Light Is Affected by Gravity

In May of 1919, the English astronomer, physicist, and mathematician Sir Arthur Eddington traveled to the island of Príncipe, off the west coast of Africa, to observe a solar eclipse which occurred on May 29, 1919. During the eclipse, he took pictures of far-away stars, which to an observer on earth, were very close in the vicinity of the sun. According to Einstein's theory of general relativity, stars with light rays passing near the sun should appear to be slightly shifted because their light should be "pulled" by the sun's gravitational field. This effect is noticeable only during eclipses, since otherwise the sun's brightness would "blow out" the visibility of any affected stars. Eddington's observations were published the following year and confirmed Einstein's theory. At the time, Eddington's observations were hailed at the time as definitive proof of that general relativity should replace the Newtonian model.