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A (seemingly) popular beliefe about SR

  1. Aug 20, 2012 #1


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    I often hear from laymen who study some SR that if sth reaches the speed of light,it completely turns into energy!!!
    Where did this crazy idea came from?

    Any way,mass increase in SR seems really mysterious to me
    E.g. when mass tends to infinity as velocity tends to c
    Can someone clarify more?

  2. jcsd
  3. Aug 20, 2012 #2


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  4. Aug 20, 2012 #3
    Nothing that has mass can reach the speed of light. Relativistic mass, i.e. the mass increase due to relativistic speeds is not mass in the modern sense, it is really kinetic energy. In modern texts mass is an invariant, i.e. a property that is the same in any reference frame.

    Therefore anything that is traveling at light speed is massless but can possess momentum.
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