Where Do Zodiac Signs Come From? Here's the True History Behind Your Horoscope

s the summer officially begins, with the Summer Solstice occurring in the Northern Hemisphere on Thursday, those who enjoy Western astrology will be checking out their Summer Solstice horoscopes to try to use the stars to figure out what the season might have in store.

While some horoscopes sites may promise predictions based on the “movement” of the stars, it’s important to remember that it’s the Earth that’s moving, not the stars. The reason why stars look like they’re moving, both throughout the night and over the course of the year, is because the Earth rotates on its axis and orbits around the Sun. But, before most humans knew that, they spent a lot of time thinking about what was happening up there in the sky.

So, though astrology — looking for answers, signs and predictions in the movements of the celestial bodies —isn’t itself a science, there’s a long history of humans looking up at the stars to plan their lives. Farmers used the skies as a calendar as long ago as Ancient Egyptians, when the rising of Sirius, the Dog Star, around mid-July, was seen as a marker of the imminent annual flooding of the Nile. Travelers used the skies as a compass, following the stars to know where to go. And many people used the skies as a source of mystical direction, too.

But who first looked up at the sky to make sense of what was happening down on the ground and why their fellow humans were behaving in certain ways? Exactly who came up with this way of thinking and when is unclear, but historians and astronomers do know a bit about how it got so popular today.

Where did zodiac signs come from?

The stars are just one of the many things in the natural world that human beings have turned to for answers over the years.

“We don’t really know who first came up with the idea for looking at things in nature and divining influences on humans,” says astronomer Sten Odenwald, the director of Citizen Science at the NASA Space Science Education Consortium. “There’s some indication that cave art shows this idea that animals and things can be imbued with some kind of spirit form that then has an influence on you, and if you appease that spirit form, then you will have a successful hunt. That was taken over by the idea of divination, where you can actually look at things in nature and study them carefully, such as tea-leaf reading.”

Some form of astrology shows up in various belief systems in ancient cultures.

In Ancient China, noblemen looked at eclipses or sunspots as portents of good or bad times for their emperor, though it’s thought that those signs had less application to the lives of other individuals. (Odenwald points out that in societies where people in the lower classes had less control over their lives, divination could seem pointless.) The Sumarians and Babylonians, by around the middle of the second millennium BC, appeared to have had many divination practices — they looked at spots on the liver and the entrails of animals, for example — and their idea that watching planets and stars was a way to keep track of where gods were in the sky can be traced to The Venus tablet of Ammisaduqa. This tablet, which is dated to the first millennium BC and tracks the motion of Venus, is one of the earliest pieces of what’s been called Babylonian planetary omens. The ancient Egyptians contributed the idea that patterns of stars made up constellations, through which the sun appears to “move” at a specific times during the year.

It’s thought that all of these ideas came together when Alexander the Great conquered Egypt around 330 BC.

“There must have been a lot of exchange that got the Greeks on-board with the idea of divination using planets,” says Odenwald, and because they were deep into mathematics and logic, they worked out a lot of the rules for how this could work.”