The theory of relativity has enriched physics and astronomy during the 20th century. It changed perceptions. For example, it overturned the concept of motion from Newton's day, into all motion is relative. Time was no longer uniform and absolute, as related to everyday experience. Furthermore, no longer could physics be understood as space by itself, and time by itself. Instead, an added dimension had to be taken into account with curved spacetime. Time now depended on velocity, and contraction became a fundamental consequence at appropriate speeds.