了解宇宙是如何运行的（2010）

How the Universe Works S08E01

Part 7 Jan. 30, 2022, 2:57 p.m.

can do some real damage
它会造成一些真正的破坏
if it were to explode
over a populated area.
为了防止这样的灾难
Narrator: To prevent
such a catastrophe,
我们需要找到所有轨道与地球轨道交叉的小行星
we need to find all asteroids
whose orbits cross our own.
探测是我们防御小行星的关键
Detection is crucial in
our defense against asteroids.
原因是它们越早被探测到
And the reason is the earlier
they're detected,
就越容易使它们偏离轨道，避免撞击地球
the easier it is to deflect them
away from hitting the earth.
你想要做偏转，第一步是探测
You want to do deflection,
the first step is detection.
问题是，小行星很难
Narrator: The problem is,
asteroids are very hard
被发现
to detect.
寻找小行星并记录它们所有的轨道
Finding asteroids
and cataloging all their orbits
确实是一项挑战
is really challenging.
它们可以在天空中移♥动♥得非常快
They can move quite fast
across the sky,
它们可能会
and they might go away
在太阳的另一边消失很多年很多年
on the other side of the sun
for years and years and years.
所以我们看不到它们
Narrator: So we can't see them.
即使它们在太阳的这一边
And even when they are
on this side of the sun,
也很难被发现
they're hard to spot.
但问题是，它们非常小
But the problem is,
they're very small
而且非常黑
and they're very dark,
我说的非常黑，就是指非常黑
and when I say very dark,
I mean really dark,
就像一块煤炭
like a lump of coal.
那么，如何才能找到一块
So how do you find
a small, dark rock
在太阳系中四处游荡的黑色小岩石呢？
just wandering around out there
in the solar system?
卡特琳娜巡天有了答案
Narrator: The catalina
sky survey has the answer.
位于亚利桑那州图森市山上的巨型望远镜
The huge telescope in the
mountains above tucson, arizona,
在20分钟内拍摄了一系列图像
takes a series of images
over a 20-minute period.
它在寻找任何移♥动♥的东西
It's hunting
for anything that moves
因为恒星不会移♥动♥，但小行星会
because stars don't move,
but asteroids do.
如果这是一颗非常明亮的小行星
Man: If it's a really
bright asteroid,
我们会在这四张图片上
we will see some bright points
看到一些亮点
of light
tracking across the four images.
哎，又来了
Ah, here we go.
这是一个实体物
This is a real object.
你可以看到它在天空中
You can see it's moving
across the sky here
从右下角移♥动♥到左上角
from the lower right
to the upper left.
我们今晚发现了一个天体，非常非常激动
We are very, very excited
to have discovered one tonight
因为这是一个接近太空的天体
because this is an object
that's approaching near space,
很可能就在地球附近
likely in the neighborhood
of earth.
卡特琳娜有局限性
Narrator: Catalina
has limitations.
它只能看到可见光
It can only see visible light,
所以特别暗的小行星可能会被错过
so a particularly dim asteroid
could be missed.
泰勒:小行星很冷
Thaller:
Asteroids are very cold.
它们通常离太阳很远
They're usually quite far away
from the sun,
但令人惊讶的是，我们找到它们的
but amazingly, the best way
最好方法是红外线
we have to find these
is infrared light
因为在人体尺度下很冷的东西
because things that are cold
by human scales
在红外望远镜里仍然是很热的
can still be very warm
to an infrared telescope.
所以即使小行星只比绝对零度
So even if asteroids are just
a few tens of degrees
高几十度
above absolute zero,
也有足够的热量来探测它们
that's still enough heat
to detect them.
当红外太空望远镜重新将目光
Narrator: When the infrared
space telescope neowise
转向小行星时
turned its gaze
onto asteroids,
立刻就有了结果
it had immediate results.
塞勒:Neowise目前已经
Thaller:
Neowise has now detected
在我们的太阳系中发现了近16万颗新小行星和彗星
close to 160,000 new asteroids
and comets in our solar system,
其中大约780颗
and about 780 of those
是靠近地球的
are things
that are near the earth.
其中10个近距离天体
Narrator: 10 of those near
objects have been classified
被归类为 p.H.A.S——有潜在危险的小行星
as p.H.A.S --
potentially hazardous asteroids.
如果没有neowise，我们可能会错过它们
Without neowise,
we would have missed them.
使用红外太空望远镜
Using an infrared
space telescope
是一种更好地探测地球附近
is a way of of better detecting
some of the smaller asteroids
一些较小的小行星和彗星的方法
and comets
in the near earth vicinity.
探测是重要的第一步
Narrator: Detection is
an important first step,
但它只是告诉我们
but it only tells us
那里有另一颗小行星
that there is
another asteroid out there.
一旦我们发现了一颗小行星
Once we've spotted
an asteroid,
我们只知道它只是一个小小的光点
all we know is that
it's a tiny dot of light.
我们对它一无所知
We don't know anything else
about it.
所以，当一颗新小行星被发现时
So when a new asteroid
is discovered,
最重要的事情是
the most important thing is
确定它的路径，然后跟踪它
to determine its path,
to track it, to figure out
弄清楚它是如何围绕太阳运行的
exactly how it's orbiting
around the sun
以及它离地球有多近
and how close
it's gonna get to earth.
为此，我们必须知道他们现在在哪里——
For that, we have to know
where they are now --
所以它现在的位置——
so its current location --
and measure how fast it's going
然后测量它的运动速度和方向
and which direction
it's travelling.
所有这些东西放在一起
All of these things together
are really important
对于追踪它们的下一个目标
for tracking
where it's gonna be next
以及它们是否会袭击我们都非常重要
and whether or not
they're gonna hit us.
为了得到这个信息
Narrator:
To get this information,
我们需要更大更强大的武器
we need something much bigger
and more powerful.
阿雷西博天文台
The arecibo observatory.
一旦卡特琳娜或其他望远镜
Once catalina
or another telescope
在我们的宇宙邻居中探测到一颗近地小行星
detects a near earth asteroid
in our cosmic neighborhood,
阿雷西博上千英尺高的望远镜就会启动
arecibo's thousand-foot dish
swings into action.
他们发现了这些小行星
They discover
these asteroids,
一旦我们知道了它们的位置
and then once we know
where they were,
我们就可以试着用射电望远镜
we can try and point
the radio telescope
对准它们看看它们现在的位置
and see where they are
at the moment
然后测量它们的准确位置和轨迹
and measure their exact location
and their trajectory.
阿雷西博通过使用无线电探测和测距
Narrator: Arecibo achieves
this level of precision
也就是通常所说的雷达