What Is the Hottest Thing In The Universe?

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Speaker 1: Hey, Daniel, do you know the concept of absolute zero? I don't mean the vodka. I mean, like, you know, the concept that there is the coldest possible temperature in the universe. Yeah, And I think that's super awesome. I love when there's something in physics that has an extreme to it, like beyond this point is impossible to go extreme physics. I feel like we should have a heavy metal guitar sound there. Yeah. This podcast brought to you by Mountain dew Rush, the physics dude. But you know, I was asking because I was thinking about what is the opposite of absolute zero temperature? Like is there a maximum temperature in the universe the hottest thing ever or possible? Well, if there's the hottest thing ever, it's probably somewhere here in southern California. But it's a fascinating concept, Like is there a point where after you pump in more energy, it just doesn't get any hotter. It's it's an incredible idea. It's too hot to handle, or two for the universe to be handled, that's right, Yeah, or maybe, uh, you know, after you pumping too much energy, like it just blows up or it crosses a singularity or restarts the universe and makes a glitch in the matrix or something. Well, at some point when you hit some sort of um, you know lights, be kind of maximum limit to the in universe. Yeah, I think the physics police would pull you over and be like, what are you doing? Explained to us how this makes any sense? Um, your your way too, You got it. You gotta cool it down a little bit, leave a little room for the rest of us to be attractive. That's right. Yeah, too much sizzle exactly. Hi, I'm for Hey. I'm a cartoonists and the creator of PhD comics. I'm Daniel. I'm a particle physicist, a part time podcast host, and I've never created an online comic. But I did once write a book about all the things we don't know in the universe together with Jorge, and it's filled with his hilarious comics. It's called We Have No Idea. So you only podcast part time, Daniel, that's right, only ninety hours a week. That's a part time schedule. I have this podcast, I'm going to have eighty nine other podcasts I also do. I thought you were gonna say that's how much editing this podcast needs to get it down to about how much research is required to boil down all these incredible insights into just one hour of time. Well, welcome to our podcast Daniel and Jorge Explain the Universe, a production of I Heart Radio. That's right, and into our podcast. We try to take some topic of general interest, a question people ask every that's something that everybody wants to know about the universe, and break it down in a way that actually makes sense to you and along the way maybe get you to laugh. Yeah, so to be on the podcast, we're doing part two in our unofficial informal series of Universal Extremes. That's right. We thought it'd be fun to take you out of your situation, to pull you out of your ordinary, everyday life, or maybe you have a very exciting life and think about the biggest, fastest, nastiest, hottest, wettest, craziest things in the universe. Sorry, there's probably some skateboarders out there, or some X Game athletes. They are like, you know, my life is pretty extreme already. Man. They have no idea there's somebody out there in the universe surfing on black holes and riding the shock waves of supernova is doing crazy tricks that nobody could have ever imagine. Yeah, so a few weeks ago we did what is the biggest thing in the universe? Then today we are tackling the subject of what is the hottest thing in the universe? Answer you, You are the hottest thing in the universe. Ye, that's right. No, no, no, no, no, not me the person listening to this. Right, that's right, you, our listener, you are the hottest thing. You look great today. Uh yeah, I don't need any flattery, but you know, it would be nice to um pride the audience a little bit, that's right. Not that we're spying on you, not that we're stalking you on social media, but have you been losing weight? You look great? Yeah, totally super hot. But you know, the universe is filled with all sorts of crazy stuff. Here on Earth we have some temperature variations, but you know, even inside our Earth, the temperatures get crazy hot, crazy high numbers that are sort of hard to understand. And so we thought it'd be fun to take a tour of the universe and to think about all the hot places, like where in the universe does it get hot? Where in the universe is the craziest, hottest nastiest furnace that you can imagine. That's right. And it's pretty cool to think. I think about these extreme examples because it really kind of pushes your mind, right, it sort of expands your understanding and your awareness of how crazy thinks and get yeah, and I think you'll be pretty surprised by the answer. I don't think that what physicists think is a hot place in the universe is the kind of thing that anybody would imagine. I was kind of surprised when I doing some reading about this. Oh wow, really, so the hottest thing in the years is maybe the most unexpected it's unexpectedly hot. Yeah, that's right. And when I was thinking about this topic, I was thinking about how often in physics we have a term that we use to describe something, which is also a term in English. You know, like temperature is definitely something we're aware of, right, you know what hot and cold means. You touch things they burn you or they or they freeze you or something. But sometimes in physics we create technical definitions for things like temperature because we want to understand it right. We want to describe it, like where does temperature come from, how does it work? What makes something hot? What makes something cold? But then this thing happens where the technical definition we use in the scientific community deviates a little bit from like the familiar term that people use in their everyday life, and sometimes they can even come into conflict. Is this one of these terms where physicists, Um, so who what? Who came first? Really? The popular conception probably came first, right, Yeah, The