To watch Game of Thrones you needed, at times, access to several family trees and photographic reminders of how each grisly British actor fit into the wider story. (So! Many! Greyjoys!)
3 Body Problem, David Benioff and D.B. Weiss’s new big series on Netflix, has fewer characters, but there are times where you may wish you had a degree from Princeton to get the science. There’s the classic physics conundrum that gives the show its name (taken from the first of three books written by Cixin Liu), plus a dalliance with higher dimensional manifolds, quantum mechanics, and a showstopper sequence based on experimental material science.
Luckily, the show, riddled with geniuses, is wise enough to be sure each important development features someone a little less familiar with the specific discipline at hand so as to provide explanations. That said, some of them fly by rather quickly, so we at IGN spoke to Dr. Erin Macdonald, who not only specializes in many of the topics discussed, but, as a longtime science advisor to Star Trek, has the inside track on how this stuff is moved from the world of theory to television. (Yes, that’s Erin as Prodigy’s Lt. Commander Macdonald and also one of the better inside jokes on Lower Decks.)
Our conversation has been edited for clarity.
And spoilers, of course, follow for the science of the show.
IGN: Dr. Macdonald, you have your PhD from the University of Glasgow and you specialized in Gravitational Astrophysics. As an advisor to producers in Hollywood, you help keep science fiction in the orbit of science fact. Indeed, you have been the official science advisor to no less august a franchise as Star Trek. Using pure Vulcan logic, I hereby deem you the best-equipped person in the galaxy to answer my questions about 3 Body Problem. I have four big questions and please do not make me feel dumb for asking.
Dr. Erin Macdonald: I will do my best.
The Titular Three-Body Problem
IGN: In both the Netflix series and Cixin Liu’s book trilogy, the instigating events stem from the actual three-body problem. Now, let me see if I have this right: You got a big heavy thing, like our Sun, and another heavy thing, like Earth, where I keep an apartment. Because of gravity, one will orbit the other in a predictable pattern. Similar dynamic with the Earth and the Moon.
EM: Correct.
IGN: Now, much like dating, if you introduce a third into this equation, it’s going to make trouble. If something roughly the same size as the Sun gets in the mix, Earth is like, “Where the hell do I go?”
EM: Yes, the main thing is that you have comparable masses, whether close to the Sun’s or Earth’s. What’s key to understand about our Solar System is that it took billions of years to form, so it had to settle out. So anything that doesn’t fit with the gravity of the Sun or, like you say, the Moon around Earth, it’s been flung out—maybe caught by Jupiter or caught in the asteroid belt or maybe expelled from the Solar System entirely. The three-body problem aspect has essentially settled these issues, though I am speaking in very broad terms here.
The three-body problem takes the basic understanding of Newton’s laws of motion and Newton’s law of gravitation—which Einstein added a pretty important “yes, but” to, but let’s put that aside for a moment—and it uses these laws to figure out how three objects of similar size will move around one another. And it is really hard to do. It really comes down to chaos theory, to quote Jeff Goldblum.
The starting conditions of all three of these objects are so temperamental that with any little change in their direction, speed, or mass, it will completely alter what you get. To move any three objects around one another in any consistent way is essentially impossible with the basic laws of physics.
IGN: See, that’s weird to me. You’d think big-ass computers could figure this out by now. If computers can beat old Russian brainiacs in chess, they should be able to predict celestial bodies. And I understand why this might be important, too—when we send satellites into deep space, we need to know the orbits of other stuff to use the gravity to get it places. But I guess our computers can only handle one thing at a time?
EM: It’s extremely difficult. We have computer simulations that try, and almost every time something flings out—it can’t sustain for any length of time.
This is why, for a very long time, astronomers felt that a planet like Tattooine with two suns was pure fantasy. Because of the three-body problem.
Now since then, discoveries have been made that refute this a bit. There are some star systems with two suns with a planet or exoplanet around it, but the stars are so close together relative to the planet that they are, effectively, just one object to that planet. The same with stars that are so far away that they are effectively two solar systems orbiting one another from the perspective of that one planet. But technically they are not.
IGN: Well this brings us to the conundrum of the aliens living on what the show calls San-Ti and in the books is called Trisolaris—this is a planet with multiple suns that keeps having cyclical extinctions due to either getting scorched (too close to a sun!) or frozen (too far from a sun!).
But wait, it’s not cyclical—that’s part of the problem! They can’t predict when it comes, so it causes great difficulty when trying to maintain their culture during what they call a “chaotic era.” Indeed, it’s the inability to know how long a “stable era” will last that is their biggest woe.
