Speaker 1: Hey, okay, I'm confused about something in the Star Wars universe. Well,
Speaker 1: I've seen those movies, which means I have a PhD
Speaker 1: in them. That's how they give out PhDs, right yeah,
Speaker 1: at Star Wars University. I think that's the only requirement
Speaker 1: sw go wookies. So my confusion is the Star Wars
Speaker 1: universe has humans in it, right, like people. Ah, well
Speaker 1: that's never clear. You know, they look like humans, but
Speaker 1: technically they're all aliens right there e t s extrat rest. Well,
Speaker 1: they're definitely biological humans. But they also have like super
Speaker 1: advanced technology, right like far future stuff. Yeah. Yeah, they
Speaker 1: have war drives and spaceships and light sabers. But it
Speaker 1: also says that it takes place a long, long time ago,
Speaker 1: So like, is it the past or is it the
Speaker 1: future with fancy technology? Yeah? Yeah, I know. That's the
Speaker 1: beauty of Georgia. Lucas is opening line a long time
Speaker 1: ago in a galaxy far far away. This is something
Speaker 1: that happened a long time ago, that's happening right now,
Speaker 1: or it's going to happen in the future. Maybe in
Speaker 1: the future I'll finally understand it. You just need to
Speaker 1: rewatch the movies a few times. Maybe it's time I
Speaker 1: get a second PhD hi am or handmade cartoonists and
Speaker 1: the co author frequently asked questions about the Universe. Hi,
Speaker 1: I'm Daniel. I'm a particle physicist and a professor at
Speaker 1: UC Irvine, and I'm not prepared to defend the physics
Speaker 1: of Star Wars. There is physics in Star Wars. That's
Speaker 1: the problem. There isn't that much, so we can't defend
Speaker 1: it well. I think from the beginning they say it's
Speaker 1: a fantasy. They never claim it's science. I think that's
Speaker 1: how George Lucas conceived it. He always thought of it
Speaker 1: as a fantasy. It's like fantasy plus Westerns in space.
Speaker 1: Anything is better in space, right except breathing? I guess
Speaker 1: I don't know. It's dessert better in space necessarily. If
Speaker 1: it's ice cream, sure that's gonna stay less and cold,
Speaker 1: isn't it. I've had astronaut ice cream. It doesn't compare.
Speaker 1: Welcome to our podcast, Daniel and Jorge Explain the Universe,
Speaker 1: a production of I Heart Radio, in which we think
Speaker 1: that the mysteries out in space are actually quite delicious.
Speaker 1: We take a deep sip of all of the questions
Speaker 1: we have about the nature of the universe, the way
Speaker 1: things work, the way things are, the way they come
Speaker 1: together to make this universe that we can somehow amazingly
Speaker 1: inexplicably analyze and understand with our tiny little brains. We
Speaker 1: can cast our simple mathematical stories over them and try
Speaker 1: to get some understanding for why things happen and how
Speaker 1: things happen. That's right, It's an amazing universe. And we
Speaker 1: like to use the Force here in this podcast to
Speaker 1: understand things like forces in the universe and particles and
Speaker 1: stars and galaxies and black holes, because one day we
Speaker 1: might be able to get really up close to these
Speaker 1: kinds of we use the force. Really, are you using
Speaker 1: the Jedi mind trick on me right now? I'm using
Speaker 1: the electromagnetic force that we're transmitting on That's true, we
Speaker 1: are using forces, But I thought there was a big
Speaker 1: difference between forces and the force. I mean, in the
Speaker 1: Star Wars universe, they have the normal forces, right, they
Speaker 1: also have the force. Mm. Well, we've always talked in
Speaker 1: this podcast how there might be one unifying force to
Speaker 1: the universe, right, so maybe there is the force. Do
Speaker 1: we also discuss miny Chlorians, where it's a far too
Speaker 1: controversial even for us. See that's an attempt to describe
Speaker 1: the force in terms of a scientific explanation. Maybe that's
Speaker 1: why it wasn't so popular that you mean the Star
Speaker 1: Wars movies weren't popular the prequels. Man, Yes, there's a
Speaker 1: lot of controversy there. Yeah, they only made three kajillion dollars. Yeah,
Speaker 1: but it is an awesome universe, full of galaxies that
Speaker 1: are far far away and lots of events that happened
Speaker 1: a long long time ago. Because the universe has been
Speaker 1: around for a pretty long time and hopefully it will
Speaker 1: be around for quite a while longer. Maybe, But because
Speaker 1: is that it is a physical universe. It is at
Speaker 1: the mercy of forces. We think that forces in this
Speaker 1: universe control the shape of everything we experience, from the
Speaker 1: reason that you don't fall through your chair to the
Speaker 1: reason you are held on the Earth and the Earth
Speaker 1: orbits around the Sun. The very structure of the galaxy
Speaker 1: and the large scale structure of the universe are determined
Speaker 1: by forces. Wait wait, wait, are you saying gravity is
Speaker 1: a force? Gravity is a fictitious force. Yes, absolutely, it's
Speaker 1: a Star Wars force. It's the Star Wars of forces.
Speaker 1: I always wonder how they can stand up in those
Speaker 1: spaceships when they're out in space fiction. That's how they
Speaker 1: can do it. But in our universe, forces do determine
Speaker 1: the large scale structure of everything if you include gravity
Speaker 1: on that list, and they control how the universe in
Speaker 1: the past has turned into universe we see today, and
Speaker 1: also they will determine the universe's future. That's right, because
Speaker 1: as still an ever lasting as the universe may seem,
Speaker 1: it's actually changing. It has been changing, and it will
Speaker 1: keep on changing. Used to be super super diverse, small
Speaker 1: or at least super super dense, and now it's much bigger,
Speaker 1: and it might keep changing in the future. Yeah, it
Speaker 1: can be difficult to sort of think on the time
Speaker 1: scale of the universe. You're used to looking up in
Speaker 1: the night sky and seeing it always be the same.
Speaker 1: The stars are not disappearing, they're not changing, they're not dancing.
Speaker 1: But we have learned in many situations that the universe,
Speaker 1: or even just the Earth changes on time scales that
Speaker 1: are well beyond what humans are used to thinking about.
Speaker 1: Millions of years ago, the Earth looked quite different. Billions
Speaker 1: of years ago, the Earth didn't even exist, and so
Speaker 1: the universe itself is rapidly changing, and we don't know
Speaker 1: if we are a significant fraction of the way through
Speaker 1: the history of the universe, or if this is just
Speaker 1: the first brief flash of a universe that will last
Speaker 1: for trillions or quadrillions or quintillions of years. Are you
Speaker 1: asking if the universe has peaked already? Exactly is it
Speaker 1: time to buy or sell shares in the universe? Well,
Speaker 1: I think by shares of the universe, you just won't
Speaker 1: be alive, probably by time someone catches in the universe.
Speaker 1: Who exactly can you sell your shares the universe too?
Speaker 1: I suppose is there a market out there in the
Speaker 1: multiverse stock market? Maybe you just enjoy the dividends. Life
Speaker 1: is pretty good, right, life is pretty good. In fact,
Speaker 1: I enjoy the universe. But I wonder how long this
Speaker 1: situation will last. How long will we be able to
Speaker 1: sit on a nice cozy rock toasting our toes by
Speaker 1: the fire of a distant sun. Is this something which
Speaker 1: will last for billions or trillions of years in our universe?
