Dante and the early astronomers

by M. A. Orr

Fig. 46. The Signs of the Zodiac as seen at sunrise from the Mountain of Purgatory at the autumnal equinox there (the vernal equinox in the Northern Hemisphere). Purg. ii. 55.

At 6 a.m. Aries is just rising, Libra the opposite constellation is just setting, while Capricornus has just reached the meridian. The signs follow one another in their diurnal course over the sky in the direction shown by the arrows, circling parallel to the celestial equator.

At the foot of the mountain they are joined by a band of spirits, and walking very slowly with them, conversing with Manfred, so much time passes that to Dante’s surprise, when they reach the place where the ascent is to be made (still on the eastern side), the sun has travelled fully fifty degrees since rising. As the sun passes over 360° in 24 hours, this indicates about 3½ hours after sunrise, or 9.30 a.m.[463] The climb to the first ledge is slow and very arduous, for as Virgil explains, the lower slopes are the most difficult, since the act of climbing becomes more and more easy as the ascent is made. Resting on a ledge, they look back and at the sun, and note how it has travelled north, so that it now strikes their left shoulders; and after a conversation with Belacqua Virgil begins to mount again, saying that it is noon. The other hemisphere consequently is all in darkness, from Ganges (“la riva”[464]) to Morocco.

Other spirits have been met and spoken with, and they are still climbing when evening comes, and Dante, thinking he is to reach the summit of the mountain and see Beatrice that day, entreats Virgil to hasten. “See,” he says, “how the mountain now casts a shadow.” For the sun has travelled round to the west, and the poets, still on its eastern side, are in deep shadow: this explains how, when they meet Sordello, he does not recognize that Dante is a living man, as all the spirits until now have done. But Virgil assures him that the way is longer than he knows: before they reach the summit, the sun, now hidden behind the mountain and not causing Dante to cast any shadow, will return again to the east.

Fig. 47. Northern slope of the Mountain of Purgatory, up which Dante climbed. Being in the southern hemisphere, this was the sunny side, and he followed the sun’s course, from east through north to west.

Immediately after this, they meet with Sordello, who tells them that it is impossible to climb even one step on the mountain after sunset, and leads them to a flowery valley, in which to rest for the night. The spirits in the valley sing the evening hymn while the sun sets; and it begins to grow dark while Dante is talking with judge Nino, explaining whence he came that morning. As soon as the stars become visible, his eyes seek the southern pole, and fix themselves on three brilliant stars which have taken the place of that constellation of four which he saw some fourteen hours before. The latter have travelled to the south-west, and are hidden behind the mountain, and the new constellation is above the pole towards the east.

Night has risen two steps and part of a third in this place when Dante falls asleep, and the most natural meaning of this is that it is somewhat more than two hours after sunset, or after 8 o’clock, in Purgatory. The moon has not yet risen, since she is like a clock which loses on an average 50 minutes every day.

Since the first morning in the Forest, when she was exactly 12 hours behind the sun and set at six o’clock, three whole days have elapsed,[465] and if she has lost 3 times 50 minutes, or 2½ hours, she will rise 14½ hours after the sun rises, that is 2½ hours after sunset, or at about 8.30. As the retardation varies much, let us say simply that she rises to-night between eight and nine o’clock. She has also moved among the stars, about 13 degrees each day, and as 3 × 13 = 39, and there are 30° in a zodiacal sign, she has passed out of Libra and is in Scorpio. Libra begins to rise at 6 p.m., and Scorpio at a little before 8, therefore part of Scorpio is now above the horizon.[466] This, then, is the meaning of the first two stanzas of Canto ix.: the mistress of Tithonus is the aurora before moonrise (the solar aurora being his wedded wife, according to classical mythology), and this pale aurora is showing white in her balcony of the eastern sky, while on her forehead shine the stars of Scorpio, the cold creature with the stinging tail.