First proof that "plunging regions" exist around black holes in space

https://www.ox.ac.uk/news/2024-05-17-first-proof-plunging-regions-exist-around-black-holes-space

by carbocation • 2 years ago

79 103 2 years ago

ox.ac.uk

gigatexal2• 2 years ago

Still continues to amaze me that the more they look the more they confirm Einstein. Yet we know — or strongly suspect — that at the singularity and within the BH general relativity breaks down. I hope we see a unification of GR and Quantum mechanics in my lifetime. Would be really neat

cdchn5• 2 years ago

Not to bring the all pervasive AI topic into this discussion, but I think the best hope we have for finding that unification depends on an AI superintelligence. I wonder if we've reached the limit of what a singular human mind can push.

klyrs5• 2 years ago

I wonder if we've reached the limit of what a singular human mind can push.

You people are becoming zombies. Get away from your computer and interact with the world. Humans with profound intellect are producing the content that LLMs regurgitate for you.

kitd• 2 years ago

It takes a singularity to comprehend a singularity?

af78• 2 years ago

AI or not, if a machine finds an answer so complex that no human can understand it, how useful is it?

z3phyr• 2 years ago

Please touch grass sir!

tbrownaw• 2 years ago

I wonder if we've reached the limit of what a singular human mind can push.

We passed that limit ages ago. The underlying technology used to do so is called "writing", which is what allows for things like libraries and letters / email and personal scratchpad notes.

vbezhenar• 2 years ago

Is it even scientific to claim anything about black hole insides? AFAIU it's impossible by definition for any information to escape black hole insides. Any observation or experiment is not possible. Any assumption can't be confirmed or rebuted. Basically it can't be falsified, so it's not a science according to Popper.

chungy• 2 years ago

We can hypothesize, but there is no known way to ever test it. At least not with the information getting out of the black hole.

disconcision• 2 years ago

AFAIU it's impossible by definition for any information to escape black hole insides. Any observation or experiment is not possible

this doesnt precisely follow. observation or experiment is possible from within the event horizon, although this might limit plausible venues for publication

card_zero3• 2 years ago

But we can have an explanation, which can be falsified by arguments, without needing to directly test the inside of black holes with instruments.

Now my reply to instrumentalism consists in showing that there are profound differences between "pure" theories and technological computation rules, and that instrumentalism can give a perfect description of these rules but is quite unable to account for the difference between them and the theories.

I think that's the right quote, Popper often lets me down when I want something terse and uncomplicated.

Sakos2• 2 years ago

This is such a weird statement. A lot of currently established science was only theorized during the early 20th century, long before we had the tools so they could be "proven" with real-world experiments. It was still science at the time.

rthnbgrredf5• 2 years ago

We have Hawking radiation and gravitational waves and the future potential to experiment with microscopic black holes in the lab, along with the hypothesis that Planet 9 might be a primordial black hole in our solar system, there is a wealth of opportunities to explore and learn more about black holes experimentally, without entering one physically.

thriftwy• 2 years ago

Yes, it is scientific. For example, Kruskal–Szekeres coordinates precisely describe movement inside the black hole.

https://en.m.wikipedia.org/wiki/Kruskal–Szekeres_coordinates

csomar• 2 years ago

Maybe if you can create nano-blackholes and explode them later in a controlled fashion?

cjfd• 2 years ago

It looks like they are mostly making statements about what is happening outside the Schwarzschild radius. These are testable statements.

gigatexal2• 2 years ago

Given our best theories we speculate what the inside of a black hole might be like. Of course we can’t know. But that’s how scientific things go: the cutting edge of human understanding is used to make predictions. Particular to the inside of a black hole, though, it’s impossible to test what we see or what happens when something passes the event horizon. I guess unless we wait basically an eternity capturing all the hawking radiation to rebuild what was sent in…

dotnet002• 2 years ago

From my understanding, that invokes the black hole information paradox. There should be some way in which the information of what went into a black hole is retained, a possible answer being with the Hawking radiation.

We just don't know enough about black holes to say for sure that the insides can not be studied in some manner. That's kind of why a theory of quantum gravity is so relevant, without it, the inaccessibility of the inside of a black hole remains at odds with key components of quantum physics.

Eg The current theory is that black holes release Hawking radiation, and studying that over the lifetime of the black hole might reveal information about the matter that went in. Understanding how this information is encoded could reveal things about the inside. Other possible explanations are that near the point of evaporation, when the black hole shrinks down to a size where quantum effects dominate, the information within becomes accessible, which could again allow potentially studying the inside.

legohead• 2 years ago

And the graphic on the page is the opposite of what they are describing...

SiempreViernes2• 2 years ago

No, the inner most stable orbit is just not very large which the graphics illustrate by the central black region around the black hole.

ganzuul• 2 years ago

Why is it that some experts say stuff falls into the center of a black hole while others say it slows down and never passes the event horizon? Is it just semantics?

anal_reactor• 2 years ago

The closer you are to the black hole the slower the time passes.

zelphirkalt• 2 years ago

Why is that again? Falling in does not seem to imply accellerating towards the speed of light. Accellerating surely, but speed of light? Why would it?

pests2• 2 years ago

Frame of reference. The object falling in experiences time as normal and actually falls in.

