Various molecules, atoms and particulates float around in the air, and these reflect light ... A decently dark site in a rural area has a sky background of about 21 mag/arcsec 2.

Of course the sky is dark at night ... talking cosmologically dark, however: the universe itself is in a state of being unlit. There are some sources of background light even then—distant ...

With no clouds and few lights, it moved steadily like a bright little star across the dark ... The short wavelength blue light of LEDs bounces around more in the sky, intensifying the brightness ...

Look up on a clear sunny day and you will see a blue ... sky, it is obviously dark, but it isn’t perfectly black. Yes, there are the stars, but the night sky itself glows. This isn’t light ...

Handzel is San Diego County chapter vice president of the International Dark Sky Association and lives ... American Medical Association’s 2016 blue light guidance which concluded lighting ...