Jeannine and I went out on cross-country skis yesterday, taking advantage of some sunny conditions and the recent snowfall. The snow wasn't that great for skiing, as there were only a few inches and in places the snow had barely covered the grass, but we had fun sliding and tromping around.
While out in a field by our house, I noticed something curious, something I don't recall having seen before. There were perfect arcs drawn in the snow, with no human footprints anywhere nearby.
It only took a moment to realize what had happened -- the snowstorm of several days previous had been accompanied by brisk and blustery winds. The winds had pressed some of the taller weeds down and then pushed them back and forth, pivoting them on their stems, allowing the tops of the plants to scrape away snow.
Not much of a mystery, really, but it was interesting to look at... one more example of geometry seen in nature. -- PL