Black holes: formation, theory, and observation

Gravity so strong that nothing escapes

A black hole is an extremely compact astronomical object whose gravity is so strong that nothing can escape, not even light. In general relativity, this happens when a sufficiently compact mass collapses so that a boundary called the event horizon forms; once an object crosses it, it becomes trapped inside and cannot send information back to the outside universe. The event horizon is therefore the “no escape” surface, and its existence is central to how black holes are defined and understood. General relativity also predicts that black holes contain a central singularity where spacetime curvature becomes infinite (ignoring quantum effects). Historically, the idea that light could be unable to escape from a massive body was considered in the late 18th century by Michell and Laplace, but the modern framework came from Einstein’s theory of general relativity and the Schwarzschild solution. Physically, black holes are studied through their effects on surrounding matter and radiation—such as accretion disks, gravitational lensing, and gravitational waves from mergers—since the interior cannot be observed directly.

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Event horizon as the no-escape boundary

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