What is a non-Newtonian fluid?

00:00:08
Speaker 1: Hey, Daniel, what are physicists favorite foods? Dark chocolate, heavy water, dark chocolate.

00:00:14
Speaker 2: Studded with chunks of dark matter. Now I heard that Newton liked chicken pot pie weirdly enough.

00:00:20
Speaker 1: Well, yeah, was it because of the nutrients?

00:00:25
Speaker 2: I heard actually that he likes a really thick gravy as high specific gravity.

00:00:30
Speaker 1: Mmm. I heard he was more of a cookie man.

00:00:33
Speaker 2: What really, Isaac Newton eating something as silly as a cookie?

00:00:36
Speaker 1: Yeah? It didn't even invent the fake newtonts.

00:00:40
Speaker 2: I think actually those cookies were named after the town of Newton, Massachusetts, where they were first baked.

00:00:46
Speaker 1: Uh, But then wasn't the town named after Isaac Newton, So technically he's grandfathered in.

00:00:52
Speaker 2: I think its name comes from it being invaded by a huge swarm of Newts.

00:00:56
Speaker 1: The next thing you're gonna tell me is that Einstein's brothers bagels was not invented by iceland on his brother.

00:01:02
Speaker 2: No, but if you need enough of them, youal curve space.

00:01:04
Speaker 1: I feel like it's a big hole in that story.

00:01:21
Speaker 2: Hi.

00:01:21
Speaker 1: I'm Jorhem mccartoonists and the author of Oliver's Great Big Universe.

00:01:25
Speaker 2: Hi I'm Daniel. I'm a particle physicist and a professor at uc Erine, and I'll always love the Everything Bagel.

00:01:32
Speaker 1: Do you like everything about bagels or the bagel that's called the everything Bagel?

00:01:36
Speaker 2: I like the Everything Bagel, though I expected you to criticize it for not being accurately named. I mean, it's not literally everything on the bagel.

00:01:44
Speaker 1: If it did, it would maybe collapse into a black hole and collapse in multiverse, as some movies would happen.

00:01:48
Speaker 2: If it literally had everything on it, it would also have to have everything bagels on it, so it'd be like a recursive bagels with bagels on it, and bagels on those, and bagels on those forever down to the tiniest little bagels.

00:02:00
Speaker 1: It goes all the way down to the center of reality. Big of the movie was.

00:02:04
Speaker 2: Right, everything bagel, everywhere, all at once.

00:02:06
Speaker 1: Welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio.

00:02:11
Speaker 2: Where we think about the universe as a huge tasty snack. You can put smeer on it, you can slap locks on it, or you can just try to understand it. We hope that the universe is intellectually devourable at least that we can gather all of the knowledge and observations that humanity has been making for thousands of years and somehow weigh them together into a story about how everything works, how the tiniest little bits interact, how they come together to make weird fluids and goofy stuff and solids and metals that we live with all the way up to planets and galaxies and black holes.

00:02:43
Speaker 1: Yes, it is a pretty delicious universe full of amazing things that will fill you up in your brain, fill up your head with knowledge and amazing facts and incredible processes going out there in the cosmos, in between galaxies, inside of galaxies, and inside of all of us sometimes because we ate it.

00:03:00
Speaker 2: One of my favorite things about physics is that it's fascinating at so many different levels. I mean, on this podcast, we usually focus on the very very very tiny, trying to understand the fundamental nature of matter, or like they're really really big thinking about the whole universe, and it's incredible that there are stories at both of those levels that we can think about, that we can understand that give us some like intuitive grasp on the workings of the universe. But don't forget that there's lots of levels in between, like the ones we live on, things about a meter scale and moving kind of slowly, and so much fascinating physics that happens here on Earth.

00:03:36
Speaker 1: Wait are you saying physics is happening everywhere, all at once, on everything, everywhere, all at once.

00:03:43
Speaker 2: I'm saying you have to have physics as a topping on your bagel if it's got everything on it, But.

00:03:47
Speaker 1: Then to put it on top would require physics.

00:03:49
Speaker 2: And I'm not saying physics on top of everything. You know, I have deep love and respect for chemistry as well.

00:03:54
Speaker 1: Maybe everything bagel is physics. That's why Eistein and his brother invented the baggel.

00:04:00
Speaker 2: Or haes bagel theory of the universe.

00:04:02
Speaker 1: Isn't a bagel a possible shape of the universe, like a taurus?

00:04:05
Speaker 2: Yeah right, yeah, I think the mathematicians call it a taurus or a doughnut, rarely a bagel. But yeah, that's possible. But I think the fact that your theory is shaped like a zero might give you a.

00:04:14
Speaker 1: Clue because it's the first thing and that the universe was made out of. It's the zero theorem.

00:04:22
Speaker 2: Yeah, let's go with that. But there is so much fascinating physics that happens, not just at the tiny scale and at the huge scale, but right here on Earth. The way the particles weave themselves together creates all sorts of fascinating chemistry and biology and of course life here on Earth. And along the way, there's lots of really interesting questions we can ask, not about the fundamental nature of stuff, but what that stuff does when it comes together.

00:04:46
Speaker 1: Yeah, because as we said, physics is happening everywhere. It doesn't just happen in a laboratory and a big research institution or a university. It also happens all the time everywhere, even in your kitchen. There are all kinds of interesting examples of physics everywhere all around us, in the foods we eat and the foods that you prepare, and also in things like slime.

00:05:07
Speaker 2: And a couple of years ago, during the pandemic, there was this huge trend of kids making slime in their kitchens, which seem to explode everywhere, all over the Internet and all over the walls of our kitchen.

00:05:17
Speaker 1: Wait literally explode or figuratively explode.

00:05:20
Speaker 2: Well, my daughter made all sorts of various kinds of slime I remember at least one of them blew up on her.

00:05:25
Speaker 1: It isn't the definition of slime that it gets all over the place and it's a big mess. Like we just made slime and kept it in a cup. It's not really slime. It's only sime if you like, pick it up and pull it apart with your fingers.

00:05:37
Speaker 2: Slime is as slime does.

00:05:39
Speaker 1: But yeah, there are all kinds of amazing physics we can observe and ask questions about it in our everyday lives. And one of those questions that we often get is about a very specific kind of liquid.

00:05:50
Speaker 2: People playing around in their kitchens and making slime and wondering about the physics of solids and gases and liquids. A bunch of them wrote in to ask us about the physics of this but particular kind of goo.

00:06:01
Speaker 1: So today on the podcast, we'll be asking the question, what is a non Newtonian fluid?

00:06:12
Speaker 2: Isn't that just something Newton wouldn't have on his.

00:06:14
Speaker 1: Chicken or his fake newtonts. Maybe it's a a schmeir on a Einstein bagel.

