English clockmaker and carpenter

John Harrison solved the so-called "longitude problem," that is, he developed the means to enable navigators to calculate their east-west (longitudinal) positions at sea. A ship's north-south (latitudinal) position is easily computed from the Sun, stars, date, and local time, but to calculate longitudinal position a navigator must also know the current time at the home port and compare it with the local time of the ship as determined by observing the Sun and stars. This calculation is based on the fact that every hour represents 15 degrees of longitude. The principle was known centuries before Harrison, but using it was not possible in practical navigation until he invented his portable, durable, and extremely accurate clock, which proved reliable under the harsh conditions of the sea.

Born the son of a carpenter on March 24, 1693, in Foulby, Yorkshire, England, Harrison early learned...