Motion of Grahas

While Galileo mulled about the relative motion and Einstein amused people by stating that ‘when the station approaches the train…’, little they would have imagined that the ancient Rishis had already appreciated up to 8 different types of speeds of the planets due to their motion perceived relative to our position on Earth.


One can simply remember yourself sitting in a moving train and seeing other trains moving in same or opposite directions and you can recall how the speed of the other train varied as it approached your train and overtook or crossed it. Now, imagine the same situation when you would have sat on a carousel horse and the horses in the inner or outer circles appeared to have moved at varying speeds though their speed was actually constant; and moving away or towards us though they are actually moving in one direction. Similar situation happens when planets are observed from the Earth, as studied in Vedic Astrology.

The planets may appear to sometimes move faster, sometimes slower, sometimes appear to be almost stationary or even move in opposite direction. This is because we are observing Moving Planets from a Moving Earth.

As per Parasara (BPHS: Chapter 27: Slokas 21)


वक्रानुवक्रा विकला मन्दा मन्दतरा समा।
चरा चाऽतिचरा चेति ग्रहाणामष्टधा गतिः॥

vakra, anuvakra, vikala, manda, mandatara, sama;
chara and atichara, these are the eight kinds of motions of the grahas.


These eight kinds of motions are understood as follows:


1. vakra (वक्र) = Retrograde Motion

2. anuvakra (अनुवक्र) = Entering the previous rAshi in retrograde motion

3. vikala (विकल) = devoid of motion, or, in other words, Stationary

4. manda (मन्द) = somewhat slower motion than usual

5. mandatara (मन्दतर) = slower than the previous

6. sama (सम) = normal

7. chara (चर) = faster than sama

8. atichara (अतिचर) = entering next Rashi in accelerated motion


Based on these motions, various strengths are assigned to these grahas.

Of the 9 grahas, Sun and Moon, for obvious reason, will never appear to go retrograde; while Rahu and Ketu always appear to go retrograde.

Speeds of Grahas

The grahas, when seen from the earth, move along the zodiac belt, at varying speeds.

Accordingly, each graha will be seen to traverse a rasi (zodiac sign) for a particular amount of time.

e.g. Sun moves at a rate of 1 degree per day.
Thus it traverses a rasi (30deg) in 30 days, which is approximately 1 Solar Month.
The Sun hence goes round the 12 signs of the zodiac / bha-chakra (360 deg) in approximately 12 Solar Months, i.e. 1 Solar Year.
The movement of the Sun from one sign to another is called Sankranti.
Where Makar Sankranti means that Sun enters the rasi Makara (Capricorn).

The Moon goes round the zodiac in 27.32 days, which is also the period of it’s revolution around the earth. This constitutes a Lunar Month.

At this stage, without going into further details about what defines a month or year etc. in astrology, following are the average speeds of the grahas around the zodiac / bha-chakra:

Graha	Completes the round of the zodiac (360 deg) in	Traverses a Rasi (30 deg) in approximately	Moves 1deg in approximately
Sun	1 year	1 month	1 day
Moon	27 ⅓ days	2 ¼ days	1 ¾ hrs
Mars	1.88 yrs	1.88 months	46 hrs
Mercury	88 days	7 ⅓ days	6 hrs
Jupiter	11.86 yrs	11.86 months	12 days
Venus	224.7 days	18 3/4 days	15 hrs
Saturn	29.46 years	2 ½ years	29 ¾ days
Rahu	18.6 years	18.6 months	18.8 days
Ketu	18.6 years	18.6 months	18.8 days

From Kepler’s Laws of Planetary Motion, we know that the orbits of the planets are elliptical, with Sun at the focus. Hence, the speed of each planet also varies at different points on its orbit – it being slower nearer to the Sun and faster when away from the Sun. This is in accordance with Kepler’s second law of planetary motion, i.e. The line joining a planet and the sun sweeps out equal areas during equal intervals of time.

Kepler's 2nd Law
Area sweeped between points a and b
is equal to area aweeped between points c and d in equal time.

A closer look at the Kepler’s 3rd law will reveal that farther the planet is from the Sun, the slower it will move. Kepler actually derived a mathematical relationship to that effect.

In the above table, you can notice that the speed of Saturn (that is farthest from the Sun) is slowest, while that of Mercury (that is nearest to the Sun) is the fastest, in the scheme of the Solar System.

However, when you take into account the 9 grahas, you will include Moon, which then becomes the fastest graha seen to be moving in the bha-chakra.