00:06:22
Speaker 2: There you go. I'd like the Newton shmer and the Einstein bagel, please.

00:06:26
Speaker 1: Yeah, but not everyone likes it. You know, it's all relative. But yeah, it's an interesting question. I feel like this is one of those terms non Newtonian fluids that you hear all the time, sort of in like physics shows or physics explanations that's used like as an explanation for a phenomenon. But it's not really an explanation to say that the fluid that has a name on it.

00:06:45
Speaker 2: Well, it's sort of weird that you define it by what it Isn't like I could serve you dinner and say, hey, this is not a bagel. I've made it for dinner. Doesn't really tell you what it is, right, It could still be lots of different things.

00:06:55
Speaker 1: Oh right, Yeah, I guess maybe that only works that there are only two kinds of something in the world, Like is this an everything bagel or not everything bigel? Technically every bagel doesn't have everything on it is a non everything bagel.

00:07:10
Speaker 2: It's true that every meal any human is ever eaten is either an everything bagel or it's not an everything bagel.

00:07:16
Speaker 1: Right, or nothing bige.

00:07:19
Speaker 2: That sounds kind of like a nothing burger.

00:07:21
Speaker 1: Exactly, it's a nothing bagel burger.

00:07:24
Speaker 2: But this is not a nothing burger of physics. There are Newtonian fluids that follow certain rules, and then weird kinds of fluids that don't follow Newton's strict laws about how fluids should go.

00:07:37
Speaker 1: Yeah, so this is an interesting question what is a non Newtonian fluid? And so, as usually, we were wondering how many people out there had thought about this question or wondered what exactly is going on in a non Newtonian fluid.

00:07:47
Speaker 2: So thanks very much to everybody who answers these questions. If you're up for us playing your answers to questions, please write to us to questions at Danielandjorge dot com.

00:07:58
Speaker 1: So think about it for a second. Are you in the non Newtonian or the pro Newtonian? Can here's a depled to say.

00:08:05
Speaker 3: Maybe it's when the molecules in a fluid don't react according to Newton's laws of gravitation.

00:08:12
Speaker 2: I don't know.

00:08:13
Speaker 3: I've heard of non Newtonian fluids, but I'm not sure what makes them non Newtonian. I think it means that you don't use the usual fluid mechanics that you would with fluids that we're used to. Examples of non Newtonian fluids might be liquid helium, and maybe the fluid in the interior of a neutron star, possibly ferrofluids, but that doesn't mean I know why they're non Newtonian.

00:08:37
Speaker 1: Non Newtonian fluid. I didn't know there is Newtonian fluid, but I'm guessing that this non Newtonian fluid doesn't follow the like three Newton's laws.

00:08:47
Speaker 4: The first example that comes to mind is a mixture of cornstarch and water. If you mix those two things together in a glass and try to pour it out, it will flow like a viscous fluid, but if you impact it quickly with your finger, will solidify. So I think a non Newtonian fluid is one that displays properties of more than one phase of matter, either liquid, solid or probably gas.

00:09:13
Speaker 5: Well, non Neutonian fluids, that's a pretty cool one. I mean, non Newtonia makes me thinks of quantum mechanics, So this must be some fluids made of super small particles, elementary particles, maybe electrons, maybe subparticles. So and then this fluid will respond to quantum chemistry quantum physics, so it would be.

00:09:37
Speaker 2: A pretty crazy fluid. What is a non Netonian food?

00:09:40
Speaker 3: I don't even know what a non Newtonian fluid is, so I'm going to say a non Newtonian fluid is most fluid.

00:09:48
Speaker 2: I don't know what a non Newtonian fluid is. I assume it's of some sort of fluid that's not like the ones I'm familiar with.

00:09:55
Speaker 1: I have a vague feeling that a non Newtonian fluid is one that is compressible, whereas a Newtonian one is uncompressible.

00:10:04
Speaker 3: I think a non Newtonian fluid is one that doesn't obey the equations made by Newton.

00:10:11
Speaker 1: A lot of interesting answers here. I guess a lot of people did assume that it has something to do with Isaac Newton.

00:10:17
Speaker 2: M hm, though I particularly like the suggestion that maybe it's an anti gravity liquid.

00:10:22
Speaker 1: Oh interesting, that'd be pretty awesome if you can make that in your kitchen.

00:10:27
Speaker 2: Yeah, Like Newton did so much in physics, it's not clear what non Newtonian means, Like which of Newton's laws are you breaking? Are you like, violating the fundamental laws of calculus or of gravity or of motion or what?

00:10:40
Speaker 1: I think the fluid kind of gives it away a little bit, right, It's not a non Newtonian math ages Newton's laws in relation to liquids or as they relate to liquids.

00:10:52
Speaker 2: It really is incredible that one of like the minor things that Newton did is still an important work of physics, one that would get any other physicists their name on an equation forever. But for Newton it's like the ninth and most important thing he did.

00:11:05
Speaker 1: Yeah, although if if something named something after not you would, can you still take credit for it? Like I have invented the non Daniel Whitson particle. That would be almost like a very passive aggressive move there.

00:11:21
Speaker 2: Hey, slap my name on something famous forever as an insult, I'll take it.

00:11:25
Speaker 1: M Like if someone discovers the truth about everything, the core nugget of reality and called it the not Weissen theorem, we.

00:11:32
Speaker 2: Have the anti white syn theorem. Go ahead and do it. You name it after me forever. Any publicity is good publicity.

00:11:38
Speaker 1: All right, Well, Stasty, you heard it on the podcast. You have it on his permission to not not name things not after it.

00:11:47
Speaker 2: You just want to be part of the conversation.

00:11:48
Speaker 1: Man, I guess if your name being spoken in a negative way, they're still talking about it.

00:11:54
Speaker 2: Yeah, I mean, what if the announce like Black Panther three not starring or hey, cham, you'd be pretty thrilled.

00:11:59
Speaker 1: Still mmm, I think I'd rather just stay out of that conversation. You know, I'm not that desperate yet. All Right, Well, let's get back to non Newtonian fluids, and maybe let's start at the beginning, like what is a pro neutuinin or regular in Neetonian fluid?

00:12:16
Speaker 2: Yeah, So fluids are fascinating things, right because they have constant volume, like they don't grow or shrink, but they don't have a fixed shape. So you can like take a glass of water and you can pour it into a bowl and the volume of it doesn't change, but it'll fill the bowl, it'll take that new shape. Or you can put it into a baggie, or you can dump it on the floor and they can do a puddle. Total volume of stuff won't change, but its overall shape is totally flexible. And that's really cool because it sits right between gases and solids. Gases don't have constant volume, they'll grow to fill any box you put them in. Solids have constant volume, but they also have a fixed shape. So fluids are this fascinating sort of half step between and solids.