concept of temperature is age old, right. People have been talking about people have been dropping hot coals in their toes and screaming curse words and thousands of languages for thousands of years, that's for sure. Um. And then people were studying heat and thinking about like, you know, what is heat and how does it transfer between things? And I had no idea like is it a flow? Is it a liquid? Is in this invisible this thing or that thing? So the study of temperature is just a few hundred years old, but the experience of it, right, the knowledge of hot things and cold things, that's age old. Right. Yeah, Well, let's get into the definition of temperature in in the episode, but fort we were wondering what people thought out there, all of you listening to this. What you guys thought was is the hottest thing in the universe. Yeah, I thought this would be interesting to see what people think about it, and and I give them some a little bit of extra time on this question. I prodded them to think about it a little more deeply if they didn't seem like they gave me an insightful answer right off. So I walked around the campus of UC Irvine, and I asked people, what's the hottest thing in the universe? And you know, here I was obviously digging for compliments, but nobody said me right, Nobody said you, Nobody, nobody. Nobody gave me a compliment on how I look that day. M Maybe it's just what you were wearing. If you had worn something else. It's sandals and shorts every day around here. So you So you walked around and asked people what is the hottest thing in the universe? And generally what what did people say? Right? Well, listen to their responses and you can tell that's the hottest thing in the universe our sun, like the center of it or the surface or say all of it. Okay, Um, probably like one of those big the big stars that you see on the Twitter videos where it's like they get bigger and they get bigger, and I don't know what they're called, scary names, super super giant stars. Yeah, alright, cool in the middle of some really dense star somewhere. Okay, so you think the center of a star is hotter than like it's surface, Yeah, okay, cool. I'd assume it's not the Sun since you're asking me this, but I'll say the sun since I can't think of anything else in the whole universe. Um, I don't know, probably like a planet. Okay, No, I don't know. Um, we'll call it the I don't know, the center of a son. Center. The sounds cool, called it. I don't think that's right, because don't think that's right, because because some of the plasmas they're saying are actually hotter than the sun that we have here, so that can't be right. Uh. Okay, the center the center of the university. Where is the son of the universe? Okay, the Sun, our son? Cool, like at the center of it, or on the surface or somewhere in the middle, somewhere in the middle from okay, cool? All right, So pretty much people said the sun. A lot of people thought it was the sun. Yeah, yeah, people thought it was the sun, and like that's pretty good, Like the sun definitely a big hot thing, so not a terrible answer, right, But I wanted people to think a little more broadly, and sometimes I needled people. I was like, you know, how about the whole universe? But still people like, okay, maybe a different sun, like another star, hotter sun. You know, I don't think we should be insulting our son. I think our son looks great. I don't want to do anything to disturb it. You know, it's I've been operating billions of years beautiful, you know, and it is sort of losing weight every day, isn't it. Yeah? Yeah, exactly despite its brilliance, and people, I guess generally feel like that must be so hot that any nothing could be hotter, right. I see, So you were prodding them to think bigger like the most people said the sun, but then you would ask him like no, I mean like the entire universe. Like I think for a minute, like is the sound really the hottest thing? Isn't there something else? Crazy? I like to think that if it was me and somebody came and asked me about it, and I've done no thinking or no research or whatever, that I would say something like, I don't know, but it must be something hotter than the sun, because I have this feeling like there's always something crazy out there. There's always something out there that blows our minds or surprises us, or it's different or bigger or denser or nastier, you know, or faster than we could ever imagine. You mean, if so many appression on the street, do you imagine that you will just say the most correct and clever, cleverest thing possible. No, No, I don't imagine I would have the answer. I think I would say, I don't know, but it must be hotter than the sun, right, because I can't imagine that the thing that's in our neighborhood happens to be the hottest thing in the whole universe, which is just so crazy. Big. Oh, I see you think that. I see you think that maybe they weren't thinking that there could be something harder than the sun. Yeah, that seems to be what people have. That seems to be the impression people have that the sun is basically peak hotness. Well, maybe they didn't, just they weren't. They weren't just thinking that our sun is the hottest. But I think maybe they were thinking like the inside of the sun that it can't possibly get any hotter than that. Yeah, and you know they're not too far off. The sun is pretty dang hot. But it's like orders of magnitude colder than what we're gonna talk about. Well great, So maybe first before we talk about like temperature and numbers and how hot things are, let's talk about what those numbers mean, so that when you hear like a really big number, you can understand, like, what does that really mean about what's going on in the side that thing, Like what really is temperature? Like, let me ask you, Jorge, how would you define temperature? How would I define um? You know, I mean, I know the scientific answer, which is related to like kinetic energy, but you know, I think on an everyday basis, it's just sort of like it's a feeling, you know. To me, I think it's a feeling whether I feel hot or whether I feel that something is hot, you know what