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Harvard Physicists Make Light Dance

Posted by kdawson on from the not-so-fast dept.

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.

6 of 109 comments (clear)

  1. Re:So, if you walk next to stopped light... by CaffeineAddict2001 · · Score: 4, Informative

    Relativity is concerned with the speed of light in a vacuum. Anytime light passes through a substance it is slowed down. It's not much different than walking past a cup of water.

  2. Re:acid by spun · · Score: 4, Informative

    Acid is for wimps. If you really want to see light dance, you want N,N-DMT or 5MeO-DMT. There is also no way to stop it from utterly demolishing your ego, so ego based people should NOT try it.

    --
    - None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
  3. Frame of reference by DAtkins · · Score: 5, Informative

    Hee hee... that's funny, despite the fact that it's wrong.

    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.

  4. Re:Is this EPR? by w33t · · Score: 2, Informative

    Entaglement is featured in this experiment, but I do not think the photons are being entangled, per se.

    The device being used for this experiment is a Magneto Optical Trap. 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 the condensate is the ideal place to slow some photons down, apparently to a stop. It's very cool (pun intended).

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  5. Re:So, if you walk next to stopped light... by BitterOak · · Score: 3, Informative

    That's absolutely correct. In fact, it is quite common for particles to travel through a medium faster than light travels through that medium. That is the principle behind how a Cherenkov detector works.

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  6. Re:relativity by Anonymous Coward · · Score: 3, Informative
    Your explaination seemed wrong to me, since wavelengths too long to be absorbed by electrons also slow in a dense medium. From wikipedia:

    It is sometimes claimed that light is slowed on its passage through a block of media by being absorbed and re-emitted by the atoms, only travelling at full speed through the vacuum between atoms. This explanation is incorrect and runs into problems if you try to use it to explain the details of refraction beyond the simple slowing of the signal. Classically, considering electromagnetic radiation to be like a wave, the charges of each atom (primarily the electrons) interfere with the electric and magnetic fields of the radiation, slowing its progress. The full quantum-mechanical explanation is essentially the same, but has to cope with the discrete particle nature (see Photons in matter): The E-field creates phonons in the media, and the photons mix with the phonons. The resulting mixture, called a polariton, travels with a speed different from light.