night for several hours, residents of the city have seen a strange glow in the sky. Clouds iridescent bluish-white light. According to witnesses, was similar to that clouds reflect light, but its sources remain unclear. But tonight month in the sky was very bright, and it is possible that its light city residents took for "Northern Lights." There is another version of what happened. It is science, as some Internet users. What they saw Chelyabinsk nothing more than a noctilucent clouds. These are the highest clouds in the Earth's atmosphere, formed in the mesosphere at an altitude of about 85 km, and are visible only when illuminated by the sun over the horizon, while the lower layers of the atmosphere are in the Earth's shadow. During the day, these clouds can not be seen.