EM: Truly, this is the nerdiest story of all time.
No, it’s all exactly right. The slightest change would have drastic effects. That’s the chaos theory that makes the extinction cycles unpredictable. The math term for this is nonlinear dynamics, and this is why it is so hard to model three-body systems. Any minute change—if something in our Solar System gets bumped or it expels gas—when you are working with a three-body mathematical problem, it throws off your system.
IGN: OK, but in the show, this alien species has incredibly advanced science. We’ll talk about their higher dimensionality in a moment, but they are way ahead of us in terms of communication and transport, and also biologically—they can shrivel into Fruit Roll-Ups during chaotic eras to maintain their culture—but they still haven’t licked the three-body problem. Does that seem far-fetched to you?
EM: I buy it. It has to do with nonlinear dynamics. There’s too much unpredictability. Now, this species would be able to predict a few years out—and we see this with chaos theory, the ability to predict the embers of something—but as you get further out, it is simply unpredictable. And that change happens quite fast; it skyrockets. It’s just the laws of mathematics!
Higher Dimensions
IGN: In the series, they write a great line for Jess Hong when she’s rambling about extra-dimensional manifolds and then essentially says, “Well, nobody really understands this stuff.”
EM: Classic.
IGN: But we do need to discuss it. Now, I read the book Flatland in high school and I do understand that one dimension is a line, two dimensions is a plane, three dimensions is a sphere or cube, and I pretty much understand the concept of spacetime, four dimensions, which is what we all live in now.
EM: Yep.
IGN: But we have no control over the fourth dimension, time. When I do jumping jacks I am moving my body in three dimensions and I am always moving in the fourth dimension—time—but always going with the arrow pointing in one direction, forward. I can only exist that way.
EM: Yes, yep, you got it.
IGN: In my head, I can think back to the idiotic thing I said to my wife last night, but I can’t go there and change it.
EM: We exist one second per second, forward.
IGN: It’s a bummer, but I’m used to it by now.
Now we get heavy. Some of these scientists throw five dimensions at you—and then they really go nuts and throw more, seven, nine, 12 dimensions—which I really don’t understand. That last bit drives me crazy. I read The Elegant Universe by Brian Greene super slowly, like, it took me a month, and I’m just like… I’m ready to say, “O.K., I will accept a fifth dimension, but how in the hell can there be higher than five when you can’t even tell me what five is?”
EM: Yeah, the 10 or more dimensions for string theory, that is a definite thing we can talk about.
IGN: I reject it! I buy a five if you say so. But above five? Give me a break! Am I just being close-minded?
EM: It depends on where those dimensions are, and where they are coming from. The string theory concept at 11 or 12 dimensions or whatever it’s at these days, this is rooted in those laws of physics and how they interpret how the universe is structured. If you are thinking about multi-dimensional, or multiverses—like a fifth dimension where our universe is one of many—it’s possible. Once you go outside of our four, though, it’s true, our brains can’t really comprehend it. It’s whatever laws of physics that person is using to describe the higher dimensions that will dictate how many there are. Ultimately, it does not matter: We live in four dimensions.
IGN: And this is all unproven theory, right?
EM: Yes, and I get this question a lot. “Whatever happened with string theory?” because it was a big deal in the early 2000s. Everyone was talking about it. Now what happened was this—and I’m going to piss off a lot of string theorists by speaking so broadly, but here goes—CERN came on-line. They found the Higgs-Boson and other things, but many of the experiments were testing string theory, and they did not bear out. String theory is not disproven, but it’s a bit on the sidelines now.
IGN: In 3 Body Problem, you have these powerful intelligence-gathering machines, called sophons, which shrink down to the size of a particle. It speeds by in the show and is a little confusing, but I was reminded of Brian Greene talking about how these extra dimensions “coil up” and I think this is supposed to be a representation of that. Can you explain this theory a little bit?
EM: Did you ever see the short film “Powers of 10” in school?
IGN: Of course!
EM: It shows the concept of zooming out. So, think about this with dimensions. The higher you go, the others seem small. The one-dimensional line is just part of the plane. And the plane is a small part of the cube. And the cube is a small part of a tesseract, which is a four-dimensional cube.
IGN: So this sophon is so small it can do anything—it can enter our computer systems to monkey with our science, it can be anywhere and spy on us, and, naturally, when it wants to physically manifest itself it becomes a badass woman with a katana.
