Luna (goddess) as Juno Covella, Juno of the crescent moon. Both Juno and Diana were invoked as childbirth goddesses with the epithet "Lucina". Luna is often depicted driving a two-yoke chariot called a "biga", drawn by horses or oxen. In Roman art, the charioteer Luna is regularly paired with the Sun driving a four-horse chariot ("quadriga"). Isidore of Seville explains that the "quadriga" represents the sun's course through the four seasons, while the "biga" represents the moon, "because it travels on a twin course with the sun, or because it is visible both by day and by night—for they yoke together one
Dynamics of the celestial spheres bodies are moved by angelic spirits, which govern and move them. He maintained, instead, that "celestial bodies are moved by their own natural inclinations similar to weight". Just as heavy bodies are naturally moved by their own weight, which is an intrinsic active principle, so the celestial bodies are naturally moved by a similar intrinsic principle. Since the heavens are spherical, the only motion that could be natural to them is rotation. Kilwardby's idea had been earlier held by another Oxford scholar, John Blund (c. 1175–1248). In two slightly different discussions, John Buridan (c.1295–1358) suggested that when God created the