00:13:01
Speaker 1: Well, you just sort of blew my mind or a little bit. I hadn't thought about the definition of the states of matter in that way. I guess, huh, is that basically what divides the three states of matter? Is that the technical definition or is there something more specific about the molecules or something.

00:13:17
Speaker 2: Well, there's fascinating history there because originally, of course, we didn't understand that matter was made out of molecules and little particles. Now we do have a molecular understanding for these phases of matter, but originally we didn't, and we still define them. It was just observational, the way a lot of physics is currently, Like, here's the kind of stuff we see in the universe. We notice there's this kind of stuff. There's drippy stuff, and this solid stuff, and there's puffy stuff. And that's how we begin. We start with observations, and we describe it, we categorize it, and then later we hope to get a microphysical understanding of where that comes from. Now, of course we know that everything is made out of molecules, and in gases, things are flying apart and basically not interacting, and in liquids there are still some bonds there, and then in solids they often form this crystal structure which is the source of their rigidity. Right, So we have an understanding now, but I think originally it just comes from observing different kinds of drippiness and gooiness.

00:14:11
Speaker 1: Yeah, that's what I mean. It's like, did we get it right all those hundreds or thousands of years ago, Like our physic is still using the same definition for the states of matter.

00:14:19
Speaker 2: It's changed a little bit and gotten a little bit more complicated as we've understood the microphysics. So now there's like thermodynamic definitions of phases and multiple versions of each of these things. You know, water, for example, has multiple different solid phases, not just ice. There's like ice one through ice nine, or maybe even ice twelve. Chemistry experts can tell you all about the different kinds of ice because water forms lots of different crystal structures under different pressures and temperatures.

00:14:45
Speaker 1: Is that why some cultures have like a lot of different words for snow sort of right? Sort of?

00:14:50
Speaker 2: Maybe there's definitely lots of different crystal structures for ice. I don't know if the linguistic history of some of those languages recognizes those subtle differences, or if that's just an accident. But it is true that there's lots of different ways to form ices, especially waters and especially complicated chemical other things only form one kind of solid, So there's definitely a lot more going on once you understand it. And there's lots of different kinds of phase transitions, the kinds that we think about gas, liquid, solid. Those are what we call first order phase transitions. We have like a discontinuity in the density. Things get much thicker as they get colder and change their density. They are also second order phase transitions, where you don't change from like a liquid to a solid, but you change like your heat capacity or other thermal properties. So there's definitely a lot more going on. But yeah, we sort of got the big picture right early on. But you know, remember, the physics is all about explaining the universe to humans, and this is our experience. We see these different kinds of things in the world. We want to understand what's going on and have explanations for that. So we're always going to want to explain the basic experience we have when interacting.

00:15:51
Speaker 1: With the world. Okay, So then you're saying that a fluid is a stuff that, when you put it inside of a cup, moves and changes its shape to adapt to that space, that volume, but it keeps its volume. That's the basic definition of a fluid.

00:16:08
Speaker 2: H that's technically the definition of a liquid, and all liquids are also fluids. Fluids, in addition, can encompass actually solids because some solids can flow. We don't need to dig into the differences between fluids and liquids. That's for like law school types. But essentially, yes, that's what we're talking about. Fluids, things that have constant volume but not a fixed shape.

00:16:30
Speaker 1: Oh. I see, some solids like sand can act in a fluid way, but it's technically not in a different state of matter.

00:16:38
Speaker 2: So liquid refers to the state of matter, fluid refers to the properties of the object, and they're very closely connected. But they're exceptions in both directions.

00:16:46
Speaker 1: I see. So which one are we talking about here? Today? Are we talking about non Newtonian fluids or non Newtonian liquids?

00:16:53
Speaker 2: We're talking about non Newtonian fluids, almost all of which are.

00:16:56
Speaker 1: Liquids, but there are some that are not.

00:16:59
Speaker 2: There might be, but I don't have an example for you. The fluids themselves also have a huge range of properties, Like you know that pouring honey is very different from pouring water. Right, One of them flows very very quickly, one of them flows very very slowly. Like there's a huge range of the goopiness of the fluid itself.

00:17:14
Speaker 1: Right, right, thinks are more or less viscous, But that has nothing to do with the state of matter, right of it, stickness of matternness of it. It's more some sort of other dimension of properties, kind of.

00:17:26
Speaker 2: Exactly within this fluid category, you have viscous fluids and non viscous fluids, basically like how thick is the fluid? This is like the subject of the pilot episode for our TV show, right, the goopiness of stuff.

00:17:39
Speaker 1: Our show ellenor Wonders Why which by the way, Arizona, Pbius Kids and under streaming apps just wanted to put that plug in.

00:17:47
Speaker 2: Yeah, exactly. So you pour water into a box, it flows very very quickly, and you pour honey into a box. You could be standing there for ten minutes right before the honey finally pours out of the jar, and even once it's in the box, it takes a while else to spread out and eventually fill up that box. Still categorized as a fluid, it still will flow, keep the same volume and fill out the box, but feel very different from water because of this difference in viscosity. So as you say, this is like another axis along which to think about fluids.

00:18:15
Speaker 1: Right, And it has maybe something to do with a different set of sort of physics, maybe unrelated to the states of matter, right or is it all just physics all of one.

00:18:25
Speaker 2: It's all just physics all the way down.

00:18:27
Speaker 4: Man.

00:18:28
Speaker 2: In the end, there is a microphysical understanding of this viscosity, which does come from how the molecules talk to each other, So in that sense it's kind of related to the states of matter. But this is just within fluids. You can understand why some things are viscous, why things are thick and goofy, and why some things are thin, and it does have to do with the intermolecular forces. Like basically, in honey, the molecules grab at each other more than they do in water. So as layers of honey slide past each other, there tends to be more friction between those layers, which makes it slower. We try to pour honey down a garden hose, it would take forever to come out the other side.

00:19:04
Speaker 1: M Okay, we're getting into a bit of a sticky subject here, and so let's get into what viscosity actually is and what it has to do with being pro or non Newtonia. So let's dig into that. But first let's take a quick break. All right, we are not talking about non Newtonian fluids today, asking the question what are they, what makes them cool? And why are there so many YouTube videos about them?

00:19:42
Speaker 2: Non Newtoni fluids are a famous physics demonstration because they do something weird and dramatic when you like bounce them on top of a speaker. But we can get into that.

00:19:53
Speaker 1: Yeah, and they're also kind of everywhere, right, like in the ketchup we eat and this lime our kids play with, even in the paint we used to thinks.

