Scientists have solved a centuries-old mystery of “bright nights” – an unusual glow that appears in the sky after dark and lets observers see distant mountains.
Researchers suggest that when waves in the upper atmosphere converge over specific locations on Earth, it amplifies naturally occurring airglow, a faint light in the night sky that often appears green due to the activities of atoms of oxygen in the high atmosphere.Normally, people do not notice airglow, but on bright nights it can become visible to the naked eye, producing the unexplained glow detailed in historical observations.
Historical accounts of bright nights go back centuries. European newspapers and the scientific literature also carried observations of these events in 1783, 1908 and 1916.Bright nights do exist, and they’re part of the variability of airglow that can be observed with satellite instruments.Modern observations of bright nights from Earth are practically nonexistent light pollution. Even devoted airglow researchers have never seen a true bright night.