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Twin paradox

  1. Oct 5, 2014 #1
    1. The problem statement, all variables and given/known data
    Anna is born in a spaceship, Bob is born on Earth (at the same time t=t'=0) just as Anna's spaceship passes earth at 0.9c (EVENT A)

    Planet Z is 45 ly away at rest in Bob's frame. Anna flies past plant Z (event B)

    Meanwhile, Carl was born at the same time (t=t'=t''=0) on a spaceship traveling 0.9c towards earth and passes planet z at event b

    event C is when he passes earth.

    bobs frame: x,ct
    anna's: x',ct'
    carl's: x'',ct''

    a) what are the coordinates of a,b,c in the rest frames of anna, bob, carl
    b) how old is bob in his rest frame when carl passes earth?
    c) what is the sum of anna's age when she passes planet Z with the amount carl ages in going from planet z to earth as measured in x,ct
    d)what is the sum of anna's age when she passes planet z as in her rest frame with the amount carl ages going from planet z to earth in his rest frame?
    2. Relevant equations
    x'=gamma(x-vt)
    t'=gamma (-v/c^2*x + t)

    3. The attempt at a solution
    a)

    Anna's frame
    A (0,0)
    B <-- i'm not sure how to get to this using the 45 ly from bob's frame :/

    This question as a whole confuses me, I'm not sure where to start.
     
  2. jcsd
  3. Oct 5, 2014 #2
    Here is my space time diagram

    Phys.jpg
     
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