I mean. Like, it's to me, it's not an abstract number. It's more like a feeling, and it could maybe be relative like something if I feel hot and the person next to me doesn't feel hot, then that's the difference of opinion. Yeah, and our experience of temperature, You're right, it's definitely relative. Right, what you feel is actually is the air or water around me hotter or cold earth than I am right. We don't have an absolute sense of temperature. You can do that experiment where you put like, what, one finger in a hot cup of water and another finger in a cold cup of water, and then put them both in a lukewarm cup of water, and then your two fingers will send you two different messages when we'll say this lukewarm water is actually hot, and the other one will say, no, it's actually cold. Because what you're measuring is the relative temperature to your finger, right, right, and also the sense that you've adapted to it as well, right, Like you get used to certain temperatures and so and then they don't feel hot or they don't feel cold, that's right. Yeah, Like you jump in the pool, it feels cold for a moment, and then you're you know, your skin temperature change is a little bit, and you get used to it and then it doesn't feel cold anymore. So our experience of cold is mostly about relative temperatures, right, It's it's actually about is heat being transferred to us or is heat leaving our body? Right, And so it's a very kind of feeling based kind of definition. But I know that there's an official physics definition of it, right, There is an official physics definition, but you know, it's not really super well defined. It's it's a bit surprised, but it's not something that exactly nail down. Like you can define temperature for an infinite number of particles that have been sitting in a box for an infinite amount of time, and that's about it. Like everything else is like sort of rough and hand wavy. What do you mean, Well, temperature, way they define it is a measure basically of how much energy is being stored in a system of particles, but that those particles have to be an equilibrium. I mean, you can't like have hot spots and cold spots and needs to have all washed down, all the all the edges and unevenness needs to have smoothed out. Because temperature, in the physics point of view, is the description of a distribution of the energy of particles in equilibrium after everything has sort of calmed down. Um, you said a lot of words there, Daniel said, I think what you're trying to say, is it's it's like an average temperature. The thing about temperature is that there's sort of two different ideas at play here, right. One is the quality of temperature. This is the feeling that you were talking about, the experience we have, right, which is really more about like the transfer of heat between hotter things and colder things. That's what we're experiencing, and that's also what thermometers are measuring. Right. A thermometer gets into equilibrium with the thing it's measuring, the heat transfers from it to the thermometer. But then scientists spend a lot of time trying to understand, like how does that arise? What is the microscopic property of something? How does that property change when things get hot or cold? Right? What is going on inside this stuff when it gets hot and cold? How can we define temperature theoretically and understand it rather than just measuring it? Right, That's what physicists want to do. So they came up with a way to define temperature, actually two different ways. At least. One way is related to like the mean energy of the particles, right, and the other is the relationship between the energy of the system and its entropy. Okay, so it gets kind of technical. But the thing to understand about these definitions are you can't actually measure these theoretical quantities directly and exactly right. You can't go in and measure the energy of particles individually. What you can do is measure the heat flow using thermometers. Right, So these theoretical things are connected to what we measure, but they're not exactly the same thing. And the other thing is that these theoretical concepts, they only really make sense for a system of particles in equilibrium because their statistical concepts. So what that means is that the theoretical definition can deviate from our intuitive experience of temperature. Some things, if they're like if they're not an equilibrium or they don't have enough particles to be called like a system, they don't even really have a well defined temperature or one that can be actually measured or practically measured. What do you mean what doesn't have a temperature? Well, for example, one particle, like a single particle, doesn't have a temperature, Like what's the temperature a single particle? It's not defined from for a for physics temperature, right, there's like, well, you know person temperature, the kind of temperature you and I talk about when we get into a pool. But when we're talking about temperature from like a physics point of view, a single particle doesn't have a temperature because it's the property of a system. Right, But what if your system only has one particle, then it doesn't have a well defined temperature. What do you mean, what if there's this cuban space that only has one particle. You can't say that that cube as a temperature. You can't. That's right, And it's even weirder systum situations that you can't say have a temperature, like say you have wait, what about two particles? How many particles you need to have a temperature? That's not even well defined technically, you need infinite number because you need to be in total thermal equilibrium. That's the thing. Temperature is only well defined for things in thermal equilibrium, which means there's no hot spots and no cold spots. Everything is sort of even down, right, You had an infinite amount of time for all the hot and the cold to wash out, right, So you're saying nothing. Technically, nothing can have a temperature because nothing can be have infinite particles. Yeah, but you know, like a drop of water has tended the twenty three or so particles and it