Who hasn’t gazed at a murmuration of thousands of starlings wheeling rhythmically above their roost at dusk, and not wondered at the majesty and mystery of natural systems? For the Italian theoretical physicist Giorgio Parisi, merely marvelling at nature wasn’t enough. In the early 1990s, he embarked on a decades-long project to install high-end commercial cameras on the rooftops of Rome, timed with millisecond-precision to capture and track every bird in the flock in three dimensions.
In this brief, crisply written memoir, In a Flight of Starlings: The Wonders of Complex Systems, Parisi takes the reader on a journey through his scientific life in the realm of complex, disordered systems, from fundamental particles to migratory birds. He argues that science’s struggle to understand and master the universe’s complexity, and especially to communicate it to an ever-more skeptical public, holds the key to humanity’s future well-being.
In 2021, Parisi shared the Nobel Prize in Physics in part for his work describing mathematically the behaviour of exotic materials called spin glasses – metal alloys with constituent atoms that have magnetic properties that interact with each other in complex ways.
His breakthrough came in 1979, when he began working with a mathematical technique called “the replica method,” in which many copies of a system – in this case, spin glasses – are processed and compared for similarities and differences. His first public presentation on the topic, a poster consisting of “two pages torn from a copy book with some scribbles on them,” didn’t make any sense, according to a colleague at the time. But crucially, his calculations worked.
“The truth is that I did not myself really know what I was doing,” Parisi writes. “It was as if I had gone into a tunnel and then found myself on the other side.”
Parisi’s book begins long before the tunnel, with his undergraduate studies at Rome’s prestigious Sapienza University in the 1960s, and quickly dives into the minutiae of 20th-century particle physics. He deftly describes collegial collaborations and conflicts, sudden insights, and regrettable oversights as he settles into the physics community. (Among other things, he relates an off-the-cuff conversation that he thinks could have led to a second Nobel prize for work in particle physics if he had simply spent a few more minutes thinking about it.)
As his career progressed, Parisi became interested in the physics of phase transitions – everyday phenomena such as the way water freezes and boils, or why certain materials lose their magnetisation as they heat up.
There’s a lovely description of the world’s longest-running lab experiment, a 96-year-old blob of pitch in Queensland, Australia, that is very, very slowly dripping into a glass beaker, demonstrating the extreme viscosity of the world’s thickest known liquid. (Its 10th drop is expected any decade now.) And Parisi neatly outlines some of the enduring mysteries of physics, such as quantum gravity, in a tour of the last century’s major particle physics theories, concluding: “However much we try to predict the future, the only thing certain is that it will surprise us.”
But such asides are few and far between in otherwise dry chapters that are neither detailed enough to be textbook material, nor accessible enough to excite.
Parisi is far more lively when talking about how science imperfectly, but usefully, models reality. Just as Monopoly is a simple model of capitalism that does not contain all of its complexity but reflects some of its characteristics, even crude and unproven scientific models can spark valuable insights and connections, he writes. It was an earlier, incomplete, theory of magnetism, for example, that inspired him to first study spin glasses and the way their magnetism varies with temperature. And while Parisi’s own replica method has never been rigorously proved, it has nevertheless since found use in fields from neural net simulations to machine learning, as a way of untangling and simulating complex systems.
Many systems in our disordered world “can be described as a large number of elementary agents that interact with each other,” he writes. “These interactions can be schematized with simple rules, but the results of their collective action are sometimes really unpredictable.”
“The elementary agents can be spins, atoms or molecules, neurons, cells in general,” he continues, “but also websites, financial traders, stocks and shares, people, animals, components of ecosystems, and so on.”
Parisi believes mathematical models can sometimes be applied to such diverse fields as exotic magnetic systems, the functioning of the brain, the behaviour of large groups of mammals, and even the economy.
But he is frustratingly silent about what such models might look like, or how they might solve wickedly complex problems like financial inequality or climate change. Instead, he tends to retreat to his ivory tower: “Recently,” he writes, “we have achieved important results while trying to solve the problem of putting into a box as many different-sized solid spheres as possible.”
For someone whose professional life is dedicated to studying complexity, Parisi’s view of his own field is actually quite simple. Science, he writes, is an enormous mosaic, every piece of which unlocks the possibility of connecting other pieces. In this optimistic view, “every scientist adds certain tesserae, with the knowledge of having made such a contribution and of the process whereby, when our own names are forgotten, those who come after will nevertheless be standing on our shoulders in order to see further.”
Many philosophers and historians have criticised such rose-tinted visions of uninterrupted scientific progress, in favour of more nuanced views that take into scientific fraud and misconduct, environmental harm, and colonialism. Not every step is a step forward.
Yet Parisi is nothing if not optimistic. “If citizens and politicians do not trust science, we will move inexorably in the wrong direction, and the struggle against any number of global ills — global warming, infectious disease, hunger and poverty, the depletion of the planet’s natural resources — will fail,” he writes. “Our job as scientists is to illuminate for everyone the truths that we discover.”
In an era of citizen science, mass community engagement, and Twitter – now called X – such a statement might seem terribly old-fashioned. But this is a terribly old-fashioned book, featuring a mostly male and European cast of researchers. The pronoun “she” appears five times in the entire book.
But at least we have the starlings. Parisi’s rooftop vigils resulted in several papers that more accurately describe the shape of murmurations and how collective decision-making occurs in flocks of birds, no matter their size.
The intricate mechanics that Parisi discovered in the flight of starlings might not reflect the emotional thrill of experiencing such a phenomenon in the moment, but he is smart enough to realise that the best way to get people interested in the science of complexity is to tie it to something mysterious in their daily lives. “Science needs to be defended not just for its practical aspects but for its cultural value,” he concludes. “We need to promote initiatives that allow people to approach modern science.”
Mark Harris is a Seattle-based investigative science and technology reporter.