Popular books about quantum mechanics almost invariably dazzle and astonish, offering tantalising glimpses into the deepest mysteries of nature, only to leave the reader ultimately baffled. The greatest populariser of physics today, Carlo Rovelli, prepares readers of his new book for this familiar fate when he warns that if “what I have described seems perfectly clear, then it means I have not been clear enough about it.”
He is too modest. His previous books aimed at the general reader, including the international phenomenon Seven Brief Lessons on Physics, have established him as a more literary heir to Stephen Hawking. In Helgoland he puts his own interpretation of quantum physics centre stage and the result is a book that allows us to share Werner Heisenberg’s almost religious “feeling that I had gone beyond the surface of things”. Quantum physics cannot be made perfectly clear, but Rovelli perfectly provides as much clarity as is possible.
The incredible implications of quantum physics are well-known. The properties of objects seem to change depending on whether they are being observed or not. Quantum entanglement means that two objects seem to be able to affect each other when they are too far apart for any information from one to reach the other: a photon on Venus could be changed by a photo taken in Venice. Yet this weird science finds practical use every day, forming “the basis of our latest technologies: from computers to nuclear power”.
Rovelli finds the competing interpretations of quantum theory that aim to resolve these puzzles all wanting. So he strips away all our assumptions and starts again, following the principle “that everything should be based on what we see, not in what assume to be the case”. This rigorous empiricism guided both Einstein, whose theory of relativity was a kind of prequel for quantum mechanics, and Heisenberg, one of the early quantum pioneers, who made his early breakthroughs on the North Sea island of Helgoland.
It sounds obvious, but even many scientists remain wedded to metaphysical assumptions that are not based on observation at all. Chief among these is the idea that behind appearances there must be a “well-defined and solid picture of the world” in which objects have inherent and unchanging properties. Science has broken down the world, first into atoms, then into elementary particles, but always assuming there was at bottom a reality with a stable, measurable nature.
The Presocratic philosopher Heraclitus challenged this assumption two and half millennia ago postulating a world in constant flux. The western mind might have taken a very different shape had his ideas prevailed over those of his successor, Plato, who saw ultimate reality as immutable.
Outside the west, the illusion of solidity has been less prevalent. The richest prescientific articulation of the alternative worldview came in the second century BCE writings of the Indian Mahayana Buddhist thinker Nagarjuna. His doctrine of sunyata, or emptiness, says that nothing exists entire unto itself but only in relation to other things. This was not quantum theory avant la lettre, but Rovelli argues that Nagarjuna’s Middle Way provides the right framework for understanding “a reality made up of relations rather than objects.”
Rovelli’s clarity of exposition would be enough to make the book a triumph. What elevates it even more is the deep humanity he brings to his subject
So it’s not true that quantum theory requires us to accept the absurdity that the properties of objects change depending on whether they are observed or not. Rather, the properties of an object always depends on what it is interacting with. Think of how a vibration of air can be invisible to one ear and an intolerable screech to another. Hence it’s not that looking at reality has a special power to alter it but that “any interaction between two physical objects can be seen as an observation”.
Quantum entanglement is similarly explained. The moment a third party — in this case, the observer — enters the picture, it’s not that the picture changes but that we’re looking at a different picture.
Rovelli’s clarity of exposition would be enough to make the book a triumph. What elevates it even more is the deep humanity he brings to his subject. For all his immense powers of rationality, this is still a man who always sniffs books before buying them.
He reminds us that many of the key players in the development of quantum theory had interests that ranged far beyond science. The young Heisenberg would learn Goethe’s poems by heart,” Schrödinger was “fascinated by Asian thought” and, like Einstein, was “passionate” about the Schopenhauer’s philosophy.”
There is so much in this short but rich book, including a fascinating detour through the dispute between Lenin and his fellow Bolshevik, the polymath Alexander Bogdanov. Rovelli concludes that for all the strangeness of quantum physics, it leaves everything we value not only in place, but more remarkable than ever. “Conventional, everyday existence is not negated.”
When the world of enduring objects dissolves, to be replaced by one of processes and interactions, we are left in a world that is not disenchanted by science, but even more magical. As Rovelli puts it: “Precisely because of its impermanence, because of the absence of any absolute, the now has meaning and is precious.”
Helgoland, by Carlo Rovelli, Allen Lane, RRP£20, 208 pages
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