I asked that question at the worldbuilding stack exchange.


Obviously if a small world had a primordial black hole with a greater mass inside, it would have a higher surface gravity and escape velocity than a world of that size made out of even the densest known materials. Thus the possibility of a fictional habitable world much smaller than otherwise would be the case.

The answers to this question What would happen if a small black hole fell into a star? indicate that I might get a good answer here.

  • $\begingroup$ The surface gravity is ~133.7 m/s^2 (~13.63 g). That's not habitable by humans. For 1 g gravity you need a BH of Schwarzschild radius 0.54963 mm, just under 0.062 Earth masses. That gives an escape speed of ~52% that of Earth. $\endgroup$
    – PM 2Ring
    Dec 7, 2023 at 2:01


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