Speaker 1: Or is it a brief moment of respite on this
Speaker 1: resort we call Earth. Yeah, because the universe has been
Speaker 1: changing and it will keep on changing, probably, and so
Speaker 1: we can ask what does the future hold? Can we
Speaker 1: predict what's going to happen to the universe and we
Speaker 1: measure it, and how do we know that's what it's
Speaker 1: gonna do? Are we better able to predict the future
Speaker 1: of the universe than we are able to predict the
Speaker 1: future of the stock market, for example? And so to
Speaker 1: be on the podcast, we'll be asking the question what
Speaker 1: is the Big Rip? As this related to anyone's pants, Daniel,
Speaker 1: It's what happens if you eat too much astronaut ice
Speaker 1: cream or you sit down to watch the Star Wars
Speaker 1: movies one too many times. No, it's a fun speculative
Speaker 1: idea about the potential future of the universe because we're
Speaker 1: still developing our understanding of how the universe works and
Speaker 1: what all the forces at play are, and there are
Speaker 1: enormous gaps remaining in that understanding. There's a large set
Speaker 1: of possible futures for the universe, and the Big Rip
Speaker 1: is one of the craziest ones. Yeah. I think we've
Speaker 1: talked a little bit in this podcast about the end
Speaker 1: of the universe, right. We had Katie Mack here talked
Speaker 1: about her book The end of everything, and she kind
Speaker 1: of walked us through a couple of the possible scenarios
Speaker 1: for the universe. Yeah, that was a lot of fun
Speaker 1: and it's a great book folks should check out if
Speaker 1: you're interested in cosmology and reading about depressing ways we
Speaker 1: can all die. And we also talked in great depth
Speaker 1: on the podcast about some of the forces that are
Speaker 1: at play there and what we understand about them and
Speaker 1: what we don't understand about how they are still shaping
Speaker 1: our universe today. Now this is called the Big Rip.
Speaker 1: Now our physicist gonna change the name a little bit
Speaker 1: later on though, the bigger rip or the even larger,
Speaker 1: the even bigger rip. I'm looking forward to the super
Speaker 1: rip because then the rs blend together. The cosmic rip
Speaker 1: would in the cosmic rip be a better name for it, yeah,
Speaker 1: or the cosmic rift. But we do have a lot
Speaker 1: of ideas about how the universe might evolve and what
Speaker 1: might happen to it trillions of years into the future
Speaker 1: or maybe billions of years into the future, and this
Speaker 1: is one of those ideas, and it's pretty interesting. It's
Speaker 1: one of maybe what like three or four possible things
Speaker 1: that might happen to the universe. I think it's actually
Speaker 1: an infinite spectrum of possible outcomes to the universe. So yeah,
Speaker 1: this is one of those, right right, that's right. They
Speaker 1: could be a big rip, a bigger rip, small rip,
Speaker 1: a medium sized rip, a pocket size rip, and then
Speaker 1: of course there's all the ideas we just can't anticipate
Speaker 1: because we are just so clueless about how the universe works.
Speaker 1: We've only understood recently pretty basic stuff about things that
Speaker 1: are controlling the evolution of the universe, so we should
Speaker 1: definitely avoid being too confident but even categorizing the amount
Speaker 1: of our understanding. All right, So today we're going to
Speaker 1: focus on one possible thing that might happen to the universe.
Speaker 1: And so, as usual, we were wondering how many people
Speaker 1: have thought about the big Rip or what it could be.
Speaker 1: So thanks very much to everybody who answers these questions
Speaker 1: for the podcast, and if you would like to parts
Speaker 1: to pay for future episodes, please don't be shy. It's easy,
Speaker 1: it's fun, it doesn't hurt at all, Just right to me.
Speaker 1: Two questions at Daniel and Jorge dot com. So think
Speaker 1: about it for a second. What do you think the
Speaker 1: big rip is? Here's what people had to say. I
Speaker 1: think the big Rip is one of the possible ways
Speaker 1: the universe might end UM where something at the subatomic level,
Speaker 1: basically the whole universe on rabbles on itself. And I
Speaker 1: want to say it has something to do with anti matter.
Speaker 1: Maybe this was disgust UM two, like a meeting UM
Speaker 1: took place where a lot of known physicists We're talking
Speaker 1: about how the universe might end and theories, and reportedly
Speaker 1: UM at this meeting, bon Laborritos were or so I
Speaker 1: think somehow it's linked to this meeting. So the Big
Speaker 1: Rip is a scenario for the end of the universe
Speaker 1: where basically space time expands so quickly that every particle,
Speaker 1: every subparticle gets ripped apart from each other and basically
Speaker 1: can never meet another because the distance between any one
Speaker 1: and another it's expanding fast from the speed of light,
Speaker 1: so it's not very fun. The big rip is when
Speaker 1: the universe just rips itself apart because it doesn't have
Speaker 1: enough mass for the gravity to crunch back in on itself.
Speaker 1: The group is a theory that posits that at the
Speaker 1: auto is the end of the universe UM, there would
Speaker 1: be almost like an inflation that causes everything in the
Speaker 1: universe to move further apart, but um at a rapid
Speaker 1: rot almost like an explosion. I think, all right, some
Speaker 1: pretty definitive answers here. It's when everything ripped apart. Yeah,
Speaker 1: in that sense, you might say it's a well named
Speaker 1: physics theory. Yeah, yeah, I'll get it to them. Oh well,
Speaker 1: let's find out what it is first though, and see
Speaker 1: if it's related to a banana barrito and ripping into
Speaker 1: a banana bridle. I'm not sure where that comment was going.
Speaker 1: It was like a burrito made out of banana peals?
Speaker 1: Is that the reference? Yeah, I don't know. That's a
Speaker 1: slippery slope there. To mess with a burrito wrappings. I
Speaker 1: don't know if you're supposed to eat a banana barrito
Speaker 1: or smoke it. That's actually not a bad idea to
Speaker 1: put plantains inside of a burrito. I think you got
Speaker 1: something here. Listener, Well, let's get into a Daniel step
Speaker 1: us through what is the big rip? So the big
Speaker 1: rip is sort of like a super accelerated version of
Speaker 1: what we already think is happening to our universe. Current
Speaker 1: accepted idea of the cosmology of the universe. Is that
Speaker 1: the universe is expanding, and that that expansion is accelerating,
Speaker 1: meaning things are getting further and further apart. New spaces
Speaker 1: being created all the time, everywhere in the universe, and
Speaker 1: that's happening faster and faster every year. So even our
Speaker 1: current universe is sort of already tearing itself apart. An
Speaker 1: expansion is happening, and it's happening faster and faster every year.
Speaker 1: The Big Rip is like a super charged version of
Speaker 1: that that's going to accelerate the acceleration of that expansion,
Speaker 1: so that everything gets pulled apart to the tiniest bits
Speaker 1: at the end of time. Right, that's something we only
Speaker 1: learned about recently, right, maybe in the last hundred years,
Speaker 1: that the universe is actually expanding, it's not sitting still. Yeah,
Speaker 1: we learned about a hundred years ago that the universe
Speaker 1: is not just like a bunch of stars floating in space.
Speaker 1: Back before Edwin Hubble, in the beginning of the last century,
Speaker 1: people thought the universe was just like one galaxy. There's
Speaker 1: just a bunch of stars out there floating in space,
Speaker 1: and it was the way it was and always had been,
Speaker 1: and the most natural theory for the universe was that
Speaker 1: it always had been that way, and it always would
Speaker 1: be that way. It was just sort of like static
Speaker 1: and constant. But then Hubble saw other galaxies super duper
Speaker 1: far away. He identified smudges in the telescopes, not as
Speaker 1: nebula in our galaxy, but actual separate galaxies far away,
Speaker 1: and he was able to measure the velocity of those
Speaker 1: galaxies to see they were all moving away from us.
Speaker 1: So surprise, the prize the universe is actually expanding. Mm hmm,
Speaker 1: super interesting. How did he measure that the galaxy super
Speaker 1: moving away? You can measure the redshift of the light
Speaker 1: from those galaxies, so it looks a little redder than
Speaker 1: the life from our galaxy, Then you know it's moving
Speaker 1: away from me. If it looked a little bluer, it
Speaker 1: would mean that it was moving towards us. Things that
Speaker 1: emit light and have a relative velocity, the frequency of
Speaker 1: that light changes. It's a basic Doppler shift kind of effect,
Speaker 1: and things that are moving away from us, the light
Speaker 1: gets stretched out to make it redder. And Hubble was
Speaker 1: also able to measure the distance to these things, so
Speaker 1: he was able to show the things that are further
Speaker 1: away are moving away from us faster than things that
Speaker 1: are closer. Now that this makes sense with our sort
Speaker 1: of like theories about the universe and the makeup of
Speaker 1: it and what it could do, Like, what did Einstein
Speaker 1: think of this? Now, this was really confusing to folks
Speaker 1: like Einstein at the time. You know, before Einstein, we
Speaker 1: had an idea of gravity as a force. Mass pulls
Speaker 1: on other mass, stuffed tugs together gently. Right. Einstein in
Speaker 1: up with this idea that actually gravity is not a force,
Speaker 1: it's a curvature of the universe, that space itself is
Speaker 1: bent by mass and energy, and that's why things tend
Speaker 1: or sort of rolled together. The problem Einstein faced, even
Speaker 1: before Hubble's realization, was that this predicted that the universe
Speaker 1: would collapse, that all the mass and the energy and
Speaker 1: the universe would sort of pull itself together and shrink
Speaker 1: the universe. At the time, they thought the universe was static, right,
Speaker 1: They thought that it was just sort of hanging out there.
