On an unpleasant summer day, the heat index often rises ... That visual evidence embraced vast expanses of blue sky, coexisting peacefully with fleets of white-topped clouds.

Mesmerizing footage captured this blue spiral in the night sky in Croatia from a SpaceX Falcon 9 rocket. The phenomenon was likely caused by frozen fuel from the second stage of the launch and could ...

Reservations will open soon for people who want to drive to the top of Mount Blue Sky in Colorado this summer. The seasonal roadway up to the top of the newly-renamed fourteener will not open ...

Of course, the sky is not always blue. And Rayleigh scattering also explains why the sky tends to be reddish when the sun is close to the horizon – at sunrise and sunset.