Final answer:
The Big Bang Theory, positing the universe's origin from a singular event 13.8 billion years ago, is supported by philosophical arguments, Einstein's theory of general relativity, and empirical evidence such as the cosmic microwave background radiation.
Step-by-step explanation:
The Big Bang Theory as a Logical Extension of Cosmological Facts
The idea that the universe began with a singular event known as the Big Bang is a logical extension derived from a combination of philosophical reasoning and empirical evidence. One philosophical argument against the possibility of an infinite regression of past events suggests the need for a beginning, and the Big Bang Theory provides a model for such a beginning.
From the standpoint of experimental physics and cosmology, two key foundations support the Big Bang Theory. First, the speed of light is finite, indicating that we can only see as far back in time as the light has had time to travel. Second, the universe is observed to be expanding, implying that it was once condensed into a much hotter and denser state approximately 13.8 billion years ago.
Notable physicists, including Georges Lemaître, postulated that the universe began from a 'primeval atom' which then fractured into numerous pieces that eventually became the atoms of our current universe. This model aligns with Einstein's equations of general relativity, which also imply a beginning for the universe. Additionally, the observation of the cosmic microwave background radiation, which dates back to about 380,000 years after the supposed Big Bang, offers strong empirical support for this cosmological theory.
The Big Bang is not meant to be understood as an explosion in space but rather an expansion of space itself that includes all matter and energy. The evolution of the universe, as dictated by the laws of physics, especially those of particle physics and general relativity, supports this cosmological model and continues to be the dominant scientific theory explaining the origin and expansion of the universe.