#7: Fluid motion at a carnival
TRANSCRIPT
Corinne Caputo 0:29
Welcome to Pale Blue Pod, the astronomy podcast for people who are overwhelmed by the universe but want to be its friend.
Moiya McTier 0:35
Yeah, we do. I am Dr. Moiya McTier. I'm an astrophysicist, a folklorist and aspiring friend to the universe.
Corinne Caputo 0:43
Oh, I love that. I'm Corinne. I am a comedian, a writer, also a friend of the universe. Yeah, you
Moiya McTier 0:48
are fully if they'll have me. I'm gonna say yes. Yes. Someone who has has channeled the galaxy, which is not the whole universe. I'm gonna say yes. You're at least on the galaxies. Galaxies.
Corinne Caputo 1:00
Good side. Okay, good. I don't want to get on the universe's bad side.
Moiya McTier 1:04
So again, I am so happy about where we're recording today asked
Corinne Caputo 1:08
me to tell me about it.
Moiya McTier 1:09
So it is a little loud. We have had to find a quiet corner of this local carnival that we're visiting. There are lots of games. You know, I see someone over there right now absolutely failing at the like the strong man game with so much joy.
Corinne Caputo 1:25
That is so rigged. There
Moiya McTier 1:27
are small rides all around us, I hear the children screaming, I hope it's enjoy. And there is so much delicious food around at the end of this Korean live corndog.
Corinne Caputo 1:39
I know I did o'clock a fried pickles thing when we came in. And I was like, I gotta get there.
Moiya McTier 1:46
But before we can eat the fried pickles and the corndogs and the funnel cakes, and all of the other delicious carnival food, we are here to talk about actually one of my favorite classes from grad school.
Corinne Caputo 1:59
I'm excited to learn about this because my gut instinct is is bad is I don't think this is her race. So I'm really hear it, I need it to be explained to me by someone who's excited.
Moiya McTier 2:10
But that's how you felt about the Big Bang too. That's true. That is true. So by the end of this, you'll be a lot more comfortable with fluid dynamics, which is the class amazing. So I have kind of always wanted to be famous enough that I could eventually sell my notebooks or so that my surviving descendants could sell my notebooks for money. Like that's the level of fame I want to read. Okay,
Corinne Caputo 2:33
I did read this is not science. But I did read Sylvia Plath, like underbridge journals, like when those are published. And that was like the coolest thing ever. So yeah, I totally get it.
Moiya McTier 2:44
So I wanted to kind of kickstart that process by going through my notes from college and my Ph. D. program, and sharing some interesting tidbits from those notes with you. So if you are one of our patrons, you can join at patreon[dot]com/palebluepod, you can get scanned copies of my notes from grad school that we're talking about today. So I will tell you now I looked at those notes. And I was like, What the fuck do these symbols mean? If
Corinne Caputo 3:12
were you a doodler? Or were you like, you know, if your focus note taker, because I was always in the margins doing something?
Moiya McTier 3:19
Oh, no, I was a very focused note taker. My notes were color coded so that equations were in one color figures and graphs were in another notes were in one color and questions that I had about those notes. Were in a different,
Corinne Caputo 3:33
it's a great idea. And is this highlighted, or you're switching colors of your pen
Moiya McTier 3:37
and just searching pen colors? Yeah, I got those multicolored pen packs. Those
Corinne Caputo 3:42
are great. I definitely always had like a burst of that at the beginning of a semester where I was like, this is the year or the course where I'm going to be the ideal student and like, quickly, it was like, I actually can't pay attention.
Moiya McTier 3:56
Yeah, I've been there. I had classes where I really did not want to pay attention. But once I got to grad school, I was like, oh, no, I need to pay attention. Yeah,
Corinne Caputo 4:06
now now the now I really picked it myself.
Moiya McTier 4:11
Not only do I opt into this program, this is how I make money.
Corinne Caputo 4:15
Yeah, this is the right to my life. Okay, so this course is called fluid dynamics. But what other classes did you take in school, just
Moiya McTier 4:25
in grad school, the classes I remember taking and I think this is in rough order of least liked to most liked. Start off being chaotic now. So I had to take a class and stellar processes. So what's going on inside of stars that was at like 8:30am Every day, I've sat in the front row of that class and fell asleep almost every day. It was awful home.
Corinne Caputo 4:52
I had an 8:30am class in undergrad for like I went to school to be an elementary school teacher and this of course was like for math, learning how to teach math to kids kind of rose at 830. In the morning, I was commuting from Staten Island to the Upper East Side. So I was like, this is set up for failure. And then I'd be like, Oh, but it's no big deal, because it's elementary math. The teacher I had two semesters in a row, she called me Connie. Oh, that's like two semesters in a row now, and I was like, I actually can't correct her now, because we're too deep into this relationship. So not only am I late, tired, exhausted, but like, she doesn't even know who I am. Well, maybe she didn't count you as late. Yeah, that's what I'm hoping I had a gym teacher like that in high school.
