Daniel and Kelly’s Extraordinary Universe - Why does our Universe have a Cold Spot?

Episode Date: March 11, 2021

Daniel and Jorge explain why scientists are puzzling over a massive cold spot in the sky. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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Through in-depth conversations with experts from across the health care community, WebMD reveals how today's health news will impact your life tomorrow. It's not that people don't know that exercise is healthy. It's just that people don't know why it's healthy. And we're struggling to try to help people help themselves and each other. Listen to WebMD Health Discovered on the IHeart Radio app or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation,

we're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. Denials easier. Complex problem solving takes effort. Listen to the psychology podcast on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hey, Jorge, does your family cook many things in the microwave oven? We used to reheat stuff, but we don't do a lot of cooking in there. So you're not a big fan of the microwave? You're not making Thanksgiving turkeys in there? Well, only if you like turkey hotspots and cold spots.

Well, what if the hotspots and cold spots were actually the best part? What? It's definitely the worst parts of cooking in the microwave. What if I told you that sometimes the hot spots and cold spots can hold secrets of the universe? I think I'd still rather live in a evenly heated universe. Hi, I'm Orham, a cartoonist and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist, and I actually have a fancy microwave oven that doesn't generate hot spots and cold spots. What? That's right. You have an AI powered microwave, right?

I do. It was given to me by one of our awesome listeners who heard our episode about how microwave, oven's work and he actually developed a fancy new kind of microwave that has a thermal camera that watches your food and decides where to target the radiation. It's pretty awesome. Wow. Has it taken over your life now? Is it now your new microwave overlord? The kids are worried that it's going to tell them what to eat and when. Just don't connect it to the internet, Daniel. No! It's probably listening to the podcast right now. Say something nice about it. It's going to scald to you in your next meal. But welcome Welcome to our podcast, Daniel and Jorge Explain the Universe, a production of I Hard Radio. In which we think about everything out there in the universe, the mysterious thoughts of microwave ovens to the interiors of black holes, to the craziest, tiniest things happening in the microscopic level.

We think about the huge things in the universe and try to understand the grand scale of the cosmos. And we think about the tiniest little particles that make up me and you and hamsters and microwave dinners. Yeah, because physics is all around us. It's in our fingertips. It's in the food we eat and how we heat it up. And it's also out there in the vast reaches of space. Physics is everywhere. Physics is everywhere and it's doing a pretty good job at revealing to us the nature of reality,

letting us like pull back a layer and see what's really going on. Sometimes the answer is staring you in the face, like learning that the earth goes around the sun rather than the other way around. But sometimes it takes some real sleuthing to pull. pull the clues out of the cosmos. Yeah, because the universe sort of screaming at us all the time, right? With data and information, it's sort of revealing itself to us all around us all the time, but it's sort of recognizing what's happening.

That's the hard part. Yeah, sometimes it's obvious. And sometimes you have to look for those subtle little clues because it doesn't seem like the universe was designed to be easy to figure out. After all, it's taken us some thousands of years. And sometimes we learn that there is evidence all around us that we didn't even no existed that tells us a crazy story about the origins of the universe. Daniel, do you feel like physicists are sometimes like reality detectives that you're trying

to reconstruct what happened in the universe and what's going on and who's guilty? Yeah, exactly. Sometimes in our best moments, I feel like we're Sherlock Holmes. You know how he's famous for like figuring out exactly what happened based on the kind of ash sprinkled on somebody's shoe, you know, or a particular form of dirt or a kind of thread used by only one factory in Northern England or something. It's cases like that when we have to figure out what happened in the universe based on really subtle little clues that I feel like physics is really doing its job.

Do you keep like a magnifying glass at your desk just in case? A clue reveals itself right next to you? Yeah, I don't know. If the universe is a murder mystery, who's getting murdered? Probably us. Well, technically we all get murdered by the universe eventually. Mystery solved. There you go.

We know what the culprit is. It was the universe with the universe in the universe. With the entropy in the gamma decay of our quarks. That's right. But it's fun, right? It's a fun mystery. Sometimes you learn something boring. You go out there and you study and you learn exactly what you expected.

But sometimes you go out there and you find something exciting, something interesting, something surprising, something puzzling that tells you there's still more to learn about this incredible cosmos. Yeah. And, you know, one of the biggest mysteries that you, I feel like you physicists are trying to figure out is basically the whole universe. Like where it came from? How did it come to be? What's it made out of? Why is it the way it is right now? Yeah, precisely. We want to know like how does it look. Is it look the same way here as it does somewhere else? How far does it go on and where did it all come from? It's basically the biggest mystery in human history. You know, I'd put it up there is one of the biggest questions in science and one of the biggest questions in like, you know, human existence. Where did this all come from? And amazingly, we actually like have some. answers. We have beginnings of ideas for how to unravel this because we've detected clues from the very early universe. Yeah. And so one thing that's interesting about the universe is that there's a

