Daniel and Jorge Explain the UniverseHow was the cosmic microwave background discovered?
Daniel and Jorge go through the crazy story of missed opportunties, accidental observations that led to one of the greatest science discoveries of all time.
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Hey Daniel, do you know what I don't understand about winning a Physics Nobel Prize.
Oh yeah, what's that?
Well, you know, to be honest, some of them seem kind of easy in hindsight.
Easy to win a Nobel Prize.
Yeah, I mean, like for Einstein, all he had to do was analyze someone else's experiment. It was just one idea that he had one day and boom, Nobel Prize.
I guess that's easy if you're Einstein.
Well, I mean also, like the discovery of X rays was totally by accident and it took about one day of work for them.
That's true if you happen to have X rays around.
Or like the Higgs boson. You know, like college physics major can do that kind of math.
All right, you win. I admit it. Getting a Physics Nobel Prize is easy. So then why don't we have.
One because we haven't tried it. Let's win one today, Daniel.
All right, great idea, Einstein, let's do it.
Hi am orhammy cartoonists and the creator of PhD comics.
Hi. I'm Daniel. I'm a particle physicist and I have not yet won a Nobel Prize, but maybe any day, someday will be the day.
Do you wake up every day, thinking maybe today's day, I'll have my great idea.
I don't expect it to ever happen, but I do love those stories when somebody has a moment of insight or stumbles across something weird, and that morning, when they woke up and had their oatmeal or whatever, they had no idea that it would be that fateful day.
Maybe that's the key. It's the oatmeal. And maybe it's a special kind of oatmeal. Daniel like a radioactive oldmeal.
Bitten by his radioactive oatmeal, he gained his proportional intelligence.
There you go.
Maybe that was secret.
I think when people say you're as smart as a bowl of oatmeal, they don't mean it as a compliment.
Well, I think that's very disparaging of odmel, because you never know, there could be sentient genius oatmeal out there in space. They could be our next alien overlords.
Yet another sci fi pitch for Netflix put it on the list.
All right, well, welcome to our podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio in.
Which we try not to turn your brain into oatmeal as we talk about all the amazing things that are out there in our universe. All the things that we have painstakingly uncovered in our search to reveal the fundamental nature of matter and radiation and everything in the universe, and all the things that science is still picking at, all the big questions that are out there, all the discoveries that might be far into the future or just around the corner.
That's right. The universe is full of mysteries, full of big questions and wonderful discoveries, just waiting for us to find them and possibly get a noble price for finding them.
In the congratulatory bowl of oatmeal. And sometimes the answer to those questions is already out there. It's beaming down at us from the cosmos, or it's in some somebody's data. They just don't even recognize it. And sometimes those Nobel prizes come just from putting one thing next to the other, from finding that the answer to a question is already out there.
Yeah, because technically, all of the secrets of the universe, all of the great big truths about it, are out there for us to discover. I mean, it's not like they don't exist through there. We just haven't seen them or having discovered them, or having known where to look.
Yeah, you know, that's a really fun question, Like, is it actually possible to unravel the nature of the universe without ever leaving the Earth? Just by watching this guys, it's sort of incredible what we have been able to figure out about like far flung corners of the universe, the way galaxies expand and collide and do all sorts of crazy stuff without ever having left the Earth. But I wonder if it's possible to actually figure out like all of it, to cut all the way down to string theory and quantum gravity without ever going anywhere else. It would be pretty cool if all that information was beaming down on us right now.
Are you saying, like, are maybe in the wrong place, Like if we were somewhere else, we could see the secrets of the universe, you know, Or maybe they're all in one box but in another part of the galaxy.
Yeah.
Or it might be that you need to do some kind of experiment like smash black holes together at very high speeds in order to get the answer to some question. Or it might be that you need to be able to look inside a black hole, which we can do from here. Maybe you need to be nearby it in order to decrypt the quantum information in the Hawking radiation. It might not be possible to gather all that information from Earth, or maybe it is. Maybe if somebody was smart enough, they could figure out all the secrets of the universe just from the data we are getting today.
Yeah, hopefully not by getting us near a black hole or by smashing a cope of black holes together here on Earth. That sounds kind of dangerous.
Anything in the name of science.
Not worth a Nobel price.
Well, you know, everybody makes their own judgment call on that.
Please, physicists, check with the rest of us before you make those kinds of judgment calls. I know this is important for you, all of you, But you know, we might have other priorities.
Used to get to name the black hole machine, right.
I want to be alive to name it and to call it that, you know. But yeah, the history of physics and science here on Earth has a long and interesting history, full of amazing discoveries. And some of them happened kind of by accident.
Right, Oh, lots of them happened by accident. People stumble across stuff they didn't even know to look for, see things they don't understand, and only later realize that they contain secrets of the universe.
So today we'll be covering one such story of an amazing discovery that really kind of illuminated in a very real way the beginning of the universe.
Absolutely, it's some of the oldest light in the universe, and it tells us a lot about how the universe began and how hot and dense and crazy it was billions and billions of years ago, and it was almost overlooked and mistaken for pigeon poop.
