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Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Star Stuff: What did Mercury ever do to you?

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Dec 7, 2017, 1:05 PM EST

Star Stuff is a weekly column by rocket scientist & astrophysicist Summer Ash highlighting some amazing things happening every day on and off the planet, especially great science done by and/or for women. She harnesses her science communication powers to smash the patriarchy and advocate for equality and inclusion across all time and space. Throwdowns with pseudoscience may occur.

This week’s column is 50% rant, 30% science, 20% universe appreciation, and 150% GIFs. It’s my column and I can make the math work if I want.

I recently discovered that Mercury is apparently up to its old tricks and went into retrograde on December 3rd. You may think it odd that an astrophysicist doesn’t know Mercury’s retrograde schedule by heart, but here’s the thing: it doesn’t matter.

I’m not here to be a hater, I swear. And studies show, I probably won’t change any minds today. I just want to distinguish between astrology as gossip at the water cooler and the kind of astrology that encourages people to take zero responsibility for their life and their interactions with others. Spoiler: it’s the second one I don’t like.

Retrograde refers to when a planet in our night sky appears to move backwards temporarily before returning to its forward motion. Of course forwards and backwards are relative, but if you combine images or track the position of a planet night to night, at certain times of the year, it’s path will trace an curvy “z” or a small loop.

The planet, as seen from Earth, doesn’t really change its motion in any way, it’s just an “optical illusion” of sorts. You witness the same thing all the time on Earth either in a car on the highway, or in an ice skating or roller rink. If you and your friend are both driving on I-95 in different lanes and you speed up to pass them, they appear to be moving backwards relative to you. If they then speed up and pass you, you will seem to move backwards to them. Now think of you and your friend as planets, and I-95 is now the solar system. Et voilà.


Astrologers believe that when a planet goes into retrograde as seen from Earth, the area(s) of life governed by that planet go into a sleeping or resting state. For Mercury, that means primarily communication since Mercury is the messenger of the gods. Mercury in retrograde comes with all sorts of warnings about how your life might fall to pieces thanks to a breakdown in communications. This Bustle article from 2015 has seven great tips for surviving Mercury retrograde: don’t break up with someone, don’t get married, don’t make any big purchases, don’t sign any contracts, don’t travel, don’t get a makeover, and don’t stress too much. Super easy. And here’s the rub, Mercury goes into retrograde 3-4 times a year for weeks at a time, so that’s 10-20 weeks out of the year that you can just write off.

But wait, there’s more! Other planets go retrograde too. In fact, all of them do. When Venus is in retrograde, your emotions can’t be trusted. When Mars goes retrograde, all your energy will be drained. Don’t do anything drastic when Jupiter enters retrograde, because any good luck you have will run out. And when it’s Saturn’s turn, put everything on hold. I’m not even going to go into Uranus, Neptune, and Pluto. If you thought you had at least 30-40 weeks of the year to be productive, think again. Something’s always in retrograde. In fact, the further out the planet is from Earth, the more often it goes into retrograde (because we are essentially “lapping” them). At any given time, 40% of the outer planets are in retrograde for us.

This is the astrological equivalent of epicycles for me. The whole system is too complicated and unwieldy and every time you think you’ve accounted for something, there are ten more things you forgot about.

Astrology is defined as the study of how the motions and positions of celestial bodies influence human affairs and the natural world, which was a good and vital thing once upon a time. I’d even go so far as to say, astrology was probably the first science. It was definitely the precursor to astronomy. We have clocks out the wazoo here in the 21st century: mechanical clocks, digital clocks, atomic clocks, potato clocks. But our first clock was the sky.

Before we even had words to describe time, we tracked the motion of the sun and the moon as they rose and set endlessly and noted how their movements changed across the sky. We realized the sun reached a high point in the sky when the temperatures were the warmest, and it reached a low point when the temperatures dropped. We connected the sun’s height to the stars we could see on the horizon just before it rose. And we drew patterns on the sky to connect the stars and told stories about those patterns so we could remember them. When the sun rose in a given pattern, we knew it was time to plant the seeds or harvest the crops.


Illustration of how the Sun appears to rise in different constallations throughout the year. 

