Chaucer and the tides

Recently I came across a blog post discussing two geniuses from the 14th century, Guillame de Machaut and Nicole Oresme.

Machaut was musical and lived from 1300 to 1377. Oresme (~ 1320 to 1382) was a priest, professor, and scientist (natural philosopher). The blogger says that he can’t think of any other genius from the 1300’s and explains this by discussing a great famine in Europe that began in 1315. It was followed by the Black Death beginning around 1347. The two events, he says, killed a huge section of European population and caused social disruption. 

Yes. Surely. 

However, Mr. Moore misses out on Geoffrey Chaucer. Chaucer’s birth date is somewhat disputed, but a biography in 1977 gave it as the year 1340. Chaucer died in 1400. Hence he fulfills the requirement for living in the 14th century. Was he a genius? I’m going to be honest and say I’ve never read him but he is thought of as tremendously important to English literature.

What brings Chaucer to my mind is that in April of 2000, the magazine “Sky and Telescope” published an article by two astronomers discussing a story Chaucer wrote. (Because the article is so old it is cached elsewhere than the S&T website.)…-a061478926

The article seems to point to an incredible understanding of tides and star calculations. Elsewhere, Chaucer wrote about the astrolabe (not poetically); it was an important astronomical instrument of the times. He also “supervised construction of wharves in the port of London” and oversaw “repairs of ditches and walls on the lower Thames” as the Sky and Telescope article says. 

Clearly, to do that job well Chaucer would have had to know a great deal about how high or how low tides can get, and how often and, even, why. This knowledge is on display in the article cited above where a story from The Canterbury Tales hinges on the chance of an incredibly high tide in Brittany. The poetry includes a discussion of the Alfonsine tables (Toledan) and ends in the appearance of a specially and shockingly high tide in December. Excerpts from the poem are included in the article and, um, tough stuff. It includes “convenient proportionals” and “equations in everything”. Also, the rising of the moon, the eighth and ninth spheres, and Aries. “Full subtly he calculated all this.” Literary discussion of the poem might have missed something. 

The two astronomers writing for S&T discovered that in 1340 there was a specially and shockingly high tide. Brittany has very high tides anyway but according to the article all the conditions for a very high tide were met in a very unusual lineup of the sun, moon, and earth. The sun and moon were in the correct alignment for an eclipse which means they were in line with each other and their gravitational attraction on earth would be increased. Also the moon was at its closest approach to the earth and the earth was at perihelion, that is, its closest approach to the sun. These conditions are all met simultaneously every one or two thousand years. 1340 was just such a year. And the poem discusses how to find this conjunction.

Clearly medieval astronomers associated the tides with the moon. I discovered this story about Chaucer when I was studying Galileo and wondering what people might have said about the moon and the tides. Edmund Campion discussed the moon and tides with Queen Elizabeth in 1566 but Chaucer is hundreds of years earlier. It was one of Galileo’s worst mistakes to deny the association of the moon and the tides. He believed that the tides were caused by the double motion of the earth, rotating on its axis and revolving around the sun.

Oresme, by the way, is credited with thinking that the earth revolved on its axis, but the article on him at the Saint Andrews website of mathematical biographies points out an interesting fact. Oresme did wonder and write about the turning of the earth but at the end of his writing he specifically decides that it isn’t true. Nicolas of Cusa (1400 -1464) also discusses this idea from a very different angle.

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