Oh wow, that is a big oops there for the physicists. So today on the program, we'll be talking about how was the cosmic microwave background discovered? Now, Daniel, this is the famous CMB, right.
This is the famous CMB that has taught us so much about the nature of the universe.
It's not the CMB are as they call it in the Marvel universe. You have a problem with that.
Well, the scientists in the Marvel universe can call their CMB whatever they like, but out here in the real universe, we tend to call it the CMB.
Just the cosmic microwave background, meaning like it's the background basically of the universe.
It's everywhere, it's all around us, photons from the early universe, plasma are aszooming all over the universe in every direction, no matter where you look. That's what we mean by background. It's sort of just like always there is everywhere.
Yeah, And it has a long and interesting history of people thinking it was there but not ceing it, or CNN and not thinking it was there. It's kind of an interesting and dramatic plotline.
Right, absolutely. And it's the kind of thing that could have been discovered very easily decades before it was, and in fact, it was discovered several times without even being understood, and so it's sort of like a story of missed opportunities and the folks who ended up winning the Nobel Prize for finding it could very easily not.
Have So it sounds like a pretty intriguing story. So we'll dig into that and go over every detail. But first we were curious about how many people know how this amazing discovery was found. So, as usual, Daniel went out there into the wilds of the Internet and asked people if they knew how the cosmic microwave background was discovered.
And so, if you would like to be interrogated about physics by a physicist without the opportunity to consult any reference materials. If that sounds fun to you, then please email me to questions at Daniel and Jorge dot com.
Here's what people had to say.
I think it was around the seventies or whenever it was. They felt it was a very powerful telescope maybe radio telescope to look at something else, and then they heard or saw so I'm like what they thought was noise from a local source. They even thought it was the pigeons stick in the telescope and actually had a big job clearing that out, trying to get rid of it. But no matter what they did, couldn't get rid of it. But obviously eventually they realized it wasn't local at all, but from almost fourteen billion light years away.
The CNBA two words, Hubble telescope. Okay, that's a tool, not an answer. Aliens told us about it, and they also told us where to look. So we pointed the Hubble telescope at the cosmic microwave background radiation, and that's how we discovered it.
I haven't really heard about it, just as an assumption. Maybe when we were trying to discover some kind of radiations.
I think the background radiation was discovered by accident. They hadn't had nothing to do with someone using their microwave up and to make eggs.
But I think it was World War Two.
Weren't they doing radar experiments and they discovered this noise?
But I think it was by accident.
The cosmic microwave background was discovered by two scientists working at Bell Labs in New Jersey who were investigating a strange buzz they picked up when actually working on something else.
I think it was discovered around nineteen sixties as one of the first discoveries of radio astronomy. After making sure it wasn't the error in data or in measurements, there was a lot of crizon what it meant and why the signal was actually hurt.
Quite possibly with a radio telescope. Maybe astronomers or scientists were looking at like certain stars or something. They're like, hey, these guys are given off a lot of radiation. And then they looked at the stars and they're like, oh, it's not the stars put something around it, but there's nothing around it. So they're like, oh, what if we just focused on the space around it? And then they focused on the space.
All right, a lot of versions of the story here from the public.
Yeah, a lot of people seem to know something about how it was discovered by accident.
Yeah, including apparently aliens told us about it. I like how this person just said two words hubble telescope, bam drops the mic an aliens. Oh, by the way, wait also aliens.
Well, how else do you know where to point your hubble telescope?
Right?
The aliens have to tell you it makes perfect sense.
It's pretty surprising how many people had heard about this and also knew a little bit about it. You know, generally people seem to know that it wasn't like this intentional thing, like there was some element of accident to it.
That's exactly right. And it took a long time for people to even know that it should be there and know that we might be able to see it. So there's sort of like progress and backsteps and forward steps on the theoretical side as well as on the actual like observational side.
All right, well, let's get into the story then, and maybe take us back Daniel, because I imagine this story starts in the early nineteen hundreds, and you know, we were sort of just starting to discover how big the universe was and that it maybe came from a big bang. You know, what were we thinking at the time, and what did we know? Because you know, I imagine that the idea that there's some background noise in the universe is not that surprising to think about, but having some special meaning maybe is.
Yeah, so we have to go back to basically Hubble. Hubble's the one who figured out that the universe was expanding. Before that, people thought that everything, which is sort of like hanging out in space, things hadn't changed in hundreds or thousands or billions of years. But Hubble discovered that there were other galaxies out there and that they were moving away from us faster and faster, and suddenly that made the universe dynamic instead of static, like things were definitely changing. And people had two totally different concepts of ways to explain what Hubbles saw that the universe was expanding. One is the idea that's very familiar to us that if the universe is expanding, then you run the clock backwards in time, then it must have been more dense, must have been more compact, must have been more squeezed together in the beginning, and you can sort of track it back to a very early moment when you reach like infinite density, the singularity. So this is the big bang idea that the universe came from some like huge early expansion, and what we're seeing now is the remnants of that continued expansion of the universe. So that was one idea, this big bang idea.
Right, because we saw the stars and the galaxies right now, they're all moving away from us. So you know, the idea is that if you rewind, then at some point everything was crunched together.
