了解宇宙是如何运行的（2010）

How the Universe Works S09E07

Part 2 March 16, 2022, 8:55 a.m.

在不到一秒的时间里
In a
fraction of a second,
这颗恒星的核心就会从一颗行星的大小
the star's core collapses
down from the size of a planet
坍缩到一个小城市的大小
to about the size
of a small city.
当这种情况发生时，一切都会变得一团糟
And when that happens,
all hell breaks loose.
巨大的能量突然被释放
A huge
amount of energy
迫使坍塌的层
is suddenly released,
which forces
向外退出去
the collapsing layers back out.
结果，就是我们称之为超新星的巨大爆♥炸♥
The result-- an enormous
explosion we call a supernova.
詹姆斯·布洛克:超新星产生的冲击波
JAMES BULLOCK: The
shockwave from a supernova
以每秒数千英里的速度扩散
rips out at thousands
of miles per second.
在很短的一段时间里
And for a brief period
of time, they're
它们比整个星系还要亮
brighter than an entire galaxy.
一颗超新星可以毁灭地球上的生命
A supernova could
devastate life on Earth.
证据在海底可以找到
And the evidence can be found
at the bottom of our oceans.
米歇尔·泰勒:这里有
MICHELLE THALLER: There
are layers and layers
一层又一层的淤泥
of silt that have built up.
大约260万年前，似乎有一层
And there seem to be a layer,
about 2.6 million years ago,
富含一种非常奇怪的化学元素
that was enriched in a very
strange chemical element,
叫做铁60
something called iron-60.
菲尔·普莱特:铁60是铁的一种放射性同位素
PHIL PLAIT: Iron-60 is a
radioactive isotope of iron,
它不会持续很长时间，只有几百万年
and it doesn't last very long,
just a few million years.
我们所知道的唯一能产生铁60的地方
And the only place that we
know of that can make iron-60
就是爆♥炸♥恒星中的超新星
is a supernova in
an exploding star.
这意味着，在过去的几百万年里
That means there must have
been a supernova close enough
一定有一颗超新星离地球足够近
to the Earth within the
past couple of million years
从而在我们的星球上沉积了物质
to have physically deposited
material on our planet.
这把我吓坏了
That freaks me out.
在我们的星球上这种令人震惊的攻击的标志
The sign of this
shocking assault on our planet
就是这种非常罕见的一薄层的铁
is a thin layer of this
very rare type of iron.
我们在每个海底的泥里都能找到它
We find it in the mud
of every ocean floor
而且总是在同一深度
and always at the same depth.
这些星际尘埃表明一定是在260万年前
This interstellar dust
must have drenched
有一次巨大爆♥炸♥浸透了我们的世界
our world in one enormous
burst 2.6 million years ago.
那是一段可怕的时光
It was a terrible time.
三分之一的大型海洋动物物种突然灭绝
A third of large animal species
in the sea suddenly died out.
那里有一些非常棒的鱼
There were some
pretty amazing fish.
也许最令人惊讶的是巨齿鲨
Probably the most
amazing is the megalodon,
一种巨大的鲨鱼——牙齿有餐盘那么大，当然还有很多
a giant shark-- teeth the size
of dinner plates and so on.
它们都在260万年前的
But they went extinct
2.6 million years ago
上新世末期就灭绝了
at the end of the Pliocene.
发生了什么事？
What happened?
菲尔·普莱特:很多海洋生物都死了
PHIL PLAIT: A lot of
sea creatures died.
它们中的很多都生活在浅水中
And a lot of them were
in shallow waters,
而深水动物往往能幸存
whereas deep-water
animals tended to survive.
这听起来有点像超新星惹的祸
That sounds kind of
like a supernova.
它可能会影响我们的大气
That can do things that
would affect our atmosphere,
会影响浅水，但不会影响深水
would affect shallow water,
but not deeper water.
超新星会产生大量的宇宙射线
Supernovas create
huge amounts of cosmic rays.
当它们与其他原子碰撞时
When they crash
into other atoms,
它们会分解并产生大量的被称为μ介子的
they break up and produce
showers of dangerous shrapnel
危险弹片
called muons.
这些带电粒子与电子相似
These charged particles
are similar to electrons,
只是重200倍
only 200 times heavier.
所以它们穿透的更深，造成的伤害更大
So they penetrate more
deeply and cause more damage.
它们可以穿透我们的大气层
They can pierce
through our atmosphere,
穿透我们的皮肤，进入细胞
pierce through our
skin, get into a cell,
并破坏 DNA
and disrupt the DNA.
它们会直接穿透老鼠
They'll go right through
a mouse but deposit
但会沉积在更大的动物体内
in the body of a larger animal.
因此，对于巨齿鲨这样大的动物来说
So the impact on an animal
the size of a megalodon,
这种影响可能是非常极端的
say, could be pretty extreme.
μ介子可以破坏 DNA，导致突变和癌症
Muons can shatter DNA,
causing mutations and cancer.
但它们在水中移♥动♥时，力量会减弱
But their power
weakens as they travel
这可能就是为什么只有深海生物
through water, which
may be why only
幸存下来的原因
deep sea creatures survived.
大灭绝告诉我们，我们并没有
The extinction really
tells us that we're not
与宇宙和宇宙中的事物
separate and apart from
the universe and the goings
分隔开，对吗？
on up there, right?
比如超新星爆♥炸♥之类的事情——
Supernova going off
and things like that--
好吧，这是一场很亮的表演
OK, it's a pretty light show.
但
No.
它对地球上的生命和我们都有直接的影响
It is a direct impact
to life on Earth and us.
那么我们有灭绝的危险吗？
So are we in
danger of extinction?
参宿四快要爆♥炸♥了吗？
Is Betelgeuse about to explode?
当恒星爆♥炸♥成超新星时
When stars explode
as supernovas,
它们可以摧毁数百光年外的行星
they can devastate planets
hundreds of light years away.
参宿四距离地球约550光年
Betelgeuse is about 550
light years from Earth.
因此，当它在2019年急剧变暗时
So, when it dramatically
dimmed in 2019,
科学家们感到担忧
scientists were concerned.
但参宿四曾经黯淡过
But Betelgeuse
has dimmed before.
亚历克斯·菲利平科:参宿四
ALEX FILIPPENKO:
Betelgeuse varies
这些年变化很大
quite a lot over the years.
有一些循环，有时
There are some
cycles, and sometimes
这些循环同时出现，就会得到一个暗的最小值
these cycles come together,
and you get a deep minimum.
因此，当恒星接近生命末期时
So dimming is part
of the star's natural cycle
变暗是其自然周期的一部分
as it nears the end of its life.
但为了获得全貌，我们测量了参宿四的温度
But to get a full picture, we
took Betelgeuse's temperature.
如果恒星在变暗，那就意味着它的表面
If the star was dimming, that
would mean that the surface
在随着时间的推移而冷却
was cooling over time.
实际上我们测量了参宿四的温度
We actually made measurements
of the temperature of Betelgeuse
发现这并没有发生
and found out that
wasn't happening.
它几乎没有冷却
It hardly cooled at all.
它只冷却了，大概50或100度
It cooled, like,
50 or 100 degrees.
如果它即将爆♥炸♥，你可能会认为
You might expect
a much, much more
表面温度会发生非常非常
dramatic change in the