358 | Solo: Vacuum Energy and the Cosmological Constant
6/22/20262 hr
The most surprising discovery in fundamental physics during my career as a scientist was undoubtedly the acceleration of the universe, announced in 1998. The most straightforward explanation for these observations is a positive cosmological constant, or vacuum energy. I talk about the origin of the idea with Einstein, how quantum physicists started to think about it and understand the "cosmological constant problem," as well as how its discovery also raised the "coincidence problem." This is the first of two connected solo episodes; the next will be on theories of dark energy that are not the cosmological constant.
Blog post with transcript: https://www.preposterousuniverse.com/podcast/2026/06/22/358-solo-vacuum-energy-and-the-cosmological-constant/
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Transcript preview
First 90 secondsSean Carroll· Host0:00
Hello, everyone, and welcome to the Mindscape Podcast. I'm your host, Sean Carroll. In physics, which is a very broad field, it includes, you know, atomic physics, plasma physics, condensed matter physics, biophysics, particle physics, gravity, cosmology, all of these things. Different fields, of course, have different rates of progress, both because of theoretical ideas and experimental input. If you focus just on fundamental physics, and let's not argue about what that means or should mean, I take it to mean figuring out the most fundamental laws of nature the best we can, so not including things like biophysics and condensed matter physics, not because they're not important. It's just a different thing. I once tried to get the field to change the name fundamental physics to the name elementary physics, the most elementary laws of physics being the idea, but no one agreed with that. That's okay. Fundamental physics is here to stay. In this subfield of fundamental physics, uh, which includes sort of particle physics and gravity, things like that, there haven't been a lot of helpful experimental surprising discoveries in the past several decades, arguably since the 1970s. There have been a few here and there, masses of neutrinos, things like that. Also, things that we expected, like the Higgs boson, gravitational waves. But in, in terms of true surprises, it's been few and far between. That makes it hard to make progress in fundamental physics because experiments are what drive us to great ideas.