Light Night, Dark Stars Thousands of people aroundthe globe step outside to gaze at their

Light Night, Dark Stars

Thousands of people aroundthe globe step outside to gaze at their night sky. On a clear night, with no clouds, moonlight, or artificiallights to block the view, people can see more than 14,000 stars in the sky, says Dennis Ward, anastronomer with the University Corporation for Atmospheric Research (UCAR) in Boulder, Colo.But when people are surrounded by city lights, he says, they're lucky to see 150 stars.

If you've ever driventoward a big city at night and seen its glow from a great distance, you've witnessed light pollution. It occurs whenlight from streetlights, office buildings, signs, and other

sources streams into space and illuminates the night sky. This haze oflight makes many stars invisible to people on Earth. Even at night, big citieslike New Yorkglow from light pollution, making stargaz-ing difficult.

Dust and particles ofpollution from factories and industries worsen the effects of lightpollution."If one city has a lot more light pollution than another,"Ward says, "that city will suffer the effectsof light pollution on a muchgreater scale. "

Hazy skies also make it farmore difficult for astronomers to do their jobs.

Cities are getting larger.Suburbs are growing in once dark, rural areas. Light from all this newdevelopment is increasingly obscuring the faint light given off by distantstars. And if scientists can't locate these objects, they can't learn moreabout them.

Light pollution doesn't onlyaffect star visibility. It can harm wildlife too. It's clear that artificiallight can attract animals,'making them go off course. There's increasingevidence, for example, that migrating birds use sunsets and sunrises to helpfind their way, says Sydney Gauthreaux Jr. , a scien- tist at Clemson Universityin South Carolina."When light occurs at night, " he says, "it has a very dis- ruptive influence." Sometimes birds fly into lighted towers, high-rises, and cables fromradio and tele- vision towers. Experts estimate that millions of birds die thisway every year.

41.When can people see 14,000 stars？

A.When they have a fairly good telescope

B.When they are in a large city

C.When the n:ght sky is clear of clouds, moonlight and artificial lights

D.When the night sky is without haze and fog