John Barrow obituary

The cosmologist John Barrow, who has died aged 67 from colon and liver cancer, was a renowned populariser of science. He combined mathematical and physical reasoning to increase our understanding of the very first moments of the universe.

This he did by giving elegant mathematical characterisations of inflationary models, in which a high vacuum energy density causes a dramatic exponential expansion of the universe in the very first instants before gradually evolving into the expansion we see today. He analysed the stability of such models in a range of gravity models that allowed slight deviations from Einstein’s general theory of relativity. In particular, he was interested in the possibility that the physical constants might vary with time, at a level of parts per million over 10bn years, and was a member of a team that claimed to detect such variations, though this claim is not widely accepted.

From 1999 he was professor of mathematical sciences at Cambridge University, and the founding director of the Millennium Mathematics Project, an outreach programme for students, teachers and the general public. In more than 20 excellent books on astronomy, mathematics and physics he took an especial delight in tackling and making comprehensible abstruse philosophical questions.

They included The Left Hand of Creation: The Origin and Evolution of the Expanding Universe (1983), The Book of Nothing (2000), The Artful Universe (1995), Pi in the Sky (1992), The Infinite Book: A Short Guide to the Boundless, Timeless and Endless (2005) and Impossibility (1998). What they said was always unexpected, and they were thoroughly researched and brilliantly written. With Frank Tipler he wrote The Anthropic Cosmological Principle (1986), exploring whether the fact that intelligent life exists has implications for the nature of the universe.

I first met John in 1978 in California, when he was a postdoctoral fellow at the University of California, Berkeley, and he was always great company, as when discussing astronomy, public affairs and other astronomers. He adapted Groucho Marx’s comment that “I wouldn’t want to belong to any club that would accept me as a member” to the universe: “A universe simple enough to be understood is too simple to produce a mind capable of understanding it.”

His play in Italian, Infinities, premiered in Milan in 2002 and won the Premi Ubu Italian theatre award. It consists of five vignettes, starting with an exploration of the celebrated thought experiment concerning David Hilbert’s infinite hotel, and going on to feature Jorge Luis Borges’ Library of Babel and a debate between the 19th-century German mathematicians Georg Cantor and Leopold Kronecker about the nature of infinity.

Born in Wembley, John was the son of Lois (nee Tucker) and Walter Barrow. From Ealing grammar school for boys he went to Durham University and gained a degree in mathematics and physics (1974). For his doctorate in astrophysics (1977) he studied non-uniform cosmological models models, exploring deviations from the usual assumption that the universe starts off completely smooth and the same everywhere, with Dennis Sciama at Magdalen College, Oxford. In 1975 he married Elizabeth East and they had three children.

After spells as a junior research lecturer at Christ Church, Oxford, and as a postdoctoral fellow at Berkeley, John joined the astronomy centre of the Sussex University as a lecturer in 1981, becoming a professor eight years later, and from 1995 to 1999 the centre’s director. He then moved to the department of applied mathematics and theoretical physics at Cambridge, where in 2006 the Millennium Mathematics Project was awarded the Queen’s Anniversary prize for educational achievement.

Invitations to other institutions included two periods of giving public lectures at Gresham College, London – as professor of astronomy (2003-07) and of geometry (2008-12), the only person since the 17th century to hold two different such posts. His lectures there included “100 essential things you didn’t know about maths and the arts”, “Let’s twist again: throwing, jumping, and spinning”, and “100 essential things you didn’t know about sport”.

In his youth he was a keen athlete, drawn especially to cricket and football and had had a trial for Chelsea juniors. At Durham he represented the university at cross-country running; there is a photo of him breasting the tape ahead of a young Steve Ovett. He was proud of the fact that he had lectured at 10 Downing Street, at Windsor Castle and in the Vatican, but steadfastly refused to appear on television.

In 2006 he was awarded the Templeton prize for “his writings about the relationship between life and the universe, and the nature of human understanding, which have created new perspectives on questions of ultimate concern to science and religion”. He was a member of the United Reform Church, which he described as teaching “a traditional deistic picture of the universe”. Earlier this year he was elected to the Pontifical Academy of Sciences.

During the recent lockdown, and knowing that he did not have long to live, he wrote his last, yet-to-be published, book, One Plus One. He also completed 11 scientific papers, adding to his total of more than 400 published during his career.

He was made a fellow of the Royal Society in 2003. His awards included the Royal Society’s Faraday rize for excellence in the communication of science in 2008, the 2015 Paul Dirac prize of the Institute of Physics, and the Gold Medal of the Royal Astronomical Society in 2016.

He is survived by Elizabeth, his children David, Roger and Louise, and five grandchildren.

• John David Barrow, cosmologist and writer, born 29 November 1952; died 26 September 2020