Relativity always turns out to be more complicated than I think, but I believe it would be correct to say that E=mc
2 is for a mass at rest with respect to the observer. If the mass were moving at velocity v then the non-relativistic version of the equation might become:
E = mc2 + mv2/2
But mass actually increases with relative velocity, so for a mass in motion I'm guessing that the equation might really be:
E = mc2 + mv2/(2 * (1-v2/c2)1/2)
But I'm just guessing. Modulous's answer in
Message 151 may be the correct one, and his equation simplifies to:
E = mc2 / (1-v2/c2)1/2
Anyone know which is correct and why? I'm trying to see how Modulous's answer reduces to mv
2/2 (the Newtonian answer) for non-relativistic velocities after subtracting out an mc
2, but I can't figure it out.
--Percy