There is absolutely no doubt that after Newton, Einstein is the most popular physicist in the history of science. Between the March and June of 1905, Einstein, then a mere patent clerk, published four papers that revolutionised modern physics forever. Although he became a household name for discovering the ever-famous E=mc2, it was time dilation that completely changed our understanding of space and time. What's more, the principle occurred to him in a daydream. Watch our new video to understand what is time dilation and find out why your head is older than your feet!