orbital

There is no good way to show that Earth was never flat... perhaps our beliefs have retroactively changed the past, and there existed an actual time when Earth was flat?

Kant's epistemological model speaks of noumena and phenomena. The phenomenal world is how the world appears to us, whilst the noumenal world is what the world actually is. We know nothing of the noumenal world, save that it exists, it is what we perceive, and that logically generable properties and similarly trivial properties apply to it. Given this framework for reality, it is entirely possible that our scientific observations (the laws of physics are but exercises in mathematics and pattern recognition) do not always accurately approximate the real world.

Having said that, I do believe that certain things are not contingent upon the veridical nature of the noumenal world. One plus one is always two, for instance. (If you are tempted to raise a counterexample featuring a different number base, don't. You know what I mean here.) Basic axioms, and statements that may be derived from them, are necessarily true. Whilst the laws of physics can differ between theoretical realities due to varying physical constants, mathematics remains invariant across the spectrum of alternate universes.

The veracity of axioms and their logical progeny, then, always exists regardless of belief.