picture of it. I mean, not just all around us. We can see the universe, but we have a picture of it from the early beginnings of the universe, like a baby picture of the universe. Yeah, it's incredible. If you sniff around through all the light that's flying around, through all the photons that are banging into each other, you can find a certain set of photons that were generated when the universe was very, very young. Put that together and you're absolutely right. You get a picture of the early universe and that picture is so rich in information that tells us about how the universe was formed, what it looked like, how much dark energy there is, how much dark matter there is. It's really a treasure trove of information about how our universe came to be and what's going to happen to

it. Yeah. And apparently something that sticks out about that picture of the universe is that it's not perfectly even. It has hot spots and cold spots. Yeah, it has wiggles, just like our universe has hotspots and cold spots, right? Like the sun, for example, is hotter than a lot of empty space. Just like that, we can backtrack to the early universe and we see that there are wiggles there also. There are little hotspots and little cold spots, but they're much more subtle in the very early universe. So we've done a lot of detailed analyses of these hotspots and cold spots to see, like, what do they mean about the distribution of matter and how did that lead to the big structures that we see today? Yeah. And so to be on the podcast, we'll be tackling the question.

Does the universe have a cold spot? Or a cold sore, Daniel? And can we put Windex on it to cure it? Do you want to take care of the universe since you already figured out it's going to murder you? Well, it also gave birth to me. So, you know, it's a complicated relationship. So it's a zero moral balance overall. Well, it's a positive for me. For now. I don't know if the universe sees me as a net positive, but I definitely see myself as a net positive for me. I think you're definitely a net positive for the universe, Jorge.

Oh, thank you. At least for this podcast. You're definitely a hot spot for the universe, yes. I definitely have a spot for the universe in my heart. But this cosmic microwave background radiation, this light we study from the very early universe, does have hot spots and cold spots. And in particular, there's one spot that's extra big and extra cold. Yeah, it's a big mystery in physics. And so we were wondering, as usual, if people out there knew that the universe had a cold spot,

like a big, glaring cold spot. And so Daniel went out there and asked people on the internet if they knew if the universe has a cold spot. So thanks to everybody who participated. If you would like to basically speculate on difficult topics in physics, please write to me to questions at Daniel and Jorge. So think about it for a second. Have you heard of the universe having a cold spot? And what would you answer?

Here's what people had to say. Sounds like a medical thing. What is the C and B? I think it probably means central, massive black hole. Like maybe the black hole that's centered the galaxy. That's just a guess. Or it's super massive, but the C is in place of the S. Sure.

That wouldn't be too off from how physicists like do their acronyms. I think it's a trick question. I don't think it has a cool spot. I think it's all cold. I actually was reading about that a little while ago. So the CMB being cosmic microwave background radiation, that map that was drawn up showed a dark spot in it that would potentially denote a void of some kind being just a massive space

where galaxies are all surrounding it, but there's nothing in it, a big void. So that's what they think it would be. but the other alternative theory to it was that it could potentially be a signal of another universe. So that would be where a parallel universe would exist. But the science behind that is completely lost on me and it goes straight over my head. Thinking of expansion and thinking of this video I saw of Legos getting smashed by a hammer from high up, there's one spot where the Legos clumped together and that was close to the point. of impact. And I, you know, back to quantum fluctuations, dark matters a big part of the creation

universe. Its fingerprints are there. So this is a part that was close to the impact that cooled down first. Well, these cold spots might be caused by like being really far away from where the big one happened. So it has had a lot of time to cool down. I remember hearing about it in movies. I don't remember, but I think it had something to do with like either time travel or bending space. All right. Well, first of all, I see you made the error of asking people with an acronym. He asked him, why does the CMB have a cold spot? And most people were like, what? What is the CMB? Central, massive black hole? Cool, mega bears. Sometimes it's hard for me to get out of my physics head and forget that CMB, you know, might have any other meaning. It's one of these

acronyms we use in physics all the time. So I forgot that it might not be something people are familiar with. So yeah, we got some fun interpretations. Shockingly, not everyone knows what CMB means. Although, I don't know if you're watching Wanda Vision, they reference the CMB. Did you see that? They do reference the

CMB, but they call it the CMBR. It's like, no astrophysicists would call it the CMBR. Because that would be the accurate acronym. Exactly. And we know how these names work, right? You call it cosmic microwave background radiation, but the acronym is CMB.

Right, because it makes no sense. And therefore, it's a name for astrophysics, exactly. I see. You're just trying to exclude more people from knowing what you're talking about. It just shows that they didn't really consult an astrophysicist when they wrote that episode. Or maybe they did and they ignored them. They decided to correct you. Yeah, they're like, that doesn't make any sense.

Come on, this is a Marvel movie television show. We need to make sense. Oh, that's a new standard for Marvel, apparently. Yeah. Well, you know, they figured that out in the course. quantum realm. I just did a whole episode on the physics of Ant Man with a fun new podcast. It's a podcast called The Marvels of Science with Dave Reenersman.

