Max Planck
Born April 23, 1858 — Died October 4, 1947
Max Planck was a German theoretical physicist who is best known for originating quantum theory in 1900 — one of the two pillars of modern physics, alongside Einstein's relativity. His introduction of the concept that energy is emitted in discrete packets called "quanta" was among the most revolutionary ideas in the history of science, winning him the Nobel Prize in Physics in 1918.
Academic Life and Early Career
Born Max Karl Ernst Ludwig Planck on April 23, 1858, in Kiel, Duchy of Holstein, he came from a family of distinguished classical scholars. He showed early aptitude in music and academics alike, and studied physics at the University of Munich and then the University of Berlin, where he was taught by Hermann von Helmholtz and Gustav Kirchhoff. In 1879 he received his PhD with a thesis on the second law of thermodynamics.
Planck spent most of his professional career at the University of Berlin, where he became a full professor in 1892 and chair of the physics department. His early research focused primarily on thermodynamics, equilibrium states, and entropy — unfashionable but rigorous areas that he mastered with precision. When a professor at the University of Munich famously told him not to study physics because "in this field, almost everything is already discovered," Planck replied that he did not wish to discover new things, only to understand the known — a modesty belied by what came next.
The Quantum Hypothesis
In 1900, Planck was working on the "black-body radiation" problem — explaining why heated objects glow with particular patterns of light at different temperatures. Classical physics predicted that hot objects should emit infinite energy at short wavelengths (the so-called "ultraviolet catastrophe"), a result that clearly violated reality. Planck found that he could mathematically derive the correct distribution of radiation only if he assumed that energy was emitted in discrete, indivisible units — quanta — proportional to the frequency of the radiation, with the proportionality constant now known as Planck's constant (h = 6.626 × 10⁻³⁴ joule-seconds).
Planck himself was uncomfortable with this conclusion, describing it as "an act of desperation" to fit the empirical data. He hoped it would prove a mathematical trick rather than a physical reality. It took Einstein's 1905 paper on the photoelectric effect — which extended quantization to light itself — to confirm that Planck had fundamentally changed how nature was understood. The quantum revolution ultimately spawned technologies from semiconductors to lasers to MRI scanners.
Did You Know?
Planck suffered extraordinary personal tragedy: his first wife died early, his eldest son was killed in World War I, and his twin daughters both died in childbirth. His remaining son Erwin was arrested by the Nazis in 1944 and executed in January 1945 — just months before Germany's defeat — for alleged involvement in the plot to assassinate Hitler.
Nobel Prize and Legacy
Planck was awarded the Nobel Prize in Physics in 1918 "in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta." He served as president of the Kaiser Wilhelm Society (later renamed the Max Planck Society in his honor) and remained a towering figure in German science even as the Nazi regime he abhorred rose around him. He stayed in Germany through both world wars, a decision he later described as deeply conflicted. Planck died on October 4, 1947, at age 89, in Göttingen. His constant, h, appears in virtually every equation in quantum mechanics and remains one of the most precisely measured quantities in all of science.