No one knows for sure. There are theories, but absolutely none of them can be proved, and I doubt we will ever find out. The universe is expanding firther into what was here before the big bang....
Space, is empty space filled with millions of matter (or atoms) and dark matter. However, dark matter is very rare.
i think thats not possable
i would assume so.
"Space Junk" gets into space because of us leaving materials behind when we visit space.