:30, 13 July 2009 (UTC)

Once your hypothesis is published in reputable, peer-reviewed journals (Nature (Journal) or The Journal of the American Meteorological Society - for example) - and has perhaps been received favorably at some prestigious meteorological conferences - then Wikipedia should probably have an article about it. But until then, it's just some idea some guy had...and if we had articles about every idea any random person had - we wouldn't be an encyclopedia anymore! Our job is to collect facts - and your hypothesis isn't yet a fact - other than "It is a fact that you thought about it"...and that's not a particularly notable fact. Good luck with turning your hypothesis into a theory!

Remember: A good hypothesis explains phenomena for which we currently have no good explanation - and it makes predictions that can be tested experimentally. SteveBaker (talk) 11:42, 13 July 2009 (UTC)

[edit] INMARSAT segment

Does anyone know what are network coordination stations (NCS)and Network operations center(NOC)in the ground segment of INMARSAT satellite system? or any other info about segments of INMARSAT..ThanksShraktu (talk) 11:58, 13 July 2009 (UTC)

[edit] What do mango pleco's eat?

What do mango pleco's eat?Mangopleco (talk) 14:23, 13 July 2009 (UTC)

This site says it's an aufwuchs eater: "Feeding off the bottom of the aquarium, it gets most of its nutrition from left over food and algae. If there is no algae or left over food present, supplement with high quality flake food, sinking carnivore pellets, freeze-dried bloodworms, and tubifex". --Sean 15:54, 13 July 2009 (UTC)

Possibly avoid too much meat and give veg. —Preceding unsigned comment added by 83.100.250.79 (talk) 16:32, 13 July 2009 (UTC)

Baryancistrus by the way - possibly L47

Wood - ie Bogwood or driftwood is a very good idea - for juveniles it can be essential - not only does the wood provide roughage - but aufwuchs can grow and colonise the driftwood far better than glass/other things in the aquarium.

They might like soft leaved plants like cabomba (they will totally eat it if they do)

Also in the aquarium catfish wafers (ie plec wafers are good)

Also any vegetable - cucumber, spinach etc.

Also algae.

[13]

or just search for "mango plec feeding"83.100.250.79 (talk) 16:31, 13 July 2009 (UTC)

Was this a question about a pet fish? What they eat in the wild is different.83.100.250.79 (talk) 17:44, 13 July 2009 (UTC)

As above, almost all plecs eat aufwuchs (also see periphyton which is pretty much the same thing)

http://www.scielo.br/scielo.php?pid=S1679-62252005000400011&script=sci_arttext Here someone cut open a dead baryancistrus (not the same species) and found - guess what - aufwuchs.

Also see this http://www.planetcatfish.com/shanesworld/shanesworld.php?article_id=382 - it's about plecs in general - some dead ones that people are going to eat (if you are very squeemish) - there are some interesting images

Image 11 - Aufwuchs - if you are wondering what aufwuchs are - they are the tiny things that live on slimy rocks that you find in a river - image 11 is of slimy rocks - they eat the slime, the things that live in the slime, and the green algae that is part of the slime.

In fact they are alot like sheep or cows - that eat grass - constantly grazing (obviously they are smaller)

Last image - very long stomach.

Also in the wild they will eat dead stuff - eg dead fish, or dead animals that have fallen in the water - ie carrion. But most of the time they just graze - they're not fussy eaters.83.100.250.79 (talk) 17:58, 13 July 2009 (UTC)

Note that aufuchs/periphyton contains a lot of small insects and larvae - so there is 'meat' in it - a bit like meat and vegetable stew.83.100.250.79 (talk) 18:00, 13 July 2009 (UTC)

[edit] Alcohol and Exertion

Not medical advise. I get exceptionally winded when working out hard for more than 20 minutes. After that, it feels like I can't go on and my lungs are gonna burst. However, one day I went to a bar before hand and had a vodka shot with a friend. 15 minutes later, I went to work out and for some odd reason, I was able to work out beyond 20 minutes and not feel like my lungs were gonna burst. I was sweating, my heartright was up and I did the same exact thing I did everytime I went to the gym. So to test this again, I repeated this the next week. Monday, no vodka shot, same situation, winded after 20 mins. Tuesday, one vodka shot, was not winded. What medically could be happening? I am not looking for medical advise. I am asking those medically inclined how the alcohol could somehow affect the lungs in such a way that it allows for more oxygen, I dunno. --Reticuli88 (talk) 15:17, 13 July 2009 (UTC)

(Wild speculation) could it be that the alcohol relaxes your muscles a little? I'm just guessing, but without my inhaler any amount of sport is liable to make me gasping for a deep breath, yet with my inhaler (a wonder of modern medicine I might add) I can compete with almost all my friends in terms of longevity of energy. Perhaps the alcohol is having a similar impact as my inhaler does (which I think is that it relaxes the ventricles/something in my lungs to make breathing easier). ny156uk (talk) 15:43, 13 July 2009 (UTC)

Alcohol is known to dilate blood vessels (see here and here), increasing blood flow. I'm unaware of any information on the effects of alcohol on the lungs. Disclaimers notwithstanding, you should direct any serious inquiries to a medical professional. — Lomn 15:52, 13 July 2009 (UTC)

Use of performance-enhancing drugs in the Olympic Games, Doping at the Tour de France, and List of doping cases in sport all list alcohol as a performance-enhancing drug (mostly from the lower-tech past). --Sean 16:04, 13 July 2009 (UTC)

While you might be correct, there may be some bias built into your experiment. The scientific controls would seem to be lacking, the exact amount of time you spend lifting vs resting, the quality of how you do the exercises, other things you've done that day, what classifies as "winded" and so on. Just the belief you have formed that alcohol has improved your performance may affect your results. Perhaps while you're trying things, however, you might have a go with caffeine - I've heard it's one of the most effective legal performance enhancing drugs and that many competitive athletes use it before events (I read specifically on runners). TastyCakes (talk) 16:33, 13 July 2009 (UTC)

I agree with this. Scientific studies say that alcohol reduces the ability of muscle cells to use glycogen, their primary fuel. Since alcohol also impairs judgement, it is likely that you're not really working as hard after the drink as without it. I have to say that for me personally, the sedative effect of alcohol is so strong that I would never think of taking a shot before working out, it would make me too lethargic. Looie496 (talk) 17:05, 13 July 2009 (UTC)

[edit] Einstein equations for scalar field plus gravitation

My question is: Is it true that static solutions to the Einstein equations for a real scalar field coupled to gravity always have a singularity? I found this statement in several research papers, but without any reference to a paper or book where this is proved (I know that there exist some explicit examples of such solutions with singularities, but I am interested in a more general statement).XYZsquared (talk) 16:19, 13 July 2009 (UTC)

[edit] Amount of life on Earth

Is this quantity fairly constant? I guess you can interpret this question in terms of the number of living cells. Whenever any living organism dies it provides food and nutrients to some other organism which then can reproduce. So, barring a global catastrophe, is the amount of life on Earth constant? —Preceding unsigned comment added by 75.52.253.33 (talk) 16:47, 13 July 2009 (UTC)

Probably not. Atmospheric carbon dioxide and oxygen levels have varied quite substantially for the last billion years, and amount of sunlight available for photosynthesis was not exactly constant, either. Besides, different species comprised the bulk of the biomass at different times. So I do not see any solid basis for your hypothesis. Sorry. --Dr Dima (talk) 17:05, 13 July 2009 (UTC)

I'm not aware of any rigorous data on this, but I would say it's surely not constant across all time scales. On a yearly time scale, the amount of land life is quite a bit higher during the northern hemisphere summer than during the northern hemisphere winter. On geological time scales, the total amount of life seems very likely to decrease during heavily glaciated periods, and also following catastrophes that lead to mass extinctions. Looie496 (talk) 17:11, 13 July 2009 (UTC)

Organic matter doesn't always get consumed by another organism. It sometimes gets turned into oil, for example. Limestone contains large amounts of animal produced calcite. There are various other examples of ways organisms get removed from the cycle. --Tango (talk) 17:40, 13 July 2009 (UTC)

The number of living cells on Earth may be constant over a decade, a century or a millennium. That is possible. I don't think there is any reason to believe that the number of living cells in one decade in time is likely to be any different from the number of cells alive in an adjoining decade. The questioner should specify what time frame is intended to be considered. Bus stop (talk) 17:53, 13 July 2009 (UTC)

[edit] white paint to fight golabal warming plan?

I read on CNN today the the US secretary of Energy wants to fight global warming by painting roads and the roofs of buildings white. My question is, will the amount of global warming fighting from the reflected sunlight be more then the penalty of producing millions of gallons of white paint? Googlemeister (talk) 18:25, 13 July 2009 (UTC)

I'm not going to calculate this. Where is that sunlight going to be reflected to? the heat will just be hanging around 4 feet above the roadways instead of 4 inches above. Overall I can't see it making any difference. The making of the paint and the labour to apply it would involve substantial costs, not to mention additional accidents from driving on glary and slippery roads. A white roof may reduce INTERNAL temperatures slightly in a building (but not as much as good insulation would). But the air above the roof is much hotter than over a dark roof which absorbs more heat (tho' this will radiate back more heat once the sun is off it). This is fine for keeping the interior of a building cool. Otherwise, this type of scheme just rearranges the deck chairs by a few feet; it won't reduce the total heat in the atmosphere....which is where global warming is happening, not under our wheels. - KoolerStill (talk) 19:01, 13 July 2009 (UTC)

Not quite true. White reflects a lot in the optical wavelengths. The atmosphere is quite transparent in the optical - that's how most of the heat came down from the sun in the first place. So a lot of the reflected light goes back into space. On a global scale this is a very small contribution. However, it reduces heat in cities and buildings, and hence reduces the need for air conditioning - which a) uses energy and hence (with the currently prevalent technology) causes CO2 production and b) adds to the urban heat island effect (there ain't no free lunch from the second law of thermodynamics...), causing cities to heat up, requiring more air conditioning... I don't know how quickly this pays of, but (some) roofs need regular painting anyways, so painting them in a highly reflective color the next time seems like a no-brainer. --Stephan Schulz (talk) 19:12, 13 July 2009 (UTC)

Painting roads a reflective white sounds like a horrible idea for a sunny day. Not to mention it would make it difficult to stay on them or anticipate curves when they are covered in snow. Livewireo (talk) 20:52, 13 July 2009 (UTC)

It sounds like another bullshit solution for a real problem; instead of addressing the problem head on, lets propose an ultimately worthless and probably even harmful solution (see Ethanol fuel, especially Corn ethanol ). The better solution is to instead work on accelerating non-combustion technologies (like solar and wind) or to get the hydrogen economy up and running. The problem with those solutions is not that they are substantially harder to implement, its that there are monied interests on maintaining the old infrastructure, or in coming up with solutions like ethanol fuel which was merely an excuse to make Archer Daniels Midland a shitload of cash. These are all distractions from the real solutions, and the sooner we get on implementing the final solutions, the better we all will be. --Jayron32.talk.say no to drama 21:17, 13 July 2009 (UTC)

Not to mention an irresistible canvas for graffiti artists. Clarityfiend (talk) 22:07, 13 July 2009 (UTC)

Does anyone know whether their "back of the napkin" calculations included the green-house gases emitted in producing that much paint? Also what type of paint were they talking? Whitewash won't stay put, so they'd have to consider something polymer like. They'd have to apply a pretty thick layer because otherwise it's just going to rub off in a hurry. With a thick layer your road will get as slippery as ice or you'll have to add grit. (OR around the corner from where I used to live in Germany a company managed to coat a bike-path in bright red polymer. They had to redo it after the first couple of cyclist's accidents.) Adding grit in turn will erode the rubber of tires like shoe-marks on no-wax floor, again leading to dark tracks. Unless they come up with a formula for white asphalt this sounds like a half-baked idea. Passing a law to have homeowners use white shingles when redoing their roof won't look pretty, will take a while to take effect (average roof life=10-15 years) but is doable. 71.236.26.74 (talk) 22:16, 13 July 2009 (UTC)

Putting the paint on roofs is not a silly idea - there are paints that aren't too harmful to the atmosphere - and it really doesn't matter if the stuff cracks and breaks up because 90% of the surface will probably still be reflective decades later. However, this isn't the thing that's going to save the planet - if it made a 1% improvement - I'd be very surprised indeed. Picking lighter materials for the roof makes more sense - pale grey roof-tile rather than dark brown or black. Waterproofed concrete roofs rather than tar-covered roofs - light-colored stone chips embedded in tar roofs where they can be retro-fitted. Rooftop gardens are probably a yet better idea. But there are two effects going on here. One is that the total albedo of the planet is improved - but that's likely to be a tiny effect. The other is that the interior of the building will be kept cooler - which in hot climates has the potential to dramatically reduce the amount of air-conditioning required. I think that's actually the main reason for doing it - and you don't have to go so far as to have a totally white painted roof to do that. Simply choosing lighter colored materials gets you most of the benefits. Painting roads does seems like a bad idea - but building concrete roads instead of tarmac is probably a reasonable alternative. The only snag is that concrete production uses a hell of a lot of energy and produces a TON of CO2. Of course when we finally realise that we have to stop oil production, there won't be any tarmac around anyway - it's basically just a waste-product of oil refining...so no more oil refining means no more tar. Currently, concrete is the only alternative...which is not so great. SteveBaker (talk) 23:06, 13 July 2009 (UTC)

Our so-called ecological footprint is largely a result of the technology we use and the energyconsumption - a person can do about 100 W of work, yet your average person's energy consumption is around 3000 W (on average, not just working hours). That's our real impact. However, our literal footprint (the amount of surface we occupy on the planet) is not all that great. And most of that is agricultural land. The actual built-up area is just a fraction of the Earth's surface. I can't find any figures, but let's assume that's on average 20 m² per person (eg 200 m² for someone living in a 10 storey building). Let's take a world population of 5 billion. That makes for a total of 100 billion m², which is 100.000 km². Earth's surface is 500 million km². So our houses occupy about 0.2 % of Earth's surface. That's a tiny amount, and even that would require a major effort. There are much better ways to invest our time and money, to put it extremely mildly.

Also, not all roofs are fit for this. In Europe, most roofs have tiles. Not that that would not be doable, but it would be butt-ugly. Especially since white buildings have a tendency not to stay white, so you'd have to do a lot of cleaning. And, as anon points out, this is especially true for roads, where you get the extra disadvantage of drivers being blinded by the light, increasing the already catastrophic deathtoll on roads (about 30 million dead and counting).

Now I don't mind if people think of alternative solutions - that's a good thing. The problem is that silly solutions like these, that can be debunked with a bit of secondary school knowledge, draw attention away from the real solutions like the development of solar cells, because it reduces them to 'just another one of the solutions'. If some politician without a clue has a silly plan that's good. At least he's thinking. What's bad is that he doesn't consult (or ignores) people who do have the brains to implement secondary school knowledge. That a news agency reports this idea makes perfect sense. But they also should have someone with some intelligence on their staff who can at the least ask the right questions, thus effectively debunking the idea.

Now I hope I haven't made any mistakes in my reasoning or calculation, because else I'll get this little rant flying back in my face. :)

Btw, Jayron is right about biofuels. Solar cells are at present already 10 times more efficient than plants can ever be (20% vs 2%). And you can put them wherever you like - on rooftops or in deserts, where they don't compete with food-production. And you don't have to harvest of process anything (which costs energy) - just install them and sit back (well, almost, but certainly in comparison). That said, it might make sense to use the parts of food-crops that are not the food-bit. That won't have a very high energy content, but if you already produce this 'waste', you might as well throw it in the oven of an power plant. The gain may be small, but the same goes for the required effort if you just use what you already have more efficiently. At least, that's just a thought of mine - please debunk where needed. DirkvdM (talk) 11:22, 14 July 2009 (UTC)

Have you ever considered that solutions being offered by a Nobel Laurette and the US government might not actually be debunked by secondary school knowledge? Either because you don't really understand the proposal, or because the implications are different than you imagine? Dragons flight (talk) 11:47, 14 July 2009 (UTC)

A Nobel Laurette perhaps, but you appear to have far more faith in the US government in scientific areas then I do. After all, the lawyers are the ones who are in charge, not the scientists, and the job of a senator is 1 part helping the country and 6 parts looking good to the voters. Googlemeister (talk) 19:08, 14 July 2009 (UTC)

The problem is that DirkvdM is only seeing one side of the benefits here. Whilst he's 100% correct that the amount of light we'd reflect back out into space would be negligable - he's neglecting the important part. A dark-roofed building is going to be hotter inside than a light-roofed one. If it's a LOT hotter - and in a place with a warm climate - that means that you're going to need airconditioning...and the amount of energy consumed by air conditioners is FAR from negligable! Worse still, the airconditioner puts out yet more heat into the outside environment - causing something of a feedback effect. Painting the roof white cuts out a significant chunk of heat - which saves on the airconditioning - which cuts yet out more heat and CO2. So the simplistic 'percentage of the earth's surface' calculation - while true and interesting - doesn't explain why the US government thinks it's a good idea. The true calculation would have to estimate the amount of additional energy expended by airconditioners in black-roofed buildings - and compare that to the total energy consumption of humanity. As I said - I doubt it's as much as 1% - but since it's a fairly cheap fix (and every little helps), new buildings really OUGHT to have lighter colored roofs (not bright white paint...but maybe lighter tiles and white gravel pressed into black tarmac roofs) - and I'd like to see the government moving towards mandating that by law. SteveBaker (talk) 20:35, 14 July 2009 (UTC)

You don't need to mandate any particular building material. Just tax energy enough while subsidizing remedies. Dirk, you seem to believe in the silver bullet. I don't. It will be extremely hard to find one technique that will cut carbon emissions by 50%. But we only need to find 50 that each reduce it by 1% (of the original, otherwise around 70, says the mathematician in me) to have the same gain. --Stephan Schulz (talk) 21:13, 14 July 2009 (UTC)

[edit] Optical Contact Bonding

What is optical contact bonding? How does it work? --72.197.202.36 (talk) 20:07, 13 July 2009 (UTC)

Google it, the google books results are particularily useful if you are looking for an explanation.

We do seem to lack an article, if no-one voluteers, of finds one, I might write it.83.100.250.79 (talk) 20:28, 13 July 2009 (UTC)

Optical contact bonding —Preceding unsigned comment added by HappyUR (talk • contribs) 20:44, 13 July 2009 (UTC)

ok stub article exists - Haven't got much time so it's not very good.

Please categorise, expand, and correct. Thanks.HappyUR (talk) 21:20, 13 July 2009 (UTC)

Thanks! --72.197.202.36 (talk) 04:52, 14 July 2009 (UTC)

[edit] amateur astronomy questions.

Lets say I buy a 8 inch telescope....

1) Are the images of moon, planets and nebulae impressive?

2) Is imaging the sun impressive?

3) Are we talking laptops and software for best effects?

I suppose the most important question....

4) Even if I get a good telescope and laptop [and a few years of observations] are we really still talking about "fuzzy dots" rather than good solid images? —Preceding unsigned comment added by 89.242.135.49 (talk) 22:21, 13 July 2009 (UTC)

I hope you realize that looking at the sun requires a special sun filter - otherwise, you could blind yourself.--SPhilbrick T 22:25, 13 July 2009 (UTC)

1) yes

2) Sure

3) why not?

4) you can get best images in the world, selling them for $$$$$ and giving names to new comets in case you got good telescope and patience to do the observations. Vitall (talk) 22:40, 13 July 2009 (UTC)

yes...ANY sun imaging would be done with a laptop..NO DIRECT OBSERVATION ... —Preceding unsigned comment added by 89.242.135.49 (talk) 22:34, 13 July 2009 (UTC)

WARNING!!! EXTREME DANGER!!! Do not EVER look at the sun through your telescope. You will quite literally burn out your retina before your eyelid has time to close. There are ways to use a telescope to project an image of the sun - but even then, you have to be really careful because you are not only concentrating the light - but also the heat. If you accidentally leave your telescope with the main lens cap off - and it happens to be pointing to a place where the sun will be in a few hours time - you could come home to a burned out house! You have to be super-careful when using a telescope in daylight.

That said:

The moon looks very impressive - it seems somehow more "real" than the naked eye view. Planets - less so. You'll be able to see the rings of Saturn - but it's not going to be a huge, sharp image. Most of the other planets are relatively featureless. Nebulae are soft smudges...this isn't the Hubble we're dealing with!
The sun...well, WARNING!!! EXTREME DANGER!!!...remember?! Let's not go there! You can safely get a good image of the sun with a home-made pinhole camera (a sheet of cardboard with a pinhole in it taped across a window works well) to produce a magnification of say 2x to maybe 8x in a darkened room. That lets you see prominances and sunspots - it costs $1 to make and it's SAFE. So just forget all about using an actual telescope to observe the sun...bad, bad, BAD idea! There are ways to do it - but you have to be really careful and do it exactly right...not the sort of thing I'd advise an amateur to attempt when the pinhole camera approach works so amazingly well.
The single greatest thing about computer-driven telescopes (those with TWO axis motorized mounts) is that when they are properly set up - you can tell the thing "Find me Jupiter" and it'll obediently take you there. That's a lot easier than messing around with star charts and ephemerus to find the darned thing - and as a beginner, one fuzzy off-white blob looks much like another - if you're trying to get the thing focussed in on Jupiter and you're actually pointing at a star five degrees away...you're in for a frustrating experience. The other thing a motorized mount does for you is to automatically counteract the slow rotation of the earth - which can be really annoying when you're trying to set things up because the star or planet you're looking at keeps moving! The computer can fix that for you - which is especially nice if you want to take long-exposure photographs.
A lot of what you see will indeed be dots...or (in the case of most of the planets) slightly enlarged dots. The moon and Saturn are very cool - but if that's all you're going to use it for, you're better off borrowing one for a few nights. When there is a comet just below naked eye visibility, the telescope will bring it into amazing clarity...probably the best thing I ever saw in my 8" reflector was comets. You can also pick up things like the space station...but without a fairly fast computerized mount, it's hard to keep it in view!

One other HUGE thing to think about is how good the "seeing" is where you live. If there is a significant city anywhere within the range of the horizon - or a small town somewhere within a mile or two - or even a street lamp 100 yards from the end of your back yard - then you may have a hard time seeing ANYTHING other than the moon and the brighter comets clearly. This cannot be over-emphasised. If you don't have REALLY dark nights - forget it - don't buy a telescope. I have an 8" reflector - which isn't a great telescope - but it was good enough when I lived out in the wilds of nowhere with a gigantic hill between me and the nearest main road. When we moved to the USA and bought a house just 20 miles from Dallas - there was simply nothing in the sky worth seeing other than the moon. Everywhere else, you just see a dim glow of the city lights reflecting off of the sky...no astronomy is possible under those circumstances.

Another consideration is the weather. You obviously need a lot of clear-sky nights (People from Seattle need not apply!) - but remember that you can't do astronomy indoors. You'll be outside - late at night - for hours (potentially). In cold climates - this is no fun! Serious amateur astronomers soon realise that they need a mini-dome system so they can be at least sheltered from the worst of the weather.

