# Black hole as a gravitational spherical shell. Why not?

I think that Leonard Susskind's holography, George Chapline's "dark energy star," the Emil Mottola and Pawel Mazur's "Gravastar," the Polchinski's "firewall," and the recent ideas of nonsingular black holes clearly suggest possibility of understanding this phenomenon as a massive spherical shell with an asymptotically thin wall.

I think that whole mass of the black hole can be located on the same place of the surface that today we call events horizon.

What could prevent the collapse of this shell, is the hypothesis that gravity has a limit of intensity. This limit only happens in the event horizon.

I imagine that the intensity of gravity should not be infinite. If this is possible, then black holes have no content, because inside them there would be no gravitational field, no space, no time. A place that does not really exist. A contour region of our universe.

Can a black hole be a spherical shell?

• +1 This is a known concept and I believe it is correct, except for one flaw in your reasoning on the "limit of gravity intensity". This hypothesis is incorrect and is completely unnecessary. IMO your last 3 sentences are exactly true. Just keep in mind that the event horizon is not a spacelike "shell", but is timelike. Touching the event horizon has the same physical meaning as achieving the speed of light. Only massless particles can do it. as things fall down, their mass is reduced and becomes zero at the event horizon, so they disappear and turn into the energy of curved space (gravity). – safesphere Jun 23 '18 at 8:48
• @Countto10 The shape of the event horizon is irrelevant. It is not spherical for a rotating black hole, but this does not change the idea. – safesphere Jun 23 '18 at 8:51
• Why were people burnt alive for saying that the Earth wasn't flat? Because the establishment is always invested in the mainstream ideology. Their well being depends on it. If black holes have a singularity "inside", which is a complete physical nonsense, fancy coast mortgages get paid off and kids go to Ivy League schools. So everyone else gets brainwashed by the "singularity" propaganda. The scientific truth has no chance to compete. – safesphere Jun 30 '18 at 22:29
• Strictly speaking, it's not "hollow", because "hollow" means a finite volume that is empty. However: "There is zero volume inside the black hole in any Schwarzschild time slice of a Schwarzschild black hole spacetime" - see p. 6 here: arxiv.org/pdf/0801.1734.pdf – safesphere Jul 1 '18 at 2:19
• Yes, an expanded point with no content, exactly. During a neutron star collapse, the event horizon expands from the point in the center and pushes all matter out keeping it at the horizon. And no Hawking radiation obviously, because there is no singularity "inside". According to the equivalence principle, the Hawking radiation is (at least partially) equivalent to the Unruh radiation. However, there is no Unruh radiation: arxiv.org/abs/quant-ph/0509151 - So, per the equivalence principle, there is no reason for the Hawking radiation to exist either, even if the singularity were there. – safesphere Jul 1 '18 at 4:48

The problem with this model of the gravitational field (a problem that was first noticed by Einstein) is that something needs to keep the mass shell from collapsing in upon itself. The simplest way to try to do this is to suppose that the mass shell is really made up of many bodies in circular orbits around the center of mass. This works fine, so long as the radius of the shell is larger than the Schwarzschild radius $R_{S}=\frac{2GM}{c^{2}}$ (the radius of the event horizon); however, as the radius approaches $R_{S}$, the orbital speed of particles approaches $c$, which is impossible. (If you try to make the shell a solid, you run into a similar problem with the speed of acoustic waves that can propagate along the solid shell.)

Einstein concluded, on the basis of this kind of calculation, that black holes were not possible. However, that is not quite correct. What is not possible is for there to be a static black hole (like the mass shell model). There is no timelike Killing vector in Schwarzschild spacetime, because at the event horizon, the variable $t$ changes from timelike to spacelike. (And $r$ becomes timelike; this represents the fact that if you are falling into the black hole, a location at smaller $r$ must lie in in your future.)

• +1 because it clarified the set up for me, but this " the orbital speed of particles approaches c, which is impossible." is not impossible in the current standard model of particle physics. The elementary particles become massless for very high energies, before symmetry breaking, so at some point in the history of the universe this would not be a counter argument for the model. It would be like a photosphere with the whole table of particles . – anna v Jul 3 '18 at 3:15
• Circular (massless) photon orbits are also not stable close to the event horizon @annav – Rob Jeffries Jul 17 '18 at 6:32
• @annav - Below the surface of the sphere of photons, nothing can orbit, because on that surface the orbit must be executed at speed c. en.wikipedia.org/wiki/Photon_sphere A spherical shell can not sustain itself based on orbiting particles. – João Bosco Jul 17 '18 at 23:54
• @Buzz - From a distant observer's point of view, objects in free fall to a black hole, seem to brake near the event horizon, even considering the irresistible action of singularity at this place. This observer does not see these objects crossing the event horizon. For him, the presence of these objects certainly produces there a indestructible spherical shell. Right? – João Bosco Dec 27 '18 at 23:13

In the case of a Kerr hole, you no longer have spherical symmetry or Birchoff's theorem to assure you that a thin shell of mass $M$ will produce the same field as the black hole itself. This, combined with the fact that the shape of a Kerr Horizon is, itself, a bit complicated (if $a > \sqrt{3}/2$, the horizon doesn't even embed into 3d flat space), this proposition becomes a bit complicated to establish in pure GR.

Black-Hole formation is really an extension of Madame Noether's Conservation Law...where a disorganized mass of particles, in a state of 3 dimensional chaos, becomes subject to a quantum-mechanical process which 'homomorphically' transforms this chaotic state into a 2 dimensional state that has perfect Noether symmetry and equilibrium. This transformed state consists only of radiation confined to the surface of a Schwarzschild sphere...in other words: a Black-hole.

Nature loves transforming matter (energy) into a minimally sized package (a Schwarzschild sphere) in which energy-density and gravity have attained the maximum values that nature will allow and are confined to the surface of a Schwarzschild boundary in the form of radiation. How does nature accomplish this unique matter-to-radiation phase-change?

• This seems to be missing nonsense through abuse of terminology. – Kyle Kanos Dec 29 '18 at 21:02
• An object in free fall to a black hole, can not undergo any transformation in its way, even if it is one homomorphic type , because this is one Equivalence Principle's imposition. The rest is equivalent to freefall. A neutron star undergoes modifications in its sub atomic structure because its parts refuse to accept the gravity effects until just before collapse. – João Bosco Dec 29 '18 at 21:24
• Hello J. Bosco...thanks for your comment. The radiation model of Black-hole structure that I am proposing does not violate any of the existing laws of physics, but it does represent a contradiction to current Black-hole theories which postulate things like infinite densities (singularities). – RobertO Dec 30 '18 at 21:36
• Matter and gravity are synomonous with energy; but there's a limit to the density of energy that can be confined within a given volume of space: a Schwarzschild sphere. There's just so much matter you can squeeze into a Schwarzschild "suitcase" before it "breaks" or its contents is transformed into a more manageable form of energy (radiation) that allows the "suitcase" to get bigger. The amount of energy-density confined in a given volume of space coincides with the value of the Schwarzschild radius and corresponds to a critical value of energy-density. – RobertO Dec 30 '18 at 22:21
• A critical event in the interior of an evolving BH, representing a change-in-state from matter to radiation, is preceded by an exponential increase in the momentum of particles confined within the volume of a contracting star (or any object). As particle velocities approach the speed of light, and as distance and time between particle collisions approach zero, the energy-density of a collapsing object will reach a limit where the transformation of gravitational force can no longer be defined in terms of particle collisions. (I welcome all critical comments regarding this new BH model). – RobertO Dec 30 '18 at 22:33