Developed by Einstein in 1915, the general theory of relativity may be the modern theory of gravity. This can be a very complicated mathematical theory which in a nutshell says that space and time, collectively known as spacetime, is curved by the presence of matter and energy, which the motion of matter and energy 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 around the sun. According to general relativity, the road of starlight which grazes the top of sun should bend by 1.75 arcseconds. This effect can be measured throughout a total eclipse. In 1919, Sir Arthur Eddington measured precisely this bending during an expedition where he observed a complete eclipse. This discovery made Einstein an instantaneous worldwide celebrity.

The next prediction is the precession of planetary orbits concerning the sun. In accordance with general relativity, the perihelion from the orbit of mercury should precess about the sun by 43 arcseconds per century. This effect was in fact observed just before Einstein's theory and unexplained until predicted through the theory.

The next experimentally verified prediction will be the reducing of your time due to gravity. This effect causes light being redshifted inside the existence of a powerful gravitational field, i.e. near the surface of an enormous star. This effect is noticed in the spectra of massive stars. Come to its extreme, this effect predicts a good black holes, i.e. objects which can be so massive that nothing, not light, can escape from their gravity. Black holes are already observed indirectly now their existence is actually undisputed.