Ideas - How Galileo revolutionized science to make way for modernity

Episode Date: April 1, 2025

Einstein’s theory of relativity, quantum physics, and finding evidence of black holes — trace the chain of discoveries that led to these breakthroughs and you'll end up with the Italian astronomer and inventor, Galileo Galilei. Renowned Italian theoretical physicist and author Carlo Rovelli says we can learn a lot from Galileo today. He explains how 400 years ago, this renaissance man of science was discovering new facts about the Universe to understand ourselves better — and so are we.

When a body is discovered 10 miles out to sea, it sparks a mind-blowing police investigation. There's a man living in this address in the name of a deceased. He's one of the most wanted men in the world. This isn't really happening. Officers are finding large sums of money. It's a tale of murder, skullduggery and international intrigue. So who really is he? I'm Sam Mullins and this is Sea of Lies from CBC's Uncovered, available now.

This is a CBC Podcast. Welcome to Ideas. I'm Nala Ayed. Four centuries ago, Galileo Galilei appeared at the heavens through a new invention called a telescope. And he saw things that nobody had seen before. The phases of Venus, the satellites of Jupiter, the rings of Saturn, the spots on the Sun. And life on Earth would never be the same. That astonished Europe at the time, because other people looked and said, wow, the world is different, out there is more than what we thought.

Carlo Rubelli is a renowned theoretical physicist from Verona, Italy. His books include Reality Is Not What It Seems and Seven Brief Lessons on Physics, which has sold more than 2 million copies around the world. He was at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario in February to help kick off a year of events to mark the Institute's 25th anniversary. Tonight he will guide us on a trip towards and into a black hole and what might be on the other side. Please join me in welcoming to the stage Dr. Carlo Ravelli. So I'm going to talk about black holes, but let me start by putting this into the big picture. From Copernicus to Newton, the late Renaissance, all the way to the beginning of the Enlightenment,

the great scientific evolution, the revolution of thinking that has given rise to modern science. Galileo is at the heart of that revolution, and indeed, a revolutionary figure himself. He insisted that the Earth was not the fixed, unmoving center of the universe, but that it orbited the Sun. The Catholic Church insisted that view was heretical. In 1633, he was forced to recant under threat of torture, and he was placed under house arrest until his death in 1642. But his work had already laid the foundations for 400 years of scientific breakthroughs,

leading up to Einstein and relativity, quantum science, and the discovery of black holes, revelations that fundamentally reshaped science's understanding of reality. In the same week as Carlo Rovelli's lecture, the Perimeter Institute hosted a traveling exhibit devoted to Galileo, as well as his instruments, inventions, writings, and drawings and paintings of what he observed.

My name is Alessandro De Angelis. I'm a professor in Padova, a professor of physics, and I live in Paris where I work for the international organizations. Alessandro De Angelis has written several books on Galileo and translated Galileo's own writing. The school where he teaches the University of Padova or Padua is one of the oldest universities in the world, and perhaps its most famous teacher was Galileo. Alessandro de Angelis also has an intimate connection with the Galileo exhibit. I am the curator of the first exhibition that was done in Sorbonne University in Paris. And then of course I got an agreement that I could bring the exposition all around the world.

And I was particularly happy to send it outside Europe. One of the instruments on display? An exact replica of Galileo's telescope. Galileo didn't invent the telescope. The telescope was invented in Holland. But at the time, Venice had a superior glass technology, so he could transform the Dutch telescope into a scientific instrument. So he made the first telescope in the year 1609, and this is a copy one of his first telescope and you can see the moons of Jupiter for example now you can see the moon of

Jupiter and it's still an emotion done by Galileo it was very very difficult so you can imagine it was the guy seen them for the first time so can you imagine the motion of this I just can't and in this exhibition, we have also some of his notebooks. Every night he wrote the positions of the moons of Jupiter. I mean Galileo had more than 200 notebooks, which are all kept in the National Library of Florence. You see, this is a notebook, and you see every day, every night, the moons of Jupiter that were changing position because they move very fast I mean they make a revolution in days And so it was puzzle that one night is so three one night is so two then four and so on just because some were

Eclipsed by Jupiter Yes every night you see but there are some holes because this was January and it rains a lot in Padua in January. Right. So it's cloudy some nights. Yes. So sometimes he couldn't observe. So he seems like a meticulous note taker. Yes. He was a meticulous note taker and he was an artist. So some of his drawings are just masterpieces, like the drawings of the moon. So he was the first one, the first person to see the mountains of the moon.

