Ask Kevin: Tropical vs. Sidereal


The short answer to your question is no – you
can’t mix and match the zodiacs. You need to choose one system and stick with it.
There are some important philosophical reasons for this, but they’re part of the long answer.
We use the zodiac as a system of measurement to track the positions of the planets in along
the ecliptic. The ecliptic is a circle – it’s the apparent orbit of the Sun around the Earth,
although it’s actually the orbit of the Earth around the Sun.
The signs are units of measurement, equal to 30 degrees of arc, and they are named after
twelve of the thirteen constellations that cross the ecliptic.
The challenge with measuring along a circle is that a circle doesn’t have a beginning
or an end. You have to define a starting point. We call this point 0� Aries.
But here’s the real problem. You can’t look up in the sky and point to 0� Aries.
The Tropical Zodiac defines 0� Aries as the moment of the Spring Equinox in the Northern
Hemisphere. This is an observable, measurable event.
Because of the wobble in the Earth’s axis, the Spring Equinox moves backwards each year,
relative to the fixed stars. This is called the precession of the equinoxes, and it’s
a 26,000 year cycle. What this means is that today, the Spring
Equinox, which we define as 0� Aries occurs in the constellation of Pisces.
When astrology was being developed over two thousand years ago, the Spring Equinox occurred
in the constellation of Aries. But over the centuries, the Spring Equinox has precessed
into Pisces. The Sidereal Zodiac attempts to use the fixed
stars to identify 0� Aries (sidereal means star). The problem is that you can’t look
up in the sky and see the start of the constellation of Aries.
Every version of the Sidereal Zodiac uses mathematical calculations to estimate the
difference between 0� Aries in the Tropical Zodiac – an observable point – and where they
believe 0� of the constellation of Aries is.
At the moment, there’s about a 23� difference between the Tropical Zodiac and the Sidereal
Zodiac. Western astrology has always used the Tropical
Zodiac. The meanings of the symbols and signs have evolved based on these seasonal cycles.
Vedic or Jyotish astrology, practiced in India, has always used the Sidereal Zodiac.
The meanings of the symbols in Vedic astrology are quite different from the meanings of the
symbols in western astrology. The Vedic interpretation of the Sun in Virgo is entirely different
from the Western interpretation of the Sun in Virgo.
There is a small, fringe group of Western astrologers who use the Sidereal Zodiac with
western interpretations, but they’re a tiny minority. The overwhelming majority of Western
Astrologers use the Tropical Zodiac. But differences in interpretation aside, you
can’t combine the Tropical and Sidereal Zodiacs. You have to use one or the other.
Things like the choice of zodiac and the choice of a house system define the context of the
chart interpretation. Once you choose a system, you have to work within that system to come
up with your interpretation.

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