**Of Planets, Stars and Eternity**

After Newton’s great achievements, it seemed to scientists and philosophers of the Enlightenment that we should be able to predict everything about the future of the physical world from a knowledge of its present state. One of the areas where that should be easiest is to predict the future of the solar system, and indeed our ability to predict the motions of the planets in the short term is extremely good. But what about the long term? Can we even say whether our planets will someday be thrown far from the sun by the cumulative forces of gravitational perturbations?

This problem has occupied mathematicians since the 19th century, and has led to great advances in our understanding of dynamical systems — but the original question remains open. Prof. Villani spoke to the Forum about the study of the long time behavior of such systems from, from the Solar system itself to galaxies and related questions from fluid mechanics.

Continue reading “Cédric Villani, Institut Henri Poincaré”