Daniel and Jorge Explain the UniverseDaniel and Jorge explain Roger Penrose's Conformal Cyclic Cosmology and what it means about the origins of the Universe.
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Hey, Jorge, do you ever get the feeling that this has all happened before?
Well, this is our two hundred and fiftieth episode, so yeah, there's a sense of deja vu.
Yeah, but think a little bigger than that, Like you know about the whole universe?
You mean, like, has there been another universe before this one?
Yeah?
Or is our universe the first one?
I hope we're the first ones that would be special.
I don't know. I'd like us to not be the first, so the universe has had a chance to like iron out some of the kinks.
You don't want to be in season one of the universe.
No, it always takes a few seasons to figure it out.
You want to be the season finale or the series phenale. Well, you know, it's tricky because sequels are you know, hit or miss? Hi I am more. Hey, I'm a cartoonist and the creator of PhD comics.
Hi. I'm Daniel. I'm a particle physicist, and I'm the first generation physicist in my family.
Oh really, hopefully the last or maybe the last. How are your kids fitting about the whole thing?
Yeah? I think I might be the physics finale in this family.
Oh h, I am definitely a first generation cartoonists from Panama.
Well, there you go. You don't have to do what your parents have done.
Well, actually, my parents are pretty good artists as well, even though they're also engineers.
Awesome, but welcome to.
Our podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio.
In which we take you on a tour of all the amazing questions about our universe, how we will end, how it began, how it works right here daying in the middle of it. And on our tour of the universe, we stop and talk about how it works, why it works, and what we don't understand, hopefully leaving you with some understanding of your own.
Yeah, because there is a lot to understand in this universe. It's big and complex and old and possibly infinite, and it may not stop there with the universe, I mean.
Yeah, exactly. We have questions about how far the universe goes on, Does it wrap around on itself, does it go on forever? And we have questions about how long the universe will continue and where it came from, was there a beginning at all, or does the universe extend back forever in time?
Yeah, because we think of the universe as everything there is and ever has been, and ever will be. But there are a lot of theories in physics that maybe this is not the only universe. You know, there's ideas about parallel universes and multi universe and there's also ideas about other universe that may come to be or that have been before.
That's right. If you are used to the feeling that the universe has dwarfed us, that we are finding ourselves to be a tiny, cosmic spec on a vast, vast, unimaginably huge scale, then get ready to blow your mind at an even deeper level, because it turns out our universe may not even be everything. It may only be one of many universes.
Yeah, this actually blows my daughter's mind a lot. She's like, how can there be multiple universes? Is in the universe all that there is? And I think she's again, you know, carrying on my tradition of complaining about naming things in physics.
There you go, she's a second generation name complainer.
Yeah, physics name complainer. I'm so proud.
But it's a good point because often we define the universe to be like everything as we know it at that moment, and then when we realize, oh, there's more, we don't just redefine the universe to also include that. We're like, oh, let's call that another universe, and so it does get pretty awkward.
Yeah, well, maybe the universe is more like everything we could potentially reach at the moment, you know, like everything that exists with us.
Yeah, well, that's sort of like the observable universe is like everything that can influence us, everything that we can interact with because it has had time to send us light. So that's definitely one fair definition of the universe. But you could also imagine, hey, there's stuff going on out there that's not like within a sphere centered around my head. Shouldn't you also include that in the universe and then you can imagine forwards in time and backwards in time, and you know, it's nice to have a definition of the universe that doesn't center a human because it doesn't feel like we are sort of centrally important to the universe.
Right, Well, I like being the center of my universe.
And our listeners are the center of our universe. For sure. They are definitely important.
Yeah, everyone's special. There's this question of where the universe came from and what's going to happen to it? And I think more important is that question about where the universe came from, Like how can so much stuff just come out of nothing?
Yeah? And it's a really fun exploration because you look at the way the universe is now you say where did this come from? And okay, cool, we understand how the Solar system formed, Well, where did that stuff that made the Solar system come from? And it's this cycle of stepping backwards and further and further into the depths of time and wondering like how far can we go to understand the origin of everything? And is there a final answer or could you go forever?
Right?
Yeah? Because we're not used to this idea of something coming from nothing, right, I mean, it would be weird if the universe suddenly appeared out of nothingness.
