April 20

This Day in History


Curies isolate radium

On this day, Marie and Pierre Curie successfully isolate the radioactive substance radium chloride from the mineral pitchblende in their laboratory in Paris. The Curies discovered radium in 1898, … (more...)


First European to Survive Timbuktu Returns Home

On this day in 1828, French adventurer René Caillié became the first European in history to successfully complete the journey to the West African city of Timbuktu and return alive. The first h … (more...)


Sun Dog Phenomenon Scares Stockholm

On this day in 1535, for two early morning hours the skies over Stockholm, Sweden, shining white halos, arcs, and additional “mock” suns surrounded the Sun. Vadersolstavlan, or The Sun Dog Painting, th … (more...)