Wikipedia:Reference desk/Archives/Science/2010 February 8

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February 8

Kangaroos

Are there any documented evidence of kangaroos using their pouches to hold things like spare change or receipts when they are not carting around their young? (98.20.170.216 (talk) 07:02, 8 February 2010 (UTC))

No. -- kainaw™ 07:09, 8 February 2010 (UTC)

light (2)

if light does not slow down as it travels through space and the red shift means everything is moving away from us. does that mean that if the process was in put in reverse everything would end up here. would it also mean the big bang started here? —Preceding unsigned comment added by 82.22.255.246 (talk) 10:15, 8 February 2010 (UTC)

No. Everything stared in one point, now everything is expanding. Imagine a ball of dough with seeds in it, now imagine it is expanding in all directions, from any seed it looks like all the others are moving away. Vespine (talk) 11:54, 8 February 2010 (UTC)

OTOH we can't say the big bang didn't start here. Cuddlyable3 (talk) 12:53, 8 February 2010 (UTC)

Technically, that's true - but without clarification, it's misleading. Vespone's cookie dough analogy is a frequently given one. The one I prefer is the balloon analogy: If you draw a bunch of dots on a deflated balloon and then inflate it - as the balloon grows, so the dots move further apart - but from the vantage point of any given dot, it looks like all the other dots are moving away from it. Now, if the balloon started out as an infinitely small speck and slowly grew to become the size of our universe - that would be a good analogy for the big bang. So - the question of where the big bang started from is analogous to asking which of the dots on the balloon was closest to where the balloon started to inflate from - and the answer (because the balloon started out as an infinitely small speck) is "all of them". All of the dots on the balloon - (and all of the points in our universe) started out at the same place because before space itself started to expand, there only was one place. SteveBaker (talk) 13:11, 8 February 2010 (UTC)

Misleading analogy. Real space is 3-D but a balloon has only a curved 2-D surface. At any time when individual dots are distinguishable, one of them is closest to where the balloon started to inflate. Balloons make their big bang after inflation and not before it. A baker should save dough and not insist on blow jobs.Cuddlyable3 (talk) 14:44, 8 February 2010 (UTC)

I'd say that almost all analogies have a degree of imperfection in them. Both have merit; the cookie dough allows for the 3-D nature of space but the balloon model is perhaps easier to visualise (balloons inflate many times in each direction, at least, to a much greater extent than dough does). Perhaps it's simplest to say the Big Bang happened everywhere, because at the time, there was only one 'here'. Brammers (talk) 16:13, 8 February 2010 (UTC)

I like to go with the balloon analogy as well, but with a slight modification. The centre of the expanding balloon is a point in 3-D space, but everything on the balloon's surface only 'knows' about 2-D space. Hence, if there were 2-D people on the balloon asking a similar question, the idea of a central 2-D point doesn't work as it is in fact 3-D. Similarly, the idea of a central 3-D point for our Universe doesn't work. --Zixtrio (talk) 17:25, 8 February 2010 (UTC)

The big bang might have started here, but where is "here"? Earth is orbiting around the Sun, the Sun is orbiting around the Milky Way, and the Milky Way is moving throughout the universe and interacting with other galaxies in the Local Group. Therefore it is not possible to identify a point called here for the time when the big bang started, and of course our universe may be four dimensional to eleven dimensional, and it is considered to be flat so the idea of a 3D point doesn't really work either. ~AH1^(TCU) 23:08, 8 February 2010 (UTC)

The Big Bang happened everywhere. Dauto (talk) 01:30, 9 February 2010 (UTC)

...so you're everywhere and nowhere, Baby. (Video 1:00). Cuddlyable3 (talk) 18:12, 9 February 2010 (UTC)

light (3)

if there were two observers in two different spaceships observing the same distant star. but with one going towards it while the other came away from it. would one observer see the light with a red shift while the observer see a blue shift at the same time from the same star —Preceding unsigned comment added by 82.22.255.246 (talk) 12:17, 8 February 2010 (UTC)

Yes. Going towards: blue. Going away: red. --Tagishsimon (talk) 12:31, 8 February 2010 (UTC)

Scar removal?

I know that this may sound like an oxymoron, but I was wondering if it may be possible to remove scars now, if not, somewhere down the future. I am not looking for medical advice, and certainly hope that this won't be considered medical advice, but I saw the wikipedia article on scars and in the treatment section it said something to the extent of, that according to the authority at aad.org, there is no scar that can be completely removed.

I was just wondering how credible that statement is, and if it will ever be possible to remove a scar?

