Harvard Physicists Make Light Dance 109
tetrikphimvin and others clued us to the latest work by Harvard's Lene Vestergaard Hau, being published today in the journal Nature. The NYTimes has a good layman's overview of how Hau's team encoded a light beam in a clump of atoms and later reconstituted it elsewhere. The Harvard Gazette offers additional details, a photo, and video links.
Dancing lights (Score:1, Funny)
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relativity (Score:2, Interesting)
Vista Help Forum [vistahelpforum.com]
Re:relativity (Score:5, Interesting)
In the experiment being discussed in the article, it sounds like they are stopping the process at the point where the photons have been absorbed by matter, and delaying their being re-emitted for quite a long time (relatively speaking). The light is being stopped, but not by causing photons to travel more slowly than c. It's being stopped by keeping the photons' energy bottled up inside the Bose-Einstein condensate.
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MOD PARENT UP (Score:2)
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Re:relativity as light is just surfing the expandi (Score:4, Interesting)
There, fixed it for ya. You were too smug to notice that you put your words into his mouth, and then accused him of making a flawed definition.
If you can define the term "expansion" without referring to temporality, I'll concede.
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A photon does not age. No time passes for a photon. This is because although a photon travels with the velocity c, it stays at the exact same place in the fourth dimension as it surfs the expanding fourth dimension. How else, other than with a moving fourth dimension, can we explain that the only way to stay stationary in the fourth dimension is to move at the velocity of c relative to the three spatial dimensions? And how else, but with a moving fourth dimension, can we explain that any o
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I'd mod your troll to something else if it wasn't for the "You are stupid" comment at the end. It's interesting, though, to see such careless disregard for other people's feelings.
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You're assuming that the 4th dimension is time. Nobody has ever said that was the case, although many people have ASSUMED it to be true. The 4th dimension is a direction, much like up, down, or sideways, but is orthogonal to all three. See here for a description.
It has nothing to do with what the fourth dimension IS. The problem is the use of the word "expanding." For something to expand, it must change size between two points in TIME. So the entire concept of expansion is ROOTED in time and cannot be u
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Consider a 4th dimension expanding relative to the three spatial dimensions in units of the Planck length at the rate of c.
And then you use the word "rate" which blows the whole damn thing out of the water. Please stop spamming us with irrelevant math.
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I'd mod your troll to something else if it wasn't for the "You are stupid" comment at the end. It's interesting, though, to see such careless disregard for other people's feelings.
As a followup to this comment, the continued spamming behavior of this user (who has now posted the same crap about 5 times) coupled with his inability to grasp the concept that a "expansion" necessarily must be described in terms of a TEMPORAL VARIABLE, puts him firmly in the set of people who's feelings I feel justified in d
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As Brian Greene points out in the Appendix to Chapter 2 of The Elegant Universe, we note that from the space-time position 4-vector x=(ct,x1,x2,x3), we can create the velocity 4-vector u=dx/d(tau), where tau is the proper time defined by d(tau)^2=dt^2-c^-2(dx1^2+dx2^2+dx3^2). Then the "speed through space-time" is the magnitude of the 4-vector u, ((c^2dt^2-dx^2)/(dt^2-c^-2dx^2))^(1/2), which is identically the speed of light c. Now, we can rearrange the equation c^2(dt/d(tau))^2-(dx/d(tau))^2=c^2 to be c^2
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If asked a question, you do not post an unformatted clipboard copy of the entire FAQ page. That just shows that
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Well, to be fair, it's entirely possible that this fourth dimension is expanding relative to some other metric which is not temporal, but that merely shifts the mystery to this new dimension. What point is there in "explaining" the flow of time if we can only do so in terms of another concept which is equally mysterious?
Unfortunately, the poor guy has been misguided by the "Whoo, mystical" style of Greene's writing. It's a good style if you want to sell books, I guess... Greene is talking about basic conc
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One Bad Joke (Score:5, Funny)
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So, if you walk next to stopped light... (Score:2, Insightful)
Re:So, if you walk next to stopped light... (Score:5, Informative)
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As I understand it, light doesn't slow down when passing through a substance. It travels with it's usual velocity of c, but merely takes the scenic route to it's destination.
Re:So, if you walk next to stopped light... (Score:4, Informative)
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Was it quicker to post an acronym, then the explanation of what you meant? I don't mean to be rude; I am genuinely confused about this practice. If you explain it to me I may do it to
Re:So, if you walk next to stopped light... (Score:5, Funny)
IANAP but I think that when virtual particles interact in a magnetic field then in the frame of reference of a photon the wavefunction collapse allows faster than light communication except when in violation of the second law of thermodynamics.
