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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 ?
These solutions (spacetimes) have been classified by using different spacetime symmetries.
d] is a characteristic of the PV model of the vacuum state, and is related to the Synge primitive (planewave) quantization of spacetime to be discussed below.
Light is the information that we receive about the effects of these movements within the swirling fabric of spacetime.
A team of astronomers recently announced their observations of these gravitational ripples in the fabric of spacetime that have, at long last, reached Earth from their distant origin--an ancient catastrophic event in a remote region of the universe.
Einstein's theme of spacetime symmetry is highlighted and then related broadly to nursing and health.
At a news conference on June 7, mission scientists announced that the orbiting facility has surpassed the precision needed for future missions to detect spacetime disturbances.
They are where the curvature of spacetime is so steep that all paths lead inwards.
The subtle distortions of spacetime are generated by cataclysmic events such as the collision of black holes or superdense neutron stars, or powerful stellar explosions.
It is important to mention that our choice of timelike ARS symmetry vector field V in this paper is due to the fact that the integral curves of such a timelike connection symmetry can provide a privileged class of observers or test particles in a spacetime.
Together they make the space-time continuum, or spacetime.
There would remain only an empty spacetime that used to receive, endure and store objects--that is, the world.
Washington, June 6 ( ANI ): New research has revealed that the accepted wisdom about spacetime not being turbulent could be wrong.