Yeah, well, it would be weird if the universe wasn't weird. Right. Basically, everything we've learned about the universe shocked and surprised us. So if we found an answer and just went like, oh, yeah, that kind of makes sense, that would be kind of surprising.
Mmm.
All right, So at some point the universe sort of came into existence, was created in the Big Bang. But I guess a big question is kind of what happened before the Big Bang and where did the universe come from? And so there are a lot of theories out there about what could have happened or what happened, but none of them are nailed down, right.
That's right. There's still a lot of speculation. We don't really know what happened before the Big Bang, and we might not ever know, and so there's a huge variety of theories out there that explain what could have happened. Maybe there was nothing, maybe there was a big crunch that preceded the Big Bang. But today I wanted to talk about one really specially interesting theory that gained popularity recently because it's proponent won a Nobel Prize last year.
Mmmmm, Yeah. This is a theory that talks about the universe as a big cycle, right, like maybe there were other universes before our universe.
Yeah, exactly. This theory sees the universe as big cycles, but not the kind you're probably familiar with. You've probably heard of the theory that the universe goes through a cycle of bangs and then crunches, and bangs and then crunches. This is a totally different idea that has a cyclic cosmology at its heart. Right.
So today on the podcast, we'll be asking the question what is the conformal cyclic cosmology theory? All right? So this is not the usual big bank to big crunch universe theory. You're saying. It's different.
It's different. It goes for the cycle approach. It says, you know, let's sweep away this question of whether there was a beginning by saying there was never a beginning. There's an infinite number of cycles. But it doesn't link up big crunches to big bangs. It's a totally different idea, a little bit more bonkers and super fascinating because it suggests that you might be able to see an imprint of the previous universe somehow left on our universe.
Well, let's maybe catch up our listeners, because the idea they might have heard about is that the universe, you know, came out of a big bang, out of a really small space. Then it was huge. It exploded basically in the big Bang, and then after you know, maybe trillions of years, it collapses back down into a big crunch, which then triggers another big bang for another universe, kind of like Season two or a sequel to the Universe. And then that the universe explodes and expands, and after trillions of years it crunches back down again, and so on and so on at infinitum.
Right, mm hmmm.
And so that's the basic idea that people usually talk about when they talk about cycles of the universe.
Yeah, exactly. So that's the typical idea, but today we're going to explore a different one.
Yeah, So, as usual, Daniel went out there to ask people on the internet if they had heard of this new theory about universe cycles.
That's right, So thank you to everybody who shared your speculation, and if you are willing to answer random questions from me online for us to use on the podcast. Please write to us to questions at Daniel and Jorge dot com.
So think about it for a second. Have you heard of any theories about the universe cycling over and over again. Here's what people had to say.
Okay, you will clearly just say birds to get to know, but I will try to give you a guess anyway. Cyclic cosmos could mean it is something about the form of own universe, so instead of being infinite, it could be somehow bent in itself so you would never reach an edge but just start over. Or it could be about its growth and its development, like there could be a big crunch at the end of the life cycle followed by another big bang and so on.
This makes me think of the theory that I've heard that the universe keeps being created over and over again, so it grows and grows and grows and then becomes a black hole, and then the black hole creates its own universe in a sort of big bang like event. And so that's what makes me think of And since the word conformal is in there, I'm guessing maybe every universe is the same over and over again.
I think it has something to do with the cycles that we see in the cosmo, like the births and the deaths of stars and galaxies.
I'm not sure, but I think it might have to do with like the universe cycling between a big bang and a big crunch.
All right, it sounds like people have heard about this general idea of crunches and banks banks banks, bang guy bangies.
Yeah, and one of the answers seems to be following in your tradition of complaining about the name. You're just sticking words together. That's fair.
Both English professors and physics professors are guilty of that. But yeah, so I guess let's talk about this idea of inflation in the early universe. I mean, where did this idea that there could be a cycle to the universe come from? And we thought of it first.
