Dark matter can also be detected when it acts as a lens due to the deflection of light by a mass, predicted by Einstein's General Theory of Relativity. A massive astronomical body (e.g., a black hole, or a galaxy) between a star or galaxy and an Earth observer will distort the image of the star or galaxy, in general, so that it is arc shaped (photo at right) instead of spherically shaped. If that massive astronomical body is on a direct line between the earth observer and the star or galaxy, however, a ring will be observed. The demonstration immediately below illustrates this phenomenon. (Use your mouse to move the observation point -|- to see how the yellow ring is affected.) The second demonstration shows lensing for several interesting patterns that have no astronomical basis. (The CDF Player may take a couple of minutes to load.)

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South Carolina State University, 01/24/2015