Sizing up the universe with cosmic illusions

Abstract

The role of gravitational lenses as valuable tools for astrophysics and cosmology is highlighted. The importance of studying gravitational lens systems for inferring the nature and distribution of gravitating matter, both luminous and dark, is examined. It is argued that cluster lenses can be profitably employed as giant cosmic telescopes to magnify remote faint objects in the Universe. It is demonstrated that with the help of observed lens system it should be feasible to attempt cosmography with view to estimate the Hubble constant, H/subo/.