What is gravitional lens?
A gravitational lens is formed when the light from a very distant, bright source (such as a quasar) is “bent” around a massive object (such as a cluster of galaxies) between the source object and the observer. The process is known as gravitational lensing, and is one of the predictions of Albert Einstein’s general theory of relativity. Although Orest Chwolson is credited as being the first to discuss the effect in print (in 1924), the effect is more usually associated with Einstein, who published a more famous article on the subject in 1936. Fritz Zwicky posited in 1937 that the effect could allow galaxy clusters to act as gravitational lenses. It was not until 1979 that this effect was confirmed by observation of the so-called “Twin Quasar” Q0957+561 The gravity from a massive object (such as a galaxy cluster or black hole) can warp space-time, bending everything in it – including the paths followed by light rays from a bright background source. This alters the time taken for the ligh
