From Big Bang to James Webb: Exploring Space with Nobel Laureate John Mather

Host: Right now, we still have the great mystery of quantum mechanics, which doesn't seem to describe gravity. Can we find places that are like home, little Earths orbiting stars like the Sun? When you look at the history of Earth, you see the history of the different forms of life growing. It's taken all of the entire history of the universe for us to turn up. We start off with, that can't be done, that's impossible. Then somebody invents something, and then somebody wants some more. And gradually, we invest our billions or trillions as it takes because there's a demand for it. Please build us another telescope to look farther back because we've got a big mystery here.

[Stage direction: Host introduces the guest.]

Host: Artificial limbs, precision GPS, firefighter suits, insulin pumps, emergency blankets, air purifiers, even the dust buster. Now, what do all of these things have in common? Well, these were actually all innovations developed through the pursuit of space. And I think there's something really profound there. Through our collective deep desire to understand our past and all that we came from, we've created technologies that enhance our future. I think it's also an important reminder that history is riddled with people who think they know what is best to build, without realizing that there are so many great things that have sprouted from projects that didn't seem immediately useful at the time. And that's why today I am so excited about our guest, astrophysicist John Mather. Now, John actually won the Nobel Prize in Physics in 2006 for his work on the COBE satellite. To which, by the way, Stephen Hawking described the imagery from COBE and its implications on the Big Bang Theory as the most important discovery of the century, if not all time. More recently, John was a senior project scientist for the James Webb Space Telescope. And that was the feat of science that produced the images of those far-out galaxies that you probably saw as the Biden administration revealed them in the last year. Now, this episode came about because I had the pleasure of seeing John speak at the Aspen Ideas Festival. And after his talk, I had to ask him, I had to shoot my shot, to see if he'd come on the A16Z podcast. And in this complex world of cosmic probabilities, John actually said yes. So here we are, venturing into the very beginnings of our cosmic history. We also talk about what we've learned in the several decades that John has been working in this space, but also the many things that we have yet to understand. So things like dark energy and dark matter. Plus, we explored the very important question of why space exploration is such a fundamental but also useful human desire in the first place. And given that the James Webb Space Telescope that John has been working on recently made its first detection of a new carbon compound, methyl cation, this conversation is all the more timely. In the best way possible, I think this is one of those episodes that may leave you with more questions than answers. But I hope you enjoy it as much as I did.

[Stage direction: Host invites John Mather to speak.]

Host: Maybe we could just go back to when you started exploring this concept of space and the work that you've done. What was our understanding at that time?

John Mather: Oh, my goodness. Well, you're asking me to jump back when I was born, which is 76 years ago. And in 1946, hardly anything was known about what we currently can tell you. We had just finished up a war. We had learned a lot about physics because we invented all kinds of new weapons, including radar and atomic weapons and things like that. So we had realized that rocket theory was possible. So then we scientists got busy and we discovered the most astonishing things. We found out the physics of the universe a lot. We've uncovered the nature of the particles. We've learned about quantum mechanics. Then the space age came along, partly because it was tied to weaponry. So we invented space travel. In 1957, the Soviet Union launched a little Sputnik. Suddenly, the government realized we better invest in science and engineering. Yes. They played Jack Kennedy's talk, announcing that we were going to go to the moon, not because it's easy, but because it was hard. And he also promised that we would do the other things, too. And what he had in mind, I'm not sure exactly, but we were clearly up against medical issues and cultural issues. And we still had the remnants of slavery very strongly in our country. There was segregation and legalized mistreatment of a good portion of our country. And so he knew that that was a big set of things to work on, too. And he's promised we would do them all. So that was pretty brave. And we're still working on a lot of them. We are. Because some things are harder even than space engineering.

[Stage direction: Host asks John about his personal journey.]

Host: Tell us about when you started getting involved in this.

John Mather: I got interested pretty young. I think I was about six years old. Wow. I heard from my dad at bedtime story time that living things are made out of cells with chromosomes. And this was before we even knew about the double helix. So that got my attention. My friends and neighbors were farmers. My dad was studying dairy cows for his research for Rutgers University. And so that was where I got started. Living out on the farm, thinking about deep things like that, the origin of everything. If you know about cells and chromosomes, then immediately you understand evolution and the huge changes that can happen through time. I think I was about eight, we went to see the Museum of Natural History in New York and the planetarium show and the giant meteorite sitting there as big as a small apartment, just sitting there. You say, where does that come from? Where do we come from? Where do we come from? So you see the bones arranged and showing evolutionary order in the museum. Oh, my golly. What a fascinating story. I want to know everything about this. Yes, yes. And we didn't know that much about space at that time. Maybe I'm getting a little too ahead of myself because I'm sure there's so many years between what you're describing and when you won your Nobel Prize. But that did seem like maybe the start of a new era of our understanding of space. And so could you speak a little more to the satellite that you had developed with your partner and what that really meant as maybe an inflection point?

