If you're in high latitudes, step outside on a clear summer night around twilight and look up. If you're lucky – and increasingly, you might be – you'll witness one of nature's most ethereal displays: noctilucent clouds. These delicate, ghostly streaks of silver and blue seem to shimmer against the darkening sky, appearing almost otherworldly…Read more Noctilucent Clouds – Ethereal Indicators of a Changing Atmosphere