Longitude Essays

November 29, 2020 12:24 PM

He listed the viable projects for determining the longitude at sea. One was proposed in 1713 by William Whiston and Humphry Ditton, involving rockets released at fixed times from ships moored at sea. Newton actively supported both men and met Ditton in March 1714. But in June he told the committee of the scheme's difficulties since it would only help tell navigators their position near the coast. Newton also mentioned the design of a watch to keep exact time, but said such a watch had not yet been made, that two such watches would be needed, and that any watch would have to be checked against astronomical observations. Both rockets and exact clocks could keep longitude once known, not find it from scratch. Only astronomy would.

This essay is by Simon Schaffer. Part of a set of longitude essays:

This collection of essays provide a rich contextual background to the Longitude material available on the Digital Library. Covering a wide range of subject matter and fully linked into the other Longitude collections, they are intended as both a guide and a map to the collection. The essays include short biographies of key figures in the history of the Board, such as Nevil Maskelyne, John Harrison and Joseph Banks, explanation of key terms and concepts, such as dead reckoning and magnetic variation, and studies of specific instruments such as the artificial horizon and marine chair.

posted by smcg (9 comments total)

Nice - thank you for this!
posted by carter at 2:23 PM on November 29, 2020

It's hard to describe the reality of the ocean to non-mariners (I'm just a small sailboater) how isolated and directionless it can seem just hours off any coast. Chatted with an owner of a small ship how he'd woken to find his crew member had been making circles all night long. A little tech (compass, watch, sextant) goes a really long way but it remains non-trivial even with gps. A really cool book is Emergency Navigation that shows non-gps methods to just keep heading the same direction, like toward a coast.

An accurate clock changed the world, perhaps more than gunpowder.
posted by sammyo at 2:32 PM on November 29, 2020 [12 favorites]

Note a clock does not even need to be "right", as long as it adds or loses seconds at a regular rate, that can be calculated and measurements adjusted.
posted by sammyo at 2:35 PM on November 29, 2020 [2 favorites]

I read Dana Sobel's Longitude years ago and loved it. Favorite fun fat: Gallileo's solution involved careful tracking of the moons of Jupiter. Which it turns out is hard from the deck of a ship.
posted by kaibutsu at 4:40 PM on November 29, 2020 [11 favorites]

Longitude was made into a great TV series, available for $2 episode, $8 total on AmazonPrime apparently.

I rented it on DVD from Netflix back in the day, dunno if they have it now....
posted by Heywood Mogroot III at 4:56 PM on November 29, 2020 [2 favorites]

I read a related book I think called Transit of Venus (no, not that other one) about the 1800s expeditions which required synchronized chronometers to measure the parallax effect.
posted by RobotVoodooPower at 5:44 PM on November 29, 2020 [2 favorites]

I read a similar book on Venus's transit shortly before the 2004 event ("Transits of Venus are among the rarest of predictable astronomical phenomena. They occur in a pattern that generally repeats every 243 years, with pairs of transits eight years apart separated by long gaps of 121.5 years and 105.5 years. ... The last transit of Venus was on 5 and 6 June 2012, and was the last Venus transit of the 21st century; the prior transit took place on 8 June 2004. The previous pair of transits were in December 1874 and December 1882. The next transits of Venus will take place on 10–11 December 2117 and 8 December 2125." - Wikipedia)
posted by neuron at 6:09 PM on November 29, 2020 [1 favorite]

If you're into this subject, and also game for some weird, verbose, smart, punny, epic, and surprisingly moving postmodern historical fiction, check out Thomas Pynchon's "Mason & Dixon". It's a lengthy tome about the 2 guys who surveyed the eponymous line... but it starts long before they undertake that feat. The first part of the story deals with the struggle to figure out how to reliably determine longitude while at sea.
posted by Artifice_Eternity at 7:29 PM on November 29, 2020 [7 favorites]

Mason and Dixon, yes!!! I also think that the Quicksilver Trilogy by Neal Stephenson gets into some of this, maybe?
posted by Snowishberlin at 10:14 AM on November 30, 2020