Yeah, the origins of it come from the realization in the last few decades that the universe might have had some sort of starting point. Remember, like one hundred or so years ago, people looked at its stars and they didn't see the stars moving by eye, and they figured, hey, I guess the universe is just static. It's just like a bunch of stars hanging out in space, and it was very natural for people to think that it could have always been that way. It looks pretty old, after all, and so why not imagine it lasted forever. But then when Hubble discovered the universe was expanding, that sort of changed the story. It suggested that the universe is changing and couldn't always have looked the way it does. And then when you extrapolate backwards in time, you think, well, if it's expanding now, then it should have been contracting. As we go backwards in time, that takes you back to something that feels sort of like a beginning, a point when the universe is much much more dense, yeah.
Much more raw, right, Like the whole entire universe, every star in galaxy you we ever see, was in a really small space about fourteen billion years ago, and everything was just like a state of plasma, right, like just raw energy.
That's right. When the universe was much younger, it was hotter, and it was denser, and so things work differently, you know, just like there are different phases of matter that you're familiar with. Water, it can be ice or liquid or gas. The universe itself sort of has phases and when stuff is much much denser, there are different rules of physics that emerge, and so like the laws of physics, they don't violate the ones we have now, but they sort of operate under different regimes. Different laws emerge, and so it was very different from the way we imagine it now, and we have some direct evidence that that actually existed. This isn't just a calculation in people's minds. We've seen light from that early universe plasma arriving at Earth. It's called the cosmic microwave background radiation, and it's sort of like the last glow from the Big Bang.
Yeah, so we can see light that kind of escaped that plasma right before it basically evaporated, right.
Yeah, exactly, and that plasma sort of faded out and cooled off and turned into neutral atoms, and then we can see that light because it's still banging around the universe. The universe sort of became transparent at that moment. So that was like a really exciting piece of evidence when people saw the microwave background radiation, this is several decades ago, really confirming that that thing actually happened, that the universe once was a big hot plasma and that's very different from the way it is today.
Right, Well, it was a hot mess back then, and it seems like it's a hot mess right now.
We're constantly on the edge of catastrophe.
But there are a lot of things we don't understand, like what happened before that big bang, with that big pod ball of plasma.
Yeah, that hot ball of plasma is an exciting threshold to reach. We're looking back fourteen billion years into the history of the universe, but you know, we want to probe deeper. We want to know where that ball of plasma came from, what explains how that got there, and what made that. You know, we want to keep stepping this ladder backwards in time to understand really what was going on. And the way to do that is to ask more questions, to say, like, do we understand the way that ball of plasma look? Can we explain it? Do we understand, for example, all of the ripples in it? Because the light we see from that ball of plasma is not all the same temperature. There's some variations up and down in that light.
Yeah, and so our prevailing theory about what happened during those first moments of the universe is called inflation, right, and that sort of explains kind of what happened since the Big Bang, but it doesn't quite explain what happened before.
As we go backwards in time from the cosmic MicroID background radiation, we add this step where the universe expanded very dramatically by a factor of ten to the thirty in ten to the minus thirty seconds, and then answers a lot of the questions that we have about the wiggles and the cosmic MicroID background radiation the temperature of the universe. And we have a whole podcast episode about that you can dig into. And so that's really cool. That's in a huge advance, sort of like taking us yet further back. But you know, we want to go to time equals zero, right. Inflation takes us to time equals ten to the minus thirty, but it doesn't explain how that got there, right. We want to take the next step up that ladder backwards in time. And that's the question that a lot of these theories are probing, is trying to explain, like, how did you get to inflation? What created the situation that made this universe inflate in such an insane way?
Yeah, because we don't really know what causes that inflation, right, I mean, it's something relterally costs the universe to.
Explode, something really made the universe explode and expand in this crazy way, and we are just the beginning of understanding what that might be. We're like putting together ridiculous sounding theories to potentially explain how that might work. One of them, for example, is that there was a field, a new field that filled all the universe. You're familiar with, for example the electromagnetic field or gravitational fields or the Higgs field. Now imagine a new field, and it's called the inflaton field, just to have a ridiculous name, and it's some new kind of matter which expands super duper rapidly and for some reason at some point decays into normal matter. And that's one idea for like nucleating our universe, that the universe was filled with this infloton field, which at some point decayed into real matter, which then became our universe. But of course that just you know, begs more questions like well, where's the infoton field come from? And what made that? And so you could go on forever if you keep your sort of stacking explanations on top of each other, which is why one sort of attractive conceptual alternative is to try to sort of loop it back to the end of the universe and make your idea be a cycle which sort of explains itself.
