Episode 5: What happens when Mercury is in retrograde?

In this episode of Void Deck by Science Centre Singapore, Lydia asks Science Centre's Manager, SK, all about Mercury in retrograde.

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Episode highlights and timestamps

00:00 - 00:33 Introduction
00:34 - 02:29 What is 'Mercury in Retrograde'?
02:30 - 03:18 Cultural Significances
03:19 - 04:20 Conspiracy??
04:21 - 04:57 Confirmation Bias
04:58 - 06:15 Retrograde of Other Planets
06:16 - 10: 45 Misconceptions & Clarifications
10:46 - 11:32 Why is it important to talk about this?
11:32 - 12:03 Outro

Transcript

Lydia - PSA: Mercury and Venus are in retrograde. So your comms, your love life... right? But of course, all of these are just cultural association/interpretation.

SK - Yes.

Lydia - Hello and welcome Void Deck by Science Centre Singapore. I'm Lydia, and today we have SK who is actually a manager from the Exhibitions department. But he's also an astronomy enthusiast on the side. And today we're going to be talking about Mercury in retrograde. But what is Mercury in retrograde?

SK - When a planet goes retrograde-- Basically, what we are saying is that it's motion through the sky against the background of so-called ‘fixed stars’ is going in the opposite direction.

Lydia - So is it actually going in the opposite direction?

SK- No, no, it's actually just an optical illusion due to the perspective of us looking at the planet as it overtakes us in its orbit.

Lydia - So it looks as if it's going backwards, but actually it's not?

SK - Correct. So the inner planets will orbit faster but the outer planets like Uranus, Neptune Because they are so far away, their orbits are so slow. The retrogrades are very long and is not very frequent. Unlike Mercury, because it zips around the sun so fast. 88 days. It's like we go one round around the sun, Mercury goes around more than three times.

Lydia - Three times! That means... Mercury in Retrograde will happen three times for us a year?

SK - On average, 3 to 4 times a year.

Lydia - Bad things will happen three to four times a year.

SK - [hesitant laughter]

Lydia - So when we are on Earth and we look out in the sky, can we actually see the the movement itself change?

SK - Yes, we actually can. The challenge is that for the inner planets, the retrograde, because they being the inner planets, you only see them during the dusk or dawn, early or late hours. So you actually see them very low in the horizon. So it's a bit hard to catch them.

Lydia - And this retrograde, how long does it take?

SK - For Mercury... It takes about three weeks.

Lydia - And right now we are we are in Mercury in retrograde right now, right?

SK - Yes. Right now we're in Mercury retrograde until I think it's about 13th/14th November

Lydia - Okay. So PSA we are currently in Mercury in retrograde.

SK - Check your headphones! (jokes)

Lydia - In Western pop culture, right, Mercury retrograde is normally associated with bad things like bad things happen in Mercury retrograde.

SK - Yes. This is a long cultural tradition, long history to it. And you probably are aware, and our viewers are aware Mercury is associated with communications. That's why during Mercury retrograde, people will say that my laptop hung today. Something went wrong. My call dropped off. And that is because Mercury is in retrograde. So every culture views retrograde with their own stories. For the Greek tradition, they look at it as Hermes -- the Greek god. Because Mercury goes around the sun so fast. And that's why it's a messenger. So that's why how it's related to communications There are some like... there's a very interesting story about 2000 years ago in Chinese Western Han. Mars was going retrograde. No, actually it was a prediction that was conjured up by the Emperor and it was actually court politics to force one of these chancellors to commit suicide, to absorb the bad omen. So that was a well-known story, because Mars at that time -- They said that it's going to retrograde near the big red supergiant Antares which is a symbol of the Emperor. And so they conjured up this story and said that there is a big threat to the emperor. Somebody must commit suicide.

Lydia - So it's like to get rid of your competition or something, then, like they made up the story.

SK- Yeah.

Lydia - And that's how, I guess, ominous vibes get associated with Mercury in Retrograde.

SK - Yes, yes. Correct. And that later on, it was calculated that events never took place. It was made up.

Lydia - Conspiracy! How do you think that evolved to the current concept

SK - Probably it’s what scientists would call ‘confirmation bias’, especially because Mercury retrogrades quite frequently. So when something wrong goes on in your daily life and then it occurred to you, Oh! Mercury is in retrograde. Must be that.

It's not always bad though. Like in the Indian astronomy, its history. They look at retrogrades as a positive sign, as a sign of strength. So it's not all bad.

Lydia - It's not all bad. So other than Mercury, do the other planets also go through retrograde?

SK - Yes. Actually, all the planets will have retrogrades. So it happens whenever a body overtakes another one. So the perspective changes.

Lydia - Even Earth goes into retrograde...?

SK - Yes, that's a good point. If you are on... let's say you're on Mercury and you're looking at Earth going by. So when Mercury overtakes Earth, when you're on Mercury and you overtake Earth, you actually see Earth going into retrograde as well.

