: : Massless particles are referred to as having 0 rest mass. Meaning that if they ever come to a stop, theory predicts they would have no mass. In a practical sense, massless particles, such as photons, never stop or slow down and always travel at the speed of light. Having 0 rest mass means they can zip away at the speed of light without suffering relativistic effects.

: : if E = mc2 then how can you have massless particles? : : it how can the speed of light squared, times zero, : : equal anything else other than zero?

: : feel free to email me as well as post the answer!

: : tate@aapi.co.uk

Ah! That makes a lot more sence. Amazing how often we forget teh "relative" part of the theory!!!