了解宇宙是如何运行的（2010）

How the Universe Works S08E09

Part 6 Jan. 30, 2022, 2:59 p.m.

严重的伤害
to human bodies.
当我们在太空中飞行时
Narrator:
As we ride through space,
地球磁场保护我们免受大多数宇宙射线的伤害
earth's magnetic field protects
us from most cosmic rays.
但2018年，我们发现了证据
But in 2018,
we discovered evidence
证明过去曾有一场
that a hail of space bullets
太空子弹冰雹淹没了我们星球的磁场
overwhelmed our planet's
magnetic field in the past.
在很多方面，我们都认为地球保护我们
In many ways,
we really take for granted
免受来自太空的伤害是理所当然的
how the earth
protects us from space,
但有记录显示，我们实际上
but there are records
that we've actually bounced
离爆♥炸♥的恒星太近了
a little too close
to exploding stars.
普莱特:海洋中的沉积物表明
Plait: Sediments in the ocean
show that
大约200万年前
about 2 million years ago,
铁60沉积在我们的海洋中
iron-60 was deposited
in our oceans.
铁60是铁的放射性同位素
Iron-60 is a
radioactive isotope of iron,
我们知道它在宇宙中存在的唯一途径
and there's only way we know of
it being made in the universe,
就是爆♥炸♥的恒星
and that is exploding stars.
♪
大约280万年前
narrator:
Around 2.8 million years ago,
一颗超新星在距离地球150光年的地方爆♥炸♥
a supernova exploded
just 150 light-years from earth.
几百年后，一股宇宙射线
A few hundred years later,
猛烈地轰击地球
a blizzard of cosmic rays
slammed into the earth,
撕裂了我们的磁场
tearing through
our magnetic field.
♪
这些太空子弹是导致超过三分之一的
these space bullets are
prime suspect in the extinction
沿海海洋物种灭绝的主要原因
of over 1/3 of
all coastal marine species.
♪
普莱特:现在，这并不一定是
plait: Now, this is not
necessarily tied to the earth
地球通过这些旋臂之一
passing through one
of these spiral arms,
但它告诉你，接近一颗超新星
but it shows you
that being close to a supernova
绝对不是你想做的事情
is not necessarily a thing
you want to do.
数百万年后
Narrator:
Millions of years in the future,
地球将穿过另一个旋臂
earth will pass through
another spiral arm
而我们的星球将继续在银河系中旅行
as our planet continues its
journey through the milky way.
我们会再次陷入危险之中
And we will wander
into harm's way once again.
但我们的太空之旅的另一部分
But there's another part of our
journey through space
仍然是个谜
that remains a mystery.
地球像一个陀螺一样绕着地轴旋转
The earth is spinning like a top
on its axis.
同时绕着太阳转
It's orbiting around the sun.
而太阳是绕着银河系中心运行的
The sun itself is orbiting
around the center
虽然离它非常遥远
of the milky way,
but that's far from it.
银河系在宇宙中加速前进
Narrator: The milky way is
speeding through the universe,
而我们也被拖着前进
and we are being dragged
along for the ride.
问题是我们看不到前进的方向
The problem is we can't see
where we're going.
地球可能会面临银河系的崩溃吗？
Could earth be headed
for a galactic crash?
♪
♪
[尖叫]
[ screaming ]
♪
就像最疯狂的主题公园里的游乐设施
narrator: Like the craziest
of theme park rides,
我们正在地球上进行一次穿越宇宙的疯狂旅行
we are riding the earth on a
wild journey through the cosmos.
♪
我们的星球在围绕太阳系旋转、倾斜和摆动
our planet spins, tilts, and
wobbles around the solar system
♪
就像在银河系中摇摆的旋转木马
while bobbing like a carousel
through the milky way.
♪
地球在宇宙空间中运动的动力学
the dynamics of the earth
moving in the cosmic void is,
就像是你所能想象的最不可思议的旅程
like, the most unbelievable
journey you could ever imagine,
当你到达更大的尺度时
and as you get to larger scales,
运动只会变得越来越大，越来越有活力
the motions only become grander
and larger and more dynamic.
♪
1977年，我们试图
narrator: In 1977,
we tried to work out
找出最大的运动——
the largest motion of all --
♪
即银河系在宇宙中的运动
the movement of our galaxy
through the universe.
线索隐藏在宇宙微波背景中
Clues hide in the
cosmic microwave background,
这是宇宙诞生时的遗迹
a remnant from the birth
of the universe.
布洛克:宇宙微波背景辐射
Bullock: The cosmic microwave
background is the radiation
是大爆♥炸♥后留下的辐射
that's left over
from the hot big bang.
宇宙微波背景像固定的东西一样
The cosmic microwave background
is shining in all directions
向各个方向发光
as sort of this fixed thing,
如果我们以一定的速度穿过它
and if we're moving through it
with some speed,
我们就能在光中看到它
we will see that
in the light itself.
你可以测量它，通过测量它
You can measure that,
and by measuring that,
你可以知道我们在这个空间中移♥动♥的速度
you can get a sense of how fast
we're moving through that space.
通过追踪我们在宇宙中
Narrator: By tracking our
movement through the universe
针对一个固定点的运动
against a fixed point,
我们可以计算出银河系的速度和方向
we can work out the milky way's
speed and direction.
♪
但在1977年，望远镜并不是完成这项工作的最佳工具
but in 1977, telescopes weren't
the best tool for the job.
特伦布雷:在1977年冷战期间
Tremblay:
During the cold war, 1977,
有一架新型解密的u-2间谍飞机
you have the newly declassified
u-2 spy plane,
这是一架高空侦察机
this very high-altitude
reconnaissance aircraft.
美国国家航♥空♥航♥天♥局将其中一架改装为朝上的窗户
Nasa retrofitted one of them
with an upward-facing window,
并安装了非常灵敏的接收器
and with very
sensitive receivers,
这架间谍飞机成为了第一个实验室
this spy plane became
the first experiment
首次明确地测量了银河系
to for the first time
definitively measure the motion
在宇宙中的运动
of the galaxy
through the universe.
当u-2侦察机在地球上空飞行时
Narrator: As the u-2 spy plane
soared above the earth,
它以前所未有的细节
it measured the
cosmic microwave background
测量了宇宙微波背景
in unprecedented detail.
♪
数据显示，我们的星系
the data revealed
that our galaxy races
在宇宙中以每秒370英里的速度运行
through the universe
at 370 miles a second.
♪
时速超过100万英里
that's over 1 million miles
an hour.
♪
萨特:想想星系有多大
sutter: Think of how big
a galaxy is.
数以亿计的恒星
Hundreds of millions of stars,
而我们以每秒数百英里的速度移♥动♥
and we're moving at
hundreds of miles per second.
这确实有点让人兴奋
That's just a tiny bit
mind-blowing.
♪
银河系的速度并不是银河系之旅中
narrator: The milky way's speed
isn't the most alarming part