According to current scientific understanding, the age of the universe is estimated to be approximately 13.8 billion years. This age is calculated based on various observations and measurements, including the rate of expansion of the universe, the cosmic microwave background radiation, and the ages of the oldest known celestial objects.
The concept of the Big Bang refers to the event that marks the beginning of the universe as we know it. It is the prevailing scientific theory that suggests the universe originated from a highly dense and hot state around 13.8 billion years ago. However, the concept of "time" itself is intricately connected to the expansion of the universe, and it becomes difficult to speculate about what, if anything, existed before the Big Bang or if the concept of "before" even applies.
It's worth noting that our understanding of the universe's history and its precise age continues to evolve as scientists refine their observations and models. Therefore, it's always recommended to refer to the latest scientific research and findings for the most accurate and up-to-date information.