The Royal Observatory Greenwich celebrates its 350th anniversary today. Founded by King Charles II on June 22, 1675, the observatory was tasked with solving “the longitude problem,” the lack of accurate east-west positioning at sea because of the difficulty of precise timekeeping during long voyages. John Flamsteed, the first astronomer royal, led meticulous observations of the Moon and stars to rectify celestial tables and perfect navigation. In 1833, Astronomer Royal John Pond installed the Greenwich Time Ball on the observatory roof, a visual signal of the time that nearby sailors could use to sync their chronometers. The Royal Observatory became considered the home of time and navigation, establishing the Prime Meridian in 1884 as the world’s zero longitude and Greenwich Mean Time as a global standard. Since Flamsteed, 14 other astronomers royal have advised monarchs on diverse scientific matters, though the modern role is largely honorary.
