Tropical vs. Sidereal

There are two main zodiacs, and they answer different questions about where a sign begins. The tropical zodiac places zero degrees Aries at the spring equinox, anchoring the signs to the seasons and the yearly relationship between Earth and Sun. It is the standard in Western astrology. The sidereal zodiac instead ties the signs to the fixed stars, keeping them aligned with the background constellations, and it is the one used in Vedic astrology. The two once matched, but they have slowly drifted apart. Earth's axis makes a slow wobble called the precession of the equinoxes, which shifts the equinox point against the stars over many centuries. That gap has grown to around twenty-four degrees, close to a full sign. The practical effect is that the same birth can produce different placements. A person with the Sun in late Aries by the tropical zodiac might have it in Pisces by the sidereal one. Neither is wrong; they measure different things, one the seasons and one the stars. Knowing which zodiac a chart uses keeps the two from being confused.