Tuesday, October 7, 2014

How a Clock Changed Hawaii

Harrison's H4 in National
Maritime Museum Greenwich
We sometimes wonder why it took ships from the west so long to find the Hawaiian Islands. European ships had reached China in 1517, hundreds of years before Captain Cook found the remote islands in 1778. Some of the mystery was solved for us when we recently learned about how John Harrison’s clock assisted Captain Cook.

Longitude is an entertaining  movie about John Harrison who invented the marine chronometer in the late 1700’s. At the time latitude (the distance of a ship north and south of the equator) could be determined from the sun or stars using a sexton, however, there was no method to determine the ship’s longitude (the east – west location) in the ocean.  Ships navigated by following the coastline, which worked when exploring Africa and Asia, but was not helpful when crossing the Atlantic to the Americas or crossing the Pacific Ocean.
So many ships were lost at sea or destroyed by crashing into reefs, that in 1714, the British Parliament offered a huge prize to anyone who could find a method to accurately determine a ship’s longitude.

The Royal Observatory at Greenwich, England was the reference longitude of zero degrees, called the Prime Meridian. The sun moves west from the Prime Meridian at a rate of 15 degrees each hour. If the time in Greenwich is known at exactly noon on a ship at sea (measured using a sextant to determine the exact moment that the sun reaches its highest point in the sky) the number of degrees of longitude the sun has crossed from the Prime Meridian to the ship can be calculated and the navigator can determine the ship’s longitude.  The problem is easily solved by having a clock on board the ship with Greenwich Time, however, in the 1700’s no clock existed that could keep accurate time over a long period or deal with temperature changes and a ship’s movement.

John Harrison was a carpenter and clock maker.  Before starting on the longitude challenge, he had already made several inventions that improved clocks including the "gridiron pendulum", which kept clocks from losing or gaining time due to temperature changes  and the "grasshopper" escapement which was a device for the step-by-step release of a clock's driving power which required no oiling. 

Harrison started working on a marine clock in 1730 in hopes of winning the prize.  “Longitude”, based on the book, Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time by Dava Sobel, tells the fascinating story of John Harrison and his son who spent decades working on perfecting a marine chronometer and proving it at sea.  Harrison’s first creation, called H1, was a monstrosity weighing almost 100 pounds.  In 1759 he finished his fourth version, called H4, which was a complete redesign and the size of a large pocket watch.  Harrison was eventually awarded the prize by the British Parliament in 1773 and recognized for having solved the Longitude problem.

In 1772, when Captain Cook sailed from England on his second voyage he had aboard a replica of Harrison’s H4 chronometer made by Larcum Kendall called the K1. Cook was able to navigate the Pacific Ocean using the K1 and discovered new islands including New Caledonia.  Cook was a superstar on his return to England in 1775 receiving honors, appointments and a promotion.  The K1 clock was exceptionally accurate during the entire voyage and Cook referred to the watch as  “...our faithful guide through all the vicissitudes of climates”.

John Harrison died in 1776, the same year Cook left for his third voyage to explore the Pacific.  On that voyage, in January 1778, Cook found the Hawaiian Islands where he met his demise.  When the ships returned to England, their report made the Hawaiian Islands and its longitude in the middle of the Pacific Ocean known to the rest of the world.

Having an accurate pocket watch, invented by Harrison, on board may have been partially or even completely responsible for Cook finding Hawaii.  It certainly allowed all the other Captains to navigate to the islands after learning the location. 

It makes us wonder what small inventions are in the works today that may alter our world in ways we may not be able to grasp.

1 comment:

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