Planck:
The Grandfather of Quantum Mechanics

By Matt McKeown

A dry and conservative mind by temperament, Max Planck helped instigate one of the most revolutionary changes of twentieth-century Academe.

By the late nineteenth century, Germany was arguably the cultural heart of Europe. Philosophical, historical, and scientific inquiry there had produced such geniuses as Kant, Hegel, Schopenhauer, and Mendel; the University of Tübingen was rapidly becoming the most prominent center of New Testament studies on the continent; politically, the unification of Germany under the leadership of the Hohenzollern monarchy had forged a new world power. Planck was born into this world in 1858, the scion of a venerable family with a history in theology and law. He showed a great talent for music, learning several instruments and even writing operas. However, when the time came for him to embark on formal academic studies, he chose to pursue physics—against the advice of his Munich professor Philipp von Jolly, who warned him that “in this field almost everything is discovered, and all that remains is to fill in a few unimportant holes.”

By the age of 22, Planck had acquired the two highest degrees European scholarship had to offer. He became a professor of theoretical physics at the University of Kiel (a city on the Baltic not far from the German border with Denmark), and his home became something of a cultural center, visited for both intellectual discussion and musical performances by such luminaries as theologian Adolf von Harnack, chemist Otto Hahn, and fellow physicists Elise Meitner and Albert Einstein.

Though far more deist than Christian in his religious views, Planck was a lifelong member of the Lutheran Church in Germany, and spoke often of his beliefs and their relationship to his work. He said in a 1937 lecture, “For believers, God is in the beginning, and for physicists he is at the end of all considerations”; he went still further seven years later: “I can tell you as a result of my research about atoms this much: there is no matter as such. All matter originates and exists only by force of … a conscious and intelligent spirit. This spirit is the matrix of all matter.”

Planck’s special area of interest was thermodynamics. The first two laws of thermodynamics—that matter and energy are interchangeable and can be neither created nor destroyed, and that entropy within a system can only increase with time—were absolutely fundamental to him, drawing on the work of Rudolf Clausius, the first man to articulate the second law. From these premises, Planck became interested in the problems of black-body radiation, or the emission of heat by a theoretical object that absorbs all electromagnetic radiation (such as light) that strikes it, regardless of angle, intensity, or other factors. While other scholars had analyzed black-body radiation, their analyses had been shown to be incomplete, applying only to certain kinds of black-body emissions and falling apart when applied to other kinds.

Science cannot solve the ultimate mystery of nature. And that is because, in the last analysis, we ourselves are part of nature and therefore part of the mystery that we are trying to solve.

Max Planck, Where Is Science Going?

Planck settled on a solution that applied to all types of black-body emissions almost by chance. He proposed an elementary unit, now known as Planck’s constant or h, that controlled rates of emission—hardly seeming to notice that the existence of h was inconsistent with the classical mechanics laid down by Sir Isaac Newton. Just a few years later, Einstein published his first few papers on special relativity, and Planck was one of the few to immediately recognize their importance. The grand simplicity of the Newtonian system was permanently upset; it had been proven inadequate to the atomic and sub-atomic scales of matter and energy. Thus, as the twentieth century dawned, so did one of its most revolutionary theories: quantum physics.

Debates about the exact implications of quantum physics proceeded for decades; like Einstein, Planck himself rejected the interpretation set forth by Bohr, Heisenberg, and others (also known as the Copenhagen interpretation, and currently the most generally accepted version of quantum mechanics). To this day, the operation of gravity has not been satisfactorily worked into the quantum model, giving rise to speculations like string theory.

In Planck’s own day, the problems were more concrete than academic. During the chaotic period following World War One, he led the German scientific community with the slogan “Persevere and continue working,” but by the early thirties this was becoming increasingly difficult. Dozens of Jewish colleagues were expelled by the new Nazi government (with little protest from Planck, though he quietly assisted some in escaping the country), and he and a number of other scientists were critiqued for continuing to promote theories like special and general relativity, instead of what the regime called Deutsche Physik, “German physics”! However, despite many hardships and griefs (including the execution of one of his sons for assisting in Operation Valkyrie), Planck lived to see the end of the war; he died in 1947 and is buried in Göttingen, one of the oldest and most illustrious cities in the country.

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Matt McKeown is a staff writer for CLT and a proud uncle to seven nephews. He lives in Baltimore.

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Published on 9th May, 2022. Page image of the Atomium in Brussels, Belgium, a World Fair exhibit and museum.

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