[Stage direction: John Mather discusses the COBE satellite.]

John Mather: So back in 1970, I was in graduate school at the University of California, Berkeley, looking for a thesis project because I was tired of studying in the library. And maybe I better build something. The people had just discovered the cosmic microwave background radiation. It is thought to be the remnant of the early universe. The hot Big Bang still fills the universe. And so can a graduate student do something to go measure it better? So the answer is yes, we'll try something. So, okay, well, I worked on a project which was an instrument to measure the spectrum, which is to say, how bright is this radiation at each different wavelength? And we built it and we sent it up attached to a high altitude balloon. And it went up and it did not work. Oh, man, what do I do now? So my thesis advisor said, okay, well, you did good work. You can write this up and you can make a thesis out of it. They've already published some other papers. So I said, okay, I'll get a job. I got a job for NASA. Five years before that, we had just landed on the moon for the first time. Wow, okay. So, okay, 1974, I'm at NASA Laboratory in New York City. And, okay, so NASA puts out this announcement of opportunity, calling for new satellite missions for science. Because what are we going to do after the moon landings? Are done, maybe do something else because we can't keep on going to the moon all the time. So, okay, boss, my thesis project failed. We should try it in outer space. So I had no idea how much nerve was required to do this, so we just did it. We wrote a little thin proposal. We said we have an idea. So after a couple of years, NASA said, well, we think it's a good idea. And I got a job at the big NASA laboratory in Greenbelt, Maryland, just outside Washington. And they gave us some engineering time to work with people who knew how to build stuff in space. And, well, in 1989, it went up. It did. And it worked. Wow. And within weeks, we had measured the spectrum. My thesis project that had failed as a balloon payload now worked beautifully in outer space. That's incredible. I showed a graph to the Astronomy Society, and we got a standing ovation for a graph. And so they knew what it meant. They knew basically that not only was the equipment working, but the story of the hot Big Bang was basically right. People don't remember now that there used to be alternate theories that said, well, maybe it wasn't so. A couple of years after that first announcement, we were able to say we made a map of this cosmic heat. And our map showed pink and blue blobs across the entire sky. And what they show is if you could see millimeter waves with your eyes, you would see this big fuzzy map. And it's very blurry. But it was enough to say the early universe was not the same everywhere. There were hot and cold spots. And that matters to us because if the universe had been completely exactly uniform, gravity wouldn't know what to do. It would not have any way to pull material back together again. To stop the expansion locally and make galaxies and stars and planets and people. So we're here because of those spots. And that's pretty revolutionary. That is. It used to be people looked at this amazing universe and thought it requires divine intervention because it's too dang complicated. Nobody could possibly see how it could work. We confuse I don't know how it works or I don't know how to do it with it can't be done or it's impossible. When it comes back to how did we get here, it used to be we couldn't understand how to calculate anything. So we figured it must be impossible. It must require divine intervention. And now I think we have a different picture.

[Stage direction: Host and John discuss the implications of the COBE satellite's findings.]

Host: Yeah. Let me divert into that a little bit because how is it that nature spontaneously produces complicated stuff.

