Could our universe be a cosmological scale black hole?

[FindailsCrispyPancakes]

1) THAT POINT IN THE GAME WHEN THERE IS NO CHOICE BUT TO SACRIFICE YOUR PRAWNS:

Having just spent the last week contending with food poisoning (nobody will ever be allowed to cook prawns for me again) it is a pleasure to be back at the computer keyboard and capable of concentrating. I can safely say that laying around with not a lot else to do but avoiding thinking about the horror show in your stomach is bad for the disposition.

Maybe it was because I was in such a cheerful mood that I found myself thinking about black holes an awful lot.

More specifically, thinking about the idea that as there is no upper bound on the size/mass of a black hole, the universe we experience may itself be the inside of a black hole... well, it certainly beat thinking about how suddenly I can NEVER contemplate eating prawns again, or wondering if my digestive system was some kind of singularity now.

So, what type of black hole could our universe be? How big would this black hole be?

By the time I felt well enough to sit at the computer and catch up with my missed week (my second try, the failed attempt from the previous day consisted of me giving up after repeatedly typing replies of varying coherence to emails/messages and somehow managing to close too many of them without remembering to hit send) I had decided on a starting point:

- Images of the cosmic microwave background (CMB) do not show the spirals/elongations that would be consistent with a rotating universe, so a rotating black hole would be an unlikely candidate.

- If that is the case then the challenge would now be reduced to working out what a conveniently simple equation said about something with an escape velocity of c (the speed of light in a vacuum). It proved to be just about possible with the few neurons I still have left that remember the maths (or math if you prefer) they tried to drum into me as a teenager.

2) THE DULL BIT YOU SHOULD SKIP IF YOU HATE THIS SORT OF THING:

It only takes three pieces of information to calculate an escape velocity (V). One of them is the strength of the force of gravity. Luckily (just like Maxwell and c) Newton worked out the value of G centuries ago, so it is a pleasure to just look the number up and avoid all that dreary calculus.

The other two things are the mass M and radius r of the object whose gravitational pull any escapee would be fighting against.

By setting the velocity to c and putting a value on M, the size of the object can be obtained by just moving a few letters around an equals sign. The good news is there is no need to go complicating matters by plugging any actual numbers into the equation until right at the end.

So, the equation for calculating escape velocity,



can simply be rewritten as



where c is the velocity of light in a vacuum (and the velocity you would have to exceed to escape a black hole), M is the mass of our black hole universe, G is the Newtonian gravitational constant and r represents the radius of our black hole universe.

Before going any further, life is easier without that square root sign. Squaring both sides of the equation gives:



Moving things around the equals sign then gives:





If you have followed this so far then you will be delighted to know that if you make a tiny notational change and replace r with rs



then you just wrote down and understood the equation for calculating the radius of a Schwarzschild (non-rotating) black hole. Sorry for sharing that, but I thought it may be the sort of thing some of the people here might get a kick from too.

3) RESULTS:

So, with the exciting bit over, the only thing that remains is programming your spreadsheet to plug some numbers back into the equation. Here is what I got back:

Scenario 1: (Implausible)

In order to be consistent with the current estimate of 9.3x10^10 light years for the diameter of the observable universe, a Schwarzschild black hole would have a mass of 2.965 x10^53 kg and a density of 8.29 x10^-25 grams per cubic centimetre. This is greater than the critical density of the universe (approximately 1 x10^-29 grams per cubic centimetre) and thus describes a contracting universe.

This could also be interpreted as an indication that our observable universe is only a small part of a much larger universe. We just cannot see the bits that are moving away from us faster than light speed.

Scenario 2: (Implausible)

Current total mass/energy estimates for the observable universe (matter + dark matter + dark energy) scale to a Schwarzschild black hole with a mass of 3.06 x10^54 kg, a diameter of 9.61 x10^14 light years and a density of 7.78 x10^-27 grams per cubic centimetre. This exceeds the critical density of the universe (~ 1 x10^-29 grams per cubic centimetre) and thus describes a contracting universe.

