James Bradley

 James Bradley was an English astronomer who lived from 1693-1762. He is known for discovering the first direct proof that the earth revolves around the sun by observing the change in starlight and the nutation of its axis. He studied at Balliol College, Oxford, and received his bachelor's and master's degrees from there (HowStuffWorks).

He learned astronomy first from his uncle, Reverend James Pound, rector at Wanstead, near London. Pound supported Bradley financially for thirteen years and took care of him when he got small pox in 1717. When Bradley was in his twenties, he and Pound were hired by astronomers Isaac Newton and Edmond Halley to observe astronomical objects. Together they observed, with great accuracy, the eclipses of Jupiter's satellites, the diameter of Venus (with a 212 foot long telescope), and the parallax of Mars (Hirshfeld).

After Bradley worked for several years for Newton and Halley, Halley endorsed his election to the Royal Society in 1718 and Newton recommended him to be the appointed Savilian Professor of Astronomy at Oxford in 1721 (HowStuffWorks). Before then, he was a reverend (Greenwich). In 1724, Bradley's uncle died and he acquired a new partner in observation: Samuel Molyneux. This led to the great discovery of the way starlight changes by observing England's most overhead star, Gamma Draconis (Hirshfeld). He worked at Molyneux's private observatory in Kew. He viewed apparent displacement in the star's position annually, leading to the discovery of the star's aberration (Greenwich). He could not detect any parallax because the star was too far away, but he noted that Gamma Draconis shifted south by 1” of arc in three days, which is in the wrong direction and too large of an amount to be parallax. Bradley concluded that the phenomenon was a “result of the finite speed of light and the forward motion of the Earth in its orbit.” His research confirmed the velocity of light to be 295,000 km/s, giving proof to Copernican theory (Hawkins).

In 1742, Bradley succeeded Halley as astronomer royal, the chief astronomer of England. He was given a grant of 1,000 pounds for more precise instruments, which he used to determine the latitude of the Royal Greenwich Observatory (HowStuffWorks). He put in a transit instrument in the Observatory, which remained there until it was replaced by Pond in 1816. The line that this transit circle is on is called the Bradley Meridian, which is used in the Ordinance Survey and is different from the Airy Meridian that Greenwich Mean Time is measured (Greenwich). 

Hawkins, Gerald S. "James Bradley (English Astronomer)." Encyclopedia Britannica Online. 

Encyclopedia Britannica, n.d. Web. 10 Oct. 2013. <http://www.britannica.com/EBchecked/topic/76818/James-Bradley>.

Hirshfeld, Alan.Parallax: The Race to Measure the Cosmos. New York: W.H. Freeman and, 2001. Print. Pages 153-154.

"James Bradley." Greenwich England:. N.p., n.d. Web. 10 Oct. 2013. <http://wwp.greenwichengland.com/heritage/people/astronomers/bradley.htm>.

"James Bradley" 23 April 2009. HowStuffWorks.com. <http://science.howstuffworks.com/dictionary/famous-scientists/astronomers/james-bradley- info.htm> 10 October 2013.