John Mather: So there are reasons. There are fundamental deep reasons why nature produces complicated stuff. So when you think of nature as just full of atoms and atoms are just little billiard balls, and they have no shapes and no properties, then, of course, it would be extremely unusual for them to stick together and form what they do. But quantum mechanics says, no, atoms are not little billiard balls. They have shapes, and they're like covered with Velcro of different flavors. So atoms stick together in certain patterns because that's how nature is. So, okay, then also we learned about thermodynamics, which tells us which kinds of reactions are favored by nature. So if energy is released when two atoms come together, then it's likely to happen. So now we say, okay, it's not completely without pattern. Nature gives patterns because of quantum mechanics and thermodynamics. So it's just built in that complicated things will occur given a chance. Yeah. So, okay, the universe spontaneously heats up. This is something they don't teach you in school. In school, they say, well, nature does not have two objects just sit there at the same temperature, and one gets hot and one gets cold. That's true in normal life. But gravity is an exception to that. Okay. So this is pretty deep and fundamental. Gravity is the reason why the universe has heated itself up. Gravity can stop the expansion of the material of the Big Bang and pull it back in to make stars. Then when it does that, the stars can light up and release nuclear energy. And now we have a state of the universe where it's hot in some places and cold in other places. So energy flows from place to place. And this is then the basis of the complexity that we now have. Yeah. And that's partially what we got from you're saying this image. Because if this wasn't the case, if you're saying gravity didn't exist and create these local changes, then what would we see? Would we instead have seen just a clean image? Yeah, if gravity could not have acted on those hot and cold spots, those dense and less dense regions, then nothing would have happened. It would just have been a completely featureless, expanding universe with no stars, no galaxies, no anythings. Yeah. All the same temperature. Completely boring as far as we're concerned. We wouldn't be here. We wouldn't be here. But nature does have gravity. Nature does have the other three forces of physics. And it does have quantum mechanics and thermodynamics. And so it's just designed in some way, if that's not really the right word, it is a universe in which complexity naturally appears. Yeah. And maybe you could just speak to what a phase change, again, this was in our understanding. Because I think even Stephen Hawking said this maybe was one of the most important images to come through science about, you know, maybe I wasn't sure if he was referring to it in terms of just our cosmic understanding or understanding of the whole world. But yeah, why was this such an important discovery?

John Mather: Okay, well, Stephen Hawking looked at our map of the pink and blue blobs, and he said it was the most important scientific discovery of the century, if not of all time. And I first thought, oh, Stephen, you're just exaggerating. But it's very nice. And then I thought, okay, well, in truth, if we could understand where those spots come from, it would tell us perhaps about the unification of the forces of nature. Right now, we still have the great mystery of quantum mechanics doesn't seem to describe gravity, but we have the opinion that it ought to. Yeah. And if it does, then it means that even space and time are randomly fluctuating and weird. And so that was, it's like one of the great mysteries of science, and we think there ought to be something there. Scientists have been working at least 50, maybe 100 years trying to figure out how gravity and quantum mechanics should go together. The other thing, of course, is where did we come from? And if those spots weren't there, then we wouldn't be here. So that's pretty cool. And it even tells us through detailed analysis that there is something called cosmic dark matter, which we can't see and perhaps never will see. So we've got all these wonderful mysteries that are all embedded in this map of pink and blue blobs. Yes. And so it's totally fascinating and draws in thousands and thousands of scientists. Since the COBE satellite was flown, two more satellites were built and flown, and they confirmed our original measurements, which was nice because that meant we could get a Nobel Prize for discovering the thing that turned out to be true. What if it weren't true? Then, of course, you don't get a prize. But now we have much, much more detail to go on.

[Stage direction: Host asks about the James Webb Space Telescope.]

Host: Let's talk about that, right? So you were the lead project scientist or senior project scientist on the James Webb Space Telescope. And I feel like that was the most recent exposure that the everyday person had to the frontier. After the Hubble telescope was launched, scientists said how wonderful it was. Yes. And by the way, we still can't tell how the galaxies grew. And it was still one of the great mysteries of science because we thought we would understand. We thought, oh, now we know about the Big Bang and the hot and cold spots, and we should be able to simulate and calculate how galaxies would grow. And then we measured with the Hubble telescope. Oh, we got it wrong. The predictions had been that galaxies would grow slowly. So the Hubble would be able to see the first ones happening. And, of course, how do you see that? Well, you see back in time by looking at things that are far away. So you've got your own time machine in your eyeballs every morning, but you don't feel it. Yes. So look back in time, see what the universe was like when it was young, and see what were the galaxies doing. And they were already pretty grown up as far back in time as the Hubble could see. So please build us another telescope to look farther back because we've got a big mystery here. So we still have a big mystery because we built the Webb telescope. It did what it was supposed to do. It produced beautiful pictures. And right away we could see that the galaxies grew even faster than we thought. And so even though we had the information from Hubble and all the simulations and calculations and predictions, we were still wrong. So we're looking for something really deep and fundamental. Don't know what it is. So that's why astronomers are thrilled right now that they've got something to work on. And it's going to take us a good long time, could be decades, before we really deeply understand what we were wrong about. And it's even possible that there's some new force of nature or some thing that happened early on that's just so different that we can't even imagine it yet.

