Each day of the year the Sun rises at a different point in the east. If we connect
these points into a circular belt around the Earth, we would have the zodiac, or
ecliptic. This is the path that the Sun and planets travel along. This imaginary
ruler forms a convenient and accurate way to measure the planets' positions.
This zodiacal ruler is divided into 360 degrees of arc—twelve 30-degree segments
which are marked by the astrological signs. There are four major points on the ruler
which divide the year into seasons. The zodiacal signs which begin at those four
points, or angles, are the Cardinal signs of Aries, Cancer, Libra and Capricorn.
The Vernal Equinox. The position of the Sun at 0 degrees Aries occurs around March
21, when day and night are equal in length. The Sun appears to cross the equator
from south to north, when observed from the northern hemisphere.
The Summer Solstice. Throughout the spring, the days lengthen until the longest day
of the year is reached, around June 21, when the Sun is at 0 degrees Cancer. The
Sun's path reaches its most northern point, the Tropic of Cancer.
The Autumnal Equinox. The Sun crosses the equator going south around September 21,
when it is at 0 degrees Libra, and day and night are again equal.
The Winter Solstice. The Sun's path is at its most southern point, the Tropic of
Capricorn, around December 21, when the Sun is at 0 degrees Capricorn. This is the
shortest day of the year.