So check it out, fans of Marvel and science. I actually gave it pretty positive reviews. You know, the physics of Ant Man, the quantum physics is pretty well done. Nice. But anyways, the cosmic microwave background radiation has apparently a cold spot and it tells us something about the universe. So I guess maybe step us through Daniel. First of all, for those of us who don't know what the CMB is,

what is the cosmic microwave background radiation with an R? Oh, you mean the CMB R? Oh, yeah, that's something totally different. No, the CNB, the cosmic microwave background, these are just photons, right? They're light like anything else, but they're light of a different frequency. And these photons are particularly interesting because they're super duper old. So they're like a picture of the very early universe. We don't know exactly what happened in the very beginning of the universe,

but we suspected that like a few hundred thousand years after the universe was born, it was still really hot. It was a nasty, wet plasma, super duper burning and hot. And like most plasmas, it was opaque. Like the sun is a plasma, right? It's a glowing ball of gas. And you can't see through it. Any light that's generated inside of it gets reabsorbed by the stuff in it.

But at some point, because the universe was cooling and expanding, that plasma cooled to the point where it couldn't absorb its own light anymore. It's sometimes called the surface of last scattering. There was this moment when it was giving off light and then all of a sudden it couldn't absorb it. So that light that was generated by the plasma just before it cooled is still flying around. That's the cosmic microwave background. Yeah, it's like that moment when the universe sort of crystallized in a way

and it became transparent, that light is still flying around. But is it still like bouncing around or like is the cosmic microwave radiation that we get like the actual original photons that were started flying at the Big Bang? They are the original photons. But it does bounce around. Like it gets absorbed. It interacts with stuff. So not every single photon that was generated back then is still around. They can interact with other things and get absorbed.

But there's plenty of them left over for us to see. But when we see one, we typically see it before it's interacted with anything else. And so what exactly happened that made the universe transparent? Like everything became crystallized or glass or what does that mean? Well, the key thing to understand is that the universe was cooling. So you have a hot plasma, which is basically like atoms, but the electrons and the nuclei are separated. So much energy that the electrons can't be trapped by the nuclei. But then as it cools, the electrons slow down and they get captured by the nuclei.

And so this goes from ionic. It's like charge and it's absorbed. and emitting a lot of radiation to neutral. And all of a sudden, those photons can just fly through a sea of neutral atoms without getting absorbed or interacted with. Before it was like a soup and it would get pulled in all kinds of directions. But now everyone is just more chill. And so photons can just fly through.

Yeah, exactly. And neutral atoms, they can absorb photons and they can give off photons but only of certain wavelengths because of the electron energy levels. You know, free electrons can absorb and emit photons of any wavelength. That's why, like, plasma glows in many more frequencies than, like, hydrogen gas, for example. So when the universe cooled from a plasma to just like clouds of hydrogen gas, that gas was mostly transparent to the light that had just been created. And another thing for people to keep in their minds, when you think about the CMV plasma,

you might be imagining like a blob of gas that's burning and giving off light like our sun. And then you think, well, that light is now, you know, flying 14 billion years away must be in a big sphere. How are we seeing it now? How is it just like coming to us now? The way to think about it, though, is that it was everywhere. And this plasma filled the whole universe, so simultaneously making photons in every direction. The ones that we are seeing now came from plasma that was really, really far away a long time ago, and it's just reaching us. But the photons we see in one direction are not from the same bit of plasma as the photons we see in another direction.

Those are two totally separate bits of plasma whose photons are both reaching Earth right now. Right, because this microwave radiation is coming at us from all around us, right? Like if you point like your small radio at the sky, you'll sort of pick up this noise, right? That's right. Every direction of the sky, you see this radiation because it's coming from everywhere in the universe. And everywhere you look, you see it from a different location. Just like if you look in one direction, you see a star, you're seeing light from a star really far away. You look in another direction and you're looking at a star, you're seeing light from a star really far away in the other

direction. Both of those have had photons flying through space for billions of years just arriving at Earth. So you're looking at very different parts of the universe when you look out at different parts of the sky. And that's also true for the cosmic microwave background radiation. Like if you look left, you'll be looking at a different part of the early universe and if you look right. But I guess the question is if I look in one particular direction and I keep looking there, am I getting the photons from the same spot of the universe? Or is it kind of like an observable universe thing where, you know, I'm looking at photons from the early universe further and further out, the longer I look. Yeah, you're looking further and further out, the longer

you look. So the CMB that we see will change as time goes on because we're essentially looking at it from a larger and larger sphere. I see. So we're sort of getting a 3D picture almost of the universe. Yes, exactly. Because it's not a continuous source in time the way a star is, right? When you look at a star, you're seeing the star where it is and it's continuing to beam photons. at you every second. And so as you look at it, you see new photons. But the CMB was generated in one moment. It's one moment in time.

And so when you look out at the CMB right now, you're seeing like a shell around the Earth. And then 10 seconds later, you see the CMB from a larger shell, 10 light seconds larger than the previous one. And it's a wiggling in time? Like, is it sort of changing in volume as well as in direction? There are some wiggles. I mean, it's pretty faint.

