Steven Strogatz asks why physicists keep testing a theory that no experiment has ever contradicted. Halliwell objects to colleagues in quantum foundations who told him the work is pointless because quantum physics is simply true, calling that a kind of fundamentalism. He then walks through what Bell and Leggett-Garg tests rule out and through Bohmian mechanics, a picture in which the world is definite but non-local, before landing here.
…for one of these big interferometries experiments with big particles to really say this is definitely quantum and not pseudo-classical, you'd need to violate a Leggett-Gog inequality, basically. That can all be done in principle. I mean, even just with the data from existing experiments, basically.
…really, but I bet you have a strong opinion, which is so far, no experiment has contradicted quantum mechanics or quantum field theory. I'm not sure how far we should push this. So why do we keep testing it? What are we hoping to learn by pushing these quantum tests to larger and larger systems?
…for the particle can depend on very distant observers. It basically says it's an entanglement situation with distant particles, that one particle really can depend on what the other one is doing or what you measure on the other particle. But that might be it. I mean, you can have a world in which everything is definite, but it's non-local. And that might also be true, actually. So, that's why I don't believe in truth. I believe in multiple perspectives.
Do you want to expand on that idea? In some of my preparation for our conversation, I was told you have an interest and have practiced things like yoga, meditation. Is that related to the sorts of perspectives you're describing here?
It's not directly related, but in terms of the sort of attitude and perspective I take towards physics and scientific ideas, it sort of helps me in that sense. So, I think in the early days, when I wanted to figure out, you know, how does the universe actually start? We really want to know. Now…
It's interesting to me, the analogy between the perspective you've described with holding different possibilities in mind at the same time and being comfortable, I want to say, sort of as a superposition, that you seem to resist collapse in your own thinking.