John Harrison’s super-accurate clock helped solve the longitude puzzle

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Today's Google Doodle celebrates the watchmaker John Harrison, whose efforts to calculate length helped people discover their place in the world, literally.
Harrison was born 325 years ago in Yorkshire, England and grew up to become a watchmaker. Before dying in 1776, he developed a series of increasingly precise clocks that could be used to determine the position of a ship on the east-west axis of the globe, also known as its length.
The sailors had long used the position of the sun or polar star in the sky to determine latitude, that is, the distance from the equator in the north-south direction, according to The Conversation. But the calculation of the length was much more complicated, which led to fatal navigational errors: in 1707, for example, a collision of five ships off the coast of Cornwall killed 1,400 people. So in 1714, the British Board of Longitude announced a competition: £ 20,000 (or £ 1.5m in today's currency, The Conversation reports) would be awarded to whoever developed the most accurate way to calculate longitude at sea. One way to do it, at least in theory, was to use time.
Since the Earth rotates 360 degrees in 24 hours, that means it rotates 15 degrees every hour. So, if you know the time you are in and the hour in degrees zero (which is arbitrarily set in Greenwich, England), you should be able to calculate its length, explains the Australian National Maritime Museum. Then Harrison entered the competition with an artisan watch that could keep time accurately even at sea. And in the next 40 years, he perfected the technology. But he did not win the £ 20,000, at least not at the beginning.
In 1765, his son, William Harrison, took the fourth generation watch, called H4, or the sea clock, for a test trip to Jamaica. The sea clock passed the test, according to the Royal Museums Greenwich. But still, the Board of Longitude was not ready to call it the winner and ordered another test, this time to Barbados, against two teams that use methods that depend on astronomy instead of clocks.
The clock was accurate, but what the Board of Length really wanted was a "practical solution," according to a blog post by Oxford University Press by science historian Jim Bennett. That meant increasing the production of the watch, which would be a challenge with such a carefully designed device. The Board then agreed to grant Harrison a partial prize of £ 10,000. He only received the full amount after King George III insisted, according to the Smithsonian Time and Navigation series.
A convincing version of the narrative is that John Harrison solved the problem of length, but was snubbed by the scientific establishment, science historian Jim Bennett writes in a blog post for Oxford University Press. But that version of the story ignores the contributions of other watchmakers in the United Kingdom and France who were also moving towards the development of reliable chronometers. "It's hard to say without an important qualification that Harrison solved the problem of length in a practical sense," he says. But Harrison's work showed that it was really possible.


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