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What happens to mass at the speed of light

  1. Apr 1, 2004 #1
    I'm trying to understand a abstract principle of travelling at light speed.

    My understanding of anything that contains mass that goes near light speed, would have one major problem, that is how would the mass stay together? Wouldn't there be varying speeds at the start of light speed that would completely destroy any mass. Even though the time references would be in the millions to billionths to... of a second. Wouldn't that be enough 'time' to separate a physical structure?

    I have the perception that, any physical structure or anything that has mass, is both or one, has a maximum limit on how fast it can go before the physical or mass collapses due to the sheer speed at wish the object is travelling at.
    Last edited: Apr 1, 2004
  2. jcsd
  3. Apr 1, 2004 #2

    From special relativity's (SR's) view point:
    An observer travelling at light speed will not notice anything different than an observer at rest. However, it is not possible to push mass to the speed of light, as the energy required would be infinite.

    I don't believe SR is correct. I think that the mass itself will not change. A perception of mass increase is caused because forces weaken near light speed. This also is responsible for the time dilation effect.
    Basically nothing will happen to mass at light speed. But an observer travelling along with it will see strange things happen (not according to SR).

    In both cases a stationary observer will record an infinite increase in the mass of the object that travels at the speed of light.

    I dont believe the mass will breakup.


    "particles of nothingness"

    Edit: I have bolded text which is not accepted theory.
    Last edited by a moderator: Apr 1, 2004
  4. Apr 1, 2004 #3


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    please keep your theories in TD. You were doing fine right up till you stated talking about YOUR theories.

    Just say that according to SR, massive objects cannot be accelerated to the speed of light.
  5. Apr 1, 2004 #4


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    Y'know, I sometime wonder if people who say they do not "believe" in so-and-so theory actually understand whatever it is they do not believe in beyond just what they read in pop-sci books, or if they even realize that they themselves are USING the stuff they do not believe in.

    SR is often the case. Unfortunately, people seem to think that SR's experiment and applications are in some esoteric experiments that have nothing to do with what they use everyday. This of course, is a major falacy. Some of the most convincing evidence of SR (and QM) validity comes from condensed matter physics/material science. The band structure calculations for many materials use in modern electronics contain relativistic corrections. That is the only way to make them agree to the various experimental results.[1] We will have an impossible time explaining the various properties of a lot of materials (common ones, not just exotic ones) without SR. Considering the fact that we know it so well that we can actually make applications out of these materials, is one big illustration of the validity of Sr.

    Secondly, if one doesn't believe in SR, one should not fly in airplanes either, or anything that uses GPS systems. GPS systems DEPENDS on relativistic corrections to make those accurate positioning, which would go haywire if SR and GR are not taken into consideration.[2]

    Luckily, physics doesn't depend on "beliefs" or "tastes". Nothing is more convincing than having a tons of experimental verification done everyday, even by the very same people who do not believe in it.


    [1] See, for example, http://www.iop.org/EJ/abstract/0953-8984/7/14/017; http://arxiv.org/abs/cond-mat/0211360; [Broken] http://www.mpi-stuttgart.mpg.de/andersen/docs/pub/abstract/and1990-38.html; [Broken] etc....

    [2] http://www.physicscentral.com/writers/writers-00-2.html
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  6. Apr 1, 2004 #5


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    Coming back to Cipher's question:

    The basic point of relativity is that "speed" is a relative concept; i.e., it only makes sense to talk about the speed of an object with respect to another. The physics for one object (i.e., its properties on its own reference frame) stays the same, regardless of its speed wrt all other objects.

    For instance, you and I are just now travelling at close to light speed with respect to many quasars out there, and I, for one, am not feeling any effect.
  7. Apr 1, 2004 #6
    I understand the POV of SR on this particular matter. But what im trying to get to is, wouldn't the acceleration to light speed ultimately destroy a physical object or mass, because of the various speed diferences there would be on a object during times of acceleration. Such as even if it only took 1 millionth of a second to reach light speed, there would be differences in speed from point 1 to point 2 (assume beginning and end) of the physical object or mass, that would complete destroy it.
    Last edited: Apr 1, 2004
  8. Apr 1, 2004 #7


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    The final speed resulting from acceleration is immaterial. It is the magnitude of the acceleration that you seem to be talking about. We live in an environment of a constant 1g acceleration, with no effect. So if we were to get in a spaceship and accelerate for a life time at 1g we would not even notice the acceleration. If you are in a car doing 100mph and run into a wall the acceleration you experience would be life threating.

    Using Newtons law one could calculate the maximum acceleration an atom can with stand. You need know the magnitude of the force which binds the atom together. When the accelerating force exceeds that binding force the atom will come apart. It does not matter what the speed is, only what the acceleration is.
    Last edited: Apr 1, 2004
  9. Apr 1, 2004 #8

    It solved my thoughts on the subject.
  10. Apr 1, 2004 #9
    What about the idea that an electron is orbiting the nucleus of an atom? If the nucleus is travelling at the speed of light, then an electron orbiting that nucleus would be travelling faster than light almost 50% of the time and slower almost 50%. Since that is not possible, matter cannot travel at the speed of light, correct? Or if it does, its electrons will not be able to keep up with it?
  11. Apr 1, 2004 #10


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    SR forbids a nucleus from reaching c. Relativistic addtion of velocities means that the electron orbiting a nucleus traveling near c will not exceed c.
  12. Apr 1, 2004 #11
    Are there any known Field Tests that could possibly hint at a probability of resolution?
  13. Apr 1, 2004 #12

    If the nucleus is travelling at the speed of light, then an electron orbiting that nucleus would be travelling faster than light
    Last edited: May 2, 2004
  14. Apr 2, 2004 #13
    I believe you have a valid point here. This covers my earlier response:
    But an observer travelling along with it will see strange things happen (not according to SR).

    I would not like to be in a craft travelling at near light speed.

    PS: Integral. Thanks for the prompt on TD and explaining the answer to Cypher's question.
  15. Apr 12, 2004 #14


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    A belated welcome to Physics Forums Cypher!

    It seems that no one responded to this question of yours; would you be so kind as to explain a bit further what you mean? For example, what do you mean by "Field Tests"? what "resolution" are you seeking?
  16. Apr 12, 2004 #15
    An important point is missed here, however:

    In SR, all velocity is relative velocity.

    If you were traveling at, or close to, the speed of light, you would not know it. You would think yourself at rest, and everythin else in motion.

    We talk about the "impossibility of traveling at the speed of light," but we never ask, "relative to what"?
  17. Apr 13, 2004 #16


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    For "close to the speed of light", relative to something else, your statement is correct. For "at the speed of light" relativity tells you your invariant mass is zero, and so is the passage of your proper time; you don't have a rest frame in that case.
  18. Apr 13, 2004 #17
    This is information that I am very interested in. I do not think that what you are describing is a consequence of the Lorentz Transform, is it? Please, please, please, flesh this out for me!!!
    Last edited by a moderator: Apr 13, 2004
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