All the data we have at this point says that the universe that is just under 13 billion years old. The universe exploded from a big bang and after a brief period of inflation, it has been expanding steadily at the speed of light. Although there are still some unanswered details, most cosmologists agree on these basic points. From here, however, there are numerous opinions and conflicting theories on the basic nature of the universe.
There are a few different mathematical models that show it’s possible that we can be living in an “open” universe which will continue to exponentially expand forever, a “flat” universe where the expansion will slow down and eventually stop at a certain size, or a “closed” universe that will reverse direction and eventually contract into a “big crunch” – presumably to explode again in another big bang (and with multiple series of “big bang/big crunch” cycles, we have an “oscillating universe”). While all of these are mathematically feasible (and yes, I’m leaving out a few other good theories), the current data strongly suggests that we are in the “open” model, where the universe will continue to expand forever, until all the stars burn through their remaining fuel and all that’s left is ashes and space dust.
Of course, there are many unanswered questions – such as, More...