Is astrology the same as astronomy? Is there science behind astrology, and should you believe in it?
First of all, let's clarify some terms you might often hear in relation to astrology. The zodiac is a group of 12 constellations that sit in a row across the sky, essentially dividing the sky into 12 segments.
The ecliptic is the plane, or imaginary line across the sky in which the zodiac, sun and planets appear to sit when viewed from Earth. They follow this plane across the sky throughout the night. Astrology is the study of how cosmic objects influence life on Earth.
Astronomy is the scientific study of cosmic objects and the physical universe beyond Earth's atmosphere.
In scientific practice, theories and laws are continuously being tested.
Some of the first civilizations such as the Aboriginal Australians, the Babylonians (approximately 2300 BC), and the Greeks (approximately 330 BC) have used zodiac signs as a way of dividing and mapping the sky, and tracking celestial motion.
Many ancient civilizations believed that the gods lived in the stars and planets, and as such the presence of certain celestial bodies was an omen for the days ahead.
Around 130 BC an important discovery was made that the Earth tilts on its axis like a slow spinning top, about 1 degree every 72 years (when viewed from Earth, 1 degree in the sky appears to be approximately the width of your pinky finger). We call this the precession of the planet.
It takes approximately 26,000 years for one complete processional cycle, so our observations of the sky are vastly different to the first Babylonian or Greek societies, as the celestial objects appear to have shifted. This means that the zodiac cycle as viewed from Earth today appears almost an entire month away from the original observation. The zodiac as used for time keeping and horoscopes has not been altered to adjust for the precession of planet Earth.
The sun moves directly through 13 zodiac constellations as it moves along the ecliptic plane, and it briefly touches seven more. The Babylonians had already developed a 12-month calendar when they discovered this, and chose to omit the 13th zodiac sign, Ophiuchus. They stretched some of the other zodiac signs out to cover Ophiuchus period, and it was largely omitted from modern western astrology practice. When the Babylonians said the sun was in Sagittarius or Capricorn, for a period of that time it truly wasn't in those constellations at all.
There is no scientific proof that astrological predictions are correct on a large scale, and it does not meet the required criteria to be considered a science - measurable results, empirical evidence, and unbiased by opinion, to name a few. In scientific practice, theories and laws are continuously being tested, improved, and updated in accordance with new information about the changing Universe. Between the precession of the planet and the omitted constellations of the zodiac, the question should be made whether the ancient predictions can accurately apply to the sky as we see it today if they have not been amended to the times, and furthermore, without rigorous testing. We can see here that while astronomy and astrology started from a singular point of study, they have evolved into two completely different fields.
- Staci Pearlman is studying arts and science at the Australian National University.