Natural Wonders and How They Work

Some things in nature look so strange that they feel like magic, even when you know the science behind them. Green curtains of light ripple across Arctic skies. Waves glow bright blue on a dark beach. Smooth, saucer-shaped clouds hang perfectly still above a mountain. In one California desert, heavy stones slide across a dry lakebed and leave long tracks behind them.

大自然中有些现象奇特得仿佛魔法，即使你知道背后的科学原理，也依然会这样觉得。绿色的光幕在北极的天空中飘动。漆黑的海滩上，海浪闪着明亮的蓝光。光滑的碟形云一动不动地悬在山顶上方。在加利福尼亚的一片沙漠里，沉重的石头在干涸的湖床上滑行，身后留下长长的痕迹。

None of this is a miracle. Every one of these events follows the same laws of physics, chemistry and biology as the rest of nature. Knowing how they work doesn't spoil them, though. For many people it makes them even more impressive. Here are some of the most spectacular natural phenomena on Earth and what causes them.

这些都不是奇迹。每一种现象都遵循着与整个自然界相同的物理、化学和生物规律。不过，了解它们的成因并不会让它们失色，反而让许多人觉得它们更加震撼。下面介绍地球上几种最壮观的自然现象，以及它们是怎样形成的。

The aurora borealis, or northern lights, is probably the most famous light show in nature. Waves of green, pink and violet light ripple across the night sky in a wide ring around the North Pole, over places like northern Norway, Iceland, Alaska and northern Canada. For centuries the lights have shaped local legends, and today thousands of tourists travel north every winter just to see them.

北极光可能是大自然中最著名的灯光秀。绿色、粉色和紫色的光波在夜空中流动，形成一个环绕北极的宽阔光环，笼罩着挪威北部、冰岛、阿拉斯加和加拿大北部等地。几百年来，极光一直是当地传说的灵感来源；如今，每年冬天都有成千上万的游客专程北上，只为一睹它的风采。

The aurora begins with the Sun, which constantly sends out a stream of charged particles called the solar wind. Earth's magnetic field steers some of these particles toward the polar regions. There they crash into gases high in the atmosphere, mostly 100 to 300 kilometers up, and make them give off light. Oxygen glows green or red, while nitrogen adds blue and purple. When the Sun is very active, the aurora spreads much farther from the poles: in May 2024, people saw it as far south as Italy and Texas. The Southern Hemisphere has its own version, the aurora australis, or southern lights.

极光源于太阳。太阳不断向外释放带电粒子流，这就是太阳风。地球磁场把其中一部分粒子引向极地。在那里，粒子撞击高层大气中的气体，高度大多在100到300公里之间，使气体发光。氧发出绿光或红光，氮则增添蓝色和紫色。太阳非常活跃时，极光会延伸到离两极远得多的地方：2024年5月，连意大利和美国得克萨斯州都能看到极光。南半球也有自己的极光，叫作南极光。

On some nights, the waves breaking on a beach glow an electric blue-green. Move your hand through the water and it leaves a trail of cold, ghostly light. This is bioluminescence, light made by living things. It is far more common than most people realize, but most of it happens where nobody sees it, in the darkness of the deep ocean.

在某些夜晚，拍打海滩的浪花会泛出亮丽的蓝绿色光芒。把手伸进水里一划，就会留下一道冰冷而幽幽的光痕。这就是生物发光，也就是生物自身产生的光。它比大多数人想象的普遍得多，只是大部分发生在无人看见的地方，也就是漆黑的深海。

The glowing waves are usually caused by dinoflagellates, tiny single-celled plankton that flash blue when the water around them moves. The light comes from a chemical reaction: a molecule called luciferin reacts with oxygen, helped by an enzyme called luciferase. Jellyfish, squid and many deep-sea fish make light too, and so do fireflies on land. A 2017 study off the coast of California found that about three quarters of the animals living in the open ocean can glow. They use light to find food, attract mates and confuse predators. Mosquito Bay in Puerto Rico and Vaadhoo Island in the Maldives are famous for their glowing water.