Speaker 1: So Einstein needed to invent something to balance the mass
Speaker 1: pulling everything together. So he added a fudge factor to
Speaker 1: his theory, something we now call the cosmological constant, which
Speaker 1: we've given outwards pressure to balance all of the mass
Speaker 1: coming in. So Einstein had this idea of a universe
Speaker 1: sort of balanced on a knife edge, this outward pressure
Speaker 1: providing exactly what you need to balance the inward pull
Speaker 1: of all the mass. And then Hubble literally blew that
Speaker 1: all up, right, because I guess if you imagine a
Speaker 1: bunch of stuff just floating out there in space as
Speaker 1: far as we knew back then, they should just all
Speaker 1: come together because of ay, right, Like, if you put
Speaker 1: two rocks out there in space, away from a lot
Speaker 1: of other stuff, is that there two rucks are going
Speaker 1: to attract each other and come together, right, And so
Speaker 1: if you have a bunch of stars or a bunch
Speaker 1: of planets out there in space, and the universe as
Speaker 1: we saw it, it should have all sort of crunched
Speaker 1: together by now, right. If things are just hanging out there,
Speaker 1: they have no relative velocity to start with. You put
Speaker 1: two rocks anywhere in the universe, they will tug on
Speaker 1: each other, and you give them enough time, they will
Speaker 1: come together. So Einstein was sort of like puzzled, like,
Speaker 1: why does my theory predict that the universe should collapse
Speaker 1: right into one giant black hole effectively? So he added
Speaker 1: a fudge factor, could in the universe be sort of
Speaker 1: like our Solar system, Like our Solar system is out
Speaker 1: out there in space, but it's not collapsing, right, Things
Speaker 1: are moving around in orbits. Yeah, there is something that's
Speaker 1: keeping the Solar system from collapsing rapidly, which is angular momentum.
Speaker 1: So the Earth, as you say, is in orbit around
Speaker 1: the Sun, just doesn't immediately collapse into the Sun. That orbit, though,
Speaker 1: will decay. You know, eventually the Earth will lose some
Speaker 1: of that velocity because it's bumping into stuff and it's
Speaker 1: really eating away energy and gravitational waves. So if you're
Speaker 1: talking about like the really deep future, then in Einstein's picture,
Speaker 1: eventually everything would collapse into a black hole. M But
Speaker 1: why did Einstein feel like you needed to add a
Speaker 1: fudge factor to make the universe static? Could in the
Speaker 1: universe be on its way to crunching down into a
Speaker 1: black hole? It could have been, and we didn't have
Speaker 1: great measurements, but the sort of prevailing view of the
Speaker 1: universe was that it was static. We didn't see anything moving,
Speaker 1: We didn't have great measurements. That which just sort of
Speaker 1: like the universe we thought we lived in. It looked static.
Speaker 1: It looks static, and so Hubble, you use this really
Speaker 1: cool observation by another astronomer, Henrietta Levitt, who discovered a
Speaker 1: certain kind of star called sephids. These are a particular
Speaker 1: kind of starring You can use a trick to tell
Speaker 1: how far away they are just by looking at the
Speaker 1: light from them. We have a whole episode about Ubble's discoveries.
Speaker 1: But Hubble was the first one to really be able
Speaker 1: to tell how far away things were, and so he
Speaker 1: could measure these velocities and he could tell that there
Speaker 1: was this trend that things further away we're moving away
Speaker 1: from us faster and faster. So that was the first
Speaker 1: clue that actually the universe is expanding. Yeah, that mustn't
Speaker 1: blown people's minds. How do you think that was received,
Speaker 1: that people believe Hubble at first, or were they like, no,
Speaker 1: you're crazy. I think the results were pretty solid because
Speaker 1: they were based on these sephids, which were pretty hard
Speaker 1: to dispute. And you can verify sephids using other distance
Speaker 1: metrics like parallax. For things that are close enough up,
Speaker 1: you can actually tell how far away something is based
Speaker 1: on how it wiggles in the sky as we go
Speaker 1: around the Sun. So there were a bunch of sefords
Speaker 1: that people could verify exactly how they work using other methods,
Speaker 1: and so it was kind of hard to dispute. But
Speaker 1: it did lead to a big puzzle. Right. People were like,
Speaker 1: hold on a second, we don't really understand what's going on.
Speaker 1: So then Einstein actually had bandoned the cosmological constant. He's like, well,
Speaker 1: scratch that. If the universe is expanding, we don't need
Speaker 1: the cosmological constant to resist the expansion. Things are just
Speaker 1: already zooming away from each other faster than gravity could
Speaker 1: otherwise pull them together. So the Einstein's fudge factor was
Speaker 1: actually holding back the universe in a way in his view,
Speaker 1: just by virtue of Einstein's equations, you're saying the universe
Speaker 1: would expand. What you're saying, No, you're saying the opposite. Right.
Speaker 1: Einstein's new view was like, all right, maybe mass is
Speaker 1: pulling the universe together, but it was already expanding. The
Speaker 1: sort of two different aspects to think about there. One
Speaker 1: is the rate of the expansion and the other sort
Speaker 1: of the acceleration. Mass tends to like slow down the
Speaker 1: rate of the expansion. But Einstein figured it's already expanding
Speaker 1: and expanding so fast that the mass doesn't have time
Speaker 1: to slow it down. It's sort of like hitting the
Speaker 1: brakes on a car that's already going super duper fast.
Speaker 1: So then he decided you didn't need that fudge factor. Yeah,
Speaker 1: he figured, look, the expansion is positive, maybe the acceleration
Speaker 1: is negative. Maybe mass is pulling everything forward, but we
Speaker 1: don't need the fudge factor the cosmological constant to explain
Speaker 1: why the universe is expanding anymore. Or he said, we
Speaker 1: don't need the fudge factor to explain why the universe
Speaker 1: hasn't crunched down. Yes, exactly, that's more accurate, thank you,
Speaker 1: because it's already like growing out of control, So you
Speaker 1: don't need to explain why it's not crunching that because
Speaker 1: it's on steroids the universe exactly. He invented the cosmological
Speaker 1: constant to explain why we had a static universe, and
Speaker 1: then we discovered, oh, the universe isn't static, it's expanding.
Speaker 1: So he sort of tossed it in the bin and
Speaker 1: apologized for it. Did it really well? Famously, he said
Speaker 1: that he thought it was one of his biggest scientific blunders. Yeah,
Speaker 1: that guy, I couldn't get anything right. I'd like to
Speaker 1: see humility in our great geniuses, you know. All right, well,
Speaker 1: let's talk about what could be causing this expansion and
Speaker 1: whether or not it's going to stay the same or
Speaker 1: maybe ripped the universe apart. But first, let's take a
Speaker 1: quick break. Alright, we're talking about the big rip, and
Speaker 1: so Daniel let it rip. So for a long time
Speaker 1: we knew that the universe was expanding, that we didn't
Speaker 1: really understand what had caused it to expand, and we
Speaker 1: thought maybe that mass in the universe was going to
Speaker 1: slow down that expansion, but we didn't understand like, is
Speaker 1: there enough mass in the universe to slow that expansion
Speaker 1: down eventually to zero and maybe bring it back to
Speaker 1: a big crunch, or is there not enough mass in
Speaker 1: the universe to slow down that expansion? Like a rock
Speaker 1: that you throw from the moon that will just go
Speaker 1: out forever, right, there's not enough mass on the moon
Speaker 1: to pull that rock back. Maybe the universe was like
Speaker 1: that and we just continue to drift further and further
Speaker 1: apart if there wasn't enough mass in the universe. So
Speaker 1: people wanted to know the answer to that question. They
Speaker 1: wanted to know. Willie universe keep drifting apart forever, gradually
Speaker 1: slower and slower, or will eventually it slowed down and
Speaker 1: come back into a big crunch That was sort of
Speaker 1: the big question around the mid nineties, right, Or is
Speaker 1: there a big plot twist in the middle there that
Speaker 1: will totally change what we thought we've been watching on
Speaker 1: the show. So spoiler alert for those of you who've
Speaker 1: been saving papers from the mid nineties and having gotten
Speaker 1: to read them yet. People developed a new way to
Speaker 1: measure distances to even further objects, to things much much
Speaker 1: further away, using type one a supernova special kind of
Speaker 1: explosion of stars that tends to happen in the same
Speaker 1: way every time, so we know how bright it should be.
