Where Do Astrology Myths Come From? The Curious Story Behind the 13th Sign, Mercury Retrograde, and the Full Moon

Mercury never actually moved backward — but it sure looks like it

Few astrological phenomena cause as much of a stir as Mercury retrograde. Every time a new retrograde season rolls around, warnings start circulating: don't sign contracts, don't send that important message, wait for the dust to settle. But it's worth asking: do planets actually move backward?

The curious answer is no — no planet in the solar system ever reverses its orbit. What happens is an optical effect: when a planet is moving more slowly than Earth at a certain point in its path, that difference in speed creates the illusion, from where we stand, that it's moving backward across the sky. It's a bit like watching a slower car through the window of a moving train: for a moment it looks like it's going backward, when really it's just moving slower than you are.

Mercury draws so much attention because, having the shortest orbit and being closest to the Sun, it goes through this effect three to four times a year, with each period lasting about three weeks. Other planets go retrograde too — Venus, Mars, Jupiter, and the rest all have their own cycles, usually spaced further apart and lasting longer the farther they are from the Sun. Mercury just gets talked about the most because it shows up on the calendar so often.

The link to communication comes from mythology: Mercury was the messenger of the gods, the planet associated with words, contracts, and travel. Interestingly, the wariness around this movement didn't start in modern astrology practices — records show that as far back as the mid-18th century, British farming almanacs tracked this phenomenon to decide the best planting times, blending practical astronomical observation with a symbolic reading of the right moment to act.

To this day, there's no evidence that the apparent motion of the planets directly affects human affairs. What does exist is a symbolic tradition within astrology itself that reads these periods as invitations to review and reflect, not necessarily as omens of disaster. Among contemporary astrologers, a less fatalistic view is becoming more common: Mercury retrograde as a pause to reread what was said, revisit what was agreed upon — not as a verdict that everything is doomed to go wrong.