SPEAKER_1: Coming up on StarTalk, it's a Things You Thought You Knew edition.
SPEAKER_1: Of course, I'm there with Chuck Nice, and we tackle Planet X.
SPEAKER_1: What's up with that?
SPEAKER_1: Is it still there?
SPEAKER_1: Who knows?
SPEAKER_1: We know, and we tell you.
SPEAKER_1: Not only that, we tackle the three-body problem.
SPEAKER_1: No, I actually haven't seen the series yet, but I do know what the three-body problem is in physics, and you're gonna hear all about it.
SPEAKER_1: And lastly, we're gonna go to the ends of time and have a chat about one scenario that's particularly disturbing about how the universe might end.
SPEAKER_1: Next, on StarTalk.
SPEAKER_1: Welcome to StarTalk, your place in the universe where science and pop culture collide.
SPEAKER_1: StarTalk begins right now.
SPEAKER_1: So, Chuck, anything been eating you lately?
SPEAKER_1: So many things.
SPEAKER_2: I don't know if we have time, you know.
SPEAKER_2: I did recently see a thing about Planet X.
SPEAKER_1: Planet X.
SPEAKER_2: Which I was very disappointed to find out had nothing to do with Malcolm.
SPEAKER_1: This can't be widely known, because I don't hear people talking about it when they talk about Planet X.
SPEAKER_1: So I'm going to give you just some back story here.
SPEAKER_1: Alright.
SPEAKER_1: William Herschel accidentally discovers the planet Uranus.
SPEAKER_1: We knew about Mercury, Venus, Earth, Mars, Jupiter, Saturn.
SPEAKER_1: There it stood for millennia.
SPEAKER_1: He discovers Uranus.
SPEAKER_1: It's a beautiful paper.
SPEAKER_1: Nobody had ever discovered a planet, because all these planets were known to the ancients.
SPEAKER_1: They're all visible in the night sky to everybody.
SPEAKER_1: Caveman knew about the planets.
SPEAKER_1: Okay, anybody freaks out, because oh my gosh, there's more than five planets.
SPEAKER_1: All right, this is late 1700s, and he's Brit, so of course he named it after his benefactor, who was?
SPEAKER_2: Oh, the king.
SPEAKER_1: The king?
SPEAKER_1: Yeah.
SPEAKER_1: King, which king?
SPEAKER_1: George.
SPEAKER_1: Of our Declaration of Independence.
SPEAKER_2: That's right.
SPEAKER_1: Ultimately, clearer heads would prevail, and it was renamed from George to Uranus.
SPEAKER_2: Uranus.
SPEAKER_1: Yeah, who are Uranus, Uranus.
SPEAKER_2: Uranus.
SPEAKER_1: Okay.
SPEAKER_2: Which by the way, is a much better name.
SPEAKER_1: Than George.
SPEAKER_2: Than George.
SPEAKER_2: And even better than Uranus.
SPEAKER_1: So we're watching Uranus.
SPEAKER_2: All right.
SPEAKER_1: And we're getting a segment of its orbit, because it's far out.
SPEAKER_1: It's not moving very fast.
SPEAKER_2: Right.
SPEAKER_1: These things take a long time to go around the sun.
SPEAKER_1: Even though we only had a small segment, we said, hey, its path is not following Newton's laws of motion and gravity.
SPEAKER_1: So someone suggested maybe we finally found the limit of Newton's laws in the universe.
SPEAKER_1: Newton, you dumbass.
SPEAKER_2: Dumbass Newton, should have known.
SPEAKER_1: No, maybe they only apply to like Earth and the Moon and Earth and the Sun and inner planets in the Sun.
SPEAKER_1: That could have been.
SPEAKER_1: Then someone said, maybe Newton's laws do apply, but there's another planet out there we've yet to discover whose gravity we have yet to reconcile in these equations.
SPEAKER_2: Which is, if you had just discovered one planet.
SPEAKER_1: Maybe there's another one.
SPEAKER_1: Because that cracked open the egg.
SPEAKER_1: That planet egg, right?
SPEAKER_1: So, some French mathematicians and Le Verrier was, what was his name?
SPEAKER_1: Le Verrier.
SPEAKER_2: Le Verrier.
SPEAKER_1: Le Verrier.
SPEAKER_1: Laplace, I think, had a hand in this.
SPEAKER_1: And they communicated this prediction to an observatory in Berlin.
SPEAKER_1: And Johann Gottfried Gallee, G-A-L-L-E.
SPEAKER_2: Okay.
SPEAKER_1: How are you pronouncing that?
SPEAKER_2: Right.
SPEAKER_1: Practically that night, he discovers Neptune.
SPEAKER_2: That's pretty wild.
SPEAKER_1: That, the power of math, the power of Newton's laws.
SPEAKER_2: Right.
SPEAKER_1: Okay?
SPEAKER_1: Okay.
SPEAKER_2: Science.
SPEAKER_1: Science.
SPEAKER_1: Neptune is moving.
SPEAKER_1: Okay, so we're now in the 1800s, 1846, something like this, mid 1800s.
SPEAKER_1: All right.
SPEAKER_1: And, all right, let's follow its orbit.
SPEAKER_2: Right.
SPEAKER_1: We do that.
SPEAKER_1: It's not following Newton's laws.
SPEAKER_1: We've been down that road before.
SPEAKER_2: Well, that must be another planet.
SPEAKER_1: Must be another planet.
SPEAKER_1: Of course.
SPEAKER_1: Okay, let's start a hunt for that planet.
SPEAKER_1: Let's start the hunt for Planet X.
SPEAKER_2: Gotcha.
SPEAKER_1: So people say, we've done this before.
SPEAKER_1: Let's predict.
SPEAKER_1: Just do the math of La Verriere.
SPEAKER_1: Look over here.