The patterns are our modern day zodiac constellations. They form a ring in the sky around Earth in the ecliptic, the plane of our solar system. Ancient astronomers broke the ring up into 12 equal pieces, each 30 degrees wide on the sky. (Yes, there is a thirteenth constellation but I'll let my colleague Phil Plait explain that whole kerfuffle.) What else do we have twelve of? Oh yeah: months. Glossing over a lot of calendar history, brings us to today when we no longer use the stars to tell time and have mostly forgotten they important role they once played in our lives.

Perhaps that’s one reason why astrology seems to be so popular. I’ve come across articles everywhere from Bustle to Refinery29 to New York Magazine. I would link you to them, but I can’t bring myself to give them the clicks. I will however highlight this op-ed of sorts in the New York Times by the resident astrologer for New York Magazine, Madame Clairevoyant, that begins by saying she doesn’t practice “real astrology” and that it’s all in fun, but then argues (I think?) that the horoscopes she writes are still meaningful. I admit, I don’t fully know what she’s trying to say.

As I said earlier, I’m not here to make fun of anyone or to tell them what they can and can’t believe, which is what astrology is - a belief system, NOT a science. To me there’s a difference between indulging in what I like to call the “Buzzfeed Quiz” version of astrology and the more dangerous version where people live their lives entirely by what their horoscope or chart or celestial consultant tells them to do. For me it’s over the line if someone (other than the occasional entertainment columnist) takes money in exchange for their services as an astrologer because more often than not, that money comes from the people who can least afford it. It’s not much different from the lottery, or the latest “as seen on TV” product that promises to save you hours of time and energy, or whatever get rich quick scheme is making the rounds. Similarly, you can rant all you like about how you lost your phone or so and so isn't calling you back because Mercury is retrograde, but please don't actually use it as an excuse for things that matter like your responsibilities to your friends and family and colleagues (well, depends on colleague...).

I’ll be the first to admit that I long for a greater connection to the natural world and to the Universe at large. And at first glance, any given horoscope will ring true to any given reader because they are just vague enough that they can speak to something in all of us. There’s a fancy term for that: confirmation bias. It means we resonate which the parts that are true or pleasing to us and we disregard the rest. Similarly, horoscopes perpetuate the misconception that correlation equals causation. Just because you were born when the Sun was in a particular zodiac constellation, you aren’t automatically bestowed a specific set of traits and abilities. If you made a list of all the characteristics associated with each zodiac sign and constructed a random poll, you would find no significant correlation between birth month and personality. Not only that but due to the precession of Earth's axial tilt, the stars are not where they used to be. A Gemini in ancient Rome is a Taurus by today's sky, but still neither sign has any more to say about that person's life

Okay, I think it’s time for the 30% universe appreciation I promised you. Let’s go back to poor, much maligned, scapegoat Mercury. What has this amazing planet done to deserve our wrath several times a year? It may not look like much in the average image you’ve seen, but Mercury is tenacious AF. It whirls around the Sun once every 88 days but only rotates once on its axis every ~58.5 days which means it’s both slow roasted by a star tens of millions of times larger than it on one side while the other side is in a deep freeze. Fun fact: the average walking speed of a human is akin to the rotation rate on Mercury, so you could take a never ending walk at sunset or sunrise (with the appropriate spacesuit of course). Mercury also lacks an atmosphere so it’s taken more than its fair share of pummeling by asteroids over the last billion years. Another fun fact: all the craters on Mercury are named after famous writers, artists, and composers.

NASA’s MESSENGER mission was in orbit around Mercury from 2011 to 2015 and has revolutionized our understanding of the planet, including the discovery that it has plate tectonics just like we do on Earth, only it’s one giant plate instead of seven. Mercury is so cool, Ryan Mandelbaum wrote an entire article about it that opens with a quote from Method Man. If not for Mercury, we might have been slower to accept Einstein’s theory of general relativity. And as Mandelbaum points out, physicists say there’s a 1% chance Mercury could be a gravitational wild card in the future of our Solar System that could one day crash into Earth, so respect your neighbors.

I could go on and on, especially because I have so many more GIFs I want to use, but I think I'll leave it here. Please just do me three favors: 1) don’t make any major life decisions based on horoscopes (especially ones involving any astronomers in your life), 2) don’t give more money to an astrologer than you would give to your hairdresser or masseuse and maybe not even that much, and 3) give Mercury some love.

Oh and last but not least, don't let this be you. 

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