Yeah, but some people didn't like that idea. They thought that's ridiculous for the universe to have a beginning and for it to begin in some sort of big bang. And in fact, the name big bang came about as a sort of like an insult, and they were like trying to, you know, make that idea sound silly by calling it a big bang, and instead they preferred a steady state theory of the universe. That was sort of hard to have a steady state idea of the universe that the universe like isn't changing on the largest scale. When you see that it's expanding, you know, how could that possibly be if things are expanding, don't they get less and less dense. Well, their idea was that there was some like source of new stuff in the universe, that stuff was constantly being created, and that was like refilling the universe. So the universe was expanding, but at a constant density because they is some like thing that was like topping it off all the time.
That is sort of what we think of now, but back then it seemed sort of counter to the evidence.
Well, that's interesting that you say that you're right that we know that the universe is expanding and that there is more space being created, but the universe is getting more and more dilute. The steady state theory involved like the creation of more stars and galaxies and more stuff in the universe to keep like the density constant. So the steady state theory was like, well, let's figure out how to make the universe so it's not getting more and more dilute. It's always been this way and lived forever.
They were thinking, like, the density of the universe doesn't change. It's somehow expanding, but the density is not changing.
Yeah, because somebody is like pouring more syrup onto these pancakes all the time, and so even though it's dribbling off the edges, you're keeping the same amount of syrup on top of your pancakes. That's my big pancake theory of the universe.
I think you missed up that analogy. I think it's more like the pancakes getting bigger, and so somebody must be pouring more syrup.
So there you go, all right, there there go, All right.
Right, that's a more delicious.
Very breakfast theme physics analogy today.
Yeah, old meal pancakes, it's the most important physics meal today.
Wait till you hear about my waffle based observation ideas.
I might have to be another episode, Daniel. I'm stuffed already.
And so these were some of the ideas people were bouncing around, like what does the expansion of the universe mean? Did it come from some early hot danse point? Or is there some place where the universe is creating new stuff so the things don't get less and less dense as time goes on.
I guess why were they finding this idea of a more, you know, kind of empty universe, Like why couldn't the universe beginning more and more dilute?
I think they didn't like the idea of a beginning, it seems sort of counterintuitive. They prefer the concept they seem more natural to them to imagine the universe had always been here, because if there's a beginning, then, as you know, there are big questions about that beginning, what came before and what caused it? Why do we have a beginning? You can avoid some of those things if you imagine the universe has just always been this way.
Like if you don't except that the universe could have a beginning, then you have to make something up, like where's all this syrup coming from?
Yeah, there are always more questions, but you know, it was sort of an aesthetic preference, and so you had physicists on both sides of the issue, some arguing that the universe must have started with a big bang and others suggesting that, you know, stuff was constantly being made in this steady state, and so that's what people were thinking about. They were like, where does the stuff in the universe come from? And they were trying to understand, for example, where heavy stuff in the universe came from, Like where does all the iron and where does all the nickel and all that stuff in the universe come from? Was it made during the Big Bang, or is it somehow made somewhere else and being like poured into the universe somehow, I.
See, because it could have been made in the Big Bang, right, like the heavier elements could have been forged in that hot, dense initial moments.
That's what people thought in the early part of the century that maybe in that incredible heat from the Big Bang, you could have made iron, and you could have made silicon and oxygen, and maybe all the elements were fused in that initial time period. People spent a lot of time doing theoretical calculations of how hot it was back then in the very early universe, What was the temperature, of what was the density? Were there the conditions needed to make all of the heavy elements. So that was the reason they started doing these calculations, and they realized, wow, in the very early universe, there must have been this very very hot plasma, and that plasma must have glowed the way plasma from the Sun, for example, glows, And then the universe cooled and at some point that plasma becomes transparent because all of the ions and it capture electrons as they cool and they become neutral. And then it's transparent. So what they were wondering about was all that energy, all that light that was now flying around the universe. Was there enough light there to like make the heavy elements. And they did a bunch of calculations and they decided no, it was impossible. And now, of course we know that those heavy elements were not made during the Big Bang. The Big Bang mostly made hydrogen and helium and very tiny amounts of heavier things. The heavier elements were made later in stars. But they didn't know that at the time, until they did these calculations.
How did they know that you couldn't have made the heavier elements.
Because there just aren't the conditions, Like you can't make iron, for example, under the conditions just after the Big Bang, Like it needs to be hotter and denser. You need the conditions inside stars.
But wasn't the Big Bang infinitely dense and super duper hot.
It was, but not for very long, you know, And so like it took time for the basic particles to form, you needed like quarks to shake out of it, and then those quarks to get bound into protons, and then those protons to find electrons. And that's basically all that happened and then things cooled down. It was very very quick early expansion. Remember the Big Bang itself is an expansion that lasts like ten of the minus thirty seconds.
I see, there wasn't enough time to make the heavier elements, is what you're saying, But just enough time to only make hydrogen and helium.
