What is the "first cause" in philosophy?

The “First Cause” in philosophy refers to the cosmic processes behind the forming of the first atoms in the universe. The pre-Big Bang universe was at some point empty and devoid of matter. “Something” had to “cause” the first atoms to form. These first atoms led to physical processes that led to the Big Bang and thus, the Milky Way Galaxy, and other galaxies were formed. A theological explanation for the first cause is that it was an act of God, a living being that was already in motion. Scientific explanations of the first cause have not been formulated and scientists presently consider the pre-Big Bang universe to be unknowable. In my opinion, this fact in and of itself makes the “First Cause” debate the most engaging philosophical debate that there is.