By: Sarah Readdean

Zodiac signs and the influence of events on Earth by the positions of astronomical objects can be traced back to ancient civilizations. Zodiac signs originated as the constellation in which the Sun falls when you were born. But maybe you’re actually reading the wrong horoscope.

As the Earth orbits around the Sun, we see different stars in the sky depending on the time of year. If the Earth was stationary, we would never see the stars positioned behind the Sun.

Picture all of the constellations in a ring around the Sun-Earth system. The constellations visible from Earth depend on Earth’s orbit throughout the year. But the constellations we see during our zodiac season are not our actual zodiac.

The constellation positioned directly behind the Sun at the time you were born (which, granted, we can’t see) is considered your zodiac sign. For instance, if we look up at the night sky tonight, we would see Virgo. But the constellation positioned behind the Sun is Aries, the zodiac for March 21 through April 19. Happy Aries season, by the way.

But that’s not even correct. During “Aries” season, the constellation actually positioned behind the Sun is Pisces. So if your birthday is today, and you thought you were an Aries ram, think again. In all technicality, you’re really a Pisces fish. Confused? Searching for a scientific reason for our signs being bumped a month earlier? It’s called precession.

The Earth is spinning on its axis. But just as a spinning toy top, the axis isn’t always pointing in the same direction. This is because of the gravitational pull of the Sun and Moon on the Earth.

Earth’s axis will slowly shift directions for 26,000 years, the Earth’s period of precession. In 130 B.C.E., Greek astronomer Hipparchus concluded the stars shifted about one degree every 100 years.

Taking this into consideration, Earth’s axis has shifted since zodiac signs were established thousands of years ago. So the Sun didn’t actually pass through the constellation you thought it did at the time you were born.

Oh, and one more thing. Have you heard of a 13th zodiac sign? There are 12 signs evenly split into 30-degree divisions of the sky to make for a 360-degree circle. But really, the constellations vary in size and distance spanned — therefore, they aren’t always behind the Sun for a full month.

The ancient Babylonians cut out the 13th constellation, Ophiuchus, to better fit their 12-month calendar. The redefined zodiac calendar includes this hard-to-pronounce serpent-bearer as the sign for Nov. 29 through Dec. 17, as calculated by the Minnesota Planetarium Society in 2011.

Chances are you’re reading the wrong horoscope. Heck, maybe your horoscope doesn’t even exist. But if you want to correct the years you spent wrongly identifying as a Cancer or a Capricorn or a what-have-you, Time released the corrected dates provided by the Minnesota Planetarium Society.

German astronomer Johannes Kepler described astrology as “the foolish stepdaughter of astronomy.” Maybe he was right all along.