Also, I was just looking into gene therapy as well, and was wondering why the skin can't produce normal skin after injury and has to form scar tissue instead of regular dermis?

Thanks. —Preceding unsigned comment added by 139.62.223.27 (talk) 12:51, 8 February 2010 (UTC)

Using an array of cosmetic techniques, it is possible to reduce the appearance of many scars, though it is virtually impossible to eliminate them completely. Dermabrasion or microdermabrasion can be used to 'flatten out' raised scar tissue. An assortment of laser techniques can be used to reduce or even out pigmentation in the scar tissue compared to the surrounding area, and may also be used to thin out blood vessels to reduce redness. Chemical peels can be used to alter (and, ideally, improve) skin texture. In more severe cases, surgical excision of the scar tissue may be required; grafts of new skin can be generated through tissue expansion. Carefully controlled conditions and the use of anti-inflammatory drugs can help to minimize the appearance of the new post-surgical scars. Google is your friend here — look for 'scar removal' and the like. TenOfAllTrades(talk) 14:37, 8 February 2010 (UTC)

An extract of onion is marketed for scar improvement but has apparently failed multiple clinical trials. Rmhermen (talk) 15:00, 8 February 2010 (UTC)

"beanie" or "paint" taste of soy flour

I have now experienced the taste difference between genetically modified soy (Now brand) and organic soy powder (Arrowhead brand) and I can tell you that I now know why GM has so much support among diners and cooks alike. However, many people still have reserves of Arrowhead they do not want to throw out so what is the conventional method of deflavoring soybean powder/flour to hide the "beany" taste? 71.100.0.210 (talk) 14:04, 8 February 2010 (UTC)

GM soy is altered to make it more resistant to herbicides, not to change its taste. The "L-Star" hybrid soybean was bred normally in Japan and has no lipoxygenase which gives the beans a "beany" flavor. However this is not GM soy, just normal field breeding. Rmhermen (talk) 14:55, 8 February 2010 (UTC)

If this question becomes another anti-GM rant, I will remove such posts on sight Nil Einne (talk) 14:57, 8 February 2010 (UTC)

How about the documentary "The Future of Food"? What is your Monsanto backed plan for that? Besides, each time you do delete a legitimate, especially one that is controversial or covers controversial subject matter you put in the minds of other participants that the Wikipedia Reference Desk is a conspiracy to perpetrate misformation. 71.100.0.210 (talk) 15:51, 8 February 2010 (UTC)

You misunderstand. We aren't removing GM questions on sight - the reference desk does not have opinions on the validity or otherwise of GM foods. We're likely to remove those questions of the kind that turn from a legitimate question into a rant and an effort to promote debate - which is NOT allowed here. You have a history of doing exactly that with GM questions - so you're skating on thin ice here and Nil Einne is correct to warn you of the consequences of posting questions that are in violation of site policy. SteveBaker (talk) 17:15, 8 February 2010 (UTC)

Since unlike your claim, both Now and Arrowhead claim to be GM-free[1][2], any taste difference is likely to be from the variance between cultivars of soy produced through normal breeding. L-Star is a notable variety bred to have less "beany" taste. Perhaps Now uses that kind while Arrowhead uses more common varieties. Rmhermen (talk) 16:11, 8 February 2010 (UTC)

Response removed to Talk: page - per earlier warning by Nil Einne. SteveBaker (talk) 17:50, 9 February 2010 (UTC)

Sport: Baseball Pitcher vs Cricket Bowler

I thought that a baseball pitcher was faster than a cricket bowler simply because a pitcher basically throws the ball while in cricket a bowler releases the ball without bending his arm when it passes his shoulder hence the term bowler and apart from it being a rule, but...

a) A pitcher pitches/throws the ball from a stationary position not forgetting that most people would instinctively throw a handheld object if they want to generate a lot of power and speed from it while...

b) A bowler bowls the ball after he has had a running start not forgetting that he also jumps in the air (almost like a catapulting movement) just before releasing the ball and thus creating momentum (from the running start) for himself which can create equal or more power.

...but I still don't know who is or can be the fastest.

