The signs, the constellations, and the precession of the equinoxes

Thousands of years ago, when the Babylonians were establishing the principles of astrology, the constellations and the signs of the zodiac were in alignment. On the vernal equinox (the first day of spring), the Sun was "in" the constellation Aries: That is, if you could see the Sun and the stars simultaneously, you'd see the Sun surrounded by the stars of the Ram. In those happy days, the signs and the constellations coincided.

Alas, this is no longer the case. On the vernal equinox today, the Sun shows up amidst the (dim) stars of Pisces the Fish - a very different kettle indeed.

The reason for this shift is that the Earth wobbles on its axis, which traces a circle in space like the spindle of a spinning top. As the axis shifts, the constellations seem to slip backwards. The amount of slippage over a human lifetime is minuscule, but over generations it adds up. As a result, every equinox takes place a little earlier in the zodiac than the one before. This process is called the precession of the equinoxes. It explains why the vernal equinox, which used to occur in the constellation Aries, now takes place in Pisces.

When the equinox moves back even further, to the constellation of the Water Bearer, the Age of Aquarius will officially begin. Astrologers differ about when that will be. Some are convinced that it's happening now. Others believe that it's decades - or centuries - away. Eventually, the cycle will begin again. Around the year 23800, the vernal equinox will return to Aries, and astrologers will be able to skip this entire explanation. Meanwhile, constellations of the zodiac and the signs of the zodiac arenít the same.

Skeptics who attack astrology - and for some reason, these wary souls can be amazingly hostile - often point to the changing position of the constellations and the precession of the equinoxes as proof that astrology is bogus. The truth is that astrologers are well aware of this phenomenon. They consider the constellations as signposts and little more. What matters is the division of the ecliptic. The stars, glorious though they are, have nothing to do with your sign.