Speaker 1: Hey, Jorgey, do you ever get the feeling that this
Speaker 1: has all happened before? Well, this is our two and
Speaker 1: fifty episode, so yeah, there's a sense of deja vu. Yeah,
Speaker 1: but think a little bigger than that, like you know
Speaker 1: about the whole universe? You mean, like, has there been
Speaker 1: another universe before this one? Yeah? Or is our universe
Speaker 1: the first one? I hope we're the first ones that
Speaker 1: would be special. I don't know. I'd like us to
Speaker 1: not be the first, so the universe has had a
Speaker 1: chance to like iron out some of the kinks. You
Speaker 1: don't want to be in season one of the universe, No,
Speaker 1: it always takes a few seasons to figure it out.
Speaker 1: You want to be this season finale or the series finale? Well,
Speaker 1: you know, it's tricky because sequels are you know, hit
Speaker 1: or miss? Hi am or Hey, I'm a cartoonist and
Speaker 1: the creator of PhD comics. Hi, I'm Daniel. I'm a
Speaker 1: particle physicist, and I'm the first generation physicist in my family.
Speaker 1: Oh really, hopefully the last or maybe the last. How
Speaker 1: are you kids feeling about the whole thing? Yeah? I
Speaker 1: think I might be the physics finale in this family.
Speaker 1: I am definitely a first generation cartoonists from Panama. Well,
Speaker 1: there you go. You don't have to do what your
Speaker 1: parents have done. Well, actually, my parents are pretty good
Speaker 1: artists as well, even though they're also engineers. Awesome, but
Speaker 1: welcome to our podcast Daniel and Jorge Explain the Universe,
Speaker 1: a production of I Heart Radio in which we take
Speaker 1: you on a tour of all the amazing questions about
Speaker 1: our universe, how we will end, how it began, how
Speaker 1: it works right here daying in the middle of it,
Speaker 1: and on our tour of the universe, we stop and
Speaker 1: talk about how it works, why it works, and what
Speaker 1: we don't understand, hopefully leaving you with some understanding of
Speaker 1: your own. Yeah, because there is a to understand in
Speaker 1: this universe. It's big and complex and old and possibly infinite,
Speaker 1: and it may not stop there with the universe, I mean, yeah, exactly.
Speaker 1: We have questions about how far the universe goes on,
Speaker 1: Does it wrap around on itself? Does it go on forever?
Speaker 1: And we have questions about how long the universe will
Speaker 1: continue and where it came from, was there a beginning
Speaker 1: at all? Or does the universe extend back forever in time? Yeah,
Speaker 1: because we think of the universe as everything there isn't,
Speaker 1: ever has been, and ever will be. But there are
Speaker 1: a lot of theories in physics that maybe does. It
Speaker 1: is not the only universe, you know. There's ideas about
Speaker 1: parallel universes and multi universe, and there's also ideas about
Speaker 1: other universe that may come to be or that have
Speaker 1: been before. That's right. If you are used to the
Speaker 1: feeling that the universe has dwarfed us, that we are
Speaker 1: finding ourselves to be a tiny cosmic spec on a vast, vast,
Speaker 1: unimaginable huge scale, then get ready to blow your mind
Speaker 1: at an even deeper level, because it turns out our
Speaker 1: universe may not even be everything. It may only be
Speaker 1: one of many universes. Yeah. This actually blows my daughter's
Speaker 1: mind a lot. She's like, how can there be multiple universes?
Speaker 1: Isn't the universe all that there is? And I think
Speaker 1: she's again, you know, carrying on my tradition of complaining
Speaker 1: about naming things in physics. There you go, she's a
Speaker 1: second generation name complainer. Yeah, physics name complainer. I'm so proud.
Speaker 1: But it's a good point because often we define the
Speaker 1: universe to be like everything as we know it at
Speaker 1: that moment, and then when we realize, oh, there's more,
Speaker 1: we don't just redefine the universe to also include that,
Speaker 1: we're like, oh, let's call that another universe, and so
Speaker 1: it does get pretty awkward. Yeah, well, maybe universe is
Speaker 1: more like everything we could potentially reach at the moment,
Speaker 1: you know, like everything that exists with us. Yeah, well
Speaker 1: that's sort of like the observable universe is like everything
Speaker 1: that can influence us, everything that we can interact with
Speaker 1: because it has had time to send us light. So
Speaker 1: that's definitely one fair definition of the universe. But you
Speaker 1: could also imagine, hey, this stuff going on out there
Speaker 1: that's not like within a sphere centered around my head,
Speaker 1: shouldn't you also include that in the universe. And then
Speaker 1: you can imagine forwards and time and backwards and time,
Speaker 1: and you know, it's nice to have a definition of
Speaker 1: the universe that doesn't center a human because it doesn't
Speaker 1: feel like we are sort of essentially important to the universe,
Speaker 1: right Well, I like being the center of my universe,
Speaker 1: and our our listeners are the center of our universe.
Speaker 1: For sure, They're definitely important. Yeah, everyone special. There's this
Speaker 1: question of where the universe came from and what's going
Speaker 1: to happen to it? And I think more important is
Speaker 1: that question about where the universe came from, Like how
Speaker 1: can so much stuff just come out of nothing? Yeah?
Speaker 1: And it's a really fun exploration because you look at
Speaker 1: the way the universe is now you say, where did
Speaker 1: this come from? And Okay, cool, we understand how the
Speaker 1: solar system formed, Well where did that stuff that made
Speaker 1: the Solar system come from? And it's this cycle of
Speaker 1: stepping backwards and further and further into the depths of
Speaker 1: time and wondering like how far can we go to
Speaker 1: understand the origin of everything? And is there a final
Speaker 1: answer or could you go forever? Right? Yeah, because we're
Speaker 1: not used to this idea of something coming from nothing, right,
Speaker 1: I mean, it would be weird if the universe suddenly
Speaker 1: appeared out of nothingness. Yeah, well, it would be weird
Speaker 1: if the universe wasn't weird. Right. Basically, everything we've learned
Speaker 1: about the universe shocked and surprised us. So if we
Speaker 1: found an answer and just went like, oh, yeah, that
Speaker 1: kind of makes sense, that would be kind of surprising.