--41.193.16.234 (talk) 15:32, 8 February 2010 (UTC) Thanks, NirocFX

From Bowler_(cricket), it mentions that the average fast bowler hurls at about 145 km/h (90 mph) and that the fastest bowl was 160 km/h (about 100 mph). I know that some major league fastballers can top out at about 105 mph, the fastest unofficial fastball thrown coming in at a scorching 173 km/h (107.9 mph). So, to answer your question, baseball pitchers can get more heat. Livewireo (talk) 15:42, 8 February 2010 (UTC)

This page list 104.8 mph as the fastest known baseball pitch (and lists a number of over 100 mph pitchers). Rmhermen (talk) 15:54, 8 February 2010 (UTC)

For what it's worth, there's also less distance between the pitcher and batter in baseball (60.5 feet) than between the bowler and batsman (66 feet) in cricket. Thus, with the respective balls moving at equal speeds, the baseball batter has less time to make his decision than the cricket batsman. — Lomn 16:18, 8 February 2010 (UTC)

I disagree with your statement. In cricket, the wickets are pitched 22 yards (66 feet) apart, but the batsman usually stands at or even in front of the popping crease (i.e. closer to the other wicket), which is 4 feet in front of the wicket. (He might stand a bit behind the popping crease for a very fast bowler). While the bowler may deliver the ball at any point as long as the front foot is at least partially behind the other popping crease, they usually try to deliver it with as little of the front foot grounded behind the popping crease as possible, to give the batsman less reaction time. The ball is released roughly directly above the front foot. This means that the batsman is usually only about 58 or 59 feet from the bowler. -- Flyguy649 ^talk 17:08, 8 February 2010 (UTC)

And in baseball, the pitcher is actually releasing the ball 5 to 6 feet in front of the rubber, so it's really 55 feet there. There's certainly variation in each sport, but I doubt it's enough to change the overall point. — Lomn 19:12, 8 February 2010 (UTC)

Good point.-- Flyguy649 ^talk 15:08, 9 February 2010 (UTC)

Of course, the ball is bouncing in cricket, but it is curving/sliding/knuckling in baseball. And a baseball bat is narrower. I wonder which sport is overall more difficult when it comes to batting... —Akrabbim^talk 17:13, 8 February 2010 (UTC)

There is also movement in the air in cricket, as well as lateral deviation off the ground. However, cricket batsmen use a bat with a flat face to deal with that. Mind you, it's more or less legal to intimidate the batsman by bowling at him. They can also hit the ball in any direction and need not run if they feel a fielder may be able to run them out. The field is defended by 11 players. In baseball, there is only a 90° arc in which to hit a ball (in order to advance) with a cylindrical bat of smaller diameter and there are 8 fielders in front of the batter. I'd say overall, advantage cricket batsman. -- Flyguy649 ^talk 17:34, 8 February 2010 (UTC)

I recall a New Scientist article from years gone by, discussing which is the more difficult ball to face. They concluded the baseball was more difficult; can't say I agree. --Tagishsimon (talk) 18:23, 8 February 2010 (UTC)

It seems that baseball pitches are faster. That said, I wouldn't fancy facing either fast balls or fast bowling. Least of all, I'd like to face bouncers, a legitimate device in cricket. It's not just about pace, it's about intent. See our article on "The Dentist". --Dweller (talk) 19:26, 8 February 2010 (UTC)

Cricket is not really all about speed, one of the most succesfull bowlers of all time recently Shane Warne was a spin bowler which doesn't bowl very fast at all, compared to fast bowlers, but no one doubts how hard it was to hit his pitches. Also cricket is a lot more about scoring then baseball, a cricketer can face well over 100 balls in an inning, even over 400 balls and on a good inning will score over a 100 runs. A baseball batter gets what? 10 swings in a game? Maybe 20? Scores a couple of runs? They're totally different games. Vespine (talk) 22:03, 8 February 2010 (UTC)

We have a nice article on one of the "pitches" Shane Warne bowled during his career: the so-called Ball of the Century --Dweller (talk) 22:13, 8 February 2010 (UTC)

It is worth noting that for any givin baseball pitch the speed as measured by various instriments and people will vary 2-5 miles per hour. When a player, team, or league wants to inflate a pitcher's speed, they simply measure the speed of the ball closer to the pitcher. This is essentially like measuring the muzzle velocity and would report values as high as 110mph if done with the intent of falsifying the numbers. By convention I believe that the speed of a pitch in baseball is measured just before the ball reaches the plate. Cheers, CoolMike (talk) 22:34, 8 February 2010 (UTC)

Those who think cricket is genteel and dull should watch this and other similar clips. Try 1.40 into it. It's not fun facing quicks who want to hurt you. --Dweller (talk) 22:47, 8 February 2010 (UTC)

