Samuel Molyneux

Samuel Molyneux (born July 18, 1689 in Chester , Cheshire , † April 13, 1728 in Kew , Surrey ) was a British politician and astronomer . Together with James Bradley he discovered aberration , the first evidence of the heliocentric worldview .

He was the second son of William Molyneux (1656–1698), who is known for his work on optics, and studied at Trinity College, Dublin (MA 1710). Since 1712 he was a "Fellow of the Royal Society . In addition to his political career (member of the British and Irish Parliament, Lord of the Admiralty 1727-1728) he occupied himself with astronomy. At his private observatory he discovered in 1727 the annual aberration with his friend James Bradley The two astronomers had intended to repeat an observation by Robert Hooke from 1674 with an improved telescope: Hooke had observed a small annual change in position of the zenithed star Gamma Draconis (Etamin) in southern England , but could not make any precision measurements Hooke interpreted the change in the star position as an annual parallax , the evidence of the earth's motion around the sun sought since ancient times.

Molyneux fortified one specifically for this task by the London equipment Bauer George Graham developed zenith telescope at a fireplace of his home in Kew. However, the measurements begun in 1725 soon showed that the change in position was, firstly, much too great and, secondly, at right angles to the expected course. After Molyneux was appointed Lord of the Admiralty , Bradley continued the measurements alone, also with a smaller telescope with a larger field of view in Bradley's aunt's house. Bradley found the explanation on a boat trip on the Thames in 1727. The light has a finite speed and therefore needs a finite time to run through the telescopic tube that is moved by the earth.

The two scientists had not only experimentally confirmed the heliocentric view of the world for the first time, but were also able to give an improved value of the speed of light compared to Olaf Römer . From the inability to measure parallax, they also concluded that the star Gamma Draconis must be more than 400,000 earth orbit radii (6 light years) away. In the 1990s, the Hipparcos satellite determined its distance to be 148 light-years.

credentials

• Robert Hooke: An attempt to prove the motion of the earth from observations made , London 1674
• James Bradley: A Letter from the Reverend Mr. James Bradley Savilian Professor of Astronomy at Oxford, and FRS to Dr Edmond Halley Astronom. Reg. & C. Giving an Account of a New Discovered Motion of the Fix'd Stars. Philosophical Transactions (1683-1775), Volume 35 (1727), pp. 637-661