00:20:00
Speaker 2: Yeah, the phrase non Newtonian gives you the impression maybe it's like a weird edge case, like a rare exception, but actually non Newtonian fluids are everywhere. Maybe Newtonian fluids should be the ones that have non in front of them.

00:20:12
Speaker 1: You mean they should be non non Newtonian.

00:20:14
Speaker 2: Fluids I'm not not saying that.

00:20:16
Speaker 1: But you're not not denying it.

00:20:20
Speaker 2: Did you know that humans can process about foreign negations in a sentence before they get totally confused?

00:20:24
Speaker 1: I did not not know that.

00:20:25
Speaker 2: Well before you did not know it, you used to.

00:20:29
Speaker 1: Yes, I did not know that also, which I think puts it in like a twelve negation.

00:20:34
Speaker 2: There, Yeah, which is turning my brain into a non white Sunian fluid.

00:20:38
Speaker 1: Yeah, which might be a thing out there maybe somebody by the time we got to this point in the conversation, somebody already invented a non whites and.

00:20:48
Speaker 2: Something something good to dip your newtons into.

00:20:50
Speaker 1: All right, well, I get the sense, and I know this from what I know about non netunin fluids is that it has to do with their viscosity. There's something weird about the viscosity of non Tunian fluids. And so you were talking about a little bit earlier about what viscosity actually is or how it presents itself in some fluids. Some fluids are thick like honey, and some fluids are super fluid, super liquid like water, Daniel, Is there an official definition of what viscosity is?

00:21:17
Speaker 2: There is an official definition of what viscosity is and it's a little bit technical and mathematical, but you can get a grip on it by imagining the garden hose. Like, say, you take a liquid and you pour it through a garden hose, and you measure the speed of that liquid through the garden hose. For something that's very very viscous, you're going to get the center traveling a lot faster than the edges because the wall of the garden hose drags on the fluid. And then if it's a viscous fluid, that first layer of fluid near the wall then drags on the next one, which drags on the next one, which drags on the next one. By the time you get to the center, it's going a lot faster than it is at the edges. In a non viscous fluid, you flow it through and basically everything travels at the same speed because the layers aren't rubbing against each other. So the definition of viscosity relates to like how quickly the friction adds up to slow things down. It's like that slope between what they call the sheer stress, which is essentially the friction and the velocity of the fluid.

00:22:15
Speaker 1: Yeah, you're right that they get very technical. Well, I guess one way that I always thought viscosity was defined was like how hard is it to stir basically in a cup or a bucket, Like if you have hunting a bucket and you stick a laddle in it or a spoon, it's really hard to move that laddle and spoon around, whereas in water it's a lot easier, isn't it sort of also sort of or equivalently defined by the laddle test or sort of like what's the resistance it gives you when you try to move through it.

00:22:45
Speaker 2: I think it's technically defined as the friction inside the liquid, So you're talking about like a lathle and the friction on the liquid. I think if you want to be really strict about it, probably viscosity is you know, fluid to fluid layers of friction. But that's definitely really like you could measure the viscosity by taking a ladle and using it to stir one liquid versus another and measuring the viscosity, and they probably are machines that do exactly that.

00:23:08
Speaker 1: Even with the hose definition, there's still like what is the friction of the liquid with the hose material, right.

00:23:15
Speaker 2: But the viscosity is related to how the velocity changes as you go away from the wall, So it's all about the friction between the layers. I don't think it's a terribly important distinction, but it is defined just in terms of the liquid itself and not some external thing.

00:23:29
Speaker 1: But like, let's say I had a teflon hose, or a hose lined with teflon inside, or like impossibly slippery stuff inside of the hose. If I put pressure behind it, wouldn't all the honey's just come out like it's being extruded.

00:23:41
Speaker 2: Yeah, if you had a frictionless wall, then the honey would just slide through it. Absolutely. This definition assumes some friction from the wall, which creates different velocities, and then you measure the viscosity by how that velocity propagates through the fluid. So it's this slope between the sheer stress and the velocity.

00:23:58
Speaker 1: Yeah, But then the same thing sort of happens and you try to move a spoon through a honey, right, there is some friction, and maybe depends on whether you use a teflon spoon or a different kind of spoon, but I think generally just to give people an intuitive sense of what viscosity is. Couldn't we just sort of say that it is sort of like how hard this to move a spoon through it on a cup?

00:24:18
Speaker 2: Yeah? Absolutely, that gives you a good intuitive sense. If you take the same ladle with the same friction on its surface in two different fluids, the one with higher viscosity will be harder to stir for sure, right.

00:24:28
Speaker 1: And I think at least in engineering, how we define viscosity is like, as you move your spoon with a different velocity through the liquid, what is the force that it pushes back to you. That's how at least engineers define it.

00:24:40
Speaker 2: Yeah, And in the end, what's happening deep down is that you have these molecules and either are gravy on each other or they're not. And if they're not gravy on each other, they can just slide past each other and in a really not very viscous fluid. Even if you put a rough surface laddle, it might move one layer of that fluid, but then that fluid will slide right by the next lege and so be very easy to move and be very low viscosity. And so it all comes down to how these layers of fluid grab onto each other or don't grab onto each other. So that's what viscosity is in these fluids.

00:25:12
Speaker 1: It's sort of like the molecules of the fluid hanging on to each other. And this is due to what kinds of forces like chemical forces or you know, electromagnetic forces, vendor Wolf forces, what makes the molecules hang on to each other or not.

00:25:26
Speaker 2: Yeah, well, all those things are electromagnetic, like what we call chemical forces, covalent and ionic bonds, those are electromagnetic. They have to do with where the electrons are and how they're grabbing onto each other. Even Vanderwall's forces come from, like how the electromagnetism is distributed around an atom, whether it's a dipole or whether it's balanced or not. So on these distant scale it's all electromagnetic forces. Like the strong force is all tightly bound inside the proton and neutron, the weak force is basically irrelevant, and gravity is also irrelevant. This is all in the end emergent phenomena of electromagnetism. Like in principle, you don't need any of this. All you need is quantum electrodynamics, and you could predict everything, But in practice that's a huge pain in the butt, right, it's like trying to do calculus. Just with arithmetic take you forever to do anything. So we like to come up with these clever shorthands, these emergent phenomena that we can use to describe the things we see in the world more easily. So in the end, it's all electromagnetism sort of zoomed out.

00:26:22
Speaker 1: Now does it have to do with the density of the fluid? Like I would imagine a really light fluid or fluid that's not very dense would have a lower viscosity, or it would be easier to push through, or would have less friction between the layers than a really dense fluid.

00:26:40
Speaker 2: Yeah, so this is where Newton's law comes in. Newton did a bunch of studies of fluids, and he found that the viscosity does not depend very much on the pressure. Like you squeeze the fluid or you don't squeeze the fluid, it doesn't really change the viscosity of the fluid very much. What does change it is the temperature, Like you heat the fluid up, you cool it down. That will change the viscosity. But Newton's law of viscosity basically says that the viscosity does not depend very much on.

