Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    Science Advisor
    Gold Member

    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


    User Avatar
    Science Advisor

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

    Hope this clarifies.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook