#11: Universal speed in an elephant sanctuary
TRANSCRIPT
Corinne Caputo
Hi, welcome to pale blue pod, the astronomy podcast for people who are overwhelmed by the universe but want to be its friend.
Moiya McTier
It's so cute. I want to be the universe's friend. And I am and you I am Dr. Moiya McTier I'm an astrophysicist. That's where I got the degree and being a friend to the universe at a folklorist. And I'm so happy to be here. And
Corinne Caputo
I'm Corinne Caputo, a writer and comedian and I was like there's a third thing I am well, I have been rubbed tufting a lot this weekend. So that's the third thing I am this week. If you hear me coughing throughout this episode, it's because I need a high quality mask and I just like breathed in all these like fibers and immediately Googled it. Tons of textile workers have died. And I'm like okay, we're in
Moiya McTier
please don't fall prey to a death from like the 1800s like don't do that.
Corinne Caputo
I do love vintage stuff.
Moiya McTier
Let me know when we would like to keep Corinne Caputo writer comedian and rub tufts around.
Corinne Caputo
I forgot to start typing outside is
Moiya McTier
currently live in a time of masks. Like
Corinne Caputo
I put on my best the one that I have. It's the best, but it's still got it set in. But I love where we are right now.
Moiya McTier
Yes. Oh, okay. So, like we said last week, it was my birthday. So for for my birthday trip. After I got my birthday hairdo. I wanted to visit some giant, loud animals in a warm place. So today, we are recording at an elephant sanctuary. In Ho unwalled, Tennessee. I have never ridden an elephant before but we have appointments to do that right after this recording. And they're just so cute with their big trucks and their floppy ears and like yeah, they're loud. But good for them. They should be taking up space both physically and and like orally.
Corinne Caputo
I encourage that. Yeah, we should be yelling whenever we want to. I love it. Elephants are like one of the cutest cartoons you can see. Oh,
Moiya McTier
that's true. There are a lot of cute cartoon elephants. Like like the the Hanna Barbera cartoons.
Corinne Caputo
They will Yeah. I'm like is Dumbo the only famous Elephant Cartoon? It's not? That can't be true.
Moiya McTier
Yeah, he's definitely not. But even if he were, he's cute enough to make this claim still makes the big years.
Corinne Caputo
Um, I have never written an elephant either. I have ridden a horse. That was scary for me. Not a horse.
Moiya McTier
I imagine this. This is just going to be more extreme and always you'll be higher. It'll have a wider seat. So maybe while we're recording this episode, we can do some some like groin stretching.
Corinne Caputo
Is what I'm gonna do. Okay.
Moiya McTier
So please excuse us if we make any like winces or sounds of pain while we're recording this episode. Because not only are we surrounded by elephants, but we're also doing just some like quick stretches and calisthenics here
Corinne Caputo
apparently, yeah, a good old fashioned warmup.
Moiya McTier
Oh, yeah. But while we are surrounded by all of these gorgeous space taking elephants, we're going to be discussing an interesting topic in astronomy, and that is, how fast are we moving through space? I
Corinne Caputo
am so excited for this. I know it's fast. I have no idea how fast right?
Moiya McTier
Well, I mean, when do you think you realized we were moving Korean? That's that's not an obvious thing.
Corinne Caputo
Yeah, I think that it was I have this memory of like elementary school. All life where you're like, I don't know, I feel like so much of childhood is like kind of getting these nuggets of knowledge and like, not rubbing it in other kids faces but like using it all the time. So it's like you think that's fast? Well, the we're on a roller coaster right now we're just like saying little thing. Maybe I was just a horrible child. This is what I did. But I have just a smartass, which is, I just have memories of like, learning that and like holding so tightly to the fact that like we are moving and and I am moving.
Moiya McTier
Good. Good. So it's less of you remembering a time when you realize this, and more that you have difficulty remembering a time before you were moving. Yeah, exactly. Love that. The human species cannot say the same. For so much of humanity's history, we believe that we are the center of everything. And only in the last, like 400 years or so did the public on mass start to believe that we were moving around other stuff? So now that we know we're not the center of the universe, we have to answer this annoying question of okay, well, if we're not standing still, how fast are we moving? And in what direction? And why? Yes. So there are a lot of ways we can answer this question. We're gonna have to, we're gonna have to dig into some layers. But I'm, I'm ready.
Corinne Caputo
I'm ready. I'm ready. Okay, my elephant ears are open. Oh, good.
Moiya McTier
So first of all, we need to establish that speed is relative. Anytime someone gives you a speed, like 65 miles an hour, or 125 kilometers per second, or whatever it happens to be that speed is relative to some stationary object. So like Corinne, if I were to throw a ball 20 miles an hour at your torso, that is with respect to your torso, right? Like your torso is the is the reference frame, that's what standing still, if you were running well, like if you were, if you were running towards me, and I threw that ball at you, from my perspective, at 20 miles per hour, it wouldn't hit you at 20 miles per hour, because you're running towards it, you're not stationary, you have also, you've added your own speed to the equation. So they get added together actually, like if you were running at five miles an hour, the ball then hits you at 25 miles an hour. Wow. But if you were moving like the other way, then it's subtractive. And the ball hits you at 15 miles per hour. So everyone remember that speed is relative to some point of reference. And that gets weird when we're talking about space. Because what what should the point of reference be in space? This gets into very confusing stuff about coordinate systems and reference frames. Some of the bane of my existence when I was doing astronomical research, were the fact that people did not clearly say what reference frame and coordinate system they were using often enough, like I did, I did this one project where I was trying to figure out how fast stars were moving in our solar neighborhood, like in our little part of the galaxy, and how that affected their ability to hold on to exoplanets. And I had to establish a coordinate system. And I was taking in data from the Gaia spacecraft, which tells us how fast stars are moving around the galaxy. But they were using different coordinate systems, like one of them was using the position of the Sun as the reference point for the coordinate system, and others were using the center of the galaxy. And they didn't say, oh, no, I had that's the this is just like an endless rant that I can always go on. But remember, speed is relative, it's always important to define what your reference system is.