This should not be taken as a statement to the effect that current total mass/energy estimates for the universe are wrong. What the statement implies is that if the mass/energy conditions measured in our observable universe were uniform across the interior of a (by necessity far larger) Schwarzschild black hole, we would observe a collapsing universe as opposed to an expanding one.

Scenario 3: (Plausible?)

A Schwarzschild black hole with a mass of 8.58 x10^55 kg and diameter of 2.69 x10^16 light years would be consistent with the density of our universe, which is currently measured at 9.9 x10^-30 grams per cubic centimetre.

This is consistent with an expanding universe as it is lower than the critical density of our universe (~ 1 x10^-29 grams per cubic centimetre).

By setting the density of a Schwarzschild black hole model to the observed value of matter density, this calculation (unlike the two previous calculations) is not subject to the restrictions imposed by estimates of the size/mass of the observable universe.

If this is what our universe is like then we live in a patch of above average mass/energy density inside a Schwarzschild black hole approximately three million times the size of the part we can actually observe.

If it is a single object on a superhorizon scale then it raises so many questions (What the hell does Hawking radiation emitted from a universe entail? Do things like entangled but causally disconnected patches of spacetime reduce the universal principle that simultaneity is strictly a localised phenomenon to a strictly localised principle? Is this the EPR paradox rearing that ugly wormhole of a head yet again? Can I finally try eating meat again today?) that it is making my brain hurt, so this is where I check out.

I still have no idea if we live in a black hole or not, but I hope you have at least been entertained by my at least entertaining the idea.

[Skyweir]

Fascinating stuff FCPs .. I was definitely entertained but alas the computational aspects of your different propositions are way beyond my ability to understand and comment... I am however greatly intrigued by the general proposition that our universe is a black hole.

A few questions of the universe that we inhabit were a black hole .. wouldnt radiation mean that there would be no life or existence as we know it? Also balckhole gravity as you say is so powerful that objects that fall into them are torn apart. Yet this planet is an object intact, with objects within it intact.

I am sure my questions are likely over simplistic as I dont possess a scientific brain but Id recommend introducing meat slowly and sticking with eggs, rice, steamed fish, maybe some lightly stewed chicken before getting stuck into a big meaty steak

[FindailsCrispyPancakes]

Hi Sky. The questions aren't over simplistic, they're exactly the same questions everyone has. It's just that black holes are really weird!

First thing to remember is the larger the black hole, the lower its density and temperature willl be.

We normally think of black holes as being roughly planet or star sized. These would be very hot, dense black holes and their gravity/radiation would kill you pretty quickly after you crossed the event horizon, if not before.

Event horizons are not objects that have a real physical existence. An event horizon is just a location in spacetime that once you cross it, you're on a journey to a singularity.

Now consider falling into a non-rotating black hole that's hundreds of trillions of light years in diameter, with a density and temperature like the universe we inhabit.

As you crossed the event horizon you would be trillions of light years away from the singularity. The spacetime wouldn't look any different to the spacetime you observed the moment before you crossed the event horizon.

Remember that our universe is almost certainly far larger than the volume we can see. As it is an expanding universe most of it is moving away from us faster than light speed, so we will never be able to observe it.

So, if you fell into a black hole that big you could fall toward the singularity at the speed of light for hundreds of billions of years without ever being able to make an observation that would enable you to become aware of the existence of the singularity!

It would all look like the perfectly ordinary spacetime of a universe with an escape velocity of light speed to you, in other words - just like what we see in our universe.

There's a very simple reason for this. Until you hit the singularity, you're still in perfectly normal spacetime. As you appraoch the singularity you might find rather hotter, denser, weirder and more lethal than you'd prefer but it is still perfectly normal spacetime.

This leads me to your second question. The difference between the universe sized black hole we're picturing here and every other black hole humans have described is subtle, but of massive importance.

In the case of our universe sized black hole, our observations would be made from the inside of the black hole.

All of our other descriptions of black holes are made from the outside, because it's impossible to observe what's going on inside them.

While it may all look like perfectly ordinary spacetime to you when crossing the event horizon, an observer from the outside would just see you slowly getting smeared across the the event horizon.

