D O C . 3 1 8 C R I S I S O F T H E O R E T I C A L P H Y S I C S 2 5 1 known to have succeeded to a certain degree. In particular, we know today that the cohesive forces are of a purely electromagnetic nature. These are not all the fruits of the Faraday-Maxwellian field theory. Recognition of the covariance of Maxwell’s electromagnetic equations with Lorentz transfor- mations led to the special theory of relativity and hence to an awareness of the equivalence between inertia and energy [8] the extension of field theory to gravita- tion, taking into account the identity of inertial and ponderous mass, led to the gen- eral theory of relativity. With the general theory of relativity one pillar of Newton’s theory sank away that had hitherto always been believed to be one of the necessary foundations of all science, namely, Euclidean geometry.[9] It had emerged in early ages from primitive experiments on solids and had been silently assumed by phys- icists to be an exactly pertinent law for the orientation of solid bodies of even tem- perature not subjected to external influences but now, by reason of important considerations based indirectly on experiment, a doctrine already proposed by Gauss and Riemann had to replace it. With the general theory of relativity the developmental phase of theoretical physics founded by Faraday and Maxwell seems to have come to a close.[10] In the last two decades it has been recognized that even a basis for physics char- acterized by the Faraday-Maxwellian field theory cannot hold up to experience any better than the mechanics grounded on it. It is rather to be expected that scientific progress will demand a fundamental change no less profound than the one we have summarized under the name “field theory.” As we are still far away from a logically clear foundation, however, we must content ourselves here with showing how the foundation has thus far proven inadequate and how well account has been taken of important groups of physical phenomena through successful yet still groping attempts subsumed under the term “quantum theory.” Quantum theory found its origins in the theory of thermal radiation, for which a unification of mechanics and electromagnetic field theory delivers a law irreconcil- able with experience and even intrinsically irrational. The fundamental problem of heat radiation can be formulated as follows. Thermodynamics teaches that in the interior of a cavity surrounded by opaque bodies at temperature T, there is a radia- tion whose composition is entirely independent of the nature of the bodies forming the cavity’s walls. If is the monochromatic radiation density, i.e., is the radi- ation energy in the cavity per unit volume whose frequency lies between and , then is a very specific function of and T. It is not determinable by purely thermodynamic considerations its derivation rather presupposes an insight into the nature of the process of generation and absorption of the radiation: Classical mechanics connected with Maxwellian electrodynamics yields for an expression of the form: [p. 4] ρ ρdv v v dv + ρ v ρ
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