Speaker 1: All right. So at some point the universe that have
Speaker 1: came into existence was created in the Big Bang. But
Speaker 1: I guess the big question is kind of what happened
Speaker 1: before the Big Bang and where did the universe come from?
Speaker 1: And so there are a lot of theories out there
Speaker 1: about what could have happened or what happened, but none
Speaker 1: of them are nailed down, right, That's right. There's still
Speaker 1: a lot of speculation. We don't really know what happened
Speaker 1: before the Big Bang, and we might not ever know,
Speaker 1: and so there's a huge variety of theories out there
Speaker 1: that explained what could have happened. Maybe there was nothing,
Speaker 1: maybe there was a big crunch that proceeded the Big Bang.
Speaker 1: But today I wanted to talk about one really specially
Speaker 1: interesting theory. They gained popularity recently because it's proponent one
Speaker 1: Nobel Prize last year. M. Yeah, this is a theory
Speaker 1: that talks about the universe is a big cycle, right,
Speaker 1: like maybe there were other universes before our universe. Yeah, exactly.
Speaker 1: This theory sees the universe is big cycles, but not
Speaker 1: the kind you're probably familiar with. You've probably heard of
Speaker 1: the theory that the universe goes through a cycle of
Speaker 1: bangs and then crunches and bangs and then crunches This
Speaker 1: is a totally different idea that has a sickly cosmology
Speaker 1: at its heart. All right, So today on the podcast,
Speaker 1: we'll be asking the question, what is the conformal cyclic
Speaker 1: cosmology theory? All right? This is not the usual big
Speaker 1: bank to big crunch universe theory. You're saying. It's different.
Speaker 1: It's different. It goes for the cycle approach. It says,
Speaker 1: you know, let's sweep away this question of whether there
Speaker 1: was the beginning by saying there was never beginning. There's
Speaker 1: an infinite number of cycles. But it doesn't link up
Speaker 1: big crunches to big bangs. It's a totally different idea,
Speaker 1: a little bit more bonkers and super fascinating because it
Speaker 1: suggests that you might be able to see an imprint
Speaker 1: of the previous universe, somehow left on our universe. Well,
Speaker 1: let's maybe catch up our listeners, because the idea they
Speaker 1: might have heard about is that the universe, you know,
Speaker 1: came out of a big bang, out of a really
Speaker 1: small space. Then it was huge. It exploded basically in
Speaker 1: the big bang, and then after you know, maybe trillions
Speaker 1: of years, it collapses back down into a big crunch,
Speaker 1: which then triggers another big bang. For another universe, kind
Speaker 1: of like Season two or a sequel to the Universe,
Speaker 1: and then that universe explodes and expands, and after trillions
Speaker 1: of years it crunches back down again, and so on
Speaker 1: and so on at infinitum. Right, and so that's the
Speaker 1: basic idea that people usually talk about when they talk
Speaker 1: about cycles of the universe. Yeah, exactly. So that's the
Speaker 1: typical idea. But today we're going to explore a different one. Yeah. So,
Speaker 1: as usual, Daniel went out there to ask people on
Speaker 1: the internet if they heard of this new theory about
Speaker 1: universe cycles. That's right, So thank you to everybody who
Speaker 1: shared your speculation. And if you are willing to answer
Speaker 1: random questions from me online for us to use on
Speaker 1: the podcast, please write to us two questions at Daniel
Speaker 1: and Jorge dot com. So think about it for a second.
Speaker 1: Have you heard of any theories about the universe cycling
Speaker 1: over and over again? Here's what people had to say. Okay,
Speaker 1: you are clearly just taking birds together now, but I
Speaker 1: will try to give you a guess. Anyway, cycled cosmos
Speaker 1: could mean it is something about the form of all universe,
Speaker 1: So instead of being infinite, it could be somehow bent
Speaker 1: in itself, so you wouldn't never reach an edge but
Speaker 1: just start over. Or it could be about its growth
Speaker 1: and its development, like there could be a big crunch
Speaker 1: at the end of the life cycle followed by another
Speaker 1: big bang and so on. This makes me think of
Speaker 1: the theory that I've heard that the universe keeps being
Speaker 1: created over and over again, so it grows and grows
Speaker 1: and grows and then becomes a black hole, and then
Speaker 1: the black hole creates its own universe in a sort
Speaker 1: of big bang like event. And so that's what makes
Speaker 1: me think of And since the word conformal is in there,
Speaker 1: I'm guessing maybe every universe is the same over and
Speaker 1: over again. I think it has something to do with
Speaker 1: the cycles that we see in the cosmos, like the
Speaker 1: births and the deaths of stars and galaxies. I'm not sure,
Speaker 1: but I think it might have to do with like
Speaker 1: the universe cycling between a big bang and a big crunch.
Speaker 1: All Right, it sounds like people have heard about this
Speaker 1: general idea of crunches and bangs, bangs, bangs bang guy bangs. Yeah,
Speaker 1: And one of the answers seems to be following in
Speaker 1: your tradition of complaining about the name, you're just sticking
Speaker 1: words together. It's fair both English professors and professors are
Speaker 1: guilty of that. But yeah, so, I guess let's talk
Speaker 1: about this idea of inflation in the early universe. I mean,
Speaker 1: where did this idea that there could be a cycle
Speaker 1: to the universe come from? And we thought of it first. Yeah,
Speaker 1: the origins of it come from the realization in the
Speaker 1: last few decades that the universe might have had some
Speaker 1: sort of starting point. Remember, like a hundred or so
Speaker 1: years ago, people looked at its stars and they didn't
Speaker 1: see the stars moving by eye, and they figured, hey,
Speaker 1: I guess the universe is just statics, just like a
Speaker 1: bunch of stars hanging out in space. And it was
Speaker 1: very natural for people to think that it could have
Speaker 1: always been that way. It looks pretty old, after all,
Speaker 1: and so why not imagine it lasted forever. But then
Speaker 1: when Hubble discovered the universe was expanding, that sort of
Speaker 1: changed the story. It suggested that the universe is changing
Speaker 1: and couldn't always have looked the way it does. And
Speaker 1: then when you extrapolate backwards in time and you think, well,
Speaker 1: if it's expanding now, then it should have been contracting
Speaker 1: as we go back in time. That takes you back
Speaker 1: to something that feels sort of like a beginning, a
Speaker 1: point when the universe is much much more dense, yeah,
Speaker 1: much more raw, right, like the whole entire universe, every
Speaker 1: star in galaxy you ever seen, was in a really
Speaker 1: small space about fourteen billion years ago, and everything was
Speaker 1: just like a state of plasma, right, like just raw energy.
