The question of what existed before the emergence of spacetime, specifically before the Big Bang, is a topic of ongoing scientific inquiry and philosophical debate. It is a challenging question because our current understanding of the universe is limited by the available evidence and the boundaries of our scientific knowledge.
The concept of "before" the Big Bang assumes a linear progression of time, which may not be applicable beyond the event horizon of the Big Bang. The singularity associated with the Big Bang represents an extreme state where our understanding of the laws of physics breaks down. Therefore, trying to understand what existed before the Big Bang becomes difficult, as the usual concepts of cause and effect, space, and time may not have operated in the same way.
Theoretical physics, particularly in the field of cosmology, is actively exploring various hypotheses and models to address these fundamental questions. Some theories propose the existence of a "pre-Big Bang" phase or a multiverse scenario, suggesting that our universe could have emerged from a different state or that there may be other universes beyond our observational reach.
However, it is important to note that such theories and hypotheses are still speculative and lack definitive observational evidence. They are based on mathematical models and attempts to reconcile the known laws of physics with the conditions before the Big Bang. As of now, we do not have a conclusive scientific understanding of what might have preceded the emergence of spacetime or if the concept of "before" even applies in that context.
So, while the limits of our understanding may prevent us from fully comprehending what existed before the emergence of spacetime, ongoing research in theoretical physics aims to deepen our understanding of the early universe and explore these profound questions.