It's impossible to make any statements about the mass/energy distribution inside a black hole you're viewing from the outside (except for its gravitational energy). When a mass is given for a black hole described from the outside, it's really describing the mass/energy content of the black hole expressed as solely as mass by means of the famously one century old E=mc squared equation.

The Schwarzschild equation may be about a century old, but trust me, it's really a three centuries plus old Newtonian equation.

If you fell into a really large diffuse black hole of density and temperature the same as in our universe, the mass/energy distribution would resemble that of our universe. The same would apply for radiation.

(I did a chicken breast last night and a bacon sandwich today by the way. I could probably smoke you a kipper without becoming unwell now!)

I'm going to start a second thread on this in a few days time because your questions made me realise there's something else I should have written about, but it would probably have been too much to put in a single post.

Simple questions are normally the best ones because that seems to be how nature works on small and large scales!

[Skyweir]

Wow superb explanation that was very easy to follow.. thank you for that .. AND your patience. Though you may live to regret the encouragement lol

From your explanation your proposition seems more credible. Of course the larger the black hole, the lower the gravitational forces and presumably radiation et al considerations.

And as seems to be widely accepted that objects crossing the event horizons of smaller denser wormholes are torn asunder .. as you say theres no way to observe what is IN a wormhole .. who knows what happens to that matter AFTER its been torn apart.

Maybe the very same thing that happens to all matter .. it merges with other gasses, dust etc and combines into other matter, objects etc. And if that IS the case .. could planetary objects form within it .. why not?

Would continually collision and bumping of objects within the black hole give rise to a universe within? And why not life?

One issue maybe, is that light cannot escape a black hole and thats possibly fine .. but may not mean no can or does light exists within a black hole, no?

And given that gasses and dust are part of a black hole .. would that be sufficient to create gas giants within a black hole .. AND gas planets like Jupiter etc and suns and stars?

[Skyweir]

Oh glad to hear you are making a full recovery .. a nice kipper with fresh bread or toast and lashings of butter, and a nice pot of black tea. When you can handle that .. you are indeed ready for upping the ante.

[Vraith]

I might come back and deal with this more deeply. Cuz I ran across a similar [sorta similar, you have some twists] thought, and thought to myself "I could write book on that...." and rapidly realized what I'd need to know to do it would take more lifetimes than I have to do it well and stay quasi-realistic even in fictional terms.

Later I thought I could do it as a super-metaphoriconcrete poem...but that would be beyond my abilities, [and remain mostly unread, cuz people fucking hate poetry for the most part, and don't think it talks about anything real---just "feelings" and shit, which of course they're totally deluded about]] too---
BUT, I do, related to that, whenever I come across interesting odd history write a few lines per century condensed just for fun, never to be seen by anyone...

And also a never to be written/completed novel that is a trio of witnesses [with no power to affect anything] watching/arguing about all of human history...in order, beginning to end, so all of them being badly and funnily [[darkly, absurdly, tearfully funny often]] wrong all the time.

What your missing is this:
IF we are inside a black hole like that...we CAN't be anywhere outside the point where the laws of physics break...that would be totally noticeable.
So we must be INSIDE that...which means all our laws are TRUE...but ONLY where we are RIGHT NOW,

It seems you are right on target that far...and the next implication you started on...we can't see anything at all in any direction where other laws apply...BUT...in the fullness of time [[though not our observable time]] they were different BEFORE, will be different AFTER. But our observable time, however long to us, is really not long at all. And no matter how far things seem they must be away, they are right next door.
WE will never see it...BUT an outside observer could theoretically see it happening. [[if they had enough time and good enough instruments, they could tell the whole story...eventually.]]

Another option, pieced together with idea-bits and pieces raided from real science that's starting to happen and from various SF over the years:
Once we UNDERSTAND basic physics, we stop being infants cuz understanding ain't shit.
Any fucktard adult, and most ignorant by age/exposure peeps can see/understand that red plus yellow is orange and all the other colors...but PAINTING is something else...DOING is the real shit. Once we understand physical laws completely, we start CHANGING them to suit our needs.