[Stage direction: Host asks about images from the James Webb Space Telescope.]

Host: Why don't we actually look at some of these images from James Webb? Okay. So we have something that Joe Biden released at the White House on July 11th last year, and it shows quite a few remarkable things. There's some stars with six legs sticking out, and that's just due to the wave nature of light, because light sort of bends around the hexagonal edges of our mirrors. But we knew about that, so stars are not that exciting right now. Then in the middle of the picture are some giant fuzzy galaxies, enormously massive, and we sort of knew they were there already. And so that wasn't so exciting, but we wanted to know exactly how massive and exactly where all that stuff is. And then in the background are little pink arcs, curved things that do not look like galaxies, but they really are. And so they are highly magnified and distorted images of very distant objects. And nature has given us lenses, extra lenses in space to magnify the more distant universe. And this is something that Einstein and predicted, and we never thought it would be useful, except in the most abstract way. So now what we see is sometimes two or three or four or five images of the same distant object, all stretched out and magnified. So this is a way to look farther back in time to see the details of the various first galaxies. So that's the coolest thing for the astronomer in that picture. So sometimes we even see that the early galaxy is filled up with little sparkly things. We call them globular clusters, like 100,000 stars that were presumably formed together. And now our big question is, well, which came first, galaxies or globular clusters? Did the universe make the little clusters first and then they joined together? Or did the galaxy form first and then break up into little clusters? So this is one of our generic questions of which came first, chickens or eggs or breadfruit? I don't know. Which brings me to another question about early galaxies. So there's a black hole, a giant black hole in every galaxy, just about. And so we know they're there because we see things orbiting around them. So we calculate that there's something immensely massive object in the middle. Sometimes they're very bright because material is falling in and getting compressed to enormous temperatures. And we can see that part. And now we want to know, well, which came first, the galaxy or the black hole? Did the universe start off with black holes all over the place? Or did it make galaxies first and then they made the black holes? So we've begun to observe black holes out there. We've even seen a few years ago black holes colliding with each other and joining together to make bigger black holes. This is with the James Webb? That was done with the LIGO observatory, which is here on the ground. And we've even more remarkably seen neutron stars colliding and making a bigger neutron star. And that has its own story to tell. Because, for instance, when you look at your ring, if you have a wedding ring of gold, And then we know that most of the gold in that writing ring came from neutron stars that collided and blew up and material came back out into space and was recycled. So this is a part of the most astonishing story about our own origins that were made out of not only recycled stars, but neutron stars that collided and blew up. And so our own personal story has got the most remarkable threads in it. I just want to ask you about this particular image, which has been referenced a lot in terms of understanding exoplanets and the composition of them. And perhaps you could speak to maybe what we've learned there and also what it may indicate in terms of life that we have maybe come across, not come across. I think the answer is the latter, but also what that maybe opens up for the future. Yeah, sure. So, yeah, everybody wants to know, are we alone? Yes. And if we're not alone, where are the neighbors? So I'll jump ahead to what I think the answer is. I think the answer is no, we're not alone. And I think life will occur quite frequently, but it will mostly be rather elementary. And when you look at the history of Earth, you see the history of the different forms of life growing. It's taken all of the entire history of the universe for us to turn up. So that does tell us that we kind of rare in history so probably life is everywhere that it could be which is perhaps in conditions like ours where there liquid water at about the right temperature But probably we not going to find the neighbors Similarly, that we're not in danger from the neighbors. So maybe we've got lots of unexplained things here on planet Earth, but it's not very likely to be space aliens. Something else that we don't understand instead. So what are we going to do about measuring? Well, of course, here in the solar system, we're sending out probes to land on Mars and visit other places where there could be life and sea. So on Mars, we're working to bring back little rocks that have the chance of having fossils in them. So that's really hard, but we're working on it. We're already putting the rocks in little caches to get ready to bring them home. We are sending probes out to orbit around satellites of Jupiter and Saturn where water is coming out. There are places where there's a liquid water ocean covered with ice. And there are cracks in the ice and the water comes out and you can see something. And so if we're lucky, we might find out there are organic molecules in those oceans. Fascinating. I would say maybe there's life under there. And so it gives us impetus to track it down and find out more. So then we get to what can we do about other planets around other stars? Can we find places that are like home, little Earths orbiting stars like the sun? So far, we don't know of any like that because it's a really hard