Speaker 1: So we can tell just by looking at the curve
Speaker 1: of those stars how far away they are. Then by
Speaker 1: looking at the red shift of them, we can also
Speaker 1: tell how fast things are moving away. And this let
Speaker 1: us look even further back in time to see the
Speaker 1: deeper history of the expansion of the universe, and we
Speaker 1: hoped it could help us decide between these two options.
Speaker 1: Is the universe going to eventually slow down into a
Speaker 1: big crunch or is it going to keep drifting apart forever,
Speaker 1: gradually slowing down but never stopping. Couldn't they guess at
Speaker 1: the time. I mean, if we had an idea of
Speaker 1: the expansion of the universe, wouldn't at the time you
Speaker 1: just be able to, you know, figure out if you
Speaker 1: had enough mass to bring everything back together. Yeah, But
Speaker 1: the data we're not sufficient to distinguish those two things.
Speaker 1: It's like, if you're tracking an asteroid in space, you
Speaker 1: can give a much better prediction of its future if
Speaker 1: you have more data points, if you can look further
Speaker 1: back in time to understand its trajectory, you can nail
Speaker 1: down its future. In the same way, we didn't have
Speaker 1: enough data points to distinguish between these two scenarios until
Speaker 1: we look much further back in time and give us
Speaker 1: like a longer lever arm to understand the evolving history
Speaker 1: of the universe. But I guess if all we had
Speaker 1: is mass out there in the universe, then even if
Speaker 1: the universe was expanding pretty fast, wouldn't it all eventually
Speaker 1: come back down? Would in gravity eventually win? Gravity doesn't
Speaker 1: always win over velocity. Like if you're on the surface
Speaker 1: of the Moon and you throw a baseball fast enough,
Speaker 1: it will leave it. We'll have enough kinetic energy to
Speaker 1: overcome the potential energy of gravity, and it can't escape.
Speaker 1: But if there's only the Moon and that rock in
Speaker 1: the entire universe, wouldn't that rock eventually come back. No,
Speaker 1: it's possible for it to escape the gravitational attraction of
Speaker 1: the Moon. If you give it enough velocity, it will
Speaker 1: lose some of that velocity because the gravitational pull of
Speaker 1: the Moon. But as it gets further and further away,
Speaker 1: that gravitational pull gets weaker and weaker, and so it
Speaker 1: starts to lose velocity slower and slower, but it never
Speaker 1: goes to zero. So eventually will feel it slow down,
Speaker 1: wouldn't it. No, it's possible to have escape velocity, right,
Speaker 1: That's what escape velocity is, having enough kinetic energy to
Speaker 1: overcome the potential energy of the gravity of an object. Well,
Speaker 1: you can escape gravi it until you maybe fall into
Speaker 1: another potential gravity. Well, but it was just you in
Speaker 1: the moon, Eventually you would come back to the Moon,
Speaker 1: wouldn't you. If it's just you and the Moon and
Speaker 1: you have enough velocity, you can escape it. Think about
Speaker 1: it this way. Two particles moving in opposite directions in
Speaker 1: the universe don't necessarily have to fall back together if
Speaker 1: they have enough velocity, there's a threshold there where, if
Speaker 1: they're moving fast enough, they overcome their gravitational attraction, even
Speaker 1: given infinite time, even given infinite time. Yeah, that's the
Speaker 1: definition of escape velocity. I mean, I can escape the
Speaker 1: velocity of the Earth, but eventually I'll come back to
Speaker 1: the Solar system. Right. One way to understand how you
Speaker 1: can actually escape the gravity of an object is to
Speaker 1: think about the reverse process of falling into the object.
Speaker 1: So think of all starting like at rest, zero velocity,
Speaker 1: super duper far away, basically infinity away. Now you're right
Speaker 1: that the Moon will tug on it, and eventually it'll
Speaker 1: fall onto the Moon, and it will hit the Moon
Speaker 1: with a certain speed, not an infinite speed. That speed
Speaker 1: represents basically the energy difference between being on the Moon
Speaker 1: and being infinitely far away. So now instead, if you
Speaker 1: throw the ball away from the Moon with that same speed,
Speaker 1: than what happens, Well, it reverses the process and it
Speaker 1: loses all that velocity as it moves away, but it
Speaker 1: has just enough to get infinitely far away before it
Speaker 1: comes to a stop. So what that means is that
Speaker 1: it takes a finite amount of velocity to get infinitely
Speaker 1: far from the Moon's surface, and the same thing is
Speaker 1: true for any surface is just a different velocity. So
Speaker 1: now what happens if you throw the ball from the
Speaker 1: Moon's surface a little bit faster than the escape velocity,
Speaker 1: then it basically gets to infinity and still has some
Speaker 1: speed left over, so it's not falling back even after
Speaker 1: infinite time. All right. So then we expanded our view
Speaker 1: of the universe and we measured the expansion of things
Speaker 1: that were really far away. And what do we find.
Speaker 1: We found, as we look deeper into the history of
Speaker 1: the universe that we can make more confident predictions of
Speaker 1: the future. And what we found was really shocking. We
Speaker 1: found that the expansion of the universe wasn't decreasing slowly
Speaker 1: or quickly. It wasn't decreasing at all. In fact, it
Speaker 1: was increasing. That is that more sometimes the expansion seemed
Speaker 1: to be happening faster and faster. That means that the
Speaker 1: expansion of the universe was accelerating rather than slowing down.
Speaker 1: So Einstein's picture of the universe expanding and somehow mass
Speaker 1: slowing that down was wrong. There was another piece. There
Speaker 1: was something else that actually was pushing out on everything
Speaker 1: in the universe, making it move away from each other
Speaker 1: faster and faster every year. Interesting, So the universe wasn't
Speaker 1: just expanding, it was expanding faster and faster. What if
Speaker 1: that was alarming, or if it was just interesting, or
Speaker 1: how interesting would have been to find out that the
Speaker 1: universe was actually collapsing. I remember when this discovery happened.
Speaker 1: I was starting grad school. It was a huge shock.
Speaker 1: Everybody was stunned. Nobody expected this result. It was a
Speaker 1: massive revelation. It's the kind of thing you always dream
Speaker 1: about in science, seeing something out there which surprises everybody,
Speaker 1: which completely changes the way you think about the universe,
Speaker 1: Like those are the best moments in science. So we
Speaker 1: were all shocked, but we also knew that it was
Speaker 1: a far future thing, like it was not going to
Speaker 1: change our lives tomorrow or next year, or even in
Speaker 1: a billion years. We're talking about the very very deep
Speaker 1: future of the universe, not prediction for whether or not
Speaker 1: you shoually have a picnic tomorrow. Right, And so we
Speaker 1: learned I guess that the universe wasn't just expanding in
Speaker 1: like a coasting kind of way. It was actually like
Speaker 1: somebody was hitting the accelerator pedal on it, which means
Speaker 1: there must be some kind of force or energy making
Speaker 1: this happen right exactly, And immediately people went back to
Speaker 1: Einstein's great blunder. Remember, Einstein added his cosmological constant, his
Speaker 1: little bit of energy to the universe to balance the
Speaker 1: mass that he thought was going to collapse the universe.
Speaker 1: And then he got rid of it when he discovered
Speaker 1: the universe wasn't static. And then people revived it there like, well,
Speaker 1: we kind of need something to push out on the universe.
Speaker 1: This cosmological constant. You stick it into Einstein's equations, and
Speaker 1: it does just that. Creates this negative pressure pushes out
Speaker 1: on everything. It expands space as time goes on. So
Speaker 1: people plug this into Einstein's equations just to describe what
Speaker 1: they saw was happening out there in the universe. That
Speaker 1: expansion was accelerating, as you said, instead of slowing down.
