This ebook stands at an intersection of science and art. From its origins, NASA has studied our planet in novel ways, using ingenious tools to study physical processes at work—from beneath the crust to the edge of the atmosphere. We look at it in macrocosm and microcosm, from the flow of one mountain stream to the flow of jet streams. Most of all, we look at Earth as a system, examining the cycles and processes—the water cycle, the carbon cycle, ocean circulation, the movement of heat—that interact and influence each other in a complex, dynamic dance across seasons and decades. We measure particles, gases, energy, and fluids moving in, on, and around Earth. And like artists, we study the light—how it bounces, reflects, refracts, and gets absorbed and changed. Understanding the light and the pictures it composes is no small feat, given the rivers of air and gas moving between our satellite eyes and the planet below.