The Sahara can produce optical effects that can be seen for hundreds of miles. For example, at sunset the rays of the sun can bounce off the sands and be refracted in the form of a horizontal rainbow. Hundreds of miles to the east, when viewed from the cruising altitude of jet airliners the blackness of the uninhabited surface of the earth is mirrored with the blackness of the night sky, and suspended between them is a horizontal band of refracted light like a brilliant multicolored ribbon.