Sidereal and Tropical: Two Zodiacs

The tropical zodiac answers a seasonal question: it fixes 0° Aries to the Spring Equinox, the moment the Sun crosses the celestial equator each year. This makes the tropical zodiac a calendar of the Earth's relationship to the Sun; reliable, precise, and entirely independent of where the actual constellations happen to sit in the sky.

The sidereal zodiac answers a different question: where are the stars, right now, as seen from Earth. It anchors its 0° point to the visible constellation of Aries rather than to the equinox.

Earth's axis wobbles slowly over a cycle of roughly 25,800 years; the precession of the equinoxes. Because the tropical zodiac is locked to the equinox and the sidereal zodiac is locked to the stars, the two systems have drifted apart by roughly 24 degrees since antiquity. A planet at "0° Aries" in the tropical system today sits closer to the constellation Pisces in the sidereal sky.

Neither system is more correct than the other at the level of measurement; they are simply measuring different things: a solar-seasonal cycle, and a stellar backdrop.

Astrosophy reads the chart as a soul's relationship to the actual, visible cosmos it descended through; not to the Earth's seasonal rhythm alone. The anthroposophical planetary-sphere doctrine describes real hierarchical beings inhabiting real regions of the heavens; the sidereal zodiac keeps the symbolic reading anchored to where those beings' visible signature; the fixed-star constellations; actually stands.

This is why the app's Incarnation Wheel computes positions sidereally, using the Lahiri ayanamsa to translate between the two systems, and why fixed-star content in Self is read as its own distinct layer rather than folded into sign meaning.