So we build a place by changing the laws narrowly "where we are" right now, so that when the universal hole EVENTUALLY evaporates [[ all black holes disperse, ask Hawking and others]], we come out of our "bomb shelter" into a bigger/real universe. One we make and remake to our needs and desires.

[Skyweir]

mmm.. interesting .. ok so all black holes eventually disperse. That in and of itself does not imply our current narrow view existence is not contained within a black hole does it? Though our universe is expanding presumably to the point of dispersal.

Maybe thats how things resolve naturally .. universal pockets contract .. matter collides and falls into higher density pockets .. within the pockets expansion occurs as more matter falls into denser pockets. Within matter collides with other matter .. a universe within ... a universe within a black hole is born

Its highly likely Im not following your logic train if so feel free to dismiss my train of thought

In reality isnt understanding the best we got? Given the scope, size and scale of the sorts of questions universes, black holes etc are?

We can see-observe bits of universes and cosmos .. what we understand or what we try to understand anyway .. but its less likely that humans will be .. perhaps some time in the very distant future they may be .. able to manipulate-wield the laws of physics to the extent of manipulating or organising a planets various stages of genesis, no?

So for the most part we can only try to understand what we can observe .. and hypothesise what we cannot, no?

I think there IS value in doing so .. not speaking personally of course .. I mean for science to do so.

But you say that we cant exist beyond or outside the laws of physics yet you also note that we-humans write such laws to suit or meet our current level of need and understanding. So maybe the laws of physics are more than we currently appreciate.

I also agree that we must be inside the black hole per your explanation .. and beyond that observation itself .. could there not also be smaller black holes within the one posited that hosts this universe?

Its all fascinating stuff .. do continue. And V why not post your poetry .. and or your story .. Id wager it would undoubtedly be a brilliant read. And no poetry is not a disdained medium but it is very often a very personal medium.

[Vraith]

mmm.. interesting .. ok so all black holes eventually disperse.

Maybe thats how things resolve naturally .. universal pockets contract .. matter collides and falls into higher density pockets


In reality isnt understanding the best we got?

But you say that we cant exist beyond or outside the laws of physics yet you also note that we-humans write such laws to suit or meet our current level of need and understanding.

And V why not post your poetry .. and or your story

On the first, yep they do. [so the best descriptions we have say, anyway] I think right now the vast majority are inside galaxies and such, so still collect faster than evaporate. [maybe a few are alone in deep space, far from stuff to grow from, I don't know] BUT once they're isolated, they evaporate. Of course I think the evaporation rate is such that it will take millions of times longer than the current age of the universe for even the smaller ones to be gone...[[think I recall that correctly.]]

On the second, that's kinda what at least one theory says. Our universe is a pocket that quantum rules/fluctuation caused to stop inflating locally, while ongoing hyperinflation continues elsewhere, and other "places" fluctuate, too...other random slow/condense spots, making other universes totally separate and unreachable from ours.

On the third and fourth jammed together...it's MOSTLY what we have now.
BUT...your house is supplied with electricity by understanding how it works, then putting it in physical constraints we built to use it. That doesn't involve changing the law, though...just the environment we put it in. There are other options. One SF novel I read [I think more than one used the same trick, actually], extreme speeds [though not FTL] are reached by creating a spot in front of the ship that ACTS LIKE it has huge mass...thereby causing the ship to continually fall into that spot due to gravity..but the spot is always a set distance in front, so the ship keeps accelerating via "falling" into the spot.

Another book...which I keep meaning to find, but I don't know what it's called...so long ago, now lost or maybe I borrowed it??...I remember liking and disliking it but not what it was about, EXCEPT most of our solar system was connected by a web of tubes that were woven??? I think???...anyway the stuff was strong enough and light enough and all because they figured out how to slightly extend the range of the one of the nuclear forces, so atoms in it were vastly more strongly bound than normal bonds, so that the stuff was literally monofilament chains [or sheets/panels?? I really can't recall clearly] of single atoms and practically unbreakable.

