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So I learned about the Schwartzchild radius, which is the radius of an object's event horizon. But how we define an event horizon is that it's a region of space where the gravitational acceleration light could not escape it. And according to Einstein no information can travel faster than light, therefore no information can escape from within a black hole, so how come we be able to observe a property of the singularity: its mass?
According to Schwartzchild's equations we can deduct the mass of a black hole from an observable property, which is the radius of its event horizon of course.
Furthermore, gravity only travels at the speed of causality/light, for instance if the sun disappeared we would continue orbiting it for 8 minutes until the deformed space-time comes back to normal, so how come any object outside of the black hole even know there is gravitational pull in that region of space?

Qmechanic
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TheOrbitHeart
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  • The "black hole" is located at the "bottom" of a gravity well of its own making; the event horizon is also located in the gravity well, and it extends in all directions. It simply continues the gravity that was present for its predecessor star. – Peter Diehr Jun 27 '18 at 12:31
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    Possible duplicate: https://physics.stackexchange.com/q/937/2451 – Qmechanic Jun 27 '18 at 12:55
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    I don't understand this question. Consider the Schwarzschild solution ('eternal' black hole). The spacetime is static - there is no 'flow' of information or anything else. But there are geometrical objects like the geodesics of the spacetime and some of those are the possible orbits of test particles far from the central singularity. It is with these that the mass $M$ of the black hole is defined. – Alfred Centauri Jun 27 '18 at 12:59
  • I think this question may result from the incorrect perception that a black hole's mass resides within the event horizon. Black holes are more complicated than that. – Lewis Miller Jun 27 '18 at 14:39

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