[Nat]

There is an excellent and brainy podcast out there called Media Astra Ac Terra which I highly recommend to anybody who might be interested. She touches a bit on astrology - and she actually addressed a lot of this in her third episode back in March of 2009.

I'm not going to transcribe the entire thing, but I want to transcribe a bit. This shift is not something astrologers have been unaware of.

So here goes:

The fact that there are different systems of astrology brings up some of the other common objections people have to astrology, especially regarding the matter of precession. I mentioned in the "Astra" section today that for astrologers, the band of the zodiac is broken up into 12 equal stations whereas to astronomers, each constellation takes up a different amount of space. Because of this difference in definitions, and because of precession, the astrological signs do not always line up with the actual constellations anymore. Because the earth is tilted on its axis, the planet wobbles in its rotation and very slowly traces out the shape of a cone. This takes 26000 years, in fact, which is sometimes called a "great year." This change in the earth's rotation is called "precession," and one of its consequences is that the orientation of the earth relative to the stars changes. Because of those changes, the constellations of the zodiac and their corresponding signs no longer line up with each other. This is also the reason we're said to be moving toward "the age of aquarius," but that's another long topic that I won't get into right now.

Sidereal astrology, as opposed to the tropical astrology that I've primarily been talking about, attempts to compensate for the changes due to precession by shifting the signs back into allignment with their constellations. This system is primarily used in Indian or Vedic astrology, and by some Western astrologers as well. I have it on good authority from people I've known who studied it, that it works extremely well, yet I've also seen good results come from tropical astrology. So here's where my prefered model may come into play. Tropical astrology, which is what I have primarily studied, defines the signs relative to the date of the spring equinox. Hence, at the spring equinox, the sun enters the sign of aries, even though it no longer enters the constellation of aries at that time. To some, this discrepancy is proof that tropical astrology is fruitless, as it is no longer in sync with the actual constellations. But my thinking is that what matters is the motion of the planets relative to earth, and whether you measure that motion using tropical or sidereal divisions of the sky, is similar to whether you measure temperature in fahrenheit or celsius.

Then recently, she's released a new podcast: What's my sign? where she says a bit more:

As I mentioned in the introduction, there was a bit of a stir last week caused by a newspaper article that started in a Minnesota newspaper, but then attracted national, even international, attention. In that article, an astronomer with the Minnesota planetarium society announced that the commonly used dates for the sun's entrance into each sign of the zodiac were wrong, and provided new dates that were more in line with the actual alignment of the stars. And, since the sun sign is the one most people know and are attached to, the answer most people give when asked, "what's your sign?" a lot of people flipped out.

Now, the astronomer wasn't wrong, but he was only right up to a point. Because the earth wobbles on its axis, the apparent position of the constellations changes over long periods of time, and the constellations don't line up with the sun signs as they were originally defined. That much is true. But the question is, how much does this affect the practice of astrology?

The answer, as with so many things, is, "it depends." For most Western astrologers and astrology enthusiasts, it doesn't matter a bit. They treat the signs and constellations as entirely different things. There are other schools of astrology, however, that do adjust their dates to account for the changes in the apparent positions of the constellations as the Minnesota astronomer was proposing. In both cases, though, this issue has been known for a very long time. In fact, it has sometimes been a source of friction between the two camps. So, I was surprised at how it was being presented and taken as something new. And that's why I thought I'd talk about it a bit on this segment of the show...

There are two primary issues from the articles from last week. One is the precession of the equinoxes and the other is the difference, or lack thereof - depending on your school of thought, between signs and constellations. I'm going to take these in reverse order, starting with constellations. Constellations are groupings of stars in the sky that appear to have some relation to one another from our perspective here on earth. They appear to form patterns or pictures, although the stars that make up these patterns may be millions of lightyears apart when viewed in three-dimensional space. But seen as if projected onto a celestial sphere surrounding the earth, they look like they are close together.

The celestial sphere is an imaginary sphere surrounding the earth which appears to hold the stars and other celestial objects embedded in it. Once upon a time, this sphere was thought of as a physically real thing, but nowadays, it's used as a metaphor that allows these objects to be related to one another as if they were all on the same surface. Things like that are quite useful for navigation, and the constellations play a key role in defining an object's place on the celestial sphere. In fact, in modern astronomy, the patterns of stars called constellations have been further abstracted to define specific areas of that celestial sphere. Areas that go beyond the explicit boundaries of the star patterns themselves. In other words, you could draw lines connecting all of the stars in, say, Leo, but the officially recognized region called "Leo" is bigger than that. So, a deep sky object like the spiral galaxy M95 would be said to be "in" the constellation of Leo even though it lies outside the area defined by Leo's stars.

All 88 internationally recognized constellations are defined as areas like this, and these areas fit together like puzzle pieces that cover the entire celestial sphere. So something is always in one constellation or another. I am harping on this a little bit because I want you to keep this in mind when we get to the definition of a "sign" in astrology. The main point is that the constellations are patterns of stars as seen from earth, which in modern times have been further extracted to mean irregular areas that fit together to cover the entire celestial sphere.

