John Harrison (March 24, 1693 – March 24, 1776) was an English clockmaker, who designed and built the world's first successful chronometer (a maritime clock), whose accuracy was great enough to allow the determination of longitude over long distances.

John Harrison invented clocks that kept accurate time at sea. The big problems were that clock technology of the day used big pendulums and metal workings. Pendulums are affected by the rolling motion of the ship, and the workings were susceptible to corrosion and extreme temperature changes. Harrison used counterbalanced pendulums, hermetic seals, vibration isolation, and bimetallic elements to solve these problems. He is mentioned on DoTheMostComplexThingThatCouldPossiblyWork because his methodology was to "just add one more sprocket/spring/balance/brace" to his designs as he found and fixed flaws. However, he also knew when to StartFromScratch, since he came up with at least four separate prototypes over the decades that he spent tackling the longitude challenge. Eventually, he concluded that the only way to counter the effect of a ship's rolling motion was to make the clock as small as possible. His prototypes got progressively smaller ending with what we would recognize as a pocket watch.

* http://www.nmm.ac.uk/server/show/conWebDoc.355
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The mystery of the longitude. Ships travelling east-west (say from Europe to America and back) would lose track of longitude. Hundreds of people died when ships blundered into the coast of England by mistake.

Harrison invented a small clock, suitable for use on ships. Using this clock, a navigator going to the New World and back could determine longitude accurately.

Jonathan Swift satirized the astronomers' misguided efforts to solve the mystery of the longitude in Gulliver's Travels.

The astronomers, hoping to win the very large prize for solving the mystery of the longitude, refused to recognize that Harrison had solved the problem. This delayed the release of the technology for a generation - and probably killed many sailors.

One of the parts Harrison invented was the bimetallic strip, to compensate for temperature changes. This became the basis of many modern thermometers. ''In fact, he got the idea from his own very accurate '''all wooden''' clocks, which used multiple types of woods for various elements to achieve the same effect.''