Peter Apian's 1524 representation of the universe, heavily influenced by Aristotle's ideas. The terrestrial spheres of water and earth (shown in the form of continents and oceans) are at the center of the universe, immediately surrounded by the spheres of air, and then fire, where meteorites and comets were believed to originate.  The surrounding celestial spheres from inner to outer are those of the Moon, Mercury, Venus, Sun, Mars, Jupiter, and Saturn, each indicated by a planet symbol. The eighth sphere is the firmament of fixed stars, which include the visible constellations.  The precession of the equinoxes caused a gap between the visible and notional divisions of the zodiac, so medieval Christian astronomers created a ninth sphere, the Crystallinum which holds an unchanging version of the zodiac.[4][5]  The tenth sphere is that of the divine prime mover proposed by Aristotle (though each sphere would have an unmoved mover).  Above that, Christian theology placed the "Empire of God".
 What this diagram does not show is how Aristotle explained the complicated curves that the planets make in the sky.  To preserve the principle of perfect circular motion, he proposed that each planet was moved by several nested spheres, with the poles of each connected to the next outermost, but with axes of rotation offset from each other. Though Aristotle left the number of spheres open to empirical determination, he proposed adding to the many-sphere models of previous astronomers, resulting in a total of 44 or 55 celestial spheres.
From Petrus Apianus; Gemma Frisius (1539) Petri Apiani cosmographia, per Gemmam Phrysium, apud Louanienses medicum ac mathematicum insignem, restituta: additis de adem re ipsius Gemmae Phry. libellis, ut sequens pagina docet, Antwerp: In pingui gallina Arnoldo Berckma[n]no [Arnold Birckmann], OCLC 1113627241. Schema huius præmiʃʃæ diuiʃionis Sphærarum. COELVM EMPIREVM HABITACVLVM DEI ET OMNIVM ELECTORVM Ⅰ0   ♌ ¦ Decimŭm Cœlŭm ♋ ¦ Primŭ Mobile ♊ ¦   ♉ ¦   ♈ ¦   ♓ ¦   ♒ ¦   ♑ ¦   ♐ ¦   ♏ ¦   ♎ ¦   ♍ ¦ 9   ♋ ¦ Nonŭ Cœlŭm ♊ ¦ Criʃtallinŭm ♉ ¦   ♈ ¦ ⊕   ♓ ¦   ♒ ¦   ♑ ¦   ♐ ¦   ♏ ¦   ♎ ¦⊕   ♍ ¦   ♌ ¦ 8 ••••••★ ♋ ¦ (•) Octaŭum •• ♊ ¦ (•) Firmamentŭ • ♉ • ¦ •••••• ♈ ¦ ••★••★••• ♓ ¦ •••★• ♒ • ¦ ••••••••• ♑ ¦ •••★ ♐ ¦ ••••••• ♏ ¦ ★•★ ♎ ¦ ••••••• ♍ ¦ ••★•••• ♌ ¦ 7 COELÛ   ♃ SATVRNI   ★ 6 ♄ IOVIS   ★ 5 ♂ MARTIS   ★ 4 ☉ SOLIS   ☼ 3 ♀VENERIS   ★ Z ☿ MERCVRII   ★ Ⅰ ☾ LVNÆ   ◯   ☽   ◯ (•) Star aligned with following word; only two sizes of stars are used, relative positions ignored English: The scheme of the aforementioned division of spheres. · The empyrean (fiery) heaven, dwelling of God and of all the selected · 10 Tenth heaven, first cause · 9 Ninth heaven, crystalline · 8 Eighth heaven of the firmament · 7 Heaven of Saturn · 6 Jupiter · 5 Mars · 4 Sun · 3 Venus · 2 Mercury · 1 Moon Latina: Schema huius praemissae divisionis sphaerarum. · Coelum empireum habitaculum dei et omnium electorum · 10 Decimum coelum primu mobile · 9 Nonu coelum cristallinum · 8 Octavum [coelum] firmamentu · 7 Coelu saturni · 6 [Coelu] Iovis · 5 [Coelu] Martis · 4 [Coelu] Solis · 3 [Coelu] Veneris · 2 [Coelu] Mercurii · 1 [Coelu] Lunae Compare to: Sacrobosco's De sphaera mundi