Originally Posted by
Rafflesiac
It's how the universe avoids its heat death since the amount of energy in existence is finite. Treat history and all of its possibilities like a tree. It all comes out from a trunk, and each divergence in history, or worldline, is a new branch. Since energy is finite, every so often worldlines that don't have humanity survive or develop past the next 100 years are denied energy and eliminated a.k.a. pruned. These points of pruning are quantum time locks, key points in history that must happen as they generally do, and are what Goetia broke trying to undo history for his master plan.
I've undoubtedly missed a few nuances but that's the gist of it.