Now these two things, their light and their movements, were all the facts concerning the stars which mediæval astronomers could observe; and the movements were thought to be in circles and inconceivably rapid. Motion in circles, and especially the movement of rotation on an axis, remaining in the same place, had been said by Aristotle to be the most noble form of motion, and the fittest for celestial bodies. Therefore, when Dante represents the redeemed and the angels as expressing their bliss by radiance and marvellously rapid motion in circles, he makes them resemble the heavenly spheres and stars among which they manifest themselves to him. The motions are directly compared with those of stars in the passage already quoted:—
“Poi, sì cantando, quegli ardenti soli Si fur girati intorno a noi tre volte, Come stelle vicine ai fermi poli.”[316]
Remembering this significance of circular motion we shall feel a little less strange the similes of a mill and a top applied to the spirits of Paradise.[317]
A third way in which the spirits express their joy is by the sweetness of their song,[318] and here also they resemble the heavenly bodies, which make sweet music as they circle. This doctrine of Pythagoras was very popular throughout the Middle Ages.
4. THE GALAXY.
The Galaxy or Milky Way is twice referred to in the Divine Comedy. In Inf. xvii. 106-108, it is in connection with the myth of Phaeton, who being allowed by his father Jove to drive the chariot of the sun for one day, lost control of his chargers, and going all astray, burned the sky in a part which still shows signs of this catastrophe, i.e. the Milky Way.
“Quando Fetòn abbandonò li freni, Per che il ciel, come pare ancor, si cosse.”[319]
This of course is only a poetical myth. But in the Paradiso, in three lines the appearance, colour, and approximate position of the Galaxy are described, and allusion is made to the difference of opinions between learned men with regard to the puzzling question of its nature. Dante is in the heaven of Mars. He sees the soldier saints, star-like and fiery red, some larger and some less, thronging thick in two great bands, which, crossing one another in the depths of the planet, form a marvellous Crucifix. The crowded lights make him think of the Galaxy, with its multitudinous points of light, differing in brightness, although that is white, and lies in a great circle between the celestial poles.
“Come, distinta da minori e maggi Lumi, biancheggia tra i poli del mondo Galassia sì che fa dubbiar ben saggi, Sì costellati facean nel profondo Marte quei rai il venerabil segno Che fan giunture di quadranti in tondo.”[320]
If we now turn to the fifteenth chapter of Treatise II. of the Convivio, we shall find the Phaeton myth and the various theories about the Milky Way set forth in due order, and shall learn which of these Dante considered to be true.