I think its possible that when the big bang took place that matter/enegry at the outer edge of the unfolding expansion were subject to asymmetrical forces restricting outward expansion. Its radiation inwards lead to a separation with inner matter Also, this matter had a restraining influence on inner matter. This unfolding scenario would result in a dense outer shell of matter at some distance from the known universe, containing ourselves and the visible galaxies. The rate of expansion of the outer shell would slow down (as per the expectations of earlier astronomers). Our inner part of the universe is expanding, and, to the amazement of astronomers, it transpires that the expansion is actually accelerating! This acceleration is caused by the gravitational attraction on the known universe by the outer shell of matter, that would naturally through time, slow down, stop and then begin to collapse.
If you consider the conventional view of the universe with regard to the accelerating expansion. This leaves a lot to be explained and I am not aware of any such attempt so far. This view is only slight less flawed than my above explanation. It would seem to me that in the absence of some unexplained driving force causing this acceleration, that acceleration of massive matter could not take place in an ad hoc manner. The simplest explanation that occurs to me is that the universe is under the gravitational influence of matter further out. One could consider a universe coming about through the initiation that was the Big Bang, and we are now experiencing the more gradual "Big Pull".
Thinking of these matters is taking up too much of my time. One would expect comfort from a better understanding of what it taking place, but the reverse is so. I am thoroughly confused now and would like to abandon all of this and get back into the real world. I am off for a shower, a cup of coffee and will resume the fight against the credit crunch. Sorry for all that silliness