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I Closing distances at rates greater than c

  1. Oct 4, 2016 #1
    Hi, I just have a brief, logistical question.

    If I have, say, two spaceships travelling towards each other at 0.6c each (from my rest frame), can I calculate the meeting time in my rest frame as the distance divided by 1.2c? I'm not saying either ship is actually going this speed, just that the distance is being closed at this rate of 1.2c.

    Is this reasoning valid? If not, how do I calculate the time for these two to meet?
  2. jcsd
  3. Oct 4, 2016 #2


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    Science Advisor

    Yes. Each ship will, as you say, see the other moving at less than c. But you measure the closure rate to be 1.2c.
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