Before the lecture, there will be a small refreshment outside the hall from 3:45 pm, where you can discuss with each other and meet the speaker.

Roger Penrose observed four decades ago that the space of light rays of a reasonable spacetime carries a natural contact structure and raised the problem of describing the causality relation of the spacetime in its terms. At about the same time, Daniel Bennequin and Yakov Eliashberg discovered the global rigidity properties of contact manifolds. This has ultimately led to a solution of Penrose's problem - and to further open questions.