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Spinning at the speed of light?

  1. Jul 18, 2008 #1

    RunSwimSurf

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    Gold Member

    Actually I have a couple of questions. First of all, I'm new here so hello to everyone.

    1) Is it possible for an object or something to rotate at the speed of light? For example, with a special record player, can a record spin at or near the speed of light or does c only refer to a straight path? Also, do the same rules apply meaning an infinite amount of energy is needed to accelerate the record to c?

    2) Let's say that it is possible for a record to spin at light speed. If the inside and the outside of the record are traveling at the speed of light, but the outside of the record must travel a greater distance, then wouldn't the outside of the record be traveling faster than the speed of light? (I vaguely remember seeing this problem in a Calvin and Hobbes comic strip)

    3) Since it's impossible to accelerate an object to the speed of light, is it possible for an object to exist which has always been faster than light? Another massless particle of some sort? Or does SR forbid this?

    Thanks.
     
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  3. Jul 18, 2008 #2

    JesseM

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    Science Advisor

    Yeah, it's impossible because it takes an infinite amount of energy to accelerate any massive object to c.
    SR doesn't really forbid it, such hypothetical particles are called "tachyons", see this article. But there's no evidence they exist, and if SR is correct any faster-than-light signalling would also open up the possibility of sending signals backwards in time for reasons relating to the relativity of simultaneity, so they'd cause problems with causality.
     
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