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Homework Help: Question Regarding Einstein's TSR

  1. Dec 8, 2004 #1
    If one was performing calculations and got a final velocity of say, 0.99999999c (or 2.99999x10^8); could one logically round that to 'c'? After all, by rounding that value to 'c', you are in a whole different situation, since now, time and distance are infinitely small, as well as mass and momentum which are infinitely large.

    Therefore, by rounding to 'c', you are completely ignoring billions of years of existance.

    Last edited by a moderator: Dec 8, 2004
  2. jcsd
  3. Dec 8, 2004 #2


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    Nope.If one finds through correct methods/calculations that a particle has a speed different from "c" with the number "10^{-n}",where "n" can be arbitrarily large,BUT SMALLER THAN "c",then that particle's speed CANNOT BE APROXIMATED TO "c",since that would change one of the particle's fundamental intrinsic atributes:the rest mass.And that is assumed fixed.

    Hopeful that i have been understood,
  4. Dec 8, 2004 #3


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    Just to add to what Dexter said - a particle can travel at the speed of light if and only if its rest mass is exactly 0. If it has a non-zero rest mass, however small it may be, then it will be limited to speeds less than light. For quite some time, it was thought that neutrinos had a zero rest mass, and therefore travelled at the speed of light. It caused a minor sensation when it was determined that neither of those was true.

    What it really comes down to is that a speed of 'c' is special. If you're mathematically inclined, you might think of it as being similar to a singularity. The rules that apply when you're close to it - however close you wish to get - are different from those that apply when you're there.
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