Josh Smith, of Cashmere High School, asks :-
Is it true that you can see the shapes of the Star Sign symbols in the sky?
Pam Kilmartin, an astronomer at the University of Canterbury's Mt John Observatory, responded.
Yes, that's where they came from. From ancient times people have made pictures in the night sky by joining the dots, the stars. Different cultures have made different pictures. We call the star pictures constellations.
The earth and other planets circle the sun in the same plane. Seen from earth they appear to slowly move around the sky along a great circle. Constellations on this circle are the `star signs' or 'sun signs'. Our culture recognises twelve constellations along the circle, though astronomers chart thirteen. We call the circle of constellations the Zodiac, 'the circle of animals'.
Over a year, as we circle the sun, it appears to make one rotation of the zodiac. At our summer solstice the sun is in the constellation of Sagittarius. At winter solstice it is between Gemini and Taurus. Two thousand years ago the sun's extreme south and north were in Capricornus and Cancer, hence the names of the tropics. A slow wobble (precession) of the earth's axis has shifted them.
We know now that it is the earth's tilt to its orbit plane that gives us the seasons. Ancient peoples hadn't cottoned on to this. They noticed that when the sun was in a particular constellations certain kinds of weather prevailed. They guessed that each constellation had an `influence' amplified by the sun.
If the seasons could be predicted from the movement of the sun then why not other events? By adding the 'influences' of the moon and planets to this notion the astrology industry got underway. It continues to thrive on modern ignorance. The dates for the star signs in the astrology columns don't even fit with where the sun is. Just as precession has moved the tropical constellations, so it has shifted all the others.