Mary Roach joins TMSIDK for a "grab bag" episode with a lot of science. (Photo: Lucy Sutton)

Mary Roach (author of Stiff, Spook, Bonk, Gulp, and Grunt) is our special guest co-host, with AJ Jacobs (author of It’s All Relative) as real-time fact-checker. If the promise of tractor beams doesn’t pull you in, our guests also explore robotic fish, counting to infinity, and more.