That may seem impossible...but physical laws have physical natures, so why CAN't we, in theory, discover a physical way to manipulate them?
AND IIRC, someone actually did it for a very short moment..."tricked" an electron into acting like another particle, so it affected things as if it had a much higher mass than it actually does.

And it's true I think we won't be/can't be us without the laws that govern/evolved us...but I'm not talking about changing all the laws everywhere permanently. I'm talking about using them for various things...like making a car [or spaceship] out of paper...or simple plastic or whatever...that is easy/cheap/abundant...but manipulating it so the material is light as a newspaper or water bottle, but stronger than any metal.
Or a sort of reverse-warp drive [which supposedly works by reshaping the space around the ship...the ship isn't moving faster than light THROUGH space, it's "shortening" the space/distance in relation to normal/unaltered space...I think that's how they "explain" it] My twist, the ship actually remains totally stationary...it reverts the space immediately around it to hyper-inflation type space, and carries the ship along with it.

Last, I don't post those, cuz they're not really a things. It's just huge random collections of raw, unconnected, jottings, snippets, notes, beginnings. [[the better ones of which will probably be worked on and worked into OTHER things I actually mean to finish and publish.

[Zarathustra]

- Images of the cosmic microwave background (CMB) do not show the spirals/elongations that would be consistent with a rotating universe, so a rotating black hole would be an unlikely candidate.

Don't all stars and black holes rotate? A non-rotating black hole seems highly unlikely.

How can we test that our universe lives in a black hole?

The last question can potentially be investigated: since all stars and thus black holes rotate, our universe would have inherited the parent black hole's axis of rotation as a "preferred direction." There is some recently reported evidence from surveys of over 15,000 galaxies that in one hemisphere of the universe more spiral galaxies are "left-handed", or rotating clockwise, while in the other hemisphere more are "right-handed", or rotating counterclockwise. In any case, I believe that including torsion in geometry of spacetime is a right step towards a successful theory of cosmology.

link

[FindailsCrispyPancakes]

I'm going to start a second thread on this in a few days time because your questions made me realise there's something else I should have written about, but it would probably have been too much to put in a single post.

Simple questions are normally the best ones because that seems to be how nature works on small and large scales!

Back at the keyboard and fully now returned to mode normal: maximal carnivorous activity...

I am now well enough to get back to work and catch up with a fortnight of things I haven't been able to do, so free time for posting is going to be a bit thin on the ground for a while.

I will start that other thread up as soon as I get enough downtime to think and write something that goes into a bit more detail about singularities, but in the meantime here is the bit I should have put in my original post.

INSIDE AND OUTSIDE:

I oversimplified a bit when I said the difference between comparing a black hole universe to the back holes we observe within our universe boils down to our observations of our (possible) black hole universe taking place from within the black hole, as opposed to our observations of black holes within our universe which take place outside the black hole in question (phew, what a horrible sentence).

Simply, the black holes we observe in nature are not isolated objects. They interact with other objects inside our universe, therefore they rotate and do not possess perfectly spherical gravitational fields.

This would not be the case if the entire universe were a black hole. It would be an isolated object with no exterior objects to interact with.

This is where Schwarzschild black holes come into play. If you want to describe an isolated object, such an object would possess a static, spherical gravitational field as any spherically symmetric solution of Einstein's vacuum field equations would be static by definition.

Another interesting property of a Schwarzschild black hole would be that from the interior, at large scales it would possess such small spatial curvature that it would be virtually indistinguishable from flat space. This is true of the universe we observe.

The simplest solution of the vacuum field equations is the Schwarzschild solution. The Schwarzschild metric describes the exterior gravitational field of an isolated black hole.

For the purposes of this little thought experiment, I decided to stick with simple Schwarzschild for a nice toy model, solely to see if it was possible to test the idea of a black hole universe and see if it withstood basic scrutiny.

I'm not sure I believe our universe is a Schwarzschild black hole, as it seems to have nonzero cosmological constant/vacuum energy/dark energy/call it what you will.