SPEAKER_2: And it should be there.
SPEAKER_1: Sure, but it was not there.
SPEAKER_2: Uh-oh.
SPEAKER_2: Maybe it was hiding from you because you are so stupid.
SPEAKER_1: So the hunt for Planet X was like this massive planet.
SPEAKER_1: It was a planet hunt like none other.
SPEAKER_2: Okay?
SPEAKER_1: All right.
SPEAKER_1: Preston Lowell of the New England Lowells loved astronomy, was not formally trained, but he had money, built an observatory, the best one in the world.
SPEAKER_1: So he found a mountain in Arizona.
SPEAKER_1: Okay?
SPEAKER_1: Where else are you gonna put it?
SPEAKER_1: Right?
SPEAKER_1: Arizona.
SPEAKER_2: There you go.
SPEAKER_1: Found a mountain, built an observatory.
SPEAKER_1: Finest optics, finest everything.
SPEAKER_1: The observatory is called?
SPEAKER_2: The Lowell Observatory.
SPEAKER_1: The Lowell Observatory.
SPEAKER_1: He initiated the search for Planet X.
SPEAKER_1: He wanted to know.
SPEAKER_2: Yes.
SPEAKER_1: Instead of choosing where to look, he starts a systematic survey in the plane of the solar system.
SPEAKER_2: Okay.
SPEAKER_1: A photographic survey.
SPEAKER_1: Now, how do you discover a planet?
SPEAKER_1: It has to be a dot of light in one photo, then in another photo, it is moved to a different spot.
SPEAKER_2: Right.
SPEAKER_2: Yeah.
SPEAKER_1: Okay?
SPEAKER_1: So he initiates this.
SPEAKER_1: Brings in Clyde Tombaugh to conduct the survey.
SPEAKER_1: He dies.
SPEAKER_1: Sorry.
SPEAKER_2: Because it was boring as hell.
SPEAKER_1: No, no, no.
SPEAKER_1: Lowell dies.
SPEAKER_2: Oh, okay.
SPEAKER_2: I thought Clyde died because it's just like, all I do night after night is look up here and wait for a dot of light.
SPEAKER_1: This is gonna kill me.
SPEAKER_2: Oh, it's gonna kill me.
SPEAKER_1: Oh, this is gonna kill me.
SPEAKER_1: 1930 is the announcement.
SPEAKER_1: Planet X discovered.
SPEAKER_1: Oh, by the way, it got named Pluto.
SPEAKER_1: There's a dot in one photo and it's moved to another place in another photo.
SPEAKER_1: He would joke about this.
SPEAKER_1: He lived into the 1990s.
SPEAKER_1: He would joke about this.
SPEAKER_1: Hey, Clyde, how did you discover where Pluto was?
SPEAKER_1: He said, oh, I looked up in the sky and there was an arrow pointing to it.
SPEAKER_1: Anytime you show the slide, there's an arrow pointing to it.
SPEAKER_1: He persists with this being Planet X into the 1990s.
SPEAKER_1: Well, how big was it?
SPEAKER_1: What mass was it?
SPEAKER_1: They assigned it the mass that Planet X would have to be to perturb Neptune in the way we discovered it.
SPEAKER_1: Even though it wasn't anywhere where the prediction said it was going to be, they said, fine, it's out there.
SPEAKER_1: Planet X, we good, we good.
SPEAKER_1: Okay, over the decades, we find out it's not as big and not as massive as they said it was.
SPEAKER_2: A lot of ice, a lot of reflection.
SPEAKER_1: We found a moon.
SPEAKER_2: Smaller than it was.
SPEAKER_1: We found a moon.
SPEAKER_1: Its mass was like one fifth the mass of our moon.
SPEAKER_2: And along comes an astrophysicist named Neil deGrasse Tyson.
SPEAKER_2: And says, wait a minute.
SPEAKER_2: There needs to be one more nail in this coffin.
SPEAKER_2: Stop.
SPEAKER_1: I was an accessory to the demotion.
SPEAKER_1: I didn't pull the trigger.
SPEAKER_2: Okay, all right.
SPEAKER_1: So, yeah, so in the 90s, it got demoted.
SPEAKER_1: He died before it was officially demoted.
SPEAKER_1: They might have just.
SPEAKER_2: That would have killed him.
SPEAKER_2: Thank God.
SPEAKER_1: Yeah, so it was not until 2006 where Pluto was officially demoted.
SPEAKER_1: But we took it out of commission here at the Hayden Planetarium when we opened to the public in the year 2000.
SPEAKER_1: We plucked Pluto from the ranks of planets and put it with the other dirty ice balls being discovered in the outer solar system where it belongs.
SPEAKER_2: You make it sound so derogatory.
SPEAKER_1: Okay, with the other.
SPEAKER_2: You filthy ice ball.
SPEAKER_2: You little dirty ice ball.
SPEAKER_1: It's happier there.
SPEAKER_2: Right.
SPEAKER_1: It's now the king of the comets rather than the puniest planet.
SPEAKER_1: Anyhow, it is so small.
SPEAKER_1: It's got so little mass.
SPEAKER_1: It can't possibly be Planet X.
SPEAKER_2: Okay.
SPEAKER_1: A researcher named Miles Standish asked a question.
SPEAKER_1: What are the observatories that obtain the positions of Neptune leading us to say that it's not following Newton's laws?
SPEAKER_1: It's multiple observatories over decades.
SPEAKER_1: And so he goes back and analyzes them.
SPEAKER_1: One of the observatories was the US.
SPEAKER_1: Naval Observatory.
SPEAKER_1: And he goes back to the observations and finds out something like the gearbox was cleaned or oiled or something.
SPEAKER_1: Somebody did something to the telescope before those observations were made.
SPEAKER_1: Anytime you do something to a scientific instrument, you have to calibrate it.
