I was born under the sign of Capricorn (please do not condemn me), yet the Sun was in the middle of Sagittarius at the time of my birth. As an emeritus professor of astronomy, I frequently asked the differences are between astrology and astronomy. Astrology has practiced since ancient times, and it predicts one’s fame and fortune based on the positions of the Sun, Moon, stars, and planets. It intertwined with astronomy at the time – in fact, many early astronomers made scientific observations that are still useful today.
However, when Copernicus, Kepler, and Galileo learned that the planets orbit the Sun rather than the Earth, and Newton established the physical principles that govern their behavior, astrology and astronomy parted, never to rejoin. Astronomy and one of the fundamental organizational elements of astrology, the zodiac dates, are currently at odds. The zodiac constellations are the stars in the sky that represent the signs of the zodiac.
The Sun appears to move through a strip of sky comprising 12 ancient constellations, or groupings of stars, during the course of a year. The zodiac made up almost exclusively of animal figures, such as the ram (Aries), crab (Cancer), and lion (Leo) (Leo). Many people are disappointed that constellations rarely resemble what they represent. How could they, given that the stars are actually random scatterings? They intended to represent rather than portray.
Although the zodiac constellations, which date back to Mesopotamia or earlier, appear to be definite, they are just one example of those created by diverse cultures around the world, each with their own, often very different, ideas about how the sky is structured. The Incas, for example, created constellations out of dark regions in the Milky Way rather than stars. The number of constellations in the Western zodiac determined the Moon’s 12.4-year orbit around the Earth. Every new Moon, the Sun appears against a different constellation, with the stars providing a distant backdrop for the Sun.
Even if the stars are not visible during the day, glancing at the night sky can reveal what constellation the Sun is. The opposing constellation can see there. According to astrology, each zodiac sign fits perfectly into a 30-degree slice of sky, which when multiplied by 12 equals 360 degrees. In reality, the constellations vary greatly in shape and size, thus this is not the case. The Sun, for example, takes only five days to pass through the constellation Scorpio, but 38 days to pass through Taurus. This is one of the reasons why astrological signs do not correspond to zodiac constellations.
Equinox precession is a phenomenon in which the equinoxes move back and forth in time. The main reason astrological signs do not align with the zodiac is due to precession, a wobble in the Earth is spinning axis. The Earth bulges somewhat at the equator because of its rotation, similar to how a skater’s skirt fanned out as she spins. The Moon and Sun’s gravitational pulls on the bulge, causing the Earth to wobble like a top, over the period of 25,800 years, the wobble causes the Earth’s axis, which is the centerline around which it revolves, to swing in a leisurely circle.
