You see things correctly, Joshua, and there is indeed a 'wall'.
I call it the Fourth Motion, which is the fastest motion we are involved in.
1. Earth's mass and spin (gravity based)
2. Earth's revolution around the Sun (gravity based)
3. Earth's dancing along in the circular motion of the Milky Way (gravity based)
4. Earth speeding along in the one-directional motion of the Milky Way (note: this is not gravity based).
#4 is the fastest speed the Milky Way is involved in. All the matter in the Milky Way is moving in a single direction at the highest speed. That is the wall. It is based on the original catapulting reality produced by the materialization process itself. So, that motion is about 13.8 billion years old, and on-going.
I do not deny that gravity plays its role, so we actually only need a tiny bit of gravity to start that collective to spin.
But I could also point to the materialization process itself, the catapulting action that put all matter of the Milky Way (and all other galaxies) in motion. This motion has not subsided; it goes on and on without stopping. The materialization process itself could already contain the push with a spinning action in it. I suspect that was the case.
Another explanation is that at soon as we have matter converging with matter (started up probably right after the CMBR), then we have some form of interaction playing out. Because we have a single direction for all that Milky Way matter, there will then be spin evolving in that setup. So, that would then be a 'simple' dynamics explanation (not going into details here).
There should be some form of drag because of the spin, so I welcome the idea that the original spin could have been faster, but that the built-up of masses in the Milky Way established something of a drag. Still, the outward motion, the Fourth Motion (actually the First motion, but Fourth from our own perspective), would remain much the same.
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At the Exploratorium in San Francisco, there is an exhibit that is a cylinder filled with water and a bunch of silver slivers. Visitors can spin the cylinder (and then stop the cylinder from spinning). Slowly, the spin inside the cylinder also subsides and the surprise is that all silver slivers collected themselves in a heap on the bottom of the cylinder, in the exact middle.
Because the spin of the water slowed down, the silver slivers that were moving about randomly can now also move toward the center of the spin, and that is where they get stuck. There is very little movement in the exact center of the whirlpool, so anything that comes close to it ends up in this dead zone. Then Earth's gravity pulls these silver slivers down, so all end up in that heap on the bottom.
In space, all silver slivers would remain in the center of the slowed-down whirlpool. They would remain in place in their center due to the whirlpool’s slowed-down action.
The Sun declares that the Solar System is not spinning all that fast. We have a lot of light-weighted material collected there with the Sun.
However, move up the speed of the spin in the exhibit at the Exploratorium and all slivers will get picked up by the faster spin, floating upward at first and then randomly again in the faster moving water.
So, in the center of a galaxy, the center spin is of such speed that no mass will stay there at all.
Because the exact center is net-zero (not how even in the enormous gravitational depression there will be a net-zero position), sometimes matter can fall into this spot (i.e. move through the Wall of the Depression toward the center, just like a truck can get picked up by the Wall of the Hurricane’s Eye and dumped into the Eye). That matter inside the Wall, in the Eye, will get torn into shreds and spewed out any which way possible. We see particularly the spouts above and below the net-zero spot of all that crud; these spout alignments are themselves also net-zero.
Thank you for thinking along with me, Joshua, I appreciate it.