I'm still perfectly prepared to accept it is plausible our universe is a non-rotating, electrically neutral isolated object.

I'll cheerfully admit that I don't know if anybody has found a solution to the Einstein equations that describes an electrically neutral non-rotating black hole with nonzero cosmological constant yet. That's something I just won't have the free time to delve into for a while.

Having said all that, the value of the cosmological constant in our universe is very close to zero and the Schwarzschild model does share a lot of features with our observations. If I had to hazard a guess, whatever the correct model turns out to be I would expect it to be a very close analogue of a Schwarzchild black hole.

If anybody fancies delving deeper into this, the Reissner - Nordstrom metric describes charged non-rotating black holes and Birkhoff's theorem is the best place to start looking.

[FindailsCrispyPancakes]

Wow superb explanation that was very easy to follow.. thank you for that .. AND your patience. Though you may live to regret the encouragement lol

Lol, Never! Glad to hear it helped. I realise now I couldn't have picked a more difficult subject to think/write about if I'd have tried.

From your explanation your proposition seems more credible. Of course the larger the black hole, the lower the gravitational forces and presumably radiation et al considerations.

And as seems to be widely accepted that objects crossing the event horizons of smaller denser wormholes are torn asunder .. as you say theres no way to observe what is IN a wormhole .. who knows what happens to that matter AFTER its been torn apart.

Maybe the very same thing that happens to all matter .. it merges with other gasses, dust etc and combines into other matter, objects etc. And if that IS the case .. could planetary objects form within it .. why not?

Would continually collision and bumping of objects within the black hole give rise to a universe within? And why not life?

One issue maybe, is that light cannot escape a black hole and thats possibly fine .. but may not mean no can or does light exists within a black hole, no?

And given that gasses and dust are part of a black hole .. would that be sufficient to create gas giants within a black hole .. AND gas planets like Jupiter etc and suns and stars?

The difficult thing about discussing black holes is that even terms like 'inside' and 'outside' of the black hole are misleading. What we're really describing is which side of an event horizon we're on.

In the case of a universe sized black hole, there would be no 'outside' to support our existence. All information/energy/matter in an object like that would be contained at or within the horizon.

As we can't observe what goes on behind the horizon of the black holes in our universe, we measure their gravitational field. This allows us to quantify their mass/energy, temperature, charge, spin and average density. Beyond that, it's impossible to measure the distribution of light/matter/energy behind the horizon.

Given that, the speed of light still applies behind the horizon. Massless quanta (photons/gluons/gravitons) will still travel at the speed of light. All of the regular laws of physics still apply right up until the moment you hit the singularity.

If that's the case then there's no reason why structure formation would not be possible inside a black hole of sufficient size.

In the case of an isolated universe size black hole, 'outside' isn't a concept that can be applied. So talking about falling into a universe sized black hole from outside its horizon is a wonderful way of explaining some of its properties, but it wouldn't really be something anyone could actually do.

I'd just settle for saying there's nothing unique about the spacetime within a black hole that makes it any different to the spacetime outside, except for the singularity.

Obviously, the closer you get to the singularity the nastier it gets! I'll be getting busy on a post about singularities over the next couple of days, if life allows.

Oh glad to hear you are making a full recovery .. a nice kipper with fresh bread or toast and lashings of butter, and a nice pot of black tea. When you can handle that .. you are indeed ready for upping the ante.

Absolutely! "It all sounds wonderfully healthy!" he said (with only the briefest flicker of guilt over his recently consumed egg and bacon club sandwich crossing his face) as he supped at his pint of diet coke and lit up his evening joint.

[FindailsCrispyPancakes]

And another thing...

Assuming there's no 'outside' for our black hole universe to evaporate away into, where does the Hawking radiation go?

If it has no choice but to stay inside the closed system of the universe, could it be the energy contained within the vacuum of empty space that we refer to as dark energy?

