Life Through a Gravitational Lens

Einstein's Theory of General Relativity predicts that light rays from a distant object will be bent by the gravitational field of a foreground object. This phenomenon is observed by astronomers as they peer through the universe, where numerous objects in space warp the light from distant objects and distort astronomers' view through the gravitational lens effect. Brian McLeod at the Harvard-Smithsonian Center for Astrophysics (CfA) and colleages developed computer software which can distort digitized photographs to show what gravitational lensing would do to images of ordinary objects here on Earth. The image at right is the Smithsonian Institution's Castle in Washington, D.C., as it would appear if a black hole with the mass of Saturn were positioned in front of the observer. Two images of the castle are observed inside and outside of a central ring. This image illustrates the types of images that scientists study at the CfA-Arizona Space Telescope LEns Survey (CASTLeS) of gravitational lenses. The objective of the survey is to learn more about distant galaxies and to determine the rate of expansion of the universe, known as the Hubble Constant. The CASTLeS website contains an online database of images that you can download for fun or research. You can also download the gravitational lens modeling software here.