Even casual sky watchers must be noticing that the Sun is staying low in the sky all day, and that it is rising and setting way in the south. I looked down this morning and spotted a sign that the Winter Solstice is approaching in just over two weeks.
An area of permafrost has formed on my deck, leftover from Monday’s blizzard that dumped nearly 1/32″ of snow in Seattle. Most of the ice is gone, except for an area in the shadow of the fence, an area that isn’t getting any direct sunlight this time of year.
Here’s where your high school geometry comes into play. The south fence is about six feet tall, and yet the shadow it is casting stretches for about 14 feet to the edge of the unmelted, unevaporated ice. A few calculations reveal that the Sun is getting less than 20 degrees above our local horizon to cast a shadow that long.
OK, I admit I just looked that up in my planetarium software, but if I remembered all of those triangle formulae I could have figured it out! Suffice to say the Sun is low in the sky, and winter is upon us.
This is one of many reasons that tomato plants prefer summer to winter. The garden bed in which our tomatoes were planted this year lies entirely inside this shadow area and is getting no Sun at all. This being Seattle, it doesn’t get so much Sun in the summer, either, but that’s another story.
You can use your astronomical knowledge anywhere! What signs have you spotted that the solstice is approaching?