Moiya McTier 5:37
So that was stellar processes, which I'm pretty sure was my least favorite grad school class. I also took a class in radiative processes, which is like, after radiation is outside of the star, where does it go? And how does it behave? Just like in space, I took one, I guess, elective course on climate systems to bring it back home to Earth. I took a class on the interstellar medium, which is the space between stars. And that was such a joke. Class. Professor was so easy going. I don't think I learned anything of substance about the ISS. But I did see that Professor do so many times. I saw that Professor do a remarkable impersonation of a ferret. Cuz he had a pet ferret? So funny. So I was the interstellar medium. I took a class in cosmology, which actually wasn't terrible. I took a class on Galaxy dynamics and evolution, which I liked, because it was just very relevant to my research. And finally, fluid dynamics.
Corinne Caputo 6:46
Here we are, that brings us back. So why did you like fluid dynamics,
Moiya McTier 6:49
part of it was just that I had a good teacher for it. That'll make all the difference. It really does. By the time you get to grad school, the people teaching those courses are researchers, they did not go to school to teach. They didn't go to school to learn how people learn. They went to school to study science, and now they teach science. So you have a huge range in grad school of professors who are actually care about teaching, and this professor did. So I had a good teacher, the homework was relatively fun, it still made me cry, I still had to do a lot of equations and derivations of stuff. But it was relatively fun because it talked about practical stuff. Like I remember, we had this one homework problem, where we looked at a traffic jam, and studied that as if it were a fluid moving, like along the road. So that was really fun. And I just love that fluid dynamics has more practical applications than any other class I took in grad school. Because we deal with fluids all the time here on Earth, those fluids move a lot. So if you've ever been in traffic, or mixed a drink, or if you've flown in an airplane, or if you've experienced weather, I'm pretty sure everyone here has experienced weather. I'm experiencing it right now. Right? This moment. Yeah, we're outside at this carnival. We're experiencing weather. That is all fluid dynamics.
Corinne Caputo 8:15
Interesting. Okay, because I was going to ask, I feel like some space words might like fluid, but it's actually no fluid I've ever interacted with or like, have understood. So I was curious how much this was like the fluids? I know. Well, yeah. All of it. So what is a fluid I guess, for how is it defined? Yeah.
Moiya McTier 8:32
Fluid is like a catch all term. It is not one of the states of matter. So the four states of matter that people might be familiar with are solid, liquid, gas, and plasma. That's the fun bonus. fourth state of matter. Is plasma.
Corinne Caputo 8:47
Did plasma join the scene later in life in my life? Because I feel like when we were in school, elementary school, it was like three or three. And it's like, all the things water can do.
Moiya McTier 9:00
Yes, yeah. It did get added later. That's like high school level chemistry and physics where they're like, oh, by the way. Yes, plasma is just like a mass of charged stuff, like electrically charged particles make up plasma. Okay, so we we don't see a lot of plasmas here on Earth. But we do see a lot of plasmas in space, like stars are basically plasma, of course. So let's focus on the three states of matter that aren't plasma. And they're solid, which has a set volume and a set shape. So if you have a solid object, you can't make it take up less space, and you can't change its shape. With some exceptions. You know, ran liquid has a set volume, so it takes up the same amount of space, but it doesn't have a set shape so it can move. It's very trying not to use the word fluid here, but it's very amorphous. And then gas has an unset volume and an unset shape. So you can change the amount of space it takes up. And it can be in any shape it wants. And a fluid is anything belonging to any of these states of matter that flows usually a liquid or gas.
Corinne Caputo 10:14
Okay, that kind of makes sense. Yeah. Um, I quickly will say, one of my favorite TV shows lasted one season, it was on like MSNBC, which is such a strange place for a reality reality show. It was called Staten Island hustle. And it was these absolute bizarro guys who would meet once a week in the top floor of this restaurant called Angelina. And they would pitch ideas to each other. It was kind of like a shark tank, but Staten Island, but Staten Island. Exactly. They would pitch business ideas to each other and they would all go around and be like, well, I can give you $1,000 for that or I can give you $5,000 for that. There was one idea for three D salad dressing. What
Moiya McTier 10:55
this is already mentioned.
Corinne Caputo 10:58
Thank you. Yes. Okay, so you got it, obviously our side. He was like, Guys, this is the first 3d salad dressing. Look at this. And he poured regular like balsamic dressing onto a plate. He was like, look, look how flat it is. And in my head watching this, I'm like, well, liquid takes the space of the container it's in so of course it's gonna like go flat. Then he pours out His 3d salad dressing. And it's like a mound on this plate of feta cheese and tomatoes. And of course, it's quote 3d Because it's a pile of cheese and vegetables. Now, so then he did like a taste test at the local grocery store, which is a grocery store my parents job. So I was especially excited. Everybody was like so confused by the 3d salad dressing part like every customer, and he was getting so frustrated. He was like, It's the world's first 3d.
Moiya McTier 11:56
He just made another Sally made
Corinne Caputo 11:57
something up. Well, we made it up. It's just it's just a P anything you experience ideal is 3d. Anything you're gonna put in that salad is 3d.
Moiya McTier 12:10
3d solid jazz, like I hate that so much anyway,
Corinne Caputo 12:12
I'm hoping he listens to this. Me too. Okay. So anyway, what is so fluid it's moving it flows, what is making it flow?
