The current scientific understanding of the Big Bang theory does not support the existence of mature galaxies prior to the Big Bang. According to the prevailing cosmological model, the Big Bang marks the beginning of the universe as we know it, including the formation of galaxies.
The Big Bang theory suggests that the universe originated from a singularity—an extremely hot and dense state—approximately 13.8 billion years ago. As the universe expanded and cooled down, matter and energy began to form, eventually leading to the formation of galaxies, stars, and other cosmic structures.
Observations of the early universe, such as the cosmic microwave background radiation and the abundance of light elements, provide strong evidence for the Big Bang. These observations support the idea that the universe was extremely hot and dense in its early stages and has been expanding and evolving ever since.
The concept of "mature galaxies" existing prior to the Big Bang contradicts our understanding of the origin and evolution of the universe. However, it's worth noting that there are still many open questions in cosmology, and our understanding of the earliest moments of the universe's history is an active area of research. Ongoing scientific investigations, as well as future advancements in observational techniques and theoretical models, may further refine our understanding of the Big Bang and its consequences.