SteveBaker (talk) 22:47, 13 July 2009 (UTC)

Uh, Steve? There are safe full-aperture solar filters for telescopes that are made from materials that block enough of the Sun's light to make it safe for direct observing. That being said, an 8" telescope, even with a filter, might deliver an image bright enough to hurt while looking at it. Large-aperture telescopes are generally not good for observing the moon, either, one reason being that the light will be very bright, and another is that the magnification required to resonably work with such an aperture might make the moon appear too large. How much an 8" telescope costs depends on the type: expect to pay roughly $450 US for a Dobsonian of that size, $1300 for a Newtonian reflector, and $2500 for a Schmidt-Cassegrain. That's without any special equipment such as CCD cameras and the like. An 8" telescope may also be good for imaging deep sky objects. ~A H 1^(TCU) 00:27, 14 July 2009 (UTC)

Yes, it IS possible to observe the sun - with care - with the RIGHT equipment and knowledge (and I said that) - but it's really dangerous - and we really shouldn't be recommending it...especially when a pinhole camera and a darkened room works every bit as well. I've heard of people who assumed that the "moon filter" that comes with many larger aperture scopes was a "sun filter" - and lost an eye in the process. On an 8" telescope - even the moon is bright enough to hurt your eyes (that's why most scopes come with a "moon filter"). Most scopes that come with a sun filter are much less than 8" aperture. Remember - the sun filter that works for a cheap 4" scope is letting through four times too much light if mounted on an 8" scope! This is totally not a thing for a novice telescope user to be messing with...losing an eye is just FAR too serious. SteveBaker (talk) 01:30, 14 July 2009 (UTC)

Extra warning: I had a telescope that came with a filter for solar observation at the ocular end (eyepiece). Someone at my astronomy club told me that that is also dangerous because, as Steven pointed out, you are not only concentrating the light, but also the heat. That heat still reaches the ocular, which may burst, as a result of which splinters may come off. If you've got your eye at the ocular, those splinters may end up in your eye. Sun#Observation_and_eye_damage also mentions this. The way to obsserve the Sun is by projection, as Steven mentioned. I believe that's how Galilei also did it - he held a piece of paper behind the telescope, on which he then copied the image. A modern alternative to Galilei's method is to mount a digital camera behind the telescope, connect that to a computer and view the image on your computer screen. And of course take photos. I'm not sure if this will work with a standard camera, but there are setups for this. Of course you still need a filter to avoid damaging the ocular or the camera's ccd (its retina, so to say). But even if that goes wrong, you'll still have your eyesight intact.

To get an idea of how beautiful the images are, you might contact an astronomy club to meet up with them on an observation night. They'll probably let you have a look through their equipment. And then you'll be able to compare and decide what kind of equipment you like best.

Btw, the most beautiful thing I ever saw was the Moon - with the naked eye. That was a few days after new moon, just after sunset, with just a narrow strip lit up by the Sun (waxing crescent). The rest of the Moon was quite visible, and suddenly I saw the Moon for what it is - a huge rock at a huge distance. Until then, I knew that, but that was the first time I saw it. Then it sunk in that that strip of light was a mere reflection of the Sun, which gave me a feel for the immense amount of light it emits. And that's just our little corner of our galaxy, which is just one of billions of galaxies. I never felt so tiny. Mind you, this was not so much what I actually saw, but the realisation of what it was that I saw. The same holds true for the zoomed in versions of whatever you see in the sky with your telescope. For example, Hubble images can be very beautiful in an abstract sense, but when you realise what they really are, they're mindboggling. A lot of beauty comes from knowing what it is that you're seeing. DirkvdM (talk) 09:11, 14 July 2009 (UTC)

The first time I had the opportunity to look at Jupiter through a relatively small refractor (perhaps 3 inches) it was literally breathtaking to see the moons of that planet standing out in clear detail. Years later, with my own similar telescope, and some care, it was possible to see the weather bands around Jupiter as well as its moons, and to see the rings of Saturn. A larger telescope such as the OP discusses, especially with a computer controlled drive, would make it much easier to find and observe planets. A CCD camera should make it possible to create some amazing photos. Edison (talk) 14:23, 14 July 2009 (UTC)

[edit] A spring in space

If you had a setup so a ball was put onto a spring and tied back with some force to compress the spring (as in space the ball would be weightless, no?), and then the ball was released would it oscillate forever? What would cause damped motion--no air in space, no friction due to it oscillating up and down without touching anything.

xxx(ball) (compressed)

xxxxxxxx(ball)

xxxxxx (ball)|[plate|

2) If the setup involved placing a plate a distance x from the compressed spring so that x was less then the amplitude of the springs oscillation would it strike the plate and come back (3rd law force of plate on ball), compress the spring and then repeat infintly? I think energy would be transferred to the plate though no?

3) Finally what happens if the plate in question to is replaced with a piezoelectric crystal. Could that serve as a battery? (obviously this is just a hypothetical question)

24.171.145.63 (talk) 23:16, 13 July 2009 (UTC)

1. There is friction within the spring.

2. Energy would be lost when the boll bounces against the plate. It would be transferred to both in the form of heat.

3. Energy would be lost to the piezoelectric crystal in the form of electricity.

Also, tiny amounts of energy will always be lost in the form of gravitational waves, so a perpetual motion machine is totally impossible. — DanielLC 00:07, 14 July 2009 (UTC)

If we're talking about a physical spring, there will be some friction inside the spring itself, so it will lose energy over time. With an ideal spring, or eg. a gravitational field working as one, it's possible for your ball to oscillate forever, at least in an isloated system. For example, a planet orbiting a star can actually be seen as oscillating along two perpeticular axes.

Regarding 2) and 3), as you've already said, when you make the ball strike the plate you transfer the energy, so you'll at best be able to recover the energy you already put in the system by compressing the spring, most of it however would be lost heating the ball and the plate. You're right that this could be used for energy storage, but the efficiency would probably not be very impressive.

85.222.93.28 (talk) —Preceding undated comment added 00:35, 14 July 2009 (UTC).

It won't work forever. As I already said, energy will be lost in the form of gravitational waves. This will be unimaginably slow, but it will happen. 67.182.169.172 (talk) 00:17, 15 July 2009 (UTC)

[edit] Sky colors on remoter stars

So If the star is white, then what will be the color of planet's sky, if Terra-like. Would white sun make white or purple sky? I know a blue star make a golden sky, what about a blue-white star will make deep yellow or pale yellow sky. A orange star is said on one site to make turquoise sky while pink star gives green sky.--69.226.33.240 (talk) 23:47, 13 July 2009 (UTC)

I believe the Sun is white. It just looks yellow because the blue light is scattered by the sky, hence the sky looking blue. — DanielLC 00:02, 14 July 2009 (UTC)

Some stars is technically white. Like is Vega was the su, will our sky still look blue, if sun was A STAR?--69.226.33.240 (talk) 00:15, 14 July 2009 (UTC)

Our sun IS white - but when the light enters the atmosphere, the blue light is scattered (that's why the sky is blue). Because our eyes basically see only mixtures of red, green and blue light - when you subtract some blue, you have more red and green than blue. Red and green makes yellow - so from down here at the bottom of the atmosphere, the sun looks a little yellowish.

Sorry, but this is not entirely accurate: white stars are classified as A-class on the spectral scale, while the Sun is G-class (i.e. a yellow star).

76.21.37.87 (talk) 08:15, 14 July 2009 (UTC)

76.22.37.87, I don't think you see the true science world. I've been told, human eyes do a terrible perception shift. Language scientifically, ur sun looks yellow in cmputer screen, white when seen in our blue sky, who knows what you'll see in space. 76 IP, you don't see strange human shifts on earth, when you go to Mars or Moon, then all your color vision cell will go hay tangle.--69.231.5.71 (talk) 21:24, 14 July 2009 (UTC)

76 IP, the source I past past discussion is found on this.--69.231.5.71 (talk) 21:28, 14 July 2009 (UTC)

Sorry i need to fix 76 IP's answers. He just don't know enough. For a gentle reminder, is just to clarify the rules the goal of desk is the answers to be "done right". If answers is not answer right then this destroys purpose of desk. Questioners won't want to go back and try to see what the answers is wrong. Questioners usually wants answers answer right at the "first time". And also we people won't want to bite newcomers. Since 76 IP answer is too simple and to general, it's good ot just fix comments and leave it ther.--69.231.5.71 (talk) 21:42, 14 July 2009 (UTC)

Perhaps I should have put in a disclaimer that astrophysics is not my area of expertise. 76.21.37.87 (talk) 01:10, 15 July 2009 (UTC)

The color of the sky is determined by the nature of raleigh scattering - and the color it scatters depends on the size of the particles in the atmosphere - not the color of the star. So if the earth was orbiting a different star, then there are two possibilities:

If there is a reasonable amount of blue light being emitted by the star - then the sky will be blue.
If there is little or no blue light from the star - then the sky will be black and you'll be able to see stars in the daytime sky.

The star itself might look a completely different color however. SteveBaker (talk) 01:23, 14 July 2009 (UTC)

Just to clarify: You can only ever see stars in the daytime if you shield your eyes from the sun or anything lit by the sun. This applies on the hypothetical planet Steve describes in the same way it does on the Moon. --Tango (talk) 02:11, 14 July 2009 (UTC)

I think the OP is referring to white as in the spectral class: OBAFGKM. -- penubag (talk) 07:48, 14 July 2009 (UTC)

I believe the Sun is considered yellow because that is the area of the spectrum where it radiates the most intensely. However, it could easily be considered white, as it emits strongly throughout the visible spectrum. -RunningOnBrains^{(talk page)} 21:53, 14 July 2009 (UTC)

The sun actually radiates most intensely in the green which makes it "techinically" a green star. Dauto (talk) 05:03, 16 July 2009 (UTC)

Is just plot of spectrum Sun counts as yellow. When you actually go in space, you look as a totally different things. Your human eyes is very sensitive. Same situation as Mars. you won't even notice the coral color at all if you actually going to it personally. That's enough.--69.231.5.71 (talk) 22:01, 14 July 2009 (UTC)

[edit] July 14

[edit] Electonic ab belts/abdominators/whatever they're called...

(I'm sure that WP has an article on these - but I'll be damned if I can find it) So, those battery-powered ab belts that supposedly use electricity to rhythmically contract the muscles of the abdomen (or the muscles of whichever body part you've attached it to) and promote muscle growth without actually having to exercise and turn flabby guy --> ripped guy - quackery or effective way? I suspect that I already know the answer to this (I bought one on a whim years ago and it didn't really do much except make my abs twitch mildly for the couple of hours that the battery lasted - and the couple of hours that the next battery lasted). Is there any real science behind these devices? --Kurt Shaped Box (talk) 01:05, 14 July 2009 (UTC)

Is Electrical muscle stimulation what you're looking for? Intelligentsium 01:24, 14 July 2009 (UTC)

Yeah, pretty much. Thanks. Redirect created there from Ab belt... --Kurt Shaped Box (talk) 01:54, 14 July 2009 (UTC)

I think this is absolute BS, they're just trying to steal your money. You want strong abs, do lots of crunches (and it won't cost you a penny). 76.21.37.87 (talk) 01:30, 14 July 2009 (UTC)

[edit] Does anything help unjoin PVC?

I have a custom shaped PVC part for electrolysis. A part inside needs fixing, the only way I can get tools close enough is to remove the PVC pipe that is bonded to it. Does anyone know of anything that helps unbond PVC pipes. It looks like the bonding material is clear light yellow substance. I don't know if it is PVC cement or something else, but it looks bonded. My current method is to slowly cut slits into the PVC pipe and chisel it out.--155.144.40.31 (talk) 01:16, 14 July 2009 (UTC)

Just heat it up with a heatgun and stick a sharp edge into it. The glue will come off quite cleanly that way. --antilived^{T | C | G} 01:27, 14 July 2009 (UTC)

Thanks I heated it up and basically peeled it off.

The stuff I use (which is for plumbers - and is a bright purple color) melts the PVC - the glue itself hardly matters because once it's done it's stuff, the two pieces of PVC have become one piece - and nothing will get it apart. Personally - I'd look for longer/thinner tools to try to fix the problem without too much destruction...but without a lot more information, it's hard to suggest what tools might help. SteveBaker (talk) 01:42, 14 July 2009 (UTC)

The glue does matter, as it fills in the spots where the melted PVC didn't touch. Interesting fact: the primer is not inherently purple, but colored that way so that building inspectors can verify that it was used. --Sean 13:27, 14 July 2009 (UTC)

When you heat up that stiff PVC pipe with a heat gun it becomes soft and flexible like rubber. It is amazing! Graeme Bartlett (talk) 06:13, 15 July 2009 (UTC)

[edit] Possibility of a strabismus drug?

In theory, could a drug be developed that would treat the neurological aspects of strabismus with amblyopia (i.e. allow the brain to properly merge images from both eyes)? Neon Merlin 01:28, 14 July 2009 (UTC)

It seems unlikely, because problems of this sort are generally due to "miswiring" that develops over time, and any treatment requires time and experience to correct the miswiring. It seems entirely possible, though, that a drug that increases the plasticity of neural circuits could make physical therapies more effective. Looie496 (talk) 03:35, 14 July 2009 (UTC)

[edit] distance light travels per cycle

How far does light travel in one transition cycle of the magnetic phase and the electrostatic phase? -- Taxa (talk) 02:29, 14 July 2009 (UTC)

This is precisely what the wavelength is. So the answer depends on the wavelength of the light. For visible light, the answer is between about 400 and 700 nanometers. But it could be anything. Some radio waves, for example, are several meters long. —Dominus (talk) 02:51, 14 July 2009 (UTC)

The answer above must be correct, eventhough the question isn't since light doesn't have an alternation between a magnetic phase and a electrostatic phase (For one thing, the word static means "no change" so it wouldn't fit here). Both the electric and the magnetic fields oscillate simultaneously in phase (that is, they reach their maximum amplitude simultaneously). Dauto (talk) 11:50, 14 July 2009 (UTC)

[edit] Gaviotas sleeve pump

There is a kind of manual water pump, invented at the "appropriate technology" Columbian town of Gaviotas which they call a "sleeve pump" (Bomba de Camisa). Most of the descriptions of it I can find are taken from Alan Weisman's book Gaviotas, which includes a diagram. A reasonable excerpt describing it, with the diagram can be found here (although a higher resolution version of the diagram can be found at this Google Books version). Also, there is an installation manual (in Spanish, scanned into PowerPoint) here.

I have not been able to make out how the thing works. The diagram shows an outer sleeve being moved, but nothing else. No description of what air or water chamber is pressurized, exhausted, or lifted; just water magically flowing up in the right illustration. Can anyone explain what's supposedly going on? Thanks. -R. S. Shaw (talk) 02:45, 14 July 2009 (UTC)

From what I've read in the text on the preceding few pages, it appears to me that the sleeve is rigidly attached to the perforated casing it encloses, which therefore moves up and down with the sleeve in relation to the immovable piston inside the casing, thus creating the pressure that pumps the water. Looks to me like the diagram is wrong. FWIW 76.21.37.87 (talk) 08:44, 14 July 2009 (UTC)

[edit] What is this plant?

This weed grows all over Philadelphia. The leaves vary greatly in size, and sometimes span 30 cm or more. It is usually a low shrub. In the summer, it bears hard spherical fruits about 2cm in diameter. What is it?

Thanks. —Dominus (talk) 02:47, 14 July 2009 (UTC)

Looks like a fig tree to me. Probably s.th. like an Alma or Celeste. The fact that it gets too cold in winter might account for the shrub size. 71.236.26.74 (talk) 03:47, 14 July 2009 (UTC)

I don't think it's a fig. I believe what you have there is Paper Mulberry. Our article doesn't seem to picture the lobate leaf forms of the immature plants, but compare the images here (particularly the bottom one, just above the map). Deor (talk) 16:13, 14 July 2009 (UTC)

Thanks. So far, I like the paper mulberry theory much better than the fig theory. This plant does indeed have a variety of leaf forms, with only the larger leaves being lobate. I will try to open up one of the fruits and see if it looks like a fig. —Dominus (talk) 17:22, 14 July 2009 (UTC)

Now that I've done some more reading and seen some more pictures, I am sure that this is correct. Thank you very much. 17:27, 14 July 2009 (UTC)

[edit] Wellness and the Wellness Wheel

I've been thinking of starting an article on the concept of the "Wellness Wheel" as per these temporary online sources:

but I'm unsure whether it is already covered somewhere else in Wikipedia or if it should be a section in the Health article or Wellness (alternative medicine)? Is the term "wellness" used in this context a separate definition apart from alternative medicine? Is this a notable enough topic to write about? From what I know of the Wellness Wheel concept is that it's used in many drug and alcohol rehab centers as a harm reduction alternative to the 12-step program (see google books) yet I see mention of this nowhere. So I'm unsure if I should start the article going of those web refs or just update Health or Harm reduction or to include this ?new? concept. Better yet, if someone more educated in the field than I could take the lead and start me off with a short stub that would be great. -- œ ^™ 03:04, 14 July 2009 (UTC)

[edit] When is it too cold for Mosquitos?

My friend and I disagree about whether I'll cause us to have mosquito bites if I leave the window open with lights on inside tonight. Thing is it's quite chilly outside at the moment! My understanding is that under such conditions mosquitos would not be a nuissqnce. So who's right? Do mosquitos not roam on very cold nights? (even if they do yesterday and tomorrow, when it isn't really chilly)? Thanks! —Preceding unsigned comment added by 82.234.207.120 (talk) 03:44, 14 July 2009 (UTC)

minimum temp for mosquito growth is 8-10°C [14] so it needs to be that cold for the mosquitoes to stop developing. Also the insects survive the winter via hibernation or as eggs[15] so they won't bother you in the winter or anywhere where it is less than 8 C.--Lenticel ^(talk) 04:02, 14 July 2009 (UTC)

ah, but I was talking about an exceptionally cold night in otherwise mosquito plagued season... So my question is not about breeding, but whether they will bite me on a cold night (where the previous or next night is a definite yes)... —Preceding unsigned comment added by 82.234.207.120 (talk) 04:23, 14 July 2009 (UTC)

As I said earlier, you have to be at winter temperatures (subzero) for the adults to to hibernate or die after laying their eggs. --Lenticel ^(talk) 04:42, 14 July 2009 (UTC)

I've read somewhere that the temperature below which mosquito activity declines dramatically is around 13°C. ~A H 1^(TCU) 09:07, 14 July 2009 (UTC)

thanks - you actually answered my question. And it was below 13degrees. 82.234.207.120 (talk) 15:02, 14 July 2009 (UTC)

[edit] HUAUZONTLE - red or green or both ???

researching Huauzontle and trying to ascertain different varieties..

on website "seeds of change" the picture is red and on gourmet sleuth the picture is green so I sent emails to relevant websites questioning this and got following replies..

from seeds of change .. "We have a great picture of it in our catalog on page 50 and it is most definitely red. It is also called Red Aztec Spinach. Chenopodium berlandieri is the species we sell. Maybe there is another one that is not red?" ..

from Gourmet Sleuth I got " I can’t speak for what product Seedsofchange.com is referring to but huazontles are long stemmed greens with tiny flower buds (which we can confuse you further because technically the buds are fruit..) The plant grows long stalks, has serrated leaves and the stalks get tipped with seed bundles. The seed bundles are prepared and eaten like a vegetable. The only huazontles I’ve ever seen are green in color so if they are selling something red.. not sure what that would be. That being said this plant does grow in the U.S. (treated like a weed) but was eaten by Native Americans. Our reference is Diana Kennedy, well known writer and considered one of the best authorities on Mexican food and culinary culture. We have more description in our dictionary (this link is to our new site which is still under development but feel free to check out the info)http://dev1.gourmetsleuth.com/Dictionary/H/Huauzontle-6125.aspx

THEN researched Chenopodium berlandieri and found pictures at Google Image Search which show most green but a couple red however no explanation as to why red or green or if 2 different varieties ... similarly on Wikipedia .. different varieties but no red .... can you please help me ... thanx 124.179.215.251 (talk) 05:21, 14 July 2009 (UTC)

Red leaves in plants are usually caused by the [anthocyanin] content. Some varieties will naturally contain more (cf red cabbage, near-black bell peppers). —Preceding unsigned comment added by KoolerStill (talk • contribs) 10:14, 14 July 2009 (UTC)

I have no idea if this is relevant, but in my garden I have both Red Orache and Fat Hen, both members of the Chenopodium family. If you look at our article on Atriplex you will see that there are plenty of members of this family which are edible. I don't know if this is what you were looking for but it might help.--TammyMoet (talk) 18:50, 14 July 2009 (UTC)

[edit] Mercury

How do humans eliminate mercury and it's compounds? It says that fish store mercury faster than they eliminate from their bodies. How does this compare with humans? Are that "natural" chelating agents that can be found in the (human) diet?174.3.103.39 (talk) 08:40, 14 July 2009 (UTC)

As far as I'm aware, humans also store mercury in adipose tissue, and eliminate it very, very slowly (over a period of years). Even worse, there are currently no known natural chelating agents, either in the human diet or anywhere else (not even the "miraculous" Acai berry). There are some synthetic chelators available (such as British Anti-Lewisite) to help the body get rid of mercury; however, they should only be used in case of severe mercury poisoning and then only with a doctor's prescription, because they are themselves somewhat toxic (like many other strong medicines). FWIW 76.21.37.87 (talk) 09:04, 14 July 2009 (UTC)

Judging from the mercury poisoning article, there's no particular elimination of mercury by the human body :-( quoting [16]: Methylmercury is believed to cause toxicity by binding the sulfhydryl groups at the active centers of critical enzymes and structural proteins. This is just my guess but i'm thinking from this, that mercury is expelled when enzymes and protein in the body are destroyed, as they frequently are. The rate of metabolism would seem to be the crucial factor then, but this is just my layman thoughts on it. Brain cells are not renewed the same way that say skin cells are, so mercury in the brain probably stays there :-(( EverGreg (talk) 09:15, 14 July 2009 (UTC)

[edit] Lack of hunger

I seem to remember reading something about a lack of hunger, even though a person hasn't eaten for several hours, as a sign of something wrong with them. Does this ring any bells with anyone? Dismas|^(talk) 09:08, 14 July 2009 (UTC)

I'm afraid that lack of hunger is a symptom of a very wide rang of diseases, though I can't recall one that has it as its only symptom. EverGreg (talk) 09:17, 14 July 2009 (UTC)

And, of course, if there was, we wouldn't be allowed to talk about it. --Anon, 11:10 UTC, July 14, 2009.

That is completely incorrect. We can discuss medical information all we like. We cannot attempt to diagnose a person through the Reference Desk if the person claims to have a lack of hunger. -- kainaw ™ 11:21, 14 July 2009 (UTC)

The symptom of lack of hunger is called Anorexia (symptom), not to be confused with anorexia nervosa, which is the well-known eating disorder. From the anorexia (symptom) article:

Anorexia (deriving from the Greek "α(ν)-" (a(n)-, a prefix that denotes absence) + "όρεξη (orexe) = appetite) is the decreased sensation of appetite. While the term in non-scientific publications is often used interchangeably with anorexia nervosa, many possible causes exist for a decreased appetite, some of which may be harmless, while others indicate a serious clinical condition, or pose a significant risk.

