October 8. 7:51 a.m. I could use this tree as both calendar and clock.
I have just topped a small rise and the sun, now above the horizon, serves as perfectly-placed spotlight to project my image onto the trunk of this tree.
Others, too. The lane has a number of trees on the north side as I near Sam's house. My image projects on all of them in turn, flickering through a filmstrip of my morning walk. And yet given just the length of a lap (about 11 minutes) my shadow has swung farther right and merely clips the edges of the trees next time around.
So clock and calendar both. And yet, as they say for a real clock, "it's right twice a day even if it's not running", this solar time is correct twice a year. Another date, just after the spring equinox, my shadow would exactly line up again (though perhaps not at 7:51 a.m.). Could I tell that date in April from this one in October? I surely could if by doing no more than looking at the state of the tree's leaves.
For another look at this phenomenon, check out an earlier blog entry by clicking here.