Space-time curve "From the preceding reflections on time dilation, we learn that Albert Einstein has overthrown commonsense assumptions about space and time that were valid for centuries. Relative to the observer, distances appear to contract while clocks tick more slowly when moving at velocities close to the speed of light. These are the practical consequences of Special Relativity, the work for which Einstein became famous. Einstein did not stop at this point. In 1916, he published his General Relativity, which further challenged conventional wisdom. The paper proposed that matter causes spacetime to curve. Gravitation is understood as the warping of spacetime, not a force acting at a distance, as Newton had suggested."