Math & science · 1896

Radioactivity

Becquerel finds uranium darkening photographic plates by itself.

Marie and Pierre Curie then isolated polonium and radium in 1898. Radioactivity revealed energy inside atoms and gave geology a clock.

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.

Nuclear electricity generation Latest: 2.81k TWh (2025) Source: Our World in Data