I’m busy with other things, so no possible way I can keep up with the claims about string theory flooding the media for some reason these days. It’s hard enough to find the time to read all of this, much less write something thoughtful about it… One obvious point to make though is that none of it acknowledges the obvious: the widely promoted idea that we can get a unified theory and explain the Standard Model by using a theory of strings has turned out to be an empty one. The result of tens of thousands of papers and more than 30 years of work is that all the evidence is that if you can get something this way that looks at all like the Standard Model, you can get anything. Normally when that happens you simply acknowledge the problem and give up, but for some reason that hasn’t happened. Instead of a description of this straightforward situation, the public gets the following:
- Frank Close describes the situation as
In recent years, however, many physicists have developed theories of great mathematical elegance, but which are beyond the reach of empirical falsification, even in principle. The uncomfortable question that arises is whether they can still be regarded as science. Some scientists are proposing that the definition of what is “scientific” be loosened, while others fear that to do so could open the door for pseudo-scientists or charlatans to mislead the public and claim equal space for their views…
Is physics moving towards an era in which elegance will suffice and into the domain of theories that are beyond the reach of experimental proof? Or will empirical evidence remain the arbiter of science?
Close correctly identifies the problematic nature of multiverse pseudo-science, but misses the basic facts about the string theory landscape. This is not a theory of “great mathematical elegance”, quite the opposite, and there is no such thing developed “in recent years”. If you go back 30 years, there were then claims of “elegant” string theory models, but those never worked out. KKLT is the opposite of “elegant”.
- Clifford Johnson takes the Close piece as a starting point to explain his own view. He lacks interest in string unification, thinks that string theory should be thought of as a “method” for solving problems. He doesn’t really explain though why it is a “method” that deserves so much more attention than any number of other methods used in physics. He also doesn’t acknowledge that, besides the huge amount of TOE hype (which he and other string theorists often appear on TV to promote), the hype problem for the string theory “method” may be just as bad. For example, he was quite proud of his efforts to promote string theory as the method to understand heavy-ion physics (see here and here), but that’s something that really hasn’t worked out very well.
- Over at Starts With a Bang, by Sabine Hossenfelder, there’s Will the LHC be able to test String Theory: Definitely maybe. The article actually does a very good job of explaining why the answer is “no”, so I have no idea why the misleading headline. The fact that the AdS/CFT heavy ion predictions haven’t worked out is explained, with the comment that
The LHC, thus, has already tested string theory!
and that this failed, which might be a more accurate headline.
- There’s a long interview with Sean Carroll at the Edge website. He’s quite defensive about the multiverse, claims it’s a prediction of our best theories, and gives his usual characterization of multiverse critics as zealots unable to understand the idea of an indirect test
But certain zealous colleagues of mine are saying that because you can’t see the other universes in the multiverse or because you can’t see the little super strings moving around, these theories are not falsifiable and, therefore, should not count as science.
He’s also defensive about string theory, there the argument is
Either we will bring it down to earth and connect it to the world we see or people will lose interest. People cannot maintain this optimistic idea that we’re going to get the right theory of quantum gravity, the theory of everything, if it’s literally decades and decades of people writing down equations and never predicting the experimental outcome of anything. But we’re not there yet. It would be a terrible shame if we gave up on string theory when maybe next year someone will figure out how to bring it in connection to observations, or maybe ten years from now it will happen. This is how science works, and this is it at work.
The problem here is that it is “literally decades and decades of people writing down equations and never predicting the experimental outcome of anything”, and no matter how many decades of this go on, someone can always argue that “maybe next year”. He’s avoiding the very real issue at the center of things: why hasn’t string theory been held to account for its failures the way any normal speculative scientific idea is supposed to?
As far as his current interests go, from what he says, he seems to be losing interest in the multiverse, which soon may no longer be a hot topic, and moving into research into complexity and consciousness.