Let's look at empirical evidence of the firmament. That means direct observation. The most recent confirmation that we have of the presence of the firmament is from the New Horizons space mission.
Empirical Evidence of the Firmament
A Pavement of Sapphire Stone
You may be uncomfortable with the idea that God uses a section of the firmament as a movable platform like a giant cosmic surfboard. We get it, this is a deep end and we went off it. It's what we do.