Glossary term: Cosmological Principle

Description: The cosmological principle is the basis for modern cosmology and is built on observations and a fundamental assumption. It states that spatially the Universe is isotropic and homogeneous on large scales (scales larger than a few hundred million light years). Observations on sufficiently large scales, show that the Universe appears to "look" the same in any direction; there is no preferred direction (isotropic). The fundamental assumption, based on the Copernican Principle (humans do not occupy a special location in the Universe), is that the Universe is the same everywhere (homogeneous); there appears to be no preferred location. The cosmological principle is accompanied by universality, where the laws of physics and the fundamental constants are the same everywhere in the Universe: here on Earth or in a distant galaxy.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

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