Two lines of runners passing each other prove that half a second equals a whole second
Zeno imagined three equal rows of bodies: one stationary, and two others moving past it and each other at equal speed in opposite directions. In the time it takes a moving row to pass every body in the stationary row, it passes twice as many bodies in the row moving the other way — implying that the same stretch of time is somehow both single and double.
Reveal the answer
Aristotle's own diagnosis still stands: how long it takes to 'pass' a body depends on their relative speed, not just the mover's own speed — passing something moving toward you takes half as long as passing something standing still. Zeno's paradox quietly assumes passing-time is fixed regardless of relative motion, which is the flaw. It's the fourth of Zeno of Elea's motion paradoxes recorded by Aristotle, alongside the more famous Achilles and the Tortoise, the Dichotomy, and the Arrow.
— Aristotle (describing Zeno of Elea), Physics, Book VI — c. 350 BC