Of course Planck had announced in 1900 his formula, now known as Planck 's radiation formula, on black-body radiation but Jeans was strongly opposed to Planck 's results, see for example . Of course Jeans' paper can be seen as a mathematical "proof" that classical physics does not suffice, but it is interesting to note that his pre-quantum ideas concerning the very long time required for systems to come into equilibrium and the observed breakdown of equipartition in specific heat measurements on molecular gases have been used again in relatively recent times more than 80 years after Jeans introduced them.

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OfcoursePlanckhadannouncedin1900hisformula,nowknownasPlanck'sradiationformula,onblack-bodyradiationbutJeanswasstronglyopposedtoPlanck'sresults,seeforexample.OfcourseJeans'papercanbeseenasamathematical"proof"thatclassicalphysicsdoesnotsuffice,butitisinterestingtonotethathispre-quantumideasconcerningtheverylongtimerequiredforsystemstocomeintoequilibriumandtheobservedbreakdownofequipartitioninspecificheatmeasurementsonmoleculargaseshavebeenusedagaininrelativelyrecenttimesmorethan80yearsafterJeansintroducedthem.