Moiya McTier 12:22
Yes, there are lots of things that can make a fluid flow that can make a gas or a liquid move around. One of them is gravity, or any sort of propulsive force, also wind convection. I will explain more about what compaction is later. But that depends on differences in temperature, density and pressure within a substance and magnetism. Any sort of magnetic energy can also make fluids move. This is not an exhaustive list. But this is the list of stuff that is relevant to what we will talk about in this episode. Okay noted. I cannot take an hour to describe all of fluid dynamics. I you know, I had to take a whole class for a semester about it. But there are some things that I feel like you might want to know about fluid dynamics, some terms, some equations that you might want to just like say you've heard before. Maybe some of them you have heard before. So one one cool. concept or idea in fluid dynamics is the difference between laminar and turbulent flow. I know you've heard the word turbulence before I have heard turbulence. Have you heard laminar? I don't think so. Yeah, it's a lesser known word. So there are two types of flow, laminar and turbulent. Laminar Flow is very streamlined. It happens when particles in a substance are flowing in parallel without mixing. So think of water flowing perfectly out of a hose. If you've ever seen a video of a water stream, where it doesn't look like the water is moving
Corinne Caputo 13:56
Yes, and then people like run their hand, right? Yes, that I've seen YouTube compilations of that.
Moiya McTier 14:00
That is laminar flow. The reason it looks like it's not moving is because when our eyes register something as motion, it's because like something is changing, right in our field of view. But for laminar flow, because there's no mixing visible, nothing appears to be changing. Interesting. So it just looks like a straight line. Our eyes
Corinne Caputo 14:19
are weird. They really are. I don't think we can trust them.
Moiya McTier 14:23
We probably shouldn't. Turbulent flow on the other hand is when the particles are mixing together as the substance is moving. So this can be caused by an external obstacle. So picture, a river flowing, any sort of rock in that riverbed is going to cause a turbulent flow, or any internal inconsistencies in the fluid like if it's a mixture of different substances, and one of them is more dense than the other, or even if it's the same substance, like two instances of the same substance, but you're pouring like beer out of two different mugs into something Sure, one cup Out of beer, one mug of beer might be higher up than the other. So their velocity would be different. And then you'd get this, this turbulent flow. There are lots of things that can produce turbulence.
Corinne Caputo 15:10
Yeah, I was gonna say I feel like turbulent flow. I mean, I don't know if it's more common, but it's certainly something that seems like I've experienced way more of than laminar.
Moiya McTier 15:18
Yeah, absolutely. I know you have experienced turbulent flow because you have been on a plane, correct. It's true. I imagine if you hadn't if I'd like caveman all confident, like you've been on a plane. The
Corinne Caputo 15:29
Victorville I actually traveled by foot everywhere. Even
Moiya McTier 15:33
across the ocean. Yeah. So airplanes work because of turbulence because of a difference in air velocity in different places around the airplane when, which is what lifts the airplane up. So I want to just explain take like a quick break from space right now to explain how airplanes work.
Corinne Caputo 15:54
Oh, my God, I'm so glad you are because okay, I used to teach at the Space Center in New York, and one of the classes was on planes, for third graders. And it was like one thing I always had a hard time getting my head around. I'd like always need a refresher like five minutes before I was about to teach the class to be like, Are you sure I have this right?
Moiya McTier 16:12
It still feels like magic. Every time I get on a plane. I'm like, No, the sorcerer's keeping me up down. Yeah, exactly. But no, I know that there is physics behind it. And that physics is held up by Bernoulli is theorem Yellowlees theorem. I'm pretty sure I'm saying that name. Right. So that's
Corinne Caputo 16:31
how I set it at the center. So.
Moiya McTier 16:35
So Bernoulli is theorem says that as a fluid moves faster as its velocity increases, the pressure of that fluid decreases. And let's just start with that as fundamental truth, as a fluid moves faster, its pressure decreases like it's pressure inside itself. So taking this to airplanes, airplane wings are designed in a way that makes air move faster over the top of them than it does over the bottom. And you can do that just by being very careful about the shape of the airplane wing. And so the air moving faster over the top of the airplane wing, because of Bernoulli theorem means that the pressure is also lower on top of the airplane wing, lower than the pressure on the bottom of the airplane wing. And because fluids or gas or like pretty much anything in physics likes to move from high pressure to low pressure, that high pressure environment under the wing pushes up and lifts the wing and lifts the whole plane. Yeah, that's how planes work. It's just like air moving faster in one part.
Corinne Caputo 17:38
It was all these forces working together to give it yes,
Moiya McTier 17:41
that's amazing. So that when like you're on a plane and someone says oh, we've reached turbulence No, you've been in turbulent air the entire time. Yes, yeah. You're just reaching you're going through rougher more turbulent air. This is actually something we can quantify. We can quantify how laminar versus turbulent fluid is with a quantity known as Reynolds number named after a scientist Okay, Reynolds number tells you how laminar or turbulent the fluid is. And it is the ratio of inertial force over viscous force in the fluid. So, inertial forces like how hard is it to get this fluid to start and stop moving Okay, high inertia means it's really hard to get it to start moving and then once it's moving, it's hard to get it to stop Okay. Whereas viscous force is kind of like how thick is the fluid like how how woozy is it? Yeah. So turbulent flows have very high Reynolds numbers because they aren't very viscous, you tend to find turbulent flows and less viscous fluids like water, whereas laminar flows have very low Reynolds numbers because you tend to find those in more viscous material.
