But vision works differently. Arab scholar Abu Ali al-Hasan Ibn Al-Haitham (965–1040) correctly proposed that the eye receives radiation emitted by other sources; some of the radiation travels straight to the eye, which makes the source visible, and some of the radiation reaches the eye after bouncing off objects that do not otherwise emit radiation, which is how these objects become visible. The major source of this radiation, called light, is the Sun. Light is the messenger of vision, and the eye is tuned to detect it.