Corinne Caputo
Yeah, so much of my experience of speed is I was briefly on the track team in my in high school. And I never knew like what was a good race or not. I mean, it's also track is so personal, like what can my body physically do? But even now, if my husband or someone is like, Well, someone just did like a marathon like at this speed. And I'm kind of like, you got to tell me what I like what a normal person would do it at. I understand it's like the Olympics, or I'm like, I actually need a regular person to be trying this just off screen, so that I can like cut back and forth and see. Improve. This is an amazing feat.
Moiya McTier
I agree 100%. With you there should be normies. Yeah, in the Olympics just to show because because it looks it doesn't look impressive when everyone is so
Corinne Caputo
to be impressive, like they deserve to make me think they are impressive, but my stupid little brain is like, I need to compare this to something else. So it's all relative,
Moiya McTier
it is all relative, but that actually brings up an important but subtle, I think distinction here. So relative, even the definition of relative is relative. So you're talking about relative speeds in terms of how the speeds compare to each other. But when I say Speed is relative and we need a reference frame, it's not a reference so that you know how much faster or slower something is than something else. Although I guess it is, its reference frame and that like you need to know where you are standing as you're watching this thing move around. That makes sense. So with that caveat, that speed is relative, we can try and find like the the total velocity of us on Earth through space. And that total velocity will be the sum of the Earth's rotation speed about its axis, the Earth orbital speed around the sun, the sun's orbital speed around the galaxy, plus the galaxies motion towards something that we'll talk about later, plus our entire, like galaxy clusters motion towards something even bigger than that. Oh,
Corinne Caputo
my god of motion, that's a lot. It's a lot of movement my Dramamine is coming out.
Moiya McTier
So we'll go through each of these factors in the equation and explain what each of these speeds are and whether or not it has any fun consequences. Starting with how fast is the earth rotating on its axis? Do? Do you know how?
Corinne Caputo
Well it rotates on its axis? Every day? Every day? Yeah. So 24 hours? Yeah, so
Moiya McTier
this is an equation that you can do in in general, you can do most of these with equations. And the equation is, how far are you traveling? And how long does it take you to travel that distance. And if you divide the distance over the time, that gives you the velocity here, when we're talking about the earth rotating about its axis, we have to know where on earth we are. So just a little bit of context. When I say earth's axis, that is the line that runs from the geographic North Pole. Remember, our episode
Corinne Caputo
where Santa is? Well, no, that is where Santa is. Graphic is
Moiya McTier
the geographic North Pole where Santa is so the line runs from there to the Geographic South Pole. And that axis is tilted towards the sun, with like a 23 degree angle, and we can talk about that in a future episode. But that is what the Earth's axis is. And that line is the line around which the Earth spins to get our day night cycle. So at the equator, you're standing at the widest part of the earth. So the circumference at the equator is about 24,000 miles, that's if you take a measuring tape and you put it around the Earth at the equator, it would be 24,000 miles, if you're standing at the equator, you travel 24,000 miles in 24 hours, so your speed is about 1000 miles an hour. But when you're standing at a different latitude, if you go any north or south, you actually travel less distance in the same amount of time. Okay, so let's say you're moving towards the south pole, and you're at a latitude of like 50 degrees south or whatever, you are now at a point of the Earth where the circumference is much smaller, you can do trigonometry to figure out what the circumference of the Earth would be at a certain latitude, but instead of 24,000 miles, let's say that it's like 17,000 miles in circumference, and you travel 17,000 miles in 24 hours. So your speed is technically slower as you move away from the equator, Whoa, yeah. So that's the rotation of the Earth. This does have some interesting consequences to our weather and our climate. If the Earth didn't spin at all, warm air would be able to go from the equator, it would rise up and traveled to the poles to the north and south poles in straight lines that would just go back and forth between the equator and the poles. But the Earth does rotate. So you get these this complicated twisting of the air in the atmosphere over the surface of the Earth. It gets twisted to the side because it's like trying to catch up with the rotation of the earth. And that gives you something called the Coriolis Effect, which is responsible for a lot of energy and heat transfer and weather patterns in in our atmosphere. It's named the Coriolis effect because of the the French scientist who discovered it. So that's a Gaspard Gustaf did Coriolis. The best I'm going to say that. And this twist or bend in the path of air due to the Coriolis effect can create weather like cyclones and hurricanes and gives you like Gulf streams and everything. So a lot of our weather comes from the fact that the Earth does indeed rotate. And if it rotated at a different speed, these weather patterns would be more or less extreme. I did this thought experiment And in my other podcast XO lore, where I imagined a planet that rotated much quicker, instead of 24 hours that rotated once every 18 hours, and we imagined what like the fun consequences of that would be.
