‘There is no such thing as past or future’: physicist Carlo Rovelli on changing how we think about time
From The Guardian:
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.
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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.
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“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.”
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He gave his conservative, Veronese parents a bit of a fright, he says. His father, now in his 90s, was surprised when young Carlo’s lecturers said he was actually doing all right, despite the long hair and radical politics and the occasional brush with the police. It was after the optimistic sense of student revolution in Italy came to an abrupt end with the kidnapping and murder of the former prime minister, Aldo Moro, in 1978 that Rovelli began to take physics seriously. But his route to his big academic career was circuitous and unconventional. “Nowadays everyone is worried because there is no work. When I was young, the problem was how to avoid work. I did not want to become part of the ‘productive system’,” he says.
Academia, then, seemed like a way of avoiding the world of a conventional job, and for some years he followed his curiosity without a sense of careerist ambition. He went to Trento in northern Italy to join a research group he was interested in, sleeping in his car for a few months (“I’d get a shower in the department to be decent”). He went to London, because he was interested in the work of Chris Isham, and then to the US, to be near physicists such as Abhay Ashtekar and Lee Smolin. “My first paper was horrendously late compared to what a young person would have to do now. And this was a privilege – I knew more things, there was more time.”
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Rovelli’s work as a physicist, in crude terms, occupies the large space left by Einstein on the one hand, and the development of quantum theory on the other. If the theory of general relativity describes a world of curved spacetime where everything is continuous, quantum theory describes a world in which discrete quantities of energy interact. In Rovelli’s words, “quantum mechanics cannot deal with the curvature of spacetime, and general relativity cannot account for quanta”.
Both theories are successful; but their apparent incompatibility is an open problem, and one of the current tasks of theoretical physics is to attempt to construct a conceptual framework in which they both work. Rovelli’s field of loop theory, or loop quantum gravity, offers a possible answer to the problem, in which spacetime itself is understood to be granular, a fine structure woven from loops.
String theory offers another, different route towards solving the problem. When I ask him what he thinks about the possibility that his loop quantum gravity work may be wrong, he gently explains that being wrong isn’t the point; being part of the conversation is the point. And anyway, “If you ask who had the longest and most striking list of results it’s Einstein without any doubt. But if you ask who is the scientist who made most mistakes, it’s still Einstein.”
Link to the rest at The Guardian