Just as this controversy was heating up, a revolutionary solution was found by a German physicist named Max Planck. One Sunday afternoon in 1900, he was entertaining a fellow physicist named Heinrich Rubens at his Berlin home. A highly accomplished experimenter, Rubens spent the afternoon explaining some of his most recent measurements and how they diverged from classical prediction.
After his colleague’s departure, Planck spent the rest of the evening trying to come up with a more accurate, and less catastrophic, theoretical description of Rubens’ observations. Amazingly, over the course of one single evening, he managed to derive a mathematical equation that was in excellent agreement with the experimental data. Before turning in for the night, he jotted his now-famous blackbody radiation formula onto a postcard and mailed it off to Rubens.
Driven by mathematical intuition, Planck derived a formula that agreed exceptionally well with measured blackbody spectra.
Planck derived his formula not using deep physical insight, but by merely playing around with mathematical equations. In his own words, he arrived at his result “by lucky guess-work.” Therefore, he could not at that stage provide any physical interpretation for his blackbody radiation formula. Nevertheless, he was sufficiently confident in its validity that he formally presented it to his peers 12 days later.
Planck would spend the following two months, which he later called the most arduous of his life, trying to find a physics-based interpretation for his equation. His efforts paid off, and he managed to formulate a simple explanation for his theory. However, since this required him to abandon a central tenet of classical physics, he described his efforts as a true “act of desperation.” He presented his findings to the German Physical Society on December 14, 1900, the day now widely regarded as the birthday of quantum physics.
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