My co-worker Eitan noted today at lunch a difference between living close to the equator and close to the pole (in a relative sense; Seattle is not really all that far north): Near the equator, one notices the rotation of the Earth; near the pole, one notices the revolution of the Earth around the Sun.

To unpack this statement slightly: near the equator, the sun’s track through the sky remains relatively constant, as do the lengths of night and day and the climate. Nearer to the pole, the sun’s track moves dramatically over the course of the year, the lengths of night and day shift quite a bit, and the climate develops seasons. (Of course these have to do also with the Earth’s tilt, and it’s the combination of tilt and revolution that cause these effects, but Eitan’s formulation is more poetic and compact.)

One of the great pleasures of living in Seattle has been for me climbing onto the roof of my building (sssh, don’t tell my landlord!) and watching the Sun set over Elliott Bay; one of the ancillary pleasures has been watching the seasons change, based on how far north or south the Sun is at sunset. It’s an elegant and satisfying demonstration of astronomical principles.