Other people doing the same experiment with different equipment or circuмstances.
Other experiments using different methods getting the same results.
It's still not verifiable science because, as you admitted:
1. The "assumption" here is that the geometric abstraction is sufficiently close to reality.
2. That light travels the same in low atmosphere as it does at a) high altitudes and b) in space
Those are HUGE assumptions and make any conclusions suspect.
The main atmospheric components are Nitrogen and Oxygen. Water vapor is a small percent.
There's a difference between low atmosphere and high atmosphere. Also, how does one measure light in the vacuum of space? I don't believe there's such a vacuum but you do. And to suggest that space can be measured the same as the atmosphere is nonsense. How do you shine a light which travels through 2 different mediums (atmosphere, vacuum) and think you could adequately measure this?
You're assuming the world is set up so anything we observe could be wrong?
You're essentially arguing we can't know anything.
No, i'm assuming the world is setup to observe those things ON EARTH alone. We can't know those things "in the heavens" because a) they don't work the same way as things on earth, b) too many assumptions involved, c) most assumptions start from a heliocentric view, d) I don't think God wants us to know all these things because it inflates our pride.