ScienceWeek

MAX PLANCK (1858-1947)

PLANCK, BOLTZMANN, AND ENTROPY

The following points are made by Martin J. Klein (The Natural Philosopher 1963 1:83):

1) If there is a single concept that unifies the long and fruitful scientific career of Max Planck, it is the concept of entropy. From the Munich dissertation which he wrote at the age of 21, right through to the papers he wrote during his late seventies, the Second Law of Thermodynamics and the associated idea of entropy were always central in his thought. Although much of his work can be viewed as an extended series of variations on what he called his pet theme ("Lieblingsthema"), the theme itself was radically altered in 1900. In that year Planck introduced, in his theory of the black-body radiation spectrum, the idea which immortalized his name, the idea of energy quanta.

2) This idea grew directly from Planck's years of study of the way in which the second law of thermodynamics applied to the behavior of radiation. But despite its connections with his work on entropy during the previous 20 years, it was the very success of his theory of radiation that forced Planck to make a thorough revision of his ideas on entropy.

3) Before 1900, Planck had resolutely followed the single line of pure thermodynamics in his work, avoiding the difficulties that surrounded the path of kinetic theory. He was willing to grant that the attempts to expose the molecular basis of macroscopic behavior offered the hope of more fundamental insight into nature; but he expressed his doubts, on more than one occasion, that these attempts to dig deeper than the laws of thermodynamics could meet with real success in the foreseeable future. At no point in any of the 40 or so papers that he wrote prior to 1900 did Planck use, or even refer to, the relationship that Ludwig Boltzmann had discovered between entropy and the probability of molecular configurations. The muse of entropy was as dear to Boltzmann's heart as to Planck's, but how different she appeared to her two admirers!

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ALBERT EINSTEIN (1879-1955) ON MAX PLANCK (1858-1947)

Many kinds of men devote themselves to science, and not all for the sake of science herself. There are some who come into her temple because it offers them the opportunity to display their particular talents. To this class of men science is a kind of sport in the practice of which they exult, just as an athlete exults in the exercise of his muscular prowess.

There is another class of men who come into the temple to make an offering of their brain pulp in the hope of securing a profitable return. These men are scientists only by the chance of some circumstance which offered itself when making a choice of career. If the attending circumstances had been different, they might have become politicians or captains of business.

Should an angel of God descend and drive from the temple of science all those who belong to the categories I have mentioned, I fear the temple would be nearly emptied. But a few worshippers would still remain -- some from former times and some from ours. To these latter belongs our Planck. And that is why we love him.

Adapted from: Albert Einstein: Preface to /Where is Science Going?/ by Max Planck. Original German text 1933, English text Ox Bow Press 1981.