SPEAKER_1: He said, what would happen if I ignore these measurements and fit the orbit to the remaining measurements that are out there?
SPEAKER_1: When he did that, Neptune landed right on Newton's laws.
SPEAKER_2: What?
SPEAKER_1: And Planet X evaporated overnight.
SPEAKER_1: There was nothing with a mass and gravity that was perturbing Neptune.
SPEAKER_1: It was bad data.
SPEAKER_2: So Pluto's mass had no effect on Neptune at all.
SPEAKER_1: No, no, no, nothing.
SPEAKER_2: Didn't make a difference.
SPEAKER_1: Didn't make a difference.
SPEAKER_2: What Pluto did, one way or another.
SPEAKER_1: And I'm saying, when you're a scientist on the frontier, you don't know what is accounting for the anomalous results you're getting.
SPEAKER_1: Is it a new law of physics?
SPEAKER_1: Is it something else that is correct laws of physics, but is influencing you in ways you don't yet know?
SPEAKER_1: Or is there something wrong with the data?
SPEAKER_1: So Planet X is a centerpiece to this much longer, larger story here about the plight of science on the frontier.
SPEAKER_1: And so I just want you to appreciate what scientists go through.
SPEAKER_2: I do.
SPEAKER_1: On that frontier, just to understand how nature works.
SPEAKER_1: And the data are not always correct.
SPEAKER_2: Right, and guess what?
SPEAKER_2: And then everything else is off from that data.
SPEAKER_1: Off from those data.
SPEAKER_2: Well, you have my understanding, but I also understand you killed Pluto.
SPEAKER_1: That is not the take away of this session.
SPEAKER_2: Stop it.
SPEAKER_1: Okay, there's been some evidence that there could be a much larger planet out there, which has been called Planet X.
SPEAKER_1: It's not affecting measurably the known planets, but it's because it's so far away.
SPEAKER_1: But there are other objects orbiting where Pluto is.
SPEAKER_1: There might be some anomalies in their orbits that could be explained by an object so far away you can't see it because it's too dark out there.
SPEAKER_2: That's what I read.
SPEAKER_2: It was supposed to be a wandering planet.
SPEAKER_1: We're getting, as a distance, 10,000 times the Earth-Sun distance.
SPEAKER_1: So it's way out there.
SPEAKER_2: Way out.
SPEAKER_1: So possibly, but the historical case of Planet X is solved.
SPEAKER_3: Hello, I'm Finkie Broke Allen, and I support StarTalk on Patreon.
SPEAKER_3: This is StarTalk with Neil deGrasse Tyson.
SPEAKER_1: You're gonna get an astrophysicist explanation of the literal three-body problem without reference to anything that's shown up on streaming services.
SPEAKER_2: And that means he's not gonna ruin the show for you.
SPEAKER_1: I don't know anything about the show, but I do know enough to describe the three-body problem to you.
SPEAKER_1: Let's start simple, okay?
SPEAKER_1: So as we know, the moon orbits the earth.
SPEAKER_2: Right.
SPEAKER_1: But that's not the right way to say it.
SPEAKER_2: Okay.
SPEAKER_1: Okay?
SPEAKER_2: All right.
SPEAKER_1: The moon and the earth orbit their common center of gravity.
SPEAKER_2: Ooh.
SPEAKER_1: So earth is not just sitting here.
SPEAKER_2: Right, and the moon's going around it.
SPEAKER_1: Going around it.
SPEAKER_1: They feel in their common center of gravity.
SPEAKER_1: You know where it is?
SPEAKER_1: It's 1,000 miles beneath earth's surface, along a line between the center of the earth and the center of the moon.
SPEAKER_2: Got you.
SPEAKER_1: So as the moon moves here, that center mass line shifts.
SPEAKER_1: Okay.
SPEAKER_1: So that means earth is kind of jiggling like this as the moon goes around.
SPEAKER_1: That's their center of mass.
SPEAKER_1: All right, this is the two-body problem.
SPEAKER_1: It is perfectly solved using equations of gravity and mechanics.
SPEAKER_2: Makes sense.
SPEAKER_1: Perfectly solved.
SPEAKER_1: Isaac Newton solved it.
SPEAKER_1: My boy.
SPEAKER_2: That's your man.
SPEAKER_1: My man.
SPEAKER_1: Isaac.
SPEAKER_2: Not a dumb guy.
SPEAKER_2: Ike.
SPEAKER_2: That's for sure.
SPEAKER_2: Let's not call him Ike.
SPEAKER_2: There's another Ike that we don't wanna...
SPEAKER_2: We don't wanna conjure up thoughts of that Ike when we think about Isaac Newton.
SPEAKER_1: Isaac Newton.
SPEAKER_1: Okay.
SPEAKER_1: So that worked.
SPEAKER_1: Then Isaac applied the equations to the Earth-Moon system going around the sun.
SPEAKER_1: Okay.
SPEAKER_1: That worked too.
SPEAKER_1: So in that system, let's ignore the moon for the moment.
SPEAKER_1: It's Earth going around the sun.
SPEAKER_1: Another two-body system.
SPEAKER_2: Another two-body system.
SPEAKER_1: All right.
SPEAKER_1: But then he worried.
SPEAKER_1: He said every time Earth comes around the back stretch, and Jupiter's out there.
SPEAKER_2: Right.
SPEAKER_1: Jupiter will tug on it a little bit.
SPEAKER_2: That's a lot of gravity.
SPEAKER_1: A little bit.
SPEAKER_2: Tug on it.
SPEAKER_1: As we come around back the other side.
SPEAKER_1: What's up, Earth?
SPEAKER_2: All right.
SPEAKER_1: And then it comes around again.
SPEAKER_1: Tugs on it again.
SPEAKER_2: What's up, Earth?
SPEAKER_2: Right.
