Expanding the Search

Abstract

When Einstein first advocated the notion that gravity could bend light, space, and time, there seemed to be little chance that he or anyone else would be able to verify it. Certainly, no one would have guessed that eventually the theory would be used to jump-start galactic surveys for extra-solar planets. Einstein had predicted that the Sun should gravitationally displace, or bend, incoming starlight by as much as 1.75 arcseconds—a significant amount (roughly equivalent to the separation of two car headlights as seen from a distance of 200 kilometers). In fact, it was only three years after he made the concept a central tenet of his 1916 theory of general relativity that a total eclipse of the Sun offered a way to test the theory. In May 1919, Arthur Stanley Eddington, an English astronomer, organized two teams of British astronomers—sending one to Brazil and the other to the West African island of Principe—to look for signs that the Sun was gravitationally bending light from the Hyades star cluster.