Okay, so, this thing:

A lot of people who’ve been around in Western occulture or astrology have probably encountered this image before in one context or another (it’s even appeared before on my own blog in a discussion about Ashen Chassan’s implementation of the Trithemian conjuration ritual and again when I discussed the Hermetic tormentors in CH XIII), and so many of us are familiar with this image to one degree or another.  True, it’s a really neat depiction of a Renaissance version of the geocentric Ptolemaic model of the solar system and cosmos, but there’s other stuff going on in it that I really want to explore and explain.

To start with, where does this image come from, and what specifically does it depict?  This illustration of the celestial spheres was originally made by the German humanist, mathematician, astronomer, and cartographer Petrus Apianus (anglicized as Peter Apian) in his 1524 work Cosmographia.  Apianus depicts this “scheme of the divisions of the spheres” for his second chapter, “on the motion of the spheres and the division of the heavens”.  At the center of the image we have the Earth, depicted as a circle of seas and land (corresponding to the elements of Water and Earth), surrounded by a sphere of clouds (Air) and that by flames (Fire). Outside the Earth, in successively larger concentric circles, we have the seven celestial spheres for the seven planets following the usual Chaldaean ascending order: Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn.  Skipping to the outermost edge of the whole thing (the eleventh “sphere”, as it were, though it’s really more like the infinitude beyond the spheres as a whole), we have “the Empyrean Heaven, Dwelling-place of God and of all the Chosen”. This is divine infinity beyond all the spheres, unlimited and unbounded and unmoving, under/within which all creation exists.  All straightforward stuff for most people, I suppose.

But it’s the stuff between the heaven of Saturn and the empyrean heaven that trip up a lot of people: the eighth, ninth, and tenth spheres.  To head off such speculation at the pass: no, it’s nothing qabbalistic or sephirothic in any meaningful sense (Apianus doesn’t appear to have been interested in such stuff).  Each of these circles in Apianus’ diagram all have the twelve signs of the Zodiac in them, but they’re respectively described as “the eighth heaven of the firmament”, “the ninth crystalline heaven”, and “the tenth heaven, the first cause”.  While all being zodiacal, they’re all somehow…different?  On top of that, they’re not all aligned with each other, only the eighth heaven has little stars in it, and the ninth heaven has this weird quartered-circle symbol at the ends of the sectors for Virgo and Pisces.  So what’s going on here, exactly?

Welcome, dear reader, to the funtime of medieval astronomy and cosmology!

Let’s start with the tenth sphere, the Primum Mobile (“First Mover”).  Ironically, despite being the most distant finite sphere of all (finite at least in comparison to the truly infinite empyrean heaven surrounding it), this is probably the easiest for us to approach.  The Primum Mobile is the outermost sphere and rotates endlessly, setting all things underneath/within it into motion as well, much like if you spin a pitcher of water, the water inside the pitcher itself won’t spin immediately but is set into motion by the spinning of its container.  In the old geocentric model of the cosmos, the Primum Mobile rotates constantly, performing one complete rotation every 24 hours, moving clockwise from the East to the South to the West to the North all the way back to the East.  According to Apianus, there exists precisely one and only one star in this tenth heaven.  Which star?  He doesn’t say and it’s not wholly clear to me, though if I were to leap to an assumption, I’d say that it’d be the northern pole star α Ursae Minoris (aka Polaris), given how this star was historically and culturally reckoned to be the axis (literally the “pole”) of rotation of all the heavens.

Let’s skip over the ninth heaven for a moment and take a look at the eighth heaven called the “firmament” in Apianus’ diagram.  This heaven is what contains the background stars of the nighttime sky that don’t wander around from night to night, month to month, or year to year.  This is why we call such stars “fixed stars”, as opposed to the “wandering stars” (ἀστέρες πλανῆται asteres planētai) of the planets (whose motion is defined according to their own heavens).  It’s because the eighth heaven of the firmament contains the fixed stars that Apianus’ diagram has all these stellated figures in this circle.  As for the motion of the eighth sphere, Apianus describes it as being subject to the motion of the tenth sphere such that they move all at once as the tenth sphere does, which is why the night sky as a whole rotates around the Earth once per 24-hour period.  Easy enough, I guess.

