The cosmological constant, as discussed last episode, provides a perfectly good (thus far) explanation for why we observe the universe to be accelerating. But it might not be the right explanation, and demonstrating that would be yet another foundational discovery. In this episode I discuss what is required to invent a plausible theory of dynamical dark energy, This includes considerations from particle physics, possible experimental tests, and the option that we should modify gravity rather than adding a new source of energy to the equations.

Blog post with transcript: https://www.preposterousuniverse.com/podcast/2026/06/29/359-solo-theories-of-dark-energy/