And we've only been observing it for a few years. So we don't expect to see like variations on that kind of time scale. All right. So that microwave radiation tells us it's like a picture of that early universe when it sort of crystallized and cooled down. And the mysteries that there are hot and cold spots on it, right? Like if you look at the temperature of that radiation, it's not even. So here physicists are sort of playing a little game. They're saying those photons themselves don't have a temperature.

We're talking about the heat of the thing that made the photons. And there's this concept in physics, this connection between the frequency of light you generate and the temperature you have. And it's pretty simple when you think about it. Hot things tend to glow. And as they get hotter, they glow in higher frequencies. Like everything around you is actually glowing in very low frequencies. You're giving off infrared radiation right now.

If you heat it up your body really, really hot, not recommended to thousands of degrees, you would glow red or you would glow blue or you would glow white. That's why the sun, for example, glows more than the, earth because it's much, much hotter. So when we talk about the temperature of the CMB, we really mean the temperature of a thing that would give off light at that frequency. I see. So when you tell your spouse that they have a special glow about them, really, you're just saying that they glow like everything else. Yeah, exactly. But if they're extra hot, then maybe they are radioactive. Or maybe they're just glowing red and angry at you or something. And so when we look at like the temperature of the C&B really mean the wavelength of the C&B.

And if something is hotter, then it's a little bit more blue shifted. If something is colder, it's a little bit more red shifted. Right. But it tells you basically at the end of the day how hot or how cold that early universe was in different directions. Yeah, it does. It can tell you that. Now, the temperature that we measure is sort of a crazy, crazy low temperature.

It's like 2.7 degrees Kelvin, which is like just above absolute zero, right? It's really, really cold. And that seems confusing because we're saying that the universe was really, really hot, right? It was like a hot burning plasma. Well, it was. It was like 3,000 degrees Kelvin when this light was made. But the light has gotten redshifted over time because the universe is expanding. And that stretches out that light, lengthens its wavelength, and lowers its effective temperature.

Right. All right. Well, so then we're noticing that it has cold spots and temperature, then radiation. And so there are hot and cold spots. So let's talk about what. that big cold spot is and what it could mean. But first, let's take a quick break. Imagine that you're on an airplane and all of a sudden you hear this.

Attention passengers. The pilot is having an emergency and we need someone, anyone, to land this plane. Think you could do it? It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control. And they're saying like, okay, pull this, until this, pull that, turn this. It's just, I can do it my eyes close. I'm Mani.

I'm Noah. This is Devin. And on our new show, no such thing, we get to the bottom of questions like these. Join us as we talk to the leading expert on overconfidence. Those who lack expertise lack the expertise they need to recognize that they lack expertise. And then, as we try the whole thing out for real. Wait, what? Oh, that's the run right.

I'm looking at this thing. Listen to No Such Thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. A small lab in Texas is cracking the code on DNA.

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it's not going to go away just because you're avoiding it. And in fact, it may get even worse. For more judgment-free money advice, listen to Brown Ambition on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast. All right, Daniel, we're trying to cure the universe of its cold sore. The universe is going on a date and it wants to look hot. Or to figure out if we live in a hot spot. It's pretty happening around here on Earth, but who knows? knows. Maybe we're in the cold spot. Or maybe our whole universe is not that hot.

Out there in the multiverse, maybe there are much hotter universes. Oh, man. See, now you're just playing that game. You're saying that the light is greener on the other side of the multiverse. I'm just saying, you know, maybe our universe should get on universe, Tinder, and consider its options. It might choose a different you? Is that what you're hoping for or worried about? No, I'm just saying, you know, hey, get some quantum entanglement going on. We can get some information from another universe.

Boy, now you sound like a Marvel movie, then you. All right, so there's a cosmic microwave background radiation. It's coming at us from all directions, and it's telling us about the early universe, and there are cold spots in it. So tell me about these cold spots, and apparently there's one big cold spot. Yeah, so when they first found this radiation, it was really exciting because it was essentially proof that the universe had once been plasma. That was really cool. And they looked at it, and it was pretty smooth at first. Like, it's basically the same temperature everywhere.

But then they made better and better measurements of it, and they found these with. They found these hot spots and these cold spots. And these are actually really, really small wiggles. Like we're talking about 20 micro-kelvins or so, like one factor in 100,000. So it's almost exactly smooth, but there are these little variations in temperature. Kind of like a texture almost to the light. Yeah, kind of like a texture. And you might think, oh, well, that's just nothing.

But they are statistically significant. Like we've measured enough of these photons to tell that it's a real effect. It's not just like noise in the data. It's fascinating because those little wiggles tell us about wiggles in the early universe, which reveal really interesting and important facts about the nature of the universe itself. And they're pretty consistent, I imagine, right? Like if you take a picture of the microwave cosmic background now, and I take another picture of it later, you'll see the same wiggles.

