Can one predict the future arrangements of planets over extremely large time periods? For centuries this issue has triggered dreams of curious people, and hot debates by specialists including Newton, Lagrange, Poincare, Kolmogorov, Laskar, and Tremaine. Cédric Villani, Professor at Université Lyon and Director of the Institut Henri Poincaré and Member (2009) in the School of Mathematics, explores the long-term behavior of plasma, evoking the advances that he made with Mouhot a few years ago, and continuing with the subject of long-term stability for incompressible fluids.