The concept of time is intimately tied to the fabric of our universe as we understand it today. Therefore, when we talk about events like the Big Bang, it becomes challenging to describe what happened "before" it in terms of conventional time.
According to current scientific understanding, the Big Bang is the earliest known moment in the history of our universe. It is considered the starting point of our universe's expansion and the origin of space, time, and all matter and energy. The reason it is difficult to discuss what occurred "before" the Big Bang is that our understanding of time breaks down near the singularity associated with it.
The singularity refers to an extremely dense and hot state where all matter, energy, and spacetime are believed to have been concentrated at the beginning of the universe. Our current theories, such as general relativity, do not provide a complete description of the physical processes at or before the singularity. In this regime, our traditional notions of time may not apply.
However, there are various theoretical models that attempt to describe the conditions before or at the moment of the Big Bang. One such model is called the "cosmological model of eternal inflation," which proposes that our universe is just one part of a larger multiverse where other universes are continually being created. In this context, time may exist beyond the bounds of our observable universe.
It's important to note that these theories are still under active investigation and subject to refinement as our understanding progresses. The ultimate nature of the Big Bang and what, if anything, preceded it remains a topic of ongoing scientific inquiry and exploration.