Corinne Caputo 18:57
Okay, yeah, that makes sense. Like a thicker substance or like what feels kind of woozy and gross, fine, right? Nickelodeon slime? Yeah.
Moiya McTier 19:06
Or like Oobleck you know, that stuff you made with? Starch. That's just some some fun, fluid dynamics vocabulary for you.
Corinne Caputo 19:24
Hi, it's Corrine, I want to give a quick shout out to our amazing patrons who are keeping this podcast going. Thank you to our sunlike stars Siân Llewellyn and Finn, thank you to our latest red dwarf star Jeremiah Franco and thank you to our latest pre-main sequence stars Scott Johnson, Jake Metzger, Tyler chat and DEX Doug tech div. And you too can support us, hear your name on this pod, make it to our patrons star chart, all by supporting us on Patreon. Find the star chart Patreon info and so much more. Well, not that much more at our website palebluepod[dot]com.
Moiya McTier 19:59
Hello Oh, it's Moiya with my sick voice on hand. I'm here to recommend another podcast that's part of the Multitude collective, and it's called the Queer Movie Podcast. QMP is a queer movie watch party hosted by Rowan Ellis and Jazza John. And you can join them every other Thursday, as they research and rate their way through the Queer Film canon, one genre at a time. From rom-coms to slashers, contemporary arthouse cinema to black and white classics, Queer Movie Podcast is a celebration of all things gay on the silver screen. And since we just did an episode about how the whole universe is one giant big rainbow that we can't see, I feel like this is pretty appropriate. You can enjoy new episodes of Queer Movie Podcast every Thursday in your favorite podcast app or by going to queermoviepodcast[dot]com. Fantastic SEO I'm so jealous of them. So go check that out. If you would like to hear more about queer movies every other week.
Corinne Caputo 20:54
This episode is brought to you by BetterHelp. I know I feel like my best when I'm confident and have a good grip on my life. But I also know that feeling can be rare. When you're at your best, you can do great things. And sometimes life just gets you bogged down and you may feel overwhelmed or like you're not showing up in the way that you want to. Working with the therapists can help you get closer to the best version of you. Because when you feel empowered, you're more prepared to take on everything life throws at you. And therapy is helpful. For so many reasons. I can't emphasize enough how much therapy has helped me. I used to describe my days like I'm feeling like I'm holding too many balloons. And if I make any movement in any direction, I might lose them all. And these days, it's so much easier to manage my anxiety myself, my goals, just everything in my life. Therapy is helpful for learning positive coping skills, learning how to set boundaries, and so much more. And I want to emphasize it's not just for those who've experienced major trauma, anyone can benefit from it. If you're thinking of giving therapy a try BetterHelp is a great option. It's convenient, flexible, affordable and entirely online. Just fill out a brief questionnaire to get matched with a licensed therapist. And you can switch therapists at any time for no additional charge. If you want to live a more empowered life therapy can get you there. Visit betterhelp[dot]com/palebluepod today and get 10% off your first month. That's betterhelp H-E-L-P [dot]com/palebluepod.
Moiya McTier 22:22
Listening the Pale Blue Pod is a great way to learn about astronomy concepts. But it's no secret that we're not here to make you better at math. If that's the type of thing you're after. I'd like to recommend Brilliant. Brilliant is a program online and in app form for lifelong learners that replaces lecture videos. With hands on interactive lessons, you can learn about the complementary angles in a triangle by actually stretching out a triangle on your screen to see the angles change in real time. And you can learn about the center of mass and physics by trying to balance a weighted beam on your digital finger. Those are just a couple of examples. Brilliant has 1000s of lessons in math, scientific thinking and even computer algorithms, and they add new ones every single month. I think that the world really needs more people who can use knowledge and logic to reason through problems. And brilliant is the best way to practice those skills online interactively. To get started for free, visit brilliant[dot]org/palebluepod or click on the link in the description. The first 200 of you will get 20% off Brilliant's annual premium subscription. Again, you can join Brilliant for free at brilliant[dot]org/palebluepod or the link in the description. And come on have a good time getting smarter.
We still have not talked about fluids in space. Let's get there. So we I'm pretty sure have discussed in previous episodes what the pie chart of the universe looks like. We know that most of it is dark energy. And of the matter the stuff that uses gravity, most of that is dark or transparent matter. So what's left the little slice of pie that's left we call baryonic matter, regular matter that does interact with gravity and light. So you and I Corinne we are baryonic matter? Yes, we are. When astronomers took essentially like a census of all of the matter in the universe, or like all that we could measure, what they found was that 90% of the baryonic matter in the universe, the regular matter, like you and me, is made up of gas of different temperatures. Whoa, so much of space is gas, and gas is a fluid. So there's a lot of fluid dynamics happening in space. Okay, of course. So we use fluid dynamics as astronomers when we are studying galaxy collisions, because we want to know how all of that gas is interacting and mixing together, where we use it when we're studying star formation because stars formed from clouds of gas that contract in on themselves, so we have to know how that Gas works before the star gets formed, even internal stellar processes because stars are collections of gas and plasma, which can flow, we use fluid dynamics to figure out what's happening inside of star winds in space, we have these these walls of particles coming off of stars coming off of black holes, anything energetic enough, can give off these cosmic winds. And my favorite, the thing that we talked about so often in this fluid dynamics class was shockwaves. Ooh, anytime any material in space moves faster than the speed of sound. So at supersonic speeds, it generates a shockwave.
