The Schwartzchild solution relates the radius to time, the speed of light,
the mass, and the gravitational constant.
Schwartzchild derived this radius from the Schwartzchild solution,
otherwise known as the Schwartzchild metric and the Schwartzchild vacuum.
It describes the radius of the event horizon of a Schwartzchild black hole.
The year after Schwartzchild solved the problem,
Johannes Droste independently found a simpler solution.
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