POUVILLON RESTORATION PROJECT - November 2011
A discussion on the precession of the zodiac
There is strong
evidence that Pouvillon had included the precession of the zodiac as one of
the complications in his astronomical clock movement. The precession of the zodiac
occurs over a very long 25,806 year cycle;
the slowest moving hand on the great Celestial
This means that the lower zodiac ring that surrounds
the tellurian rotates once in nearly 26 centuries! Below is a description of
is and how it occurs due to the natural phenomenon of the Earth's
The Ecliptic is the Great Circle that describes the apparent path of the Sun
around the Earth (but which is really the orbit of the Earth around the Sun.
The Ecliptic extends approximately 8-9 degree of arc above and below (North and
South of) the actual path of the Earth/Sun. The other planets in the solar
system are always visible within this band of sky. The longitudinal
(East-West) position of celestial bodies (i.e. planets, asteroids, etc.) is
measured along the ecliptic
, see red ellipse in the first diagram. To the
observer on the ground the sun would be traveling through the sky past the
12 zodiac signs.
The Signs are units of measurement each equal to 30 degrees of arc along the
ecliptic and are ascribed in a fanciful way to local clusters of stars that
are visible to the naked eye at or very near each 30
demarcation, second diagram.
Vernal Point. The point measured along the ecliptic which represents the
apparent position of the Sun at the moment of the Vernal (Spring) Equinox.
At the moment of the Spring Equinox, the Sun is directly overhead
at mid-day along the Tropic of Cancer.
At one time in history, the Vernal Equinox used to indicate New Year's Day
in our annual calendar until Julius Caesar moved it to January 1 in 45 BC.
The names of our months still reflect March as the first month of the year.
In Latin, Septem is seven, Octo is eight, Novem is nine, and Decem is ten.
This is why the name of an age is determined by where the sun is on the
Vernal Equinox. The megalithic monuments like Stonehenge, Chichen Itza, and
Casa Grande are all trying to find the Vernal Equinox or the first day of
spring in the Northern Hemisphere.
Precession and Zodiac
However, the earth's axis is not stable. The earth is
not a perfect sphere, but flattens out at the poles and bulges at the
equator. It reacts to the the gravitational influence of the sun and moon
like a spinning top whose rotation is distorted by some external force: this
causes what has been termed the earth's precession - which means that the
earth's axis itself rotates in a circle, leading to a conical movement
around the fixed pole of the ecliptic. One complete rotation around this
cone takes roughly 26000 years. This shifting of the earth's axis causes the
celestial equator to shift so that the point of intersection between it and
the ecliptic - the vernal equinox - moves from east to west along the circle
of the ecliptic, i.e. in the opposite direction to the standard zodiac.
These three diagrams illustrate this wobble of the Earth's axis and its
effect on the apparent position of the stars in the sky. Note that the star
Polaris also known as the North Star which is currently directly over the
our Earth's axis of rotation will, in about 12,000 years, or just under one
half the precession cycle, be replaced by Vega.
First diagram, path taken by the point of
along the ecliptic over the past 6000 years
a view of the Vernal precession as seen from the ecliptic pole over a full
The Earth's precession can be easily observed by
standing at the Earth's north pole, where the north celestial pole is at the
zenith, and watching how that point changes over time (note the year in the
lower-left corner) in the animation.
It takes about
26000 years for the vernal equinox to make one complete revolution around
the ecliptic, i.e. through all of the twelve constellations. It takes around
one twelfth of this time - roughly 2160 years - to traverse one sign of the
zodiac. In antiquity the vernal equinox was situated between the signs of
Pisces and Aries, and because of its retrograde movement through the zodiac
is at present situated in the border zone between the constellations of
Pisces and Aquarius, moving slowly towards Aquarius. Because the
constellations lack clear boundaries, it is difficult to say exactly when
the vernal equinox will move from the constellation of Pisces into that of
Aquarius, i.e. when the so-called Age of Aquarius will begin. Depending on
where the boundary is drawn this will occur somewhere between 2100 and 2500
AD. The first diagram shows this progression as seen by an observer on the
ground. The second and third diagrams shows this as seen at a 90 degree angle from far
above the Earth north pole.
