Big Bang is and always has been a theory and not accepted as Law. By being theory, scientifically it is tested with new evidence and analyzed, debunking or confirming the first theory.
The problem occurs when theories are considered Law, like the Earth being flat, the center of the Universe, or that man is causing global warming.
The Earth was never flat in the Bible, only in the Roman Church’s definition for 2 or 300 years.
Same with the center of the Universe.
And evolution.