tended to one particles in it. That's a good approximation of infinity. And so yes, you can talk about the temperature of a drop of water. You know, it's an excellent approximation of infinity. One particle, No, two particles, no, five particles, no. How many particles do you need before you can call a temperature that's not even well defined? And then also how much do you have to wait until you can claim that there's it's an equilibrium? Right? That's right. So for people to who don't know what I mean when I say equilibrium, take for example, so you have like a bag of gas, and that gas is that like ten degrees. You have another bag of gas that's like, I don't know, ninety degrees or something. Now those are both in equilibrium. They have temperatures, right, so you put them together into another bag. Right, what's the temperature of that new gas? What you might say, I don't know the average of ten and ninety, Well that's fifty, right, But until those wash shout and all of smushes around, physicists say there is no temperature, like you just can't define it. So that's frustrating, right, because it can. It's like gets in your mind, like that doesn't make any sense. And you're right because you're using like the temperature that you think about in English, right, temperature is a word in English. We have defined this other thing, you know, call it physics temperature, which is very closely related to English temperature. Right, but it's not exactly the same thing. And later on I'll give you an example of something which physics says is super duper hot. It has a huge high temperature value. But if we drop doing it, you would freeze. Hm. There is no true temperature technically, but you know, we can't work with ideals, so we kind of approximate it. That's right, exactly, And anything more than you know, a billion particles, it's not a big deal. It works fine, um, But for if you want to talk about one particle, two particles, three particles, there isn't really a definition of temperature. And I feel like the whole this whole episode could have just been like, hey, what is temperature? And we could I could spend an hour talking about this. I know that's a pretty hot rabbit hole. Yeah, it's a hot topic. But um so, so you're saying it's the mean energy, but I've heard it's the mean kinetic energy. What's the difference. Well, kinetic energy applies to speed, right, how fast are these particles dipping around? And it makes a lot of sense intuitively when you think about an object, like in a solid, things are colder and things and they're not moving around as much, maybe they're even trapped in a lattice, and a liquid things are moving around more, which allows a liquid to flow. In the gas, things are zipping around really fast. Right, it's related to the speed. But particles can store energy in other ways. It just don't. They don't just have to move quickly. They can also like spin or you know, they can vibrate if they have complex chemical bonds, etcetera. So they can store energy in other ways. So really, temperature is related to all the ways a particle can store energy. The speed is a great one, okay, Yeah, And it makes perfect and tutive sense. And so as you're thinking about these things being hot or cold, you know, think about them wiggling more right, like the way temperature arises. The reason things are hot is that the particles in them are wiggling more. And that's also like why you get burned. You know, you get burned because you touch something hot. Those particles are wiggling a lot, so they're bouncing off your finger and depositing a lot of energy, which is why your temperature heats up. Right, it wiggles the particles in your finger. That's how heat is transferred, right, Okay, cool, All right, So that's a that's a definition of temperature. It only took us twenty minutes to get here. I know these things sometimes are surprisingly subtle. Yeah, but so let's get into then, now the universe, and let's talk about like the coldest thing and the hottest thing. But first let's take a quick break. All right, we're talking about the hottest thing in the universe, and so let's take a tour of hotness in the universe. I feel like we're back in the nineties. Remember that website Are You Hot or Not? I think that website. Even mentioning that website is sexual harassment for all of our listeners. Oh boy, Yeah, the nineties were pretty frog with people made some bad choices in the nineties. Yeah exactly, But no, I do remember that website, not that I ever participated, And I didn't objective by anybody in the internet. But I did hear about that website from people. Oh I see, you only heard about it, got it absolutely? All right, Well, let's let's start with that in in on Earth. What some of the hottest things on Earth? Right? Well, first of all, let's clarify what we're talking about. Let's do everything in celsius. Right, So for those listeners in the US, you have to get calibrated. Remember zero twenty minutes talking about celsius versus fahrenheits. We're not going to debate it. We're just going for celsius um for the for the world listeners, um. Zero degrees celsius is the temperature at which water freezes, right, and a hundred degrees, of course is where water boils. And you know, somewhere in the middle is you and me, like our body is about thirty seven degrees celsius, right, And you can have things colder than zero celsius, right, that's right. Absolutely, you can get down to like negative two hundred and seventy three degrees. That's absolute zero, right, And that's where they're the particles of molecules, the things in your thing have no kinetic energy. The things in your thing? Is that a Dr Seu's book about physics? The things in your things, the universal things in your universe. Oh, the things that will wiggle in your things. Um, exactly. Absolute zero is when things are doing no more wiggling, right, They're just to rest. There's no kinnetic energy. Yeah, no, Connecticut, you have masks. You can have energy stored in the particles and atoms, but it's just not moving. That's right, exactly, it's an absolute zero. So that's a negative three degrees c. And then zero is