00:27:07
Speaker 1: The pressure of the pressure of the liquid exactly, because I guess liquids can have different pressures, right, I guess, like the water at the bottom of the ocean is under a very different pressure than the water at the top of the ocean.

00:27:20
Speaker 2: Exactly, And for Newtonian fluids like water, the viscosity at the bottom of the ocean is not very different than the viscosity at the top of the ocean if they're the same temperature. Water's viscosity does depend on temperature a lot, Like if you heat water up from twenty ceed to fifty c then it gets fifty percent less viscous. So warm water is less viscous than cold water, but the pressure doesn't make a big difference. And that's essentially Newton's law of fluids.

00:27:46
Speaker 1: So Newton's laws of fluids, what you're saying, has only to do with pressure, not temperature.

00:27:51
Speaker 2: That's right. You can be a Newtonian fluid and have your riscosity depend on temperature. That's not a problem. But if you're a Newtonian fluid, you can't have your riscosity depend very strongly on the pressure.

00:28:01
Speaker 1: Well, I guess, just to be clear, and Newton didn't own any fluids, Well, let me say Newton's fluids. We just kind of mean like what Newton noticed about most fluids.

00:28:13
Speaker 2: Yeah, we don't mean like the literal cups of stuff in Newton's.

00:28:16
Speaker 1: Like, he didn't discover all of these fluids. He just discovered like, hey, most fluids behave in this very sort of nice way, right, And so that's why that's what got named Newton's fluids or Newton's laws of fluids.

00:28:29
Speaker 2: Yeah, exactly. Like if we had two kinds of mass, one that followed eth equals MA, and we'd call it Newtonian masses, and if there was some other weird kind of mass that didn't obey Newton's law ethicals MA, we might call that non Newtonian mass or something. It doesn't mean that Newtonian mass would only describe like the stuff Newton owned himself. So you're right, Newton noticed his behavior in some fluids, and so we call those Newtonian fluids ones that follow the laws that he described.

00:28:54
Speaker 1: Okay, and then just to repeat for folks, what is that law again?

00:28:57
Speaker 2: Essentially it's that the viscosity doesn't on the pressure.

00:29:01
Speaker 1: So, for example, water is a Newtonian fluid because it's viscosity at the bottom of the ocean is the same as its viscosity at the top of the ocean.

00:29:09
Speaker 2: If they're at the same temperature. Right, Viscosity does depend on temperature, and typically the bottom of the ocean can be colder than the top of the ocean. Like if you control for temperature, like maybe in your swimming pool, for example, where it's all the same temperature, then the viscosity the bottom is the same as the viscosity on the top. You don't like get down to the bottom of the swimming pool and find that you're suddenly swimming through honey.

00:29:28
Speaker 1: Right right, Although that sounds delicious and dangerous, you could dip your fake mutons and bagels just by walking out to your honeypool.

00:29:36
Speaker 2: Please, folks, do not fill your pool with honey. It's a terrible idea.

00:29:43
Speaker 1: Unless you really love honey and or wanted to know what it was like to swim in honey.

00:29:50
Speaker 2: I'm terrified to even type that into my Google search window over here.

00:29:53
Speaker 1: Oh, I'm sure there are YouTube videos about it.

00:29:56
Speaker 2: Some poor grizzly bear.

00:29:57
Speaker 1: But so that's an interesting definition of non of a Newtonian fluid, because the way they define it in engineering, or at least the way I've heard it define, is that a Newtonian fluid, or like regular viscosity, is when the force that the liquid pushes back on you when you try to steer it with a spoon is related or is proportional to how fast you're trying to move that spoon. So, like regular viscous fluid, like honey, the faster you try to stir it, the harder it is to stir it, but in a very linear way, like if you try to steer it slowly, it'll push back a little bit on you, and if you try to steer it really hard, it'll push back on you proportionally harder. I imagine they're the same thing, maybe, but it seems like you're approaching it from a different point of view.

00:30:46
Speaker 2: Yeah, they are the same thing. You're right that, technically, viscosity is this relationship between velocity and sheer stress, right, how fast the layers are sliding past each other and the friction that they exert on each other. And Newtonian fluids expressed in that life language. The relationship is linear, right, So higher velocity means higher shear stress, which means more friction. So as you say, the faster you try to stir, the more force you're feeling.

00:31:10
Speaker 1: Right, And I think you didn't sort of observe that that relationship was linear. Like if you plot how fast you're trying to stir the spoon versus how much force it's pushing back on you, it's like a straight line. That's what I thought was or heard was a Newtonian viscosity.

00:31:25
Speaker 2: Yeah, I think that's totally right. I was trying to avoid getting into the technical details of derivatives and slopes and sheer stresses, but I underestimated your appetite for the math of sticky fluids.

00:31:33
Speaker 1: Well, I think it's important because a non neetunin fluid then is something that doesn't have that linear relationship. Right.

00:31:39
Speaker 2: It still has that relationship, but it's non linear. It still has more friction as a velocity grows. It's just not a strictly linear relationship, right, Right.

00:31:47
Speaker 1: So I think when people say a Newtonian fluid, it's one where you kind of know what you're going to get, like if you if it's honey, you know that the faster that you try to stir it, the harder is going to push back on you proportionally, right, mm hmm.

00:31:59
Speaker 2: Yeah, And that's a frictory linear relationship in Newtonian.

00:32:02
Speaker 1: Fluids, right, that's sort of like what need and observe, and so that's why it's called a Newtonian fluid.

00:32:06
Speaker 2: Mm hmm exactly. And what that means, sort of less mathematically, is that the viscosity is essentially constant with pressure.

00:32:13
Speaker 1: Or maybe because of viscosity is constant with pressure. That gives that curve a linear shape.

00:32:18
Speaker 2: Yeah, that's right, And viscosity is like super important in fluid dynamics. Like the people who try to understand how fluids flow, they have to solve these really gnarrowly differential equations called the Navier Stokes equation, for which there is no like nice solution. There's like a million dollar X prize for anybody who can solve these equations. They're famously complex, and they're complex because of the viscosity. It's like this viscosity term in those equations, and often people just set that to zero because otherwise it's impossible to solve. And so viscosity is like a really important thing mathematically, and then like fluid dynamics and understanding like the atmosphere and the ocean and climate change. It's an important thing.

00:32:56
Speaker 1: All right. Yeah, so that's a Newtonian fluid. That's what the new To notice about most fluids. And that's because that's kind of true for most things around us, right, like water, milk, oil, honey. Those things all have different viscosity, but they all sort of have this regular type of viscosity, which is this linear viscosity, right, and.

