August 15th: Chaucer’s Astronomy & Treatise on the Astrolabe

Date: August 15, 2009

Title: Chaucer’s Astronomy & Treatise on the Astrolabe

Podcaster: Dave Wilton

Links: http://www.wordorigins.org

http://www.sfaa-astronomy.org/

Description: Geoffrey Chaucer (c. 1340-1400) is most famous for writing The Canterbury Tales, but relatively few know that he also wrote the oldest surviving technical manual in English, The Treatise on the Astrolabe, which describes how to use that astronomical instrument. This podcast discusses Chaucer’s knowledge of astronomy, his Treatise on the Astrolabe, and touches upon various astronomical references in his poetry.

Bio: Dave Wilton is a graduate student studying medieval English literature and the editor of www.wordorigins.org. He is also an amateur astronomer and a member of the San Francisco Amateur Astronomers.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by the American Association of Variable Star Observers, the world’s leader in variable star data and information, bringing professional and amateur astronomers together to observe and analyze variable stars, and promoting research and education using variable star data. Visit the AAVSO on the web at http://www.aavso.org/

Transcript:

Whan that Aprill with his shoures soote

The droghte of March hath perced to the roote,

And bathed every veyne in swich licour

Of which vertu engendred is the flour;

Whan Zephirus eek with his sweete breeth

Inspired hath in every holt and heeth

Tendre croppes, and the yonge sonne

Hath in the Ram his halve cours yronne,

And smale foweles maken melodye,

That slepen al the nyght with open ye

(so Priketh hem Nature in hir corages);

Thanne longen folk to goon on pilgrimages,

And palmeres for to seken straunge strondes,

To ferne halwes, kowthe in sondry londes;

And specially from every shires ende

Of Engelond to Caunterbury they wende,

The hooly blisful martir for to seke,

That hem hath holpen whan that they were seeke.

I’m Dave Wilton, editor of the website wordorigins.org, student of medieval English literature, and an avid amateur astronomer. For the next few minutes, I’m going to be talking about Geoffrey Chaucer and his interest and expertise in astronomy. You may recognize those lines that I just read—they’re among the most famous in English literature—the opening to Chaucer’s The Canterbury Tales, written circa 1387, about a group of pilgrims traveling to Canterbury to visit the shrine of St. Thomas Becket. But what do these lines have to with astronomy? Did you catch the line that reads, “and the younge sonne hath in the Ram his halve cours yronne”? Chaucer is using an astronomical reference here, the fact that the sun is in the second half of its journey through the constellation Aries, or the Ram, to tell us when the events in the poem are happening, in mid-April to be specific. The sun is “younge” because it is close to the beginning of the new year, which in medieval times was reckoned as starting on the vernal equinox, and not in the beginning of January as we do today.

Astronomical references like this are littered throughout Chaucer’s poetry and the poet knew quite a bit about astronomy. And not just astronomy, his poems include references to alchemy, medicine, and physics as well. In fact, alongside his poetry, he also penned what may very well be the oldest surviving technical manual written in English—his Treatise on the Astrolabe.

For those of you whose last class in English literature was a long time ago, Geoffrey Chaucer was the greatest English poet of the Middle Ages, and he rivals Shakespeare as the greatest of all time. He was born around 1340 and died some sixty years later in the year 1400. A government bureaucrat by profession, he wrote poetry on the side. (Like it is today, back in the Middle Ages poetry did not pay a living wage.) He wrote in what we now call Middle English, a blend of Anglo-Saxon and Norman French. He is most famous for The Canterbury Tales, but he is also the author of The Book of the Duchess, The Parliament of Fowls, Troilus and Criseyde, and numerous short poems. He is often called the Father of English Poetry and credited with making literature in the vernacular of English, as opposed to French or Latin, legitimate. These are exaggerations, as there were skillful and inventive poets writing in English before Chaucer, but old Geoffrey is without a doubt the first among them. But here at 365 Days of Astronomy we’re not primarily interested in his poetry, but in one of his prose works, the Treatise on the Astrolabe.

Chaucer’s interest in astronomy strikes us as strange today because we don’t normally consider poets to be inclined toward, or even capable of, scientific work. But this was not true in the medieval world, where astronomy was considered one of the essential subjects in the education of a cultured man. Medieval universities taught seven subjects. The first three, grammar, rhetoric, and logic, were taught to beginning students and were called the Trivium, and from this we get our words trivia and trivial, topics that even a beginning student would know. Advanced students would go on to study the Quadrivium of geometry, arithmetic, music, and astronomy. We know almost nothing about Chaucer’s education, and it is unlikely that he attended university, but it is clear that he was extremely well-read and very well educated. He was the son of a wealthy London merchant and would have had many opportunities to attend the various schools in London, some of which were quite excellent with extensive libraries, and he would have had ample opportunity to learn about astronomy and how to use an Astrolabe.

