- #1

Roberto Pavani

- 6

- 3

- TL;DR Summary
- It would be possible to have the gravity acceleration experienced by an observer close to an event horizon so "little" to let a spaceship to stay above the event horizon?

From "standard" formula we have that the gravity acceleration a = GM/r^2 and that the Schwarzschild radius rs = 2 GM / c^2

Is it possible to compute the gravity acceleration at Schwarzschild radius putting r = rs?

In this case we will have a = c^4 / (4GM) This mean that a very very ultramassive black hole can have a gravity acceleration for an observer O1 close the event horizon, similar to the Earth gravity acceleration ?

If the above formula is wrong (a = GM/r^2) , what is the gravity acceleration formula for a black hole?

From a very far observer O2 the observer O1 is seen slowed down.

Is O1 able to hover the event horizon because of the "relative small" gravity ?

If yes can that observe send a probe "below" the event horizon and using the probe engines, retrieve it ?

Another question is, when the probe will be below the event horizon, the radio signals from the probe aren't able to "escape" (e.g. will never reach O2) because the escape velocity is greater than the speed of light.

Would be possible for the light however to reach O1 ?

Probably most of the assumption above are wrong, otherwise it would be possible for a light ray from the probe below the event horizon to hit O1 and by scattering or reflection, "escape" from the black hole.

There should be some error on all the description, because also without a spaceship at O1, a photon could exit the event horizon, hit an incoming particle outside the event horizon and "flee" away by scattering or reflection.

Is it possible to compute the gravity acceleration at Schwarzschild radius putting r = rs?

In this case we will have a = c^4 / (4GM) This mean that a very very ultramassive black hole can have a gravity acceleration for an observer O1 close the event horizon, similar to the Earth gravity acceleration ?

If the above formula is wrong (a = GM/r^2) , what is the gravity acceleration formula for a black hole?

From a very far observer O2 the observer O1 is seen slowed down.

Is O1 able to hover the event horizon because of the "relative small" gravity ?

If yes can that observe send a probe "below" the event horizon and using the probe engines, retrieve it ?

Another question is, when the probe will be below the event horizon, the radio signals from the probe aren't able to "escape" (e.g. will never reach O2) because the escape velocity is greater than the speed of light.

Would be possible for the light however to reach O1 ?

Probably most of the assumption above are wrong, otherwise it would be possible for a light ray from the probe below the event horizon to hit O1 and by scattering or reflection, "escape" from the black hole.

There should be some error on all the description, because also without a spaceship at O1, a photon could exit the event horizon, hit an incoming particle outside the event horizon and "flee" away by scattering or reflection.