Light Pollution
Written by Jean Tate
Polluted rivers, lakes and oceans; air pollution; even noise pollution … but what on Earth is light pollution?!? Well, when there's too much unwanted light, it pollutes the dark … sky, that is.
If you could get in a time machine and go back to a time before our ancestors left Africa, and if you could look down on the Earth at night then, what would you see? Apart from aurorae, around one or both poles, and the occasional forest fire and volcano (if you were lucky), nothing … the Earth would be completely dark (OK, only if you ignored the light reflected back from the Moon, and the very faint bioluminescence in the seas).
Compare that to today (see above)!
If you live in, or near, a big city – any big city – the night sky is dull, dishwater dull (even when there are no clouds and no Moon). If you live far from any cities, towns, or villages, a clear, moonless night is one of nature's greatest delights. The difference is light pollution.
Now if the Earth had no atmosphere it wouldn't matter all that much (well, apart from the fact that there'd be no life!), but the atmosphere (and clouds) scatters and reflects light (after all, that's what makes the sky blue, or white).
Of course, some lights at night are good, even essential … but an awful lot of those lights are sheer waste. For example, street lights which shine in all directions, even up … all the light which doesn't end up illuminating the street (or footpath) is simply wasted (and pollutes the night sky).
Lots of people are trying to do something to reduce light pollution, for example the Dark Sky Association. And you can help measure it, by joining G.L.O.B.E. (Global Learning and Observations to Benefit the Environment) at Night.
Measure Light Pollution and Help Save Our Dark Skies, Prescription for Light Pollution, A Day for Earth, but a Whole Week for Dark Skies, and Astrophoto: Star Trails over Namibia by Josch Hambsch, just some of the Universe Today stories on light pollution.
Hear more by listening to the Astronomy Cast episode Dark Skies.
Filed under: Astronomy
Related stories on Universe Today
- Pictures of Pollution
- Prescription For Light Pollution
- Help Map Our Dark Skies
- Where's Spirit Now?
- Measure Light Pollution and Help Save Our Dark Skies
