- #1

Ivo Draschkow

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- TL;DR Summary
- If the object, at some point, were to start accelerating in the opposite direction and in this way reach the point where it is at rest relative to the black hole, what happens from the perspective of the distant observer as soon as it comes off the accelerator pedal?

First of all, I wish everyone a Happy New Year.

I am interested in your expertise on a special constellation, which I will first briefly describe.

If you observe an object that is approaching the event horizon of a black hole, it is said that at some point the distant observer will have the impression that it is slowing down - even though it is actually speeding up. The reason for this is the increasing time dilation - everything sounds plausible so far.

However, since the whole thing seems like a braking process, the following question arises regarding an idealized, non-rotating black hole:

If the object, at some point, were to start accelerating in the opposite direction and in this way reach the point where it is at rest relative to the black hole, what happens from the perspective of the distant observer as soon as it comes off the accelerator pedal? It can't get any slower, so how does the time dilation for the observed movement process manifest itself now? The object would accelerate again towards the event horizon and the external observer would also have to see this acceleration. At the same time, that would be paradoxical, because everything else that moves towards the event horizon is perceived in a decelerating form.

Or would the object, from the observer's perspective, simply remain at the appropriate distance from the event horizon at which it canceled out the acceleration effect of the black hole based on its own acceleration? That would also be paradoxical, since from its own perspective it would accelerate towards the event horizon again... The external observer would no longer receive this information - which would actually be akin to the event horizon having shifted to the point where the object came to a standstill.

I am very curious about your answers.

I am interested in your expertise on a special constellation, which I will first briefly describe.

If you observe an object that is approaching the event horizon of a black hole, it is said that at some point the distant observer will have the impression that it is slowing down - even though it is actually speeding up. The reason for this is the increasing time dilation - everything sounds plausible so far.

However, since the whole thing seems like a braking process, the following question arises regarding an idealized, non-rotating black hole:

If the object, at some point, were to start accelerating in the opposite direction and in this way reach the point where it is at rest relative to the black hole, what happens from the perspective of the distant observer as soon as it comes off the accelerator pedal? It can't get any slower, so how does the time dilation for the observed movement process manifest itself now? The object would accelerate again towards the event horizon and the external observer would also have to see this acceleration. At the same time, that would be paradoxical, because everything else that moves towards the event horizon is perceived in a decelerating form.

Or would the object, from the observer's perspective, simply remain at the appropriate distance from the event horizon at which it canceled out the acceleration effect of the black hole based on its own acceleration? That would also be paradoxical, since from its own perspective it would accelerate towards the event horizon again... The external observer would no longer receive this information - which would actually be akin to the event horizon having shifted to the point where the object came to a standstill.

I am very curious about your answers.