ice seven degree C is the human body. And then the hottest person ever is point five degree c. That's like the hottest anybody ever got? Um with a fever? Wait, that's recorded in the history books. Yeah, exactly what happens when you get hotter than forty six point five? Well, I think your brain cooks and you turn into somebody's meal, you know, Like, I don't think your brain can really survive much more than that. But this is not a biology podcast or a cannibalism podcast, right, um soum. So that's the hottest fever and one has ever gotten and survived. I think is the and survived exactly, yes, um, And then the hottest place on Earth. You know, I think there's a a tight race here because Death Valley. I gotta give my props to Southern Califorment and Death Valley is one of the hottest places on Earth, but it's just edged out by this desert in Iran called the Lute Desert, and it reached seventy one degree celsius, which is really smoking hot. That's the temperature you would feel if you were standing in this desert, exactly. And that is the hottest temperature ever recorded on the surface of the Earth. Is that the hottest air temperature? Do you know what I mean? Because there's definitely hotter things on Earth, Like my frying pan is hotter than that. But you're saying, like, if I just put a thermometer and hold it up in the air, not touching anything or you know, not touching any stoves, that's the hottest place you would feel on Earth. Yeah. No, I think I'm composing an email right now to the Guinstpoker World Records to consider your frying pan to be the hottest place on Earth. Yeah. No, you're right. We do create things on Earth that are hotter, but the hottest naturally occurring air temperature. Man in the caveats just to like, how did defy in the hottest place on Earth. So it's air temperature, hottest air temperature on Earth, barring any sort of like standing next to wildfire. That's right exactly. UM is seventy one degreased C. And you might think, well, that's pretty hot, right, but you know it gets hotter, like even on the Moon. The on the Moon, the the average the average daytime temperature on the Moon is a hundred and one degreas C. I'm just nodding along because that I'm used to fahrenheit. So I'm gonna take your word that that's pretty hot. That's the boiling point of water, dude, Like you put water on the Moon, like it just boils. It's crazy, right, Well, it just it would boil. Um, it would boil anyway because there's no atmosphere. Yeah, that's not surprising. Um on Earth at our regular air pressure, a hundred is when water would boil, yes, exactly. So you know two degrees fahrenheit that's a pretty hot temperature for the surface of the Moon. Um. And then here's this is one of my favorite ones. The hottest temperature ever revived by a living thing. That's a hundred and fifty one degrees celsius, right, that's why. Yeah, that's like much hotter than the boiling point of water. That means that whatever this thing is like, it's uh, it really got fried. And that's of course our friend the Tartar grade. These crazy little water bears that can survive like outer space and being frozen. They're like the hardiest thing on Earth right through tiny little microscopic bugs. Right, yeah, exactly, And you should if you've never heard of a Tartar grade, you should google them. They're incredible. Yeah, scary looking though, I think they look friendly. I'd like to have dinner with the targe. Really, have you been a life size Tartar grade, you would have run the other way immediately. They look like a big snuggle. I mean they're look at the big pillow. I would jump onto a Tartar grade and treat like a bean bag, all right, So that that can to that's the heart that they can survive a hundred and fifty degrees celsis. Yeah, that's the hottest temperature ever survived by a living thing. That's a pretty impressive record. Right, So you could put this in boiling water and put it in boiling water under pressure and it would still survive. That's right exactly. Um. But then leaving the surface of the Earth, the hottest spot of the hottest naturally occurring spot in the Solar System is the surface of Venus, which is four hundred and sixty degrees celsius. And that's because Venus is such a thick cloud layer. It's basically basically climate change gone crazy. All the carbodox in the atmosphere means it's a huge blanket and just soaks up the sun. That's why Venus is hotter than mercury, because it just holds onto the onto the Sun's energy and cooks and cooks and cooks cool And that's in our space. So um, well it's on the surface of Venus, right, That's like the air temperature if you were standing on Venus, that's right, if you weren't cooking eggs, but you were just holding up the thermometer in the surface of Venus, that's what you ad measure, right, Okay, God, But then if you you know, went to the Sun, like a lot of people said, Okay, the sun is the hottest thing. Right. Well, it's true, the Sun is really hot. If you jump to the surface of the Sun, then it gets to like five thousand, five hundred degrees celsius. Wow, that's a that's a lot. Yeah it is. It's really hot. But you know, there are places here in the Earth that are even hotter than the surface of the Sun. Like we talked once in the podcast episode about how the center of the Earth is this crazy liquid iron. Right, Well, the center of the Earth is six thousand degrees um celsius. So that's hotter than the surface of the Sun. So the molecules at the center of the Earth are moving faster than the molecules in the on the surface of the Sun. Yeah, that's right exactly. But the Sun is a huge variation. Like the surface of the Sun is pretty hot, but the corona, like the atmosphere around the Sun is even hotter, hotter than the surface. Yeah, it's weird hot. On the surface, it's five thousand, five hundred degrees celsius, but the atmosphere of the Sun, the corona, is a million degrees celsius. Just because things are moving faster, you know, they're just more chaotic, you know, I don't even think it's that well understood. Like the dynamics of the Sun, how that all works is something that we're still really studying. In