It is with great sadness that we learnt of the death of John Barrow. John was a member of FQXi's scientific council and contributed in shaping our research direction and focus. John was an accomplished physicist as both researcher and teacher, and played a large part in many successful outreach activities. He was committed to improving the teaching of mathematics at schools, taking on the role of director of the Millennium Mathematics Project, and writing dozens of books for the general public.
John was a central figure in classical cosmology, investigating areas that would prove counter-intuitive or unexpected, such as "big rip" and "sudden" singularities. His academic interests pushed the boundaries of the field - he was also a central figure in understanding the role of anthropic arguments in physics, and together with Frank Tipler wrote the central text on the issue. Just this year he was working on approaches to the fundamental issues - providing a novel method for estimating the entropy of a black hole.
On a personal level, I first met John in 2012 when I went to Cambridge as a postdoc; he was to be my supervisor. He was the driver of a range of fascinating discussions of physics; every week John would suggest a new area to look at citing papers from a remarkably broad array of fields from electrical engineering to philosophy. Beyond that, however, our discussions would consist of his teaching me about aspects of the world of which I wasn't even aware that I knew nothing. His breadth of knowledge was intimidating - from how to write plays in Italian to the furniture of bishops. He was a fabulous storyteller with a quick wit and keen sense of humour. He was an accomplished athlete; on telling him I was going for a run one day he gave me routes, and times to attempt them in, from his past. I got about half-way through the first one.
John deservedly won a long list of prizes, any one of which would be the highlight of many careers - the Templeton Prize, the Kelvin Prize, the Dirac Medal and many more. He was an excellent physicist, a true renaissance man and fine mentor. We will miss him.