Watch Episode #5 of Neil deGrasse Tyson’s Cosmos: Unlocking the Mysteries of Light (US Viewers)

Episode 5 of Neil deGrasse Tyson’s Cos­mos series aired last night on Fox. Thanks to Hulu, US view­ers can now watch it online. The episode, called “Hid­ing the Light,” explores the wave the­o­ry of light. It moves across 2000+ years of his­to­ry and even­tu­al­ly gets into the sci­en­tif­ic work of Isaac New­ton, William Her­schel and Joseph von Fraun­hofer, before wind­ing up in mod­ern times and touch­ing on big ques­tions con­tem­plat­ed by astronomers. (For a deep­er dive into this mate­r­i­al, see our col­lec­tion of Free Astron­o­my Cours­es.) If you need to catch up on ear­li­er episodes, you can find them below.

Pre­vi­ous Episodes:

Episode #1: “Stand­ing Up in the Milky Way”

Episode #2: “Some of the Things That Mol­e­cules Do”

Episode #3: “When Knowl­edge Con­quered Fear“

Episode #4: “A Sky Full of Ghosts”