Where is the coldest place in the Universe?

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Speaker 1: Hey, Daniel, what's your least favorite topic in physics? Oh, man, don't make me say something negative about physics. Well, now I really want to know. Fine, Fine, it's thermodynamics. You don't like thermodynamics. But it's such a hot field, Daniel, or cold, depending on the state. It's just too hard to get my mind around. There's so many particles involved, you know, So you don't know much about thermodynamics, then I wouldn't say I know that much. Really, like you know zero about it? You're getting close. What if we talk about absolute zero? That's a reasonable approximation of how much I like thermodynamics. I am or handmade cartoonists and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist, and I'm not a lover of thermodynamics. Now, welcome to our podcast, Daniel and Jorge Explain the Universe, a production of I Heart Radio in which we find all the amazing and crazy things about the universe, the extreme things, the fast things, the hot things, the cold things, and we explain them all to you. That's right. We explore all of the hot topics in physics and science out there in the universe, but also the coldest thing sometimes, that's right. We try to touch on the hot topics and we try to be cool at the same time. We are. We are pretty cool for a physics podcast. We're definitely cool. Yeah, all all three of them were probably the coolest, but yeah. This is part of a series of podcast episodes about the extremes of the universe. Should we cue the heavy metal sounds, Danny Wild Stallions, where we're gonna get Bill and Ted on the podcast, Oh we should build or Ted just before their reunion tour. We like talking about the crazy bits of the universe because where the extremes are sort of where you learn the most about the universe. How hot can things get? What is the densest thing, what is the strongest magnetic field? And that's why we explored all those topics in previous episodes. Yeah, it really makes you kind of push or stretch the boundaries of your mind, you know, to think of the hottest things, the dancest things, the brightest things. Those are all things we've covered in other episodes, and today we'll be talking about another one of those extremes in the universe. So today on the podcast, we'll be talking about what is the coldest place in the universe. Instead of heavy metal guitar, we should just have a cold wind or something. No, we should have the theme music from Frozen, of course, come on, just let it go, Just let it go. No. I love the extremes of the universe because they remind us that where we live is not usual. And this is this big lesson in physics that you can't just look the stuff around you and then try to generalize to the whole universe. You can't assume that everything around you is typical, that things on other planets and other parts of the universe follow the same rules. We've often made that mistake in physics and then learned that the universe works in totally different ways. And we learned that when we look far and wide, we explore the extremes, we look for the hottest, the fastest, the brightest, the weirdest stuff. That's where lessons lie, that's where we find new physics. And so today we'll be talking about what is the coldest place in the universe, And um, I hear it that it's probably not what most people expect. I hear it's not Nancy Pelosi's cold Stare that was pretty chilling though, But yeah, this is a topic in statistical and thermodynamics, and I to admit this is not my number one favorite field of physics. Not because I don't think it's awesome. It is really awesome, and the kind of things that people have developed are really pretty cool, but it's it can be sort of frustrating to think about, and I particularly find it um sort of intimidating as a topic to talk about coldness or or just temperature and thermodynamics in general. Well, just thinking about like systems of particles. I mean, let me reaf you. And as an example, the opening paragraph of the Statistical Mechanics book from grad school. Oh please, no, I know it doesn't sound riveting, but whole lover a moment, all right, all right. Ludwind Boltzmann, who spent much of his life studying statistical mechanics, died in nineteen o six by his own hand. Paul Aaronfest, carrying on his work, died similarly in three Now it is our turn to study statistical mechanics. That's that's the scene right there. You know, the legends of the field killed themselves thinking about this, So now let's study it. Do you think because it was just such an intense topic or that, um, it's a dangerous thing to study. I don't think. I don't think the topic itself is dangerous. Something you're like summoning demons from below that infest your mind or anything. But it is hard. It's tricky stuff. You have to understand. You know, how gases move and how they flow in terms of these tiny, little microscopic particles, and so there's a lot of complicated statistics and difficult mathematics. It's amazing what they have achieved. And one of the greatest accomplishments, of course, is understanding like our experience of temperature. You know, you touch something it feels hot, you touch something feels cold, understand that in terms of what that means for the microscopic particles. That connection kind of makes you uncomfortable. Yeah, well it's it's not makes me uncomfortable. It's just sort of difficult sometimes to think about what it means mathematically. But it's also awesome because it lets you understand how things around you arise from the most you know, those microscopic particles. We'll dig into into that in a moment, but you know, this, this