362 THE QUANTUM THEORY
The quantum theory: Lines of influence.so much the details of Planck's work on radiation as the very introduction by
Planck of his new universal constant h was decisive for Bohr's ideas about atomic
stability. An account of Bohr's influence on Heisenberg and of Heisenberg's and
Schroedinger's impact on Dirac is beyond the scope of the present book.
In the case of Einstein and Bohr, it cannot be said that the work of one induced
major advances in the work of the other. Therefore, the simplified diagram does
not and should not contain links between them. Nevertheless, for forty years there
were influences at work between Einstein and Bohr and these were in fact intense,
but on a different plane. In a spirit of friendly and heroic antagonism, these two
men argued about questions of principle. Chapter 22 deals with Bohr's resistance
to Einstein's idea of the photon. This was but a brief interlude. It ended with the
detailed experimental vindication of the photon concept, to which Bohr fully sub-
scribed from then on. Their far more important debate on the foundations of
quantum mechanics began in 1927. On these issues, the intellectual resistance and