RajeshTrivedi
Valued Senior Member
Fantastic, thanks for elevating this thread to a nice qualitative discussion.
Color and bold by me. (pl expand the quote above)
I agree with your uncolored part in entirety. The Paddoboy's photon hovering link (quite famous once upon a time here on SF) is fine but photon comes inside as soon as even a single additional photon is accreted by BH.
But I disagree with the color portion. consider the qualitatively most simple density distribution, uniform density spherical symmetry object just inside its Schwarzschild radius. I have given an example say of 1 million solar mass. Except the outer most surface, every other inner part is outside its Schwarzschild radius (Uniform density just at its EH, apply mass / volume formula to get the radius of inner 0.1 - 99.99% mass (any fraction), you will see that fractional sphere is out of its Schwarzschild radius. Now freely apply Newtonian or Birkhoff's (in relativity) and you will see that a photon emitted just inside has no bar in moving away from center. (of course it will remain trapped inside outer EH), and of course I am just going with you, it may be swayed down with the collapsing mass.
But it does not end here, the object keeps collapsing from 3 million km. And as per my assumptions a stage comes, R(p) = 640 Km, (640 to 3 million is empty and 0 to 640 is densely packed Neutrons, a sphere of uniform density, say), here too as I have shown even when one million solar mass is compressed to 640 Km, the innermost 3.24 Solar Mass is still outside its schwarzschild radius, suggesting that a photon produced anywhere between 0-10 kms (3.24 solar Mass will be within 10 km), has no bar (Birkhoff's or Newtonian) to travel away from r = 0.
Now You may say that I am questioning the veracity of Kruskal diagram, may be yes, may be no, because this diagram is not talking about any photon produced inside, this diagram is either about the collapse once the object falls below EH or of any incoming particle. I am talking about photons produced at r = 0, while the object is collapsing. Thats why I am also seeking some one else intervention, like you are also seeking.
But let's take this one step further: what about photons (or other massless particles)? Let's make one adjustment: we define the inner bound of the Schwarzschild region as also taking into account photons, and steering clear of those. This will make its radius a tad higher (the Schwarzschild region will start out a bit smaller), but nothing spectacular (we are talking about an infinitesimal distance here: instead of the inner bound being an inclusive border, it will now be exclusive).
But there's a problem: the photons are "on the edge" of this inner bound, so the "escape velocity is c". Can they just hover there?
Time to switch to Kruskal–Szekeres coordinates. Let's use this picture:
https://en.wikipedia.org/wiki/Kruskal–Szekeres_coordinates#/media/File:Kruskal_diagram_of_Schwarzschild_chart.svg
(Remember especially that light-cones in this depiction works as in special relativity.)
Any photons emitted from r < 1 will be emitted towards the center: it is impossible to find a light-cone in region II where the light-like lines of the light-cone allow a rise (or even constancy) in the value of r. In other words, only photons emitted at r = 1 can stay at r = 1. In fact, that's their only option!
Now throw a single neutron (or any tiny bit of energy) into the event horizon. This mass/energy will traverse the Schwarzschild region, and fall towards the inside object, increasing its mass. The Schwarzschild radius grows the tiniest bit, and what previously was r = 1, now becomes r = 0.99999… All photons that were at r = 1 now start falling towards the inside object. Since there is no radiation emitting matter or anything at r = 1 (only stuff falling into the object that passes by r = 1), there will no longer be any photons at r = 1.
Conclusion: Even if one has many photons trapped at r = 1, the tiniest addition of mass will cause all these photons to fall towards the inside object. Such a situation is meta-stable at best.
Color and bold by me. (pl expand the quote above)
I agree with your uncolored part in entirety. The Paddoboy's photon hovering link (quite famous once upon a time here on SF) is fine but photon comes inside as soon as even a single additional photon is accreted by BH.
But I disagree with the color portion. consider the qualitatively most simple density distribution, uniform density spherical symmetry object just inside its Schwarzschild radius. I have given an example say of 1 million solar mass. Except the outer most surface, every other inner part is outside its Schwarzschild radius (Uniform density just at its EH, apply mass / volume formula to get the radius of inner 0.1 - 99.99% mass (any fraction), you will see that fractional sphere is out of its Schwarzschild radius. Now freely apply Newtonian or Birkhoff's (in relativity) and you will see that a photon emitted just inside has no bar in moving away from center. (of course it will remain trapped inside outer EH), and of course I am just going with you, it may be swayed down with the collapsing mass.
But it does not end here, the object keeps collapsing from 3 million km. And as per my assumptions a stage comes, R(p) = 640 Km, (640 to 3 million is empty and 0 to 640 is densely packed Neutrons, a sphere of uniform density, say), here too as I have shown even when one million solar mass is compressed to 640 Km, the innermost 3.24 Solar Mass is still outside its schwarzschild radius, suggesting that a photon produced anywhere between 0-10 kms (3.24 solar Mass will be within 10 km), has no bar (Birkhoff's or Newtonian) to travel away from r = 0.
Now You may say that I am questioning the veracity of Kruskal diagram, may be yes, may be no, because this diagram is not talking about any photon produced inside, this diagram is either about the collapse once the object falls below EH or of any incoming particle. I am talking about photons produced at r = 0, while the object is collapsing. Thats why I am also seeking some one else intervention, like you are also seeking.
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