Felix Pirani, who died aged 87, was a mathematical physicist whose research into Einstein’s theory of relativity included outstanding work on gravitational waves; he was also a populariser, an author of fiction for children, a political activist, and, in retirement, a sculptor and mosaicist.
Felix Arnold Edward Pirani was born in Britain on February 2 1928, although evacuation to Canada during the Second World War left him with a pronounced Canadian accent. After taking degrees at the University of Western Ontario and the University of Toronto and a DSc at the Carnegie Institute of Technology, he took his PhD in Physics at Cambridge University in 1956.
After a short period at the Dublin Institute of Advanced Study, he was appointed to a lectureship at King’s College London, where he spent the key part of his career as a mathematical physicist.
At King’s he joined a team headed by Hermann Bondi, famous for the “steady state” theory of the universe. Under first Bondi and then Pirani, King’s became a major centre for relativity research, and produced a series of papers establishing that relativity predicts the existence of gravitational waves. Experimentalists have been hunting these waves ever since, with many predicting that direct detection by the Laser Interferometer Gravitational Wave Observatory, a US-based physics experiment, is now imminent.
When Bondi suddenly left Kings in 1967 to become head of the European Space Agency (and later chief scientific officer to the Ministry of Defence) Pirani became professor of applied mathematics in his place, taking forward his work on gravitational waves and also on the so-called Petrov classification, at which he was said to have worked ferociously for 14 hours a day for a long period.
According to the theory of relativity there is a sense in which the “pull” of gravity which we feel is not real. Instead what is real is the variation in the strength of gravity over short distances, expressed by a certain mathematical object. Independently of Petrov, Pirani showed that this object could be classified in certain ways, and that this classification was key to mathematical and physical understanding of gravity.
Pirani inherited about a dozen research students, an extraordinary load for a new professor. A visitor to his room in the late 1960s might find him simultaneously conducting a technical discussion with one visitor, writing on a blackboard, organising a series of seminars in London or Cambridge with one secretary and dictating departmental business with another.
A man of strong Leftist views, Pirani supported the British Society for Social Responsibility in Science, joined the Left Scientists’ Group and was a member of CND. In his last months he was delighted by the election of Jeremy Corbyn as leader of the Labour Party.
As early as 1960 he had revised a popular book, The ABC of Relativity by Bertrand Russell, and after his retirement in 1983 he emerged as a prolific author; his L’Astronomie sans aspirine was one of his more popular publications.
He also wrote several books for children featuring a character called Abigail, named after his daughter. In a bizarre episode one book prompted the tabling of an Early Day Motion in the House of Commons on the grounds that it encouraged violence. (It had a little girl on the beach saying to nasty boys: “I’ll get my daddy to break both your arms and frazzle your bike. He’s in the Secret Service.”)
Latterly, he turned to sculpting and mosaics, with typically startling accomplishment.
Pirani was twice married, but both marriages were dissolved. He is survived by his partner Julia Vellacott, by a daughter and three sons, and by two stepsons.