宇宙（2007）

The Universe S05E06

Part 3 April 22, 2021, 1:50 p.m.

we know where those objects are.
足以让我们通过观察来定位
So, we'd have long, long lead time and warning.
所以我们有很久的准备和警戒时间
It's actually the smaller ones
事实上更大的威胁
that are the bigger risk,
是小型行星
as they happen more often and they're harder to find.
因为其频率更高而且不易于发现
Imagine that one of these smaller asteroids
想像一下其中一颗小行星
is streaking toward a city.
正向城市俯冲
It may not be spotted
而直到迫在眉睫的时候
until just a few hours before impact,
人们才发觉它
leaving little time for evacuation
来不及疏散人群
and no chance to try and deflect it in space.
更没有机会将它扼杀在宇宙中
If it's about 100 feet wide on impact,
假设撞击宽度为100英尺
then it will hit with the energy of
那将产生
a five megaton nuclear blast,
五百万吨♥核爆♥炸♥的能量
400 times more powerful than the atomic bomb
是当年在长岛爆♥炸♥的原♥子♥弹♥能量的
dropped on Hiroshima.
四百倍
When it hits the earth, it can cause a lot of damage,
撞击地球的时候将会带来极大的破坏
because the crater that's produced is
因为由此产生的
typically 10 or 20 times
陨石坑大小往往是
the width of the incoming object.
撞击物体宽度的10到20倍
So, that would be a thousand or a few thousand feet.
因此陨石坑将达到几千英尺直径
And many miles surrounding the impact region
并且周圈的大♥片♥地域
are affected by all the debris that gets ejected.
也会受到喷射出来的碎片的影响
You'd have all this stuff raining down upon you.
这些东西将倾盆落在你身上
But even if the asteroid hit
然而即使小行星的撞击地点
hundreds of miles from the city,
是在城市的几百公里之外
it could still create chaos
仍然会把那里人们的生活
for the millions of people living there.
搞得糟糕不堪
The food supply for the city residents
如果小行星撞击的是大型农业区
could be drastically altered
那么居民食品供应
if the asteroid hit a major agricultural area nearby.
将会极度短缺
Not only would all of the humans
不仅仅是人类
there be very likely dead,
面临死亡的威胁
but it would sear
但是这能够烧焦
hundreds of square miles of the growing lands.
数百平方英里的植被
It would destroy all the current crops
它能摧毁所有种植的庄稼
and it would render
并且导致大面♥积♥的土地
the area pretty unusable for quite a period of time.
在很长一段时间内成为废地
And smaller asteroids
而一些体积更小的小行星
don't even need to impact the ground
甚至根本不用撞击地面
to cause widespread destruction.
就能造成大面♥积♥的破坏
In 1908, an air burst
1908年在西伯利亚通古斯卡河附近
from an asteroid that broke apart in the atmosphere,
由于一颗小行星在大气层中爆♥炸♥
leveled an estimated 80 million trees
从而导致了
over hundreds of square miles,
数百平方英里内
near the Tunguska river in Siberia.
八千万棵树木的死亡
When an asteroid or a comet is coming toward the earth,
当一颗小行星或是彗星袭击地球时
it first encounters the atmosphere
首先碰到的是大气层
and it squeezes it,
大气层会挤压它
it compresses it, and that pressure
强烈的压缩所产生的压力
causes the asteroid or comet to explode.
会使得小行星或者彗星发生爆♥炸♥
That explosion then spreads the energy
如此的爆♥炸♥会将其
over a vast region
所带来的能量释放到
of the ground below it.
位于大气层之下的很大一片区域
So, these atmospheric air bursts
所以在大气层中的
are very dangerous as well.
爆♥炸♥也非常的危险
But the rock that caused all of that destruction
但是陨石所产生的破坏性
may have been even smaller than first thought.
或许要比我们开始想象的那样小
When it hit the atmosphere,
当它撞击大气层时
the Tunguska object
若是把通古斯卡看做一个物体
may have been only a few dozens of yards across,
那么这个物体或许仅仅只有几十码宽
instead of hundreds of yards,
而不是像起初估计的那样
as originally estimated.
有数百码宽
