Proving Einstein Right

Proving Einstein Right

Sir Arthur Stanley Eddington, the British astronomer whose observations during a solar eclipse confirmed part of Albert Einstein`s general theory of relativity was born on December 28, 1882. Sir Stanley Eddington who served as Director of Cambridge University Observatory for almost a third of a century, also significantly advanced our understanding of the internal workings of stars.

Eddington was an outstanding theoretical and observational astronomer. In 1909, while working at the Royal Observatory at Greenwich, he was dispatched to Malta to determine the longitude of an observing station there. In 1912, he led an eclipse expedition to Brazil.

Eddington distinguished himself in his studies of stars. He determined that the reason stars do not contract under the influence of gravity is because outward pressure from heat and radiation counterbalances gravity`s inward pull. He was also the first to show that the interior temperatures of stars must be several million degrees and that a star`s luminosity depends on its mass.

The Milky Way Galaxy Viewed from Afar

One of his greatest areas of interest, however, was relativity. In 1919, Eddington led an expedition that confirmed a basic point of general relativity. According to the theory, relativity should bend light rays; the stronger the gravitational field, the greater the angle of deflection. Eddington realized that it would be possible to test this point during a total solar eclipse, when stars that appear near the Sun in our sky become visible.

On May 29, 1919, Eddington observed a total solar eclipse from the island of Principe in West Africa. True to Einstein`s predictions, the Sun`s gravity bent the light coming from stars near the solar limb, deflecting their apparent positions slightly away from the solar disk.