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Gravitational Lensing Discussions of real Einstein rings and ring arcs caused by strong foreground gravitating masses, and pseudo-gravitational lenses that are probably foreground quasars producing multiple images by refraction when their jets are pointed our way.
Gravity & Relativity Observational evidence suggests that gravity propagates faster than the speed of light. How can such evidence be reconciled with Special Relativity? What is the physical nature of gravity?