The question of what existed before the Big Bang is highly speculative and currently beyond the reach of scientific investigation. The Big Bang theory is our best scientific explanation for the origin and early development of the universe, but it does not provide information about what might have preceded it. The reason for this limitation is that the Big Bang marks the beginning of the observable universe, and any events or conditions before that point are not directly accessible or testable through scientific methods.
At the moment of the Big Bang, the universe is thought to have been in an extremely hot and dense state, but our understanding of the exact nature of that initial singularity is incomplete. Various cosmological models and theoretical frameworks, such as inflationary cosmology or string theory, have been proposed to describe what might have occurred in the earliest moments of the universe. However, these models generally do not offer explanations for what existed before the Big Bang itself.
Some physicists and cosmologists speculate about the possibility of a "multiverse," which suggests that our universe is just one of many universes that might exist. According to this idea, the Big Bang may have been a local event within a larger cosmic structure. However, it is important to note that the concept of a multiverse is still a matter of speculation, and there is currently no direct observational evidence to support or refute its existence.
In summary, the question of what existed before the Big Bang remains an open and challenging topic of scientific inquiry. It is an area where our current understanding is limited, and further research and theoretical advancements are necessary to gain deeper insights into the nature of our universe's origins.