Explanation: Why would the sky still glow after sunset? Besides stars and the band of our Milky Way galaxy, the sky might glow because it contains either noctilucent clouds or aurora. Rare individually, both are visible in the above time lapse movie taken over Caithness, Scotland, UK taken during a single night earlier this month. First noted in 1885, many noctilucent clouds are known to correlate with atmospheric meteor trails, although details and the origins of others remain a topic of research. These meandering bright filaments of sunlight-reflecting ice crystals are the highest clouds in the Earth's atmosphere. The above...