 One of Newton's laws of motion states that an object in motion remains in motion at a constant speed in a straight line unless acted on by a force. In this view, gravity is a force that can act on light and divert it from its usual straight line motion. Einstein, on the other hand, had massive objects curving the space around them. An object in motion traveling through this curved space follows geodesics, the shortest path between two points, unless acted on by a force. It's important to remember that in general relativity, gravity is not a force, but light will bend. Both theories have light bending when traveling near a massive object. The larger the mass of the object, the larger the bending, and the closer to the center of the object, the larger the bending. But the two theories predict different amounts of bending for the same mass and distance measurements. Light passing near the surface of the sun, Newton's theory predicts a deflection angle of 0.87 arc seconds. Einstein's theory predicts a deflection angle of 1.74 arc seconds, twice Newton's prediction. Einstein pointed out that the best way to test his theory was to study apparent star locations during a total eclipse of the sun. In 1919, a solar eclipse was slated to occur with the sun silhouetted against the Hiades star cluster, the nearest open cluster to our solar system. The British astrophysicist Arthur Eddington took up positions off the coast of Africa and Brazil, and simultaneously measured the cluster's light as it brushed past the sun. The images were then superimposed on top of an image taken at night earlier in the year. When the eclipse and night images were compared, a gap was found. And when the gap was measured, it confirmed that Einstein's prediction was correct. There's an enhanced picture produced 100 years later by the Heidelberg Digitized Astronomical Plates Project and released by the European Southern Observatory. They scanned one of Eddington's photographic glass plates and applied modern image processing techniques like noise reduction. This version identifies some of the stars used in Eddington's analysis. But the sun's corona is strong. It interferes with all the measurements. It is estimated that errors as large as 20% are inherent in Eddington's and other visible starlight-bending experiments around the sun. But other tests have produced much more accurate results. For example, the European Space Agency's Hipparchus Satellite, from 1989 to 93, designed to measure parallax distances to 100,000 stars, charted to positions of stars so accurately that no eclipse was needed to see the effect of the sun's gravity. They produced numbers with only a 0.1% error. In 2003, using radiofrequency light and measuring techniques that eliminated the error-producing impact to the sun's corona, astronomers measured how much waves sent from the earth to the Cassini satellite and back again were deflected by the sun. Their error rates were around 0.03%. These and many other light-bending experiments have confirmed that Einstein's equations are correct.