海浪发光通常是由甲藻引起的。这种微小的单细胞浮游生物在周围海水晃动时会闪出蓝光。光来自一种化学反应：一种叫荧光素的分子在荧光素酶的帮助下与氧气发生反应。水母、鱿鱼和许多深海鱼类也会发光，陆地上的萤火虫同样如此。2017年在加利福尼亚近海进行的一项研究发现，生活在开阔大洋中的动物约有四分之三能够发光。它们用光来寻找食物、吸引配偶和迷惑捕食者。波多黎各的蚊子湾和马尔代夫的瓦度岛都以发光的海水闻名。

Ball lightning is the strangest and least understood event in our weather. For centuries, people have described glowing balls of light, anywhere from the size of a golf ball to the size of a beach ball, that appear during thunderstorms. They float through the air for a few seconds, sometimes drift into rooms or even pass through windows, and then either fade quietly or disappear with a loud bang.

球状闪电是天气现象中最奇怪、也最不为人所了解的一种。几百年来，人们一直描述在雷暴中出现的发光球体，小的如高尔夫球，大的如沙滩球。它们在空中飘浮几秒钟，有时会飘进房间，甚至穿过窗玻璃，然后要么悄然熄灭，要么伴随一声巨响消失。

Because it is rare and lasts only seconds, ball lightning was very hard to study, and some scientists doubted that it existed at all. Then, in 2012, Chinese researchers who were studying ordinary lightning on the Tibetan Plateau happened to record a glowing ball with their cameras and instruments. It shone for about a second and a half, and its light showed silicon, iron and calcium, elements found in soil. This supports a popular theory: a lightning strike turns soil into hot vapor, and that cloud glows as it burns. Other theories involve plasma or microwaves, and scientists still don't agree on the cause.

由于球状闪电罕见，而且只持续几秒钟，研究起来非常困难，一些科学家甚至怀疑它是否真的存在。后来在2012年，一批在青藏高原研究普通闪电的中国科研人员，用摄像机和仪器意外记录下了一个发光球体。它发光约一秒半，光谱中显示出硅、铁和钙，这些都是土壤中的元素。这一发现支持了一种流行的理论：闪电击中地面后把土壤变成炽热的蒸气，这团蒸气在燃烧时发光。也有理论认为与等离子体或微波有关，科学家对其成因至今仍未达成一致。

During some volcanic eruptions, lightning flashes through the huge cloud of ash rising from the volcano. Scientists sometimes call this a “dirty thunderstorm.” It is one of the most frightening sights in nature, and one of the oldest on record: the Roman writer Pliny the Younger described flashes like lightning in the dark cloud over Mount Vesuvius in AD 79.

在一些火山喷发中，闪电会划过从火山升起的巨大火山灰云。科学家有时称之为“脏雷暴”。这是大自然中最骇人的景象之一，也是最早有记载的景象之一：公元79年，古罗马作家小普林尼就描述过维苏威火山上空黑云中如闪电般的火光。

The lightning comes from electric charge. Inside the ash cloud, bits of rock and ash rub and crash into each other, and if the cloud rises high enough, ice forms in it too. These collisions build up positive and negative charges in different parts of the cloud, much as in an ordinary thunderstorm, until the charge is released as lightning. Volcanic lightning has been seen over Eyjafjallajökull in Iceland in 2010, over Mount Etna in Sicily and over Sakurajima in Japan. The 2022 eruption of Hunga Tonga in the Pacific produced the most intense lightning ever recorded, with hundreds of thousands of flashes in less than a day.

这种闪电来自电荷。在火山灰云中，岩石碎屑和火山灰互相摩擦、碰撞；如果云团升得足够高，里面还会形成冰。这些碰撞使云的不同部位分别积累正电荷和负电荷，与普通雷暴十分相似，直到电荷以闪电的形式释放出来。人们曾在2010年冰岛埃亚菲亚德拉冰盖火山、西西里岛的埃特纳火山和日本的樱岛上空看到火山闪电。2022年太平洋洪阿汤加火山的喷发产生了有记录以来最强烈的闪电活动，不到一天就有数十万次闪电。

On Racetrack Playa, a dry lakebed in a remote corner of Death Valley in California, rocks sit at the ends of long tracks in the cracked mud. Some of the tracks are straight, others curve or zigzag, and some of the rocks weigh more than 300 kilograms. The tracks clearly showed that the stones moved, but for decades nobody had ever seen one move.

