English astronomer especially interested in stellar motion and time determination. He initiated the public broadcasting of time signals by the British Broadcasting Corporation over the radio 1924.
Dyson was born in Ashby-de-la-Zouch, Leicestershire, and studied at Cambridge. He was Astronomer Royal for Scotland 1906-10 and for England 1910-33.
Dyson was one of a number of astronomers who confirmed the observations of Jacobus Kapteyn on the proper motions of stars, which indicated that the stars in our Galaxy seemed to be moving in two great streams. These results were later realized to be the first evidence for the rotation of our Galaxy.
Dyson organized several expeditions to study total eclipses of the Sun. Other areas to which he made important contributions include the study of the Sun's corona and of stellar parallaxes.