One of the more poignant moments in the movie Star Wars, is when Luke Skywalker gazes wistfully into the sunset on the planet Tattoine.

What makes the moment more striking is Tattoine orbits a double star, so there are two stars embedded in the sunset. This piece of movie magic is dramatic but not scientifically realistic. Orbiting two stars as close as it appeared in that sequence, would render the planet uninhabitable.

When Isaac Newton came up with his idea of gravity, he ran into a problem. He could calculate precisely what is happening with two bodies orbiting around one another, but when he tried to calculate what would happen with three similarly sized bodies orbiting one another, he got stuck.

Since then, other mathematicians, including Euler and Lagrange had a go at the problem and got stuck too. The issue became known as the "Three Body Problem".

Now we have computers, we can use a different approach. We can just set up three bodies, assign them speeds and directions, and then........

© Castanet