SPEAKER_1: And of course, everybody's moving in the same direction around the sun.
SPEAKER_1: So the Earth would have to go a little farther in its orbit to be aligned again with Jupiter.
SPEAKER_2: Right.
SPEAKER_1: But it's gonna tug on it.
SPEAKER_1: Okay.
SPEAKER_1: He looked at all these little tugs, and he says, I'm worried that the solar system will go unstable.
SPEAKER_2: Right.
SPEAKER_1: Because if it keeps tugging on it, it keeps pulling it away.
SPEAKER_2: Yeah, it just keeps pulling away.
SPEAKER_1: And the previously stable orbit would just decay into chaos.
SPEAKER_2: Okay.
SPEAKER_1: Okay.
SPEAKER_1: He was worried about this.
SPEAKER_2: Okay.
SPEAKER_1: You know what he said?
SPEAKER_1: I know my equations work, and it looks stable to me.
SPEAKER_2: Right.
SPEAKER_1: So clearly it is stable, even though it looks like maybe it wouldn't be stable.
SPEAKER_1: You know what he says?
SPEAKER_1: He said, every now and then, God fixes things.
SPEAKER_2: Well, there you go.
SPEAKER_1: That's the answer.
SPEAKER_2: Even Isaac Newton.
SPEAKER_2: Wow, look at that.
SPEAKER_2: When in doubt.
SPEAKER_1: When in doubt.
SPEAKER_2: Just let God figure it out.
SPEAKER_1: I can't figure it out.
SPEAKER_2: God did it.
SPEAKER_1: Clearly, we're all still here, and we haven't been yanked out of orbit by Jupiter, but Jupiter is pulling on us.
SPEAKER_2: So it's a God correction.
SPEAKER_1: God correction, okay.
SPEAKER_1: So, this is the first hint that a third body is messing with you, okay, in some way that maybe is harder to understand.
SPEAKER_1: Fast forward 113 years.
SPEAKER_1: We get to Laplace.
SPEAKER_1: He studied this problem, okay?
SPEAKER_1: And he developed, I don't think he invented, but he developed a new branch of calculus called perturbation theory, okay?
SPEAKER_1: Unknown to Newton, even though Newton invented calculus.
SPEAKER_1: He invented calculus, all right?
SPEAKER_1: So he could have done it.
SPEAKER_1: He could have said, in order to solve this problem, let me invent more calculus.
SPEAKER_2: I just need more calculus.
SPEAKER_1: I just need more calculus.
SPEAKER_1: He couldn't do it.
SPEAKER_1: Didn't do it.
SPEAKER_1: So Laplace develops perturbation theory, and it comes down to, we have two bodies, the sun and the earth in this case, and the third one, the tug is small, but it's repeating.
SPEAKER_1: Jupiter's not sitting right here.
SPEAKER_2: It's way out there.
SPEAKER_1: Way out there.
SPEAKER_1: It's just a little tug.
SPEAKER_1: And so you can run the equations in such a way and realize that a two-body system that is tugged often by something small, that it all cancels out in the end.
SPEAKER_2: Got you.
SPEAKER_1: Okay, so when it's out here, the tug is a little bit that way, but now it's over here, and the tug is less.
SPEAKER_2: Right.
SPEAKER_1: All right?
SPEAKER_1: And then sometimes it's tugging you in this direction when that's the configuration.
SPEAKER_1: You add it all up, it all cancels out.
SPEAKER_1: But Newton could not have known that without this new branch of calculus.
SPEAKER_2: Okay.
SPEAKER_1: Okay, perturbation theory.
SPEAKER_1: So that took care of that third body.
SPEAKER_2: Got you.
SPEAKER_1: Where solar system is basically stable, okay, for the foreseeable future in ways that Newton had not imagined, in ways that Newton required God.
SPEAKER_2: Right.
SPEAKER_1: Okay.
SPEAKER_1: Oh, by the way, just a quick aside, this is now, we're up to the year 1800.
SPEAKER_1: You know who summoned up these books to read them immediately?
SPEAKER_1: Because there's a series of books called Celestial Mechanics.
SPEAKER_2: Okay.
SPEAKER_1: Napoleon.
SPEAKER_2: Ah, I am Napoleon.
SPEAKER_1: Napoleon, who read all the books he could on physics and engineering and metallurgy.
SPEAKER_2: Look at that.
SPEAKER_1: Okay, he wasn't just a tyrant.
SPEAKER_1: He was like a...
SPEAKER_2: He was a smart tyrant.
SPEAKER_1: A smart tyrant, all right.
SPEAKER_1: So he summons up the book, doesn't have to be translated because they're both in French.
SPEAKER_2: Right.
SPEAKER_1: He reads it, goes to Laplace and says, Montier, this is a beautiful piece of work, brilliant, but you make no mention of the architect of the system.
SPEAKER_1: He's referring to God.
SPEAKER_1: And Laplace replied, sir, I had no need for that hypothesis.
SPEAKER_2: Ooh, that's a mic drop.
SPEAKER_2: Ooh, that is tough.
SPEAKER_2: Man.
SPEAKER_1: That's a dig on Napoleon and on Newton.
SPEAKER_2: And on Newton.
SPEAKER_2: Yeah.
SPEAKER_1: And on Newton.
SPEAKER_2: I have, oh man, look at that.
SPEAKER_1: All right, so let's keep going.
SPEAKER_2: Go ahead.
SPEAKER_1: So now, let's say we have not just the planet and one of its moons, but let's say we have a star and another star, a double star system.
SPEAKER_1: Famously portrayed in what film?
SPEAKER_2: Star Wars.
SPEAKER_1: Star Wars.
SPEAKER_1: All right, of course.
SPEAKER_1: So, those two suns and the planet is stable, and I'll tell you why in a minute.
