In the west, since about 2000
years ago, there have been two schools of astrology that appear, to the
outsider, to be fundamentally opposed – tropical and sidereal - but astrologers
claim that there is no conflict. Astrology is a hugely complicated subject that
has grown and developed over 5 millenia in many different traditions. Here I'm
not planning to question the astrological interpretations themselves – tripe
though they may all be; but instead I'd like to focus on the astronomy involved
and what it can tell us about these two different astrological models.
Astrology basics
So as you probably know,
astrologers seek to make predictions about our lives, and about world events,
based on the “influences” of certain heavenly bodies. Of particular importance
in developing a person's chart are the relative positions of these heavenly
bodies at the time of birth. Depending on which system is used, the position of
the sun, the moon, the other planets of the solar system and various distant
stars are used and the angles between them are calculated and plotted in a
special way to develop the chart. The positions of each of these relevant
heavenly bodies are looked up and referenced using a chart called an ephemeris.
Of course there are numerous disagreements about how this process should be
done, and numerous different, contradictory ephemera. And numerous, different
interpretations of the influences. But don't let that put you off this
scientific, results-driven science.
Terran orbital mechanics
and how we see the universe
If you are already familiar
with the language and concepts in planetary geometry, you may want to skip this
bit. In order to make it is simple as possible, I'm going to explain everything
at a basic level.
The
Earth moves in three main ways – it
spins round on its axis, it orbits the sun, and it wobbles on its axis. The
period we call a day is the time taken for the Earth to do one revolution on
its axis. It takes a bit shy of 365 and a quarter days to go all the way around
the sun, which is simplistically the period of time we call a year. More on
this later. The wobbling on the axis is what is called precession, and is much
slower – one whole cycle of the wobble, known affectionately as a great year,
takes approximately 25,800 years (no one seems to be able to agree on the exact
length of time).
So, when we look from the
Earth at the skies, all these three motions play a part in the way we observe
the rest of the universe.
The daily spinning of the
Earth on its axis means that, through each 24-hour period, looking directly up,
we see a whole 360 degree panorama of the universe appearing to rush across the
sky from East to West.
The yearly motion of the
Earth's orbit round the sun means that over the course of a year, the time of
day that we see a particular star or constellation (from a given location on
the Earth's surface) gradually rotates around, coming round full circle in a
year's time. I'll make that simpler with an example. As I write, here in Los
Angeles at 130am, the constellation Perseus is just rising from the Eastern
horizon. At the same time of the night in a couple of month's time, it will
already be high in the sky. Next spring it will be invisible to the naked eye,
as it will only be in the sky during the day. On this day next year, it will once
again be rising in the sky at around 130am.
The
sun can be seen to “appear” in a series of certain constellations throughout
the course of the year. What this means is, that constellation is directly
behind the sun, from the Earth's perspective, depending on the time of year. (That is, assuming that there are no light bending effects of the type known to be exerted by dark matter and black holes). In
a way, the sun traces a path across the heavens, always “appearing” in the same
series of constellations in a constant cycle, year after year. This path is
called the ecliptic line. The movement of the moon across the skies is
essentially the same is this, tracing roughly the same line, except it cycles around the heavens in about a month
instead of a year. The other planets of the solar system can only be seen on or
close to this line, since the solar system is basically a flat plane. Their
periods and locations in the sky are more complicated.
Most of the stars, galaxies,
nebulae and so on can be said to have “fixed” positions relative to the Earth,
and to each other. Of course, this is bullshit. They are all moving at
thousands of miles per second, as is our own solar system, but since they are
all so far away we can't see this movement (without lab equipment) as it
appears to happen extremely slowly.
Precession and the
different ways of defining a year
So when you talk about a
year, what do you mean exactly? The period from New Year's Day to New Year's
eve? 365 days? Another cup final day?
In fact there are several
distinct and precise ways of defining a year. Two are important here:
a tropical year is the time taken for the Earth to complete one
360 degree orbit around the Sun, being defined by the time from one vernal
equinox to the next.
a sidereal year is the time taken for a “fixed star” to return
to the same position (at the same place and time).
