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Our future, our universe, and other weighty topics

Wednesday, June 13, 2018

Real Physics Versus String Theory's Chimerical “Landscape”

At Quanta magazine, there is an article written by string theorist Robbert Dijkgraaf. It's a batty-sounding piece entitled “There Are No Laws of Physics. There's Only the Landscape.” To explain the goofy reasoning behind this piece, I have to give a little background on the history of string theory. String theory started out as a speculative exercise to try to unify two types of physics theories that seem in conflict with another: general relativity (which deals with large-scale phenomena such as solar systems and galaxies) and quantum mechanics (which deals with the subatomic world). The hope of string theorists was that they could find one set of equations that would uniquely describe a reality in which general relativity and quantum mechanics would exist harmoniously. To try to reach this goal, the string theorists had to do all kind of imaginative flights of fancy such as imagining twelve different dimensions.

Eventually it was found out that it was not at all true that string theory predicted a reality only like the one we have. It was found that there could be something like 10500 possible universes in which something like string theory could be true, each with a different set of characteristics. Did the string theorists then give up? No, they invented the name “the landscape” to describe this imaginary set of possible universes. They then started speaking as if speculating about this “landscape” is some proper business of physicists.

This makes no sense. It is the business of science to study reality, not imaginary possibilities. The only case in which it makes sense to study an imaginary universe would be to throw some light upon our own universe. For example, I might study a hypothetical universe in which the proton charge is not the very exact opposite of the electron charge, as it is in our universe. This might shed some light on how fine-tuned our universe is. But except for rare cases like these, it is a complete waste of time to speculate about imaginary hypothetical universes.

String theorists like Dijkgraaf use various verbal tricks to fool us into thinking that they are doing something more scientific than Tolkien spinning stories about the imaginary landscapes of Middle Earth. One trick they use is to call their imaginary universes “models.” Such a word is inappropriate when talking about any speculation about a hypothetical universe different from the one we observe, such as a universe with different laws or different fundamental constants. In science a model is a simplified representation of a known physical reality. So, for example, the Bohr solar system model of the atom is an example of a model. But you are not creating a model when you imagine some unobserved universe with different laws. That's just imaginative speculation, not model building.

Another trick used by Dijkgraaf is to try to make it sound like the weird speculations of string theory have become accepted by most physicists. For example, he writes the following:

The current point of view can be seen as the polar opposite of Einstein’s dream of a unique cosmos. Modern physicists embrace the vast space of possibilities and try to understand its overarching logic and interconnectedness. From gold diggers they have turned into geographers and geologists, mapping the landscape in detail and studying the forces that have shaped it. The game changer that led to this switch of perspective has been string theory.

With this kind of talk you would think that string theory has taken over physics, wouldn't you? But that didn't happen. During the late 1980's there was talk about how string theory was going to take over physics. But as we can see in the diagram below (from a physics workshop), the popularity of string theory has plunged since about 1990. String theory is now like a weird little cult in the world of theoretical physicists, not at all something which most physicists endorse.
physics papers
Another verbal trick used by Dijkgraaf is to use metaphors that might make us think that string theory is talking about something more substantial than speculations about where angels fly about or how long ghosts haunt a house. So in the quote above he compares string theorists to geographers and geologists and gold diggers and mappers, who are all hard-headed down-to-earth people who deal with solid physical reality. But string theorists are not at all like such people, since string theorists deal so much with imaginary universes for which there is no evidence.

Dijkgraaf also tries to insinuate that the so-called models of string theory (a plethora of imaginary universes) are “results of modern quantum physics.” He states the following:

First of all, the conclusion that many, if not all, models are part of one huge interconnected space is among the most astonishing results of modern quantum physics. It is a change of perspective worthy of the term “paradigm shift.”

A result in physics is something established by observation or experiments. Quantum mechanics has results, but string theory has no results. It has merely ornate speculations. You don't get a paradigm shift by speculating about the unobserved.

What Dijkgraaf conveniently fails to tell us is that string theory has been a complete bust on the experimental and observational side. String theory is based on another theory called supersymmetry. Attempts to find the particles predicted by supersymmetry have repeatedly failed. There is no evidence for any version of string theory.

As for Dijkgraaf's claim that “there are no laws of physics, there's only the landscape,” this seems to be a bad case of confusing reality and the imaginary. The “landscape” of string theory is imaginary, but the laws of physics are realities that our existence depends on every minute. For example, if there were no laws of electromagnetism, none of us would last for even 30 seconds. Claims like “there are no laws of physics” by a string theorist suggests that string theory is just an aberrant set of science-flavored speculations out-of-touch with reality. You might call it runaway tribal folklore, the tribe in question being a small subset of the physicist community. And when a string theorist speaks about an imaginary group of possible universes (what string theorists call the landscape), and says that scientists are “mapping the landscape in detail and studying the forces that have shaped it,” as if the imaginary “landscape” was real, it again seems to be a case of confusing the real and the imaginary. Similarly, a Skyrim player might get so lost in the video game's fantasy that he might say, “There's no America, there's only Tamriel.”

Given string theorists, it's hardly a surprise that nbcnews.com has a story entitled “Why some scientists say physics has gone off the rails.” In that story the cosmologist Neil Turok is quoted:

"All of the theoretical work that's been done since the 1970s has not produced a single successful prediction," says Neil Turok, director of the Perimeter Institute for Theoretical Physics in Waterloo, Canada. "That's a very shocking state of affairs."

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