Sir Robert Stawell Ball (1 July 1840 – 25 November 1913) was an Irish astronomer who founded the screw theory. He was Royal Astronomer of Ireland at Dunsink Observatory. Life He was the son of naturalist Robert Ball, and Amelia Gresley Hellicar. He was born in Dublin. and was educated at Trinity College Dublin where he won a scholarship in 1859 and was a senior moderator in both mathematics and experimental and natural science in 1861. Ball worked for Lord Rosse from 1865 to 1867. In 1867, he became Professor of Applied Mathematics at the Royal College of Science in Dublin. There he lectured on mechanics and published an elementary account of the science. In 1873, he became a Fellow of the Royal Society. In 1874, he was appointed Royal Astronomer of Ireland and Andrews Professor of Astronomy in the University of Dublin at Dunsink Observatory. Ball contributed to the science of kinematics by delineating the screw displacement: When Ball and the screw theorists speak of screws they no longer mean actual cylindrical objects with helical threads cut into them but the possible motion of any body whatsoever, including that of the screw independently of the nut. Ball's treatise The Theory of Screws (1876) is now in the public domain. His work on screw dynamics earned him in 1879 the Cunningham Medal of the Royal Irish Academy. In 1882, Popular Science Monthly carried his article "A Glimpse through the Corridors of Time". The following year it carried his two-part article on "The Boundaries of Astronomy". He was knighted in 1886. Ball expounded the tides in Time and Tide: a Romance of the Moon (1889). He published in 1891 The Cause of an Ice Age and in 1892 An Atlas of Astronomy. In 1892, he was appointed Lowndean Professor of Astronomy and Geometry at Cambridge University at the same time becoming director of the Cambridge Observatory. He was a fellow of King's College, Cambridge. In 1900, Cambridge University Press published A Treatise on the Theory of Screws. It followed works meant for a more general audience, such as The Story of the Heavens, first published in 1886. Much in the limelight, he stood as President of the Quaternion Society. He was also President of the Mathematical Association in 1900. In 1908, he published A Treatise on Spherical Astronomy, which is a textbook on astronomy starting from spherical trigonometry and the celestial