observational problem. What we're doing at the web, we are looking at planets orbiting smaller stars that are called M stars. So these are very weak little stars. They're hardly as big as Jupiter, but they're warm enough to... Hardly as big as Jupiter. It's just funny with our sizes, tiny little humans. As a matter of scale, Earth is 8,000 miles across, Jupiter's 88,000 miles across, and the sun is about a million miles across. It's good framing, good reference. Roughly each one is 10 times bigger than the other. So yes, we're able to study planets around small stars because some of the time the little planet will go in front of the star and it'll block some starlight. So okay, now we know it's there. We can calculate its temperature and its size and whether it possibly hosts an ocean. Okay, now does it have an atmosphere? So yes, maybe. So look to see if any of the starlight's going through the atmosphere of the planet on its way to the telescope. And yeah, we can do this. And we have a pretty large catalog of large planets that do have an atmosphere with interesting molecules in them. And so the technique works. And now we're just now busy analyzing the small stars that have potentially small Earth-like planets. And I can't say that we're really surprised, but so far the little ones do not have atmospheres that we can tell. So we shouldn't be too disappointed because we didn't really expect it. But we still do really want to know. So what's next in this subject? Well, we need to build different telescopes. Tell me more about that. We are finishing up one now called the Nancy Grace Roman Space Telescope, and it will have an equipment to look for planets as direct images, a device called a coronagraph. So if we can get that to work, you never know, we might see some signs of more or less Earth-like planets. And the next one we're going to build is called Habitable Worlds Observatory. And so when we do that, we'll be able to see an image with a little dot next to the other big dot, and it'll be an Earth-like object around a star like the sun, which is a much more likely place to find signs of life. Because, of course, we've got one observation, which is us. Yeah. Here we are. So please look for another place like us. So we're building that, or I should say we will be building that because that's what NASA wants to build. The Congress wants to build it. National Academy of Sciences said to build it. Astronomers want us to build it. And I think the public wants us to build this because, oh, I sure want to know. We all want to know, are we alone? We want to know. I mean, let me ask you a tangential question, which is, there is this question, are we alone? Where did we come from? But then there are also all of these questions that impact maybe our day-to-day, right, or us understanding what we're building, engineering, science on the ground. A few things. One general observation is that we, NASA, take on incredibly hard engineering challenges, like going to the moon with people or building this great telescope. And then we say, yeah, we actually can design, build, and cooperate to build something incredibly hard and difficult, and it can work. So it should give us reason for confidence and optimism that when we take on other challenges like managing our own little planet, that we can do that. We also, of course, at NASA, we take pictures of the planet. We watch little Earth all the time. We have dozens and dozens of things looking down to map the circulation of the oceans, the clouds, and various atmospheric constituents like carbon dioxide. We see where it comes from. Methane, we see where it's being emitted from various sources on Earth. So we're providing the data that it takes to understand our little planet. Then some of the potential answers for how do we stabilize our planet and protect ourselves might have pieces of technology from space also. Some people are working on, well, can you generate electrical power and beam it down from space? Or can you block some sunlight with something in space? So there are lots of creative ideas, some of them might work. Yeah. Most of them probably too hard or won't work, but we can make up our minds sometime. Other thing that sort of generally observe is that we have exponential growth of problems and we exponential growth of capabilities. Like it used to be Moore's law about transistors. I was going to say semiconductors is kind of the... So we knew that just got bigger and better, faster all the time. And people don't really understand any of the details, but they just see that happens. And so we start off with, that can't be done. That's impossible. Then somebody invents something and then somebody wants some more. And gradually we invest our billions or trillions as it takes because there's a demand for it. And now we have a pocket computer that's far more powerful than we could have going to the moon with on the Apollo. So as an example, somebody heard this story. If you have a digital key fob in your car, it's more powerful than what we sent to the moon with on the Apollo astronauts. Is it? Is that true? Yeah, honest. So that tells you the power of exponential growth. You just wait a long time and invest trillions of dollars and something will happen. Yeah. So when we say, can we solve the engineering problems of little planet Earth? Can we manage our climate? Can we manage our resources? Can we manage pollution? Well, yes, of course. The capabilities to manage also grow exponentially with time. And so when you say, oh, it can't be done, it just means we don't know how it can be done. But if it's important enough, we will do it. I've been to science fairs quite a few times to see what the young people are working on. And in the physics and engineering, there is a really large fraction of the kids are working on batteries, engineering, energy supplies, pollution control, and