Produced by Einstein in 1915, the general theory of relativity is the modern theory of gravity. This can be a very complicated mathematical theory which in a nutshell claims that space and time, collectively called spacetime, is curved by the presence of matter as well as, which the motion of matter and is relying on this curvature.
When Einstein devised his theory, he'd three experiments in your mind to test its predictions. One was the gravitational bending of starlight across the sun. In accordance with general relativity, the trail of starlight which grazes the top of the sun should bend by 1.75 arcseconds. This effect can result in measured throughout a total eclipse. In 1919, Sir Arthur Eddington measured precisely this bending throughout an expedition by which he observed a total eclipse. This discovery made Einstein an instantaneous worldwide celebrity.
The second prediction may be the precession of planetary orbits concerning the sun. In accordance with general relativity, the perihelion from the orbit of mercury should precess in regards to the sun by 43 arcseconds per century. This effect was in fact observed just before Einstein's theory and unexplained until predicted from the theory.
The 3rd experimentally verified prediction will be the slowing of your time due to gravity. This effect causes light to be redshifted within the existence of a powerful gravitational field, i.e. nearby the surface of a huge star. This effect is seen in the spectra of massive stars. Taken to its extreme, this effect predicts the existence of black holes, i.e. objects that are so massive that nothing, not even light, can escape from their gravity. Black holes have been observed indirectly now their existence is actually undisputed.