## Quick Reference

The radius of the event horizon of a black hole. At the Schwarzschild radius the escape velocity becomes equal to the speed of light. The more massive the black hole, the larger the Schwarzschild radius. For a body of mass *M* the Schwarzschild radius is 2*GM*/*c*^{2}, where *G* is the gravitational constant and *c* is the speed of light. It was first calculated in 1916 by K. Schwarzschild.

*Subjects:*
Astronomy and Astrophysics — Physics.

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