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Loading contentThe cycle of observation, hypothesis, prediction, and test that turned the study of the heavens from stargazing and myth into a science — and the reason astronomy's claims can be checked, challenged, and improved rather than merely believed.
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.