Speaker 1: So he was a genius, right, He didn't have to
Speaker 1: be a falsely modest history justified his genius nous exactly.
Speaker 1: His equations were so powerful in general they can even
Speaker 1: describe discoveries made after his death. Yeah, so they called
Speaker 1: this mysterious or energy making the universe expand faster and faster.
Speaker 1: They give it a name dark energy. Yeah, and dark
Speaker 1: energy is really just our observation that the acceleration of
Speaker 1: the universe is expanding. We can describe it using Einstein's equations.
Speaker 1: If we plug a number in and we can measure
Speaker 1: that number and figure out what number we have to
Speaker 1: put into Einstein's equations. That doesn't mean we understand why
Speaker 1: that number is there or what this mechanism is dark energy.
Speaker 1: It's not like dark energy is a theory, a piece
Speaker 1: of physics that we understand we can make predictions for.
Speaker 1: It's really just sort of like a descriptive framework for
Speaker 1: something we don't yet understand. Right. And the name comes
Speaker 1: from to words dark and energy. And it's dark because
Speaker 1: you can't see it, right, It's not like the universe
Speaker 1: is glowing from this energy g and it's energy because
Speaker 1: it's doing work, right. Yeah, you definitely can't see dark energy.
Speaker 1: That's always nothing called it dark because it was mysterious,
Speaker 1: something we had been missing, something we couldn't yet explain.
Speaker 1: It was like a gap in our understanding. But yeah,
Speaker 1: it is also technically invisible. You can't look at a
Speaker 1: piece of space and see whether or not there's dark
Speaker 1: energy in it. What do you think they named the
Speaker 1: dark energy just for the it's mysterious sounding name, not
Speaker 1: because it's invisible to the visible light. I think so,
Speaker 1: for example, they are also theories of like dark gravity
Speaker 1: gravity that we hadn't accounted for yet. I think in general,
Speaker 1: dark is applied to like mysterious things in physics that
Speaker 1: doesn't seem very scientific then it. I'm not going to
Speaker 1: defend the name of dark energy. Well, it just so
Speaker 1: happens that it's also invisible, right, which is which makes it,
Speaker 1: either by coincidence or on purpose, a an app name
Speaker 1: for it, I suppose. I mean, to me, dark would
Speaker 1: describe something that's not invisible but black, like charcoal is dark.
Speaker 1: It's not invisible the invisible man, it's not dark, right,
Speaker 1: you can't see through him. So a more accurate name
Speaker 1: would be like visible energy or invisible matter. To me,
Speaker 1: dark is not a very visually descriptive name for it. Well,
Speaker 1: darkened as in it's not glowing. Yeah, that's true. It's
Speaker 1: definitely not glowing, and it's an energy because it's doing work.
Speaker 1: I guess, But where is this energy coming from? I guess, Well,
Speaker 1: that's the big question. We don't know where this energy
Speaker 1: is coming from. Einstein's equations tell you what the sort
Speaker 1: of shape of spaces and how it transforms, but as input,
Speaker 1: they require you to describe the universe, to say how
Speaker 1: much mass is there, how much radiation is there, and
Speaker 1: also how much potential energy is there. So Newton said
Speaker 1: gravity is only between massive objects. Einstein's generalization is to
Speaker 1: say no, gravity comes not just from objects with mass,
Speaker 1: but all forms of energy, including potential energy and potential
Speaker 1: energy actually has the opposite effect gravitationally as mass does.
Speaker 1: So things with potential energy form a negative pressure. They
Speaker 1: can expand the universe, they can push things apart. So
Speaker 1: in order to describe the expansion of the universe, you
Speaker 1: have to have some fields with potential energy that fill
Speaker 1: the universe, that give you enough energy to accelerate the
Speaker 1: expansion of the universe super dramatically. So you're saying that
Speaker 1: maybe the universe just by itself in a vacuum and nothingness,
Speaker 1: just space itself, has this potential energy, right, which is
Speaker 1: making things expand. But why is it called potential, Like,
Speaker 1: what's its potential, like it has the potential to do work.
Speaker 1: Or what potential energy is the energy of configuration, right,
Speaker 1: like a book on a shelf has gravitational potential energy
Speaker 1: rather than kinetic energy, and waves can also have potential energy.
Speaker 1: If you have a guitar string, for example, and you
Speaker 1: pull it out but you don't yet release it, then
Speaker 1: the tension in that string is giving it a lot
Speaker 1: of potential energy. When you release it, the string that
Speaker 1: vibrates it turns into kinetic energy, but that energy is
Speaker 1: slashing back and forth between potential and kinetic as the
Speaker 1: string vibrates. And quantum fields are the same way. The
Speaker 1: fields that we think fills space can either oscillate with
Speaker 1: kinetic energy and those are particles, or they can have
Speaker 1: potential energy because of their configuration. For example, the Higgs
Speaker 1: view we think has energy stored inside of it even
Speaker 1: when it's not wiggling, sort of like stuck on this shelf,
Speaker 1: it has a bunch of energy stored inside of it
Speaker 1: just because of its configuration M and so we think
Speaker 1: that's what dark energy is. It's some kind of potential
Speaker 1: energy that the universe has, or that space has. We
Speaker 1: know that space has some potential energy because of these
Speaker 1: quantum fields. We think the quantum fields are real, We
Speaker 1: think they have potential energy. We think all of space
Speaker 1: really does have some potential energy. We also observe that
Speaker 1: the universe is expanding, as if there is some potential
Speaker 1: energy causing this gravitational repulsion. We try to bring these
Speaker 1: two ideas together and say, is our estimate of the
Speaker 1: amount of potential energy we already know exists in space
Speaker 1: enough to describe this repulsion we see in the universe,
Speaker 1: this expansion of the universe. People do that calculation, but
Speaker 1: those two numbers do not agree. In fact, they disagree
Speaker 1: by more than ten to the one hundred. So we
Speaker 1: don't have an understanding of where the potential energy comes
Speaker 1: from to create the expansion that we see in space.
Speaker 1: We know the space has some potential energy in it,
Speaker 1: it doesn't seem to have the right amount of potential
Speaker 1: energy to cause the expansion we see out there in
Speaker 1: the universe. You mean from a quantum field, we can
Speaker 1: measure how much potential energy there has to be in
Speaker 1: order to create this expansion, and then we can calculate
Speaker 1: how much potential energy we think there is from the
Speaker 1: quantum fields and those two numbers disagree by ten to
Speaker 1: the one hundred. Well, at least you can't explain it
Speaker 1: with the quantum fields that you know about, right exactly?
Speaker 1: Could there be another quantum field or something or something
Speaker 1: you're not seeing we're thinking about. Absolutely, there can be.
Speaker 1: There has to be. There has to be some other explanation.
Speaker 1: The point is just that we observe some expansion. We
Speaker 1: think it might be due to some potential energy, but
Speaker 1: we really do not have any understanding of the mechanism
Speaker 1: for that potential energy to exist in the universe. All right, Well,
Speaker 1: let's then assume there is some sort of potential energy
Speaker 1: hidden in the universe, and there's quite a lot of it, right,
Speaker 1: because it's making the universe expand faster and faster. But
Speaker 1: it's just it's it's one of those things that only
Speaker 1: you can only tell from over the whole universe, right,
Speaker 1: can't tell, like looking at your hand in front of you,
Speaker 1: that there is dark energy between you and your hand,
Speaker 1: although there is dark energy between you and your hand,
Speaker 1: that's right. Something people are often confused about is why
Speaker 1: this expansion seems to be happening only between galaxies or
Speaker 1: clusters of galaxies and not between you and your friend
Speaker 1: or you and your lunch. And the answer is that
Speaker 1: it is happening everywhere. All of space is expanding. The
Speaker 1: distance between us and the Moon, and the distance between
Speaker 1: us and the Sun. All of space is expanding simultaneously
Speaker 1: at the same rate, all the time. It's actually a
Speaker 1: very very small amount of expansion over many millions of
Speaker 1: light years. Every second space grows by like a seventy kilometers.
Speaker 1: It's a tiny, tiny level of expansion over short distances.
