It’s easier to say that when the universe was young everything was greatly denser. We look at a scattered embryos or cosmic egg galactic size mass or single big bang it all comes to the same point and area. After the super nova the left over debris scattered in a repulsive area bubble pushed outwards than inwards after the explosion finished peeking. The boiling hot debris pushed back together not because of its physical mass but because it warped and pushed against the repulsive fabric – thus after the peek it subsided and slowly attracted back together in a erotic formation. Hot young planets stars and scattered groupies.
There does not have to be a big bang to have a universe. Galaxies are scattered all over the expansion of the bubble. The Quanta Physics Theory this an alternative belief and universe origin The Popcorn Universe Theory. The galaxies are scattered because they were formed independently in what might be assumed smaller little galactic bangs. The pressure of the expanding balloon is considered round shaped because liquid or gaseous pressure flows that comes to exist in a vacuum media outside the balloon needs not have to exist a liquid or anything emptiness’ is a valid word and definition for the realm of space. The bubble can be filled and still filling with air. Such phenomenon does exist in nature.
Outside this bubble of inflation exist the debris from a hot thermo explosion that through its process formed solid heated elements that make up nature. What causes this debris to expand is the inflation of the balloon. If the existing realm outside the bubble besides planetary debris it will cling towards the bubble surface acting as the only existing momentum infinity. If the space outside the bubble inflation is truly empty retaining a zero volume pressure not in the bubble the inflation of the bubble pushes outwards assuming the planet debris inwards towards into it. Enough pressure in a zero point empty vacuum of empty space would cause a surface tension curvature on the grid surface.
It is the bubble that retains a volume pressure force pushing outwards allowing the deception of matter putting tension of the balloon surface grid. In lure of all this the space outside the bubble has zero volume is the reason its instantaneous towards force. Lack the volume pressure outside the bubble Force (F) = p (propulsion capacity).