The kitchen as sundial

We notice that calibrated instruments are not always necessary.

These days, the first light of dawn coming in through the kitchen window hits the wall just to the left of the shelf with water glasses on it.  (This is in the apartment in the eighteenth-century house, where the window faces north.)  It doesn’t get to the globe, and won’t, because from now it’ll shine more and more to the right.  By the middle of hurricane season the refrigerator won’t get direct sunlight, and about the last time the air-conditioner is run the kitchen won’t see it at all.  After that, the next time the plants on the windowsill get to bask in sunlight will be about the time the first blossoms appear on the trees.

Of course all these points in time can be predicted with a little spherical trigonometry.  We have the textbooks with the formulas and can do it manually, if we need to.  If we’re feeling lazy, there are websites to do the calculations for us.  They’ll tell us the direction of the Sun as it first appears for any day of the year and any place on Earth.  If we’re willing to sacrifice exact accuracy, we can look up the time and bearing of sunrise for our region; it won’t change much from the nearest weather station to here.

But that wouldn’t be quite right.  Those figures assume a flat, uncluttered horizon and a person of nominal height; we’re two stories above the ground, and there are other houses around.  We’d have to get a theodolite or some such instrument and map out the actual shape of our horizon.  Then we would look up the solar declination, map it to dates (for a given year), and in the end have a table of various numbers.  (There are websites to do similar things for photographers who want to set up particular shots.)

Instead, we’re using our own observations and tying together things we see.  Yes, we’re aware of the solstices and equinoxes, useful signposts for a window that faces almost exactly north.  But instead of measuring a direction in degrees and a date on the calendar, we’re marking (for example) the season of direct sunlight on the shelf of glasses as an indication of the impending hurricane season.  This has two important features.  First, we avoid a deceptive sharpness about times and directions that are inherently rather fuzzy.  Second, we give a meaning to our own sky, the one we see.

What does your sky tell you?