The orbits of a trio of stars can be so chaotic that it’s impossible to precisely calculate the stars’ future trajectories. That’s the real science behind the name of the hit Netflix show, 3 Body Problem. Much of the sci-fi show’s action hinges on a variety of other physics concepts. But in service of the plot, some of that science is taken to implausible — or even physically impossible — lengths.
To get a handle on what’s real and what’s fiction, Science News spoke with cosmologist Jacques Delabrouille of CNRS in Paris and Lawrence Berkeley National Laboratory in California.
Note to those who haven’t yet watched: Spoilers follow.
What is the three-body problem in physics?
For two objects orbiting one another, scientists can precisely predict the locations and speeds of those objects far into the future. But for three or more orbiting objects, the motion can be chaotic. That means the results depend so sensitively on the initial locations and velocities of the three objects that the future is unpredictable (SN: 4/6/20).
In 3 Body Problem, an alien race called the San-Ti inhabits a planet in a triple star system four light-years from Earth. The stars’ unpredictable orbits lead to “stable” and “chaotic” eras. Chaotic eras wreak havoc on the planet’s climate, decimating entire civilizations.
In reality, the closest neighboring star system to the sun, Alpha Centauri, does host three stars, and even planets, about four light-years from Earth (SN: 8/24/16). But that system isn’t chaotic. Two larger stars orbit close to one another, and a less massive star orbits them, farther out. “This particular system has a solution which is quite stable,” Delabrouille says.
For a hypothetical system in which three stars do orbit chaotically, however, the planet probably wouldn’t survive long, Delabrouille says. “Most probably what would happen very fast is that the planet would either fall in one of the stars or just be ejected.”
Does quantum entanglement allow instantaneous communication?
In the show, the San-Ti are able to manipulate events on Earth, controlling video screens and particle physics experiments from afar and even making stars appear to blink. These powers are explained via sophons, which the series describes as supercomputers the size of a proton.
A single proton can become a supercomputer, the show explains, because the San-Ti make use of extra dimensions. Extra dimensions are a real physics idea: In string theory, for example, scientists propose that there are 10 or more dimensions, instead of just the three space and one time dimension we know. But, Delabrouille points out, those extra dimensions must be tiny (SN: 10/5/18). In the series, the extra dimensions unfold to an enormous size to allow a computer to be etched on the proton. “This is complete science fiction,” Delabrouille says.
Another head-scratcher: The San-Ti accelerate the sophons to send them to Earth, but it’s not explained how the sophons decelerate and arrive unscathed in Earth’s atmosphere. High-speed protons from space hit Earth’s atmosphere on the regular; they’re called cosmic rays (SN: 11/23/23). When those cosmic rays arrive, they are obliterated in showers of particles. Likewise, the sophon “would hit the atmosphere and disintegrate,” Delabrouille says.
What’s more, the sophons can transmit information to and from the San-Ti faster than the speed of light. That’s explained in the show by quantum entanglement — a real feature of physics frequently abused by science fiction authors (SN: 10/4/22). Entangled particles have properties that are linked. Make a measurement of one entangled particle, and you know the result its partner would give, even if the two particles are separated by light-years.
But physicists are crystal clear on one thing: Quantum entanglement cannot transmit information. Each measurement of an entangled particle gives a random result. So, Delabrouille says, “the best we could do is make measurements, get random numbers, and then on the other side … they would get random numbers, too.”
Could nuclear blasts power a space probe?
With the San-Ti barreling toward Earth, slated to arrive in 400 years, humans send out a probe to meet them. To get the probe up to speed — around 1 percent of the speed of light — the team decides on a series of nuclear blasts, carefully timed to catch the probe’s radiation sail as it passes by.
The numbers could work out, Delabrouille says, but the efficiency of each explosion would be small — most of the energy of each blast would be lost into space and wouldn’t go into propelling the probe. “I think it’s a little bit optimistic,” he says.
There were plenty of other moments in the show that, while based in real science, end up not being plausible, Delabrouille says. Nanofibers can make impressively strong materials, for example (SN: 1/10/18). But individual ones couldn’t slice through a ship. And scientists have attempted to send messages to aliens, but the sun wouldn’t amplify a radio signal humans broadcast (SN: 2/24/23). And no, Delabrouille says, an army wouldn’t float off the San-Ti home planet if the three stars lined up with each other. Lofting the army would require immense tidal forces that would rip the whole planet apart.
Despite the scientific leaps, Delabrouille says he enjoyed both the show and the novel it’s based on. “It’s extraordinarily imaginative, and I like that,” he says. “It makes me think: ‘Is this plausible? Is this possible?’ And then you have to think why it’s not possible, so even in that respect, it’s interesting.”
