" The Uncertainty Principle states that you can know where a particle is, or you can know where it's going, but you can't know both at the same time. The same, it turns out, is true of people. And when you try, when you look too closely, you get the Observer Effect. By trying to work out what's going on, you're interfering with destiny. A particle can be in two places at once. A particle can interfere with its own past. It can have multiple futures, and multiple pasts. The universe is complicated. "

― Harriet Reuter Hapgood , The Square Root of Summer