Linked from
The 20 pages that link to Gravitational lens, each with the reason it gives.
Black holeRelated: A black hole can distort background light and reveal its mass and surroundings.
Dark matter haloRelated: Halo mass can be mapped from the distortion of background light.
QuasarRelated: Lensed quasars reveal intervening mass and can produce measurable time delays.
SpacetimeRelated: The bending follows light's paths through curved spacetime.
AstronomyBroader topic: Lensing makes distant objects visible and maps otherwise unseen mass.
Curved spacetimeBroader topic: The bending of light directly traces curvature along its path.