No idea is a bit strong - we understand quite a lot about it. But not everything by a long shot.

We believe we understand a lot about it, but we're not - yet? - absolutely certain.

That is, once we get to the end, then and only then will we be certain of what it took to get there.

Yes, no idea isn't accurate. We've got ideas. We just can't say the ideas are correct.

There are layers of explanations needed. The typical explanation is inertia, but there is the question of what causes inertia and what causes whatever causes inertia and so on. There are always going to be new questions.