He did four, five sets of drawings of the moon in water painting. So this is watercolor. Yes, this is watercolor, yes. So like it's, he knows how to draw. He knows a lot how to draw. Yes, he was making also drawings of Venice and so on because he was living between Padova and Venice. You walk the

streets of Padova. Yes, I live in the center of Padova. You drink the same water. And we drink also the same amount of wine. Yes. I would hope so. But I mean, again, I'm going to keep asking the same question, just what it's like to be walking in his footsteps, essentially. Well, for me, it's really an emotion also to, I mean, to see his chair, his chair is still kept in Padova. To touch his chair is quite an emotion also, as well, yes. Most of the instruments are in Florence, by the way. Right, okay.

So is his finger, apparently. His finger was brought to Florence after his autopsy. The vertebra was stolen and then the finger and the vertebra was still kept in Padova and the finger was sent to Florence. There was no chance to bring it here I guess. I think that this is one of the things that because you know this is one of the most visited memories of Galileo. I mean you have the cherry or the samizzo, but people like the finger. Yes, and it's not just any finger. It is the middle finger.

Yes, it is the middle finger. I can see the appeal. Galileo also has a special place in Carlo Rovelli's heart. It's a source of inspiration for every physicist, but I would say for an Italian physicist in particular. There is the idea that science is sort of independent of the personalities and the cultures is not true at all. Scientists are very different from one another and if you look at the great scientists of

the past, they're completely different personalities and ways of being. And Galileo is sort of more Italian than everybody else, you know, in the good and in the bad. He was passionate, he was picking up fights, he was emotional, he was certainly a towering figure in the great scientific revolution that opened modernity. It's a completely different person than Newton, who was perhaps the greatest figure of that revolution. How do we know what his personality was like? Oh, he was a very public figure and he got involved in all sorts of things. We know his books, we know his letters, and we have a lot of accounts by other people of his life and what he did.

He picked up a fight with the Catholic Church in Italy and lost badly. And like in everything he did, how to put it, Newton was always right. Galileo was very often wrong in many things, in his physics, in his intellectual ideas, even in his fight with the church. And yet, he's probably, and that's why he's a great inspiration, he's probably the person who most clearly understood that to understand something about the world, you have to be ready to drop something that seems obvious to you. And knowledge comes with conceptual revolutions.

You wrote that, quote, the ability to understand something before it's observed is at the heart of scientific thinking. I'm wondering what it was about Galileo and his intellect and temperament that made him able to understand a new scientific fact when he observed something that nobody else had seen or noticed before him? It's an intellectual product of a combination of two things. And I think it's exactly the kind of combination that produces science. On the one hand, he builds on past knowledge a lot. He was enamored of Archimedes, of Plato, of Aristotle, and of course Ptolemy. He built on the knowledge of the time, but the other half of the legacy on which he built is recent

Italian renaissance, which came as a profound cultural rethinking of everything and putting everything in discussion. So, it's not that he created everything from nothing, he created with building on something, but in a spirit of, okay, let's start from scratch and be ready to think the world anew. There were social changes in Italy, the old powers were losing grip, there were new social classes, everything was happening at the time. It's close to the time of Michelangelo or Raphael or Leonardo da Vinci, it was not much before that. So new world, new ideas and his capacity of bringing all this together with ancient mathematical and physical knowledge.

But he was able to kind of believe in his own eyes and having reason and insight to kind of draw new conclusions from his observations. You wrote that experimental science begins with Galileo. A lot of things begins with Galileo and experimental science is one. The actual contributions of Galileo are remarkably numerous and different for one another. One is, of course, he used the telescope and saw things out there that nobody had seen before. It was spectacular.

It was the first time humankind looked out of the window somehow using this little object, the telescope, that he got from the Dutch and he ameliorated. But it's not just he looked up. He started a very careful campaign night after night of looking up and taking notes and making pictures. And he saw things that nobody had seen before. The phases of Venus, the satellites of Jupiter, the rings of Saturn, the spots on the sun, et cetera, et cetera.

That astonished Europe at the time because other people looked and said, wow, the world is different. Out there is more than what we thought. The second thing, he invented mathematical physics because he wrote the first mathematical equations that describe how things move on Earth. The way mathematical equations since two millennia that described things, how they move on the sky. That was the ancient astronomy that worked very well, was spectacular.

But nobody thought that you could do the same on Earth. And he wrote an equation on how things fall. So he understood that you can use mathematics to describe what happened here, which was completely new. And the third thing, which is perhaps the most important of all, he invented experiments. Which doesn't mean he invented observations, obviously. People have been observing since ever. Science based on observation is very old.