00:33:15
Speaker 2: There's a huge range. What's really amazing is how many different kinds of fluids can be described in this way. Right. This is why this law persists for so long, because it describes so many different kinds of things, you know, like honey and water and oil. These are the things we experience. But we've also discovered things on both edges, like super low viscosity fluids and super duper high viscosity fluids, all of which obey these principles.

00:33:39
Speaker 1: Yeah, so fluids that have a linear viscosity law. There's stuff that has very little viscosity and stuff that has high viscosity. Right.

00:33:47
Speaker 2: Yeah, And one of my favorite experiments in science has to do with trying to measure the viscosity of super duper goopy stuff. There's an experiment that's been going on since nineteen twenty seven and finished. It's still going because it's so slow. They're trying to measure the viscosity of asphalt. They call it pitch, but it's basically like the tar you spread on the road, and this stuff is super duper thick, so thick that it takes like ten years for a single drop to form. So in nineteen twenty seven they poured some of this thing into a funnel and they've been watching it flow down that funnel and make drops that come out the bottom. It's been going for almost a century and they've only ever seen nine drops come out the bottom.

00:34:32
Speaker 1: So you're saying, asphalt, or this thing called pitch is a fluid like it'll eventually flow down to the bottom of a cup, but it's as super duper high viscosity, so it's going to do it really slowly.

00:34:43
Speaker 2: Yeah, it has like two hundred and thirty billion times the viscosity of water. So imagine like trying to take a spoon and stick it in the road and stir right, there's a whole lot of friction there.

00:34:53
Speaker 1: But you could technically do it, I think, is what you're saying. Like it is a fluid, it is viscous. You could stick a spoon an asphal defense their it. But like the force at which it would push you back is huge, right.

00:35:06
Speaker 2: Yeah, it might take you more than a century or just to get your spoon into the asphalt.

00:35:10
Speaker 1: Right, or you would need a huge amount of force to push through it.

00:35:13
Speaker 2: Yeah, exactly. And this experiment is really fun because they started it in nineteen twenty seven and you know, it takes like ten years for a drop to fall, and in all of that time, nobody has ever actually witnessed a drop fall because the drop takes like a tenth of a second to fall over.

00:35:30
Speaker 1: Ten years a tenth of a second.

00:35:32
Speaker 2: Once the drop actually breaks off the bottom, it falls in like a tenth of a second, and nobody's ever actually seen this happen. Like you can walk by this thing every single day. You can see it drop about to break off and fall, and people have been hoping to actually like see it fall this incredible moment. It takes like ten years to pass, but nobody's ever actually been there to see it.

00:35:52
Speaker 1: Mmmm. But I'm sure it's been recorded.

00:35:54
Speaker 2: Well, it's actually pretty funny because they tried and in nineteen eighty eight, the experiment was actually on display at a World Expo when a drop fell, but nobody noticed it. The professor who runs the experiment, Professor Mainstone, had stepped out to get a drink and he missed it. So ever since then they set up a webcam to watch this thing. The next drop happened in November two thousand, but the camera happened to be on the fritz and so it missed it again. And then twenty fourteen was the ninth drop, but it broke off when they were like adjusting the experiment because the beaker below the funnel had finally filled up and it was interfering with the experiment. So nobody's ever actually watched a drop form from this thing. Everybody's waiting for the tenth drop to happen.

00:36:37
Speaker 1: Oh man, sounds like a lot of falling here. Maybe I should put more than one camera on it.

00:36:45
Speaker 2: And the professor who started it in nineteen twenty seven, Mainstone, he died in twenty thirteen, never having seen a drop form.

00:36:52
Speaker 1: Mmmm, should have just picked the lower viscosity fluid, I guess.

00:36:56
Speaker 2: So it's a pretty awesome experiment that shows you the incredible range of Newton's law of viscosity.

00:37:02
Speaker 1: Mm. Interesting. All right, Well that's what a Newtonian fluid is. And now let's get into what a non Newtonian fluid is. What makes these weird? Why are they the subject of so many interesting physics demonstrations online? So we'll dig into that, but first let's take another quick break. All right, we're talking about non Newtonian fluids, and we talked a lot about viscosity and what it is and what makes a Newtonian fluid. So basically a Newtonian fluid is one where you said that the viscosity depends on pressure on the pressure of the liquid, which sort of we agree. I think translates to like how hard it pushes back on you when you try to steer it or when you try to swim through it, for example.

00:37:55
Speaker 2: Yeah, I think the most accurate way to describe it is how you did, which is a relationship between the friction and the velocity. As layers start moving faster and faster adjacent to each other, you get more and more friction on those layers.

00:38:09
Speaker 1: Right, So like if you try to swim at one meter per second through honey, it's going to push you back with a certain force. If you double your speed, if you try to swim through it at two meters per second, then it should push back with you with twice the force. That's what a Newtonian fluid is.

00:38:22
Speaker 2: That's a Newtonian fluid where that relationship is linear, and the slope of that linear relationship is the viscosity. So things that have different viscosity have a differently sloped line, but it's always still a line. For a Newtonian fluid, it follows this linear relationship. For non Newtonian fluids, you get away from that line, things change in a different way as you increase the velocity.

00:38:43
Speaker 1: Right, and again, like nothing is perfectly linear, right, Like I think maybe what Newton's was just kind of looking at things at a first approximation and he noticed that it's like roughly linear for all of these materials within a certain range, and so that he's like, oh, this is the law of viscosity. M hmm, Like in reality, not even water is perfectly linear, is it.

00:39:01
Speaker 2: Yeah, nothing is perfectly Newtonian, but these are a good approximation. But some things, as we'll talk about in a minute, are very non Newtonian. They deviate dramatically from this linear relationship.

00:39:11
Speaker 1: All right, let's talk about no in neetonia, or let's not not talk about Newtonians, let's not avoid talking about netunias non Newtonian fluids. So then what is a non Newtonian fluid?

00:39:22
Speaker 2: So non Newtonian fluid is one where this relationship is not linear, and so the amount of friction you get as you push on it can change very very quickly if you push on it fast or push on it slow.

00:39:33
Speaker 1: So like in our assumming example, like if you're swimming through a non Newtonian fluid at one meter per second, is going to push it back with a certain force. If you try to soon twice as fast, it's maybe not going to push back with twice the amount of force. It might push back with less than twice the amount of force, or push back with more than twice the amount of force, exactly.

00:39:52
Speaker 2: And the classic example of a non Newtonian fluid is this stuff called ublek, which is basically what happens when you take cornstarch and you mix it with water into a suspension, and what you find if you have a bowl of oubleck is. If you push on it very gently, you can slide through it just like it's water. Right, It just feels normally like water. But if you try to move really fast, all of a sudden it gets very very stiff. So if you just stick your finger and it slowly, you can go right through. If you try to slap it, then it feels like a solid. It's incredibly viscous very quickly if you try to move through it at higher speed.

