Ball, Sir Robert Stawell (1840–1913), astronomer and mathematician, was born 1 July 1840 at Granby Row, Dublin, son of Robert Ball (qv), LLD, curator of the museum at TCD and secretary to the Queen's University, and Amelia Ball (née Gresley Hellicar) of Bristol. Initially educated at Dr John Lardner Burke's school at North Great George's St., he was sent to Tarvin Hall near Chester. After his father's death (1857) he returned to Dublin and began a distinguished academic career at TCD, studying mathematics and experimental physics. He won several prizes including the Lloyd exhibition (1860), a university scholarship, and in 1861 (the year of his graduation) the gold medal for mathematics. Between 1861 and 1865 he continued to study mathematics at the college, winning prizes in the fellowship examinations for three successive years (1863–5), before taking up the post of tutor to the sons of the earl of Rosse (qv) at Birr Castle. Given use of the earl's observatory at Parsonstown, he made his first forays into practical astronomy and established himself as one of the country's foremost astronomers. In 1869 he was appointed to the chair of applied mathematics and mechanism at the new Royal College of Science in Dublin. He regularly addressed the RDS on astronomical topics, and his popularity created a demand for his lecturing skills throughout Britain and Ireland. A volume of his discourses, Experimental mechanics, was issued in 1871, coinciding with a series of mathematical studies relating to screws published in the Transactions of the Royal Irish Academy. His election as a fellow of the Royal Society (1873) confirmed his growing reputation.
In 1874 he succeeded Franz Brünnow as astronomer royal of Ireland and as Andrews professor of astronomy at TCD. He continued Brünnow's work on stellar parallaxes at the Dunsink observatory, but his studies in this area proved fruitless. From 1883 onwards his work as a visual observer declined owing to failing sight in his right eye, and he concentrated on writing and mathematical work. He published The theory of screws: a study in the dynamics of a rigid body (1876) which earned him the RIA's Cunningham gold medal, Dynamics and modern geometry: a new chapter in the theory of screws (1887), and A treatise on the theory of screws (1900). He also wrote thirteen popular works on astronomy, including The story of the heavens (1885), The earth's beginning (1901), and A popular guide to the heavens (1905). Lucidly written, his works brought the science of astronomy within the range of the average man's imagination and understanding, popularising the science without vulgarising it. His public responsibilities were increased by his appointment as scientific advisor to the commissioners of Irish lights (1882). In 1886 he was knighted, and in 1892 he was awarded an honorary doctorate by TCD. He accepted the position of Lowndean professor of astronomy and director of the observatory at Cambridge University in 1892, a position that he held for the rest of his life. He became a fellow of King's College and continued to extend his subject beyond the confines of academia.
Ball was a very talented amateur photographer. His membership until 1911 of the Commissioners of Irish Lights inspection committee that circumnavigated the Irish coast each year gave him the opportunity to capture many splendid images, not only of lighthouses and other navigational facilities, but also of everyday life in the more remote coastal areas. Many of these photographs are held in the National Photographic Archive (NLI).
Throughout his career he was a prominent member of several academic and scientific institutions: secretary (1877–80) and a vice-president (1885–92) of the RIA, and president of the Royal Astronomical Society (1897–9), the Mathematical Association (1899–1900), and the Royal Zoological Society of Ireland (1890–92). He was also an active member of the TCD dining club and the Athenæum, and an honorary member of the TCD common room and the Royal Irish Yacht Club. Always involved in university politics, he was invited to become the parliamentary candidate for Dublin University in 1902 and for Cambridge in 1911, but on both occasions he declined. He died 25 November 1913 at his home in the Cambridge University observatory after a long illness; his funeral took place after a special service in King's College chapel. He married (1868) Frances Elizabeth, daughter of W. E. Steele, MD, registrar of the RDS and later director of the National Museum of Ireland. They had four sons and two daughters.