While I've understood that some moments in history are more important than others I've never been able to understand how historians determine which events are the most important.
I know it's a rule to not discuss politics within the past 20 years, but are historians today aware of which current events are going to be the most impactful on human history, or does it require a certain period of separation to recognize what was the most important?
Good question. If I had to break it down and keep it as short and simple as I can: I'd go about it in two different ways, starting at the same point.
The question is: Does the moment make a difference, and how big is this difference.
Does this moment make a difference for the contemporaries; e.g. the fall of the Berlin wall, the end of a (modern) war, the death or stepping down of an important and long reigning ruler etc. for a lot of the people of the time this may be a momentus change, a change that seems to them to make a difference in their collective lives, do they see everything/ a lot changing and attribute ist to said moment/event. They may be wrong in their assessment, e.g. the idea of some that after the Fall of the Berlin Wall and the following Ending of the Cold War the US-Russia duality and animosity will end and we will have peace at last... that didn't hold up but for the people at the time this may have been an important thing when looking at the world as well as for personal and political decision making.
Does this moment make a difference structurally, or does said moment change something, which at the time may be too small or hard to see but looking back was fundamental. E.g. the invention of the printing press; the nailing of the thesis during the Reformation, as well as gradual changes that are difficult to tie to a moment a point in time the rise of capitalism or the abolishment movement etc. It may not have been apparent and may not have made a large enough difference at first as things didn't really seem to change massively for most people at first before over time (and how long this is may of course vary) it turns out that it made a massive difference for the following years and decades. The Reformation is at first just a theological discussion as the Church had seen a lot with varying results (mostly the death of or recasting by the uppity party) nobody/or at least very few people would have seen the theological split of the denominations coming. So looking back this was (also made to be as such) an important historical event/moment but at the time that importance was not seen... Same for the role of printing, it seemed like a interesting idea at first, but actually changed the world like almost nothing else!
So in conclusion: is it part of a fundamental change (or is it a symbol of such a change) and/ or was it seen as such by enough contemporaries to make that difference not (just) in the event itself but also in the reaction to it.