On sidereal and tropical zodiacs

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Sorry it took a bit longer to get the drawing scanned. Here is the

text. The file in the library area contains a few diagrams to help

understand the issue:

 

A recent discussion on the Jyotish remedies board prompted this

little piece written by me, as

promised.

It is a widely held belief that the sidereal and tropical zodiacs are

similar to two rings that twirl at

a very slow rate completing one turn in approximately 25500 years or

so and this then gives rise

to the wildly debated matter of ayanamsha, the precessional

correction to be applied to the

synetic vernal point or simply stated, the moment of vernal equinox

(in northern hemisphere)

which determines the starting point of the tropical zodiac used in

western astrology – and gives

rise to the sun-signs which has prompted the writing of many books to

describe it.

A thought was presented to indicate that this widely held belief may

not be correct and perhaps

the two zodiacs never really meet!

Some basic facts now: The zodiac named so for the animal shapes

(zoon=animal) is a belt of

stars that lie close to the annual path of the sun. The sun is not

really moving but the earth goes

around it and we project that motion through our geocentric vantage

and depict this as the sun's

motion through the 12 signs. The sun also has a declinational

movement. It moves 28 degrees

north from equator and 28 degrees south, through any given year.

Again, this is not the sun

moving but the earth's tilted rotation giving this impression. When

we are on one side of the sun,

(See panel A in the diagramme), say in December, the northern

hemisphere is tilting away from

the sun, while the southern hemisphere is closer to the sun. This

gives winter in the north and

summer in the southern hemisphere at that time of the year. When the

earth is on the other side of

the sun, say in June, the opposite happens. The north is closer to

the sun and the south is farther

away, reversing the seasons – summer in the north, winter in the

south. At the equator itself, the

seasons do not change significantly because it remains at pretty much

the same distance from the

sun, throughout the year while the north and south seasaw around it.

The equator is at the

fulcrum or pivotal point, if you can visualize it so.

So if you visualize and project this 56 degree wide apparent path of

the sun onto the sky, the stars

falling within that belt are known as the zodiac. When we look up in

the sky and see this belt

with the animal shapes, this represents the nirayana (without ayan or

declinational movement of

the sun) zodiac. When you are looking up and seeing the shape of a

scorpion in the sky, your are

looking at the sidereal (made out of stars) scorpio, or nirayana

scorpio. This is the zodiac that we

jyotishs use. This is the what you see is what you get zodiac. There

should be no confusion about

this. This zodiac is also known as the fixed zodiac and does not move

over a long period of time

(relatively speaking). However, there is strong indication of the

universe expanding and thus

stars are moving with respect to each other. This motion is

infinitismally slow and maybe in a

billion years or more, the starry shapes in the sky would be

different. I would let the astrologers

of the future (if they still exist) worry about that. For us for

thousands of years, we will have the

same fixed zodiac peering down at us, when we look up.

Now let us look at the tropical or western zodiac. In a sense it is

not a zodiac that has links to

stars, unlike the sidereal zodiac. There is no orientation point to

trace, up there. This is important

to understand and remember. The tropical zodiac is also related to

seasons. During the wobbly

path of the earth which moves around the sun, there are four seasonal

orientation points of

importance. At spring and autumn, there are two days when the days

are equal to nights in

duration. These are the vernal or spring equinox and the autumnal

equinox. Please note that the

seasonal reference is for the northern hemisphere. On these very

days, while spring and autumn

will begin in the north, the opposite season, namely, autumn and

spring will begin in the southern

hemisphere (so for the south these same points would represent

autumnal equinox and vernal

equinox). It can all get very confusing for the beginner or dabbler.

For simplicity, people take

these equinoctial days on fixed dates each year but in actuality, the

dates could vary by a few

days from year to year (the day when the day and night is actually

equal). The other two points

are the solstices, the points at which the north hemisphere is at its

closest or farthest from the

sun, giving rise to the longest or shortest day in the year (summer

and winter). It pays to repeat

that this is all because of the tilted axis of the earth in respect

to the sun. The confusing part is

that the tropical zodiac uses the same naming convention or aries,

taurus etc – even though those

names are not related to the constellations in the sky. This is

interpreted by people as being a

carryover from the beginnings of tropical astrology, a couple of

thousand years ago when the two

zodiacs coincided and sidereal aries zero was at the same point where

tropical aries zero was.

Another way of describing this is that the point of vernal equinox

(tropical aries zero) happened

on the same day when sun entered the aries constellation according to

the sidereal zodiac.

Over a period of years this coincidence slips because the beginning

of the seasonal zodiac (vernal

equinox) moves forward. While the nirayana, sidereal, jyotish zodiac

is fixed, the seasonal zodiac

keeps moving. This happens extremely slowly. Why does it happen?

Imagine the earth as it goes

around the sun. Due to varying gravitational pulls on it, as the

other heavenly bodies pull and

push the earth, it wobbles ever so slowly, like a top (lattoo). Over

a peiod of thousands of years,

this wobbles changes the relationship with the sun. The axis of earth

which is now tilting about

23.3 degrees away from the sun (during December) would after some

13000 years be tilting

about 23.3 degrees towards the sun (during December). See panel B for

a visual representation.

So, at that time, in future, the northern hemisphere will experience

summer in December and

Winter in June! The vernal equinox that in in March now, will be in

September 13000 years in

future! If the same convention is followed then by tropical

astrologers, then tropical aries would

be in September or actually, sun would be considered in tropical

aries in September.

As the earth wobbles around its axis like a top, please note that the

top part of the earth or north

pole wobbles a lot more than the south pole. The movement of the axis

is like an icecream cone,

fixed at the bottom and more wobbly at the top. As the pole wobbles,

it would over a long period

of time, point at a different north star! Our current pole star will

not remain the pole star 13000

years in future. We will have a different one to look up to.

Now please take a look at the panel C and pardon me for my sloppy

drawing abilities. This is a

bit complex picture which shows a bird's eye view (top-down) of the

sun and earth and the

ecliptic belt or sidereal, fixed zodiac surrounding it. The signs are

depicted in a counterclockwise

progression (like the north indian kundali). Picture for a second

from the other end and you can

visualize the arrangement in a clockwise fashion (like the south

indian kundali). I have written

about it elsewhere. So as the earth spins counterclockwise, the signs

rise and set and give the

lagnas. The earth moves around the sun and we perceive this as the

sun entering and leaving the

different sidereal signs and so on. The current vernal equinox is

when sun is in the first part of

sidereal pisces, in 13000 years it would be when sun is in the first

few degrees of sidereal virgo.

Please note that it is paradoxical that though sidereal zodiac is the

visible one, its orienting point

does not exist. There is no known star at sidereal aries zero. Hence

other stars such as revati (zeta

piscicum) and chitra (spica) have been utilized to justify one or the

other ayanamsha. Some have

also taken the galactic centre as an orientation point (this takes

into account the even slower

expansion of the universe and perhaps goes even beyond the zodiac as

we know it today and

indeed `see' it today.

So, I hope this article reduces the confusion a bit. The tropical

zodiac or seasonal orientation

point does move against the fixed, immovable, starry zodiac and as

seasons shift, so does the

tropical orientation point known as tropical aries zero which then

describes the western zodiac

that uses the same symbolic names and extent of the signs, without

those matching the ones in

the sky. Thus the confusion.

2006-06-10 (Rohiniranjan)