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• Space-time continuum

The term space has two general meanings. First, it refers to the three-dimensional extension in which all things exist and move. We sometimes speak about outer space as everything that exists outside our own solar system. But the term space in astronomy and in everyday conversation can also refer to everything that makes up the universe, including our own solar system and Earth.

Mathematicians also speak about space in an abstract sense and try to determine properties that can be attributed to it. Although they most commonly refer to three-dimensional space, no mathematical reason exists not to study two-dimensional, one-dimensional, four-dimensional, or even n-dimensional (an unlimited number of dimensions) space.

Space-time continuum

One of the most important scientific discoveries of the twentieth...