A new study says that there could be an “anti-universe” where time moves backwards. The idea is based on the fact that nature has basic symmetry, which experts think could be true for the whole universe. In the Annals of Physics article, the idea was talked about.
It talks about a well-known idea in physics called Charge, Parity, and Time (CPT) symmetry. CPT symmetry is one of the laws of physics. It says that after a transformation, things like charge and time can be turned around.

Scientists believe that the Big Bang, which started the universe, was definitely a change, so the CPT theory could be true. Before the Big Bang, the researchers think there was a back-wards universe that was later turned upside down to make the universe we live in now.
We investigate the idea that the universe before the Big Bang is the CPT reflection of the universe after the bang, both classically and quantum mechanically.
The universe before the bang and the universe after the bang may be viewed as a universe/anti-universe pair, emerging directly into the hot, radiation-dominated era we observe in our past.

This, in turn, leads to a remarkably economical explanation of the cosmological dark matter.
The wild theory says that the fact that dark matter exists in our world isn’t so strange after all. Scientists think that dark matter is made up of ghostly particles called right-handed neutrinos. Neutrinos are real, but they can only spin to the left.
Scientists find it strange that they haven’t found one that spins to the right, which is what the laws of physics say should happen.

The researchers think that the right spinning particles may not be visible in our universe and that dark matter is just a stand-in for them.
We don’t know much about dark matter in the universe, except that it is invisible and affects other things in a physical way.
Scientists think that learning more about neutrino particles and dark matter could be a step toward proving the “anti-universe” theory. Scientists don’t think that people will be able to go to the “anti-universe” because it existed before the Big Bang.
Astronomy Daily / ABC Flash Point News 2023.