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Negative light speed

  1. Mar 1, 2010 #1
    If e=mc^2, then (e/m)1/2= either +c or -c. What is the physical meaning of minus c?
  2. jcsd
  3. Mar 2, 2010 #2


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    e=mc^2 shouldn't be used to try to find "c". "c" is a defined constant of 299792458 m/s.
  4. Mar 2, 2010 #3
    Mathematically -c exists, but this is a non-physical result, and is therefore ignored when using the e=mc2 equation. :)
  5. Mar 2, 2010 #4


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    Precisely. Imagine the equation like this:
    [tex] 2=\pm \sqrt{\frac{E}{m}} [/tex]

    Hope this clarifies.
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