Like the wiggles won't go away. Yeah, exactly. These come from wiggles in the original plasma. And so we're seeing those. Exactly. They're still there. Yeah. Like if you point your antenna at one spot.

the sky, you'll get consistently a little cooler measurement there, right? Or a hotter. Exactly. And you need a really, really refined measurement in order to even see this because it's like one part in 100,000. You need a very, very fine instrument to capture that. Right. And so what causes these variations in the temperature of the universe?

Like, why is it colder or hotter in some places than others? Yeah, it's fascinating. There are two main reasons. One is that there just were hot spots and cold spots like in the original. plasma, quantum fluctuations. You know, you might imagine the universe starting sort of like smoothly, like homogeneously, like every place in the universe when it was born, however that happened was the same. So then how do you go from that to like having a star here and not having a star there? Well, that has to begin somewhere. And we think that quantum fluctuations in the

very, very early original universe well before this plasma, then got like blown up by cosmic inflation, this process where you take the universe and you expand it by like 10 to the 30 in 10 to the minus 30 seconds. So you get these random quantum wiggles in the very early universe, which then get blown up into macroscopic wiggles in the real universe, which would lead to like little hot spots and little cold spots in this original plasma. And that's because the early universe was so small, right? Like it was so small and so compact and everything was crunched together so much that the quantum uncertainty of this quark or this particle made a big difference. It's hard to talk about the original universe as small because I think it was always infinite.

And so we had an infinite universe, which then got like expanded massively to an infinite universe. And, you know, it's harder to think about it as bigger or smaller. There's some like subtle mathematics there. Like, are there more numbers between zero and one than there are between zero and ten? Yes. There aren't actually. There's a one-to-one mapping between those two things. So the universe is like technically the same size, even though it expanded.

That's a whole other mind-bending discussion. But you're exactly right. Little like quark-to-quark fluctuations, little quantum randomness, right? The only way something can happen differently in one spot than in another, if you have the same initial conditions, is through quantum mechanics. It's the only source of actual randomness. Usually we don't notice that it doesn't affect anything. But if all of a sudden random quantum fluctuations get blown up to the macroscopic sense, size by inflation, then it does matter.

That it can have a real impact on the shape of the universe. Right. It's sort of like when you zoom in on a picture on your phone or a computer screen, like you blow it up, but you can see all the imperfections in it, right? And then we can actually do some really amazing physics. We can model that plasma. We can say, well, that plasma was probably some percentage dark matter

and some percentage quarks and some percentage light. And we understand how those things like attract each other and bounce off each other. So people have done incredibly detailed. studies of like the acoustic oscillations of that plasma, understanding how those things are bouncing against each other and measuring from that plasma how much dark matter there was in the universe because dark matter and quarks interact very differently. So they change the shape of those oscillations in that original plasma. Right. That's one of the ways we know that dark matter exists and that it exists at a certain percentage of the universe is because it cosmic microwave

background radiation tells you how much dark matter there was. and is in the universe. Exactly. And it's those hotspots and cold spots that tell you. Like if there was more dark matter, then you would have different kinds of wiggles and oscillations in that original plasma. And then you would see a different pattern of hotspots and cold spots in the CMB today. So that's one source of the hotspots and cold spots like the original primordial plasma itself was hotter or colder. But then there's another super fascinating, really interesting way that this light can get hotter and colder. What is it? Well, it turns out that as this light flies through the universe to us, it basically measures how much matter is along the way.

If that light passes through really dense regions of the sky, it picks up some energy and it gets bluer. If the light passes through like really, really empty regions of the sky, then it loses some of its energy as it leaves like the previously more dense region and it gets redder. So some of the red and blue shifts in the CMB, the hot and cold spots, come from differences in how much stuff there is now between us and where the light started. So it's sort of like measuring the density of the universe along a line. Right. Interesting. So can you tell the difference? Like how much a variation in the radiation is due to its original fluctuations or

its present fluctuations? Can you tell the difference? Yeah, we can. We think they make very different sort of scale effects. Like these variations due to structure and density make very large scale effects. They have like effects of the size of like 10 degrees on the. the sky. Whereas the other ones that indicate like, you know, the barion acoustic oscillations and the fraction of dark matter make much smaller effects. And so it's fascinating because you can sort of like pull apart this information. You can learn very different things about the universe. What's going on today, the density of stuff and what happened to the very early universe by

studying the hotspots and cold spots at different scales. All right. Well, for the most part, these variations in the cosmic microwave background are sort of small, right? Like if you look at a picture of the cosmic microwave background radiation, it sort of looks like almost television noise, right? For the most part. Yeah, exactly. It's pretty smooth. Like, you look around the CMB and you see typically variations of about, you know, 20 microcalvins. And they tend to be like, you know, about one angular degree. Sometimes there are larger effects because like we're moving through the rest frame of this radiation, et cetera. But typically we see like, you know, 20 microcalvins about one angular degree. And that's about what you expect. You know, you expect, you

expect some variation, some hotter, some colder, some a little colder, some a little hotter, but we expect it to follow like a pretty nice and tidy statistical distribution. Yeah, like I was saying, it sort of looks like television noise. But if you look in some spots, though, you do see kind of bigger features in this noise, right? Almost like some ghostly features in your TV static. Yeah, there's one spot that has astrophysicist and cosmologists puzzling for like more than a decade. And it's called the cold spot. And it's a spot in the sky where this radiates. is surprisingly cold. It's much colder

than it is anywhere else and it's a much bigger spot than you expect to see. So this thing is like 70 or up to 150 micro-calvins colder than the average CMB temperature. And it's like five angular degrees.

