Why is the sky blue? Parents don't know what to say when their children ask. Why the Sky Is Blue answers this ancient and surprisingly complex question in a more entertaining and accessible way than ever before. Götz Hoeppe takes the reader on a historical and scientific journey to show the various ways people in different times and places have explained why the sky looks blue. The richly illustrated story begins with ancient myths and philosophy and ends with the cutting-edge science of optics, statistical physics, and ozone depletion. Most importantly, it is the story of how scientists discovered that the sky's blue depends on life on Earth and the makeup of our planet's ozone layer. Without microbial life's impact on the composition of the atmosphere, the clear daytime sky would probably lack its distinctive color. And without the ozone, the twilight sky's color would also be very different--not the sapphire tone of l'heure bleue, but rather a yellowish or greenish hue. Why the Sky Is Blue shows that skylight can be viewed from a surprising variety of vantage points. We learn how our physiology and cognitive capacities govern our perception of the sky's color. And we discover why this everyday experience has been such a source of fascination and controversy over the centuries. Delightful and intriguing, Why the Sky Is Blue shows how the attempt to answer this age-old and deceptively simple question only enhances the magic of the blue sky we see above us.