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Lost at Sea—The Search for Longitude

Program Overview


NOVA chronicles the seventeenth-century journey to determine longitude.

  • In 1714, following a maritime disaster, British Parliament offers £20,000 for the first reliable method of determining longitude on a ship at sea.

  • It is known that longitude can be found by comparing a ship's local time to the time at the port of origin. The challenge is finding a clock—a chronometer—that can keep time at sea, where temperature changes, humidity, gravity and a ship's movement affect accuracy.

  • Early attempts are based on the assumption that astronomy can solve the problem.

  • Self-taught clockmaker John Harrison believes the answer lies in large mechanical clocks. Through careful observation and experimentation, he invents many adaptations to improve clock accuracy. After decades of work, he realizes pocket watches are a better choice and redirects his efforts to pursue this smaller technology.

  • In 1764, Harrison's watch proves accurate in helping determine the longitude on a six-week voyage to Barbados.

Teacher's Guide
Lost at Sea—The Search for Longitude
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