Royal Observatory, Greenwich

Bradley (1693-1762) was the third Astronomer Royal, in office 1742-1762. Bradley entered Balliol College, Oxford, in 1711 and graduated B.A. in 1714 and M. A. in 1717. Under the influence of his uncle, James Pound, he showed great aptitude for observational astronomy early in life. By the time that he was appointed to be Halley's successor at Greenwich, his scientific reputation was established; today we recognize his rigorous demonstration of the aberration of starlight in 1729 to be of fundamental importance. Further observations made in this investigation lead him to note what he suspected was the nutation of the Earth's polar axis caused by the gravitational attraction of the Moon on a slightly asymmetric Earth, an effect predicted by Isaac Newton, though Bradley resolved to make observations of the effect throughout the 18.6 year cycle of the nodes of the Moon's orbit before conclusively showing the cause and effect. It was Halley himself who recommended that Bradley succeed him as Astronomer Royal, indeed offering to resign in the latter's favour, through in the event Halley died in office. As his predecessor had, Bradley managed to persuade the government of the day that the Greenwich Observatory should have new instruments and with these he carried out stellar observations of unprecedcented accuracy, pursuant to the expressed intent of the original warrant founding the Observatory that the stars should be newly obs

erved for the purpose of finding the longitude. Towards the end of his life, in 1758 Bradley observed the return of the comet predicted by his scientific patron Edmond Halley, and though ill health prevented him from participating, he was instrumental in arranging for observations of the transit of Venus of 1761 to be made at wide geographical separations, again as Halley had suggested.

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