Sir Frank Watson Dyson, KBE, FRS, FRSE (8 January 1868 – 25 May 1939) was an English astronomer and the ninth Astronomer Royal who is remembered today largely for introducing time signals ("pips") from Greenwich, England, and for the role he played in proving Einstein's theory of general relativity.
Dyson was born in Measham, near Ashby-de-la-Zouch, Leicestershire, the son of the Rev Watson Dyson, a Baptist minister, and his wife, Frances Dodwell. The family lived on St John Street in Wirksworth while Frank was one- to three-years-old. They moved to Yorkshire in his youth. There he attended Heath Grammar School, Halifax, and subsequently won scholarships to Bradford Grammar School and Trinity College, Cambridge, where he studied mathematics and astronomy, being placed Second Wrangler in 1889.
In 1894 he joined the Royal Astronomical Society, the British Astronomical Association and was given the post of Senior Assistant at Greenwich Observatory and worked on the Astrographic Catalogue, which was published in 1905. He was appointed Astronomer Royal for Scotland from 1905 to 1910, and Astronomer Royal (and Director of the Royal Greenwich Observatory) from 1910 to 1933. In 1928, he introduced in the Observatory a new free-pendulum clock, the most accurate clock available at that time and organised the regular wireless transmission from the GPO wireless station at Rugby of Greenwich Mean Time. He also, in 1924, introduced the distribution of the "six pips" via the BBC. He was for several years President of the British Horological Institute and was awarded their gold medal in 1928.
Dyson was noted for his study of solar eclipses and was an authority on the spectrum of the corona and on the chromosphere. He is credited with organising expeditions to observe the 1919 solar eclipse at Brazil and Príncipe, which he somewhat optimistically began preparing for prior to the Armistice of 11 November 1918. Dyson presented his observations of the solar eclipse of May 29, 1919 to a joint meeting of the Royal Society and Royal Astronomical Society on 6 November 1919.