See also: Bradley
James Bradley (March 1693 - July 13rd 1762) is a British astronomer , Astronomer Royal of 1742 with 1762.
Biography
It is born with Sherborne in the Gloucestershire in March 1693, its studies do not have anything remarkable until the moment when it contracts the Variole. His/her uncle, James Pound, an astronomer amateur, look after it and makes him share its taste for astronomy. Bradley enters to the Balliol College to the Université of Oxford the March 15th 1711. He obtains his Bachelor off Arts in 1714 and his Master off Arts in 1717. In 1718, Edmund Halley recommends his election to the Royal Society.It takes the orders and becomes Vicaire of Bridstow the following year, and a small sinecure with the Wales which was gotten to him by a friend, Samuel Molyneux. He resigns of his ecclesiastical responsibilities in 1721 when it is engaged to hold the Savilianne pulpit of Astronomie at the university of Oxford while it carries out also readings in experimental Philosophie with the Ashmolean Museum.
In 1725, it begins observations to measure the Parallaxe stars. At the time of two successive observations of the position of γ Draconis in the constellation of the Dragon, he discovers that the position connects star did not move in the awaited direction. At the end of one year, the successive positions form a small ellipse. Three years later, after having observed the modification of orientation of a flag floating with the wind on a moving boat, he discovers the Aberration of the light. He also understands that its measurements enable him to evaluate the ratio between the Speed of light and that of the displacement of the Ground which he estimates at 10.000. The rate of travel of the Earth is not known at this time, but it of deduced time that the light puts to arrive of the sun at the Earth and it evaluates with a margin of 8 minutes and 12 seconds, value correct at 10 seconds. These results are published in 1729 in the Philosophicals Transactions of the Royal Society. For the same period, he discovers also the Nutation, but before 1748 does not announce it after being assured its reality by observing a complete cycle (18,6 years).
In 1742, it succeeds Edmund Halley like Astronomer Royal with the royal Observatoire of Greenwich, its reputation enables him to acquire of more powerful instrument for the observatory and it accumulates a great number of observations during the 20 years with its direction. In 1748, it receives the Médaille Copley.
In bad health, it withdraws in 1762 with Chalford in the Gloucestershire where it dies the July 13rd 1762. The publications of its observations are delayed during several years of with controversies in connection with their paternity. Work of Bessel will be however necessary to include/understand their fundamental importance.
One published in 1798 with Oxford, his Observations made in Greenwich , and in 1832, his works posthumous and his correspondence.
Sources
- a foreword of Stone with Miscellaneous Works and Correspondence off James Bradley, D.D. (Oxford 1832) is almost exhaustive.
- New and General Biographical Dictionary , xii. 54 (1767)
- Biographia Britannica (Kippis)
- History of astronomy at the 18th century Delambre p. 413
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