Corinne Caputo 25:40
Okay, that's like the Superman animation. So he like takes off and there's like stuff residual stuff? Absolutely.
Moiya McTier 25:46
Yeah, there's that that boom. And like there's a, there's a pressure wave that you can study going through a sort of medium. We talked about shocks so much in the fluid dynamics class, that the three, there were three grad students in my cohort, we were all three women. I love that for us. We're all three queer women. And I really love that for us.
Corinne Caputo 26:07
Okay, that I feel like that's all of them were in that.
Moiya McTier 26:12
We collected them all. You found each other and did it? And at the end of that class, we took shock shots.
Corinne Caputo 26:21
That's so cute. Yes.
Moiya McTier 26:22
Which might be why I don't remember what all of the symbols in my
Corinne Caputo 26:26
notes. Yeah, the final.
Moiya McTier 26:30
So I mentioned before that the fluids and space can be moved by convection, and magnetism. I didn't explain what that meant, or how it worked. So let's get into that. Let's get into it now. Starting with convection. Have you heard this term convection before?
Corinne Caputo 26:46
Correct? Yes. But in terms of like a convection oven? Yeah. Or like something like a kitchen word? Yeah, absolutely.
Moiya McTier 26:53
I don't know what the point of a convection oven is, like, I used to have the oven that had the different settings. And I was like, I don't know, there's
Corinne Caputo 27:01
like a convection button too. I think it's kind of like it just circulates better, I want to say but I'm probably wrong.
Moiya McTier 27:08
Okay? Because their definition of convection does not match up with my physicist understanding of convection. So I'm just very confused.
Corinne Caputo 27:15
Well, if you Google it, it says conventional ovens feature heating elements on the top and bottom of the oven cavity. Convection ovens have these elements, in addition to a fan that helps circulate hot air throughout the oven cavity. Oh, it is what I thought. It's usually like a fan symbol. Also, I have the world's tiniest oven, it doesn't do anything fancy. So I'm not working with a convection oven.
Moiya McTier 27:39
Just just like conventional ovens. Yeah,
Corinne Caputo 27:41
very conventional.
Moiya McTier 27:44
Okay, so in in space, I'm not gonna touch on convection in your oven. But convection in space, or in most other circumstances, works by taking advantage of differences in density, temperature, and pressure. So imagine you have a fluid, let's imagine you're boiling a pot of water on your stove. You have a fluid water, and there will be bubbles in it, there will be little pockets of air or of water, there'll be little water bubbles there. If you have a bubble that is less dense than the material surrounding it, it will rise. Okay, we are very familiar with this. Yeah. In other areas of life. I'm
Corinne Caputo 28:26
thinking boats. I'm thinking about buoyancy. Yeah. I feel like how a plane flies and how boats work are like the two big questions in everyone's life. Absolutely, yeah. So we're touching on a little bit of all.
Moiya McTier 28:40
This is a kind of spaceflight day. I'm talking about a lot of things here on Earth. Yeah, fine, I think it's good to make the connection. It's all connected. Yes. So less dense material will rise. And the opposite is also true. If you have a packet or a bubble that is more dense than its surroundings, it will sink. And that's that's essentially how convection works. You find it in your everyday life when you're boiling water, even like wind can be like a kind of convection. But in astronomy, we care a lot about convection and planetary atmospheres and in stars as a method of transporting heat. So when I was in high school in a physics adjacent class, I learned that there are three ways to transport heat from one place to another, you can do that through radiation. That means heat that can just travel through any vacuum like medium, like it doesn't need a physical thing to transport the heat. You can do that through conduction, which is when things physically touch each other and transfer their heat that way or you can do it through convection, which is very efficient in fluids. Okay, so different types of stars have different heat transfer methods that they will use, just radiation and convection. But it gets kind of complicated. Did because stars have layers, they're like an onion. And if we're just paying attention, for example, to stars, like the sun, their innermost layer would use one of these methods like radiation, and then their next layer would use convection. And then the next layer after that would use radiation again, and it changes depending on the density of that part of the star. It's really complicated.
Corinne Caputo 30:22
I'm nodding, I'm like, okay, okay,
Moiya McTier 30:25
yeah. So all you need to know is that convection is good at transporting heat from the center of a star to the surface of that star, because at the very center, things are very hot. That's where the fusion is happening. That's where all the energy and heat is produced. So you have these little pockets, these little bubbles of star material at the center that are very hot. Okay, we know about things that are very hot, if you have a high temperature, you likely have a low density, okay, a high temperature because it will expand and you'll have the same amount of material but in a larger space, so you will be less dense. Okay, so you have these less dense bubbles coming from the core of the star and rising. Got it? Because that's, that's how the convection do. And then when you're closer to the surface of the star, you have cooler pockets. Okay, they're not as close to the fusion reactor in the core of the star. Yeah, yeah, yeah, they get cooler, they get denser, because they can Tract on themselves, they get denser, and then they fall down and then you get this like turning Oh, it's like a nice little. Okay. So when you watch a pot of water boil on your stove, you're seeing that turning wave,
Corinne Caputo 31:38
this is like a lava lamp. Yes, yes. It is. Yeah, yeah. A second. I know this.
