“Some crows are perfectly still and have their heads tucked into their breast,” Granger says. “Some crows don’t have their ...

Astronomical twilight is the transition to fully dark skies, when the sun is between 12 and 18 degrees below the horizon. Volcanic activity at Anak Krakatoa ("Child of Krakatoa") in Indonesia.

The best time to view Venus illuminating the sky is during the twilight hours while looking to the west. Astronomical twilight begins in the morning or ends in the evening when the sun's ...