Relativity question

  • Thread starter crosbykins
  • Start date
  • #1
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Homework Statement



A distant star has been measured as moving at a speed of 0.8c away from Earth. If a planet of this star sends radio signals to Earth once every second (according to their time scale), how often would we recieve them (according to out time scale)?

Homework Equations



Δts = Δtm/ √(1 – (v^2/c^2)

The Attempt at a Solution



Δts = Δtm/ √(1 – (0.8c)^2/c^2)
= 1/ √(1 – (0.8c)^2/c^2)
= 2.24 s

f = 1/2.24 s
= .45 signal/second

Therefore, we would receive .45 signal/second

*does this look ok?
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
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hi crosbykins! :smile:

have you taken account of the fact that the distance each signal has to travel is increasing?
 

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