Light pollution 'continues to obscure the stars'
Astronomers say the glow of streetlights means most urban dwellers never experience real darkness.
US and Italian researchers say in some places the sky never gets darker than it would during natural twilight.
They have just published the first world atlas of artificial night sky brightness.
Astronomers have complained for decades that the stars are increasingly obscured by light from streetlights, floodlights and illuminated signs.
The researchers claim to have made the first systematic measurement of artificial light, reports said.
They found half of Europeans, two-thirds of Americans and a fifth of people in the world lived where they could not see the Milky Way - the hazy band of light that marks the plane of the galaxy - with the naked eye.
Pierantonio Cinzano and Fabio Falchi of the University of Padua and Chris Elvidge of the US national geophysical data centre in Boulder, Colorado, began working with data from a US defence satellite in 1996.
They calculated ways in which light is propagated through the atmosphere and arrived at a set of maps showing the extent and severity of light pollution.
"Large numbers of people in many countries have had their vision of the night sky severely degraded," said Dr Cinzano. "Our atlas refers to the situation in 1996-97. It is undoubtedly worse today."
