There has been some controversy about this for years, see for example: https://www.chemistryworld.com/news/mpemba-effect-in-hot-water-after-doubt-cast-on-its-e

There has been some controversy about this for years, see for example: https://www.chemistryworld.com/news/mpemba-effect-in-hot-water-after-doubt-cast-on-its-existence/2500087.article https://www.chemistryworld.com/news/mpemba-effect-in-hot-wat... https://www.repository.cam.ac.uk/handle/1810/263847 https://www.repository.cam.ac.uk/handle/1810/263847 This new paper may prove to be conclusive in supporting its existence, but as I'm not an expert I'll give it some time in peer review before coming to any conclusion.