The conspicuousness of astronomical lore in the poetry of Chaucer is due
to its importance in the life of his century. In the mediaeval period,
astronomy (or 'astrology,' for the two names were used indifferently to
cover the same subject) was one of the vital interests of men. The
ordinary man of the Middle Ages knew much more than do most men to-day
about the phenomena of the heavens; conveniences such as clocks, almanacs,
and charts representing celestial phenomena were rare, and direct
observations of the apparent movements and the relative positions of the
heavenly bodies were necessary for the regulation of man's daily
occupations. Furthermore, the belief in a geocentric system of the
universe, which in Chaucer's century was almost universally accepted, was
of vast significance in man's way of thinking. Accepting this view, all
the heavenly bodies seemed to have been created for the sole benefit of
man, inhabiting the central position in the universe; their movements,
always with reference to the earth as a center, brought to man light,
heat, changes of season--all the conditions that made human life possible
on the earth.
Not only did the man of the Middle Ages see in the regular movements of
the celestial spheres the instruments by which God granted him physical
existence, but in the various aspects of heavenly phenomena he saw the
governing principles of his moral life. The arrangement of the heavenly
bodies with regard to one another at various times was supposed to exert
undoubted power over the course of terrestrial events. Each planet was
thought to have special attributes and a special influence over men's
lives. Venus was the planet of love, Mars, of war and hostility, the sun,
of power and honor, and so forth. Each was mysteriously connected with a
certain color, with a metal, too, the alchemists said, and each had
special power over some organ of the human body. The planet's influence
was believed to vary greatly according to its position in the heavens, so
that to determine a man's destiny accurately it was necessary to consider
the aspect of the whole heavens, especially at the moment of his birth,
but also at other times. This was called "casting the horoscope" and was
regarded as of great importance in enabling a man to guard against
threatening perils or bad tendencies, and to make the best use of
favorable opportunities.
It is not astonishing, then, that the great monuments of literature in the
mediaeval period and even much later are filled with astronomical and
astrological allusions; for these are but reflections of vital human
interests of the times. The greatest poetical work of the Middle Ages,
Dante's _Divina Commedia_, is rich in astronomical lore, and its dramatic
action is projected against a cosmographical background reflecting the
view of Dante's contemporaries as to the structure of the world. Milton,
writing in the seventeenth century, bases the cosmology of his _Paradise
Lost_ in the main on the Ptolemaic system, but makes Adam and the
archangel Raphael discuss the relative merits of this system and the
heliocentric view of the universe. The latter had been brought forth by
Copernicus a century earlier, but even in Milton's day had not yet
succeeded in supplanting the old geocentric cosmology.
The view of the universe which we find reflected in Chaucer's poetry is
chiefly based on the Ptolemaic system of astronomy, though it shows traces
of very much more primitive cosmological ideas. The Ptolemaic system owes
its name to the famous Alexandrian astronomer of the second century A. D.,
Claudius Ptolemy, but is based largely on the works and discoveries of the
earlier Greek philosophers and astronomers, especially Eudoxus,
Hipparchus, and Aristarchus, whose investigations Ptolemy compiled and,
along some lines, extended. Ptolemaic astronomy was a purely geometrical
or mathematical system which represented the observed movements and
relative positions of the heavenly bodies so accurately that calculations
as to their positions at any given time could be based upon it. Ptolemy
agreed with his contemporaries in the opinion that to assign causes for
the celestial movements was outside the sphere of the astronomer. This was
a proper field of philosophy; and the decisions of philosophers,
especially those of Aristotle, were regarded as final, and their teaching
as the basis upon which observed phenomena should be described.
According to the Ptolemaic system the earth is a motionless sphere fixed
at the center of the universe. It can have no motion, for there must be
some fixed point in the universe to which all the motions of the heavenly
bodies may be referred; if the earth had motion, it was argued, this would
be proportionate to the great mass of the earth and would cause objects
and animals to fly off into the air and be left behind. Ptolemy believed
this reason sufficient to make untenable the idea of a rotatory motion of
the earth, although he was fully aware that to suppose such a motion of
the earth would simplify exceedingly the representations of the celestial
movements. It did not occur to him that to suppose the earth's atmosphere
to participate in its motion would obviate this difficulty. The earth was
but a point in comparison with the immense sphere to which the stars were
attached and which revolved about the earth once in every twenty-four
hours, imparting its motion to sun, moon, and planets, thus causing day
and night and the rising and setting of the heavenly bodies. The irregular
motions of the planets were accounted for by supposing them to move on
circles of small spheres called 'epicycles', the centres of which moved
around the 'deferents', or circles of large spheres which carried the
planets in courses concentric to the star sphere. By giving each of the
planets an epicycle and deferent of the proper relative size and velocity
the varied oscillations of the planets, as far as they could be followed
by means of the simple instruments then in use, were almost perfectly
accounted for.
Though it was a purely mathematical system which only attempted to give a
basis for computing celestial motions, Ptolemaic astronomy is of great
importance historically as it remained the foundation of theoretical
astronomy for more than 1400 years. Throughout the long dark centuries of
the Middle Ages it survived in the studies of the retired students of the
monasteries and of the few exceptionally enlightened men who still had
some regard for pagan learning in the days when many of the Church Fathers
denounced it as heretical.
Ptolemy was the last of the great original Greek astronomers. The
Alexandrian school produced, after him, only copyists and commentators,
and the theoretical astronomy of the Greeks, so highly perfected in
Ptolemy's _Almagest_, was for many centuries almost entirely neglected.
