The Heavens and the Earth
Rudolf Kippenhahn on how astronomy has altered our vision of the universe - from 10th-century Cairo to the Big Bang.
The astronomer Ibn Yunus had waited for over an hour until the first stars could be recognised in the evening twilight. The reddish Arcturus now shone over the city of Cairo. In the east, the moon had appeared over the horizon. In the west, Mercury and Venus were less than the breadth of a full moon apart in the twilight. Ibn Yunus had watched how they approached each other every evening for the past week. Now he seized the astrolabe to determine the separation between them.