Once again a scientist has criticized astrology without knowing what he's talking about (see here and here). I wish they'd just talk with an astrologer. So many clients and students have written to me with concerns after reading the above articles that I find it necessary to re-publish an article I wrote many years ago.

The Tropical Zodiac

The Tropical Zodiac, that used by Western astrologers to determine the location of the Zodiacal signs in the sky, is based on the relationship between the Earth and the Sun. The Sidereal Zodiac, used by astronomers and Indian astrologers, is based on the relationship between the Earth and the stars, in particular the stars that make up the traditional Zodiacal constellations. Put simply, Western astrologers see no relevance in the positions of the constellations when determining the location of the Zodiacal signs.

Astronomers find this surprising, and indicative of a basic flaw in the reasoning of astrologers. I don't really understand why. Perhaps the astronomers think that because astrology was born during a time when the two Zodiacs lined up, there is an error in now separating them.

The problem stems from a phenomenon called the Precession of the Equinoxes. Due to a wobble in the Earth's axis of rotation, the point of the Vernal Equinox is slowly moving across the sky, in relation to the background stars. That is to say, the position of the Sun in the Spring when the lengths of day and night are equal - the "Equinox" - is slowly shifting year-to-year across the background constellations. Astrologers measure the position of the signs of the Zodiac based on this Vernal Equinox position. The first sign, Aries, extends 30 degrees along the Ecliptic from the Equinox position. The next 30 degrees is Taurus, then Gemini, and so on. The astronomers simply refer to positions along the Ecliptic as celestial longitude. They reserve the Zodiacal terms for what astrologers consider to be sections of the sky very vaguely indicated, not even defined, by the constellations.

The choice of the Tropical Zodiac by astrologers is not accidental, nor from their point of view erroneous. It is completely consistent with their overall approach to their ancient art. Astrology is essentially geocentric. It is an interpretation of the pattern of the planets of our Solar System in the sky as seen from the Earth. While many people think of astrologers as interpreting the "stars", actually most astrologers never deal with stars (other than our Sun) at all. We are focused on our local neighborhood, the positions and movements of the bodies that make up our Solar System. And again, we chart these bodies as viewed from the Earth. Our primary reference grid is based on the position of the Sun, as viewed from the Earth, on the Vernal Equinox. The apparent path of that Sun throughout the year - the Ecliptic - divided up into 12 equal sections of 30 degrees each, is that primary reference grid. The position of any given planet or other body along the ecliptic is stated in reference to that Vernal Equinox position. And that Vernal Equinox position is again based on the geocentrically viewed relationship of the Earth and the Sun.

The Sun is the primary body in the sky for inhabitants of the Earth. Both our daily cycle of day and night as well as that of the seasons are a direct result of that earth-Sun relationship. For astrologers the meanings of the Zodiacal signs are strongly connected to the cycle of the seasons (as experienced in the temperate zone of Northern hemisphere - the area where astrology has primarily developed). The meaning of Aries as an energy of initiation, beginning, surging forth, is strongly connected to the experience of organic life in the Spring. The meaning of Scorpio as an energy of death in preparation for rebirth is obviously connected to the retreating of organic life in the Fall so that it can re-emerge the next Spring. Again, the seasons are the result of the relationship between the Earth and the Sun (particularly the tilt of the Earth's axis toward or away from the Sun). As this axis wobbles, the seasons and the astrologers remain in sync with the current relationship. The positions of the stars in the constellations play no part in either our seasons or our Zodiac.

Please note an even more basic assumption at work here. Astrologers seek correspondences between our experience here on the Earth and the patterns observed in the sky. A primary aspect of our collective experience is that of the seasons. We find a correspondence between these seasons and the Earth-Sun relationship, so we direct our attention to this relationship. We see no correspondence between the seasons and the position of the Sun in relation to the constellations. An astronomer would agree with this. When mathematical astrology began perhaps 2600 years ago, the Earth-Sun relationship was such that the Vernal Equinox occurred against a background of the constellation Aries. While myth-makers and priests and story-tellers may have associated the experience of the seasons with the constellations, and further may have then maintained this association despite the increasing disparity between them, astrologers were not so misled. Astrology is essentially an empirical art. As precession moved the Vernal Equinox, the astrologers moved with it.