The question of what lies beyond our observable universe and what exists in other parallel universes is still an open and speculative topic in cosmology and theoretical physics. Since we are confined to our observable universe, which is the portion of the universe that we can detect and study, we have limited information about what might lie beyond it or what exists in parallel universes, if they indeed exist.
Here are a few possible scenarios that have been proposed:
Universe beyond the observable: Our current understanding suggests that the universe is vast and potentially infinite. It is conceivable that beyond our observable universe, there may be more regions of space, matter, and energy extending further than we can currently detect. However, our ability to gather information about these regions is limited by the finite speed of light and the age of the universe.
Multiverse landscapes: Some theories, such as certain versions of the inflationary multiverse theory or string theory, propose the existence of a multiverse—a vast collection of multiple universes with different physical laws and properties. Each universe in the multiverse could have its own unique features, such as different constants of nature, fundamental particles, or dimensions. In this framework, there could be an enormous variety of parallel universes, each with its own set of physical laws and potentially different structures or entities.
Mathematical structures: Another idea put forth by some physicists is that the fundamental nature of reality may be described by mathematical structures. In this view, different mathematical structures could correspond to different universes or realities. The existence of parallel universes would then be a consequence of the underlying mathematical structure of reality.
It's important to emphasize that these concepts are still speculative and largely theoretical. The nature of what lies beyond our observable universe and the existence of parallel universes are currently areas of active research and debate. Scientists and theorists continue to explore these questions through mathematical models, simulations, and observations, but definitive answers are yet to be found.