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What did the 1919 solar-eclipse observations reveal about starlight near the Sun?

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Brian Greene sits in a living room, holding a pen, with handwritten equations m = E/c^2 and E = mc^2 on a whiteboard beside him, highlighting c^2 as the speed of light. — relativity Brian Greene kicking off his *Your Daily Equation* video series with Albert Einstein's famous equation E = mc².

The 1919 solar-eclipse observations provided critical evidence for Albert Einstein’s general theory of relativity by confirming that gravity bends light.12

During the total eclipse of May 29, 1919, expeditions led by astronomers such as Arthur Eddington photographed stars near the Sun’s disk. By comparing these images to photographs of the same stars taken when the Sun was not present, researchers observed that the stars appeared slightly displaced from their usual positions.132

This shift occurred because the Sun’s gravitational field deflected the starlight as it passed close to the solar edge, just as Einstein’s theory had predicted. While the measured deflections—approximately 1.98 arc seconds in Sobral and 1.61 arc seconds on Príncipe—were not perfectly uniform, they were sufficiently close to the predicted 1.75 arc seconds to provide significant support for the theory and establish Einstein as a leading physicist.123