Math & science · 1905

Light quanta

Einstein explains the photoelectric effect with particles of light.

His paper argued light itself is quantised, the photon. It won him the 1921 Nobel Prize and underlies solar cells and digital camera sensors.

Arcs above join it to what it stood on, arcs below to what it led to. The bar places this stretch on the tree's whole timeline.

What it built on 2

The dashed line marks when it first worked.

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