Have you noticed the light changing? It's the best thing about autumn. In midsummer, and even well into September, the sun bleaches everything in sight. The sky will be milky-white, rarely blue, even on a cloudless day. There's a hard, brassy shimmer to the air.
Come October, though, and the light softens. It starts to angle in, instead of pouring down. Walk out now any late, clear afternoon and the sun will be acting like a medieval illuminator, daintily gilding the scene, not blasting it like a fellow with a blowtorch. Welcome to the subtle season.
While the effect is magical, it is not magic, just plain old science, at work. As everyone will recall from their school days, the sun is higher in the sky in summer than it is in winter because Earth's rotation axis is tilted relative to the plane of its orbit. Starting at the autumnal equinox, the sun rides lower and lower in the sky, and its rays are spread over a larger area. In short, they slant. It's all just physics -- or maybe geometry, a trick of changing angles -- but the aesthetic effect could not be more striking. As any photographer can tell you, sideways light flatters most.