Sailors knew how to measure latitude, their location north or south of the equator, but they could not measure longitude, their location east or west of their home port. Because of this, many lives were lost worldwide. The key to solving this problem lay in devising a clock that could keep absolutely accurate time while at sea, unaltered by rough water or weather conditions.
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Sea Clocks: The Story of Longitude
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Thomas Earnshaw and the Marine Chronometer
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History of longitude - Wikipedia
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Lost at Sea: The Search for Longitude (TV Movie 1998) - IMDb
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An illustrated version of a modern classic
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This Marine Chronometer Was the First Global Positioning System
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The Greenwich longitude exhibition on tour, History of science
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John Harrison's Marine Chronometers – London, England - Atlas Obscura
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John Harrison and the Longitude Problem Naval History Magazine - October 2019 Volume 33, Number 5
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Book review: Dava Sobel's “Longitude”
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Book Review: The genius who solved the longitude problem - SAFETY4SEA
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F】 Book Review: Longitude By Dava Sobel