1900Reputable sourceWell documented
Planck and the Birth of the Quantum
On the timeline · around 1900 ·
What happened
Trying to explain the colours of light glowing from hot objects, the German physicist Max Planck was forced in 1900 to a radical assumption: that energy is not continuous but comes in tiny discrete packets he called 'quanta.' He thought it a mathematical trick, but it was the seed of a revolution.
Why it matters
Planck's quantum was the first crack in classical physics and the beginning of quantum theory — the physics of the very small that would remake our understanding of matter, light, and reality itself.