Rambam- How Many Spheres Are Out There- Yisodei Hatorah perek 3 halacha 5

In this halacha the Rambam seems to contradict his previous assessment of how many Spheres there are. He says,


מספר כל הגלגלים המקיפין את כל העולם שמונה עשר. ומספר הגלגלים הקטנים שאינן מקיפין שמונה. וממהלך הכוכבים וידיעת שיעור סביבתן בכל יום ובכל שעה ומנטייתן מרוח דרום לרוח צפון ומרוח צפון לרוח דרום ומגבהן מעל הארץ וקריבתן יודע מספר כל אלו הגלגלים וצורת הליכתן ודרך הקפתן. וזו היא חכמת חשבון תקופות ומזלות. וספרים רבים חיברו בהן חכמי יון:


"The number of all of the Spheres that surround the Universe is 18. The number of all of the small Spheres that do not surround [the Universe] is 8. Knowing the path of the stars, the measurements of their rotations every day and hour, whether they lean towards north or south, and [knowing] how high above or close to the Earth they are will lead one to figure out how many Spheres there are, their form, their movement, and their circular path. This is the wisdom of calculations of seasons and the station of the stars (the zodiac). There are many books [on this subject] that have been compiled by the Greek sages."

The numbers 18 and eight seem to contradict the Rambam's previous number of 9. The first halacha in this perek says that there are 9 Spheres, so why does the Rambam contradict himself? The truth is that the Rambam does not contradict himself, rather these 18 Spheres are a description of the Spheres found within the 9 greater Spheres. This goes back to the Rambam's statement in the second halacha where he says that all of the 9 greater spheres are made up of many smaller Spheres.

The Peirush (unknown elucidation) on the Rambam describes how we come to the number 18 for the Spheres that surround the Universe. He tells us that the Sphere for the moon, that the Rambam mentioned in the first halacha, is really divided into three sub-Spheres. Also, the Sphere of Mercury, that the Rambam also mentioned in the first halacha, is also divided into three sub-Spheres. The next five Spheres Venus, the Sun, Mars, Jupiter, and Saturn are split into two sub-Spheres. Together thes sub-Spheres all add up to 16 Spheres and the remaining two are the last two Spheres mentioned in the first halacha, the Sphere that contains all other stars and the Sphere that goes from east to west that surrounds all the other Spheres and causes all other Spheres to rotate.

Before describing the 8 smaller Spheres, I think it is important to point out something from The Guide for the Perplexed. The Rambam states (Section 1 Chapter 72), "The number of these spheres encompassing the Universe cannot possibly be less than eighteen: it may even be larger; but this is a matter for further investigation." The Rambam clearly states that he did not have a perfect knowledge of the Universe, but still attempted to explain it according to the science of his time. Showing us that, eventually, his ideas about the planets might be outdated and that his ideas are not the sole way of learning these sciences. This shows his idea that, although halacha is unchanging, that doesn't mean scientific knowledge does not progress. However, one does not effect the other.

The number eight comes form the fact that the first seven of the Spheres, that are mentioned in the first halacha in this perek, all have a local Sphere that exists inside of them. It is called Pelech Tadvir(Which I believe translates into the continual spinning of the planets.) The Sun, however, is the only one of the first seven that does not have this quality and therefore, does not have this mini-Spheres. The last two Spheres, mentioned in the first halacha, also do not have this mini-Sphere because they do not contain a planet that can have the qualities of spinning continuously. This brings us to 6 mini-Spheres. However, Mercury and Venus are considered to have two mini-Spheres. Perhaps this is because they spin much faster than Earth and that is why it seems like they have an extra spin.