From: gerry@bindweed.com   
      
   In article <_qqdnTewsJF8KUrEnZ2dnUU7_83NnZ2d@giganews.com>, tjroberts137   
   @sbcglobal.net says...   
   >   
   > On 10/1/17 11:20 AM, Gerry Quinn wrote:   
   > > if we assume that gravity is an effective spin-2 field, we expect it to   
   > > break down at some point.  The Schwarzschild radius is the obvious point,   
   >   
   > Why? Remember that a horizon is a global property of the manifold, and "all   
   > physics is local" [Einstein and others]. For black holes more massive than   
   the   
   > sun, the LOCAL properties of spacetime at the horizon are not remarkable at   
   all.   
   > For a super-massive black hole, the LOCAL properties at the horizon are less   
   > extreme than here on earth.   
      
   If general relativity is false, there exists a local property which   
   we may call gravitational potential (at least after lumping /   
   scalarisation), and this property becomes extreme at the Schwarzschild   
   radius[*].  So your argument above has no validity.   
      
   You're assuming general relativity is true, and deducing from it the   
   truth of general relativity.  In short, this is a circular argument.   
      
   > The "obvious" point for our models to break down is near the singularity.   
   That's   
   > where local properties of the manifold become extreme, and something new must   
   > happen. This is also a region where the topology is very different from   
   anything   
   > we are familiar with, and that could be important.   
      
   If we don't believe general relativity is exactly true, there's a   
   physically significant singularity at the Schwarzschild radius, so   
   that's where we expect a breakdown.   
      
      
   [*] The extreme gravitational potential is identified in the form   
   of extreme time dilation from the point of view of distant observers,   
   which is easy to see but of course not in itself local or distinguishable   
   from geometry.  The local manifestations will depend on the exact   
   nature of the difference between general relativity and actual   
   physics.  But we can make guesses on the basis of broad general   
   principles.   
      
   Remember, also, Hawking radiation, which most people believe in,   
   even when they agree with you about a central singularity.  Hawking   
   radiation contradicts GR.  But it's not coming from a central   
   singularity. It's coming from at or near the Schwarzschild radius.   
      
   It's essentially an interaction between that region and the distant   
   observers, right?  So if all is geometry... why is anything happening   
   there?   
      
   - Gerry Quinn   
      
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