The nature of what exists "outside" or beyond the universe is currently a topic of speculation and remains largely unknown. The universe, as we understand it, refers to the entirety of space, time, matter, and energy that we can observe and interact with. It encompasses all the galaxies, stars, planets, and other celestial objects.
When we talk about the universe, we typically refer to the observable universe, which is the portion of the universe that we can see or detect through our instruments. It is vast, but it is not necessarily the entirety of what exists.
It is important to note that our current scientific understanding is limited when it comes to comprehending what lies beyond the observable universe or if there even is anything beyond it. There are several hypotheses and theories put forth to explore this question:
Multiverse Theory: One hypothesis suggests that our universe may be part of a larger "multiverse" comprising multiple universes, each with its own set of physical laws, dimensions, and properties. These universes may exist alongside or interact with our own in ways that we cannot directly observe.
Cosmic Inflation: According to the theory of cosmic inflation, the early universe underwent a rapid expansion shortly after the Big Bang. This theory suggests that regions of the universe may have expanded beyond our observable horizon, creating separate "bubble" universes or pockets of space that are disconnected from our observable universe.
Mathematical Constructs: Some theories propose that the concept of "outside" the universe may not have any physical meaning or existence. The universe may be self-contained and described by mathematical constructs or fundamental principles that define its properties and behavior.
It is essential to understand that these ideas are theoretical and not yet substantiated by empirical evidence. Exploring what lies beyond the universe or if there is an "outside" to it remains an open question in cosmology and theoretical physics. Our current scientific understanding is limited to what we can observe and study within the bounds of the observable universe.