Download Tropical Zodiac versus Sidereal Zodiac

Tropical Zodiac versus Sidereal Zodiac
Writen by : Tanvir Chowdhury
http://www.scienceoftime.com
© Tanvir Chowdhury
The planetary position that Vedic Astrology (Jyotish) uses is not used by rest of the world.
Let us call what this Rest of the World does 'Western Astrology'. So, we have two models
of planetary position The 'Tropical' model (Sanskrit: Sayana), used in Western Astrology
The 'Sidereal' model (Sanskrit: Nirayana), used in Vedic Astrology
Based on the year for which you are making the horoscope, the two systems have a
difference of 23-24 degrees. That is a big difference because a sign is of 30 degrees, so
almost all the planets change signs when you are moving from one system to another. So,
which one is correct?
The Tropical position is based on an incident called vernal equinox. It is an incident
regarding the mutual position of the Sun and Earth in March every year, when the tilt of
Earth's axis neither inclines away from the Sun, nor towards the Sun. The axis is straight
standing with respect to the Sun. Just like the illustration on the next page.
Western Astrology directly takes this Tropical position of planets, which is based on the
incident vernal equinox, as stated above.
However, we must take something into consideration. We know Earth rotates on its own
axis. This axis is also moving very slowly. According to NASA's Jet Propulsion Laboratoy,
the movement in a year is as little as around 0.01°, so to move just 1° (one degree) the axis
takes almost 72 years. Thus, the axis of Earth takes around 25,771 years to complete one
cycle of circular movement. This movement is called precession (of the axis).
Now, because the axis of Earth changes place every year (for precession), the abovementioned vernal equinox (foundation of Tropical Zodiac) also changes place every year.
In simple words, vernal equinox of 2014 did not have Earth tilting (inclining) in the exact
same way, as it was tilting during the vernal equinox of previous year (2013). Because,
for the precession (movement), Earth's tilting-axis in 2013 has changed its place in one
year, and took a slightly different position (angle) in 2014 (than 2013).
So, since there is a precession (movement) of the equinox, anything which is based on
the equinox will also be influenced by this movement, and will have the same precession.
As Tropical zodiac is based on vernal equinox, it is also subject to the precession. So we
must correct the value for this precession (movement).
Vedic Astrology, takes this precession of equinox into consideration and makes correction
for the planetary position. This correction is called ayanamsa and what we get after
correction is Sidereal Zodiac. So,
Tropical zodiac + Ayanamsa = Sidereal zodiac
In 2001, when I encountered this topic for the first time, I actually could not believe that
the whole astrology-world is making such a big mistake. So I did quite a bit of study in
different astronomical websites. Astronomy has nothing to do with astrology, but it deals
scientifically about the stars, planets, their motions etc. as used by NASA for sending
satellites, rockets etc. So their opinion is both scientifically factual and impartial. And
guess what? All the astronomy sites clearly said that the vernal equinox is moving back,
it has moved to the constellation Pisces from Aries, and is slowly approaching Aquarius!!
So even modern astronomy says that Tropical Zodiac is wrong.
In fact, knowledgeable people, who disapprove astrology for being 'unscientific', have it
as one of their prime weapons against astrology, saying - "For the leaning of Earth's axis,
the zodiac is not in the same place where it was at the time of its discovery. So the
planetary positions are not true or real, which makes whole astrology fake!"... They are
actually right because they talk about Western Astrology (Tropical zodiac) and by using
an incorrect zodiac, Western Astrology indeed gave them the opportunity for critizing
astrology! But the non-believers do not know that there is another system of astrology, ie
Vedic Astrology, which does use the correct zodiac by applying an astronomical
correction.
Since this tilt of Earth's axis, with respect to the Sun, causes season-changes in
Earth, vernal equinox is important for marking the seasons. However, when we are
talking about planetary positions (of all planets), then we mean where the planets
are with respect to (comparing to) the zodiac- signs, or clusters of stars (constellation).
So in this second case, we must also calculate how much the Earth's axis tilted or moved
with respect to the zodiac-signs. Else, we are in a big, BIG mistake!
So in a nutshell, Tropical Zodiac focusses on the mutual position of the Sun and Earth,
but it does not make necessary correction to find out "Which location are the planets
staying in".
The planetary position we can see with our naked eye every night matches to the Sidereal
Zodiac, and not to Tropical Zodiac. I remember an institution of meditation,
named 'Clairvision School', used to offer a free Astrology software in 2001, named
'Canopus'. Though the software followed analyzing concepts of Western Astrology, it
clearly said that for planetary positions it preferred Sidereal Zodiac because it matches to
the astronomical reality more! So, Tropical Zodiac, is factually wrong.
Actually, Western Astrology is greatly influenced by the ancient Egyptian
astronomer Ptolemy who lived in the 2nd century AD. In that era, the Tropical and
Sidereal zodiacs WERE actually of the same position (roughly), but for the above-said
precession (movement), the zodiac moved for around 24° in the last 2,000 years (roughly)
- and we do need to make the necessary adjustment!
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