Einstein attempted to broaden the framework of the principles of relativity by applying it to all cases, and produced the theory of general relativity. He explained that the gravity of a body deforms locally the space and time, producing a deviation of light rays passing near to it. This property was confirmed in 1919 by Eddington’s observations conducted during a total solar eclipse. It is also responsible for the gravitational lenses, that are larges mass like a cluster of galaxies which amplify and distort images of galaxies or quasars located at larger distances. Black holes and gravitational waves are other consequences of this theory, which renews the Newtonian approach of the gravitational interaction between bodies.

caption : Image of a very distant quasar which has been multiple-imaged by a relatively nearby galaxy acting as a gravitational lens, sometimes referred to as the Einstein Cross - credits : NASA/ESA/STScI.