John Barrow obituary

Cosmologist who asked whether the existence of intelligent life has implications for the nature of the universe

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.