fascinating extension is like how cold can things get? How much can you push that? You know, if coldness really is about the motion of the particles inside something slowing down, then like can you push it as far as you can go? And how far exactly can the universe take you on the temperature scale. Yeah, So part of what we'll be talking about today is this concept of absolute zero, as in that is theoretically possibly the coldest that you could possibly ever get in the universe. And so the question is there such a place out there in the universe? Can there be such a place out there in the universe? That's the question we'll be tackling today. And so I was wondering if people had heard about this phrase. It seems sort of common and awesome. You know, it's got a nice zing too. It's got pizzazz right as most physics terms don't. And just to be clear, this is not an endorsement for a vodka drink. It also not not an endorsement for vodka, though we're not anti vodka on this show. Are you saying are you saying call us? Are you saying to absolute callus? Well, we'll totally take a case of your vodka. We're saying absolute zero about vodka. Right, we're not saying anything positive. We're not saying anything negative about vodka. But maybe the podcast would be funnier if sample there is that drunk history show, which is pretty funny. I don't think there's a drunk physics show yet, So yeah, put that on the list of projects. We should start a new series of episodes physics. Daniel and Jorge slur their way through the universe. But which one would be drunk? Do you or me? The audience should be drunk so they can understand us, or so they can like our jokes. Daniel and Jorge drinking game. Every time Daniel says that's right, or every time Jorge says bananas, somebody takes a shot. I can see this being all the rage in college Fra Trinity houses. Speaking of colleges, I walked around campus that you see Irvine, and I asked people what they knew about absolute zero and if they thought it was just sort of a crazy theoretical idea or something we could possibly achieve. So, as usual, Daniel went around and asked the question what is absolute zero? So before you hear the answers, think about it for a second. If someone approached you out of the blue and ask you what absolute zero is, what would you answer. Here's what people had to say, absolute zero. It's something that I can't recalltop my head. I've heard it before. Temperature zero kelvin. Is it possible for anything to actually get to absolute zero? I don't think so. I believe that's like a measure of temperature. I think if we were measuring in kelvin, that's like the lowest anything could ever go. Can something actually get to absolute zero? Uh? Theoretically yes, but physically we haven't gone there yet. Of some understanding, I actually don't know, but it sounds somewhat familiar. Absolute zero is zero kelvin. It's the coldest possible temperatures, eat, death of the universe, or however you want to say it. So is it possible for something to physically achieved zero? Uh? So. I believe it is extremely difficult to get to absolute zero properly, but people have achieved some number of desmal places very very close to this. But I think that some of the matter based effects can be realized at maybe higher temperatures and capsolute zero, like the helium three and things like that. Superfluidity, Yes, superfluid. It's the coldest possible temperature when everything stops moving and we've never gotten there. So is it physically possible to get something absolute zero? Uh? I don't know. I'm the wrong person as zero on the Kelvin scale just no movement, no energy. Is that physically achieved? Just theoretical? I believe theoretic here, So it's impossible to get to epsoide zero. I don't think so. All right, some pretty good answers. I thought, no mentions of vodka. Yeah, I guess vodka is pretty expensive for college students. Well, you see, Irvine does have the reputation of being sort of the nerdy you see campus, like, that's where you go if you want to really be serious about your studies. I think, Santa Barbara, you might to get different answers. All right, so you're saying, um, that you're not surprised then that people a lot of people knew what absolute zero was, and some people evedn't talked about the heat death of the universe and how it's sort of theoretical as well. Yeah, these were some seriously good answers, and I think there's a lot of interest there so I think, um, let's dig into it and talk to people about what absolute zero is and how cold we can actually get and if we can find it somewhere in the universe. I think the answer is might be pretty surprising. I guess maybe let's just start with what is coldness? Like, what does it mean for something to be cold at all? Yeah, it's sort of fascinating. Um, whether like coldness or heat is a thing? Right, Like, if heat is a thing, then coldness is sort of like the sense of that thing. But if you were sort of like an early person thinking about thermodynamics, it could have been that like coldness was a thing and heat was the opposite of it. But it turns out that like heat is a thing, heat is the motion of particles. We were talking earlier about this connection between your experience of temperature and that what's happening for the microscopic particles, and that's really what it is. Temperature is a measurement of sort of the speed of how fast these particles are moving or shaking. That sounds like a really deep question, like is heat the absence of coldness or is coldness the absence of heat? Yeah? What is the sound of one thermometer measuring. Yeah, it's a it's a fascinating question. But it turns out that heat is the thing, right. Heat