So it might be something; it might be nothing, but please consult a qualified doctor if you're worried.AlmostReadytoFly (talk) 12:13, 14 July 2009 (UTC)

Hmm, thanks for the link to the symptom of anorexia. And to those who didn't get their "we don't give medical advice" jackboots on, thank you! Dismas|^(talk) 16:43, 14 July 2009 (UTC)

[edit] Jenkem

[post removed by user]

You asked this question yesterday, then removed it today, along with an answer. 87.114.25.180 (talk) 13:00, 14 July 2009 (UTC)

[post removed by user]

I didn't decline to participate in helping you, I declined to participate in an experimental test of the hypothesis. I agree that you're asking a different question now. Before you asked whether the idea could be ruled out in principle, and I said I thought not. Now you're asking whether there is evidence, and the answer is that I don't know. It would surprise me if anybody had studied this, but I don't know for sure. Snopes has a lot of information about this, and classifies it as an urban legend. Looie496 (talk) 19:45, 14 July 2009 (UTC)

I think Snopes classifies it as a legend that "Jenkem" is popular in the USA. They don't seem to have any references on whether or not it's possible. APL (talk) 18:48, 15 July 2009 (UTC)

Remove your own posts if you want, but don't touch others'. If you don't like the replies given you for free by volunteers, feel free to ask your questions elsewhere. 87.114.25.180 (talk) 21:14, 14 July 2009 (UTC)

Oh joy the "it's free so don't complain" line. Sure is an easy excuse for not trying. I've removed MY OWN posts and left everyone elses, as you suggested. Onesevensix 77 (talk) 23:06, 14 July 2009 (UTC)

Someone has tried to help you. You just don't like the answers, for whatever reason (since you haven't bothered to explain why that person who has tried isn't answering your question) Nil Einne (talk) 01:08, 15 July 2009 (UTC)

If I have to explain why the question isn't being answered there isn't much hope for getting a good answer anyway. Onesevensix 77 (talk) 04:44, 15 July 2009 (UTC)

That's funny... You think you should be entitled to "complain" about a free service and people not "trying", and you don't even have the decency to explain why you are complaining or you think people are "not trying" after waiting less then a day. I was reasonably polite before, but I don't care anymore. It seems to me Looie496 has answered both your questions quite well. You just don't like the answers, because the answers are that 1) No you can't say it's impossible or rule it out in principle because a lot of weird things can be produced under fermentation 2) It's unlikely anyone has studied whether you can get high off the fermentation products of shit, because no one gives enough of a shit about a silly hoax to waste their time on such a thing and so there's likely no definite evidence either way; and it appears to me you want to be able to say the jenkem thing is impossible but you can't. I'm sorry to have to tell you, but life is like that. There isn't always definitive evidence for something and sometimes you have to accept that, or if you really want definitive evidence, do the experiments yourself. Nil Einne (talk) 13:01, 15 July 2009 (UTC)

If the replies had bothered to explain that there was no evidence to cite then I might agree with you. As it was Looie496 reply just stated the obvious and implied I had asked him to sniff his shit. Of course I did not expect anyone to actually attempt this themselves to answer my question, I was expecting someone to just provide a few links to articles and web pages (of which do exist, despite your claims that no one gives enough of a shit to research into it). Then when I politely removed my original question and rephrased it to get better replies (note that I was entirely civil and did not even comment on Looie496s reply, I simply wanted to ask my question again in a better way) I was berated with "you've already asked this" responses and resistance to helping me. Onesevensix 77 (talk) 06:14, 16 July 2009 (UTC)

[edit] faster then the speed of light?

I understand that light will travel through a vacuum at something like 3*10^8 m/s, but are the individual photons actually traveling faster since they are not going straight, but are instead traveling as a sine wave? What is the actual speed of the particles then? Googlemeister (talk) 14:42, 14 July 2009 (UTC)

When an electromagnetic wave is depicted as a sine wave, the sine wave represents the magnitude (and possibly the orientation) of the wave's electric field. It does not represent a displacement in space of the photons or anything else. -- Coneslayer (talk) 14:57, 14 July 2009 (UTC)

boy is that the wrong answer. The real answer is that WHATEVER LIGHT DOES WHEN YOU SEE IT AS A SINE WAVE (even if it did move up and down, or in and out, or back and forth, or whatever else) is something ENTIRELY DIFFERENT FROM WHAT IT DOES WHEN YOU SEE IT AS A PARTICLE. Read wave/particle duality. You simply can't apply particle physics to the waveform of light, and vice versa. Beyond that, what a sine wave WOULD represent to a particle, is irrelevant. 82.234.207.120 (talk) 14:59, 14 July 2009 (UTC)

I've corrected a minor spelling error in the link, it should work all right now. 76.21.37.87 (talk) 01:48, 15 July 2009 (UTC)

That's not really a helpful way to think about wave-particle duality. Light doesn't behave like particles travelling in a wavy trajectory. It behaves a bit like a wave travelling in some sort of medium (which made people think there was a luminiferous ether), or a bit like particles travelling in straight lines. AlmostReadytoFly (talk) 15:08, 14 July 2009 (UTC)

It looks like we need Stephen Hawking again. Is Stephen Hawking in the house? Bus stop (talk) 15:15, 14 July 2009 (UTC)

You can imagine light to be an EM wave. The electric and magnetic field vectors are sinusoids perpendicular to each other and the direction of propogation. This wave travels at the speed of light. Or, you can imagine light to be a photon, that is, a particle, moving at the speed of light. Hence, it has properties of both waves and particles. What property it will exhibit depends on the experiment. For example, you can imagine an experiment of Diffraction. Assume the source is such that it emits a single photon. The diffraction pattern is still seen. This means light is released as a particle and diffracts as a wave. However, by the complimentarity principle, it can neber exhibit both particles simultaneously. So, its your choice how you imagine light, but it still travels at the constant speed of light. Rkr1991 (talk) 16:29, 14 July 2009 (UTC)

Obviously the light itself travels at the speed of light, there is no question on that. But the photons that make up the light are going faster or not? They have to exist, if it behaves as both right? Googlemeister (talk) 16:48, 14 July 2009 (UTC)

To make it easier to understand... You are imagining that there are little particles called photons. Your imaginary particles are travelling at whatever speed you like. Realistically, there are no particles. The thing you are calling a particle is a thing that, at times, exhibits behaviour similar to a particle. At other times, it does not. You can consider the fact that it should travel faster than light if it was actually a particle an instance of when it is not behaving like a particle if you like. -- kainaw ™ 16:54, 14 July 2009 (UTC)

From my understanding of light, it behaves either as a particle, or as a wave, only based on if it is being observed or not. Thus when it is not being observed, it is both. Thus particles would have to be able to travel faster then the speed of light. Is the logic incorrect, or is my understanding of the quantum nature of light off? Googlemeister (talk) 18:09, 14 July 2009 (UTC)

Photons travel in straight lines, not in sine curves. They travel in straight lines at exactly the velocity of light. Nothing about light travels in a sine curve. When people depict the electric and magnetic fields as being shaped like sine waves, it is a metaphor for a certain mathematical abstraction, which you are taking too literally. People also talk about alternating electric currents as being sinusoidal, but that does not mean the electricity travels through the wires along a sinusoidal path, or that there is anything else taking a wiggly path through space. —Dominus (talk) 18:25, 14 July 2009 (UTC)

BTW what you said about it behaving as a wave or particle based on wether or not it was being observed: I thought it always did so regardless. Theres something that doesn't happen when you observe it but it is still wave/particle. Isn't the photoelectric affect proof of light as a particle, and that affect is valid when you look or don't, as is the double slit correct?66.133.202.209 (talk) 04:39, 15 July 2009 (UTC)

Wow... This discussion has gotten way off. Light is not a particle or a wave. It is merely light. Depending on how we set up our experiment, we can show particle-like properties or wave-like properties. However, that is not because light "changes" between the two (as though it knows what experiment we are doing???) nor does it mean that light is "both" a particle and a wave; as though it were simultaneously two things at once. It is just one thing; light, and its behaving the same way all the time. Our models which require us to assign it into a binary system of either "particle" or "wave" is what is the problem... --Jayron32.talk.say no to drama 06:10, 15 July 2009 (UTC)

[edit] Periodicity of ionization energies?

I've been set an exercise which consists of putting in order a series of chemical elements according to their first ionization energy, knowing only their atomic numbers. My textbook says that the first ionization energy increases within each period of the table, but Al has a lower IE than Mg, and S has a lower IE than P, for example. How am I supposed to do the exercise then? Can someone give me a nudge in the right direction? Thank you! --83.34.232.200 (talk) 15:02, 14 July 2009 (UTC)

There are rules-of-thumb as you see, but sometimes there's no way to be sure without looking up the actual values. Our ionization energy article is quite detailed and surprisingly complex--tells you that the actual specifics of IE are well beyond the general picture. There's a nice graph at ionization too, and you can see both the periodic nature and also the exceptions that don't follow the general trends. DMacks (talk) 15:40, 14 July 2009 (UTC)

Yes - read the article and look at the graph(s), as a possible hint - try comparing ionsiation energies diagonally if you want to avoid exceptions, also for all but the most dedicated (~~anally pedantic~~) of scientists the difference between Al/Mg is really just a blip (though it is real - not a measurement error)

Look at the bigger picture.83.100.250.79 (talk) 16:06, 14 July 2009 (UTC)

[edit] Artists' impressions of planet surfaces

Can anyone please indicate a good web-site with lots of (scientifically based) artists' impressions of views from the surfaces of planets in our Solar System - thanks. --AlexSuricata (talk) 18:51, 14 July 2009 (UTC)

[17] Cuddlyable3 (talk) 22:34, 14 July 2009 (UTC)

[18] will take some digging around in. 71.236.26.74 (talk) 19:31, 15 July 2009 (UTC)

If you're interested in some very fanciful paintings from before we had close-ups of the actual cratered, uninhabited planet surfaces, Time-Life published a book in the 1960s or even 1970s that imagined planetscapes for all of them — there were forests on Venus with flying alien gasbag creatures. Beautiful. I am pretty sure it's Planets in the Life Science Library, written by Carl Sagan (looks like his first book). Tempshill (talk) 23:18, 17 July 2009 (UTC)

[edit] Big Bang, how did it happen?

I really have no reason to disbelieve the big bang theory, and cosmic background radiation seems to outright prove it in my eyes. But I don't know how it could have actually happened.

The beginning of the universe, as Steven Hawking seems to explain, was a singluarity, similar in type but not scale to black holes. If there was infinite gravitational pull because it was a huge amount of mass in an infitesimal area, how could it possibly blow up?

I don't see it as likely that black holes, no matter how large they are, would explode, and they have some forces tugging outwards on their centers (the gravity of other black holes for example). The singularity at the beginning of the universe would have have gravity, obviously, holding it together, and that would simply overpower every other force that could exist.

I know an explosion happened, but black holes don't explode, and explosions need something to cause them right? Bah, just reading a discover article about steven hawking and this came back into my mind. Please help me understand. Thanks! —Preceding unsigned comment added by 192.234.122.9 (talk) 19:54, 14 July 2009 (UTC)

All of physics breaks down as you go back towards the original singularity. Therefore, notions of gravity that we understand now did not apply when the big bang occurred. -- kainaw ™ 19:58, 14 July 2009 (UTC)

Is gravity a theory or a law? Googlemeister (talk) 20:09, 14 July 2009 (UTC)

Well, Newton's law of universal gravitation is a "law" - but it's modified by things like General relativity - which is a "theory". All that we know about gravity is a mixture of laws and theories. But I hope you are aware that scientists don't use the words "Law" and "Theory" in the sense of "that which must be obeyed" and "theoretical". In science, those words mean something quite different. SteveBaker (talk) 20:17, 14 July 2009 (UTC)

Newton's "laws" of gravity are wrong and have been superseded by Einstein's "theories" of relativity. A Quest For Knowledge (talk) 02:58, 18 July 2009 (UTC)

The fact is that we don't know why. We know for sure that it happened - but there is a real problem here. Just as with black holes, when distance goes to zero - many other numbers become infinite. Density is infinite, gravity is infinite, but any distance-related repulsive forces (such as the forces that keep the atoms nicely spread apart - or perhaps any repulsive forces due to dark matter and dark energy) also become infinite. Weirder still - all of space was ALSO compressed into that infinitesimal dot. Worse still, the fundamental particles we know about today probably didn't exist back then. Fundamental laws like the Pauli exclusion principle and the Heisenberg uncertainty principle are violated. So the physics of that first gazillionth of a second are really tough to figure out. We have a pretty good idea of the way things were a few milliseconds after the big bang started...but we don't (yet) have a good handle on the absolute zeroth instant. The physics of the interior of a black hole where some of those weirdnesses ought to be playing out - might (in theory) give us a useful starting point to study that - but the event horizon of black holes forever prevents us from studying them in any useful manner. SteveBaker (talk) 20:17, 14 July 2009 (UTC)

We don't know that it happened, if "it" means "the beginning of time". When you extrapolate the original big bang model backwards you get a singularity about 14 billion years ago, but people stopped taking that seriously when inflationary cosmology caught on, because inflationary models don't have an analogous singularity at a well-defined time in the past. Physicists still talk about the "beginning of the universe" being 14 billion years ago, but they don't really mean it (see Age of the universe#Explanation). In chaotic inflationary models the expansion that we see started as literally a kind of explosion in a pre-existing universe triggered by a certain kind of quantum fluctuation. The background universe in which that happened could have existed forever for all we know. Hawking has a pet idea about the origin of the universe called the no-boundary proposal which he talked about in A Brief History of Time, possibly misleading readers into thinking that it's part of the standard cosmological model. It's not, it's actually pretty fringe. Other physicists take Hawking seriously but they don't necessarily agree with his ideas about cosmology and quantum gravity (and they certainly don't see him as a genius the way the general public seems to). -- BenRG (talk) 22:09, 14 July 2009 (UTC)

And it's worth pointing out that Brief History of Time is, by the standards of cutting-edge theory, getting a bit long in the tooth. --98.217.14.211 (talk) 22:47, 14 July 2009 (UTC)

The general public (I include myself here) considers anybody who can understand this mindbending stuff in anything more than a superficial way to be a genius, for some definition of "genius". --Sean 22:54, 14 July 2009 (UTC)

[edit] Alumina ceramic

What is it. in laypersons terms? What does it look like? I read in a book that it is elastic - seems very odd for a ceramic. Is it partly metal, partly silicon, since ceramics are made from clay, and clay I think is mostly silicon? Is it a recent invention? 78.147.131.187 (talk) 20:19, 14 July 2009 (UTC)

They make sharpening stones (whetstone) out of it, amongst other things - it's usually light grey (or white when pure) in colour, and just like unglazed ceramic - except maybe a bit harder than the average. There's no silicon in it.83.100.250.79 (talk) 20:57, 14 July 2009 (UTC)

This image is almost certainly an alumina whetstone - if not it looks identical to one

Alumina ceramic looks like this

See Ceramic for a wider definition of a ceramic which is not confined to "made from clay through heat"83.100.250.79 (talk) 22:19, 14 July 2009 (UTC)

It's not elastic in any real, common world sense. At all. 83.100.250.79 (talk) 22:22, 14 July 2009 (UTC)

See Elastic for the different definitions of the term - they are different.83.100.250.79 (talk) 22:37, 14 July 2009 (UTC)

[edit] Backup Heart

After reading a news story about how a girl survived with two hearts I started to wonder if humans could conceivably live with a backup heart their whole lives. Would it be possible to have a circulatory system with two pumps where if one fails the system remains viable? TheFutureAwaits (talk) 20:22, 14 July 2009 (UTC)

In principle, sure. The biological concept is accomplished by the lungs, kidneys, and eyes, among other organs. — Lomn 20:26, 14 July 2009 (UTC)

It seems a bit iffy to me. If the two hearts didn't beat in PERFECT synchronism - and with approximately the same pressures - then high pressure blood from one heart would flow against the tricuspid valve of the other - and those things are only held shut by the pressure - so they'd blow back open...right? I could imagine all manner of Very Bad Things happening. But we probably need a biologist to tell us more about that. Obviously, other heart designs would be possible that could overcome this...but the Mark I human heart doesn't sound like the right machine for the job. SteveBaker (talk) 20:51, 14 July 2009 (UTC)

Thanks Steve, this is exactly what I'm getting at. Say you could redesign the human circulatory system. Would it be possible to design a system which could function despite one or many pumps failing? What would such a system look like? TheFutureAwaits (talk) 21:09, 14 July 2009 (UTC)

Not sure if this is an appropriate analogy, but many invertebrates, such as octopuses, have multiple hearts. -RunningOnBrains^{(talk page)} 21:20, 14 July 2009 (UTC)

We're trying to answer a question with woefully incomplete information. Were there were actually two functioning hearts linked to the same circulation? Was it actually a birth defect in which instead of a four-chamber heart there were two two-chamber hearts serving the two sides of the circulation (pulmonary circulation and systemic circulation)? The "news" is notorious for hyping up some oddity yet not providing real information about what was going on. Can the OP at least link to the news story? --- Medical geneticist (talk) 21:21, 14 July 2009 (UTC)

Here's the story if you're really interested [19]. Please note I'm not really interested in learning more about this case, it was just the inspiration for the question. What I'm really interested in knowing is as follows: TheFutureAwaits (talk) 21:30, 14 July 2009 (UTC)

Say you could redesign the human circulatory system. Would it be possible to design a system which could function despite one or many pumps failing? What would such a system look like? TheFutureAwaits (talk) 21:30, 14 July 2009 (UTC)

It would look like a guy with two or more hearts, each capable of pumping hard enough to support life. They would be connected in parallel and share the same nervous impulse. In the event of failure there would have to be some sort of sphincter or valve preventing back flow round the failed organ. —Preceding unsigned comment added by 83.100.250.79 (talk) 22:43, 14 July 2009 (UTC)

I don't see how they could be in parallel. If the second heart fails then the first one can only pump into the opening of the second, after which everything gets clogged. I suppose there could be some side artery between the first and second heart where blood could go around the second and back into the main artery. Not sure if this could actually work though. TheFutureAwaits (talk) 23:46, 14 July 2009 (UTC)

You may have misunderstood. See Parallel circuits. APL (talk) 00:36, 15 July 2009 (UTC)

Serial hearts could also (in theory) work. By the way, real hearts actually do have such valves. Axl ¤ [Talk] 16:09, 15 July 2009 (UTC)

[edit] What are the odds?

I just ate a bag of peanut M&M's...yes, I know...an entire bag is kinda piggy. Anyway - I tore the end off of the bag and dumped out the usual 30 or so randomly colored M&M's into a shallow dish on my desk. I'm working - concentrating on a tough programming problem (rendering shadows cast from a non-uniform point source - if you must know) - and I swear that I am paying zero attention to picking up M&M's...until there are only seven left - when I happen to notice that they are ALL blue. This seems like a rather improbable thing...there are maybe 5 colours - so the odds are something like eighty-thousand to one against this happening by chance. So I'm wondering whether my subconscious doesn't really like blue M&M's and hasn't been telling the conscious "me" all this time? I should probably repeat the experiment a few times...right? SteveBaker (talk) 20:46, 14 July 2009 (UTC)

There could have been an error at the packaging plant and some bags did not get the proper mix of colors. I also recall a couple of contests from years ago where the winning bag was all 1 color. You could have just eaten a $1,000,000 bag of M&Ms. Googlemeister (talk) 20:51, 14 July 2009 (UTC)

No - I'd have noticed immediately when I dumped them out if they were all blue. I was obviously concentrating on the bag when I opened it

Maybe blue ones are heavier? but tell us more about you're non uniform point source - that sounds more interesting - though not that difficult on the surface - a point source always produces sharp shadows no matter what the intensity of the light - sounds like you just need more bits in the shadow map to express the non-shadowed intensity - it's always easier to say rather than do isn't it.83.100.250.79 (talk) 20:53, 14 July 2009 (UTC)

Yes - but it's omnidirectional so I can't do the usual "planar rendering from the point of view of the light source" trick - I've got to mess around with rendering to a cube-map. Anyway - I don't need help with that - I need to know about my brain's hitherto unsuspected aversion to blue food! SteveBaker (talk) 20:56, 14 July 2009 (UTC)

Coincidences do happen. Also, while the odds may be one in 80,000, how many packets of M&M's have you eaten in your life? Enough, I imagine, for the odds of the last seven M&M's in one of those packets being all the same colour being significantly higher. Also, it isn't 80,000:1, it is more like 16,000:1 - you don't want the odds of the last 7 being blue, you want the odds of them all being the same colour. You would have been just as surprised had they been all red. --Tango (talk) 21:24, 14 July 2009 (UTC)

Excuse *ME*! 80,000 bags of M&M's?! If I'd consumed M&M's every day since 1954 (when Peanut M&M's were first introduced) that would make 4 bags a DAY! Every single day! Now THAT would be "piggy"! SteveBaker (talk) 05:06, 15 July 2009 (UTC)

You don't need to have had 80,000 bags. Say you've had 1,000 bags, at odds of 80,000:1 (which are wrong anyway, but I'll go with that number), the chance of one of those bags having the last 7 blue would be $1-\frac{79999}{80000}^{1000}=0.012\dots$ , that's over 1%. Plenty of 1 in 100 chances happen and you wouldn't think twice about it. --Tango (talk) 16:55, 15 July 2009 (UTC)

You should play the lottery ;) --Mayfare (talk) 21:58, 14 July 2009 (UTC)

It's a very, very common elementary school science "experiment" to see whether the color distributions in M&Ms and other candies are identical. They are often not, probably due to poor mixing. There is no a prior reason to suspect that the packet actually has even distribution to begin with, which obvious affects the odds-making quite a bit. --98.217.14.211 (talk) 22:29, 14 July 2009 (UTC)

(edit conflict) Yes that's right, I work in a M&M's factory (peanut division), and the blue ones always go in first. Somedays, when the boss isn't looking we don't bother to shake them to mixed the different colours, sometimes people just forget - "did you shake that one", "think so"... (lie)83.100.250.79 (talk) 22:47, 14 July 2009 (UTC)

That might actually be close to the truth. Presumably, the open bags are moved beneath a series of hoppers that each spew forth a set amount of M+Ms of a particular colour... --Kurt Shaped Box (talk) 00:29, 15 July 2009 (UTC)

But they'd have gotten shaken up when loaded into the vending machine, shaken more when dropped three feet into the output hopper - and completely mixed up when I dumped them into the bowl. It's hard to imagine that there would be much correlation between the order they were dumped into the bag and the order they were in the bowl. SteveBaker (talk) 05:10, 15 July 2009 (UTC)

Color distribution on M&Ms is not even. In the mid-70s Cecil Adams claimed that they were 90% brown and yellow. If the color distribution is still close to that (And I can't say I've noticed.) then your coincidence is even more surprising. APL (talk) 22:46, 14 July 2009 (UTC)

Of course it's dangerous to interpret any given event, but there's quite a bit of experimental work in the psychophysics literature showing that people are generally averse to blue-colored food. In fact there is even evidence that coloring a food blue influences the way people perceive its flavor, for example this paper. Looie496 (talk) 22:48, 14 July 2009 (UTC)

As someone who likes blueberries, I respectfully disagree. 76.21.37.87 (talk) 07:01, 17 July 2009 (UTC)

That's what I was wondering. SteveBaker (talk) 05:10, 15 July 2009 (UTC)

Before concluding that anything miraculous has occurred I want to know more about how one pays zero attention to picking up M&M's but picks them up anyway. Some brain activity must be involved in reaching out to a particular M&M. Were the M&M's in the field of view? What colour was the dish? Were more than one M&M touched at a time? Can the subject taste the difference between any M&M colours while blindfolded (a follow-on experiment) ? Which colour(s) of M&M eaten to excess would cause the subject to feel the most shame about being piggy? A point source cannot be non-uniform. It sounds like you have a ray tracing exercise. Cuddlyable3 (talk) 23:00, 14 July 2009 (UTC)

Well - my conscious mind was not carefully picking the non-blue ones first. One can grab a random candy from a dish without actually consciously thinking about it. I wasn't CONSCIOUSLY choosing to eat the non-blue ones...which is what makes me wonder whether this decision had been made by some lower level brain function. The M&M's were in a chromed plastic dish - it would have been visible in my field of view - but I wasn't conscious of looking at the dish - my gaze was mostly fixed on my computer screen. I don't know what you mean by "were more than one M&M touched at a time". I'm pretty sure I can't tell the difference in the flavor. Piggyness comes about from not PLANNING to eat more than a couple of M&M's but then belatedly noticing that there were only seven left. It's computer graphics - not physics - the point source does whatever the heck I tell it to do. If I say it's a non-uniform point source...then that's what it is! In this case, imagine a very small lightbulb with a lampshade over it (idealised as a point source because it makes the math easier) such that the light from it is not evenly distributed. This is for computer games - performance is at a premium and ray tracing is WAY out of the realms of the possible! SteveBaker (talk) 05:01, 15 July 2009 (UTC)

I would imagine a "non-uniform point source" would be a source which emits different light in different directions, but all from one point. --Tango (talk) 00:06, 15 July 2009 (UTC)

Yes, exactly. SteveBaker (talk) 05:01, 15 July 2009 (UTC)

Like an airport beacon (rotating white / green)? 76.21.37.87 (talk) 06:15, 17 July 2009 (UTC)

