of the astrological ages. Consequently, the beginning of any age cannot be defined to a single year or a decade but blend its influences with the previous age for a period of time until the new age can stand in its own right. In Nicholas Campion's The Book of World Horoscopes there are six pages listing researchers and their proposed dates for the start of the Age of Aquarius indicating that many researchers believe that each age commences at an exact date. Other opinions Ages exactly 2,000 years each Many astrologers find ages too erratic based on either the vernal point moving through the randomly sized zodiacal constellations or sidereal zodiac and, instead, round all astrological ages to exactly 2000 years each. In this approach the ages are usually neatly aligned so that the Aries age is found from 2000 BC to AD 1, Pisces age AD 1 to AD 2000, the Aquarian Age AD 2000 - AD 4000, and so on. This approach is inconsistent with the precession of the equinoxes. Based on precession of the equinoxes, there is a one-degree shift approximately every 72 years, so a 30-degree movement requires 2160 years to complete. Ages involving the opposite sign An established school of thought is that an age is also influenced by the sign opposite to the one of the astrological age. Referring back to the precession of the Equinoxes, as the Sun crosses one constellation in the Northern Hemisphere's spring Equinox (21 March), it will cross the opposite sign in the spring Equinox in the Southern Hemisphere (21 September). For instance, the Age of Pisces is complemented by its opposite astrological sign of Virgo (the Virgin); so a few refer to the Piscean age as the 'Age of Pisces-Virgo'. Adopting this approach, the Age of Aquarius would become the Age of Aquarius-Leo. In his writings Ray Grasse also espouses the link between each sign of the zodiac and its opposite sign. History Hipparchus The great demarcation point in the history of the astrological ages is around 127 BC when the Greek astronomer-astrologer Hipparchus from observation discovered that the great immovable sphere of fixed stars was not fixed but slowly moving eastwards due to what is now known as precession of the equinoxes. It is possible that some other astronomers before Hipparchus had also noticed the phenomenon, but it is Hipparchus who is credited with this discovery (See