Aristotle biology is a fabulous science based on observation, huge amount of observation. Astronomy of Alexander was based on very, very careful mathematical, working on very careful observations of the position of the planets. But nobody had really the idea that you can do more than observe. You can go in your basement, that's what he did, and put up a specific setting up things to ask nature a question. You see things falling, okay, but then you say, okay, nature, please tell me exactly how things fall and tell me how things fall if I make them roll

slowly so I can measure them better. So set up a special situation where you can put a specific question to nature. So what's the question that he put to nature? This one, how things fall. Because there was a theory about how things fall, it worked very, very well as Aristotle, but there were hints that there was something wrong, especially at the beginning of the fall, when you let something fall, how it goes from zero velocity, how it accelerates. So Galileo carefully built these inclines, inclined plane, and had balls rolling through

them and he measured the time it takes for rolling down and he realized just experimentally that things start slowly and then accelerate and he measured this acceleration. So that's how he got to write the first equation. The first equation is an equation we all studied at school. They said x equal 1 half a t squared. In other words, in plain language? Acceleration is constant. Things fall with constant acceleration.

They start slowly and then they go faster and faster. The velocity grows, but the acceleration is constant. Galileo took two years to understand that. And it was revolutionary. It was completely revolutionary. That's what put Newton on the track for doing mechanics. And now every engineering working on anything works with Newton equations,

which are based on this experimental result of Galileo. Galileo asked nature, how do things fall? Nature answered with constant acceleration and bingo, acceleration was now the key for doing mechanics. And asking questions of nature has now become second nature to all of us, or to science and to physics. Yes, yes. The immense explosion of science which has happened in the following centuries, which has given us modernity, it's very much rooted in this idea that you can do experiments.

So back to the drawings, can you just explain what it is that we see, I mean, what is it about the moon that we learn through his drawings? He observed and painted the moon in different phases. So if you compare the position of the shadow with the reliefs of the moon, with heights, you can measure the height of the of the mountains. So he gave us a sense that there was it wasn't just a smooth surface, there were ups and downs and craters and mountains. Yes, it was the first one to determine for sure that this was an up and down. I wonder if you could just take a moment and help us think about how his observations through the telescope actually changed the way that humans see the world and how we see ourselves

and our relationship with the cosmos. Yes, and that's the greatness of Ganelio. So it didn't do just one thing. This is a completely independent thing in a sense. He was in Padova at the time, which was under the power of Venice. He was essentially a university professor, we would say today.

And he started this campaign of observation of the sky with a telescope and he saw all this marvels. What was so revolutionary and dramatic and momentous in the history of humankind is that in a sense, up to that point, humans thought that, well, what we can see is what we see around us, right? Mountains and then your blue sky with the little dots which are the stars and some other planets which seem to move around with respect to other ones, whatever, and that's it. The fact that he used a telescope to look at the sky opened up first the new idea that

you can see better with a telescope, which was far from obvious at the time because a telescope, it's a piece of glass which distorts things. So people reasonably would say, why should I believe what I see through a distortion? Okay. He got convinced that he was not seeing something distorted. He was really seeing something happening out there. And of course he was right. And it was like, you know, a person who has lived all his or her life in a room and opened the window and looked outside. So humankind looked outside, found a way to look outside and see what had happened after

he saw the ring of Saturn. But now we see galaxies, black holes, the immensity of the universe. We see this astonishing richness of the universe. We see this astonishing richness of the universe. It completely changes our sense of ourselves, right? Because now it's not this little planet where we are in the center of the universe and we are the masters of it. And now we are in a little small, teeny, teeny, teeny piece of rock spinning around in this immensity of the universe, which is full of fabulous things we're not used to. These things, black holes, are playing today a very similar role

to what Galileo saw in the sky played at the time. These are a surprise for us, even for people who studied general relativity at school. I studied Blackhawks at school when I was at university, except the book was saying these probably don't exist. Now we know these things are there. So Blackhawks are a confirmation of Einstein theory and at the same time they are a tool and possibly our best door for going beyond generativity and for telling something about this open problem which is generativity and quantum mechanics together. Because inside this black hole or in the future of this black hole there are precisely situations which cannot be accounted for described with generativity alone nor

with quantum mechanics alone, we need the two of them. So let me tell you what we know and what we suspect about black holes. So black holes are something round, essentially, whose size is... Most black holes are around a few kilometres, the size of London. This London. There it is. where I spend most of my time, or Waterloo, but very massive. But the black hole is much bigger than this, it's much, much bigger.

This one is in the centre of our galaxy, it's a million times bigger, so in mass which is probably the size of, the astronomical size, the size of the orbit of the Earth, I don't know, something like that. But there are black holes which are a billion times bigger, so colossal things, immense things. These are black holes we have evidence of, very massive, right? So to make a black hole, you have to squeeze a mass in a very, very small region. I wondered why you think it's important to know about black holes as opposed to something that is, you know, that some powerful people today

would say is more urgent or practical, like, for example, colonizing Mars. Oh, well, colonizing Mars is becoming too political for a science discussion. Understanding black holes is important, I think, because of the theoretical aspect of science and because of scientists understanding the world. What happened with Galileo and Newton, his friends, is that they were fascinated by just understanding discoveries, something about the universe. And they changed civilization entirely. I mean, the way we live, it's rooted in what they did. And this way of going ahead and understanding, it's a path of science that has given us modernity.