is the motion of particles and coldness is the absence of that motion, and so there's all sorts of fascinating consequences of that. And we really got into this when we talked about um we had an episode about temperature about and I got really confused about how you know, you were saying temperature is actually not like it's a thing, but it's sort of an average thing. Like you can't measure the temperature of a single particle. That's really weird to me. Yeah, in our episode about what is the hottest thing in the universe, we got into that because there's a lot of weird stuff that's like really hot things that are three d million degrees, but if you went inside them you would freeze to death because they're really dilute um. So the concept of temperature is very confusing, especially as you get two very high energies. And you're right, temperature is not the property of a single particle to property of a system of particles. That has to do with the essentially the average motion. And I got really hung up on like um. So you can't take the temperature of a single particle. Can you take the temperature of two particles? You can't take the temperature of a single particle. In theory, you can only take the temperature of an infinite number of particles. But in practice a large number of particles approximated infinite number pretty quickly, So to definitely not a billion, probably a million, almost certainly a thousand, maybe circumstances. It's one of these fuzzy things, you know, like when does the practical match the theoretical. It's like saying, like, what's the death of an ocean? You know, you can't apply that to a single water molecule. You have to apply to a huge number of water particles. It's a concept that only exists for a system of particles, bunch of things, Yeah, not for an individual. Yeah. And so for coldness, it's the it's not the emotion of the stuff, it's the lack of motion. So I guess maybe coldness is not a thing. Then you're saying heat. Heat is a thing because you can measure it, but coldness is just like if the thing is not there, there's no motion of the particles. Yeah, coldness is to heat, what like silence is to noise. Right, is silence a thing or it's the lack of noise In the same way, coldness is the lack of heat. You know, heat is the motion of these particles. They can move, they can spin, they can vibrate. All that stores energy, right, and that energy is the heat of the system. And as that energy leaves that the object gets colder and colder, those little particles move less and less. I feel like we're asking some really deep questions, Daniel. Well, this is what I love about physics, you know. It touches on really simple, basic d questions. And this is why we're always bumping into sort of philosophy questions because physics is important. And so if you think about you know, this is like the motion of particles. You can imagine the particles like moving more and more and more and getting hotter and hotter and hotter, and that's sort of continuing off to infinity. Right, there's no limit to how much these particles can shake or wiggle or whatever. But the other direction, as things get colder and colder, things move less and less. It's fascinating if there is sort of a negative limit there that you approach like zero motion like silence, right, Like you can have zero silence, but you can't have negative silence. Yeah, you can't have negative silence or like super silence. You know, you can't have like extra extra silence a silence. You can't have negative noise. I guess, yeah, yeah, And that's what it is for amperature, right, it's um. Once you had zero, you can't get any colder. It's that's what it's called absolute zero. Yeah. Absolute zero is the idea that maybe you have a bunch of particles together and then they just stopped moving, that they formed like a perfect crystal. There's no entry be left at all. There's only one way to arrange the system. There's no motion, there's no rotation, there's no vibration. So that's the idea of it, right, that every particle in your system is not moving at all. Zero right now, kinetic energy, if you could achieve that, then that would be absolute zero. And it's it's really a fascinating topic if you look in the history of this concept, like people start first started thinking like huh, could this be possible? Even before people try to make things super duper cold, to try to achieve it. They started to think about is it theoretically possible? And one thing they noticed was they were like, let's look at how things change as a function temperature. And you know, different substances like have different melting boiling points, and that depends on the substance. Water melts or boils at different temperatures than you know, oil or other substances. Right, Like, let's just play around with sticking things in the freezer and see what happens. Yeah, but all of these things all point towards the same zero point, right, water or hydrogen or oil or whatever, they all have the same same absolute zero. This concept of an absolute zero is universal. Would be the same temperature for every substance at zero. Like it's you're saying, it's just when everything, no matter what substance you are or what you're made out of, you at some point might or could reach zero. Precisely, it doesn't vary depending on what you are, Like when you're freezing or boiling. It's like it's it's there for everybody, including you and me and everyone listening. Because those other transitions like melting and boiling, those have to do with like how the molecules are sticking together or not sticking together, whatever. So they're really dependent on the structure in the shape of those molecules. That's