What if the best person to solve the mystery of alien communication isn't a SETI researcher, a radio astronomer, or even an actor or an actress, but instead is a theoretical physicist trained in the deepest notions of physical law, symmetries, and quantum field theory. Well, today, I'm speaking with an expert, Latham Boyle, whose day job is to explore the fundamental symmetries of the universe and perhaps develop new ideas to understand how the universe began and how it would relate to the groundbreaking data that new experiments like the Simons Observatory and others are coming up with. But he has even more to his research repertoire than just that. Perhaps the answer to one of the greatest paradoxes of all time, the Fermi Paradox. The universe teems with life. Where are the aliens? I think you're gonna love the deep dive that we go into and solving, perhaps, the physics of communicating with aliens and solving the Fermi Paradox once and for all. So, Latham, thank you so much for joining us today from Edinburgh.

Oh, Oh, well, thanks so much for having me. It's a pleasure to speak with you.

Like I said, I've wanted to have you on for quite some time. We had your colleague, Neil Turok, on for his second appearance just recently. I do want to get to that topic of the Fermi Paradox and your unique kind of solution to it, which resonates with, completely different part of my brain than any of the resolutions that I've heard before. But as I said before we get to that later on in the interview, I really want to understand what drives you working on these deep mathematical mysteries and uncovering and maybe predicting new structures that ties all your research together. It seems like you have a thread that goes through it and it's asking these big questions. How did you get here? How did you get to this kind of unique position where you could be as conversant talking about mirror universes as the Fermi paradox?

I don't really think of myself as an expert on the Fermi paradox. There's a lot of people who are much more expert on it. I just realized one thing that hadn't been pointed out about it that seemed important to me. I just I guess I've worked on the things that that that struck me as the most fascinating. And I find that if I work on what I'm most interested in, that I'm much more productive. And if I try to work on what someone else is interested in, I'm incredibly unproductive. I just end up wandering around to to to whatever. I think that's the best I can tell you.

I don't know exactly what why these why the particular topics I'm interested in have grabbed me.

Let's talk about this, the mirror universe. And first of all, let's define some terms for the audience that might not be as familiar with your research. What are symmetries and in particular, what is the importance of CPT symmetry and its violations?

Well, symmetry in general refers to any change that you can do to anything that leaves it the same. So, the most famous example is mirror symmetry, where if you reflect something in a mirror and it looks the same. Another example would be if you have a cube, all the different ways you can rotate the cube that, you know, if you rotate it by 90 degrees about any axis connecting two opposite faces, that'll carry the cube into itself. And but the laws of physics have a lot of symmetries. That seems to be the most basic principle we know that's emerged over centuries of research as kind of the organizing principle for how the laws, as we best understand them, can be described. They are the laws that have such and such symmetries in which the constituent fields and particles transform in such and such a way under those symmetries. In particular, CPT symmetry is believed to be an exact symmetry of the laws of nature, and it's the symmetry where you reflect a process in a mirror and then run it backward in time, and then also replace every particle by its anti particle. And if you do any of those three things by itself, it's not a symmetry of the laws of nature.

But if you do all three of them together, it is. And that's believed to be a symmetry of the law of nature. It's believed to relate any microscopic process to another related microscopic process that has the same amplitude, people say. The amplitude is the quantum mechanical quantity that you calculate from quantum mechanics and then you square it to get the probability of that process happening. But the universe as a whole, if you just look at the portion of the universe after the Big Bang, doesn't naively seem to have that symmetry. It seems that there's a particular going one direction in time away It seems that there's a particular going one direction in time away from the Big Bang where the universe expands and cools is very different than the other direction in time where it gets hotter and you go back toward the Big Bang. So that was one of the one of the things that led us to this alternative picture that we've been getting more and more excited about over the past few years is developing a picture of the cosmos in which it actually does respect CPT symmetry and then trying to understand what a model like that can explain about the observed cosmos and what it can predict for future experiments.

With Neil, was there sort of an exact moment when you both realized the math was pointing you to somewhere, someone say, pretty radical?