Samuel Molyneux

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

He was the second son of William Molyneux (1656-1698), known for his work on optics, and studied at Trinity College, Dublin (MA 1710). Since 1712 he was a " Fellow of the Royal Society. Apart from his political career (Member of the British and Irish Parliament, Lord of the Admiralty from 1727 to 1728 ), he dealt with astronomy. At his private observatory he discovered with his friend James Bradley in 1727, the annual aberration. of starlight, the two astronomers had intended to repeat an observation Robert Hooke in 1674 with an improved telescope. Hooke had observed a small annual change of position in the south of England passing through the zenith of the star gamma Draconis ( etamin ), but could not perform precision measurements this change in the star position was interpreted as annual parallax, this since ancient evidence of the movement of the earth around the sun Hooke.

Molyneux attached to a specially developed for this task by the London device manufacturers George Graham zenith telescope at a fireplace of his home in Kew. The 1725 started measurements showed, however, soon realized that the change in position was firstly too big and on the other hand was at right angles to the expected course. After the appointment Molyneux to Lord of the Admiralty Bradley sat alone, the measurements continued, even with a smaller telescope with a larger field of view in the home of Bradley's aunt. In a boat trip on the Thames then found Bradley 1727 Statement. The light has a finite speed and therefore requires a finite time to run through the comoving from the earth telescope tube.

The two scientists had thus not only confirmed the heliocentric world view for the first time experimentally, but could also indicate an opposite Olaf Romans improved value of the speed of light. From Immeasurement the parallax, they concluded, moreover, that the star Gamma Draconis more than 400,000 Earth's orbit radii ( 6 light years) had to be removed. In the 1990s, his removal was determined by the Hipparcos satellite to 148 light years.


  • 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 astronomer. 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
  • Member of the House of Commons (Great Britain 1707-1801 )
  • Member of the Irish House of Commons
  • Astronomer (18th century)
  • Briton
  • Born in 1689
  • Died in 1728
  • Man