I recently finished watching the 3 Body Problem on Netflix so this question came to mind. Can anyone explain (in simple terms) why the 3 body problem was deemed unsolvable even by the advanced alien race in the series? Even better, can anyone here simplify what the 3 Body Problem actually is in Physics? It really got my curiosity. Thanks! 🙂
In: Physics
It’s not that it’s unsolvable. We don’t have the solution because it’s extremely complex because the result is very sensitive to initial conditions.
In 2 body problem (for example, Moon orbiting around Earth), you can predict very accurately where the Moon is exactly at any given point in time because the orbit of the Moon is not affected to a significant degree by any third body.
But in a 3-body problem, body A affects body B, body B affects body C, body C affects body A, which affects body B, so the position of bodies at some future point in time is very sensitive to initial positions.
Imagine a simple pendulum. Just a simple ball hanging off a simple string. With the pendulum formula, if you know the initial position of the ball, you can predict where the ball is going to be after, say, 10 seconds of swinging. If you **slightly** change the initial position of the ball, the position of the ball after 10 seconds is also going to **slightly** change.
However, if you have a double pendulum ([Double Pendulum (youtube.com)](https://www.youtube.com/watch?v=U39RMUzCjiU), if you **slightly** change the initial position of the pendulum, the position of the pendulum after 10 seconds is going to be **very** different, which makes it very difficult to solve mathematically.
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