The big bang is not still going on in the sense of rapid expansion that it would have had. It's pretty much drawing the line to say the big bang ended about when the universe became transparent, but that's just what I consider it. The universe IS expanding, though, and I'm pretty sure science is doing research to figure out whether or not there's going to be infinite expansion or a Big Crunch (that's what it's called).
I'd like to add that we don't know what started the big bang, or if the universe is infinite. Just because we don't know something doesn't mean we need to fill the gaps with bullstuff and then defend the bullstuff when we have a real, scientific explanation. Here's an example.
People don't know how diversity of life happened -> They create a god or supernatural being to explain it -> All's well until science comes up with an explanation (evolution) -> It's far from the time the god was invented and it's now being taken 100% literally -> People defend their beliefs that were originally founded to explain an unknown phenomenon.
So don't defend creationism, it's just an old explanation for how life was created. Leave the fact discovering to science, and get rid of the arrogant belief that humans know the answers to these questions already. No matter how hard you defend your precious god and your beautifully flawed creationism, evolution and atheistic beliefs are going to be the acceptable norm one day, and you or your descendants will realize just how foolish you are.
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