Sean M. Carroll’s Latest Book “Contains Complex Formulas!”
It doesn’t seem like the best selling point for a work that wants to conquer the masses. But the theoretical physicist – who also masters the art of the scientific bestseller – perfected it in the USA with “The Biggest Ideas in the Universe: Space, Time and Movement” (2022). In it, he examines the history of fundamental physics in nine concepts: conservation, change, dynamics, space, time, spacetime, geometry, gravity, and black holes. He wrote the book after being encouraged by the success of the lectures he posted on YouTube during the pandemic. It’s the first in a trilogy that he promises will “grow in complexity” until it reaches the abstract debates about the present and future of the discipline that are the focus of his popular Mindscape podcast.
“Equations are like poems,” he says in an interview with EL PAIS in May in his office at Johns Hopkins University in Baltimore. Across the street from campus is the institute that controls the James Webb Telescope.
Born in Philadelphia, Carroll, 56, moves easily between science and culture: last semester he taught a course he designed called “Natural Philosophy”. “Like a good poem, an equation demands thought and interpretation,” he muses. “It’s short, intense…nothing is left. And it’s impossible to paraphrase it, just as it’s impossible to tell the plot of “The Waste Land” (by TS Eliot). The popularization of physics uses analogies, metaphors and anecdotes. I wanted to go further and show the readers what’s behind the scenes. Although not a textbook, it is not necessary to know how to solve it [the formulas] – it is enough to understand them.”
Ask. What is natural philosophy?
Answer. It’s a kind of knowledge that reminds us that philosophy and science used to be the same thing. What we now call science was a branch of philosophy. Around 1800 there was a separation. Today knowledge is much more extensive than in Aristotle’s time – it is impossible to be an expert in everything.
Q You are a leading theoretical physicist who, like Aristotle, also theorizes on the dramatic arts. Is it no longer possible to be a polymath?
TO. There is exceptional access to knowledge in many different fields, but I find it very difficult to be a top researcher in more than one field. That reminds me of Edward Witten: [he’s] one of the leading theoretical physicists of our time, who is also the best in mathematical physics. But [this doesn’t happen much] in very different disciplines, such as biology or history. Nowadays everything is more fragmented, also due to the organization of universities. I plead for more [fusion]. There is practical knowledge that does not require philosophy…for example, if you want to locate the farthest galaxy. [But] If you are interested in why the big bang happened, [philosophy] will be useful to you. There is a joke that when philosophy starts answering questions, it becomes something else: psychology, physics, biology…
Newton – who we assume was essentially a mathematician or a physicist – would have called himself a philosopher. Nobody would call me that anymore these days, even if some of my questions are quite philosophical: what is quantum mechanics? Where does the universe come from?
Q Why is there something instead of nothing?
TO. The short answer to this question is that I think it is an unanswered question. Certainly it belongs more to the realm of philosophy than physics. When you ask why there is something and not nothing, assume there is a reason, some basic fact. [as to] why the universe exists. Well, I don’t think there is such a basic fact. I believe the universe just exists.
Q In the book you explain that in an expanding universe, energy is not conserved.
TO. It depends on what you mean by energy. In physics, if you were living in the time of Isaac Newton, there were ideas that made perfect sense. But then came general relativity and quantum mechanics, [where the concept] of energy changes in meaning. If you take the energy of this table, this chair, this building and every planet and add up all the photons in the universe – and factor in time – then the answer is that energy is not conserved. Because [time and space are] Change. It’s like putting a cup of coffee on this table: energy is saved, but throwing it into the sea isn’t. It’s as if the waves are space-time driving the mug.
Q Do you share the idea that philosophy is somewhat stagnant?
TO. No. It seems to me that scientists [treat] Philosophy unfair by demanding tangible results. We’re so obsessed with getting the right answers. Philosophers are very patient and insightful. You have to make sure that all of their words mean something. And they definitely help us shed light on the foundations on which science is built.
Q The book begins by stating a wish: to live in a world where dark matter is discussed after work in the pub. What would have to change for that to happen?
TO. A lot. [In my books]I am saying that more details need to be given to people. Physics is usually reduced to a set of facts [that need to be] memorized. But the process of science is quite different: it involves formulating hypotheses – which are often wrong – and collecting data which are very rarely definitive. Science is the simultaneous sum of being willing to change your beliefs based on new knowledge and knowing that some of those beliefs are very difficult to change. People are usually willing to believe one of two ideas…almost never both.
