Bruno Lévy, Director of the Inria Nancy - Grand Est Centre, Roya Mohayaee, CNRS researcher at the Paris Institute of Astrophysics (Sorbonne University - CNRS) and Sebastian von Hausegger, researcher at the University of Oxford, have recently published a noteworthy article in Physical Review Letters. Their work - at the crossroads between mathematics, computer science and cosmology - focuses on a new mathematical method for turning back time using a three-dimensional map of the cosmos. Roya Mohayaee and Bruno Lévy explain the specifics.