The fact that preheated liquids freeze faster than those that are already cold was observed for the first time by Aristotle in the 4th century AD. A team of researchers from Universidad Carlos III de Madrid, the Universidad de Extremadura and the Universidad de Sevilla have defined a theoretical framework that could explain the Mpemba effect, a counterintuitive physical phenomenon revealed when hot water freezes faster than cold water. The researchers, who have recently published the findings in Physical Review Letters, have confirmed how this phenomenon occurs in granular fluids, that is, those composed of particles that are very small and interact among those that lose part of their kinetic energy. Thanks to this theoretical characterization, "we can simulate on a computer and make analytical calculations to know how and when the Mpemba effect will occur," said Antonio Lasanta. Lasanta is from the UC3M Gregorio Millán Barbany University Institute for Modeling and Simulation on Fluid