Just enough time to make hydrogen and helium exactly, and little trace elements of what comes next. And so the other elements were later made in stars. And this is where cosmologists kind of lost interest. They were like, all right, so there must have been this hot plasma and it must have generated a bunch light, but we're not interested anymore because that couldn't have made the heavy elements. That was the question they were asking. So they had the idea that there might be this light from the early universe flying around, but they didn't care because they didn't answer the question they were asking At the time.
They were more interested in, like how did the planets come about and had its stars and galaxies? Like the stuff that you can actually kind of that is interesting to them, at least at the time in the universe.
Yeah, so it's very much motivated by like what questions scientists are asking. Sometimes you stumble across an idea and you don't realize, oh, this could actually be really interesting and important for a totally different question. They were focused on, you know, how do you make these heavy elements? And on top of that, nobody imagined that you could even see this light. Even if they thought, well, that light is cool, and if you could see it, it would prove that there was this hot, dense state in the early universe, they didn't imagine to be possible to see it today, and so they just sort of like wrote it off and cosmologists sort of like moved on. This is calculations done in the forties some guys named Alfred and Herman and George Gammou and they did it, and people thought, m well, I guess you can't make heavy elements in the Big Bang. And then they sort of turned to other stuff.
They thought the Big band was too boring. They're like, you know, like all right, yeah, that's where the universe came from. It was a big flash, but nothing interesting happened.
Nothing interesting that we could see today. These photons, they started out really hot, you know, like thousands of degrees Calvin. But then they got cooled down as the universe expand they got stretched out as the universe expands, down to very very cold temperatures, which means long wavelength, which means radio waves. And so at the time, radio astronomy was like really a brand new field that had just begun a few years earlier. So nobody imagined you could actually detect these faint signals. Nobody even bothered to propose that somebody do that.
All right, well, let's get into a little bit more detail about what they were expecting to see and then how it was accidentally discovered. But first, let's take a quick break.
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All right, we're talking about the cosmic microwave background and how it was discovered. Now, Daniel, some of our listeners might not know exactly what the cosmic microwave background is or where it comes from. You want to go as a quick recap of what it is and what exactly it is that we're seeing when we look at it.
So the cosmic microwave background are photons from about three hundred and eighty thousand years after the Big Bang. Right, big bang happens things really hot and dense and stuck together, and the universe expands, which means everything is getting more dilute and more cool. And by about almost four hundred thousand years, the universe had cool to the point where atoms could form, like electrons were slow enough that they could now be captured by protons and turned into hydrogen, for example. And that means that the universe became transparent. So there's this moment when the universe goes from like really hot and glowy but opaque to slightly less hot, slightly less glowy, and transparent. Right, it becomes like glass all of a sudden. So what happens to those photons that were made just before the universe became transparent. Well, they were flying around and they're still flying around, and fourteen billion years later, most of them are still flying around. And so they were everywhere because the Big Bang was everywhere, and this plasma filled the entire universe and filled it with these photons. So that means that everywhere, all around us are these photons, not from the Big Bang itself, but from this hot plasma that existed about four hundred thousand years after the Big Bang.
Yeah, I'm thinking like, it's like you're in the middle of a giant fire and then suddenly the fire, the air all around you becomes transparent, and so you sort of get that one last flash of light from that fire right before the universe became kind of solid.
And because it happened everywhere all at once, then there are always photons wherever you look. Right, we look out and we see this just in the night sky. Right. If you point to a radio telescope to the night sky in any direction, you see this because there's always a place where fourteen billion years ago, almost a photon was created and it has been flying towards us ever since. And as time goes on, we're seeing these photons from further and further slices of that early plasma. So we're always seeing it. We always will see it.
And so you were saying that in the beginning of the nineteen hundreds and through the middle of it, we sort of knew this story. We knew that what had happened or possibly happened at the Big Bang and what happened to all those that light. But you're saying, nobody really cared about seeing this light.
Nobody imagined that you could, right, Nobody thought, wow, you could actually go and detect this stuff. It seemed like it would be a really faint signal and you'd need really impressive technology, and so people just sort of like, well, I guess that existed, just like lots of other things probably existed in early states of the universe. Doesn't mean we think we can see clues of them now. It's sort of like incredible to imagine that you could see today remnants of something that happened fourteen billion years ago, right, that's sort of incredible. Most of the stuff that happened a long time ago is gone, right, Like you can't see most of the dinosaurs that were on Earth, just a very few that happened to get fossilized.
I think part of it is that, you know, we were at that time stuck on like visible light astronomy, Right, We're trying to look at the entire universe only through like the visible light spectrum.
Yeah. At the same time, people were just starting to figure out that there were other ways to look at the universe. It was in the thirties that radio was stronomy was accidentally invented because somebody built a big antenna to try to communicate across the Atlantic and realized, oh, my gosh, there are crazy radio signals coming from space. What why is space making radio signals? And that was the discovery, for example, the big radio source at the center of our galaxy, which turns out to be from a black hole's accretion disk. And so we'd just begun to understand that radio astronomy was a possible thing. You could do another way to look at the universe. Right, everything in the universe is glowing. Everything that interacts electromagnetically gives off some kind of light, and it just depends on the temperature. So you're not very hot, so you don't glow in the visible light the way like a white hot piece of metal does, or the sun does. You and the Earth do, however, glow in the infrared, and so if you're cold enough, then you glow at longer and longer temperatures which are not visible. So if you look at the night sky or any sky really and look at it in the frequency of radio waves, then you can see colder stuff stuff that and glow in the visible things like gas and dust and planets and other kinds of things. So it's a different way of looking at the universe. A different filter shows you different stuff.
