After puzzling scholars for 600 years, an astronomical riddle in the writings of Geoffrey Chaucer now at last appears to be understood. So says Donald W. Olson, a physics professor at Southwest Texas State University, who describes his detective work in the April issue of Sky & Telescope magazine.
Using modern astronomical calculations, Olson and two colleagues discovered a rare configuration of the Sun and Moon that actually occurred during Chaucer’s lifetime. It must have produced exceptional ocean tides similar to those described by Chaucer in one of his works.
Chaucer, who probably ranks second in importance only to William Shakespeare among English poets, left behind a famous collection of stories known as The Canterbury Tales. The one called “The Franklin’s Tale” is about a young squire eager to win the affections of a beautiful woman who lives in a castle on the rocky coast of Brittany, France.
To impress her the youth hires a magician and begs him to make the menacing offshore rocks disappear. After exacting an enormous fee, the magician performs an elaborate astronomical calculation and finally succeeds in making the rocks go away on a particular day in “the cold, frosty season of December.”
While the magician’s trick can be explained by an extremely high tide, most scholars have assumed the rocks’ disappearance was pure fiction, something dreamed up by the poet to suit the needs of his plot.
But Olson, aided by colleagues Edgar Laird and Thomas E. Lytle, notes that Chaucer was quite well versed in the astronomy of his day and even wrote a treatise on the use of an astrolabe. They felt there might be more to this story than meets the eye.
Their modern calculations show that on December 19, 1340, not only were the Sun and Moon aligned to produce an eclipse, but each body was very nearly at its least possible distance from the Earth – a rare combination that must have led to exceptionally high tides. This type of alignment has only occurred a handful of other times in recorded history; it will not happen again until A.D. 3089.
Of course, medieval astronomers (and Chaucer) lacked our modern concept of how tides are produced. But they did associate tidal ranges with astronomical phenomena.
A 13th-century treatise, for example, explained that “when the Sun and Moon are in conjunction, the power of the Moon becomes stronger and the tide increases and becomes strong.”
The same work went on to note that when the Moon “approaches the point nearest the Earth, its power increases, and then the rise of the sea is strong.”
Chaucer is known to have visited France several times in the 1360s and 1370s, and he must have been familiar with the remarkable tides for which the Brittany coast is so famous.
For centuries, tourists visiting Mont-St. Michel have walked out to the abbey at low water, then watched the rapidly rising flood tide turn the site into an island at high water.
But why might Chaucer have been aware of an exceptionally high tide that occurred years earlier, in 1340? Olson and his colleagues offer a fascinating theory.
Chaucer is believed to have been born in 1340, or perhaps early in 1341. As an older man learning about astronomy and astrolabes, he is likely to have investigated his own horoscope.
While calculating the positions of the Sun and Moon at the time of his birth, Chaucer might well have discovered the remarkable tide-raising configuration of December 19, 1340, and used it as the central plot device in “The Franklin’s Tale”!