Between the eighth and tenth spheres is the ninth, described as “crystalline or aqueous” by Apianus (though just labelled as “crystalline” in the diagram).  First, what we can pick out is those two quartered circles.  Although they occur at the ends of the sectors for Virgo and Pisces, they’re really intended to be between these signs and the ones that follow to mark the equinoxes: the September equinox (occurring at the end of Virgo and the start of Libra) and the March equinox (occurring at the start of Aries and end of Pisces) respectively.  As for the motion of this heaven, Apianus says that the ninth heaven “vibrates” (trepidat), which causes the fixed stars in the eighth heaven to move forward and backward.  This would make no sense to modern folk today, but what Apianus is describing was a feature of older forms of astronomy: trepidation, a sort of oscillation in the precession of the equinoxes.  While an obsolete theory nowadays, trepidation has its origins as far back as the 4th century CE and was popular generally from the 9th to 16th centuries (putting Apianus roughly at the end of that period).

First, let’s back up a bit and talk about precession of the equinoxes (and yes, the ancients knew about axial precession all the way back in the 2nd century BCE).  Imagine a top, like the child’s toy: you pick it up, you give it a twist, and it spins around on its point upon a flat surface until it loses enough momentum to keep itself balanced.  At first, when the momentum is fast, the top stands upright, but as it continues, it eventually develops a kind of “wobble”, such that the axis of rotation is no longer precisely upright but ends up rotating on its own in a circle.  As the axis itself wobbles and rotates around, it causes the whole top to rotate in a different way on top of its already ongoing rotation around the axis, including the relative position of where such rotation around its axis “starts”.  This is what is meant by “axial precession”, and when it’s applied to the Earth as a whole, we call it “precession of the equinoxes” because it’s what causes the whole of the background sky to appear to “rotate backwards” relative to its daily regular motion—which includes the equinox points where the ecliptic (the Sun’s path around the sky) crosses the celestial equator.  The axis of the Earth precedes in a complete loop roughly once every 26000 years (currently 25772 years given our current observed rate of precession).

The theory of trepidation, on the other hand, suggested that the rate of the precession of the equinoxes was not a constant rate, but varied and could go either forward or backward.  In the original theory from the classical era, reversing its direction every 640 years or so.  Thus, given a rate of precession of 1° every 80 years, after 8° (thus 640 years), the precession would reverse into procession, such that the equinoxes would move forward eight degrees for the next 640 years, then reverse again, and so forth.  In later and more popular models from the medieval period (especially in Islamic astronomy), trepidation was more of a smaller, less-rigid variation that added to the motion of precession, where the oscillation provided by trepidation occurred over 7000 years, causing the precession of the equinoxes to take place over 49000 years rather than 26000.  It’s this later model that Apianus was describing and subscribed to when he says that the ninth heaven “trepidates”.

Interestingly, the ninth heaven (at least in Apianus’ model) was starless.  While the eighth sphere was full of fixed stars (all conceived of as being roughly the same distance away from the Earth in this geocentric model) and the tenth having just its one sole star (Polaris?), the ninth is a void having nothing in it—except, perhaps, the “waters which were above the firmament” (Genesis 1:7).  Apianus using this biblical model to describe the distant heavens would explain his description of the ninth heaven as being “aqueous”, and would moreover suggest that the wobbling of trepidation could be accounted for by the ripples and waves occurring in such celestial waters.

So there we have it!  We’ve finally knocked out what those intermediate heavens are in Apianus’ famous cosmological diagram, situated between the planetary heavens and the ultimate divine one.  While some of this might be a new thing for some, when placed in its own historical context, all of this is the natural development and expected evolution of a Renaissance take on the geocentric Ptolemaic cosmic model, depicted in a beautifully concise diagram.

