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Question about C and Mass

  1. Mar 18, 2009 #1
    Please forgive me for mistakes I am learning.

    If as an object approaches the speed of light it gains infinite mass then would an object in a absolute reference state have zero mass? (I understand the problems with an absolute reference state existing, but I am talking theory here)
  2. jcsd
  3. Mar 18, 2009 #2

    Doc Al

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    Staff: Mentor

    I don't know what you mean by "absolute reference state". Perhaps you mean a reference frame in which the object is at rest? In any case, it's only the so-called "relativistic" mass that increases without bound in a frame in which the object's speed approaches light speed. In the rest frame the mass would be the normal, everyday invariant mass. (Not zero mass!)

    [tex]m' = \frac{m}{\sqrt{1 - v^2/c^2}}[/tex]

    where m' is the relativistic mass, and m is the ordinary mass. When v = 0, m' = m.
  4. Mar 18, 2009 #3

    I actually meant a reference frame of absolute zero velocity.

    Can there be a true "rest frame" Since everything has velocity in reference to something?
  5. Mar 18, 2009 #4
    There is not such a thing as a true rest frame. This was shown in 1887 when the Michelson-Morley experiment was done. They tried to prove the existence of aether, but they failed and showed there was no such thing as aether (and thus absolute rest).

    It is quite a long story to post it all, but you should google on Michelson-Morley to find out how it works :) .
  6. Mar 18, 2009 #5
    I will and thank you for all your time and assistance.

    I promise I am learning.

    just a question.. there may not be a True Rest Frame now.. but what about before.

    Before the big bang when everything was in a finite space - would that not have been a True Rest Frame?
  7. Mar 18, 2009 #6

    Doc Al

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    Staff: Mentor

    Right, there's no such thing as an "absolute" or "true" rest frame, as all velocities are relative. But an object can certainly be at rest with respect to some particular inertial frame.
  8. Mar 18, 2009 #7


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    The phrase 'before the big bang' is difficult because there was no time until the BB, so nothing can be earlier. This sounds contradictory but I've been told ( and I've read ) that this is not a paradox. To me it is but I don't lose sleep over it.
  9. Mar 18, 2009 #8
    This becomes a totally different question. I'm not sure if there was space before the big bang (I guess it is believed by physicists that there was no space-time before then), so then it doesn't make sense to talk about frames of reference, because there wasn't anything to refer to.

    I'm not sure though, maybe others have a different opinion.

    You're welcome, by the way!
  10. Mar 18, 2009 #9

    Thank you again.

    I must turn off my dads computer or he will be angry.
    I will move the rest of my questions to another forum as they have now evolved to another topic.
  11. Mar 18, 2009 #10
    Tell your dad you're doing physics and he'll go nice on you :smile:
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