Hmmm, all right, well, let's get into this interesting new theory, the conformal cyclic cosmology theory by Roger Penrose, and let's talk about whether or not it could actually let us see a little bit of the previous universe. But first, let's take a quick break.
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All right, we're talking about a small question. You know, where did the universe come from? And has it always been here? And we talked a little bit about the idea of inflation that the universe somehow expanded really quickly at the beginning of time or at a tequals zero as we know it. But the question is what happened before T equals zero time equals zero in the universe? Was there a previous universe or did the universe come out of nothing? And there's this idea, Daniel, that maybe before our universe expanded, there was another universe that maybe crunched together. And that's kind of I think what a lot of people have heard about. But you're saying that there's problems with this idea.
Yeah, Well, one problem with that idea is that it starts from a singularity. You know, you project backwards in time, our universe gets more and more dense. Eventually it gets infinitely dense. That's the singularity.
You know.
I think a lot of people in their minds when they talk about the Big Bang, they're imagining a very dense dot of matter in an empty, infinite universe. But instead you should be imagining a universe filled with stuff. But that stuff is of infinite density. So the Big Bang, as we imagine it, sort of happened everywhere all at once. It's a question of density rather than a question of location and matter exploding into empty space. And the problem really is that singularity. The singularity is not a physical thing. It's not something that we can understand it. It reflects a breakdown in our theory. General relativity tells us if you sort of follow its laws naively, that things get denser and denser, and then the curvature gets infinite as the density gets infinite. But that's not something we can deal with, we can grapple with, Like general relativity fails when the curvature gets infinite. So if you want to connect our universe to a previous universe by saying it went through singularity, then that's kind of a problem because the singularity feels sort of like nonsense. It feels like when a theory is failing, when the theory needs a new idea.
H Well, it seems like maybe the real problem is that this big bang and big crunch idea requires you to have a big crunch, right, but we don't know if the universe will actually come back together to create a big crunch.
That's right, You need some mechanism to reverse what we see happening now. What we see happening now is that the universe is expanding, and that expansion is accelerating. It's happening faster and faster, so our universe certainly doesn't look like it's heading for a big crunch. On the other hand, we have no idea what's causing that expansion to accelerate. There's some mechanism there that goes by the name of dark energy, but we don't understand it, so we don't know whether it will continue. Turned on about five billion years ago, and it might turn off, it might turn around. So we don't necessarily see a big crunch happening in our universe, but we also can't really rule it out because we just don't understand the basic mechanisms at play. But you're right, if you want to have a big crunch, something's got to do the crunching.
Yeah, And we kind of had this idea before we knew about the accelerating expansion of the universe, Like before it made sense that you know, the universe would kind of expand and then gravity would win out at the end and the universe would contract and collapse back into a singularity perhaps, and then another universe would come out of that, but again, that requires you to have a big crunch. And what happens if you can't really have a big crunch? Does that mean that, you know, we can't have any more universes, like we're the last one maybe.
Yeah, Well that's where Penrose's idea comes in. He has this concept for allowing cycles even if the universe never crunches back. That's sort of the heart of his idea.
Hmm, right, because well that would be the only thing that could work at this point, right, because if we never have a big crunch, like if a big crunch is not in our future or any other universe that have was created like ours, then this idea of a big crunch to a big bang can happen.
Yeah, exactly. You can't go from crunch to bang if you don't go to the crunch.
So there's two possibilities. It seems like either we're the only and last universe because we're going to expand out into nothingness. Or maybe there's a clever new idea that less has come up with a new universe out of this infinite expansion.
Yeah, and that's Penrose's idea. He says, let's think about the very very end of the universe and try to connect that, try to loop that back to the beginning of the universe without going through a big crunch. And what he ends up doing is sort of like a weird mathematical trick, which might be physical, but it sort of blows your mind. It's pretty cool idea.
So it is the idea that it looped back to the beginning of our universe or to the beginning of a different universe.
The idea is that it would begin a new universe. And here's the basic concept. You think about the very very far future of the universe. We're talking like ten to the one hundred years. What's our prediction for how our universe.
