It's a wonderful story and should be told to every youngster:
The effect is named after Tanzanian
Erasto Mpemba. He described it in 1963 in Form 3 of Magamba Secondary School,
Tanganyika, when freezing ice cream mix that was hot in cookery classes and noticing that it froze before the cold mix. He later became a student at Mkwawa Secondary (formerly High) School in
Iringa. The headmaster invited Dr.
Denis Osborne from the University College in
Dar es Salaam to give a lecture on physics. After the lecture, Mpemba asked him the central question:
Mpemba was at first ridiculed by both his classmates and his teacher. After initial consternation, however, Osborne experimented on the issue back at his workplace and confirmed Mpemba's finding. They published the results together in 1969, while Mpemba was studying at the
College of African Wildlife Management.
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HOWEVER:
In 2016, Burridge and Linden defined the criterion as the time to reach 0 °C (32 °F; 273 K), carried out experiments, and reviewed published work to date. They noted that the large difference originally claimed had not been replicated, and that studies showing a small effect could be influenced by variations in the positioning of thermometers: "We conclude, somewhat sadly, that there is no evidence to support meaningful observations of the Mpemba effect."
[1]
In controlled experiments the effect can entirely be explained by undercooling and the time of freezing was determined by what container was used.
I would still tell it to youngsters and encourage them to have an observant, questioning attitude and to be prepared to tackle perceived wisdom. IMO that is how the human race has progressed.
Gordon
