I'll ask him that question.
Last night, though, I asked him about string theory in general. Here is a paraphrase of what he said:
It's an interesting idea, but just that, ideas. It is not physics, because it is not measuring anything nor is it measurable. A good, publishable paper in string theory is so called not because of any intrinsic truth -- because something that was predicted was discovered, or because existing results were integrated into a theory -- but because of more subjective criteria, about whether it "makes sense."
He says that physicists sometimes call string theory "mathurbation."
I asked if it was a travesty along the lines of cold fusion, and he said, no, no, it's an interesting idea. I said CAN they ever prove it one way or the other?, and he said well they've been trying for over 20 years. I asked about Einstein's relationship to string theory, and he scoffed. He said that Einstein had his theory of everything/ unified field theory, yes, but was not involved in string theory per se.
My own answer to your question is that string theory was trying to solve a problem that physicists are trying to solve in other ways, my husband included. Right now there is not enough known matter in the universe for general relativity to "work." The jump string theorists made is, well, let's throw out our current thinking and start new. One of the many jumps particle- and astrophysicists made is, well maybe these things that we thought were only light -- neutrinos -- have a tiny bit of mass. There are so many of them, that the tiniest bit of mass can supply some of the missing matter.
In the last 7 years or so, they have found that to be true. Neutrinos have a tiny bit of mass, but it looks like not quite enough to make up the missing mass. The missing mass has collectively been called dark matter, and the search for the rest of the dark matter is on, and that's a new frontier. (Dark matter isn't new, but there are newly interesting discoveries.)
So, most physicists are saying: Einstein's theory almost
works, so we are going to keep searching and see if enough measurable evidence surfaces to make it work perfectly. If the measurable evidence seems to contradict his theory, we'll have to revise the theory as we continue to gather more evidence and search for a measurable, objective truth.
String theorists are saying: Einstein's theory almost
works, so we are going to create this other, unmeasurable, theory because it makes sense to us.
More on neutrinos/ dark matter: