Day 351: Vapour trails

No, not the Rush album - real vapour trails, in the sky :-) I was out trying to get a good picture of something else when I noticed this vapour trail. At first it was two bright white and parallel straight lines, but it quickly began to break up into a wonderful wavy pattern. I've seen helical vapour trails before, and I wonder if the shorter wavelength ripples are like that. Within a minute of taking this shot they'd disappeared completely.

Like a vapour trail...