Moiya McTier 31:48
Boats and lava lamps, and lava lamps.
Corinne Caputo 31:50
This is my language.
Moiya McTier 31:55
So convection, and like this, this focus on the temperature and density and pressure of different parts of a fluid can lead to some instabilities. And when I say instability as an astrophysicist, and maybe other areas of science sees it this way, too, what I mean is like a runaway effect. Okay, kind of like the snowball Earth was a runaway effect where the earth got very cold and covered in ice, and then that ice reflected a lot of the sun's heat, so the earth got even colder, and then the whole process just got worse and worse and worse. Okay, that's how instabilities work for astrophysicists, okay. Like once you start this process, it will just snowball or cascade or get more and more unstable. So, one of these instabilities is called they are named after scientists. Of course, one of these instabilities is called the Rayleigh Taylor instability. I know that you have all seen this, this happens between fluids that have different densities, so, like oil and water, when you have mix those together, and you see like the oil dripping down into the water. Yeah, that is a Rayleigh Taylor instability. Oh, okay. That's, you know,
Corinne Caputo 33:06
take it back to the salad dressing, I know exactly how that one works.
Moiya McTier 33:11
Everything goes back to salad dressing. And then the other instability that you might find because of convection is the Kelvin Helmholtz instability, which happens when there is a shear stress in a fluid, a shear stress is like when things are slipping by each other, and there's a little bit of friction involved. Okay. So Kelvin Helmholtz instabilities can happen through that type of stress. Or it can happen when you have two fluids moving in an opposite direction. Okay, so actually, you usually see these instabilities happening at once because if you imagine like a like a lava lamp or oil on top of water, it drips down the water is going up. So now you have this difference in densities but you also have the difference in direction so you'll see these little like Eddie's or swirls and the interface between these two fluids
Corinne Caputo 34:05
Sure. Yeah. I love that like meeting points in them. I feel like that was such an experiment in elementary school of like oil and water and like dyeing it maybe a specific color to like watch it better.
Moiya McTier 34:17
Yes, so you know, something that I often do and I'm not condoning or encouraging the use of mind altering substances but if you're into that maybe consumed some mind altering substances and then light some incense and just watch the smoke. This
Corinne Caputo 34:34
is exactly it. Oh my God watching smoke in that headspace is incredible. Yes, this is definitely like it because
Moiya McTier 34:42
when I watch smoke in any headspace, but like especially that one, I am thinking about the fluid dynamics of the smoke. I'm literally sitting there going like, Ooh, look at that. swirly Kelvin Helmholtz instability.
Corinne Caputo 34:56
You're having a totally different time than I am. I'm looking at it and I'm like, That's magic. That right there, there's no explanation for that. Now I'll think of this. Good.
Moiya McTier 35:10
Please do anyone if you're watching smoke or if you're watching any sort of interaction between fluids and like, yes, the smoke is is one fluid the air that the smoke is moving through is is the other fluid involved.
Corinne Caputo 35:23
It's so interesting to think of smoke or gas as a fluid because I so associate the word fluid with liquid. I know most people do. It explains so much of like, smokes movement, or things like that was it just feels like a liquid in the air or like it's moving in that river kind of way. Exactly. Yeah,
Moiya McTier 35:42
it's it's a vertical River. Yeah, exactly. Okay, so that's convection. Those are two of the major instabilities that we'll see in fluids due to convection. But I also mentioned magnetism. There are magnetic energies and magnetic charges everywhere in the universe, magnetic energy or magnetic fields happen because of the motion of charged particles. So here on Earth, we have a magnetic field, because of the movement of our liquid iron core in the center of our planet, okay, that creates a magnetic field out in space, you can have stars with electric charges, you can have individual particles with electric charges, you can have whole columns or jets of material with electric charges. So there's a lot of magnetism out in space and the shape of that magnetic field, we will often draw lines indicating like the motion of the magnetic field, that shape depends on how those charged particles are moving around. Okay. And because those particles often aren't moving on perfectly straight lines, it's kind of chaotic motion, because those particles are moving according to fluid dynamics. And then influencing the magnetic field line shape, which then influences the fluid dynamics. It's
Corinne Caputo 37:00
all it creates that cycle again. Yes, exactly.
Moiya McTier 37:04
This is why we have a feedback loop. But what I'm trying to say here is that because the charged particles themselves are moving in a kind of wild way, the shapes of these magnetic fields can also be kind of wild. I buy that. So now we're going to start talking about plasma. Okay, which can be a fluid, often is a fluid. And is
Corinne Caputo 37:26
this anything like blood? Plasma? No. Okay. All right.
Moiya McTier 37:30
That is a totally different word. I don't know what blood plasma is, but it is not plasma in the way that astronomers talk about because a plasma for us is a very hot, electrically charged
substance. Yeah, my blood can't be that hot. It is. Your blood is not millions of degrees. It's not me. Maybe somebody. Maybe if we were a cold blooded species,
and we were stood right by the sun, yeah. Our blood is not astrophysical plasma. Got it. But we do find astrophysical plasmas out in space. And so these plasmas or other charged fluids, like it has to be, it has to reach a level of electric charge to be considered a plasma. So any fluid with an electric charge can follow these magnetic field lines, but those lines aren't always stable, and their shapes are ridiculous. So there are there are a couple of instabilities that we get, because of magnetic field lines out in space. And unlike I'm getting getting the instabilities for convection, which are named after scientists, these ones apparently just have stupid names.
