groups of people were aware of the phenomenon
much earlier. To recall some basic science, the
seasons are the result of the slant of Earth’s axis:
When the Earth’s hemisphere is inclined away
from the Sun, this results in winter; when the
hemisphere is inclined toward the Sun, this is
summer. The spin of Earth makes it behave like
a gyroscope (always tending to maintain the
same angle), but, because Earth is not perfectly
round, it tends to “wobble” a little. One result of
this wobble is that each year the Sun appears to
have moved ever so slightly backward (against
the backdrop of the relatively unmoving stars)
from where it was at the same point (e.g. at a
solstice or an equinox point) the preceding year
(at the rate of 1° every 71.5 years).
This precession is the reason that the
tropical zodiac, which most Western astrologers
use, is a “moving” zodiac: Following the admo-
nitions of Ptolemy, the great astrologer-
astronomer of antiquity, the beginning of the
Zodiac—0° Aries—is located where the Sun is
positioned during the spring (vernal) equinox.
Thus, each year the zodiac is moved very slight-
ly. This movement keeps the zodiac aligned
with the seasons, but it is always slipping back-
ward with reference to the stars. This is discon-
certing to anyone who feels that sign influence
emanates from the constellations after which
the signs of the zodiac take their names. Howev-
er, if one switches over to one of the sidereal
zodiacs (which align the zodiac with the stars), then the zodiac—which contains
much seasonal symbolism—slips out of alignment with the seasons. This means that it
is possible to make a good argument for either system.
Sources:
Bach, Eleanor. Astrology from A to Z: An Illustrated Source Book.New York: Philosophical
Library, 1990.
Filbey, John, and Peter Filbey. The Astrologer’s Companion.Wellingborough, Northamptonshire,
UK: Aquarian Press, 1986.
PRIMEVERTICAL
The prime vertical is the great circle that intersects the east point, the west point, the
nadir, and the zenith at any given point on Earth. It is perpendicular to both the
meridian and the horizon. Some systems of house division utilize this great circle as
THEASTROLOGYBOOK [543]
Prime VerticalRobert Fludd’s attempt to illustrate the theory of
precession. From the 1617 edition of Technica
Macrocosmi Historia. Reproduced by permission of
Fortean Picture Library.