For 2,000 years, the signs of the zodiac have moved relative to the constellations. According to detractors of astrology, they no longer correspond to today's astronomical reality: a "Taurus" would therefore no longer be a "Taurus", but an "Aries".
The Tropical Zodiac is the part of the sky in which the trajectories of the sun, the moon and the other planets of the solar system are located (seen from Earth). It begins at the vernal point, that is to say at the intersection of the ecliptic (apparent trajectory of the sun) and the celestial equator, and is divided into 12 equal sectors of 30° called “zodiacal signs”.
However, the tropical zodiac moves very slowly (clockwise) compared to the constellations of stars of the same names that make up the the sidereal zodiac. As this shift takes place at a rate of 1° every 72 years, there is indeed an increasing gap between the tropical zodiac and the sidereal zodiac, which is currently 23°.
This phenomenon was discovered by the Greek astronomer and mathematician Hipparchus of Nicaea around 130 BC, more than 2000 years ago. This phenomenonwas called precessional movement, because the constellations seem to recede from the signs of the tropical zodiac. This is due to the inclination of the Earth's axis, which rotates very slowly on its axis (see diagram opposite). Seen from space, the Earth seems to be affected by a spinning top.
Historically, the discovery of precessional motion, or "precession of the equinoxes," preceded by three centuries the writing of the first complete treatise on astrology, the Tetrabiblos by the Egyptian astronomer and astrologer Ptolemy of Alexandria. It is therefore on the confusion of the 12 signs of the zodiac with the star constellations of the same names that this obviously false argument is based, since astrology studies the movement of the stars in the tropical zodiac and not in the constellations. Whether born today or under Julius Caesar, a “Taurus” therefore remains a “Taurus”!