An object that deflects light by gravitation as described by the general theory of relativity; it is analogous to a lens in optics. The prediction of a gravitational lensing effect in general relativity theory has been confirmed in observations on quasars. In 1979 a ‘double’ quasar was discovered, due to the multiple image of a single quasar caused by gravitational lensing by a galaxy, or cluster of galaxies, along the line of sight between the observer and the quasar. The images obtained by gravitational lensing can be used to obtain information about the mass distribution of the galaxy or cluster of galaxies.
An effect in which light rays are bent by the gravitational field of a massive object, such as a galaxy or black hole. The Sun produces a slight gravitational lens effect (see gravitational deflection), but on cosmological scales the effect is seen as the formation of double or multiple images of a distant galaxy or quasar by a foreground object (as in, for example, the Einstein Cross). More complicated lensing effects also occur, including the formation of Einstein rings, luminous arcs, and microlensing. Gravitational lensing is divided into strong lensing, which creates obvious arcs and rings, and weak lensing, which only subtly distorts the shapes of background objects.
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- Progressive Parties (1912)((US))
- progressive scanning
- progressive tax
- progressive wave
- progress, royal
- Progress Space Centre
- Progymnospermopsida
- progymnosperms
- prohairetic logic
- Prohibition era (1920–33)
- prohibitive tariff
- project
- Project 921
- Project for On-Board Autonomy – Vegetation
- Project Gutenberg
- project Gutenberg
- projectibility
- projectile
- projection
- projection formula
- projection function
- projection lithography
- projection(of a point on a line or plane)
- projection pursuit
- projective geometry