Gravitational arc from a distant galaxy behind a foreground galaxy cluster [36]. Credit: NASA, ESA, and A. Gonzalez (University of Florida, Gainesville), A. Stanford (University of California, Davis and Lawrence Livermore National Laboratory), and M. Brodwin (University of Missouri-Kansas City and Harvard-Smithsonian Center for Astrophysics) The giant arc, an incomplete Einstein Ring shown is an example of strong gravitational lensing. The more typical effect is weak gravitational lensing [37]. The process is described in more detail by Massey et al. [38].
