Within the world of quantum physics, which, to the layman at least, resembles a Gordian knot of indecipherable logic, Italian professor Carlo Rovelli slices through the confusion with poetic clarity. As the founder of quantum loop theory and one of the world’s most influential thinkers, the depth of Rovelli’s knowledge is matched only by his ability to explain it to those with none. Whether in his weekly newspaper columns, fantastically popular books or online catalogue of talks and lectures, Rovelli has opened the minds of millions to what he regards as the universal beauty of his subject.

In recent years, this has led to near-celebrity status for Rovelli within popular science, though his humility forbids him from admitting it. That self-effacing attitude is perhaps not surprising when one considers that for him, science is about embracing a radical uncertainty within our knowledge and continuously rebelling against what is considered true. This pursuit of truth demands a wider net be cast, with physics just one of many tools at Rovelli’s disposal. His most recent book, The Order of Time, references classical music, pop culture and philosophy in addressing the most pressing mysteries of our existence. Yet arguably its biggest achievement is convincing us they matter.

Finn Blythe: In addition to books and lectures, you have written extensively about theoretical physics for several Italian newspapers. Why is it important for everyday readers to have that kind of daily access to the subject?
Carlo Rovelli: Well, if people don’t know what’s happening in physics today, they’re missing something beautiful and interesting. So imagine we were in the Renaissance and discovered that the Earth goes around the sun and is not the centre of the universe. People say, “Why do you want to write about it?” Well, because people want to know it. I find science deeply connected to our human concerns, to the way we see ourselves in the world. So I’m not imposing that on people to read these things but I think they are missing something if they are not interested in that. It’s like music, right? Nobody wants to force people to listen to music but people do want to listen to music because it’s beautiful.

FB: From what I gather, your interest in physics was grounded in your own youthful rebellion. Do you feel as though that rebellion of your early twenties ever ended?
CR: Yes and no. To some extent, I’m a much more conservative person than when I was twenty, of course. But having said so, I still think that what makes us human, what makes civilisation, is change and evolution. This instinctive rebelliousness that we have, some more and some less, it’s part of us. It’s a creative part of humanity and it’s also what pushes us ahead. Everything that has been built by humans has been built by young people that rebelled against what was before. So even people who are conservative, they’re just defending the rebellion, the revolution of young people. So yes, my heart is still in this spirit – what attracts me is not what defends the past, the past is boring, it’s what opens new directions.

FB: You have a diverse range of interests beyond physics. You’ve written a book on the Greek philosopher Anaximander and each chapter in The Order of Time begins with quotes from Horace. How does an understanding of philosophy both help your understanding and explanation of physics?
CR: This is a good point. First of all, I think we live in historical periods in which the excessive specialisation of our education exaggerates costs for our understanding of the world. Just in physics, which is my domain, I was recently reading biographies of great 19th century scientists. They all were profoundly knowledgeable of philosophy: Schrödinger, Einstein, Heisenberg, and the previous century even more. Science doesn’t go ahead just by itself, neither does philosophy or art. Civilisation is a big conversation in which everything gets involved and we learn from one another.

Of course everybody does their own job. The painter paints, the physicist does their calculations, the philosopher does their thinking, but not in isolation, by learning from one another. So there might be scientists who are just completely specialised in their own thing and they might be good, but as a whole, science doesn’t go ahead without philosophy. I’m deeply convinced about that.

And the second part of the story which you mentioned; what’s exciting about science is not the specific details of a calculation or model. I mean nobody cares if the particles of the sun are more than sixteen or fifteen. Nobody cares if the specific neutrino is left-handed or right-handed. What people are interested in are more general questions. What is matter? What is the world made of? What is time? To go straight to the core is not an issue of just physics, it’s an issue of our understanding of the world. So I think that a larger cultural perspective obviously makes communicating science easier.

“Science doesn’t go ahead just by itself, neither does philosophy or art. Civilisation is a big conversation in which everything gets involved”

FB: Why does our perception of time change the older we get?
Carlo: Well, I guess you should ask a neuroscientist this or a biologist, not a physicist. But the main reason I think is because time, or our experiences of time, of ‘the clock’ in our experience, is mostly memory. So what you call time is really this window in physical time which is opened by the fact that you get memories of the past and divinations of the future. We humans, in particular, are good at this, but I think all mammals at least have a vision of some future in front of them.

So we live in this timespan of memory and anticipation, and part of it is direct memories of our life, part of it is a cultural memory that remembers the old kings of England or the Romans of Italy. But the part which is ours, our memory, changes completely of course. I mean, if I’m young I have short memories, if I’m old I have long memories. So my own time is completely different when I’m 60 and when I’m 20.

They’re both very beautiful in a sense, I mean the time of the 20s is a burning time with an infinite future. It’s fantastic. And the time when you’re 60, you’re sort of saying, “Well, here I am, this is my life.” And most of it’s already happened and I’m happy and this is it, I’m immersed in it. The perspective is completely different and obviously so, because the perspective is based on our different experience.

FB: Do you think during Covid-19 the realisation of human fragility has led to a better understanding of our place in time?
CR: Nobody knows what lessons we are learning from this experience, which is probably not over yet. I think we have learned, or we should have learned, that we’re much more fragile than we thought. The big epidemics, like the one in London at the time of Newton, or the huge epidemic in Athens 2,000 years ago, were almost the symbol of how much civilisation had changed. We believed we were strong and we’d learned how to deal with things. That’s completely fake.

