Where the Blue Begins

Orthodox theories of light say that the sky is blue overhead because the sun's rays are sorted out by the atmosphere, and the shorter waves (the blue ones) get through. At sunrise and sunset the rays must struggle through the thicker and denser atmosphere at the horizon, and the long red rays only can penetrate to our sight.

Now Professor Vigard, of the University of Christiania, Norway, claims he has discovered another and better reason. Just outside the earth's atmosphere, he says, is a wall of crystalline particles of nitrogen. This is what makes the sky blue. It also explains, he thinks, why radio waves follow the contour of the earth, instead of flying off from it at a tangent. This would seem to indicate that radio communication with other planets will always be impossible.