跑道干湖位于加利福尼亚州死亡谷一个偏远的角落，是一片干涸的湖床。在龟裂的泥地上，一块块岩石停在长长痕迹的尽头。有的痕迹笔直，有的弯曲或呈之字形，有些岩石重达300多公斤。这些痕迹清楚地表明石头移动过，但几十年来从没有人亲眼见过它们移动。

Geologists puzzled over the stones for more than 60 years. The answer finally came in December 2013, when a team using GPS trackers and time-lapse cameras caught the rocks in motion. In winter, rain and melting snow sometimes form a shallow pond on the playa. On cold nights its surface freezes into a sheet of ice only a few millimeters thick. On a sunny day the ice breaks into large floating panels, and a light wind pushes them across the water. The panels push the rocks ahead of them, a few meters per minute, and the stones leave tracks in the soft mud underneath. So the stones don't move by themselves, and they don't float: thin, almost invisible ice pushes them.

地质学家为这些石头苦思了60多年。答案终于在2013年12月揭晓：一个团队利用GPS追踪器和延时摄影相机，拍到了岩石移动的过程。冬天，雨水和融雪有时会在干湖上积成一个浅浅的水塘。在寒冷的夜晚，水面冻结成一层只有几毫米厚的冰。到了晴天，冰层碎裂成漂浮的大冰片，被微风推着在水面上移动。冰片推着岩石向前，每分钟移动几米，石头便在下面柔软的泥地上留下痕迹。所以石头既不是自己移动的，也不是漂浮着的，而是被一层几乎看不见的薄冰推动的。

Lenticular clouds, known to scientists as altocumulus lenticularis, look like something from another world. They are smooth, lens-shaped discs that hang over or just behind mountain peaks, sometimes stacked like a pile of plates. Strong winds blow all around them, yet they stay in the same place for a long time. Not surprisingly, people often report them as UFOs.

荚状云，科学上称为荚状高积云，看起来像是来自另一个世界。它们是光滑的透镜状圆盘，悬在山峰上方或山峰后面，有时层层叠叠，像一摞盘子。周围狂风呼啸，它们却能长时间停留在同一个地方。难怪人们常常把它们当成不明飞行物报告。

They form when a steady, moist wind blows over a mountain. The mountain pushes the air up and sets off a series of waves in the air behind it, a bit like the ripples in a stream behind a rock. Where the air rises to the top of a wave, it cools and its moisture turns into cloud. Where it sinks again, it warms up and the cloud disappears. Air keeps flowing through the cloud, but because the cloud keeps forming on one side and disappearing on the other, it seems to stand still. Lenticular clouds are often seen over lone mountains such as Mount Fuji in Japan, Mount Rainier in the United States and the Matterhorn in the Alps.

当一股稳定而湿润的风吹过山峰时，就会形成荚状云。山体把空气向上推，并在身后的空气中激起一连串波动，有点像溪水在石头后面泛起的涟漪。在空气升到波峰的地方，空气冷却，其中的水汽凝结成云；在空气重新下沉的地方，空气变暖，云就消散了。空气不断穿过云体，但由于云一侧不断生成、另一侧不断消散，看上去就像静止不动。荚状云常出现在孤立的山峰上空，例如日本的富士山、美国的雷尼尔山和阿尔卑斯山的马特洪峰。

Every fall, hundreds of millions of monarch butterflies fly south from Canada and the northern United States. Some travel more than 4,000 kilometers to reach the fir forests in the mountains of central Mexico. There they spend the winter packed together on the trees in such huge numbers that their weight can bend the branches.