Speaker 1: That's right. When the universe was much younger, it was hotter,
Speaker 1: and it was denser, and so things work differently, you know,
Speaker 1: just like there are different phases of matter that you're
Speaker 1: familiar with water, you can be ice or liquid or gas.
Speaker 1: The universe itself sort of has phases, and when stuff
Speaker 1: is much much denser, there are different rules of physics
Speaker 1: that emerge, and so like the laws of physics, they
Speaker 1: don't violate the ones we have now, but they sort
Speaker 1: of operate under different regimes. Different laws emerge, and so
Speaker 1: it was very different from the way we imagine it now,
Speaker 1: and we have some direct evidence that that actually existed.
Speaker 1: This isn't just a calculation in people's minds. We've seen
Speaker 1: light from that early universe plasma or diving at Earth.
Speaker 1: It's called the cosmic microwave background radiation and it's sort
Speaker 1: of like the last glow from the Big Bang. Yeah,
Speaker 1: so we can see light that kind of escaped that
Speaker 1: plasma right before and basically evaporated, right, yeah, exactly, and
Speaker 1: that plasma sort of faded out and cooled off and
Speaker 1: turned into neutral atoms, and then we can see that
Speaker 1: light because it's still banging around the universe. The universe
Speaker 1: sort of became transparent at that moment. So that was
Speaker 1: like a really exciting piece of evidence when people saw
Speaker 1: the microwave background radiations is several decades ago, really confirming
Speaker 1: that that thing actually happened, That the universe once was
Speaker 1: a big hot plasma, and that's very different from the
Speaker 1: way it is today. Right, Well, it was a hot
Speaker 1: mass back then, and it seems like it's a hot
Speaker 1: mass right now. We're constantly on the edge of catastrophe.
Speaker 1: But there are a lot of things we don't understand,
Speaker 1: like what happened before that Big Bang with that big
Speaker 1: hot ball of plasma. Yeah, that hot ball plasma is
Speaker 1: an exciting threshold reach. We're looking back fourteen billion years
Speaker 1: into the history of the universe. But you know, we
Speaker 1: want to probe, but we want to know where that
Speaker 1: ball of plasma came from, what explains how that got
Speaker 1: there and what made that? You know, we want to
Speaker 1: keep stepping this ladder backwards in time to understand really
Speaker 1: what was going on, and the way to do that
Speaker 1: is to ask more questions, to say, like, do we
Speaker 1: understand the way that ball of plasma look? Can we
Speaker 1: explain it? Do we understand, for example, all of the
Speaker 1: ripples in it? Because the light we see from that
Speaker 1: ball of plasma is not all the same temperature. There's
Speaker 1: some variations up and down in that light. Yeah, And
Speaker 1: so our prevailing theory about what happened during those first
Speaker 1: moments of the universe is called inflation, right, and that
Speaker 1: sort of explains kind of what happened since the Big Bang,
Speaker 1: but it doesn't quite explain what happened before. As we
Speaker 1: go backwards in time from the cosmic microway background radiation,
Speaker 1: we add this step where the universe expanded very dramatically
Speaker 1: by a factor of ten to the thirty intend to
Speaker 1: the minus thirty seconds, and then answers a lot of
Speaker 1: the questions that we have about the wiggles and the
Speaker 1: cosmic microwave background radiation. The temperature of the universe, and
Speaker 1: we have a whole podcast episode about that you can
Speaker 1: dig into. And so that's really cool. That's in a
Speaker 1: huge advance, sort of like taking us yet further back.
Speaker 1: But you know, we want to go to time equal zero, right.
Speaker 1: Inflation takes us to time equals ten to the minus thirty,
Speaker 1: but it doesn't explain how that got there, right. We
Speaker 1: want to take the next step of that ladder backwards
Speaker 1: in time. And that's the question that a lot of
Speaker 1: these theories are probing, is trying to explain, like, how
Speaker 1: did you get to inflation? What created the situation that
Speaker 1: made this universe inflate in such an insane way? Yeah,
Speaker 1: because we don't really know what causes that inflation, right,
Speaker 1: I mean, it's something literally cost the universe to explode.
Speaker 1: Something really made the universe explode and expand in this
Speaker 1: crazy way, and we are just the beginning of understanding
Speaker 1: what that might be. We're like putting together ridiculous sounding
Speaker 1: theories to potentially explain how that might work. One of them,
Speaker 1: for example, is that there was a field, a new
Speaker 1: field that filled all the universe. You're familiar with, for example,
Speaker 1: the electromagnetic field or gravitational fields, or the Higgs field.
Speaker 1: Now imagine a new field, and it's called the inflaton field,
Speaker 1: just to have a ridiculous name, and it's some new
Speaker 1: kind of matter which expands super duper rapidly and for
Speaker 1: some reason at some point decays into normal matter. And
Speaker 1: that's one idea for like nucle eating our universe, that
Speaker 1: the universe was filled with this in phloton field, which
Speaker 1: at some point decayed into real matter, which then became
Speaker 1: our universe. But of course that just you know, begs
Speaker 1: more questions like well, where does the in photon field
Speaker 1: come from? And what made that? And so you could
Speaker 1: go on forever if you keep just sort of stacking
Speaker 1: explanations on top of each other, which is why one
Speaker 1: sort of attractive conceptual alternative is to try to sort
Speaker 1: of loop it back to the end of the universe
Speaker 1: and make your idea be a cycle which sort of
Speaker 1: explains itself. All right, Well, let's get into this interesting
Speaker 1: new theory, the conformal cyclic cosmology theory by Roger Penrose,
Speaker 1: and let's talk about whether or not it could actually
Speaker 1: let us see a little bit of the previous universe.
