Ask a Scientist

Courtesy of The University of Tennessee, Knoxville.

I’ve had a couple of friends complain about how crummy they’ve been feeling recently. Things just aren’t adding up; they’re bummed out all of the time; they seem to be in a low-energy funk; they get sick a lot.

Whatever the case might be. I casually shrugged this off due to weather. Seriously, up until recently, Knoxville has been getting absolutely dumped on with rain, it’s been pretty cold outside and all those clouds haven’t helped either.

The idea that weather makes people feel worse isn’t just a hunch either – rainy weather can give you a sense of the blues. Winter can also make things worse, being responsible fora mood disorder known as, “seasonal affective disorder.” Either of those seemed to be good explanations. The weather sucks and it’s still kind of wintery – of course things are going to be a bit wonky.

But then I heard an alternative explanation: Mercury retrograde. Now that was causing all the fuss. Like the planet? Or the element? What is “retrograde?” Seemed fishy. I’ll admit, the first time I heard this, I was on Snapchat and I didn’t even know why the app was even telling me this. But my colleagues insisted that this could be creating all the hubbub. Naturally, we at Ask a Scientist dug a little.

What did we find? Starting at the beginning, retrograde generally refers to “retrograde motion,” and that’s where an object is orbiting in the opposite direction that the object it’s orbiting is spinning. The moon, for instance, orbits in prograde relative to the earth. If it orbited in the opposite direction, it would be in retrograde motion.

But we’re talking about something different: Mercury doesn’t orbit the Earth, it orbits the sun. What does retrograde or prograde mean in that sense? Well, astronomers use the terms “apparent retrograde” or “apparent prograde” to describe how Mercury appears to move relative to us.

We’ll use an analogy to talk about this. You might remember those spiral coin donators in public places like malls and museumslike this one? You put the coin in a shoot at the top, and it rolls along the surface, sort of orbiting the hole where the coins eventually fall into. Now, imagine you’ve put two coins down the same shoot a few minutes apart, and you’ve got a camera on one of the coins in our well. Eventually, because the orbits are at different speeds, the other coin might look like it’s moving backwards relative to the direction it normally is. That’s apparent retrograde.

And that’s the same thing as Mercury Retrograde:Mercury appears to move backwards compared to it’s normal pathway relative to us on earth. In daily life, Mercury will look like it’s traveling across our sky west to east. Which is opposite of the moon, and why the distinction is important. It’s apparent prograde motion, not plain or prograde motion. Because it’s orbiting the sun, on occasion it looks like it’s going east to west instead. That’s when Mercury reaches apparent retrograde motion, and that’s what people are talking about when they mention Mercury Retrograde. This event lasts about 21 days due to the timing and speed of the earth relative to Mercury. All of the other planets are different, of course.

So, that’s the science in a nut shell. But where do bad omen come into play? Well, Mercury Retrograde, as a thing that affects people, isn’t astronomy. It’s astrology.

Astrology, being the study of how planets, stars, galaxies and constellations can affect and predict characteristics about people – horoscopes and zodiac signs. Astronomy, by contrast, is just the study of these massive objects.That image of a black hole that sent the internet on fire? That’s astronomy. It’s a coordinated effort to try and map and understand all those big objects in the universe. Astrology, by contrast, would try to figure out how this black hole affects your personality or how it would predict events in your life. Already,astrologists are looking into that.

Mercury retrograde is therefore used in the same way to predict the negative behaviors and feelings people will have during that time period, or so astrologists claim. Is there any science to back this up?

Well, the fact thatastronomers often gripe about being associated with astrology, and that astrological predictions are often incorrect, should raise some red flags. We did our own search into the validity of astrology, but when we looked at peer reviewed studies, we found nothing that supported astrology.We did find a study showing that astrologist predictions were bogus though.

But we’re not just looking at astrology overall. Some parts of astrology could be more scientifically sound than others, I suppose. No, this column is about a specific part of astrology: Mercury

Retrograde. So, is mercury retrograde a real thing despite astrology being wrong fairly often? Well, we searched for hours trying to find studies on Mercury Retrograde’s effects on people specifically and found nothing that suggested it had any effect in peer-reviewed studies. We did find a study that saidMercury Retrograde didn’t affect behaviors in capital markets as predicted by astrologers, however. Even if there were some effects, some of them may come from superstition. A sort of self-fulfilling prophecy – which changes things, of course.

So, Mercury Retrograde is a real thing that astronomers see. Mercury does look like it’s changing direction in our sky for a few weeks out of the year. But when talking about how it affects our personalities and lives, Mercury Retrograde probably – if not definitely – has no effect.

It’s a convenient explanation people have used when things in their life are awry, or why they shouldn’t take on new risks, and we get that. If something unfortunate feels like it can be explained, especially by circumstances out of your control, that’s often compelling. But it doesn’t make it true, and when we start looking for the effects of Mercury Retrograde on people using science, we get a different message; it doesn’t.

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