Erasto B. Mpemba

Erasto Bartholomeo Mpemba (1950 – 2023) was a Tanzanian game warden who, as a schoolboy, discovered the eponymously named Mpemba effect, a paradoxical phenomenon in which hot water freezes faster than cold water under certain conditions; this effect had been observed previously by Aristotle, Francis Bacon, and René Descartes.

He discovered the phenomenon at Magamba Secondary School in 1963 while preparing ice cream to earn pocket-money.[1] Due to lack of time, he skipped the cooling phase when preparing the ice cream and immediately put it into the freezer; unexpectedly, his milk mixture froze faster than that of his classmates.[2] His physics teacher at the time told him that his Observation was clearly not possible.[2] A few years later, the head of Mpemba's school invited British physicist Denis Osborne (1932-2014) from the University of Dar es Salaam to give a guest lecture on his work.[3] At the end of the presentation, Mpemba asked the question that had been bothering him for so long: “If you take two beakers with equal volumes of water, one at 35°C and the other at 100°C, and put them into a refrigerator, the one that started at 100°C freezes first. Why?”[2] Teachers and classmates present thought the claim absurd and mocked Mpemba for the question. Osborne was also caught off guard; he, too, had never heard of such behavior, but was later able to prove experimentally the correctness of his observations.[2][3] During Mpemba's studies at the College of African Wildlife Management near Moshi, he published in 1969—together with Osborne—a paper on the phenomenon.[4]

Mpemba later studied in Australia and the USA[5] and became Principal Game Officer for the Tanzanian Ministry of Natural Resources and Tourism and a member of the African Forestry and Wildlife Commission's working party on the management of wildlife and protected areas circa 2002.[6] He has since retired.[7]

Mpemba died in 2023 in his home in Dar es Salaam, Tanzania.