James Prescott Joule
1818–1889 · British · Victorian Era
Known for: Established the mechanical equivalent of heat, proving energy conservation
James Prescott Joule was a brewer by trade who proved the first law of thermodynamics in his spare time. He measured the heat produced by mechanical work with extraordinary precision—his most famous experiment measured the temperature increase of water stirred by falling weights.
He was initially ignored by the scientific establishment. The joule unit of energy is named after him.
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