00:40:23
Speaker 1: Yeah, that's the most famous kind of non Newtonian fluid. It's so you take corn stars it's just like regular kitchen cornstarch, and you add a little bit of water at a time until it feels liquid when you try to steer it really slowly. But then if you try to steer it really fast, it suddenly feels like it's a solid block of something.

00:40:41
Speaker 2: Right, Exactly. If it was a Newtonian fluid, it still would feel thicker as you stir it faster, but it would be linear, and here it's very nonlinear. It suddenly gets extraordinarily viscous as you try to move through it faster.

00:40:53
Speaker 1: Yeah, it's crazy. I mean, you can look up all kinds of demonstrations online. People have made pools of.

00:40:58
Speaker 2: Ublek right, Oh my gosh, I hope no. The bears have fallen into those pools.

00:41:02
Speaker 1: Yeah, they thought it was a honeypool, but really it was a hopit pool.

00:41:07
Speaker 2: You should have gone to Newton's house. Man, he's got a pool full of honey.

00:41:11
Speaker 1: No, he's got a pool full of fick Newtons.

00:41:14
Speaker 2: I don't think the bear cares.

00:41:17
Speaker 1: Yeah, either way, it's delicious. I think he barely cares. But yeah, people have made pools of this stuff, right, And so like, if you have a pool of this, you can actually run through it and step on it.

00:41:28
Speaker 2: It acts as a solid if you're applying enough pressure, Like you can slap the surface and it feels like concrete. But if you very gently put your finger through it, you pass through it just like.

00:41:37
Speaker 1: Water or like I think, like if you stand on top of it, you'll sink, but if you try to run across it, you can actually not sink and just stay on top of it. Or if you stay, if you keep jumping on it, you won't sink. You'll actually sort of bounce on it. But if you just stand and not do anything, you're gonna sink down.

00:41:54
Speaker 2: Exactly, you might wonder, like, what's going on in terms of the microphysics, how can we understand this weird behavior? And it has again to do with how the little bits inside are sliding past each other or not sliding past each other. And critically it's because you have two different things there. It's not just water, which is a Newtonian fluid, but it's this combination of water and corn starch, and cornstarch in particular is very grabby. It's not very easy for cornstars to slide past itself.

00:42:21
Speaker 1: Right, And it sort of also has to do with the fact that, like if you try to move through Oublick too fast, you actually sort of like sort of push the water out kind of in a way, and so then it's just cornstarch, and so then those grab onto each other, right.

00:42:35
Speaker 2: Exactly, if you're moving slowly, then it's dominated by the water because it's time for like the water to get between the corn starch and act like little ball bearrings. Doesn't really matter that the corn starch is there, because the water makes everything slippery. If you move really really fast, the water gets pushed out between the corn starch and then you're basically trying to push through just corn starch, which is very, very thick. So it's sort of like there's two different personalities to it, and one comes out when you move and slow, and the other one comes out when you're moving fast. It's like the juckle and hide of fluids.

00:43:04
Speaker 1: Yeah, and this is a really cool effect. Everyone can do it at home. Just take some corn starch to put it in a cup and add water a little bit at a time until you get this weird liquid exactly.

00:43:12
Speaker 2: And if you put it on top of a speaker, for example, you get this really weird effect where it just looks like a liquid, but then the balancing of the speaker makes it suddenly solid momentarily, and so it forms these weird globs which will like dance on top of your speaker.

00:43:27
Speaker 1: Yeah, it's pretty wild. I highly recommend that all of you at home to try making uplick with your kids or by yourself. I did it before I had kids.

00:43:36
Speaker 2: Super fun. Yeah, it's fun, it's easy, It's only a little bit messy. Don't try to eat it though.

00:43:41
Speaker 1: Oh what happens if you eat it? You turn into a fig neating or not. I guess In general, doing in just high large amounts of anything.

00:43:53
Speaker 2: Yeah, though there are some non Newtonian fluids which people eat every single day. They have them on their burgers, have them with their fries.

00:44:01
Speaker 1: Yeah. Ketchup is a famous non Newtonian fluid.

00:44:04
Speaker 2: Right, Yeah, ketchup is sort of the opposite kind of non Newtonian fluid ubleck. If you try to move through it really fast, the viscosity grows really really quickly. But ketchup is sort of the opposite. Like, if you want ketchup to flow better, you actually shake it. You get it moving fast, right, you shake the bottle and then it'll flow out.

00:44:23
Speaker 1: Wait, is that why, like a ketchup you have to hit the bottom of the bottle to put it on your burger.

00:44:28
Speaker 2: Yeah, that's exactly why. You shake the bottle or you slap the bottom, and then suddenly it will flow. So you like increase the pressure of this thing, the viscosity actually goes down. You can flow better when you squeeze it.

00:44:38
Speaker 1: Mmm. So it's non Newtonian because that viscosity relationship is not linear, But it's the opposite of ublick, where like the faster you try to strimp through ketchup, the easier it is exactly.

00:44:49
Speaker 2: So Newtonian fluids are the ones that are just along this line, but you could be non Newtonian either above the line or below the line, or anything that deviates from the line. Essentially, so ketchup is super you're to actually call it a pseudo plastic. And there isn't a good microphysical understanding for why this works. Like we have this whole story about water and corn starch for ubleack, but there isn't a similar story we can tell for what's going on in ketchup.

00:45:13
Speaker 1: Wait, what do you mean? Like it's a mystery.

00:45:16
Speaker 2: It's a mystery of physics. People are doing experiments trying to understand it, but there is not a good concise understanding for why ketchup behaves the way it does.

00:45:23
Speaker 1: I guess maybe the simplest way to understand it is like if you take a ketchup bottle and you turn it upside down. The ketchup is not going to float out necessarily or very fast or very quickly, but if you sort of shake it, then it becomes a more liquid.

00:45:38
Speaker 2: Exactly, the viscosity drops when you shake it, when you apply some pressure to it, or you increase the velocity between the layers, the viscosity drops and so then you can slide and it flows out onto your burger.

00:45:49
Speaker 1: Mmmm. All right, what are other examples of non Newtonian fluids?

00:45:53
Speaker 2: So other things you might find around your house, Like slime is a non Newtonian fluid, silly putty?

00:45:58
Speaker 1: Right, what do you mean slime? That's different.

00:46:01
Speaker 2: Slime is in the oublick category. Like it can flow, but if you pick it up and you squeeze it, you can feel more solid. Right, that's one of the things that makes it sort of slimy. I mean, I try to avoid playing with slime whenever my daughter makes it, But this is what I noticed when I'm cleaning up after her.

