Astrological Drama

Every few years or so, people in the media get around to noticing things that are new news to them, but which essentially amount to the ideas that water is wet and that the sky is blue. This week, there's apparently some big to-do about how the dates for the Zodiac have changed. About how, for example, someone who has always considered themselves to be a Virgo might now be a Leo, or any of the 11 other retrograde changes in someone's sign (Leo to Cancer, Cancer to Gemini, Gemini to Taurus, Taurus to Aries, etc.).

This is not really a big deal or cosmic event, and any astronomer and/or astrologer - be they amateur or professional - will just roll their eyes and sigh when the concept is mentioned. But journalists looking for readers tend to not know or care about actual facts, so they find a way to make it into a big deal when they can't find anything else to write about. Gotta love human nature, eh?

In any rate, the tacit "change" in the dates of astrological signs is the result of something call the Procession of the Equinoxes, which has been going on since the formation of our solar system. Over the course of a year, the sun moves through the entire 12 constellations of the zodiac in the sky, and traditionally your "sign" would be the constellation in which the sun stood on the day of your birth. Historical consensus is that the zodiac was developed by the Babylonians, about 3000 years ago. At that time, the start of Aries (which was the first day of the astrological year, and also the first day of spring) was measured by two astronomical events that essentially coincided. First, the sun - in its progression through the constellations that it makes (roughly) every year - passed from the area of stars that marked the constellation Pisces into the area of starts that marked Aries. Second, on about the same day, the sun crossed the ecliptic from south to north, which it does once every year, at the spring equinox. In ancient times, that day was called the "First point of Aries," and marked both the start of spring, and the start of the period where the sun was in the constellation Aries. Because the position of the sun and earth and stars in their eternal dance all lined up in that way at that time (3000 years ago), it was deemed important, and was set as the starting point of the Zodiac.

The problem is that we measure years based on the position of the earth relative to the SUN, rather than relative to the STARS. As we measure calendar years, the defining points are not the location of the sun in any given constellation, but instead are the equinoxes and solstices; the changing of the seasons. Because of the physics of planetary movement, there is a slight discrepancy between one calendar year (the time it takes the earth to make one complete orbit of the sun) and one "sidereal" year (the time is takes for the sun to make one complete circuit through the sky's constellations).

What this means is that there is a slight change in the position of the sun relative the the stars from year to year, called the procession of the equinoxes. For example - and as above - 3,000 years ago, the sun (when viewed from earth) passed from the area of the constellation Pisces into the area of the constellation Aries on about March 20, the vernal equinox. But if you happen to be paying attention to the sky this year (2011), the sun doesn't pass from Pisces into Aries until around April 18, weeks after the equinox (which is still on March 20). This is because in the last 3,000 years, the procession of the equinoxes means the stars behind the sun have slowly changed position, by about one degree every 72 years.

So the question is what day does someone's "sign" begin or end? Way back at the creation of the zodiac, that was an easy answer: the first day of Aries was BOTH the spring equinox, and the day that the sun passed from the constellation Pisces into the constellation Aries. But with the procession of the equinoxes, those two events no longer coincide: the spring equinox is now on March 20, but the sun doesn't pass from Pisces into Aries until April 18.

Most western astrology is (and has always been) based on the position that the start of the zodiac year (and the first day of Aries) is the spring equinox, rather than the date that the sun actually passes from Pisces into Aries. Since the equinox essentially always happens on March 20, and since the passage of seasons are much more noticeable here on earth than the movement of distant stars, we generally measure the zodiac the same way we measure years: by the SUN, not by the STARS.

So, the sun probably will not be in your "sign" on your birthday this year. But the sun was probably not in your "sign" on the actual day of your birth either. Since the calendar year and the zodiac year differ by less than one day every 70 years, the location of the sun relative to the stars on any given day is about the same today as it has been for decades. It's only when you measure time in centuries or millennium that the procession of equinoxes results in changes that the human eye can discern.

Periodic articles about signs "changing" reflect this difference in dates of the two central astronomical events: the equinox and the passage of the sun into the constellation Aries. All of the posts you see about the "new" dates for various signs are simply the dates that the sun is present in the various constellations. Use of those dates to define astrological signs ignores a central point of tropical astrology, which is that the first day of Aries is BY DEFINITION the spring equinox, with the other signs following in their various turns. Eventually, the procession of the equinoxes means that we will get back to square one, where the sun moves into the constellation Aries from the constellation Pisces on the same day as the spring equinox. But it is going to take a while, since the procession of the equinoxes makes one cycle every 26,000 years. We still have about 23,000 to go before we're back to that point.

In the meantime, your "sign" is still the same, so long as you apply the same definition of "sign" as you've been using your whole life, which is almost certainly based on the equinoxes. Regardless of the position of the stars bearing the same name as the "sign," Aries - by definition - starts at the spring equinox. If you want to calculate your sign based on the position of the stars rather than by the position of the sun (which is called the sidereal zodiac, as opposed to the tropical zodiac), then you can change your "sign." But even then, you've been that sign for your entire life, and the only thing you're actually changing is the definition you apply.

Hopefully I'm making this clear. But if not, the overwhelming point to take away from all this is that a slow news day will cause bored writers and columnists to try and make a big deal about pretty much anything, including astronomical/astrological points that have been in place since before any of us were born.