why water and other materials boil at different temperatures. But when it comes to not moving at all, it doesn't really matter what shape you are or what size you are, and you're just doing nothing, and everybody does nothing in the same way. Right, what about absolute vodka? Would that also have an absolute zero? Absolutely? Absolutely? All right? So that's that's coldness, and that's absolute zero. It's this theoretical limit of when everything is no longer moving. And so let's get into have we reached absolute zero and we if we can even get there, or if there are places in the universe that are that have absolute zero temperature. But first let's take a quick break, all right, Daniel, how cold are physicists or how cold have physicists gone? We're a pretty cool group of dudes. Um. But there's this, really there's a really fun sort of history, a race to the bottom or everybody was wondering like how cold can you get something? And people were developing technology try to make stuff colder and colder, and it's not that easy, right, You want to make something really cold, you need something else really cold. And so to make something colder than anything you've ever seen before, take some cleverness, right, because you're trying to take away To make something colder, you have to take away energy, right, And to take away energy you have to kind of like grab it, right. You need something that is colder to take it away from the thing you're trying to cool down. So it's a it's a tough problem, I guess. Yeah, if you want to freeze your ice cream, you put it in the freezer, and the freezer the stuff around the ice cream and the freezer is colder, so the heat leaks out of that ice cream um into this stuff in the freezer warms up the air and the freezer a little bit. It doesn't come back. And I think it's the key. Like if you leave ice cream out in outside of the freezer, there's you know, there's energy going into it and out of it, into it and out of it, but mostly going into it. But in the freezer, it just leaves the ice cream and it doesn't come back, Yeah, because the freezer is actively cooling it down. But you can also do it in a cooler, right, say, just pack ice cream surrounded by really cold stuff and a cooler so it's all sealed off. Then if the stuff around the ice cream is colder, then they'll tend to equilibrate. The heat will flow out of the ice cream and into the colder stuff. So classic way to make something colder is to put it next to something that's even colder than it. Right, But if you're trying to make the coldest thing ever, you can't do that because you would need something even colder. And so the race to reach the coldest temperature started a long time ago. It seems you wrote here that it started in the eighteen hundreds. Yeah, people were trying to make stuff really cold. Back in eight It was Michael Faraday. He's a famous guy in physics, and he achieved a temperature of negative a hundred and thirty degrees celsius. That's a hundred and forty three degrees calvin. That's really cold. It's pretty impressive for the eight hundreds, isn't it. I mean they didn't even have telephones. They couldn't call each other and brag about how I got some ice cream on guys coming over. Nope, you have to send a letter. Yeah, the first thing they tried to do is to take gases from the air, hydrogen or oxygen and stuff like this, and to liquefy it to make it, you know, liquefied or even solid. He was the first one to do that, to liquify any gas. And then thirty years later some French guys whose names I can't pronounce because I can't read French very well, they liquefied air. They got it down to negative a hundred and ninety five degrees celsius. That's just seventy eight degrees kelvin, right, and for those of us who are in fahrenheit, that means um also a negative large number exactly. And you might wonder, like, how are these guys doing this, how are they making this cold? Well, the the basic trick they were doing is they're lowering the pressure, because these gases are complicated things, and if you lower the pressure of a gas, it ends up cooling down. If you keep like the amount of gas constant and use and you somehow stretch it or lower the pressure, then it automatically gets colder. Right, yeah, precisely. And that's the kind of stuff that always melted my brain, you know, like you have the same amount of frozer brain and gave your brain freeze or melted your brain, both at the same time. And that's why. But then we have a series of guys making advancements. In eighty three, somebody liquefied oxygen down to fifty five degrees kelvin and then in door liquefied hydrogen, and of course he's famous for inventing the doer, right, which is this like cold flask. You've probably seen a lot of laboratories that's down to twenty one degrees kelvin. So they're little by little, sort of one up in each other, you know, getting colder and colder because they use different gases or did they just have better techniques. They just sort of expanded on this technique of figuring out ways to suck heat out by expanding the volume and then pulling out the coldest parts, and then expanding that and then pulling out the coldest parts. So it's all about this sort of experimental chemistry cleverness. And this is way before you know, any sort of advanced technologies, right. So these guys were just kind of like you know, experimenting with um like flasks and boilers and things like that, right, pretty basic, you know chemistry setups. Yeah, they had you know, glass tubes and rubber valves and this kind of stuff, and they had no complicated technology at all. Um And then it was in nineteen o eight they finally liquefied helium that brought them down