Corinne Caputo 38:43
A totally different group of scientists behind this one, naming it what they wanted. Exactly.
Moiya McTier 38:47
They're like, I don't need this instability name doesn't need to be by name. Exactly. I'm gonna give it a name that I think is demonstrative or illustrative of what it actually is. But it's not, it's not friends. So, so funny. One of these instabilities is called the sausage instability. That's
Corinne Caputo 39:08
so funny. I'm googling it just to confirm if it looks like a sausage or not, kinda does,
Moiya McTier 39:14
kind of does, does. So imagine you have this column of plasma. Actually, I will give you an example of where we might find this so I can talk about specifics. One place that we might expect to find plasma, like a stream of plasma out in space is around a black hole. We have a powerful enough black hole. It's massive enough, it's accumulating enough material, there's enough energy there. What you'll see are these two giant bright jets that shoot out of the black hole, basically going towards the north pole and towards the south pole of the black hole. Okay. Those jets are made from material that gathers around the black hole that gets shot out away from it. For a long time. It was a big mess. story how that happened. Now we're starting to learn more about it. And we think it might have to do with these magnetic field lines. So it's very exciting. But picture one of those jets coming off of a black hole.
Corinne Caputo 40:11
This is a fun thing to Google image to another gorgeous.
Moiya McTier 40:16
Imagine you have these jets coming off of the black hole. And they are columns, they're like cylinders. The magnetic field lines can move around them like spiral around these jets. So you essentially end up with rings of magnetic field line going around the jet. Those rings can contract. Like if you build up enough magnetic energy, you'll get a lot of magnetic pressure in a certain point. And the ring will contract until it like pinches off. Okay, inches off the jet coming from the black hole.
Corinne Caputo 40:50
Is that a sausage? Are we still talking sausage. So that's why it's called a sausage
Moiya McTier 40:53
because pinches off on either end. They didn't want to call it like the the poop instability
Corinne Caputo 41:00
links.
Moiya McTier 41:03
Yeah, it looks like links of sausage. And that's when the energy pinches the whole column. But you can also get something where the magnetic energy and the magnetic pressure build up at a certain point on one side of the column, that pressure will push against the column making it bend, which then invites more magnetic energy and pressure because you're concentrating the magnetic field lines. So it bends even more. And that cycle just continues until the column until this jet snaps in half, basically, okay, like snaps to the side. And, and that instability is called the kink instability. For some reason why don't we do this to ourselves?
Corinne Caputo 41:50
I get it. I get I do get it. It's good to keep it fun. Yeah. Yeah. It feels like like a dented can is kind of like how I'm picturing something like, yes,
Moiya McTier 42:00
that's a good image. But I guess that's a weirder.
Corinne Caputo 42:04
That's definitely a worse name than the kink instability.
Moiya McTier 42:09
Yeah, I remember being in fluid dynamics class. And when our professor said the words, kink instability,
Corinne Caputo 42:17
I'm sure you'd lost it or I hope we kept
Moiya McTier 42:20
her cool. But, uh, two other people in my cohort and I, we all made eye contact around the room. And there was that moment where we were like, Okay, we can't react now. But I'll talk to you later. We're gonna laugh our asses off.
Unknown Speaker 42:34
And we did. That's really special.
Moiya McTier 42:39
So yeah, that is fluid dynamics. Do you have any, any questions about fluids? Or their dynamics or this class?
Corinne Caputo 42:45
We talked about smoke, but I'm curious what like the most common fluids in this kind of context are that I interact with probably, I guess, smoke. Steam.
Moiya McTier 42:56
Dude, air. I read the fluid all the time. That's crazy water that you drink. Maybe we should play a little game of
Corinne Caputo 43:05
what? Okay. All right. Let's see. Should I list things or should you alternate?
Yeah, well, waters blowing my mind. Not water. air is blowing my mind. Yeah,
Moiya McTier 43:19
so air is definitely a fluid. What about like, oobleck? I'll just go straight to the hard ones. That mixture of cornstarch and water. Is that a fluid? Well,
Corinne Caputo 43:31
I feel like I want to say yes. But I Okay. So I interacted with like, last summer when I was running a camp for kids. And we were just like, it was raining every day. And I was like, great. You can go make goop like in the corner again. So they made that a lot. It was a really interesting thing. Like that's what they find so interesting about it of like, it's so hard to interact with something like that, and day to day basis, because it's not quite flying. And it's not quite water,
Moiya McTier 43:58
right. It's something in between, we actually call it a non newtonian fluid. Ooh, in science because it doesn't adhere to the typical rules of Newtonian dynamics. Right? So this is a this is a tricky one. Maybe I shouldn't ask. Yeah, what is this right away? Well, okay, so the thing about Oobleck is that its state varies based on how much pressure you apply to it. Yes. Yeah. So if you hit it really hard, it becomes a solid because you're applying a lot of pressure and it contracts it becomes a solid but if you don't apply much pressure if you just like slowly put your hand into it. Yeah, then it acts more like a fluid.
