One of the issues with the big bang theory and observations of the cosmos is that there ought to be more stuff. The presence of dark matter must be there because we can measure it’s effects via gravitational waves. A possible explanation for why dark matter exists at all is that there is an anti-universe—the same as “our” universe but with neutrinos spinning the opposite way and time going backwards. If that’s true, it would be expanding in the opposite direction as the big bang.
See also:
- Absolute time does not exist and in an anti-universe relativity probably also exists
- The symmetry of a universe/anti-universe sounds similar to black hole / white hole theories and our universe existing inside of a black hole