In “The Case against Copernicus,” authors Dennis Danielson and Christopher Graney detail the evidence-based reasons why 17th-century astronomers doubted the Copernican model of the universe, which held that Earth revolves around the sun (and not the other way around). After all, the ancient geocentric universe of Ptolemy was able to account for the observed motion of the sun, moon and planets by using the complicated motion of epicycles—circles embedded within circles. The dispute was only resolved hundreds of years later, as apparent problems in the Copernican universe could only be resolved with the conceptual and experimental advances of the 17th- and 18th-centuries. In this video we see just how intricate the Ptolemaic universe was.