Using simplified scientific language, this book discusses one of the most important revolutionary accomplishments in the history of science: Einstein's theory of relativity. It is the theory that brought about a revisiting of the central concepts of physics, such as place, time, movement, speed, energy and matter. Interestingly, place and time have been grouped in one category, while mass and energy have been grouped in another. This was expressed by Albert Einstein himself in a profound quote in which he stated: "in the past, the common belief was that if matter were to disappear, space and time alone would remain. With relativity, they would disappear concurrently with the disappearance of matter".