This is a much more complicated question than a simple measurement of the speed of the ball. Yes, the pitcher in baseball typically throws the ball maybe 10% faster than a cricketer does - but the ball weighs less. A baseball is supposed to weigh 5oz (141grams) and a cricket ball is around 160grams. Even though the kinetic energy in the ball is proportional to the square of the speed, that additional mass counts for a lot and the kinetic energy of a baseball is only about 5% more than a cricket ball. However, there is more to it than that because the force that is felt on the bat is the mass of the ball times the deceleration as it hits the bat. Both cricket and baseball bats are pretty solid so the slowing down that goes on is mostly due to the hardness of the ball - and a cricket ball is incredibly solid compared to a baseball. I recall seeing some slow-motion video of the two and you'd be amazed by how much the baseball squishes - and then by how little the cricket ball does. So the sheer impact force from a fast cricket ball is going to be considerably more than from a baseball - even though the baseball will likely be moving a but faster and have a little more kinetic energy behind it. Then there is the curve and bounce to consider. A baseball pitcher has all of those interesting curved stitches to use to make the thing curve weirdly - but the seam on a cricket ball adds a lot of that too. However, the rebound off the ground offer a wealth of additional variables for the bowler to play with. The distance of the impact from the batsman - the state of the ground where he aims it (cricket is played on natural grass - and it wears out during the game - so there are hard bits and soft bits and so forth), the amount of spin and the axis of rotation all serve to allow the ball to ricochet at all sorts of strange angles. There is also the matter of exhaustion on the part of the bowler - he has to throw perhaps a hundred balls a day - way more than a baseball pitcher. An international cricket game goes on all day long for three days solid! Worse still, everyone in a cricket team is required to bat. So you can't really be ONLY a good bowler - you need to be able to do at least some good with the bat too. I think cricket is a vastly more difficult and technical game than baseball - but it's not such a good spectator event IMHO. The best way to enjoy cricket is by listening to the BBC live coverage via radio. You can dip into listening to the game for a while - go off and walk the dog, come back and catch up on what you missed. It's an entirely different game - for an entirely different lifestyle. SteveBaker (talk) 23:34, 8 February 2010 (UTC)

Just to correct a few of Steve's statements about Baseball vis-a-vis Cricket; in baseball the Starting pitcher will generally throw 100-120 pitches in a game, so that's perfectly comparable to the 100 balls/day that Steve quotes above for a criket bowler. Also, while baseball has relief pitchers in a game, most teams use at least three per game (a starter for innings 1-6 or 7, a set-up man for the 8th and a closer for the 9th), a cricket team also doesn't use the same bowler for a whole test. Since cricket mandates that only one ball has to be used for the entire test, different bowlers will be used at different stages of the game. The starting bowler is often the best at using a fresh ball, once the ball starts to get some wear on it, other bowlers who specialize in dealing with beat-up balls step in. Though both games share the common "smack the ball with the stick" theme, I don't think one could compare the two in terms of skill involved. There is probably a comparable level of skill between the best crickteers and the best baseball players at the highest level; I wouldn't say that there is any reliable test on whether either sport is objectively "harder" or requires more skill. They are just different. --Jayron32 05:10, 9 February 2010 (UTC)

And international cricket Test matches, the highest level of the game, last five days and bowlers may be expected to bowl 180+ balls per day during that time, as well as batting and fielding while not bowling. Most bowlers don't tend to bat very well though. True All-rounders are precious and become superstars of the sport. For context, it's arguable that since the end of Ian Botham's international career in 1992 (ie 18 years), England have had just one true all-rounder of international class, Andrew Flintoff (who retired during in 2009, with no like-for-like replacement). --Dweller (talk) 07:22, 9 February 2010 (UTC)

Note also that the same ball isn't used throughout the entire test. Each innings (not inning in cricket) starts with a new ball, and a new ball can be taken by the bowling team at regular intervals - typically every 85 overs. [Footnote: an over is 6 balls and each bowler bowls in sessions one over long. At the end of the over they must swap bowlers over]. Taking the new ball in this way leads to some bowlers being described as "new ball bowlers" - i.e. they are good at swinging a new ball (moving it through the air) or seaming the ball (making it deviate off the pitch). I've watched both cricket and baseball live, and the major difference is that batsmen in cricket usually hit the ball, and frequently score runs - it's not hugely uncommon for them to score off every ball in an over. In baseball, hitting the ball is much rarer and it's an event when it happens. (Phil Holmes, not signed in). --205.168.109.130 (talk) 12:16, 9 February 2010 (UTC)

The style and quality of placekicking in American football was improved when European soccer kickers were brought in in the 1960's, raising the success rate from about 58% to 80%. If cricket bowlers have such great throwing arms, have any become baseball pitchers? Are there any well known "two sport" athletes who have both bowled cricket and pitched baseball. as in colletge students who transferred one way or the other partway through their careers? Edison (talk) 17:19, 9 February 2010 (UTC)

