Dutch astronomers prove last piece of gas feedback-feeding loop of black hole | Hacker News Reader

Dutch astronomers prove last piece of gas feedback-feeding loop of black hole

phys.org

47 pointswglb19 comments

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.

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?

It looks like the Nature paper can be viewed from the page [1] of Raffaella Morganti, one of the authors of the paper.

[1] https://raffaellamorganti.wordpress.com/

looks at the name, looks at the headline

> In 2014, I received the Honor of “Commendatore della Stella d’Italia” (Commander in the Order of the Star of Italy)

Not many Dutch people have been bestowed the honor of receiving an Italian commendation.

She might still have the Italian nationality. Citizen from the EU are allowed to work in any EU country and can keep their nationality. From the Dutch Wikipedia page (translated with Google Translate):

Morganti graduated with honors in astronomy from the University of Bologna in 1982 with a thesis on radio galaxies. In 1987 she obtained her PhD from the University of Bologna with the thesis Morphology and Physics of Radio Galaxies. From 1988 to 1989 she was a fellow at the European Southern Observatory in Garching. She then served as staff astronomer at the Istituto di Radioastronomia in Bologna from 1989 to 1999. In 1999, Morganti moved to the Netherlands and became a researcher at ASTRON in Dwingeloo. In 2005 she also became a part-time lecturer at the University of Groningen. In 2011, she was appointed professor by special appointment of Structure and Evolution of Radio Galaxies at the University of Groningen.

First words from the article (emphasis added): “Three astronomers FROM the Netherlands”

Because of that and her Italian-looking name, I suspect she’s Italian. Wikipedia thinks so, too (https://en.wikipedia.org/wiki/Raffaella_Morganti)

> Not many Dutch people have been bestowed the honor of receiving an Italian commendation.

I expect quite a few will have minor ones, as it’s customary to bestow them on ambassadors and politicians.

Reading https://en.wikipedia.org/wiki/Order_of_the_Star_of_Italy), this one isn’t minor, but still follows that pattern.

Reads very weird, also, scientists don't prove anything

Science proves some things. You can prove that something is possible by demonstrating it or with a good enough model even.

Technically not because it's induction vs deduction but it can sometimes be "close enough" for some things.

You can certainly prove that a ball falls down once on Earth. It’s more difficult but still possible to prove that all balls will fall down. I don’t think that you can prove laws of gravitation in general.

Observing a ball falling down once, even if you are 99.999% sure of what you saw, is still not a deductive process so it’s still a categorically different thing than a mathematical proof.

(The remaining 0.001%: maybe you were hallucinating and there was no ball)

maybe you were hallucinating and there was no ball

...at which point you've left the domain of science and have entered the philosophical domain of epistemology. Neither the existence of the term "mathematical proof" nor epistemic quandaries invalidate the concept of scientific proof, and what that term means within the domain of the natural sciences.

The root of every logical proof is an inductive step to assert some group of axioms or believe something. So all possible logical proofs are tainted by induction. If you believe induction makes a proof invalid, then all proofs are invalid.

The inductive and deductive reasoning separation is useful just to categorize each step and identify where your beliefs/probabilities enter the proof so you can manage them.

Sure, but I doubt any honest scientist has axioms that lets them prove anything related to a gas feedback-feeding loop, especially one they can't interact with.

If you have some data, you can prove that it is consistent with a model or that your methodology will extract useful information from noisy data assuming it fits your model of it.

Especially in physics and number-crunching tasks like these, there is enough overlap with mathematics to have plenty of opportunity for proving steps of your process correct.

Also mathematics does not have a monopoly on employing pure reason.

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