The Zodiac was created about 2,000 years ago as a way to track time. Each month, the sun appears to pass through 1 of 12 constellations that are each tied to a sign (In 1930, the International Astronomical Union, actually defined 13 constellations that the Sun passes through, but one does not have a sign). These constellations define the zodiac. The Sun and the constellations do not actually move, but Earth’s orbit around the Sun creates the illusion that the Sun is moving against the background of stars. It takes about a month for the Sun to pass through each constellation, and those days are assigned an astrological sign, which are the basis for horoscopes. For hundreds of years, many people have thought that the constellation passing through the sun on their birthday (your astrological sign) says something about your personality. But nowadays your astrological sign, does not necessarily correspond with the constellation that was near the Sun on your birthday. The constellations appear to have shifted. This is because over time the moon’s gravitational pull on the Earth has caused it to wobble on its axis, which is called precession. Precession makes the earth move similarly to how a top does. The Earth slightly wobbles as it rotates around its axis, tracing a circle in the sky, so the poles are not always pointing exactly to the same background stars. Although the wobble is very slow—it takes about 26,000 years to complete a full wobble circle—the movement affects the apparent location of the stars we see. Since it has been about 2,000 years since the zodiac signs were created, the corresponding constellations have shifted about a month. 2,000 years from now the signs will be 2 months off the constellation that can actually be seen in the sky. Due to Earth’s constant precession, the astrological signs will continue to get further off track from their corresponding constellation, but the zodiac constellations do help us track all of Earth’s movement.
