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The single physical entity into which the concepts of space and time can be unified such that an event may be specified mathematically by four coordinates, three giving the position in space and one the time. The path of a particle in spacetime is called its world line. The world line links events in the history of the particle.

The concept of spacetime was used by Einstein in both the special and the general theories of relativity. In special theory, where only inertial frames are considered, spacetime is flat. In the presence of gravitational fields, treated by general relativity, the geometry of spacetime changes: it becomes curved. The rules of geometry in curved space are not those of three-dimensional Euclidean geometry.

Matter tells spacetime how to curve: massive objects produce distortions and ripples in the local spacetime. The question of whether the spacetime of the real Universe is curved, and in what sense, has yet to be resolved. If the Universe contains sufficient matter, i.e. if the mean density of the Universe is high enough, then the spacetime of the Universe must be bent round on itself and closed.

References in periodicals archive ?
But the theory of general relativity describes the interaction between matter and spacetime, and how matter curves the spacetime field.
Implicit in this conceptualization is the widely held expectation that spacetime should play a dynamic role in its own right, rather than being a passive observer.
Empty spacetime in/outside/about and beyond being and beings, either in the middle of things--crack, interval, cloud, environment, etc.
They were stunned when their analysis showed that spacetime did become turbulent.
com/cosmos, the COSMOS: A SPACETIME ODYSSEY by Celestron line features the following licensed products:
At San Diego Comic Con, or SDCC, a trailer for "Cosmos: A Spacetime Odyssey" was revealed on July 21.
The spacetime of special relativity is a flat, 4-dimensional structure.
The Spacetime 3D architecture employs time, rather than space, as a third dimension, rapidly reprogramming every resource on the chip to perform multiple, different functions per user cycle - up to 12 in the current generation.
The special relativistic spacetime invariant is the measure of our space, which is [s.
The second epoch was further work on black holes, and his adventurous and highly successful work on quantum field theory in a curved spacetime.