Neat! On the old forum
I also talked about the idea of surrounding a region of space with a sufficiently massive shell such that it forms a black hole and dooms the interior, even as the interior doesn't notice anything weird whatsoever until it gets swept up in a singularity. The challenge question posed about trying to escape this scenario is interesting!
Added: And yes, one of the two plans will definitely NOT work, while the other potentially could work, and by common intuition that is not necessarily obvious. But the fun part, which I won't spoil, is showing why
one plan is better, using the Penrose diagram. If you understand how the Penrose diagram works from his presentation, then this is actually not too hard to demonstrate, and the physical interpretation of it is very cool. If anyone is trying this challenge and is stuck or confused about some aspect of it, feel free to ask questions.