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Cosmology

(Courtesy: iStock / sakkmesterke)
10 Feb 2021
Taken from the February 2021 issue of Physics World. Members of the Institute of Physics can enjoy the full issue via the Physics World app.

Frank Wilczek is that rare creature: a first-class scientist who is also an extremely talented communicator. His 2004 Nobel prize, awarded jointly to David Gross and David Politzer, was given for work elucidating the strong force that binds quarks into particles like those in the atomic nucleus. But he is known too for his creativity in other areas of physics, such as postulating the axion. A particle he confesses to naming after a laundry detergent, it was originally designed to explain charge–parity violation in particle interactions, but is now considered a candidate for dark matter. Wilczek has also championed the idea of quasiparticles called anyons in condensed-matter systems, which have properties intermediate between bosons and fermions (with, respectively, integer and half-integer spins). And he coined the notion of time crystals: dynamical systems that are periodic in time.

All these pet topics make an appearance in his latest book Fundamentals: Ten Keys to Reality, but it is no survey of Wilczek’s greatest hits (fascinating though that would be). Instead, he sets out to identify the core concepts underpinning modern physics: what they are, how they arose, and why we believe they are true. The latter aspect is one of the most valuable facets of this delightful book. Wilczek takes great pains to explain the empirical reasons why he and his colleagues believe what they do – a crucial issue, given how exotic and counterintuitive some of these ideas are.

While many of the topics on display here – from special and general relativity to the Higgs boson and inflation – are well-trodden, Wilczek constantly finds fresh ways to present such ideas, so that you emerge with new insight into what they mean. For example, he tells us that space–time can be regarded as an extremely stiff material: it takes something truly cataclysmic, like a collision of neutron stars, to shake it and generate gravitational waves. Or take his description of the theory of the Big Bang: “Fundamentally, [it] is a strange hybrid of two opposing ideas. It postulates complete equilibrium for the non-gravitational interactions, but maximal disequilibrium for gravity.” I, for one, had never thought of it that way before.

In general, his fundamentals come as no surprise: the idea of atoms and particles, say, and the economy of their description: “According to our present best understanding, the primary properties of matter are these three: mass; charge; spin. That’s it.” He points to the dizzying range of scales in space and time, and describes the emergence of complexity from simplicity. “From different perspectives, we are both small and large”, he writes. “Both perspectives capture important truths about our place in the scheme of things. To get a full and realistic understanding of reality, we must embrace them both.”

One of the virtues of Wilczek’s perspective is that, despite the title, there is a practical slant to his questions: science is a useful tool, not a way to know “the mind of God”. “ ‘What happens next?’ is a more approachable question, and proves to be a much more fruitful question, than ‘Why are things the way they are?’ ” he says. That grounded view makes it much easier to forgive the rare lapses into the language of the Romantic Sublime – “Atoms sing songs that bare their souls, in light.” – that seems so beguiling to much “big picture” science writing, especially in the US.

Behind it all is the physicist’s search for unifying principles: concepts and theories that let us carve the bafflingly complex into manageably small and comprehensible pieces. That this is possible at all – that reductionist science boils down to just a few fundamentals – is perhaps the greatest insight of all, and it’s clear that Wilczek is not just grateful but aesthetically moved by the fact. What is sometimes lost in that process is an acknowledgement that taking items apart doesn’t necessarily tell us how they work. Critics of reductionism are often pitching at a straw man, but in this respect at least they are correct. This is nowhere more true than in the question of why we are asking about fundamentals in the first place, and how we conceive of them: that is, the nature of the human body and mind.

The distance between the physicist’s view and the human one is illustrated in this claim by Wilczek:

“Here, in sixteen words, I will supply a simple algorithm for producing the complete works of Shakespeare, at least one proof of Fermat’s Last Theorem, and the paper that will win the Nobel Prize for Physics in 2025:
1. Choose an ASCII character – a letter, number, space, or punctuation mark – at random.
2. Record it.
3. Repeat.
…This outrageous thought experiment illustrates how a very simple – that is, easily described – structure can contain vast complexities within it.”

I’d argue that in fact none of those works would be produced by the algorithm. They would merely be incidental and meaningless repetitions, indistinguishable from all the junk. In the originals, minds inserted meaning at the outset. The works of Shakespeare are not permutations of symbols on paper, but mental constructs that assume certain types of observer: their information is not self-contained. Mind, agency and evolution all involve the construction of meaning – the very quantity that Claude Shannon’s information theory excluded. Fundamentals do not speak to that, because it is intimately connected to notions such as history, context and environment.

What elevates Wilczek’s book above other surveys of the bedrock of physical theory is that he recognizes this. He dismisses the fallacy that all can be understood by building up from a handful of physical fundamentals: “It is tempting to say that this is the ideal description, while other, high-level descriptions are mere approximations – compromises, which reflect weakness in understanding. That attitude…is superficially deep, but deeply superficial. In order to answer questions of interest, we often need to change focus.”

To do so Wilczek enlists Niels’ Bohr’s notion of complementarity, which for him means holding onto multiple viewpoints at once. “The world is simple and complex, logical and weird, lawful and chaotic. Fundamental understanding does not resolve those dualities. Indeed, as we have seen, it highlights and deepens them.” That’s why, as well as consulting the canonical scientific pantheon – Galileo, Newton, Darwin, Maxwell – he says he often goes back to the likes of Plato, St Augustine and David Hume, “to converse with great minds, and to practice thinking differently”.

Fundamentals is, then, not only an exceptional piece of science communication but also a deeply humanistic book. It celebrates what we know without pretending that is more than it is: “The world is complex beyond our ability to grasp, and rich in mysteries, but we know a lot, and are learning more. Humility is in order, but so is self-respect.”

  • 2021 Penguin 272pp £20hb
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