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

ox.ac.uk

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

#81

Post by cdchn »

redundantly wrote: post #8
klyrs wrote: post #4

Earlier quoted context omitted.

> 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.

I read their comment more as a nod to The Last Question than speaking about the recent "AI" in the news. https://archive.org/details/Science_Fiction_Quarterly_New_Se... https://en.wikipedia.org/wiki/The_Last_Question

Yes, it was more along the lines of The Last Question, wasn't even thinking about LLM.

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

#82

Post by cdchn »

af78 wrote: post #19
cdchn wrote: post #3

Earlier quoted context omitted.

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.

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

Abstractions are a thing. We use devices all the time that we don't understand entirely the workings of.

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

#83

Post by knodi123 »

db48x wrote: post #59
knodi123 wrote: post #31

Earlier quoted context omitted.

Uh... But how do you get there? My understanding as a lay-person is that you can't get past the event horizon without getting spaghettified, and cooked by high-energy blue-shifted radiation.

“Spaghettification” only happens to large enough objects near small enough gravitational sources. If the Moon got too close to the Earth, closer than the Roche Limit, then it would break up into a ring of debris. But a communications satellite can exist at that same distance with no ill effects. The same is true for black holes. A rocket or a human diving into a stellar mass non–spinning black hole would be “spaghett…

> you could build an actively–stabilized structure around the black hole to create a livable environment of truly insane proportions with Earth–normal gravity

Which was also a rocketship into the future, moving you super fast towards the heat death of the universe?

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

#84

Post by knodi123 »

vikingerik wrote: post #58
knodi123 wrote: post #31

Earlier quoted context omitted.

Uh... But how do you get there? My understanding as a lay-person is that you can't get past the event horizon without getting spaghettified, and cooked by high-energy blue-shifted radiation.

Most lay-person discussion of black holes just ignores the spaghettification and radiation problems. Those don't really have anything to do with space-time or information propagation or cosmology or such, those are just limitations of material strength and biology. The discussion is more like, if we had infinitely resilient materials or biology, what could they observe and experience.

> what could they observe and experience

Observe? Nothing, once you're inside the event horizon, right? The event horizon isn't a solid wall, it's just the point at which light can only move further inward, never outward. So even inside the event horizon, we still can't observe anything further in.

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

#85

Post by lambdaxyzw »

idiotsecant wrote: post #73
BurningFrog wrote: post #69

Earlier quoted context omitted.

You can orbit a black hole like any other gravity source, without spending fuel. I don't know how near the event horizon a safe orbit can be?

That's kind of the definition of the event horizon. You cannot be 'safe' once you're inside. All paths lead to the event horizon. No matter which direction you point, you're pointed at it.

I am not too knowledgeable about black hole physics, but it was my understanding that there's nothing locally interesting about event horizon: it's just the point of no return that doesn't change much for the local observer. Your definition of the event horizon make it sound more locally important.

In fact, I know that as a local observer falling into a black hole you can still see some of the outside world after falling into the event horizon (by looking "behind you"), you just can't send anything back. This also seem to contradict the statement that all paths point inside (or I may misunderstanding something).

Edit again: I did some research and it looks like that while parent's comment may be true for simplified model of a black hole, it is conjured to be possible for rotating black holes where you can stay inside. Also Google "penrose diagram kerr black hole" for some weird physic if you want to follow this rabbit hole. Keep in mind that I'm not a physicist and this is my understanding after 40 minutes of watching YouTube and Wikipedia.

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

#86

Post by db48x »

knodi123 wrote: post #83
db48x wrote: post #59

Earlier quoted context omitted.

“Spaghettification” only happens to large enough objects near small enough gravitational sources. If the Moon got too close to the Earth, closer than the Roche Limit, then it would break up into a ring of debris. But a communications satellite can exist at that same distance with no ill effects. The same is true for black holes. A rocket or a human diving into a stellar mass non–spinning black hole would be “spaghett…

> you could build an actively–stabilized structure around the black hole to create a livable environment of truly insane proportions with Earth–normal gravity Which was also a rocketship into the future, moving you super fast towards the heat death of the universe?

Not exactly. Time does run more slowly near a strong gravitational source, and if you are near the event horizon of a stellar–mass black hole this effect can be extreme. However, the larger the black hole is, the flatter the space around it. Furthermore, “near” is relative. A Birch world would be built around a black hole which is approximately a light–year in diameter. The structure would be “near” the black hole’s event horizon in relative terms but in absolute terms it would still be pretty far away, perhaps a quarter of a light year. Expect a time dilation of just 2:1, meaning that for every year on the Birch world two years pass for the rest of the universe.

It might seem like this costs you a lot, since it halves the amount of time you can live near your black hole. However, the lifetime of that black hole will be somewhere between 10¹⁰⁰ and 10¹⁰⁶ years, which is pretty insane even if you only get to use half of them. Furthermore, this is many orders of magnitude longer than the lifetime of a galaxy, so your civilization could potentially outlive everything else in the universe. Large stars burn out the quickest, but with black holes it is the other way around: small black holes evaporate the soonest. You might think that storing hydrogen in brown dwarf planets for use in fusion reactors would power a civilization for a long time, but fusion reactors are surprisingly inefficient. A civilization built around a rotating supermassive black hole can take advantage of the Penrose process to extract more usable energy from the same mass than the fusion reactors would.

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

#87

Post by fmobus »

golem14 wrote: post #72
sliken wrote: post #21

Earlier quoted context omitted.

No need to perish, current theories explain that the innermost region of a spinning black hole (all real world black holes spin) has a low gravity region where arbitrary navigation is possible. You can't escape, but you also don't have a death date with the singularity.

I always wondered if you can orbit inside the event horizon of a large black hole and wait until its hawking radiation shrinks the event horizon so that you find yourself outside. You would have to wait a long time I guess.

Won't this "long time" be only for the outside observer? Won't the person orbitting experience much less time and actually could get to watch the black hole evaporate?

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

#88

Post by gravescale »

> 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).

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

#89

Post by klyrs »

cdchn wrote: post #79
klyrs wrote: post #4

Earlier quoted context omitted.

> 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.

Thats the distinction I think between an LLM and a real AGI. One is a stochastic parrot, the other can come up with new ideas.

The distinction I focus on is that one exists, while the other remains a futuristic pipedream.

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

#90

Post by sliken »

evo wrote: post #51
sliken wrote: post #22

Earlier quoted context omitted.

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.

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.

I've seen this vaguely referenced, but when I dig in I don't find support for it.

It's far from obvious that just because the event horizons (which is just a mathematical concept and a 3D area of space) should control the trajectory of the singularity.

With two identical blackholes, with a event horizon of radius R, why should a singularity 2R away be unable to escape?

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