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Light and my speed

  1. Sep 3, 2003 #1
    if iam travelling along a light beam and if my speed matches (dosent happen,if) can i see the ligth standing still....
  2. jcsd
  3. Sep 3, 2003 #2


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    No, light will always be measured to have speed c, for every observer, irregardless of your speed with respect to other objects.

    So if you were able to attain .9999c with respect to the earth any experiment to measure the speed of light would yield c.
  4. Sep 3, 2003 #3
    Allow me to modify the question
    somewhat to satisfy my curiosity
    about this: Let us stipulate two
    laser beams traveling in space
    as parallel as possible. The
    photons in these beams are con-
    sious and intelligent and they
    have eyes. If the photons in one
    beam look at the photons in the
    other do they seem to be motion-
    less or whizzing by at C?
  5. Sep 3, 2003 #4


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    Photons do not know time or distance. To a photon the universe is a point, it takes zero time to traverse it. So they cannot observe antother photon, being as they spend zero time in transit.
  6. Sep 3, 2003 #5
    How is it that crossing the Univer
    -se takes 0 time from the photons
    perspective when it seems to us
    to take trillions, or whatever,
    years? Why is the universe a
    point to a photon?
  7. Sep 3, 2003 #6


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    Are you familiar with the Lorentz transforms? When your velocity is c, time dilation and length contraction reduce time and distance to nothing. So as far as a photon is concerned, the instant it is emitted it is adsorbed, it has gone no distance in no time.

    Edit: Typo
    Last edited: Sep 3, 2003
  8. Sep 3, 2003 #7
    Yes, I'm familiar with the Lorentz
    Transformation, and, I see what
    you're saying makes sence in light
    of them (pun intended).

    I'm sure you can understand that
    this situation presents as a
    contradiction: we measure light
    to go at 300,000 kilometers a
    second, but light perceives its
    own travel as instantaneous. This
    bothers me.

    Regardless, thanks for your expl-

    Last edited: Sep 3, 2003
  9. Sep 3, 2003 #8


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    Perhaps it the precieved speed is in reality a Quantum effect, haveing to do with the Plack Time and Distance. I feel your pain, why if Light sees no time and no distance, do we preceive a finite speed.

    Wonders of the universe.
  10. Sep 3, 2003 #9
    Once again, it has been forgotten that Lorentz transformations have been set up and derived for observer systems of coordinates with a speed v less than c between them. In order to arrive at the transformation, light must be capable of going from one observer to the other and back again, at any time, according to either observer's clocks. The transformation is not expected to work when v is set to c and the Lorenz factor becomes 1/0. Light itself cannot comprise an observer system under this scheme.
  11. Sep 3, 2003 #10
    Still learning here so help me out fella's. Photons do/don't have mass? If they do, and since they are already at c, why don't they have infinite mass already? If they don't, how can they be captured, stalled, and/or held as I've seen in so many experiments that have been reported as of late?

    Does the time dilation and length contraction bit, for a photon, equate to tunnelling(sp)?

    Thank you in advance.

  12. Sep 3, 2003 #11


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    Photons don't have rest mass. But they do have energy, which we translate to "relativistic mass".

    Uh... stalled/held? Which experiments?

    The key postulate of relativity is that light travels at c regardless of frame of reference.

    Tunnelling is IIRC a quantum phenomenon, due to quantum uncertainty in particle involved.
  13. Sep 3, 2003 #12
    I'm almost positive that I followed a link from this site to a BBC story where a group of Scientists were able to at least "delay" a photon a measurable amount of time. I want to say they were Nederlanders but that part I'm not sure of. I believe either AMES RC or SWRI duplicated it, but then again, I could be completely wrong.

    DANG! Not a whole lot of concrete info coming from me nowadays. If I find it would you like a PM or a re-post here?

  14. Sep 3, 2003 #13


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    What happens in these experiments is the the photon is absorbed by an atom, and the atom stores the properties of the photon until triggered. It then emits an exact copy of the original photon. The effect is as if the photon was delayed, but waht really happens is that it ceases to exist as a photon while its information is stored in the atom. As long as a photon exists as such, it will travel at c.
  15. Sep 4, 2003 #14
    SWEET work man!!! You just asked yourself the same question Einstien did before he invented relativity to deal with it. The answer (known before relativity) is that no matter how fast you go, light is always travelling the speed of light faster. You can never see a beam of light standing still. This is precisely why you can never REACH the speed of light, since it's always faster! This mind boggling answer is what leads to time distortion and all that confusing stuff.
  16. Sep 4, 2003 #15


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    Janus: from the links he supplied, it looks like Echo etc was referring more to experiments involving the production of BECs, where what you said may not apply. (But then again, I am mostly ignorant as to the nature of Bose-Einstein condensates) In any case, can you (or anyone else) enlighten us?
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