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How John Harrison Stole the Longitude Prize

On my trip to the Royal Observatory in Greenwich, I learned about how important time was for navigation. In the 1700s, sailors had no reliable way to determine their exact position at sea, which often led to ships being lost and many lives being endangered. The primary challenge was determining longitude, as latitude could be measured with relative ease using the stars.

This became such a big problem that the King of England issued the longitude prize in 1714 to anyone who could find a practical solution to determine a ship’s longitude at sea. This substantial reward, worth £20,000 (equivalent to millions today), was intended to encourage innovation and provide a definitive answer to this critical navigational problem. The prize was administered by the Longitude Board, a group of astronomers and other experts who were tasked with evaluating the proposed solutions. They were primarily focused on astronomical methods, believing that the answer lay in the stars.

Over the next several decades, the prize languished. Solving the longitude problem even became a joke, with many attempts being ridiculed for their impracticality. One such attempt involved a scheme to use wounded dogs and a synchronization system based on the supposed healing powers of powdered dog bones. Another involved a plan to place stationary ships at intervals across the ocean to serve as reference points. Various methods were proposed, but none met the rigorous standards set by the Longitude Board.

Even though the astronomers couldn’t solve the problem, John Harrison, a self-taught clockmaker, managed to win the prize. The key to determining longitude is knowing the exact time difference between a reference location (like Greenwich, England) and the ship’s current location. By comparing the local noon (when the sun is at its highest point in the sky) with the time on the H4 chronometer, sailors could calculate how far east or west they were from the reference point.

Harrison’s H4 chronometer was tested on a trip to the West Indies in 1761. The clock’s accuracy was remarkable, losing only 5 seconds over a journey of 81 days. After a long voyage across the Atlantic, it allowed the crew to determine their position with unprecedented precision. For example, during the trip to Jamaica, Harrison’s chronometer enabled the ship to calculate its longitude correctly and avoid dangerous reefs and shoals. This successful demonstration proved that the H4 was capable of providing sailors with reliable longitude measurements, revolutionizing navigation and ensuring safer sea travel. Harrison’s accurate clock allowed for precise timekeeping, enabling sailors to determine their longitude accurately and safely navigate the seas.

Though Harrison’s clock clearly solved the longitude problem, the Longitude Board was loath to award the prize. Over the 40 years of their objections, they claimed that Harrison’s solution needed more testing and validation. They argued that his mechanical approach did not align with the astronomical methods they favored.

The biggest issue was that the longitude problem was an engineering problem rather than a scientific one. Harrison did what good engineers do: he focused on solving the problem effectively, not adhering to a specific method. This was very different from the scientific approach, which emphasizes the importance of methodology.

From Dava Sobel’s Book Longitude.