Our ancestors enjoyed a cleaner world. The water and air were cleaner, and when people went out at night, they could look at the stars above and ask questions about our place in the universe. Nowadays, in modern cities, we can barely see the stars at night because our view of them is not only obscured by the quality of the air, but by the quality of light as well. Not many people realize that the misuse or misdirection of light is a form of pollution. Quite simply, it is called light pollution.

Like other forms of environmental damage, light pollution is created by man and contaminates our surroundings. Like other forms of pollution, it also harms the environment. Just as our opportunities to enjoy rain forests are being taken away by human carelessness, so is our view of the stars at night. However, unlike other forms of environmental damage, the effects of light pollution can easily be reduced and even reversed.

The damage caused by light pollution comes from poorly designed outdoor lighting. Most cities in the world today use outdoor lighting that is not only far too bright, but also directed to places where it is not needed. This wasted light reflects off tiny particles of dust and moisture in the air, causing skyglow. Skyglow causes clouds to glow white, orange, or pink, and destroys our view of the nighttime sky.

The solution to light pollution is to use lower-wattage outdoor bulbs and full cutoff shielding. An electric lamp should send all its light down, not upward or sideways. Full cutoff means that no light rays from the lamp go above the horizon and that at least 90 percent of the light is blocked from going sideways.

Many cities in the world have made changes in the use of outdoor lighting. The result saves money and energy. It also restores our nighttime sky to the way it was when our ancestors gazed above.

我們的祖先享有比較干凈的世界。那時(shí)的空氣和水都比較干凈，人們晚上外出時(shí)，可以看著天上的繁星，探討我們在宇宙空間的位置的有關(guān)課題。如今，在現(xiàn)代化的都市中，我們晚上幾乎難得一見天上的星星，由于空氣和光線的質(zhì)量，使星空的景像變得模糊不清。很多人不知道光線的濫用和亂射也是一種污染。簡單地說，這就叫做“光污染”。

就像其它形式的環(huán)境破壞，光污染是由人類一手造成的，而且污染了人類自身的環(huán)境。和其它形式的污染一樣，光污染也會對環(huán)境造成損害。晚上我們觀賞星星美景和我們本就享有的欣賞雨林的機(jī)會，都因?yàn)槿祟惖氖韬龆粍儕Z。然而，和其它形式的環(huán)境破壞不一樣的是，光污染的影響是可以輕易被減輕，甚至被轉(zhuǎn)變?yōu)楹锰幍摹?/SPAN>

光污染造成的破壞，來自戶外照明的設(shè)計(jì)不當(dāng)。大多數(shù)城市現(xiàn)在所使用的戶外照明，不僅遠(yuǎn)遠(yuǎn)超過所需的亮度，還照射到不需照明的區(qū)域。這些多余的照明，碰到空氣中的微塵粒子和水分子后發(fā)生反射，就造成空中的“霞光”現(xiàn)象。“霞光”使云彩發(fā)出白色、桔色，或是粉紅色的光，就破壞了我們的夜景。

解決光污染的方法就是使用低瓦數(shù)的戶外燈泡與完全阻隔溢光的遮罩。電燈的光線應(yīng)該向下照射，而不是向上或向旁邊照射。“完全阻隔”是指電燈光線的照射不高出地平線，而且至少可以阻擋百分之九十的光線向旁邊照射。

世界上許多城市改變了戶外照明的使用方式，因而省下了金錢和能源。還使我們的夜空恢復(fù)到以前我們祖先所仰望凝視的模樣。