Corinne Caputo
That's really cool. What was one of them? One of them is that. So
Moiya McTier
it happens here on earth too. But the effect is smaller, you technically weigh less at the equator. Because the the centripetal force as the Earth is rotating counteracts the effect of gravity just a little bit. Oh, wow, on a planet with a faster rotation speed. That effect is magnified. So you're you way less at the equator, all of the water or much of the water rushed to the equator again, because of the centripetal force. And so what we ended up with was this band around the equator where it's mostly water, and a few mountains that peak up. So we imagined, like a bird type species inhabiting the planet. And like once a year, the birds who usually live at the poles, they come to the equator, and they have a big orgy. And that was,
Corinne Caputo
as I'm sure they would if that were.
Moiya McTier
It's surprising how many of my worlds end up with orgies on excellent. Or maybe it's not surprising, I don't know. But this is not a world building podcast, all you need to know is that the Earth at the equator spins about 1000 miles per hour. And if it were faster or slower, we would have different weather.
Corinne Caputo
This doesn't make me think like, and I've said this so many times through these episodes that this circumstances for humans and Earth are so specific, and like so perfect. That led us to this like, gosh, how lucky are we that this is not an 18 hour day?
Moiya McTier
Exactly. Although that does bring up an interesting point. And Corinne, there's a little pop quiz here. So, right now the Earth takes 24 hours about to do one full rotation. Do you think that that speed has been constant throughout time? Or are we slowing down? Or are we speeding up?
Corinne Caputo
Oh, I feel like we're speeding up.
Moiya McTier
Okay, why?
Corinne Caputo
I don't know. I'm imagining like some kind of like if I spotted a dreidel or something like it slows down and stops. But I don't think that we're gonna stop or at least I hope not. So I'm just praying that if anything, it just picks up pace. Oh,
Moiya McTier
yeah. So so when you say do you think we're speeding up? What you meant was that you hope this
Corinne Caputo
is a deep hope there's a deep wish that I'm manifesting by saying it out loud.
Moiya McTier
Alright, well, Corinne, I have bad news. Oh, we are indeed slowing down. If you went back to like, I don't know, 2 billion years ago, the rotation period of the Earth would have been closer to 18 hours, it was probably about, like 20 hours. Oh, wow. Several billion years ago, we are losing about 1.8 milliseconds every century. So every every century, the the Earth Day becomes about 1.8 milliseconds longer.
Corinne Caputo
That's fine with me. It turns out this doesn't affect me much. Because I'm gonna die. Because I'm gonna stop spinning.
Moiya McTier
Right? Right. Yeah, it's 1.8 milliseconds per like human lifespan. That's totally fine. And listeners, you couldn't see it. But Corinne, I really did see the wheels turning in your head to determine whether or not you were okay with this. Yeah,
Corinne Caputo
I checked in with all the parts of me and we were all like, yeah, it's good to go.
Moiya McTier
Remember when I told you that the moon is moving away from us by about an inch and a half? Thinking just now it is related. It is indeed related. Our earth spins and that takes energy takes energy to make the earth rotate. And the moon is slowly stealing away a little bit of our rotational energy every year. So the moon moving away and the earth slowing down. They are they are linked.
Corinne Caputo
I'm okay with the moon doing that to the moon can take whatever it wants for me. Okay,
Moiya McTier
okay, cool, right? Because the moon is for the people. The moon is for the people. So the people should also be for the moon. Yes,
Corinne Caputo
absolutely. I'm trying to think of ways we can support the moon later.
Moiya McTier
Okay, good. Because now we need to talk about the Earth's orbit or the earth revolution. It is one of my greatest pet peeves as an astrophysicist. When people confuse rotation and revolution rotation is spinning. It's about an axis revolution is orbiting it is around some central point. So we are revolving around the sun, a revolver, you know those chambers they revolve around the central point, right? Yes, so rotation does not equal revolution. Let's all remember that. This can also be done to calculate the revolution speed of the Earth. This can be done with that same equation taking the distance over the time. So we know that we are about 93 million miles from the sun at any given time. I'm with that number we can calculate the whole circumference of our orbits. So how far do we travel over the course of a year? I'm not going to ask you to do that math career, don't you worry.
Corinne Caputo
I think it's 525 6000 minutes is not even a number.
Moiya McTier
That's not the right number. It's not the right units, but like your heart was in the right place. Yeah. And I was honestly, when you started saying that I was a little bit shocked because it is about 500. When I started the five.
Corinne Caputo
This is the one thing I know well,
Moiya McTier
we travel around the sun, about 584 million miles every single year. If you divide that by about 365 days, and then do unit conversions, two miles per hour, we are traveling around the Sun at about 67,000 miles per hour, oh my God, that's fast, right, so on at a time when the speech just happened to line up so that we are rotating in the same direction that that the earth is going around the sun like we always are. Our rotation is in the same direction as our revolution, which is really nice. But we would be traveling at like 68,000 miles per hour, because we add them up. Just a little bit of information about planets going around the sun, and especially Earth's orbit around the sun. It's not a complete and perfect circle. It is what we call an ellipse or we say that this orbit is eccentric, and the earth is the third most eccentric planet in our solar system after Venus and Neptune. So Venus has a nearly perfectly circular orbit. Neptune has a slightly less circular orbit. And then Earth is right after that other planets in the solar system have even more eccentric orbits, meaning their orbits are even less circular than ours. But that means because it's not a perfect circle. Sometimes we're further away from the sun. And sometimes we're closer to it. When we are furthest away from the sun that's called App Elian. And at that point, we're about 94 and a half million miles from the sun. The opposite is the perihelion. That's when we are closest to the sun. And then we're about 91 point 4 million miles. So it's a it's a difference of like 3.1 million miles, which is big. Yeah,
Corinne Caputo
this is the opposite of like the seasons I would expect. But that's me thinking the US is the center of the world. Like I experience.
