Many cultures ascribed strong religious qualities to Earth's sky, believing it to be the home of the heavens and various deities. Among the Chinese, in certain situations, sky means god. For example, people may say "They became friends after several fights: this is the idea of the sky" or "Why does the sky always fool me?" Some religion and art historians believe that in Christianity, in particular, the connection between heaven and sky arose because of a medieval painting technique, where different places were drawn separately on the same picture. Heaven, a different and more important world, was usually painted above the earthly world and was separated from it by clouds.
Tomorrow I'll post some heavenly photos. ;)