This is an interesting question that I can't seem to sort out. Since photons are massless, they travel at the speed of light(3*10^8 m/s). Why must photons travel at the highest possible speed (the speed of light)? Why is it when a photon is created, it doesn't start off at a speed zero and then once a force(whatever the magnitude) is acted upon it cause it to move at the speed of light? How could this happen?