The Big Bang theory is widely accepted because it provides the most comprehensive explanation for the observed expansion of the universe, the abundance of light elements, and the cosmic microwave background radiation, among other pieces of evidence. It describes the early state of the universe as a highly dense and hot singularity, not as an explosion in the conventional sense.
It's important to clarify that the Big Bang theory does not claim to explain the origin of the universe or what may have existed before it. The theory describes the expansion and evolution of the universe from an extremely hot and dense state to its current state over billions of years. The Big Bang is a model that begins when the universe was already in a highly compressed and hot state, not a description of the precise origin or cause of that initial state.
The notion that the Big Bang emerged from "nothing" is often a source of confusion. In physics, the term "nothing" can be nuanced. From a scientific perspective, "nothing" refers to the absence of matter and energy but not necessarily the absence of the underlying physical laws and principles that govern the universe. These laws may have been in operation even before the Big Bang, but our current understanding of physics is limited in providing a complete explanation for that early phase.
Furthermore, advancements in cosmology, such as inflationary cosmology and quantum physics, suggest that our universe might be just one among many universes or part of a larger multiverse. These concepts are still speculative and under active investigation.
In summary, the Big Bang theory is the prevailing scientific model that explains the observed expansion and evolution of the universe. While it does not provide a definitive answer regarding the origin or cause of the initial state, it is supported by substantial empirical evidence. The question of what existed before the Big Bang, if anything, and what may have caused it remains a topic of ongoing scientific research and speculation.