Twenty years ago, scientists were surprised to discover that the universe’s expansion is accelerating. The unknown and invisible force causing this acceleration was named “dark energy,” and in the years since, researchers learned more about what the phenomenon is not — but have yet to crack the puzzle of what it actually is. Physicists say it could be an as-of-yet undetected form of energy permeating the cosmos, or it could be an unmeasured property of the force of gravity. Either way, the answer will reshape our models of the universe.

In this episode, we speak with Nobel Laureate Saul Perlmutter (the co-discoverer of dark energy) and rising astrophysics instrumentation scientist Claire Poppett about what we know so far, and how new technology could finally shed (metaphorical) light on this fundamental mystery.