How Gravitational Lensing Reveals the Geometry of the Universe
Don't forget to check the recommendations at the end! Decoding Spacetime Geometry: How Gravitational Lensing, Mass Functions, and de Sitter vs Anti-de Sitter Universes Shape Reality Gravitational lensing happens because gravity bends spacetime itself, forcing even massless photons to move along curved paths called null geodesics. In de Sitter and Anti-de Sitter universes, spacetime can remain curved even without ordinary matter because the cosmological constant itself becomes the source of geometry. That idea sounds almost unreal initially. Most people grow up thinking gravity is an invisible pulling force between objects. Einstein completely destroyed that picture. According to General Relativity, gravity is not a force in the traditional sense. Gravity is geometry. Mass and energy distort spacetime. Everything moving through spacetime follows those distortions naturally. Even light. That single principle explains black holes, cosmic expansion, gravitational lensing, dark matter ...