The Big Bang model of the universe is a theory brimming with difficulties – I mean difficulties beyond the obvious, “where did all the matter come from” and “what caused it to begin expanding.” The problems I'm talking about are a little less obvious but still very substantial. Please note too that these aren't my objections to the theory. These are objections raised by secular scientists and discussed in this Wiki article.
The Horizon Problem: If we looked toward the eastern sky, we could see galaxies that are estimated to be 10 billion light years away. We could see the same thing in the western sky. So if one galaxy is 10 billion light years away in one direction and another is 10 billion light years in the other, then they would be 20 billion light years apart from each other. Are you with me so far? OK. Now, secular scientists date the universe to be around 13.8 billion years old. Assuming that is true, the light from the “eastern” most region of space has not had enough time to reach the “western” region. Even though we can see both ends, they should not be able to see each other because their light could not have traveled the 20 billion light years of distance between them in only 13.8 billion years. Are you still with me? OK. Here is the problem: everywhere we look, the universe appears to be homogenous.
If I dropped an ice cube into hot water, the cube would melt and the water would cool a little. Eventually, it all becomes the same temperature. That's homogeneity and it always happens eventually once the two things begin to interact. It seems to have already happened in the cosmos. The cosmic background microwave radiation, for example is the nearly the same everywhere we look. But how could the entire universe have evened out so uniformly if all the regions have not had enough time to interact?
The Flatness Problem: Matter produces gravity. Objects in motion have kinetic energy. When the supposed Big Bang happened, matter began to expand. Once the expansion began, kinetic energy would have carried the matter forward while gravity would have been slowing the expansion. Let me see if I can explain it in lay terms.
If the rate of expansion were too slow, gravity would have quickly pulled everything back into a Big Crunch. If the expansion were too rapid, the matter would have accelerated too quickly for stars to form. From the very beginning there must have been a perfect balance, a “fine tuning,” between the expansion and the slowing or else the universe could not exist as it is now. The precise balance of 1 is represented by the value Ω. The margin is so narrow as to be incredible. This illustration helps visualize a too fast or too slow expansion.
Missing Magnetic-monopoles: The Big Bang would have been a hot event, or so I'm told. Such an event should have produced magnetic-monopoles (a magnet with only one pole). Now, I confess the physics behind this prediction is a little beyond my understanding. Monopoles themselves sound a little “exotic” to me and when we consider that we've never observed such a thing, I'm not sure why anyone would predict there should be many of them. But the fact that there haven't been any found sure has cosmologists concerned. Failed predictions are usually evidence against a theory and the fact that the Big Bang predicts magnetic-monopoles yet none have been found should raise more than a few eyebrows. Nevertheless, scientists confidently stand by their model and seek a new theory that explains this lack of evidence!
Enter now Inflation cosmology! To help smooth out some of these serious difficulties in the Big Bang model, it was suggested in the 1980s that in the very early seconds after the initial expansion, the universe when through short period of hyper-expansion where it figuratively exploded from about the size of a grape to trillions of miles across in just a fraction of a second. They say such an event would solve a few difficulties.
First, they suppose that the homogeneity we observe occurred prior to the hyper-expansion, while all of space was still close together. When inflation occurred, it carried the homogeneity out with it.
Concerning the flatness problem, the inflation supposedly forced the value of Ω to that fine-tuned balance of 1. One web site compares it to a how a balloon smooths out as it inflates. I'm not sure how well the analogy describes the solution but, as the article says, most cosmologists are satisfied with it.
Lastly, cosmologists use inflation to solve the missing magnetic-monopoles problem. According to them, inflation was not only a rapid event, it was a cooled event. That is, as the inflation began, the super hot Big Bang cooled during the inflation epoch by about 100,000 times to just under the temperature where the monopoles would form. How convenient.
So what is the evidence for all of this? We'll, it's pretty much like the evidence for Oort cloud – they simply need it for their theory to be viable. It's a sort of fudge factor to get around some of the serious difficulties they know exist with the Big Bang. What caused inflation? They don't know. What stopped the inflation? They don't know. Why was it cool? They don't know. How did it reheat? They don't know. Actually, the idea of inflation is even less credible than the Oort cloud. In the case of the Oort cloud, at least we know that icy bodies exist in the universe. We've never seen an event like the inflation epoch and there's nothing in physics that would otherwise suggest such an event could or should occur.
I think scientists have become numb to what's credible. After all, once you accept the idea that all the universe could literally poof into existence out of nothing, then why couldn't there also be an imaginary event like inflation that immediately followed it? Once again, this isn't a case of going where the evidence leads. They know the Big Bang happened in spite of all its difficulties. Even the most serious problems with the theory could never cause them to even question it. Rather, it would only spur them to become more and more creative in explaining how it happened regardless. How could the Big Bang ever be disproved if scientists are allowed to invent exotic theories to explain away any objection?