So at the societal level, we are far more fragile and far less powerful than what we thought. But also as humans, the virus somehow brought a moment of fear to us all, I think. I could die here, or my father could die or my older brother. In a sense it’s more a perspective, we should have known that from before, but now are we going to forget and start as before, feeling strong, or is it a lesson we’ve learned? I hope it’s a lesson because there are new dangers for humanity coming and if we are aware of our fragility, it’s much better for everybody.

“The big epidemics, like the one in London at the time of Newton, or the huge epidemic in Athens 2,000 years ago, were almost the symbol of how much civilisation had changed. We believed we were strong and we’d learned how to deal with things. That’s completely fake”

FB: Do you think that misplaced belief in continuous human development is a result of our basic misconception of a linear progression of time?
CR: A little bit, yes. Humanity definitely has progressed, life is much better today than in the past for a huge amount of people. So the sense of progress and getting better is not an illusion, it is real. But nothing tells us that it’s forever. Nothing tells us that it doesn’t come with huge risks and there are back and forths and that we make mistakes. And it could stop at any time. Civilisations are born and die, and ours has not been particularly long-living and doesn’t seem particularly solid, either. It’s a global civilisation and it’s fragile, so it could break down. So yes, we organise our thinking in time at different scales and at each one I think we make a mistake with periods too simply, too linearly. Things go back and forth.

FB: I wanted to ask you about the capacity of our brains to conceptualise space and time at quanta scale, things that are virtually unintelligible for most people. I know you had a formative experience with hallucinogens, do you think the normal-functioning brain is the best tool we have for comprehending these measurements?
CR: I think we have the wrong idea that something comes naturally to us and we have a common-sense view of the world and that’s it. What is called the common-sense view of the world, the one we have of space and time, it’s not the natural way of thinking for us. It’s the result of centuries of civilisation and thinking and changing minds. In fact, if you ask anybody in the street what is space and what is time, the person will give you an answer which remarkably, is just Newton. And it’s different from the answer that a person from the Middle Ages would have given, profoundly different. Because we change our view of space and time.

Humans evolved for dealing with distances of metres, maybe kilometres and times of minutes, hours, days, but humans are characterised by curiosity and a remarkably flexible brain which has allowed us to adapt our way of thinking. We have no difficulty today visualising the whole of England or planet Earth. We have no difficulty visualising the moon and what’s on the moon and the difference between here and there. We have no difficulty thinking that in Australia people live upside down, the head down and the feet up, with respect to us. So all this would have been super hard to conceptualise 5,000 years ago. People wouldn’t have understood all that because they need help. I mean how is it possible that people in Australia live upside down? They would fall, surely? But we learned that.

“What is called the common-sense view of the world, the one we have of space and time, it’s not the natural way of thinking for us. It’s the result of centuries of civilisation and thinking and changing minds.”

More than that, we have learned to organise time in certain ways. Today, not many people are surprised by thinking that a piece of iron, which is solid, is in reality made by some atoms, very cleanly and attached in a strong way to one another. So our common sense has adapted to that. The reason the physics I’m doing, relativistic physics, seems so strange is only because we’ve not gotten used to it. It’s not easy to learn but we learn. So I think the brain is capable of conceptualising things differently and we have this capacity to adapt. The hard part is never to understand something new. The hard part is to get out of the old habits. To accept that ideas which seem natural to us, are not so. Natural to us is up is up and down is down, but it’s not true, it’s more complicated. Up in Sydney is different to up in London.

And you mention my young man LSD psychedelic experience. I think these were useful for me in that I got the sense that, if a little chemical goes into your body and you see the world so differently, it means that the way you see the world normally isn’t necessarily so obviously right. So we should know this and this openness is the main lesson I got from that period.

FB: Finally, I wanted to ask about the theory of everything. How closely do you subscribe to the idea and do you think it’s futile?
CR: I think it’s futile. We are very far from a theory of everything. I think humanity has made many times this mistake of learning something new and jumping to the conclusion that we are at the end of the story. There are moments in which we have enthusiasm but I see no signs whatsoever that they’re close to the theory of everything. There are big pieces of nature that we don’t understand. We don’t know what dark matter is, so how can we be close to the theory of everything if we don’t know about the thing that makes up half of the matter in the universe?

“We don’t know what dark matter is, so how can we be close to the theory of everything if we don’t know about the thing that makes up half of the matter in the universe?”

There was a moment of excitement with string theory, which was a testable theory of everything, but I think the moment has passed and the excitement is fading. So I’m not saying we cannot understand everything, I don’t know. It’s remarkable how much we are understanding. It’s fantastic how much we know, but somehow the more we know, the more we discover things we don’t know. So my impression is that we are still looking at a space of ignorance around us.

It’s like that letter by Newton in which he says that, at the end of his life, I know not how others see me but I see myself as a boy on a beach who is looking for beautiful stones while ignoring the ocean of truth all around. I don’t know the exact words, but I think we’re still there. We’ve learned much more and that is great but we’re not at the end of this story. There are so many more things in the universe to find out.

Originally published in HERO 24.