The idea of parallel universes is an idea popularized by superhero comic books, but what is the secret origin of this concept? Who was the first to explore this idea in fiction? What basis does it have in actual science? How do Marvel and DC Comics utilize the concept? What would motivate a company to explore the concept of the multiverse?

Music and audio from "Spider-Man: The Animated Series" is the property of Shuki Levy, Kussa Mahchi, Udi Harpaz, Bob Richardson, John Semper, Marvel Entertainment Group, Marvel Films, New World Productions, and ABC-Disney Domestic Television.

Music and audio from "Supergirl" is the property of Blake Neely, Greg Berlanti, Ali Adler, Andrew Kreisberg, Berlanti Productions, DC Entertainment, and Warner Bros. Television.

Music and audio from "Justice League: Crisis on Two Earths" is the property of James L. Veneble, Christopher Drake, Bruce Timm, Bobbie Page, Warner Bros. Animation, Warner Premiere, DC Entertainment, and MOI Animation.

Music and audio from "Spider-Man: Far From Home" is the property of Michael Giacchino, Kevin Feige, Amy Pascal, Columbia Pictures, Marvel Studios, and Pascal Pictures.

Music and audio from "Mighty Morphin' Power Rangers" is the property of Shuki Levy, Haim Saban, Saban Brands, MMPR Productions, Hasbro, and Toei Company Ltd.

The intro and outro music was created by Cackles and Jeremy Eckert. We thank them for their generous support of this podcast.

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