The Mass Of Light, If it's only energy

If light has no mass why does it convert to mass when it is absorbed?

This is really an issue of how you define "mass". "Rest mass" is what is typically being referred to when someone says "mass".

Light photons cannot have a rest state and thus cannot have a rest mass. But when the photon is absorbed into something that does have a rest mass, then the energy that was restless, adds to the rest mass of the object.

Light photons have measurable momentum and anything that has momentum has the ability to affect anything else with momentum or inertia. A more consistent definition of mass does not refer to "rest mass", but the property of inertia or momentum.

So we end up with some saying that light has mass and some saying that it is massless. It all depends on which they are referring to as the "mass".

This post has been edited by Siau on Aug 5 2007, 01:55 AM

Msss is dynamic. Put mass into motion and its motion(kinetic energy) is more mass.

But that is matter. The Gamma fastor increases from ONE.

This post has been edited by Nick on Aug 6 2007, 12:11 AM