Click above to listen to Part 2 of 100% Invisible, featuring Michael Lemonick, science writer and an editor at Scientific American magazine, on the history of the search for a 9th planet and the evidence for its discovery.
100% Invisible:
Part 1: Mike Brown / New Planet
Part 2: Michael Lemonick / Planet X
Part 3: Arthur McDonald / Neutrino Nobel
Part 4: Lisa Randall / Dark Matter







