All the planets that are easily visible to the unaided eye were known in
Chaucer's time and are mentioned in his writings, some of them many times.
These planets are Mercury, Venus, Mars, Jupiter, and Saturn. According to
the Ptolemaic system, which as we have seen, held sway in the world of
learning during Chaucer's century, the sun and moon were also held to be
planets, and all were supposed to revolve around the earth in concentric
rings, the moon being nearest the earth, and the sun between Venus and
Mars. The circular orbit of each planet was called its "deferent" and upon
the deferent moved, not the planet itself, but an imaginary planet,
represented by a point. The real planet moved upon a smaller circle called
the "epicycle" whose center was the moving point representing the
imaginary planet. The deferent of each planet was supposed to be traced as
a great circle upon a transparent separate crystal sphere; and all of the
crystal spheres revolved once a day around an axis passing through the
poles of the heavens. As the sun and moon did not show the same
irregularities[108] of motion as the planets, Ptolemy supposed these two
bodies to have deferents but no epicycles. Later investigators complicated
the system by adding further secondary imaginary planets, revolving in
Ptolemy's epicycles and with the actual planets attached to additional
corresponding epicycles. They even supposed the moon to have one, perhaps
two epicycles and we shall find this notion reflected in Chaucer. The
eighth sphere had neither deferent nor epicycle but to it were attached
the fixed stars. This sphere as we have seen earlier, revolved slowly from
west to east to account for the precession of the equinoxes, while a ninth
sphere, the _primum mobile_, imparted to all the inner spheres their
diurnal motion from east to west.
Chaucer's poetical references to the planets, as we have found to be true
in the case of the sun and moon, do not give us satisfactory evidence of
the extent of his knowledge, but occasional passages from his prose works
again throw light on these allusions. Chaucer refers to the planets in
general as 'the seven stars,' as, for instance, in the lines:
"And with hir heed she touched hevene,
Ther as shynen sterres sevene."[109]
and
"To have mo floures, swiche seven
As in the welken sterres be."[110]
Chaucer was undoubtedly familiar with the irregularities of the planetary
movements, and with the theory of epicycles by which these irregular
movements were in his day explained, although it is not from his poetry
that we can learn the fact. He uses the word 'epicycle' only once in all
his works. In the _Astrolabe_ when comparing the moon's motion with that
of the other planets, he says: "for sothly, the mone moeveth the contrarie
from othere planetes as in hir episicle, but in non other manere."[111]
In the _Astrolabe_[112] Chaucer explains a method of determining whether a
planet's motion is retrograde or direct.[113] The altitude of the planet
and of any fixed star, is taken, and several nights later at the time
when the fixed star has the same altitude as at the previous observation,
the planet's altitude is again observed. If the planet is on the right or
east side of the meridian, and its second altitude is less than its first,
then the planet's motion is direct. If the planet is on the left or west
side of the meridian, and has a smaller altitude at the second observation
than at the first, then the planet's motion is retrograde. If the planet
is on the east side of the meridional line when its altitude is taken and
the second altitude is greater than the first, it is retrograde; and if it
is on the west side and its second altitude is greater, it is direct. This
method would be correct were it not that a change in the planet's
declination or angular distance from the celestial equator might render
the conclusions incorrect.
Chaucer mentions the irregularity of planetary movements in _Boethius_
also when he says: "and whiche sterre in hevene useth wandering recourses,
y-flit by dyverse speres."[114] The expression "y-flit by dyverse speres"
may have reference only to the one motion of the planets, that is, their
motion concentric to the star-sphere; or it may be used to include also
their epicyclic motion. Skeat interprets the expression in the former way;
but the context, it seems, would justify interpreting the words "dyverse
speres" as meaning the various spheres of the planets to-gether with their
epicycles; i. e., both deferents and epicycles.
