imminent danger facing humanity

If a person is said to be grounded, it means that they are sensible and stable – solid individuals who can be relied upon to give a careful and considered opinion. The very meaning of the term comes from the solidity and stability of the ground on which we walk. However, recent reports in the media have painted a different picture of what goes on beneath the ground – one in which the core of the Earth is doing some very surprising and unexpected things.

如果一个人被说成是脚踏实地的，这意味着他们是明智和稳定的——可靠的人，值得信赖，他们会给出谨慎和深思熟虑的意见。这个词的真正含义来自于我们行走的地面的坚固和稳定。然而，最近媒体的报道描绘了一幅不同的画面——地核正在做一些非常令人惊讶和意想不到的事情。

A recent paper published in the journal Nature Geoscience describes a change in the motion of the Earth’s core – and with that news, headlines proliferated, some claiming that the Earth’s core has stopped rotating.

最近发表在《自然地球科学》杂志上的一篇论文描述了地核运动的变化——随着这条新闻的出现，头条新闻激增，一些人声称地核已经停止旋转。

But this interpretation is actually misleading. The Earth’s core is not literally stopping; however it is changing.

但这种解释实际上具有误导性，地核并没有真正停止。然而，情况正在发生变化。

The Earth is not a solid ball; it consists of several layers. There is the innermost core, which is a solid sphere about the same size as the planet Mars. Surrounding that is the outer core, which is liquid rock. The next layer is the mantle, which is sort of taffy-like in consistency. Finally there is the crust, which is the outermost layer– the place where we live.

地球不是实心球体，它由好几层组成。最里面的地核是一个实心球体，大小和火星差不多。围绕着它的是外核，是液态岩石。下一层是地幔，它的粘稠度有点像太妃糖。最后是地壳，这是最外层——我们生活的地方。

If the Earth were a solid ball, every layer would rotate in sync, spinning once per day. However, because of the layered structure, it is possible for the core of the Earth to rotate at a slightly different rate from the surface and other layers. And, in the 1990s, researchers used geological data taken over the previous few decades to show that the core of the Earth was rotating slightly faster than the rest of the Earth. The difference is tiny – about 1° per year faster than the surface of the Earth.

如果地球是一个实心球，每一层都会同步旋转，每天旋转一次。然而，由于分层结构，地核可能以与地表和其他层略有不同的速度旋转。在20世纪90年代，研究人员利用过去几十年的地质数据表明，地核的旋转速度比地球其他部分略快。这种差异很小——大约比地球表面每年快1°。

This more recent study found that the rotation of the core is slowing. It isn’t stopping, but is now rotating at the same speed of the Earth. Furthermore, it appears that the core might be slowing so that it will eventually rotate slightly slower than the Earth. This is scientifically interesting, but rather less dramatic than some of the headlines have suggested.

这项最新的研究发现，地核的旋转速度正在变慢。它没有停止，而是以与地球相同的速度旋转。此外，看起来地核可能正在减速，因此它最终会比地球旋转得稍微慢一些。这在科学上是有趣的，但并不像一些头条新闻所暗示的那样引人注目。

Researchers have seen this periodic change in the speed of the rotation of the Earth’s core before and they still debate the rate at which it occurs, with some suggesting a 70 year cycle, while others suggest a much faster one.

研究人员之前已经看到了这种地核自转速度的周期性变化，他们仍然在争论它发生的速度，一些人认为一个70年的周期，而另一些人认为一个更快的周期。

For geologists, this is fascinating stuff. The radius of the Earth is just shy of 4,000 miles and the deepest well anyone has ever dug is a little over 7.5 miles deep. The crust under the Earth’s continents can be about 40 miles deep, although the crust under the oceans can be much thinner. Figuring out the structure of the Earth requires indirect methods, involving studying how fast the waves from earthquakes travel through the Earth, or studying the rich treasure trove of data of how the sound from nuclear blasts pass through the Earth. With a few exceptions, nuclear testing stopped?in the mid-1990s.

