On starry nights

THE CAMPAIGN by astronomers to stop artificial light in cities from affecting stellar views, which prevents them studying stars, is gaining a wider audience. Relentless light from surrounding cities has shut down the largest telescope at Mount Wilson in Southern California.

Scientists believe artificial lights should be shielded so that the overhead glow is cut off. As the downward beam is more concentrated, a lower-watt bulb can give the same amount of ground light.

At Tuscan in Arizona, authorities have already installed downward-facing fixtures on all 14,000 street lights and have switched from mercury vapour to sodium lights.