Light Pollution Is Dimming Our View of the Sky

光污染正让天空“暗淡 ”

Most stars are invisible against the overhead glare from city lights. At best， there is only a hint of the Milky Way to see： the combined radiance of a hundred billion stars dims to near nothingness by bright streetlamps and storefronts.

This is light pollution—human-generated lights cast up into the heavens—causing the sky itself to glow and washing out the stars. Astronomers have known for years the situation is bad for stargazing， and it also has real and negative effects on the well-being of many living things—plants， animals and even human beings. More than 80 percent of humanity is affected by light pollution， their view of the skies being stolen away.

Christopher Kyba， the light-pollution researcher of the GFZ German Research Center for Geosciences， and his team examined an astonishing amount of data from more than 50，000 citizen scientists from around the world who sampled their local sky brightness from 2011 to 2022. While there was considerable place-to-place variability—for example， on average， Europe saw a 6.5 percent increase in light pollution per year， while North America saw a 10.4 percent increase—the researchers found that globally， light pollution increased by 9.6 percent per year over the time period.

This may not sound like much， but a year-over-year growth of about 10 percent means sky brightness is doubling about every seven years. A moment’s thought should make clear why this is deeply troubling.

在我们头顶上方的城市强光下，大多数星星都看不到了。在最好的情况下，我们能看到的也只是银河光带的一小部分：一千亿颗星星汇合起来的光芒在明亮的路灯和店面的映衬下变得近乎虚无。

这就是光污染，人造光源投射到天空中，导致天空本身发亮，冲淡了星光。天文学家多年前就意识到这一情形不利于观星，它也对许多生物的健康造成了实实在在的负面影响，包括植物、动物甚至人类。超过80%的人类受到光污染的影响，他们欣赏天空的权利被剥夺了。

德国波茨坦地球科学研究中心的光污染研究员克里斯托弗·凯巴和他的团队研究了来自世界各地的5万多名民间研究人员的大量数据，这些研究人员从2011年到2022年对当地的天空亮度进行了采样。尽管存在相当大的地区间差异（例如，平均而言，欧洲光污染每年增加6.5%，而北美增加10.4%），研究人员发现，在全球范围内，光污染在这段时间每年增加9.6%。

这听起来可能不多，但每年大约10%的增长意味着天空的亮度每7年就会翻一番。稍微思考一下，你就会明白这为什么会令人深感不安。

As Kyba and his co-authors explained in their paper， published in the journal Science， if there are 250 visible stars in the sky when someone is born， by the time they’re 18 they’ll see only 100， and over that same period the sky will have increased in brightness by more than a factor of four.

All this extra light at night has a large effect on the life under it. Researchers have shown that it has negative impacts on many animals and plants; light pollution disrupts the great migrations of birds， the delicate blossoming of flowers， and even the luminous courtship of fireflies， to name just a few examples. It affects humans as well， possibly causing insomnia among many other health problems.

So what can we do about our brightening skies？ There is a lot already happening. Groups like the International Dark Sky Association， advocate not for more lighting but for more intelligent lighting; smarter street lights that concentrate their light downward are one example. Because these lights offer more efficient light， they save energy， too， eventually paying for themselves. At the moment， simple awareness is one of our greatest benefits. Turning off your own outdoor lighting at night might not seem like a big deal， but if you tell others， that helps. Awareness grows.

Many people don’t even know that they—and their descendants—are losing this cosmic experience just over their heads. We need the dark night sky， and it’s up to all of us to make sure it’s still there every time the sun goes down.

正如凯巴和合著者发表在《科学》杂志上的论文中解释的那样，如果一个人出生时天空中有250颗可见的恒星，到他18岁时，他只能看到100颗，而在这一时间段，天空的亮度将增加4倍以上。

夜晚的这些额外的光线对生活在其下的生物有很大的影响。研究人员已经证明，夜晚的额外光线对许多动植物都有负面影响；光污染会干扰鸟类的大迁徙，干扰娇嫩花朵的开放，甚至影响萤火虫发光的求偶行为，这只是几个例子。夜晚的额外光线也会影响人类，可能会引发失眠和许多其他健康问题。

那我们能做些什么来应对过亮的夜空呢？人们已经采取了许多措施。国际暗天协会等组织倡导更智能的照明，而不是更多的照明。例如，智能路灯向下集中光线。因为这些路灯提供了更有效的照明，它们也节省了能源，最终收回了成本。目前，能清晰地认识这些是我们最大的优势之一。晚上关掉自己的户外照明可能是件小事，但如果你告诉别人，那会有所帮助。民众的意识会增强。

许多人甚至没有意识到他们和他们的后代正在失去头顶上的这片星空。我们需要黑暗的夜空，我们所有人都有义务确保每当太阳落山后夜色仍在。

Word Bank

dim /dɪm/ v. 变暗淡；变昏暗

disrupt /dɪs'rʌpt/ v. 扰乱；打断

descendant /dɪ'sendənt/ n. 后代；子孙

cosmic /'kɒzmɪk/ adj. 宇宙的