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Comment by Blikkentrekker | Hacker News Reader

I don't understand this article at all. Is it some kind of discovery that gas that exists somewhere can be attracted to a supermassive black hole, or a body with mass of any type? I don't see the relevance to that the gas was once ejected by the black hole; it's well known that mass attracts.

Also:

> Supermassive black holes at the centers of galaxies have long been known to emit enormous amounts of energy. This causes the surrounding gas to heat up and flow far away from the center. This, in turn, makes the black hole less active and lets cool gas, in theory, flow back.

This is a very strange way to word that the immense friction in the accretion disks of black holes creates immense heat and light, is it not? As far as I know, the actual energy black holes emit in the form of hawking radiation is rather very minute and undetectably low with current censors.

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I think what they mean is that matter falling into black hole emits A LOT of energy.

One of less well known facts about black holes is that they are best known method to convert mass into energy. Black hole can be used to recover up to 40% of falling mass as energy.

Also, technically, Hawking radiation is not the only way to get the energy out of black hole. You can extract energy from a rotating black hole. Normally, rotational energy contributes to the total mass of the black hole, but you can extract that energy, robbing black hole of some of its rotational energy and consequently, reducing its total mass. Essentially, it can be used to accelerate objects (this is called Penrose process).

When two black holes collide, a portion of their mass is radiated as gravitational waves. This has been verified by LIGO showing that the resulting black hole has less mass than the sum of mass of black holes before collision.

I am also pretty sure that a charged black hole could act as a fantastic battery, except there is no known mechanism that could create a significantly charged one.

Does the OT potentially confirm models of superfluid quantum space that have Bernoulli's, low pressure and vorticity, Gross-Pitaevski,?

https://news.ycombinator.com/item?id=38370118 :

> > "Gravity as a fluid dynamic phenomenon in a superfluid quantum space. Fluid quantum gravity and relativity." (2017) :

>> [...] Vorticity is interpreted as spin (a particle's internal motion). Due to non-zero, positive viscosity of the SQS, and to Bernoulli pressure, these vortices attract the surrounding quanta, pressure decreases and the consequent incoming flow of quanta lets arise a gravitational potential. This is called superfluid quantum gravity*

Also, https://news.ycombinator.com/item?id=38009426 :

> Can distorted photonic crystals help confirm or reject current theories of superfluid quantum gravity?

"Closing the feedback-feeding loop of the radio galaxy 3C 84" (2023) https://www.nature.com/articles/s41550-023-02138-y

Very basic explanation here, you will only need the visualization powers of high school physics:

Most gas that approaches a black hole does a gravitational slingshot and escapes.

This paper proves that the majority of escape trajectories eventually return to the black hole (effectively multiple attempts at getting absorbed). This has long been an assumption for running low-fidelity statistical modeling but it is now proven that the assumption is valid and that therefore the models are (mostly) valid.

In that case how is it a slingshot and a very eccentric orbit?

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