bold added to make point. Even if we see the universe/membrane expanding at luminal speed, because of the geometry, we could only see 1/4 of the universe from any given) point. it is the question of the ratios. In the time sliced sausage model, the ratios are not right. Should not the ratio of distance from the BB and the radius of each space slice be equal? Time goes on the x axis that is right, the slice (space) has expanded, that is right, but the expansion of slice should equal the movement through time, so should the radius of the slab not be equal to the distance from the beginning, particularly if the expansion of space is independent, even beyond the speed limit of c, the max movement of any energy, matter in it? In the Expanding Sphere Membrane model, even 3/4 of the universe that would have expanded at less than the speed of light would not be accessible. (for somebody fixed in one position in the universe, membrane). travel to see more. If time is infinite, but space is not, are we paying enough attention to it? should we look seriously at models that picture time more prominently ?