地球的顶部是北极 地球的底部是南极 当然了……
The north pole is the top of the earth, and the south pole is the bottom, of course…
except that the earth is kind of a ball, and they don’t really have tops and bottoms.
Granted, the earth isn’t exactly spherical and it’s spinning through space – spinning
about an imaginary axis of rotation.
地轴穿过地球的其中一个点 就是这儿 在北冰洋
One of the points where that axis goes through the earth, right here in the arctic ocean,
where the Russians planted their flag on the sea floor in 2007, is called the north pole…
or rather, it’s the “geographic” north pole.
因为 正如有不同的方法定义“年” 也有不同方法来定义北极
Because, just like there are different definitions for what a “year” is, there are different north poles.
For example, compasses don’t point to the geographic, or spinning-top, north pole.
它们指向磁北极 那么其对立面就是 磁南极
They point to the MAGNETIC north pole, which is incidentally a magnetic south pole since opposites attract.
The magnetic north (actually south) pole and south (actually north) pole are an electromagnet
caused by swirling convection currents in the earth’s liquid iron outer core.
These currents are heavily influenced by the rotation of the earth, so the magnetic field
they generate roughly aligns with the earth’s axis of rotation – but not precisely, and not unchangingly.
A hundred years ago, the magnetic north pole was located in northern canada – over 2000km
south of the geographic north pole.
And it’s been moving consistently north-west since then, currently sitting in the middle
北冰洋中部 在地理北极向南450千米处 而且每年都向俄罗斯
of the Arctic Ocean 450km south of the geographic north pole, and drifting about 55 kilometers
closer to Russia each year.
What’s more, the magnetic south pole is not on the exact opposite side of the earth from
the magnetic north pole – it drifts around in a somewhat independent fashion and is currently
20° closer to the equator than magnetic north!
Such is the nature of magnetic fields generated by confusingly swirly molten iron deep inside the earth.
But if you imagined, instead, that there were just a giant, perfect bar magnet inside the
earth, then that perfect bar magnet would point towards the GEO-magnetic north pole.
Which is currently located in Ellesmere Island, Nunavut, Canada.
This pole, together with the geomagnetic south pole which IS on the exact opposite side of
代表地球磁场的大致走向 特别是 它延伸到太空
the earth, represents the general, overall trend of the earth’s magnetic field, especially as it extends into space.
So while it’s not at all useful for compass navigation on the earth’s surface, it does
heavily influence the paths of solar wind particles that cause the aurora – that is,
the northern lights. Beautiful.
In short, the north pole’s whereabouts depend on what you care about.
The earth spins like a top around the “geographic” north pole, compasses point to the “magnetic”
north pole (which is actually a magnetic south pole), and the northern lights are strongest
in a ring around the “geomagnetic” north pole (also a magnetic south pole).
All three north poles move, too – the magnetic and geomagnetic poles change quite drastically,
but even the geographic north pole moves up to ten meters a year as the earth wobbles
on its axis due to seasonal air pressure differences across the globe, melting ice caps, and so on.
Assuming that the Russians planted their flag exactly at the geographic north pole in August
2007, not once since then has it been exactly at the pole – it was as far as 12 meters away
2010年的时候很接近 只有20厘米 而现在偏离了3.5米远
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.
地球的顶部是北极 地球的底部是南极 当然了……