On this day in 1858, German physicist Max Planck, the founder of quantum theory of physics, was born.
Born Max Karl Ernst Ludwig Planck to a family of intellectuals in Kiel, Germany, Planck was gifted in music as a child but decided to pursue his studies in physics at the Universities of Berlin and Munich, where he received his doctorate in 1879. He became a professor in both Munich and Kiel.
Planck’s earliest work was in thermodynamics, the branch of physical science concerned with heat and its relation to other forms of energy. But Planck was especially interested in investigating radiation from hot materials. For decades, physicists were trying to understand the process of heating black bodies, surfaces that absorb all frequencies of light that hit it. The problem: researchers’ observations of the wavelength distribution of energy emitted by a black body as a function of temperature were at odds with the predictions of classical physics. Classical physics wasn’t enough to explain this phenomenon. In 1900, Planck discovered the equation and deduced a hypothesis that explained the relationship between energy and the frequency of radiation. His revolutionary idea was that energy did not flow in a steady continuum, but was delivered in discrete parcels Planck would later call quanta. He discovered this equation to explain the results of these black body tests: E=Nhf, whereas E=energy, N=integer, h=constant, and f=frequency. The “h” in this equation, which Planck himself came up with, is now known as “Planck’s constant.” He published his findings in the Annalen der Physik and summarized them in two books, Thermodynamics and Theory of Heat Radiation.
As opaque as the finding was for some, Planck’s discovery was an enormous feat for the scientific community. He discovered that energy was not emitted in wavelengths, as previously believed, but in small packets, or quanta. With his work, Planck founded the discipline of quantum theory. His theory revolutionised physics and paved the way for Albert Einstein’s theory of relativity.
Sadly, Planck’s personal life was tragic. His first wife, Marie, died after 23 years of marriage. He remarried his cousin Marga. Three of his children died young, leaving him with two sons. In 1944 his second son was executed for plotting to assassinate Hitler. Planck openly opposed Hitler and Nazi persecutions.
Planck received a Nobel Prize in Physics in 1918.