[Skyweir]

Psssst FunCakes Im not sure Id hang my hat on the health or nutritional benefits of smoked kippers and lashings of butter

Glad to hear your fully carnivorous again

On your on topic points ... I look forward to mulling them over with a nice glass of red later this evening ..and returning with some well intentioned but arguably misplaced questions and-or comments

[Skyweir]

And I read the article that Z linked .. it is indeed a fabulous read and totally on point.

[Vraith]

First, kudos to Z...I don't know how it happened considering how much I read on this kind of shit, but I had never seen anyone talking about torsion on the grand scale like that.
Considering what we've seen lately in actual measurements, I'd guess clues/info about it MUST be in the data somewhere...maybe no one has analysed either fully or correctly yet. [[the amount of data we already have will never actually be fully analyzed till we have really good, really powerful AI...there just aren't enough people with enough brains and enough raw speed to do it. And the gap is growing, and the rate it is growing is growing even faster...a double exponential] I'm not exaggerating that, I'm massively underestimating.

Anyway...we're not likely inside a black hole, no matter how fun [and perhaps useful...as the man said, all models are wrong, but some are useful anyway] to play with.

But FinPants: I object to the "no outside" thing. But, disregarding that, a number of people lately have pointed out [and others have gotten interested] that in a black hole, the internal volume is always expanding, heading towards [but never reaching] infinite. Because there is a distance between the horizon and the stuff at the "center." WHILE it's growing [gaining more material] the mass is increasing which expands the horizon...AND...the center is still collapsing/getting smaller, which ALSO increases volume. But even after it's consumed all available material, the center is STILL shrinking, increasing the internal volume. At least until many trillions of years have passed and it is significantly evaporating.
The universe isn't expanding outwards at the boundary, it's expanding inwards. [[[also highly improbable. It's expanding, there is no singularity rapidly receding everything from everything...it would be noticeable]]].

On non-rotating black holes...they're POSSIBLE, but ridiculously unlikely...to the extent that unless the universe is literally infinite in every way, there probably ain't one in it anywhere.
They have a purpose though, in that they're so much easier to calculate [wrong, but useful].

Anyway, FineCakes: a cosmological black hole is insufficient for what we see. IF there is one, our cosmos must actually be FAR [like orders of order of orders of magnitude] larger than anything we have the slightest hint of in order to be correct AND include the things we CAN see.

[Skyweir]

Yet it is an intriguing possibility V ... is the explanation below flawed? If so, how so?

Any event in the universe occurs as a point in space and time, or spacetime. A massive object such as the Sun distorts or curves spacetime, like a bowling ball sitting on a canvas. The Suns gravitational dent alters the motion of Earth and the other planets orbiting it. The sun's pull of the planets appears to us as the force of gravity.

The second is quantum mechanics, which describes the universe at the smallest scales, such as the level of the atom. However, quantum mechanics and general relativity are currently separate theories; physicists have been striving to combine the two successfully into a single theory of quantum gravity to adequately describe important phenomena, including the behavior of subatomic particles in black holes.

What is the problem with torsion as explained by Poplawski?

Finally, torsion could be the source of dark energy, a mysterious form of energy that permeates all of space and increases the rate of expansion of the universe. Geometry with torsion naturally produces a cosmological constant, a sort of added-on outward force which is the simplest way to explain dark energy. Thus, the observed accelerating expansion of the universe may end up being the strongest evidence for torsion.

Torsion therefore provides a theoretical foundation for a scenario in which the interior of every black hole becomes a new universe.

[Skyweir]

Fincakes and FinePants are uber cute but might naturally be reducible to Fin

A rose by any name ...

[FindailsCrispyPancakes]

I remember reading Poplawski's paper a few years ago when he put it up on arXiv.org for peer review. It was absolutely fascinating, but I'm almost certain he described his model as being incomplete and listed the further work that was required at the end of the paper.

Anyway, Poplawski's paper is based on an Einstein-Cartan gravitational framework.

Einstein-Cartan models have some very interesting features. There are no singularities in Einstein-Cartan models. The result of the absence of singularites is 'big bang' events are replaced with 'big bounce' events.

The inherent feature of such models are that they are models of cyclic (expanding/contracting) cosmologies that presuppose the existence of time before the 'big bang/bounce' event and the existence of an ancestor universe.

