Comment Re:f=ma? Last post I promise (Score 1) 50
Any massive object bends space-time, light rays appear to be bent by massive objects but really they are following a straight line and it is space-time which is bent in that area. The bending is so extreme around black holes that light doesn't escape a circular path.
The quick and dirty proof of photons having no mass is from E=mc^/sqrt(1-v^2/c^2) which is the correct Einstein equation. (It is so frustrating that people insist on using E=mc^2, which is only a special case) You can see that in a vacuum v=c, therefore E=infinity unless m=0. Obviously infinite energy is impossible so m=0. If m=0, then E=0/0 and 0/0 is an indeterminate number which is allowed, but doesn't give a solution. You can't use this equation to find the energy of the photon. For that you have to use the QM equation E=hf. For a good FAQ on the topic see http://math.ucr.edu/home/baez/physics/photon_mass. html
The quick and dirty proof of photons having no mass is from E=mc^/sqrt(1-v^2/c^2) which is the correct Einstein equation. (It is so frustrating that people insist on using E=mc^2, which is only a special case) You can see that in a vacuum v=c, therefore E=infinity unless m=0. Obviously infinite energy is impossible so m=0. If m=0, then E=0/0 and 0/0 is an indeterminate number which is allowed, but doesn't give a solution. You can't use this equation to find the energy of the photon. For that you have to use the QM equation E=hf. For a good FAQ on the topic see http://math.ucr.edu/home/baez/physics/photon_mass
