There was a Big Bang but the universe is infinite. Therefore, the universe is not expanding outwards from a single point like the Metagalactic Center in James Blish's The Triumph Of Time. So how does the expansion work?
Poul Anderson's Tau Zero assumes a cyclical universe which does not fit with current cosmology. However, Tau Zero expresses the cyclical myth which is much older than current cosmology and which also reflects experience.
The Triumph Of Time has a matter and an anti-matter universe colliding and mutually annihilating whereas current cosmology has many matter universes occasionally impinging. These novels remain good hard sf.