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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
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.
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".
John Harrison (3 April [O.S. 24 March] 1693 – 24 March 1776) was an English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of how to calculate longitude while at sea.
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.
In 1770, due to ill-health, Mudge quit active business and left London to live in Plymouth with his brother Dr John Mudge. From that date Mudge worked on the development of a marine chronometer that would satisfy the requirements of the Board of Longitude, which had been amended after the earlier work of John Harrison.
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.