13 Oct
2012
13 Oct
'12
1:06 p.m.
"MS" == Mike Stay <metaweta@gmail.com> writes:
MS> E = mc^2 only holds for objects at rest. The more general statement is MS> E^2 = (mc^2)^2 + (pc)^2 But momentum is mass * velocity, so cannot be +ve if mass == 0, so a massless particle is still energy-less. And all photons have energy. (Or is there a concept of non-finite wavelenght?) Put another way, since velocity increases the mass-energy of a particle, a photon would have to have zero mass-energy at rest also to have it at any non-zero speed, including at c. -JimC -- James Cloos <cloos@jhcloos.com> OpenPGP: 1024D/ED7DAEA6