Chronometer

A highly accurate timekeeping instrument, specifically designed for determining longitude at sea.

A chronometer is a precision timepiece used aboard ships to aid in navigation by providing an accurate measure of time, which is crucial for determining a vessel’s longitude. Before the invention of the marine chronometer in the 18th century, sailors had no reliable method to calculate their position east or west of a known point, which often led to navigational errors and shipwrecks. The chronometer solved this problem by allowing mariners to compare the local time (determined by celestial observations) with the time at a known reference point, such as Greenwich Mean Time (GMT). The difference between the two times could then be used to calculate the ship’s longitude.

Marine chronometers are built to withstand the harsh conditions of life at sea, including temperature fluctuations, humidity, and the constant motion of the vessel. They are typically housed in gimballed boxes to keep them level and minimise the effects of the ship’s movement. The development of the marine chronometer by John Harrison in the 18th century revolutionised navigation and made long-distance sea voyages far safer and more predictable. Even with modern GPS technology, chronometers are still valued for their precision and reliability, especially as a backup system in case of electronic failure.