13. The Heavenly Spheres

Yesodei HaTorah 3:1

There are spheres that are called “heavens,” “firmament,” “habitation” and “skies.” All together, there are nine. The closest sphere is that of the moon. The second sphere contains the planet Mercury. The third sphere contains the planet Venus. The fourth sphere contains the sun. The fifth sphere contains the planet Mars. The sixth sphere contains the planet Jupiter. The seventh sphere contains the planet Saturn. The eighth sphere contains all the stars that can be seen in the sky. The ninth sphere is the one that turns from east to west each day. This sphere surrounds and encompasses everything else. The planets and stars all look as if they are in one sphere, even though they are actually in layers, one inside the next. This is because the spheres are transparent. This causes the stars, which are in the eighth sphere, to appear closer than the first sphere.

Yesodei HaTorah 3:2

Each of the eight spheres containing planets and stars are subdivided into many smaller spheres, one inside the next like the layers of an onion. Some of these spheres turn from west to east, others from east to west as the ninth sphere does. There is no empty void between any of the spheres.

Editor’s note: I am not able to explain the Rambam’s astronomy. In Hilchos Kiddush HaChodesh (17:24), he says that it is based on the science of Greek astronomers. In Moreh Nevuchim, he is willing to disregard Talmudic dicta (3:14) and even Biblical verses (2:25) in favor of observable science when necessary. Readers are free to assume either that the Rambam was sharing the best science of his day, or that he is describing spiritual rather than physical phenomena.