Max Planck, April 23 1858 - October 4, 1947.Today is the 150th birthday of Max Planck. He was born on April 23, 1858, the son of a professor of law at Kiel on the Baltic coast in northern Germany, and grew up in Kiel and Munich.
(Credits: Max Planck Society)
(Credits: Max Planck Society)
In December 1924, in a lecture at Munich on the occasion of the 50th anniversary of the begin of his studies at the university there, he remembered how he came to study physics. Actually, he had been given quite a discouraging advice by physicist Philipp von Jolly back then in 1874, when young Max Planck was unsure whether to chose physics or music. Jolly was convinced that physics had become a mature field and an elaborate science, crowned by the recent, firm establishment of the principle of the conservation of energy, and that only minor "grains of dust and bubbles" were left to explore. Nevertheless, Planck was fascinated by the then brand-new theories of thermodynamics and electrodynamics, and wanted to understand them in depth. And he succeeded in that.
Applying the concept of entropy to electromagnetic radiation, he found in the late 1890s a new constant of nature - today known as the Planck constant. This constant, when combined with the speed of light and Newton's constant of gravitation, allowed to formulate units of mass, length and time "completely independent of special material bodies and substances, and valid for all times and even extraterrestrial and non-human civilisations" - natural units now known as the Planck units. And of course, most of all, this constant allowed Planck to write down the correct theoretical description for the spectrum of electromagnetic radiation emitted by a hot body. Curiously, this formula implied that the energy of this radiation comes in small packets of energy - it is quantised. The rest is history, as they say.
Happy birthday, Max Planck!
- For more about Max Planck, check out the biographies at Wikipedia, Encyclopedia Britannica, or MacTutor. His role in establishing quantum theory is discussed by Helge Kragh in a short essay for PhysicsWorld, Max Planck: the reluctant revolutionary.
- Besides opening the door to the quantum, Max Planck was a very gifted organiser of science and long-term editor of the prestigious Annalen der Physik. He "discovered" and strongly supported Albert Einstein. The Max Planck Society, which arose from the Kaiser Wilhelm Gesellschaft presided by Planck over a long time, has organised an interesting online exhibit on the occasion of the 50th anniversary of his death in 1997.
- Today's Planck Units see the light of day in an addendum to the paper Über irreversible Strahlungsvorgänge, ("On irreversible radiative processes"), published as Sitzungsbericht Deutsche Akad. Wiss. Berlin, Math-Phys Tech. Kl 5 440-480 (1899), and Annalen der Physik 306  (1900) 69-122. The Planck Spectrum was published in Über das Gesetz der Energieverteilung im Normalspectrum ("On the law of energy distribution in the normnal spectrum"), Annalen der Physik 309  (1901) 553-563.
- Planck relates the story about Jolly in a guest lecture on Vom Relativen zum Absoluten (From the relative to the absolute) at the University of Munich on December 1,1924. The German text of the lecture can be found in the collection Max Planck: Vorträge, Reden, Erinnerungen.
Tags: Max Planck, physics