Right, And it also travels differently through space, right, which is why it's sort of like clearer to see things in the radio spectrum.
Longer wavelengths are less obstructed by like small particles and stuff, so radio can travel more easily through like big clouds of gas and dust and this kind of stuff. So let's you see through different things, because every object is transparent or opaque at different frequencies.
Right.
For example, your walls are transparent in X ray, right, but opaque in visible light. You can see through them with some kinds of light X ray light with very high frequency, but you can't see through them in other kinds of light like visible light.
So that's kind of the picture that sets up the discovery. So we knew there was this light out there where we didn't think we could see it. And also we were just discovering, you know, the radio spectrum of signals out there in space. So then how did they finally put the two together?
So people put the two together of accidentally at first, and it wasn't even realized until decades and decades later. Because it was World War Two that really improved our radio technology. Obviously that was important for signaling during the war, and so it gave a great boost to like a lot of our electronics and radar and radio technology. And so after World War Two, people started playing around with radio a little bit more, and there were folks that were like looking at the sky and surveying it at various wavelengths. And for example, a Frenchman named Emil LaRue in nineteen fifty five made a measurement of radiation from the sky and he found this source of radiation at just the right frequency, which we now understand was the CMB. He just didn't understand what it was, and nobody recognized it.
I see. He just hooked it up and he heard like ah or something through his earphones or something.
Yeah, And people are looking for sources, right, They're like pointing this telescope at various things, trying to find things that generated radio waves. So like the center of the galaxy generated radio waves, the Sun generates radioas Jupiter. You're looking for like objects. You're trying to understand what's out there. But what they were seeing was, in addition, this noise that you hear from every direction. Right, it doesn't matter where you pointed the center of the galaxy, of the center of the Solar system, doesn't matter where. It's coming from every direction. And so that's sort of weird. And people had sort of forgotten this prediction by the theorists that there would be this like radio noise from the early universe out there, and then they started to hear it, and they didn't understand what it was.
I see, But I guess how did they know it wasn't just noise like just general noisy equipment, you know, thermal fluctuations, you know, noise in the air. How did they know it was something special and not just like, hey, I have bad equipment.
Yeah, that's a great question. That took a more detailed comparison between what was expected and what was predicted and what was actually seen. But we'll get there at a moment. To me, it's super fun to look back into history and see evidence of future discoveries in people's data, to see people who could have claimed the discovery of something which later won the Nobel Prize. They just didn't understand what they had. And so this actually happened twice for the CMB. In nineteen fifty five, it was Emil LaRue, and two years later a Russian guy named Shimanov observed a signal at the same temperature in every direction and didn't understand it, and they just sort of like went hmm and then moved on and never really figured it out. Now, of course we know that was all the data they needed to claim discovery of the CMB. They just didn't really have the context for it.
Yeah, I mean, like, is it directional this noise or is it only coming from space? If I pointed back towards the Earth, I don't hear it, you know. I guess paint us a picture like if I'm in the sixties and I haven't sentenna, what would I be experiencing.
Yeah, so it comes from space right. Earth actually is a big source of radio noise, so not just electronics, but like everything around us is constantly emitting light, just like we said earlier, it's glowing, and so you got to get rid of that by only pointing your antenna up at the sky, so you're listening to radio from the sky only. The interesting thing about this is that there doesn't seem to be any particular source of it. It doesn't seem like it's coming from the center of the galaxy, doesn't seem like it's coming from Jupiter or from the Sun or any particular source. Once you point your radio telescope up of the sky and listen, you see it equally from every direction, which is really weird. And it's a clue that it's not coming from any particular object out there. It's just sort of like the cosmos are filled with this bath. And of course you have to make sure it's not instrumental, that it's not just like noise in your you know, electronics or something like that. And so you can spend a lot of time trying to like find that noise and remove it and make sure you know that it's not from your electronics, but you can tell that it's not from any particular object because it's coming from every direction in the sky.
It was definitely coming from somewhere, is what you're saying.
It was coming from space, right, It was definitely not coming from.
Earth all right. So then what was the big breakthrough? How did they piece it all together?
It was in the sixties when one group at Princeton realized, hold on a second, we might be able to see this radiation. They sort of like dug back into these old calculations from the forties to think about this light from the early universe and realize that with the advance in radio technology, it might actually be possible. And so this is like go back and read old papers people, because there are great ideas out there that people wrote down that they didn't follow up on because the technology wasn't there. And so there was a guide Princeton named Dickie who realized, you know what, we could probably see this light. We think it's out there. It would be evidence that the universe was one hot and dense enough to generate this light. And now we think we might be able to see it. So let's go build a radio telescope so we can go and look for it. So this was Dickie at Princeton.
