Einstein's theory of relativity is one of the cornerstones of modern physics but it requires a total rethink of our notions of time and space. Strange things happen in a relative universe: length and time are not fixed and depend upon your frame of reference. If you move at high speed, time slows down, space contracts and weight increases. So a period of time for someone on Earth that lasts for hundreds of years may only be a couple of hours for someone travelling in a rocket close to the speed of light. It's mind-boggling stuff, but the theory of relativity has a real impact on our world today. A car's GPS navigation system, for example, uses information received from orbiting satellites and is designed to account for the fact that time ticks at a different rate on these satellites than it does on the ground. Without allowing for relativity's effects, after just a day, your whereabouts according to GPS could be up to 8km from your actual location. So to find out more about how our universe works and how space and time are connected, look no further than this fascinating, illustrated guide to relativity.