At first, it may seem like a good thing,
在一开始这看起来是件好事
Tunguska smaller than we thought.
因为通古斯卡远比我们想象的要小
But it's actually a bad thing
但事实上这对于
for our future predictions,
我们日后的预测是件坏事
because there are more smaller objects
因为小型小行星
than larger ones.
比大型小行星要多
So if a small object
所以如果一个小的天体
can cause that much damage,
就能产生如此大的破坏
then that means
那么意味着
it's going to happen more often than
大型天体撞击的频率
if it were a big object.
比原先想象的要更快
We may have that impactor
我们或许每几百年里
every very few hundred years,
就会受到次撞击
instead of every few thousand years.
而不是几千年
At the really small end of the scale,
体积小于
below about 100 feet,
一百英尺的小型太空石块
space rocks are often known as meteoroids
通常被称为流星体
instead of asteroids.
而不是小行星
Shooting stars are caused by meteoroids
流星雨就是由于流星体
burning up in the atmosphere.
在大气层中燃烧形成的
They're sometimes captured by amateur cameras,
流星雨不时的会被业余相机捕捉到
with some small chunks hitting the ground
伴随着一些小石块撞击到地面
or even cars or buildings.
或是汽车和建筑物上
In fact, the earth's atmosphere is
事实上地球的大气层
pelted with objects from outer space far more often
受到外太空物体撞击的频繁度远远
than most people realize.
超过人们的了解
I'm here at this active rock quarry,
我现在来到这个工作当中的采石场
next to this big pile
在这巨大的碎石堆旁
of crushed rock, because this is about
因为这就是冲撞地球的
the amount of stuff,
物体的总量
the amount of dust and sand and pebbles
包括灰尘沙石子
that hit the earth's atmosphere every day,
它们每天都在撞击着地球的大气层
about 100 tons.
大约有一百吨♥之多
That's enough to fill about
这足够装满
six or seven of these dump trucks.
六至七辆自卸卡车
Now, down here, we've got a basketball-sized rock.
这儿有个篮球大小的石头
On average, about two of these
平均每天有两个这样大小的石头
slam into the earth's atmosphere every single day.
猛烈撞击着地球的大气层
Next is the small car-sized object.
接下来是小汽车大小的物体
Imagine this pile of rocks as one object slamming
想象一下一个有这堆石头大小的物体
into the earth's atmosphere,
猛烈撞击到地球的大气层
about the size of a small car.
物体和一辆小汽车的大小一样
This happens about once every two weeks.
这样的撞击每两个星期就发生一次
But even something this big is
但是即使是这样庞大的
probably gonna burn up completely
物体也将在到达
before reaching the earth's surface.
地球表面之前被完全燃尽
For a typical object
对于一个典型的
hitting the earth's atmosphere,
物体撞击地球大气层来说
it needs to be at least 100 feet in diameter
这个物体的直径至少要在一百英尺
to actually do serious damage to the surface.
才能够对地球表面造成严重的破坏
Now, 100 feet is a really big rock.
然而直径为一百英尺的石头非常巨大
That's like going from the front of
这段距离大约是从
the dump truck over there
卡车的前端一直到
all the way to that orange cone over there.
那边的橘色交通锥的长度
At the other end of the spectrum is earth's largest
在这幅光谱图的另一末端处
confirmed impact crater,
是地球最大的一个陨石坑
located in Vredefort, South Africa.
陨石坑位于南非的弗里德堡
It stretches more than 180 miles across,
陨石坑可延伸长达一百八十多英里
and drastically changed the ancient earth,
二十亿年前的撞击
when it hit about two billion years ago.
使地球发生了巨变
It would have sent a sheet of material into space,
这会将物质又反送回太空
which would then have come back
而这物质将再返地球
and impacted on the earth,
并对地球产生影响
ignited fires if there was anything to burn.
比如点燃任何可♥燃♥物♥
And the climactic effects from that impact
并且气候效应也会受到影响
would have lasted for decades.
而且有可能持续数十年
The oceans would have been completely acidified.
海洋可能会被完全酸化