Astrology 101

Settle down at the back. Nathan, is that gum I see? Something amusing you, Aeriela? How about sharing it with the whole class?

Today’s astrology is based on a system developed by the ancient Greeks. (The word ‘horoscope’ comes from the Greek ‘horoskopos’, meaning ‘hour-watcher’.)

Imagining the Earth to be unmoving, the Sun appears to traverse between east and west horizon daily, varying its path slightly over the course of the year. The stars can be imagined to be on the inside surface of a sphere overhead — the celestial sphere — and this appears to rotate laterally one revolution per year. Noting which stars were in, say, the eastern sky meant The Greeks could develop a reliable calendar. And taking account of the 29½ days between full moons, the equinoxes, etc., they divided this calendar into 12. A person’s star sign (traditionally called their sun sign) was taken from the constellation (see below) the Sun intersected at birth — in other words, the name of the month they were born in.

Over millennia, a process called the precession of the equinoxes (a cycle of variation of Earth’s orbit lasting 26,000 years) has ‘moved’ the constellations such that, on any given date, the Sun now intersects the constellation following the original one. In other words, an ancient Greek astrologer looking up at today’s sky would determine a Taurus to be a Gemini.

Yet — in the Northern Hemisphere — the familiar traits of the original star signs seem to widely hold true. Why? Well, according to, er-herm, Al’s Theorem, because star signs have nothing to do with the stars and everything to do with the seasons.

In fact, the seasons of the Northern Hemisphere have long been integral to astrology. The transition from Pisces to Aries occurs at the vernal (spring) equinox, Gemini to Cancer at the summer solstice, Virgo to Libra at the autumnal equinox and Sagittarius to Capricorn at the winter solstice.

Because of this link with the equinoxes and solstices, the Greeks’ 12-month calendar — unlike the current one — was in tune with the cues in nature used by our internal clocks. The different traits of someone, say, born shortly before the autumnal equinox compared to someone else born shortly after it, were not hard to spot. Mythological tales were used to pass the knowledge on and 12 suitable constellations were named in the night sky. The Signs of the Zodiac had their genesis.

Any questions?