Hessdalen lights

The Hessdalen lights are unidentified lights that have been observed periodically since at least the 1930s along a roughly twelve kilometer stretch of the Hessdalen valley in rural central Norway. They appear both day and night, typically as white, yellow or red lights, and have been reported moving at extreme speed or, at other times, hovering or swaying gently. Proposed explanations include an incompletely understood combustion of airborne dust from historical mining in the area, dusty plasma formed by ionized air and radon decay products, and piezoelectric effects generated by strain in the valley's quartz rich rock, though no single explanation has been confirmed.