People new to astrology are often confounded by the two main schools of thought within it: tropical and sidereal. This brief lecture covers the development of the zodiac by the Babylonians and the introduction of tropical astrology by the Greek astronomers Hipparchus of Rhodes and Claudius Ptolemy. During Ptolemy’s time, the signs and constellations were closely aligned; but due to the precession of the earth’s spin axis, they have slowly separated at a rate of one degree every 71.6 years.  The current divide between sidereal and tropical zodiac reckoning is 25 degrees. In three and a half centuries, that separation it will be 30 degrees, an entire sign. This raises the question: do trait characteristics come from the stars, as astrology was originally practiced, or from the tropical signs later introduced by the Greeks? The lecture covers the mechanism of precession that separates tropical from sidereal reckoning, the discovery of the ecliptic, the centerline or backbone of the zodiac, and the reemergence of sidereal astrology in the West.