Explaining Were more than one M&M touched at a time?: this question investigates the process by which each M&M was selected unconsciously. The subject might A) have aimed to pick a particular M&M and operated arm, wrist and fingers appropriately, or B) grabbed a bunch of M&Ms and then used the sense of touch in the fingers to drop all except one M&M to eat, or C) none of the above. Supplementary question: how many M&Ms does the subject typically have in the mouth at the same time? I'll repeat the question Which colour(s) of M&M eaten to excess would cause the subject to feel the most shame about being piggy?.Thank you for explaining your non-uniform point source. Perhaps you use a this or this shading of objects. Look towards the light source and apply the same model. Multiply the modelled illumination with the modelled reflection and then you can play. Cuddlyable3 (talk) 12:59, 15 July 2009 (UTC)

Yeah - I've been doing computer graphics for 25 years...I know about shading algorithms (which is what Gouraud and Phong are...well, almost, they are actually surface normal interpolation strategies). My problem is to do with casting shadows - not those kinds of "self-shadowing" things. I was certainly eating them one at a time...I wasn't paying attention to how I was picking them up - but I'd have to say it was almost certainly one at a time. The subject's conscious brain doesn't give a damn about the colors - piggyness is an approximately linear function of number of M&M's consumed divided by elapsed time between first and last M&M - the value of the function is explicitly defined to be zero when the number of M&M's consumed is less than 2. The subject's unconscious brain doesn't seem to comment on piggyness - since it's shovelling them in at a high rate. However, the issue of color is the question at hand. SteveBaker (talk) 19:26, 15 July 2009 (UTC)

If you told us the number of M&Ms in the bag, and the total number of blue ones, then the probability could be calculated. Its an example of the classic beads in an urn (no replacement) combinatorial problem. I'm trying to remember the formula. But, assuming that the probability is the same as the first 7 m&ms being blue, then the probability would I think be B/M x (B-1)/(M-1) x (B-2)/(M-2) ..... x (B-7)/(M-7). Note that the other n million people who have eaten a bag of M&Ms and whose last seven items were not blue, have not reported it to Wikipedia. 92.27.155.47 (talk) 23:18, 14 July 2009 (UTC)

Assuming he didn't count them in advance you have to assume they are independent with equal chance of each colour (you could assume each bag has equal numbers of each colour, but that doesn't seem to be the case), so it is just 5⁶ (there are 6 M&M's which need to be the same colour as the first one, you don't care what colour the first one it). --Tango (talk) 23:39, 14 July 2009 (UTC)

Please explain how you caculated " 5⁶ "? I am not familiar with M&Ms, but if you are supposing that there are five different colours and that they are in equal proportions, then your estimate for all-blue would be (1/5)⁷ which is one in 78125, or (1/5)⁶ which is one in 15625 for seven in a row being the same colour. Actually, that is correct only for bags of infinate size or for where the M&Ms are put back in the bag: when a blue M&M is removed, it changes the proportions of the remaining colours in the bag, so the B/M x (B-1)/(M-1) x (B-2)/(M-2) ..... x (B-7)/(M-7) calculation is more correct. 78.145.23.157 (talk) 20:26, 16 July 2009 (UTC)

You might care about the color of the first one. If his final seven M&Ms had all been brown, the most common color, would he have considered it notable? APL (talk) 00:33, 15 July 2009 (UTC)

Are brown significantly more common? It's been ages since I've had a packet of peanut M&M's. --Tango (talk) 03:15, 15 July 2009 (UTC)

You can actually order M&M's in 60 pound bags of single colors of your choice from the M&M web site, including colors that you don't find in the normal retail packs, like black and white. 70.90.174.101 (talk) 04:02, 15 July 2009 (UTC)

This describes the color distribution: http://joshmadison.com/article/mms-color-distribution-analysis/ 70.90.174.101 (talk) 04:05, 15 July 2009 (UTC)

Not really - these were PEANUT M&M's. SteveBaker (talk) 05:01, 15 July 2009 (UTC)

The whole point here is that, while it is unusual, such event occuring truly randomly is not impossible. It isn't that YOU at 80,000 bags of M'n'Ms. It's likely that 80,000 bags are consumed pretty regularly (I'd even hazard DAILY), so such an event happens to someone every day. That it was your turn today is rare, but not impossible. Look, I have a buddy that lost a poker hand (7-card stud, no wilds) where he had a straight flush and lost to a higher straight flush. You can play poker your whole life and probably never even play in a hand where a straight flush occurs; and yet he was in one with two. It is weird, but any event based on random chance DOES happen. --Jayron32.talk.say no to drama 06:03, 15 July 2009 (UTC)

The current page at mms.com doesn't have percentage information but this archived page does: 12% brown and red, 15% yellow and green, 23% blue and orange. I wonder how much they paid the consulting firm that came up with those percentages. Anyway, the chance of n randomly selected Peanut M&Ms being all the same color (with replacement) is 2·(12ⁿ+15ⁿ+23ⁿ)/100ⁿ. For n=7 that's about one in 14,000. Without replacement it would be somewhat more unlikely, but I'd need to know the total M&M count per pack for that. -- BenRG (talk) 09:45, 15 July 2009 (UTC)

Hmmm... The color distribution has changed drastically since that Cecil Adams column in the 70s. APL (talk) 12:51, 15 July 2009 (UTC)

Alien hand syndrome shows that the hemisphere which doesn't have access to the speech center can indeed have its own opinions about things. I guess we can assume your two hemispheres aren't in serious disagreement over whether you like blue M&Ms, but I'm just saying that the psychological explanation is feasible, and perhaps a more likely explanation than the 1 in 80,000 chance. It seems likely to me that it takes some small but significant degree of conscious effort for you to recognise bright blue things as food, and so you're less likely to put those ones in your mouth automatically. 213.122.68.146 (talk) 06:41, 15 July 2009 (UTC)

If they were in your peripheral vision you may have subconsciously been picking the ones that stood out more/had higher contrast against the bowl/other M&M's given the ambient lighting. Zunaid 11:50, 15 July 2009 (UTC)

My guess is: you actually prefer the blue ones and therefore subconsciously saved the best ones for last! Sort of like the old Smarties commercial: "Do you eat the red ones last?" I found myself saving the red ones to the end without even realizing that I was doing so! Now, I consciously eat my M&Ms from my least favorite color (they all taste the same!) to my most favorite (blue and red). —Preceding unsigned comment added by 216.154.20.38 (talk) 14:52, 15 July 2009 (UTC)

I just ate a whole bag of peanut M and M's and didn't pay attention to any of the colors. after reading this post, I will in the future! cheers, 10draftsdeep (talk) 18:13, 15 July 2009 (UTC)

"M&Ms are Tasty! They melt in your mouth, not in your hand. Melting before being consumed was a problem with chocolate, which was otherwise highly useful as an emergency ration for soldiers. In World War 1, the U.S. Army issued chocolate bars to soldiers to be eaten for energy needs when normal food could not be brought to the at front line positions. Knowing that any normal guy would eat a tasty chocolate bar long before the hypothetical emergency, the Army adulterated the chocolate bars with sawdust and kerosene. Edison (talk) 01:50, 16 July 2009 (UTC)

EWWWWWWWWW!!! 76.21.37.87 (talk) 05:18, 17 July 2009 (UTC)

[edit] Solubility of Ionic Compounds

Hello. If ionic compounds are polar and like dissolves like, why are some salts water-insoluble at SATP? Thanks in advance. --Mayfare (talk) 21:51, 14 July 2009 (UTC)

"like dissolves like" is a general observation of a certain trend, not a fact (and definitely only a result not a physical law or the cause of anything). If "whatever holds molecules together and to each other" is stronger than "whatever interactions happen between solute and solvent", the chemical is not very soluble. See solubility for a detailed discussion. DMacks (talk) 22:11, 14 July 2009 (UTC)

In the case of ionic salts, that would be the relative strength of the ions' electrostatic attraction to each other vs. water molecules. If the ions are more attracted to each other than to water, then the salt will not dissolve. Generally, salts where one or both ions are monovalent (with the exception of some fluorides) are water-soluble, whereas those where both ions have a valence of 2 or more are water-insoluble because their electrostatic attraction is much stronger. Note also that for the purpose of determining solubility, fluoride ions behave as though they have a valence of 2 or more, even though they really are monovalent.

76.21.37.87 (talk) 01:04, 15 July 2009 (UTC)

In my quest for knowledge: this is because of fluorine's very high electronegativity, right? -- Aeluwas (talk) 16:15, 15 July 2009 (UTC)

When they say "fluoride ions behave like they have a valance of 2" I think what is meant that fluoride ions (F-) show similar solubility characteristics as 2- ions eg sulphate - this is because of F- ions small size ... small size or high charge makes the ion more strongly interact with electrophiles. It's not the electronegativity.

Also if a compund is only partially ionic the solubility is affected (eg CuI is insoluble, but KI is soluble) - there are a lot of factors, but it's simpler when both the anion and cation are good at forming ions eg Cl- , K+ , Mg2+ , NO3- etc...83.100.250.79 (talk) 22:25, 15 July 2009 (UTC)

Yeah, that's what I meant to say. Thanks! 76.21.37.87 (talk) 01:02, 16 July 2009 (UTC)

[edit] The Limit of heat?

I understand that there is a limit to the degree of cold (absolute zero), but is there a limit to how hot things can get? Obviuosly in the moments after the big bang, the temprature would of been huge, but can there be a higher temprature, either naturally (in supernovas etc) or synthetically (in collisions and heating [I read that scientists have heated a substance to 510 million degrees!]). Andy (talk) 23:57, 14 July 2009 (UTC)

There is no theoretical limit to the best of my knowledge. There is a practical limit imposed by the total amount of energy in the observable universe, of course. You may be interested in the concept of negative temperature, which is, in a sense, temperature hotter than infinitely hot. --Tango (talk) 00:04, 15 July 2009 (UTC)

Absolute hot 87.114.25.180 (talk) 00:34, 15 July 2009 (UTC)

Good stuff, very interesting, just out of curiousity, what is the hottest temprature ever created, both in a lab or naturally? Cheers. Andy (talk) 00:41, 15 July 2009 (UTC)

That would be the temperature of a thermonuclear explosion, which is in the billions of degrees (Celsius). 76.21.37.87 (talk) 00:53, 15 July 2009 (UTC)

On second thought, some blue giant stars or supernovas may be even hotter. FWiW 76.21.37.87 (talk) 00:55, 15 July 2009 (UTC)

Stars are thermonuclear explosions. --Tango (talk) 03:10, 15 July 2009 (UTC)

The temperature was ludicrously high just after the Big Bang. --Sean 14:10, 15 July 2009 (UTC)

That's not quite analogous to absolute zero. Absolute hot isn't the highest temperature achievable, it's the highest temperature that our theories are capable of describing meaningfully. --Tango (talk) 03:13, 15 July 2009 (UTC)

Planck temperature is theoretical limit. --manya (talk) 04:35, 15 July 2009 (UTC)

As Tango states, defining a limit is difficult, because what is "hot" can be counter-intuitive. Your scale goes in a loop from kind of +0K (cold) to -0K (hot). Hotter than 10^32 K is of little physical relevance (or at least doesn't make sense until we figure out quantum gravity), though, as Ranemanoj said. —Anonymous Dissident^Talk 16:33, 15 July 2009 (UTC)

Indeed, as AD states, we need to figure out quantum gravity before knowing what happens around Planck temperature. It might well be that there is a limit, but it won't be necessarily the current definition of Planck temp. (also because the choice of using G instead of 8πG in that def. is quite arbitrary, and one which I'd disagree with). There might well be no limit at all. We just don't know it yet. --A. di M. (talk) 16:55, 15 July 2009 (UTC)

Show me a system in a container which you claim is at the highest possible temperature, and I claim I could heat it up a bit. There is no "highest possible temperature" unlike absolute zero. Edison (talk) 01:45, 16 July 2009 (UTC)

This does not prove that there is no highest possible temperature --- it just proves that it cannot be reached. See Achilles and the Tortoise (same holds with speed of light and acceleration). (Might be there is none but your argument isn't a proof for it.)95.112.156.108 (talk) 20:31, 16 July 2009 (UTC)

[edit] July 15

[edit] Beetle factoid

Something I heard on the radio the other day.

"If you were to randomly arrange all the macroscopic animal life on earth in one long line - then every fifth creature would be a beetle."

Confirm/debunk? --Kurt Shaped Box (talk) 00:23, 15 July 2009 (UTC)

I see what they were getting at but if you were to arrange them in a truly random nature, then there is no telling just where in the line the beetles would fall. I know, I'm picking nits... Dismas|^(talk) 00:28, 15 July 2009 (UTC)

They are claiming that 1/5th (20%) of all macroscopic life is beetles. See beetle. The percentage is closer to 25%. So, every 4th creature would be a beetle. -- kainaw ™ 01:59, 15 July 2009 (UTC)

That figure appears to refer to number of species, not of individuals. Algebraist 02:00, 15 July 2009 (UTC)

Indeed, the source has "Beetles comprise 25% of all described animals and plants, single-handedly making them the primary contributor to earth's biodiversity. The 350,000 descrubed beetle species are members of largest order of life on Earth. Coleoptera." Algebraist 02:03, 15 July 2009 (UTC)

There are lots of beetle species, but I'm pretty sure that if you did this over half of the animals would be ants. Looie496 (talk) 02:18, 15 July 2009 (UTC)

The term "macroscopic" is kinda vague - I'm sure you could make the answer come out anyway you wanted by picking a more exacting standard for what size of creature you're talking about. Haggling over whether the number is 20% or 25% is kinda silly in the face of that. SteveBaker (talk) 04:40, 15 July 2009 (UTC)

The famous biologist J. B. S. Haldane was once asked what he had learned about God from his study of biology. He said: "The Creator, if He exists, has an inordinate fondness for beetles." SteveBaker (talk) 04:37, 15 July 2009 (UTC)

Also see The Last Continent :-) 71.236.26.74 (talk) 18:32, 15 July 2009 (UTC)

"The Creator, if He exists, has an inordinate fondness for beetles." -- Was that what John Lennon meant when he said that the Beatles were "more popular than Jesus"? ;-) 76.21.37.87 (talk) 05:08, 17 July 2009 (UTC)

I suspect that what he meant was that the Beatles were never publicly crucified, which is not what one usually a great sign of popularity. Googlemeister (talk) 13:51, 17 July 2009 (UTC)

[edit] Ultimate Revenge/Punishment - Paralysis with no possibility of communication

Is it theoretically possible to perform an operation on someone/dose them with something that would render them completely and permanently paralyzed with no way to communicate (no blinking, no twitching etc) but still leave them completely aware of themselves and their surroundings (without killing them of course)?

They could then live out a full lifespan knowing that someone did this to them but never being able to tell anyone who - the ultimate revenge/punishment? Exxolon (talk) 00:39, 15 July 2009 (UTC)

Disregarding the fact that I now hope I never meet you in real life (☺), yes, it is certainly possible, although they would have to be on life support, and future advances in medicine may be able to tap directly into people's brains, allowing them to communicate despite any neurological damage.^{[citation needed]} -RunningOnBrains^{(talk page)} 00:43, 15 July 2009 (UTC)

I think that if you sever the spinal cord just below the medulla oblongata, you can paralyze the subject from the neck down. FWiW 76.21.37.87 (talk) 00:51, 15 July 2009 (UTC)

How about we cut the brain off and keep it alive in a jar (relatively easy) and make it aware that it is a brain in a vat and can't do anything about it (still sci-fi).--Lenticel ^(talk) 01:08, 15 July 2009 (UTC)

It would probably be simpler with present technology to simply (in addition to the above) put out the eyes, puncture the eardrums and use chlorine gas to destroy the senses of taste and smell for a similar effect. The victim's conscious mind would probably vanish into a black hole after a few weeks/months. --Kurt Shaped Box (talk) 01:24, 15 July 2009 (UTC)

The OP says "still leave them fully aware of their surroundings". So personally, I'd go with severing the spinal cord, and pull out the tongue so the subject can't say anything to anyone (not that I'd do that to anyone, of course, except to a terrorist or to a child molester).

76.21.37.87 (talk) 01:59, 15 July 2009 (UTC)

This is not the ultimate revenge or punishment. As covered many times in literature for thousands of years, loss of hope is the ultimate punishment. To lose hope, you must first have hope. Classic example: Imprison a person for, say, 30 days. On the last day, punish the person for something that happened over the imprisonment and extend the punishment another 30 days. On the last day, punish the person again with another extension. Repeat this until all hope is lost. -- kainaw ™ 02:03, 15 July 2009 (UTC)

I deem your portrayal of hope to be a good thing as somewhat facile. It's only when we lose hope that we begin to gain some beginnings of a true, sustainable, authentic self. To hope is to dislike your present reality. Vranak (talk) 18:28, 16 July 2009 (UTC)

It's certainly possible. All you would have to do is take somebody with locked-in syndrome and paralyze the eyes. People with end-stage Parkinson's disease may be in a state something like this. In principle it would still be possible to communicate with such a person by directly reading brain activity, but if you ignore that approach, it is definitely possible. Looie496 (talk) 02:12, 15 July 2009 (UTC)

As Looie496 pointed out, even with complete loss of motor control, communication is still theoretically possible. I recall recently seeing a news report or documentary on experiments where subjects were able to control a mouse cursor using brainwave activity picked up by a sensor filled skull cap. I wasn't able to find a wikipedia article, but did find this similar story on the web. Such technology could allow your paralyzed victim to pick letters off the screen, form words, and eventually tell the police who dunnit. -- Tcncv (talk) 02:19, 15 July 2009 (UTC)

Actually, this is the state we are all in, all the time. We think we can communicate with people. But that is actually an illusion. We are just a brain in formaldehyde. The formaldehyde has wikipedia molecules added to it. Bus stop (talk) 02:21, 15 July 2009 (UTC)

Nonsense. There is no 'we'. My consciousness is the entirety of existence. Everything else I may perceive is merely a delusion constructed unconsciously in order to maintain my sanity. --Kurt Shaped Box (talk) 02:42, 15 July 2009 (UTC)

Is it working? Algebraist 02:46, 15 July 2009 (UTC)

50% of the time, on average. I suppose that existence would be boring otherwise. --Kurt Shaped Box (talk) 02:49, 15 July 2009 (UTC)

The most relevant Wikipedia article is brain-computer interface. Looie496 (talk) 02:48, 15 July 2009 (UTC)

I believe I could send Morse code (slowly) by turning the Alpha waves on and off, even if all sensory nerves and motor nerves were out of commission. These are easily monitored by scalp electrodes. Regardless of whether they were in fact monitored, I would amuse myself by cursing my captor. The role model for this is Malcolm, the black guy in 2001 Maniacs who is about to be crushed by a large press controlled by an antebellum racist zombie, Mayor Buckman. Mayor Buckman says "Do you have any last wish?" Malcolm says,"Yeah. Kiss my black ass!" and spits in the zombie's one functioning eye. Zombie says to assistant, "Next year remind me to omit the'"Last wish' part." Edison (talk) 04:19, 15 July 2009 (UTC)

locked-in syndrome, in which sometimes the patient even looses control of her eyes, would be a nightmare scenario for most. But as this article [20] documents, some people can cope even with this. EverGreg (talk) 10:30, 15 July 2009 (UTC)

I have actually suffered from this a couple of times on waking up. It only lasts about 10 seconds though and a huge hypnic jerk knocks me out of it.

This is actually known as sleep paralysis, caused by a persistence of REM atonia after waking. I used to get it regularly when I was younger, definitely the scariest thing I ever experienced, until I understood what was going on and could just relax until I woke up properly.Mikenorton (talk) 15:24, 15 July 2009 (UTC)

The trick is to hold ones breath. Under sleep paralysis I have found that I still have control over my breathing. Asphyxiation wakes up whatever part of me that is still sleeping. EverGreg (talk) 21:30, 15 July 2009 (UTC)

Anyway, an equally harsh punishment would be to gas the person with an amnesia-causing drug, then inject them with MPTP. If permanent Parkinson's is too harsh, then maybe inject one of those long-lasting anticholinergics (EA-3167 or 3-quinuclidinyl benzilate) --Mark PEA (talk) 11:07, 15 July 2009 (UTC)

(EC) I would question both the efficiency and the costs of any such measure. Punishment has three major functions: deterring other individuals from committing the same type of crime, motivating the individual who committed a crime to change his/her behavior in future to conform to legally/socially accepted behaviors and preventing the individual who committed the crime from doing it again. The effectiveness of [{capital punishment]] in general is debated. Your method would exacerbate the costs and further reduce any impact. Since your prisoners would be unable to communicate, there would be no reports from them on the horrors of their situation. So you'd have to bank on prospective perpetrators finding the mental image of locked-in syndrome and pictures of individuals in prison hospital beds connected to a barrage of tubes and monitors more objectionable than life in prison or a death sentence. IMHO not very likely. More likely would be that this type of punishment would add to the suffering of the victims and their families. Even if they feel entitled to retribution at first they may feel remorse later because this punishment doesn't provide sufficient closure. Depending on their moral and ethics views they may feel diminished by the harshness of the punishment. (They are also much more likely to consider the punishment harsh than someone who has stepped so far out of society as to consider committing a crime.) Most societies have a hard time these days covering the cost of caring for critically ill individuals. Your version would artificially increase the numbers in the category requiring the most intensive care and that on a long term basis. (Most patients requiring intensive care are either so ill that they die after a while or they recover sufficiently to classify for less intensive care options or even release from hospital.) I couldn't think of any way to justify that. At least in the US, there's criticism that a large portion of the prison population is suffering from some mental illness. Providing adequate care for those and improving living conditions in high crime areas would be a better use of funds to reduce the rate of violent crimes than the method you are considering.71.236.26.74 (talk) 17:20, 15 July 2009 (UTC)

You have a good point here -- why go to all that trouble paralyzing a terrorist or child molester and then keeping him alive for many years, when it would be more effective to just shoot him and be done with it?76.21.37.87 (talk) 01:14, 16 July 2009 (UTC)

The above is a good review of penology i.e. reasons for punishment. It does not admit the motive of revenge that the OP considers. Cuddlyable3 (talk) 09:37, 16 July 2009 (UTC)

Dramatic results of Sensory deprivation of a person in an Isolation tank were shown in the movie The Mind Benders (1962). Here is a clip. Cuddlyable3 (talk) 17:06, 15 July 2009 (UTC)

Note: the movie cuddlyable mentions is a work of fiction and not a documentary. Effects scientific studies report for isolation tanks are usually positive [21]. 71.236.26.74 (talk) 08:24, 16 July 2009 (UTC)

That link is to a 600+ page book. Which page? Cuddlyable3 (talk) 09:37, 16 July 2009 (UTC)

Sorry I came to it via a more direct link p227/278 have something. Probably not the best reference, but there are quite a few studies out there. It's used in therapy. Will try to post better stuff if I can find the time. 71.236.26.74 (talk) 01:36, 17 July 2009 (UTC)

Sensory deprivation used in therapy?! With all due respect, I really have trouble believing that. I know that it was one of the tests used for astronaut training, and most astronaut interviews state that even a few hours of sensory deprivation is extremely distressing. Also, there are (unconfirmed) reports that the Soviets used sensory-deprivation-like techniques for prisoner interrogation / punishment, and almost all of the prisoners either spilled the beans within a few days (couple of weeks at most), or lost their mind. I don't see how sensory deprivation can be used in therapy.

