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A black hole is a region of spacetime from which nothing can escape. More formally, the future light cone of any observer within the black hole is completely contained in the black hole, and the black hole region is not within the past light cone of any observer that goes to spatial infinity in an infinite amount of time.

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Will a mass $m$ rotating around a black hole with mass $M$ form a new black hole together wi...

A mass $m$ rotates around a black hole with mass $M$ at a distance $r$ from the horizon. The combined system has an energy depending on the mass $M$ and the rest energy and kinetic energy of $m$. When …
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How far does a particle fall before it hits the singularity of a black hole?

Even though a black hole has a Scwarzschild radius that indicates a finite small distance to the center of the hole, the distance traveled by an infalling particle seems a lot bigger than the Schwarzs …
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How can the distance to the event horizon, as measured by a tape attached to a falling mass,...

When hovering 2km. above the horizon of a black hole with a mass of the sun, at r=5km., the distance you measure with a measuring tape attached to a mass you throw in the hole will tell you the distan …
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How fast must an incompressible ball, with mass $M$ and radius $R$, rotate to form a black h...

An incompressible sphere with a uniformly distributed mass $M$ and radius $R$ is rotating in empty space. How fast must the sphere rotate to form a black hole? Will this happen when the kinetic energy …
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