For centuries, the greatest minds in physics believed the universe was filled with an invisible medium millions of times more rigid than steel yet frictionless enough for planets to glide through. This episode traces the luminiferous aether from the Newton-Huygens debate over whether light is a particle or a wave, through Young and Fresnel's proof that light is a transverse wave, to the uncomfortable conclusion that only a solid could carry such waves across empty space.

The conversation explains George Gabriel Stokes's proposal that the aether behaved like pine pitch, fluid for slow planets and rigid for fast light, Maxwell's sea of molecular vortices that produced the speed of light from his equations, and why a fixed speed of light demanded an absolute stationary frame. It then follows the hunt for the aether wind, from Bradley's stellar ...