cosmological principle
  • noun the theory that, on a very large scale, all the matter in the universe is distributed evenly, so that hypothetical astronomers a long way from the earth would see the same universe, on the biggest scale, as we do. Observational tests of the principle are difficult to carry out and are complicated by the fact that looking into the universe over different distances also involves looking back over different time periods.
  • The idea that on a very large scale all the matter in the universe is distributed evenly, so that hypothetical astronomers a long way from the Earth would see the same universe, on the biggest scale, as we do. The problem with testing the cosmological principle is that it operates on a scale so vast that even galaxies and clusters of galaxies are merely local clumps of material by its standards. This means that observational tests of the principle are difficult to carry out and are vexed by the fact that looking into the universe different distances also involves looking back over different time periods. The Cosmological Principle can be viewed as a modern restatement of the Copernican Principle on a bigger stage. Patterns seen in the universe on a massive scale, such as ‘bubbles’ of galaxy clusters, could be regarded as arguments against the principle.

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