There is space between the orbiting electrons and the central nucleus of protons and neutrons. There is space between one atom and the next. There is space between one solid body of atoms and the next solid body like two apples, for example. There is space wherever an area sufficiently occupied by atoms or by the particles of atoms that anything in between can be said to be subject to their electromagnetic influences. Thus space is not the emptiness inside the expanding balloon, nor is it that into which the expanding balloon is steadily encroaching by its enlargement outward.
Space is strictly the film of the balloon itself.
It therefore has a finite depth which is the thickness of the shell, but an object can move indefinitely through it by go round and round. Thus arises the concept of a space which is curved. It is apparent that the rate of expansion is so great even now that galaxies diametrically opposite each other in this vast shell are already flying apart at speeds approaching the speed of light. By all present standards of measurement, the universe is indeed growing old. If the picture which we have presented of the universe as being the film of a bubble or the shell of a balloon is valid, what better descriptive phrase could one possibly apply to the necessary consequence which would follow if God suddenly withdrew the energy by which He sustains it all, than that it would fold up like a garment.