Charlotte Higgins writes:

What do we know about time? Language tells us that it “passes”, it moves like a great river, inexorably dragging us with it, and, in the end, washes us up on its shore while it continues, unstoppable. Time flows. It moves ever forwards. Or does it? Poets also tell us that time stumbles or creeps or slows or even, at times, seems to stop. They tell us that the past might be inescapable, immanent in objects or people or landscapes. When Juliet is waiting for Romeo, time passes sluggishly: she longs for Phaethon to take the reins of the Sun’s chariot, since he would whip up the horses and “bring in cloudy night immediately”. When we wake from a vivid dream we are dimly aware that the sense of time we have just experienced is illusory.

Carlo Rovelli is an Italian theoretical physicist who wants to make the uninitiated grasp the excitement of his field. His book Seven Brief Lessons on Physics, with its concise, sparkling essays on subjects such as black holes and quanta, has sold 1.3m copies worldwide. Now comes The Order of Time, a dizzying, poetic work in which I found myself abandoning everything I thought I knew about time – certainly the idea that it “flows”, and even that it exists at all, in any profound sense.

We meet outside the church of San Petronio in Bologna, where Rovelli studied. (“I like to say that, just like Copernicus, I was an undergraduate at Bologna and a graduate at Padua,” he jokes.) A cheery, compact fellow in his early 60s, Rovelli is in nostalgic mood. He lives in Marseille, where, since 2010, he has run the quantum gravity group at the Centre de physique théorique. Before that, he was in the US, at the University of Pittsburgh, for a decade.

He rarely visits Bologna, and he has been catching up with old friends. We wander towards the university area. Piazza Verdi is flocked with a lively crowd of students. There are flags and graffiti and banners, too – anti-fascist slogans, something in support of the Kurds, a sign enjoining passers-by not to forget Giulio Regeni, the Cambridge PhD student killed in Egypt in 2016.

“In my day it was barricades and police,” he says. He was a passionate student activist, back then. What did he and his pals want? “Small things! We wanted a world without boundaries, without state, without war, without religion, without family, without school, without private property.”

He was, he says now, too radical, and it was hard, trying to share possessions, trying to live without jealousy. And then there was the LSD. He took it a few times. And it turned out to be the seed of his interest in physics generally, and in the question of time specifically. “It was an extraordinarily strong experience that touched me also intellectually,” he remembers. “Among the strange phenomena was the sense of time stopping. Things were happening in my mind but the clock was not going ahead; the flow of time was not passing any more. It was a total subversion of the structure of reality. He had hallucinations of misshapen objects, of bright and dazzling colours – but also recalls thinking during the experience, actually asking himself what was going on.

“And I thought: ‘Well, it’s a chemical that is changing things in my brain. But how do I know that the usual perception is right, and this is wrong? If these two ways of perceiving are so different, what does it mean that one is the correct one?’” The way he talks about LSD is, in fact, quite similar to his description of reading Einstein as a student, on a sun-baked Calabrian beach, and looking up from his book imagining the world not as it appeared to him every day, but as the wild and undulating spacetime that the great physicist described. Reality, to quote the title of one of his books, is not what it seems. [Continue reading…]

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