Existing comment:
Determining Longitude:
Sailors could determine their position north or south of the equator -- their latitude -- with reasonably accuracy by the 1400s. Determining their longitude -- their position east or west of a base line (the prime meridian in Greenwich, England) -- was a far harder task. As lives continued to be lost due to mistakes in navigation, in 1714 the British government offered a prize of 20,000 pounds to the first person who could devise instruments sufficiently accurate to provide a ship's longitude to within half-a-degree accuracy.
An Englishman named John Harrison eventually solved the problem through his invention of not one, but four remarkable clocks. His early marine chronometers gave sailors the capability of keeping the time at sea accurate to within two minutes of the time in Greenwhich. With this information, they could then measure the angle of the sun or certain stars at a precise moment and, by consulting pre-printed mathematical tables, calculate their longitude. |