Street lights outshine real sky at night

 

Special report: space exploration

 

Tim Radford, science editor

Tuesday August 14, 2001

The Guardian

 

The glow of urban and suburban lamps means that for many the sky never gets darker than it would during natural twilight, according to US and Italian astronomers.

 

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 the ground.

 

Researchers claim to have made the first systematic measurement of artificial light and human settlement.

 

Pierantonio Cinzano and Fabio Falchi, of the University of Padua, and Chris Elvidge, of the US national geophysical data centre in Boulder, Colorado, began work 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. "And our atlas refers to the situation in 1996-97. It is undoubtedly worse today."

 

The scientists found that half of Europe, two-thirds in the US 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.