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Comment by hinkley | Hacker News Reader

There's a theory out there that our universe is a pocket universe inside of a supermassive black hole. My relativistic gravity is pretty rusty and was shaky to begin with. If that theory isn't pure fantasy, and we were a pocket universe, and large masses were spinning above the event horizon, we'd experience forces from those objects, right?

I'm still kinda fond of the Flatland theory myself. Us poor 4 dimensional beings can't figure out how to build tools that can take 5 dimensional measurements, so we see weird behavior we can't explain.

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What if our sense of scale is off and the universe isn't curved we're just orbiting a black hole 10x the mass of the visible universe. It's not expanding that's us travelling through the gravity well at 99% the speed of light relative to it.

Have things along these lines ever been seriously investigated as a possible explanation for dark energy and the phenomenon observed here?

It doesn't necessarily need to be your exact hypothesis, but if you generalize it and look at our universe (just our observable universe, or perhaps "the whole thing" in some sense) as possibly being a small object in a much vaster medium, perhaps a medium we could never directly access or observe, what implications could that have, and what could it potentially explain? Perhaps even a medium abiding by a completely different kind of physics.

Yes, most of the random "what if" ideas put forth by laypeople have been investigated and either ruled out by theorists/experiments lists or are non-falsifiable.

Not to offend anyone here, but unless you have a solid grasp of the theory, nobody here is going to be "solving" the mystery of dark matter

You never know. Doug Forcett made an almost perfectly accurate guess as to the inner workings of the afterlife while stoned.

For those unaware, it's from the show The Good Place. Good fun for me, highly recommend it.

Edit: Apparently a joke with the meaning of "you never know who might get lucky and have an interesting insight" was... disliked. My thoughts on being able to have insight from anywhere come at least partially from the (somewhat recent) story of physicists that noted a connection between eigenvalues and eigenvectors (iirc) that mathematicians did not (after many years). Sometimes, insight comes from the outside.

Think of it like this: how many degree-level lectures can you give in physics as compared to whatever your profession is? Now imagine what someone who knows as much about your profession as you do about physics sounds like to you.

Half my questions on Physics stackexchange are so naïve they’re not even wrong, they are so bad they get closed as nonsensical. Looking at past exam papers, I could probably get a grade B in A-level physics (A-level is UK qualification taken at age 18 between secondary school and university currently used to decide which university you go to).

The other half of my ideas are right, but actual physicists tell me they’re “obvious” and “not worth writing about”.

The fact that pretty much all thoughts from people outside the field are either obvious, false, or nonsensical... doesn't invalidate the idea that flashes of insight can come from anywhere. I get what you're saying and agree the odds of it happening are pretty much zero. But sometimes even things with a probability of pretty much 0 can happen. The eigenvalue thing is an example of that, in my opinion.

A layperson could unwittingly trigger a cognitive leap by asking naive questions. A la Feynman saying he can't explain magnetism in a way that I could understand it, the effort could spark an insight or novel angle.

Name a single instance of a lay person without a background in physics discovering the basis behind a phenomenon since 1900.

For some reason, physics seems to be disproportionately popular among armchair theorists compared to other fields like math or chemistry.

> disproportionately popular among armchair theorists compared to other fields like math or chemistry.

I’ve heard this before, but I wonder how true it is? I know my experiences are just anecdotes, but I knew a guy who was convinced the Hotel Room/Bellboy/Missing Dollar problem “broke maths”, and I’ve had countless frustrations with family members promoting homeopathy and acquaintances talking about chemical X being “one atom away from being bleach” like that doesn’t apply to water.

I’d be interested if anyone has done a real analysis of rates of armchair nonsense by sector.

I think people don't like your post because your example is from fiction and is therefore not insightful as to whether or not layman speculation can provide value.

The eigenvalues and eigenvectors example is in there now, and that one is not fiction. It's also really cool.

Physicists providing an insight into math is absolutely not what I was talking about - I was talking about lay people providing an insight into theoretical physics.

To suggest that theoretical physicists are lay people with respect to math is silly. Also, I don't understand what you mean by a "connection between eigenvalues and eigenvectors" as the two seem quite obviously connected a priori?

