•In 1887 the King of Sweden offered a prize to the person who could answer the question "Is the solar system stable?" •Poincare, a French mathematician, won the prize with his work on the three-body problem •He considered, for example, just the Sun, Earth and Moon orbiting in a plane under their mutual gravitational attractions •Like the pendulum, this system has some unstable solutions •Introducing a Poincare section, he saw that homoclinic tangles must occur •These would then give rise to chaos and unpredictability                                       @