False-colour image of Mercury made by MESSENGER | Photo: NASA Goddard Flight Center, CC BY 2.0
Mercury’s going retrograde today, folks! Here’s what it means and why it doesn’t make a lick of difference.
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Mercury, the internet tells me, is “going retrograde” today. Unfortunately the parts of the internet telling me this are the astrology parts and not the astronomy ones, which means it comes with an insufferable amount of woo. For example, this site tell us that, Mercury “rules” such things as “all types of communication, including listening, speaking, learning, reading, editing, researching, negotiating, selling, and buying. Mercury also rules all formal contracts and agreements, as well as important documents such as book manuscripts or term papers, agreements, deeds, contracts, leases, wills, and so forth.” And because Mercury’s going into “a resting or sleeping state” when it goes retrograde, you shouldn’t “make any important moves”:
This, like all astrology, is complete and utter nonsense. There is no reason to believe the motions of the planets have any effect on humans, and believers have been able to posit no reasonable means by which they might even correlate with changes in human behaviour, let alone cause change. Here’s a quick rundown of astrology if you haven’t really taken a look.
But what causes the apparent retrograde (backward) motion of Mercury in the sky? That’s much cooler.
Check out this video. It shows what Mercury would look like if you were to hover directly above the Earth between the Earth and Mercury, staring at Mercury the whole time. Those vertical lines are the relative position of the sky and the other distant stars. Mercury, for much of its orbit, appears to go from right to left from our perspective. But, as it comes on the near side of its orbit (between us and the Sun), it appears to switch direction temporarily to left to right, until our rotation and its rotation conspire together to make it look like it’s going right to left again.
Supremely cool stuff.
This is all because Mercury’s orbiting the Sun so much faster than we are. If Mercury’s orbit took 364 1/4 Earth sols to orbit the Sun, its relative position to the Sun would be the same all year and the only movement it would have in the sky would be due to Earth’s rotation and its axial tilt (like the Sun).
All planets appear, at some point in their orbit, to move retrograde to their usual direction, and they have done for the lifespan of the Solar System. They did so before humans, and they will continue to do so long after humans have died out. So go ahead: communicate while Mercury’s in retrograde. Start a PR campaign. Start a magazine. Send e-mails. Talk to your loved ones. Make important moves. No planet’s position in the sky is going to make a lick of difference to your communication abilities.
But then, you knew that already, didn’t you?
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Richard Ford Burley is a human, writer, and doctoral candidate at Boston College, as well as an editor at Ledger, the first academic journal devoted to Bitcoin and other cryptocurrencies. In his spare time he writes about science, skepticism, feminism, and futurism here at This Week In Tomorrow.