The weird way we discovered longitude

Originally published at: The weird way we discovered longitude | Boing Boing

The book, Longitude, is a really excellent read on the topic and I highly recommend it.

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As an alternative to Dava Sobel’s excellent book try this

That Will Self didn’t like it is a recommendation

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I’ll just add my recommendation. Well worth reading. John Harrison’s sea clocks are on display, still running, at the Royal Observatory in Greenwich, UK

Donning my pedant’s pendant for a moment (well actually, I never take it off (well to be precise I do take it off to shower)) we didn’t “discover” longitude. It was there all along as a way of mapping the globe. What was discovered was a practical means of determining longitude at sea.

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Just going to jump on the bandwagon here. The Dava Sobel book is terrific.

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According to wiki it was Hipparchus who invented the concept and came up with a method to determine it by using lunar eclipses. You needed to know the Earth was a sphere and know some math and astronomy before longitude would be useful. Lunar eclipses may have been good enough for placing cities on a map, but it was hardly useful for navigating ships.

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If you had the math chops, there were techniques on calculating longitude without clocks. Look at the early (pre 1930s) American Practical Navigator by Nathanial Bowditch. Before then, ships navigators would sail to the destinations Latitude and then follow the line till the destination. I can’t remember the specific term but it is still used today if your clocks are suspect.

If you want to read a good JA on Bowditch, check out “Carry On, Mr. Bowditch”. An excellent read I enjoy to this day.

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37.812010

-122.246110

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I see you!
image

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You see the historic landmark that I specifically chose to rep The Town.

:wink:

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You mean you’re not the national landmark?

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Adding my voice to this recommendation. It’s a superb read on so many levels.

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Decades ago I saw the Nova episode based on that book.

There were some interesting other ideas being considered, including a series of cannons spaced strategically across the ocean on islands and anchored ships to periodically mark the time with a loud blast. Would have been a pretty impractical solution but it tells you how desperate the British government was to find an answer.

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Instead of as a replacement, I would suggesting reading both, Sobel first so you can really get an appreciation for that telescope chair floating in mercury.

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Agreed, a great read. And the clocks are gorgeous objects even outside of their history; they were my prime (pun intended) reason for visiting Greenwich when I was in London the first time. (Seeing The Meridian was a nice bonus, and the park is lovely.)

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Dead Reckoning? Speed over Time on a specific bearing. Not just for latitude but to calculate a position relative to a last known position. It is affected by current and wind which can make it quite imprecise. Because of that, navigators would intentionally err to one side (say right), so that when they hit the opposite coast, they knew to turn left and sail down the coast to their destination.

Which is probably how the Vikings discovered North America, although to be fair they were hopping from land-mass to land-mass - Scandinavia > Scotland >Faroe Islands >Iceland >Greenland >Newfoundland and all points south.
Unlike Columbus who ignored what the Greeks had already worked out, the actual circumference of the world and underestimated by 5000 miles. Muppet.

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Would that be lunar distances

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