Quantum Theory Introduced
Max Planck proposed that energy is quantized, founding quantum mechanics
December 14, 1900
A Problem With Hot Objects
In 1900, German physicist Max Planck was trying to explain why hot objects glow the way they do. Classical physics predicted that a heated object should radiate infinite energy at high frequencies — an obviously wrong result called the "ultraviolet catastrophe." Planck found a mathematical formula that matched experimental data perfectly, but to make it work he had to assume something radical: that energy is not continuous but comes in discrete packets, which he called "quanta." He described the idea as "an act of desperation" — he didn't fully believe it himself. But the formula worked, and it changed physics forever.
Einstein Extends the Idea
In 1905, Albert Einstein took Planck's quantum idea further. He proposed that light itself is made of discrete packets — now called photons — to explain the photoelectric effect: why shining light on certain metals ejects electrons. Classical wave theory could not explain this, but the photon hypothesis did exactly. Einstein won the Nobel Prize in 1921 for this work, not for relativity. Over the next two decades, physicists including Niels Bohr, Werner Heisenberg, Erwin Schrödinger, and Paul Dirac built quantum mechanics into a complete theory — one of the strangest and most accurate in all of science.
The Strangeness That Runs the World
Quantum mechanics describes a world that defies common sense: particles exist in multiple states simultaneously until observed; objects can tunnel through barriers they classically cannot cross; particles separated by vast distances affect each other instantly. Yet its predictions match experiments with extraordinary precision. Without quantum mechanics, there would be no transistors, no lasers, no MRI scanners, no solar panels, and no modern computers. The theory that began as a mathematical fix for a problem about glowing objects now underlies the technology of the entire modern world.