Since 2015, there has been a spectacular boom in a nearly 200-year-old delusion — the idea that we all live on a flat plane, under a solid dome, ringed by an impossible wall of ice. It is the ultimate in conspiracy theories, a wholesale rejection of everything we know to be true about the world in which we live. Where did this idea come from

Michael Shermer speaks with journalist Kelly Weill whose work covers extremism, disinformation, and online conspiracy theories in current affairs. The conversation is based on her book Off the Edgewhich tells a powerful story about belief, polarized realities, and what needs to happen so that we might all return to the same spinning globe.

Shermer and Weill discuss: the binary/black-and-white thinking of conspiracy theorists; how Flat-Earthism is ultimately a conspiracy theory about how NASA and the government are covering up the biggest secret in history; how Flat-Earthism is a proxy for other conspiracy theories (i.e., 9/11 truth, QAnon, and anti-Semitic beliefs about nefarious Jewish organizations conspiring to achieve world domination); and the role of social media in propagating conspiracy theories.