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Silly question

  1. Aug 3, 2008 #1
    This question will show the superficiality of my understanding of relativity, so any help will be appreciated.
    The question: When one says that gravitational collapse will occur to create a neutron star (or black hole) if the mass of the star is above a certain amount, is this referring to the rest mass?
    The reason for the guess: the relativistic mass can be above this limit for one observer and below the limit for another observer, and the object cannot be collapsing for one observer and not for another observer.
  2. jcsd
  3. Aug 3, 2008 #2


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    Yes, it's the rest mass.
  4. Aug 3, 2008 #3
    Thanks, nrqed.
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