Carlo Rovelli, the Italian theoretical physicist, is one of the great scientific explicators of our time. His wafer-thin essay collection, Seven Brief Lessons on Physics, sold more than 1m copies in English translation in 2015 and remains the world’s fastest-selling science book. In The Order of Time and Reality Is Not What It Seems, Rovelli illuminated the disquieting uncertainties of Einsteinian relativity, gravitational waves and other tentative physics. Nobody said that post-Newtonian physics was easy, but Rovelli’s gift is to bring difficult ideas down a level. His books continue a tradition of jargon-free popular scientific writing from Galileo to Darwin that disappeared in the academic specialisations of the past century. Only in recent years has science become, in publishing terms, popular and attractive again.
Rovelli’s new book, Helgoland, attempts to explain the maddeningly difficult theory of quantum mechanics. The theory was first developed in 1925 by the young German physicist Werner Heisenberg during a summer holiday he spent on the barren North Sea island of Helgoland. It was there that the 23-year-old, stricken by hay fever, conceived of the “strangely beautiful interior” of an atom’s mathematical structure and, at a stroke, overturned the certainties of classical physics. Gone was the old idea that atoms consisted of tiny electrons that moved mechanically round heavier protons – as planets orbit the sun. Heisenberg’s intuition was that electrons moved in diffuse, cloudlike waves.
Excited, he devised mathematical tables (“matrices”) to predict the electrons’ wave mechanics. His work was soon refined by other forward-looking physicists such as Erwin Schrödinger and Paul Dirac. Quantum theory was sired out of Heisenberg’s observations and Einstein’s earlier relativity theory. Until Einstein, scientists believed in a predictable, deterministic universe – one driven by clockwork. Newton’s idea of absolute “true time” ticking relentlessly across the universe was countered by the Einstein theory that there is no single “now” but rather a multitude of “nows”. Heisenberg and his followers, more radical even than Einstein, held that we cannot know the present state of the world in full detail, but only by models of uncertainty and probability. The riddle of quantum theory may ultimately be beyond our tentative, Earth-bound comprehension, says Rovelli; but Newtonian mechanics, though far from obsolete, can no longer account for every aspect of the world we live in.
Our world is understood to be non-deterministic and essentially unpredictable; moreover it works in ways that often strike us as non-intuitive. Quantum theory invites us to see the world as a giant cat’s cradle of relations, where objects exist only in terms of their interaction with one another. Ultimately, says Rovelli, Heisenberg’s is a theory of how things “influence” one another. It forms the basis of all modern technologies from computers to nuclear power, lasers, transistors and MRI scanners.
Fortified with reflections on Vedanta Hinduism (the author has a hippyish past), Buddhism, Dante, Empedocles and Democritus, Rovelli applies quantum theory to various philosophies. Humans exist by virtue of their continuous interactions with one another; so, too, do atoms and electrons. As a happy integration of science, literature and philosophy, Helgoland owes something to the Italian chemist-writer Primo Levi, whose literary-scientific memoir, The Periodic Table, reached the UK bestseller list in 1985 alongside Dick Francis. Rovelli’s book displays a very Levi-like enthusiasm for abstruse facts of all kinds. (The German director FW Murnau, we learn, had filmed parts of Nosferatu on Helgoland in 1922 a couple of years before Heisenberg arrived.)
Undeniably, the book is hard going at times. (“I hope I have not lost my reader,” Rovelli says at one point.) The American physicist Richard Feynman presumably meant it when he said that “nobody understands quantum mechanics”. In his trademark lucid prose, Rovelli does his best to explain why this might be so. Known for his work on loop quantum gravity theory and the pre-Socratic Greek philosopher Anaximander, Rovelli is a deep-thinking, restlessly inquiring spirit who sees no incompatibility between physics and philosophy – only mutual attraction.
Science, in Rovelli’s estimation, is not about certainty; it is informed by a radical distrust of certainty. What is real? What exists? Helgoland, beautifully translated by Erica Segre and Simon Carnell, is the beginning of wisdom in these things.