Speaker 1: And over short distances like between me and my chair
Speaker 1: or between the Earth and the Sun, other forces are
Speaker 1: more powerful. So, for example, the Sun is powerful enough
Speaker 1: to hold the Earth in its orbit even if space
Speaker 1: is very gently expanding between it. But over very long distances,
Speaker 1: like between galaxies, gravity gets very very weak, and dark
Speaker 1: energy gets very very powerful, and so over those bigger distances,
Speaker 1: dark energy winds. So in our current understanding of the universe,
Speaker 1: dark energy is only effective at pushing apart things that
Speaker 1: are very very far away from each other, like galaxies,
Speaker 1: not things that are closer together like you and your lunch. Well,
Speaker 1: it's more noticeable for things that are really far apart,
Speaker 1: like galaxies, but it is sort of affecting our orbit
Speaker 1: with the Sun, right Like, it's making it just a
Speaker 1: little bit harder for the Sun to keep the Earth
Speaker 1: in its orbit, and in a way, it's sort of
Speaker 1: helping the Earth from collapsing into the Sun a little bit. Yeah,
Speaker 1: it definitely plays a role, almost negligible, but yeah, not quite.
Speaker 1: Universe would be a little bit different if that didn't happen.
Speaker 1: All right, Well, I think the assumption so far is
Speaker 1: that this dark energy is constant, that it's sort of
Speaker 1: like there as a feature of the universe, and it's
Speaker 1: always been there and maybe always will be there. But
Speaker 1: the question is what if it's not. What if dark
Speaker 1: energy changes? What if it decides that it wants to
Speaker 1: join the dark side? And so let's get into what
Speaker 1: might happen. But far ast, let's take another quick break.
Speaker 1: All right, we're talking about the Big rip now, Daniel.
Speaker 1: Is that what happens when the mind Cloreans decide to
Speaker 1: go on strike and the whole universe falls apart. No,
Speaker 1: that's when Disney by Star Wars and puts out a
Speaker 1: bunch of low quality stuff. It's called the Big rip Off.
Speaker 1: Not a fan huh of the new stuff? Why did
Speaker 1: you just join the Star Trek camp while you're added.
Speaker 1: I'm in both camps. I love Star Wars and Star Trek.
Speaker 1: You just like stars do? I do like Stars Intact
Speaker 1: anything with stars and sip almost anything. Yeah, but have
Speaker 1: you seen and or Daniel? I have seen it? Yeah,
Speaker 1: all right, I'm guessing your silence means that I'm not
Speaker 1: a fan either. I like to say positive or silent
Speaker 1: on the podcast. All right, Well, we're talking about the
Speaker 1: Big Rip, which is a possible thing that might happen
Speaker 1: to the universe, and it's related to a dark energy
Speaker 1: which is making the universe expand faster and faster now.
Speaker 1: But the universe hasn't always been expanding at the same
Speaker 1: rate in its history, right, Yeah, the history of the
Speaker 1: expansion the universe is quite complicated. We have some very
Speaker 1: rapid expansion early on that we call inflation. Is sort
Speaker 1: of like the last stages of the Big Bang, when
Speaker 1: things expanded like by a factor tended the thirty intended
Speaker 1: the minus thirty seconds. And then for a while the
Speaker 1: universe was matter and radiation dominated. So the expansion was
Speaker 1: still happening, but it was decelerating. It was slowing down
Speaker 1: a bit. But dark energy was quietly building, and around
Speaker 1: five billion years ago dark energy became the dominant component
Speaker 1: of the universe and that's when the acceleration really took off.
Speaker 1: And so the last five billion years, the expansion has
Speaker 1: been accelerating. Now, when you say the dark energy kind
Speaker 1: of agreed, did it actually grow or is it just
Speaker 1: that the universe got bigger. What's the difference between those two, Well,
Speaker 1: like for the same size universe, if the universe had
Speaker 1: been the same size, what are you saying that dark
Speaker 1: energy got stronger in the meantime or did it just
Speaker 1: get more powerful because the universe is at bigger and
Speaker 1: dark energy gets bigger the bigger spaces. Now, the current
Speaker 1: theory is that dark energy is constant, that in a
Speaker 1: certain amount of space you have a certain amount of
Speaker 1: potential energy and that doesn't change. So dark energy, we think,
Speaker 1: is a constant strength through time. But we do think
Speaker 1: that the universe is expanding and is making new space
Speaker 1: and therefore making more dark energy. Most of the stuff
Speaker 1: in the universe dilutes as space gets bigger, Like you
Speaker 1: have a certain amount of mass in the universe and
Speaker 1: then things expand then the mass gets less dense. Dark
Speaker 1: energy doesn't get less dense as the universe expands, because
Speaker 1: it's an aspect of space itself. It's like inherent in space,
Speaker 1: and so as the universe expands, dark energy doesn't shrink,
Speaker 1: and so proportionately it grows to be a larger fraction
Speaker 1: of the energy budget of the universe. So when you
Speaker 1: say that the universe like it inflated really rapidly, then
Speaker 1: it slowed down, then it picked back up again, that's
Speaker 1: still consistent with a constant dark energy. But is that
Speaker 1: only because you're assigning the accelerat a shan to slow
Speaker 1: down to other things that you also don't know what
Speaker 1: they are. Well, we think we know if the rest
Speaker 1: of the universe is right. We think there's normal matter,
Speaker 1: there's some radiation. We think there's a lot of dark matter.
Speaker 1: We don't know exactly what dark matter is made out of,
Speaker 1: but we have a pretty good sense of how much
Speaker 1: of it there is and where it was and how
Speaker 1: it controlled the large scale structure of the universe. But
Speaker 1: in order to describe the expansion history that we see,
Speaker 1: you need to plug in a certain amount of energy
Speaker 1: per unit of space, and then it actually describes the
Speaker 1: history quite nicely. But we still don't know what costs
Speaker 1: in the initial inflation, right, the big bank. That could
Speaker 1: have been also dark energy, but instead you're assigning it
Speaker 1: to something else, right, I see, Yes, And there's still
Speaker 1: a lot of confusion about what happened early on. The
Speaker 1: current theory is that inflation may have been due to
Speaker 1: some other field with a lot of potential energy, like
Speaker 1: the inflaton field, because that expansion was quite different from
Speaker 1: the expansion we're seeing now, different and just the rate
Speaker 1: or different in the nature of it. Definitely different in
Speaker 1: the rate, possibly also different in the nature. It could
Speaker 1: have been a different field providing potential energy to create
Speaker 1: at that expansion. We just don't know, huge question. Or
Speaker 1: or it could have been dark energy to right, Or
Speaker 1: it could have been dark energy that was changing. And
Speaker 1: in fact, it's not quite accurate to say that the
Speaker 1: picture of dark energy it's constant, describes the universe very well,
Speaker 1: because there's some controversy there. We measure the dark energy
Speaker 1: in the universe in late times using supernovas and also
Speaker 1: in early times using its effect on the cosmic microwave
Speaker 1: background radiation, we actually get different numbers by a little bit,
Speaker 1: and that's been a persistent tension. It's called the Hubble
Speaker 1: Tension whole podcast episode about that. That inspires people to
Speaker 1: come up with other ideas, something called early dark energy,
Speaker 1: to like add a little bit more dark energy early
Speaker 1: on in the universe. So the very very beginning of
Speaker 1: the universe, big question marks about how much expansion there
Speaker 1: was and what caused it. After that, it's more steady
Speaker 1: and it's well described by universe with almost constant dark energy.
Speaker 1: But I say it's it's sort of a theory, right,
Speaker 1: there's still the possibility that maybe dark energy will increase again,
Speaker 1: or maybe this mysterious you know Inflanton or other quant
Speaker 1: and field with potential energy might kick back in exactly
Speaker 1: because we don't have a good theoretical description, so we
Speaker 1: can't really make predictions. We're just observing things. It's like
Speaker 1: if you're watching the weather and you're noticing some trends, like, hey,
Speaker 1: in southern California, it seems to be the same temperature
Speaker 1: every single day, because I mean, I could predict confidently
Speaker 1: it's always going to be the same temperature only if
Speaker 1: I actually understood what caused them, Like why is it
Speaker 1: the same temperature every day? If I had some understanding
Speaker 1: of the underlying mechanism that I could make some prediction. Otherwise,
Speaker 1: I'm just observing and extrapolating ignorantly. And that's basically what
Speaker 1: we're doing now. We don't understand the mechanism underlying it
Speaker 1: at all. We just see these trends and we make
Speaker 1: simplifying assumptions. I feel like you just described my job
Speaker 1: on this podcast anyway, to extrapolate ignorantly for money, and
Speaker 1: listeners shouldn't take this as a criticism, right, This is
Speaker 1: the first step. This is very, very fresh science. We
Speaker 1: only discovered this was happening a couple of decades ago.
