James Bradley
Nicaragua, 1994
James Bradley (1693–1762) was Britain’s third Astronomer Royal, serving from 1742 until his death. Before his appointment he had already made one major discovery, that of the aberration of starlight, the first direct proof of the Earth’s orbital motion around the Sun (hence the inset portrait of Copernicus, whose heliocentric theory was finally vindicated).
While Astronomer Royal, Bradley made his second great discovery, the effect known as nutation, a nodding of the Earth’s pole caused by the gravitational pulls of the Sun and Moon on the Earth’s equatorial bulge. During his tenure at Greenwich, Bradley re-equipped the Observatory and took its observations to a new level of precision.
On this stamp, Bradley is shown in front of the Greenwich Observatory buildings with the famous time ball on top. However, this is an anachronism as the time ball was not installed until 1833 by a later Astronomer Royal, John Pond.
Stanley Gibbons no. 3347