In the beginning marks the start of time - before this, God was. He inhabits Eternity past and Eternity future. How can we understand eternity? I'm not sure we are entirely capable. How can the finite mind comprehend the infinite? God is outside time. He is the creator of time. God always was and always will be.
In the beginning God is the beginning of God creating and then revealing himself to his creation. For us, it is the beginning of the answers to our deepest questions. Who are we? Where did we come from? Where are we going?
The word for God in verse 1 is Elohim. This word is plural used in a singular fashion. This is the trinity. Elohim is the Father, Son and Holy Spirit. - One God in three persons. We can read John 1:1 and know Jesus was there in the beginning. All things were created by Him and for Him.
Colossians 1:15 says:
He is the image of the invisible God, the firstborn over all creation. 16 For by Him all things were created that are in heaven and that are on earth, visible and invisible, whether thrones or dominions or principalities or powers. All things were created through Him and for Him. 17 And He is before all things, and in Him all things consist.
In the beginning God created. The word for created is explicitly speaking of creating out of nothing. God created ex nilo or "out of nothing".
So, by the first line of the bible, you know there is an eternal God. Knowing that, you are forced to make a decision. Do you believe in this eternal God, the creator of all things? Many don't...........
One day, students in one of Albert Einstein's classes were saying they had decided there was no God. Einstein asked them how much of all the knowledge in the world they had among themselves collectively, as a class. The students discussed it for a while and decided they had 5% of all human knowledge among themselves. Einstein thought their estimate was a little generous, but he replied: "Is it possible God exists in the 95% you don't know?"
To make the claim to be an atheist is a claim to know all 100% is void of God. To know all that is to claim you are a god (all-knowing). There is no such thing as an atheist. Either you believe in God, or believe you are a god.