How the three-body problem explains cosmic chaos

The Three-Body Problem became one of the most popular series on Netflix in 2024. It is based on a real physical phenomenon. Let’s figure out how it was discovered, what it is connected with, and why this problem has not yet been solved.


This text contains spoilers for the Netflix series The Three-Body Problem. If you don’t want to know them, come back to the material after watching the third episode.

Series “The Three-Body Problem”

In March 2024, the first season of the series “The Three-Body Problem” was released on the Netflix streaming service. This is an adaptation of the first book in the science fiction trilogy “Remembrance of Earth’s Past” by Chinese writer Liu Cixin. The novel intertwines the events of the Cultural Revolution in China with modernity, in which humanity is forced to think through its defense against alien invaders arriving after several centuries. The work was translated into film language by Game of Thrones showrunners David Benioff and Daniel Brett Weiss.

Film critic Stanislav Zelvensky noted: “The novel by the leading Chinese science fiction writer Liu Cixin, published in the 2000s, was called unfilmable many times, after which, naturally, it was filmed four times. The Chinese full-length film, however, lay unfinished on the shelf, but the Chinese TV series, released last year [2023], honestly retold the book in 30 episodes. But to the average Western eye, it can look hazy, overloaded, and generally too unfamiliar.”

The Netflix adaptation received mostly positive reviews. This is largely because Benioff and Weiss managed to successfully transfer the rather impressive scientific part of the trilogy to the silver screen. The central place in it is occupied by a real phenomenon – the “three-body problem”. To understand what it is, it is important to first study the physical phenomena associated with the location of astronomical bodies in space.

Two body problem

The Earth revolves around the Sun as the gravitational field of the star attracts our planet and everyone else in its system. However, none of the other planets has sufficient power to influence others. Similarly, the Moon falls into the Earth’s gravitational field and therefore moves in space along with it.

In other words, two objects whose gravitational fields interact will always form stable orbits along a predictable and unchanging path. Isaac Newton proposed this law and developed a formula for calculating orbits in 1687. His discovery is sometimes called the “two-body problem.” In this context, “bodies” is a scientific term that refers to planets, moons, stars, and any other massive astronomical objects.

Newton’s equation allowed astronomers to model the relationship between two large bodies, such as the Earth and the Sun. Our planet moves in an orbit with a regular period lasting approximately 365.24 days – one solar year. Likewise, the Moon orbits the Earth approximately every 27.3 days—another stable two-body system. Astronomers and physicists can easily map them and predict their orbital movements.

Chaoticity of three bodies

Predictability only occurs in the case of two objects with gravitational forces. If you add a third, everything changes dramatically. It creates chaos and causes celestial bodies to interact in completely unpredictable ways – to rotate in space, crash into each other, or bounce and fly apart in completely different directions.

Chaos in the mathematical sense does not mean “disorder and disorganization.” It is often characterized by what scientists call “initial condition sensitivity.” A popular name for this phenomenon is the “butterfly effect.” According to it, the behavior of two identical chaotic systems, which are launched with similar, but not identical initial conditions, will differ greatly from each other as time progresses. The three-body problem arises.

Three body problem

The three-body problem is a specific motion of three points by the laws of motion and Isaac Newton’s law of universal gravitation. Due to the chaos factor, humanity has not yet been able to solve it.

Indiana University Bloomington astrophysicist Charles Horowitz explains in a commentary to Vox that the key to the three-body problem is the law of conservation of energy. According to it, the energy in a closed system remains constant. The researcher emphasizes: “Conservation of energy implies that the planet will forever revolve around one star and can never go to infinity. In other words, once a planet is in the gravitational field of a star, it will not be able to generate the additional energy needed to escape from it. On the other hand, several stars can exchange energy and eject each other.”

For centuries, scientists have been unable to find a reference point from which the three objects could form stable orbits relative to each other. In the 21st century, researchers have come closer to this thanks to computer algorithms. Neural networks have been helping in the last few years, but full success has still not been achieved. The fact is that most of the solutions are very difficult and even impossible to simulate in reality due to the maximum chaos of the system. Because of this, it is unclear how well they work outside the realm of theory.

Aliens and the Three-Body Problem

The central idea of ​​both the book and the series The Three-Body Problem is that an alien species can become a technologically advanced civilization. However, it exists on a planet within a system with three different Suns. Because of this, stars constantly exert gravitational forces on each other, throwing each other around space and wreaking climate havoc on the planet at the center of events. For example, due to the blocking of light, a long-term night may occur on it, which will bring cold that destroys all living things. Or, conversely, parallel radiation from several stars will significantly increase the temperature on the planet and plunge it into global warming on a gigantic scale.

The alien race Trisolarans have repeatedly faced the destruction of almost their entire civilization throughout thousands of years. In the novel and TV series, they were saved by “dehydrogenation” – before the chaotic era, the aliens quickly got rid of any water in their bodies and went into storage to wait out the unstable climate.

Is it possible to live in a three-body system?

Charles Horowitz notes that the scenario invented by Liu Cixin is quite realistic. The scientist explains: “If life takes billions of years to evolve (as happened on Earth), then such a planet may not be a suitable environment. However, there may be certain three-body configurations that are stable over long periods and may be suitable for life. In addition, it may also evolve faster than on Earth.”

This is exactly the situation the Trisolarans faced: from time to time, the three bodies of their system stabilize for a long time. This respite gives their civilizations enough time to quickly develop and prosper. However, stable epochs inevitably give way to “chaotic” ones, when the stars resume their instability.

The existential problem of the Trisolarans, to which a group of earthlings devotes themselves in both the books and the series, is how to recognize and prepare for a chaotic era if it is impossible to predict it. In other words, they solve the three-body problem in real-time.

Mehran Khan

Mehran Khan is a tech enthusiast who also has a great passion in writing. During his 8 years of career, he has covered news, features, and evergreen content on multiple platforms. Apart from keeping a close eye on emerging tech developments, he likes wasting time at the gym.