Ok then....all science knows is that it was there and it expanded...so the universe could be eternal...yes....it may not have had a beginning? Of course if you say it had a beginning, then we want to know from where it came and why.
But I must say I find this all bizarre, I started out trying to understand the science of big bang theory.....but as I get to the beginning part...the singularity mystery presence, and ask if it was always present or appeared from nowhere, I am told there are plenty of theories about where the singularity came from. Presumably some of those other theories includes the "God created it" theory....and "it's all a computer simulation by advance civilizations" theory? ....