fact, there's ending a probe right now to go like orbit the Sun and try to make a bunch of measurements because the Sun is a pretty big mystery. It has this crazy magnetic field we don't understand, and uh, you know, these crazy flares and it's a pretty big deal. So people are trying to understand the Sun. We should do a whole podcast episode about mysteries of the Sun. Wow. So if you grew up in the Earth core and then went to visit the surface of the Sun, you'd be like, oh man, this is like minus five hundred degrees celsius. That's right, you have to pack a jacket. But first you have to get through the Sun's atmosphere in a million degrees celsius. So that'd be pretty tough. Oh I see, really it goes from a million degrees to five thousand degrees. Yeah, it's crazy, right, Like, how can those two things co exist anywhere near each other? And it doesn't really make sense. But I think a lot of that is because the Sun is expelling all this energy, right, and so the the gas the correct in the corona gets heated up. But also I think there's there's something going on here about the definition of temperature. Right. The Sun's corona is not as dense as the surface of the Sun, and some of these things that are really hot are not actually very dense. Yeah, that's kind of what I was alluding to earlier. Right, Like you can if you take the temperature of something that doesn't have a lot of particles or molecules in it, it can still have a temperature, it just wouldn't have a lot of things in it. Yeah, So we can have a high temperature without having a lot of heat, right, Like, there's not a lot of heat to deposit on you. If you put yourself in a box with a very dilute gas that's really really hot, but there's not that much gas in there, right, then it's not going to cook you because it's not that much energy being deposited on your body. For the energy deposit in your body, the particles have to hit you and transfer their energy. But if there's not that many particles, there's not that much to do the cooking. Oh, I see both. Wait when you say, temperature is the average kinetic energy. What do you take the average of like particles? Do you You know, you take the total energy and you divide by the number of particles. What does it mean to take the average? Yeah, it's act the property of the distribution. Actually, so yeah, what we're looking for is the mean of that distribution. Yeah, but you know that's a dangerous we could we could go down that rabbit hole the definition of temperature for another twenty minutes. Be careful. Well, I'm still confused. I know it's tricky. It's tricky. Um, but let's keep going. Um. Then you come back to on Earth, right, and it turns out that we can generate things on Earth that are even hotter than the corona of the Sun for example. Um, when we still used to test nuclear bombs, like on the surface of the Earth. At the core of a nuclear explosion, you get up to like ten to fifty million degrees celsius. Right, These are crazy high numbers that are hard to even think about. Okay, so that means that the molecules at the center of the nuclear exupportion are moving super duper, duper, duper fast. Yeah, exactly, super duper duper fast. And that number fifty million degrees celsius. You know, that's comparable to like really hot astronomical stuff. You know, like for example, when a supernova happens, right, a star goes goes, no, it explodes. Well, that's a similar temperature. Like it's fifty million degrees celsius um in the gas that's expelled by the supernova. Right, that's when I start collapses. Right, That's right, the star collapses and then explodes um. And you know what's left is like a little neutron star or a black hole in the center, and the rest is all this gas that's that's spelled out. That's a spewed out and that's a fifty million degrees celsius. Okay, cool. This surprised me a little bit. It turns out that like supernovas are not even the hottest thing out there in space, even though they're hotter, you know than our sun, and they're hotter than nuclear nuclear bombs going off. The hottest thing that's out there in space is stuff like the intercluster medium that's just like all this gas that's between galaxies. You know how galaxies have a huge amount of gas in the mixed stars, etcetera. But between the galaxies is not totally empty. We did a whole podcast episode about like how empty is space? And then there's these tendrils of gas that connect the galaxies together, and they're pretty thin. That's like not a whole lot of stuff out there. You need like a thousand cubic meters of space just to have one particle. But they are really really hot, Like those particles are really moving and the temperature never number you get is a hundred million degrees celsius. Are they all moving in one direction, you know, like wind? Or are they just sitting in place vibrating really fast? I think there are currents because the reason that this stuff is hot is that they're getting heated, right, They're getting heated by like the black holes at the centers of these galaxies that are pushing on them and the crazy like you know, rubbing of of huge clouds of gas that's spewing stuff out. So I think they're getting the sources the galaxies that probably they're all spewing away from the galaxies, but they're probably our currents. As these galaxies spin and things hit each other, it's probably really complicated. So it's actually kind of in the empty spaces between galaxies that we see some of the hottest stuff in the universe. Yeah, and that's the weird thing. It's it seems empty, and if you went out there and like look for particles, you wouldn't find very many. But if you have, you would get burned to a crisp. You would not get burned to a crisp because there are hardly any particles out there, And you can ask a physicists like, hey, what's the temperature out here, and they'd be like, m, it's a hundred million degrees celsius. But if you got dropped there without a space suit, you would not get burned. You would freeze. I see there there are a lot of hot pins out there in that space, but if you stood there, you wouldn't. You would hardly feel them exactly. They're