Speaker 1: But let's take a quick break, all right, we're talking
Speaker 1: about a small question, you know, where did the universe
Speaker 1: come from? And has it always been here? And we
Speaker 1: talked a little bit about the idea of inflation that
Speaker 1: the universe somehow expanded really quickly at the beginning of time,
Speaker 1: or the ti equals zero as we know it. But
Speaker 1: the question is what happened before to equal zero? Time
Speaker 1: equals zero in the universe? Was there a previous universe
Speaker 1: or did the universe come out of nothing? And there's
Speaker 1: this idea, Daniel, that maybe before our universe expanded, there
Speaker 1: was another universe that maybe crunched together, and that's kind
Speaker 1: of I think what a lot of people have heard about.
Speaker 1: But you're saying that there's problems with this idea. Yeah, well,
Speaker 1: one problem with that idea is that it starts from
Speaker 1: a singularity. You know, you project backwards in time, our
Speaker 1: universe gets more and more dense. Eventually it gets infinitely dense.
Speaker 1: That's the singularity. You know. I think a lot of
Speaker 1: people in their minds when they talk about the Big Bang,
Speaker 1: they're imagining a very dense dot of matter in an empty,
Speaker 1: infinite universe. But instead you should be imagining a universe
Speaker 1: filled with stuff. But that stuff is of infinite density.
Speaker 1: So the Big Bang, as we imagine, it's sort of
Speaker 1: happened everywhere all at once. It's a question of density
Speaker 1: rather than a question of location and matter exploding into
Speaker 1: empty space. And the problem really is that singularity. The
Speaker 1: singularity is not a physical thing. It's not something that
Speaker 1: we can understand it. It reflects a breakdown in our theory.
Speaker 1: General relativity tells us if you sort of follow its
Speaker 1: laws naively, that things get denser and denser, and then
Speaker 1: the curvature gets infinite as the density gets infinite. But
Speaker 1: that's not something we can deal with. We can grapple with,
Speaker 1: like general relativity fails when the curvature gets infinite. So
Speaker 1: if you want to connect our universe to a previous
Speaker 1: universe by saying it went through a singularity, then that's
Speaker 1: kind of a problem because the singularity feels sort of
Speaker 1: like nonsense. It feels like when the theory is failing,
Speaker 1: when a theory needs a new idea. M hmmm, well,
Speaker 1: it seems like maybe the real problem is that this
Speaker 1: big bang and big crunch idea requires you to have
Speaker 1: a big crunch, right, But we don't know if the
Speaker 1: universe will actually come back together to create a big crunch.
Speaker 1: That's right, You need some mechanism to reverse what we
Speaker 1: see happening now. What we see happening now is that
Speaker 1: the universe is expanding, and that expansion is accelerating. It's
Speaker 1: happening faster and faster, So our universe certainly doesn't look
Speaker 1: like it's heading for a big crunch. On the other hand,
Speaker 1: we have no idea what's causing that expansion to accelerate.
Speaker 1: There's some mechanism there that goes by the name of
Speaker 1: dark energy, but we don't understand it, so we don't
Speaker 1: know whether it will continue. Turned on about five billion
Speaker 1: years ago, and it might turn off, it might turn around.
Speaker 1: So we don't necessarily see a big crunch happening in
Speaker 1: our universe. But we also can't really rule it out
Speaker 1: because we just don't understand the basic mechanisms at play.
Speaker 1: But you're right, if you want to have a big crunch,
Speaker 1: something's got to do the crunching. Yeah, And we kind
Speaker 1: of had this idea before we knew about the accelerating
Speaker 1: expansion of the universe, Like before it made sense that
Speaker 1: you know, the universe would kind of expand and then
Speaker 1: gravity would win out at the end, and the universe
Speaker 1: would contract and collapse back into a singularity perhaps and
Speaker 1: then a none of the universe would come out of that.
Speaker 1: But again, that requires you to have a big crunch.
Speaker 1: And what happens if you can't really have a big crunch.
Speaker 1: Does that mean that, you know, we can't have any
Speaker 1: more universes, like we're the last one? Maybe? Yeah, Well
Speaker 1: that's where Penrose's idea comes in. He has this concept
Speaker 1: for allowing cycles even if the universe never crunches back.
Speaker 1: That's sort of the heart of his idea, right, because well,
Speaker 1: that would be the only thing that could work at
Speaker 1: this point, right, because if we never have a big crunch,
Speaker 1: like if a big crunch is not in our future
Speaker 1: or any other universe that have was created like ours,
Speaker 1: then this idea of a big crunch to a big
Speaker 1: bang can't happen. Yeah, exactly. You can't go from crunch
Speaker 1: to bang if you don't go to the crunch. So
Speaker 1: there's two possibilities. It seems like either we're the only
Speaker 1: in last verse because we're going to expand out into nothingness,
Speaker 1: or maybe there's a clever new idea that let's just
Speaker 1: come up with a new universe out of this infinite expansion. Yeah,
Speaker 1: and that's Penrose's idea. He says, let's think about the
Speaker 1: very very end of the universe and try to connect that,
Speaker 1: try to loop that back to the beginning of the
Speaker 1: universe without going through a big crunch. And what he
Speaker 1: ends up doing is sort of like a weird mathematical trick,
Speaker 1: which might be physical, but it sort of blows your mind.
Speaker 1: It's pretty cool idea. So it is the idea that
Speaker 1: it looped back to the beginning of our universe or
Speaker 1: to the beginning of a different universe. The idea is
Speaker 1: that it would begin a new universe. And here's the
Speaker 1: basic concept. You think about the very very far future
Speaker 1: of the universe. We're talking like ten to the one
Speaker 1: hundred years. What's our prediction for how our universe will
Speaker 1: look then, tend to the one hundred years, tend to
Speaker 1: the one hundred. It's like a one with a hundred zeros.
