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极光是怎么产生的 – 译学馆
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极光是怎么产生的

What Causes the Northern Lights (and where you should see them)

感谢德雷珀公司及其登月黑客计划
Thank you to Draper and its Hack the Moon initiative Draper
对PBS数码工作室的支持
for supporting PBS Digital Studios.
每个冬季都有数以千计的人到北方旅行
Every winter thousands of tourists head North,
他们越过绝境长城 冒着遭遇异鬼的危险
past the Wall and risking White Walkers
就是希望能够看上一眼 这些令人惊叹的绚丽彩光
hoping to get rewarded with a glimpse of these amazing multicolored lights.
尽管有不少人如愿以偿 但也有很多人未尝所愿
And while many succeed, many leave un-auroraed.
这便带来了这样的疑问
Which begs the question:
观赏极光的最佳时间、地点是什么?为什么?
when where and how is the best place to see an aurora?
在哪儿观看极光
极光源自太阳
Auroras start with the sun.
尤其是当太阳向地球发射大量带电粒子的时候
Specifically, when the sun decide to shoot billions of tons of charged particles
这些带电粒子以质子和电子为主
mostly protons and electrons at the Earth,
如果没有地球磁场的保护
at speeds that would do some serious damage
这些高速粒子会造成某些严重的破坏
If we were not surrounded by a protective magnetic field
尽管 我们周围绝大多数质子和电子 都被地球磁场改变了方向
Our magnetic field redirects most of these protons and electrons around us,
不过 还是有一部分 会沿着地球磁力线
but some of them follow Earth’s magnetic field
飞向磁力线源头:地球的磁极
lines to their source: the magnetic poles.
这些粒子在飞向磁极的途中
On their way to the poles,
会和地球上层大气中的原子和分子产生碰撞
those charged particles crash into atoms and molecules in our upper atmosphere,
从而生成了极光
producing this.
考虑到地球磁场的形状
Because of how our magnetic field is shaped
以及极光通常产生的高度
and the height auroras typically happen above the Earth’s surface,
观看极光的最佳区域
the best place to see an aurora
实际上并非只在地球的磁极
is actually not right at the magnetic poles,
而是 在一个椭圆形区域内的任何地方
but anywhere in an oval shaped zone
这个区域边缘 距离磁极大概有2000公里
about 2,000 km from the poles.
这个区域被称为 极光环带
This zone is called the auroral oval
你向北方走的话 抵达极光环带会更加容易
And it’s much easier to be in the auroral oval if you go north.
这是因为 地球南端的极光环带
Because the southern one is mostly over
主要的覆盖区域 是南极洲和南大洋
Antarctica and the Antarctic ocean.
期待看到什么
幸运的话 会看到绿色的极光
If you’re lucky, green.
特别幸运的话 会看到紫色 粉色 甚至蓝色的极光
If you’re extra lucky, purple, pink, even blue.
如果拥有世界上最好的运气 则会看到红色的极光
If you’re the luckiest person on the planet, red.
不过你最有可能看见的 还是绿色的极光
But the most common aurora you’ll see is green.
原因有那么点复杂
The reason is kinda complicated,
不过 我们慢慢地来说
but we’ll take it slow.
首先 你需要了解一些事情
First, you need to know a few things.
第一点 能产生极光的 通常是太阳发射的电子 而并非质子
One, it’s the electrons from the Sun, not typically the protons that make auroras.
第二点 地球大气层越往高处 大气就越稀薄
Two, as you go further up in our atmosphere, there’s less and less of the atmosphere
而且 大气成分会发生变化
and the gases that make it up change.
在海平面高度的空气中
Down here at sea level, air
氮气占78%
is 78 % nitrogen,
氧气占21%
21 % oxygen,
其他气体占1%
and 1 % other stuff.
而在大约8万多米高的地球上层大气中
In our upper atmosphere, about 80 kilometers and up,
氧气实际上要比氮气含量更高
there’s actually more oxygen than nitrogen.
第三点 在这样的海拔高度上
Three at those high altitudes,
太阳发射的紫外线 事实上会把氧气分子 分解成氧原子
UV light from the Sun actually splits oxygen molecules into oxygen atoms.
好的 一个电子在与一个氧原子发生碰撞后 会让氧原子变得活跃
OK. So, when an electron crashes into an oxygen atom, it excites it to what
科学家们很有想象力地称之为 “激发状态”
scientists imaginatively call ‘an excited state’.
最终 氧原子将额外的能量 以光子的形式释放出来
Eventually, the oxygen will release its extra energy as a photon of light.
而这一个光子 则能够传播到地球的表面
That photon can travel down to the surface of the Earth,
成为我们观赏的极光的一部分
where you see it as part of an aurora.
光子确切的颜色 由光子拥有多少能量决定
The exact color of the photon depends on how much energy it has.
光子能量越高 颜色越绿
Higher energy photons are greener,
光子能量越低 颜色越红
and lower energy photons are redder.
氧原子另一个有趣的事实是
Now here’s another fun fact about oxygen:
它具有多种不同的激发状态
it has multiple different exciting states,
因此 氧原子能够吸收不同能量的电子
so it can absorb electrons of different energies.
如果它吸收的是 一个高能量的电子
If it absorbs a high energy electron,
那么 就会产生一个高能量的光子 又称为绿色光子
then a high energy photon is produced, aka green.
如果它吸收的是 一个较低能量的电子
If it absorbs a lower energy electron,
