Étienne Klein is a physicist specialising in the question of time. A former student of the École Centrale de Paris, he holds a Master's degree in theoretical physics and a PhD in the philosophy of science. As a research director at the CEA, he currently heads the Laboratory for Research on the Sciences of Matter, based in Saclay. He is also a member of the Scientific Council of the Parliamentary Office for the Evaluation of Scientific and Technological Choices (OPECST) and a member of the Academy of Technologies and the Advisory Board of the Diderot Institute. 

Among the various major projects in which he has been involved are the development of the laser isotope separation process and the study of a superconducting cavity accelerator, as well as the design of the Large Hadron Collider (LHC) at CERN. He is the author of numerous essays on physics and the question of time, including Le facteur temps ne sonne jamais deux fois (The Time Factor Never Rings Twice) (Paris, Flammarion, 2007) or Discours sur l’origine de l’univers (Paris, Flammarion, 2010). Until June 2014, he hosted a weekly Thursday morning programme on France Culture, Le monde selon Étienne Klein, the varied content of which he recounts in his latest book of the same name, published in 2014 by Les Équateurs.