The Roman State gave no encouragement to the study of theoretical
astronomy and produced no new school of astronomy. Although it was the
fashion for a Roman to have a smattering of Greek astronomy, and famous
Latin authors like Cicero, Seneca, Strabo and Pliny wrote on astronomy,
yet the Romans cared little for original investigations and contributed
nothing new to the science. The Romans, however, appreciated the value of
astronomy in measuring time, and applied to the Alexandrian school to
satisfy their practical need for a calendar. What Julius Caesar obtained
from the Alexandrian Sosigenes, he greatly improved and gave to the
Empire, as the calendar which, with the exception of the slight change
made by Gregory XIII, we still use.
The pseudo-astronomical science of astrology, or the so-called 'judicial
astronomy' was pursued during the Roman Empire and throughout the Middle
Ages with much greater zeal than theoretical astronomy. The interest in
astrology, to be sure, encouraged the study of observational astronomy to
a certain extent; for the casting of horoscopes to foretell destinies
required that the heavenly bodies be observed and methods of calculating
their positions at any time or place be known. But there was no desire to
inquire into the underlying laws of the celestial motions or to
investigate the real nature of the heavenly phenomena.
If the Roman State did not encourage astronomy, the Roman Church
positively discouraged it. The Bible became and long remained the sole
authority recognized by the Church Fathers as to the constitution of the
universe. By many of the Patristics Ptolemaic astronomy was despised; not
because it did not describe accurately the observed phenomena of the
heavens, for it did this in a way that could scarcely have been improved
upon with the facilities for observation then available; and not because
it was founded upon the false assumption that the earth is the motionless
center of the universe about which all heavenly bodies revolve; but
because there was no authority in Scripture for such a system, and it
could not possibly be made consistent with the cosmology of Genesis.
Allegorical descriptions of the universe based on the Scriptures held
almost complete sway over the mediaeval mind. The whole universe was
represented allegorically by the tabernacle and its furniture. The earth
was flat and rectangular like the table of shew bread, and surrounded on
all four sides by the ocean. The walls of heaven beyond this supported the
firmament shaped like a half-cylinder. Angels moved the sun, moon, and
stars across the firmament and let down rain through its windows from the
expanse of water above.
By no means all of the early Church Fathers were wholly without
appreciation of the fruits of Greek astronomical science. Origen and
Clement of Alexandria, while believing in the scriptural allegories, tried
to reconcile them with the results of pagan learning. In the West, Ambrose
of Milan and later Augustine, were at least not opposed to the idea of the
earth's sphericity, and of the existence of antipodes, although they could
not get away from the queer notion of the waters above the firmament. A
few enlightened students like Philoponus of Alexandria, Isidore of
Seville, the Venerable Bede, and Irish scholars like Fergil and Dicuil,
studied the Greek philosophers and accepted some of the pagan scientific
teachings.
Fortunately the study of those ancient Latin writers whose works had
preserved some of the astronomy of the Greeks had taken firm root among
the patient scholars of the monasteries, and slowly but steadily the
geocentric system of cosmology was making its way back into the realm of
generally accepted fact, so that by the ninth century it was the system
adopted by nearly all scholars.
About the year 1000 began the impetus to learning which culminated in the
great revival of the Renaissance. One cause of this intellectual awakening
was the contact of Europe with Arab culture through the crusades and
through the Saracens in Sicily and the Moors in Spain. The Arabian
influence resulted in an increased sense of the importance of astronomy
and astrology; for, while the scholars of the Christian world had been
devising allegorical representations of the world based on sacred
literature, the Arabian scholars had been delving into Greek science,
translating Ptolemy and Aristotle, and trying to make improvements upon
Ptolemaic astronomy. The spheres of the planets, which Ptolemy had almost
certainly regarded as purely symbolical, the Arabs conceived as having
concrete existence. This made it necessary to add a ninth sphere to the
eight mentioned by Ptolemy; for it was thought sufficient that the eighth
sphere should carry the stars and give them their slow movement of
precession from west to east. This ninth sphere was the outermost of all
and it originated the "prime motion" by communicating to all the inner
spheres its diurnal revolution from east to west. In mediaeval astronomy
it came to be known as the _primum mobile_ or "first movable," while a
tenth and motionless sphere was added as the abode of God and redeemed
souls. The sun and moon were included among the planets, which revolved
about the earth in the order Moon, Mercury, Venus, Sun, Mars, Jupiter,
Saturn.
At first the astronomy taught in the universities was based on Latin
translations of Arabic commentaries and paraphrases of Aristotle, which
had made their way into Europe through the Moors in Spain. For several
centuries Aristotle represented in the eyes of most scholastics "the last
possibility of wisdom and learning." But by the middle of the thirteenth
century Ptolemy began to be rediscovered. The Ptolemaic system of
planetary motions was briefly described in a handbook compiled by John
Halifax of Holywood, better known as Sacrobosco. Roger Bacon wrote on the
spheres, the use of the astrolabe, and astrology, following Ptolemy in his
general ideas about the universe. The great mediaeval scholar and
philosopher, Thomas Aquinas, was also familiar with the Ptolemaic system;
but to most of the men of the thirteenth century Ptolemy's works remained
quite unknown. The real revival of Greek astronomy took place in the
fourteenth century when scholars began to realize that new work in
astronomy must be preceded by a thorough knowledge of the astronomy of the
Alexandrian school as exhibited in the _Syntaxis_ of Ptolemy. It was then
that Greek and Latin manuscripts of works on astronomy began to be eagerly
sought for and deciphered, and a firm foundation constructed for the
revival of theoretical astronomy.