Why Is The Night Sky Turning Red?

The idea of a red sky at night used to invoke beautiful images of vibrant sunsets, the product of warm sunlight bathing the sky near the horizon. The adage of 'red sky at night, sailor's delight' refers to a calm night ahead; a red sunset suggests a high-pressure system in the west is bringing calm weather.

But red skies at night have taken on a new meaning in recent decades. As outdoor lighting become increasingly prominent, our night skies are gradually turning from black to red.