A scientist's crisis of faith

Sabine Hossenfelder is no stranger to trouble and controversy. A theoretical physicist and widely read blogger, she was once described by Roger Penrose as that German woman “who makes rude comments about other people’s theories.” Here she has rude things to say about what she perceives as the way some of her peers lose themselves down mathematical wormholes, concocting ideas such as string theory, supersymmetry and the cosmic multiverse that have no experimental support, and in some cases lack all prospect of attaining it.

String theory, for example, is an attempt to delve far beyond the “standard model” of particle physics that constitutes the current best (and firmly supported) picture of the fundamental building blocks of the universe. It supposes that the yet more fundamental entities are vibrating one-dimensional objects (“strings”) so small that we have no means of observing their existence. String theory rests only on arguments about “mathematical elegance,” “beauty” and what physicists call “naturalness”—basically an absence of unexplained huge or tiny numbers in their theories. It is “post-empirical science.”

The arguments about whether such untestable theories constitute science at all have been raging for years, and the account of them offered in Lost in Math is thorough and accurate but sometimes rather technical. What makes the book compelling reading, however, is that it is not so much a polemic as a forlorn confession of Hossenfelder’s crisis of faith. She quizzes eminent figures (sometimes a little rudely) as if searching for reasons to believe her branch of physics has not lost its way. On her blog she has all but accepted that her book is a career-suicide note. But whether her scepticism ultimately proves valid or not, her criticisms of the use of vague aesthetic, intuitive and metaphysical arguments in science in place of empiricism need to be heard and debated.

Lost in Math: How Beauty Leads Physics Astray by Sabine Hossenfelder (Basic Books, £17)