Because of precession, being
the Earth's wobbling on its axis, these two years are of slightly different
lengths. This is because the two measurements are topologically different. A
tropical year is a function only of the Earth's orbit around the sun; whereas a
sidereal year is measured from the surface of the earth, which has it's own
independent movements. The sidereal year system has another degree of freedom,
as there are two mechanisms contributing to it.
To illustrate by example:
this year, the sun was very close to the star Omega Pisces (i.e. the Earth, the
Sun and that star were in approximate alignment) on the vernal equinox. They rose from the
horizon at about the same time. Next year, the sun will be about 50 seconds
ahead of that star. In 2018, the difference in rising times will be closer to 5
minutes. This is because, since the Earth has wobbled slightly, a given
location on Earth, at a given time each tropical year, is pointing in a
slightly different direction towards the heavens.
Another way of expressing
this is to go back to the apparent “motion” of the sun through the different
constellations of the ecliptic. On a particular time and day of the year (lets
say the vernal equinox) the Sun's position will gradually shift across the sky,
over thousands of years, such that at the end of the precession cycle it will
have cycled all the way around the ecliptic and back to it's start point.
Zodiacs and different
types of astrology
A zodiac is a map of the
ecliptic line that astrologers use. Most western astrologers use a zodiac that
is divided into twelve equal sections of 30 degrees each. These are just like
grid references on a map of a section of the Earth. The sections are named
after the real star patterns – Scorpio, Leo etc. but only loosely. (The real
constellations have varying angular widths and there are in fact at least
thirteen real constellations along the ecliptic).
The
starting point for the zodiac was set a long, long time ago as the “first” star
in Aires, Mesarthim. The sun was
directly on the line between the Earth and this star on the vernal equinox. In
a tropical zodiac, which defines a
year as a tropical year, this starting point of the zodiac always occurs on the
vernal equinox, March 21st.
However, because of
precession, over many years the position of the sun, (relative to the real
constellations along the ecliptic) on this date and time changes. Therefore a sidereal
zodiac takes into account the
precession cycle by shifting the start times of each “sign” according to what
is observed from Earth.
The difference means that
over time, these two different zodiacs have become out of sync with each other.
In fact, while Tropical astrologers have always defined the start of the sign
of Aires on March 21st, sidereal astrologers currently define its
beginning on April 15th.
(There is a third type that I'll
mention only briefly – where the “signs” are of varying length, defined by the
movement of the sun through the actual constellations in the ecliptic as
defined by the International Astronomical Union in 1930. This zodiac usually
has 13 signs (14 in some systems).
Even most astrologers think this system is bogus. “Reputable” western
astrologers generally agree that there should be twelve signs of equal length.)
What does this mean for
astrology?
To the lay observer, it seems
that at least one of these systems must be fundamentally flawed. If your
birthday is today, then in one system you're a gemini and the other you're a
cancer. All that gobshite about this sign means this and that sign means that,
its meaningless. At first glance it seems that tropical astronomy is the one
that is bunk, because the dates are so out of sync with the real
constellations. So if your horoscope is telling you that Jupiter is rising in
Aires, whilst a quick glance out the window clearly reveals it to be in Taurus,
it makes you question the validity of this amazing ancient divination tool...
But to be fair you need to
look a bit deeper than this really. According to most writers, the zodiacs were
never meant to be representative of the actual starscape, they were only
supposed to serve as a referencing grid system. One way of thinking about
tropical astrology is that its zodiac measures cycles of solar time and,
therefore, remains linked to the seasons on Earth. OK, well if that's the case,
why all the significance and symbolism around the constellations themselves
then? Why do we have to hear about Aires, god of war being influential in our
relationships and Libra bringing harmonious balance to our lives?
The tropical zodiac
preserves the Earth's solar cycle
Imagine each zodiac like a
measuring stick against the heavens. The tropical “measuring stick” is fixed to
the Earth's Solar cycle. The cycles and patterns of all other heavenly bodies
are out of sync with it. This means that the positions of the “constellations” themselves, and
the position of the planets in relation to them, should be meaningless in
tropical astrology, since the predictions of their locations via a tropical
ephemeris are incorrect.
