This week marks the 100th anniversary of an eclipse that forever changed physics and our understanding of the universe.

In May 1919, scientists set out for Sobral, Brazil, and Príncipe, an island off the west coast of Africa, to photograph the momentarily starry sky during a total eclipse. Their scientific aim was to test whether the sun’s gravity would indeed bend light rays from faraway stars, as predicted by Einstein’s theory of general relativity. After analyzing the data from the brief minutes of darkness, they declared Einstein correct.

Carlo Rovelli, physicist and author, tells Ira the story.

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