well he needs a big place to put him and all the good souls who will stay with him for all eternity. Thats the simple answer!
God is not contained in the universe. He created the universe, it is not bigger than He is, and it does not contain Him. Also, Heaven is not contained in the universe.
As for the OP, the universe is constantly expanding and has been constantly expanding since it was created. At one point in time it was unimaginably tiny. God created the laws of nature which have been governing the universe’s constant expansion since the beginning. How big is big, how tiny is tiny? When it comes to the physical universe, and when you think of it in comparison to God’s infinite greatness, its “size” really is relative. Even from a purely scientific POV, strictly speaking there (likely) isn’t anything “outside of the universe” (there isn’t even any way to talk about “outside of the universe”), and so when discussing its “size” there is no absolute or standard against which to judge it. Distances within the universe of one object to another are intelligible and measurable, but it makes no sense to talk about the size of the universe absolutely speaking. Now, if you’re wondering why God made the universe to expand to a “size” so unimaginably “bigger” than we are, or the tiny space we take up, who knows?
The universe exists, and it does what it does. God made the universe this way. The universe obeys the natural laws that God set up for it, laws which are sustained by His constant will. The universe operates with a space-time continuum; God does not. He is “outside” of space and time. He created all of this stuff and He sees to it that it behaves in certain very well-defined and fine-tuned ways. There is a lot about this stuff that He created that we don’t fully understand. There is a lot about Him that we don’t fully understand. Additionally, there is genuine “interaction” of a sort between the eternal spiritual stuff that He created (and that He is) and the material stuff that He created. The physical laws of the universe are various and manifold, and we have no control over them. Only He does. However, the more important eternal and spiritual stuff that He created (our souls) are partly under our control, but there are ultimately only two destinations. However, the states that our souls can be in at different times are also various and manifold. Maybe there’s a kind of similarity there. Maybe one reason God created the universe to expand, and to be as “big” as it was and is when he created us was to show us, 1) how great and grand and magnificent was its creator, and 2) how great and grand and eternal and precious are our souls. If something like the universe, which is not under our control, and whose ultimate destiny is unimportant (even if terribly interesting), is so magnificently huge and beautiful and awe-inspiring; how much more important (infinitely so) to us and to Him are each one of our souls, and how much more magnificent, beautiful, and awe-inspiring? Concommitently, how much more integral and important is our free will to God’s plan, which determines (in the end) the final destiny of our infintely precious souls, than the laws of nature which expand this beautiful universe and sustain our bodies? Then, how much more infinitely great is the God who created our free wills, souls, laws of nature, and the universe than all of these? How much “bigger” is His love? How magnificent!
These are just some thoughts that are popping up.
God Bless
Jon Winterburn