Not really current news, but based on recent papers, about something I find very interesting.

In the 50s, J A Wheeler proposed that Black Holes could be formed by a suitably large concentration of EM radiation, and he introduced the term Geons, for such concentrations.
Recent ( within the last couple of years ) papers make these processes extremely unlikely ( by 50 orders of magnitude ), due to pair creation effects of QED, and the ability to carry energy/momentum out of the system.

As always, this guy does an excellent job of explaining the whys and hows of this process ...

And I'm getting tired of all the non-science discussion.
( it's in the forum name people ! )

Edited Wednesday at 02:10 PM2 days by MigL

In the case of a sufficiently large black hole, the energy density is low enough for pair production to be insignificant. Whereas for an ordinary object, mass increases with R³, for a black hole, mass increases with R. Thus, very large black holes have low density and one could construct such a black hole with bricks if one had a sufficient number of them. This kills any "immovable object meets irresistible force" type arguments with regards to black holes.

5 hours ago, KJW said:

This kills any "immovable object meets irresistible force" type arguments with regards to black holes.

I guess you haven't watched the video.

QED keeps the concentration of EM radiation from ever reaching an energy density allowing creation of a BH, due to the Schwinger Effect ( pair creation in a vacuum with sufficiently strong EM field ).
It has nothing to do with conditions after BH creation.

Edited Wednesday at 08:54 PM2 days by MigL

8 hours ago, MigL said:

  13 hours ago, KJW said:

This kills any "immovable object meets irresistible force" type arguments with regards to black holes.

I guess you haven't watched the video.

QED keeps the concentration of EM radiation from ever reaching an energy density allowing creation of a BH, due to the Schwinger Effect ( pair creation in a vacuum with sufficiently strong EM field ).
It has nothing to do with conditions after BH creation.

I did watch the video. It focused on small black holes for which the energy density is so high that the Schwinger Effect would prevent their formation. But to form a very large black hole, the energy density would be low enough for the Schwinger Effect to be negligible. The point I made about constructing a black hole from bricks is that one doesn't need matter-crushing forces to produce a black hole if the total mass is large enough. I will admit that I am somewhat of a black hole skeptic. Nevertheless, I recognise that simply accumulating sufficient mass into its Schwarzschild radius will create a black hole without the need of any forces that could possibly be thwarted. The invokation of the Schwinger Effect seemed to me to be not entirely unlike the "immovable object meets irresistible force" type argument that one might use against the formation of a black hole.

However, I should remark that I fairly recently derived a result that contradicted a belief I had about black hole formation. I had believed that during the gravitational collapse of matter, the event horizon doesn't form from the centre and expand outwards, but rather forms at the surface of the matter at the instant the entire matter is inside the Schwarzschild radius. My error was due to a misapplication of Birkhoff's theorem and a failure to fully appreciate that the event horizon is due to the gravitational potential. The result I derived is that the event horizon starts to form at the centre of the matter before the surface of the matter is inside the Schwarzschild radius, and expands as the matter shrinks until it reaches the surface when the entire matter is inside the Schwarzschild radius.

Edited Thursday at 06:23 AM2 days by KJW

6 hours ago, KJW said:

I did watch the video. It focused on small black holes for which the energy density is so high that the Schwinger Effect would prevent their formation. But to form a very large black hole, the energy density would be low enough for the Schwinger Effect to be negligible.

He does address that in the video, saying that the scaling effect of surface area increases faster than energy density, so the flux actually increases.
Still, over 50 orders of magnitude is a very high bar to get over ( although not impossible ).

6 hours ago, KJW said:

I had believed that during the gravitational collapse of matter, the event horizon doesn't form from the centre and expand outwards, but rather forms at the surface of the matter at the instant the entire matter is inside the Schwarzschild radius

The center-out formation of the EH has been accepted science since J A Wheeler ( what a coincidence ) in the 50s.
I first came across that in K Thorne's book, in the 80s.

I thought Birkhoff simply said that the space-time of a spherically symmetric distribution is described by a unique Schwarzschild metric ?

20 hours ago, MigL said:

He does address that in the video, saying that the scaling effect of surface area increases faster than energy density, so the flux actually increases.
Still, over 50 orders of magnitude is a very high bar to get over ( although not impossible ).

