This is a fun idea. You can illustrate it by drawing your classic 2D universe on a piece of paper, sprinkle metal dust around, and move it with magnets held above or below the paper. To the 2D creature, matter in their universe seems to be affected by forces from entirely invisible objects, but 3D creatures can observe exactly what's happening. Likewise our "dark matter" would simply be matter on different planes in the same >3D universe as us. We neither see it nor collide with it, but we observe its gravitational pull.
Mind you, I'm not a physicist, and I'm not (necessarily) proposing this as a serious model. Just an internet commenter riffing on a fun idea.
There’s not actually any proof for multiverses, that’s a hypothetical, related to the whole sims theory.
Not saying that could not be true but there’s more proof that this isn’t the first or the last universe than there are other universes.
Why would there have to be an "into"? It seems like the most parsimonious expansion is that there isn't one.
My limited understanding of the math is also that that's what the math says.
The universe being small and it’s expansion just a mirage is one attempt to square the data and theory.
I’m not an expert so I don’t have any answers or anything. I just went into this rabbit hole recently when I got sick recently.
The universe doesn't appear to be infinite. The observable universe has a very definite size.
We can't really say much about what comes beyond. But the paper the linked article talks about tries.
> Gravity is a product of interaction between parallel 3D universes.
You might like https://en.wikipedia.org/wiki/Holographic_principle
> The holographic principle is a property of string theories and a supposed property of quantum gravity that states that the description of a volume of space can be thought of as encoded on a lower-dimensional boundary to the region — such as a light-like boundary like a gravitational horizon.[1][2] First proposed by Gerard 't Hooft, it was given a precise string theoretic interpretation by Leonard Susskind,[3] who combined his ideas with previous ones of 't Hooft and Charles Thorn.[3][4] Leonard Susskind said, “The three-dimensional world of ordinary experience––the universe filled with galaxies, stars, planets, houses, boulders, and people––is a hologram, an image of reality coded on a distant two-dimensional surface."[5] As pointed out by Raphael Bousso,[6] Thorn observed in 1978 that string theory admits a lower-dimensional description in which gravity emerges from it in what would now be called a holographic way. The prime example of holography is the AdS/CFT correspondence.
So basically the opposite of what you are describing: gravity emerges because we are in a higher dimension.
> And dark matter is just matter from other universes.
Dark matter can be seen as the label we give to a bunch of experimental findings / problems. https://en.wikipedia.org/wiki/Dark_matter says:
> [Dark matter's] existence is implied by various astrophysical observations which cannot be explained by general relativity unless more matter is present than can be seen. Evidence for dark matter comes from many different angles, such as galaxy dynamics and formation,[2] gravitational lensing,[3] and the cosmic microwave background, along with astronomical observations of the observable universe's current structure, the formation and evolution of galaxies, mass location during galactic collisions,[4] and the motion of galaxies within galaxy clusters.
Positing matter that has gravity but doesn't otherwise interact (much) with the rest of the universe can explain those observations. But other observations are also possible. Eg some people like to fiddle with the laws of gravity to explain why the galaxies don't fly apart.