Moiya McTier
That is the confusing thing. So a lot of people think that seasons are caused by the earth moving closer and further away from the sun. The seasons are actually caused by the tilt of our axis, which is why I briefly mentioned it earlier. But it's counterintuitive if you live in the northern hemisphere, because during the Northern winter, slightly just a few weeks after the December solstice, that is when we are closest to the sun. So ah ha ha ha like that. north north northern hemisphere centrism. You can calculate a planet speed going around at Star. If you know that stars mass and how far the planet is from the star. This this equation that we use is called Kepler's Third Law. And we should do an episode on on Kepler and Newton's laws. That would be fun. I love how I'm just using these episodes as a way to document what episodes we want to do in the future. Yeah,
Corinne Caputo
like I should got this down.
Moiya McTier
But Kepler's third law relates the period of a planet as it orbits to the distance that it orbits or, in astronomy terms, we call that the semi major axis of the planet. It goes with the period squared is proportional to the distance cubed. So if you know how much a star weighs, and you know how far a planet is from it, you can figure out how long it takes that planet to go around the star. But planets can move in a solar system, they can migrate in and out like they can move closer to the star, they can move further away from it. And we are pretty sure that this has happened in our solar system. People have done simulations of the early solar system and they think that especially the gas planets have moved around a lot. I saw this one simulation, and it will be included in the research notes for this episode from a paper from a research project saying that Uranus and Neptune were much closer to Saturn at one point and that Neptune was further in so it went Neptune then Uranus but then they migrated and they swapped places. So this happens often. For a long time after we started discovering exoplanets. One of the most common types of planets we would see were what we called Hot Jupiters. These are Jupiter sized planets that orbit really close to their stars close enough that they can orbit the whole star in like 10 days. but more or less, really close a lot of birthdays. Yeah, those planets are super old. But just like in terms of their years, yeah, like their personal years. And people were confused, they're like, Jupiter's should only form far away from the star, because that's where you get the gases and the ices that will combine to form this type of planet. Why are we seeing so many of them close to the star? And so there's there was this big debate that still kind of going on over whether these planets formed in situ. So like, do they form in that location? Or do they form somewhere else and then migrate. So a lot of people are studying the migration patterns of planets so that we can learn more about how Jupiter's
Corinne Caputo
Wow, I can't believe I had no idea that they would switch. But again, space is so much bigger than that, like I really think of the solar system in the very 2d model, because that's like how it was originally presented to me. So I have to imagine this like 3d thing where they like, it's not like checkers, where they're like hopping over each other, like, there is literal space to move around.
Moiya McTier
I would love that, though. Yeah. If it was just that leap, frogging was just strategic.
Corinne Caputo
And that's why they
Moiya McTier
know, they move by each other, usually when they're nowhere near each other. Because space is really big. Those are the two things that I think people don't know about space, or at least they don't understand the full magnitude of, of how big space is, and how dynamic space. A lot of people think of space is something that's static, that's not changing. It changes all the time. Yeah,
Corinne Caputo
I get that. I think it is scary to think of it as changing, it makes it feel like the deep depths of the ocean are like this mystery. And like, who knows what's there, and like, that is all true. But I mean, that's why this podcast is here so that it doesn't feel horrifying,
Moiya McTier
right? I mean, I actually am very comforted by the dynamic nature of space, because it has always been dynamic. To me, the really scary change would be if space stopped changing. This is the movie the
Corinne Caputo
core again, you got to see one of the worst movies you can imagine.
Moiya McTier
We got to do an episode reviewing the Patreon episode during
Corinne Caputo
the core maybe. Yeah, the core stops turning and he has to go in
Moiya McTier
Yeah. When when you have this system, like the universe that is constantly in flux, and then it stops. That to me is the true scary thing. I did just get a chill. So I like that the that the universe is constantly moving and changing, including on scales, small and as small as our solar system.
Corinne Caputo
Hey, it's grin here to give a shout out to our amazing patrons who are supporting this podcast. Thank you as always, to our sun like stars Sharon Whelan, Finn and Ian Williams. And of course, thank you to our latest pre main sequence stars that could Tizard Charles hunt and ash Meyer. You too can support us hear your name on the podcast, make it to our patrons star chart, all by supporting us on Patreon. Find the star chart Patreon info and more at our website pale blue pod.com or by going right to patreon.com/pale blue pod.
