Time to turn off the lights

Abstract

Cities needlessly shine billions of dollars directly into the sky each year and, as a result, a fifth of the world's population cannot see the Milky Way. Malcolm Smith explains why a dark sky has much to offer everyone. Marking the International Year of Astronomy (IYA), Jeff Kanipe takes a look at the prospects of the 'big four' major new telescopes. They have a tough act to follow, as a trawl through 'Hubble's greatest hits' reveals. The 'Dark Skies Awareness' campaign is part of IYA 2009; Malcolm Smith argues the case for a transformation that would not only help astronomers but would also benefit human health and energy conservation. Also part of IYA 2009 is the celebration of 400 years of the telescope; Owen Gingerich tracks the link between technology and our changing world-view. Robert Poole's book Earthrise focuses on the psychological impact of the Apollo 8 image of Earth over the lunar horizon, though our reviewer feels that our attitudes towards our planet have not changed enough. 'Hidden treasures' visits the Paris Observatory and astronaut Alan Bean talks about his moonscape paintings. In Futures, David Blair looks back on 2009 and in a Letter, Alyssa Goodman et al. reveal the importance of self-gravity in star formation. See the Editorial and visit http://www.nature.com/astro09 for more. COVER PICTURE: Hubble Space Telescope/Christian Darkin