Lost in Math: How Beauty Leads Physics Astray

"Lost in Math is a firecracker of a book—a shot across the bows of theoretical physics. Sabine Hossenfelder, a theoretical physicist working on quantum gravity (and author of the blog Backreaction ) confronts failures in her field head-on. The foundations of physics have not improved, she reminds us, for more than three decades. Hossenfelder contends that theoretical physics—specifically, theoretical particle physics—is in thrall to seductive concepts that act as hidden rules. Faced with new but untested theories, many physicists draw on aesthetic concepts such as naturalness, simplicity, elegance and beauty. ‘Naturalness’, for example, is the idea that a proposed theory should not have to have parameters tuned to tally with observations. “Theoretical physics—specifically, theoretical particle physics—is in thrall to seductive concepts that act as hidden rules” Hossenfelder notes that these concepts can be valuable—a “hard-earned intuition for what works”—while also being opposed to objectivity. She argues that their dominance has contributed to a crisis in the field. The development of theories needs to be guided by data, but where there is no data, many theorists fall back on these concepts. When that doesn’t work, she reveals, confusion ensues. Or, worse, rhapsodies. Of course, testing theories is beyond tough, and takes time. She reminds how it took 25 years for the neutrino to be detected, almost 50 to confirm the Higgs boson, and a century to detect gravitational waves. A scientist testing a new law of nature may not see results in her lifetime. So in deciding which research to follow, what Hossenfelder calls “empirical adequacy” may not be the only criterion; ‘beauty’ may become another, introducing “systematic bias”. Get the weekly Five Books newsletter This is a book of mordant wit and bold immediacy. Hossenfelder interviewed a number of physicists in the thick of this vast debate—including Steven Weinberg, Nima Arkani-Hamed and Frank Wilczek. Their frank exchanges are illuminating. As is Hossenfelder’s trouncing of theories such as wormholes in space (“pretty but useless” and nearly impossible to test), or the lack of evidence for dark matter particles. Hossenfelder is by no means trashing her own field. She is simply breaking away from the pack to examine it, and that has to be salutary for any scientific endeavour. She’s in worthy company, too. Lee Smolin trod this territory in The Trouble with Physics (although that focused far more on string theory), as did Jim Baggott in Farewell to Reality . But she adds a pungency all her own: We don’t use math because we want to scare away those not familiar with differential geometry . . . we use it because we are fools. Math keeps us honest—it prevents us from lying to ourselves and to each other. You can be wrong with math, but you can’t lie. Basically, we need to find the right maths."