What is the 3 Body Problem in physics? Is there a solution to it?

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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

24 Answers

Anonymous 0 Comments

Other people here in this thread already explained it well, so I will just add my observations.

The problem is, most of the 3 body systems are not stable. With two bodies – typically one massive – such as a Sun and other much smaller, such as a planet, the system is stable, so it is possible to predict their behavior far into the future based on measuring of their initial positions and velocities. With three bodies, the smallest deviation in starting conditions might grow exponentially over the time, so it is impossible to predict where bodies would be in future.

This is best demonstrated by a double pendulum – also sometimes called a chaotic pendulum. Have a look at some videos talking about this. It is much easier to see.

The Sun, Earth and Moon are three bodies, with other planets adding complexity, but the Earth + Moon behave towards the Sun as a one tiny body for practical purposes of us predicting their rotation far into the future.

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