"You Light Up My Life!"

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A man named Arthur Eddington helped make Einstein a star—by using stars! Einstein first predicted that mass would bend space and, as a result, the path of light. This idea is part of his General Theory of Relativity .

Diagram of Sun and Earth on a grid, with lines bending around the Sun and diagonal lines showing the apparent and actual position of other stars

In 1919, Eddington used observations to test Einstein 's idea during a solar eclipse, when he was able to measure the position of stars in the direction of the Sun . Eddington found that the daytime and nighttime positions of the stars appeared to be different! Why? The Sun's mass causes space to bend, and starlight follows the path of bent space. This experiment proved that Einstein's light-bending prediction was right, and it made him famous all over the world!

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Image Credits:

Kid photos: courtesy of Denis Finnin, AMNH; It's All Relative: Jim Paillot; Rabbit, elephant, and ant: Francesco Santalacia; You Light Up My Life!: Cathy Sanchez Duvivier