Beauty isn't truth, but it's still very nice

Who doesn’t like a pretty idea? Physicists certainly do. In the foundations of physics, it has become accepted practice to prefer hypotheses that are aesthetically pleasing. Physicists believe that their motivations don’t matter because hypotheses, after all, must be tested. But most of their beautiful ideas are hard or impossible to test. And whenever an experiment comes back empty-handed, physicists can amend their theories to accommodate the null results.

This has been going on for about 40 years. In these 40 years, aesthetic arguments have flourished into research programmes – such as supersymmetry, the multiverse and grand unification – that now occupy thousands of scientists. In these 40 years, society spent billions of dollars on experiments that found no evidence to support the beautiful ideas. And in these 40 years, there has not been a major breakthrough in the foundations of physics.

I dunno, hasn't that been the case literally forever ? In what era did people prefer ugly ideas ? Beauty is in the eye of the beholder and all that. I suppose quantum theory might be the major exception... anyone ever think that was "beautiful" ? I'd guess not, but you never know.

How far can you push this programme before it becomes absurd? Well, if you make a theory simpler and simpler it will eventually become unpredictive, because the theory no longer contains enough information to even carry through calculations. What you get then is what theorists now call a ‘multiverse’ – an infinite collection of universes with different laws of nature.

I think it’s time we take a lesson from the history of science. Beauty does not have a good track record as a guide for theory-development. Many beautiful hypotheses were just wrong, like Johannes Kepler’s idea that planetary orbits are stacked in regular polyhedrons known as ‘Platonic solids’, or that atoms are knots in an invisible aether, or that the Universe is in a ‘steady state’ rather than undergoing expansion.

When Kepler suggested that the planets move on ellipses rather than circles, that struck his contemporaries as too ugly to be true. And the physicist James Maxwell balked at his own theory involving electric and magnetic fields, because in his day the beauty standard involved gears and bolts. Paul Dirac chided a later version of Maxwell’s theory as ugly, because it required complicated mathematical gymnastics to remove infinities. Nevertheless, those supposedly ugly ideas were correct. They are still in use today. And we no longer find them ugly.

There's the rub : what is beauty anyway ? I think GR is hugely ugly and inelegant compared to Newtonian gravity (though perhaps I'd allow it win the naturalness competition). The multiverse is a complete crock because it replaces all physics with statistics, solving nothing. The Universe doesn't have to do whatever we think it should do, so the multiverse theory might be true but it would still be useless, and in terms of beauty then from a physical perspective it's not even wrong but from a statistical perspective it's the Platonic form of beauty. Again, all in the eye of the beholder.

The problem is that if you replace the drive towards theories which are beautiful and simple and all that, you have to have something to do instead. Making theories too simple is indeed awful because they lose predictive power and eventually converge either on statistics or religion. Making them too complex also destroys their predictive power and makes them harder to test. It's no good going by how well the theory agrees with observation either, because radically different interpretations can give the same equations (e.g. Maxwell's vorticies).

For my part, I'm convinced no-one knows what the hell is going on. We just have to muddle our way through.

https://aeon.co/ideas/beauty-is-truth-truth-is-beauty-and-other-lies-of-physics