Patrick d'Arcy, Date of Birth, Place of Birth, Date of Death

    

Patrick d'Arcy

Irish physicist

Date of Birth: 27-May-1725

Place of Birth: Athenry, Connacht, Ireland

Date of Death: 18-Oct-1779

Profession: physicist, mathematician

Nationality: France

Zodiac Sign: Gemini


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About Patrick d'Arcy

  • Patrick d'Arcy (27 September 1725 – 18 October 1779) was an Irish mathematician born in Kiltullagh, County Galway in the west of Ireland.
  • His family, who were Catholics, suffered under the penal laws.
  • In 1739 d'Arcy was sent abroad by his parents to an uncle in Paris.
  • He was tutored in mathematics by Jean-Baptiste Clairaut, and became a friend of Jean-Baptiste's son, Alexis-Claude Clairaut, (Alexis Clairaut), who was a brilliant young mathematician.
  • d'Arcy made original contributions to dynamics.
  • He is best known for his part in the discovery of the principle of angular momentum, in a form which was known as "the principle of areas," which he announced in 1746.
  • See the article on areal velocity.
  • d'Arcy also had an illustrious military career in the French army.
  • He obtained the title of "Count" in the French nobility.
  • He was a generous patron of Irish refugees in France.
  • In addition to his contributions to dynamics, he performed research on artillery and on electricity.
  • An experiment of his, reported in 1765, on visual perception is often referred to: he built a machine in his garden to measure the duration of visual impressions.
  • A burning coal, attached to an arm of a cross rotated by the machine, would be made to spin just fast enough to give the impression of a full fiery circle.
  • With the collaboration of a dedicated observer with better eyesight than D'Arcy, he measured a 0,13 second duration for the visual sensation of the rotating burning coal, as seen in the dark from a circa 50 meter distance.
  • He planned further experiments to measure the suspected differences between individuals, colors, viewing distances and light intensity of objects.
  • The experiment is often mentioned by film scholars in the context of persistence of vision. D'Arcy was elected to the Academie Royale des Sciences in 1749.
  • He died from cholera in Paris in October 1779. There is a copy of a portrait of d'Arcy in Wade (1997), [1], which was found in Charbonnier (1928).

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