I don't think the data shows that cricket bowlers do have particularly better throwing arms. They throw a heavier ball a little more slowly - and the total kinetic energy that they impart is about the same as for a baseball pitcher. The difference is in the nature of the spin (and in the case of cricket, the bounce) of the ball. The skills needed to handle that might possible transfer from one sport to the other with enough practice - but all of the little strategic tricks presumably wouldn't. SteveBaker (talk) 18:46, 9 February 2010 (UTC)

Not sure why Jayron quoted Steve as having said a boler pitches 100 balls in an inning of cricket, i didn't see steve say anything like taht. It was actually me above that said a cricket BATTER faces 100 balls in an inning, as opposed to a baseball batter who faces only a fraction of that. Vespine (talk) 00:06, 11 February 2010 (UTC)

Two ton wheel

What actual potential for destruction does this thing contain? Here's another example of it in motion. Bus stop (talk) 17:51, 8 February 2010 (UTC)

Considering that it is a well-understood machine that would have been found in almost any factory of 150 years ago, I think that the potential for destruction is mainly that of killing the idiot walking that close to it without the correct guards in place. Rmhermen (talk) 18:25, 8 February 2010 (UTC)

I've heard a story (unverified) that some decades ago Lawrence Berkeley National Lab had a series of large flywheels for energy storage, and that one tore loose one day. According to the story I heard, it traveled over a kilometer into the city of Berkeley (aided by the generally downhill topography) before finally coming to a rest. I don't know if that story is accurate, but if you have a large amount of energy in a multiton flywheel it would certainly have the ability to crash through a lot of things before coming to a rest. Dragons flight (talk) 18:56, 8 February 2010 (UTC)

Fortunately for the motorcyclist its direction of travel is away from the motorcycle. Bus stop (talk) 19:57, 8 February 2010 (UTC)

errr... getting from Livermore to the city of Berkeley is (a) a good bit more then a kilometer, and (b) involves traveling over a good-sized mountain (unless the fly wheel used the tunnel, or traveled west and took a strong right turn before the bay). --Ludwigs2 20:11, 8 February 2010 (UTC)

You are confusing Lawrence Livermore National Laboratory and Lawrence Berkeley National Laboratory. The latter is in the city of Berkeley. Dragons flight (talk) 20:39, 8 February 2010 (UTC)

ah. my mistake, sorry. --Ludwigs2 04:16, 9 February 2010 (UTC)

The article Panjandrum describes a big wheel that was built to destroy fortifications but never lived up to its expected potential. It was rocket powered rather than motorcycle powered as the one in the video. A Counterfactual history exercise for armchair generals is "What if Panjandrums had led the Omaha Beach assault?". Cuddlyable3 (talk) 22:34, 8 February 2010 (UTC)

Yeah, that thing was really designed to be destructive, or at least deceptive. Bus stop (talk) 04:17, 9 February 2010 (UTC)

faster than light?

If Black hole(s) can absorb light then it means accordingly that as the stronger force attacts the weaker force the light is attracted towards to the black hole and not (black hole towards the light). So can we say that gravity is a stronger force than light or(light particles)? Morever if gravity is a stronger force than it means that it has the capacity to travel faster than light or the (graviton travels fast than light??). So can we say that there is something which travels faster than light (maybe graviton)?? —Preceding unsigned comment added by 61.1.110.77 (talk) 19:54, 8 February 2010 (UTC)

Your post is somewhat incoherent. Light is not a force, so your comparison does not make much sense. Gravitational fields propagate at exactly the same speed as light. Dragons flight (talk) 20:07, 8 February 2010 (UTC)

(Edit conflict) No. To begin with, Light is a form of radiation energy , not a force, and different forces do not attract one another. Moreover, the speed at which a force "travels" (or rather propagates) does not depend on its strength. If gravitons exist (which is as yet unproven) they would according to current theory travel at the speed of light, not faster. Note that the "Speed of light" is thought to be a fundamental property of the universe and is the velocity that all massless 'particles', including photons, have to travel at it in order to exist; it does not arise from the nature of light, rather light has to conform to it. This has been a "quick and dirty" explanation; I'm sure others will be able to give more elegant ones. 87.81.230.195 (talk) 20:22, 8 February 2010 (UTC)

