Hi, new. Welcome to A2K.
Here's my two cents on the matter: what will happen to the world in a million years, or a thousand years, or even tomorrow is irrelevant to today. One reason it's irrelevant is because, to a large extent, it's beyond our control. I can do nothing about a tsunami in the Indian Ocean, let alone a comet zipping its way here to put a new ocean the size of the Pacific right into the middle of what right now is the USA. It doesn't matter. What matters is how I live my life today because today is all I have.
I love physics, astronomy, archeology, history and all other studies of my environment. But they are all academic. All that they have to do with me is to increase my knowledge, not necessarily my understanding. I know a lot; in fact, I understand very little. To cite Aristotle, everything has a begining, a middle and an end. Through our studies we try to discover what the beginings were. Wee're pretty good at that but not so good at making exact predictions about the end.
The start or the end of the known universe is not my responibility. Living my life as well as I can today is. Which reminds me -- I have to start thinking about dinner.