76.21.37.87 (talk) 04:01, 17 July 2009 (UTC)

I am going to say, considering the excellent points presented above, it is impossible to do so whilst leaving the person as a conscious, sapient mind. The mind is just something the brain is doing, and far from being the mysterious black box of puzzles it once was, we now have the capacity to look in and watch the brain doing that. That mouse cursor brain thing shows the key point. No matter how much you detach the person's mind from any natural, "everyday" output channel (speech, hand gestures, eyebrow waggling, whatever), there is still an output channel you can't possibly disconnect (that is, the brain activity that makes up the mind itself) without killing the mind. Maelin (Talk | Contribs) 12:52, 16 July 2009 (UTC)

[edit] Staying upright on a bike

Why is it easy to stay upright on a bicycle when moving forward, yet very difficult when at a standstill? —Preceding unsigned comment added by 86.176.50.146 (talk) 02:45, 15 July 2009 (UTC)

I assume the answer is in Bicycle and motorcycle dynamics somewhere. Algebraist 02:48, 15 July 2009 (UTC)

I haven't looked at that article, but the basic reason is because when you're moving, you can compensate for an error by turning the wheel a little bit to the side you're falling toward, but that doesn't work when you're at a standstill -- you can only compensate then by shifting your weight, which involves a much longer time delay. Looie496 (talk) 02:55, 15 July 2009 (UTC)

Read Angular Momentum conservation. Rkr1991 (talk) 03:37, 15 July 2009 (UTC)

The first answer is correct. Angular momentum plays very little role on a bicycle. it is more important for the understanding of the motorcycle dynamics. Dauto (talk) 05:29, 15 July 2009 (UTC)

Our Article says Angular momentum conservation plays more of a role on lighter vehicles like bicycles. Angular momentum conservation through counter leaning un addition to balancing with the handlebars is the complete answer, as given in our article. Rkr1991 (talk) 05:52, 15 July 2009 (UTC)

The article is wrong. Dauto (talk) 07:01, 15 July 2009 (UTC)

^{[citation needed]} Algebraist 10:08, 15 July 2009 (UTC)

Non-technical answer: The spinning wheels act like a gyroscope. -- penubag (talk) 06:00, 15 July 2009 (UTC)

Non-technical, perhaps - but quite utterly wrong - definitely! Gyroscopic forces have little if anything to do with it. SteveBaker (talk) 07:21, 16 July 2009 (UTC)

Nuh-uh, Looie's answer is correct. There have been experiments with bicycles with locked steering. I suppose I ought to be able to cite that, and I can't, and anyway I probably read it on the reference desk in the first place ... but I believe it's true. Bike wheels do make nice gyroscopes but aren't significant in that capacity in stopping you falling off. 213.122.68.146 (talk) 06:58, 15 July 2009 (UTC)

Just to clear up any confusion: 213.122.68.146, Dauto and Looie496 are correct, as is our article on Bicycle and motorcycle dynamics. Bikes and motorcycles stay upright primarily through small steering corrections, gyropscopic and angular momentum effects play a minor role (if any). See all the external links from our bike dynamics article, or do a Google search. — QuantumEleven 10:16, 15 July 2009 (UTC)

The idea here is that because the contact-patch of the wheel is BEHIND the axis it pivots on, when you lean it automatically tends to steer into the lean. Exactly what you would want it to do to keep you upright. This built-in feedback makes it very easy to stay balanced because the bike is constantly "trying" to steer itself under your center of gravity. APL (talk) 13:06, 15 July 2009 (UTC)

In other words, the angular momentum does help by providing a force which completes a (mechanical) negative feedback loop; the actual balance is accomplished with the steering corrections. As Dauto has pointed out, the net effect of the angular momentum is small; but the bicycle attempts to self-right because of the fork mounting of the front tire. (Consider the front tire fork mounting as a mechanical "amplifier" which senses deviations in angular momentum, and magnifies them via the kinetic energy sourced from the forward motion of the bicycle). The human can hold the handlebars and assist in the steering. Perturbations from balance upset the angular momentum, and push the tire back towards the upright steering. This is why minutely different designs of front wheel mounting dramatically change the steerability and stability of the bike. Nimur (talk) 22:04, 15 July 2009 (UTC)

Nimur, the fork feedback works even if the bike is not moving at all (try it) and therefore has nothing to do with angular momentum. A bike's wheel doesn't spin fast enough to have any important effect. A motorcycle is a different matter. Ask anybody that knows how to drive a motorcycle if steering it is any different than steering a bike. Ask them if they have to pull right in order to turn left Dauto (talk) 04:56, 16 July 2009 (UTC)

WP:OR... I know how to drive a motorcycle... Nimur (talk) 08:57, 16 July 2009 (UTC)

I strongly recommend that everyone who is even considering replying to this thread carefully re-read our Bicycle and motorcycle dynamics article before replying. IMHO, it's one of the finest science articles in the whole of Wikipedia (why isn't it an FA?^†) - and it's correct, well written, approachable, beautifully illustrated - and properly referenced - as opposed to about half of the replies here so far that are complete twaddle! SteveBaker (talk) 07:21, 16 July 2009 (UTC)

^†It's presently a Good Article, but it looks like there are still some TODO items listed on its talk page from the unsuccessful FA nom a few years ago. DMacks (talk) 08:05, 16 July 2009 (UTC)

The simple answer is that the wheels of a bike can be easily moved back under the center of mass, in response to an undesired lean, when moving forward, by steering the front wheel in the direction of the lean. The faster the bike is moving, the more quickly the contact patches move for the same steering input. When stationary, there is some ability to move the front wheel contact patch from side to side because of the front wheel steering geometry, specifically the feature called trail, but it is limited and slow compared to when moving forward.

The geometry and mass distribution of many bikes is such that the torque necessary to turn the front wheel appropriately can be generated by the bike itself, if moving forward at the right speed. The factors that influence this self-stability include the "trail" mentioned above, mass distribution of the entire bike and of just the front end, and inertia of the wheels, especially the front wheel.

While the gyroscopic effects of the spinning wheels is often cited, David Jones proved by experimentation that they are not necessary for a bike to be "easily ridden" in his famous 1970 Physics Today article. A spinning wheel provides no direct resistance to tipping. Instead, when the spinning front wheel is subject to a tipping torque, it reacts be precessing about a third axis, perpendicular to both its spinning axis and the axis of the applied tipping torque. This is approximately the steering axis. Thus, this precessing can contribute to the bike's ability to steering in the direction of a lean automatically. -AndrewDressel (talk) 12:16, 16 July 2009 (UTC)

[edit] light beams repel each other?

What's this about? Do we have an article explaining the effect?

http://www.sciencedaily.com/releases/2009/07/090713131556.htm

Thanks. 70.90.174.101 (talk) 03:55, 15 July 2009 (UTC)

Article here (doi:10.1038/nphoton.2009.116), poorly formatted draft at arXiv:0903.5117. They seem to be talking about a nonlinear interaction in a medium which (they say) is already predicted by Maxwell's equations, so it's theoretically very old. It isn't literally a force between electromagnetic waves, but between charged particles in the medium. The reason for the newspaper reports is not that the paper is important, it's that Yale issued a press release, and most science reporters don't know how to do anything but parrot press releases. Why they issued the press release I don't know, but inevitably they're going to inflate the importance of the work because the point is to get free advertising for Yale. I would ignore it. The paper is science as usual, the reporting is horrible science reporting as usual. -- BenRG (talk) 10:08, 15 July 2009 (UTC)

Here is another recent article on the subject from LiveScience. ~A H 1^(TCU) 13:22, 15 July 2009 (UTC)

[edit] Psychology / Lying Videos

There are plenty of studies on facial tics, or microexpressions related to lying, but I'm curious if anyone knows of a source of videos or other resources on the specific issue. What I'm ultimately interested in are source videos that compare people lying to those that aren't, and in high enough format that they're useful. Bonus points if they involve law enforcement. I realize this is a tall order, but if there are any good studies (even without video) outside of what I can find on pubmed/jstor I'd be interested. Thanks. Shadowjams (talk) 05:27, 15 July 2009 (UTC)

Cross posted to the humanities page.

Click! Cuddlyable3 (talk) 13:25, 15 July 2009 (UTC)

[edit] torque

I want to show that the torque caused by gravity is equal to the torque that would be produced by an point particle of mass M at the centre of mass. I've been trying to evaluate the sum Σ (m_i*g*r_i*sin(θ)_i), but I haven't been able to reduce this to MRg*sinθ (where R denotes the position of the centre of mass). Is there a way to do this, or does it suffice to show that the total force due to gravity is equal to the force produced by a point particle of mass M at R, and then multiply this by R to get the torque? (I wouldn't think so). —Preceding unsigned comment added by 70.52.44.188 (talk) 05:44, 15 July 2009 (UTC)

I don't understand. About which point are you taking Torque ? If it is the centre of mass, as conventionally taken, wouldn't the torque that would be produced by an point particle of mass M at the centre of mass be zero ? Rkr1991 (talk) 05:58, 15 July 2009 (UTC)

Oh, well maybe this is a clearer explanation of what I'm asking (sorry if I can't explain myself properly!): Supposed an object is fixed in such a way that it will pivot about a certain axis. Assuming that the gravitational field is constant, what is the torque produced by gravity? I know that the answer should be MRxg, where R is the position vector of the centre of mass, but I don't know how to derive it. My normal approach would be to sum all the torques τ_i acting on each particle of the object, which by Newton's Third Law should equal the total external torque (ie the total torque produced by gravity, should that be the only external torque acting). On the other side of the equation, I get Σ (m_i*g*r_i*sin(θ)_i), which I'm having trouble evaluating. PS I know that the total force due to gravity can be treated as if the entire mass were concentrated on the centre of mass, but can we extrapolate from this that the total torque due to gravity is equal to MRxg? —Preceding unsigned comment added by 70.52.44.188 (talk) 06:29, 15 July 2009 (UTC)

$\mathbf{\tau}=\sum_i\mathbf{\tau}_i=\sum_i\mathbf{r}_i\times \mathbf{f}_i=\sum_i\mathbf{r}_i\times (m_i\mathbf{g})=(\sum_im_i\mathbf{r}_i)\times \mathbf{g}=M\mathbf{R}\times \mathbf{g}$ . Dauto (talk) 06:54, 15 July 2009 (UTC)

LoL that was easy, thanks. —Preceding unsigned comment added by 70.52.44.188 (talk) 07:03, 15 July 2009 (UTC)

[edit] Jade

What is the maximum percentage of iron in Tremolite (which forms jade). Is it possible to make tremolite and mix it with iron in, say, a factory?174.3.103.39 (talk) 08:32, 15 July 2009 (UTC)

The Nephrite variety of Jade consists of amphiboles in the solid solution series tremolite-actinolite-ferroactinolite. Jade is either iron-rich tremolite or actinolite, the former being lighter green and the latter darker. The maximum iron content for tremolite is 10% Fe of the total Fe+Mg, from 10-50% it's an actinolite, any higher then it's a ferroactinolite. Synthetic tremolite and actinolite certainly exist, but I doubt it would be cost effective to try to produce large quantities. Mikenorton (talk) 09:30, 15 July 2009 (UTC)

[edit] Water Wheel Power

Would it be possible to power a household which uses 1000 kWh per month using a water wheel? How big would it have to be and could I possibly build several smaller ones or is one big one the way to go? TheFutureAwaits (talk) 12:24, 15 July 2009 (UTC)

Micro_hydro#External_links shows other households that have done it. One of them is only getting 90W though, which wouldn't meet your needs. It seems worth further investigation. AlmostReadytoFly (talk) 13:12, 15 July 2009 (UTC)

By the way, 1000 kWh per month is 1369W. — DanielLC 14:15, 15 July 2009 (UTC)

A household usually has peak energy demands around 10kW though, so if you are only generating 2kW, probably can not run the refrigerator, the oven the AC and the clothes dryer at the same time. Googlemeister (talk) 14:29, 15 July 2009 (UTC)

The short version: yes. "Power via water wheel" is a useful approximation of hydroelectric power. Examining industrial applications, it's clear that multiple smaller systems are a useful way to scale requirements. As for "how big", a more useful question is what sort of water flow you need. This thermodynamics book includes a sample problem for ideal power generation at the Hoover Dam. Note that both water flow rate and elevation change are relevant to the power that can be supplied. — Lomn 14:45, 15 July 2009 (UTC)

Water power is far more reliable and continuous than solar or wind (unless the creek goes dry or the pipe freezes or the intake gets clogged with twigs). Your water wheel or Pelton wheel microgenerator should be sized to supply your peak load.This will be several times your average load. If you cogenerate, then the utility absorbs the excess and supplies the deficiency, reducing the required size and cost. For a Pelton wheel, high pressure water from a point quite elevated is desirable. The flow of water is the limiting factor for how many kilowatt hours you can produce before the water level drops. An old water wheel like mills of the 19th century is not the ideal way to run a generator, but is has been done. Years ago on TV they showed a former textile mill where a man had hooked up the old water wheel to an alternator,. It produced 30 kilowatts continuously. This would be 518,000 kilowatt hours each month, worth perhaps $20,000 when sold to the utility. It was probably extremely inefficient. The typical microhydro has a 100 foot drop from water intake to Pelton wheel and the flow is a few gallons per minute. As for number, for such a small load it would be practical and economical to buy one turbine/generator. If you set up to sell the surplus to the utility, then you should be able to use the utility as a backup, eliminating any advantage of multiple units. Keep things simple. See Micro hydro or Google the term. Some of the vendors can advise you on components suitable for your situation. Edison (talk) 16:20, 15 July 2009 (UTC)

Before you go ordering parts online and calculate a setup, check local EPA regulations and county water resource/use rules. Depending on your location you may have to provide alternative habitats for local wildlife, have to pay a fee for operating your water-wheel or it may be outright prohibited. Try to find an official in charge at your county government who can help you finding out what laws and regulations apply. Work your way up from there. (If you take this as legal advice, I'd have to instruct you to contact a lawyer instead.) 71.236.26.74 (talk) 17:41, 15 July 2009 (UTC)

This water wheel would give DC right? And most houses I know are wired to use AC, so there might need to be other modifications as well. Googlemeister (talk) 18:45, 15 July 2009 (UTC)

Probably - yes. But you're probably going to need to store the power for when you need it and to smooth out variation in your day/night demand cycle - so most likely, you'd have a basement full of car batteries that you'd charge from the water wheel - and then use an Inverter (electrical) to convert the output of the batteries to AC. SteveBaker (talk) 19:07, 15 July 2009 (UTC)

It might be more efficient to build a dam and only let through the amount of water you need at any given time. During off-peak times the water level behind the dam will build and then go down again during peak times. You might annoy being further downstream, though! --Tango (talk) 19:38, 15 July 2009 (UTC)

If you build a dam, the level of permitting needed may be quite high, since a dam which holds back a large volume of water can cause considerable damage if it fails. Microhydro often uses an intake which is not really a dam, above the falls of a stream, rather than having a dam sufficient to produce the required head. Microhydro often produces say 24 volt DC which is stored in batteries and converted to AC through an inverter. An inverter which ties to the utility may eliminate the need for batteries, as you cogenerate. Utility permission should be sought. They have brochures on how elaborate the interface and protective relaying has to be. It gets more complex as the generator gets larger. For a few kilowatts it should be minimal. Edison (talk) 21:58, 15 July 2009 (UTC)

Thanks for all the great info! So if I were to use a Pelton wheel to generate 1000 kwh per month is there a reasonable estimation of what the radius of the wheel would need to be? The water flows at about 5 mph and drops about 10 feet in the area I want to build the wheel although I suppose I could use tubes to divert the flow and create a steeper, higher pressure drop. TheFutureAwaits (talk) 21:03, 16 July 2009 (UTC)

Well, I'm not an expert on water-wheel design - but I'd guess that you want the weight of the water to be pushing down on the wheel for as much of the drop as possible because any water that falls through any distance without being attached to the wheel is wasting energy. However, to do that - you'd have to have a 20' wheel with the hub of the wheel level with the surface of the water - and having it drag through the water would cause a lot of energy loss...hence, I presume the basic design for a classic over-shot wheel (like in the photo to the right) where the water is fed in at the top of the wheel - roughly level with the inlet height - falls with the wheel for as close to half a rotation as you can manage - then empties out at the bottom - roughly level with the outflow height. That would require (in your case) a 10' diameter wheel. That would capture as much of the energy as possible. However, knowing the speed of the water doesn't help unless you also know the volume (ie the flow rate. After all - I could probably get a 5mph, 10' drop water flow from a super-soaker...but that's not going to turn a 10' diameter water wheel! You would need to vary the width of the wheel and/or the size of the 'buckets' or 'scoops' in order for it to store all of that volume of water as it falls - without any spilling over and going to waste. The knowing the volume of water that the wheel is holding would allow you to calculate the torque that the wheel could exert - and with appropriate adjustments for frictional losses, you could use that to estimate the energy output.

If you knew the flow rate (cubic feet per second or whatever) - we could make an estimate of the energy you might be able to extract...but without that information, we have no clue. SteveBaker (talk) 23:59, 16 July 2009 (UTC)

You may need a water turbine instead of a water wheel. (I would have thought they are synonyms, but there seems to be only a partial overlap.) This page says there are several options depending on the specifics of your site. [22] 71.236.26.74 (talk) 02:19, 17 July 2009 (UTC)

So would a Pelton wheel be considered a "water wheel" or a "water turbine"? 76.21.37.87 (talk) 04:08, 17 July 2009 (UTC)

I've just read the article Water turbine -- from what I gather, a 10' drop ain't enough for a Pelton wheel (it needs at least 15' for best efficiency), but a Kaplan turbine would be right at home with a 10' drop (in case you don't know, a Kaplan turbine is the kind of turbine that looks like a ship's propeller). So, TheFutureAwaits would be better off putting in a Kaplan turbine instead of a Pelton wheel. Also, SteveBaker, a Pelton wheel ain't like your regular water wheel cause it don't use the weight of the water but its velocity for propulsion -- so you don't have to install it level with the inflow, and in fact it's better to place it as low as possible so's you get the most velocity from the drop.

76.21.37.87 (talk) 04:25, 17 July 2009 (UTC)

Have you considered using a Banki turbine?71.236.26.74 (talk) 05:43, 17 July 2009 (UTC)

Good idea, 71 IP -- a Banki turbine's a better choice for a small / variable flow rate, while a Kaplan turbine's better for a fairly big, more-or-less constant flow rate. It really depends. 76.21.37.87 (talk) 05:59, 17 July 2009 (UTC)

There's also the maintenance issue. It says Bankis are easier to maintain. I remember the first private wind turbines often overtaxed their builders' time, energy and abilities that way. 71.236.26.74 (talk) 06:14, 17 July 2009 (UTC)

On second thought, the chart in the Water turbine article says a 10' drop's still not quite enough for a Banki turbine... 76.21.37.87 (talk) 06:43, 17 July 2009 (UTC)

I should get a job at Nasa :-). The chart's in meters. OP only has a 3 m drop. Kaplan it is. (I should buy myself a trout and whack myself.) 71.236.26.74 (talk) 18:17, 17 July 2009 (UTC)

Hahaha, good one! LOL! 76.21.37.87 (talk) 01:38, 18 July 2009 (UTC)

As an aside, if the flow rate is more-or-less constant, the OP should consider a Kaplan turbine with fixed-pitch blades instead of variable-pitch, it should save him / her a whole bunch of maintenance. If the flow rate is very variable, though, then variable-pitch blades are the only option.

76.21.37.87 (talk) 01:38, 18 July 2009 (UTC)

[edit] What are pavement cells?

The English wiktionary defines "pavement cell" as Brachycystidia in the gills of some species of Coprinus. But pavement cells also exist in plants. So what exactly is a pavement cell? --Leptictidium (mt) 13:28, 15 July 2009 (UTC)

I'm not familiar with pavement cells of any sort, but I can tell you that it is quite common in microbiology for names like that to be given to multiple things that have no meaningful relationship to each other. In the brain, for example, there are "granule cells" all over the place, and the only thing they have in common is that they are all small. Most likely "pavement cells" are just cells that look sort of like they are paving a surface, under a microscope. Looie496 (talk) 14:26, 15 July 2009 (UTC)

In plants a pavement cell is an unspecialized epidermal cell, from which the other types of cell in the epidermis (outer covering of the plant) develop. Mikenorton (talk) 14:35, 15 July 2009 (UTC)

In fish, pavement cells are also known as 'respiratory cells' and in saltwater fish they are very flat, so Looie is likely to be right in suggesting that they have been named for their shape, rather than any biological similarity to plant epidermal cells. Mikenorton (talk) 14:59, 15 July 2009 (UTC)

[edit] Cleaning oil stain from thermal plastic elastomer

How would one clean oil off of the surface of a thermal plastic elastomer (mixture of PVC and silicone)? I've tried soap and water. Also alcohol, but no luck. --68.102.170.184 (talk) 13:43, 15 July 2009 (UTC)

Use WD40 on an absorbant rag or towel.

You can clean the wd40 off with soap.

83.100.250.79 (talk) 16:11, 15 July 2009 (UTC)

Wouldn't that melt the PVC? --68.102.170.184 (talk) 11:27, 16 July 2009 (UTC)

No.83.100.250.79 (talk) 13:57, 16 July 2009 (UTC)

[edit] Computer chassis of sisal?

How likely do you think it is that a small computer which makes a computer case made of water-proofed sisal woven over a frame, will be adopted by major computer companies like Dell and HP? N.B. sisal would save energy by allowing heat to escape. (Cross-posted to computing board) --Patar knight - ^chat/_{contributions} 17:43, 15 July 2009 (UTC)

People who run their computers with the case off not uncommonly fry some part because the airflow generated by the fans no longer reaches that part. Manufacturers'd have to start over with testing for airflow/heat management. Other than the flow in an enclosed case, the leakage through your "open" case would be hard to quantify and would likely vary wildly. Dust entering the case and sisal fibers disintegrating from the weave would be other factors to consider. You could coat the fiber to prevent that, but that would somehow run counter to the whole "natural" idea. Admitting that most computers would be obsolete and replaced before the case got too grimy would also not in the manufacturers' best interest. There might possibly be a small market in the ecologically conscious home computer market, but for most business applications it's rather unlikely to become a widespread option IMHO. 71.236.26.74 (talk) 18:01, 15 July 2009 (UTC)

It strikes me as a remarkably bad idea to make a computer case out of flammable material. Looie496 (talk) 18:12, 15 July 2009 (UTC)

I thought of that at first, but quite a few plastic materials used for cases start out as "Class A" and just reach higher grade by having Flame retardants added. If it works on cotton it should work on sisal, too. (See the article why that would make the case a lot less "green") 71.236.26.74 (talk) 18:46, 15 July 2009 (UTC)

I think you could extract fibres from the sisal and make some sort of a paper mache-like substance that would make a reasonable case - it could easily be treated to make it fire-resistant. The problem would certainly be heat though - a metal case acts like a huge heat-sink - a case made of pretty much any kind of plant material would probably make a good insulator - and that's a disaster.

However, this is all really unnecessary. Computer cases are commonly made of aluminium^{[citation needed]} - and that's a VERY recyclable metal. It would be simple to dump computer case panels into the same recycling stream as old coke cans. The difficulty with recycling computers isn't the case - it's the circuit boards, hard drives, keyboards and (especially) displays. These are very 'mixed' materials which are almost impossible to separate out into useful recycling streams. A typical circuit board has fibreglass and resin for the board itself - with layers of valuable copper buried inside it and bonded very firmly to it's surface - with lead/tin alloy solder firmly affixed to it, plastic and ceramic chip casings, all manner of little plastic and brass parts. Steel connectors often with gold plating. Then inside the chips you've got silicon, more gold, who-knows-what nasty stuff inside resistors, capacitors and any little batteries and such - all kinds of exotic metals inside things like LED's. Glass and LCD-panel monitors are an even bigger nightmare - lead and phosphors in the CRT, weird liquid crystal chemicals in the LCD's. Power supplies often have toxic chemicals in the windings of the transformer coils. It's really a mess to sort this out in a cost-effective way.

So fixing the problem of recycling the cases of old computers is solving a non-problem and creating a bunch of new problems (as alluded to above) in the process. What's needed (and it's hard to see how it'll happen) is to figure out how to recycle everything OTHER than the case.

If for some reason we were really passionate about case recycling, the solution (since cases never break or wear out) would be to require the circuitry of all new computers to fit into a standard sized case (deskside computers pretty much do that already). The manufacturers could then offer to sell you a new set of electronics that slotted right in to your existing case. This isn't difficult for an individual person to deal with. I haven't bought a new computer for 16 years! I just keep swapping out parts (and occasionally cases) from one generation of machine to the next.

