Of all the big ideas floating around – long termism, degrowth, space colonization and so on – is any as radical as quantum physics?
For a century, physicists have known that the classic assumptions about the universe are wrong — electrons do not orbit the nucleus of an atom, but exist in waves around it. So an electron can be in more than one place at a time until we observe it. Schrödinger’s cat is alive or dead: we can only know by looking, which determines the answer. Why this is so is unclear.
This realization is “almost psychedelic,” argues Carlo Rovelli, the Italian physicist who specializes in making complex ideas seem simple. Quantum physics was used to develop semiconductors and lasers. But the first thing you need to understand is that you can’t really understand it because nobody does.
Rovelli tries to explain the problem in his book Helgoland, and finally meditating on the nature of science and uncertainty. In times of climate change and pandemics, his popular physics remains one of the bestsellers. “Melting glaciers are important, but the most powerful aspect of science for me was precisely that it challenges our worldview,” he tells me informally, with unrelenting curiosity, on a trip from his native Canada to London. However, the public thirsts to understand the universe, as Rovelli writes Helgoland: “Knowing that my girlfriend obeys Maxwell’s equations won’t help me make her happy.”
It helps that Rovelli likes to push scientific boundaries, citing Buddhist philosophy and organizing letters for global disarmament. For him, physics inspires culture. “Good philosophers have always listened to physics. Kant would not have been Kant without Newton; Half of what Kant does is to understand Newton. Conversely, without Kant, Einstein would not have been Einstein. Einstein read Kant, and Kant’s thoughts about space and time were the key ingredient for him to write equations predicting black holes.”
Rovelli’s hope now is that popular culture will absorb the implications of quantum physics. films such as Spider-Man: No Way Home and Everything everywhere at once have done this through the theory of many universes: that is, the solution to Schrodinger’s cat is that the cat is both alive and dead, since there are infinite universes covering every possible outcome. Rovelli himself dismisses the theory as “crazy”.
How is it possible that physicists have such different interpretations? “Science is not just about writing equations and making predictions. It’s about rethinking the world. If you think what happened to Copernicus, let’s tell the story so that he understood that the earth revolves around the sun. But can you prove that the earth is not the center of the universe? No, you couldn’t do an experiment. The point is that if you change your conceptual structure, everything makes a lot more sense.” Similarly, black holes were predicted by Einstein’s equations before they were discovered.
Rovelli wants us to accept that certainty is often unattainable: “We’re never sure.” In fact, there’s only one place in our conversation where he expresses certainty: when I ask if we could live in a simulation, like Elon Musk says it’s “highly likely”. “No. I’m sure of that. We’re not in a sim. It’s a stupid idea. Who’s the simulator? Some guy?” The theory is that any species that could run a simulation of their ancestors, with increased computational power, would run many of them, so we can’t be sure we’re not in a simulation. “Come on, did you play with AI? It’s very different from reality,” Rovelli despairs.
Uncertainty does not mean that all ideas are equally valid. “We don’t learn a little more about reality by making absurd hypotheses and asking how they can be disproved. It’s stupid because anything can happen and nothing can be disproved,” says Rovelli. “We learn more about reality by taking what we know and seeing what it plausibly implies.”
Rovelli, now 66, came to fame late. In his fifties he began writing for a wide audience; his 2014 book Seven short lessons in physics was a surprise hit. His way had been unusual. After a phase of hippie activism failed, he applied to study physics at the university, partly because the queue was shorter than for other courses. “I went into science out of the disappointment of the dream of changing the world.” But in science, as in politics, he felt outside the mainstream for a long time.
His particular contribution was the Loop Quantum Gravity Theory, which posits that space itself is not continuous but granular, and that the grains are interwoven by loops (“the Financial Times was one of the first media outlets to take it seriously”). It remains a theory. “I don’t know if I’m right or wrong. I’m more optimistic than I was 10 years ago. . . Most of our competitors are in trouble.”
