The three-body problem is a longstanding puzzle in physics that has perplexed scientists since the time of Isaac Newton. But what exactly is this problem, why is it so difficult to solve, and how does it relate to the sci-fi series of the same name?
The three-body problem involves a system where three bodies exert gravitational forces on each other. While this may sound straightforward, it is notoriously complex. Billy Quarles, a planetary dynamicist at Valdosta State University, notes that this problem was “the first real worry of Newton.” In a two-body system, like a planet orbiting a star, predicting their movements is relatively simple: they follow predictable, circular paths around their center of mass. However, adding a third body disrupts this balance, causing unpredictable and chaotic motion due to the additional gravitational forces.
Shane Ross, an applied mathematician at Virginia Tech, likens it to walking on a mountain ridge where a small change in position can lead to vastly different outcomes. The motions of the three bodies depend heavily on their initial conditions—positions, velocities, and masses—and even a minor change can drastically alter the system’s behavior. This lack of constraints makes solving the three-body problem with equations impractical.
Despite its complexity, some solutions have been found. Under specific initial conditions, such as three bodies of equal mass, they can follow a figure-eight pattern. However, such solutions are rare. In more typical scenarios, the orbits of the bodies are unstable, often resulting in collisions or one body being ejected from the system. This ejection process may explain the existence of “rogue planets” that do not orbit any star.
There are instances where the three-body problem can be simplified. For example, in the fictional “Star Wars” universe, the planet Tatooine orbits two suns. If the planet’s orbit is far enough away, the system can be approximated as a two-body problem because the planet’s gravitational influence is negligible.
In reality, scientists use computers to approximate the motions in three-body systems, enabling predictions for rocket launches or the stability of planets in multi-star systems. This computational approach is essential for understanding complex gravitational interactions.
The Netflix series “3 Body Problem” features a planet in a chaotic orbit around three stars. According to Ross, such an environment is unlikely to support stable conditions for life, highlighting the show’s departure from scientific plausibility.
In summary, the three-body problem illustrates the intricate and unpredictable nature of gravitational interactions among multiple bodies. While exact solutions are rare, computational methods provide valuable approximations, helping us understand and navigate the complexities of such systems.