Now, today, black holes have a special point in all that, I believe. First because they are the most spectacular discovery of science in the last decades, I would say. I studied black hole at school at the university, but at the time nobody believed that they were real. It was just a strange prediction of Einstein theory. It's a theoretical concept. It's a theoretical concept. The theory predicts that they might exist, but it doesn't mean that they do exist. So they're too strange to be real. Just to get a sense, to make a black hole out of the earth, you should squeeze the earth

inside a table tennis ball. I mean, it's unreasonable. It is. Exactly, it's true. There are plenty of these things in the universe. And the fabulous things about black hole is that they are out there by billions and billions and billions of billions and they are exactly how Einstein's theory predicted. That's the astonishing power of theoretical science.

So Einstein writes this equation, you look at this equation, you decode them, you understand what they predict and you say, come on, I mean, this cannot be. And yes, Isaac Lack asked the equation predicted and they behave the way the equation predicted because we see their gravitational waves, we see the effect on the stars around them. We even have pictures of black holes today, incredible picture of black holes and they are exactly how the theory would predict today. But there are missing aspects in our understanding of the world. It's not that we know everything with science, we know something about science, and so we want to know more. And one of the key missing things is the combination of quantum

physics with the Einstein discovery. And black holes might be the key to address these problems because we understand black holes so well, but there are things about black holes we don't understand. And what are those things that we don't understand? What could they tell us about the nature of the universe and the world and the nature of reality? What we don't understand about black hole is very simple to understand. It's very simple to understand what is it that we don't understand about black hole is very simple to understand. It is very simple to understand what is it that we don't understand. Black hole is something that can eat stuff, right?

You can throw things inside a black hole. That's why it's called a black hole. Things disappear. It's like a hole. You can throw it. And we actually do see things which matter, which is sort of spiraling around the black hole and clearly falling into the black hole. Okay?

So there's stuff that falls the black hole and clearly falling into the black hole. Okay? So there's stuff that falls into black hole. Now every kid can ask the obvious questions. Okay, what happened to the matter that falls into the black hole? Okay, so the matter goes through the horizon of the black hole, which is the surface of the black hole, falls in, and Einstein's theory tells us what happened for a little while after that. It goes sort of toward the center in some sense. It goes down, down, down, and then what happened? We don't know. We don't

know because Einstein theory, which is so good, it doesn't tell us. The theory goes completely wrong. The theory goes wrong because it doesn't include quantum effects. We know that quantum effects become crucial at that point, So we need the quantum theory of gravity, which is my job, which I've been paid for all my life to work about. So are, to all that work that you've been doing, are we any closer to understanding than we were in the time of Einstein, to what happens to matter

when it enters a black hole? Yes, I think we are. We definitely are, we're not sure. So we might be wrong. And there are also different opinions about scientists, which is good because that's how science works. Different opinions and discussion and trying and trying and experiments. But definitely we're closer because we have tentative theories that do bring together

quantum mechanics with Einstein theories. And these theories are theories of quantum gravity. These theories exist. What they reasoned is a theory of quantum gravity which has been validated, supported by many experiments and proved right and therefore there's a consensus around it. That's the way science works. Einstein wrote a theory in 1915, nobody believed it, just him at the beginning. And then it's right, it's right, it's right, it predicts the right things, predicts gravitational

waves is true, predicts the deflection of light by the sun is true. And so now we'll believe it. Carlo Rovelli is a faculty member at the Rotman Institute of Philosophy at Western University in London, Ontario, and distinguished visiting research chair at the Perimeter Institute for Theoretical Physics. Ideas is a podcast and a broadcast, heard on CBC Radio 1 in Canada, on US Public Radio, across North America, on Sirius XM, on World Radio Paris, in Australia, on ABC Radio National, and around the world at cbc.ca slash ideas. Find us on the CBC News app and wherever you get your podcasts. I'm Nala Ayed.

I'm Sarah Trelevin, and for over a year, I've been working on one of the most complex stories I've ever covered. There was somebody out there who was faking pregnancies. I started like warning everybody. Every doula that I know. It was fake. No pregnancy. And the deeper I dig, the more questions I unearth.