Correct me if I'm wrong about this (I freely admit to being very rusty on these subjects), but I believe Einstein-Cartan gravity is normally part of the framework of multiverse models due to its power to resolve singularities.

Which brings me to the viability of non-rotating back hole models. The distinction is once again subtle, but important. A multiverse model by definition implies that our universe is not an isolated object, or closed system if you prefer.

A Schwarzchild model assumes the universe is an isolated object. In fact, it's possible to argue that a universe sized Schwarzschild black hole that contains other smaller black holes within is itself a multiverse model.

In that case, the argument between whether the universe is the isolated object or the multiverse is the isolated object becomes semantic in nature.

The question is, is the sum total of all things that exist (whether you refer to it as a universe or a multiverse) an isloated object?

If your answer is no, then you're not describing the sum total of all things that exist.

If your answer is yes, then the exterior geometry of an isolated object with an escape velocity of c cannot be described by anything other than a purely Schwarzschild (non-rotating) geometry.

As I mentioned in my previous post, if you want to delve deeper into this you need to check out Birkhoff's theorem and start from there.

In fact, I'll go right back to the start of my original post and expand on pretty much the first consideration that came into play. If our universe were a rotating black hole, we should be able to observe the rotation by simply looking at our images of the cosmic microwave background (CMB).

If our universe were rotating, the CMB would look like this



or this



or this.



It doesn't look like that. It looks like this



Also, be cautious with the word 'infinity'! There are different orders of infinities, and they're not all the same size. If you want to dig into that, check out Georg Cantor's diagonalization argument and the cardinality of the continuum.

EDITS: (Almost certainly incomplete) typo and syntax correction

[FindailsCrispyPancakes]

Fincakes and FinePants are uber cute but might naturally be reducible to Fin

A rose by any name ...

Lol, I'm sure I had a christian name many aeons ago, but I've been answering to Finn for so long I forget what it was!

Hi Rose!

[FindailsCrispyPancakes]

A quick addition while I've got another 5 minutes waiting for the computer to do some work...

I'm in complete agreement that the idea of a non-rotating black hole existing on the interior of our universe is fanciful at best. But once again, it's important to differentiate between the interior and exterior geometry.

I'd point out that any statement about the volume of black holes always increasing and asymptoting toward infinity must surely be case specific for non-dormant black holes that are in the process of feeding from their exterior environment.

If not, the model would have to exclude the possibility of black hole evaporation. This may take place over an incredibly long time scale that we have difficulty picturing, but that's the nature of the subject.

The same goes for the cosmos being many orders of magnitude larger than our observable universe... that's a pretty mainstream idea these days in both single shot universe and multiverse models, as is the idea our universe could be a black hole due to the observational evidence suggesting it began its existence as a singularity.

The idea that our universe is significantly larger than the patch of spacetime we refer to as the observable universe is the essential point of inflation theory.

In inflationary theory, once the big bang is underway you safely inflate away from the singularity at velocities many orders of magnitude greater than c. After that it is impossible for you hit the singularity if you're in an expanding universe.

It was inflation theory that led to the staggering estimates for the size of the string landscape (the number of different vacuua within the multiverse) and the concept of eternal inflation.

Cyclic models which use Einstein-Cartan gravity solve many of the same problems as inflationary theory (measure problem, curvature, magnetic monopoles) via singularity resolution.

It's at this point that the whole chicken and egg scenario looms large and we're back to the old chestnut of how something appears out of nothing.

Thus far there's a limited amount of models.

1) The simple big bang model, which could essentially be argued to boil down to everything emerging out of nothing when time starts with the big bang.

2) The extended big bang model, which tacks inflation on to the simple big bang model to explain the questions it poses. This leads to the concept of eternal inflation and the string landscape.

3) The cyclic model which solves all of the same problems inflation solves with (arguably) less tinkering and fine tuning, but does not rest on the assumption that everything emerges out of nothing.

Take your pick, they've all got issues lol.

EDITS: Rearranging sentences and correcting yet more typos