Weren't (some)new super conductors discovered by just trying a bunch of crap already on the shelves in the labs once the concept existed?

Anyway, I just thought every device we make to measure something, there's some event the blows the scales. So what if you really just make shit up where does that go?

I like the other commenter defending the post about Cthulhu, It's just as made up as what I posted. Perspective is healthy.

and - the nilometers have just been fired up.

I understand that, and understand this likely falls into the unfalsifiable category, but when everyone, even physicists, are grasping at straws, laypeople don't have many options other than to throw around random "what if" ideas. It's fun.

I doubt that hypothesis is actually true, and it may never be testable, but it's also true that a lot of things believed to be untestable eventually do become testable.

It can be a bit exhausting when online physics forums get crowded by people who clearly have no understanding of physics asking for an explanation of whether their "pet theory" makes sense.

I don't know why, but physics seems to be a much more popular target for these type of people than any other field.

I can definitely understand that. I wouldn't post such ignorant armchair speculation on a physics forum. But on HN? Why not?

Meta-physics is inscrutable (unless something leaves the realm of meta-physics). What's the harm in speculating about it? Like the simulation hypothesis, for example.

I understand it touches on real things here, like dark energy, but it's just dumb fun to try to conceive of if anything could lie beyond the universe and what it could possibly be if there is anything. It's likely forever unfalsifiable, but in some sense that's what makes it a fair subject for laymen. If it were testable, then you have to leave it to the professionals.

I know I have zero understanding of physics. I don't have any attachment to this or any other speculation. I'm not a crank or something. But it's impossible to not wonder about the nature of reality and the formation of the universe, you know? The fact that it's unknowable within our lifetimes, and probably forever, is the driving factor.

I like seeing how real physicists answer this question, too, in interviews and podcasts. They always hedge it with "of course this is wild speculation", like everyone should. I see I didn't really hedge my initial post, which was a mistake. This was a random thought triggered by that other post, not something I actually believe whatsoever.

This is giving me an unexplainable amount of anxiety right now, thanks...

Strangely, I'd love to read more on this if anyone can point me in the right direction

Why? It wouldn't be able to cause you any harm, if true (according to our understanding of physics).

Yeah, I'd be a lot more worried about that big ball of fire that scientists all agree will one day consume us.

Yeah, this'll rightly induce some anxiety!

https://twitter.com/universal_sci/status/1217314288085479426

Nothing a bit of stellar lifting can't fix. ;-)

The one I'm terrified of is the switch where the laws of physics all change at the speed of light. We will simply cease to exist and not even see it coming.

Don't worry, we won't notice it either, if it does happen. :)

Nah you’d never see it coming and have no prior for believing in it, so not scary. What is scary: a super intelligence alien race enveloping all matter into Dyson swarms. You’d see stars shifting into uniform infrared emissions in an expanding sphere at nearly the speed of light. Suddenly the stars go dim... and then it reaches you.

Well, that gets into game theory stuff, though. For example, one could say that logically any aggressively expansive intelligent species on that scale should take the position of being friendly and supporting to lesser-advanced intelligent species by default, as a way to encourage other more-advanced species than them to take the same position.

The real danger would be a super but unintelligent race doing the same (think "giant space ants"), since they wouldn't have philosophy department chairs.

Why would that encourage any higher intelligence aliens to do the same?

If you're smart enough to think about it logically, you're probably also smart enough to realize there's always a bigger fish.

The exception would be the fanatically oriented, as acting in opposition to logic is part of the basic premise.

A bigger fish would have already taken over the universe.

The universe is really, really big.

Think Rorschach from Blindsight.

I am a simple man, I am just afraid of sharks and box jellyfishes.

Have you read "Schild's Ladder" by Greg Egan?

It's a great book. I might be the only person in the universe writing fanfiction of it, so I'm biased, but I think it's one of his best.

Can't quite make myself claim it's better than Orthogonal.

Is this in reference to a particular named theory or just a random musing?

Sounds like they’re referring to vacuum decay: https://en.m.wikipedia.org/wiki/False_vacuum

Ech, I'km ok with that, becauase we eouldn't really experince it. There are much grimmer things out there

Depends where it happens. The speed of light is quite slow relative to the size of the universe. So Higgs field collapse could happen a long way away and take millennia to reach us. Perhaps as the collapse propagates across the in universe it meets some huge energy event which pushes the Higgs field up again and rescues matter.