SPEAKER_1: But if you take a third sun and put it there, about approximately the same size, then what kind of orbits will they have, okay?
SPEAKER_1: So, I'm feeling this one, but now I feel that where's my gravitational allegiance?
SPEAKER_1: Am I gonna come through?
SPEAKER_1: But then am I gonna go that way or this way?
SPEAKER_1: It turns out, the orbits of a three body problem are mathematically chaotic.
SPEAKER_2: Yes, I was about to say, that did not seem very stable.
SPEAKER_1: Something has to give.
SPEAKER_2: Well, this is in the series, what we're talking about.
SPEAKER_1: Something, I haven't seen the series.
SPEAKER_2: I know.
SPEAKER_1: I'm just saying, something has to give.
SPEAKER_2: That's odd.
SPEAKER_1: Two of these are gonna collide.
SPEAKER_2: Right.
SPEAKER_1: One is gonna get ejected.
SPEAKER_2: Right.
SPEAKER_1: Okay, that is the classical three body problem.
SPEAKER_1: Three objects of approximately similar mass, trying to maintain a stable orbit.
SPEAKER_1: And it goes chaotic with just three objects.
SPEAKER_2: Look at that.
SPEAKER_1: It is unsolvable.
SPEAKER_1: You can, let me say that differently.
SPEAKER_1: You can calculate incrementally what's happening and track it until the system dies.
SPEAKER_1: Or splits apart or whatever.
SPEAKER_1: But you cannot analytically predict the future of the three body system because what chaos will do for you in your mathematical model is if you change the initial conditions by a little bit.
SPEAKER_2: Right.
SPEAKER_1: A little bit, the solution diverges.
SPEAKER_2: Further down the line, it goes crazy.
SPEAKER_1: It's not just a little bit different later on down the line.
SPEAKER_2: It is exponentially different.
SPEAKER_1: Correct.
SPEAKER_1: Wow.
SPEAKER_1: With the smallest increment of distance.
SPEAKER_1: So I'll say, I'll move you in this direction in this model and then in a slightly different direction in the other model, it goes chaotic.
SPEAKER_1: That's what we mean by chaos.
SPEAKER_2: Right.
SPEAKER_1: Okay.
SPEAKER_1: It's mathematically defined.
SPEAKER_1: Okay.
SPEAKER_1: So now there's something called the restricted three body problem.
SPEAKER_2: Oh, right.
SPEAKER_2: Okay.
SPEAKER_1: Okay.
SPEAKER_1: The restricted three body problem.
SPEAKER_2: Never heard.
SPEAKER_1: So there's restricted three body problem.
SPEAKER_1: We have two masses of approximately equal and one that's much less than the other two.
SPEAKER_1: That is solvable.
SPEAKER_2: Right.
SPEAKER_1: It's called the restricted three body problem.
SPEAKER_2: Gotcha.
SPEAKER_1: In the Star Wars case, that's the restricted three body problem.
SPEAKER_1: Right.
SPEAKER_2: Because you have the two stars and you have the little planet.
SPEAKER_1: The little planet.
SPEAKER_1: There it is.
SPEAKER_1: And it's even better because the planet is so far away that it only really saw one merged gravity of the two stars.
SPEAKER_2: Right.
SPEAKER_2: Okay.
SPEAKER_1: If you're far enough away, that difference is not really mattering to you.
SPEAKER_1: You maintain one stable orbit around them both.
SPEAKER_2: Around both stars.
SPEAKER_1: Both stars.
SPEAKER_1: Okay?
SPEAKER_1: Now, if it got really close, then you'll have issues.
SPEAKER_1: Because then, again, gravitational allegiance matters.
SPEAKER_1: The stars are not going to care, but you will.
SPEAKER_1: Because you'll get eaten.
SPEAKER_2: You don't know where to go.
SPEAKER_1: You don't know where to go.
SPEAKER_2: I'm in love with two stars.
SPEAKER_2: And I don't know what to do.
SPEAKER_2: Which way do I turn?
SPEAKER_1: So, anyhow, so the three body problem, the takeaway here is it's unsolvable.
SPEAKER_1: Not just because we don't know how to do it yet.
SPEAKER_1: Because it's mathematically unsolvable.
SPEAKER_2: It's built into the system.
SPEAKER_1: The system is chaotic.
SPEAKER_1: Unless you make certain assumptions about the system that you would then invoke so that you can solve it.
SPEAKER_1: And so one of them is a small object around bigger ones.
SPEAKER_1: Another one, oh, by the way, in this solution with Jupiter out there, slightly tugging, it turns out over a very long time scale this is chaotic.
SPEAKER_1: But much longer time scale than Newton ever imagined.
SPEAKER_1: Because yes, we are small compared to the sun, but Jupiter isn't, and we're trying to orbit between them.
SPEAKER_1: So that's all.
SPEAKER_1: It's not deeper than that.
SPEAKER_2: It's not, yeah.
SPEAKER_1: I could have said the four-body problem, but this problem begins at the three-body problem.
SPEAKER_2: Because you're gonna have the same thing in the four bodies or five bodies.
SPEAKER_2: It's gonna be the same.
SPEAKER_1: And we have star clusters with thousands of stars in them, and they're all just orbiting.
SPEAKER_1: We can model it, but we cannot predict with precision where everybody's gonna be at any given time.
SPEAKER_1: Because it's chaotic.
SPEAKER_2: The chaos, so basically it's about the chaos.
SPEAKER_2: It's all about the chaos.
SPEAKER_1: Yeah, so what we do is we model the chaos.
SPEAKER_1: We say this will be statistically looking like this over time.
SPEAKER_1: You're not gonna track one object through the system for eternity.
SPEAKER_1: That's not gonna work.
SPEAKER_2: That's so cool.
SPEAKER_1: Yeah.
