Is string theory dead? | Don Lincoln and Lex Fridman

Added: 2026-06-02

[00:00:03]We got to talk about string theory. In your view, is it basically dead? As I understand, uh, one of the primary flaws of string theory outside of the testable experiments that we were talking about is uh because it's relies on these unobserved extra dimensions. there was a hope that it uh it uniquely could explain our universe, but it turns out this quote landscape, there's an enormous so-called landscape of possibilities that it'll lead to. And so it renders the theory basically unpredictive because you can describe all kinds of universes and therefore you can just select >> uh tune it to describe ours. I I agree to a degree, >> but I bring it back to my prior objection. It is absolutely true that super string theory um in its current manifestation, aside from the extra dimensions, which are some level small potatoes, it allows for an extremely large number of possible universes.

[00:01:15]But if we were able to take those predictions and somehow connect it to a physical measurement, then what we would do is we'd lop off those alternatives.

[00:01:28]We'd throw them away as saying, well, you know, those are like an equation, you know, x + 5. I can put in any number I want in there. It doesn't matter. But if x + 5 equals 9, then I've ruled out a whole bunch of pe numbers except four.

[00:01:44]And so this is a case of string theory does allow for many predictions. But if we could rule them out by connection to a measurement, then it would no longer do it. We would modify string theory and we would retain the vibrating string concept, which I really really like. I mean, I really like it. But until we can can validate this, it's it's I we can't.

[00:02:10]So now you ask is it dead or not? In my opinion, it is very difficult to kill such a theory. I mean really truly kill it cuz kill it means make a prediction and it fails. But what can happen and what is happening is people have been working on it since the 70s. So we're talking of order 50 years. people have been working on it and it has not solved the problem. And so I think what's happening is people are looking at that and saying I do I want to spend my life working in this direction with a very likely possibility that 30 years from now we'll be not much farther along than we are now. It's a lot like back in the 1940s when people started thinking about the meaning of quantum mechanics. And I wanted to do that when I was a kid in in the 70s. But then when I went to grad school, I realized that people very smart people, people smarter than me had been working on that for most of their lives and made no definitive progress.

[00:03:13]And so you have to decide as a scientist who wants to answer questions. Do I really want to take on a question that is so hard that it will not be answered in my lifetime? And I think that's what's happening with a lot of super string theory is people are saying it's really neat. It might be right, but I don't want to devote my life to something that I might not see progress forward in my lifetime.