Speaker 1: It's a lot of years. It's like more than trillions,
Speaker 1: it's like bazillions. I don't think we've even named those
Speaker 1: scientific prefixes. You know, right, if the Universe is a
Speaker 1: television series, we are like still in the opening credits
Speaker 1: of episode one, right, because even a trillion years is
Speaker 1: like one tend to the twelve. This is tend to
Speaker 1: a hundred. Yeah, this is tend to the one hundred.
Speaker 1: So it's just a ridiculous number. And you'll understand why
Speaker 1: in a minute. Because he wants to get to the
Speaker 1: point when the universe is smooth again. He wants to
Speaker 1: wait for all the black holes to die. So the
Speaker 1: current trajectory for our universe if nothing changes with dark energy,
Speaker 1: is that everything is getting pulled apart. But you have
Speaker 1: these local gravitational clumps like our galaxy and our solar system,
Speaker 1: So those things will eventually collapse gravitationally, forming black holes,
Speaker 1: and these black holes will get really really far apart
Speaker 1: because of dark energy. Well, what happens to a black hole?
Speaker 1: Do black holes live forever? We actually know that they don't.
Speaker 1: Write Hawking radiation is a way that they can give
Speaker 1: off little bits of energy really really massive black holes
Speaker 1: and made a very very small amount of Hawking radiation.
Speaker 1: So he's thinking in the deep, deep far future, when
Speaker 1: you form all these black holes, they get separated by
Speaker 1: dark energy, and then they leak their radiation back out
Speaker 1: into the universe. You have to wait for them all
Speaker 1: to die. So the end of our he calls them eon,
Speaker 1: is when all of our black holes sort of just
Speaker 1: turned into radiation. They basically evaporated into photons or or
Speaker 1: what black holes evaporate into all kinds of things exactly.
Speaker 1: They can evaporate into electrons or into other kinds of corks,
Speaker 1: or into photons or whatever. So they've got to give
Speaker 1: up all of their light. And then he's imagining this
Speaker 1: universe is sort of smooth again, and he's trying to
Speaker 1: make a connection between the end of our universe and
Speaker 1: the start of the next universe. And the connection he
Speaker 1: makes is like, well, our universe started out kind of
Speaker 1: smooth before, like quantum fluctuations and everything and inflation blew
Speaker 1: it up into actual interesting structure. So if the end
Speaker 1: of the universe ends up sort of like smooth fields
Speaker 1: of radiation, he's going to try to connect that to
Speaker 1: the beginning of the next universe, which also starts smooth.
Speaker 1: I feel like it's a little different because you know,
Speaker 1: our universe that far into the future sounds kind of cold.
Speaker 1: It might be smooth, and it might be you know,
Speaker 1: kind of random and homogeneous, and there's electrons and quarks
Speaker 1: flying around, but things are still pretty discreet, like things
Speaker 1: are in the form of electrons or quarks. Right, it's
Speaker 1: not like pure energy like we think of at the
Speaker 1: beginning of our universe. Yeah, exactly. The density feels different.
Speaker 1: And here's when the mathematical trip comes in. It turns
Speaker 1: out that if our universe has only photons in it,
Speaker 1: or more specifically, only massless particles in it, then you
Speaker 1: can change the length scale of the universe without changing
Speaker 1: any of the physics. You can say, what used to
Speaker 1: be a light year is now a millimeter, and all
Speaker 1: the physics will work the same. All the massless particles
Speaker 1: will operate the same way they had before. They won't
Speaker 1: notice what. Yeah, I thought particles had kind of like
Speaker 1: a minimum distance to them. Well, these particles we don't
Speaker 1: think of as having a size, right, We don't think
Speaker 1: of the photon is having like a physical extent to it.
Speaker 1: Just think of it. It's like a little blip in
Speaker 1: the field. And these fields, at least the massless fields,
Speaker 1: have this weird property that you can scale them by
Speaker 1: a number and nothing will change. All the physics will
Speaker 1: be the same. It's sort of like if we just
Speaker 1: changed all the rulers and made everybody smaller. Nobody would
Speaker 1: notice the difference, right, all of a sudden, we're all
Speaker 1: much tinier than we were before. But we also changed
Speaker 1: the rulers, so nobody can tell. If the laws of
Speaker 1: physics are invariant to that kind of transformation, then you
Speaker 1: wouldn't notice the difference. So he noticed this about the
Speaker 1: universe very specifically that only has massless particles in it.
Speaker 1: You can do this and not change anything. Doesn't work
Speaker 1: if there are any particles that have mass. Right, But
Speaker 1: it sounds like we skipped the step though, Like how
Speaker 1: do we go from black holes evaporating into electrons and
Speaker 1: cords to now everything just being photons? Yes, a very
Speaker 1: good point. He did skip a step. But you know,
Speaker 1: the way these theoretical laration's work is like, m that
Speaker 1: seems like an unsolvable problem. He'll put it on the
Speaker 1: shelf for now and get back to it. What what
Speaker 1: do you mean? I mean because we talked about how
Speaker 1: an electron well might never decay, right, Yeah, exactly, He's
Speaker 1: got a problem with electrons. You know, like most particles
Speaker 1: in the universe, top corks takes bosons will decay and
Speaker 1: go down to lighter and lighter particles. And there's only
Speaker 1: a very small number of particles in the universe that
Speaker 1: are stable. And so the photon, for example, is stable.
Speaker 1: You can have a photon, it can hang out forever,
Speaker 1: it can fly across the universe. But also electrons are stable.
Speaker 1: We don't know of any way for an electron to
Speaker 1: turn into something lighter, right or quarks? Right aren't? Don't
Speaker 1: quarks also last forever, like if they're in a proton. Yeah,
Speaker 1: quarks can last forever. They can turn into other stuff.
