CHAPTER 1

THE MECHANICS OF RETROGRESSION

Throughout the book we will be reminded constantly that retrograde motion ispeculiar to our earth-based viewpoint. We look both inward to the Sun and thetwo 'inferior' planets, and outward at the 'superior' planets towards theboundary of the solar system. The inferior planets whose orbits lie inside theorbit of our Earth—Moon system are Mercury and Venus; those beyond our orbit Mars,Jupiter, Saturn, Uranus, Neptune and Pluto - are the superior planets. Ofthe superior planets, astrologers have come to know the first three as the'social' planets and the outermost three as the 'transpersonal' or, moreaccurately, 'trans-Saturnian' planets.

Retrogression is the period of time during which a planet in our solar systemappears to be moving backward as we see it against the fixed backdrop of thestars. The phenomenon is entirely due to our Earth-based perspective and waswell known to the ancient astronomers.

The ancient sky-watchers were, however, in some confusion about the cycles ofthe inferior planets - retrogression in particular - because they thought thatMercury and Venus were both two different bodies. This was because they can beboth morning and evening 'stars' at different times in their cycle of orbitalrevolution and retrogression. The confusion is quite understandable, becausewhen we look towards Mercury and Venus it appears as if they are passing backand forth across - rather than orbiting around - the Sun. Because of theirorbital proximity to the Sun they are clearly observable only when at their mostdistant from the Sun in zodiacal longitude. This visibility occurs for two shortperiods of time, as Mercury and Venus head 'towards' us in their orbits to forman inferior conjunction with the Sun, and as they head 'away from' us,continuing in their respective orbits around the Sun to the superiorconjunction.

The social planets - Mars, Jupiter and Saturn - are most clearly visible whenthey are moving in the opposite part of the sky to the Sun - in the night sky andare retrograde for much of the time when in this zodiacal zone. This sameSun-planet opposition principle applies also to Uranus, Neptune and Pluto, butthey are invisible to the unaided eye.

The primary difference, therefore, between inferior planets and superior planetsretrograde is that:

1. Superior planets only appear to turn retrograde when they are about to opposethe Sun. Earth is then posited between the Sun and the planet in its orbit.

2. Inferior planets only appear to turn retrograde when they are about toconjoin the Sun. The planet is posited between Earth and the Sun.

The point in common between all planets is that they are closest to Earth whenretrograde. With these facts in mind, let us examine the cycles of inferior andsuperior retrogression.

RETROGRADE CYCLE OF INFERIOR PLANETS

From a geocentric viewpoint Mercury and Venus can make two kinds of conjunctionwith the Sun:

1. Inferior: when the planet is between Earth and the Sun, and the planet isretrograde.

2. Superior: when the planet is on the other side (from Earth) of the Sun, andthe planet is direct.

Both Mercury and Venus orbit the Sun in shorter periods than the Earth. Mercurygoes around the Sun once every 88 days, and Venus about every 225 days (Earth'sorbital period is 365 ¼ days). As the Earth and inferior planets orbit the Sun intheir respective periods, occasionally they are all found on the same side ofthe Sun, occasionally on opposite sides of the Sun. Sometimes they are runningalongside each other, sometimes not. When an inferior planet moves around theSun and 'catches up' with and passes the Earth, the planet appears to movebackwards against the zodiac. At that point it is in close proximity to the Sunin zodiacal longitude (in the ephemeris), and is then retrograde. From aheliocentric viewpoint, it is an Earth-Mercury or Earth-Venus conjunction.

For Mercury this retrograde motion occurs three times approximately everythirteen or so months; the planet catches up with Earth at the inferiorconjunction with the Sun every 116 days. Venus - which orbits the Sun every 225days - passes through the inferior conjunction with the Sun about every 584 daysand is therefore seen retrograde only once approximately every eighteen months.Though the times of Mercury's and Venus' retrograde cycles are considerablydifferent, the system operates in precisely the same way.

At superior conjunction (point 1 in fig. 1.1, p. 6) the Earth is looking beyondthe Sun to the inferior planet, which is trotting along in direct motion roundthe Sun. At a certain point the inferior planet begins to head around in itsorbit again towards the Earth and passes between the Sun and Earth. When theplanet is between the superior conjunction (point 1) and Greatest EasternElongation (point 2), it is direct in motion. It begins to decelerate justbefore point 2 and stations, turning retrograde at point 3, after which time itappears to move backward against the zodiac for a period of time (an average oftwenty-two days for Mercury and forty-two for Venus). At the midpoint of theretrograde period, the planet will have moved back to conjoin the Sun atinferior conjunction (point 4). Some days after the inferior conjunction (forMercury this is about ten days and Venus about twenty-one days), the planet willappear to slow again, stop and then begin...