Pluto Discovered (1930) — The Mathematics of Invisible Worlds

On February 18, 1930, Clyde Tombaugh discovered Pluto by comparing photographic plates taken on different nights — a tiny point of light had moved. But the true story is mathematical: Pluto was found because it was predicted to exist. Percival Lowell had noticed that Uranus deviated slightly from its calculated orbit, and he used the mathematics of gravitational perturbation to predict the position of an unknown planet. The same mathematical method had discovered Neptune in 1846: Urbain Le Verrier calculated where an unseen body must be, and Johann Galle pointed a telescope there and found it the same night. Mathematics revealed worlds before telescopes did.