Speaker 1: And the first thing you do is observe and characterize
Speaker 1: and look for patterns, and then you try to build
Speaker 1: up some theory that describe And people are hard at
Speaker 1: work and exactly that, trying to understand what's causing this
Speaker 1: and what its future might be, because, as you say,
Speaker 1: we don't know what's causing it. We don't know if
Speaker 1: it's going to change in the future. Right, And so
Speaker 1: I think we've talked about in the podcast before how
Speaker 1: there are three possibilities. So the dark energy, or at
Speaker 1: least whatever is powering or whatever power is, the expansion
Speaker 1: of the universe could do one of their things. It
Speaker 1: can go away, you can stay the same, or it
Speaker 1: can get even stronger. Right, And so if it goes away,
Speaker 1: then what happens to the universe? It crunches down. If
Speaker 1: it goes away, then the universe is now matter and
Speaker 1: radiation dominated, and those things tend to pull things back together.
Speaker 1: And so then it's back to the question of like,
Speaker 1: is there enough matter to slow things down and pull
Speaker 1: them back together into a big crunch, or is there
Speaker 1: enough velocity already in that expansion so that things skeet
Speaker 1: away from each other, slowing down but never actually coming
Speaker 1: back together. If you just like turned off the dark energy,
Speaker 1: we don't know we can make that calculation. I can't
Speaker 1: make that calculation today on the podcast, but maybe somebody
Speaker 1: out there knows. But nobody's ever done it. It's sort
Speaker 1: of a particular scenario where you had dark energy in
Speaker 1: the universe or fourteen billion years and then suddenly turn
Speaker 1: it off. I don't know if anybody's actually done that calculation.
Speaker 1: All right, Well, that yours may may not crushed together.
Speaker 1: What happens if dark energy stays the same, It's if
Speaker 1: it stays constant that the way it is now. Then
Speaker 1: the expansion of the universe continues, and it continues to accelerate,
Speaker 1: which means that space between things grows faster and faster,
Speaker 1: and over very large distances. That expansion is faster than
Speaker 1: the speed of light, which means that things are disappearing
Speaker 1: past the edge of our cosmic horizon. There are galaxies
Speaker 1: out there who are shooting photons at us, and those
Speaker 1: photons will never arrive because the space between us and
Speaker 1: that galaxy is increasing faster than light is making progress
Speaker 1: through that space. So, in that scenario where dark energy
Speaker 1: stays constant, the observable fraction of the universe gets smaller
Speaker 1: and smaller as time goes on, things start to disappear.
Speaker 1: We don't think in that scenaria of the galaxy will
Speaker 1: there at the party will always have enough gravity to
Speaker 1: hold itself together, and the Earth will still orbit around
Speaker 1: the Sun, but our galaxy will become more and more
Speaker 1: isolated relative to other galaxies. Right. We talked about how
Speaker 1: in this scenario, the nights guy gets dark and darker, right,
Speaker 1: because all the stars, or at least all the galaxies
Speaker 1: out there, will move out of our view, but will
Speaker 1: add the stars move out of out our view the
Speaker 1: ones in our galaxy. Isn't the opposite going to happen? Now?
Speaker 1: The galaxy is probably strong enough, has enough gravity to
Speaker 1: hold itself together if dark energy stays constant, so the
Speaker 1: other galaxies will disappear, and future astronomers will look up
Speaker 1: at the night sky and only see stars in our galaxy,
Speaker 1: and they will think our galaxy is the whole universe
Speaker 1: because they won't be able to see anything else. WHOA,
Speaker 1: but how about future future future astronomers. Isn't there enough
Speaker 1: stuff in our galaxy that it will eventually crunch down
Speaker 1: into a black hole eventually? Yes, it will crunch down
Speaker 1: into a black hole. Gravity will eventually win. Things are
Speaker 1: swirling around and avoiding the inevitable. But you know, things
Speaker 1: bump into each other and lose angular momentum, and they
Speaker 1: radiate energy through gravitational waves. So the very very far
Speaker 1: future is that the supermassive black hole eats our galaxy.
Speaker 1: So the very deep future of the universe, if dark
Speaker 1: energy is constant, is a bunch of black holes isolated
Speaker 1: from each other. Yeah, too far away to even see
Speaker 1: each other, right or affect each other, Yeah, exactly, Each
Speaker 1: one will be past the other's cosmic horizons. Wow, not
Speaker 1: a bright future for the universe. You don't want to
Speaker 1: buy shares in that universe. Unless shares are for flashlights,
Speaker 1: then yeah, those are going to become very, very valuable
Speaker 1: in the future. So then there's a last scenario, which
Speaker 1: is that maybe dark energy will somehow kick back in
Speaker 1: or whatever made the initial inflation of the universe happen,
Speaker 1: that might come back and which will make the universe
Speaker 1: expand even faster than it is now. Yeah, there's this
Speaker 1: fun idea that dark energy will convert into something called
Speaker 1: phantom energy. This is energy which will grow even more
Speaker 1: rapidly than just the expansion of space, so that as
Speaker 1: space expands, the fraction of energy in each chunk of
Speaker 1: space also goes up, which means that the acceleration increases
Speaker 1: faster and faster. Wait, the idea is that dark energy
Speaker 1: somehow evolved like a pokemon like it levels up. You
Speaker 1: just need to buy more and more packs. That's all
Speaker 1: that has to happen for this scenario to unfold. Nobody
Speaker 1: is that the idea that it's like the same energy,
Speaker 1: but somehow it gets kicked up the level or something.
Speaker 1: The theoretical underpinnings of phantom energy are pretty fuzzy. They
Speaker 1: require a bunch of really weird fields that have strange
Speaker 1: things like negative kinetic energy. It's possible for them to
Speaker 1: exist in the universe and sort of wake up only
Speaker 1: in late times. This is the theories that people have developed,
Speaker 1: and they would accelerate the expansion of the universe in
Speaker 1: even more surprising ways because they have very strange kinetic
Speaker 1: and potential energy. But the end result, I guess is
Speaker 1: that it levels up to something called phantom energy, because
Speaker 1: that just sounds more mysterious. I guess it's actually named
Speaker 1: after the movie The Phantom Menace. Guy wrote this paper
Speaker 1: called The Phantom Menace the Future of the Universe, So
Speaker 1: he was a fan. He was defan, he writes in
Speaker 1: the paper quote, a phantom is something which is apparent
Speaker 1: to the site or other senses, but has no corporeal existence,
Speaker 1: an appropriate description for a form of energy necessarily described
Speaker 1: by unorthodox physics. So he's sort of putting in the
Speaker 1: like ghostly category. But did he reference the movie? Oh absolutely,
Speaker 1: it was very much a reference to the movie The
Speaker 1: Phantom Menace that was mentioned in the academic paper The
Speaker 1: Phantom Menace is part of the title of the paper. Yes,
Speaker 1: the Phantom energy totally named after the movie The Phantom Menace,
Speaker 1: or maybe he just named the title after the movie.