Moiya McTier
Hello friends of mine and friends of the universe. I have a podcast recommendation for you. It's star tripper with two exclamation points. It's a travelogue podcast of former file clerk festen Pyxis as he searches for the Zacchaeus experiences the galaxy has to offer, and I know the Galaxy quite well. There are a lot of Zoe experiences out there. So go follow festen Pyxis on his adventures. In the tradition of classic sci fi anime and Saturday morning cartoons, you can dive into the action and explore the thriving Cosmos with Dustin and his crew as they zoom through an intergalactic Death Race. Ooh battle a mega beetle live on a popular cooking show. navigate their way back from the eerie dunes of the package dimension and chase a local interdimensional cryptid no big deal. There's so much more in these adventures of Fest in Pyxis. And also the show has fully immersive sound design killer music. The sound design is by the same person who does the sound design on pale blue pod so how could it not be awesome? Plus, there's an unquenchable can do spirit that makes the show and instant mood lifter popular science called Star tripper. Pure joy in a zippy little sci fi package and polygon put them first on their list of podcasts that are unabashedly positive. Don't we love positivity here? There are two complete seasons and two space holiday specials for Arbor Day and Purva ween you'll know what that is. If you listen to the show. They are available now. You can listen to them on your pod bank of choice or go to the website star tripper hq.com, S T A R T R I P P erhq.com. And you will not regret it. Join
Corinne Caputo
the party is an actual play podcast with 10 Double worlds genre pushing storytelling and collaborators who make each other laugh every week. DM Eric and the emphatic players, Amanda, Brandon and Julia. Welcome everyone to the table from longtime RPG players to folks who have never touched a role playing game before. You are all welcome here. And if you're not sure where to start hopping to the campaign, the monster of the week story set in a weird and wild summer camp or marathon the d&d games jump into campaign two for a modern day comic book super powered story, or campaign one for a high fantasy epic. Whatever adventure you choose, you're invited to hang out each month for their after party, a session held to discuss campaigns joke around and answer listener questions. So what are you waiting for, pull up a chair and join the party search for and join the party in your podcast app or go to join the party pod.com.
Moiya McTier
So that is the Earth's revolution around the sun. Now we can talk about the sun's motion around the entire galaxy, which I think we've talked about a little bit before, but I can give you numbers now. So I'm not going to use miles because miles here would be so useless. Like I would have to tell you truly huge numbers. So I'm I'll give you the speed and miles per hour, but the distances now are in light years. Okay. The sun is 25,000 light years from the center of the Milky Way galaxy about the whole diameter of the Milky Way galaxy is about 100,000 light years. So we are like halfway between the center and the edge of the Milky Way's disk. And I would really love to paint you a little word picture here, so that everyone is imagining the galaxy in the same way that I do because when I close my eyes, I have this like gorgeous vivid map of the Milky Way. So Korean if you if you didn't go with me for a second and close your eyes, let's do it. And let's imagine the galaxy so there's there's this inky black void around it. And you're zooming in on the Milky Way galaxy. In the center, you see this chaotic bulge. It's a spherical region where there are a lot of stars packed tightly together and they're moving on on weird orbits, like figure eights and exes and they're passing by each other. And that's that's a chaotic time. But outside of the Bulge, you have the disk, the beautiful swirling disk of the Milky Way with its spiral arms, and they're all spinning in one direction. And then around that disk, you have the dark matter halo that you can't see because it's transparent. But imagine feeling the weight of all of this invisible matter around you. Wow, that's the Milky Way. floating through space. Beautiful. She is beautiful. And our son is in that gorgeous circularly moving disk of stars where the spiral arms are, most of the stars in the disk move on orbits that can basically be called circular. So we know that we are 25,000 light years from the center. It takes us about 230 million years to orbit so we can do that equation again to figure out our velocity around the center of the galaxy and it is roughly 500,000 miles per hour.
Corinne Caputo
whoo boy, okay. Dramamine is I can't do anything in the face of this.
Moiya McTier
No know it is moving real fast, real fast around the center of the galaxy. But it still takes us more than 200 million years to make it all the way around. The sun is like four and a half billion years, which means it's done about 18 orbits around the center of the galaxy, the suns an adult, finally,
Corinne Caputo
so little teenage, thinks it's all grown up. Right.
Moiya McTier
But back when the dinosaurs were around the sun was still a minor. Yeah. Now now we have to deal with the adult son. Yeah, I think I would rather have I would rather deal with with a child with a child
Corinne Caputo
I have. I love kids. So I would love a child star.
Moiya McTier
Oh, therein lies the difference between you and me.
Corinne Caputo
Well, we balanced each other out perfectly.
Moiya McTier
So that is the sun's motion around the galaxy. And it is very similar to a planet's motion around a star. Anytime you have this big, massive object in the center, and then there's stuff orbiting around it in a disk that can be described as capillary in motion. So Kepler's laws can be applied to that type of motion. But it only works under those conditions where there's a massive thing in the center and then other stuff orbiting around it. By the time you get out to galaxy clusters. They aren't organized in the same way there isn't like a single identifiable central mass. And there isn't a simple disk that things are orbiting in. So this is the last stage where capillary in motion is going to be important for the velocities. But as we've talked about in The episode about Dr. Vera Rubin, we know that the rotation curves of galaxies aren't as simple as just like straightforward capillary in motion, because with capillary in motion, the further you are away from the central massive object, the slower you move. So, we talked about rotation curves of galaxies in that Vera Rubin episode, we expect that the velocity of stars should decrease as you get out to the edge of the galaxy. But instead, it kind of flattened out. And that was an indication that there was some massive object out there, keeping the speed of the stars faster than it should be. Ooh, spooky. So the sun is at a point in the galaxy, where we are still experiencing pretty capillary in motion. We're not too affected by the dark matter, Halo, or the mass of stars outside of our orbit. But it does affect us a little bit, because instead of moving on a perfectly circular orbit around the center of the galaxy, the Sun and other stars in the disk move with what we call epicyclic motion. Have you heard this word epicycle? I
Corinne Caputo
have I couldn't tell you where or what it means. But I feel like I've heard it, maybe it sounds like a medication to me. So maybe I'm thinking of something completely unrelated. It
Moiya McTier
does kind of sound like like a medication. You may have heard it when you were doing Space Camp stuff and talking about the slow march towards heliocentrism. Because back when people thought the earth was the center of the universe, they would have to explain things like retrograde motion and seeing seeing planets moving away that didn't make it seem like those planets were moving around us. So they explained it using epicycles. They said that those planets were moving on their own little circles, as they were also circling around us. I
Corinne Caputo
google image it as I often do, and I see like shapes around the little loops, which look a lot like what I would like Doodle in a notebook or something.
