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Why can collisions between black holes produce detectable gravitational waves?

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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.

According to general relativity, the curvature of space-time is determined by the distribution and motion of masses. When these masses change over time—such as when two black holes spiral inward and collide—they create ripples or "wrinkles" in the fabric of space-time that propagate outward as gravitational waves.123

These waves are essentially the radiation of energy caused by the acceleration of massive objects. Because gravity is intrinsically much weaker than electromagnetism, only extremely energetic cosmic events, such as the merger of two black holes, produce disturbances significant enough to be detected by instruments like the Laser Interferometer Gravitational-Wave Observatory (LIGO). During such a collision, a portion of the system's mass is converted directly into energy in the form of these gravitational waves.124