Essentially, a tropical
zodiac is little more than a solar clock. Predictions made from it can only
really relate to cyclical effects of the Earth-Sun system. Some attempts to
justify astrology point to the possibility of the seasons having an influence
on foetal development, as a possible mechanism by which time of birth could
help predict personality. Of course, even if this were true, it would only
explain a tiny minority of the claims astrologers make.
The tropical zodiac does
allow comparison of the solar system bodies, however. Astrologers are very
concerned with the angles between Earth and the different planets. Using this
system, calculations of these angles
will be correct, although it does depend on where you get your data. Of course,
prediction of where in the sky the
planets actually appear will be skewed. But that doesn't matter to a tropical
astrologer as long as they are in the correct sign of the chart.
Also, position on the earth
isn't relevant either. This is because, over time, a particular place on Earth
moves slightly for the same date each year. It doesn't observe the same part of
the "measuring stick".
Say a prediction is made
about the influence of Sagittarius on someone born in New York. In tropical
astrology the same prediction might be made year after year for children born
at that place and time of year, but after hundreds of years, Sagittarius would
instead be rising over Oregon at that time, and Capricorn would be the actual
part of the zodiac “influencing” the birth (with whichever planets are
currently in that constellation).
The age of Aquarius is
only possible in Sidereal astrology
This is because the so called
ages come about due to the precession cycle. The Age of Aquarius is supposed to
begin when the Vernal Equinox shifts into the part of the zodiac known as
Aquarius. So if you hear any astrologers who follow the tropical system (most of the ones in the western world), talking about the dawning of a new age,
they are talking complete horseshit.
The sidereal zodiac
preserves the cycle of the ecliptic
On the flipside, sidereal
astrology maps the ecliptic with its zodiac in way fixed to a given location on
the Earth. It effectively charts and maps the constellations themselves. The
“measuring stick” is fixed to the distant stars. When these guys talk about the
positions of constellations and planets in the sky, over a particular place at
a particular time, they really mean it. However, this is at the expense of the
influence of the cycles of the seasons. This zodiac is out of sync with the
Earth-solar cycle. Also, it must be noted that the precise mechanics of
precession are not perfectly understood, so the length of a precession cycle is
not precisely known. It may oscillate and never be the same from one cycle to
the next, which means there will be inaccuracies in the sidereal zodiac also.
But as long as it is is based on (and updated according to) actual observation,
this doesn't matter too much.
Most writers agree that
Sidereal astrology was around long before it's tropical cousin, and sidereal
(and complex versions thereof) is still the most common form in the East.
Indian writers refer to tropical astrology simply as “Western”. Some say that
Tropical astrology is simply a more esoteric and mystical form, whereas
sidereal is more practical and factual. Some think that tropical is better for
predicting psychology, whereas sidereal is better for predicting events.
However, the best conclusion to come to, is that right from the off,
tropical astrology is complete crap. One huge mindfuck of a mistake that people
have been labouring under for the last 2000 years, and are still in denial
about it.
Think about it. In ancient
times, people believed that gods ruled the world and that the movements of
stars and planets had a real effect on peoples' lives. It's entirely
understandable that they would then invent a system for predicting the movement
of the stars and planets, in the hope that it could be used to predict events.
Before the days when humans really understood anything about astronomy, this
sort of logic is reasonable, if a little flawed.
|
Was Ptolemy on drugs when he made this? |
But then, someone came along
and said, “Ah ha! Well instead of using the real movements of the stars and planets, why don't we
simply refer to a fantasy one instead? We can use inaccurate information about
the heavens to make even more inaccurate predictions about our lives!”
Thinking about it, Ptolemy
was probably high as a kite when he came up with the first tropical zodiac
system. Looking over it the next day, and realising he'd made a big fuck up, he
probably invented all this new age stuff about linking the zodiac to the cycles
of the Earth, just so he could avoid losing his status and employment. Not that
I'm cynical about these things or anything.