What Really Happens When Mercury Is in Retrograde

The first planet from the sun would like to be excluded from this narrative.

A picture of Mercury as a bright crescent against the darkness of space, taken by NASA's MESSENGER spacecraft in 2008

You’ve probably heard some version of the line, usually delivered with a sigh. Someone is having a crappy day. Or they’re in a weird mood. Or nothing seems to be going right, despite their best efforts. And they’ve laid the blame on Mercury, the smallest planet in our solar system, nearest to the sun. “It’s Mercury’s fault.” The darn thing is in retrograde. And in fact, it’s happening right now.

The idea that planets can influence people’s lives is a core principle of astrology, a practice of divining meaning from the cosmos that has been around for thousands of years, in various incarnations. The belief that Mercury, in particular, can have some prickly effects is a fairly recent development, starting around the 1980s, according to a recent Harper’s Bazaar deep dive on the topic. And it achieved its modern-day, meme-like quality in the past decade, a story that involves, of all things, Taylor Swift complaining about Mercury’s supposed astrological chaos in an MTV clip from 2014.

Astrology is not a science. But “Mercury in retrograde” is a real phenomenon, best explained by people who, like astrologers, think about Mercury quite a bit, but, unlike those astrologers, would never dream of blaming the planet for making them forget their keys: planetary scientists. Mercury in retrograde doesn’t mean there’s anything funky happening with the planet’s actual orbit; it’s all about the way it appears to us in the sky, as a tiny white dot in the dusky hours after sunset and before sunrise, says David Rothery, a planetary scientist at the Open University, in England. Most of the time, Mercury moves west to east relative to the stars in the night sky. But several times each year, that steady progression changes, moving from east to west instead.

The reason has to do with the relative positions of Mercury and Earth around the sun. Mercury orbits closer to the sun than Earth does, which means the small planet travels much faster around the star, circling it in just 88 Earth days to our 365. That swiftness means that Mercury occasionally laps Earth on our planet’s own journey around the sun, “overtaking us on the inside track,” Rothery told me. And when that happens, that tiny white dot in our sky appears to reverse course and move, little by little each night, in the opposite direction. Eventually Earth catches up, and Mercury appears to switch direction again, becoming “prograde.” This phenomenon occurs about three or four times a year, and lasts about three weeks.

So, though Mercury retrograde is a thing, it is an optical illusion. All the action happens from our vantage point here on Earth. Such a visual trick even occurs on the surface of Mercury itself, with a different celestial object. “There are times when the sun actually moves backward as viewed from Mercury’s surface,” Nancy Chabot, a planetary scientist at Johns Hopkins University Applied Physics Laboratory, told me. Trippy!

When Mercury appears to shift from our perspective, the planet itself is just chilling, tracing its usual path around the sun. If Mercury actually stopped and started moving backwards in its orbit, we’d have a lot more to unpack than the missed emails and commuting delays astrologers warn about. And Mercury, of course, has no bearing on the daily goings-on of humans. Neither does any other planet. So I feel an irrational impulse to defend Mercury, which has drawn the short stick in this context.

Mercury is already one of the most overlooked planets in our solar system. Mars gets all the rovers. Jupiter enjoys glossy photo shoots. Venus is at the center of a dramatic maybe-it’s-aliens-maybe-not debate. Even Uranus is getting a lot of attention recently. Mercury doesn’t have any moons or rings. Even Pluto has moons! And what does Mercury get? Groans and eye-rolls from people who, as the writer Jo Livingstone wrote in Harper’s Bazaar, “may well know more about Mercury as an astrological entity than a physical planet.” To paraphrase Taylor Swift, I think Mercury would very much like to be excluded from this narrative.

“So far as I’m concerned, the only bearing this has on events on Earth is that for most of the time when Mercury is ‘in retrograde,’ it is so close to the sun in the sky that radio communication with a spacecraft at Mercury is compromised by interference with the signal,” Rothery said. “I take no notice of any astrological fuss,” he said, and those who do should seek out Mercury for themselves in the night sky, or look up pictures of the planet from space missions that show “what a fascinating world it is.” Mercury has the most craters of any planet in the solar system. And it’s actually shrinking, very slowly over billions of years, its crust cracking and crunching as it shrivels.

Mercury’s retrograde phase can affect Chabot’s mood, but not for the reason astrologers might think. Whenever Chabot spots a headline about Mercury being an astrological menace, she checks whether the picture in the story came from MESSENGER, a NASA spacecraft that orbited the planet from 2011 to 2015. (The mission’s name stands for “Mercury Surface, Space Environment, Geochemistry and Ranging.” NASA loves its acronyms.) “Mercury being in retrograde multiple times a year means that I get to see the MESSENGER images used in stories multiple times a year, which makes me happy,” Chabot, who worked on the mission, said. She gets bummed when the astrology posts use pictures from NASA’s Mariner 10 spacecraft instead. That mission, from the 1970s, captured less than half of the planet’s surface. It wasn’t until MESSENGER that humankind could see the planet in its entirety—every crater and crevice on its sun-baked terrain, and the hardened ash that meant the planet once crackled with volcanoes.

The MESSENGER mission ended when the spacecraft ran out of the propellant necessary to remain in orbit and crashed into Mercury’s surface. The latest mission dedicated to Mercury, led by the European Space Agency and JAXA, the space agency of Japan, departed Earth in 2018. The spacecraft is still on its way, relying on a series of flybys past Mercury and Venus to steer toward its target. The BepiColombo mission, named for the 20th-century Italian mathematician who did the calculations for Mercury flybys, will nestle into orbit around Mercury in late 2025.

By the end of next week, Mercury will switch acts in the optical illusion in our sky, moving out of retrograde. In late June, BepiColombo will make its latest flyby, zooming within just 124 miles (200 kilometers) of the planet's surface. And as it goes, it will capture stunning images of this richly textured and astrologically maligned world. It will not find any evidence of why your day feels like it’s going haywire. The answer to that is much closer to home.