At the crossroads of physics and neuroscience, this unique book offers a new approach to brain function based on Einstein's work on relativity and the cosmological constant. "The book goes back and forth between what we know about these two universes, the cosmos and our brain, their energy and their matter, be it black, grey or white. It alternates between the fundamental questions of contemporary physics and cosmology, and our knowledge of the functioning of the brain based in particular on the revelations of neuroimaging." D. L. B. The revolutionary hypothesis of a relativistic brain space-time sheds new light on our perception of the world, on our consciousness, on our social interactions and on mental illness. A masterful, daring book that invites us to a journey in thought, from the confines of the universe to the depths of the brain. Author of the best-selling book Le Cerveau de cristal (2012), Denis Le Bihan, a physician and a physicist, is a member of the French Academy of Sciences and of the National Academy of Medicine. He founded and directed NeuroSpin, and has received numerous prestigious international awards for his work in neuroimaging. On the cover: the letter represents the cosmological constant, Einstein's error, while the two brains, with their clocks, can be seen as two mental states of the same person or as two people interacting, within the framework of a relativistic brain space-time.