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A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation.It is used to determine longitude by comparing Greenwich Mean Time (GMT), and the time at the current location found from observations of celestial bodies.
William Harrison (20 May 1728 – 24 April 1815) was an English instrument maker, the son of John Harrison, inventor of the marine chronometer. The Harrison H4 marine chronometer Early life
After Harrison, the marine timekeeper was reinvented yet again by John Arnold, who, while basing his design on Harrison's most important principles, at the same time simplified it enough for him to produce equally accurate but far less costly marine chronometers in quantity from around 1783. Nonetheless, for many years even towards the end of ...
Other innovations in timekeeping during this period include the invention of the rack and snail striking mechanism for striking clocks by the English mechanician Edward Barlow, the invention by either Barlow or Daniel Quare, a London clock-maker, in 1676 of the repeating clock that chimes the number of hours or minutes, [140] and the deadbeat ...
To determine "longitude by chronometer," a navigator requires a chronometer set to the local time at the Prime Meridian. Local time at the Prime Meridian has historically been called Greenwich Mean Time (GMT), but now, due to international sensitivities, has been renamed as Coordinated Universal Time (UTC), and is known colloquially as "zulu time".
Thomas Earnshaw (4 February 1749 – 1 March 1829) was an English watchmaker who, following John Arnold's earlier work, further simplified the process of marine chronometer production, making them available to the general public.
John Arnold was the first to design a watch that was both practical and accurate, and also brought the term "chronometer" into use in its modern sense, meaning a precision timekeeper. His technical advances enabled the quantity production of marine chronometers for use on board ships from around 1782.
Chronometer of Jeremy Thacker c. 1714.. Jeremy Thacker was a possibly apocryphal 18th-century writer and watchmaker, who for a long time was believed to be the first to have coined the word "chronometer" for precise clocks designed to find longitude at sea, though an earlier reference by William Derham has now been found.