Twelve Houses
Think of the sky as a circle. Now divide it into twelve parts. Each “part” is a house. As the Sun travels over the course of a year, it makes a circle, passing from one house to the next. Your “Sun sign” is where the Sun was on the day you were born, in relation to where you were born, i.e., which part of the world. Your ascendant is determined by what hour and minute of the day you were born in relation to this.
Because there are no “lines” in the sky dividing up the universe into precise parts, there are some discrepancies that remain in terms of determining a person's Sun sign. Those who were born at the edge of a house — during the days when one Sun changes to another — are considered to have been born “on the cusp” and may show traits from the two signs they border.
To fully understand how it all works, it's necessary to talk briefly about the signs and their rulers. In the natural order of the zodiac, the signs begin with Aries and progress through the months to Pisces. Why couldn't the signs start with January? Why April and Aries? And why end up in March and Pisces instead of in December and Sagittarius?
Part of the reason for the order that starts with Aries in Western astrology is due to the nature of the signs themselves. In other words, in astrology, we believe that Aries is the pioneer who goes out into the world first. Pisces swims through the waters of the imagination, and his dreams eventually root in the physical world and become the reality of Aries.
