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Why does general relativity predict that gravity bends light?

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Brian Greene sits in a living room, holding a pen, with handwritten equations m = E/c^2 and E = mc^2 on a whiteboard beside him, highlighting c^2 as the speed of light. — relativity Brian Greene kicking off his *Your Daily Equation* video series with Albert Einstein's famous equation E = mc².

In general relativity, gravity is not a force in the Newtonian sense but a consequence of the geometry of space-time. Massive objects, such as stars or galaxies, warp the fabric of space-time around them, creating a curvature.12

Light travels along the shortest natural paths in this space-time, known as geodesics. When space-time is flat, these paths are straight lines. However, in the presence of a massive body, the curvature of space-time forces these geodesics to bend. Consequently, as light passes near a massive object, its path is deflected by the geometry of the space-time through which it travels. This phenomenon allows massive objects to act as a gravitational lens, bending and distorting the light from more distant objects. As physicist John Wheeler summarized, matter tells space-time how to curve, and space-time tells matter—and light—how to move.12