Ok, so light is both a wave and a particle. That's fine, I accept that. If a photon is a particle it must therefore have a mass. But, Einstein's theory of relativity states that material bodies cannot travel faster than the speed of light. As a particle approaches the speed of light it becomes heavier i.e. its mass increases. If a particle is travelling at the speed of light, its mass is infinite. It would require an infinite force to move it. So.....how does this account for light being a particle-the photon?