Zero Was the Hardest Invention

Zero seems obvious — the amount of water in an empty glass. But for most of human history, zero did not exist as a number. Babylonian tablets left blank spaces where we now write 0. Romans wrote "nothing" in words. Zero arrived in India around the 7th century AD with Brahmagupta, who defined its arithmetic rules: a + 0 = a, a × 0 = 0.

Without zero, place-value notation is impossible — you cannot distinguish 102 from 12. Without zero, algebra cannot express "a − a = 0." Islamic scholars brought zero westward by the 9th century; Europe adopted it in the 13th. The hardest conceptual leap in math history is now the number a toddler learns first.