Originally Posted by Steve Limpus

As I understand it, yes, the 'shape' of space could be spherical, but so large as to appear flat over that portion of the universe we can observe. (I believe the observations are that the universe is flat within 2% margin of error.)

But... the 'sphere' is a two dimensional analogy of our three dimensional space. Try to think not of the whole sphere (its volume), rather just it's surface. Then try to extrapolate that two dimemsional spherical surface shape to higher dimensions, three, four, more.

Don't worry you can't. No one can. Even the experts can't visualise that 2d sphere surface in higher dimensions, they use mathematics instead.

Once you're ok with that, you can see that our real 3d space isn't the crust of a large hollow sphere. And it isn't necesarily a sphere. Maybe a cube, donut, soccer ball etc.