Generally I've chalked these feelings up to a certain type of existential dread. Described in this article[1] fairly well.

Kind of reminds you of the total perspective vortex from the hitch hikers guide to the galaxy. Truly, on a universal scale even the most important and impacting human on an earth scale does about as much as a neutrino interacting with us.

[1] https://medium.com/s/story/are-you-suffering-from-existentia...

Hey, still better than the universe being just a feeble dream of a shapeless older god, that will cease the exist if it ever wakes up. ;-)

Part of the problem with that is that we'd see an uneven amount of expansion. We'd see lots of it along the axis between us and the supermassive blackhole (towards and away from), but roughly perpendicular to it we'd see a ring/plane of matter going roughly the same speed as us towards it. Instead we see an equal expansion in all directions. Now I don't know what kind of scale that might change at though so maybe it's possible still with a seriously large one?

To expand upon this idea, take a look at http://www.flatuniversesociety.com/

My pet hypothesis is that the universe we experience is on the surface of the singularity of our black hole. This neatly explains some things:

- The Great Attractor would simply be the volume deeper in singularity. The cone of influence for the entire universe tends towards the center of our singularity.

- Dark energy, and the varying quantity of it, would simply be the amount of matter falling into our black hole. It would naturally start as a large amount (consisting of our parent star/mass) and later see variation as matter falls into it.

- Dimensionless physical constants may have been fields in the parent universe. As an infinitely small point, our universe singularity would resolve a continuous gradient to a single value. Our child universes would have a single value of gravity, for example, which could change over time (but would be constant across the universe as they changed).

I've got a huge list of interesting consequences, but as an armchair physicist it's probably all quack science :)

You might be interested in the Holographic Principle [0]

[0] https://en.wikipedia.org/wiki/Holographic_principle

Maybe you already know all this, but to other curious readers:

The great attractor is about 200 Mly away. Directly behind it, 600 Mly away from us, is the Shapley Supercluster, towards which the great attractor is itself moving. In the opposite direction is a underdensity, called the "Dipole repeller", and between the two, where we are, is a "dark flow".

https://en.wikipedia.org/wiki/Shapley_Supercluster

https://en.wikipedia.org/wiki/Dipole_repeller

https://en.wikipedia.org/wiki/Dark_flow

If this thread continues any further, we're going to start talking about the dark side of the Force.

I welcome our dark lord, Cthulhu. May his comings bless us for generations to come.

If i could write i would write a novel about the great flow. That was awesome and terrifying to read.

Someone is probably going to vote your comment down on the premise that Cthulu is unhelpful to the conversation. They shouldn't: it's not any more fantastic than the various laymans' pet theories here which have, for some indecipherable reason, been upvoted to the top of the discussion, despite having no connection to real physics whatsoever.

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In a more serious note; i actually think the imagination and fantasy they is born in alot of people after reading about the mysteries of the universe is responsible for a many physics grad.
Taking things /seriously/ is, imo, what keeps people out of stem. Stemmers are, if anything, fantasy rich and colorful people, physicists in particular!
Im glad not many people chose to downvote me too :)

You would see effects of tidal forces in the scenario you described, I think.
The other thing is, if it's not curved then you still need to explain Mercury's orbit precession (43 arcseconds per century is it?). This is not an easy thing to do

EM redshifts alone would invalidate that hypothesis. It doesn't matter how fast you travel, EM redshifts follow specific laws that we cannot see breaking at any point observed in the universe.
It is more likely that physical laws have localised variations that we cannot tell from any discernible distance. Maybe pockets of vacuum do shit that we cannot fathom and if we observed it, we'd break the code for reality.

https://www.nationalgeographic.com/news/2010/4/100409-black-.... Personally I always preferred the theory that galaxies were just atoms in a much larger world.

