Planck Introduces the Quantum
An act of despair to fit a formula to data ends up breaking classical physics
Quick facts
- Radiation formula announced
- October 1900
- Quantum hypothesis presented
- 14 December 1900, Berlin
- New constant
- Planck's constant, h
- Recognition
- Nobel Prize in Physics, 1918
What happened
Trying to explain the spectrum of light emitted by a heated black body, a problem classical physics could not solve without predicting infinite energy at short wavelengths, Max Planck announced a new radiation formula in October 1900 that matched experimental data. He then had to find a physical justification for it. On 14 December 1900, at a meeting of the Physikalische Gesellschaft in Berlin, Planck presented his theoretical explanation: energy could only be emitted or absorbed in discrete packets, or quanta, whose size depended on a new constant he called, in his own words as recorded by MacTutor, the elementary quantum of action, now known as Planck's constant. Planck himself later admitted, in a remark MacTutor also preserves, that the whole procedure was an act of despair because a theoretical interpretation had to be found at any price, no matter how high that might be.
Why it matters
Planck's quantum hypothesis, adopted reluctantly and initially treated as a mathematical trick rather than a physical claim, turned out to be the first crack in classical physics that would grow into the full quantum revolution. Physics Today's retrospective on Planck notes that his insight not only accurately explained experimental data but also provided impetus to the new quantum theory, work recognized with the 1918 Nobel Prize in Physics.
How we know
Planck's October and December 1900 papers and lecture were published in the proceedings of the German Physical Society and are treated by physicists and historians as the founding documents of quantum theory; his private reflections on the discovery, including the act of despair remark, are preserved in his later correspondence and recollections.
Sources
- MacTutor History of Mathematics, University of St Andrews. Max Planck (1858 - 1947) · Primary source (author-declared)mathshistory.st-andrews.ac.uk · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- Physics Today, American Institute of Physics. Max Planck (1858-1947) · General sourcephysicstoday.aip.org · Cited as a "reference" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
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