Why science
I’ve always had an innate, child-like curiosity about the nature of physical reality – matter, force, space, time, and the universe. I was influenced in the direction of science by some truly great schoolteachers, and I became a chemist, for the simple reason that my competence in maths wasn’t strong enough for me to contemplate a career as a physicist. But my desire to seek root explanations for things led me to physical chemistry (or even ‘chemical physics’). I trained as an experimentalist, publishing research papers on high-energy molecular vibrations and the kinetics of short-lived free radicals containing carbon and silicon. Despite my mathematical shortcomings, it was with a great sense of pride and pleasure that I did manage to publish some papers on the quantum mechanics of molecular vibrations.
I left academia carrying a very strong desire to maintain my interests in science and, with the conspicuous help of a one-time features editor at New Scientist magazine, I learned quite a bit about writing popular science. I write principally to learn about a subject that interests me, a process that has been made considerably easier in the last 20 years by the emergence and development of some fantastic resources on the web.
Why this book?
I wrote a book published in 2013 titled Farewell to Reality: How Fairy-tale Physics Betrays the Search for Scientific Truth. This was an attempt to set the record straight on the status and prospects for superstring/M-theory, supersymmetry, hidden dimensions, and various kinds of multiverse theory. I had read quite extensively about string theory and slowly became aware that many (if not all) of the claims being made about it were rather empty, if not deliberately misleading. The continued absence of evidence for supersymmetric particles at CERN’s Large Hadron Collider has only served to deepen my unease. Today there are a few authors prepared to put their hands up and argue that this is just metaphysics (or ‘fairy-tale’ physics), and that some sections of the theory community have retreated into their own little worlds, seemingly unconcerned about whether or not their ideas are ever going to be tested scientifically. In my view, this is no longer science.
The new book Quantum Space, continues this general theme. Loop Quantum Gravity (LQG) represents an alternative approach to a quantum theory of gravity that does not demand that we believe six impossible things before breakfast (such as supersymmetry and hidden dimensions). It starts from Einstein’s general theory of relativity and finds a way to ‘quantise’ this, yielding a structure in which space itself is quantum in nature – with ultimate units or quanta of area and volume. The passage of time is then derived from the restless fluctuations of the quanta of space. Now, this is no more scientifically proven than approaches based on string theory but, unlike some string theory popularisers, leading LQG theorists such as Lee Smolin and Carlo Rovelli have never made any claims to the contrary. In fact, LQG and string theory are quite closely related, and Smolin has spent many years trying (unsuccessfully) to bring these different approaches together.
Although Smolin (and, later, Rovelli) have helped to popularise LQG through their own books, I felt that more could and should be done to raise the profile of the theory. I wanted to offer something a little deeper and more detailed, so that readers could better appreciate what’s involved (and why quantum gravity is so darn difficult). I had the idea to write a book based largely on the work of Smolin and Rovelli, but which doesn’t overlook key contributions from others, such as Abhay Ashtekar. I wrote to Rovelli in July 2016 – he liked the idea and contacted Smolin. We agreed an approach in which I would research and write the book, but then share draft chapters. In essence, I wrote the book with Smolin and Rovelli reading over my shoulder.
Of course, the theory remains unproven. But there are some features of LQG that string theory doesn’t provide. The possibility that space might consist of indivisible quanta eliminates all the singularities that plague general relativity and the Big Bang model. If the universe can’t be compressed to dimensions smaller than a quantum of space then perhaps the Big Bang was actually a Big Bounce. Recent calculations based on Loop Quantum Cosmology suggest some subtle differences in the temperature spectrum of the cosmic background radiation, the cold remnant of the radiation released when protons and electrons first combined, some 380,000 years after the Bang/Bounce. The standard Big Bang model predicts a slightly different spectrum. The errors associated with current data are too large to allow a definitive decision one way or the other, but a test might be possible as the quality and precision of the data improves.
What's exciting you at the moment?
In the short term I have a couple of talks to prepare for, including one on Quantum Space at the Royal Institution on 12 February. These events are at once immensely challenging and enjoyable, and I learn something new every time I do one. I’m also looking forward to giving a talk in Bucharest about one of my earlier books Origins: The Scientific Story of Creation, and a TED-X talk in Berlin on the subject of reality.
What's next?
I’m currently working on the manuscripts of two new books, both to be published by Oxford University Press in late 2019 or (more likely) 2020. The first is tentatively titled A Game of Theories: The Quest for the Essential Meaning of Quantum Mechanics, though I’m pretty confident that this title won’t survive to publication. Writing about Rovelli’s relational interpretation of quantum mechanics in Quantum Space renewed my interest in the subject and, although there was a plethora of excellent popular books on quantum mechanics published last year, A Game of Theories offers a very different perspective. I want to try to persuade readers that how you interpret quantum mechanics very much depends on what you think a scientific theory actually represents about reality.
The second book is also about quantum mechanics, but this is a technical book, not a popularisation. I’ve long held the belief that it is possible to comprehend the mathematical foundations of the theory without getting lost in the abstract formalism. As the title implies, The Quantum Cookbook: Mathematical Recipes for the Foundations of the Quantum Theory, presents ‘recipes’ for the derivation of some of quantum theory’s most iconic equations. Each recipe lists ‘ingredients’, which vary from some simple standard integrals to more complicated vector calculus identities, and a step-by-step guide to the derivation that less mathematically competent souls (like me) can follow. The book fulfils another ambition. With the possible exception of Dirac’s derivation of the relativistic wave equation for an electron (which I’ve just finished working on), it’s interesting to note that all the recipes put the physics first and do varying levels of violence to the mathematics. Arguably, Dirac’s Principles of Quantum Mechanics (published in 1930), and von Neumann’s Mathematical Foundations of Quantum Mechanics (published in German in 1932), put mathematical rigor on a pedestal, and gave us a formalism that continues to baffle science students to this day. Students can’t avoid it, but in the Cookbook I really want them to understand where it came from.
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