Scientific Autobiography: And Other Papers by Max Planck | eBook

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Scientific Autobiography and Other Papers

By Max Planck, Frank Gaynor

Philosophical Library

CHAPTER 1

A Scientific Autobiography

My original decision to devote myself to science was a direct result of the discovery which has never ceased to fill me with enthusiasm since my early youth—the comprehension of the far from obvious fact that the laws of human reasoning coincide with the laws governing the sequences of the impressions we receive from the world about us; that, therefore, pure reasoning can enable man to gain an insight into the mechanism of the latter. In this connection, it is of paramount importance that the outside world is something independent from man, something absolute, and the quest for the laws which apply to this absolute appeared to me as the most sublime scientific pursuit in life.

These views were bolstered and furthered by the excellent instruction which I received, through many years, in the Maximilian-Gymnasium in Munich from my mathematics teacher, Hermann Müller, a middle-aged man with a keen mind and a great sense of humor, a past master at the art of making his pupils visualize and understand the meaning of the laws of physics.

My mind absorbed avidly, like a revelation, the first law I knew to possess absolute, universal validity, independently from all human agency: The principle of the conservation of energy. I shall never forget the graphic story Müller told us, at his raconteur's best, of the bricklayer lifting with great effort a heavy block of stone to the roof of a house. The work he thus performs does not get lost; it remains stored up, perhaps for many years, undiminished and latent in the block of stone, until one day the block is perhaps loosened and drops on the head of some passerby.

After my graduation from the Maximilian-Gymnasium, I attended the University, first in Munich for three years, then in Berlin for another year. I studied experimental physics and mathematics; there were no professorships or classes in theoretical physics as yet. In Munich, I attended the classes of the physicist Ph. von Jolly, and of the mathematicians Ludwig Seidel and Gustav Bauer. I learned a great deal from these three professors, and I still retain them in reverent memory. But I did not realize until I came to Berlin that in matters concerned with science they had really just a local significance, and it was in Berlin that my scientific horizon widened considerably under the guidance of Hermann von Helmholtz and Gustav Kirchhoff, whose pupils had every opportunity to follow their pioneering activities, known and watched all over the world. I must confess that the lectures of these men netted me no perceptible gain. It was obvious that Helmholtz never prepared his lectures properly. He spoke haltingly, and would interrupt his discourse to look for the necessary data in his small note book; moreover, he repeatedly made mistakes in his calculations at the blackboard, and we had the unmistakable impression that the class bored him at least as much as it did us. Eventually, his classes became more and more deserted, and finally they were attended by only three students; I was one of the three, and my friend, the subsequent astronomer Rudolf Lehmann-Filhés, was another.

Kirchhoff was the very opposite. He would always deliver a carefully prepared lecture, with every phrase well balanced and in its proper place. Not a word too few, not one too many. But it would sound like a memorized text, dry and monotonous. We would admire him, but not what he was saying.

Under such circumstances, my only way to quench my thirst for advanced scientific knowledge was to do my own reading on subjects which interested me; of course, these were the subjects relating to the energy principle. One day, I happened to come across the treatises of Rudolf Clausius, whose lucid style and enlightening clarity of reasoning made an enormous impression on me, and I became deeply absorbed in his articles, with an ever increasing enthusiasm. I appreciated especially his exact formulation of the two Laws of Thermodynamics, and the sharp distinction which he was the first to establish between them. Up to that time, as a consequence of the theory that heat is a substance, the universally accepted view had been that the passing of heat from a higher to a lower temperature was analogous to the sinking of a weight from a higher to a lower position, and it was not easy to overcome this mistaken opinion.

Clausius deduced his proof of the Second Law of Thermodynamics from the hypothesis that "heat will not pass spontaneously from a colder to a hotter body." But this hypothesis must be supplemented by a clarifying explanation. For it is meant to express not only that heat will not pass directly from a colder into a warmer body, but also that it is impossible to transmit, by any means, heat from a colder into a hotter body without there remaining in nature some change to serve as compensation.

In my endeavor to clarify this point as fully as possible, I discovered a way to express this hypothesis in a form which I considered to be simpler and more convenient, namely: "The process of heat conduction cannot be completely reversed by any means." This expresses the same idea as the wording of Clausius, but without requiring an additional clarifying explanation. A process which in no manner can be completely reversed I called a "natural" one. The term for it in universal use today, is: "Irreversible."

