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Astronomy

Gravitational Lensing and Its Uses

Quick fact

The first confirmed gravitational lens was discovered in 1979 as a 'twin quasar'—two images of the same object caused by a galaxy in the foreground bending its light.

Why this is interesting

Light always travels in straight lines—except when gravity bends it. Einstein predicted this, and now astronomers use it as a giant cosmic magnifying glass to see the invisible universe.