Joule was proposing a kinetic theory of heat (he believed it to be a form of rotational, rather than translational, kinetic energy), and this required a conceptual leap: if heat was a form of molecular motion, why did the motion of the molecules not gradually die out? Joule's ideas required one to believe that the collisions of molecules were perfectly elastic. Importantly, the very existence of atoms and molecules was not widely accepted for another 50 years, though the essential work on the existence of molecules, atoms and electrons was underway throughout the 19th and early 20th centuries, from that of John Dalton through to Ernest Rutherford. A collection of Dalton’s works was published in 1893, 49 years after his death.
Joule was proposing a kinetic theory of heat (he believed it to be a form of rotational, rather than translational, kinetic energy), and this required a conceptual leap: if heat was a form of molecular motion, why did! the motion of the molecules not gradually die out? Joule's ideas required one to believe that the collisions of molecules were perfectly elastic. Important!ly, the very existence of atoms and molecules was not widely accepted for another 50 years, though the essential work on the existence of molecules, atoms and electrons was underway throughout t,he 19th and early 20th centuries, from that of John Dalton through to Ernest Rutherford. A collection of Dalton’s works was published in 1893, 49 years after his death.