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French scientists discover method to change the speed of light.

  1. Aug 22, 2005 #1
  2. jcsd
  3. Aug 22, 2005 #2
    Wow sounds like this could have actual pratical applications. "Part" of the signal moving FTL? Anyone have some Kaku-like insight into this?
  4. Aug 22, 2005 #3


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    From the link:
    1) It's in a MEDIUM (the fiber) not a VACUUM.
    2) It's about PULSES, not BEAMS.

    Every time some scientists show a useful trick with light in media, some reporter has a conniption fit about FASTER THAN LIGHT!
  5. Aug 22, 2005 #4
    I just wanted to here peoples thoughts on this.
  6. Aug 22, 2005 #5
    I think you are missing a large point which is the usefulness of bing able to slow down light in a standard fiber cable. It's not like they claim to have built a time machine. This could be a huge step in providing a seamless communications network for the planet couldnt it? As far as speeding up light in a standard fiber cable I'd like to hear the concept, the article didnt really explain nor could I find it elsewhere.
  7. Aug 22, 2005 #6
    Dr. Kaku has often described light as not truly having been slowed down but given more area to move in, so it seems as if it's been slowed.
    Sort of like if you ride your bike zig zaggy, it will take you a lot longer to get from point A to B than it would if you biked in a straight line.
    You could also say like an obstacle course slows an athlete down.
  8. Aug 22, 2005 #7
    Yes that makes sense but what is their theory behind speeding it up since you can't make the distance shorter? I can't imagine that that part of it has any practical application but the idea behind it would be of interest.
  9. Aug 23, 2005 #8

    It is the group velocity of a light pulse made up of various frequencies that is said to go ftl.

    No single photon actually goes ftl, but the velocity of the pulse of photons appears too. It is similar to an interference phenomena.

  10. Aug 23, 2005 #9
    It would truly become helpful if we could do this in space. Especially when sending messages between earth and mars. But from what I understand, this speeding up and slowing down can only be controlled in a medium.
  11. Sep 6, 2005 #10
    since light travels slower than the 'speed of light' in media like optic cables, it is not actually the 'speed of light' that is being changed, but the speed of propagation in a medium. The difference seems huge to me. On one hand, you have photons flying through space at the true speed of light (c), and on the other, you have light being absorbed and re-emitted in a bucket-brigade arrangement through a medium.
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