Lost in Math

For more than a hundred years, physicists have taken as nearly gospel John Keats’ admonition that “beauty is truth, truth beauty, — that is all/Ye know on earth, and all ye need to know.” Whether they are pondering the existence of black holes or predicting new discoveries at the Large Hadron Collider, physicists believe theories of physics must be natural and beautiful: no numbers in them should be very big or very small and they should reflect putative symmetries in nature. Together, naturalness and beauty then produce elegance; elegance is the hallmark of truth, and messiness the sign of error. Those are the standards that separate trusted theories from disposable ones. And that is why, argues Sabine Hossenfelder, physics hasn’t made a major theoretical breakthrough in more than four decades. Indeed, this modern preoccupation with beauty has become so dogmatic that it is now in utter conflict with what we actually see in the natural world. Led by their aesthetic criteria, physicists have concocted mindboggling new theories and invented dozens of new particles. They have declared that we are projections of a higher-dimensional space, and that space is spawned with wormholes that tie together distant places. But observation has been unable to confirm almost all of these ideas. Worse, these theories are in fact so difficult to test, that they are actually untestable. Some are untestable even theoretically. Still, theoreticians are convinced that their math contains an element of truth about nature, simply because it strives towards elegance and beauty. These “too good to not be true” theories have left the field stuck in a cul-de-sac. To escape, physicists must rethink the way they build physics theories. By embracing messiness and complexity in mathematics, Hossenfelder shows, they can bridge the gap that has separated theoreticians and experimentalists in recent decades. Only then can science discover the truth, not as our preoccupations would have it, but as it is.