From: gehrab@gmail.com   
      
   On Wednesday, February 15, 2023 at 7:47:38 AM UTC-6, Stefan Ram wrote:   
   > jt writes:   
   > |But this "freezing" is an optical/radio illusion: the object actually   
   > How is it an "illusion"? As I understand causality,   
   > an event can only influence events in its future light cone.   
   >   
   > So, where's the future light cone of the event "the faller   
   > crosses the event horizon here"? This future light cone does   
   > not seem to be in the space outside of the event horizon!   
   >   
   > This would have the very real effect that this event cannot   
   > influence anything in the space outside of the event horizont,   
   > which is not an illusion.   
   A better way of saying this is that you need to look at a Kruskal   
   diagram (there is a good one on Wikipedia). The event horizon is   
   along the positive speed of light line for the physical universe.   
   Note that the time-like hyperbolae accumulate as you get closer to   
   the event horizon. To reach the event horizon you must cross ever   
   more curves of constant time. To an outside observer the object   
   never truly reaches the event horizon since it can only do so in   
   the limit as time approaches infinity.   
      
   In the frame of the observer, this does not happen. They are pulled   
   in by the normal gravitational forces/spacetime curvature as for   
   any other object.   
      
   George   
      
      
   [[Mod. note --   
   There's a great discussion/explanation in figure 32.1 (pages 848-849)   
   of Misner, Thorne, and Wheeler's classic graduate general-relativity   
   textbook "Gravitation: (W. H. Freeman, 1973).   
      
   There's also a nice discussion/explanation in the first answers at   
     https://physics.stackexchange.com/questions/173554/formation-o   
   -the-event-horizon-seems-impossible-with-singularity-inside-seem   
   -im/173638#173638   
   But there are, alas, some quite bogus answers farther down on that page.   
   -- jt]]   
      
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