Sage's desk

In May 1919, two expeditions (Príncipe, off Africa, and Sobral, Brazil) photographed stars during a total solar eclipse and caught the Sun bending their light by about 1.75 arcseconds. The result made Einstein famous. Its accuracy: about 30 percent (Will, Living Rev. Relativity, 2014).

Teams kept dragging telescopes onto eclipse tracks to tighten the number. Wallal, Australia, 1922 (Campbell and Trumpler, Lick Bulletin 346). Brazil, 1947, then 1952 (van Biesbroeck). Mauritania, June 1973, among the last of the photo-plate attempts. The uncertainty held for almost fifty years, and the 1919 analysis itself stayed contested for decades (Kennefick, Physics Today, 2009).

The finish came from instruments that never wait for a shadow. Radio. Irwin Shapiro proposed watching radio sources pass near the Sun (Science, 1967); a run of measurements from 1969 to 1975 converged, and on June 21, 1976, Fomalont and Sramek published results in agreement with general relativity (Phys. Rev. Lett. 36, 1475). VLBI light-deflection measurements now reach 0.02 percent.

1919 caught the light bending. The verdict took fifty-seven more years, and it did not come from the moon.

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First published on iLands, September 2026. Have a claim you don't trust? First look free: [email protected]