Calculating the trajectories of two gravitating bodies is straightforward mathematics. But introducing even just one more variable into an orbital system can make its long-term trajectory impossible to predict. In 2009, two researchers at the University of California, Santa Cruz investigated just how difficult this mathematical phenomenon – known as the ‘N-body problem’ – makes forecasting the eventual fate of our own corner of space. The team ran 2,000 simulations of the solar system’s trajectory up to 5 billion years into the future, with the only variable being less than a millimetre difference in the distance between Mercury and the Sun. The simulations yielded a stunning array of results, including the possibility of Mercury careening into the Sun, colliding with Venus and destablising the entire inner solar system. This animation from TED-Ed breaks down the N-body problem with rich visuals and methodical clarity, and concludes with scientists’ efforts to minimise N-body unpredictability as humans press further into space.
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