Universe

The universe is the whole spacetime continuum in which we exist, together with all the energy and matter within it. Attempts to understand the universe in this sense, on the largest possible scales, are made in cosmology, a science that has grown from physics and astronomy. During the second half of the 20th century, the development of observational cosmology, also called physical cosmology, led to a split in the meaning of the word universe, between observational cosmologists and theoretical cosmologists; where the former (usually) abandon the hope of observing the whole spacetime continuum, the latter retain this hope, attempting to find the most reasonable speculations for modeling the whole of spacetime, despite the extreme difficulty in imagining any empirical constraints on these speculations and the risk of declining into metaphysics.

Other terms

Different words have been used throughout history to denote "all of space", including the equivalents in various languages of "heavens", "cosmos" and "world".

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Although words like world and its equivalents in other languages now almost always refer to the planet Earth, they previously referred to everything that exists—see Copernicus, for example—and still sometimes do (as in "the whole wide world"). Some languages use the word for "world" as part of the word for "outer space", e.g. German "Weltall".

Related Topics:
World - Earth - Copernicus - German

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