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Relativistic Thought Experiment

  1. Nov 28, 2014 #1
    Let's imagine say, a spaceship is going through space at 99% the speed of light. Relativity says (to my understanding) that as the spaceship increases in speed it's mass will increase and it shall also get slightly shorter. Let's assume that energy isn't a problem, should the spaceship continue accelerating and gets up to speeds extremely close to the speed of light, could it theoretically become massive enough and compact enough to have gravity take over and turn that spaceship into a black hole? Thank you!
  2. jcsd
  3. Nov 28, 2014 #2


    Staff: Mentor

    Hi Zack,

    The short answer is no. Here is a more detailed explanation:


    Note also, the idea of a particle increasing in mass as it gets faster is called "relativistic mass". Although it still appears in the popular science literature and in some poor-quality textbooks, it is a concept that has largely been discarded by professional scientists. Generally, the term "mass" refers to what is known as the "invariant mass".

    https://www.physicsforums.com/threads/what-is-relativistic-mass-and-why-is-it-not-used-much.783220/ [Broken]
    Last edited by a moderator: May 7, 2017
  4. Nov 28, 2014 #3
    Hi that's a common misunderstanding of relativity and black holes.

    For a traveler inside the spaceship, the spaceship is just the same as it was at take-off (that's what relativity is about!).
    Thus, the black hole theory applies to the mass as measured with such a co-moving reference system.
  5. Nov 28, 2014 #4
    Okay. I think I'm beginning to comprehend why the answer would be no. Thank you all! People like you guys are why this site is so fantastic!
  6. Nov 28, 2014 #5


    Staff: Mentor

    You are welcome, glad we could help.
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