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Regarding Twin Paradox

  1. Jun 9, 2015 #1
    1. The problem statement, all variables and given/known data
    In the twin paradox suppose the twins are named Dick and Jane. And they both are 20 years old.Dick takes off on a voyage at a speed of 0.8c to a star 20 light years away.Lets say that both the twins send each other signals once a year while Dick is away.How many signals does Jane receive?

    2. Relevant equations
    This problem is from the book "Concepts of Modern Physics" by Arthur Beiser. I have understood the part about how many signals are receive by Dick. And I am utterly at a loss to explain the signals received by Jane.

    3. The attempt at a solution
    Since for Jane the total journey by Dick is 50 years (25 going and 25 returning). And by relativistic calculations each twin receives 1 signal per 3 years while they are being separated and they receive 3 signal per year when Dick is returning. So while Dick is on his way to reach the star Jane should receive (25/3) = 8 signals.But the book mentions that Jane receives ( (25+20)/3 ) = 15 signals while Dick is journeying to the star. I cant understand where this 20 came from.
     
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  3. Jun 10, 2015 #2

    SammyS

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    From Dick's point of view, how far is the journey ?
     
  4. Jun 16, 2015 #3
    According to him the journey is 15 years going and 15 years returning... total 30years
     
  5. Jun 16, 2015 #4

    SammyS

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    So, Dick sends 15 signals while he journeys to the star. Of course, Jane will not receive some of these until Dick is on his return portion of the journey.
     
    Last edited: Jul 9, 2015
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