But there’s still one issue left: why do the zodiacal sectors not line up in those eighth, ninth, and tenth heavens?  If you look at the eighth and ninth spheres, they line up exactly at Aries and Libra (the equinox points), but they seem to diverge slightly (starting at the east-north-east part of the diagram) before converging again (at the opposite, west-south-west part).  I have honestly no explanation for this beyond it being an artistic whoopsie; after all, sometimes considerations of space and communicability (in the form of the stellated figures and the circle labels) make accuracy and precision a secondary concern.  I feel like there should be a better reason than that, but I haven’t honestly found one beyond it just being something handmade in a constrained space.

But then there’s the dramatic mismatch between the zodiacal sectors of the eighth and ninth heavens with that of the tenth heaven, which can’t possibly be just a slip.  The tenth heaven has Aries starting at the due east point of the diagram, while the eighth and ninth heavens have it starting to the northeast.  What gives?

Well, using my handy-dandy free-to-use planetary observer software Stellarium for the year 1524, we can see exactly what’s going on:

The bright slightly-slanted orange line is the ecliptic, with the faint orange grid of lines being the ecliptical coordinate grid based off it to look at points in the night sky.  The bright more-slanted blue line is the celestial equator (which divides the sky into a “north” part and “south” part).  The ecliptic intersects with the equator at two points, which is where we call the equinox points.  In this case, the image above is centered on the March equinox point, where the ecliptic goes from being below the celestial equator (on the right) to above it (on the left).  The small squiggly faint blue lines in the background indicate constellations, and as you can see, the March equinox point is hanging out somewhere in Pisces, with Aries to the left and Aquarius to the right.

It should be remembered at this point that Western astrology (and historical astronomy, for that matter) has been founded on the notion of a “tropical zodiac”, which is to say a zodiacal system comprising twelve equal 30° segments of the night sky (according to the ecliptic) where the starting point of it (0° Aries) aligns with the March equinox point (where the ecliptic crosses to rise above the celestial equator).  Thus, we consider the segment from 0° to 30° of the ecliptic to be the sign Aries, from 30° to 60° Taurus, from 60° to 90° Gemini, and so on through from 330° to 360° (o°) to be Pisces.  The issue here—as many of my astrologer friends on Twitter are tired of hearing—is that this notion of “sign” doesn’t match up cleanly with the actual physical constellations of the night sky.  Although the constellations were more-or-less aligned with the signs once upon a time, due to precession of the equinoxes, the constellations began drifting “forward” from the signs while the signs drifted “backwards” from the constellations.  Again, precession here was something known to older astrologers from a very early date, so this came as no surprise to any of them—and it’s precisely this mismatch that Apianus is documenting between the eighth/ninth heavens and the tenth heaven.

Thus, in Apianus’ diagram, the tenth heaven’s zodiacal sectors represent the tropical zodiac (aligned to the seasons and the ecliptical crossing of the celestial equator), while the eighth and ninth heavens represent the actual constellations and stars of the sky (which would be a sidereal zodiac, literally “according to the stars” as opposed to according to ecliptical intersections).  This is why the equinox markers (those quartered circles) are placed in Pisces and Virgo in Apianus’ diagram (because technically we have those equinoxes occur while the Sun is in one sign according to the tenth heaven but in another constellation according to the eighth/ninth), and why the Aries sector of the eighth/ninth heavens in Apianus’ diagram start in the northeast rather than th eeast, just as it does celestially if you consider the March equinox point to be due (celestial) east.

Also, one more note: yes, it’s true that while the tropical zodiac doesn’t align with the constellations, neither does the sidereal zodiac.  In both of these zodiacal systems, we’re working with signs, not constellations, and a sign is defined as being a 30° segment of the ecliptic.  The tropical and sidereal zodiacs are identical in every regard except for one: at what point along the ecliptic it should start as being o° Aries.  The tropical zodiac defines this to always be the intersection between the ecliptic and the celestial equator, but the sidereal zodiac…well, it’s a little more complicated.  The sidereal zodiac aims to be closer to the constellations by using what’s called an ayanāṃśa to account for the precession of the equinoxes, and there are a number of different ones in use with some more popular than others (resulting in what’s technically a number of sidereal zodiacs rather than just one).  The issue with even this sidereal approach, however, is that the actual constellations themselves that lend their names and symbolism to the signs don’t neatly align with this equal-segments-of-30° approach.  Some signs are much shorter than 30° (as short as Scorpio’s 6°), some signs much larger (as large as Virgo’s 44°), and there’s even that dumb stupid notion of there being a “thirteenth sign” (Ophiuchus) because its constellation is considered close enough to the ecliptic to make it count (it doesn’t).