Will look then ten to the one hundred years, ten to the one hundred that's like a one with one hundred zeros.
It's a lot of years.
It's like more than trillions. It's like bazillions.
I don't think we've even named those scientific prefixes. You know, if the Universe is a television series, we are like still in the opening credits of episode one.
Right, because even a trillion years is like one ten to the twelve, this is ten to one hundred.
Yeah, this is ten to the one hundred. So it's just a ridiculous number, and you'll understand why in a minute. Because he wants to get to the point when the universe is smooth again. He wants to wait for all the black holes to die. So the current trajectory for our universe if nothing changes with dark energy, is that everything is getting pulled apart. But you have these local gravitational clumps like our galaxy and our solar system. So those things will eventually collapse gravitationally, forming black holes, and these black holes will get really really far apart because of dark energy. Well, what happens to a black hole? Do black holes live forever? We actually know that they don't. Write Hawking radio is a way that they can give off little bits of energy. Now, really really massive black holes amid a very very small amount of Hawking radiation. So he's thinking in the deep, deep far future, when you form all these black holes, they get separated by dark energy, and then they leak their radiation back out into the universe. They have to wait for them all to die. So the end of our he calls them eon, is when all of our black holes sort of just turn into radiation.
They basically evaporate it into photons or what.
Well, black holes evaporate into all kinds of things exactly. They can evaporate into electrons or into other kinds of quarks or into photons or whatever. So they got to give up all of their light. And then he's imagining this universe as sort of smooth again, and he's trying to make a connection between the end of our universe and the start of the next universe. And the connection he makes is like, well, our universe started out kind of smooth before, like quantum fluctuations and everything and inflation blew it up into actual interesting structure. So if the end of the universe sort of like smooth field of radiation, he's going to try to connect that to the beginning of the next universe, which also starts smooth.
Hmmm.
I feel like it's a little different because you know, our universe that far into the future sounds kind of cold. Yeah, it might be smooth, and it might be you know, kind of random and homogeneous, and there's electrons and quarks flying around, but things are still pretty discreete Like things are in the form of electrons or quarks, right, It's not like pure energy like we think of at the beginning of our universe.
Yeah, exactly, the density feels different. And here's where the mathematical trick comes in. It turns out that if our universe has only photons in it, or more specifically, only massless particles in it, then you can change the length scale of the universe without changing any of the physics. You can say, what used to be a light year is now a millimeter, and all the physics will work the same, All the massless particles will operate the same way they had before. They won't notice.
What, Yeah, I thought particles had kind of like a minimum distance to them.
Well, these particles we don't think of as having a size, right, We don't think of the photon as having like a physical extent to it. Just think of it as like a little blip in the field. And these fields, at least the massless fields, have this weird property that you can scale them by a number and nothing will change. All the physics will be the same. It's sort of like if we just changed all the rulers and made everybody smaller. Nobody would notice the difference, right, all of a sudden, we're all much tinier than we were before, but we also changed the rulers, so nobody can tell. If the laws of physics are invariant to that kind of transformation, then you wouldn't notice the difference. So he noticed this about the universe very specifically that only has massless particles in it. Hmmm, you can do this and not change anything. It doesn't work if there are any particles that have mass.
Right, But it sounds like we skip the step though, Like how do we go from black holes evaporating into electrons and quarks to now everything just being photons?
Yes, very good point. He did skip a step. But you know, the way these theoretical explorations work is like, hmm, that seems like an unsolvable problem. I'll put it on the shelf for now and get back to it.
What what do you mean. I mean because we talked about how an electron will might never decay, right.
Yeah, exactly. He's got a problem with electrons. You know, like most particles in the universe top quarks, higgs bosons will decay and go down to lighter and lighter particles, and there's only a very small number of particles in the universe that are stable, and so the photon, for example, is stable. You can have a photon, it can hang out forever, it can fly across the universe. But also electrons are stable. We don't know of any way for an electron to turn into something lighter.
Right, or quarks? Right, don't quarks also last forever, like if they're in a proton.
