理工类考试辅导：补全对话Light Night
Thousands 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， Colo1. But when people are surrounded by city lights， he says， theyre lucky to see 150 stars.
If youve ever driven toward a big city at night and seen its glow from a great distance， youve 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 stargazing2 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 cant locate these objects， they cant learn more about them.
Light pollution doesnt only affect star visibility. It can harm wildlife too. Its clear that artificial light can attract animals， making them go off course3. Theres 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.
词汇：
astronomer n. 天文学家 migrate v.迁移，迁徒
Illuminate v. 照明，照亮 disruptive adj.扰乱性的
haze n.薄雾 obscure v.使变模糊
faint adj.微弱的，暗淡的
注释：
1. University Corporation for Atmospheric Research (UCAR) ： 大学大气研究社团，于1960年在美国科罗拉多州(Colorad0，缩写为Col0.)的玻尔(Boulder)市成立。该社团是一个由国内外大学组成的非营利性协会，致力于大气周围的空气和气候变化研究。
2. stargazing ： 该词是个合成词，由star和gaze in9组成，在此意为：观望星星。
3 making them go off course： 使它们偏离飞行路线。course：路线。
练习：
1. 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.
2. 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.