Recent content by Tomas Vencl

….and we can continue with the experiment. Take second rod with the same properties and length. Divide it into n smaller elements. Then lower the elements beside the original hovering rod and attach rockets to each part of the element so that they provide the entire prper acceleration required...

I do not understand, how we choose the exact position of each infinitensimal part, where it hovers ? How we measure , that it is at right place relative to other parts ? What is the right place ? Thinking about positions with no stress at all, but then there are no remain streses. (Maybe this is...

Yes, but are not the tidal gravity forces just those originating from the difference between flat and curved spacetime ?

Yes, thank you all. The infalling observer’s proper time (\tau_1) is ultimately not important. What matters is that all observers agree that at the moment the infalling observer crosses the horizon, the black hole had mass m_1 from his point of view. We take this mass to be computed by the...

Yes, that exactly is the point of the question.

While reading the neighboring thread I came up with the following question: consider an evaporating black hole and an observer falling into it. The observer crosses the horizon at a finite proper time \tau_1; at the moment of horizon crossing the black hole has mass m_1 from the infalling...

As JimWhoKnew has already noted: In other words, this scenario assumes that the photons emitted from the shell itself during the collapse are not affected by the mass of the shell, but only by the mass of the original black hole, which I think is quite an unphysical assumption.

Yes, agree.

I’m not sure whether this definition of reality is physically useful. It is fulfilled by every event in a block universe, and I can’t imagine a physical process that wouldn’t qualify as reality in this sense.

Would it be possible to draw diagrams of the more realistic models considered by both of you? Thank you.

Maybe I am mising something important. Imagine green observer with its proper time. You say that mass of bh decreases to zero between points (and greens times) 1 and 2 ? Then, how he can see some photons at point 3 eventually emmited from collapsing surface ? Or he cant ?

I think that solving this guestion honestly is behind relativity framework, and needs deeper quantum gravity theory. For example: https://en.wikipedia.org/wiki/Causal_dynamical_triangulation

Here is first principles consideration: Since it is a black hole there is an event horizon where timelike worldlines can enter but not exit, this is what defines a black hole instead of a white hole. When evaporation is finished there is no more event horizon, this is what defines the...

Yes,you are right. I am leaving the discussion for now. Thank you and Dale for your ttime.

OK, perhaps it would be fair to also inform the inquirer that the assumptions may not be realistic (which I clumsily tried without any successs to do in my second comment).