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Light Night, Dark StarsThousands of people around the globe step outside to gaze at their night sky. On a clear night, with no clouds, moonlight, or artificial lights to block the view, people can see more than 14,000 stars in the sky,says Dennis Ward, an astronomer 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 driven toward a big city at night and seen its glow from a great distance, you've witnessed light pollution. It occurs when light from streetlights, office buildings, signs, and other sources streams into space and illuminates the night sky. This haze of light makes many stars invisible to people on Earth. Even at night, big cities like New York glow from light pollution, making stargazing difficult.

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

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

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

Light pollution doesn't only affect star visibility. It can harm wildlife too. It's clear that artificial light can attract animals, making them go off course. There's increasing evidence, for example,that migrating birds use sunsets and sunrises to help find their way, says Sydney Gauthreaux Jr. , a scientist at Clemson University in South Carolina. "When light occurs at night," he says, "it has a very disruptive influence." Sometimes birds fly into lighted towers, high-rises, and cables from radio and television towers. Experts estimate that millions of birds die this way every year.

36. 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 night sky is clear of clouds, moonlight and artificial lights.

D When the night sky is without haze and fog.

37. Which of the following statements is NOT related to light pollution?

A A haze of light is formed from artificial lights such as streetlights and building lights.

B Lights from different sources in the city stream into space and illuminate the night sky.

C The night sky is illuminated by the lights from big glowing cities in the night.

D Stargazing becomes difficult because there is a layer of haze in the air.

38. Does the writer think growing cities affect astronomers' work? Why does he think so?

A Yes. Because the once dark rural areas are polluted by lights.

B No. Because they can still see stars in rural areas.

C Yes. Because rural areas are not a good place for astronomers to study stars.

D No. Because faint light given off by stars can still be seen on a clear night.

39. How does light pollution affect wildlife.9 Which of the following is NOT correct?

A Animals may go off course due to the attraction of artificial lights.

B Animals might be attracted by artificial lights to go into cities.

C Artificial lights at night may make migrating birds lose their way.

D Attracted by artificial lights, birds fly into lighted buildings.

40. Which of the following is closest in meaning to the title "Light Night, Dark Stars" ?

A The night sky is light colored and stars are black.

B Lights appear at night and stars are seen in the dark.

C City lights illuminate the night sky and make stars invisible.

D City lights at night illuminate stars in the sky.