Samuel Molyneux

Samuel Molyneux
Born (1689-07-16)16 July 1689
Chester, England
Died 13 April 1728(1728-04-13) (aged 38)
Nationality United Kingdom
Fields Astronomy
Known for Aberration of light

Samuel Molyneux FRS (16 July 1689 – 13 April 1728), son of William Molyneux, was an 18th-century member of the British parliament from Kew and an amateur astronomer whose work with James Bradley attempting to measure stellar parallax led to the discovery of the aberration of light. The aberration was the first definite evidence that the earth moved and that Copernicus and Kepler were correct.[1][2][3] In addition to his astronomical works, Molyneux wrote about the natural history and other features of Ireland.[3]


Molyneux was born in Chester, England in 1689 and died in Kew in 1728. He was the second son of William Molyneux, who was known for his work related to optics. His mother was Lucy Domville, daughter of Sir William Domville, the Irish Attorney General. Molyneux studied at Trinity College, Dublin, where he earned a Bachelor of Arts (BA) in 1708 and a Master of Arts (MA) in 1710. He was elected a Fellow of the Royal Society in 1712. and served as a member of the Parliament in 1715, 1726, 1727 and Ireland 1727, and as Lord of the Admiralty from 17271728.

Astronomical Work

Molyneux is best known for his work with Bradley in attempting to measure the parallax of Gamma Draconis leading to the discovery of the aberration of light. Molyneux was interested in detecting parallax that others such Robert Hooke had attempted but failed to detect. Unlike Hooke, Molyneux had large amounts of patience and had resources to expend. Like Hooke, Molyneux decided to take advantage of Gamma Draconis always being over London. Molyneux commissioned a larger set of telescopes and employed James Bradley as an expert who had more astronomical and mathematical knowledge. Working together, Bradley and Molyneux performed over 80 observations to a precision of greater than 1 arcsecond from December 1725 until late in 1727. Measurements of this precision had never before been performed with telescopes. Bradley and Molyneux were surprised to find that rather than detect a parallax they detected an unexplained wobble of the star. Moreover, similar wobbles were found by Bradley using another high-precision telescope for some 200 other stars. Molyneux died shortly before Bradley realized that the observed changes they were seeing was in fact due to the aberration of light.[2]


Molyneux was Member of Parliament (MP) for Bossiney from 1715 to 1722, for St Mawes from 1726 to 1727, and for Exeter from 1727 to 1728. Between 1727 and 1728 he represented Dublin University in the Irish House of Commons.[4]

In 1728, Molyneux suffered a fit while in the House of Commons. He was treated by court anatomist Nathaniel St André, but the treatment did not prove successful, and Molyneux died in April. On the night of the death, St André eloped with Molyneux's wife, Elizabeth, the two marrying in 1730. Samuel Madden, a relative of Molyneux's, claimed that St André had poisoned the MP. Although St André won an action for defamation, he found himself unable to secure regular work.[5]


  1. Science and Its Times via"William Molyneux Summary". Retrieved 24 July 2007.
  2. 1 2 Hirschfeld, Alan (2001). Parallax:The Race to Measure the Cosmos. New York, New York: Henry Holt. ISBN 0-8050-7133-4.
  3. 1 2 "Samuel Molyneux". Ricorso). Retrieved 24 July 2007.
  4.  Clerke, Agnes Mary (1894). "Molyneux, Samuel". In Lee, Sidney. Dictionary of National Biography. 38. London: Smith, Elder & Co.
  5. Todd, Dennis (2004). "St André, Nathanael (1679/80–1776)". Oxford Dictionary of National Biography. Oxford University Press.
Parliament of Great Britain
Preceded by
Sir William Pole, Bt
Paul Orchard
Member of Parliament for Bossiney
with Henry Cartwright

Succeeded by
Robert Corker
Henry Kelsall
Preceded by
Sidney Godolphin
Samuel Travers
Member of Parliament for St Mawes
with Sidney Godolphin

Succeeded by
Henry Vane
John Knight
Preceded by
Francis Drewe
John Rolle
Member of Parliament for Exeter
with Francis Drewe

Succeeded by
Francis Drewe
John Rolle
Parliament of Ireland
Preceded by
Edward Hopkins
Marmaduke Coghill
Member of Parliament for Dublin University
with Marmaduke Coghill

Succeeded by
John Elwood
Marmaduke Coghill
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