EM: Heck yeah!
IGN: But when it “uncoils” or “unfolds” it is enormous and blocks out the sun, in what seems like a violation of physical space—like a Transformer or Marge Simpson’s hair. Does this make sense?
EM: Yes. It all depends on how the projection of those higher dimensions shrink down. Let’s go back to the line example, one dimension. You turn that line on its side and just see a single point not knowing that there's a whole line there. Or you can take a two-dimensional plane and turn it over so it appears to be one line. An extremely advanced scientific being may have the ability to down-project multiple dimensions, and that would get you a tiny particle. But since we are only aware of lower dimensions, they would project it into a lower dimension for us to see.
IGN: So this wacky show has real science in there.
EM: Yes, on the spectrum of science to fiction, this is square in the middle. We’ve got a lot of “yes, and” ideas from multiple dimensionality and what could we do with it.
Quantum Entanglement
IGN: Another part of the show is how the sophon particles are able to communicate back with the home planet four light years away, because they are entangled. I think this is what Albert Einstein called “spooky action” and this is a real thing, somehow?
EM: “Spooky action at a distance,” yes.
IGN: I remember this from the movie Only Lovers Left Alive with Tom Hiddleston and Tilda Swinton, and they made some grand romantic metaphor out of it—that no matter how far apart they were, they could sense each other.
EM: It is easy to get romantic about quantum entanglement. Or upset. It’s one of the things about quantum mechanics that makes you cry in the shower because it is so hard to understand.
Subatomic particles have a property we call spin. If it is spinning one way, we say that it's spinning up. If it's spinning in the other direction, we say it's spinning down. Coil your fingers in the direction that it's spinning and your thumb points in that direction: thumbs up or thumbs down. Now, if you take particles that are atomically bonded and split them up, and you flip the spin of one, the other one will flip instantaneously—not accounting for the speed of light. No communication happens between them. It just knows that the other one has flipped. It’s kooky, it’s weird, it should not happen, but it has been proven. And at vast distances, too.
IGN: I’m freaked out.
EM: The big push is to use this as a form of communication, because the way we're talking now, on Zoom, we're talking on machines that are just processing zeros and ones, right, which could be interpreted as thumbs up and thumbs down.
IGN: Aha!
EM: So if you're able to do that you're able to communicate zeros and ones faster than the speed of light instantaneously.
IGN: This is how we get in touch with the Vulcans and tell them to visit.
EM: The issue, though, is you have to know you're still entangled, and that can only be communicated normally. Right? You can't say like, “It just flipped?” “Yep, it just flipped.” This is a lot of what fiber optics does, with constant pings.
IGN: You need a second entanglement. A control entanglement.
EM: Yeah, so this is what is limiting our technology now. However, we see quantum entanglement as a means of faster-than-light communication in tons of science fiction. The Mass Effect series lays it out quite explicitly that this is what is going on.
IGN: Where communication starts, transportation follows, so this is maybe how we get to beaming?
EM: If we are able to understand spin flips and control them in that manner then, yes, that’s moving closer to a Heisenberg compensator. It’s all about knowing and controlling where subatomic particles are.
Killer Nanofibers
IGN: 3 Body Problem shows the future of nanotechnology with ultra-thin cables that are finer than human hair, but are strong enough to rip metal in half like an enormous, deadly wire cheese cutter. It looks cool on screen but is this a bit much?
EM: Material scientists will vomit in their mouths watching that. You can’t structure atoms and molecules in a way that is that strong. So, in a way, that’s hot nonsense. However, the science they are coming from—ignoring material sciences—just looking at the nuclear forces? That is a different story.
From a physics perspective, not an engineering perspective, you can say that atom bonds are extremely strong. That’s the nuclear bomb, right? Splitting an atom and releasing the energy that holds that atom. There’s tons of energy there. So, could you then chain them so they could cut through anything and destroy things? Suuuuuuuure. If you are going down that route, then yes.
It also plays with quantum physics. The uncertainty of where particles are.
IGN: Like in Oppenheimer when he says the glass could fall through the table.
EM: Exactly. If I slam my hand on this desk, there is a non-zero chance that my atoms and the atoms of the table will pass through each other. So, could you somehow create a technology to manipulate those subatomic structures and cut through them cleanly? Or separate atoms from one another manipulating that uncertainty? That is a little extreme.
But what dumb (or smart!) questions do you have about 3 Body Problem’s science? We probably can’t answer them, but maybe someone in the comments can!
