Some scientists are pretty sure that it is a mirror world that affects gravity in our current universe.
Three researchers published their findings this week in the journal Physical Review Letters and said their hypothesis was based on problems with the Hubble Constant. According to a report on the study, predictions for that constant are a lot slower than we have measured, and scientists are trying to figure out what is causing the discrepancy. They think the cause could be a mirror world.
Researchers said in a statement that this might provide a way to understand why there appears to be a discrepancy between different measurement of the Universe's expansion rate.
Scientists have created models of the universe. The task is to create one that doesn't violate any of the rules we've learned so far. If the universe is exploiting what we know about its physics and symmetry, there could be an invisible mirror world very similar to ours but invisible except for the impact on our world.
It might seem crazy at face value, but such mirror worlds have a large physics literature.
It's not the craziest theory we've heard, but we still want to see it for ourselves.
There's a secret society in the Pentagon that is hiding secrets about aliens.