I have just simple Knowledge, but recently a question came To my mind. An Entity Living in 2d Space cannot Directly Observe a sphere, but rather a Circle Changing its Size when a sphere is traversing trough the observable 2d plane. Similar, a 4d sphere would Appear To us as 3d sphere Changing its Size when traversing trough our observable 3d Space. What if Spacetime is a 4d sphere that we Observe as 3d Ball, but we are obviously Inside. Wouldnt it be Logical, that the Expansion of Space is just the geometrical property of this traversal?