Why Light Can Be Trapped Even Though It Has No Mass

Light is the fastest thing in the universe. It has zero mass. Nothing weighs less than a photon. So how can a black hole, a gravitational phenomenon, trap it completely? Everything we learn about gravity says it acts on mass. No mass, no gravitational pull. And yet, black holes seize light with absolute authority. Light goes in. Light does not come out. The answer isn't what most people expect. Light isn't trapped because it's heavy or because some invisible force overpowers it. It's trapped because spacetime itself has been curved so severely that every possible path, every direction a photon could travel, including outward, bends back inward. The prison isn't built from walls or force. It's built from geometry. In this video, we explore how Einstein's general theory of relativity replaced Newton's idea of gravity as a force with something far deeper: gravity as the curvature of spacetime. We follow light as it bends near stars, orbits in the photon sphere, and ultimately encounters the event horizon, the boundary where the concept of "outward" ceases to exist. Inside a black hole, the direction toward the center isn't a direction in space anymore. It becomes a direction in time. And just as you cannot travel backward in time, you cannot move outward from within an event horizon. Sources: Misner, C.W., Thorne, K.S. & Wheeler, J.A. (1973). Gravitation. W.H. Freeman and Company. Event Horizon Telescope Collaboration. (2019). "First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole." The Astrophysical Journal Letters, 875(1), L1. https://doi.org/10.3847/2041-8213/ab0ec7 GRAVITY Collaboration, Abuter, R. et al. (2018). "Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole." Astronomy & Astrophysics, 615, L15. https://doi.org/10.1051/0004-6361/201... Abbott, B.P. et al. (LIGO Scientific Collaboration and Virgo Collaboration). (2016). "Observation of Gravitational Waves from a Binary Black Hole Merger." Physical Review Letters, 116(6), 061102. https://doi.org/10.1103/PhysRevLett.1... Carroll, S.M. (2003). Spacetime and Geometry: An Introduction to General Relativity. Addison-Wesley. #blackhole #spacetime #gravity #einstein #generalrelativity #eventhorizon #physics