to four degrees kelvin and then even further down to one and a half degrees calvin. And this guy who did it, he won the Nobel Prize for that. It was like such an achievement to get such cold temperatures. That was like the forefront of exploration because he went from like twenty calvin to one kelvin. Yeah, that's a huge jump. Yeah, that's a pretty big change fractutionally, and it gets you pretty close to absolute zero. Did they have a sense that there was an absolute zero? You know? Do you know what I mean? Like, did they know that at some point you would hit rock bottom? Yeah? They had this idea because they were studying sort of the temperature as a function of pressure and volume and all this stuff, and you know, these temperature curves all point in the same direction, and no matter what gas you're talking about, helium, hydrogen, oxygen, all those lines were sort of converging at the same point at absolute zero. So they had the idea that this existed, and they were sort of pushing to see how close they could get. But they were all wondering, like, is it possible to actually achieve something at absolute zero's just sort of a theoretical concept, or can it actually exist in and how is it you could have this like theoretical concept that you could never actually achieve in practice. That's sort of weird, right, if you can or cannot achieve it, right, it's sort of it's a big unknown, Yeah, but it would it would be weird to have this theoretical a concept that's a just a straightforward extrapolation of things we observe, but then have it be sort of unachievable. If that's the case, it tells you something pretty deep about the universe. And so people kept going, right, people, and nowadays, what's like, what's the record lowest temperature we can get to? Yeah, so people work really hard on this now and the current record is much better than like the Nobel Prize winning record at one point five degrees kelvin. Right now we're at a hundred pico Kelvin's Pico Kelvin's that's like one with nine zeros in front of it or behind it. Yeah. Yeah, it's a zero point zero zor zero zero or zero zero zero zero one kelvin. Wow. So we've been able to cool something down that cold. Yeah, well, I mean not me and not you. Some people out there working really hard and it's the collective we a is in the part of humanity that I'm proud to call myself a part of. Yeah. So that's the current record, and you know, the is fascinating theoretically, but it's also it's hard to do. You know, it's it's hard to accomplish this. As we were saying before, Like you get something super duper cold, you need clever tricks. Do they use something kind of special trick there? Yeah, they do this thing which is really fascinating. It sounds um counterintuitive. They use laser cooling like a cold ray. No, No, it's a hot ray, just like normal, right, it's not like a cold laser. That would be awesome. And in the comic book version of US, I definitely want eyeballs that shoot out cold lasers that can freeze things. There's a Batman villain called Mr. Freeze. Yeah, precisely. But okay, but this is not This isn't like a regular you know, zapping laser, and somehow that cools things. And the way it makes things cold is not by touching them and taking away their heat. It's by selecting the hot stuff and pushing it out of the way. So imagine you have a big blob of gas. Not every atom in that blob of gas is moving at the same speed. That's a distribution. Some are moving after some removing colder. If you could just select the cold ones, then the average temperature would go down. Oh, I see, but you can actually aim this laser or how does that work? Or like the lasers some somehow only picks out the fast moving atoms. Yeah, it's pretty complicated, but essentially the idea is to get the fast moving atoms in the path of the laser and so they didn't knocks them out of the way. And you use a laser because it's you can't just like go in there and flick out individual atoms with a mechanical object. The laser is the best way to interact with an individual atom. You can just like blow on it. They tried that six years later that guy still hadn't graduated. No Nobel prize for no PhD even No. So that's the idea instead of trying to cool down the whole sample, right, which is what you do when you put your ice cream in the freezer, instead they just pick out the cold bits. It's like if I gave you a bowl of ice cream and you're like, hey, it's kind of melted, and I just sort of scooped out the hot bits and left you with the colder bits of ice cream. You know, that's not really cooling down your ice cream, but the temperature of the ice cream you're left with is colder. And so that's the current record right now, is that the cold is that humans have been able to cool something down is a hundred pico kelvin. Yeah, and that's colder than outer space. You know, the average temperature out there in space is like two point seven three degrees kelvin, which sounds kind of hot in comparison. Yeah a minute ago that sounded chili, right, but compared to a hundred peeko kelvin's it's like bust out your swimsuit. Um. And that's the temperature average temperature out there in space there's some spots out there in space where lots of gases have been like blowing out of a star, and that expansion cools it down to maybe one degree kelvin. But the coldest natural thing, we think is one degree kelvin and the current record is a hundred peco kelvins. But humans are not finished. You think we can go further colder than Yeah, there's a there's an instrument right now on the International Space Station. That's where they're doing this experiment. And it's like you've got to be surrounded by m D space just to even have