SPEAKER_1: Alright.
SPEAKER_2: That is so cool!
SPEAKER_1: There it is.
SPEAKER_1: Alright, another explainer.
SPEAKER_1: Slipped in.
SPEAKER_1: Torn from the pages of science fiction.
SPEAKER_1: Just a simple description of the three body problem.
SPEAKER_1: I'm gonna tell you some of the ways the universe will end.
SPEAKER_1: All right, so let me give you some scenarios that are on the docket.
SPEAKER_2: Okay.
SPEAKER_1: Okay.
SPEAKER_1: As you may know, we are currently expanding.
SPEAKER_2: Yes.
SPEAKER_1: All right.
SPEAKER_2: That's right.
SPEAKER_2: Growth, damn it.
SPEAKER_1: And as we expand, the universe gets thinner and thinner, less and less dense.
SPEAKER_2: If you're not growing, you're dying.
SPEAKER_1: Well, consider, how do you make a star?
SPEAKER_1: Well, you have a gas cloud, and it collapses, and it collapses, right.
SPEAKER_1: to make a new object, right.
SPEAKER_1: But if things continue to expand, then there's an interesting sequence of events.
SPEAKER_1: First, there are galaxies that have already used up all their gas.
SPEAKER_1: They have these elliptical shapes.
SPEAKER_1: We call them elliptical galaxies.
SPEAKER_2: Oh.
SPEAKER_1: They don't have any gas, but they have stars that will live a trillion years.
SPEAKER_2: Wow.
SPEAKER_1: After a trillion years, those stars start dimming out one by one.
SPEAKER_2: That's the actual sound that a star makes when it's gone.
SPEAKER_1: Yes, in the vacuum of space.
SPEAKER_2: In the vacuum of space.
SPEAKER_1: They will pluck out one by one trillions of years from now, because that's their life expectancy.
SPEAKER_1: Okay.
SPEAKER_1: They're burning their fuel very efficiently, very slowly and very efficiently.
SPEAKER_1: These are the dim red stars, of which there are many in every galaxy.
SPEAKER_1: Right.
SPEAKER_1: But there's no gas in the elliptical galaxies.
SPEAKER_1: There's no fresh generation to be made.
SPEAKER_1: All right.
SPEAKER_1: In spiral galaxies, such as ours, the Milky Way, we have stars that will also live a trillion years.
SPEAKER_1: They'll pluck out at around the same time these other stars do.
SPEAKER_1: But we have residual gas.
SPEAKER_2: Right.
SPEAKER_1: So we're making stars today.
SPEAKER_2: Yes.
SPEAKER_2: Tell our nurseries.
SPEAKER_1: Yes.
SPEAKER_1: The JWST is all up in that.
SPEAKER_2: Yeah.
SPEAKER_1: So that will only continue until there's no gas left.
SPEAKER_2: Right.
SPEAKER_1: So for a spiral galaxy, it might go another 5 billion years, perhaps.
SPEAKER_1: And when we run out of gas, that's the last generation of stars to get made.
SPEAKER_2: You're literally out of gas.
SPEAKER_2: That's when the universe makes this sound.
SPEAKER_1: Oh, by the way, in the distant future, as we continue to expand, galaxies will expand beyond the horizon that we have established from our location here.
SPEAKER_1: So what is that horizon?
SPEAKER_1: That's where they're moving away from you faster than the speed of light.
SPEAKER_1: So their light tries to reach you, but it can't.
SPEAKER_1: It can't.
SPEAKER_1: Wow.
SPEAKER_1: All the energy gets sucked out of it.
SPEAKER_1: And so every galaxy in the night sky will go beyond that horizon, okay?
SPEAKER_1: With or without its stars, it'll go beyond the horizon.
SPEAKER_1: So if we look outside of our own galaxy, there'll be nothing there.
SPEAKER_1: As far as we know, our entire universe is just the stars living or dead in the Milky Way.
SPEAKER_2: The Milky Way, oh, that's...
SPEAKER_1: So our entire understanding of cosmology in a post-apocalyptic civilization in that very distant future will have no idea the universe had a beginning at all because we know about the beginning by looking at other galaxies.
SPEAKER_2: Right.
SPEAKER_1: So a page in the history of the universe will have been removed and they will not even know it.
SPEAKER_2: Look at that.
SPEAKER_1: But wait, there's more.
SPEAKER_1: There's the matter of the black holes.
SPEAKER_1: Okay.
SPEAKER_2: Interesting.
SPEAKER_1: All right.
SPEAKER_1: So the black holes, they, the small black holes, actually will evaporate.
SPEAKER_2: Okay.
SPEAKER_1: Okay.
SPEAKER_1: Using Hawking radiation.
SPEAKER_1: Right.
SPEAKER_1: So just outside the event horizon, there are these spontaneous particle pairs that are formed out of their gravitational energy field.
SPEAKER_2: Right.
SPEAKER_1: And one particle escapes, the other falls in, and that effectively subtracts mass from the black hole.
SPEAKER_2: Okay.
SPEAKER_1: So, we will lose those black holes, and around then, our best hypotheses for the survival of the proton.
SPEAKER_2: Okay.
SPEAKER_1: Okay.
SPEAKER_1: We think the proton might decay.
SPEAKER_1: If the proton decays, that's it.
SPEAKER_1: The proton decay, we're thinking, also happens at around 10 to the 30th years.
SPEAKER_2: Wow.
SPEAKER_1: Last I checked.
SPEAKER_1: It could be an up to maybe 10 to the 32 years.
SPEAKER_1: But that's around where we are.
SPEAKER_2: I mean, but who's counting?
SPEAKER_1: Who's counting?
SPEAKER_1: A factor of 10 or 100.
SPEAKER_1: Who's a factor of 10 or 100?
SPEAKER_1: Who's counting?
