In 1941, Isaac Asimov defined psychohistory as “the branch of mathematics which deals with the reactions of human conglomerates to fixed economic and social stimuli”. His trilogy Foundation and Empire describes how this science steers the Galaxy through difficult times, from the end of the Empire to the emergence of a new and better world. Nearly eighty years later, psychohistory still is a fiction, but the questions raised by Asimov are still valid : can we use mathematical models to predict the future of mankind? If so, can we steer it away from unpleasant possibilities and towards better ones? How do we factor in human behavior? These questions are particularly urgent today, as the planet faces climate change. Ivar Ekeland will try to describe how mathematical models work, how far into the future they can look, to what extent they can anticipate human behaviour, and what the likely outcomes of the present crisis are.

Ivar Ekeland is a mathematician and economist. He has worked in chaos theory, mathematical finance and the economics of climate change. He was president of the University of Paris-Dauphine, director of the Pacific Institute of Mathematical Sciences in Vancouver BC, and he is a Fellow of the Royal Society of Canada. He has written for the general public (The Best of All Possible Worlds, 2006) and also for children (The Cat in Numberland, 2006). His website is https://www.ceremade.dauphine.fr/~ekeland/ .