A Tanzanian schoolboy insisted his warm ice-cream mix froze before the cold batch. Physicists have fought over the Mpemba effect for 50 years — and still can't agree whether it's even real.
The claim that hot water can freeze faster than cold — noticed by Aristotle, named for a 1960s Tanzanian student whose teacher mocked him before a visiting physicist took him seriously.
A clear primer on why something so simple refuses to be pinned down, and what evaporation, convection and dissolved gas each contribute.
Science News on experiments that do reproduce the effect — and why supercooling of the cold sample may be the hidden ingredient that makes it appear.
Evaporation, convection currents, dissolved gases and supercooling — a rundown of the competing mechanisms and why none of them fully wins.
A careful review concluding the effect shows up only under narrow conditions — when the colder water supercools several degrees below the hotter one before freezing.
Physicists strip the problem down to tiny glass beads and watch a 'hotter' system cool faster than a warm one — hinting the effect is real physics, not just kitchen chaos.
A fresh study argues the effect in pure water has a stochastic origin — it appears only when the freezer sits near the random temperature at which ice happens to nucleate.