Historically, 12 of these 88 constellations have been considered part of the zodiac. These 12 constellations lie along the ecliptic, which is the apparent path of the sun across the celestial sphere. Because the sun and the moon and the planets all appear to travel through these constellations, they have been given special importance by societies at least as old as ancient Babylonia. Because constellations are groupings of stars as seen by people from a particular culture, there are actually many different zodiacs just as the other constellations can differ from culture to culture. The division of the zodiac into 12 signs originated in Babylonian astrology, though they didn't necessarily use the exact same constellations to base those signs on. The Babylonians were a big influence on ancient Greek astronomy and astrology, however, and it's the Greeks who gave us the zodiac best known to us in the West today. In fact, it was primarily the work of Ptolemy in ancient Greece that gave us the system of astrological interpretation that dominated Western astrology for centuries. Very different systems of astrology, predominate in other parts of the world, however. Most notably Indian astrology and Chinese astrology. Neither of these is a subject I know much about, but I think it's important to be aware that there is nothing privileged about our particular definitions of the constellations and their meanings. These definitions arise not simply from the stars themselves, but from each culture's imaginative interaction with the stars as they appear from our perspective on Earth.

Even within Western culture, there are differences regarding what constellations are included in the zodiac, as highlighted in recent news articles about the "new" sun sign. Those articles mention a possible 13th constellation of the zodiac, named Ophiuchus, the serpent-bearer.



The serpent in question, by the way, is a separate constellation named Serpens, which is split into two pieces: Serpens Caput, or the Head of the Serpent and Serpens Cauda, or the Tail of the Serpent. Ophiuchus stands between the two halves. Ophiuchus was actually officially added to the band of the zodiac back in 1930, when astronomers mapped out and decided what the "official" boundaries of the constellations were going to be. So Ophiuchus bears the interesting distinction of being considered a zodiacal constellation by astronomers, but not an astrological sign. At least not for most astrologers, though there are exceptions. Mind you, references to the constellation date back to the 4th century BCE and it was included in Ptolemy's list of constellations in the 2nd century as well. It was just not considered part of the zodiac, historically speaking. But Ophiuchus highlights one of the central issues of the astronomy/astrology debate - the idea that the astrological signs of the zodiac are not the same as the constellations for which they are named. Basically, just as modern astronomers abstracted the constellations into larger puzzle-piece areas of the celestial sphere, the ancient originators of astrology as its come down to us, abstracted the zodiac into 12 equal divisions of the ecliptic. When they did that, they divided the ecliptic into signs that roughly corresponded to the constellations that appeared within each segment at the time. But even then, it was still an approximation. In both cases, we're dealing with abstract, artificially defined regions of the celestial sphere, each named for the grouping of stars that lies within it. But in the case of the zodiac signs, those regions are divided evenly into 12 equal stations, and in the case of the modern constellations, each one takes up a different amount of space.

The other major difference between these two schemes is that in astronomy, the region of the celestial sphere that defines a constellation is fixed relative to the stars within it, but, at least in Tropical astrology, which is still the most common system of astrology in the West, the region of the ecliptic that defines a sign is not fixed relative to the constellation behind it. This is an issue and a matter of some contention, because of a little thing called the precession of the equinoxes.

You know how if you spin a top, it might spin nice and evenly, its axis staying straight up, for a little while, but then it starts to wobble and that axis starts to move in wider and wider circles until the top falls over? That's precession and it's caused by gravity. In the case of the top, gravity is generally pulling along the axis of its rotation. But for the earth, the gravitational pull of the sun and the moon are coming from directions almost perpendicular to its rotation. Now, they aren't making the earth fall over, but because the earth spins on an axis that is tilted with respect to the ecliptic, and the earth is not a perfect sphere, the combined gravitational forces on the planet make it wobble. And because the earth wobbles on its axis, our position relative to the celestial sphere slowly changes. Which means the position of the constellations relative to earth slowly changes. This doesn't just affect the zodiac either. It's also why the North Star is currently Polaris, which is in the constellation of Ursa Minor, but it used to be a star called Thuban in the constellation Draco.

(Here she repeats some of what she said in episode 3)

It looks like the astronomer was using the international astronomical union definitions of the constellations to define the signs - which makes them all different sizes. Well, most sidereal astrologers hold to the idea of 12 equal 30 degree segments. They just line up the signs by aligning the start of the sign of aries with the brightest star in the constellation of aries.

On the other hand, tropical astrology, which is what I've primarily studied, keeps the starting point of the cycle fixed to the date of the spring equinox. So at the spring equinox, the sun enters zero degrees aries by definition, even though it's no longer in the constellation of aries at that time. The rest of the signs follow from there, which makes them more closely related to the cycle of the seasons than to the actual positions of the stars. what's important in tropical astrology is the position of each planet in a given 30 degree segment of the ecliptic - not its position in front of a particular set of background stars. And so, as I've mentioned, they simply see the signs and the constellations as two different things, with no need to adjust the one to line up with the other. This is the system of astrology most people are using when they look up their sun sign in a newspaper horoscope.

But there is one other concept related to the precession of the equinoxes, and that's the idea of astrological ages. The age of aquarius is the one we're all probably most familiar with, but what exactly does that mean?

When the zodiac signs were originally developed, the sun was in Aries at the spring equinox. Hence, it could be considered the age of Aries. Because of precession, though, this allignment changes, and in fact, the spring equinox appears to move backwards through the signs. Obviously in this case, we have to be talking about the signs in sidereal astrology since in tropical astrology, the spring equinox is always considered to be in Aries. So, when we're talking about the ages, after the age of Aries came the age of Pisces, and next up is the age of Aquarius.