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'''Gravitational lensing''' is a gravitational-optical effect whereby a background object like a distant [[quasar]] is magnified, distorted and brightened by a foreground [[galaxy|galaxies]]. An intervening concentration of [[matter]] is declared to bring 'focusing' effect attributed to [[general relativity]] so that even objects normally beyond [[Scientific observation|observational]] distance can bee seen by [[astronomer]]s at the [[Earth]]. It is alleged that, for example, the [[galaxy cluster]] Abell 2218, distorts and magnifies light from galaxies behind it.<ref name="Samec">{{cite web

'''Gravitational lensing''' is a gravitational-optical effect whereby a background object like a distant [[quasar]] is magnified, distorted and brightened by a foreground [[galaxy|galaxies]]. An intervening concentration of [[matter]] is declared to bring 'focusing' effect attributed to [[general relativity]] so that even objects normally beyond [[Scientific observation|observational]] distance can be seen by [[astronomer]]s at the [[Earth]]. It is alleged that, for example, the [[galaxy cluster]] Abell 2218, distorts and magnifies light from galaxies behind it.<ref name="Samec">{{cite web

|title=No sign of gravitational lensing in the cosmic microwave background

|title=No sign of gravitational lensing in the cosmic microwave background

|author=Ron Samec

|author=Ron Samec

==External Links==

==External Links==

*[http://csep10.phys.utk.edu/astr162/lect/galaxies/lensing.html]

*[http://csep10.phys.utk.edu/astr162/lect/galaxies/lensing.html Gravitational lensing]

==References==   

==References==