At KITP: Report from a Writer-in-Residence

Graham Farmelo

“Art is I, science is we,” wrote the nineteenth-century physiologist Claude Bernard. His aphorism gets to the heart of the difference between the arts and sciences: without Jane Austin, Pride and Prejudice would never have been written, though the theory of relativity would have emerged sooner or later even if Einstein had  never been born.

No institution better embodies science’s communitarian character than the KITP. For the past three decades, I have often heard praise for its sublime location, for its unique atmosphere and above all for the many ways it helps to foster new ideas and collaborations. I ceased to be a practicing theoretician long ago, so I had all but given up hope of visiting this secular Mecca, until former director David Gross approached me. In a long Skype call, he invited me to visit as part of the Institute’s writers-in-residence program - “However long you spend here,” he concluded with a smile, “you’ll regret that you didn’t stay longer.”

The arrangements for my visit were swiftly finalised by director Lars Bildsten, who was eager to support the research for my next book about the relationship between mathematics and theoretical physics. I wanted to meet theoreticians who are working in subjects – notably modern theories of gravity – that are cast in terms of modern mathematical concepts and that also appear to be difficult – or even perhaps impossible – to test experimentally. Are most of these theoreticians really doing ‘fairy-tale physics’ and indulging in ‘recreational mathematics,’ as many critics have alleged? The KITP’s spring 2015 program on the foundations of the quantum theory of gravity was an opportunity to talk with physicists working at the frontiers, and to hear their side of the story. As a bonus, a program on quantum entanglement was scheduled for the same time.

At first, it felt slightly odd to be a licensed interloper. I am used to working alone, but was suddenly a colleague of dozens of top-rate theoretical physicists who would use language and techniques that are only vaguely familiar to me. I did not want to interfere too much with their deliberations but hoped nonetheless that they would grant me a little of their time to help me get a better sense of what they are doing and why they are doing it. At all costs, I wanted to avoid being an irritant or hindrance.

I need not have worried. The participants warmly welcomed me and were generally happy to try to explain their work in plain language. Particularly helpful to me were the lectures. It struck me that the methods used by today’s theoretical physicists to present their research – talking at a blackboard, writing academic papers – are essentially identical to those of the very first professional theoretical physicists, notably Rudolf Clausius, a hundred and fifty years ago. But today there are crucial differences. Talks are now routinely broadcast live all over the world and can be made available free to anyone, anywhere at any time. The KITP’s policy of making its talks so widely available is hugely helpful to physicists all over the world, and will one day be a priceless resource for historians seeking to understand how solid scientific knowledge emerged from the confusing mush of the past.

Those first professional theoretical physicists would have been nonplussed, or even mystified, if they could have heard the deliberations at the quantum gravity meeting. For those scientists, gravity was a phenomenon that Newton had pretty much understood, and neither relativity nor quantum theory had been discovered. Today, theoreticians are struggling to find a viable quantum theory of gravity, armed with a host of powerful theoretical and mathematical insights, but precious little new data to give guidance from Nature. In all the talks I attended, I heard only one reference to an experimental measurement. Otherwise, most of the talks focussed on attempts to understand better the currently favoured theoretical framework for addressing the problem. This framework is extremely impressive – and is underpinned by the vast experimental support for quantum theory and relativity – though it still cannot give a rigorous account of processes such as the flow of information across the event horizon of a black hole.

It was a great privilege for me to talk in detail with several of the leaders in this field about the challenges facing their field. Steve Giddings, one of the program’s coordinators, was open-minded about the current state of the quantum gravity research. He speculated that much of the theoretical speculation may ultimately prove to have been on the wrong track. Like many of his colleagues, he believes progress can be made using pure thought but longs for the subject to be enriched by experimental input. In separate conversations, KITP’s Joseph Polchinski and Stanford University theorist Eva Silverstein went out of their way to emphasise that their aim is to understand nature better, certainly not to advance knowledge of mathematics. These conversations and many others gave me the impression that, contrary to popular opinion, most leading quantum-gravity theorists have their feet very much on the ground and are not given to whimsical speculation or to mathematical adventurism.

One exceptionally pleasant memory was the sight of the physicists from the quantum gravity and entanglement programs intermingling and exchanging ideas in the KITP’s courtyard. There were even introductory talks on key subjects in both subjects, including one for entanglement experts ‘who don’t know what a metric is’. Best of all, the groups were on common ground during discussions of new ideas on how space and time might, in some sense, have emerged from bits of quantum information. In the corridors and over afternoon tea, I sensed exciting new, inter-disciplinary collaborations taking shape. As I prepared to leave KITP, I realised that David Gross had been right – I wished I had been able to stay longer. But it was time to return home, to concentrate on the lonely ‘I’ of writing, nourished and enlightened by six weeks of ‘we’.

- Graham Farmelo is author of “The Strangest Man,” a biography of Paul Dirac, and of “Churchill’s Bomb” (Basic Books)
KITP Newsletter, Fall 2015

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