How long has she been doing this? What does she have to gain from this? From CBC and the BBC World Service, The Con, Caitlin's baby. It's a long story. Settle in. Available now. Galileo was truly a renaissance man of science. His experiments and thought covered a staggering range of natural phenomena, from tides and gravity to inertia and the atmosphere. His inventions included as sort of analog calculator and a mechanical means of determining longitude on Earth through observing the moons of Jupiter. Yeah, really. But the instrument Galileo is most

associated with is his refinement of the telescope. Through it, he saw the solar system as it had never been seen before, and challenged the accepted wisdom that the Earth was the center of the universe. We rejoin Alessandro de Angelis at the Galileo exhibit at the Perimeter Institute. Here you look to the replica of one of the two telescopes by Galilei, which are left. So, both in Florence. This is a magnification factor of 30. So this is perfect for watching the moons of Jupiter.

Does it work? Like, can you actually look at it? It works. I look to it. Focusing this is not easy because the focus is done by changing the length of the instrument. Which we can't do right now. We cannot do right now. And by the way, they made the choice to replicate it with the same materials as the original,

with the same lenses. If you look through this, you can understand really how difficult it was to observe. It took me one hour before watching to the trees far away because the field of view is extremely narrow and they decided to redo the leather in the conditions in which it was 400 years ago. It's extraordinary, it's gorgeous, I mean it's a it looks like leather it's sort of alternating red and brown it's got some gold filigree kind of work on it. It's a beautiful work of art Yes, and it was in the original was like this just now It's brownish by the way a copy of this

Not so faithful was sent to the space station because the Australians want to have it Yes, they flew with a copy of this. They watched the stars. Wow. I'm getting goosebumps thinking about that. By the way, I could touch the telescope. I went to the space station and back. And this was also an emotion. If Galileo could know that what happened, I mean, that they made a replica, a replica went to the space station, then went down, people touched.

Oh my God, yeah, can you imagine what he would think? Yeah. Yes. Wow. That epic journey to the International Space Station is just part of what Rovelli sees as a much grander journey of science. In the book, reality is not what it seems. You refer to theoretical physics as, quote, Reality is not what it seems. You refer to theoretical physics as, quote, a magic journey out of our common sense view of things. So most people would sort of equate common sense with reality. But in that statement that I just read, you seem to be suggesting that

common sense actually prevents us from actually seeing reality? Ah, this is subtle. Yes, and no. Common sense is right, it's not wrong. It becomes wrong when, and this happened very often, we pretend that that's it. There's nothing else to learn. So imagine we all lived in a plane, okay, and saw mountains in the distance, okay, and we saw these mountains covered with a uniform velvet green stuff, right? And then we all believe, oh, common sense in the distance, there are mountains with green velvet stuff, okay. And then the scientists actually decide to go there and discover that, well, it's not a green uniform thing, it's a forest. And a forest is trees and animals and branches, it's very complicated and there's a huge richness

there, okay? Does this contradict the view of the mountains with a uniform green thing? No, I mean, it's perfectly compatible that a forest looks something when looked from a distance and different when looked from inside. So it's nature. Our common sense is a view of nature from our little, very parochial, our little garden without viewing too precisely the details, so far away and so on. So if we take common sense for the ultimate picture of reality, we are profoundly wrong. But that does not mean that there is actual contradiction between the so-called manifest view of the world and the so-called scientific view of

the world. They're perfectly compatible. We just don't have to take the manifest view of the final one. Can you explain how you see theoretical physics as a magic journey then? Yes, because it's exactly going out from our little garden and looking around discovering more. And that's what moves us also emotionally profoundly because it changes not just our mathematics, our view, it changes the way we think about values. So it changes us deeply, profoundly, I think.

And a few things give us an intense emotion, like when we learn something new. I mean, we all have been through adolescence, right? This magic moment of life in which you thought that your father knew everything and your mother as well, and everybody speaks the same dialect or language as you and your little villages is everything and then at some point you realize no, there's so much more to learn out there. There are friends, ideas, things to do, ways of doing things. That's beautiful.

That's intensity of life, so magic in the sense of destroying what seemed real before and opening up to a much wider view of reality. That's the beauty of science for me. Do you still experience that after all these years of doing what you do? Oh yes, yes enormously, because to be a scientist is not to discover how much we know about the world. To be a scientist is to discover how much we don't know about the world. The friends of mine who know less about reality are the ones who think they know everything there is to know about reality. The friends of mine who know more about reality are the ones who are more aware of how much

we don't know. So if you do a job like mine, which is sort of to walk at the boundary of what we know, you're constantly confronting our ignorance. And I think nobody said it so well as probably the greatest of all the scientists, which is Newton. And Newton, at the end of his life, famously, writes in a letter, he talks about himself, and he says, I don't know how the future will look at me, but the way I look at myself is like a kid on a beach looking at some pebbles

and being marveled by them in front of the immense ocean of our ignorance. Wow. So this is a guy who had the deepest insight in understanding nature, and he's the one who is more aware of our profound ignorance. I love you describing it as a boundary. You're walking a boundary between what we know and what we don't. How comfortable a space is that for you? It's the best possible spaces of all.