对于地质学家来说，这是令人着迷的事情。地球的半径接近6437公里，而迄今为止人们挖的最深的井也只有12公里多一点。地球大陆下面的地壳可能有64.4公里深，尽管海洋下面的地壳可能要薄得多。弄清楚地球的结构需要间接的方法，包括研究地震产生的波在地球上传播的速度有多快，或者研究核爆炸发出的声音如何穿过地球的丰富数据宝库。除了少数例外，核试验在20世纪90年代中期停止了。

Breathy headlines aside, this recent study confirms earlier results showing that the inner core’s rotation changes over time and helps geologists trying to figure out the mechanism whereby those changes occur. What geologists care about is the interplay between gravitational and magnetic forces within the Earth that speed up and slow down the core’s rotation.

撇开这些耸人听闻的头条不提，最近的这项研究证实了早期的结果，即内核的旋转随着时间的推移而变化，并帮助地质学家试图找出这些变化发生的机制。地质学家关心的是地球内部引力和磁力之间的相互作用，这种相互作用会加速和减缓地核的旋转。

However, there is a much more important lesson to be drawn here, which is that scientists are able to make extremely precise measurements of what is going on under the surface of the Earth. This is a big deal – after all, it’s the only planet we have. What goes on under the Earth has huge potential consequences for humanity.

然而，这里有一个更重要的教训，那就是科学家能够对地球表面下发生的事情进行极其精确的测量。这是一件大事——毕竟，这是我们唯一拥有的星球。地球下面发生的事情对人类有着巨大的潜在影响。

Consider the supervolcano that is slumbering below Yellowstone National Park. Every half a million years or so (sometimes longer), Yellowstone transforms into a volcano that spews hundreds or thousands times of more ash into the atmosphere than the 1980 eruption of Mt. St. Helens. While some have worried that perhaps the Yellowstone supervolcano is due for another eruption, recent studies have allayed the concern that the danger is imminent. However, given the magnitude of the damage such an eruption would occur, it is imperative that geologists continue to monitor what is going on.

想想沉睡在黄石国家公园下面的超级火山吧。每隔50万年左右(有时更长)，黄石公园就会变成一座火山，向大气中喷出的火山灰是1980年圣海伦斯火山喷发时的数百或数千倍。虽然有些人担心黄石超级火山可能会再次爆发，但最近的研究已经减轻了危险迫在眉睫的担忧。然而，考虑到这样的喷发所造成的破坏程度，地质学家必须继续监测正在发生的事情。

And there is much more going on under the Earth’s surface. The Earth’s magnetic field guides ships at sea and lost hikers to safety. It’s easy to believe that the familiar compass will always work, however geologists have shown that the Earth’s magnetic field isn’t constant. Indeed, every few hundred thousand years, the field flips, with magnetic south becoming north, and vice versa.

在地球表面下还有更多的事情在发生。地球磁场引导海上的船只和迷路的徒步旅行者到达安全的地方。人们很容易相信，我们熟悉的指南针总是有效的，然而地质学家已经证明，地球的磁场不是恒定的。事实上，每隔几十万年，磁场就会发生翻转，磁南变成磁北，反之亦然。

And, while a flip is probably not imminent, the location of magnetic north changes even on human time scales. In the early 1900s, it was located in northern Canada, however it has moved out into the Arctic Ocean and is now approaching Siberia.

而且，虽然磁极翻转可能不会马上发生，但即使在人类的时间尺度上，磁极的位置也会发生变化。在20世纪初，它位于加拿大北部，但它已经移动到北冰洋，现在正在接近西伯利亚。

By understanding more about the inner workings of the Earth, scientists will be able to help humanity prepare for significant changes in the Earth’s magnetic field. If it happened, we’d have to change all instrumentation that relies on compasses to navigate.

通过更多地了解地球的内部运作，科学家将能够帮助人类为地球磁场的重大变化做好准备。如果发生这种情况，我们将不得不改变所有依赖罗盘导航的仪器。

We have but one planet and what happens inside of it can affect all of us. It is imperative that geologists continue to study what’s going on inside our globe – and this recent measurement of changes in the rotation of the Earth’s core gives us some comfort that we are staying up to speed.

我们只有一个星球，星球上发生的事情会影响到我们所有人。地质学家必须继续研究地球内部正在发生的事情——最近对地核旋转变化的测量让我们感到宽慰，因为我们正在跟上速度。

And…come on and admit it… that’s pretty cool.

承认吧，这很酷。

原载January 26, 2023，CNN网站

原题：The Earth’s core is changing. What does that mean for us?

作者：Don Lincoln

翻译：皮建华