If you ever watch the night sky for long enough, you will notice a moment when something strange seems to happen to the planets that orbit in our solar system. Their journeys across the cosmos start off in one direction and then go into another, seemingly without rhyme or reason.
This is known as planetary retrograde, and it is a phenomenon that has stirred up much intrigue (and misunderstanding) for centuries. The term has been thrown around in horoscopes, memes, and even tech support forums, but, at its core, retrograde is nothing more than a natural optical illusion.
Both astronomy and astrology have fought to stake their definition on what retrograde means for humanity, but some people might not even know what it actually means. Intrigued? Click through this gallery to find out.