Yeah, quarks can last forever. They can turn into other stuff. But basically quarks can last forever. Protons, however, might decay. Right, We don't know. Protons we think last forever. We've never seen one decay, but there are some theories in which they can decay into lighter stuff. But you'd be stuck with some massive particles. And so to go from a universe that has like photons and a few electrons in it to universe with just photons. He has to invent some sort of new physics thing. And he calls it the Arabon field that turns all these massive particles somehow now into photons.
He calls it the wave my hand feet a field.
It's very hand wavy. But you know, Penrose is a big thinker. He's like trying to get the big structure right. He's like, you know, can I somehow work out this bigger problem. Then I'll come back in and patch up these other holes and see if I can find something that fills them in m.
So he's saying, let's say that eventually, maybe in a long time, all matter particles decay into massless photons or massless particles. Right, that's the leap of faith here, And then that creates a state that's basically pure energy, right, in which case it sort of is scaleless, like a millimeter and of a light yeer, make no difference between the two.
Exactly, it's scaleless. So you can change your scale and nothing is.
Different because things that don't have mass are scaleless.
Yeah, exactly. A photon sees the whole universe anyway as shrunken to a point. Right, it's moving at the speed of light, and so distance doesn't really make any difference to the photon. See, the whole universe is length contracted anyway, It doesn't matter ten light years, one light year, one millimeter mm.
Like space itself, the idea of distance doesn't make sense anymore.
Yeah, or at least if you scale everything the same way, nothing changes. And so he says, well, let's take this huge expanded universe and then just sort of like redefine it to be a very dense, smooth universe, and boom, you have the conditions that were at the beginning of our universe. Right at the beginning of our universe there was a state. We don't understand it, but it's postulated that it was there, and it was very very dense with energy and it was very smooth, and that that then, you know, expanded to turn into our universe. So the image of Penrose's universe is like every universe is a further expansion than previous one. It's like this endless series of expansions. We just redefine the terms. Wow.
But then each new universe is bigger than less.
Yes, by a lot exactly. We just keep changing the scale. So the whole previous universe would be contained within like a tiny dot of our universe, and our entire universe would be contained within a tiny dot of the next one.
Whoa kind of like a Russian doll put at a ginormous.
Scale, yes, and going on forever.
Ah, backwards and forwards in time.
Backwards and forwards in time exactly. And so he gets this sort of like cyclic structure where the end of the universe connects to the beginning of the universe. But it doesn't have to have a crunch, right, It doesn't need to explain the crunch. He needs lots of other stuff. He's got to explain to me it work, but he doesn't need the crunch. And there's a big advantage there because the crunch destroys all the information. Like, if there was a crunch, then it went through singularity and any information about that previous universe is gone, it's destroyed. But if this series of infinite expansions is remapping and then expansion, then you could find traces of the previous universe in our universe.
Right, it's kind of like a more like a blooming universe rather than a cyclic universe.
Yeah, exactly. It's pedals within pedals within pedals, right, each one nested within the previous one.
Yeah, like an infinite fractal or something.
Yeah, it's like a fractal universe theory. It's pretty cool, all right.
Well, let's get into whether or not this theory even makes sense. It may not, and talk about whether or not there is evidence out there in the cosmic microwave background radiation to support this theory. But first, let's take a quick break.
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All right, we're talking about the infinite universe as a Russian doll theory. This is Roger Penrose's conformal cyclic cosmology theory that says that the universe came from another universe expanding infinitely out, and that after our universe expands almost infinitely out, another universe will grow from that state of pure energy.
M hm.
You should meagine like a trumpet with its horn, and then another one coming out of its horn, another one coming out of its horn, and this is just like endless cycle of growth.
Hmm.
So I'm curious, or hey, what would you have named this theory if you could come up with it?
The trumpet theory? He the ruck and doll theory. I don't know. I think cycle though, is kind of a weird name though, because it's not quite a cycle, right, It's more like a blooming universe theory maybe, yeah, big bloom. There you go.
It doesn't run the same forwards and backwards, right, It doesn't have that sort of time symmetry to it. It definitely just keeps expanding as time goes forwards. So the thing I like about the big Crunch Big Bang idea is that it does have some sort of time symmetry. You can imagine running things backwards in time and it would look sort of the same.
Hmmm. All right, so let's talk about whether this makes sense. This is something that the physicists are actually considering. Like, I know he won a Nobel Prize, but he didn't win a Nobel price for this theory.
