The Debate Regarding
the Tropical and Sidereal Zodiacs
— a Simple Resolution
By Peter Meyer
Written May 2010, published 2012-09-14.
The difference between the tropical (Western) and sidereal (Vedic) zodiacs is explained in my article The Influence of the Tropical and Sidereal Zodiacs on Personal Transits (where it is shown that the choice of zodiac affects the starting time and duration of personal transists).
The main debate among Western astrologers regarding the two zodiacs concerns the interpretation of the locations of planets in the natal chart in the signs. For example, someone born at noon GMT on March 28, 1957, will have Sun, Mercury and Venus all in Aries with the tropical zodiac, but with the sidereal zodiac these planets will all be in Pisces. The "qualities" of Aries are held to be leadership, enthusiasm, courage, impulsiveness, quick-temperedness and originality, whereas the "qualities" of Pisces are held to be joyousness, playfulness, poetic ability, sympathy for others, spirituality and intuition. So it surely follows (neglecting the other planets) that someone with Sun, Mercury and Venus in Aries will have a very different character to someone with these planets in Pisces, right? In which case the choice of zodiac is of major significance for the interpretation of a natal chart.
But there is a simple solution to this debate between supporters of the tropical zodiac and supporters of the sidereal zodiac, and that is to acknowledge that the signs have no value when interpreting a natal chart — only the aspects are significant.
When astrology began, in Mesopotamia in the 1st or 2nd millennium BCE, it was not possible to calculate the positions of the planets in a natal chart accurately, but with the help of tables the planets could be located with some broad degree of precision, perhaps to within 10° of their true value. By dividing the ecliptic into twelve equal parts, and locating the natal planets within these "signs", it was possible to get some idea of the aspects formed by the planets. For example, if a natal chart has Mercury in Pisces and Saturn in Scorpio then there's a good chance that these planets form a trine aspect. If Venus is in Taurus and Jupiter is in Leo then there's a good chance that these planets form a square aspect. And this is true regardless of how zero degrees Aries is defined.
Astrologers being what they are, in time meanings became attached to the signs, and came to play a role in the intepretation of a natal chart. It is likely that this occurred in Babylonia, before astrology spread west to the Greek world and east to the Indian world, which would explain why the signs have the same meanings in both Western and Vedic astrology.
But the signs are a human invention, whereas aspects are not (in the sense that the angular difference of the longitudes of two planets is what it is and does not depend on any human choices). The signs in which planets are located depends on the choice of a reference direction, the so-called zero degrees Aries. Vedic astrologers make one choice and Western astrologers make a different choice, and the result is that Vedic and Western astrologers locate planets in different signs (and thus, since they agree on the meanings of the signs, they give different and inconsistent intepretations of natal charts). In fact the two zodiacs are simply conventional ways of locating planets on the ecliptic, and to assert that one is superior to the other is like asserting that measuring distance in miles is superior to measuring distance in kilometers, or that measuring longitude in degrees is superior to measuring longitude in radians.
If one acknowledges that only the aspects between planets are meaningful, and that the signs that planets are in results from of an arbitrary choice of direction for zero degrees Aries, then there is no reason to debate which zodiac is superior, because (with the exception of personal transits as discussed here) aspects and transits are the same in both zodiacs. Whether one's Mars and Neptune are in Leo and Aquarius in the tropical zodiac, or in Virgo and Pisces in the sidereal zodiac, is of no significance compared to whether or not these planets are conjunct, square, trine, etc. So rather than interpret a natal chart in terms of which signs the planets are in, it is more reasonable to interpret the natal chart in terms of which aspects (if any) are formed by the planets — and how close those aspects are, and (in the case of personal transits) how long they last. The meaning of these is given by the qualities of the aspects and the archetypal qualities of the planets forming those aspects, which meanings are already well-known to astrologers.
The Influence of the Tropical and Sidereal Zodiacs on Personal Transits Archetypal Astrology Planetary Aspects and Transits Home Page