Courtesy of this article from Kosmic Mind, here’s a depiction and comparison of the tropical zodiac (inner circle), rough sidereal zodiac (middle circle), and the constellations (outer circle):

Apianus’ diagram makes use of a sidereal zodiac for the eighth and ninth heavens but a tropical zodiac for the tenth heaven, but does not bother with trying to use the constellations themselves (because they weren’t ever really used except perhaps in classical Babylonian or otherwise ancient Mesopotamian times).

Anyway, I thought this was all pretty neat to consider and learn about.  While we today all understand, given the advances of astronomy and physics we’ve had over the past five centuries since Apianus’ time, that a heliocentric model of our solar system is a more accurate descriptor of what’s going on, the geocentric model is still what we intuitively “see” and “feel” from our perspective down here on Earth.  It’s for that reason, coupled with the various and varied religious and cultural traditions that we inherit, that the geocentric model likewise helps us for innumerable spiritual endeavors and systems, too.  I mean, as a comparison, consider the following diagram, produced by Walter Scott in volume 3 of his Hermetica, page 374 in his discussion of the sixth Stobaean Fragment (SH 6):

SH 6 talks about the decans and their relationship to the signs and how their energies affect us down here, and in the course of such a discussion, we end up with a cosmological model again consisting of ten spheres: with the Earth in the center, there’s the seven planetary heavens around that, the eighth heaven of the Zodiac, the ninth heaven of the decans, and then the outermost heaven that wraps around everything.  In this fragment, Hermēs describes the heaven of the decans to be “in between the circle of the universe and that of the zodiac, dividing both circles”, and that the decans “buoy up, as it were, the circle of the universe and define the shape of the zodiac”.  Hermēs describes here also the motion of these heavens with each other, with the tenth heaven whirling constantly, the ninth heaven slowing it down and throttling it, and the planets being whirled around and accelerated by the motion of the decans; in this, the decans move both the planets as well as the outermost sphere of the cosmos itself.  It’s certainly not the same model as what Apianus was describing over a thousand years later, but there are certainly commonalities as both share in a common geocentric Ptolemaic ancestor, and both aim to describe the cosmos according to what we can see and observe down here on Earth.

Notably, we should also remember that what Apianus was getting at wasn’t so much to describe a spiritual reality of the cosmos, but rather a scientific one according to the science of his time.  His Cosmographia is an incredible and well-designed work, and besides the fascinating woodcarved illustrations also included little movable dials and tools that allowed readers to interact with the illustrations to learn about cosmology, geography, cartography, and other sciences.  As a result, it’s been argued that such a work as his not only facilitated better understanding of such topics popularly, but also spurred on the field of amateur astronomy precisely by equipping people with the basic tools they needed, preparing for and facilitating the later scientific revolutions that were to come.  However, even if his aim was more purely “scientific” in the modern sense of the word, we can’t neglect that such sciences are just one part of our lives, with the physical aspects to be integrated with the spiritual, which would also go a ways in explaining why Apianus’ cosmological diagram depicting the various heavens is so popular in occult discussions even today.  (And which also lends itself to some rather beautiful modern pieces of art as well.)

And yes, as the astrologer and geomancer Eric Purdue (yes, the same one who recently translated Cornelius Agrippa’s Three Books of Occult Philosophy afresh and correctly into modern English!) took the opportunity to reiterate on Twitter: the signs lie outside the stars, and we shouldn’t conflate signs with constellations.

The above post was originally a thread on Twitter, which you can read here but which I’ve reformatted and expanded into a proper blog post.  Although I made it earlier this summer and then promptly forgot about it, a conversation on one of the Discord servers I’m on reminded me that I wrote about it, so I figured that I may as well make it a bit more visible and readable.