Showing posts with label Twilight. Show all posts
Showing posts with label Twilight. Show all posts

Twilight

After sunset, until the Sun is roughly 18° below the horizon, the Earth's atmosphere is illuminated. Its duration is determined by the time it takes the Sun to travel this distance. At the Equator, this takes roughly an hour at any time of year, although it takes significantly longer during the summer. The gap lengthens in the summer and shortens in the winter when one gets beyond 40° N. latitude.