[jbakhos]

I posit this hypothesis that does away with both dark matter and also dark energy. I posit that at a distance of approximately 1.5 million light-years gravity becomes slightly repulsive, gradually increasing with distance to achieve a peak repulsion, and then decreasing with distance to zero.

Thus, cosmological expansion is caused by galaxies pushing against each other, and galactic rotation can be explained by the fact that each galaxy is surrounded by a "womb" of dust, gas, and other galaxies, and this "womb" pushes with repulsive gravity upon the outer stars of a galaxy to keep them in orbit at a higher speed than expected.

I give a cosmological / mathematical justification for this behavior in my Reddit article:

https://www.reddit.com/r/MyTheoryIs/comments/87pcgq/what_dar...

At the bottom, in the responses, I explain how General Relativity can be adjusted so as to retain time dilation while rejecting curved space and retaining flat, 3D, Euclidean space.