Note that Sun, Moon, Rahu and Ketu are not considered to be Planets, but are Grahas.

Rahu = North Node and Ketu = South Node are the points of intersection of the Moon’s orbit with that of the Elliptic (Sun’s orbit) as seen moving in the skies when you view them from the Earth.


With Earth as the reference point, as studied in astrology, the speeds of grahas are seen to vary, with even the Sun appearing to move faster at times and slower at other times. Remember that the Sun appears to move in the Elliptic, when viewed from the Earth.


The grahas, from geocentric point of view, will also appear to move at varying speed when seen relative to the motion of the Earth. They sometimes appear to move very fast, or even appear to be stationary or moving in reverse direction, much like when you observe a moving train, while sitting in another moving train. This phenomenon is similar to what Galilieo discovered and Einstein refined about Relative Motion.

More about the Speeds of Grahas later…

Zodiac or Bha-Chakra (भ-चक्र)

As seen from the Earth, the 9 graha (ग्रह) travel along a belt like path called the Zodiac or the bha chakra (भ - चक्र).

The Sun appears to move in an Elliptic Path that marks the center line of the Zodiac belt.

The zodiac belt has a span of about 8 degrees on either side of this elliptic.



The term zodiac is derived from the Latin word zōdiacus and from the Greek zōdiakos kuklos, that means a "circle of animals".

“Zoon” means "animal" and 6 of the 12 signs of the classical Greek zodiac are represented as animals.
In Vedic Astrology, the term used for Zodiac is bha-chakra. bha = to shine; chakra = wheel.



According to bR^ihat parAshara horA shAstra (BPHS), Chapter III:

शृणु विप्र प्रवक्ष्यामि भग्रहाणां परिस्थितिम्‌।
आकाशे यानि दृश्यन्ते ज्योतिर्बिम्बात्यनेकशः॥ २॥

Listen O Brahmin, I speak of the state of graha that shine;
In the sky there can be seen various luminous bodies.



तेषु नक्षत्रसंज्ञानि ग्रहसंज्ञानि कानिचित्‌।
तानि नक्षत्रनामानि स्थिरस्थानानि यानि चै॥ ३॥

Of these (some) are named the Nakshatras and the others as graha;
Those that are stationery are called Nakshatras.


गच्छन्तो भानि गृह्णन्ति सततं ये तु ते ग्रहः।
भचक्रस्य नगश्व्यंशा अश्विन्यादिसमाह्वयाः॥ ४॥

Those shining (bodies) that move continuously, grasping the Nakshatras, are the Grahas;
The bha-chakra (zodiac) comprises of Ashwini etc. (27) asterisms.


तद्‌द्वादशविभागास्तु तुल्य मेषादिसंज्ञकाः।
प्रसिद्धा राशयः सन्ति ग्रहास्त्वर्कादिसंज्ञकाः॥ ५॥

This (zodiac) divided into 12 parts is correspondingly named as mesha etc.;
(these parts are) known as Rashi; the Graha are named as Sun etc..




Just like a circle, the Zodiac has 360°.

Each Zodiac Sign / rāśi (राशि) thus spans 360/12 = 30°.

The 12 zodiac signs or 12 rāśi (राशि) are:
 

Order	Western Name	Vedic Name
I	Aries	meSha (मेष)
II	Taurus	vR^iSha (वृष)
III	Gemini	mithuna (मिथुन)
IV	Cancer	karka (कर्क)
V	Leo	siMha (सिंह)
VI	Virgo	kanyA (कन्या)
VII	Libra	tulA (तुला)
VIII	Scorpio	vR^iShchika (वृष्चिक)
IX	Sagittarius	dhanu (धनु)
X	Capricorn	makara (मकर)
XI	Aquarius	kumbha (कुम्भ)
XII	Pisces	miina (मीन)

rāśi = heap; and refers to a “heap of stars”.

The groups of stars or Asterisms span the zodiac and are these called nakṣatra (नक्षत्र).


27 nakṣatra (नक्षत्र) span the zodiac hence each nakshatra spans 360/27 = 13°27’

In other words, each rāśi harbors 2 ¼ nakṣatra (नक्षत्र).

The nakṣatra (नक्षत्र) are Fixed Stars. i.e. they appear to be in a fixed position when seen from Earth.


The 9 graha (‘planets’) move through the zodiac belt (grasping the nakshatras) at varying speeds.