Rebecca Todd of Ilam School asks :-

Why does light travel so fast?

Andy Edgar, a physicist at the Victoria University of Wellington, responded.

The honest truth is that we don't know - and certainly a speed of three hundred thousand kilometres each second, which is equivalent to seven times around the world every second, is pretty fast.

When we try to explain the complicated world around us, it is always in terms of some simpler ideas or a smaller set of facts. At some stage we hit bedrock and can't go any lower, and the rather high speed of light, and the fact that it never changes, we accept as one of the foundation stones of modern physics. For example, you may have heard of Albert Einstein; his famous theory of relativity is based on the simple idea that light always travels at a fixed speed.

But is light really so fast? Light is a kind of wave, so let's think of other waves that we know about. We use waves of pressure in the air - sound waves - to speak to each other, and these messages travel at about the speed of a Skyhawk jet, a hundred times faster than say a typical bike-rider. On the other hand light acts as the "message service" between atoms - they exchange energy through light waves. But inside an atom, the electrons move at a speed of about one-hundredth that of light. So for electrons, light isn't really any faster than are sound waves for us.