Gravitational lenses

Predicted by Einstein and discovered in 1979, gravitational lensing helps astrophysicists understand the evolving shape of the universe. On March 29, 1979, high in the Quinlan Mountains in the Tohono O'odham Nation in southwestern Arizona, a team of astronomers at Kitt Peak National Observatory was scanning the night sky when they saw something curious in the constellation Ursa Major: two massive celestial objects called quasars with remarkably similar characteristics, burning unusually close to...