a chance to do this. And it's called the Cold Atom Lab, and their goals to get down to one pico calvin down from a hundred which is the current record. Maybe helped me paint a picture here what's going on at that temperature like or the atoms? Not very much? All right, that's that's about. It's like the conversation at your average physics party, you know, just like nobody's talking, everybody just sitting there, everyone's just thinking about absolute zero. Now, there is some wiggling. If you were to zoom down microscopically and look at these things, there would be some energy. There's some motion of these particles, like like each atom is maybe not moving across the room, but they are sort of wiggling and vibrating. And these are all crystals, right, so you imagine they have bonds with each other. They're not totally separate atoms. Imagine like a lattice and you have these atoms with these bonds holding them in place, and then occasionally you get like a little wiggle, a little bit of sound goes through the material. Hey, that's a cool connection actually between temperature and sound. Right. Sound probably does have a temperature because it's the wiggling and motion of these of the material. I never thought about that. Man, I'm gonna need another shot just to consider that question, Daniel. When you get down to those temperatures, things form into a crystal, because what else are they going to do. Can you take a gas down to that cold of a temperature or does it have to form into a solid by that? I think it has to form into a solid idea. And I'm not a chemist, So maybe somebody out there who knows more chemistry than I do knows whether or not you could keep something a gas and still make it really cold. I think it would have to be super duper dilute, right, But essentially, you know, these molecules have no vibrational energy, no rotational energy anymore, and no translational energy. They're not moving, so they're just all sitting in place. Whether or not it's a crystal or a gas, I guess just depends on how tightly you're packing them. But effectively this becomes how you define a gas or a solid, right, yeah, and probably an absolute zero. You know, it's one of those places where the phases are not well to find, you know, how the chemistry they have these like triple points where something is like, what is it exactly if you're right at the triple point? Absolute zero is probably like that. But you know, the fascinating question is like how close absolute zero could you experimentally get, Like is it possible to make a material with exactly zero motion? All right, well, let's get into that, whether it's even possible to reach absolute zero. And I think for me, the more the interesting question is if there are places in the universe that are absolute zero. So let's get into that. But first let's take another break. All right, Daniel, can we get there? Can we get to absolute zero? Without drinking absolute vodka. I think it is. They're totally not sponsored by liquor company um. But yeah, can we get too absolutely Is it even possible or like many of the people you interviewed on the street, isn't only theoretical that you can get to absolute zero? I think unfortunately, there is no amount of you can drink to get us down to absolute zero. I think theoretically it's impossible. It's impossible. Yeah, it's just not possible. I think in the sort of the classical theory that the folks who were first coming up with thermodynamics thought about, you know, they're thinking about particles is a lot of tiny little balls, and so you can talk about their motion and their location in that context. It is possible. But we know better now. We know that when you get down to tiny particles, there are different rules that apply. These particles don't have classical paths, they don't move in a way that makes sense to us. Their quantum mechanical Maybe even the idea of energy at that point gets fuzzy, right, like the idea of kinetic energy, whether there's something's moving or not. At the quantum level, it's sort of like undefined, right, yeah, well, we'll dig into that in a whole separate episode of energy. I gotta say, if several folks, like maybe dozens of folks have written in asking us to do a podcast episode about energy and what does it mean? And how do you transfer one form to the other and quantum mechanically doesn't make any sense. So we'll dig into that a whole separate episode when we get the energy to do it will after we're done drinking that bottle of vodka. But the problem is that as you get really really cold, you come down to this zero point energy. Right. Quantum mechanics says that there are fluctuations everywhere, even in empty space. There's a small amount of energy, and that energy is constantly fluctuating. You have these quantum fields that are going up and down, so you have particles being created, and so it's impossible to get down to zero energy because there's always some energy even in empty space. But is it fluctuations or is it just uncertainty? Do you know? Do you know what I mean? Like it's or like randomness or is there even a difference? Well, there's both. There's you know, we think that the mean energy of empty space is not zero, that there is energy stored in empty space, and so you just can get rid of this is just a property of space itself to have energy. Not even nothingness is absolute zero, yeah, because there is no such thing as nothingness. You can't have space without nothing. That's the property of space is that it has quantum fields. And these quantum fields that we talked about the Higgs Boson episode don't settle at zero. They settle it's some energy above zero. Space is something, space is something. So