Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Frezing light

  1. Dec 14, 2005 #1
    at the Univeisty of Austrilla they found a way slow down light:confused:They slowed it down from 670 millies per hour to 670 miles per hour:surprised :confused:
    http://www.sciencentral.com/articles/view.php3?type=article&article_id=218392702 [Broken]
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Dec 15, 2005 #2
    What exactly is so shocking about this?
  4. Dec 15, 2005 #3
    I'am confused how are you soppesed to slow light Einstien said you couldn't
  5. Dec 15, 2005 #4
    I haven't read the link but I'm assuming they aren't - the light is travelling at c but it's continually absorbed and emmitted by electrons in the medium it's being passed through, so it takes significantly longer to get from A to B, effectively 'slowing' the speed the light takes to travel the distance.

    That's why the speed of light in air is slower than the speed of light in a vacuum (iirc particles produced by high energy cosmic rays can actually travel faster than light in air, producing some kind of shockwave akin to that of a sonic boom)
  6. Dec 15, 2005 #5
    Yup, it's called Cherenkov radiation:

  7. Dec 15, 2005 #6
    The idea of puting the nuclear spin usage into computesr is inegnious. I mean, you think we have fast comptuers now, just think about getting the computations that take several minutes today, take less than a millionth of a second! Shwew!
  8. Dec 16, 2005 #7


    User Avatar
    Science Advisor

    No, he said the speed of light in vacuum is the same to all observers, irrespective of how fast they are moving relative to one another. That's a completely different thing from what's happening here.
  9. Dec 17, 2005 #8
    the speed of light is the same in any medium. The reason it appear slower is because of absorption and the reemition of a new ray.
  10. Dec 19, 2005 #9

    In other words, light only travels in a vacuum. A single photon does not push through matter.

    Transparent matter lets light through, because its particles absorb the photons as they come in, then emit another one out the other side.

    This absorbing and emitting takes time, and the resulting slowdown is called the "refractive index" of the matter.

    But the light itself, the photons, only ever travel at full lightspeed.
    Last edited: Dec 19, 2005
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook