Hubble’s Inside the Image: Lensed Supernova Refsdal - YouTube - NASA Goddard - astrophysics

Albert Einstein predicted gravitational lensing,the warping of spacetime by the gravitational pull of massive objects such as galaxies.Gravity is actually a curvature in spacetime and can have the effect of enabling observation of very distant objects.This can also be used to ascertain how fast the universe is expanding.