All of which begs the question of the value of
astrology and the popular belief in human characteristics being attributed
to the astrological sign one was born under. So the next time you're at that
tacky bar and someone asks you your sign, the appropriate response might be
'It all depends, which millennium were you thinking of?'
A Bit on Astrology and the
astrology no longer uses the background of fixed stars as a point of
reference. Modern western astrology uses the same system of reference as
that of astronomy, i.e. it divides the ecliptic into segments starting at
the vernal equinox. Although these segments have been given the same names
as the fixed star constellations, the earth's precession means that they are
no longer in line with the constellations of the same name. It is only in
certain specialist areas of astrology - such as mundane astrology when
studying larger epochal changes - that the relationship between these
constellations of fixed stars and the ecliptic has any significance.
References are then made to the "Ages" of Pisces, Aquarius etc. Other
non-western systems of astrology still work to some extent with alternative
systems to the ecliptically equinoctial coordinate system used by western
astrologers. Indian astrology uses a system which refers to the fixed stars
as its method of measurement, leading to a situation in which the position
of the zero-point has become a matter for dispute. This is because different
astrological schools in Indian astrology refer to different zero-points.
One of the most common arguments used against astrology
is that the statements astrologers make have long become obsolete. Astrology
claims that someone born on 30th March has the sun at 10° Aries, whereas in
reality on 30th March the sun is clearly in the fixed star constellation of
Claims such as this one are very confusing for those
interested in astrology. Do astrologers really live on the far side of the
moon, continuing to cling onto beliefs that science has long since debunked?
Confusion arises because both of the above statements regarding the sun's
position on 30th March are correct. On this date the sun is in both the
zodiacal sign of Aries and in the fixed star constellation of Pisces. These
statements differ because they are made within different frames of
reference. Something similar would occur if you were to call a friend in
London from Germany to discuss the time of day. The person in London might
claim that it is 10 am, whereas for you in Germany it would be 11 am. Both
claims are, of course, correct - within different frames of reference i.e.
The constellations are groups of fixed stars in the
sky. Since ancient times humans have pondered over their significance. The
strip of sky which is particularly relevant for astrology is the ecliptic
within which the planets of our solar system move. It is here that we find
(going round anti-clockwise) the twelve fixed star constellations of Aries,
Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn,
Aquarius and Pisces. These constellations are of widely varying sizes and at
times they even overlap. Because the patterns formed by these constellations
can be interpreted in a variety of ways, it impossible, for example, to say
where Capricorn ends and Aquarius begins. It is into this zone of the sky
(or celestial sphere) that astronomers project a perfect circle - the
ecliptic - formed by the earth's yearly orbit around the sun - or, for an
observer on the earth, the sun's apparent orbit around our own planet. The
ecliptic remains practically stable against the background of the fixed
stars. Astronomers today continue to use this circle as a point of
reference. In the ecliptical coordinate system a planet's location
is given using two numbers: the ecliptical longitude is
ascertained by measuring in an anti-clockwise direction from the zero-point
on the ecliptic, and the ecliptical latitude by measuring the planet's
deviation from the circle. Both of these readings are given in degrees. The
ecliptical longitude is measured from 0 to 360°. But where is the zero-point
on the ecliptic? The fixing of the zero is necessarily arbitrary - i.e. a
matter of definition. For geographical coordinates on earth, for example,
zero degrees longitude has been fixed at the astronomical observatory at
Greenwich in London. The zero-point on the ecliptic has been established by
using the vernal equinox in the northern hemisphere (Aequinoktium) - 20th or
21stMarch - the day on which day and night are of equal length over the
entire planet. This point is mathematically defined using the point of
intersection between the equator and the earth's orbit around the sun, i.e.
the ecliptic. The celestial equator is given by the position of the earth's
axis in space. If this axis were to remain stable the vernal equinox on 21st
March would be a fixed point in space.
At astronomy's high point in antiquity during the
hellenistic age from around 200 BC - 200 AD, the vernal equinox in the
northern hemisphere was situated on the border between the fixed star
constellations of Aries and Pisces. Astrologers at the time divided the
circle of the ecliptic into twelve equal segments of 30° using this
zero-point as a frame of reference. These segments were given the same names
as the fixed star constellations lying behind them. It is important to
distinguish these 30° degree segments of the ecliptic (or signs of the
zodiac) from the background of fixed star constellations carrying the same
name, which are both vaguely defined and of irregular size.