Lydia - So it's mutually.... It’s like a mutual relationship both of us retrograding each other?

SK - Yes. Correct. A common analogy is when you're driving on a highway and you catch up with a car and overtakes it. This is a very common analogy.

Lydia - Cause they're both going in the same direction at the same time, just different speeds and it looks like it's going backwards...?

SK- Moving backwards. Yeah, Yeah. But there's a small problem with this analogy. If you catch up with a car, it doesn't really appear to move in the opposite direction if you are catching up steadily. So the big difference is that retrogrades must be viewed from the background stars. you can see the planets moving in the opposite direction as opposed to what they normally do.

Lydia - When Mercury is in retrograde -- Like when it looks like it's changing direction. Does its gravity pull changes for us?

SK - That's a good question because especially Mercury's orbit is very -- not very -- but quite elliptical compared to the other planets. Meaning it's not exactly a circular shape. So at certain points it is closer to Earth, at certain points its further. So there is a very, very slight gravitational effect. But it's a very small amount. So actually there is negligible effect.

Lydia - So... while it is retrograding does anything happen to that planet specifically?

SK - No it doesn't. it's really just the viewpoint? It is... doing its thing.

Lydia - Okay, so now let's try to bring up our little solar system model. For those without any visual reference, you can take note that we are using a solar system model. You can refer back to it on our eMagazine website or YouTube channel.

SK - So I think first of all -- they're not exactly to scale. So we'll move Venus out of sight just so that we can see Mercury and Earth clearly. Looking from the top, we will actually see the planets going around this direction. They all go in this direction. But the thing is, Mercury goes around much faster than Earth. So it will catch up with Earth. So as it catches up and we'll see Mercury here during the sunset. Because we are turning we are rotating, spinning on our axis. As we turn into the night, we will start to see Mercury in the dusk in the evening times. And as it catches up, this is when the retrograde action will begin. Because as it overtakes Earth. Then, it begins a retrograde period and you don't see it anymore. It drops below the horizon during the daytime because it's just too bright and only to appear later as it zips past Earth on the other side. But now Earth is spinning, still spinning, and we see it during the early morning hours and it's still going in retrograde, and it goes faster, and then it starts to go back into the motion and then it disappears again. So this is basically the retrograde phase of Mercury. And it happens about 3 to 4 times a year.

Lydia - So what happens if let’s say the sun is out of the picture., right. During that days where it's supposed to disappear, what actually happens? It's just normal movement backwards?

SK - Yes. Correct. And then you look at the video, you will see which date it dips below. I think about 31st October. It dips below.

Lydia - So this is going the correct way? (points to video)

SK - No, this is retrograde. It's going west already.

Lydia - How come all the stars in the background here going in that side also?

SK - It's correct.

Lydia - It’s correct!?

SK - So because we we go around the sun this way. So as we go around the sun think of the background stars as let's say we imagine it is a 2D canvas. So every day we move like that. That's why the stars are moving westwards every night. Not not the daily nightly east to west, because that is from our rotation. Right. But because we are doing this. So we are seeing different parts of this canvas every night.

Lydia - Because normally the stars will look like it's setting and stuff like that also?

SK - Correct. And that's east to west right. Every night. That's quite fast. But next night at the same time you look, it has actually shifted west because of the orbit the next night.

Lydia - So night one is here (points to a spot). Then it goes down down down down.... Then night two, it’s here (points to shifted spot to the right), then it goes down down down Correct. Yeah. So it's against this backdrop that the planets go very fast. They don't follow this pattern. They just go.

Lydia - So the other stars are going... Slowly, night by night this way. But Mercury is going (the other way)?

SK - The other planets as well. The planets are all wanderers. So you can imagine why retrogrades get stuck in the collective memory. Because you see everything, you can predict and see the pattern there. You know, even for the movements of the planets but suddenly they just move backwards. It's like a big thing.

Lydia - I think my understanding is better a bit.

Why is it important to us that we talk about it?

SK - I think we talk about it partly to understand the historical traditions from many different cultures and do a comparative study, and also to understand how science and knowledge of the cosmos have evolved over time as well, that now we can actually predict solar eclipses, lunar eclipses. We understand these orbits very well. And it wasn't overnight. It was a very long process. How civilizations, different societies over time, slowly came to have a better understanding of the cosmos. Mercury retrograde I think, after this one, is probably (happening) early next year. If I'm not wrong, I think it's early next year January around there.

Lydia - All right. And that's the end of our episode. So if you are interested in more astronomy information, do check out our vodcast episodes, the previous vodcast episodes on our YouTube channel, or our eMagazine articles. You can also check out the planetarium live planetarium shows that's happening on Friday nights. But do take note that the last one is on 20th November. Other than that, we will see you in the next episode.