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Loading contentThe view that our best scientific theories describe a real world — that atoms, black holes, and dark matter are not merely convenient fictions but things that actually exist, even when they cannot be seen directly. It is the working assumption of most astronomers, and a live question in philosophy.
Facts on this topic will be cited from these primary and reference sources.
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.