00:46:16
Speaker 1: Yeah, So meaning like if you try to steer it, you feel a certain resistance to it. Or if you try to swim through slime, but you try to swim fast, the faster it'll push back on you more.

00:46:24
Speaker 2: Yeah. The viscosity is not constant. It changes depending on the stress and the forces apply to it. You pull it apart quickly applying a large force, it becomes very viscous and can like break in half. So you take like slime, you just pull on it gently, it'll stretch you pull on it really really fast, it'll actually crack into two.

00:46:40
Speaker 1: Pieces because I guess the force gets higher the faster you try to do it. But at some point the material can't take it and it just breaks exactly, It just gives up. Also, silly putty is a non newton of fluid, right.

00:46:53
Speaker 2: Yeah, silly putty in the same way. And the weirdest non newton in fluid. The thing that surprises me most is paint. Paint is also a non Newtonian fluid.

00:47:02
Speaker 1: What do you mean?

00:47:03
Speaker 2: Imagine what would happened if you painted your walls with honey or with water. You take your brush, you dip it, and you spread it along. You expect to see lots of drips, right, But paint, when you apply it to the wall, it's very easy to apply. But then it becomes very very viscous, so it doesn't drip very much. So paint is like specially formulated chemically to not drip, to become viscous when you apply it to the wall.

00:47:26
Speaker 1: But isn't that because it's drying out.

00:47:28
Speaker 2: So the crucial thing is that you're applying paint to a vertical wall, right, and so the fluid starts to drip down the surface, but because of its non Newtonian nature, this acceleration then increases the velocity, so instead of slipping along the surface, it forms sort of large and dense droplets with limited dripping, So it forms like a little bit of texture, but the drops never actually form.

00:47:50
Speaker 1: Well what does that mean when I try to stir it?

00:47:52
Speaker 2: Though it's not as dramatic as Ubleck, but it's in the same direction as Ubleck that as you go faster, it rapidly becomes more viscous, which is what you want. So as drips are starting to form on the wall, it becomes more viscous in order to essentially prevent those drops from forming.

00:48:08
Speaker 1: And also I imagine it's also drying out right and solidifying a little bit too.

00:48:13
Speaker 2: Yeah, but you want to avoid drips forming while it's still liquid, because if you form drips then those dry it looks pretty ugly.

00:48:19
Speaker 1: Well, is there a sort of a quick explanation we can give us to why some things are non Newtunin or not, like why some things are not linear and some things are.

00:48:29
Speaker 2: We don't have a good overall understanding of it. It seems like the general direction of the explanation is that it comes from complex interactions between heterogeneous materials. So if you have something which is only made of one kind of thing, it's going to tend to have a pretty simple relationship between the velocity and the friction. If you don't. If you have complicated mixtures the way we do with oobleck water and cornstarch, then you sometimes get different relative densities of those two things. You can get a much wider range of behavior, and that behavior can emerge under different conditions. And so probably that's why like paint is non Newtonian whereas water isn't, because it has to do with like having droplets of these dyes in suspension and ketchup is a complicated combination of water and all sorts of other things. So how those molecules interact with each other, and whether you're having more of one kind of thing or another, it's probably the source of it. But the real takeaway I think is like, Wow, the world is complicated that these fairly basic interactions we understand about how molecules and particles interact with each other, but they can create all sorts of incredibly complicated behavior when you zoom.

00:49:33
Speaker 1: Out, Yeah, I know, it's amazing. I think you're saying, like it maybe has something to do with how complicated the liquid is inside, right, Like, if it's just one thing, like water molecules, only water molecules, then they sort of behave kind of predictively. But if you have more than water, if you have water and corn storage molecules, then maybe because they're so different, the faster you try to move through it, then they sort of gets into these different regimes. Maybe, like it it gets into things where're like, oh, now the cornstarch is dominant because all the water came out or things like that, and so the whole property how it behaves when you try to stir it is different depending on how fast you're trying to steer it.

00:50:09
Speaker 2: Yeah, exactly. So it can do many more different kind of complicated things because it's got two components to it, and sometimes you're seeing more of one and sometimes more of the other.

00:50:17
Speaker 1: Hmmm, all right, well that's great because I feel like, you know, sometimes people say, oh, they use the word non intonin fluid as an explanation like oh, why does oubleake do that or why does kets do that? And then people would say, oh, it's because it's a non intone in fluid as if that was the explanation.

00:50:32
Speaker 2: Right, Yeah, a label is not an explanation. It's just a name. You could give it any name, or you could call it a yaka block of fluid. It's not an explanation.

00:50:40
Speaker 1: Yeah, which is also the name of a great bagel, now it is. But maybe the point is that, you know, if you see this phenomenon, the phenomena is called the non Newtonian but it has maybe more to do with what's going on at the molecular level.

00:50:54
Speaker 2: Yeah, in the same way we think probably everything in the world comes out of these molecular interactions in different ways. But you know, it's amazing. It's not all just chaos. It's not just a crazy swarm of frothing nonsense. You get these weird behaviors that we can summarize and understand, and this like linear relationship between these two quantities. It's sort of amazing that that happens at all. So I'm just grateful that the universe is at all understandable at our level.

00:51:19
Speaker 1: Yeah, you can make lost and maybe predict things and then design things also, Right, it's really important for engineering to know how these things are going to.

00:51:27
Speaker 2: Behave, Yeah, absolutely, Thank you to all the engineers.

00:51:31
Speaker 1: Yeah, although sometimes you come up with a law and then people find exceptions and then they call those not laws.

00:51:37
Speaker 2: But your name is still on it, so you still win.

00:51:42
Speaker 1: I'm not sure I subscribe to the idea that all fame is good fame. I think there are plenty of examples in tabloids about that. But still, it's nice to be part of the mix.

00:51:52
Speaker 2: As you say, Hey, everybody remembers Benedict Arnold, right, not fondly, though not fondly, but they remember.

00:51:58
Speaker 1: It all right, set the future physicists, super villain.

00:52:03
Speaker 2: That's right. I'm gonna close out my movie with the line better to be hated than.

00:52:07
Speaker 1: Forgotten, And then people will forget your movie because they didn't like it because it has such a terrible message.

00:52:16
Speaker 2: Dude.

00:52:17
Speaker 1: All right, Well, as you said, it's interesting to think about the physics of everyday objects like cornstarch and ketchup and slime and even paint.

00:52:25
Speaker 2: And swimming pools filled with honey.

00:52:27
Speaker 1: Thanks for joining us, See you next time.

00:52:37
Speaker 2: Thanks for listening, and remember that. Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple podcasts, or wherever you listen to your favorite shows.