there, and they're really hot, Yeah, they wouldn't. You wouldn't get hit by enough of them to keep you warm, right, you would lose. You would radiate all your heat into the pretty empty space and freeze into a block a block of ice, right, And you wouldn't get warmed up by the hundred million degrees celsius plasma that surrounds you because it's hardly any part of hitting you, all right, see, but the average speed of those few that are there is a lot there wouldn't exactly just wouldn't be enough to really burn you or feel them exactly. Yeah. Wow. Right, so it's zoom back to Earth because it turns out that here on Earth we've created some pretty crazy hot stuff. And that's not just your frying pan. But when we collide particles at the Large Hadron Collider, we very briefly create a situation where the particles have a huge amount of energy. Okay, but again it's not about energy you're saying. You create a situation where the particles are moving really really really fast. Yeah, the particles are moving really really really fast. But you don't really consider the temperature of a particle, right, So if you say, like, well, what's the temperature of a proton zooming around the Large Hadron Collider, we can't talk about the temperature of one particle. But sometimes in the Large Hadron Collider, we don't just collide protons. We take big stuff like the nucleus of a gold atom or lid atom, and we smash those together, and the reason is that they're trying to break up the matter and create this this condition that they think existed in the early universe. It's called the cork gluon plasma. So when you break the proton up and the corks and the gluons have so much energy that they're not bound anymore. They're just like floating around free. So you smash enough particles together so you know, lead and uh and gold atoms have hundreds of protons and neutrons in them. Then very briefly you create this thing which they think is in equilibrium, so you can define the temperature. It's like, you know, bounced around for a few you know, bill of seconds, and this thing they say, he gets to five and a half trillion degrees celsius trillion with the T trillion with the T exactly, Like that's a big number. Well, let's get into now the hottest the absolute champion most hot thing in the universe. But first let's take a quick break. All right, Daniel, here we go. Here's the answer to the question that we post at the beginning. The hottest things in the universe, the absolute extreme most hot things in the universe exactly, and here I think we got to give some credit to the scientist for coming up with names. Is you know, on this podcast we're always poking fund of scientists for naming things in a silly way. I think they did a great job here. Because the maximum the temperature in the universe, the condition of something being at the absolute maximum temperature. They call it absolute hot, which I think is pretty cool. You mean, wait, you're saying that there is a maximum temperature in the universe. That's right, there is a maximum temperature, and it's a crazy number, and it's kind of a hard thing to think about, Like why would there be a maximum temperature? You might think you can give an infinite amount of energy to a particle, and that's true, right, Like you take a single particle, you can dumb as much energy as you want into it. You know, there's a state of light issue. But we're not talking just about speed. We're talking about the energy of the particles. No limit to how much energy you can give a particle. But now we're talking about a system of particles, so we're talking about energy density. What happens when a bunch of particles have a huge amount of energy. Well? Gravity, right, gravity? Remember bends space, and it bends space when you have particles with mass, but also it bends space and you have energy density. Alright, gravity is not just something that responds to mass, a response to energy. So what happens if you pour too much energy into a little blob of space? Black hole? What? Yes, black hole? Right, there's a maximum amount of energy you can have in a certain in a volume of space. More energy than that turns into a black hole. So you can't heat something up past that. Wait to wait wait wait wait wait wait, So the I mean I would think that the maximum temperature in the possible theoretically is when you have a box of particles and every particle in it is moving pretty much at the speed of light. Because you know, temperature we said before is related to how fast things are moving. So what if every particle was moving close to the speed of light. You're saying that's not possible or we wouldn't even get there. That's possible, it's just not even that very hot because remember the speed speed is not the limitation, right, Like, you can get particles up to the speed of light without even having that much energy. Okay, and not bad to the speed of light, just like close to the speed of light. But remember, as you dump more energy into these particles, their speed doesn't go up very much. That's why temperature is not just the speed of the particles, it's their energy. Remember, relativity separate speed and energy, and there's no limit to how much energy you can put into an individual particles. You have your box. You can keep pumping energy into those particles. Their speed doesn't go very much, but their energy increases. But you keep doing it. Eventually your box turns into a black hole. Oh what point does it turn into a black hole? Are you ready for the number? All right? For here's absolute hot is a billion trillion trillion degrees celsius, billion trillion trillion degrees. Is there a name for that, or it's called absolute hot, or more technically it's called the plunk temperature. But wait, is it a billion trillion trillion degrees or is it you know, two point seventy three or four? It's just a round number. Oh no, it's not exactly a billion trillion trillion degrees. But the number, if you want to know the exact value, is one point four one six times ten to the thirty two kelvin. All right, that's like a hundred and forty two million yadda kelvin's or a hundred