Separating science fact from fiction in Netflix’s “3 Body Problems.”

Note to those who haven’t seen it yet: Spoilers ahead.

What is the three-body problem in physics?

For two objects orbiting each other, scientists can accurately predict the location and speed of these objects in the future. But for three or more rotating objects, the motion can be chaotic. This means that 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 Problem with the bodya race of aliens called the San-Ti inhabit a planet in a triple star system four light years from Earth. The stars’ unpredictable orbits lead to “stable” and “chaotic” periods. Chaotic epochs wreak havoc on the planet’s climate, destroying entire civilizations.

In reality, the sun’s nearest neighboring star system, Alpha Centauri, hosts three stars, and even planets, about four light-years from Earth.SN: 24.8.16). But this system is not chaotic. Two larger stars orbit close together, and a less massive star orbits them, further away. “This particular system has a solution that is quite stable,” Delabruille says.

However, for a hypothetical system in which three stars orbit chaotically, the planet probably wouldn’t survive long, Delabruille says. “Most likely what would happen very quickly is that the planet would either crash into 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 twinkle. These powers are explained through sophons, which the series describes as supercomputers the size of a proton.

A single proton can become a supercomputer, the show explains, because San-Ti uses extra dimensions. Extra dimensions are a real idea of ​​physics: In string theory, for example, scientists propose that there are 10 or more dimensions, instead of just the three spatial and temporal dimensions we know. But, Delabruille points out, those extra dimensions must be small (SN: 10/5/18). In the series, the extra dimensions unfold to a size large enough to allow a computer to be carved into the proton. “This is pure science fiction,” Delabruille says.

Another head-scratcher: San-Ti speeds up the Sophons to send them to Earth, but it’s not explained how the Sophons slow down and arrive unscathed in Earth’s atmosphere. High-velocity protons from space hit the Earth’s atmosphere regularly; they are called cosmic rays (SN: 23.11.23). When those cosmic rays arrive, they are hidden in bottles of particles. Likewise, the sofone would “hit the atmosphere and disintegrate,” Delabruille says.

Additionally, phones can transmit information to and from San-Ti faster than the speed of light. This is explained in the show by quantum entanglement – a real feature of physics often abused by science fiction authors (SN: 10/4/22). Entangled particles have properties that are related. Take a measurement of an entangled particle and you know what its partner would give, even if the two particles are light years apart.

But physicists are clear about one thing: quantum entanglement cannot transmit information. Each measurement of an entangled particle gives a random result. So, says Delabruille, “the best we can do is take measurements, get random numbers, and then in turn … they will also get random numbers.”

Could nuclear explosions power a space probe?

With San-Ti moving towards Earth, expected to arrive in 400 years, the humans send a probe to meet them. To increase the speed of the probe – about 1 percent of the speed of light – the team decides on a series of nuclear explosions, carefully planned to intercept the probe’s radiation cruise as it passes.

The numbers might work, Delabruille says, but the efficiency of each explosion would be small—most of the energy of each explosion would be lost to space and not go into propelling the probe. “I think that’s a little optimistic,” he says.

There were many other moments in the show that, while based on real science, end up not being believable, Delabruille says. Nanofibers can make impressively strong materials, for example (SN: 1/10/18). But individual ones could not pass through a ship. And scientists have tried to send messages to aliens, but the sun would not amplify a radio signal transmitted by humans (SN: 24.2.23). And no, Delabrouille says, an army wouldn’t sail off home planet San-Ti if the three stars aligned with each other. Raising the army would require tremendous tidal forces that would tear the entire planet apart.

Despite the scientific jumps, Delabruille says he enjoyed both the show and the novel it’s based on. “It’s wildly imaginative, and I like that,” he says. “It makes me think: ‘Is this believable? Is this possible?’ And then you have to think why it’s not possible, so in that respect too, it’s interesting.”