Which theory earned Max Planck the 1918 Nobel Prize in Physics?

Quantum theory earned Max Planck the 1918 Nobel Prize in Physics. The award recognized his discovery of energy quanta, which became a foundation of modern quantum physics.

In 1900, Planck proposed that electromagnetic energy could be emitted or absorbed only in discrete amounts related to frequency. The relationship is expressed as E = hν, where h is now called Planck’s constant. He introduced the idea while studying the spectrum of thermal radiation from hot objects.

Planck initially viewed quantization as a mathematical device rather than a complete description of nature. Later scientists, especially Albert Einstein and Niels Bohr, extended the concept to explain the photoelectric effect and atomic structure. Planck’s quantum theory is distinct from Einstein’s theory of relativity, which concerns space, time, gravity, and motion.