(after multiple ecs) I don't have a scientific explanation to that either, so I ask all to comment on what I think is a wrong explanation, but the best I can think of now: Gravitation sucks away kinetic energy. For objects with a rest mass this means they are slowing down. For light with no rest mass, this means the frequency goes down. Electromagnetic waves will still travel away from the black hole at the constant speed of light but lose more and more energy up to the point where they reach the event horizon and no energy is left. 95.115.129.147 (talk) 20:31, 8 February 2010 (UTC)

Also... The gravity of a black hole doesn't make light stop and back up. It bends light. The light particles remain travelling at the speed of light - they just change direction. instead of heading out and out and out, they start turning, a little more, and a little more. Eventually, the light travels at the speed of light back into the black hole. -- kainaw™ 20:38, 8 February 2010 (UTC)

I don't believe this is true in all cases. What if the direction light is exactly radial? 95.115.129.147 (talk) 21:11, 8 February 2010 (UTC)

For what you are proposing, there must be absolutely no force applied on the light except a direct pull into the center of the black hole. However, the black hole is moving, spinning, and constantly pulling in all kinds of mass and energy (technically, most theories that I know claim that everything pulled in is energy by the time it enters the black hole). So, it is not reasonable that a light particle will attempt to leave the black hole without being bumped slightly one way or another on the way out. -- kainaw™ 21:23, 8 February 2010 (UTC)

If the hypothetical photon was moving exactly radial to the center of the black hole, it would still be trapped, but instead of spiriling towards the center in a series of concentric spirals, it would instead just oscillate back and forth through that center. Imagine the motion of an object dropped in a hypothetical hole through the exact center of the earth. Same idea... --Jayron32 21:38, 8 February 2010 (UTC)

"Oscillate"? I'm pretty sure that all paths that reach the singularity will terminate there. Dragons flight (talk) 22:56, 8 February 2010 (UTC)

Surely if it's going radially outward and it starts off outside of the event horizon - then it has enough escape velocity to head out and not come back. If it starts off exactly on - or inside the event horizon - it never has enough velocity to leave. It's only the ones that spiral in curved paths around the singularity that do anything interesting! SteveBaker (talk) 23:05, 8 February 2010 (UTC)

I just remembered something I read in a book (not by Hawking) that theorized that a ball of energy (like a photon) could travel at the speed of light to the edge of the event horizon. Once there, some of the energy could escape, while most of it returns in the opposite direction. So, there is never a point at which the ball of energy is not moving at the speed of light. Instead, there is an instant at which it changes from one ball of energy into a large one and a small one with the large one travelling in the opposite direction. I am certain that this theory is not accepted, but it leads to a very similar idea of Hawking radiation which allows bits of energy (radiation) to escape from the fringes of the event horizon. -- kainaw™ 02:19, 9 February 2010 (UTC)

Warning to the readers: If the description given above of the behaviour of a blackhole seems confusing, it's because it is confusing. Most folks in this ref. desk have a view of GR that's best described as an inconsistent almagamation of relativity with newtoninan mechanics and would best serve the readers by refraining from writing any answer at all. Here's what happens to an outward moving light ray: It is still seen as moving otwards at the speed of light by all local observers all the way down to the center of the blackhole. Think of it as reference frames being dragged inwards faster than the light can move outwards. Steve, how is that for something interesting done by a non-spiralling light ray? Dauto (talk) 20:35, 9 February 2010 (UTC)

How is a light ray seen by observers at smaller radius... unless a photon moves towards them and hits them? If the photon is moving away from the observer, then how can they see it? Perhaps you mean a "light source" moving outward radially - but that can not move at the speed of light. An actual photon, which does move at the speed of light, is only observable if it ever reaches the observer. If it's moving outward, the observer will never see it - even if the photon does not escape. Nimur (talk) 22:58, 9 February 2010 (UTC)

The photon and the observer are both falling in as they pass each other. The observer notices that the photon is moving at the speed of light. What's the problem with that? Dauto (talk) 23:52, 9 February 2010 (UTC)

That sounds consistent. The speed of the photon is still observed as c - as it should be in all circumstances. I might have misunderstood your earlier comment. Nimur (talk) 00:06, 10 February 2010 (UTC)

An edit conflict has disrupted this comment, which I am restoring.

