The age of the Big Bang Universe is estimated to be approximately 13.8 billion years based on current scientific understanding and observations. This estimation is derived from a variety of observational data, including the cosmic microwave background radiation, the abundance of light elements, and the redshift of distant galaxies.
The age of the Universe is closely linked to the concept of the Hubble parameter, which describes the rate at which the Universe is expanding. By measuring the rate of expansion and then extrapolating backward in time, scientists can estimate the age of the Universe.
However, it's important to note that the concept of "before" the Big Bang is not well-defined within the current framework of our understanding. The Big Bang theory describes the rapid expansion of the Universe from a highly dense and hot state, but it does not provide insight into what might have preceded it or what caused it. Our current understanding of the Universe's origins is limited to a fraction of a second after the Big Bang.
While the estimated age of the Universe is 13.8 billion years, it's crucial to acknowledge that further scientific advancements and discoveries may refine our understanding of cosmic history. The field of cosmology continues to evolve, and ongoing research and observations may shed more light on the precise age and origin of the Universe.