No, there are a lot of things named after Penrose and physics, Penrose diagrams, Penrose tilings, and he recently won a Nobel Prize for thinking about black hole. So definitely a smart guy. But a lot of these really smart physicists get famous for a few ideas, and those few ideas are like a small fraction of all the ideas they toss out there and see which ones stick. So often they come up with a lot of crazy, bonkers ideas that you know, never really hang together. So this is not one that's in the mainstream of cosmology, Like, this is not one that a lot of people are working on. And Penrose proposed in about twenty and twelve in a paper in a book, and it got a lot of attention for a while also because he claimed he could actually see the evidence of a previous universe.
Mmmmm, so meaning it sort of works mathematically like if we can get the universe to this state of pure energy without any massive particles, then the math does kind of suggest that you could get another universe out of that. Yeah, so that's what made it interesting.
Yeah, Mathematically, there is an idea there that you can map the end of our universe to the beginning of our universe that have a very similar sort of structure to them. So there is a cool idea there. But you know, you've got to stick in something that makes the universe turn into just photons, and that's not something we understand at all. And then you also got to look for the evidence of it. You know, the best theories are ones that make predictions and say, if this is true, there would be some sort of like indistinguishable mark in the universe. That's what was so exciting. For example, about the cosmic microwave background radiation. It was predicted. People said, well, if there was a big bang, then there should have been this moment when the universe went from opaque plasma to transparent neutral ions, and we should be able to see it. And so that's pretty awesome to actually go out and find that fingerprint that you predicted. So then Penrose, you know, he rose to this challenge and he made predictions for what he said should be out there evidence of previous universes.
Right, and so he looked into the cosmic microwave background radiation, and what did he see? Did he see evidence for this blooming universe theory the big bloom.
He actually did. He claimed very significant evidence of previous universes in the cosmic microwave background radiation. And the way he thought it would look are these things called Hawking points. And Hawking point is where there was a huge super massive black hole in the previous universe which then evaporated, but a left sort of a mark. It's a place in that universe where there's maybe more radiation density than others. It's like a non smoothness in the previous universe because you had so much radiation from this really massive black hole, and then when you map it back to the beginning of the universe, it sort of gets squeezed down. You squeeze all that radiation together and it makes basically a little hot spot in the next universe. So every super massive black hole should leave like a little hotspot in the next universe, and that should be seen in the cosmic microwave background radiation. You should get like a little bit of a warm spot in that radiation.
Like a little scar kind of from the previous universe.
Yeah, like a little scar. And so the cosmic microwave background radiation, you know, it's data that's out there, it's public. Anybody can go download it and look at it and analyze it. It's complicated, you know, you've got to really be an expert to understand what you're seeing. But when Penrose put out this thing, he also put out of paper claiming six sigma discovery of twenty Hawking points in the cosmic microwave background radiation. That means that he was claiming to see something that was not just like random fluctuations of noise. Six sigma means that he's like ruled out the fact that this could just happen by a random chance. He was very convinced he was actually seeing these Hawking points super massive black holes from a previous universe.
Mmmmm, all right, So the idea is that you know, in the previous universe there probably were a lot of super massive black holes or are you saying there was just one?
No, they were probably a lot.
Yeah, yeah, because everything would eventually crunch into a black hole, and those black holes might crunch together. And so you in the previous universe, if you run time long enough you get these super massive black holes. And he's saying that even these kind of super massive black holes would survive this process that makes everything massless, or some evidence of them would survive, and that would survive also this reblooming of the universe.
Yeah, exactly. Their radiation would leave like a little warm spot when the universe blooms to the next eon, and because they're so massive, that would be enough radiation that it would sort of leak through a little bit. Remember that's maybe the fate of every galaxy. Every galaxy has at its heart a big black hole, and the reason that we haven't fallen into that black hole is just because we have enough sort of speed to zip around it the way the Earth zips around the Sun. But eventually we can lose that speed, we can radiate off energy or collide with stars, and the fate of basically everything is eventually to fall into that black hole and make it even more massive. So the whole Milky Way will eventually be a super massive black hole and then evaporate its energy through Hawking radiation.