resource management. So kids are already aware that's where the opportunity is. And our world is actually sponsoring the job. Yeah. Now, when I was only like 10 or 15 years ago that people were very confidently telling us that electric everything was either it's impossible or too expensive or it'll cost too much and we shouldn't do it. And now anybody that wants can buy an electric car. Exactly. We actually just did a podcast on not just electric cars, but electric boats, electric planes, electric school buses. Every week I get another aerospace engineering story that says we have electric airplanes coming. Oh, okay. So we don't know how to do it. Is not the same as we're not going to do it. And we don't know how to do it doesn't mean we can't afford it. It just means we are lacking of imagination and patience. We've already touched on this idea that there's just still so many question marks about this universe around us. Is there a specific question mark that, you know, you would just love to see solved in your lifetime? Just even out of personal interest, there's something that really gnaws at you. I guess the ones that are obvious, that already are recognized by thousands of scientists, cosmic dark energy, cosmic dark matter, they seem to be there. We can describe them mathematically. They seem to fit practically everything that we know, and we did not expect them. There was no sort of basic understanding of anything that said they should be there. So cosmic dark matter appears to be transparent. We shouldn't call it dark. We should call it transparent. There's a lot more of it than there is of ordinary matter, the protons and neutrons and atoms that you all see every day. So it's out there. It has been detected by its gravity. So back in the 1930s, we already had a hint that galaxies were spinning too fast, which means they're being held together by more gravity than you can find. You cannot find the stars to explain that amount of gravity. So something is weird. So it took from then until about 1980-something before we had a lot more evidence. And we can say, yeah, it's really there. Do we know what it is? No. We have been hunting in laboratories for decades. And darn it, there isn't a single thing that's ever said this is a good promising candidate. So that means it's a wide open mystery. Then we have the cosmic dark energy, which is something that in principle Einstein imagined. There's a place in his equations of the universe that could be called dark energy. But we thought, generally, astronomers thought that, well, that would never happen. So we imagined and believed that the universe expansion will be slowing down because gravity is pulling on things and will slow the expansion, which seems to be true up for the first roughly 10 billion years of the expanding universe, or 9 billion. And then it seems to be accelerating. Who asked for that? Well, it was discovered by people who are planning to measure the deceleration. And oh, there's something wrong here so they got a Nobel Prize for discovering the acceleration it's going faster and faster every year which means that if you were to come back in another say 100 billion years most of the galaxies that we know about would have receded from us so far away that we couldn't see them anymore so the universe will be in the process of appearing to empty itself out and if you imagine going far enough into the future with just one Milky Way left, all the other galaxies are gone, the evidence of the history of the universe might have disappeared from science. Oh, that's fascinating. Just to confirm though you saying it still exists it would just be so far away that we can detect it We too far away to see it Wow So anyway we are here at a particularly interesting time where we still have evidence and can still write the story and tell ourselves how did we get here from something What comes before the Big Bang? There is the Big Bang, and then you have all of this matter expanding, creating galaxies, etc. But it's hard for me to wrap my brain around this idea of what comes before it. Yeah, well, maybe that's because maybe there isn't anything for it. So the way I think about it is from the observer's perspective. Because what we see today is distant galaxies running away from us, and we see the cosmic microwave radiation that tells us what it was like when it was young. And we imagine running it backwards in our minds. Yes, like a play button, literally. Run the play button backwards. So the galaxies go crushing together. The stars are ripped apart. The temperature goes up and up. Eventually, the atoms are ripped apart. Even the protons and neutrons are ripped apart and separated into quarks. And then we picture this soup of quarks and leptons, they're called. And then we say, well, what came before that? And so we have a guess that there's something called an inflation field, a purely conceptual quantum mechanical idea. And we say, if this could happen in this particular way, then it would produce the expanding universe that we have today. And so it seems to hold up in the sense that there are a few predictions that it makes that we verified by observation of the cosmic background radiation. So when this was first proposed, I thought, well, that'll never work. We'd never know. But there is a little bit of evidence that this cosmic inflation story could be correct. But it's still pretty much a guess. So then you say, well, what could come before that? And what does the theory predict? So the theory predicts maybe there could be other universes. Erupting out of this inflation field, and we would never know they were existing. There could be billions or trillions or an infinite number of other universes according to this idea, and we'd never know. But because this is so much of a guess, we honestly can't tell you what came before that. Yeah. And then we get to,