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The Age of Aquarius

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Wednesday 29 March 2017  •   1 Willow Moon 2017 (night)

For decades now people have been saying that the Age of Aquarius was on its way in, but nobody could really say exactly when it would start. The problem is the way modern Western tropical astrology works. The ecliptic, or line of the zodiac, passes through twelve or thirteen constellations, but not in equal measure, nor is it always clear where one constellation ends and another starts.

At some time over 2000 years ago, the good decision was made to split the ecliptic into 12 equal signs of 30° each, using the northern spring equinox as the starting point. The signs were named after the constellations that roughly co-incided with them. Since then the equinox has drifted, until now the signs are on average one constellation away from the one they were named after. It is this very drifting, the precession of the equinoxes, that determines the Great Ages.

The equinox takes about 25,000 years to move all the way round the sky, and during that time gives us twelve Ages, according to which constellation the Sun is in at spring equinox. However, exactly the same problems mentioned above now arise. There are currently thirteen, not twelve, constellations along the ecliptic, and they are not spaced equally. What is more, over the long periods involved, the angle between the ecliptic and the celestial equator varies, and the stars themselves move around. The constellation boundaries are fixed by the International Astronomical Union (IAU), but are subject to change.

Perhaps there is a more reliable measuring stick: the intersection of the ecliptic and the galactic equator, and the equal division of the ecliptic into twelve from that point. This nicely reflects the way the signs are determined by the equinox, which is the intersection of the ecliptic and the celestial equator (the projection of the Earth’s equator on to the celestial sphere), and isn’t subject to the vagaries of long-term drift. Using this method, and keeping to the current naming system, the Age of Aquarius began on about 7 May 1998. If you have a good astronomical program, you might like to try and discover when ecliptic longitude 270°, ecliptic latitude 0° co-incides with galactic latitude 0°. Using Starry Night Pro 5.0.1 (Mac version), the best time achievable is 12:06 UT ± 2 minutes on 7 May 1998, and this may be straining the accuracy of the program.

The term Galactic Ages can be used for Ages reckoned by this galactic method. According to data obtained from Starry Night, the Galactic Age of Pisces started in May 149 BCE, the Age of Aries in May 2314 BCE, Taurus in 4496 BCE, Gemini in 6689 BCE, Cancer in 8867 BCE and Leo in 11015 BCE. The next Age of Capricorn will start on 25 December 4124 (projecting the western calendar back and forwards). You can argue that the Age of Aquarius doesn’t start until the equinox is in the actual constellation Aquarius and, if we use current IAU boundaries, this doesn’t happen until the year 2597, as the constellation Pisces is rather large.

In the printed Moonwise Diary there is a measure of the Galactic Age at the beginning of each lunar month. This is the ecliptic longitude of the point where ecliptic latitude = galactic latitude = 0°, reversed so that longitude 270° is Aquarius 0°, 271° is Aquarius 1°, 299° is Aquarius 29° and 300° is Capricorn 0°.

The movement between Ages is slow and gradual, and we are very much in a transition period still.

William Morris
updated July 2005
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