Hindu Predictive Astrology Part 2: The Zodiac and the Solar System

The zodiac is a broad band or belt in the heavens extending 9 degrees on each side of the ecliptic. The ecliptic — the apparent path of the Sun through the sky — passes exactly through the centre of the zodiac longitudinally.

The ancients divided this imaginary circle into 12 equal parts of 30 degrees each, each named after the constellation it corresponds to. Though each sign differs considerably from the others, there is a sort of continuity through all twelve. The quality of each sign is not equally spread — every degree in a sign has its own peculiar qualities.

In Sanskrit, the zodiac is known as the Bhachakra. It revolves on its axis once in a day, from east to west.

Each of the twelve signs has a Sanskrit name, a Western name, a symbol, and a corresponding image. These are the permanent divisions of the celestial highway:

The planetary orbs which the ancients recognised as having the most powerful influences on our earth are seven, leaving aside the shadowy planets Rahu and Ketu. Hindu astrology does not recognise the so-called newly discovered planets Uranus, Neptune, and Pluto.

According to the Surya Siddhanta (the foundational Hindu astronomical text), the planets are arranged in the following order of distance from the Earth, with Saturn being the most distant:

All the planets perform a double function: revolving on their own axes once in a day (from west to east) and also revolving around the Sun. The velocity of each planet diminishes as its distance from the earth increases — Saturn, the farthest, is the slowest.

This is critical practical knowledge. The speed at which a planet moves determines how long it influences a particular sign and degree. Raman gives the following average rates:

Raman singles out Mercury for special attention because of its unique orbital behaviour. Mercury moves at an average rate of 1¼ degrees per day, but on account of his closeness to the Sun and the solar influence, he is very unsteady.

Rahu and Ketu are unique in that they are not physical bodies — they are mathematical points where the Moon's orbital plane intersects the ecliptic (the Sun's apparent path). These are the points where solar and lunar eclipses occur.

All the planets except the Sun, the Moon, and the shadowy planets Rahu and Ketu undergo vakra or retrogression — an apparent backward motion as seen from Earth.

Retrogression is an apparent phenomenon caused by the relative speeds and orbits of the planets. When Earth overtakes a slower outer planet (or an inner planet overtakes Earth), that planet appears to move backwards against the starry background. Raman notes that the astronomical details of retrograde motion are "somewhat cumbersome" and defers to standard astronomy texts, but the astrological significance of retrogression is covered in a future chapter (Part 7 on Planetary Strengths & Avasthas).

This is the single most important conceptual difference between Hindu and Western astrology, and understanding it is essential before you proceed further in this series.

Now that you understand the celestial stage, in Part 3, we'll explore the Hindu system of measuring time — the 60-year cycle, the six seasons, lunar months, ghatis and vighatis, and why the Hindu day begins at sunrise rather than midnight.