How small can a black hole get?
According to General Relativity (the theory that predicts, and explains most of the features of black holes), there is no lower limit to the size of a black hole. But, a full theory of how gravity works must also include quantum mechanics, and such a theory has yet to be constructed. Some hints from recent work on this theory suggest that a black hole can be no smaller than about “10-to-the-(-33)” cm in radius — 0.000000000000000000000000000000001 cm. On that small a size scale, even the apparently smooth nature of space will break down into a “rat-trap” of tunnels, loops, and other interwoven structures! At least, that’s what current work suggests.