there so there's no nothingness. Actually yeah, well, and that's a whole other concept. You know, how do you get something from nothing? And what is nothingness? Or maybe maybe it's fair to say space without anything in it still has energy. Space can't have nothing because it always have quantum fields which have energy. Yeah, there's no nothing, Yeah, there's no nothing. That's the zero point energy concept. That's like you can't get down to zero energy. But even if somehow the universe, you know, even if we like destroy the Higgs field and we got down to a state or vacuum energy of zero, and we talked about that in a separate episode, um, even still there would be quantum mechanical problems because imagine what you do there. You're taking a particle and you're setting its location, right, has no motion, so you have to know its location, and that means you also know it's momentum. But the Heisenberg uncertainty principle says you have a minimum uncertainty in the location and the motion. But when now we're talking about a state where we know exactly the location and the motion, and so that seems like it would violate the uncertainty principle. Well, maybe that just means that there's no like, the absolute coldness of the universe is not zero point zero zero zero zero zero, But could there still be like a minimum temperature of the universe, like a point oh you know one pico pico, pico Keilen or something like that. Oh, that's fascinating. You're saying the minimum might not be zero, but there could be a zero or could you or pretty much zero? I want to hear that announcement scientists announce the achievement of pretty much zero. We did it, We got pretty much nothing. No, that's a really interesting question. Can you ask them topically a pro absolutely zero getting closer and closer forever, or is there a minimum non zero temperature. I think because of the zero point energy of space, there must be a minimum temperature. But if you somehow collapsed the Higgs field and got rid of that minimum energy, then I think you could ask some topically approach zero forever. You're saying, unless the universe destroys itself, there is a limit. And I'm not encouraging anybody to destroy the universe just to win that Nobel prize, just to ask for Horace question, We're going to destroy the universe. That is physicists being drunk with power. Okay, So then, uh so there might be sort of a minimum and you're saying, it's really difficult to get there because space itself doesn't get to zero. So that does that mean that nowhere in the universe do we get that cold or like there's nowhere in the universe that's actually zero. That's right. We think that there is nowhere in the universe it's actually zero, and absent physics labs here on Earth and on the space station, we think the coldest thing in the universe is a out just one kelvin out there in you know, the heart of a frozen planet in the middle of nowhere. It's still about one kelvin. Yeah, most of the stuff out there is about two point seven degrees kelvin. If you really work hard, you might be able to find something at one degree kelvin. But here on Earth we have stuff that's like a hundred Pego Calvin's going down to one Pico Calvin. We hope. Wow. So the coldest place in the entire universe might be here on Earth in somebody's lab, depending of course, on whether there are aliens. So basically we're in a race with alien physicists to get the coldest place on Earth to see who has the who's the coolest species in the universe. You knew I was going to have to bring it back to aliens. Eventually. Every topic has to touch on aliens, right, Yeah, there could be aliens out there who have a lab because they would have to do this on purpose, right, they have a lab that maybe goes down to even colder than us at a hundred people Calevin. Yeah, there could be alien civilizations out there that have been doing physics for a billion years, and you know, to them, like a hundred Pekokelevins is laughable, man, That's like a kindergarten science fair project. For them. Really, they could be way way down further in the cold spectrum. Wow, But we won't know until those aliens come and visit. All right, But as far as we know, barring super advance cool aliens, the coldest place in the universe is here, probably in in the United States, or in the lab in Europe or something. Right, Yeah, and very soon the coldest place in the universe, we think, will be on the International Space Station at the Cold Atom Lab. All right, Well, I think we answered the question pretty well. Where is the coldest place in the universe and whether we could maybe get even colder might not be possible unless we destroy the universe, it seems. But absolute zero is a fascinating topic theoretically, and it's a fascinating goal. We keep pushing more and more, and as we do so, we learn more and more about cooling technology and how to achieve that, and and how things operate into very extremes of the universe, which is where we hope to reveal some new secrets about how the universe works. So the next time you have a scoop of ice cream, think think about how how cold it is and how cold you could get it if you went to your local physics lab and recruited some physicist to give you a better ice cream. Thanks for tuning in for this tasty topic. See you next time. Before you still have a question after listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us on Facebook, Twitter, and Instagram at Daniel and Jorge That's one Word, or email us at Feedback at Daniel and Jorge dot com. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of I Heart Radio from more podcast from my Heart Radio. 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