SteveBaker (talk) 18:57, 15 July 2009 (UTC)

Computer cases=steel not Al, Transformer windings = not toxic at all really - just glue. (Large industrial transformers from the 1960s ~10kW+ = toxic yes). 83.100.250.79 (talk) 22:31, 15 July 2009 (UTC)

(83.100.250.79: Please don't interpose your replies in the middle of someone else's comments - it rapidly gets very confusing. I've moved your reply to the proper place). Anyway - the cases of all three of my home PC's are aluminium - including all of the internal rails and bracings...there may be the odd steel one - but it doesn't change the conclusions. Steel (like most other pure metals) is also childishly easy to recycle. It's not the problem here. Consider recycling CRT's, hard drives and motherboards...it's tough. I'll take your word for the nature of the goop in the transformer windings - but again, the precise details don't matter - the issue is that there are a LOT of weird and wonderful materials (many of them toxic) inside a typical computer - and sorting them out at any reasonable price is FAR beyond our current ability. SteveBaker (talk) 07:14, 16 July 2009 (UTC)

sorry that was an accident

Actually I don't totally agree on the toxicity of computer parts - in a landfill there's no much issue, BUT if they are incinerated then yes there is a toxicity issue.

One part that is trivially recyclable is the solder. It's also possible to extract the copper by shredding and density separation - I'm not sure if this is economically viable. As part of the desoldering recycling operation there should be all the surface mount components separated - as for re-using these - I doubt intel et al would be very keen on losing out on the obsolescence/replace product lifestyle. The chips, capacitors, and resitors I wouldn't know what to do with - possibly the caps could be density separated and recycled. That leaves the ICs mostly - as far as I know they are totally unrecyclable in terms of materials/energy - especiallly in an economic sense. (Though they do have a store of energy as order - so if you can make a "order converts to entropy=electricity" machine you might be onto a winner. One product of the recycling process I've left out is the shredder glass fibre/epoxy board - any suggestions as to what to do with this.

Recycling of electronic parts can be done, and is done - though not total recycling. And only a fraction of the waste goods actually gets recycled as far as I know.83.100.250.79 (talk) 14:59, 16 July 2009 (UTC)83.100.250.79 (talk) 14:19, 16 July 2009 (UTC)

The capacitors and resistors could be taken out and resold, as long as they're still in working order. 76.21.37.87 (talk) 04:30, 17 July 2009 (UTC)

Desktop and deskside computer cases are easy to re-use if you really want to. If you don't want to re-use the case, they are also trivially easy to recycle, since they have effectively the same mix of materials as an automobile body. On average there are thousands of times more material in car bodies than in computer cases, so the computer cases have effectively zero additional impact on recycling if done correctly (i.e., throw the old case in the back of a car on the way to the car recycling center, or if your municipal garbage system uses magnets to separate out the steel, the cases will be treated like "tin" cans.) For servers and other large installations, the industry is trying to find more elegant solutions such as blade computers that have relatively less case material per computer. As Steve said above, the stuff inside the case a a much bigger problem. If you have a computer at home, you should worry about the energy it uses, not about recyclinghte case. You can also worry about all tjhe plastic in a laptop case, but these are more similar to other small appliances. Computers are becomming a whole lot more effecient by every purely technical measure: cost per instruction executes, power per instruction exececuted, weight (material to recycle per instruction executed.) A modern Mac mini or plug computer is massivley more capable than a ten-year-old desktop, but uses less tha a tenth of the energy or material. Unfortunately, we all just keep upgrading to better conputers and then don't actually use the extra capability. This appears to be changiong somwhat with the advent of the netbook. -Arch dude (talk) 22:05, 15 July 2009 (UTC)

Arising from the above, are computer cases made out of aluminium rather than steel

because it's cheaper,
because it's lighter, or
because it prevents people using office/fridge magnets to attach things, thereby damaging the disks? 87.194.161.147 (talk) 12:54, 16 July 2009 (UTC)

I'm still amazed that computer cases are made of Al, the ones I'm aware of have all had a skin of steel or plastic.(Not counting mac books etc) However I accept SteveBakers comments about the rails (ie the internal frame and attachment points) being made made out of Al - there is one really good reason for this - and that's that alumimium is a lot easier to machine than steel - specifically putting screw holes in steel is a lot harder. Al is not cheaper. I doubt the reason is lightness (excluding laptops were this matters)83.100.250.79 (talk) 14:04, 16 July 2009 (UTC)

I'm skeptical about the aluminium case too. All the aluminium cases I've seen are premium cases like Lian-Li cases, whereas most normal cases are made from SECC (most, if not all, of these and these are made from steel). I'm putting a [citation needed] tag on Steve's claim. --antilived^{T | C | G} 01:39, 17 July 2009 (UTC)

[edit] decarboxylation

I assume carbon dioxide a good leaving group? What's the mechanism of heat-driven decarboxylation usually, e.g. like in THC? I can't imagine protons being good nucleophiles, however... does the CO2 usually take the electrons with it? Does the bond cleave homolytically?

I suspect the CO2 LG takes the bonding electrons with it, such that you get a carbocation (or a carbocation-like transition state?) -- would that explain why longer-chain COOH's are easier to decarboxylate? Is a tert-COOH group the easiest to decarboxylate? John Riemann Soong (talk) 18:24, 15 July 2009 (UTC)

Generally, it's aromatic COOH groups (such as the one in salicylic acid that are the easiest to decarboxylate (even easier than tert-COOH groups). FWIW 76.21.37.87 (talk) 01:26, 16 July 2009 (UTC)

Someone uploaded an image displaying the mechanism for the decarboxylation of a ketoacid. I haven't been able to find the mechanism of decarboxylation of something like acetic acid.

http://commons.wikimedia.org/wiki/File:3-ketoacid_decarboxylation_mechanism.PNG Calamus Fortis 21:17, 15 July 2009 (UTC)

"does the CO2 usually take the electrons with it" sounds like you will have a redox problem, unless you plan on losing H^– (hydride) later:

RCOOH → R⁺ + ^–COOH

And homolytic cleavage of C-C bonds is also unlikely unless you have some radical initiator. Is there a reason you need to look further than

RCOOH → RCOO^– + H⁺
RCOO^– → R^– + CO₂

? The two examples given, salicylic acid (which looks like the relevant substructure in THC) and β-ketoacid, in essence each just help accelerate one or both of those steps. A Lewis base intramolecular deprotonation (step #1) via 6-membered transition-state looks even better than "just" an acid doing its acidic business, and making it a 6-e^– pericyclic reaction with no formal charges in product is easier than two steps with charged alkyl structures. DMacks (talk) 05:13, 16 July 2009 (UTC)

[edit] coommon cold

why do we get cold after we drench our head in rain for long19:02, 15 July 2009 (UTC)117.197.208.57 (talk) 19:02, 15 July 2009 (UTC)

Several reasons come to mind. One would be that the temperature of the water you are drenching your head with is usually cooler then the ambient air temperature and almost certainly cooler then your body surface temperature. Added to that, when the water evaporates, it takes away heat similar to how an ice cube works to cool your drink. Finally, sometimes your sense of touch has a difficult time telling the difference between damp and cool. Googlemeister (talk) 19:18, 15 July 2009 (UTC)

The OP might be referring to contracting the common cold rather than feeling the sensation of coldness. Algebraist 19:21, 15 July 2009 (UTC)

Our article on the common cold notes that current science finds no causal link between cold weather and the cold. While behavior favored in cold weather increases your likelihood of getting sick, and while exposure to cold weather can cause cold-like symptoms, standing in the rain does not increase your chances of getting the cold. — Lomn 19:45, 15 July 2009 (UTC)

Lowering your body temperature weaksn your immune response, doesn't it? Could make catching a cold easier. Vimescarrot (talk) 23:15, 15 July 2009 (UTC)

That's actually a back-formed explanation for the old-wives tale that having a wet head causes the common cold. While having a chronicly low body temperature (like hypothermia levels) may weaken the immune system, at that point you have other things to worry about than the sniffle you may get. When studies have been done, there is no causal link between ANY non-infectious external stressors and getting a cold. You get a cold because you have been in contact with someone else with a cold. And that's about it. --Jayron32.talk.say no to drama 01:15, 16 July 2009 (UTC)

According to these British researchers the final word isn't out yet on cold weather and colds [23]. However OP seems to have the top and bottom confused according to this link [24] also featured in our article it's cold feet, rather than a cold head that contributes to catching a cold. 71.236.26.74 (talk) 05:22, 16 July 2009 (UTC)

It's very simple really. Water, in it's native state, is cold. Our heads are very warm. So, cold things make hot things colder. Vranak (talk) 18:44, 16 July 2009 (UTC)

And exposure to cold temperatures can cause vasoconstriction, which keeps white cells from getting where they're needed -- so it could make it easier to catch a bug (although it doesn't by itself cause the common cold). FWIW 76.21.37.87 (talk) 05:37, 17 July 2009 (UTC)

[edit] question about ticks

I was reading our article about ticks and came across this

"Some species stalk the host from ground level, emerging from cracks or crevices located in the woods or even inside a home or kennel, where infestations of "seed ticks" (the six-legged stage of newborn ticks) can attack in numbers up to 3,000 at a time[citation needed]. Weak or elderly dogs and puppies are particularly endangered and can die from anemia from a sudden influx of seed ticks[citation needed]. Seed ticks also attack horses, cattle, moose, lions and other mammals, causing anemia, various diseases, paralysis and even death."

This sounds rather unlikely, but I do not know enough about ticks to know if this is vandalism, or what. Does anyone know about these seed ticks? Googlemeister (talk) 19:05, 15 July 2009 (UTC)

wikipedia seems broken, google keywords from your text and you'll find the pages it's from. Could't save edit with links - getting "out of captcha". 71.236.26.74 (talk) 20:04, 15 July 2009 (UTC)

I poked around in Google Book search, and although I didn't find any mentions of seed ticks specifically causing anemia, I did find many references to ticks causing anemia, and to seed tick infestation of livestock. So it doesn't seem too improbable to me, based on the minimal amount of research I did. —Dominus (talk) 20:49, 15 July 2009 (UTC)

I know original research is frowned upon but I witnessed in southern Spain, several years ago, many hundreds of tiny ticks ascending the wall of an enclosed yard where two dogs had previously been kept. It was an unnerving experience. Richard Avery (talk) 21:41, 15 July 2009 (UTC)

Hope it'll work this time. googling gave following ghits [25] mentions anemia, [26] seems like a likely source for the numbers. 71.236.26.74 (talk) 04:35, 16 July 2009 (UTC)

[edit] Calculating the odds

How the heck does Spock calculate the odds on things? He is always doing this in Star Trek. Are the odds quoted in the dialogue accurate or are they just technobabble? —Preceding unsigned comment added by 216.154.20.38 (talk) 19:32, 15 July 2009 (UTC)

Star Trek is fiction. The circumstances it portrays are fiction. Any odds related to those circumstances are fiction. We could make in-universe guesses about "how Spock does it" (my guess is that computers are good at math), but at the end of the day, the writers pick a number backed up by an uncertain degree of educated guesswork. — Lomn 19:40, 15 July 2009 (UTC)

It's probably just technobabble. If you give a specific example we can try and see if we can work out how the odds would be calculated. --Tango (talk) 19:44, 15 July 2009 (UTC)

No - that's really the whole problem. Jim will say "Call the guards - I'll pretend to have a mild tummy ache and when they rush in you just do the old Vulcan neck pinch - then we'll grab their guns and fight our way out through that army of guys with oddly wrinkled foreheads." - then Spock will say "But the odd of that working are only 2.34574950596%" - and then they go do it anyway and it works. There is simply no way to put "odds" on that because the 'unknowns' are easily enough to push the error bars on the estimate out to 100% such that any decision based on that estimate would be no better than flipping a coin. The problem with writing a script for a supremely logical being is that scripts are written by script writers - who are without doubt NOT supremely logical people! SteveBaker (talk) 22:00, 15 July 2009 (UTC)

Obviously he asks C3PO Googlemeister (talk) 19:52, 15 July 2009 (UTC)

Who, in turn asked Twiki <shudder> - who asked B-9 (who is 97.43% likely to continue have no Wikipedia article written about him by about the middle of next week) SteveBaker (talk) 21:53, 15 July 2009 (UTC)

Who IS B-9, anyway? 76.21.37.87 (talk) 01:34, 16 July 2009 (UTC)

B-9 is the robot from the original "Lost in Space" TV series who says "DANGER, Will Robinson, DANGER!"...whilst waving his arms around crazily (I'd like to meet the programmer who thought THAT was a useful engineering feature!) and being completely unable to tell anyone what the danger actually is! He also gave probability estimates with crazy over-precision for unfathomable events. (You can just imagine the scene at NASA's robotics division: "Hey boss - I'm coding the emergency response subroutine for the new B-9 'bot. I'm thinking that it should say "DANGER!" in a loud, assertive voice, flash it's front-panel lights and then carefully explain the reason for the emergency?"..."Well, that's alright but could you maybe make it also mention the names of any nearby crew members whom it happens to like? Oh - and how do you feel about making it wave it's arms around in a wild and panicky way? But do we really need to bother explaining what the danger is? I think we could save some money and not bother implementing that part.") SteveBaker (talk) 09:02, 16 July 2009 (UTC)

Thanks for the answer, Steve, I'll try and create an article about B-9 if I have time. 76.21.37.87 (talk) 04:36, 17 July 2009 (UTC)

The worst thing about Spock's estimates is that they are ALWAYS wrong. SPOCK: "Well Captain, we've only got a 1.234% chance of getting away with your crazy plan." - KIRK: "That's good enough for me!"...and Kirk is always right (or at least extremely and consistently lucky). You're left just itching to hear: SPOCK: "Your plan has a 99.99% chance of working!"...but we just know that Kirk would then think of an even sillier plan. SteveBaker (talk) 21:53, 15 July 2009 (UTC)

Ironically, the law of large numbers should start to kick in (well, 72 episodes or something). If Spock consistently suggests the odds of success are 10%, doesn't that mean that by the end of 10 shows, there should have been 9 catastrophic failures? There are only so many times you can "beat the odds" before you must conclude that the odds were not properly calculated. Nimur (talk) 22:15, 15 July 2009 (UTC)

And that's really the horrible part of it: Spock is supposed to be amazingly logical - yet he seemingly ignores his own utter failure at estimating realistic odds. Worse still, he always gives a ridiculous amount of precision to his estimates - which is really not the sign of a logical mind. The script writers couldn't resist doing the same thing with "Data" in STTNG - but at least the remainder of the crew are given the opportunity to mock him for doing it. They made an entire plot-line out of Data's inability to speak 'contractions' (do not - rather than don't, etc) - where his "brother" is able to do so easily. Data continually strives to be more human no matter the cost - and is able to reprogram himself and teach himself singing, painting, playing a musical instrument and (with rather less success), dancing...yet he is quite unable to add the following five lines of code to the input of his speech unit:

  if ( situation == casual && word [ n ] == "do" && word [ n+1 ] == "not" )
  {
    word [ n ] = "don't" ;
    word [n+1] = "" ;
  }

...but this is why it's fiction...other than that the scriptwriters needed this in order to 'sell' the character - there is no reason for it. Why did Suung fail to use a more realistic color of plastic on Data's skin when almost every other aspect of his master-work is so stunningly human? And for chrissakes why doesn't the Enterprise raise it's shields automatically when an unrecognised craft comes within 10,000km rather than waiting for some dithery old captain to tell the weapons officer guy to do it?!? SteveBaker (talk) 23:07, 15 July 2009 (UTC)

"Captain, what shall we do?" "Commander Data? Commander Data?". --Sean 13:48, 16 July 2009 (UTC)

Fortunately, Data isn't programmed in C++... SteveBaker (talk) 23:40, 16 July 2009 (UTC)

Steve you raised the subject of English contractions. Check your usage of it's and its. Cuddlyable3 (talk) 10:39, 16 July 2009 (UTC)

I'm not self-reprogrammable. Hence fixing that bug is a little harder! SteveBaker (talk) 23:40, 16 July 2009 (UTC)

Two points here : 1) Even if I knew that it was standard operating procedure for the computer to raise shields automatically on a "Red Alert", I might still give the order to double-check. Especially with the number of automation problems Enterprise seems to have. (It would also give me a few extra seconds to think before my crew expected some brilliantly unorthodox solution to the crisis.) 2) There are probably lots of times where Spock estimates some mundane thing and is right. If Spock says "I estimate a 97.25% chance we will survive this with no difficulty." and then he turns out to be right, it wouldn't wind up on TV. We have to assume that there are 'ordinary' missions between the exciting ones that make it on the show. Otherwise the entire crew would be insane by the end of the first season. APL (talk) 05:36, 16 July 2009 (UTC)

"Red Alert" is supposed to raise them automatically, according to an episode of ENT. So why the captain needs to say so is unfathomable. If you calculate it, the chances of a 10% plan working 10 times in a row are small - but not impossible. If you were enacting daring plans that were fairly likely to succeed - who'd want to watch something that boring? Vimescarrot (talk) 23:14, 15 July 2009 (UTC)

In their defence, his problem may have been with working when they should and shouldn't be used - it isn't as simple as casual vs formal. It depends on the emphasis, intonation and even cadence of the sentence. --Tango (talk) 00:23, 16 July 2009 (UTC)

The new film made similar mistakes. In the early sequence, everybody on the bridge of whatever ship it was is being blinded by some time travel anomaly thing, which is looming huge and ridiculously bright out the viewscreen. Finally the captain arrives on the bridge and says, "Computer: polarise viewscreen" which causes a sunglasses-style darkening to slowly wipe down over the viewscreen. I almost choked at the idiocy of this and the way it heralded further potential idiocies almost ruined the film for me. Why didn't the viewscreen do that automatically? I wondered. Why does nobody else on the bridge have the authority to order that? Star Trek - especially the original series - is written to be cinematic and entertaining to the seething masses who aren't likely to think too much about it, not to be realistic or sensible. Maelin (Talk | Contribs) 01:18, 16 July 2009 (UTC)

Even the captain's order doesn't make sense. The viewscreen isn't some kind of periscope where the same light as is emitted by the object you are looking at gets to your eye - it's a camera and a screen. Polarised lenses block light, that isn't needed when there is a computer inbetween the object and the image. --Tango (talk) 04:42, 16 July 2009 (UTC)

No. A polarizing filter reduces reflections from non-metallic surfaces and can increase the contrast of sky views. It is equally useful with the eye or with a camera. Cuddlyable3 (talk) 10:52, 16 July 2009 (UTC)

Yes, but I don't think that's what was intended. I haven't actually seen the film yet, but it sounds like it was just meant to darken the image in the same way sunglasses work. --Tango (talk) 12:44, 16 July 2009 (UTC)

It's not as bad as Total Recall, though. They have a big red button that has to be pressed to close the shutters and prevent the air being sucked out and taking the people with it. --Tango (talk) 12:44, 16 July 2009 (UTC)

Um, why is this at the Science desk anyways. Let's see, for those of you that take this shit WAY to seriously, Dramatic tension and Plot device and Macguffin are good places to start. The whole point is that Spock makes the situation look worse because he decides there's no way Kirk can work his way out of it. When Kirk does it's even more amazing. There's not anything more complicated than that. Of course, since it is a work of fiction, 100% of the time the ending is predetermined. --Jayron32.talk.say no to drama 01:11, 16 July 2009 (UTC)

Spock could be making some rough assumptions, and then estimating the odds out to way too many decimal places. (Perhaps to show off his innate Vulcan ability for mental math?) It's like he's doing a Fermi problem and giving the answer to the nearest hundredth of a piano tuner. APL (talk) 05:30, 16 July 2009 (UTC)

The best place I know of to discuss this is here: [27]. — DanielLC 04:36, 17 July 2009 (UTC)

[edit] What is the danger of using 3-ohm speakers with 4-ohm receiver?

(Cross-posted from Entertainment desk on advice of someone there) My A/V receiver says the minimum speaker impedance it supports is 4 ohms. You have to set it to a special setting for 4-ohm speakers which I have done. But my front left and right speakers say that their impedance is 3 ohms. What is the danger in this? Is the danger to my speakers (which would be okay), or to my receiver (which would not be okay)? Thanks, Mike R (talk) 19:58, 15 July 2009 (UTC)

This discussion (http://www.soundreproduction.com/discussion/loudspeaker/messages/528.html) suggests running 3-ohm speakers on 4-ohm receiver will potentially lead to overheating. ny156uk (talk) 21:11, 15 July 2009 (UTC)

There isn’t that big of a difference between 3 and 4 ohms in this situation. You’re unlikely to cause damage to either your receiver or your speakers. The power that your speakers would need to handle if the volume was cranked all the way up will be a little more than if they were 4 ohm speakers, but that’s unlikely to be a problem as long as the volume is kept at a reasonable level. Because of the lower speaker impedance, the damping factor is going to be a little lower than the designers intended when they were planning the receiver’s impedance bridging, so the audio quality may be slightly lower than if the speakers were 4 ohms. But most people wouldn’t hear a noticable difference. Red Act (talk) 21:20, 15 July 2009 (UTC)

It would be difficult to say whether the speakers or the output stage transistors would fail first if you connected 3 ohm speakers to an amp rated at 4 ohms minimum and cranked up the volume, but as a testing engineer, I wish I could be there when the smoke test was performed. Edison (talk) 01:40, 16 July 2009 (UTC)

Would you by any chance know the power rating (wattage rating) of your amp, and of your speakers? That would be helpful to help judge which of your amp or your speakers would get smoked first if the volume got cranked too high.

Edison’s EE-fu is much stronger than mine (I have a minor in EE and a little professional experience with electronics, but Edison's a fully qualified, experienced pro), but it seems like your amp probably ought to be safe as long as it wasn’t turned up more than about ¾ of the way. If I were in your shoes, though, I would probably limit it to turning it up to no more than half way, though, just to provide an extra margin of safety. Depending on the power rating of your speakers, it’s possible that they wouldn’t be able to handle the volume turned up even half way (or they might possibly be able to handle the volume turned all the way up), but it sounds like you aren’t as concerned about potential damage to your speakers as to your amp.

When I said that you were unlikely to cause any damage to your amp or speakers, I guess I was making the assumption that you like listening to your music at a peaceful, calm level like I do. I never come anywhere close to pushing the limits of my amp or my speakers. However, rereading your post, there’s actually nothing in your post that precludes the possibility that you’re someone who’s wanting to crank your system as high as you can possibly take it. Were you hoping to blast some AC/DC at full volume, or were you just wanting to peacefully mellow out to a little Bach? (The type of music isn’t actually important, of course, just the volume.) Red Act (talk) 05:01, 16 July 2009 (UTC)

Fry's no longer is as well stocked in small parts as they used to be, but it should be no problem to find a small case, a 1 ohm resistor and a couple of connectors (plug/socket) online. Heck, if you don't trust yourself with a soldering iron you can probably even find the wire-wrap no-solder type somewhere. Tinker, tinker plug-in, problem solved. 71.236.26.74 (talk) 08:48, 16 July 2009 (UTC)

Actual loudspeaker impedance is more complicated than just the quoted nominal impedance. The output power of audio amplifiers is usually specified for a simple resistor load even though that is not typical of a loudspeaker. The shape of the curve in the above link suggests that changing from a 4 ohm to a 3 ohm speaker would only cause a slight loss of damping at a few hundred Hz which might give some barely perceptible ringing. (Putting a 1 ohm resistor in series makes this worse not better.) Cuddlyable3 (talk) 11:21, 16 July 2009 (UTC)

Besides damping factor, there is the actual power dissipation to consider. Voice coils on loudspeaker can overheat and burn out. If the amp were putting out an average power of 40 watts per channel the 1 ohm resistor would have to dissipate 10 watts when in series with a 3 ohm speaker (ignoring resistance of the resistor versus impedance of the speaker). A 1 watt resistor would burn out after a while. Avoid injury or property damage which might result from smoking the resistor. Speaker cones can also tear, which the OP did not indicate was a big worry. Edison (talk) 19:12, 16 July 2009 (UTC)

[edit] July 16

[edit] The Cancer Genome Atlas

Did they name it that just so the abbreviation would be composed of letters that represent the bases of DNA? or is it just a coinkydink? —Preceding unsigned comment added by 129.64.55.234 (talk) 13:35, 16 July 2009 (UTC)

I like your explanation. You could be right, it's certainly been noted before. AlmostReadytoFly (talk) 13:43, 16 July 2009 (UTC)

While I don't see a specific "what's the name mean?" on their site, "TCGA" strikes me as too topical to be a coincidence. I would guess that there's a degree of backronyming at work. — Lomn 13:45, 16 July 2009 (UTC)

I mean, "Atlas" is an interesting word to use. They could have easily named it The Cancer Genome Project. Maybe they got bored of the word "Project" 129.64.55.234 (talk) 14:02, 16 July 2009 (UTC)

A "gene atlas" (hmm...no article?) is a common term for this kind of thing. DMacks (talk) 14:58, 16 July 2009 (UTC)

[edit] Plants listed by oxygen production/toxin removal

I recently watched a Ted Lecture [28] by Kamal Meattle in which he outlines how to create an oxygen neutral building by using 3 varieties of plants that:

-Remove Toxins from the air (Money Plants)

-Provide oxygen during the day (Areca Palms)

-Provide oxygen during the night (Mother-in-law's Tongues)

The specific plants he names might not work for me because of sunlight/space/decor/availablity reasons in my home. Where can I find a list of common household plants in order of oxygen production? Or by Toxin removing ability (I know that can be ambiguous)? How much do these attributes vary from plant to plant (Does it even matter what plants I get?)

