What do propaganda posters have in common across nation and time, and how is that related to the medial prefrontal cortex? What is behind repeating cycles of societal polarization? What does any of this have to do with the American Civil War, hippies vs soldiers, border ruffians vs free-staters, hanging chads, Pearl Harbor, and why education can serve as an immune response to mind viruses?

Would a utopia be possible? Or does our innate tribalism and jealousy make perfect societies difficult to achieve? Do we secretly love hierarchies? Why are primate brains such excellent detectors of unfairness? Why do things become more desirable when we’re told we can’t have them? Did the church’s disavowal of first-cousin marriage lead to better politics? This week Eagleman talks with psychologist Paul Bloom about the (im)possibility of achieving societal utopias.

Imagine we eventually meet some alien scientists. If they can see electrons or smell photons, would their science look like ours? Is physics a universal language, or just a local dialect of the human brain? Would aliens use math, or might their truths be organized unrecognizably? Are the “laws of nature” really laws, or simply our interpretations? Join Eagleman with particle physicist Daniel Whiteson, author of the new book “Do Aliens Speak Physics?”