except that the earth is kind of a ball, and they don't really have tops and bottoms. Granted,

地球是個球形，所以 它沒有真的所謂的 "頂端" 和 "底端"。倘若

the earth isn't exactly spherical and it's spinning through space - spinning about an

地球不是完美的球形，而且是 在太空中運轉 - 運轉在一個

imaginary axis of rotation. One of the points where that axis goes through the earth, right

我們想像中的自轉軸。有一個自轉軸 通過地球的一點，就在

here in the arctic ocean, where the Russians planted their flag on the sea floor in 2007,

這北冰洋裡。在2007年，俄羅斯人 把他們的國旗插在海底下

is called the north pole... or rather, it's the "geographic" north pole. Because, just

並把這點命名為 "北極" ... 或者 更正確地說是 "地理北極"。因為，就像

like there are different definitions for what a "year" is, there are different north poles.

有很多個定義描述什麼是 "一年"，這裡也有很多個 "北極"。

For example, compasses don't point to the geographic, or spinning-top, north pole. They

舉個例子: 指北針不是指向 地理 - 或者是紡頂北極。指北針

point to the MAGNETIC north pole, which is incidentally a magnetic south pole since opposites

會指向 "磁北極“，也就是指 地球裡的南極 因為異極相吸。

attract. The magnetic north (actually south) pole and south (actually north) pole are an

磁北極 (其實是南極) 和磁南極(其實是南極)是從

electromagnet caused by swirling convection currents in the earth's liquid iron outer

一個在地球外核心裡的液態鐵 在地球裡對流。

core. These currents are heavily influenced by the rotation of the earth, so the magnetic

這些對流被地球自轉 重重地影響，所以這被

field they generate roughly aligns with the earth's axis of rotation - but not precisely,

產生出來的磁場排得大概和自轉軸一樣。 但不是恰好，也不是不會變的。

and not unchangingly. A hundred years ago, the magnetic north pole was located in northern

一百年前， 磁北極位在於加拿大的北方 -

canada - over 2000km south of the geographic north pole. And it's been moving consistently

位於地理北極2000公里以南以下， 而且還一直朝西北方移動

north-west since then, currently sitting in the middle of the Arctic Ocean 450km south

目前正位於北冰洋裡 位於地理北極450公里以南，

of the geographic north pole, and drifting about 55 kilometers closer to Russia each

而且正在以每年大概55公里 移動朝向俄羅斯。

year.

還不只喔。磁南極不是 剛好在磁北極的

What's more, the magnetic south pole is not on the exact opposite side of the earth from

正對面，它以一個獨特的方式 自己移動，而且比磁北極

the magnetic north pole - it drifts around in a somewhat independent fashion and is currently

靠近赤道20度呢! 這是大自然的磁場，從

20° closer to the equator than magnetic north! Such is the nature of magnetic fields generated

不解的地球裡的液態鐵產生出來。

by confusingly swirly molten iron deep inside the earth.

但是如果你想像，我們地球裡 有一個完整的磁鐵條，

But if you imagined, instead, that there were just a giant, perfect bar magnet inside the

那這個完整的磁鐵條會 剛剛好指向"地磁北極"。

earth, then that perfect bar magnet would point towards the GEO-magnetic north pole.

目前位於加拿大, 努納武特地區 的埃爾斯米爾島。這地磁北極和

Which is currently located in Ellesmere Island, Nunavut, Canada. This pole, together with

位於地磁北極正對面的地磁南極

the geomagnetic south pole which IS on the exact opposite side of the earth, represents

代表著概括性的地球磁場， 尤其當它延伸到太空 。

the general, overall trend of the earth's magnetic field, especially as it extends into

所以即使地磁極 對指北針並沒有完全的幫助時，

space. So while it's not at all useful for compass navigation on the earth's surface,

它對太陽鋒粒子有很大的影響， 也順辦產生了北極光

it does heavily influence the paths of solar wind particles that cause the aurora - that

很美吧!

is, the northern lights. Beautiful.

總之，北極的位置在哪裡 要看你在乎哪一點。 地球轉起來像

In short, the north pole's whereabouts depend on what you care about. The earth spins like

陀螺一樣圍繞著 "地理北極"， 指北針指向 "磁北極"

a top around the "geographic" north pole, compasses point to the "magnetic" north pole

(其實是地球的"磁南極")， 然後北極光的光環在"地磁北極"

(which is actually a magnetic south pole), and the northern lights are strongest in a

環繞是最強的 (事實上也是地磁南極).

ring around the "geomagnetic" north pole (also a magnetic south pole).

這三個北極端也都會動 - 磁極和地磁極的位置改變幅度很大,

All three north poles move, too - the magnetic and geomagnetic poles change quite drastically,

但是連地理兩極也會由於 季節性氣壓、融化的冰山、以及

but even the geographic north pole moves up to ten meters a year as the earth wobbles

其他的原因下在自轉軸移動， 而造成以每年10公尺的速度改變位置。

on its axis due to seasonal air pressure differences across the globe, melting ice caps, and so

假設在2007年8月，俄羅斯人把 他們的國旗剛剛好插在地理北極上

on.

後來北極點就一直環繞著移動 - 它在2009年距離最遠12公尺

Assuming that the Russians planted their flag exactly at the geographic north pole in August

，最近距離20公分 - 現在 它在大概在3公尺半外。 簡單的說，

2007, not once since then has it been exactly at the pole - it was as far as 12 meters away

地球正在環繞著俄羅斯國旗 做有史以來最大的鋼管舞。

in 2009 and as close as 20 cm in 2010 - right now it's about 3 and a half meters away. Basically,

the earth is doing the biggest, slowest, pole dance ever around the Russian flag.