The reason we don't know is that we live by faith and belief. In other words, we are religious beings, and live religious lives.
Some of us trust God, so we know by faith. No big crunch. No big bang. Destruction of this universe soon. But loss of this universe to all of us when we die.
Do you think faith is a reliable way to discover what is true and what is false?
Have you examined all the principles and application of all - or at least most - science? Or do you have faith in scientists and the media, that they are telling you the truth?