It was in the fourteenth century that Chaucer lived and wrote, and his
interest in astronomical lore is, therefore, not surprising. Although the
theories of astronomy current in Chaucer's century have been made
untenable by the _De Revolutionibus Orbium_ of Copernicus, and by Kepler's
discovery of the laws of planetary motion; although the inaccurate and
unsatisfactory methods of astronomical investigation then in use have been
supplanted by the better methods made possible through Galileo's invention
of the telescope and through the modern use of spectrum analysis; yet, of
all scientific subjects, the astronomy of that period could most nearly
lay claim to the name of science according to the present acceptation of
the term. For, as we have seen, the interest in astrology during the
Middle Ages had fostered the study of observational astronomy, and this
in turn had furnished the science a basis of fact and observation far
surpassing in detail and accuracy that of any other subject.
Practically all of Chaucer's writings contain some reference to the
movements and relative positions of the heavenly bodies, and to their
influence on human and mundane affairs, and in some of his works,
especially the treatise on _The Astrolabe_, a very technical and detailed
knowledge of astronomical and astrological lore is displayed. There is
every reason to suppose that, so far as it satisfied his purposes, Chaucer
had made himself familiar with the whole literature of astronomical
science. His familiarity with Ptolemaic astronomy is shown in his writings
both by specific mention[1] of the name of Ptolemy and his _Syntaxis_,
commonly known as the 'Almagest,' and by many more general astronomical
references.
Even more convincing evidence of Chaucer's knowledge of the scientific
literature of his time is given in his _Treatise on the Astrolabe_.
According to Skeat, Part I and at least two-thirds of Part II are taken,
with some expansion and alteration, from a work on the Astrolabe by
Messahala[2], called, in the Latin translation which Chaucer used,
"Compositio et Operatio Astrolabie." This work may have been ultimately
derived from a Sanskrit copy, but from Chaucer's own words in the
_Prologue to the Astrolabe_[3] it is clear that he made use of the Latin
work. The rest of Part II may have been derived from some general
compendium of astronomical and astrological knowledge, or from some other
of the treatises on the Astrolabe which Chaucer says were common in his
time.[4]
Other sources mentioned by Chaucer in _The Astrolabe_ are the calendars of
John Some and Nicholas Lynne, Carmelite friars who wrote calendars
constructed for the meridian of Oxford[5]; and of the Arabian astronomer
Abdilazi Alkabucius.[6] In _The Frankeleyns Tale_ Chaucer mentions the
Tabulae Toletanae,[7] a set of tables composed by order of Alphonso X,
king of Castile, and so called because they were adapted to the city of
Toledo. Works which served Chaucer not as sources of information on
scientific subjects but as models for the treatment of astronomical lore
in literature were the _De Consolatione Philosophiae_ of Boethius, which
Chaucer translated and often made use of in his poetry; and the works of
Dante, whose influence on Chaucer, probably considerable, has been pointed
out by several writers, notably Rambeau[8] who discusses the parallels
between _The Hous of Fame_ and the _Divina Commedia_.