SPEAKER_1: Well, we have factors of trillions and gazillions.
SPEAKER_1: All right.
SPEAKER_1: That means the structure of all matter, which is our foundation is on the nucleus, composed of protons and neutrons.
SPEAKER_1: But neutrons, free neutrons decay, but protons are the stablest particle we know.
SPEAKER_1: They're gone.
SPEAKER_2: Right.
SPEAKER_1: Okay.
SPEAKER_2: Well, that's it.
SPEAKER_1: Wait.
SPEAKER_1: There's the supermassive black holes in the centers of galaxies.
SPEAKER_2: All right.
SPEAKER_1: They take longer to evaporate.
SPEAKER_2: That's true.
SPEAKER_1: They'll still be there.
SPEAKER_1: They don't just go away just cause the universe expanded every other galaxy out of it, and just cause all the stars died.
SPEAKER_1: How about those?
SPEAKER_1: They take 10 to the hundred years to evaporate.
SPEAKER_1: Wow.
SPEAKER_1: You can do the math on this.
SPEAKER_2: No, I can't.
SPEAKER_2: I'm sorry.
SPEAKER_2: This is what we fail to realize.
SPEAKER_1: You know what 10 to the hundred is?
SPEAKER_1: What number that is?
SPEAKER_2: 10 to the hundred?
SPEAKER_1: Yeah.
SPEAKER_2: That's a thousand.
SPEAKER_1: 10 to the third power is a thousand.
SPEAKER_1: 10 to the hundredth power, that's a Google.
SPEAKER_2: I did not know that.
SPEAKER_1: So that's a lot of years.
SPEAKER_2: That's beyond the line.
SPEAKER_1: That's a lot of years.
SPEAKER_2: Yeah.
SPEAKER_1: All right, so all matter is just scattered evenly into the vacuum of space.
SPEAKER_1: Whatever's left of matter and the universe dies.
SPEAKER_1: There's no more phenomenon to happen.
SPEAKER_2: Okay.
SPEAKER_1: You don't even have black holes evaporating.
SPEAKER_2: Right, everything's done.
SPEAKER_1: And the temperatures have been dropping the entire time.
SPEAKER_1: Early on, it was very hot.
SPEAKER_2: Right.
SPEAKER_1: It was glowing hot.
SPEAKER_2: Glowing hot.
SPEAKER_1: Right now, it has cooled to 3 degrees absolute zero.
SPEAKER_2: Right.
SPEAKER_1: That's very cold.
SPEAKER_1: But it got even colder.
SPEAKER_2: Even colder.
SPEAKER_1: Cold to near absolute zero in the very distant future.
SPEAKER_1: So, in that scenario, the universe will not die with a bang but with a whimper.
SPEAKER_1: And not in fire, but in ice.
SPEAKER_2: Oh, that sounds cold and lonely.
SPEAKER_2: That is a cold, lonely ending.
SPEAKER_1: That's one scenario.
SPEAKER_1: Okay.
SPEAKER_1: So for a while, people call that the heat death of the universe.
SPEAKER_1: But these are thermodynamicists saying that because to them, there's no such thing as cold.
SPEAKER_2: Right.
SPEAKER_1: There's only heat or the absence of heat.
SPEAKER_2: That's it.
SPEAKER_2: So now all the heat is gone, so the heat death.
SPEAKER_1: But that's so misleading.
SPEAKER_2: Exactly.
SPEAKER_1: So I just prefer to call it the big freeze.
SPEAKER_1: We know what's driving that.
SPEAKER_2: Okay.
SPEAKER_1: What we do know about it tells us that it is unrelenting.
SPEAKER_1: So it's not just an expansion that'll continue forever.
SPEAKER_1: It's an expansion that will accelerate.
SPEAKER_2: Forever.
SPEAKER_1: Accelerate.
SPEAKER_2: Wow, that's crazy.
SPEAKER_1: Because it is a property in the vacuum of space.
SPEAKER_1: That's what we call dark energy.
SPEAKER_1: So the more the universe expands, the more vacuum you have.
SPEAKER_2: Right.
SPEAKER_1: And the weaker gravity becomes because all the matter is getting thinned out.
SPEAKER_2: It's getting thinned out.
SPEAKER_1: Okay.
SPEAKER_2: Like butter on hot toast.
SPEAKER_1: All right, so you can do the math on this.
SPEAKER_1: So first, yes, all the galaxies will accelerate beyond your horizon.
SPEAKER_1: That'll happen.
SPEAKER_1: We got that in the first one.
SPEAKER_1: Okay?
SPEAKER_1: But here's what the difference is.
SPEAKER_1: If that acceleration goes unchecked, then it'll start ripping apart things that would otherwise retain their integrity from their gravity.
SPEAKER_1: So first, they're galaxy clusters that even in an expanding universe, they'll want to stay together with the accelerating expansion.
SPEAKER_1: It'll start pulling them out, pulling them away.
SPEAKER_1: Then, once it's destroyed the galaxy cluster, now it's gonna start working on the galaxies.
SPEAKER_2: Right.
SPEAKER_1: Which are tightly bound systems of stars.
SPEAKER_1: As the universe continues to expand, the strength of that expansion will become greater than the binding gravity of the systems themselves.
SPEAKER_1: So it'll start ripping apart galaxies.
SPEAKER_1: Okay?
SPEAKER_1: Then, you don't have galaxy clusters, you don't have galaxies.
SPEAKER_1: Now you just have stars and their planets.
SPEAKER_1: It'll start plucking the planets away from the stars.
SPEAKER_2: Home record.
SPEAKER_2: Just a home record is what you are.
SPEAKER_1: It'll start ripping apart the stars and the planets themselves.
SPEAKER_1: These forces are strong.
SPEAKER_1: So it'll start becoming stronger than the electromagnetic forces that holds matter together.
