In 1930, American naturalist William Beebe began his descent in a spherical, unpowered submarine known as a Bathysphere -- and in doing so visited a world previously unseen by human beings. In this two-part Stuff to Blow Your Mind exploration, Robert Lamb and Joe McCormick discuss humanity’s prior understanding of the deep ocean and Beebe’s astounding reports from the world a half mile down. (Originally published March 29, 2018)