American Revolutionary War: Battle of Guilford Court House: Near present-day Greensboro, North Carolina, 1,900 British troops under General Charles Cornwallis defeat a mixed American force numbering 4,400 in a Pyrrhic victory.
French physicist Augustin-Jean Fresnel wins a contest at the Académie des Sciences in Paris by proving that light behaves like a wave. The Fresnel integrals, still used to calculate wave patterns, silence skeptics who had backed the particle theory of Isaac Newton.