I see. It was somebody who said, like, hey, radio astronomy is a thing. You could find interesting signals out there in the radio spectrum. And oh, by the way, you should be able to see this early light, this dim light from the universe beginning.
Yeah, it was a great idea, you know, the technology had come around. The question was interesting. I realized, Wow, I have the hammer to bang in this nail. And actually, as a weird aside, Dicky didn't believe in the Big Bang as the beginning of the universe. He didn't think the universe had a beginning, but he did think that the universe had an early, really hot, dense state. He had this other idea. He thought of the universe as a sort of a cycle. He thought the universe expanded and then slowed down and crunched back together again. And he was trying to understand if that crunch was sort of like intense enough to break apart all of the matter. He wanted to find this early radiation as evidence of how matter was destroyed rather than created. He thought this fireball destroyed the previous universe and then ours was birthed out of that.
What like a crunch from the Big Bang or before the Big Bang.
From before the Big Bang. He thought that our universe was just like the latest and an infinite series of universes, and that before our big bang there was a big crunch, and that this sort of like cleansed the universe from all the stuff from the previous universe, you know, sort of like wipe the table and sets it for a new meal.
He was thinking, maybe you can hear the crunch or see like this crunching the current universe.
Yeah, and you thought that maybe this cosmic microwave background radiation, if you could spot it, would be evidence for this like cleansing radiation that basically destroyed the previous universe and helped create ours I see.
And what made them think that radio would be a better way to see it than other wavelengths?
So they did this calculation. They thought how hot was it back then? And it was about three thousand degrees kelvin And if that light was still around, what would be its wavelength now? So it's a little confusing. We talk about the temperature of light. What we really mean when we say the temperature of light is we mean the temperature of a thing which would generate light at a certain frequency. So, for example, when we say the light was three thousand degrees kelvin, we really mean a plasma that was three thousand degrees kelvin would glow a certain frequency. Something that's colder from the three degrees Calvin, for example, would glow at a much longer frequency. But if you have a plasma from a long, long time ago that glowing at three thousand degrees calvin, it made very high frequency light. Light that like zigs and zags really quickly. As the universe expands, member space stretches, that light gets to longer and longer frequencies. That light gets stretched, doesn't get slowed down. Light always moves to the same speed, but the wavelengths gets stretched. So now that light is much longer frequency or as we say, colder temperature. And so they did that calculation. They figured what the frequency of the light should be, and they figured it should be something corresponding to radiation from an object around three or five or ten degrees calvin.
So they sort of knew that if this light from the early universe glowed at a certain frequency or a frequency range, it's not like you can measure that glow in the X rays or in the visible light, like it only glows in that certain frequency.
Yes, it'd be characteristic at that temperature.
All right, And so they were pois then to go look for it basically and then realize what an amazing discovery it was. So let's get into how they found it and when they realized what they were sitting on. But first let's take another quick grade.
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All right, we're talking about the cosmic microwave background and how it was discovered, and it feels like people news there and this new technology, this radio astronomy was just coming into fashion and so people were ready to see it.
People were ready to see it, you know. But just like to recap the crazy history. It was like predicted in the forties and then it accidentally discovered twice in the fifties and then ignored and then in the early sixties, Dicky at Princeton is like, hold on a second, I bet we could see this. Let's build a telescope to look for it. So he's the first one to like really bring this idea together and decide to look for this thing on purpose. But he's not the one who actually found it.
Oh really, But did he build a telescope for it to look for it.
No, he got started and they were like getting going and starting to build this thing. Meanwhile, at the same time, totally coincidentally, sixty kilometers away from Princeton, at Bell Labs, there was another couple of guys working on a totally different project looking for something totally different. They built a radio telescope because they were working for Bell Labs and they were trying to communicate with balloon satellites. Bell Labs was experimenting with like building a telecommunication networks using floating balloons in the upper atmosphere. So they built this thing to talk to balloons.
Oh wow, So they had already built one, but not to do astronomy, to do like communication.
Yeah, to do communications. And so they had built this thing and they were like trying to talk to balloons, and then Bell Labs decided, you know what, we're not interested in this. Let's cancel the whole project. We're not interested in like balloon satellites as a way to build a telecommunications network. But these guys Penzis and Wilson, the ones working for Bell Labs, they had done radio astronomy for their PhDs. They knew how to do that, and they were like, all right, well, we have this awesome telescope. Why don't we pointed the sky and see what we see. We've got some questions about you know. They wanted to follow up from basically from their THESS and do some more research. So they just sort of like took advantage of this existing thing and started trying to do some research.
I see. So they were originally science, isn't They probably hoped they could use it for science, but they had this pesky engineering problem they had to work on. But then when that got canceled, they could do science on it.
