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High speed collisions

  1. Nov 24, 2005 #1
    Lets say that there is a man flying in a spaceship going fast enough that to another observer standing on the earth he appears to be twice as big as normal due to relativistic mass (I might be wrong here, and relativistic mass doesn't make you look bigger). From the man's frame he would say he is at rest, and that everything else is going near c. Thus wouldn't everything else (planets, asteroids, sun, etc.) appear to be twice as big as normal to him? And if so, why wouldn't he see the earth and moon collide because they're bigger? Especially with length contraction. This doesn't seem right, but I don't know what I'm not getting.

  2. jcsd
  3. Nov 24, 2005 #2


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    Staff: Mentor

    No, the increase in relativistic mass does not make things "look bigger". Moving objects contract along the direction of motion, and maintain the same size perpendicular to the direction of motion.
  4. Nov 24, 2005 #3
    OK, thanks.
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