posted on Oct, 30 2012 @ 04:40 PM
Do photons have mass?
They have relativistic mass. Photons have 0 rest mass, but, since photons are never at rest, they gain apparent mass from their kinetic energy because
of mass-energy equivalence.
Technically, what photons have is momentum, which (and I feel like I'm repeating myself when I say this) is the principle behind things like solar
Obviously they do because they are affected by gravity.
Photons follow the curvature of spacetime caused by gravity. In General Relativity, gravity is described by a stress-energy tensor field, meaning
spacetime is curved by energy. Therefore, even photons, being energy, exert their own gravitational force.
Also, if gravitons exist, then they too have their own gravity, which is comprised of gravitons that also have their own gravity...which is comprised
of gravitons that also have their own gravity...which...well...you get the picture.
So if you put a flahlight on a set of scales, would it lose weight if kept on?
It would lose a negligible amount of mass by the time the batteries die.