4 ms·

There is a feedback loop between accuracy of clocks and accuracy of charts. Measuring longitude requires an accurate clock on a ship, which can keep a reference

There is a feedback loop between accuracy of clocks and accuracy of charts. Measuring longitude requires an accurate clock on a ship, which can keep a reference time to compare with local solar time. The obvious challenges include motion of the ship and huge ranges of temperature encountered on global voyages. Britain invented the best maritime clocks by encouraging open competition for a large prize. https://en.wikipedia.org/wiki/Longitude_rewards https://en.wikipedia.org/wiki/Longitude_rewards See the book Longitude by Dava Sobel. You can see John Harrison's chronometers at the Royal Observatory in Greenwich - on the top of a small hill in a park in south-east London. It really is amazing how the original desktop clock monsters were shrunk down to a pocket watch that had better accuracy. Greenwich was the prime meridian because Britain invented the best clocks.

perilunar 3y ago
> Measuring longitude requires an accurate clock Not 'requires' — there are other ways to determine longitude. I've read the book and seen the clocks. They are amazing. > Greenwich was the prime meridian because Britain invented the best clocks. I think that's backwards though. They would have ruled the waves regardless, and Greenwich would have still been the prime meridian.
- mikhailfranco 3y ago
  Trafalgar 1805. Waterloo 1815. International Meridian Congress (Washington) 1884. France waits until they can adopt a name that does not mention Greenwich ... 1978. The French are very tenacious in their (to put it politely) arrogant obstructionist individualism. Shrug. https://en.wikipedia.org/wiki/International_Meridian_Conference https://en.wikipedia.org/wiki/International_Meridian_Confere... Resolution 2, fixing the meridian at Greenwich, was passed 22–1 (San Domingo, now the Dominican Republic, voted against); France and Brazil abstained. The French did not adopt the Greenwich meridian as the beginning of the universal day until 1911. Even then it refused to use the name "Greenwich", instead using the term "Paris mean time, retarded by 9 minutes and 21 seconds". France finally replaced this phrase with "Coordinated Universal Time" (UTC) in 1978.

perilunar 3y ago

> Measuring longitude requires an accurate clock Not 'requires' — there are other ways to determine longitude. I've read the book and seen the clocks. They are amazing. > Greenwich was the prime meridian because Britain invented the best clocks. I think that's backwards though. They would have ruled the waves regardless, and Greenwich would have still been the prime meridian.

mikhailfranco 3y ago
Trafalgar 1805. Waterloo 1815. International Meridian Congress (Washington) 1884. France waits until they can adopt a name that does not mention Greenwich ... 1978. The French are very tenacious in their (to put it politely) arrogant obstructionist individualism. Shrug. https://en.wikipedia.org/wiki/International_Meridian_Conference https://en.wikipedia.org/wiki/International_Meridian_Confere... Resolution 2, fixing the meridian at Greenwich, was passed 22–1 (San Domingo, now the Dominican Republic, voted against); France and Brazil abstained. The French did not adopt the Greenwich meridian as the beginning of the universal day until 1911. Even then it refused to use the name "Greenwich", instead using the term "Paris mean time, retarded by 9 minutes and 21 seconds". France finally replaced this phrase with "Coordinated Universal Time" (UTC) in 1978.