Moiya McTier
Yeah, yeah. So the sun moves on one of these epicyclic orbits. It's kind of like take a slinky, take a giant slinky, and, and stretch it around so that it makes a circle so that it connects with itself. And that's what the Sun is doing. It's like spiraling as it's revolving around the center of the galaxy. And it gets that spiral motion because of gravitational influence from other stars around it, like pulling it up, pulling it down, pulling it out a little bit, and just deviating it ever so slightly from its circular orbit. Whoa,
Corinne Caputo
that's a lot of movement.
Moiya McTier
things, things are moving. That's what this whole episode about. Things really are moving. They're booking it out there.
Corinne Caputo
Oh, wait, okay, I found a gift that kind of was the first time when I realized, Oh, we're moving around the sun and we're moving forward in a way or wherever and I'll share that on the Instagram Everyone, please do
Moiya McTier
I know which which gifts you're talking about. And that's one of my faves. It's a good one. So that's the the motion of the Sun around the galaxy at about 500,000 miles per hour. You can add that to our rotation speed and our revolution speed around the sun. And you're getting like 500 and 60s something 1000 miles per hour as a total velocity. But now we have to talk about the motion of entire galaxies as a whole. So we are moving within the galaxy, but the galaxy itself is also moving. We are now outside the realm of kabalarian motion. So the Milky Way is moving mostly because of gravitational attraction to another galaxy in our little cluster called Andromeda. You've heard of Andromeda. I have. I love the Andromeda Galaxy. I love that name. Andromeda, is from a lot of our space names are from Greek mythology. Andromeda is a princess in Greek mythology, although she's said to be Ethiopian, but also historically, the definition of what Ethiopia is and who gets called Ethiopian is it's complicated. But I think the name means like Man Eater.
Corinne Caputo
And there she goes, she can munch she can a munch of the Milky Way. Next, is that was that what's coming? That is
Moiya McTier
what's coming. Let me I just want to check that it does mean that Oh, not at
Corinne Caputo
all. So we want her to be
Moiya McTier
it means leader of humankind. Where did I get this man eater thing from? Oh, well. But Andromeda, the galaxy is named after the constellation Andromeda because that's what the Galaxy appears to be in. Like that's its position on the sky. That constellation is named after the princess. It's a whole thing. But I do love the Andromeda galaxy and so does the Milky Way. They aren't really moving on a straight line towards each other. Although it kind of seems like it. Technically they are both orbiting the center of mass of their system. But they're just they're just like moving towards each other. If we know and we do kind of know the maths of both objects, we can calculate the force of attraction between them. And one of the most useful equations in physics is F equals MA force equals mass times acceleration. With their mass, we can calculate the force, and we know their mass. So that means we can solve for their acceleration towards each other. So we know their velocity and an estimate of when they should collide. And we've done this calculation so many times, it's actually a pretty common calculation for early career astronomer like people who are who are still in training to be astronomers. But we know that Andromeda is about two and a half million light years away, and that the two galaxies will really collide and about four or 5 billion years, although their extended halos are already touching, like this collision is already starting. And it will take it will last billions of years, which is really cool. And they are moving towards each other with a velocity of about 250,000 miles per hour, which I think is interesting. The sun is actually moving around the galaxy faster than the galaxy itself is moving towards Andromeda.
Corinne Caputo
Oh, yeah. I mean, I'm so used to these numbers being something I can't fathom or like, big and huge and of course, but that feels like obviously, I could not survive that speed. But like, like a speed that's manageable. Like I was watching the new avatar. Oh, great. This is not a I don't think this is a spoiler. There's a scene where they like have this special, like liquid and he's like this can stop human aging. This is gonna go for $80 million. And I'm like $80 million. There's you're not getting your money's worth do. That's
Moiya McTier
fair for something that stops human aging. It should be more valuable. Really? I don't Yeah, no, no one should be able to afford
Corinne Caputo
80 million. Do 80 million. I cannot do 80 million. But it feels like a number maybe.
Moiya McTier
Right. So the point here is that these numbers feel kind of familiar to you. Yeah, they do. Yeah. And to your point, Corinne about you not being able to survive these feeds. You already are you? We're already moving?
Corinne Caputo
I know. I know. And here I am on the right.