SPEAKER_1: One way to imagine this is we have a rubber band.
SPEAKER_1: You take one end and I'll take one end.
SPEAKER_1: So you feel the force tugging at you.
SPEAKER_1: So this was originally the gravitational force that was holding galaxies together.
SPEAKER_1: But this dark energy broke that apart.
SPEAKER_1: Then there's the force of the intermolecular force that broke that apart.
SPEAKER_1: But the universe is getting more and more stretched.
SPEAKER_1: What we don't know is that is there a limit to how much the physical universe can stretch in response to this dark energy?
SPEAKER_1: Because once you're down to a proton and it rips apart a proton, then you're left with quarks.
SPEAKER_1: But then what happens, can you rip a quark apart?
SPEAKER_1: We don't know, we don't know.
SPEAKER_1: But then what could possibly happen is we call this the big rip.
SPEAKER_1: So we call it the big rip.
SPEAKER_1: And to do the calculations, that'll happen in 10 to the 22 years.
SPEAKER_2: Oh wait.
SPEAKER_1: Way sooner.
SPEAKER_2: That's much sooner than 10 to the 100.
SPEAKER_1: Yes, it'll happen before the black holes evaporate.
SPEAKER_2: Oh, I'm very worried at this point now.
SPEAKER_2: That is disturbing.
SPEAKER_1: Okay.
SPEAKER_2: So long before the big freeze, the big rip will just go ahead and pull everything apart.
SPEAKER_1: It'll be still pretty cold by then.
SPEAKER_1: I lay awake at night wondering what that would be.
SPEAKER_1: Because it rips and what's in the rip.
SPEAKER_1: Yeah, what's there?
SPEAKER_2: I'm trying to figure out what's gonna be left.
SPEAKER_1: Now, third and last, there's no data to support this next idea.
SPEAKER_1: There's nothing to tell us that we will ever re-collapse.
SPEAKER_1: Because our expansion speed is greater than anything the collective gravity of all galaxies could possibly muster to try to bring it back.
SPEAKER_1: All right, so, but if something gets discovered that will slow down the expansion and then have us re-collapse, then everything will happen sort of in reverse.
SPEAKER_1: The universe will get hotter and hotter and hotter instead of cooler and cooler.
SPEAKER_1: Things will get more and more concentrated.
SPEAKER_1: And ultimately, we'd all come back to the same point.
SPEAKER_2: Same singularity.
SPEAKER_1: And they call that the big crunch.
SPEAKER_1: But that implies that things are like crackers.
SPEAKER_2: Right.
SPEAKER_1: If you take a physical cracker, but I think it's really the big squeeze.
SPEAKER_1: Ooh.
SPEAKER_1: To me, that's a more accurate term, the big squeeze.
SPEAKER_1: Now, the whole universe becomes the size of an atom again.
SPEAKER_1: And if you look at the quantum physics of this, once you're in the quantum realm, you can, like, tunnel.
SPEAKER_2: All bets are off.
SPEAKER_1: You can tunnel.
SPEAKER_2: You can tunnel out.
SPEAKER_1: You can tunnel out.
SPEAKER_1: Okay?
SPEAKER_1: And all that energy and all that matter in one place, Right.
SPEAKER_1: there's only one thing it can do, and that's expand.
SPEAKER_1: Once again, into another big bang.
SPEAKER_2: Big bang.
SPEAKER_1: Big bang number whatever.
SPEAKER_2: Right.
SPEAKER_1: These are scenarios, all of which will happen long after we're dead.
SPEAKER_2: Which is why I'm not going to worry about it.
SPEAKER_1: I'm just saying, the stuff that will kill us long before it happens.
SPEAKER_2: Long before it is, yes.
SPEAKER_1: Okay, we'll be running for the hills as the sea levels rise.
SPEAKER_2: Yes, I was going to say.
SPEAKER_1: The climate change, the next virus where nobody wants to get vaccinated.
SPEAKER_2: Exactly.
SPEAKER_1: It'll kill all of them off.
SPEAKER_2: We're not making it out of the next century.
SPEAKER_2: Let alone have to worry about any of this stuff.
SPEAKER_1: And you know what worries me most?
SPEAKER_1: Is ask anybody in the year 1900 what they fear the greatest in terms of the survival of our species.
SPEAKER_1: They'll say population, they'll say consumption.
SPEAKER_1: They'll say things that aren't even on our list today.
SPEAKER_1: The stuff that's on our list, they didn't even know about that.
SPEAKER_2: Think about it.
SPEAKER_1: They didn't even know that it was something.
SPEAKER_1: Think about it.
SPEAKER_1: So in the year 2100, I don't fear what we fear today.
SPEAKER_2: Yeah, people won't be worried about cancer.
SPEAKER_1: I fear what we don't yet know to worry.
SPEAKER_2: Right, and I fear what we do know to worry, which is us.
SPEAKER_1: We being awful shepherds of our own fate.
SPEAKER_2: There you go.
SPEAKER_2: Like, yeah, just, we are terrible stewards of the future because we are terrible stewards of the present.
SPEAKER_1: Ooh.
SPEAKER_2: And that's what I fear.
SPEAKER_1: Ooh.
SPEAKER_2: Yeah.
SPEAKER_1: All right.
SPEAKER_2: On that happy note, have a nice day.
SPEAKER_2: Hey.
SPEAKER_1: All right, these are the ways the world would end.
SPEAKER_1: With Neil and Chuck.
SPEAKER_1: A fireside chat.
SPEAKER_1: Sleep tight.
SPEAKER_1: Sleep well, people.
SPEAKER_2: Oh, God.
SPEAKER_1: This has been a StarTalk Things You Thought You Knew edition.
SPEAKER_1: Thanks for joining us.
SPEAKER_1: As always, I bid you to keep looking up.