The true nature of this planet can change whether we observe it or not.

It's not that earth is a globe is that space and time warp around mass, giving the illusion of gravity, and thus the illusion of it being a globe.


So the earth is flat when you're on earth, because you are within its spacetime.

Earth is a globe, when you get far enough to observe it being a globe, because you are observing it from outside of the spacetime of earth. That's why you can see lighthouses on a clear day from over a hundred miles away even though the curvature of earth should block it.

Same thing with other planets. When you're on Mars mars is flat. Because you are within it's spacetime.

Existence bends around mass.