An Update on Garrett Lisi’s Exceptionally Simple Theory of Everything

In 2011, I wrote a story for MauiTimes’ predecessor publication, MauiTime, about a Maui-based theoretical physicist named Garrett Lisi who thought he may have discovered the shape of the universe. He came to it, in a moment of inspiration, via a structure known as E8, a Lie group, named after Norwegian mathematician Sophus Lie. Lisi wrote a paper for Scientific American—along with physicist James Weatherall—titled “An Exceptionally Simple Theory of Everything,” and lit up the scientific community, including vehement pushback from string theorists. (Read the full piece for a more detailed explanation.) I caught up with Lisi, who is also an avid waterman, to get an update on where things stand as we were emerging from the pandemic.

MT: The last time we spoke, you said you had an “unusually high confidence” that the E8 theory was at least “going toward a correct description of the universe.” A decade-plus later, where do you stand on the theory and the shape of the universe? How have things evolved?

There has not been dramatic progress in high-energy theoretical physics in general, so I don’t feel too bad that I also haven’t made especially dramatic progress in expanding the ideas proposed with E8 theory. I and some others have pushed forward in some significant directions though. In 2015 I proposed the idea of Lie group cosmology, in which our universe is a spacetime surface evolving inside a Lie group such as E8. … That was a fun idea that I’m pretty happy with because it describes the universe and everything in it as coming from and returning to just one perfect mathematical structure. An idea I’ve been working with more recently is to use infinite dimensional generalized Lie groups with these ideas to come up with a full description of quantum reality; deriving the entire structure of quantum field theory, particle physics, including three generations of fermions, and quantum gravity from one mathematical structure, but I haven’t fully succeeded in that yet.

MT: At the time, you said the Large Hadron Collider particle accelerator was looming as a major test for your theory as well as the theories of string theorists. What did, and didn’t, the LHC reveal?

In 2012 the LHC found the Higgs, which was expected by everyone, including me, so that was good. But the LHC hasn’t found any other new particles, which is disappointing. It would have been nice to see some new force particles associated with grand unified theories or some colored Higgs bosons associated with E8 theory, but not seeing them yet isn’t a deal-breaker. Not seeing super-particles though has been a huge blow to string theory, which requires them for consistency, and mostly predicts they should have been visible at the LHC by now if they were to help balance the Higgs mass—which we now know they don’t. So string theorists are really hurting right now because we’re not seeing super-symmetry. I was happy to win a bet against Frank Wilczek, a great guy, that super-particles wouldn’t be seen at the LHC. Fortunately E8 theory doesn’t rely on super-symmetry like string theory does, so it’s not yet in the super-cemetary.

MT: On a personal level, where are you with regard to your work and life in general? Where does the balance we discussed between your love of the waves and your love of scientific inquiry and answering the big questions stand?

I’ve been staying mostly sane by surfing and kiting my butt off. I’ve also been getting more into paragliding, which is super fun on Maui and elsewhere.