256 Chapter 17
becoming a close friend, participating in Helmholtz ’ s musical evenings.^5 That year, Helm-
holtz published the fourth edition of his Tonempfindungen , including his latest thoughts
on sound and space; Planck surely studied this work closely, both as a student and admirer
of Helmholtz and out of his own deep-seated philosophical interests.
In later life, after Planck had returned to Berlin in 1889 as a professor, his own home
music-making included collaborations with such outstanding musicians as the preeminent
violinist Joseph Joachim and the no less remarkable Albert Einstein. Every other week
Planck conducted an informal chorus that included his children, neighbors, and friends.
Ironically, the very sensitivity that made him feel music so deeply also made it hard for
him to endure anything less than absolute perfection in intonation. His pitch sense was
especially acute as a child; he remembered not being able to play on a piano tuned to
lower than normal pitch because of the strong tonal disorientation he felt between the
nominal pitches and the actual sounds.^6 According to the recollections of his friends,
Planck ’ s sense of pitch was so acute that he could scarcely enjoy even a professional
concert, but, in the view of John Heilbron, “ like his politics and his thermodynamics, his
ear gradually lost its absolutism and allowed him greater satisfaction. ”^7 What follows will
examine further these interrelations between music, physics, and Planck ’ s search for
the absolute.
Beginning with his doctoral dissertation (1879), Planck was concerned with the status
of the first two laws of thermodynamics as absolute laws, exemplars of the nonanthropo-
morphism he was later to state as a guiding principle. Until 1914, far longer than most of
his peers, Planck maintained that the second law of thermodynamics was an absolute law
of nature, not merely valid with high probability, as Ludwig Boltzmann had argued. Planck
was long skeptical of the physical reality of atoms, compared to what he regarded as the
absolute certainty of the laws of mechanics and thermodynamics. He was largely respon-
sible for showing the practical consequences of the concept of entropy in physical chem-
istry, which occupied him from 1887 until 1893. In the process, Planck gradually became
convinced that physicists had to rely on the atomic hypothesis to make progress, lacking
any other fruitful fundamental theory, but in 1893 he still preferred not to make use of the
atomic hypothesis if at all possible. Because atoms remained for him hypothetical, at that
point he felt that mechanics and mechanical thermodynamics were “ the deepest form of
coherence. ”
At this turning point in his scientific biography, Planck entered a curious musical bypath,
which Erwin Hiebert and Alexandra Hui ’ s pioneering work has illuminated.^8 Planck
recounts in his scientific autobiography that “ by a sheer whim of fate, no sooner had I
reported to my post in Berlin [in 1893] than I was temporarily assigned a task in a field
quite remote from my self-chosen special branch of physics. Just at that time, the Institute
for Theoretical Physics happened to receive a large harmonium, of pure untempered
tuning, a product of the genius of Carl Eitz, a public school teacher in Eisleben, built by