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The Light barrier

  1. Apr 21, 2006 #1
    Hi, just got into the topic of relativity and got curious. Is it possible to break the light barrier similiarly to the sound barrier? I have just found an article that someone had done it. http://www.lastek.com.au/light.htm What are your views on this?
  2. jcsd
  3. Apr 21, 2006 #2


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    It should be impossible for a message (information) or energy or particles to travel faster than light. But waves can travel faster than light--as an analogy, imagine a long row of people on a giant bench "doing the wave", with each person having a pre-arranged time to stand, you could easily arrange things so that two people 1 light-year apart would stand up less than a year apart, so the wave of people standing would travel faster than light.

    This article goes into more detail on the experiment you linked to, and why it does not conflict with relativity, if you're interested.
  4. Apr 22, 2006 #3


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    This account is highly misleading. They did NOT send signals faster than light; they exploited a strange medium that permitted them to "invert" the leading edge and the trailing edge of the signal envelope so the trailing edge came out of the medium before the leading edge. There was a lot of hoo-hah about the experiment at the time (2000) and it was eventually straightened out. Relativity does not allow massive objects to travel faster than light.

    That said, in an ordinary medium like water light is slowed down, and there it is possible for a fast moving particle to outstrip its own light. When that happens you get an optical equivalent of the sonic boom that accompanies breaking the sound barrier. This is called "Cerenkov radiation"
    (the C in Cerenkov is supposed to have a little v-mark over it to indicate it's pronounced like the ch in chair: CHAIR-en-koff).
  5. Apr 23, 2006 #4
    Thanks for the information guys, this proves to be very interesting indeed.
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