Rovelli likens the process of scientific discovery to zooming in on a forest. At first you only see the forest, “you go further and see that it is different: there are trees. And then you go closer and see the trunk, animals, insects. And then closer and closer. . . You get layers and layers and layers of understanding. . . We accumulate knowledge. What Newton understood is correct; it can just be better understood.”
The task is not so much to work out the answer as it is to find out what is wrong with the question. “You always have to find something in your assumptions that you can throw away in order to take the next step.” His own process, he imagines, “is very similar to that of a novelist. When I think of the most cited work I’ve done, the ideas came to me while I was driving, walking in the woods, or doing something else entirely. You must know the subject very well. So you keep walking around the edge of knowledge and you say, “This doesn’t work.” Then, at some point, when you think of something else, it clicks.”
His preferred form of quantum physics is the relational interpretation – the view, developed since the 1990s, that all objects influence each other, so that the properties of an object are defined only in the moments when it relates to another object. This brings him close to Buddhism. What is the difference between physics and philosophy? “The tools of the trade are vastly different, but there’s a big gray area in between.” Rovelli is an atheist but says he has “very devout students . . . I understand people who care about the idea of God and they are great scientists.”
For Rovelli, it’s an easy leap from believing that objects are in fact interactions to advocating collectivist, left-wing politics. Since becoming famous, he feels politically responsible again. When we meet, it looks like Italy, where he still spends a lot of time, is about to vote for a far-right coalition. “It’s a country that can’t find itself, that has a low opinion of itself,” he laments. “It is a country that has decided internationally not to have a voice. . . Internationally, it is a very unhappy country because of fascism and because it lost the war. Italians think they are a third world country, which is not true. They think Portugal is more powerful than Italy, which is nonsense.”
Last year, Rovelli organized a group of eminent scientists and public figures, including former Beatle Paul McCartney and experimental psychologist Steven Pinker, to call for redirecting military spending to climate change and other causes under the banner of The Global Peace Dividend Initiative. Russia’s invasion of Ukraine a few months later seemed inconvenient. He suggests his move was misinterpreted: “The global peace dividend isn’t the idea, ‘Tell your government to stop spending on the military.’ It’s the idea, ‘Tell your government to negotiate with your enemy so you both spend less on the military.’”
Favorite science fiction?
The Mars Trilogy by Kim Stanley Robinson.
The best thing about Canada?
The friendliness of people and nature. We had wolves in our yard.
What’s the hardest thing about getting old?
No, it’s the other way around. I grew up thinking that everyone over 30 is an idiot. To my incredible surprise, life gets better.
How worried are you about artificial intelligence? I don’t think it’s that dangerous. All my life I’ve heard the wonderful things that will happen in artificial intelligence; most have not come true.
If military spending is a waste of resources, what about space travel? “It’s like asking a football fan whether building a stadium saves resources! I wish mankind would return to space travel in earnest. I was 13 when man went to the moon and it was clear to me that when I grew up I would have my own spaceship and orbit the solar system.”
Rovelli’s politics can be frustrating. The day before Russia invaded Ukraine, he tweeted: “Five words are enough to stop the Ukraine madness: ‘NATO will not expand into Ukraine’. So hard to say?” The next day he doubled down: “Putin is disgusting: How dare he invade a country and kill people? Only Americans have the right to do this on a regular basis!” He defends his stance: “The West is making a long-term mistake by not realizing that we need to share power with the rest of the world.”
That leaves a lot missing, but reveals something about his discipline. After World War II, many nuclear physicists felt guilty about the atomic bomb that created their field. Instead, Rovelli feels obligated to avoid conflict. He is angered by British Prime Minister Liz Truss’s insistence that she will launch nuclear weapons. “You have a new prime minister who has said publicly that she is ready to push the button. I think humanity is underestimating the catastrophe that is very possible.” Nuclear physics seems radically divorced from everyday life, but there is only a limited amount of time you can spend thinking about it without worrying about nuclear war make.
Additional reporting by Dylan Neri
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