Speaker 1: But basically quarks can last forever. Protons, however, might decay, right,
Speaker 1: We don't know. Protons we think last forever. We've never
Speaker 1: seen one decay, but there are some theories in which
Speaker 1: they can decay into lighter stuff. But you'd be stuck
Speaker 1: with some massive particles. And so to go from a
Speaker 1: universe that has like photons and a few electrons in
Speaker 1: it to universe with just photons, he has to invent
Speaker 1: some sort of new physics thing, and he calls it
Speaker 1: the arab On field that turns all these massive particles
Speaker 1: somehow now into photons. He calls it the wave my
Speaker 1: hand fee field. It's very hand wavy. But you know,
Speaker 1: Penrose is a big thinker. He's like trying to get
Speaker 1: the big structure right. He's like, you know, can I
Speaker 1: somehow work out this bigger problem, then I'll come back
Speaker 1: in and patch up these other holes and see if
Speaker 1: I can find something that fills them in m M.
Speaker 1: So he's saying, let's say that eventually, maybe in a
Speaker 1: long time, all matter particles decay into massless photons or
Speaker 1: massless particles. Right, that's the that's the leap of faith here,
Speaker 1: and then that creates a state that's basically pure energy, right,
Speaker 1: in which case it's sort of scale less, like it's
Speaker 1: a millimeter and of a light ear make no difference
Speaker 1: between the two. Exactly, it's scale less, so you can
Speaker 1: change your scale and nothing is different because things that
Speaker 1: don't have mass. Our skill is yeah, exactly. A photon
Speaker 1: sees the whole universe anyway, is shrunk and to a point, right,
Speaker 1: it's moving at the speed of light, and so distance
Speaker 1: doesn't really make any difference to the photons. The whole
Speaker 1: universe is length contracted anyway, it doesn't matter ten light years,
Speaker 1: one light year, one millimeter, like space itself. The idea
Speaker 1: of distance doesn't make sense anymore, or at least if
Speaker 1: you scale everything the same way, nothing changes. And so
Speaker 1: he says, well, let's take this huge expanded universe and
Speaker 1: then just sort of like redefine it to be a
Speaker 1: very dense, smooth universe, and boom, you have the conditions
Speaker 1: that were at the beginning of our universe. Right at
Speaker 1: the beginning of our universe there was a state. We
Speaker 1: don't understand it, but it's postulated that it was there,
Speaker 1: and it was very very dense with energy, and it
Speaker 1: was very smooth, and that that then, you know, expanded
Speaker 1: to turn into our universe. The image of penrose Is
Speaker 1: universe is like every universe is a further expansion on
Speaker 1: the previous one. It's like this endless series of expansions.
Speaker 1: We just redefine the terms. Wow, but then each new
Speaker 1: universe is bigger than less, yes, by a lot exactly.
Speaker 1: We just keep changing the scale. So the whole previous
Speaker 1: universe would be contained within like a tiny dot of
Speaker 1: our universe, and our entire universe would be contained within
Speaker 1: a tiny dot of the next one, kind of like
Speaker 1: a Russian doll, but at a ginormous scale, yes, and
Speaker 1: going on forever backwards and forwards in time, backwards and
Speaker 1: forwards in time exactly. And so he gets this sort
Speaker 1: of like cyclic structure where the end of the universe
Speaker 1: connects to the beginning of the universe. But it doesn't
Speaker 1: have to have a crunch, right, doesn't need to explain
Speaker 1: the crunch. He needs lots of other stuff he's got
Speaker 1: to explain to me work, but he doesn't need the crunch.
Speaker 1: And there's a big advantage there because the crunch destroys
Speaker 1: all the information. Like, if there was a crunch, then
Speaker 1: it went through a singularity and any information about that
Speaker 1: previous universe is gone, it's destroyed. But if this series
Speaker 1: of infinite expansions is remapping and then expansion, then you
Speaker 1: could find traces of the previous universe in our universe. Right,
Speaker 1: it's kind of like a more like a blooming universe
Speaker 1: rather than a sickly universe. Yeah, exactly. It's pedals within
Speaker 1: pedals within pedals, right, each one nested within the previous one,
Speaker 1: like an infinite fractal or something. Yeah, it's like a
Speaker 1: fractal universe theory. It's pretty cool, all right. Well, let's
Speaker 1: get into whether or not this theory even makes sense
Speaker 1: it may not, and talk about whether or not there
Speaker 1: is evidence out there in the cosmic microwave background radiation
Speaker 1: to support this theory. But first, let's take a quick break.
Speaker 1: All right, we're talking about the infinite universe as a
Speaker 1: Russian doll theory. This is Roger Penrose's conformal sickly cosmology
Speaker 1: theory that says that the universe came from another universe
Speaker 1: expanding infinitely out, and that after our universe expand ends
Speaker 1: almost infinitely out, another universe will grow from that state
Speaker 1: of pure energy you should measure like a trumpet with
Speaker 1: its horn, and then another one coming out of its horn,
Speaker 1: another one coming out of its horn, and it's just
Speaker 1: like endless cycle of growth. So I'm curious, or what
Speaker 1: would you have named this theory if you could come
Speaker 1: up with it the trumpet theory? They had the Russian
Speaker 1: ball theory. I don't know. I think cycles cycled though.
Speaker 1: It is kind of a weird name though, because it's
Speaker 1: not quite a cycle, right, It's more like a blooming
Speaker 1: universe theory maybe, yeah, big bloom, there you go. It
Speaker 1: doesn't run the same forwards and backwards, right, It doesn't
Speaker 1: have that sort of time symmetry to it. It definitely
Speaker 1: just keeps expanding as time goes forwards. So the thing
Speaker 1: I like about the Big Crunch Big Bang idea is
Speaker 1: that it does have some sort of time symmetry. You
Speaker 1: can imagine running things backwards and time and it would
Speaker 1: look sort of the same. All right, So let's talk
Speaker 1: about whether this makes sense. This is something that the
Speaker 1: physicists are actually considering. Like, I know, he won a
Speaker 1: Nobel Prize, but he didn't win a Nobel price for
Speaker 1: this theory. No, there are a lot of things named
Speaker 1: after Penrose in physics Penrose diagrams, Penrose tilings, and he
Speaker 1: recently won a Nobel Prize for thinking about black hole.
