“Nature's Deepest Secrets” or Just Mist-Castles in the Clouds?

A new book by Graham Farmelo has a title brimming with triumphalist hubris. The title is The Universe Speaks in Numbers: How Modern Math Reveals Nature's Deepest Secrets. The book is a reverent treatment of speculative physics in which mathematicians and physicists create intricate realms of conjecture that have little contact with empirical reality: things like supersymmetry theory and string theory.

It is rather misleading to be using the term “modern math” to refer to things like string theory and supersymmetry. Speculative and unverified theories in physics should not be called math or mathematics, since those terms have such connotations of certainty. Such theories should be called physics theories that use mathematics. There is no basis for claiming that such theories have in any sense “revealed nature's deepest secrets.” “Reveal” is a word to be used when an observational discovery has been made. There have been no observational discoveries made to support theories such as supersymmetry and string theory.  The universe has not spoken in numbers to give us string theory or supersymmetry theory.  It is merely speculating physicists who have spoken in numbers to give us such things. 

On page 174 Farmelo quotes the eminent physicist Sheldon Lee Glashow as saying, “In Europe, supersymmetry seems to be a religion.” This is a very revealing quote that Farmelo should have carefully pondered, but it seems to have gone in one of Farmelo's ears and out the other. He has no insight into the sociological and groupthink factors involved in the cult-like cliques of modern theoretical physics.

Farmelo admits on page 249 that there is no evidence for string theory, saying that “it is disappointing that the framework has not yet made direct contact with experiments.” But Farmelo still supports it. He says on that page, “In my view, it is both wise and prudent to trust the judgment of the overwhelming majority of the world's leading theoretical physicists, who are confident that this theory is well worth pursuing.”

This is the kind of very dubious ad populum argument that people use to try to get you to believe in theories for which there is little or no evidence. Such an argument will typically make some dubious claim about the popularity of some theory among some group of scientists, without providing any actual hard polling data showing that the theory has the popularity that is being claimed. Are there actually any polls of “the world's leading theoretical physicists” in which they assert that string theory is true or “well worth pursuing”? I doubt it. And since Farmelo has told us that a leading physicist said that supersymmetry (a leading physics theory) “seems to be a religion” in Europe, why should we not believe that the popularity of string theory is like the popularity of some religion, something based in sociology and groupthink rather than sound judgment?

On page 251 Farmelo says, “Some undeniably first-rate thinkers – including Gerard 't Hooft, Sheldon Glashow and Roger Penrose – worry from their different perspectives that theoretical physics has taken a wrong turn towards sterile, ultra-mathematical approaches, many of which have become divorced from reality.” But Farmelo ignores such criticism. On page 250 he predicts that supersymmetry will “sooner or later, be demonstrated experimentally to be a fundamental feature of the laws of nature.” He gives no reason at all for predicting this other than saying “such a discovery would help to justify the faith of many theoreticians that beautiful mathematics serves as a useful lodestar,” referring to a star that guides a ship on which direction to move. So we should believe in theories simply because they seem to have beautiful mathematics? That doesn't make sense.

We get a contrary view from physicist Sabine Hossenfelder:

"And not only is there no historical evidence that beauty and elegance are good guides to find correct theories, there isn’t even a theory for why that should be so. There’s no reason to think that our sense of beauty has any relevance for discovering new fundamental laws of nature."

This year cosmologist Ethan Siegel had a post entitled “Why Supersymmetry May Be the Greatest Failed Prediction in Particle Physics History.” Referrring to supersymmetry theory under its acronym of SUSY, Siegel states, “No reasonable person can justifiably conclude that SUSY is supported by the evidence.” He also states the following:

"There's a large and powerful group of (mostly) theorists who will go to their graves as true believers in not only SUSY, but electroweak-scale SUSY, regardless of what the evidence says. Yet with every new proton the LHC collides, we see the same answer again and again: no SUSY. No matter how often we fool ourselves, nor how many scientists get fooled, nature is the ultimate arbiter of reality. The experiments do not lie. As of today, there is no experimental evidence in favor of SUSY."

I guess we can put down Farmelo as one of the true believers who will go to their graves believing that the supersymmetry theory is true. We should note the tendency of certain people in the world of physics to develop life-long attachments to dubious unproven theories, a tendency that also exists very abundantly in the world of biology.

There are several reasons why the “beauty” argument for supersymmetry is not convincing. One reason is that there are always millions of possible ways in which the physics of nature could be configured in a beautiful manner. So if you imagine some hypothetical configuration of particle physics that seems beautiful to you, you have no basis for saying, “This must be how nature really is, because it's so beautiful.” There will be always be a million other possible ways that nature could be configured on a fundamental level, that would be just as beautiful as what you imagined.

Similarly, I may imagine some very beautiful design that Heaven might have, but it would be foolish for me to say, “This is so beautiful, it must be how Heaven looks.” For even if we assume that there must be a beautiful Heaven, there would always be a million other beautiful designs that such a Heaven might have.

The other reason why the “beauty” argument for supersymmetry is not convincing is that supersymmetry isn't really very beautiful at all. The theory has a little symmetry, but it's not very beautiful because it isn't a functional symmetry. The hypothetical “superparticles” imagined by supersymmetry theory are not necessary for our existence. So while supersymmetry imagines a symmetry situation, the situation is not a functional symmetry, so it isn't particularly beautiful.

There actually exists a functional symmetry in the fundamental layout of nature, a beautiful exact symmetry that is very necessary for our existence. This symmetry is the fact that the electric charge on each electron in the universe is the very exact opposite of the electric charge on each proton in the universe. This is both a symmetry and a functional symmetry. If such an exact symmetry did not exist, the laws of chemistry would not work, our bodies would not hold together, and planets and stars would not be able to hold together (as the electromagnetic repulsion of particles in them would overwhelm the gravitational attraction that holds them together).

Our theoretical physicists virtually never talk about this very exact and functional symmetry that we know exists in nature. Instead, they spend a thousand times more time talking about imaginary, non-functional symmetries for which there is no evidence. Go figure.

Not really beautiful, because it's not a functional symmetry