Having completed his calculations, Dr Cinzano compared his map with estimates of light pollution in Italy that were made in the 1970s.

ECONOMIST: Going, going, nearly gone

The extent of the problem, at least at optical frequencies, has recently been catalogued by Pierantonio Cinzano and Fabio Falchi at the University of Padua, Italy, and Christopher Elvidge at the National Geophysical Data Centre in Boulder, Colorado.

ECONOMIST: Going, going, nearly gone

What is new about Dr Cinzano's research, which is about to be published in the Monthly Notices of the Royal Astronomical Society, is that he and his colleagues have managed to take account of the effects of back-scattering by clouds and dust in the atmosphere, as well as the effects of the original sources of the light themselves.

ECONOMIST: Going, going, nearly gone