If you travelled at the speed of light, your relative time reduces to zero; this means, whatever the distance you travel, the journey is instantaneous. Firsty, Its impossible to travel that fast because your mass increases all the way to infinity at the speed of light. Light itself (photon) is massless so it can do this. From a very early age, Einstein thought about what would it be like to travel on the back of a photon, and this is what he eventually discovered. A photon of light travelling from a star 100,000 light years away takes 100,000 years to hit your eye, from your perspective. But from the photons perspective, the journey was instantaneous.