Yet, it seems impossible to eradicate an error which arises out of an all too narrow interpretation of Clausius' law, an error against which I have fought untiringly all my life. To this very day, instead of the definition I just mentioned, one often finds irreversibility defined as "An irreversible process is one which cannot take place in the opposite direction." This formulation is insufficient. For it is quite possible to conceive of a process which cannot take place in the opposite direction but which can in some fashion be completely reversed.

Since the question whether a process is reversible or irreversible depends solely on the nature of the initial state and of the terminal state of the process, but not on the manner in which the process develops, in the case of an irreversible process the terminal state is in a certain sense more important than the initial state—as if, so to speak, Nature "preferred" it to the latter. I saw a measure of this "preference" in Clausius' entropy; and I found the meaning of the Second Law of Thermodynamics in the principle that in every natural process the sum of the entropies of all bodies involved in the process increases. I worked out these ideas in my doctoral dissertation at the University of Munich, which I completed in 1879.

The effect of my dissertation on the physicists of those days was nil. None of my professors at the University had any understanding for its contents, as I learned for a fact in my conversations with them. They doubtless permitted it to pass as a doctoral dissertation only because they knew me by my other activities in the physical laboratory and in the mathematical seminar. But I found no interest, let alone approval, even among the very physicists who were closely concerned with the topic. Helmholtz probably did not even read my paper at all. Kirchhoff expressly disapproved of its contents, with the comment that the concept of entropy, whose magnitude could be measured by a reversible process only, and therefore was definable, must not be applied to irreversible processes. I did not succeed in reaching Clausius. He did not answer my letters, and I did not find him at home when I tried to see him in person in Bonn. I carried on a correspondence with Carl Neumann, of Leipzig, but it remained totally fruitless.

However, deeply impressed as I was with the importance of my self-imposed task, such experiences could not deter me from continuing my studies of entropy, which I regarded as next to energy the most important property of physical systems. Since its maximum value indicates a state of equilibrium, all the laws of physical and chemical equilibrium follow from a knowledge of entropy. I worked this out in detail during the following years, in a number of different researches. First, in investigations on the changes in physical state, presented in my probationary paper at Munich in 1880, and later in studies on gas mixtures. All my investigations yielded fruitful results. Unfortunately, however, as I was to learn only subsequently, the very same theorems had been obtained before me, in fact partly in an even more universal form, by the great American theoretical physicist Josiah Willard Gibbs, so that in this particular field no recognition was to be mine.

While an instructor in Munich, I waited for years in vain for an appointment to a professorship. Of course, my prospects for getting one were slight, for theoretical physics had not as yet come to be recognized as a special discipline. All the more compellingly grew in me the desire to win, somehow, a reputation in the field of science.

Guided by this desire, I decided to submit a paper for the prize to be awarded in 1887 by the Philosophical Faculty of Göttingen. The subject to be discussed was, "The Nature of Energy." After I had completed my paper, in the spring of 1885, I was offered the associate professorship in theoretical physics at the University of Kiel. This offer came as a message of deliverance. The moment when I paid my respects to Ministerial Director Althoff in his suite in the Hotel Marienbad, and he informed me of the particulars and conditions of my appointment, was, and will always be, one of the happiest of my life. For even though my life in my parents' house was as beautiful and contented as any man could wish for, my longing for independence kept growing within me, and I was yearning for a home of my own.

To be sure, I suspected, and by no means without reason, that this smile of good fortune was actually not so much a reward for my scientific accomplishments as a practical result of the circumstance that Gustav Karsten, Professor of Physics in Kiel, happened to be a close friend of my father. Nevertheless, this realization could not mar my supreme happiness, and I was firmly resolved to justify the confidence in me in every way in my power.

I soon moved to Kiel, where I put the finishing touches on my paper, and submitted it in Göttingen. It won second prize. Besides my entry, two other papers had been submitted on the subject, but these two were awarded no prize at all. Obviously, I was wondering why my paper had failed to win first prize, and I found the answer in the text of the detailed decision of the Faculty of Göttingen. The judges set forth a few points of criticism of minor import, and then stated: "Finally, the Faculty must withhold its approval from the remarks in which the author tries to appraise Weber's Law." Now, the story behind these remarks was: W. Weber was the Professor of Physics in Göttingen, between whom and Helmholtz there existed at the time a vigorous scientific controversy, in which I had expressly sided with the latter. I think that I make no mistake in considering this circumstance to have been the main reason for the decision of the Faculty of Göttingen to withhold the first prize from me. But while with my attitude I had incurred the displeasure of the scholars of Göttingen, it gained me the benevolent attention of those of Berlin, the results of which I was soon to feel.

