Bradley, James (1693–1762)
James Bradley was an 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.