SatNav and the man who “cracked” Longitude


“Here lies the real, hard-core difference between latitude and longitude—beyond the superficial difference in line direction that any child can see: The zero-degree parallel of latitude is fixed by the laws of nature, while the zero-degree meridian of longitude shifts like the sands of time. This difference makes finding latitude child’s play, and turns the determination of longitude, especially at sea, into an adult dilemma—one that stumped the wisest minds of the world for the better part of human history.”


To be brief, discovering a method of measuring Longitude in the 1700s was a “bit of a pig” until an amateur clockmaker entered the fray and battled royal astronomers, politicians, mathematicians, The Admiralty, and academics who believed that the “moon and stars” method was the answer. John Harrison was a simple carpenter from Yorkshire who they delayed, hindered, cheated, lied to, threatened ……. but they were wrong in their assumptions, and John Harrison eventually proved it to claim the £20,000 prize with his H4 model.


It’s a heck of a story you can read in Dava Sobel’s book Longitude, “The true story of a lone genius who solved the greatest scientific problem of his time” and you can see all of John Harrison’s models H1 to H4 at The Royal Observatory, Greenwich. These four mechanisms inside glass cases changed the world, saved countless lives, enabling navigation not only on the high seas but also within our modern day satnavs. We stood in awe of Harrison just looking at them, the final day of our Tour of England South Coast. You can also watch a marvellous 3 hour movie in two parts of John Harrison’s struggle on YouTube here Longitude

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