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Finite speed of signal transmission and conservation laws

  1. Apr 23, 2009 #1
    Hi all,
    This is my first post, so please forgive me if this has already been discussed.
    There is a question that has perplexed me for years, and I am hoping someone at this forum can shed light or point me in the right direction.
    If two like charges separated by a distance, d, quickly and simultaneously move toward each other some small incremental distance, the new larger field strength of one particle on the other must take a finite amount of time to reach the other particle. So it should be possible for each particle to move to its closer position before the new larger field of the other 'takes effect'. So each particle moves in the weaker field E1, but then the fields increase to E2. How is the conservation of energy preserved?

    Similarly, if they suddenly and simultaneously return to their original positions, they move back in the stronger field, then the weaker field catches up to them after some finite time.

    Sorry if this is a stupid question. What am I missing here? Thanks!
  2. jcsd
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