I know some people go into science because they want certainty. I like science because it questions certainty. The beauty is accepting the idea that we can live without certainty, without foundations, accepting our ignorance. It's also true in life, right? Isn't the best thing you want to hear even from your teacher when they say, I don't know this, because that's opened up reality. I mean, it allows us to realize that there's space for freedom and for learning.

But people demand certainty from scientists. There's a misunderstanding there somewhere. Yes. They shouldn't ask for certainty. They should ask for good advice and good opinions. The confusion here is that thinking that if you don't have certainty, you don't have knowledge. That's stupid, right? Because if I want to drive to Toronto, I want information how to go and I want reliable

information. I mean, is that information certain? I mean, no. I mean, maybe there's a roadblock ahead. I mean, I know they cannot get certainty. We want us to have reliable information that we can in life and that's good enough. And if we ask for certainty, we're blocked. First, we might be wrong, never get certainty, but we're blocked from learning.

This year, 2025, is the International Year of Quantum Science and Technology, the 100th anniversary of the beginnings of quantum physics. And clearly quantum science has completely revolutionized science and technology and our view of reality as you've touched on. Can you provide a sense of how much of that is ocean and how much of that is pebbles? I mean, how far have we gone towards being able to harness quantum physics and what the potential of it is? Quantum physics is the other half of the great scientific evolution of the 20th century. But Einstein theory, it's marvelous, it's clear.

Once you go into it, it's clear. Quantum physics, it's less clear because it's even more radical. In fact, it's far more radical than Einstein theory. Einstein theory changed our understanding of space, time, cause, the difference between past and future, those kind of things. But quantum theory changed our understanding of what stuff is, what matter is, what observation is, what variable properties. So really the grammar we use to describe Nietzsche. And it works really well, it works fantastically well, it's the basis of so much of our technology, but it still raises discussions, debate of what it means. So there is a future which is using it more for doing stuff.

I mean, I don't know, maybe we'll be able to do quantum computing in a useful way, maybe not, I don't know. I mean, this is, for a scientist like me, it's more an engineering problem. But for a philosopher, it's really, what have we really understood? What is really quantum mechanics telling us, right? It needs time to digest big revolutions and we haven't digested the big revolution of the 20th century. And I think partially is also because we don't have a quantum theory of gravity, so the two pieces of revolution haven't been put together. So we are halfway through the woods, so to say.

And that's fascinating because somehow we have discovered that we have to think nature in a completely different way, but we don't have yet clear how we have to think nature. We're sort of learning as we go. We're learning as we go, we're walking through the wood, hoping to come out the other side. Often we think that science is faster. That's profoundly wrong. Science is slow. It's very slow. You know, journalists come, say, what has happened in science the last week? Nothing. Right? What happened in science the last month? Nothing. I mean, slowly. Everything's, we learn slowly, but we're learning, definitely.

You're right. It's hard to combine the idea of science moving slow with something as revolutionary as quantum physics or it's such a large leap. So I'm just curious though, I think maybe we can answer the question of the possible dangers of proceeding with something that is so revolutionary and yet knowing so little of what its potential possibly could be. There's a lot of talk today of the dangers of new technologies. I think the real danger is not new technology, it's humans being stupid. That's always a danger. Yes, doing stupid things. I mean, one of the greatest dangers today for humankind is nuclear weapons, no doubt

about that, which logic sense is based on understanding quantum mechanics. I'm not afraid at all that artificial intelligence system by mistake starts, triggers a nuclear war. But I am very, very worried that humans are going to do that because politicians, if we just look at the history of our speeches, have done that all the time and then we all say they have been stupid, but we go into war and we have nuclear weapons. So unfortunately, it seems likely unless we change our way of thinking that a nuclear catastrophe is coming.

So how would you balance for those who are concerned about pushing the boundaries while still exploring of what I assume would be incredible progress due to AI powered by quantum computing. How do you balance the caution with pushing ahead and learning more? I am not worried about the danger of technology in itself. And in fact, I even think that pointing to the danger of technology by itself is a way of hiding the other dangers. We killed, what is it, 100 million of us in the first and second world war. The majority were just killed with guns.