As the size of the black hole increases, the total energy required to form the black hole increases, but because the energy density decreases, the mechanism that prevents the formation of the black holes (Schwinger Effect) is no longer significant. Therefore, with sufficient energy, even if that is the product of the total annihilation of a pair of matter and antimatter stars, black hole formation would not be prevented, at least not by the Schwinger Effect.

20 hours ago, MigL said:

The center-out formation of the EH has been accepted science since J A Wheeler ( what a coincidence ) in the 50s.
I first came across that in K Thorne's book, in the 80s.

I had not come across this in my reading. Actually, the event horizon expanding from the centre seems rather intuitive anyway. I didn't really give much thought to it until it occurred to me that before the event horizon has fully expanded to the surface, there is not enough mass inside the event horizon to form a black hole, and therefore the event horizon forms at the surface when all the matter crosses the Schwarzschild radius. However, this reasoning was based on an apparently incorrect understanding of the event horizon. Intriguingly, a corollary of an expanding event horizon is that if one encloses a black hole inside a spherical shell of mass, the black hole will expand.

20 hours ago, MigL said:

I thought Birkhoff simply said that the space-time of a spherically symmetric distribution is described by a unique Schwarzschild metric ?

Yes, and a consequence of this is the shell theorem.

Edited 22 hours ago22 hr by KJW

4 hours ago, KJW said:

Yes, and a consequence of this is the shell theorem.

ahhh !
Thanks.

On 9/24/2026 at 1:29 AM, KJW said:

The point I made about constructing a black hole from bricks is that one doesn't need matter-crushing forces to produce a black hole if the total mass is large enough.

If you constructed a structure out of bricks, how would it become a BH without matter-crushing forces? The structure would always have a radius larger than the Schwarzschild radius.

Alternately, such bricks can’t exist whose structural integrity remains intact as the size gets arbitrarily large

17 hours ago, KJW said:

Therefore, with sufficient energy, even if that is the product of the total annihilation of a pair of matter and antimatter stars, black hole formation would not be prevented, at least not by the Schwinger Effect.

Sure. A large enough system of water, with a density of 1kg/l will gravitationally collapse to form a BH.
The problem that makes it extremely unlikely ( no one ever mentioned impossible ), is the amount of water needed.
You would need about 10³¹ kg, or over 20 solar masses.

So ... extremely unlikely.

3 hours ago, swansont said:

  On 9/24/2026 at 3:29 PM, KJW said:

The point I made about constructing a black hole from bricks is that one doesn't need matter-crushing forces to produce a black hole if the total mass is large enough.

If you constructed a structure out of bricks, how would it become a BH without matter-crushing forces? The structure would always have a radius larger than the Schwarzschild radius.

No, the Schwarzschild radius of a black hole is proportional to the mass, and the mass of a ball of uniform density is proportional to the cube of the radius. Therefore:

[math]r_s = \dfrac{2 G M}{c^2}[/math]

[math]M = \dfrac{4 \pi \rho r^3}{3}[/math]

[math]r_s = \dfrac{8 \pi G \rho r^3}{3 c^2}[/math]

[math]r_s \geqslant r \implies \dfrac{8 \pi G \rho r^3}{3 c^2} \geqslant r[/math]

[math]\implies r \geqslant \sqrt{\dfrac{3 c^2}{8 \pi G \rho}}[/math]

That is, even for a material of low density, if the ball of material has a large enough radius, the Schwarzschild radius of the ball will exceed that radius.

3 hours ago, swansont said:

Alternately, such bricks can’t exist whose structural integrity remains intact as the size gets arbitrarily large

Whether or not the ball of bricks can support its own weight under its own gravity is irrelevant to the point I'm making. Even if the ball of bricks can support its own weight, the mere size of the ball if large enough is sufficient to produce a black hole. That is, it is not necessary for the ball of bricks to collapse under its own weight to produce a black hole.

Edited 3 hours ago3 hr by KJW

On 9/23/2026 at 4:09 PM, MigL said:

And I'm getting tired of all the non-science discussion.

I feel the same way (which is why I don’t post here so often anymore) - too many threads that have nothing to do with science.