The Big Bang is not a physical point or location in space. It is a scientific model or theory that describes the early expansion of the universe from a highly dense and hot state. The term "Big Bang" is often mistakenly associated with an explosion that occurred at a specific point in space, but that's not an accurate representation of the concept.
The reason why scientists believe in the Big Bang theory is because of the considerable amount of observational and theoretical evidence that supports it. Some of the key pieces of evidence include the observed expansion of the universe, the cosmic microwave background radiation, the abundance of light elements, and the distribution of galaxies.
The expansion of the universe, as indicated by the redshift of distant galaxies, provides strong support for the idea that the universe was once in a highly compact state and has been expanding ever since. The discovery of the cosmic microwave background radiation, which is a faint remnant of the early universe, is consistent with the predictions of the Big Bang theory.
Additionally, the relative abundances of light elements, such as hydrogen and helium, are in line with what is expected from the conditions in the early universe. The distribution and large-scale structure of galaxies and cosmic structures can also be explained by the initial conditions set forth by the Big Bang.
While we may not know the precise "center" or exact location of the initial singularity of the Big Bang, the evidence from various fields of study, including cosmology, astrophysics, and particle physics, provides strong support for the theory. The Big Bang is widely accepted within the scientific community as the most compelling explanation for the origin and evolution of the universe based on the available evidence.