'Tis a matter of perception, is it not?

When perceiving only two dimensions, th'Earth appears as a disc. When perceiving only three dimensions, it appears as a sphere. When perceiving only four dimensions, it appears as a hypersphere; and so on and so forth.

When perceiving only two dimensions whilst looking at the full Moon, it is very clear to see exactly where its edge is.

To perceive the Earth as a hypersphere, is to see that th'Earth is growing.