I had been under the assumption that oxygen production was based off sun facing surface area of the plant and how much of that sunlight it processes, since the oxygen is a byproduct of photosynthesis, but then it seem strange that plants would produce any oxygen at night, like the Mother-in-law's Tongue, so I am now comptelely lost as to what determines the above attributes.

Any other advice to what plants I can use to improve air quality in my home will be greatly appreciated. Anythingapplied (talk) 20:09, 16 July 2009 (UTC)

I suspect that guy is a crank and should be ignored. His biography (linked to from that page) doesn't suggest any scientific training and his technique makes no sense. As you say, oxygen is produced by photosynthesis, it can't be produced at night (unless you leave your office lights on over night, I guess). As for removing toxins, as far as I am aware the only "toxin" plants remove from the air is carbon dioxide, also by photosynthesis, and you don't need to worry about that as long as you have reasonable ventilation. --Tango (talk) 21:04, 16 July 2009 (UTC)

People who give talks at TED (conference) are not usually cranks - and should almost certainly not be ignored. As it happens, it looks like all of his claims have at least some truth to them. Our article on Sansevieria trifasciata (Mother-in-law's tongue) says (with a pretty decent reference) that they remove "certain" toxins from the air and can flourish in low light levels. That may well mean that they can continue to do photosynthesis under artificial lighting - which may be why Meattle thinks they emit oxygen at night...but in complete darkness, that seems impossible. There are three completely different plants called Money plants - but I suspect he means Epipremnum aureum which (according to our article) is good at sucking up all sorts of pollutants. Areca is a family of about 50 different kinds of palm tree - we only have articles on a few of them - and most of those are slim on details - but Areca catechu is claimed to be a popular indoor plant so that's probably what this guy is talking about...however, pretty much all green plants will produce oxygen during the day...so that's an easy choice. SteveBaker (talk) 23:34, 16 July 2009 (UTC)

Your "decent reference" is a broken link... Given that any half decent ventilation will get plenty of oxygen into a building, I'm still voting crank. Even TED can get fooled. --Tango (talk) 00:19, 17 July 2009 (UTC)

You are entirely wrong. The reference is to a scientific paper - the link to a copy of the paper on the NASA site is broken - but simply typing the title into Google and accepting the first hit gives you the paper. Did you watch the TED lecture? Ventilating a building is not "oxygen neutral" and it wastes heating/airconditioning energy. The goal of making a building oxygen-neutral has value. SteveBaker (talk) 02:49, 17 July 2009 (UTC)

Nasa has a couple of pages, this one works [29] and discusses TCE, Benzene and Formaldehyde reduced in a chamber of plants. They don't single out Sansevieria. A place called Stennis Space Center seems to have studied plants for cleaning air and waste water. BTW: Pollutant would probably be a better term than Toxin here. Maybe that's what is causing the confusion. 71.236.26.74 (talk) 00:36, 17 July 2009 (UTC)

Actually, that's a good ref. The reason why words like "toxin" and "polutant" and things like that are often dismissed is because of their non-specific nature which makes claims which use those terms largely unfalsifiable. If you want to believe a claim, find one that lists specific compounds which are filtered by the plants. Which it looks like you have done. But in general, that's why words like "toxin" are clear bullshit markers. Nothing filters "toxins". Things may filter or remove specific compounds or classes of compounds, but if so then those compounds can be identified, and any serious scientificly-based report on such methods WILL list those compounds. If it doesn't, it's bullshit. --Jayron32.talk.say no to drama 01:48, 17 July 2009 (UTC)

If anyone could find an explanation of the mechanism somewhere could you post a link? I've found a couple of studies for quantative analyses, but nothing explaining the mechanism so far. 71.236.26.74 (talk) 02:43, 17 July 2009 (UTC)

Is someone here planning to build a spaceship / nuclear submarine? Cause these are the only two applications I know of where being "oxygen-neutral" would matter at all.76.21.37.87 (talk) 04:42, 17 July 2009 (UTC)

Thanks guys for all your help. I'm not sure I know much about which ones produce more oxygen than others, but the NASA link was very helpful for toxin. Apparently the NASA stuff was already on Wikipedia and I wasn't looking hard enough: List_of_air-filtering_soil_and_plants. While you do have a point 76.21, by putting enough plants in my house to cancel out my oxygen use in addition to it already be ventilated I am actually creating an oxygen rich environment, so perhaps I shouldn't be expressing my desire as specifically archiving an "oxygen-neutral" environment. Plus, I think ANY submarine would probably want to be oxygen neutral, not just nuclear ones. The scientific names were actually in the video now that I look back at it:

Chrysalidocarpus lutescens, Epipremnum aureum, and Sansevieria trifasciata

Which are actually all from the NASA list, credited for removing xylene and toluene for the first one in the above list and formaldehyde for the second two.

Out of curiosity, any idea how many plants I would need to provide for 1 person's oxygen needs? Anythingapplied (talk) 05:16, 17 July 2009 (UTC)

[edit] Parasympatholytica

Where can I find a list of parasympatholytic drugs? (Need not be drugs prescribed by medics, just chemicals that act as parasympatholytica no matter of strength or side effects.)

Second question: if the parasympathic nervous system was malfunctioning (to any degree) what would be the effects on the body?

No, I'm not trying to poison someone, there would be easier ways and besides, wikipedians are not to give legal advice anyway. 95.112.156.108 (talk) 20:41, 16 July 2009 (UTC)

Did you see our article on Parasympatholytic drugs? There are some links and references on there that may be able to help you out. Livewireo (talk) 20:55, 16 July 2009 (UTC)

The little there is to see, yes. That's why I'm posting here. 95.112.156.108 (talk) 21:06, 16 July 2009 (UTC)

Acetylcholine#Antimuscarinic Agents lists a few, but I'm sure there are a lot more. Looie496 (talk) 03:59, 17 July 2009 (UTC)

These sound like homework questions. Anyway, a quick look at anticholinergics leads to antimuscarinics and antinicotinics - which both list many drugs. For the second question, well the effects of anticholinergics basically is what would happen if the PNS wasn't working.. --Mark PEA (talk) 10:29, 17 July 2009 (UTC)

[edit] Atmosphere and Gravity

How much gravity on another planet would be necessary to have an atmosphere where people could thrive (assume other factors such as average temp, composition, are similar to earth although I'm interested in what other factors would have an influence). Also, how much gravity could people comfortably live with? TheFutureAwaits (talk) 20:57, 16 July 2009 (UTC)

We really don't know what gravity humans can live in. Pretty much no research has been done on gravity greater than Earth's, and pretty much the only research on lower gravity is zero gravity and humans can't survive in that for long without taking some precautions (lots of exercise, mainly, I think). I'm not sure about gravity and atmospheres. I know temperature is a big factor - it is easier to "hold on to" cold air than hot air. That's why Titan has a thick atmosphere (about 50% greater pressure than Earth) despite being much smaller than Earth. The composition also matters - humans can survive (at least temporarily) with about a fifth of Earth's atmospheric pressure if it is pure oxygen or with pressure of about 10 times Earth's if you replace most of the air with something inert like Helium (see Heliox). I think composition also affects pressure and density - Venus has about the same gravity as Earth and is really hot, so you would expect it to have a thinner atmosphere, but it is actually about 100 times thicker. I'm guessing that's because it is mainly CO2 which is a little under twice as heavy as air (per mole). --Tango (talk) 21:28, 16 July 2009 (UTC)

(after ec without rereading the new contribution) Sorry that I don't have sources to cite but from what I have heard, the size of our earth is on the verge of being too light and loosing hydrogen (THE key element for live as we know it) and being too heavy and attracting excessive hydrogen and finally becoming a gas giant. I'm hoping for answers that are less based on private memory and hearsay. 95.112.156.108 (talk) 21:30, 16 July 2009 (UTC)

We have lost all our (free) hydrogen. The only hydrogen that remains is that in compounds with heavier elements (particularly oxygen in water). Any hydrogen that gets released into the atmosphere escapes sooner or later. Free hydrogen isn't important for life. --Tango (talk) 21:36, 16 July 2009 (UTC)

As far as I understand, on a geological time scale any hydrogen, temporarily bound or not, will escape a lighter planet with a temperature comparable to earth. Look at venus, look at mars. 95.112.156.108 (talk) 21:50, 16 July 2009 (UTC)

The hydrogen on Earth is pretty permanently bound. It undergoes various chemical reactions but that just changes what it is bound to. There aren't many naturally occurring reactions that produce free hydrogen. I've certainly never heard of any risk of running out of water before the sun heats up and boils it all off. --Tango (talk) 23:03, 16 July 2009 (UTC)

Besides, Venus and Mars don't have a "temperature comparable to Earth"... 76.21.37.87 (talk) 04:47, 17 July 2009 (UTC)

The temperature on Mars CAN get up to Earthlike values - they've recorded 70 degF on a few occasions. However, mostly it's way colder - and Venus is crazily hotter. SteveBaker (talk) 14:12, 17 July 2009 (UTC)

The question is how much gravity is necessary for a planet to have an atmosphere where humans could thrive. The answer is just enough gravity to hold water vapor for a large amount of time. A Mars sized planet is likely close to the right answer. Dauto (talk) 05:51, 17 July 2009 (UTC)

Then how come there ain't no water on Mars anymore? 76.21.37.87 (talk) 06:29, 17 July 2009 (UTC)

No one knows at the moment (No one even knows how much water is gone and how much is just "hidden", e.g. subsurface). There are some hypothesis were the water went and why and when, but the history of mars is not really known to any degree of certainty. And btw, also for venus we do not understand at the moment what "planetary development" has led to its present state. So science cannot answer these questions at present, because we do not have any additional samples beside earth for a habitable planet. --TheMaster17 (talk) 09:57, 17 July 2009 (UTC)

We know from studies of craters and erosion that water has been on the Martian surface 'recently in geological terms'. The gravitational force of Mars hasn't changed measurably for a billion years - so how come the water would have stayed around for all that time if a lack of gravity was the cause of it 'going away'. That means that it wasn't a lack of gravity that caused the water to "go away" - or all of the evidence of flowing water would long ago have been eradicated by meteor impact and wind erosion. SteveBaker (talk) 14:12, 17 July 2009 (UTC)

There is water on Mars. May be your question should have been 'how come there ain't no ocean on Mars anymore' The answer is related to surface temperature and pressure. The question was about surface gravity. Some of Mars water has likely been lost due to low gravity over a period of hundreds of millions of years. That's more than enough time for humans to thrive which was the citerion stablished by the question. Dauto (talk) 16:20, 17 July 2009 (UTC)

Wouldn't the low pressure be bad for people too? 76.21.37.87 (talk) 01:44, 18 July 2009 (UTC)

Yes, if the atmospheric pressure is too low it can be bad for people. But that's a separate question because surface pressure is not determined by surface gravity alone. You also must take into consideration the atmospheric total mass. Dauto (talk) 04:03, 18 July 2009 (UTC)

So would it be possible to have a decent-sized atmosphere on a Mars-sized planet? 76.21.37.87 (talk) 04:41, 18 July 2009 (UTC)

[edit] Pluto's diameter and why gas giant's moon number keep growing

Is Pluto 1400 miles or 1500 miles (0.18 or 0.19 x Earth). [30] say Pluto is x0.18 Earth, NASA say is 0.19 x Earth. Which one is accurate. I thought Microsoft Windows, any kids website is not a valid source. Is Saturn up to 61 moons right now? Anyways, how we know gas giant's moon keep growing. First when last Voyager 2 went to Uranus and Neptune, they had 15 and 8 moons, then in 2000 Uranus had 22 moons then finally Uranus have 27 moons, and finally Neptune have 13 moons. When last Voyagers visit Jupiter, it had 16 moons, then few in 2000 Jupiter's moon jump to 20s, then 30s in 2003 Jupiter's moon skyrocket to 61 moons then finally it's 63. Saturn's moon start with 18 moons, then 30s, then 56 in 2006, then finally 61. Did they use HST or what tools to find new and new moons. Is this possible numbers of Uranus and neptune will continue skyrocketing? Could somday Uranus have up to 40 moons and Neptune have over 19 moons? adn jupter and Saturn over 100 moons?--69.228.145.50 (talk) 21:00, 16 July 2009 (UTC)

I don't think we know the diameter of Pluto very accurately. It depends on its albedo - how bright its surface is. If it is quite dark then it must be quite big in order to reflect the amount of sunlight it does, if it is brighter then it must be quite small. As for the moons, we just keep discovering more (they've all been there the whole time, we just hadn't noticed them). A lot of them are very small and there is no reason to believe we've found them all or will do any time soon. You also have to remember that there isn't really any difference between the tiny dust particles in the rings and the smallest moons (other than size, obviously), so you could argue that we already know of millions of moons around each gas planet - it depends where you draw the line. --Tango (talk) 21:34, 16 July 2009 (UTC)

O, this explains why scientific plotting always fails. Even surface temperatures can't be pin right. By the way nothing is space is exactly pin right, always universally error bars. People can literally say Venus is >1000 F, this is why we have book say Venus is 600 C. I would say Jupiter and Saturn have 100s of moons if 100% is found, for Uranus and Neptune, this is impossible to be over 50 moons if 100% of them if found.--69.228.145.50 (talk) 22:18, 16 July 2009 (UTC)

There are always error bars, you are right, but for some things they are pretty small. We've sent probes for Venus, so we have a pretty good idea of its temperature. The error bars on our measurements will be much smaller than the variation in the temperature. --Tango (talk) 23:05, 16 July 2009 (UTC)

[edit] Glycerin free personal lubricants

I notice many new "personal" (sexual) lubricants proclaim they are glycerin and paraben free. What about those ingredients are bad during sex? --70.167.58.6 (talk) 21:51, 16 July 2009 (UTC)

Substances that dissolve your condom counteract the reasons why you were using it. It has nothing to do with sex itself. 95.112.156.108 (talk) 22:05, 16 July 2009 (UTC)

True, but not applicable to the substances the OP listed. Only water-based lubricants (i.e. not Vaseline) should be used with condoms, for the reason you state. Glycerine is a common allergen, and parabens are both allergens and potential carcinogens; these are the reasons for wanting lubricants without those ingredients. jeffjon (talk) 12:50, 17 July 2009 (UTC)

[edit] African plate

I wonder the valid source of this site. Most showing I see is African plate moving north, the slide show African plate moving east only, eventually it suppose to collide with European plate closing Arabian and Black Sea. Isn't North and South Amercan plates moving west only no north. I don't expect over 15 lattitude north shifting in about another 100 million years. I expect at least the Northern Africa would be up to Artic Circle in 100 million years. Australia is just quickly moving north, and will collide and form a huge nountain in East Asia.--69.228.145.50 (talk) 22:23, 16 July 2009 (UTC)

[edit] healthy diet and muscle spasms

What vitamins or minerals are supposed to be linked to muscle spasms when in deficiency? 76.123.145.220 (talk) 23:39, 16 July 2009 (UTC)

Potassium. --Tango (talk) 23:44, 16 July 2009 (UTC)

And Calcium. Please see Hypokalemia and Hypocalcaemia, respectively. --Dr Dima (talk) 01:10, 17 July 2009 (UTC)

Iron? -- 71.236.26.74 (talk) 06:20, 17 July 2009 (UTC)

And magnesium. It should be noted that fasciculation can be caused by many things other than vitamin/mineral deficiency. --Mark PEA (talk) 10:20, 17 July 2009 (UTC)

[edit] Man on Moon

Have anybody else besides those 3 people in July 1969 Buzz what's his name, Neil Armstrong and anyther guy all 79 right now have been on Moon. Have anybody been on dayside of Moon, or only night side. Do we have 1000s of people been on Moon or it's only those 3 peoples in 1969. Space travel is not a vacation spot. It is not just few days to get to Moon, I expect two weeks from Earth to Moon. Plus to survive in space, people have to bring gravity to hold things together, and lots of foods and fuels and liquids, and place to sleep and shower on.--69.228.145.50 (talk) 23:49, 16 July 2009 (UTC)

Twelve people have walked on the moon. Only two did so in July 1969 (the other guy stayed in orbit). We do not yet have a way of taking portable gravity into space. Algebraist 23:52, 16 July 2009 (UTC)

"The other guy" is Michael Collins. The poor guy, nobody ever remembers his name... --Tango (talk) 00:12, 17 July 2009 (UTC)

Nobody except for you and me, that is. 76.21.37.87 (talk) 04:49, 17 July 2009 (UTC)

If it’s seeming like that tiny Lunar Module is too small to hold everything needed for a trip to the moon, you are right. Although the most exciting photos and videos of the moon landing only show the lunar module, the lunar module was only one piece of the Apollo spacecraft, which did hold enough stuff. Not much fuel is needed to get back from the moon, since it’s relatively easy to escape from the moon’s gravity, due to there being a lot less gravity on the moon than on the earth. Escaping the earth’s gravity, however, does require a lot more fuel, which is why the Apollo spacecraft started out on the tip of a huge launch vehicle.

A bed to sleep in and the ability to take showers are luxuries of modern living, that aren’t really requirements when you’re on a monumental adventure.

Gravity isn’t required to hold things together. The main thing that holds thing together are chemical bonds.

I could go into the details of how the energy content of the fuel used on the Apollo missions was enough to get the Apollo spacecraft traveling fast enough so that it could get to the moon in only a few days. However, no offense if I’m wrong, but I’m guessing that you’re fairly young, and haven’t yet taken the elementary physics classes that would be required for you to understand the explanation. However, the idea of it being impossible to reach a speed fast enough to get to the moon in three days isn’t even something that we have listed as being one of the objections of the moon landing hoax conspiracy theorists. Red Act (talk) 01:24, 17 July 2009 (UTC)

As to the question about which side of the Moon, all of the Apollo missions landed on the near side of the Moon (the side facing the Earth), so they could communicate with the Earth by radio; and they all landed when it was daytime at the landing site, and left when it was still daytime, so they didn't have to deal with the day/night temperature change and so they had full sunlight to work by. (Remember, daytime on the moon lasts for almost two weeks. Apollo 17 stayed longest on the lunar surface, about 75 hours.) --Anonymous, 04:46 UTC, July 17, 2009.

LOL. Two gravity to go, hold the ketchup- KoolerStill (talk) 13:20, 17 July 2009 (UTC)

ec. the sides of moon they been on is nighttime with most photos we have with no suns, yes the image always fails when trying to make things look true when try to pin a green dot to show you what it will look like when you actually on moon. Different gravity and lighting conditions on moon, beleive it or not; the images we take is 99.99% hopelessly wrong, then our orange, blue, green light go haywire. Dummies think it is so easy to say Moon is gray, that's just balonies! We had this discussion many times in past, that's over!--69.228.145.50 (talk) 21:21, 17 July 2009 (UTC)

They landed during lunar morning for idea temperature, and on the side facing earth for best radio contact. We will soon be celebrating the 40th anniversary on earth, but I would like to point out that the moon's phase will not be correct (because Earth's revolution around the sun is not closely linked to Moon's revolution and orientation around Earth). Flimsy human calendars fail to capture useful astronomical information! LCROSS arrived around lunar morning a few weeks ago; it's probably a better "anniversary" than July 16 or July 20, from the point of view of the Moon. Nimur (talk) 14:30, 17 July 2009 (UTC)

At the risk of stating the obvious : The Moon has its own gravity. It does not have as much gravity as Earth, but it still has a useful amount. The astronauts don't need to bring any with them. This is a good thing because there is no known way to make gravity "portable". (When NASA needs to "hold stuff down", they usually glue Velcro to everything Velcro.) APL (talk) 14:52, 17 July 2009 (UTC)

Gravity is portable, you just need a really huge engine. If you built a spaceship of the same dimensions and weight as earth, and you could move it around, then you would in effect have portable gravity. You would have to ask if the endeavor would be worth the resources though. Googlemeister (talk) 18:30, 17 July 2009 (UTC)

[edit] July 17

[edit] Some people smell bad. Why?

I've found over the years that some people smell very bad to me. I'm not talking about people who're dirty or flatulent or unwashed or have bad breath or have body odor typically associated with heavy exertion and/or sweating; rather, it seems more that some people's body chemistry creates an odor I find extremely unpleasant. It's difficult to characterize or describe; it smells of nothing but "smelly person". I have also noticed that others often seem not to detect any such an offputting smell from the same people I find smelly, at the same time I find them smelly. What's at work here? Is it akin to the ability (or lack thereof) to taste PTC? 00:04, 17 July 2009 (UTC)

Body odor? —Preceding unsigned comment added by 79.75.79.236 (talk) 00:42, 17 July 2009 (UTC)

It's mostly to do with what you've been eating, what they've been eating and what you're used to. The compounds in many aromatic substances survive just fine in the body and then get exuded with the various bodily fluids, including the sweat we make almost constantly. Curry, for example, has a very distinctive odour and people that eat a lot of it will tend to exude that smell from their breath and bodies. If you're not used to that because you and your family don't eat lots of curry, then you'll be very aware of the change in odour. It works the other way as well: you may be smelling very strongly of milk, or pepper, or any one of a number of things, but you'd be unaware of it because it's part of your background smell. Matt Deres (talk) 13:16, 17 July 2009 (UTC)

Let's not overlook the smeller's own nose. If you've got too much X in your system, certain odors will repel you more than the usual person. Vranak (talk) 14:35, 17 July 2009 (UTC)

[edit] Putting fiber in my fiber

Is there any downside to adding Benefiber to Metamucil? Are two types of fiber compatible (one is a guar gum and the other is psyllium husks) --70.167.58.6 (talk) 00:08, 17 July 2009 (UTC)

I'm afraid we can't give medical advice, but I will point out that, baring very unusual circumstances, you can get plenty of fibre in your diet by just eating plenty of vegetables. --Tango (talk) 00:15, 17 July 2009 (UTC)

I'm not asking about medical advice. I'm asking if mixing compound A and compound B have a chemical reaction or produce any harmful substances. It's a science question, not a health question. --70.167.58.6 (talk) 12:37, 17 July 2009 (UTC)

You are asking for advice on dietary supplements. That seems like a health question to me. --Tango (talk) 20:14, 17 July 2009 (UTC)

Not offering any advice here, but consumption of very high levels of fiber (along with inadequate water, I think) has been known to cause intestinal blockages. ike9898 (talk) 17:35, 17 July 2009 (UTC)

"I'm asking if mixing compound A and compound B have a chemical reaction or produce any harmful substances." -- It shouldn't, cause neither compound is reactive under normal conditions (they're both mostly cellulose anyway, i.e. sawdust). FWiW 76.21.37.87 (talk) 01:51, 18 July 2009 (UTC)

[edit] Perception of square-wave sounds

Considering this very cool toy (http://www.ladyada.net/make/drawdio/, that produces square-wave audio) caused even more consideration:

is there a simple passive filter that would "round off" the lower-frequency square waves (i.e. low-passing the fundamental of the square waves so they would approximate sine waves) without attenuating the higher frequencies?
the nominal human hearing cut-off of 20kHz would suggest that any periodic wave above 10kHz would sound the same since higher harmonics can't be heard (very well). Is this actually the case? If so, are distortion specs on tweeters above 10kHz worth much?