Of all the planets, that most often mentioned by Chaucer is Venus, partly,
no doubt, because of her greater brilliance, but probably in the main
because of her greater astrological importance; for few of Chaucer's
references to Venus, or to any other planet, indeed, are without
astrological significance. Chaucer refers to Venus, in the classical
manner, as Hesperus when she appears as evening[115] star and as Lucifer
when she is seen as the morning star: "and that the eve-sterre Hesperus,
which that in the firste tyme of the night bringeth forth hir colde
arysinges, cometh eft ayein hir used cours, and is pale _by the morwe_ at
the rysing of the sonne, and is thanne cleped Lucifer."[116] Her
appearance as morning star is again mentioned in the same work: "and after
that Lucifer the day-sterre hath chased awey the derke night, the day the
fairere ledeth the rosene hors _of the sonne_,"[117] and in _Troilus and
Criseyde_ where it is said that
"Lucifer, the dayes messager,
Gan for to ryse, and out hir bemes throwe;"[118]
Elsewhere in the same poem her appearance as evening star is mentioned but
she is not this time called Hesperus:
"The brighte Venus folwede and ay taughte
The wey, ther brode Phebus doun alighte;"[119]
Occasionally Venus is called Cytherea, from the island near which Greek
myth represented her as having arisen from the sea. Thus in the _Knightes
Tale_:
"He roos, to wenden on his pilgrimage
Un-to the blisful Citherea benigne,
I mene Venus, honurable and digne."[120]
and in the _Parlement of Foules_;
"Citherea! thou blisful lady swete,"[121]
The relative positions of the different planets in the heavens is
suggested by allusions to the different sizes of their spheres and to
their different velocities. In the _Compleynt of Mars_ the comparative
sizes and velocities of the spheres of Mercury, Venus and Mars are made
the basis for most of the action of the poem. The greater the sphere or
orbit of a planet, the slower is its apparent motion. Thus Mars in his
large sphere moves about half as fast as Venus and in the poem it is
planned that when Mars reaches the next palace[122] of Venus, he shall by
virtue of his slower motion, wait for her to overtake him:
"That Mars shal entre, as faste as he may glyde,
Into hir nexte paleys, to abyde,
Walking his cours til she had him a-take,
And he preyde hir to haste hir for his sake."[123]
Venus in compassion for his solitude hastens to overtake her knight:
"She hath so gret compassion of hir knight,
That dwelleth in solitude til she come;
. . . . . . . . .
Wherefore she spedde hir as faste in her weye,
Almost in oon day, as he dide in tweye."[124]
When Phebus comes into the palace with his fiery torch, Mars will not flee
and cannot hide, so he girds himself with sword and armour and bids Venus
flee. Phebus, who in Chaucer's time was regarded as the fourth planet, can
overtake Mars but not Venus because his sphere is between theirs and his
motion is consequently slower than that of Venus but faster than that of
Mars:
"Flee wolde he not, ne mighte him-selven hyde.
He throweth on his helm of huge wighte,
And girt him with his swerde; and in his honde
His mighty spere, as he was wont to fighte,
He shaketh so that almost it to-wonde;
Ful hevy he was to walken over londe;
He may not holde with Venus companye,
But bad hir fleen, lest Phebus hir espye.
"O woful Mars! alas! what mayst thou seyn,
That in the paleys of thy disturbaunce
Art left behinde, in peril to be sleyn?
. . . . . . . .
That thou nere swift, wel mayst thou wepe and cryen."[125]
In spite of his sorrow, Mars patiently continues to follow Venus,
lamenting as he goes that his sphere is so large:
"He passeth but oo steyre in dayes two,
But ner the les, for al his hevy armure,
He foloweth hir that is his lyves cure;[126]
. . . . . . .
After he walketh softely a pas,
Compleyning, that hit pite was to here.
He seyde, 'O lady bright, Venus! alas!
That ever so wyde a compass is my spere!
Alas! whan shal I mete yow, herte dere,'" etc.[127]
Meanwhile Venus has passed on to Mercury's palace where he soon overtakes
her and receives her as his friend:[128]
"hit happed for to be,
That, whyl that Venus weping made hir mone,
Cylenius, ryding in his chevauche,
Fro Venus valance mighte his paleys see,
And Venus he salueth, and maketh chere,
And hir receyveth as his frend ful dere."[129]
Mercury's palace was the sign Gemini and Venus' valance, probably meaning
her detrimentum or the sign opposite her palace, was Aries. 'Chevauche'
means an equestrian journey or ride, and is here used in the sense of
'swift course.' The passage, then, simply refers to the swift motion by
which in a very short time Mercury passes from Aries to a position near
enough to that of Venus in Gemini so that he can see her and give her
welcome. Mercury's sphere being the smallest of the planets, his motion
is also the swiftest.
The size of Jupiter's orbit is not mentioned in Chaucer and that of
Saturn's only once. In the _Knightes Tale_ Saturn, addressing Venus,
speaks of the great distance that he traverses with his revolving sphere
but does not compare the size of his sphere with those of the other
planets:
"'My dere doghter Venus,' quod Saturne,
'My cours, that hath so wyde for to turne,
Hath more power than wot any man.'"[130]
Besides the reference in the _Compleynt of Mars_ to the conjunction of
Venus and Mars[131], there are occasional references in Chaucer to
conjunctions of other planets. In the _Astrolabe_[132] Chaucer explains a
method of determining in what position in the heavens a conjunction of the
sun and moon takes place, when the time of the conjunction is known. A
conjunction of the moon with Saturn and Jupiter is mentioned in _Troilus
and Criseyde_, in the lines:
"The bente mone with hir hornes pale,
Saturne, and Iove, in Cancro ioyned were,"[133]