Black holes might be defects in spacetime

[helicon]

For your perusal...

https://phys.org/news/2023-05-black-hol ... etime.html

[Juno16]

For your perusal...

https://phys.org/news/2023-05-black-hol ... etime.html

Whew!
Thanks Michael!

[helicon]

For your perusal...

https://phys.org/news/2023-05-black-hol ... etime.html

Whew!
Thanks Michael!

Yeah Jim it was an interesting article I thought.

[messier 111]

thx .

[Michael131313]

Thanks for the post. Interesting, may be possible but "incredibly hypothetical objects". If it looks like a duck.......

[Gfamily]

The article says "...theory predicts that their centers are singularities, which are points of infinite density. Since we know that infinite densities cannot actually happen in the universe..." - which raises two questions
1 - do we actually 'know' that, as such, or is it that we don't know how to handle the situation?
more fundamentally though,
2 - as far as I have been able to determine, it is not possible to state the interior volume of a Black Hole. Yes, from the outside, it's possible to calculate the the volume of space within the Event Horizon as determined by a co-moving observer, but once you have passed beyond the EH, the spacetime metric changes, and all distance and volume measurements become indeterminate because any matter is going to be moving on its own geodesic, and will have its own timeline - which means that them 'reaching a point of infinite density' may not apply.

[Gmetric]

1 - do we actually 'know' that, as such, or is it that we don't know how to handle the situation?

Hey Gfam

Since you haven't had a reply to your questions as of yet, and I have a little time at the moment, I'll take a quick stab at them for you.

1 - Einstein's theory 'predicts' singularities, but it is only that, a prediction. In reality, we have no idea what happens beyond the event horizon of a black hole, and you are right that singularities don't exist in nature. Thus, whenever theories predict infinities, it is usually the case that they are lacking in the complexity required to handle the given situation. Once a quantum theory of gravity has been worked out, it is likely that the infinities, along with their pesky singularities, will disappear. Besides, there are current theories that get rid of singularities within the realm of Einstein but have their own inherent problems. TBH, we aren't even 100% sure that neutron degeneracy is the final stage of a star prior to a black hole. It could be that there is some form of quark degeneracy along with repulsive electromagnetic forces. Highly hypothetical and currently untestable. Alas, we still have a long way to go.

2 - as far as I have been able to determine, it is not possible to state the interior volume of a Black Hole.

Most black holes are characterised by three parameters mass, spin and charge. Volume is tricky, but it is possible to calculate the densities of black holes. There is a correlation between density and the radius of the event horizon which is connected to the mass of the black hole. So smaller black holes have higher densities, and larger black holes are less dense. Hence the tidal forces of a smaller black hole will spaghettify you. The problem here is that densities also depend on volume and volume and density depend on the position (coordinate) so beyond the event horizon different observers might measure different values. Given the correlation between density distribution, space curvature, and our current understanding of Einstein, we get infinities. However, for the Schwarzschild radius observer (at the EH), it's easy enough to work out apparent densities based on simple physics with the caveat being that the volume used for the calculation is just the volume within a sphere of the Schwarzschild radius size as you stated. Beyond that, who knows?