Of course (of course?) I thought of S and Z twist in yarn. Crazy, right?
But it got me thinking: does lightning always travel counter-clockwise when it strikes a tree? You know, sort of like the principle behind water in a drain: in the Northern Hemisphere, it always circles counter-clockwise. In the Southern Hemisphere it travels clockwise.
Well, on our walk the following day, I got my answer.
Z twist! Lightning traveled down THIS birch tree clockwise. So lightning spins both ways. And the trees are still standing.