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Neutron Star at Near Light Speed

  1. Sep 16, 2014 #1
    What would happen to a neutron star (on the cusp of becoming a black hole) if it were sped up to near the speed of light? Or more easily done, if I sped up to near the speed of light. Would the additional mass from the near light speed cause the neutron star to collapse in on itself and form a black hole?

    I am guessing that a black hole would not form, but I am curious as to the reason why. If my guess is wrong and a black hole would form, then what would a person stationary to (and light hours away from) the black hole see? The stationary person would not detect an increase in mass to cause the collapse.

    Any insight would be appreciated.
     
  2. jcsd
  3. Sep 16, 2014 #2

    phinds

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    You, right now as you read this, are traveling at .999999999999999c. This is enough speed to cause you to become REALLY massive in the sense that you mean. Do you feel any heavier now that you know that? The accelerated particle that I used to make that determination of your speed is in a rest frame from which you appear to be going as fast as I said, and from that IRF you "appear" very massive, again, "in the sense that you mean".

    The point here is that in the rest frame of any object, it is standing still.

    Does that answer your question?
     
  4. Sep 16, 2014 #3

    Chronos

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    You are talking about relativistic mass, which is a misleading concept that is rapidly disappearing from scholarly use. It is basically only useful for talking about the force necessary to further accelerate a massive body traveling at relativistic speeds.
     
  5. Sep 16, 2014 #4
    Interesting. I had not heard that. So, if two bodies were traveling at near the speed of light relative to one another and they interacted gravitationally, would their interaction happen according to their rest masses or to their apparent, relativistic masses?
     
  6. Sep 16, 2014 #5
    I read a little on relativistic mass, so maybe I can answer my own question. From what I can gather, it is an effect of space-time itself and not the internal structure of the object itself. The neutron star would not turn into a black hole no matter how fast it went.

    However, I am still unclear how two objects approaching each other at near the speed of light would interact gravitationally. Since relativistic mass is a space-time effect, I would guess that the two objects would interact as if they were more massive. But that is just a guess.
     
  7. Sep 16, 2014 #6

    Chronos

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    Correct! A massive body that is not a black hole in its own inertial reference frame is not a black hole in any inertial reference frame. Gravitational interactions between bodies traveling at relativistic speeds looks complicated, but, is not. It still looks like plain old Newtonian gravity. This, of course, is theoretical. Stars of any kind are not known to travel anywhere near relativistic velocities.
     
  8. Sep 16, 2014 #7

    phinds

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    Although I understand, and in fact agree w/ what I believe you mean, it does lead to the question of whether or not that way of putting it is consistent with SR. After all, according to an accelerated particle at CERN, they DO travel at relativistic speeds.
     
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