Astronomy Picture of the Day

Mammatus Clouds Over Olympic Valley Credit & License: Matt Saal (Wikipedia) Explanation: What's happened to these clouds? Normal cloud bottoms are flat because moist warm air that rises and cools will condense into water droplets at a very specific temperature, which usually corresponds to a very specific height. After water droplets form that air becomes an opaque cloud. Under some conditions, however, cloud pockets can develop that contain large droplets of ... Full Story