Spacetime

Article By:

Barger, Vernon D. Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin.

Last reviewed:October 2021

DOI:https://doi.org/10.1036/1097-8542.639800

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• Spacetime, published June 2020:Download PDF Get Adobe Acrobat Reader

A term used to denote the geometry of the physical universe as suggested by the theory of relativity. Also called the spacetime continuum, spacetime represents an intertwining of the three dimensions of physical space with a fourth dimension, time. Per this formulation, when massive bodies warp the three dimensions of space—an effect that forms a gravity well, or depression in spacetime—the bodies also warp time. As a result, the passage of time is experienced differently by an observer (or a measurement device) located at different points within a gravity well. A practical example of this manifested spacetime is the accumulation of timekeeping discrepancies between clocks onboard satellites in orbit above the Earth, and thus higher up the planet's gravity well, and clocks located lower in the gravity well on Earth's surface (Fig. 1). See also: Geometry; Gravity; Mass; Satellite (spacecraft); Time

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