Speaker 1: So definitely a smart guy. But a lot of these
Speaker 1: really smart physicists get famous for a few ideas, and
Speaker 1: those few ideas are like a small fraction of all
Speaker 1: the ideas they toss out there and see which one sticks.
Speaker 1: So often they come up with a lot of crazy,
Speaker 1: bonkers ideas that you know, never really hang together. So
Speaker 1: this is not one that's in the main stream of cosmology, Like,
Speaker 1: this is not one that a lot of people are
Speaker 1: working on. And Penrose proposed in about two thousand and
Speaker 1: twelve in a paper in a book, and it got
Speaker 1: a lot of attention for a while also because he
Speaker 1: claimed he could actually see the evidence of a previous
Speaker 1: universe m so meaning it sort of works mathematically like
Speaker 1: if we can get the universe to this state of
Speaker 1: pure energy without any massive particles, then the math does
Speaker 1: kind of suggest that you could get another universe out
Speaker 1: of that. Yeah, so that's what made it interesting. Yeah, mathematically,
Speaker 1: there is an idea there that you can map the
Speaker 1: end of our universe to the beginning of our universe
Speaker 1: that have a very similar sort of structure to them.
Speaker 1: So there is a cool idea there. But you know,
Speaker 1: you gotta stick in something that makes the universe turned
Speaker 1: into just photons, and that's not something we understand at all.
Speaker 1: And then you also got to look for the evidence
Speaker 1: of it. You know. The best theories are ones that
Speaker 1: make predictions and say, if this is true, there would
Speaker 1: be some sort of like indistinguishable mark in the universe.
Speaker 1: That's what was so exciting. For example, about the cosmic
Speaker 1: microwave background radiation. It was predicted people said, well, if
Speaker 1: there was a big bang, then there should have been
Speaker 1: this moment when the universe went from opaque plasma to
Speaker 1: transparent neutral ions and we should be able to see it.
Speaker 1: And so that's pretty awesome to actually go out and
Speaker 1: find that fingerprint that you predicted. So then Penrose, you know,
Speaker 1: he rose to this challenge and he made predictions for
Speaker 1: what he said should be out there evidence of previous universes, right,
Speaker 1: and so he looked in the cosmic microwave background radiation
Speaker 1: and what did he see? Did he see evidence for
Speaker 1: this blooming universe theory? The big bloom he actually did.
Speaker 1: He claimed very significant evidence of previous universes in the
Speaker 1: cosmic microwave background radiation. And the way he thought it
Speaker 1: would look are these things called Hawking points. And Hawking
Speaker 1: point is where there was a huge supermassive black hole
Speaker 1: in the previous universe which then evaporated. But a left
Speaker 1: sort of a mark is a place in that universe
Speaker 1: where there's maybe more radiation density than others. It's like
Speaker 1: a non smoothness in the previous universe because you had
Speaker 1: so much radiation from this really massive black hole, and
Speaker 1: then when you map it back to the beginning of
Speaker 1: the universe, it sort of gets squeezed down. You squeeze
Speaker 1: all that radiation together and it makes basically a little
Speaker 1: hot spot in the next universe. So every supermassive black
Speaker 1: hole should leave like a little hot spot in the
Speaker 1: next universe, and that should be seen in the cosmic
Speaker 1: microwave background radiation. You should get like a little bit
Speaker 1: of a warm spot in that radiation, like a little
Speaker 1: scar kind of from the previous universe. Yeah, like a
Speaker 1: little scar. And so the cosmic microwave background radiation, you know,
Speaker 1: it's data that's out there. It's public. Anybody can go
Speaker 1: download it and look at it and analyze it. It's complicated,
Speaker 1: you know, you've got to really be an expert to
Speaker 1: understand what you're seeing. But when Penrose put out this theory,
Speaker 1: he also put out a paper claiming six sigma discovery
Speaker 1: of twenty Hawking points in the cosmic microwave background radiation.
Speaker 1: That means that he was claiming to see something that
Speaker 1: was not just like random fluctuations of noise. Six sigma
Speaker 1: means that he's like ruled out the fact that this
Speaker 1: could just happen by random chance. He was very convinced
Speaker 1: he was actually seeing these Hawking points super massive black
Speaker 1: holes from a previous universe. Alright, So the idea is that,
Speaker 1: you know, in the previous universe there probably were a
Speaker 1: lot of super massive black holes, or are you saying
Speaker 1: there was just one. No, they were probably a lot
Speaker 1: to you know, yeah, because everything would eventually crunch into
Speaker 1: a black hole, and those black holes might crunch together,
Speaker 1: and so you in the previous universe, if you run
Speaker 1: time long enough, you get these super massive black holes.
Speaker 1: And he's saying that even these kind of super massive
Speaker 1: holes would survive this process that makes everything massless, or
Speaker 1: some evidence of them would survive, and that would survive
Speaker 1: also this reblooming of the universe. Yeah, exactly. Their radiation
Speaker 1: would leave like a little warm spot when the universe
Speaker 1: blooms to the next eon. And because they're so massive,
Speaker 1: that would be enough radiation that it would sort of
Speaker 1: leak through a little bit. Remember, that's maybe the fate
Speaker 1: of every galaxy. Every galaxy has at its heart a
Speaker 1: big black hole. And the reason that we haven't fallen
Speaker 1: into that black hole is just because we have enough
Speaker 1: sort of speed to zip around it the way the
Speaker 1: Earth zips around the Sun. But eventually we can lose
Speaker 1: that speed. We can radiate off energy or collide with
Speaker 1: stars and the fate of basically everything is eventually to
Speaker 1: fall into that black hole and make it even more massive.
Speaker 1: So the whole Milty Way will eventually be a supermassive
Speaker 1: black hole and then evaporate its energy through Hawking radiation
Speaker 1: m M. And so in this theory, you don't need
Speaker 1: perfect smoothness in the universe to retrigger a new universe.
