Why does the Bible talk about a third heaven?

In the beginning God created the heaven and the earth (Genesis 1:1).  When God began creating the universe and everything in it, He started out with just one heaven.  However, He quickly divided it into three heavens.  In Genesis 1:8 we see that God created a firmament and called it Heaven, this is key to understanding the different heavens.  The first heaven is our sky and atmosphere, it is what we see by day and what the birds fly in (Genesis 1:20).  The second heaven is the universe, what we see at night (Genesis 1:12).  The third heaven is God’s abode, this is where God’s presence is and where Paul was shown (2 Corinthians 12:2).