Centuries before, we just killed in huge proportions with just swords and arrows. It's not technology. The real problem if we have worries about the future, I think we should, is not to look at technologies, look at politics. So keeping that in mind, does it concern you the possibility that a few huge companies dominate what happens

in the development of quantum computing and AI. Yes, that's a worry. It's one expression of the concentration of power in the few people who have a lot of money, which I think is a problem for humankind. Back to Galileo. It could be argued that he is relevant today, not just because of what he discovered and all the things that we've discussed already, but because of the political ramifications of his work. The church declared his observations to be heretical and they forced him to recant. Is there anything in our time that you think

has echoes of this? No, I don't think so. And I'm not really worried of strong denial of science fear. If you look closely, everything is far more complicated. The clash between Galileo and the Church was complicated. Galileo was obviously ultimately right from the point of view of science and from the point of view what's good for humankind about free research. But it was also wrong in a number of things. He pretended to be telling the church how the scripture had to be interpreted. Right. With church reacted, obviously saying, it's not your business. And he also, he pretended

very strongly that he had proven that Copernical system was right and he hadn't. Copernical meaning it's the earth going around the sun rather than the other way around. Exactly. The spinning and the earth going around the sun and he hadn't. So if you look at the details, things are always more complicated. Now of course, from the perspective today, he was ultimately right in the sense that that was not a good reason for threatening it with torture or closing him in his home at Chetri. And today, I think science has been misused by the power as a screen behind which to hide political decisions. What's an example? Well, the typical example is COVID. COVID was a very complicated political

issue in all the countries. Each country was dealing it in a way very hard because it's not an easy political choice to have more people dying versus more people becoming poor. And within each country, obviously, there were opposite pushes because people have different moral values, because people have different interests. Many countries allowed a lot of old people to die to save part of their economy. Now, where to put the balance? It's a hard political issue and it's up to the politicians to decide. I have my own ideas, but others have different ideas. I thought it was a profound mistake from the politics to say, science tell us to do this. Science

never tell us to do this or that. Science tell us, look, if you close the schools, as far as we know, presumably less people will die. Now it's up to you. But if you use this, close the school and say, oh, we're just doing what science does, obviously you generate a reaction of those who have a different set of values against science. Was that a disservice to science and scientists? It was a profound disservice to science. And that happened in all the countries, both the ones who went in one direction or the other direction politically, many of them just hid the politicians.

But the result is that a lot of people who disagreed with the decisions took this against science. And that was a mistake for all of us. Because a politician who doesn't listen to science is stupid because science is what we know. But a politician shouldn't do what science says, should take into account what science says and then decide on the basis of the complexity of reality. You know, as you say, there's a long tradition of scientists resisting having their work being politicized, but can they really avoid that anymore, especially where things like

public health and climate are concerned not to mention AI research? Is it possible? I think that, again, it has to be embraced. The idea of keeping science neutral, it's only good up to some point. I think there's no science. There are scientists. Everything we do is political.

Science is not neutral. Science is political by its very existence because it changes our living together and living together is politics. That is the complexity of the... So I don't think that even if it seems different than what I was saying before, I don't think we can really think about science as an abstract, pure set of results. When you study one thing rather than another, you're making a political choice, not just a scientific choice.

When you put all your resources in one direction, you're making a political choice. I think we have to get a scientist. The solution is not, all right, so let's separate ourselves from politics. It's the opposite. Our scientists, not as a whole, individually, let's talk about politics, not be afraid of that. And the scientists who did that, like Einstein after the Second World War, for instance, were profoundly useful for humankind.

The Einstein-Russell manifesto triggered the Pugwash conference and it's the root of the path that led to the Soviet Union, United States, START treaties for nuclear control, which perhaps saved humankind from a catastrophe. So I would tell to my fellow scientists, get involved in politics, don't be afraid of that. But of course, when you want to solve an equation, politics has nothing to do with that, obviously. Or do an experiment, you just take politics out. But in your engagement in what you're saying, what you decide to study, we are all citizens of the world and we should be responsible for the good of the world, as individual persons, I believe.

Yeah. When you look at so many of the biggest challenges of our times, AI, climate change, you know, the almost certainty of another pandemic, these are issues, as you rightly said, you know, they require policy responses informed by science. Yes. How do you feel about our ability to tackle these issues effectively and responsibly with the way our society

looks towards science, our attitudes towards science. Are we prepared? Can we do that? Can I say something controversial? I love it when you say something controversial. With all my love for liberal democracies, liberal democracies are not very well prepared to that because the politicians, by the way, structure society, need to be re-elected, need to win the next power struggle. So they have in very, very large majority, the top politicians in the Western liberal societies, a very short sight in front of them. They think in terms of next week, next month, maximum two years the next election, the next

big election. Now we all know that if we think shorter, we make mistakes. Today with respect to the big questions, the system like a communist one in China are much more prepared to look at long distance. They have their own, I'm not saying that it's something we should totally copy, obviously, but they definitely do at long distance. And not surprisingly, they are engaged in climate change very seriously. They talk about world collaboration and other things.

