Here is my theory on whats going on. (repost from an early thread).
Many religious people are becoming more accepting of a big bang because it matches their own genesis story closely with minor modifications.
The current scientific theory indicates from the repeatable evidence of Hubble's red shift phenomena, that all viewable galaxies appear to be expanding away from a central point in our universe. Extrapolating back in time, we get to the point, where all matter must have been in a single tiny place/volume, a singularity, which consequently exploded to give us our expanding universe ie the "Big Bang". Lets call this singularity the Alpha point. Yes there s a chance this is wrong and it was actually used as a football at Wembley Stadium, but most of the available evidence points to this rather large singularity back at our beginning.
It would be bit foolish to challenge this evidence, it is fairly strong. This leads us to 3 possible types of Universe. The first as initially proposed by Einstein and Hoyle was consistent with the historical concept that the universe was locked in a continually static state. In 1927, Georges Lemaître, a Belgian physicist and Roman Catholic priest, predicted that the recession of a nearby spiral nebulae was due to the expansion of the universe. Keep up the good work, Brother. Because of the red shift phenomena this static model has been demonstrated to be false. This leaves us with the remaining two possibilities.
It could be a continually expanding universe, in other words the gravitational attraction of the total universe is not enough to arrest the expansion, so the universe will expand add infinitum. The down side of this is that eventually the stars will run out of fuel, die and drift further and further apart until we end up with a dilute wide spread dead cold dark universe and that's that. It also implies the big bang was a one off event, very suspect (Who put it there? Where did it come from?)
The final choice is one where the universe expands rapidly initially but slows down under the influence of the universal gravity, eventually stopping and then collapses back on itself, to a tiny point again (lets call this the Omega Point). It is fully possible immediately following the collapse that this omega point becomes an alpha point which then immediately explodes again repeating the process in a new big bang and off we go again as a cyclic universe. (So our universal singularity is the alpha and the omega point. - PUN)
I concur with Einsteins later model, this final explanation seems most logical, as in nature, the simplest possibility is usually the correct mechanism. However many of my scientific colleagues have done some serious maths and physics concluding that from current observations there is not enough matter to produce the gravity needed to arrest the expansion and initialize a contraction. There is a short fall in the mass by about a half. Hence the current massive research into this hidden stuff called "Dark Matter". There is also the general assumption that time and the universe started uniquely at this "big bang" event and that nothing existed before this event, This is often based on the scientific comment that the physics gets a bit weird with these super particles so as we cannot observe them or anything prior we can therefore not demonstrate anything that would be acceptable scientifically as we have no evidence prior to the big bang. There may be nothing before the Big Bang or there may have been something that existed prior to the Big Bang, or possibly a God took it from Wembley Stadium and put it there.. again a probability but this time there is no evidence to support any of the hypothesis.
In terms of our current universe this is true, since it was born in this big bang, This does not mean that there was nothing before. It just says we don't have enough evidence yet to comment on anything before this period. I therefore would suggest one major possibility is the cyclic universe. It then relies on the relatively simple concept that it has always existed and will always continue to exist naturally, without having any super deity having to have whipped it up in his kitchen.
But I have just stated that my colleagues have proved this is not possible. The beauty of science. After testing of new ideas a hypothesis can be modified as many times as are necessary, gradually honing it, ultimately culminating with a match that is the truth.
OK what I am about to hypothesize is my own theory based on the knowledge I have gained in my 40 years as a scientist. The above calculations boil down to the simple GMm/R^2, ie the gravitational equation.
Now our old mate Einstien came up with another simple formula himself ie E=mc^2.
Lets do a quick substitution
E=mc^2
therefore
m=E/c^2
Now we have
GMm/R^2
Substitute m=E/c^2
(Gx(E/c^2)x(e/c^2))/R^2
=GEe/c^4R^2
Why have I substituted Mass for its energy equivalent?
Consider the Big Bang an explosive event packing a lot of energy. Whether immediately because of breach of the Schwartzchild radius equivalent or delayed due to the intense gravitational force, one of the first things to expand away at the speed of light from the "big bang" alpha point, is light itself, photons. If the Universe is 15 Billion years old then this would represent a sphere of 30 billion light years diameter at present. (Although its SN distance would calculated as a much greater distance.)Lets call this the photoshell. (have you ever watched footage of an old nuclear blast?). As the embryonic universe cools various Bosons and Fermions coalesce out of the chaotic maelstrom of very hot quark soup cools immediately after the big bang. This might have been 3 minutes or 300,000 years later (not important) matter and anti matter annihilate each other generating a large number of photons, and a small residual excess of matter.
As I wasn't actually there at the time, I will have to put my neck out a bit here. May I suggest that it started as basically a massive spherical explosion, with an initial central single very large detonation (read Impulse) radiating force outward. This seathing blob bang thing has huge inertia so a lot of the energy remains contained for a short time while it expands to accommodate being continuously blown outward and apart. The outer surface of the expanding cloud will be cooler than the inner zone allowing earlier condensation of quarks to hadrons and generating vast quantities of photons. Given conservation of momentum laws, the rate a particle will move away from an explosion (its Velocity) is inversely proportional to its mass. Thus given, all particles came under the influence of this explosive force almost simultaneously, assuming the same impulse (ie Force x time), then we could expect to see, a series of expanding shells where the outer ones consist of the lightest particles traveling a extremely high velocity (eg Leptons such as electrons) followed by succeeding shells of heavier slower particles, proton (Hydrogen) shell, neutron shell, alpha particle shell (Helium).... Uranium shell etc...etc. traveling away at slower speeds. It would be nice to see some these shells but they are probably so far away now we may never be able to observe them.
Would they emit any detectable radiation?
Larger coalesced objects were quasi-stable, exploding regularly until smaller lumps (Hadrons) that were more stable remained all moving outward from the force of the initial impulse. Now these particles all have measurable mass, are affected by gravity and the laws of conservation of momentum apply. Because of the difference in mass between our lightest particles eg electrons and the "mass less" photons (although one would think they must have some tiny mass because they are affected by gravity), there would be a huge distance between the outer Photo shell and the next inner Hadron shells the first of which will be the neutrino shells then the negative electron shell. Muons in close succession then a big gap to the positively charged inner Hadron layers of the Proton and neutron shells
Another interesting feature of this model, if I am correct so far, would be the presence of a larger outer negatively charged shell composed of lighter leptons such as electrons. Well within this shell will be the smaller heavier shell of protons this time with a positive charge. Given positive attracts negative one might ponder what interesting effects and interactions these two spatially separated charged spheres may initiate.
The whole point of this model is that it consists of a number of shells within shells, a bit like an onion. We as humans on earth reside within the inner most shells, the heaviest zone. So how can I prove all this? I am not sure I can at present, but as another hypothesis such as those by supernatural creator "anti-chance" theorists here. I believe it is as valid and probably has more thought process in it. Importantly it is not excluded by anything in physics.
But whats all this got to do with the universe contracting you say?
Continued Part 2....