The longitude problem

For centuries, sailors crossing the open ocean had no reliable way to find their longitude, their position east or west. Latitude could be worked out from the height of the Sun at noon, but longitude depended on knowing the exact time at a home port while at sea. Pendulum clocks were useless on a rolling ship, and many vessels were wrecked because navigators guessed wrongly. In 1714 the British government offered a large prize to anyone who could solve the problem. The winner was not a famous astronomer but John Harrison, a self-taught carpenter and clockmaker. Over more than thirty years he built a series of marine timekeepers, each smaller and more accurate than the last. His fourth design, about the size of a large pocket watch, lost only a few seconds during a long voyage to the Caribbean. The officials in charge of the prize were slow to accept that a mere craftsman had succeeded where scholars had failed. Harrison received his full reward only near the end of his life, after the king himself intervened. Today his clocks are displayed in Greenwich, a reminder that persistence and practical skill can matter as much as formal learning.