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Definition of SPACE-TIME
: a system of one temporal and three spatial coordinates by which any physical object or event can be located —called also space-time continuum
: the whole or a portion of physical reality determinable by a usually four-dimensional coordinate system; also: the properties characteristic of such an order
First Known Use of SPACE-TIME
Single entity that relates space and time in a four-dimensional structure, postulated by Albert Einstein in his theories of relativity. In the Newtonian universe it was supposed that there was no connection between space and time. Space was thought to be a flat, three-dimensional arrangement of all possible point locations, which could be expressed by Cartesian coordinates; time was viewed as an independent one-dimensional concept. Einstein showed that a complete description of relative motion requires equations that include time as well as the three spatial dimensions. He also showed that space-time is curved, which allowed him to account for gravitation in his general theory of relativity.