Corinne Caputo 44:35
Yeah, yeah. And that's what's so cool about it also, isn't it crazy easy to make it's just like cornstarch and something else it's
Moiya McTier 44:43
just cornstarch and water.
Corinne Caputo 44:44
Oh my god, everyone go make this go make it
Moiya McTier 44:49
so Oobleck we have decided to sometimes a fluid Oh,
Corinne Caputo 44:51
okay. So things can sometimes be it depending on the pressure and Okay.
Interest thing?
Well, I can't think of another thing I've ever interacted with. What
Moiya McTier 45:09
about people? Corinne? Yeah. What about people? Are we fluid?
Corinne Caputo 45:13
That's crazy? Like to think I'm always changing? Yeah.
Moiya McTier 45:17
There are definitely aspects of myself that are always changing genders sexuality. Some people are very fluid and that fluid. And we certainly have many fluids in us. Yeah. As humans.
Corinne Caputo 45:31
Well, we even have Plasma fields, if you follow my school. I feel like maybe we can be like oobleck. This,
Moiya McTier 45:40
this is interesting, because when you start thinking larger than the scale of individual objects, and put them together, like cars, an individual car is not a fluid, but
Corinne Caputo 45:52
a bunch of cars is jam before. Okay.
Moiya McTier 45:54
Yeah, like because you talk you can talk about the flow of traffic. Yeah. As a group, they are a fluid. Humans, when you get us into groups, we can move as a fluid,
Corinne Caputo 46:06
like crossing the street in New York City can feel like that. Yeah, exactly.
Moiya McTier 46:11
Or even, you know, this is like a terrible tragedy. But when when crowds swarm like when you get a big crowd of people, and it starts to move as one yeah, that is that is fluid motion. Like you can really see it at big concerts or something. Yes,
Corinne Caputo 46:28
yes, totally. I went to a very crowded High School, there are 4000 kids in this building. There's 1000 kids per grade. I know you had a very starkly different experience. But that's just made me think that there were a series of classes I had where it was like, There's no way I'm gonna get to my next class in time because the bell rings, everyone floods out. And then we're all jumping through this hallway. Yeah, exactly. We're moving to this hallway. And I remember it felt so crowded. I was like, I I am sandwiched between bodies right now in a way that I could lift my legs up, and I would still be carried forward in this group.
Moiya McTier 47:04
Oh, my God. Terrifying. But yeah, that is that's a fluid.
Corinne Caputo 47:08
And me that you know, the good student is just sweating that I'm going to be late to this class.
Moiya McTier 47:14
I know the feeling. I also hate being late especially. Yeah, especially the class.
Corinne Caputo 47:19
I know. I want to settle in.
Moiya McTier 47:23
You want to be there. You want to calm down and you want to be able to wipe all the sweat off? Yeah, I gotta like before you crack comes into the room. Sec.
Corinne Caputo 47:29
That was that hallway was so crowded. Speaking of crush,
I had a friend who had like, you know, large curly hair, and she weren't down often. And a boy and his girlfriend were like making out in the hallway. And like he reached for his girlfriend's like heads, like, touch your hair. And he fully put his hair in hers, not knowing. And she was just like, What do I do now? Do I? I think she kind of like, because we're just all moving. In a way. It was like, she got out of it. But definitely like, this is what happened. That's
Moiya McTier 48:02
unfortunate. For multiple reasons. It was so gross. Don't Don't touch my hair. But also like, Don't involve me in your kissing shenanigans. Unless I want to be.
Corinne Caputo 48:11
Yeah, exactly. It was clearly like, Okay, we should be staggering. The dismissal of class
needs to be different, you should go back to your high school and I'm gonna, I'm gonna give them this one idea. You can
Moiya McTier 48:25
bring up laminar and turbulent flow, like look like
Corinne Caputo 48:28
I went off, I graduated, I explore the world and look at all I learned, I think you can apply it.
Moiya McTier 48:34
No, that actually is a really good example of laminar versus turbulent flow. Because when you have all of these students packed in the hallway, they're going in different directions. That's very turbulent. Yeah, if you had a less dense medium, then people would be more able to move in parallel direction. Exactly. So I think the the rule here or the lesson here is that most things can be a fluid, especially if you put them in a big enough group.
Corinne Caputo 49:03
Yeah, that's really cool to think about.
Moiya McTier 49:04
I love that cool. Hey, Karen. My tummy is growling I really want one of those corndogs I
Corinne Caputo 49:11
am dying to eat something maybe a big lemonade to
Moiya McTier 49:15
those maybe a fried Oreo.
Corinne Caputo 49:16
Oh, yeah, yeah, we can get that with the pickles. Okay, so we're
Moiya McTier 49:21
gonna go and eat all of the unhealthy for our bodies but very healthy for our souls. carnival food and whether you are eating a corndog or not remember, both you and that corndog are space. You
Corinne Caputo 49:35
are space by.
Moiya McTier 49:47
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 McMullin. Our audio editing is handled by the incomparable Mischa Stanton.
Corinne Caputo 50:01
Stay in touch with us and the universe by following @PaleBluePod on Twitter and Instagram. Or check out our website palebluepod[dot]com. We're a member of Multitude, an 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 50:20
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Corinne Caputo 50:46
Thanks for listening to Pale Blue Pod. You'll hear us again next week. Bye!