每年秋天，数以亿计的帝王蝶从加拿大和美国北部向南飞去。有些要飞行4000多公里，才能抵达墨西哥中部山区的冷杉林。它们在那里成群挤在树上过冬，数量之多，压得树枝都弯了下来。

The strangest part is that no single butterfly makes the whole round trip. The monarchs that leave Mexico in spring lay eggs in the southern United States and die. Their young continue north, and only after three or four generations does a new generation fly all the way back. So the butterflies that arrive in Mexico each fall have never been there before: they are usually the great-great-grandchildren of the ones that left. Scientists believe they find their way with a sun compass, corrected for the time of day by a clock in their antennae, and they may also sense Earth's magnetic field. How an insect with such a tiny brain finds a small patch of forest it has never seen is still not fully understood.

最奇特的是，没有一只蝴蝶能独自完成整个往返旅程。春天离开墨西哥的帝王蝶在美国南部产卵后便死去。它们的后代继续向北飞，要经过三四代之后，才会有新的一代飞完全程返回。因此，每年秋天抵达墨西哥的蝴蝶从未去过那里：它们通常是当初离开的那批蝴蝶的玄孙辈。科学家认为，它们靠太阳罗盘辨别方向，触角中的生物钟会根据一天中的时间对罗盘进行校正；它们可能还能感知地球磁场。一只大脑如此微小的昆虫，是怎样找到一片从未见过的小树林的，至今仍没有完全弄清楚。

Long before science could explain them, natural phenomena found their way into stories and beliefs. In Finnish folklore, the northern lights were sparks thrown into the sky by the tail of a fox running across the snow, and the Finnish word for them, revontulet, means “fox fires.” The Sami people of northern Scandinavia treated the lights with respect and told children not to wave or whistle at them. In Mexico, the monarchs arrive around the Day of the Dead in early November, and many people believe they carry the souls of the dead.

早在科学能够解释之前，自然现象就已融入了各种故事和信仰。在芬兰民间传说中，北极光是一只狐狸在雪地上奔跑时用尾巴扫上天空的火花，芬兰语中极光一词revontulet的意思就是“狐狸之火”。斯堪的纳维亚北部的萨米人对极光心怀敬畏，告诫孩子不要向它挥手或吹口哨。在墨西哥，帝王蝶在11月初的亡灵节前后到来，许多人相信它们承载着逝者的灵魂。

These events still affect us today. Psychologists who study awe, the feeling we get in front of something so vast that we can't fully take it in, have linked it to lower stress, a stronger sense of connection to other people and more generous behavior. Standing under the aurora or on a beach full of glowing waves, many people say they feel small, but in a good way.

这些现象至今仍在影响着我们。研究敬畏感的心理学家发现，敬畏感，也就是我们面对浩瀚到无法完全理解的事物时产生的感受，与压力减轻、与他人联系更紧密以及行为更慷慨有关。许多人说，站在极光之下或满是发光海浪的海滩上时，他们觉得自己很渺小，但那是一种美好的渺小。

Auroras, glowing seas, sailing stones and migrating butterflies all have scientific explanations, or at least good working theories. Some, like ball lightning, still keep part of their secret, and discoveries keep coming: the sailing stones were caught moving for the first time only in 2013.

极光、发光的海洋、移动石和迁徙的蝴蝶都有科学解释，至少也有可靠的理论。有些现象，比如球状闪电，仍保留着一部分秘密，而新的发现还在不断出现：移动石直到2013年才第一次被拍到移动的过程。

Science has not taken the wonder out of these events. Knowing that a butterfly steers by the Sun with the help of a clock in its antennae, or that a wave glows because of billions of tiny plankton, only makes them more interesting. Many of these sights are also easy to reach. A winter trip to the far north or a dark beach on a warm night may be enough to see one for yourself.

科学并没有让这些现象失去魅力。知道蝴蝶借助触角里的生物钟依靠太阳导航，或者知道海浪发光是因为数十亿微小的浮游生物，只会让它们更有意思。而且，许多这样的景象并不难看到。冬天去一趟遥远的北方，或在温暖的夜晚走上一片漆黑的海滩，也许就足以让你亲眼目睹其中之一。