In other words, at the moment of observation, the outward-bound photon is still interior to the position of the observer (the photon's radial distance from the black hole singularity is less than the observer's radial distance). The photon, outward-moving, hits the observer's detector. The observer can estimate the photon energy and trajectory. But, the observer interacts with the photon, changing its energy, momentum, and trajectory... so, what we have here is much much more complicated (literally, a quantum/relativistic effect - and to ignore these effects would be qualitatively wrong!). After the photon hurtles on its way back out moving radially away (and now more distant from the black hole than the observer), the observer no longer knows what that particular photon is doing ever again. Whether the photon actually escapes the event horizon or becomes trapped inside is unknown to the observer at this point, unless some other photon comes back conveying information about the final outcome. (The observer may make any theoretical claim about the photon's possible trajectory - but it's unverifiable until information comes back indicating or counterindicating the prediction). Nimur (talk) 00:02, 10 February 2010 (UTC)

You seem as confused about quantum mechanics as Jayron is confused about GR. Quantum Mechanics doesn't tell us that the state of a photon jumps to a different (and unpredictable) state right after beeing measured. On the contrary, QM tells us that the evolution of the photon is completely predictable and described by an unitary operator. The hole point is moot though because there is no need to invoque QM to understand what is happening here. Dauto (talk) 04:00, 10 February 2010 (UTC)

I suppose you prefer a non-quantum treatment for the photon, which is the quantum of light? Nimur (talk) 06:38, 10 February 2010 (UTC)

I don't mind a quantum treatment as long as it is a correct one. Dauto (talk) 13:33, 10 February 2010 (UTC)

Melamine microwave

I know melamine is not safe for microwave because it can crack but aside from this are any carcinogens released when it is heated up in the microwave. I've used melamine dishs to heat up food a lot and sometimes I accidentally overheat it and it browns and or cracks I was wondering if there was any cancer/health risk from that. —Preceding unsigned comment added by Jarwulf (talk • contribs) 20:10, 8 February 2010 (UTC)

This [[3]] official website advises (near the bottom) against microwaving melamine tablewear, as do some others (found by googling "melamine microwave safety"). See also the Toxicity section of our article Melamine (the chemical used in melamine resin tableware). Others I have quickly checked advise not to microwave melamine tablewear for more than a couple of minutes to avoid overheating, browning and cracking. Overall it looks to me as if there is some suspicion that it might not be safe, but the jury is still out. Since at the very least you risk ruining the dishes, I would advise against it. 87.81.230.195 (talk) 20:33, 8 February 2010 (UTC)

Protein structure and function

I'm taking a fourth-year molecule bio+biochem course titled "Protein structure and function". The course content is not challenging at all, but I'm struggling in it just because the prof is making the course needlessly difficult by making lecture disorganized and covering materials not found in course text. The two course texts (the famous Lehninger biochem text and "Protein structure and function" text by Branden and Tooze) and lecture are very unrelated. Most things that the prof covers aren't covered in the text. So we need to take comprehensive notes during lecture. The problem is that I can't listen well and take great notes due to ESL problem. In other courses, I could always go back to text for materials I didn't understand in lecture. I can't do that in this course. I went to prof office hours several times but he was condescending and very unhelpful. I'm wondering if such materials the prof covers actually appear in some text. I'd appreciate recommendation of such text. The materials he covers include (not exhaustive): -Distinguishing features -Cylinder/Plank diagrams -Protein architectures represented by cylinder/plank diagrams -Open and closed sheets and their packing -Molecular volume and van der Waals radius -Surface representations of proteins -Structure prediction -Open and closed sheets and their packing —Preceding unsigned comment added by 142.58.43.83 (talk) 22:02, 8 February 2010 (UTC)

I would recommend two things: Go above this professors head and complain to your department head, college dean, or dean of students. This will help the faculty understand that you are serious about learning the material. Also, this will make the management aware that there is a problem, I think it is safe to assume that you are not the only student in the lecture in a similar situation. Next I would talk to the appropriate person in charged of student health and wellness and ask about getting help taking notes. If this is a public university they might even require the professor to hand out written lecture notes. As always, be firm but polite when dealing with people who are condescending and unhelpful. Its your education, take charge! Cheers! CoolMike (talk) 22:48, 8 February 2010 (UTC)

Are Cylinder Plank diagrams (I've never heard of that term) a synonym of Ribbon diagrams? Also, you can try asking your Prof where he is getting his lecture material from. Most of them have papers or other books they will source their lectures from. It might help if you you ask where he got his illustrations from too; if it is from a textbook, there is an excellent chance the textbook contains relevant info. Also if the course has a Teaching Assistant, bug the TA. 152.16.15.144 (talk) 04:54, 9 February 2010 (UTC)

There is an expectation that students, by the time that they reach the fourth year of their undergraduate degree in a science program, will be able to record and learn information conveyed in lectures. There is an expectation that they will use the recommended/required course textbooks as a source for information and that they will do the required assignments and reading — but also that they will be able to locate additional relevant reference material. The topics that you've listed above (assuming that 152.16 is correctly interpreting 'cylinder/plank diagram' as 'ribbon diagram') are all pretty basic concepts in protein structure. Lehninger and Branden & Tooze are both very popular works in this field, and do cover the topics you've mentioned.

