Hoop Conjecture

The ring criterion is a concept from the general theory of relativity, which should enable the decision whether a compact object into a black hole collapses or not. An object of mass M satisfies the ring criterion if it is compact enough to fit in any orientation through the opening of a ring with the circumference, wherein the associated with the object mass Schwarzschild radius.

A hitherto unproven, but confirmed by all known descriptions of black holes guess the American physicist Kip Thorne says that every body that is compact enough to satisfy the ring criterion collapses to form a black hole.