For millennia, on every clear night, humans have wondered at the awe-inspiring spectacle of the starry heavens, traversed by the Milky Way and adorned by shifting planets, speeding meteors and the ghostly curtains of the aurora. Nature's grandest free show leads us to consider our place in the great scheme. It has permeated our religions and cultures, and has inspired artistic achievement and scientific endeavour. The starry sky is, unofficially but undeniably, a site of special scientific interest, and an area of outstanding natural beauty. Ill-directed artificial light has quietly stolen it away from many people in the developed world.
Orion and Taurus struggle to be seen against urban skyglow (image: Bob Mizon)
Light carelessly or sometimes deliberately shone into the sky veils the stars. Upward light (especially travelling at low angles) from poorly designed lamps is scattered and reflected in the atmosphere and returns to our eyes – so paradoxically it is light coming downwards that causes skyglow! The glow from a distant town will colour the sky for an observer tens of kilometres away. It is almost never the deliberate intention of the owners of the lights to illuminate beyond the boundaries of their premises. The enormous amount of wasted light we see around us is the product of ignorance as well as of poorly designed luminaires.
The sad irony behind light pollution is that, while trying to ensure a more welcoming and easier outdoor night-time environment through lighting technology, we often lose sight of the near and far universe revealed to us in more and more detail almost daily by technologies of another kind: those of spacecraft and imaging. A virtual-reality mask is replacing our real experience of the night sky.
The light from distant stars and galaxies takes hundreds, thousands, even millions of years to reach us – what a tragedy to lose it in the last millisecond of its journey!