The speed of sound is approx 700mph - the speed of light is way faster (light takes approx 8 mins to get from the sun to hear and thats millions and millions of equivalent miles - you could get your calculator out and work out how long sound would take but of course, sound doesn't travel in space due to the vacuum). My understanding of the theory of relativity (and it may not be entirely accurate) is that for a body to achieve the speed of light (or "infinite" speed) you would require "infinite" energy (i.e. all the energy in the universe) and therefore would require infinite mass (i.e. all the mass or matter in the universe). As you can imagine, for a layman such as myself, that is why it is easy to agree with Einstein, that speed of light travel is not possible. Of course, noone told also those light photons that go around! The theory also goes on about: what if you were on a train at the back of the carriage, travelling at the speed of light and then moved to the front, you would in fact be travelling at faster than light speeds (which Mr E stated is impossible). Lastly, Mr E bangs on about if you were on the train doing the Speed of Light (S.O.L.) your perception would be different to someone standing by the side of the "train track" - imagine you are looking at a tree; what you are actually seeing is the light (that took 8 mins to arrive from the sun) bounce of the tree to your eyes, which sends the electric signal to your brain which tells you you're seeing a tree. Apply that example to the bystander watching the S.O.L. train - what can you see when the train is moving at the same speed as the light that needs to bounce off the train to reach your eyes? I think this is why Mr E called it the theory of relativity because of this taking into account of the relative perceptions of the train passenger and the track bystander. As I said, this is my understanding and I could be way wrong - I would recommend you read "A Brief History of Time" by Stephen Hawkings, although I've read it 3 times (last time was about 5 years ago) and I still feel like a caveman grappling with a Nintendo DS! Good luck in your journey towards enlightenment - may the force be with you!