In talking to your professor, you need to consider matters from his perspective as well as your own. For every student who sees a professor as "condescending and unhelpful", I can find a professor who sees a student as 'self-important and entitled'. Neither assessment (or both) may apply in your particular case — but if you go into the office with a chip on your shoulder and looking for a fight, it's human nature for the other guy to respond in kind. Whenever a student complains that the professor makes a course "needlessly difficult by...covering materials not found in [the] course text", you'll find a professor who wants to address important topics without having to write a new textbook just to teach one undergrad course. The whole point of having experts teach senior undergrad courses is to allow you to learn something more than just a bare recitation and regurgitation of the textbook.

If you find that you can't listen and take effective notes at the same time (and it is a challenging skill, particularly when you're new to a topic and don't know what the 'important' bits are yet) then you should consider alternative strategies.

• Record the lectures.
• Get together with classmates to discuss the material and compare notes. (This may also give you a sense of whether or not the prof's expectations are reasonable, and inform you decision about whether or not to bring more formal complaints.)
• As the professor or the TA to recommend relevant readings to review before you attend each class.
• Talk to the course TA (if there is one), but recognize that the TA's job isn't solely to act as your tutor.
• Hire a tutor.
• Drop by the university's biochemistry/chemistry/biology club/society/union and bribe the students there with donuts/cookies and coffee. Really helpful volunteers may deserve beer. (This is cheaper than hiring a tutor, but often just as effective if you're only stuck on a few things. Besides, you might make some friends.)
• Visit the university's health services, student assistance, or disability office to seek help with your note-taking. Not only will they be able to refer you to resources which can help you to improve your note-taking, but they may also be able to arrange for things like videotaping of the lectures.

If you've tried (at least some of) these approaches but still are having trouble, then you might take CoolMike's suggestion and escalate the issue. You're not going to get far in formal processes if you haven't demonstrated some independent effort to solve the problem. TenOfAllTrades(talk) 14:47, 9 February 2010 (UTC)

If you were UK based, your university would have a Student Services department, who would be able to help you find the solution to this. Students Unions over here have traditionally also fulfilled that mediation role. If you decided to tape the lectures, you would have to get the permission of the lecturer (and probably all of the other students, whose contributions would be recorded and who would be entitled to object). Don't let this put you off, though. You may also wish to ask for past exam papers to see how much the lecture material is used in the assessment. --TammyMoet (talk) 18:16, 9 February 2010 (UTC)

Difficulty taking notes during lectures can be helped through the use of "study buddies"/study groups - that is, get together with other people taking the course to discuss the material. Each of you are likely to take down slightly different material, and so you can then literally "compare notes" during the study group. It is highly likely others are having similar difficulties to you, and so would also benefit from a study-group. -- 174.21.247.23 (talk) 04:46, 11 February 2010 (UTC)

time machine

whats the latest development in the research related to time machinepiyush (talk) 22:28, 8 February 2010 (UTC)

See Time travel Nil Einne (talk) 22:45, 8 February 2010 (UTC)

Basically nothing. Aside from some really "out there" theoretical ideas that nobody seriously expects to come to fruition, there is no active work in backwards time travel because it's impossible for all practical purposes. Forwards time travel is really just a matter of waiting! Although you can get to the future a bit faster by accelerating to close to the speed of light. SteveBaker (talk) 22:59, 8 February 2010 (UTC)

I was planning to say a similar thing but Time travel#Experiments carried out has some stuff that may be of interest to the OP even if it wasn't what he? was thinking of. Some of the people involved appear to have some credible even if their claims don't (or they never made any claims in the first place). Nil Einne (talk) 23:04, 8 February 2010 (UTC)

It's still refutable by merely thinking about in full sobriety. Vranak (talk) 14:00, 9 February 2010 (UTC)

Time exists to stop everything happening at once. Now is the start of your voyage into the future...ah, I see you've arrived already. "Oh dear! Oh dear! I shall be too late!".Cuddlyable3 (talk) 19:31, 9 February 2010 (UTC) i know this wudnt be classified as time travel but I have flown from Dubai International airport at 18:05 local time on a given day and have touched down at Doha International Airport at 18:00 local time. Which means I experienced two 18:00 that day. Does this qualify as time travel?