Before electricity, street lights, and skyscrapers, once the sun went down, one of the primary sources of light for humanity were the stars. Imagine, looking out into the great beyond without any understanding of the universe or solar system, and watching hundreds of lights in the sky as they would slowly change positions while the seasons passed.

Our ancestors were bound to make out patterns in the sky—just like how we can look at a cloud long enough and see one that’s animal-shaped. They played celestial Connect the Dots and came up with stories to go along with the characters they imagined. Then, they connected those stories to their own lives. That, at its roots, is how astrology formed. And centuries later, many of us still feel that the positions of the planets and stars in the sky can affect our everyday lives. Astrology, for as much as it may not have any scientific basis, still fascinates many of us.

So, even if you’re a stargazer or if you never look up at night as long as you have the orange glow of a blunt in front of you, you may have heard of a little thing called Mercury in Retrograde. That one girl from high school may post about it on Facebook, or you might get spam email in your inbox warning you not to make any significant life changes during the three or four times a year that it happens.

So, what the hell is this all about? Don’t worry, we’ve explained everything you need to know about Mercury in Retrograde.