[HN Gopher] Dutch astronomers prove last piece of gas feedback-f...
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Dutch astronomers prove last piece of gas feedback-feeding loop of
black hole
Author : wglb
Score : 41 points
Date : 2023-12-01 20:29 UTC (1 days ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| Blikkentrekker wrote:
| 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.
| onetimeuse92304 wrote:
| 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.
| westurner wrote:
| 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?_
| neovialogistics wrote:
| 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.
| fjfaase wrote:
| 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/
| tremon wrote:
| _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.
| 7373737373 wrote:
| Reads very weird, also, scientists don't _prove_ anything
| kadoban wrote:
| Science proves some things. You can prove that something is
| possible by demonstrating it or with a good enough model even.
| Vecr wrote:
| Technically not because it's induction vs deduction but it
| can sometimes be "close enough" for some things.
| adrianN wrote:
| 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.
| jl6 wrote:
| 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)
| tremon wrote:
| _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 science.
| arcbyte wrote:
| 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.
| Vecr wrote:
| 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.
| chmod775 wrote:
| 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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