Moiya McTier
So yeah, and about 5 billion years, the Milky Way and Andromeda galaxies will collide. And I would I would love to just spend a little time here talking and thinking about galactic collisions. If that's okay with you, Corinne. Yeah. What is on the other side of this? Yeah. So I will sometimes talk about the eventual collision between Andromeda and the Milky Way. When they collide, astronomers have given them a couple name, they'll be called Milk Komeda. Which were just, it's fine. It's better for ya, it's the benefit of galaxies. So this will happen in about 5 billion years. But in general, galaxy collisions are quite common. Right now. Like as we speak, astronomers estimate that anywhere between five and 25% of galaxies that we can observe are actively involved in a merger or a collision. Right now, mergers were much more common in the early Universe. And that is indeed how a lot of bigger galaxies got to their size, they are the outcome of many smaller galaxies colliding with each other. Oh, okay. And anytime you see a really big elliptical galaxy, remember back to our episode on Galaxy shapes. Those big elliptical galaxies are likely the outcome of mergers between smaller spiral galaxies. So Galaxy mergers happen all the time. There are broadly speaking two types of mergers. Minor mergers happen between galaxies of unequal size. So if the Milky Way galaxy were to collide with a dwarf galaxy, like the Small Magellanic Cloud, that would be considered a minor merger. And it all has to do with like the ratio of their masses. These mergers are actually pretty common. Now they're the most common and the Milky Way does this all the time. Like just a billion years ago, it had a pretty consequential minor merger with a galaxy called Gaia Enceladus right now. There's this stream this thing called the Sagittarius stream that astronomers are actively studying right now. And that is leftover from the Milky Way absorbing or having a minor merger with the Sagittarius dwarf galaxy. So so this is still happening. And astronomers are having a grand old time trying to figure out which parts of the Milky Way came from other galaxies.
Corinne Caputo
That's that'd be fun. That sounds fun. Yeah, and you can
Moiya McTier
do it in a few different ways you can study the chemical. Usually, these leftovers will be clusters of stars that we call globular clusters. And we can study the chemical composition of those globular clusters to see if it matches the rest of the Milky Way. If it doesn't, we assume that it comes from another galaxy. We can also study the motion of these globular clusters or the streams, right? Like the Sagittarius stream is this, the stream of stars leftover, and we can study their motion and their shape to figure out if they if they came from another galaxy. Like essentially, if they if they're moving too fast, then that's an indication that they are from a galaxy that had some energy, it had some momentum when it hit the Milky Way. Oh, wow. So those are minor mergers. They're also major mergers that happen between galaxies of more equal size. So the merger between Andromeda and the Milky Way will be a major merger, because their their masses are pretty similar. When these mergers happen, I'll focus on major mergers here, when a major merger happens, the galaxies don't just like come together and hit and then stick. It's kind of like a dance, they are moving on orbits, even though they appear to just be moving in a straight line. So they'll pass by each other a few times exchanging material each time, until eventually, they have like, absorbed each other's energy. And they they do stick together. And then they'll have a whole new shape. So if you have two spiral galaxies coming together, they'll they'll dance, they'll pass by each other. And what's left after that is most likely not going to be a spiral galaxy. But when that happens when when they are doing that dance, a lot of people get worried that the stars will actually collide, that's not going to happen. Because the space between stars, the distance between stars is so much bigger than the size of the star itself. I saw this one comparison that I loved it was if the sun is the size of a grapefruit, and that sun is here in New York, the nearest star than the nearest grapefruit is all the way over in San Francisco. Oh, wow.
Corinne Caputo
Okay, yeah, that makes sense. Because like I said earlier, it's feel it's like feel so 2d When you like, think of it, because that's kind of how we're taught on paper. But again, it's not checkers.
Moiya McTier
There is a lot of space. So yeah, the stars will just pass right through each other, but the gas will collide. And when the gas collides, it will hit each other. It will condense and it will set off this cascade of forming new stars, which is very exciting. Yeah, that's Galaxy mergers. They happen all the time. I highly recommend you look up. Galaxy mergers, especially Stevens quintet is one of my favorites to look at. It is four galaxies, actively merging. And then in the image we see there's this fifth galaxy that is technically much closer to us. But it does look like it's in the quintet. So I like to say that those galaxies are, those four galaxies are colliding and the fifth galaxy is just like watching. It's just here to watch. It's just here to watch. You know, they're exhibitionist galaxies, there are voyeur galaxies. And Stevens quintet, perfectly.
Corinne Caputo
Data article, I am looking at a picture I'll put that on Instagram too.
Moiya McTier
So in my book, The Milky Way and Autobiography of our galaxy, I wrote about galaxy collisions as romance, but also as cannibalism. Because galaxy, galaxies eat each other. So I was like, yeah, all of these minor mergers, that's cannibalism. That's galaxies eating each other so they can survive. But Major mergers are romantic flings and some romantic Flings are, are very emotional, there are a lot of feelings involved. And the two galaxies will like you know, make a life together like a marriage and that's what the Milky Way and Andromeda are going to do. They're going to come together, they'll combine their lives and what's left will be something that is unlike whatever the two galaxies had before. But there are also some Galaxy mergers that are more fleeting them that like there are flings. There are hookups in these Galaxy mergers where sometimes the galaxies have a fly by but they don't really merge that well
Corinne Caputo
or leave a shirt at the other one's house and yeah, exactly
Moiya McTier
some galaxies are polyamorous like and Stevens quintet where they, they want they want multiple partners merging at the same time. So yeah. In the book, I wrote about Galaxy mergers as one of the main ways that galaxies interact. And I had to anthropomorphize it, and I had a lot of fun thinking about how like queer and and kinky these galaxies are.
