I would be grateful if someone could point me to a description of how a sphere of freely infalling matter ---- say equivalent to that of a collapsing massive star --- generates an finite-sized event horizon, as observed far from the incipient black hole. I can only imagine that the event horizon nucleates at a point near the sphere's centre, where infall creates the densest matter, and "then" dilate as it gobbles up more matter. But I get confused about how an external observer would "see" this black horizon nucleate and grow: for such an observer any event horizon must be eternally frozen in time. Then I tell myself that the horizon is after all only a coordinate singularity, not a physical object, and that it could (in principle, somehow) be observed over a finite time as a black dilating sphere that propagates outward through the infalling matter until all has been consumed and an appropriate sized black hole has developed. Otherwise how would finite-sized black holes ever come to "exist" for external observers, such as ourselves studying our galaxy centre? A possible 1-dimensional analogy would be behaviour of speeding nose-to-tail freeway traffic when someone momentarily brakes. This can cause a density wave of cars (analagous to the event horizon) to propagate backward ---- just a traffic pattern rather than a physical entity (although the wave amplitude can rise and cause multiple crashes!). If my fevered imagining is anywhere correct, do black holes nucleate as point singularities? If so, are the tidal forces during nucleation not extreme? at an event horizon they increase as the mass of the hole gets smaller.