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Bradley, James (1693–1762)




James Bradley
English astronomer who, in searching for stellar parallaxes, discovered, in 1728, the aberration of starlight – an apparent change in the positions of stars caused by Earth's annual motion. This provided the first direct evidence for the revolution of our planet around the Sun and enabled him to calculate the speed of light to within 2% of its correct value. Bradley became the third Astronomer Royal (1742) and subsequently discovered the periodic shift in Earth's axis known as nutation.


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   • ASTRONOMERS AND ASTROPHYSICISTS