Kind of like this? https://www.youtube.com/watch?v=JUOGxePBs50

Or the 1997 documentary on the subject: https://www.youtube.com/watch?v=OKnpPCQyUec

I've always wondered about the relationship between the future observable universe and black holes. Since space is expanding, far away objects that we now see will eventually move away from us faster than the speed of light so there would be no way to get at them any more. This seems similar to dropping yourself in a black hole: when you cross the event horizon you won't be able to get back to the objects outside of the black hole, unless they're dropping into the black hole too. Also, the bigger the black hole you drop yourself into, the less you'll feel it because the tidal forces become smaller. I wonder what you would see if our galaxy and surrounding galaxies were dropping into a super big black hole. Would the black hole take up more than 50% of the celestial sphere? Would everything then be moving away from us at an accelerating rate?

There would be strong anisotropy in our observation. Alas things are moving away from us in ALL directions.

Right, it would seem that they should only be moving away in one direction, and eventually we'd even see a difference between the forward and backward direction. However, I've heard people claim that eventually, all directions go toward the singularity?

That's once you're inside the black hole, and not entirely true; "past" points outwards. I'll admit it's close enough to true.
Which is not to that's how it would look. Photons are also falling, so you'd still be able to see the external universe even if the apparent direction it's in isn't traversable. (The photons are coming from the past. See above...)

>"past" points outwards.
I don't think that grasps space-time as one thing and why black holes are so mental. The event horizon is where the past no longer points outwards, that path is broken. There's no direction in space or time with which to point your space engine to escape. No time you could travel to were that is restored.

If string theory is correct, there are a number of higher dimensions, the existence of which would influence gravity at short distances. The idea is that some gravity leaks away to the other dimensions. This is a function of distance, so at short distances less gravity has leaked, and gravity should be stronger. Efforts to find this effect haven't turned anything up yet, though.

Was this not dispelled by LIGO’s measurement of a merger that we observed both gravitationally and with EM?

Iirc, LIGO confirmed that there was no leakage from/to other dimensions, hence that we can safely reason (at least on this problem) within our current 4D manifold.
It doesn't (cannot, really) state about the possibility that our universe, though self-contained in 4D, might be floating in a higher-dimensional space, like a 2D surface would float in 3D (and could be internally very consistent).
String theory, by the way, might not prove or disprove any of that (see my other reply to parent).

Actually just to nitpick, even if we could find one string theory that works, remember that it's "only" math. Meaning that it could totally work to describe a phenomenon without having any physical reality to it.
Even if it predicts observation, like Bohr's model of the atom did, you have some degree of abstraction between the model and the physical implementation, so to speak.
And that's the ultimate problem of string theories: even if we crack some math model, if it can't be observed directly, we just don't know. Quantum mechanics currently sit in-between the purely theoretical (where we do have a model that works, minus gravity, if applicable at that level) and the barely observable (we can infer, a lot, but not much in the way of actually seeing things; although I think nowadays we've crossed that bridge anecdotally enough to be confident but don't quote me on that).
Therefore, string theory models may require higher dimensions in the math to hack the problem, but it doesn't mean these actually exist — like Clifford's algebra, Geometric Algebra, you reason with 4-dimensions to treat 2D (x, y) problems, and 8-dimensions to treat 3D problems — but that's just the math, and the beauty of that is indeed to "unify" other algebras which become essentially subsets.
It's really important to keep that in mind when "gunning for" string theories, or seeing them as "explicative", interpretable. They're really not, at least not now, and possibly ever due to their construction. In truth, it's more about brute-forcing the issue (kinda like current deep learning?), hence the wild ranges of "possible solutions", from 11 to 26 dimensions (some go in the hundreds in suggestion) because they're basically trying to use computers to identify dimensions wherein our universe "fits" quite well, and derive what we don't know (e.g. quantum gravity, or whatever that means in the "promised dimension level"). At a "basic principle" level, that's what string theories are after. It's pure math, it's crazy smart, it's really elegant and almost godly, noble because it requires the state of the art of our evolution and technology; but like quantum mechanics the "interpretation" will not be delivered with the equation, and it may never mean anything to us.

I think you have a point

Alas, a point is 0-dimensional.
(I deserve downvotes for this!)

OT: That reminds me of the great album by Yello, named Pocket Universe. https://en.m.wikipedia.org/wiki/Pocket_Universe

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