From an outside observer they never cross the event horizon, due to the time dilation mentioned by the other comment.

knodi1234• 2 years ago

From an outside observer they never cross the event horizon, due to the time dilation mentioned by the other comment.

Doesn't that imply that if we look at a black hole from a safe distance, the event horizon will appear to be a cluttered frozen motionless ring, full of all the stuff that is in the process of falling in but which from out point of view, never will?

ghighighighilo• 2 years ago

I think only the last photons at the event horizon of you never escape the event horizon. So as you're falling toward the horizon you're colour shifting as the photons move slower and slower until you cross the event horizon at which point your last reflected photons outward speed matches their inward gravity and they freeze, balanced on the edge. You actually keep falling toward the singularity but no one will ever see you after the horizon because any reflected photons can't escape the gravity well.

You won't actually see the frozen photons though, just the ones before it. Once you see them, though, the image on the horizon is gone.

ben_w4• 2 years ago

IIRC, it depends on the frame of the observer.

An outsider will see in-falling objects slow down, redshift, and never cross the horizon; but if you're falling in, this happens in finite time, you don't get to see the universe rapidly age, the black hole doesn't evaporate from Hawking radiation before you reach it.

sliken11• 2 years ago

From the external view you never enter, just get dimmer as you approach the speed of light and the time dilation keeps increasing.

From the viewpoint of the one falling in, you just fall in and cross the horizon without noticing.

Does make you wonder if time dilation gets so extreme, could another black hole wonder by, offset the gravity of the black hole, and let you escape. Even if it takes a billion years.

rthnbgrredf5• 2 years ago

Does make you wonder if time dilation gets so extreme, could another black hole wonder by, ... Even if it takes a billion years.

This could even be the most likley scenario, since ultra massive black holes eats vast amounts of smaller over the course of billion years.

pavel_lishin2• 2 years ago

Once you've crossed the horizon from your point of view, there is no escape. If another, larger black hole passes by, at best you'd be within a larger event horizon comprised of both, I think.

evo• 2 years ago

I suspect that would fall under the rule that if two black holes’ respective event horizons ever cross, they merge and initiate the eventual merger of the two respective black holes.

Filligree• 2 years ago

The time dilation does not act in that way. You will not experience the outside universe speeding up, at least not by very much; the reason for this “paradox” is primarily that photons coming off you take longer and longer to climb out, and the ones from right when you crossed the event horizon never will.

willis936• 2 years ago

PBS SpaceTime had a recent episode that helps with this apparent paradox.

Really their entire playlist on black holes (and entire catalog for that matter) is worth a watch.

https://youtu.be/Rogm_lpVZYU

x3n0ph3n3• 2 years ago

I believe there is nothing actually inside a black hole -- to us, it appears as a giant sphere, where all of the matter is at the surface, but there is no "inside." It' s like a giant shell with no interior because spacetime breaks down. All matter on the shell is at zero distance from all the other matter on the shell.

woopsn• 2 years ago

There is also a theory that as you approach the horizon you'll be incinerated by a kind of hidden firewall. This apparently contradicts GR - but on the other hand if you're allowed to fall in it seemingly contradicts QM.

SiempreViernes2• 2 years ago

Here's the paper: https://academic.oup.com/mnras/article/531/1/366/7671518

X-ray astronomers, how weird is it that they show their fits in physical space and not in instrument space?

gravescale• 2 years ago

sufficiently close to a black hole it is impossible for particles to safely follow circular orbits.

Health and safety gone mad!

Weirdly, it's hard to actually find information about this using the phrase "plunging region", as if you search for it everyone is currently regurgitating the strange Oxford press release wording of "safely". Which is an ironic turn of phrase because the result of the plunge is falling into a black hole. Though I think they probably mean that the circular orbit itself would be safe, not that the particle is falling in deliberately to avoid orbiting in some unsafe manner within a circular orbit!

But the Wikipedia article is actually pretty clear: https://en.wikipedia.org/wiki/Innermost_stable_circular_orbi.... So closer than 3 Schwarzschild radii, you can in theory have an circular orbit instantaneously, at a speed lower than light (until the photon sphere at 1.5Rs, where you have to orbit at c). If it was Newtonian rules, you could just orbit here. But because spacetime is warped inwards, anything actually in such an orbit will tip off the circular orbit and into a lower orbit, where it tips inwards and so on, into an inward spiral.

It seems a bit like one of those coin spiral games/charity boxes where the coin spirals down a curved cone-like funnel into the central hole. Even a coin injected tangentially eventually falls in, because the continously curved inward slope of the surface always makes the coin turn inwards and resists a stable orbit (even if it had no friction or air resistance).

First proof that "plunging regions" exist around black holes in space

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