- #1
robheus
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In the perception of General Relativity a Black hole can form in which anything (including light) is trapped inside the horizon of the Black hole and can never escape, because nothing can exceed light speed.
However, still something escapes the Black hole, which is the presence of the gravitational field outside of the horizon of the Black hole. Since in General Relativity also gravity itself can not be faster then light speed, this is - in a sense - some kind of peculiarity.
One could (in theory) propose that a Black hole, after it has formed, would withdraw it's presence of the gravitational field outside the horizon altogether under the assumption that also the gravity field itself can not escape from the Black hole, and with which the Black hole would effectively disappear for outside observers, and only objects that cross the horizon (without being drawn in by the Black hole as there would be no extreme force of gravity outside the horizon), would experience the presence of the Black hole and disappear inside the horizon. A black hole would then just be a 'gap in space' without making it's presence observable for outside observers.
Appearently, however, this is not the case, since Black holes manifest themselves by the strong gravity fields that exists outside the horizon of the Black hole, which makes a Black hole observable for observers outside the horizon. Else, we would probably not know that a Black hole exists.
What does this mean in terms of the theory of Gravity? In so far particle physics for example predicts the existence of 'gravitons' (particles that exert the force of gravity, similar to how photons exert the electro-magnetic force), those particles can't themselves 'sense' the force of gravity, although a 'graviton' would not exceed light speed.
However, still something escapes the Black hole, which is the presence of the gravitational field outside of the horizon of the Black hole. Since in General Relativity also gravity itself can not be faster then light speed, this is - in a sense - some kind of peculiarity.
One could (in theory) propose that a Black hole, after it has formed, would withdraw it's presence of the gravitational field outside the horizon altogether under the assumption that also the gravity field itself can not escape from the Black hole, and with which the Black hole would effectively disappear for outside observers, and only objects that cross the horizon (without being drawn in by the Black hole as there would be no extreme force of gravity outside the horizon), would experience the presence of the Black hole and disappear inside the horizon. A black hole would then just be a 'gap in space' without making it's presence observable for outside observers.
Appearently, however, this is not the case, since Black holes manifest themselves by the strong gravity fields that exists outside the horizon of the Black hole, which makes a Black hole observable for observers outside the horizon. Else, we would probably not know that a Black hole exists.
What does this mean in terms of the theory of Gravity? In so far particle physics for example predicts the existence of 'gravitons' (particles that exert the force of gravity, similar to how photons exert the electro-magnetic force), those particles can't themselves 'sense' the force of gravity, although a 'graviton' would not exceed light speed.
