The question of what existed before the Big Bang and what happened to the matter and energy that might have been present is still a topic of speculation and active scientific inquiry. Our current understanding of the Big Bang theory, based on the available evidence and the framework of general relativity, describes the expansion of the universe from a highly compact and dense state.
According to this theory, the universe as we know it began to expand and evolve from an extremely hot and dense state around 13.8 billion years ago. Prior to this event, the conditions are not yet well understood, and our current theories cannot make definitive statements about what happened before the Big Bang. The singularity, a point of infinite density and temperature, is where our understanding breaks down.
Some theories propose that the Big Bang was not the absolute beginning but rather a phase transition from a pre-existing state. These theories suggest the possibility of a "cosmic bounce" or a cyclic universe, where the universe undergoes a cycle of expansion and contraction, with each cycle starting with a Big Bang.
However, these ideas are still speculative, and more research is needed to determine their validity. It is important to note that the current understanding of the Big Bang theory, supported by observations such as the cosmic microwave background radiation, focuses on the early expansion and evolution of the universe from an extremely dense and hot state, but it does not provide a complete explanation for the origin of the universe or what may have existed prior to the Big Bang.