Yeah, so in this theory, you don't need perfect smoothness in the universe to retrigger a new universe. You can have these kind of hotspots.
You can have these little hot spots. What you need is the universe only filled with massless particles, and then you can map it back down to a new universe. So this is pretty exciting. You're like, wow, Penrose claims he sees like an imprint of a previous universe. That's sort of amazing, right, But but of course we don't think we live in these universe Nobody takes this theory seriously. And the reason is that other people went and looked at the data. They downloaded it and they analyzed it. And there are a lot of experts out there who really know what they're doing, and they didn't see these things.
They don't see these circles that Penrose claims he sees with six sigma confidence.
Yeah, exactly. He claimed he saw them, and they analyzed them and they didn't see them. And then multiple other groups analyzed them and they also didn't see them.
What like, isn't the data there? How can some people see something and others not?
Well, it depends on how you're analyzing the data. You know, there's a lot of steps involved in the assumptions you're making and how you're calculating these things, and for a while nobody could reproduce Penrose's team's results, and then people found the mistake. Turns out he had run some sort of special version of an analysis code that nobody else agreed was really accurate, and he wasn't really comparing what everybody understood to be the predictions for hawking points to the actual data. It sort of felt a little bit cooked up.
Mmmm, all right, So then maybe what he saw wasn't there. But that doesn't mean I guess that the theory is necessarily wrong, right.
It doesn't mean the theory is wrong. And in the last decade or so he's come up with other predictions, you know, he said, oh, well, if my theory is right, then we should see some interesting pattern of gravitational waves or various other predictions. So he still believes in it. He's still talking about it, he's still excited about it. He still makes up ideas for how we could test it. And you're right, it's not something we've ruled out. You know, maybe that we don't see those hawking points, but maybe we just haven't looked, or maybe they're too subtle, or maybe there are other ways to test this theory. And this is a challenge for a lot of these theories. You know, many cosmologies don't predict things that we can test. They're talking about things that happened a long time ago at really tiny scales, and it's hard to come up with an experiment to test these things. So kudos to him for coming up with the new cosmology and a way to test it. That's pretty awesome.
Yeah, And it's sounds like we have a lot of other ideas lying around, right, Like we have nose what happened before the Big Bang. There's no real theory, and this theory of a big crunch may never happen or may never have happened.
Yeah, and may not be testable. So it's definitely a time when people should be creative and it should be out there exploring and creating new ideas and thinking broadly about what could explain the universe that we see.
Right, It's time to go big, think creatively.
Yeah. And one of my favorite quotes from Penrose about this theory is when he says, and I quote, of course the theory is crazy, but I strongly believe that we have to take it seriously.
He's like, it's a crazy theory. But it's also a crazy universe.
Exactly, it's a crazy universe. It's gonna need a crazy explanation. And also we got to be creative. You know. Sometimes you come up with a bad idea, but it stimulates other better ideas in other theorists, So you shouldn't just you know, like only share your totally finished ideas as A marketplace is a conversation of ideas. That's how we get to these answers.
Right, yeah, physics marked, it's where you go and buy ideas off the shelf.
I think of it more like a salon, you know, sipping tea and chatting about ideas about the universe.
All right, Well that's Roger Penrose's conformal cyclic cosmology, and it kind of gets you to think about where the universe came from and whether distance really means anything at all, because apparently it doesn't.
If you're a photon, then it certainly doesn't. You're happy to rescale an entirely enormous inflated universe down to a tiny, little dense universe to a photon. A millimeter is the same as a light year, exactly. It takes the same amount of time so if you're building a house for a photon, you know, don't worry so much about getting the measurements right.
Yeah, and if you can save yourself a lot of a building equipment, just make it a millimeter big. All right. Well, that gives us all a lot to think about, and to think about our origins and where we came from, and could there have been other universes before hours? Like maybe are we season two hundred and seventy seven of the Universe series.
When the writers finally figure out what's going to happen to these characters.
When we jump the shark twenty universes ago. All right, 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. 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 digesters 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.
There are children, friends, and families walking, riding on passing the roads every day. Remember they're real people with loved ones who need them to get home safely. Protect our cyclists and pedestrians because they're people too. Go safely. California. From the California Office of Traffic Safety and caltrans.
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