Thanks. Saintrain (talk) 02:04, 17 July 2009 (UTC)

To the first question, yes — a suitable low-pass filter will attenuate the higher frequencies, leaving the fundamental (and lower harmonics, depending on the filter) essentially intact. Here's a YouTube video demonstrating the principle with square and sawtooth waveforms: [31]. The simple RC circuit shown in our article would serve. TenOfAllTrades(talk) 02:47, 17 July 2009 (UTC)

I’m not sure if I’m understanding your first question correctly, but if I’m correctly rephrasing it, it sounds like maybe you’re wanting the amplitude of the fundamental frequency on the filter’s output to be higher than the amplitude of the fundamental frequency on the input, due to the presence of the higher frequencies on the input? Like by having the filter somehow phase-shift the higher frequencies such that they’ll contribute to the fundamental frequency on output, rather than just being attenuated? That isn’t possible with a linear passive filter, e.g., any filter consisting of just resistors, capacitors and inductors, but it would be possible to do something like that with a nonlinear passive filter.

It isn’t true that any periodic wave above 10kHz will sound the same. For example, an 11kHz sine wave sounds quite different from a 19kHz sine wave. So if a tweeter attenuates those two frequencies differently, that’s going to make an audible difference. Red Act (talk) 03:35, 17 July 2009 (UTC)

Sorry. English is a dangerous language in unskilled hands.

The toy can produce a wide tonal range but the (555) oscillator produces square waves. I was wondering if the lower frequencies can be (simply) "sine-ufied" without attenuating the higher ones. I'm guessing not.
What I meant was, since a 15kHz square wave is made up of 15kHz, 30kHz, 45kHz, 60kHz, ... sinusoids and nothing above (nominally) 20kHz can be perceived, that any 15kHz waveform would sound the same as a 15kHz sinusoid. Sounds (haha) too easy.

Thanks. Saintrain (talk) 05:32, 17 July 2009 (UTC)

“Not with a linear passive filter” would be an answer to your first question.
That’s true, a 15kHz sine wave would sound the same as any 15kHz waveform, as long as the 15kHz component of the waveform had the same amplitude and phase as the sine wave. However, your original question number 2 asked if distortion specs were worth much above 10kHz. If a frequency response distortion causes the tweeter to disproportionately attenuate the 15kHz component of a sound, that’s going to be audible. Was the 10kHz a typo, and you meant to say 20kHz? If you meant to say 20kHz, then the answer would be yes.

I’m afraid some audiophile is going to come along and point out that some people can actually detect distortion above 20kHz, and I’m sure that’s true, particularly with younger people. But this discussion is a theoretical one based on the assumption that people can’t hear anything above 20kHz. Red Act (talk) 06:56, 17 July 2009 (UTC)

To provide a mostly-useless answer to the first question: yes. A Fourier series decomposition of a 15kHz square wave shows that the 15kHz component is already a sine wave. The higher frequencies that you desire not to attenuate are what turn your 15kHz sine wave into a square wave (see the animation in square wave). So, if you really seek to turn a 15kHz square wave into a 15kHz sine wave with all the higher frequencies unattenuated, your passive filter of choice would be … a wire. – 74 08:33, 17 July 2009 (UTC)

[edit] lcd and tft

what is the diference between lcd and tft —Preceding unsigned comment added by 122.163.144.201 (talk) 03:22, 17 July 2009 (UTC)

You probably want Thin film transistor liquid crystal display. Algebraist 03:27, 17 July 2009 (UTC)

[edit] voltage and charging batteries.

Here in China the voltage is 220V. I've recently bought a Game Boy Micro which comes with a power cord (not an adaptor) to charge the battery saying it should only be used with 110V.

I'm currently using a stepdown converter, but am wondering if this is really necessary.

Why? Because I see kids all over the place playing JPN Game Boy Advanceds and Game Boy Micros and charging them willy-nilly.

I know that improper voltage can hose appliances... but what does it do (if anything) to batteries? 61.189.63.221 (talk) 03:52, 17 July 2009 (UTC)

Too high a charge voltage could make the batteries blow up, and also fry the diode rectifier that changes the AC from your socket to the DC needed to charge batteries. Stick to using your stepdown converter at all times. 76.21.37.87 (talk) 04:57, 17 July 2009 (UTC)

[edit] Theory vs. law

I have some homework which states:

Discuss how theories such as those above [Newton's/Galileo's theories about gravity] develop into laws with time & experimental testing.

Now, this is implying that laws are somehow better or more solid than theories. My understanding is that a law is simply a description of what happens, while a theory is an explanation for observations. How would I answer the homework question? (This is going to be marked, and I have NO way of talking to my teacher about the question at any point before the work is due.) --wj32 ^t/c 04:16, 17 July 2009 (UTC)

It looks to me like your understanding of the difference between a physical law and a theory is more accurate than your teacher’s! Unfortunately, the “theories develop into laws” idea that they teach at some schools does not mesh well with how those terms are actually used by scientists. My impression is that the “theories develop into laws” idea is just something they teach in like junior high or high school, and isn’t something you’d be likely to encounter in college. I don’t know the best way to explain to your teacher that this wasn’t a very good homework question. Red Act (talk) 04:52, 17 July 2009 (UTC)

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt to solve the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Thank you. —Scheinwerfermann ^T·_C05:00, 17 July 2009 (UTC)

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Judging from the idea that the development occurs after time and testing, your teacher may be confusing the difference between theories and laws with the difference between hypotheses and theories. Maelin (Talk | Contribs) 05:02, 17 July 2009 (UTC)

As far as marks are concerned, just give what the teacher expects. Assume a Law to mean something like indesputably proved beyond doubt fact of life, and explain how a theory matures into a "Law" over time through tests by experiments and observation. However, afetr you are marked, do have a discussion with the teacher about this. Rkr1991 (talk) 05:31, 17 July 2009 (UTC)

Seems like a good idea. Thanks for all the suggestions, everyone. :) --wj32 ^t/c 06:03, 17 July 2009 (UTC)

It’s kind of intellectually repulsive to intentionally give an incorrect answer, but I think that probably really is the best advice. There’s no point in getting marked down just to prove a point, and actually knowing the right answer is what’s really important, anyway, not whether the teacher acknowledges you for knowing the right answer. It’s also probably best to point the teacher’s mistake out to him quietly, after class, rather than pointing it out to him during class. I pointed out a couple of my high school math teacher’s errors in class right after he made them, and it really made him kind of not like me a little. In my experience, college profs are much less flustered by being corrected in class than high school teachers; in fact, they’ll often thank you for correcting their mistake. Red Act (talk) 11:16, 17 July 2009 (UTC)

Your should tell your teacher (in a tactful way) that their hypothesis that "theories develop into laws with time & experimental testing" is not supported by the way that these terms are used in the scientific community. As evidence, show your teacher these pages - [32], [33], [34]. Clear consensus is that there is no hierarchy of proof or reliability between theories and laws - the only difference in usage (and it is a very marginal one) is that the term "law" is usually applied to a short and concise statement or principle whereas a "theory" is a larger and more complex body of interrelated concepts with a wider, more general scope.

Quite often the historical progression of a scientific field starts with the discovery of empirical laws and progresses to a general theory that incorporates and explains the separate laws. For example, the kinetic theory of gases incorporates the ideal gas law, which in turn combines Boyle's law and Charles's law; Hubble's law is incorporated into and explained by the Big Bang model; the law of multiple proportions is explained by atomic theory; and Mendel's laws are explained by genetics.

Maybe I am being cycnical here, but it seems to me that the erroneous idea that "theories develop into laws with time & experimental testing" could be used to set the stage for the bogus "evolution is just a theory" argument. Gandalf61 (talk) 11:28, 17 July 2009 (UTC)

No, here in Australia we aren't anti-evolution :) --wj32 ^t/c 23:59, 17 July 2009 (UTC)

Well, I think you can do this right and still get good marks - and since you CLEARLY have a better grasp of this than your teacher, I'm strongly of the opinion that you should stick to the truth no matter what. The trick here is to write the truth - and yet still answer what the question is really seeking for you to explain - which is how a "hypothesis" turns into either a theory or a law with time and experimental testing. This is more work for you - but that's what happens when you stand up for a principle.

I think you need to write two sections:

Firstly, you need to deflect the question into one that you CAN answer. You must explain how the standard dictionary definition of the words "theory" and "law" differ sharply from common scientific usage - look the words up in a dictionary - and quote what it says. I found this, for example. Explain that you are assuming that the word "theory" in the question is being used in the non-scientific sense of the word (As Merriam-Webster puts it "6 a: a hypothesis assumed for the sake of argument or investigation b: an unproved assumption". However, you can't make it sound like this is just your opinion because essays like this aren't about opinion. You also can't make it sound like this is something you heard from a bunch of random guys on the Wikipedia reference desk (which it's not because you already knew it). You are going to have to find some solid references that you can point to that say this - preferably more than one. You need to be able to say that "so-and-so (a highly respected scientist/organisation) said such-and-such (which supports your claim) in such-and-such document (hopefully something your teacher can easily find and read - but at least something respectable...but not Wikipedia - which many teachers hate)". For example, you could quote the American Association for the Advancement of Science here - in the section "Is evolution "just a theory"?" - they say "In detective novels, a "theory" is little more than an educated guess, often based on a few circumstantial facts. In science, the word "theory" means much more. A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter or the germ theory of disease. Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.". This clearly says that a theory is a RESULT of time and experimental testing - not the STARTING POINT for such work. That done and clarified, you can proceed to do the assignment you were given - because you can't use this little misunderstanding to duck out of doing the work!

Now, having established (eg from Merriam-Webster) that the word "hypothesis" would be a better choice, you must proceed to explain how a scientific hypothesis can develop into either a scientific theory OR a law with time and experimental testing...because that's what the homework assignment is all about - and if you don't do it, you won't get a good grade. You've actually increased your workload in the process - because now you need to describe how a THEORY gets made as well as how a LAW comes into being. But it's worth the effort.

I'm 99% certain that your efforts will be rewarded with a decent grade IF you do it like that - subtly and with style and integrity - and not whining at the teacher's incompetence!! On the off-chance that you have an utterly bone-headed teacher (I sure hope not!) - you might ask your teacher to "help you understand" by providing an example of a "theory" that turned into a "law" - we know that there aren't any - so you're on solid ground here - you may have to say "but that wasn't a theory - that was just a hypothesis". If all else fails, you may need to get your parents to appeal the grade to a student councillor or the head of the science department - or the principle...whatever it takes. I had to fight for my son's (correct) answers to bogus questions on many occasions...and every time, we won and he got a good grade in the end. But if you do it right - and back up your assertions with solid references - I'm sure you'll be OK without any fuss whatever.

You're in good company by the way - my personal hero (Richard Feynman) was particularly displeased with these kinds of errors in assignments and school books and took on a personal crusade to try to eradicate them that wound up with him having to write three of the best Physics books in existance - "Feynman's Lectures on Physics". The fight over the teaching of evolution in US schools lies entirely in the misunderstanding (intentional or not) of the word "theory". I applaud your knowledge and your desire to stand by your principles. No matter what, you'll always know that "You were right" - and that's worth more than a grade.

SteveBaker (talk) 14:00, 17 July 2009 (UTC)

Thinking about this a little, my guess is that the OP’s textbook is correct, which is where the OP got his correct information from, and it’s just the teacher that’s made a mistake. If the textbook matched the teacher, the OP wouldn’t have gotten confused and asked us for a clarification. So pointing the teacher’s mistake out to the teacher might be as simple of a matter as pointing out the pertinent page(s) in the textbook. Red Act (talk) 14:52, 17 July 2009 (UTC)

Well, the homework is actually taken directly from our science syllabus. Pretty depressing, I know... --wj32 ^t/c 00:01, 18 July 2009 (UTC)

[edit] Falling objects

There is an article [35] which states:

Also intriguing is Galileo's report, based on experiment, that balls of unequal weight do not only fall at different rates, but that the lighter one initially pulls ahead of the heavier one until the heavier catches up. In the early 1980s the science historian Thomas Settle tried to repeat Galileo's falling-body experiments and, astonishingly, noted the same thing. He suggested that fatigue induced in the hand holding the heavier object tends to cause this hand to let go more slowly, even when the dropper believes the objects are released simultaneously.

I'm a bit confused. Is this actually true, or is the article just saying that Galileo observed it but it's wrong? Why would this (the lighter one being faster at first) happen? --wj32 ^t/c 06:20, 17 July 2009 (UTC)

If the two objects are mechanically released at precisely the same time in a vacuum chamber, the two objects will fall at exactly the same rate, even initially. The effect of the lighter one falling faster initially only applies to the sloppier situation in which the objects are dropped in air, by hand.

The fatigue hypothesis seems reasonable to me. Another hypothesis that seems reasonable to me is that it isn’t due to fatigue, per se, but that it takes longer for a tightly clenched hand to unclench than a lightly clenched hand, simply due to it involving a greater change in physiological state. Another hypothesis that seems reasonable to me is that when one’s fingers move rapidly out from under something really light, something like the Bernoulli effect will basically cause the feather to get sucked downward slightly. But the latter two hypotheses are purely original research. Red Act (talk) 07:22, 17 July 2009 (UTC)

Galileo's result is only approximate because he couldn't test it in a vacuum - and air resistance has an effect. But done 'properly' with some kind of mechanical release system in a vacuum, there would be no such effect as our OP describes. SteveBaker (talk) 13:12, 17 July 2009 (UTC)

Didn't Galileo roll same sized but different weight spheres down an incline, rather than merely dropping things? The effort of holding on an ioncline would not be great. A mechanical release would be an obvious control. Ref checking is indicated. Edison (talk) 14:41, 17 July 2009 (UTC)

[edit] kindly help....for spectrophotometer

1) how to calibrate and standardise visible spectrophotometer using aquous solutions? 2) which aquous solutions should be used for it? and what should be their concentrations? —Preceding unsigned comment added by Ddrcpan (talk • contribs) 06:56, 17 July 2009 (UTC)

I believe you calibrate by putting a test tube with distilled water, which will reflect, refract and absorb the minimal amount of light of any liquid, into the machine and taring it so that that whatever is reflected, refracted or absorbed is blanked. DRosenbach ^{(Talk | Contribs)} 17:19, 17 July 2009 (UTC)

[edit] Documenting 2009 solar eclipse

Someone else may have asked something similar already, sorry if this is a repost!

I'm going to be observing the solar eclipse next week and I hope to take some footage/pictures, and I'm just wondering how careful I should be. I've got a recent Canon Ixy (Powershot) just so that I can have some sort of video record, and I will be photographing using my Nikon D60 and a 200mm lens. I've never photographed an eclipse before so I'm not really expecting anything spectacular (besides it won't be complete where I live) but I'm mainly concerned for the safety of my cameras! Basically every website I look at warns me that the eclipse could harm the lens/sensors of my digicam, and I guess I need a solar lens? of some sort to protect them, but what exactly am I looking at purchasing here, how much will it set me back, and where can I get one? Also, is it possible to make my own? If anybody knows a site with some easy instructions to make a home-made eclipse glasses, please let me know! And lastly, is it really necessary to use a solar lens for a digicam, or is that just a precaution for when you're getting in really close? Thanks! 210.254.117.186 (talk) 08:31, 17 July 2009 (UTC)

What do you mean by "getting in really close"? The distance to the sun won't change. I can assure you that taking pictures with a normal digicam without any filter will destroy the sensor of the cam. When there was a total solar eclipse here in germany, where I live, two friends of mine destroyed their cams in this way. NEVER look at the eclipse with your naked eyes, use an appropriate filter! In germany there were special glasses on sale weeks before the eclipse, which were certified to protect human eyes. Normal sunglasses won't do! It might seem that the sun is "dark" enough, but in reality it isn't. You will damage unprepared optical equipment, including your eye, if you point it to the eclipse. There are cases in the literature where people went partially blind from staring into an eclipse, so I'm begging you not to take the risk of loosing your sight. --TheMaster17 (talk) 10:10, 17 July 2009 (UTC)

I don't know about damaging the sensor - I think that quickly pointing the camera, taking the photo and then pointing it away again should be OK...but perhaps it's not worth the risk. But in any case, the problem is that in a non-total eclipse, the amount of light coming from the sun will overwhelm the sensors and you won't get a decent picture. Digital cameras can only handle so much light before they have hit the maximum number that the sensor can output and everything goes completely white. So I think you could benefit from having a filter of some kind to cut the amount of light down to something reasonable. You could test this by trying to take photos of the un-eclipsed sun...which will be only maybe twice as bright as a half-eclipsed sun. Obviously (I hope!) you understand that staring at the eclipse with unprotected eyes is very dangerous - and looking at it through your camera's optical viewfinder is possibly even more dangerous...especially if you have an optical zoom. By all means line up the shot using the LCD viewfinder if your camera has one...that's entirely safe. I've been saying this a lot recently - but I'll say it one more time. Observing the sun (and even photographing it) can be done very effectively by projecting an image of it through a pinhole into a darkened room. If you have a window facing where the sun will be during the eclipse - you can tape some thin (preferably black) cardboard to the windows to make the room completely dark - and poke a small pinhole into the cardboard to let in some sunlight (this is effectively just a 'pinhole camera'). This will project an image of the sun onto any flat, white surface held up in front of the pinhole - which you can move closer to make a smaller but brighter image or further away for larger and dimmer. You can also make the image brighter - but fuzzier - by slightly enlarging the pinhole - dimmer but sharper by using a finer pinhole. It's easy to experiment. You won't hurt your eyes or your camera by looking at this image. It's very cool (especially now that the sunspots are coming back) and everyone should do this at least once - eclipse or no eclipse! Using a conventional camera with flash turned off and a 'macro' or 'closeup' lens setting if your camera has one - lets you take photos of the projected image that will look really great. Best of all, you can get everything set up and take practice photos of the uneclipsed sun any time to be sure you have everything right for the big day. That's a good idea - because you only have a few minutes to get what you need - and you don't want to be fiddling around getting the camera settings right. Just be sure to do the setup at the same time of day as the maximum amount of totality that's predicted so you'll have the best-facing window for the event. SteveBaker (talk) 12:51, 17 July 2009 (UTC)

I forgot a piece of pinhole camera advice. To get a really SHARP image - cut a square hole a couple of inches across in your cardboard and tape some aluminium kitchen foil across it. Then punch your pinhole in the foil. It makes a much smaller and more accurate hole for the ultimate in sharpness. SteveBaker (talk) 13:09, 17 July 2009 (UTC)

Total solar eclipse during totality, March 29, 2006, Sallum, Egypt

,

Playing with double shadows during an eclipse

You can use an ordinary camera to take pictures during a solar eclipse. Be sure to SECURELY mount a piece of #14 welder's glass in front of the camera (Not the side with the display the other side i.e. before the light hits the camera.) I tried a mylar filter last time and was unhappy with the results. (It was expensive but buckled and got me reflections on the images.) Friends used the welder's glass and got awesome pictures. Since your eclipse is not total you don't have to worry about removing/putting on the filter arrangement during the event. That usually makes for more difficult constructions. Build yourself a solid frame or box. Sticky tape or Duck tape are not suitable for this task. Make sure absolutely no light can enter the setup except through the welder's glass. There are many things to observe apart from the sun turning into pac man. See if you can spot double shadows as in my pic. (No the guy was not Aquaman or an alien with extra knuckles between his fingers:-). Have fun, but be safe. --Lisa4edit (talk) 15:40, 17 July 2009 (UTC)

Thanks Lisa, I'll see if I can find me some welder's glass then and make a little box for it. 210.254.117.186 (talk) 16:12, 17 July 2009 (UTC)

My brother travels the world photgraphing solar eclipses as an enthusiastic amateur. There are some tips from him here: http://myweb.tiscali.co.uk/steve.holmes/eclphoto.htm. --Phil Holmes (talk) 12:05, 18 July 2009 (UTC)

[edit] gold plated connectors

is there a true difference between regular cables (hdmi, USB, internet) and those made by "boutique cable" manufactures that include gold plated connectors?

puzzles me is that the cable is still copper so would any benefits from the gold connectors be negated by the copper wire? im looking for scientific reasons (from a metallurgy, engineering perspective) for a difference or lack thereof. Im not looking for an audiophiles perspective, they tend to buy anything if its expensive. seems as though they are victim to the the placebo effect.

EDIT so it seems that gold plating prevent corrosion, makes sense, but is there any true sound difference between monster cable(and similar cables) and normal priced audio cable. one of the claims ive heard is that with monster cable you hear "more of the nuances of the music"

Thanks —Preceding unsigned comment added by 71.98.64.15 (talk) 10:13, 17 July 2009 (UTC)

Well, for digital signaling, there is no difference. All decent cables that follow the standards are plenty good enough to carry the digital signal. Boutique cables for digital signals are a scam. For analogue transmission, cable quality can make a difference. But even there, gold plating is not going to have a significant difference. If you can hear the difference between decent and overpriced cables, James Randy has ONE MILLION DOLLARS for you.[36] --Stephan Schulz (talk) 11:39, 17 July 2009 (UTC)

The gold plating isn't actually that expensive - you can get fairly cheap gold plated cables if you want.

The gold plating ensures that the connector will not corrode or rust, but a rust free alloy would do just as well.

There's and additional complication that a junctions between different metals have properties (eg think thermocouple) - which potential could actually degrade the signal - in practice there is not a difference.83.100.250.79 (talk) 11:49, 17 July 2009 (UTC)

It's probably a good idea to match the platings - ie if a device has tin plated connections then don't use gold plated connectors.83.100.250.79 (talk) 11:55, 17 July 2009 (UTC)

The theory to gold plated connectors is that gold resists corrosion better than copper, so gold plated connectors can wind up having a lower contact resistance than copper ones, particularly in a damp environment. I have had a 50-year-old copper phone connector corrode to the point that it made for a staticky phone connection, and perhaps that problem wouldn't have occurred had the connector been gold-plated. Of course, digital devices become obsolete way before they’re that old. Red Act (talk) 12:20, 17 July 2009 (UTC)

Gold plating is most useful on cables you will need to plug and unplug often. Gold is soft and will somewhat lubricate the connection as it slides in and out. For connectors that stay in place for most of their life - that are maybe unplugged when you move house or something...meh - any old cable of the appropriate standard will do. The most ridiculous thing is when audiophiles claim to be able to hear the difference between gold plated cables and the regular kind. Audiophiles have a problem. They are like most of us geeks who love to debate the merits of Linux versus Windows or MINI Cooper's versus Mustangs - to endlessly tweak the object of their joy to get another 1% of performance out of it...except that their field of interest is 'solved'. We can't buy the perfect car or the perfect computer - but we can all have essentially unlimited quantities of perfect (in the sense of 'better than human perception') audio at any time we want from a sub-$100 box that you can buy at any Walmart. There is nothing left to be geeky about...no conceivable reason to rush out and buy this years sexiest $10,000 stereo system beyond the shape of the knobs and the color of the LED's. Sadly, these people retreat into a world of their own where they claim they can tell the difference between two ethernet cables used to connect their PC to their media center (yes, really!) when it's a completely lossless digital connection with error recovery built in at the software level. These people will happily pay $1000 for a set of cables just so they can "one-up" their audiophile buddies. Check out these [37] nut-jobs who sell cables with silver conductors instead of copper at hundreds of dollars for what would normally be a $1 cable. Their advert reads: "These cables allow deeper insight into the textures of the critical mid-range, leading to improved intelligibility of vocals, greater resolution of acoustic spaces around the instruments, more real-sounding instrumental timbres, etc. It’s not only beneficial on acoustic

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