Schwarzschild Radius

r_s = \frac{2GM}{c^2}

Radius where escape velocity equals light speed—the event horizon of a non-rotating black hole.

By Karl Schwarzschild

Space Sciences

1916 · Karl Schwarzschild

Why it matters: Made black holes a prediction of physics, not science fiction.

Discoverers: Karl Schwarzschild (1916)

What does it mean?

Radius where escape velocity equals light speed—the event horizon of a non-rotating black hole.

Made black holes a prediction of physics, not science fiction.

Symbol	Name	Unit	Meaning
$r_s$	Schwarzschild radius	m	Event horizon radius
$G$	Gravitational constant	—
$M$	Mass	kg	Black hole mass
$c$	Speed of light	—

Solar mass black hole: r_s ≈ 3 km.

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r_s = \frac{2GM}{c^2}

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Radius where escape velocity equals light speed—the event horizon of a non-rotating black hole.

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