and forty two million quadrillion degrees kelvin. It's pretty hot. It's a lot of YadA, it's a it's a lot of And then you might ask like, well, you know, is that possible, like that ever existed in the universe, And you know, we don't think it's happening right now. There's nowhere in the universe that's absolute hot right now. Um, but we think that just after the Big Bang, like you know, this this crazy moment when the universe was inflating, right when they expanded really really rapidly. We think that just before that that the universe was at the plunk temperature, and that uh, you know, that's the absolute hottest moment in the history of the universe. But there's a lot of handwaving there because we really don't understand what happened during the Big Bang and why did it cause inflation and not just all collapse into a black hole. Anyway, there's a lot of questions about that, Okay, there is. So the main point is that there is an absolute like if I take a if I heat something in my frying pine forever. At some point it's gonna get super hot, and at some point it's it's just gonna turn into a black hole and it can't get any harder or what. You cannot create a black hole on your stovetop working, I'm sorry, No matter how long you cook that bacon, it'll get black, it'll turn into charcoal, not a black hole. But if you had like laser beams and all sorts of stuff, and you could like pour energy into a tiny area, then in principle, you could create a black hole. Yes, well, how to First of all, how do you know I don't have lasers in my kitchen already? You're an impressive chef, and you're right. I shouldn't have ruled anything out. I issue formal apology. Um, But I mean basically, if you heat something out long enough and you put enough energy into it, at some point you're saying it's going to turn into a black hole and then it can't get any harder or what happens. Then we don't know what happens then, right, because then it turns into like quantum gravity questions and we just don't even have a theory, so we don't I mean we don't know what's happening inside a black hole. If you poor energy into a black hole, we don't know what happens. Um. Basically, it's a huge question mark. So it's sort of a breakdown of the definition of temperature. Like stuff definitely happens, things get crazy, or the universe gets weirder, but it's not according to our definition of temperature. Does that the number we define as temperature doesn't go up anymore? So maybe calling it absolute hot is a little premature, right because it really you've called it super duper crazy hot, yeah, or like super duper I don't know what happens after this hot is really sort of more accurate, right, But we should have called it Jog's frying pan hot. Yeah, there you go. Jore is black bacon hot exactly exactly. Okay, So that's a lot um And you're saying that happened at the beginning of the universe, right, like it. So the hottest thing in the universe ever is the Big Band. Just once again, that's the answer for everything. The hottest thing in the universe is the Big Bang, yes, as far as we know. Okay, but that happened a while ago. But if we looked at the universe. Now, what what would you say is the hottest thing, Well, the hottest thing recently is this cork glue on plasma we create the at the large hage On collider. Right, that's five point five trillion degrees celsius. That's hotter than we think, you know, most things in the universe. Um, otherwise, like the inside of a neutron star we think is about a hundred trillion degrees celsius, and that's probably the otherwise hottest thing in the universe, like on a day to day basis, because you know, the large Hagron collider, these things exist for ten to the might is twenty three seconds, so they don't really stick around very long. But the intside of a neutron star is super hot and very stable at a hundred trillion degrees celsius. Wow, a cool and chili hundred trillion celsius, which is what like fifty fahrenheit or how much is that? I have no concept something like that, something like that. Yeah, exactly. Um, don't pack any jackets. I don't think you'll need them because you won't be alive. That's right, Okay, cool, So okay, so that's the hottest thing in the universe. It's the big Bang ever and it's the inside of an intrance star out there possibly right now. That's right, that is the hottest place in the universe right now. All right, Well, stay tuned for future episodes in our Extreme Physics series will be tackling also the brightest thing in the universe and maybe also the densest thing in the universe. We should also tackle like the funniest thing in the universe. That's obviously that's this podcast like done. Yeah, but speaking of funny things, yea, I have a request for you from a listener. All right, we have a listener in New Zealand who's a huge fan of limericks and often tells physics limericks to his class of ten and eleven year olds where he teaches in New Zealand. Well, I said a limerick in our podcast a few weeks ago. We were talking about tacking on and uh, he noticed that you didn't laugh at my limerick, so he sent me a different physics rick to see if we can make you chuckle. All right, So here you go, you ready, right right, all right? Hit me. There was a physicist called Joe who wanted the whole world to know that those stars that we say are far far away are actually long long ago. Nice. That's cute. That's pretty cool. Yeah, that's pretty cute. Thank you Ryan. Let's say with Jorge, I thought it was somehow related to me. No. Um, Well, let's ask our our listener to send in one tailor for you. But that's for Isaac Garmet from Coromandel, New Zealand. So thanks for sending that in. Yeah. Great, And if you have any other limericks or ideas or questions for us, maybe a banana related limerick for Jorge, send them in two feedback at Daniel and Jorge dot com. We love your emails. Great, thanks for listening and we hope you enjoyed this. Tune in next time the hot person you. Yeah, if 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 at 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. 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