No sooner had I finished my paper for Göttingen than I returned to my favorite subject, and wrote a number of monographs, which I published under the collective title, On The Principle of the Increase of Entropy. In these articles I discussed the laws of chemical reactions, of the dissociation of gases, and finally the properties of dilute solutions. With respect to the latter, my theory led to the conclusion that the values of the lowering of the freezing point, observed in many salt solutions, could be explained only by a dissociation of the substances dissolved, and that this finding constituted a thermodynamic foundation for the electrolytic dissociation theory advanced by Svante Arrhenius approximately at the same time. This conclusion, unfortunately, got me into an unpleasant conflict. For Arrhenius challenged, in a rather unfriendly manner, the admissibility of my arguments, pointing out that his theory related to ions, i.e. electrically charged particles. I could reply only that the laws of thermodynamics were valid regardless of whether or not the particles carried a charge.

In the spring of 1889, after the death of Kirchhoff, I accepted the invitation, extended to me upon the recommendation of the Faculty of Philosophy of Berlin, to take his place at the University, to teach theoretical physics. First, I was an associate professor, and from 1892, a full professor. These were the years of the widest expansion of my scientific outlook and way of thinking. For this was the first time that I came in closer contact with the world leaders in scientific research in those days—Helmholtz, above all the others. But I learned to know Helmholtz also as a human being, and to respect him as a man no less than I had always respected him as a scientist. For with his entire personality, integrity of convictions and modesty of character, he was the very incarnation of the dignity and probity of science. These traits of character were supplemented by a true human kindness, which touched my heart deeply. When during a conversation he would look at me with those calm, searching, penetrating, and yet so benign eyes, I would be overwhelmed by a feeling of boundless filial trust and devotion, and I would feel that I could confide in him, without reservation, everything that I had on my mind, knowing that I would find him a fair and tolerant judge; and a single word of approval, let alone praise, from his lips would make me as happy as any worldly triumph.

I had this experience on several occasions. One of them was when he thanked me emphatically after my memorial address on Heinrich Hertz, delivered before the Physical Society; another, when he expressed his agreement with my theory of chemical solutions, shortly before my election to the Prussian Academy of Sciences. I shall treasure the memory of every one of these thrilling moments to the end of my days.

Besides Helmholtz, I was soon on amicable terms with Wilhelm von Bezold, whom I had known from Munich. Likewise, with August Kundt, the temperamental Director of the Physical Institute, universally liked for his genuine kind human feelings.

The other physicists were not so easy to approach. There was, for instance, Adolph Paalzow, the physicist of the School of Engineering of Charlottenburg, a gifted experimenter, and a typical Berliner. He would always treat me cordially, yet always make me feel that he had really not much use for me. In those days, I was the only theorist, a physicist sui generis, as it were, and this circumstance did not make my debut so easy. Also, I had a distinct feeling that the instructors at the Physical Institute were politely but clearly trying to keep me at arm's length. But in the course of time, as we got better acquainted, our relationship assumed a friendlier aspect; one of them, Heinrich Rubens, eventually became my close personal friend, and our friendship was ended only by his death, at an all too early age.

By a sheer whim of fate, no sooner had I reported to my post in Berlin 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 the Schiedmayer piano factory of Stuttgart for the Ministry. I was given the task of using this musical instrument for a study of the untempered, "natural" scale. I delved into the problem with keen interest, in particular with regard to the question concerning the part played by the "natural" scale in our modern vocal music without instrumental accompaniment. These studies brought me the discovery, unsuspected to a certain degree, that the tempered scale was positively more pleasing to the human ear, under all circumstances, than the "natural," untempered scale. Even in a harmonic major triad, the natural third sounds feeble and inexpressive in comparison with the tempered third. Indubitably, this fact can be ascribed ultimately to a habituation through years and generations. For before Johann Sebastian Bach, the tempered scale had not been at all universally known.

(Continues...)

Excerpted from Scientific Autobiography and Other Papers by Max Planck, Frank Gaynor. Copyright © 1949 Philosophical Library, Inc.. Excerpted by permission of Philosophical Library.
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Scientific Autobiography: And Other Papers

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