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One uses an acronym to reduce the characters used to explain a topic, useful when limits are imposed on message lengths (such as text messages). But 1. I was unaware that
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What is a "frame of reference"? What does it mean to be "in a frame of reference"? What does it mean for one thing to be in a different "frame of reference" to another?
Why is it that when people talk about physics they completely discard most of the contents of their brain and start spouting drivel. Just speak ordinary English and you'll find that your physics makes sense too. A frame of reference is nothing more than some rulers and
Frame of reference (Score:5, Informative)
Frame of reference is an idea that actually had it's beginnings in Einstein's work. The idea being, can a person determine the absolute velocity of [something]. For example, from the frame of reference of the earth, my car goes 65 miles per hour. From the frame of reference of the sun, my car goes 2.9 km/s (because the earth moves that fast around the sun.
Why is this important? Well, Einstein used this to question why the speed of light seemed constant despite your frame of reference. On a ball of rock orbiting the sun at 2.9 km/s, the speed of light is c. On the surface of the sun (which has no orbital velocity in comparison to the earth), the speed of light is still c. From the frame of reference of the center of the galaxy (where the sun has extremely high relative velocity - which I'm too lazy to look up) the speed of light is still c.
Which means that, either the speed of light somehow knows how fast you are going and adjusts itself (which is, of course, retarded) or there is something about spacetime that makes it seem that way. Hence the general theory of relativity was developed to explain it. (Which, in case you are curious, states that the ruler that you are using lenghtens or shortens depending on your "frame of reference")
So, it's actually quite important.
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No it didn't. I don't think this point needs arguing. A frame of reference is an ordinary everyday concept that has been in use by physicists and mathematicians for centuries.
Ah...at least you're giving me enough information to tell me what you mean by "your frame". By "the frame of X" yo
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It has nothing to do with frames of reference. One of the conclusions of the special theory of relativity is that light's speed in a vacuum (c) is a constant in all frames of reference. The rule here is that you can't move faster than light does in a vacuum.
This is because as you approach the speed of light, various physical properties of your frame start to break down as viewed from other frames (in your frame of reference you're not moving at all; it's everyone else who sees you blazing by at light spee
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DDR Lights... (Score:5, Funny)
Meanwhile (Score:5, Funny)
acid (Score:3, Funny)
Re:acid (Score:5, Informative)
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Tell me more about the orgasm! (Score:1)
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I'm jealous too. (Score:1)
heh
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wow. (Score:1)
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Is this EPR? (Score:2)
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The device being used for this experiment is a Magneto Optical Trap [wikipedia.org]. This cool-ass device uses lasers and magnetism to suspend a cloud of ultra-cold atoms in a bonafide Bose-Einstein condensate. This is a state in which all the particles act together as though they were a single, very large, particle. I believe they are entagled - but of course, I Am Not A Physicist.
Apparently the ultra-cold environment of
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If you want to know more about BEC, Physics 2000 [colorado.edu] is a good place to start.
Electric slide? (Score:1)
Meteorologically speaking... (Score:2)
Head asplodes...
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Implodes or Explodes, but there is not such word as asplode, unless this has something to do with getting shifted to where the light does not shine?
Light TCO (Score:1)
Is it that cheap to create a Bose-Einstein cloud? Okay, Corporations would be able to afford it but only for extremely critical applications. A case of worse being just good enough.
And I am stumbling over how slowing light down by such a relatively large degree would end up with a reasonably valuable increase of calculation speed. We d
invisibility (Score:1)
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And soon (Score:1)
Credit to the Experimenter, Link to the article (Score:3, Interesting)
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Where do you get CMOS? Do you see any complimentary metal oxide semiconductors in there? And it behaves nothing like a transistor.
Light released from matter? (Score:2)
With any luck, they can put these atoms in a phial to be released when all other lights are dark. I know someone who could really use it.
Any technology sufficiently advanced is indistinguishable from magic.
what's the point? (Score:1)
My hamster, Melvin, is slow when he's cold and "stops" light. Coincidentally, he can then "release" the light when hit with a laser.
Not old news...ancient (Score:1)
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Well, if the 38 miles per hour development was in 1999 [cnn.com] and the article states that development occurred two years ago, I would guess that this is a really, really old article.
Moo (Score:1)
It's about time those stuffed-shirts had some fun. And being it's just a "light" dance, they won't even break a sweat.
ehm. they made a .. Disco ? (Score:1)