&gt; This is the exact same conceptual issue as the formation of a single black hole (BH).<p>I know. No one has ever explained how those can form either.<p>&gt; From the outside, this is indistinguishable from a BH for all practical purposes<p>Except without the physics breaking properties of black holes. So not the same at all.<p>&gt; The problem with this argument is that there is no preferred global time coordinate with respect to which you declare that &quot;the BH has formed&quot;.<p>I don&#x27;t need a global time, my own time frame is perfectly fine with me. If a black hole can never form, as viewed by me, then black holes don&#x27;t exist.<p>&gt; This is a free choice because causality flows one-way across the boundary<p>This presupposes the black hole exists already, but we have not gotten there yet. First it has to form, and it can not.<p>&gt; and a natural choice is the proper time of in-falling particles&#x2F;observers. In that case, the BH definitely forms at a finite values of that time coordinate.<p>It gets interesting here - what does happen from the POV of that particle? I suspect it never sees a black hole. This particle is moving exponentially close to the speed of light, relative to the center of mass of the forming black hole.<p>This means that time is stopped for the center of mass of the black hole from the POV of the particle, which means the center of mass can never form a black hole since it can never do anything at all (since time is stopped for it).