Tropical Astrology is the old astrological division of the sky. A tropical year (solar year) is the time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth.
For example, the time from vernal equinox to vernal equinox (March), or from summer solstice to summer solstice. This differs from the time it takes Earth to complete one full orbit around the Sun as measured with respect to the fixed stars (the sidereal year) by about 20 minutes because of the precession of the equinoxes.
When the Zodiac was developed, the position of the constellations were written down and recorded. But since then, the whole Zodiac has shifted almost a whole sign due to the “Precession of The Equinoxes”. This is the “wobble” of the earth on its axis which takes 25,920 years to complete.
What this means is that whoever was once born a Virgo, is now probably born a Leo – with the personality changes that come with it. Tropical Astrology ignores this, and keeps using the old tables – which have nothing to do with where the planets actually are in the sky.
Meanwhile, Sidereal Astrology acknowledges the problem with the shifting signs, but some might say that it digs itself deeper into the ludicrous: The more sidereal astrologers try to follow the real division of the sky, the more they are distancing themselves from the old wisdom. This affects the lineage of a concept back to its source, it raises questions of authenticity of claims for antiquity when aligning a current concept with an ancient wisdom.
It is said that Sidereal astrologers cannot claim to build on ancient knowledge, but instead have to change the signs and characteristics over time. They are thus making the whole [invalid?] concept of Astrology invalid. The real astronomical signs are a few days off from the Sidereal system by now – so not even Sidereal Astrology is using the correct star signs. Yeah, it gets confusing when we look into astrology not as an operating metaphor, but more as a “science” of the ancients.
Sidereal astrology uses the actual constellation in which the sun is located at the moment of birth as its basis; tropical astrology uses a 30-degree sector of the zodiac as its basis. Tropical astrology is the most popular form and it assigns its readings based on the time of the year, while generally ignoring the positions of the sun and constellations relative to each other. Sidereal astrology is used by a minority of astrologers and bases its readings on the constellations near the sun at the time of birth.
According to some astrologers, the data supports the hypothesis that there is a connection between heavenly bodies and human events. There are correlations too synchronous to be mere chance between astrological signs and such things as personality, emotions and human destiny.