那么 就会产生一个较低能量的光子 又称为红色光子
then a lower energy photon is produced: aka red.
好的 那么你现在也许会问
OK so at this point, you might be asking:
如果 氧原子那么棒 能够同时产生绿色和红色的极光
if oxygen is so cool that it can produce both green and red auroras,
那为什么绿色极光更加常见呢
how come green ones are much more common?
如果 一个氧原子吸收了一个高能量的电子
If an oxygen atom absorbs a high energy electrons,
那么 氧原子发射出一个光子并从激发状态中恢复过来 只需要一秒钟
it relaxes back down and emit s a photon one second later.
而如果 一个氧原子吸收了一个较低能量的电子
But if it it absorbs a low energy electron,
那么 氧原子处在激发状态的时间 会变长很多
it stays excited much longer
确切地说 是110秒
–110s,to be exact.
这些短暂的时机 你可以看作是扼杀极光的机会
You can think of those time windows as aurora-killing opportunities,
这是因为 如果附近有一个分子 撞到了一个激发状态的氧原子
because if a nearby molecule crashes into an excited oxygen atom,
那么 这个分子就会让这个氧原子完全丧失激发能力
it totally throws the oxygen off its game.
原本应该给光子的额外能量
The extra energy that would have gone to the photon
就会反而传递到撞到氧原子的那个分子上
gets transferred instead to the molecule that crashed into the oxygen.
由于 红色光子激发 需要110秒
And because red photons need 110 seconds to brew,
因此 与发射绿色光子的氧原子比
those red-photon-emitting oxygens are much more likely to get
发射红色光子的氧原子 在释放出光子之前 更加有可能被撞击
Bashed before they release photons than the green-photon-emitting oxygens
产生极光的好办法 还有不少
There are more wrinkles to this story
比如 氮原子也能够产生粉色 蓝色 红色 紫色的极光
–for example, nitrogen can also make auroras — pinks, blues, reds, and purples…
而且 氢原子和氦原子也同样可以
and hydrogen and helium can too,
不过 那些原子就更加稀少了
but those are ever rarer.
现在让我们说一说
Now let’s talk about…
什么时候观看极光
你很有可能已经知道答案了 不过还要说 是在晚上
You probably already knew this, but… At night.
由于 极光比太阳光要暗淡上一百多万倍
Auroras are over a million times dimmer than sunlight,
因此 你在白天是无法看到极光的
so you’re not gon na see one during the day.
除非是世界末日了
Unless it’s the apocalypse.
不过 这也意味着
What that means, though, is that
在夏季 你几乎不可能看到北半球这边的极光
you’re much less likely to see a Northern aurora in the summer,
因为 白昼时间是如此地漫长
because the Sun is up so much longer.
就这样 在晚上 在北方 在冬季
So,at night, up North, in the winter.
如果可以 尽量避开有月亮的时候
and try and avoid the Moon, if you can.
还有 多云的时候
And well, clouds.
而且 太阳这头凶兽 变化无常
Also, the Sun is a mercurial beast.
这些粒子的数量和飞行速度
The number of particles and how fast they’ re going changes
根据不同类型的太阳活动 每天都在发生着变化
day to day based on different types of solar activity
不过 由于这些粒子抵达地球 需要花费几天的时间
but since it takes a few days for the stuff to reach us,
因此 我们实际上可以提前几天预测出观看极光的最佳地点
we can actually predict the best aurora-spotting a few days beforehand.
是的 它就是这样的应用程序
And yes, there’s apps for that.
PBS推出《Summer of Space》栏目 向你介绍我们的宇宙
PBS is bringing you the universe with Summer of Space
其中包含了六个非常棒的关于全新科学和历史的流播节目
which includes six incredible new science and history shows streaming
通过PBS.org网址和PBS视频应用程序也能观看
on PBS .org and the PBS video app
还有很多来自PBS数码工作室创作者的精彩片段
along with lots of spacey episodes from PBS Digital Studios creators.
感谢德雷珀公司及其登月黑客计划
Thank you to Draper and its Hack the Moon initiative
对PBS数码工作室的支持
for supporting PBS Digital Studios.
你知道登月宇航员的故事
You know the story of the Astronauts who landed on the Moon.
而你现在登陆网址www.hackthemoon.com
Now, you can log onto www.hackthemoon.com
则可以发现 男性及女性工程师们的故事
to discovery story of the male and female engineers
是这些工程师 让宇航员们能够安全地往返月球
who guided them there and back safely.
登月黑客网站 记录了阿波罗任务背后的工程师和技术
Hack the Moon chronicles the engineers and technologies behind the Apollo missions.
网站里有很多这些登月黑客们的照片 视频 和故事
Brought to you by Draper, the site is full of images, videos
它们均由德雷珀公司提供
and stories about the people who hacked the moon.
你将启程开始一场极光之旅吗
Are you heading out on an auroral journey?
一定要给自己穿上暖和的衣服
Make sure to bundle up aurorally,
在评论里告诉我们 关于你的极光故事吧
tell us your auroral stories in the comments,
我们下周再见
and we’ll aurora aurora aurora next week.
尝试十倍快地念出上文
Try saying that ten times fast.
谢谢观看
Thanks for watching.

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视频概述

介绍极光形成的原理 讲述何时何地来观赏极光

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视频来源

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