So you can see this thing with your eye. Like, what? Oh, not with your naked eye. Like if you see a picture of the cosmic microwave background. Yeah, that's right. You can't see the CNB with your eye,

right? It's in microwave frequencies. Although I guess it does gently cook your food. But you can't see it with your eye. But if you look at a plot of this stuff, you see this spot. You're like, ooh, there's an extra dark blue spot there where you might not otherwise expect it. Now, is that a lot?

Five angular degrees? How big in the sky are we talking about? Like the size of the sun as we'll see it or the moon or the eyes of Texas? Well, the moon is about a half a degree in the sky. And so, yeah, this is a pretty big effect. I see. So like if you were to look out, you would see like something 10 times larger than the moon. and that's how big this cold spot is.

Yeah, exactly. And it's in the southern hemisphere. So if you looked in the direction of the constellation Irodanus, then that's the direction from which this light is extra cold. All right, so there's a big cold spot in the sky that may tell us that the universe had a big cold spot when it was born, maybe. So let's dig into that and let's talk about what it could mean. But first, let's take another quick break.

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All right, the early universe had a cold spot, Daniel, possibly, at least from what we can see right now. If we look out into the sky at the cosmic microwave background radiation, we see that there's one spot that is colder than the rest of. of the universe. So what's going on? Yeah, it's a big cold spot. And, you know, we can never really definitively know because there are a few possible explanations.

And they range from like the total yawn-fast boring explanation to like the crazy, mind-blowing, revealing the nature of reality kind of explanation. I mean, I guess which one you're hoping for? Not the boring one. I'm hoping for aliens, but there's no alien explanation for this one. Not yet, but we still got 15 minutes. on this podcast. We'll figure something out for you. Yeah, or when we write our pitch script to Marvel,

we'll include aliens somehow. Oh, yeah. Microwave Guardians of the Universe. Guardians of the micro-universe. All right, so what are these possible explanations for this cold spot? Now, I know we see it out there in the microwave radiation, but do we think that it's like a hole through the universe or like a sphere out there of coldness?

What do we think it looks like? Well, really there are two basic explanations. explanations. One is that like the light was generated itself from a colder spot in the original plasma. And, you know, we're talking about quantum effects here and quantumness is random. And sometimes randomness gives you weird stuff. You know, if you flip a coin 10 times, you do have a chance, however small, to get 10 heads in a row. It can happen. And so one possible explanation is that those original quantum fluctuations in the early universe just happen to create a spot with less density of stuff. a slightly colder spot in the original plasma. Like maybe that's just how the universe rolled, you know, or like that's what the universe got in their role-playing character role when it determined what it looked like. It just happened to have a cold spot.

Yeah, it's a possibility. That's one explanation. Yeah, it's sort of like a non-explanation. But, you know, every time you have random effects and you have a statistical distribution, you never really know. And so this is pretty unlikely. We can quantify how unlikely it is. we have a model for what those quantum fluctuations should have looked like.

And just like you can calculate how likely is it to get 10 heads in a row when you flip a coin, we can calculate how likely is it to see this coldest spot, this size in the sky. You know, it's like a one in 200 chance. So it's like right on the edge there where it seems kind of improbable, but it's not impossible. You know, we only had this one universe. If we had a bunch of different universes and we have a bunch of different CMBs, we could ask, how often do you see something like this? Is it really wanting 200 or is there something else going on?

Right. Like if you had 200 universes, one of them would probably have a cold spot, just natural. Exactly. Yeah. And so you never know. Like, did we just get a weird one? Do we have an odd universe in some way? Or do we not have an understanding for how that quantum randomness happened and something else is going on?

We really just don't know. So the most boring vanilla explanation is, you know, we just happen to get a weird universe. The most boring explanation is just, oh, well, delavi, you get what you get and you don't complain. And it's also sort of boring because there's not really like much to follow up on. Like, well, it just is what it is. Like, you know, sometimes you get double zero when you spin the wheel and there's not much else to say about it. Unless you can prove that it's controlled by a different probability distribution than the one we expected. But if it is just sort of like a weird outlier, then, hey, you know, that happens.

