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Homework Help: Age difference problem due to space travel

  1. Jul 30, 2016 #1
    1. The problem statement, all variables and given/known data
    The identical twins Speedo and Goslo join a migration from the Earth to Planet X, 19.0 ly away in a reference frame in which both planets are at rest. The twins, of the same age, depart at the same moment on different spacecraft. Speedo's spacecraft travels steadily at 0.945c and Goslo's at 0.625c.

    (a) Calculate the age difference between the twins after Goslo's spacecraft lands on Planet X in years.
    (b) Which twin is older?

    2. Relevant equations

    3. The attempt at a solution
    Not really sure how to attempt this, im assuming that the speed of the space craft, 0.945c means 0.945 times the speed of light?
    this is a guess but would you calculate the time it takes each spacecraft to get to Planet X and then the difference in those times would then be the difference in the twins age ?
  2. jcsd
  3. Jul 30, 2016 #2


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    Science Advisor

    Yes, .945c means .945 times the speed of light.
    Yes, you can calculate how long it takes (according to the rest frame) for each spacecraft to get to Planet X. But the question is not about elapsed time in the rest frame. It is about the time experienced by Goslo and Speedo.

    If you are attempting to work this problem you should have learned something about time dilation and, perhaps, the Lorentz transform. The time elapsed according to Goslo and Speedo need not match the elapsed time according to the rest frame.
  4. Jul 30, 2016 #3
    Nah we have our first relativity lecture tomorrow, Im just trying to get this assignment done and bceause we havent learned anything about this so far, im stuck.
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