> black holes remain a mostly theoretical phenomena The fact that there are compact objects in our universe that, from the outside, look like the black holes t

> black holes remain a mostly theoretical phenomena The fact that there are compact objects in our universe that, from the outside, look like the black holes that GR predicts, is not "theoretical", it's observation. The theoretical question is whether these objects really are classical GR black holes "all the way down", so to speak, or whether there is some new physics that comes into play deep inside them (which many physicists think will involve some form of quantum gravity) that changes things. Even if the latter is the case, the objects might still look like classical GR black holes from the outside for a very, very long time, on the order of the Hawking evaporation time (10^67 years for a one solar mass hole, and the time goes up as the cube of the mass). So for all practical purposes, treating them as classical GR black holes works fine now and for the foreseeable future.