Problem 3.7: What frequency does the moving twin observe?

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One twin, Pink, remains on Earth while her twin brother, Green, travels the universe in a fast rocket ship. The animation shows everything from Pink's reference frame (distances are given in light years and time is given in years).  Pink sends out light pulses at a given frequency.   Restart.  For each animation,

  1. What is the frequency of Pink's pulses in Pink's reference frame?
  2. What is the frequency of the pulses in Green's reference frame?