A collapsing universe theory is interesting, though I don't think we're below some "event horizon", but perhaps that gets changed as well.
Something else interesting which comes to mind is the "galaxy rotation problem". One of the biggest mysteries today, which gave birth to the "dark matter" theories, is the measured rotation of arms, of spiral galaxies, do not spin as expected according to Keplerian dynamics.
So to explain this phenomenon, additional gravity is needed in the form of dark matter (since we can't see it).
But could a spiral galaxy residing inside a collapsing universe explain the phenomenon through conservation of energy in the same way an ice skater pulls in her arms to increase her spinning motion? Would a shrinking galaxy inside of a shrinking universe impart unusual and observable characteristics to its rotational speed? And if so, would measurable rotational characteristics vary for galaxies located at the boundary from those galaxies located near the universe's center?
As always, more questions than answers!
You mean Conservation of Angular Momentum, not Energy.
But yes, that’s also a possibillity.
But again, I don’t have the Math skills...