Have you seen the Milky Way lately?

SYDNEY: Light pollution has caused one-fifth of the world's population – mostly in Europe, Britain and the U.S. – to lose their ability to see the Milky Way in the night sky.
"The arc of the Milky Way seen from a truly dark location is part of our planet's natural heritage," said Connie Walker, and astronomer from the U.S. National Optical Astronomy Observatory in Tucson, Arizona.
Yet "more than one fifth of the world population, two thirds of the U.S. population and one half of the European Union population have already lost naked eye visibility of the Milky Way."
Star-free night
The phenomenon, caused by the reflection of manmade light by the Earth's atmosphere, impacts astronomical research and can even affect human health, warned Walker, who will present her research on Wednesday at a meeting of the American Astronomical Society in Pasadena, California.
One study of 147 Israeli communities, published in 2008 in the journal Chronobiology International, found an increased risk of breast cancer for women living in areas with the most light pollution. This is thought to be due to unnatural light at night affecting levels of hormones such as melatonin and estrogen.
Light pollution comes in a variety of forms such as 'over illumination', 'light trespass' and 'sky glow' – the orange glow that hangs over cities and is produced by upwards directed light.
Walker's research has found that cities using light fixtures that direct just 3% of their light upwards can almost double the sky glow experienced by astronomical observatories 100 km away. "Allowing 10% direct uplight increases this figure to 570%," said Walker, who is chair of the U.S. Dark Skies Working Group, part of the Dark Skies Awareness program, a global citizen science effort to raise awareness of light pollution.