IDEAS AND OPINIONS, “Max Planck in Memorial, 1948” by Albert Einstein (Three Rivers Press, NY: 1954, 1982), p.78-79:
“[T]he standard of our ideal search for truth is being held aloft undimmed. This ideal, a bond forever uniting scientists of all times and in all places, was embodied with rare completeness in Max Planck.
“Even the Greeks had already conceived the atomistic nature of matter and the concept was raised to a high degree of probability by the scientists of the nineteenth century. But it was Planck’s law of radiation that yielded the first exact determination—independent of other assumptions—of the absolute magnitude of atoms. More than that, he showed convincingly that in addition to the atomistic structure of matter there is a kind of atomistic structure of energy governed by the universal constant ‘h’, which was introduced by Planck.
“This discovery became the basis of all twentieth-century research in physics and has almost entirely conditioned its development ever since. Without this discovery it would not have been possible to establish a workable theory of molecules and atoms and the energy processes that govern their transformations. Moreover, it has shattered the whole framework of classical mechanics and electrodynamics and set science a fresh task: that of finding a new conceptual basis for all physics. Despite remarkable partial gains, the problem is still far from a satisfactory solution.”