Any gravitating body whose size is less than its Schwarzschild radius becomes a black hole. As the article remarks (can’t quote it exactly because I’m using a c

Any gravitating body whose size is less than its Schwarzschild radius becomes a black hole. As the article remarks (can’t quote it exactly because I’m using a client that has an irksome modal interface) some of the ideas floated is that this black hole could be about fifteen centimeters across, and have the a mass of a very large planet. Science fiction fodder notwithstanding, from a suitable distance this kind of body would behave exactly like any other gravitationally interacting body, and would perfectly obey the usual laws of motion (Einstein’s General Relativity if you’re insisting on investigating it up close or in minute detail, classical Newtonian dynamics if you’re observing on a broader scale). It has mass, it has inertia, and it would be interacting gravitationally as the textbook “product of masses, reciprocal of square of distance” law. It would be a big, dark, featureless bowling ball with the mass comparable to a gas giant.