Schwarzchild radius

The Schwarzschild radius (sometimes historically referred to as the gravitational radius) is a characteristic radius associated with every mass. It is the radius for a given mass where, if that mass could be compressed to fit within that radius, no known force or degeneracy pressure could stop it from continuing to collapse into a gravitational singularity. The term is used in physics and astronomy, especially in the theory of gravitation, general relativity.
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The radius within which a The radius within which a celestial object must be compressed if it is to become a black hole . The value of the radius is determined by the mass of the object in question: the more massive the object, the less it needs to be compressed and hence the larger the Schwarzchild radius. For the sun it would be 3 km; for Earth 1 cm. The Schwarzchild radius demarks the distance of the event horizon from the centre of the black hole, which is known as the singularity and is where the escape velocity is greater then the speed of light.