You might as well say: "What we perceive the earth to be made of rock, but it's actually made of whipped cream outside of that perception?" The shape of the ea

You might as well say: "What we perceive the earth to be made of rock, but it's actually made of whipped cream outside of that perception?" The shape of the earth has innumerable physical consequences, all of which we observe and measure to be consistent with it being approximately spherical. If you want to say that it behaves in every observable way like a sphere, but somehow is "really" flat, then the definition of "reality" you're using is not a very useful one.