It is unfair of me to be jumping in on so many threads so I will try again here.

It is descriptive because ds^2=x^2+y^2 has not been well received. If one uses a formula like that to describe an enclosed body there is a non zero base to allow flow (think blood pressure). In this case the proposed flows are time and gravity which determine the shape and composition of space.

First density can not be a solid so the closest thing I can think of is a sponge. A sponge occupies only a portion of the volume it is in and the rest is structure ergo voids and cosmic web.

For flow there needs to be a return structure and "if" it is the proton then the difference of 10^119 orders of magnitude of vacuum energy would be sufficient to enable the gateway to be kept open. I dislike this word now, a wormhole from the inside 'may' look like a tube. The ends may bunch up or feather out depending on speed and direction. Depending on speed the tube may appear flattish in shape.

Flow in a body. A blood cell for instance travels along one side of an artery (inside) and continues forwards back along one side of a vein (inside). If the blood vessel had charge then there may be an alignment of positive blood cells one side of the artery and negative the other. This would continue into the vein maintaining charge and flowing back to the starting point via a different route so flow continues in one direction.

If and this is the big "structure if", if the blood cell is paired to an opposite charge blood cell on the other side of the artery or vein via a wormhole then each blood cell would have an asymmetry. The thing about wormholes is that one is able to see the gate but not the connection or the connection but not the gate.

If viewing is possible (and space is clear) across from artery to vein or vein to artery it is possible the blood cell could see where it has been. If the flow speeds up and slows down in time for the transition artery to vein then there may be an equal point in time where the blood cell sees itself future or past tense in the same frame. Meaning at certain points a common universal time frame for the blood cell at time future and time past.

For space insert cosmic web for artery and vein, proton for blood cell and time is measured relative only to the location of the proton (blood cell) for each point it is in the system. Dark energy is the result of slowing down in real time for the turn. Time for the proton is constant relative to the proton (perceived time).

Based on the size and twist of the universe it may be cycle to cycle or if on a greater helix from beginning to end. I do not intend to guess at that last set of possibilities. Either way it is centrally bound with no inner or outer and fully contained where the central in six dimensions acts as both inner and outer.

General relativity work just fine from a certain point upwards of the centre of the earth and fine to where the time through distance becomes noticeable but fine for planetary orbits and satellites.

Draw pictures ... it helps.