How Caring Too Much About Beauty Led Physicists Astray
One astrophysicist challenged the most popular theories in theoretical physics. She's made criticisms that indict the entire field.
Few people are qualified to question quantum physicists. Theoretical physics is one of the most technical scientific fields, combining one of the most abstract branches of science with the most dense.
But in her book, Lost in Math, Sabine Hossenfelder takes establishment opinion on in one of the most difficult sciences. Hossenfelder is a theoretical physicist and a research fellow at the Frankfurt Institute for Advanced Studies.
Lost in Math challenges the foundation of some of the most popular theories in theoretical physics. She takes aim at ideas like:
The multiverse
Higher dimensions
Wormholes and the formation of space
Some of the new particles in particle physics
Her biggest issue is that many theoretical physicists use beauty as a standard to judge how credible their theories are. Instead of testing theories to see whether they describe reality, some “physicists draw upon the concepts of naturalness, simplicity or elegance, and beauty.” This disconnect led Hossenfelder to lament:
“…I have become increasingly alienated by colleagues who on the one hand preach the importance of unbiased empirical judgment and on the other hand use aesthetic criteria to defend their favorite theories.”
While this sounds like a dramatic breakdown of a foundational scientific discipline, Hossenfelder’s concerns don’t come out of nowhere.
Physics Doesn’t Have to Be Pretty
It’s difficult to explain why theories like the multiverse and string theory are likely true. Physicists like Brain Greene and Michio Kaku have offered explanations as clear as the math supporting those theories allows.
Hossenfelder explains some of the most popular theories, including eternal inflation. It builds off the idea that the early universe expanded during an “inflation” period. Eternal inflation is a massive expansion of this idea:
“…because the inflation has quantum fluctuations, bubbles where inflation ends can appear, and if such a bubble becomes large enough, galaxies can form in it. Our universe is contained in such a bubble. Outside our bubble, space still inflates, and randomly occurring quantum fluctuations spawn other bubble universes - eternally. These bubbles form the multiverse. If one believes that this theory is correct, say the multiverse proponents, then the other universes must be just as real as ours.”
Hossenfelder’s explanation paints a clearer picture than equations will to most readers. It’s easier to imagine an expanding surface with bubbles than to understand what a multiverse would mean in the real world.
But that’s a large part of Hossenfelder’s point. Theories like this capture imaginations wherever physicists can explain them. That doesn’t mean they have predictive value or describe reality.
The Multiverse is Particularly Shady
One of Hossenfelder’s greatest pet peeves is the misuse of the multiverse theory. The idea of many universes is fun to entertain, but it can also be used as a cop-out. Part of the multiverse’s appeal is that it fills in blanks that can’t be filled with experiments. We can’t go back to the Big Bang to measure the proportions of matter and dark matter. Instead, we can guess that the many possibilities indicate multiple universes. Hossenfelder gives examples of this thinking:
“Newton, for example, could have refused to just measure the gravitational constant and instead argued that there must be a universe for each possible value. Einstein could have argued that all solutions to the equations of general relativity must exist somewhere in the multiverse. You can create a multiverse for every theory - all you have to do is to drop a sufficient amount of assumptions or ties to observation.”
It’s a strong passage that vents much frustration with the overly abstract theories that support the multiverse, string theory, and some particle physics. The multiverse can be a way out of explaining gaps in our knowledge. Hossenfelder concedes that not every invocation of the multiverse is bogus:
“The existing predictions demonstrate the multiverse is in principle amenable to experimental test, but these tests are useful only for very specific scenarios. The vast majority of multiverse ideas are presently untestable, and will remain so eternally.”
Theoretical Physics is Still Crucial to Scientific Inquiry
Hossenfelder isn’t all doom and gloom for theoretical physics. Sometimes, the technology doesn’t exist to run an experiment until decades later. Albert Einstein predicted the existence of gravitational waves, but they weren’t measured for the first time until February 2015.
Eventually, experiments must support theories, and theories that remain unsupported must fall out of favor. Hossenfelder’s book explores how unsupported theories have failed to fall out of favor in modern theoretical physics.
Even if one of the physicists she criticizes by name is proven right, Lost in Math remains a powerful example of scientific inquiry at its best. Hossenfelder invokes the scientific method, the goals of scientific inquiry, and empirical data to challenge established theories.
Anyone hoping to find ways to challenge authority without resorting to conspiracy theories should read through Hossenfelder’s writing at least a few times.