The zodiac circle is an imaginary belt in the sky and its twelve divisions are known as the zodiac signs. This zodiac belt however is closely linked to how earth moves through the celestial sphere. The zodiac belt is 16° wide, extending 8° on each side of the ecliptic, which is the path of Sun through one year as visible from the Earth. All other planets and their orbit including Moon lie within this zodiacal sphere in the sky. The zodiac belt consisting 360° is divided into twelve equal parts of 30° each, which makes 12 zodiac signs.
But how do we know the starting point or where does the first sign called Aries start? The beginning of the zodiac is taken from the Vernal Equinox point, where Sun’s apparent path that is ecliptic intersects the Equator of the earth. From here, Aries begins followed by the subsequent signs in anti-clockwise namely, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.
Different planets moving around the celestial sphere cross these zodiac signs. Through one year, the Sun looks like moving through different signs and constellations as seen from earth. One month, it would be in Cancer, and the next, it would be in Leo. Since Sun takes one year to complete a circle around earth (when we consider earth as the fixed reference point instead of Sun), it stays in the area constituted by one sign for around 1 month, because the sky is divided into 12 signs. These are the dates of the usual Sun sign horoscopes that you read in magazines like March 21 to April 19 for Aries. But these dates were fixed 2000 years ago based on the position of constellations at that time. It does not mean that the Sun would be in the constellation that it aligned to at that time. This is because apart from revolution around the Sun, the earth also rotates on its axis and forms a circle in the celestial sphere. While it takes around 26000 years to complete one circle on its axis, this eventually leads to shift in the point of Vernal Equinox. Vedic astrology however takes into account this Precession of the equinoxes thus there is a difference of one month in the starting point of Aries in western and Vedic astrology.
Vedic astrology gives more value to the placement of Moon, which is also known as the Moon Sign. This is the sign where Moon is transiting at the time of birth. Every day feels different, as Moon that signifies our inner feelings and instincts changes its position more frequently than Sun. If we base our predictions on Sun sign alone, we would be missing out on these finer changes. Moon represents the mind, emotions, feelings, inner self and temperament of a person and these affect us on a deeper level. Sun on the other hand represents the exterior, outer self that we project to the world.
Along with Sun and Moon sign, you must have also come across the term the Rising Sign. Quite often, people struggle to relate to the attributes of their Moon or Sun sign. This is on account of the influence of their rising sign. It is also called Ascendant. The degree of the zodiac sign that is rising on the eastern horizon at the time and place of birth is called the rising sign or Ascendant.