sravana said:
Actually, that's an easy one to answer. John Frawley covers this elegantly in Real Astrology; I'm gonna paraphrase badly, but witht he hopes you'll go see how he discusses it...
Basically, our zodiac and the signs are no more than a circular measure, a 360-degree scale of twelve equally spaced 30º segments. But the signs of the zodiac are not literally connected with the constellations which bear their name. Skeptics (and siderealists) will gleefully rush to inform you that the astrological signs are no longer in sync with their ancient placements in the Wheel of the Year. Taking it further, many historians seem convinced that somewhere in the distant past a caveman looked up at the sky and said one group of stars looks exactly like a man pouring a jug of water, and then spread the word to all the other imaginative cavepeople… and that anyone who suggested that group of stars looked like a tree or a muskrat was ostracized until they were willing to tow the zodiac line. The thing is, if someone actually goes an looks at the sky they'll observe that the signs are not, nor could they ever, be equivalent in size or distribution. Scorpio is MASSIVE and Aries is a blip, to take two extremes. Only astrologers who have never gone and
looked at the sky could suggest that the 12 signs of the zodiac were literally the constellations upon which they were mapped.
Again an important thing to remember, before Leo & Naylor got hold of Astrology the Zodiac was not the dominant concern. That only happens after the advent of newspaper sunsign astrology.
For thousands of years the planets were the primary concern and astrologers were expected to make predictions with provable results. Only in the dingdongy, mass-market 20th century did astrologers start suggesting that humanity can be boiled down into 12 simple flavors like E-Z cheese and that astrology was some kind of mushy affiirmational pablum. Which in turn gave science ample opportunity to ridicule and demolish whatever real astrology Leo hadn't trashed.
Anyways...
For the astrologer, the signs are differentiated by the process of creation. The primal matter of the Cosmos comes into manifestation as (what appears to us as) hot, cold, moist, dry. Onto these four possibilities fall the three modes of creation: the outgoing, which carries the initial impulse from the source into the creation, the expansive, which maintains and explores the creation, and the returning, which turns the impulse back towards its source. Three principles (outgoing, expansive, returning) falling on four qualities (hot, cold, moist, dry) give twelve combinations which each possesses its own distinctive nature. For each nature, an image was revealed which describes (a picture being better than a thousand words) that nature. These are the signs of the zodiac. Once the image was known, a group of stars in roughly the right place were joined to create a picture of it as a mnemonic. The constellations are not and never were equal in size or distribution; they are a mnemonic that helped astrologers map the landscape of time with some degree of accuracy.
Does that make sense?
Now house systems: that's a more delicate quandry...