This scenario is described by Lenard Susskind in a lecture on general relativity starting at time stamp 44:23 in the following video. The scenario is that a spherical shell of radiation is directed inward to a point. The shell contains enough energy to form a black hole. He states that inside the shell is just flat space-time. This part I'm comfortable with because it is simply the GR version of Newton's shell theorem. He then goes on to say that from the outside the shell looks like a Schwartzchild geometry. I question this assertion because a person just outside the shell is still causally disconnected from the energy on the opposite side of the shell. Suppose an observer is 1 light-second from the center focal point of the shell. It seems to me that the transition from flat space-time (when the shell is > 1 light-second from the center) to a Schwartzchild geometry would be a gradual transition taking 2 seconds. 1 second after the shell passed you until it collapses to a singularity, and 1 second for the geometrical ramifications of the collapse to reach you 1 second away. Put another way, if I am 1 light-second away from the center of the sphere when the shell passes me, I am 2 seconds away from causal contact with the energy on the other side of the shell. I can't imagine that this he really missing this. It seems like such an obvious flaw I can't imagine that he doesn't see it. Is he deliberately overlooking it in in order to simplify the lesson he's trying to teach or is there something wrong with MY reasoning? Much of the logic from the rest of the lecture seems to rest on this transition from flat geometry to Schwartzchild geometry. It doesn't seem to me like an insignificant detail. Susskind is such an intelligent physicist I'm going to assume that either my reasoning is flawed or the difference between an instantaneous and a gradual transition is an insignificant detail. Could someone please explain either why I'm wrong or why it's insignificant?