So again, I don't want to say they're good, we are bad, that's not the point. But to your question, we do have a problem in liberal democracies because of the lack of attention of long distance. And the long distance is where the problems are. What would Galileo make of the quantum physics world that we have delved into today? I like to think that he will be enthusiastic and happy about, super happy about that because he was obviously so open-minded about profound conceptual changes. He was in the middle of that.

Even if, I mean, it would deny so much of what he has written, because in a sense he contributed largely to put up a conceptual scheme that now we have demolished. But again, at the end of his life he wrote a letter in which he says the following, he spends his life attacking Aristotle, okay, and the Aristotelians, and saying how stupid are the Aristotelians, how wrong is Aristotle and in the dialogue, which is his greatest book, in which he sort of argues for the earth spinning and going around the sun, it's a dialogue between three persons and one is representing the Aristotelians, it's called Simplicio and it's treated as

stupid, as an idiot, right? And even today, we look down at Aristotle science under the influence of Galileo. Galileo has a powerful rhetoric, very convincing. So basically convince everybody that Aristotle science was stupid, okay? And now, at the end of his life, he writes this letter in which he says, actually, I consider Aristotle my master and I have immense respect of him. And I would like to think that if he came down, he would accept me as a humble pupil of him and he would look with appreciation of a little correction that I bring to his side. Wow.

Okay? So that's what he was really thinking. So what we're doing is, of course, changing Galilean intuitions, but just building on his. That's a great discovery of science and also philosophy. You can learn, build on the past, but not by taking it for granted, past knowledge, but changing something crucial into past knowledge. And it's a saying that you build on common sense, but you find that it might be wrong. That's the subtle third way between believing something and

not believing something that made science possible. You actually brought that book to life with your own voice. You read the part of Simpichio, is that? No, I read the part of Salviati. Okay, sorry. You read the part of Salviati. Yes, in fact, that's my weakness, I should say. The Dialogue of Galileo, it has been released in English as an audio book.

And I was asked to read it. What was it like for you, given that he's influenced you so much? Well, first of all, as I said, my weakness said, yes, I'm going to do it, but I'm not doing the part of the stupid one. I'm good. Only if I can do the part of the one who is right, who is a representative of Galileo himself. It was difficult for me because, you know, reading in English,

it's an English tradition of Italian. Galleduo's prose is spectacularly beautiful. He was actually one of the best Italian writers. It's very beautiful. But it's complex. It's a sort of 17th century rich Italian with long sentences. So, he translated in English with long sentences. So translating English with long complicated involved sentences was harder. At the same time, it was sort of a big emotion to put my own voice on Galileo thinking. It's a beautiful book because it's a book that leads you slowly out of your mind, right? So it's a book written for somebody who is deeply convinced that the earth does not move? Of course it doesn't move.

Look around. Is it moving? No, it's not moving. Okay? It's so obvious that it's not moving. And the book is written for taking this belief and slowly undermining it, taking you to the point in which you say, actually, it could move. But given the times that we live in and how polarized we can be on science and on everything

else, what inspiration can we draw, not just from the dialogue, the book that he wrote, but from him as a figure of science? What do you think we can learn from him in times like these? I think the openness. While he was ready to get into a fight, an intellectual fight, in any moment, in that he was Italian in the negative sense also, but he wanted to dialogue with everybody. He was open to dialogue. He was not thinking, I'm right, you're stupid, you're wrong.

He wanted to talk to his enemies and convince them. He got into trouble with the Catholic Church, was their enemy, because he wanted them to listen to him. He went to Rome. He could have remained in Venice, happily protected by the Venetian Republic, and it was very protected intellectually. The university was protecting him. But he went to Florence and then he went to Rome because he wanted to open a dialogue with everybody. So this profound desire of him to engage everybody in a common discussion about what we know, what we don't know, it's something I think we should learn from him.

Carlo Rovelli, thank you so much. Thank you. Sono onerato di conoscerti. Oh, fantastico. Grazie. Grazie mille. Honored to meet you. Oh, fantastic, thank you. Thank you very much. Carlo Rovelli is a theoretical physicist and the author of the bestselling books Reality Is Not What It Seems

and seven brief lessons on physics. Special thanks to Alessandro de Angelis for taking us on a tour of the Galileo exhibit and to Hilary Potts, Mark Healy, and David Fairthorne at the Perimeter Institute for Theoretical Physics. This episode was produced by Chris Wadskow. Our technical producer is Danielle Duval. Our web producer is Lisa Ayuso.

Senior producer, Nikola Lukcic. Greg Kelly is the executive producer of Ideas and I'm Nala Ayed. We have a couple of minutes to make sure Chris doesn't miss something. Are you sure it's taped? Oh yeah. You did press record, right? You turn the thing on and push it back and you didn't forget. For more CBC podcasts, go to cbc.ca slash podcasts.