See my post "SOLUTION" earlier.
OK - so the cosmos is the thin layer of a 'sphere'. Two people have set off in opposite directions and met up again on the other side of this sphere. This is why big-bang radiation is detectable in all parts of the sky, as "all roads lead to the big-bang" so to speak (similar to "all roads from the north pole lead to the south pole")
A sphere must have a diameter, and a core.
What's at the core?
If the sphere of the cosmos is like the expanding skin of a ballon - or better yet, the outer skin of an onion, the deeper layers of this onion represent the same cosmos, but at earlier periods in time. The core of this onion represents the beginning of time, and the beginning of the cosmos. At the core is all matter, but concentrated in one point at the starting point of time itself. Descending through the onion layers of the cosmos to its core and the big bang is only possible if you have a time machine.
when you look at the radiation from the big bang - you're looking at the very deepest layers of this 'onion', where it's 'diameter' is extremely short and its age extremely young.
So - if the cosmos is expanding and everything is moving away from everytjhing else as it expands, then the driving force of this expansion is time.
There is NOTHING at the core of our expanding universe, nothing to arrest the expansion - unless - that is - gravity can reach out across time as it does across space.
So how can it all collapse again without reversing time?
Hope I've made myself understood here? LOL