quote:

*Originally posted by unstman*

What actually causes a ' light photon ', to travel at the speed of light???

Light is an electromagnetic wave. Have you ever asked yourself: "why does sound travels (given material, pressure, temperature ecc.) at the speed of sound?" Or "why does water waves (I hope my english is good) travel at their speed?"

Solving the wave equations we can find exactly the propagation speed.

For what concerns light, solving the electromagnetic wave equation in the void, we see that the waves propagates with the speed v = 1/square[mu(0)*epsilon(0)], where mu(0) is the magnetic permeability of void and epsilon(0) is the electric permeability of void.

Given the values of these two constants (we can calculate them from electric and magnetic strenght) we can compute the speed v, that we call c: 299,792,458 m/s

Said in a more simple way: when you move an electric charge here, you produce a variable electric field there. A variable electric field there, produces a (variable) megnetic field, which in turns, produces a (variable) electric field and so on. So you have a variable electromagnetic field moving in the void.

You don't have to accelerate particles having a mass, so the speed can be very high, without limit, actually. Infact, the speed of light is actually infinite, but I don't want to explain this now.