Physics
The Wave Equation: Describing Vibrations in Space and Time
Quick fact
The wave equation was first formulated by Jean-Baptiste le Rond d'Alembert in 1746 to describe vibrating strings, and it still underlies modern quantum mechanics and general relativity.
Why this is interesting
Ever wondered why a ripple in a pond spreads as a perfect circle, or why a guitar string vibrates to produce a specific tone? There's a single equation that governs all such wave motions—what is it?