Yeah, And so they had this instrument. Now, Dickie was building one for himself over at Princeton because he knew what to look for. Penzs and Wilson they already had it, but they didn't know what to look for. They weren't looking for the cosme microwave background. They didn't know what existed. It wasn't on their radar, so to speak, at all. They were just trying to build a sensitive instrument so they could listen to the sky. And you know, they were great engineers, and they built this really awesome telescope. If you look at pictures of it, it looks kind of funny. It doesn't look like a telescope you see often because it's only part of a parabola. It looks sort of like a big shovel, like a big scoop, because it's only a little sliver of a parabola. Because they wanted to be really careful and only pointed towards the sky, so it's like really well shielded from the ground and just gathers a bit of the radio waves from the sky.
Now, did they set out to look for this cosmic microwave background or were they, you know, hoping to look at stars and black holes and things like that.
They were not looking for this at all. They had no idea this thing existed as a concept. They had no idea that it was possible to see it. One of them was interested in, like finding big clouds of hydrogen that were glowing, so they wanted to look for other stuff. But they were really good engineers and builders, and so they built this thing and they cooled it really really cold, because what you want to do for your radio telescope is not absorbed signals from like the telescope itself. Remember, everything glows, including your telescope. So they had to cool the whole telescope down to four point two degrees calvin, so they didn't like swamp itself with its own radio signals. And then finally in July of nineteen sixty five, while Dicky is over there building his own telescope, they turn it on and what they saw was a lot more noise than they.
Expected because they had done such a good job of like cooling everything that they'd expected to hear this clean signal. But really they saw this like giant hiss in the radio wave spectrum.
Yeah, they saw this giant hiss, and they pointed their telescope in different directions. It's on a big wheel, so you could like turn it this way and that way an the other way, and they just couldn't get rid of this hiss, and they like took apart all their electronics and replace them. They like put another layer of shielding on everything, they cooled everything down a little bit. All this made like a very small amount of difference, reducing the noise a very small amount. But they couldn't get rid of this hiss.
I see, they were trying to get rid of the science signal, but they did because they didn't know it as a science signal.
Yeah, exactly. They thought it was just noise that was going to interfere with their science. And at one point they found a bunch of pigeons that were nesting in their telescope and it had covered part of the electronics with pigeon poop or as they called it in their paper, white poultry dialectic material, And they cleaned all that off, but it didn't help anything, and so they were very disappointed. You know, at the time, Wilson says, this was a huge disappointment for us scientifically, and they spent like a year plunking away at this thing, trying to get rid of this noise. They had no idea what they were looking at.
Well, in a way, they were right, you know, like if they were trying to get you know, radio waste signals from a cloud of hydrogen somewhere. This is sort of noise that gets in the way, right, Like the universe just has this noise. They just didn't know it was a feature of the universe absolutely.
You know, one man's noise is another woman's signal is another woman's Nobel prize. And we have that in particle physics. All the time we were looking for the top cores, and now the top quark is an obstacle in finding other particles. We wish we could like turn it off and get it out of the way so we could see other stuff. And so yeah, it's very subjective, all right.
So then they thought they had some sort of error or some sort of equipment failure for over a year, and then how did they realize that this was something of interest?
So Penzias, one of the guys who built this telescope, happened to run into one of his friends, Bernard and Burkie, on an airplane who told him that Dickie over Princeton was looking for this exact thing. So Penzias is like complaining about how we have this hiss in our telescope. My gosh, we don't understand it, and he says, you should talk to these guys at Princeton because I think they know what you found.
Oh wow, no kidding on an airplane.
On an airplane, just like by chance.
And I'm guessing this is you know, the sixties. So they were, you know, wearing ties, drinking cocktails, smoking, yeah, smoking in the plane right over the loud propeller noises.
Yeah. So Penzis calls up Dickie at Princeton and says, I heard about this thing you're predicting. Dickie sends them a paper written by his student John Peebles, predicting this noise and explaining exactly what it should look like. And Penzias is like, wow, this is exactly what we are seeing in our telescope right now. They had no idea.
You know, what does it mean? What it looks like? Shit like it? Should it have a specific like signature and when you look at the signal in the frequency spectrum, or should it have this particular shape to it or what is that like? How would you recognize it?
Yeah, it looks like what we call black body radiation. So, as we said earlier, everything in the universe that has a temperature glows, and it glows at a specific frequency, but not at only one frequency. It tends to peak at a frequency and then have a particular shape. So at one frequency you'll have the highest intensity of radiation, and then at the nearby frequencies it'll sort of fall off in a very characteristic pattern that we call black body spectrum. And so what they saw was the frequency of something at two point seven degrees kelvin glowing with black body radiation. And so it wasn't just like we saw a bunch of photons of this one number, like they saw the whole shape.
You know.
It's like if you saw a mountain of a very specific shape and somebody predicted seeing a mountain of exactly that shape, you'd be like, Okay, you've understood how that mountain came to be.
Because black body radiation, I think it doesn't just look like a bell curve, like a random noise curve. It actually has kind of a shape to it.
Right, Yeah, it has a shape. It's asymmetric around the peak. So it's very characteristic.
All right. So then Dicky's like, oh, oh, like I'm building the telescope, but these guys already have it and we've been scooped.
Yeah, exactly there's a famous story where Dicky gets off the phone from talking with Penzias and says, boys, we've been scooped. And that's really kind of a bummer for Dicky because he's the one who had this idea to look for it and started building his telescope like that was really the ingenuity, and Penzias and Wilson just sort of like stumbled across it, had no idea what they had found until Dicky.
