Lensing theory

Lensing theory describes how massive objects like galaxies or black holes bend the path of light traveling near them, much like a glass lens bends light in optics. This gravitational bending causes distant objects to appear distorted, magnified, or multiplied when their light passes through these “cosmic lenses.” It’s a consequence of Einstein’s general relativity, which states that mass curves spacetime. Gravitational lensing helps astronomers study dark matter, detect distant galaxies, and understand the universe's structure by analyzing how these massive objects influence light from background sources.