What Do Astronomers Mean When They Say Mercury Is In Retrograde?

Astronomers have known about the planet’s apparent retrograde motion for centuries. Is there any truth to the astrological phenomenon?

By Sofia Quaglia
Jul 6, 2023 6:00 PMJul 7, 2023 3:59 PM
(Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)


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Every three to four months, Mercury appears to travel backward across the sky and the internet becomes ablaze with worries about the mayhem that a Mercury retrograde has in store for us. Brands have even jumped on the bandwagon, offering Mercury retrograde merch, deals and sales.

To astrologists, this planet’s vocation is communication and tech; according to Roman mythology, Mercury was the god of messages. Therefore, a Mercury in retrograde is often associated with a range of misfortunes and miscommunications for those of us on Earth.

Yet we cannot blame the planet Mercury or its position in the sky for any mundane mishaps and communication issues we might be experiencing. If planets and stars affected life on Earth, things would be very different.

“I feel like life is chaotic as it is,” says Paul Byrne, an Earth and planetary sciences expert at Washington University in St. Louis. “I'd hate to think that the planets were having any kind of effectiveness, and I think we can pretty confidently say that they don't.”

Plus, most astrology is based on the classical planets, those we have known about for centuries and can see with the naked eye. But many more discoveries are added to our understanding of the universe every year.

Read More: Why Are People So Into Astrology Right Now?

What Is Mercury Retrograde?

Mercury retrograde is called “apparent Mercury retrograde” by astronomers because it’s an optical illusion. All planets travel around the sun in a counter-clockwise orbit; and in most cases, when we look up at the sky at night, they all appear to be traveling in that same direction.

But because not all planets travel at the same speed around the sun — and because they embark on differently sized orbits — sometimes Earth “laps” other planets. And sometimes, other planets lap us.

When we overtake a planet that is farther from the sun than us, like Mars, it can look like the planet is moving backward against a backdrop of stars. It’s the same phenomenon that occurs when you overtake a slower car while driving: It may appear as if the other car is not moving, or moving backward, but both vehicles are still traveling in the same direction.

On the flip side, when planets that are closer than us to the sun — Venus and Mercury — overtake us and begin to curl back around the sun, they also appear to be moving backward from our perspective.

How Long Is Mercury in Retrograde?

Mercury takes only 88 of our 365 days to complete its circumnavigation. This means that every three to four months, the planet starts to circle back. It takes three to four weeks for Earth to catch up, at which point Mercury goes back into prograde.

“We basically overtake Mercury for a little while, and then it outpaces us again. But its retrograde is purely an optical effect because we're both going around the sun … at different speeds,” says Byrne.

Read More: The Cannibalistic Chaos Within Planetary Systems

When Is Mercury in Retrograde?

Interest in Mercury’s influence on human life has once again picked up in popularity over the past few years, together with enthusiasm about astrology in general. In fact, there’s a website dedicated solely to telling you whether Mercury is currently retrograding.

Since Mercury is closer to the sun and has a shorter orbit, its apparent retrograde happens frequently. Mars’ apparent retrograde is easier to see because the Red Planet is right next door, but it takes about two Earth years to go around the sun completely.

Still, because of the planet’s location between us and the sun, Mercury’s apparent retrograde motion is only visible to the human eye around sunrise and sunset. At these times, the sun’s light isn’t strong enough to wash out the planet from our sky.

You’ll also want to keep your eyes trained on the horizon, as it rises and sets nearly in step with the sun. “The best way to see Mercury is to go out to a flat plane field where there are no buildings and big trees in the way,” Byrne says, “and then you have a much better chance.”

In the rare case that you’re able to see the apparent retrograde in person, remember that what you’re seeing is an optical illusion. The planet isn’t actually moving backward — it just looks like that from your vantage point.

Any “bad vibes,” therefore, are entirely of your own making.

Read More: Optical Illusions Are Weirder Than You Think

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