Told them, that's what you get for answering the phone, Daniel, that's why I never asked my phone. It could be somebody trying to scoop it.
So then they worked together. Everyone was a very good science citizen at that point, and Dicky like explained to them what they were looking for, and they all agreed to publish together. So Dicky and his crew publish a paper saying, we predict that if you looked in the sky this frequency, you could see the afterglow of remnants from the Big Bang and it would look just like this, and you can do it and it'd be very interesting. And then in the same journal the next paper is Penzias and Wilson saying, by the way, we've looked in the sky and we see this weird glow. We think it might be explained by this previous paper you just read by Dickie and his group.
Interesting, it was a two part series.
It was a two part series. And this is nice. You know when scientists who are working on something and realize they're sort of in competition or in working in parallel, they decided to publish together rather than like have some crazy race to who gets their paper in one minute.
Before m Yeah, that's that's pretty cool. So then, because I guess Dicky didn't have his telescope ready. It's not like he could have just like jumped in and found the signal. He just still ways away from having a functioning telescope.
Yeah, he had been scooped, right, and just by chance. If Penzias and Wilson had waited another year or something, then Dickie could have had the idea and the data, but he didn't. And Penzias and Wilson went on to win the Nobel Prize in nineteen seventy eight for this observation.
Wow, and also people's got it too.
Right, peoples who originally had this idea and wrote the paper. He won the Nobel Prize in twenty nineteen for like other contributions to cosmic microwave background theory. But Dickie in the end never won the Nobel Prize.
I see, So back then it went to the people who had discovered it, not the people who predicted that it would be there.
Yeah, because if you look back in history, it turns out that other people had already predicted it, right. People in the forties had the idea that this would be there, And there was this other Russian group which in the early sixties had also published a paper saying, by the way we might be able to see this, people should go look for it. So that was an idea which was sort of old and bubbling up around the world at the same time.
And maybe by nineteen seventy eight a lot of those people had died or something, right that you couldn't give him the Nobel Prize for it.
That's true. You can't give the Nobel Prize to somebody if they've already died.
Yeah, all right, Well, and so that's how we humans discovered the cosmic microwave background. And it's something that's pretty significant, right. It tells us a lot about the conditions for the early universe, about the composition of the universe. It confirms things like dark matter, dark energy. I mean, there's a lot in that signal.
Yeah. Hawking says it's the greatest discovery of the century, if not of all time. And the reason is that it is really very, very rich, like how the cosmic microwave background looks, and specifically how it's not exactly smooth but has these little ripples in It tells us a lot about how that early universe plasma was operating, what it was doing, and like ripples in that plasma are sensitive to things like is the dark matter fraction of the universe twenty percent or five percent, because it changes how that matter sort of slashes back and forth if the dark matter is interacting or not. So, as you say, we can fit a lot of the parameters of the universe. A lot of the questions about what the universe is made out of and how it came to be come from understanding that in great detail. And you know, years later people launched a satellite to measure the cosmic microwave background radiation very precisely. That was called the Kobe satellite, and then that won a Nobel Prize. So it's like a very rich area of research.
Right, there's not just a lot of information in it, but it also kind of basically confirms our theories about the early universe, right, Like it's like perfect evidence for all these series about the Big Bang and inflation and the you know what was happening in ing in those early few seconds.
Yeah, it definitely confirms the Big Bang, right. It tells us that the steady state theory just doesn't work because the universe was once much more dense and hot and crazy. So it rules out the steady state theory and confirms the Big Bang. It doesn't exactly confirm inflation precisely. There are some predictions for like weird little wiggles in the CNB we might be able to see that would confirm inflation, And several years ago there was an experiment called BICEP two that thought they had seen that, but it turns out they were wrong. But in the future, there's a lot more we can learn about the universe. Whether inflation was right, is it the right theory of what caused the Big Bang in the very ear the universe? We still don't know, but we hope that there's more layers of information in the CMB that will one day reveal even more about the early universe and how it all came to be.
Yeah, there might still be more Noble prices in there.
Yeah, there might be information in that data right now which you could download onto your laptop and if you knew how to interpret, could win you a Nobel prize.
Sometimes everything you need is right in front of you, or I guess the dangerous you could download it, have it on your computer and then not discover something, and then in the future some physicists and a podcast saying, see that person had that data in his or her laptop and didn't.
See it, so better to just not download it.
Better to just ignore it and go about your.
Death, or just donate the you never hear about how you were scooped.
You'll have an easier life, all right. Well, that is how we discover one of the greatest discoveries of human history, apparently, although I would argue that you know, that bowl of ome I had this morning was a pretty good discovery as well.
I think brown sugar ioemeal that was a pretty big discovery that No thanks, Oh you're a purist. Huh, that's a level too far, all right, that's for the future. All right, Well, we hope you enjoy that story. Thanks for joining us, See you next time. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of iHeart Radio. For more podcasts from iHeart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases. Many farms use anaerobic digestors to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's Last Sustainability to learn more.
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