Speaker 1: You can have these kind of hot spots. You can
Speaker 1: have these little hot spots which you need is the
Speaker 1: universe is only filled with massless particles, and then you
Speaker 1: can map it back down to a new universe. So
Speaker 1: this is pretty exciting. People like wow. Penrose claims he
Speaker 1: sees like an imprint of a previous universe. That's sort
Speaker 1: of amazing, right, But but of course we don't think
Speaker 1: we live in these universe Nobody takes this theory seriously.
Speaker 1: And the reason is that other people went and looked
Speaker 1: at the data. They downloaded it and they analyzed it.
Speaker 1: And there are a lot of experts out there who
Speaker 1: really know what they're doing, and they didn't see these things.
Speaker 1: They don't see these circles that Penrose claims he sees
Speaker 1: with six sigma confidence. Yeah, exactly. He claims he saw them,
Speaker 1: and they analyze them and they didn't see them. And
Speaker 1: then multiple other groups analyzed them and they also didn't
Speaker 1: see them. What like, isn't the data there? How can
Speaker 1: some people see something and others not. Well, it depends
Speaker 1: on how you're analyzing the data. You know, there's a
Speaker 1: lot of steps involved in the assumptions you're making and
Speaker 1: how you're calculating these things. And for a while nobody
Speaker 1: could reproduce pen Rose's team's results, and then people found
Speaker 1: the mistake. Turns out he had run some sort of
Speaker 1: special version of an analysis code that nobody else agreed
Speaker 1: was really accurate, and he wasn't really comparing what everybody
Speaker 1: understood to be the predictions for Hawking points to the
Speaker 1: actual data. It sort of felt a little bit cooked up. Alright,
Speaker 1: So then maybe what he saw wasn't there. But that
Speaker 1: doesn't mean I guess that the theory is necessarily wrong, right,
Speaker 1: It doesn't mean the theory is wrong. And in the
Speaker 1: last decade or so he's come up with other predictions,
Speaker 1: you know, he said, oh, well, if my theory is right,
Speaker 1: then we should see some interesting pattern of gravitational waves
Speaker 1: or various other predictions so he still believes in it,
Speaker 1: he's still talking about it, he's still excited about it,
Speaker 1: he still makes up ideas for how we could test it.
Speaker 1: And you're right, it's not something we've ruled out. You know,
Speaker 1: maybe that we don't see those hawking points, but maybe
Speaker 1: we just haven't looked, or maybe they're too subtle, or
Speaker 1: maybe there are other ways to test this theory. And
Speaker 1: this is a challenge for a lot of these theories.
Speaker 1: You know, many cosmologies don't predict things that we can test.
Speaker 1: They're talking about things that happened a long time ago
Speaker 1: a really tiny scales, and it's hard to them up
Speaker 1: with an experiment to test these things. So kudos to
Speaker 1: him for coming up in the new cosmology and a
Speaker 1: way to test it. That's pretty awesome. Yeah, And it's
Speaker 1: not like we have a lot of other ideas line around, right,
Speaker 1: Like we have no idea what happened before the Big Bang.
Speaker 1: There's no real theory, and the theory of a big
Speaker 1: crunch may never happen or may never have happened, yeah,
Speaker 1: and may not be testable. So it's definitely a time
Speaker 1: when people should be creative and it should be out
Speaker 1: there exploring and creating new ideas and thinking broadly about
Speaker 1: what could explain the universe that we see. Right, it's
Speaker 1: time to go big, think creatively. Yeah. And one of
Speaker 1: my favorite quotes from Penrose about this theory is what
Speaker 1: he says, and I quote, of course the theory is crazy,
Speaker 1: but I strongly believe that we have to take it seriously.
Speaker 1: He's like, it's a crazy theory, but it's also a
Speaker 1: crazy universe. Exactly, it's a crazy universe. It's gonna need
Speaker 1: a crazy explanation. And also we got to be creative.
Speaker 1: You know, sometimes you come up with a bad idea,
Speaker 1: but it stimulates other better ideas in other theorists, so
Speaker 1: you shouldn't just you know, like only share your only
Speaker 1: finished ideas. There's a marketplace is a conversation of ideas.
Speaker 1: That's how we get to these answers, right, yeah, physics mart.
Speaker 1: That's where you go and buy ideas off the shelf.
Speaker 1: I think it was more like a salon, you know,
Speaker 1: sipping tea and chatting about our ideas about the universe.
Speaker 1: Al Right, Well that's Roger Penrose is conformal cyclic cosmology,
Speaker 1: and it kind of gets you to think about where
Speaker 1: the universe came from, and whether distance really means anything
Speaker 1: at all, because apparently it doesn't. If you're a photon,
Speaker 1: then it certainly doesn't. You're happy to rescale an entirely
Speaker 1: enormous inflated universe down to a tiny, little dense universe.
Speaker 1: To photon, a millimeter is the same as a light year, exactly.
Speaker 1: It takes the same amount of time. So if you're
Speaker 1: building a house for a photon, you know, don't worry
Speaker 1: so much abou getting the measurements right. And if you
Speaker 1: can save yourself a lot of a building equipment, make
Speaker 1: it a millimeter pig. All right, Well, that gives us
Speaker 1: all a lot to think about and to think about
Speaker 1: our origins and we're we came from? And could there
Speaker 1: have been other universes before hours? Like maybe are we
Speaker 1: season two hundred and seventy sevens of the Universe series
Speaker 1: when the writers finally figure out what's going to happen
Speaker 1: to these characters when we jumped to Shark twenty universes ago.
Speaker 1: All right, we hope you enjoyed that. Thanks for joining us,
Speaker 1: see you next time. Thanks for listening, and remember that
Speaker 1: Daniel and Jorge explained the universe is a production of
Speaker 1: I heart Radio or more podcast from my heart Radio.
Speaker 1: Visit the I heart Radio app, Apple Podcasts, or wherever
Speaker 1: you listen to your favorite shows.