A huge reservoir of oxygen atoms (and to a minor extent nitrogen atoms) is present in the upper atmosphere, extending upward from about 100 kilometers. This abundance of atoms would be sufficient for substantial illumination of the night sky if appropriate reactions could be found. In the pressure region of 1 millimeter to an atmosphere, the 2-body collision reactions yielding light play a minor role. At pressures substantially below one millimeter, these reactions become dominant and may be the answer for this problem. A series of reactions, including nitrogen and sulfur compounds, the resulting light emission, and related problems are discussed.