Speaker 1: Doesn't mean that Phantom energy was based on the movie,
Speaker 1: does it, Well, the science of Phantom energy is not
Speaker 1: based on the movie. But yeah, he named it phantom
Speaker 1: energy because he was inspired by the use of the
Speaker 1: word phantom from The Phantom Menace. I guess you could
Speaker 1: say he was a fan. I don't know if his
Speaker 1: name was Tom, he should have changed it, But I
Speaker 1: guess the point is that maybe this energy is going
Speaker 1: to increase, level up, get stronger, which is going to
Speaker 1: make the universe expand faster and faster and faster and
Speaker 1: faster and faster, which might rip the universe apart. Right exactly,
Speaker 1: Dark energy by itself will already rip galaxies apart, but
Speaker 1: phantom energy will get more powerful, and so eventually it
Speaker 1: will overcome even the gravity of our galaxy, holding the
Speaker 1: galaxy itself apart, and as time goes on, it will
Speaker 1: increase in power, eventually pulling our Solar system apart, and
Speaker 1: then shredding the Earth and in the deep deep future
Speaker 1: even pulling all atomic bonds apart. WHOA, So you're saying,
Speaker 1: like like space itself will become like inhospitable almost in
Speaker 1: a way. Space will be expanding so much, even at
Speaker 1: the molecular sub atomic level, then not even quarks will
Speaker 1: be able to hang onto each other. Not even quarks
Speaker 1: will be able to pull each other apart. All bonds
Speaker 1: eventually will be weaker than the phantom energy, which will
Speaker 1: overcome everything. It's this which will overcome everything. So like
Speaker 1: two quarks will be hanging out to each other, but
Speaker 1: then space will rip it apart, and then they'll never
Speaker 1: see each other again ever, right, Yeah, the final end
Speaker 1: of the universe is sort of similar to what we
Speaker 1: described with dark energy, where you had black holes separated
Speaker 1: by essentially infinitely expanding space, so they can't communicate as
Speaker 1: no interaction except the phantom energy. Version of that is
Speaker 1: that particles are now separated by infinitely expanding space, so
Speaker 1: they can't interact with each other. They can't even tell
Speaker 1: that there are other particles in the universe. WHOA. So
Speaker 1: then like every single particle in the known existence in
Speaker 1: the universe will be by itself with no way to
Speaker 1: communicate with any other particle unless I guess the space
Speaker 1: makes a new particle next to it or something. Right, Well,
Speaker 1: that's the really complicated thing about corks, right, is that
Speaker 1: corks do not like to be by themselves. We think
Speaker 1: that as you pull quarks apart, there's so much energy
Speaker 1: in the strong force that it pops new corks out
Speaker 1: of the vacuum. So nobody actually knows what's going to
Speaker 1: happen to quirks. It might be that as phantom energy
Speaker 1: pulls them apart, it creates this exponential cascade of particles
Speaker 1: being produced, filling space with all sorts of quirks. So
Speaker 1: we don't know who who's gonna win in the end.
Speaker 1: They're the strong force or phantom energy. You mean, like
Speaker 1: as the universe rips apart, it's also gonna make new quarks.
Speaker 1: So what you're saying, like opening a bag of popcorns,
Speaker 1: you rip it open, all these corks pop out. That's
Speaker 1: what happens when we make pairs of quarks with the
Speaker 1: large Hadron collider that have a large velocity relative to
Speaker 1: each other. They created back to back. They're zooming away
Speaker 1: from each other near the speed of light, and they
Speaker 1: create this enormous shower of new corks. Between them out
Speaker 1: of the energy contained in the strong force bonds between them.
Speaker 1: And so we think the same thing might happen to
Speaker 1: all quarks in the universe when phantom energy tries to
Speaker 1: pull them apart from their partners. M hmm, but I
Speaker 1: guess it will be sort of. I mean, things will
Speaker 1: happen in order, like we won't be around to see that, right, Like,
Speaker 1: first the galaxy is gonna, you know, rip the stars
Speaker 1: within the gas. They're going to rip apart, but maybe
Speaker 1: it's not strong enough to rip apart solar systems, but
Speaker 1: eventually it's going to rip apart solar systems. And then
Speaker 1: eventually it's going to rip apart stars and planets. So
Speaker 1: the final big rip, according to some calculation, is going
Speaker 1: to be in about twenty billion years. Wait what we
Speaker 1: have a time estimate here? We have a time based
Speaker 1: on estimates of the amount of phantom energy that might
Speaker 1: be in the universe. This is total speculation, just like
Speaker 1: pick some numbers and see how it plays out. But
Speaker 1: it's fun to think about, like if dark energy starts
Speaker 1: to accelerate, now, is that what you mean at a
Speaker 1: certain value, like a random value, or what would value
Speaker 1: like at a random value. Yeah, there's a whole spectrum
Speaker 1: of possible different levels of phantom energy that might exist
Speaker 1: in the universe, and they just would like pick a
Speaker 1: number and they put it in and they can make
Speaker 1: specific predictions. Though these are not like weather reports. You
Speaker 1: shouldn't base your life around these. It's just like illustrative,
Speaker 1: like to think about how fast things would happen. But
Speaker 1: with enough phantom energy happening tomorrow, the universe could be
Speaker 1: rip apart the day after tomorrow. Right, So the twenty
Speaker 1: two billion years is just based on a number. It's
Speaker 1: just based on a number, but it's a plausible number
Speaker 1: when it's not completely inconsistent with what we see today
Speaker 1: in the universe. Oh, meaning like if our measurements are
Speaker 1: a little bit off and that we're rang in the sands,
Speaker 1: then maybe the universe is expanding faster and faster and
Speaker 1: dark energy is not constant. Than this is how much
Speaker 1: time we have, Like this is the worst case scenario
Speaker 1: based on our the fuzziness of our measurement. Yeah, and
Speaker 1: the good news is that we have twenty billion years
Speaker 1: until the final big rip. And the double good news
Speaker 1: is that we think that the Earth will survive until
Speaker 1: about thirty minutes before the end. Oh, that's good, So
Speaker 1: we'll be around except for the last thirty minutes of it.
Speaker 1: And between thirty minutes and the end is when the
Speaker 1: Earth will get ripped apart and then eventually atoms, so
Speaker 1: we'll miss the last fireworks, but we'll still be here
Speaker 1: for most of it. Well, assuming the Earth is still here, right,
Speaker 1: this is the Earth supposed to be swallowed up by
Speaker 1: the Sun in like eight billion years. Yeah, the Sun
Speaker 1: only has a few more billion years. But assuming that
Speaker 1: we know, we move the Earth to some other Sun,
Speaker 1: or we rehab the Sun or something like that, or
Speaker 1: we maybe change the Earth's orbit and we end up
Speaker 1: orbiting a white dwarf for billions of years. That could
Speaker 1: happen if we managed to do that sort of solar
Speaker 1: system engineering. Then the timeline is we have twenty billion
Speaker 1: years until phantom energy pulls the universe apart. If phantom
Speaker 1: energy even is a real thing, right, it might even
Speaker 1: be like the descendants of Luke Skywalker who are watching
Speaker 1: this happen may or may not be human. As we
Speaker 1: discussed Earth, they certainly look human, well so do I, Daniel.
Speaker 1: I do have my doubts about that, and you know,
Speaker 1: the current evidence suggests that dark energy seems mostly constant.
Speaker 1: We don't see it ticking up. That we do have
Speaker 1: some questions about what's going on in the early universe.
Speaker 1: There are a few measurements that disagree with that, like
Speaker 1: studies of distant quasars that might suggest some slight increase
Speaker 1: in the energy density of dark energy in recent times.
Speaker 1: But for the most part, mainstream cosmologists think that dark
Speaker 1: energy is constant. That's the simplest explanation. Though again, we
Speaker 1: don't understand the mechanism for it, so we can't confidently
Speaker 1: make hard predictions. Right, we don't know what it is.
Speaker 1: And in fact, I feel like we're sort of defining
Speaker 1: it to be constant, and so we're measuring it to
Speaker 1: be constant. But actually the history says that it maybe
Speaker 1: wasn't constant. That's actually true, and as we make observations,
Speaker 1: we add bells and whistles to our models to accommodate
Speaker 1: what we see, and then we try to explain it
Speaker 1: and describe it. Wow to me. In the far future, though,
Speaker 1: somebody will make a movie that says, a long time ago,
Speaker 1: n galaxy, far far away, you figured out the phantom
Speaker 1: energy and two guys talked about it on a podcast.
Speaker 1: Not a very exciting movie. But you know that's as
Speaker 1: you say, as you seem to think that's the trend
Speaker 1: for these Disney Plus shows. No comment, We're just doing
Speaker 1: it in with less special effects. All right, Well, I
Speaker 1: guess stay tuned for two two billion years and then
Speaker 1: we'll find out if that's true or not exactly. And
Speaker 1: as time goes on, we'll learn more and more about
Speaker 1: the universe, and we will refine our models and hopefully
Speaker 1: be able to anticipate it long before it happens, or
Speaker 1: just hang on as long as we can. All right, Well,
Speaker 1: we hope you enjoyed that. Thanks for joining us, See
Speaker 1: you next time. Yea. Thanks for listening, and remember that
Speaker 1: Daniel and Jorge Explain the Universe is a production of
Speaker 1: I Heart Radio. For 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.