Twenty-five years ago, I moved from San Francisco to the UK, from a fellowship at Berkeley to a permanent job at Imperial College, London. A lot has changed since then. I was 35; now I am 60. It was two weeks before 9/11; the world hasn’t seemed as open and free since.

I arrived from the Bay Area just after the first dot-com bubble burst. London, adjusting to New Labour after almost two decades of Thatcher and Thatcherism, felt exciting and vibrant. But just weeks after I arrived came the horror of 9/11, and its years-long aftermath, especially the Iraq war which eventually doomed Blair’s premiership and probably led the way to the 2010 election, the disaster of “austerity” as a wrong-headed attempt to deal with the 2008 recession, and eventually to the more-disastrous Brexit on this side of the Atlantic. Similar politics, though with very different timing, led back in the USA to Obama, one of the few rays of political hope over the last quarter-century, but then, of course, to Trump. And everywhere since 2001 the rise of nativist populism making me feel at home, well, pretty much nowhere — a rootless cosmopolitan. Higher education, scientific funding, and curiosity-driven research are in a parlous state in both the US and the UK.

But: despite a few difficult years in the mid-2000s, I have prospered. Our analysis of data from the Planck satellite has solidified our standard cosmological model — but also given us new problems and puzzles to think and worry about. I have written a book, The Random Universe, trying to explain how we know what we know as scientists and as human beings. And my family, my wife and two daughters, are a source of joy and excitement that inspire me every day.

So now I am 60. I was honoured and humbled a couple of months to ago to be joined by many of my colleagues and scientific friends at a conference here in London. That, and getting a Transport For London 60+ Travel Card, makes it hard to avoid feeling old. But those colleagues and friends (many of whom are older than me) reassured me that it’s only the beginning of a new chapter.