All right. Well, then what's the next more interesting explanation? Well, the next more interesting explanation is that the CMB got cold as it flew to us. Remember, we talked about how the light as it comes to us from where it was originally generated is affected by how much stuff there is in the universe. And so in that sense, looking at this light is a way to probe how much stuff there is between us and that original plasma. So if there's a really big cold spot in the CMB, it could mean that there's like a huge void

of stuff. There's like a huge blob of space between us and that original plasma that just like has nothing in it. I see because an empty void like that would cool the macrowave background radiation, right? Exactly. As the light enters the void, it loses some energy. It's going to lose some energy because it's more like stuff behind it. And, you know, we expect there to be voids. Like we know that the structure of the universe is you start from stars, which form galaxies, those galaxies form clusters and those clusters themselves form these like walls and these filaments and these huge sheets around bubbles around big voids in which there is nothing and those things are pretty big but those voids would not explain this gap like you would need a super void like a void the size

of five angular degrees basically right yeah like a humongous like multi galaxy empty space yeah much bigger than multi galaxy we're talking about something that's like a thousand times the volume of the voids we see. This thing would have to be like billions of light years across, some ridiculously unusual spot in the universe that happens to just contain nothing. Yeah, I guess the big question would be then, where did this void come from, right? Because don't voids come from those original quantum fluctuations do? They do come from that, exactly. The way the universe gets its structure is you have those fluctuations, which then build on themselves. Because there's anything that has a little bit more density that has a little bit more gravity.

And so it's tugging more stuff in. Then it gets denser and it's a runaway effect. And so the matter tends to clump together where there were original like over densities. And you tend to get voids where there were under densities. But that doesn't explain how you got that under density, right? It's sort of like again the same question. How is it possible that we look at and we see a bunch of voids of a particular size? But then there's one super duper void.

How did that happen? Right. And it goes back to the same question almost, right? Like, was there a big cold spot like that in the early plasma of the universe? It's almost the same question, isn't it? Yeah, it's almost the same question. But this one would be even bigger, right? In order to create this sort of cold spot, you'd need a really, really massive void that would extend across a much bigger region of the universe. Such a void is like, it's hard to gel with like our ideas about dark matter and dark energy. You just don't get this kind of thing. We've run lots of simulations of universe. and you never see this kind of structure. So this is maybe even more unlikely, but it would be more awesome for that reason. I guess the less likely it is,

the more interesting it is scientifically too, right? Yes, exactly. We want to see something weird that we can't explain with our current theories because that tells us how we might be able to change our theories and learn something new about the universe. We want to see our theories fail, right? Scientists are not out there like,

my theory will win out. We're trying constantly to do it. prove our theories because that means finding a clue to solving the murder mystery of the universe. And so one thing people have done is like, well, let's look directly for this void. I mean, if there really is a huge gap in stuff out there, we could literally see it. Right. This is something we could see not just through the CMB, but by directly looking to see, are there a bunch of galaxies missing? Right. But we would have to be looking pretty far out, right? We would have to be looking pretty far out, but we can, right? We can look really far out into the universe. This is something

which would exist in the universe between us and the edge of the observable universe. Because remember, the C&B comes from almost the edge of the observable universe. And so it would have passed through this super void. So we should be able to see it. And have we seen it? Have people looked and seen any big empty spaces? We have looked. And in 2014, a study from University of Hawaii actually did find a super void, like a really massive void. And they called it the largest individual structure identified by humanity, which is sort of hilarious because like I keep seeing that in astronomy papers. People keep saying, this is the biggest thing in the universe.

No, now this is the biggest thing in the universe. It's like their claim to fame. Yeah. But technically it's the largest empty space they found, right? Yeah, exactly. It's like a bubble surrounded by galaxies and galaxy clusters with nothing inside it. So they found a really big super void, roughly in the right direction, but it's not actually big enough and it's not sort of voidy enough. Like it needs to be like really empty of stuff in order to explain this cold shift.

And if you take this super void and you think, well, what would happen to photons passing through it? They don't actually get chilled enough to explain the cold spot that we see. It explains like 20 or 30 microcalvins of cooling, not the full 70 to 100. I see. So it's not cool enough. this super void. This super void is too hot. Not hot enough or cool enough, sadly.

Exactly. Even though it lives in Hawaii. Exactly. So it doesn't really match up. Like you'd love to see like a massive super void just in the same direction that explained that it'd be a really sort of nice connection there. But this one, though it's interesting, doesn't actually explain the data. The two stories don't really fit together quite well enough.

But that's just only what we've seen. Like there could still be a giant void. We just haven't seen it or be. able to make it out. Yeah, exactly. There's always more stuff to look at and better telescopes and new ways to analyze the data, but we have not found a super void out there that explains this cold spot. All right. So then what's the craziest idea we have about this cold spot? The craziest idea about this cold spot is that maybe it comes from even earlier in the universe. Maybe it comes from the very, very birth of our universe. People talk about how the universe was made. And one possible

explanation is that our universe is like a little bubble, a bubble of some pre-universe stuff that decayed into normal matter. And here we are going way out into like crazy no basis speculation for how the universe might have been formed, right? No data to support this. But it's possible that the universe sort of turned into normal matter from some sort of pre-universe matter. They call this like the inflaton field. And you have to imagine sort of like a meta universe filled with this stuff. which then like births individual universes. So like our entire universe created in a little bubble inside this larger universe. Along with other little bubbles.