Sean M. Carroll, during his interview with EL PAÍS, in Baltimore, on May 24, 2023. LENIN NOLLY (Lenin Nolly/El Pais)
Q Her book can also be read as a treatise on the history of physics with all its turning points. Where is discipline now?
TO. In terms of fundamental physics, we are not at a turning point. Some people complain that we don’t have revolutionary ideas like we did a century ago. That seems unfair to me: It was a very, very special time. We discovered relativity and quantum mechanics, particle physics and the big bang theory. You can’t expect that to happen every 50 years! But at the same time there are parts of higher physics – complex systems, thermodynamics, statistical mechanics, fluctuations, biophysics – where fruit is still within reach because we are still at a very basic level. That’s what my third book will be about.
Q How is it possible that a century later we still cannot explain more than 5% of the universe?
TO. It is true that the particles that we have discovered in experiments make up only 5%. That’s 25% [made up of] Dark matter. And 70% is dark energy. We haven’t discovered them in the lab, but we know they’re there and we know some of their properties. We actually know quite a bit about it [these particles], although we’re not quite done figuring out what they are just yet. It seems to me that understanding 5% of the universe is already a lot.
Q Everyone remembers what they did on 9/11 or when Michael Jackson died. In your job, the question must be: What were you doing when the Higgs boson was discovered in 2012?
TO. [Laughs]. I was at the CERN (European Organization for Nuclear Research) press conference. I even wrote a book [about this]. It was very exciting. But to be fair – and without wishing to belittle that – we expected to find something different, lots of other things [instead of the Higgs particle]. We were waiting for a revolution, the beginning of a new golden age. It did not happen.
Q Did you enjoy the Oscar-winning film Everything Everywhere All at Once?
TO. I loved it. The idea of the multiverse arises in physics from string theory, [specifically] the 10 dimensions and how they can interact with each other. They would be different universes with different physical laws.
Q The big question of humanism is: where does this theory leave identity? The film’s main character not only discovers that the multiverse exists, but also that she lives in the worst of its versions…
TO. The moral of the film is that it isn’t. But yeah, the thought of Gemini out there making slightly different decisions than you certainly raises some deep questions. It is useful to distinguish between multiverses. There is the cosmological implication that there are very distant regions of the universe in spacetime where conditions are very different. [Then there’s the] Concept derived from string theory: that the world is not made of particles but of loops of strings, or what we call “cosmic inflation” (the rapid expansion of the universe). Both [ideas] belong to speculative physics and are anything but proven, but very popular. Then there are the many worlds of quantum mechanics – [the discipline] which is actually much more likely to be true. It’s a pretty deep subject – we’re still struggling with how to deal with it as physicists and as philosophers.
Q Was the recent announcement – that the United States is on the verge of nuclear fusion – an exaggeration?
TO. I’m always frustrated with these press releases because there is clearly a vested interest in communicating a great discovery. In reality, [the researchers involved] have not yet achieved a reaction that produces more energy than is required for the reaction. What they do is quick accounting: they don’t take into account some of the energy they invest. [Nuclear] Fusion could be a breakthrough…but it doesn’t seem to me that it will be a matter of a few years, it will be a matter of decades.
Q Are you worried about the advancement of artificial intelligence?
TO. I’m not worried about that. I don’t think there’s a realistic chance that millions of people will be killed or humanity will become extinct as a result. What is far more likely is that [AI] will pave the way for human rights abuses, attacks on privacy and misinformation in political campaigns.
Q Do you allow your students to use ChatGPT?
TO. I didn’t stand a chance [to make a decision]. The software was released right after the end of my lectures last semester. It seems to me that there is no other [option]… it’s like a math teacher doesn’t allow their students to use a calculator at home to multiply five-digit numbers. I’ve used ChatGPT: I know it doesn’t write very good essays, lies constantly, makes things up and misinterprets others… but it knows a lot and can be very useful, even inspirational. The trick is to treat it as a tool.
Q Let’s wrap up with another one of your obsessions: free will.
TO. I am for free will. As with energy, it depends on what you mean by free will. The best way to think of other people is to see them as actors making decisions for specific reasons. Sometimes they will [make decisions] for irrational reasons. So it is, even if we admit that the underlying laws of physics are perfectly deterministic – which, by virtue of quantum mechanics, they are not. But even if this were the case, it would be too complicated to predict exactly what a human will do. For me that is free will.
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