Corinne Caputo
There is a theme in today's episode of all the kings oops,
Moiya McTier
um, yes. Okay, so that's, that's Galaxy murders. So again, we're coming back to the velocities where it We add it all up between the Earth's rotation and revolution, the sun's revolution around the galaxy and the galaxies motion towards Andromeda. We are now at like 750 miles per hour. Okay. And that is, if it all happens to line up like in the same direction, which is very unlikely. But now we get to the motion of galaxy clusters as a whole, the Milky Way and Andromeda both belong to a little galaxy cluster with about 50 or so galaxies in it. We call it the Local Group. But there are also other clusters of galaxies nearby, and clusters of galaxies can come together to form super clusters of galaxies, fantastic. All of these clusters can move together on mass. And we know that we are back in the 1970s, when astronomers were trying to better understand the cosmic microwave background, they were they were pointing their telescopes all around the sky. And they noticed that we are moving very fast in a direction that lines up roughly with the center of the galaxy, which we used to call the zone of avoidance because there was so much dust and gas and like black hole stuff and stars in the way that we couldn't actually see anything on the other side of our galaxy if we looked towards the center. So we noticed that we were moving towards this big thing, but we couldn't see it to figure out what it was until our ultraviolet like our UV, and our x ray and our infrared telescopes got better. So then we were finally able to look into the zone of avoidance. And we were able to see what was uh, what was attracting us a huge eyeball that's staring back at us the big Hi, can you fucking imagine that'd be so scary.
Corinne Caputo
It'd be the scariest thing I've ever heard. I'm sorry to scare just anyone who's already afraid. Am
Moiya McTier
I out in space? Yes, exactly. Not us from the other side of the galaxy. No, thank you. No, luckily, space isn't that scary. They were calling this thing that we're moving towards the Great Attractor for a long time, from the 1970s. And it's only recently that we figured out what it was. So it seems that it's the central focus point of a giant Super Cluster of galaxies that we call the Laniakea Supercluster. So when we finally were able to see into the zone of avoidance, we started seeing more galaxy clusters with 1000s of galaxies in them. One of them was the normal cluster that had 1000 galaxies in it and was like a billion times the mass of the Sun. Then we saw something called the shapely or Shapley cluster, this has more than 8000 galaxies in it. And it's 10 quadrillion times the mass of the Sun, that's 10, followed by 16 zeros. And the Great Attractor itself is like the central point and all of these galaxy clusters. We're just we're moving at it. We're zipping through space towards this Great Attractor at a speed of 1.3 million miles an hour.
Corinne Caputo
Oh my gosh, that's a really Oh,
Moiya McTier
your gosh is right, Corinne it's. So that brings our total velocity, our maximum total velocity through space to 1000 plus 67,000 plus 500,000 plus 250,000. Plus 1.3 million, which is basically just 1.3 million. Wow. Yeah. So I guess, if you zoom out far enough, our motion is dominated by this gravitational attraction we feel to the Great Attractor. But yeah, we're moving through space very, very quickly. That is
Corinne Caputo
really fast. And to think that I can walk around as if nothing's happened.
Moiya McTier
To think that there are people like you have to learn that we are moving. Yeah, even even though we are zipping through the universe at 1.3 million miles an hour.
Corinne Caputo
That's really crazy. I did look up what the fastest, like how fast a person has ever been. And of course, there's like, you know, if we put these people in a rocket, and they win this fast or whatever, but I meant just like a regular human on their own. And maybe you know the name Usain Bolt's, but he set the record for the 100 meter dash and 2009. And they like there's a New York Times article that kind of tracks his speed during that dash it was he did it in 9.58 seconds, which is crazy. And he peaked, like just after the midpoint of this record at 27 and a half miles an hour, which feels crazy, just to do on your own. But I did try to find what, what we can do and it seems like we can briefly hit 27 and a half my Half an hour if you're the fastest man on the planet
Moiya McTier
got it? Well, it's good to know what our bounds are as a species. Interesting. Yeah. So if you are listening to this episode in a car or on a plane, you can add your personal velocity to this equation but no that was that 1.3 million mile an hour factor at the end it's not going to make much of a difference, unfortunately, but yeah, that is how that is how fast we are moving so if anyone ever tries to tell you that you're like, I don't know braking a speed limit or something and tell them well officer know already moving. We're all already moving along by 3 million miles an hour. Hey, Karan, you know what time it is.
Corinne Caputo
Is it time for our riding lesson? It is our appointments
Moiya McTier
coming up and I see them saddling the elephants, so let's go I can't wait. And wherever you are, however fast you're moving listeners, please remember that you are space by.
pale blue pod was created by Moiya McTier and Corrine Caputo with help from the multitude productions team. Our theme music is by Evan Johnston and our cover art is by Shea McMullen. Our audio editing is handled by the incomparable Misha Stanton, stay
Corinne Caputo
in touch with us and the universe by following at pale blue pod on Twitter and Instagram. Or check out our website pale blue pod.com we're a member of multitude and independent podcast collective and production studio. If you like pale blue pod you will love the other shows that live on our website at multitude dot productions.
Moiya McTier
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Corinne Caputo
Thanks for listening to pale blue pod. You'll hear us again next week. Bye