Exactly. Along with other little bubbles. Where do those bubbles get made? Well, it's quantum mechanical. So it's random. And sometimes those bubbles might be really close to each other and maybe bump up against each other. And if they did that, they might leave a mark on each other. You might get like evidence on your bubble that you bounce.

against another bubble and in some of these theories this effect this sort of like bruise on a universe which show up as a cold spot which would lead to a super void wait what you mean like the ideas that these universe are being created in this froth of a meta universe and sometimes the bubbles bump into each other and that would create a cold spot wouldn't it create like I don't know like a dent maybe more a dent is basically a cold spot you know it gets like suppressed. It gets like squeezed down. And you would expect actually a cold spot surrounded by like a little bit of a hot spot. You get like a hot ring inside of it a cold spot. And that's actually kind of what we see. Like if you look at this cold spot, it is cold, but the stuff around it is a little

bit unusually hot. And so it sort of looks like a bruise on the cosmic microwave background from a parallel universe. And you know, again, this is speculation on speculation on speculation. There are many other possible explanations and we have no evidence that there was this meta universe or other bubble universes but it's sort of a fun idea. Like they have a model of this crazy multiverse and you can actually model like what happens

when two universes bump into each other? Yeah, they do. Although, you know, you have to wonder like, are these models designed to explain this cold spot? This is not like a prediction. This is sort of like more like a postdiction. It's not like 50 years ago people are saying we're going to discover the CMB and it's going to have a cold spot from the previous universe.

It's more like, hmm, a cold spot. I wonder if I could explain that using a parallel universe. So here's a theory I cooked up. And you probably like tweak the parameters until you get the cold spot, right? Yes, that's the tricky thing. And so what you've got to do always when you make a theory that explains the data is then you have to predict future data so you can test your theory. Otherwise, it's just an explanation. Wow.

All right. Well, so this big cold spot in the sky. in the universe background radiation. It sounds like it's still a big mystery. Like, nobody really knows what could be causing it. It's still a mystery. It's still something people are puzzling over. There are even crazier ideas out there

that we didn't cover things like cosmic texture and all sorts of weird stuff. And aliens, aliens. Let's not forget aliens. Here's my alien theory, Daniel. They build a Death Star that's billions of light years across and that's what's causing the cold spot.

It's blocking the CMB. And it's coming our, way. Yeah. And there's a 1% chance that I'm totally making that up. I love your theory. It sounds just about as plausible as the parallel universe theory. Yeah, there you go. I am right up there with the leading physicist on this matter. Yes, absolutely. You're on the cutting edge. But you're right. It could be nothing. It could just be like a random quantum fluctuation, but it's not something we currently understand. And so it could be that 20 years from now, we look back and we say, oh my gosh, that was the clue that told us something deep about how the universe works. Because

Because remember, the CMB is filled with super rich information about how the universe came to be and how it evolved and why it looks the way it does today. So I wouldn't be surprised if this really in the end taught us something deep about the universe. We just don't know what yet. Yeah. Or maybe the universe just doesn't like to talk about it. You know, maybe it's a little embarrassed by that cold spot. In which case, maybe we should just look away, Daniel. Just ignore it.

That's the polite thing to do. Don't stare that zit on your friend's head. I just pretend it's not there. Yeah, yeah. That's what a good friend of the universe would do. All right. Well, again, just another reminder that the universe is all around us. It's giving us clues all the time and that there are big cold spots of mystery in it,

in that information that it's bathing us with. Exactly. There are big giant voids of knowledge that we still don't have about the universe. Yep. And we have figured out the CMB is there, but there's probably other kinds of information that we're swimming in right now that contains incredible facts about the universe. origins of our universe, we just don't even know how to look for it and how to interpret it.

In later generations, Will's chuckle when they look back at how silly and how foolish we were. Right. Maybe all we had to do is check the CMBR, not the CMB, and we would have seen the answer. And we should have checked the CMBSS and the CMBT. I mean, like, let's follow up on these things, man. All the Marvel movies right there. All right. Well, we hope you enjoyed that. Thanks for joining us. See you next time. 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. Do we really need another podcast with a condescending finance brof trying to tell us how to spend our own money?

No thank you. Instead, check out Brown Ambition. Each week, I, your host, Mandy Money, gives you real talk, real advice with a heavy dose of I feel uses. Like on Fridays when I take your questions for the BAQA. Whether you're trying to invest for your future, navigate a toxic workplace, I got you. Listen to Brown Ambition on the IHeart Radio app, Apple Podcast, or wherever you get your your podcast. From tips for healthy living to the latest medical breakthroughs, WebMD's Health Discovered podcast keeps you up to date on today's most important health issues. Through

in-depth conversations with experts from across the health care community, WebMD reveals how today's health news will impact your life tomorrow. It's not that people don't know that exercise is healthy, it's just that people don't know why it's healthy, and we're struggling to try to help people help themselves and each other. Listen to WebMD Health Discovered on the iHeart radio app or wherever you get your podcasts. Hi, it's Honey German, and I'm back with season two of my podcast. Grasias, come again. We got you when it comes to the latest in music and entertainment with interviews with

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