The last polarity reversal took place some 770,000 years ago.

最近一次极性倒转发生在大约77万年前。

Without the magnetic field Earth would be an airless waste devoid of life.

如果没有场球将没有空气，无法生存。

What can be done about it? Well there's something called the world magnetic model.

对此可以采取什么措施？有种模型名为世界场模型。

Within the iron core, the rotating ball of molten iron generated a remarkable magnetic field.

得益于球的铁质核心不断旋转对流逐渐产生了场。

Here, they can create geomagnetic storms capable of disrupting long-range communication and causing blackouts.

掀风暴，由此能扰乱远距离通信并引大规模停电。

Without the geomagnetic field, that solar wind would hit the Earth's atmosphere directly.

如果没有场，太阳风就会直接撞击球的大气层。

The more natural way that this could happen is with a severe geomagnetic disturbance, or GMD.

发生这种情况的更自然的方式是发生严重的扰动（GMD）。

But Earth's magnetic field deflects the solar wind and preserves our air.

但是场能使太阳风转向，保住了大气层。

We call it a geomagnetic storm or a geomagnetic disturbance.

我们称之为风暴或扰动。

Around the same time, there was a " geomagnetic storm watch" listed by the U.S. Space Weather Prediction Center.

大约在同一时间，美国空间天气预报中心列出了一个" 风暴观察" 。

Did the sunspots cause the geomagnetic fields or did the geomagnetic fields cause the sunspots?

是太阳黑子导致了场还是场导致了太阳黑子？

Not the intensity of the geomagnetic disturbance itself.

不是干扰本身的强度。

He said that the incident is believed to be the largest collective loss of satellites from a single geomagnetic event.

他说，该事件被认为是单次事件造成的最大规模卫星集体损失事件。

Without satellites, we wouldn’t be ready for geomagnetic storms either.

没有卫星， 我们也不会为风暴做好准备。

The needle's naturally drawn to the Earth's magnetic North Pole.

指针会自然指向场的北极。

We've known since the middle of the 19th century about geomagnetically induced currents.

- 我们从 19 世纪中叶就知道感应电流。

No? Well, geomagnetic activity, the natural variations in Earth’s magnetic field, it fluctuates in 11-year cycles.

嗯，活动，球场的自然变化， 它以 11 年的周期波动。

I am actually building mathematical  models to understand how birds are using the geomagnetic field to migrate.

实际上，我正在建立数学模型来了解鸟类如何利用场进行迁徙。

It's no longer just that, as you go further south you have on average, less intense geomagnetic disturbances.

- 不仅仅是这样， 随着你向南走得更远，平均而言，干扰强度会减弱。

A team from the US found that exposing the fish to different magnitude fields made them changed the direction they were swimming in.

美国的一个研究小组发现将这种鱼放在不同的场中，它们就会改变游的方向。