Whether the universe goes on forever is a question modern telescopes have not settled, and this film traces it back to the Greek thinkers who first tried to make infinity make sense. Pythagoras and his followers built their worldview on numerical ratios, until they discovered that pi, the ratio of a circle's circumference to its diameter, could not be expressed as a simple number; legend holds that Hippasus was drowned for revealing the existence of such irrational numbers. Computer scientists have since calculated pi to five trillion digits with no repeating pattern in sight. Zeno's paradoxes follow, illustrated with a modern update: crossing a street by covering half the remaining distance each step requires an infinite number of steps to cover a finite space. Aristotle enters last, drawing a line between the 'potentially infinite,' like pi's endless digits, and the 'actually infinite,' which he reserved for a prime mover beyond human comprehension, an idea that became the basis of the Cosmological Argument for God's existence.