An observatory perched above smog-choked Los Angeles sounds like a bad idea, but the same inversion layer that traps the city’s haze gives Mount Wilson unusually steady air. This episode follows George Ellery Hale from his 1904 lease of the 5,710 foot peak, with a clause guaranteeing public access, through the Snow Solar Telescope, the 60-foot and 150-foot solar towers built to escape ground heat shimmer, and his 1908 discovery of magnetic fields in sunspots via Zeeman splitting. The hosts recount the 60-inch mirror gifted by Hale’s father, its mount barely surviving the 1906 San Francisco earthquake, and the 100-inch Hooker telescope floated on vats of liquid mercury and housed in a dome pre-assembled in a Chicago lot.

The conversation then turns to the discoveries: Edwin Hubble’s 1923 Cepheid variable in Andromeda proving it was a separate galaxy, his 1929 redshift work with Milton Humason showing the universe is expanding, Fritz Zwicky’s early dark matter evidence, Walter Baade’s wartime blackout observations that doubled the known scale of the cosmos, Eric Becklin’s 1966 infrared fix on the galactic center, and interferometry from Michelson’s 1920 measurement of Betelgeuse to the CHARA Array’s 330 meter virtual mirror. The episode closes with light pollution retiring the Hooker in 1989, its 2014 rebirth as the largest public-use telescope, wildfire evacuations in 2009, 2020 and 2025, chamber concerts in the dome, and the archive of strange letters from the public.

• Why the Los Angeles inversion layer made the mountain ideal for astronomy
• A tower inside a tower: how the 150-foot solar telescope beat the wind
• Cepheid variables and redshift explained as cosmic yardsticks and sirens
• The CHARA Array’s 2007 first image of a main sequence star’s surface
• Fires, funding and the museum exhibit built from letters to the observatory