"The light that is wasted upwards reflects off the atmosphere, causing the smog that hangs over all major cities at night (this smog is usually yellow thanks to ill-designed sodium street-lights) . The iris in your eye shrinks over the lens to stop this back-scattered light (the smog) from blinding you - but that also prevents you from seeing fainter stars. If you get far away from any light pollution, the pupil is allowed to expand to its maximum, letting as much light in as possible - and this allows you to see many more stars, including the beautiful disk of the galaxy in which we live stretching overhead."

~ Campaign for Dark Skies

England, Scotland & Wales 2009