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Information speed limit

  1. Feb 2, 2009 #1


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    hi, this just came into my mind yesterday (while trying to sleep)..

    i've got a very long, unstretchable ribbon. one end is installed on a plug of laser beam (turned off). the other end is in my hand. the ribbon is 5 light seconds long.

    what happens, if i pull the ribbon?

    a) i'd see the laser is on after 10 seconds => the ribbon was stretched or the space did something (what?)
    b) i'd see the laser on after 5 seconds => the information travelled faster than light
    c) .. ?

  2. jcsd
  3. Feb 2, 2009 #2


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    Science Advisor

    The simple answer is that unstretchable rigid objects are impossible in relativity--see here.
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