What, you may ask, is an Astrolabe? The word comes from Greek roots meaning star-taker. You’re probably familiar with its modern, and much-simplified, descendant, the Planisphere, those round plastic disks used by amateur astronomers to orient themselves to the night sky. With an Astrolabe, you can determine the location of the sun and the stars in the sky for any particular day and time. An Astrolabe is a series of disks, a hollow disk called a Mater, or mother, that holds one or more other disks called Tympans, or climates. The rim of the Mater is engraved with gradations of time and degrees of arc. Each Tympan is made for a specific latitude and is engraved with a projection of the celestial sphere. Above the Tympan is another disk, the Rete, which is Latin for net. Most of the Rete is cut away, like a net, so you can see the Tympan below it. The Rete contains pointers to several fixed stars and a circle showing the sun’s annual progression along the ecliptic, divided into thirty degree segments, each representing one of the signs of the Zodiac. By manipulating the disks, the user can determine the time of day or night, calculate the time of a celestial event, like sunset, on a particular day, or use it to locate objects in the night sky. Linear and spherical versions of the device were also made, but the circular model was by far the most common.

Astrolabes date back to the ancient world—they were known to Claudius Ptolemy in the second century C.E.—but they reached their peak of development in the Arab world around the year 800, and were introduced into Europe around 1200. So for Chaucer, writing his Treatise on the Astrolabe around 1391, this was a state-of-the-art astronomical instrument.

Chaucer wrote his treatise for his son, Lewis, and the prose is appropriate for an instructional text intended for a young boy. Chaucer intended the work to consist of five parts, but he seems to have finished only the first two. Part One is a description of the device and its parts. Part Two are instructions for its use. Part Three was to be a list of the tables of longitudes, latitudes, and declinations for use with the Astrolabe. Part Four was to be a theory on the motions of celestial bodies. And Part Five was to be an overall introduction to Astrologie, a word which, to Chaucer, would include both of what we now call astrology and astronomy.

Chaucer drew on a number of sources for his treatise, most notably Masha’allah ibn Athari’s Composition and Operation of the Astrolabe. Masha’allah was a Persian Jewish astronomer from Basra who died in the year 815. Sections of Chaucer’s work are direct translations from Latin copies of Masha’allah’s earlier work. A second major source for Chaucer was Johannes de Sacrobosco’s Tractatus de Sphaera (or A Treatise on the Spheres.) Sacrabosco was a thirteenth century English astronomer who taught at the University of Paris. The idea of a poet with the stature of Chaucer lifting text from other authors may be surprising to us today, but the concept of plagiarism was unknown in Medieval times and writers freely took ideas and text from the work of others without recrimination.

Chaucer is also sometimes credited with writing another astronomical work, The Equatorie of the Planetis, which describes how to build a larger device, a Planetary Equatorium, that can determine the position of the moon and five planets, as well as the sun and the stars. It was written a year or so later than The Treatise on the Astrolabe, but the authorship is not known for certain; others ascribe it to Simon Bredon, a fourteenth century English astronomer, mathematician, and physician who taught at Oxford. Most scholars do not include The Equatorie of the Planetis among Chaucer’s works, believing instead that it was written by Bredon or someone else.

Other astronomical references in Chaucer’s works include in the poem The House of Fame, where he is the first English writer known to use the term Milky Way in a description of the night sky that appears in lines 935-39 of that poem:

“Now,” quod he thoo, “cast up thyn yë.

Se yonder, loo, the Galaxie,

Which men clepeth the Milky Wey

For hit ys whit (and somme, parfey,

Kallen hyt Watlinge Strete).

Milky Way is a calque, or translation, of the Latin phrase lactea via. These lines are also the first known use of the word galaxy in English. Chaucer isn’t using galaxy in the sense we do today, that of a large group of stars, but rather as another name for the Milky Way — the word galaxy comes from the Greek word for milk. And Watling Street is an old Roman road linking London with Dover; the reference here is probably to white paving stones.

And in Book III, lines 624-25 of his Troilus and Criseyde, Chaucer describes a planetary conjunction:

The bente moone with hire hornes pale,

Saturne, and Jove, in Cancro joyned were

Some scholars date the poem from these lines, as a planetary conjunction of the Moon, Jupiter, and Saturn in the constellation Cancer happened on 9 June 1385.

We generally don’t think of the Middle Ages as being a period of science, but the average medieval person was probably more familiar with the night sky than most people of our own time. The sky was essential for the calendar and for timekeeping, and astronomy was one of the core subjects in the curriculum of any good school. So while it may seem surprising at first that a poet of Chaucer’s stature would be so familiar with the skies as to make regular use of accurate astronomical data in his poems and was even proficient enough with the astronomical instruments of the day to write a manual on their use, when we think on it, it shouldn’t surprise us. Perhaps we should take a page from the medieval lesson book and blend astronomy and literature more often — it could only lead to a greater appreciation for the science, and add some poetry to what is often considered to be an exercise in mathematics and physics.

Thanks for listening, and here’s wishing you clear skies.

Sources:

Chaucer, Geoffrey. The Riverside Chaucer. Edited by Larry D. Benson. 3d ed. Boston: Houghton Mifflin, 1987.

Gray, Douglas. “Chaucer, Geoffrey (c. 1340-1400).” In. Dictionary of National Biography. Oxford University Press. 2004. http://www.oxforddnb.com/view/article/5191. Accessed 22 June 2009.

Oxford English Dictionary Online. June 2008. Oxford University Press. http://www.oed.com. Accessed 22 June 2009.

Price, Derek J. The Equatorie of the Planetis. Cambridge: Cambridge University Press, 1955.

Schmidt, Kari Anne Rand. The Authorship of the Equatorie of the Planetis. Cambridge: D. S. Brewer, 1993.

End of podcast:

365 Days of Astronomy

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