The real story
In 1822 the French physicist Augustin-Jean Fresnel designed a lens made of rings of glass prisms that bend a small flame into one powerful beam. A big Fresnel lens could be seen more than 20 miles out at sea. Keepers spent their nights trimming wicks, winding the clockwork that turned the light, and polishing that glass.
Most keepers also kept weather logs that sailors and forecasters relied on. Through the 20th century lighthouses were automated one by one, and the keepers packed up and left. Many of those lights still turn every night, with nobody inside.
