了解宇宙是如何运行的（2010）

How the Universe Works S03E06

Part 2 Dec. 22, 2021, 6:46 p.m.

It Would Be Like A Hard Restart For The Planet Itself.
这场噩梦有可能成真吗
Could This Nightmare Become A Reality?
目前就连最近的流量行星
Right Now Even The Closest Rogue Planets We've Discovered
离地球都有万亿英里远
Are Still Trillions Of Miles From Earth.
我们临近的行星
And Our Neighboring Planets Have Settled
已经形成稳定的轨道
Into Calm, Stable Orbits.
我们短期内
We're Not Gonna Get A Planetary Collision
不会碰到行星撞击
Any Time Soon,
但是行星的引力会互相影响
But All The Gravity Of The Planets
并改变彼此的轨道
Play With Each Other And Change Each Other's Orbits.
所以你将时间
So Clearly If You Run The Clock Work Of Time Forward
放大到几十亿年以后
Billions Of Years,
我们当然有可能
Yes, It's Entirely Possible
再度遭遇行星撞击
That We Might Have Another Planetary Collision.
但那会是很久以后的事情了
You Just Don't Have To Worry About It For A Long, Long Time.
40亿年前
4 Billion Years Ago,
一场天崩地裂地撞击为地球带来生命
A Devastating Collision Made Life On Earth Possible.
20亿年后
2 Billion Years Later,
地球的生命却有可能自我毁灭
That Life Threatens To Destroy Itself.
我们的蓝色星球
Our Blue Planet --
在充满敌意的宇宙里滋养着生命
In A Hostile Universe, It Sustains And Nurtures Life.
24亿年前
2.4 Billion Years Ago,
简单的单细胞生物
Simple, Single-celled Organisms
漂流在富含营养的海洋里
Drift Through The Nutrient-rich Oceans.
但是他们的世界即将被摧毁
But Their World Is About To Be Destroyed.
我们现在谈论的大灭绝
When You Talk About Mass Extinctions,
至少有两种表现形式
You Have At Least Two Types --
一种是来自外太空的威胁
One Danger Coming From Outer Space,
另外一种则来自我们地球本身
Another From Our Own Very Backyard On The Planet Earth.
地球绕着太阳运行
The Earth Circles The Sun,
但是这条轨道并不稳定
But This Orbit Is Unstable.
它在数十万年间不断改变
Over Hundreds Of Thousands Of Years, it Changes
地球一边在自转
Swinging The Planet Further Out Into Space
同时也在远离太阳
And Pivoting On Its Axis.
地球远离太阳便会使得温度下降
Tilted Away From The Sun, The Earth Cools.
24亿年前
2.4 Billion Years Ago,
某种原因使得这种自然降温现象
Something Turns This Natural Cooling
变成了全球大灾难
Into A Global Catastrophe.
那就是宇宙间最危险的东西
It Is One Of The Most Dangerous Things
一种生物
In All The Universe Life.
海洋中遍布着微生物
Tiny Organisms Populate The Oceans.
当时没有氧气
There's No Oxygen Around
大多数的生物也很习惯
And That's The Way Most Of Them Like It.
后来地球演化出新的细菌
But Then A New Kind Of Bacteria Evolves --
蓝藻细菌
Cyanobacteria.
蓝藻细菌造成了严重的气体问题
And These Guys Create A Serious Gas Problem.
想象一下几十亿年前的地球
Imagine Earth Billions Of Years Ago.
当时没有氧气大家也非常适应
There's No Oxygen. Everybody's Happy.
后来蓝藻细菌开始制♥造♥氧气
Then Cyanobacteria Start Making Oxygen.
在当时这是有毒的污染物
It's A Toxic Pollutant.
要是当时有大气管制单位
If There Was A Regulatory Agency At The Time,
蓝藻细菌会被当做危险生物
They Would've Been Outlawed.
最后蓝藻污染了全世界
Eventually They Polluted The Whole World.
造成了全球性的生态危机
They Had Really Precipitated
严重的氧气危机
An Ecological Crisis Of Global Proportions.
严重的氧气危机
The Great Oxygen Crisis
扰乱了让地球保暖的温室效应
Upsets The Greenhouse That Keeps The Planet Warm.
全球气温骤然下降
Global Temperatures Plummet.
最大的元凶是生物
The Ultimate Culprit Is Biology.
生物将地球弄的一团糟
Biology Makes A Mess Of The Planet,
它们制♥造♥氧气
Produces Oxygen.
而氧气会破坏甲烷的温室效应
The Oxygen Destroys The Greenhouse Of Methane
所以地球就结冰了
And That Freezes Up The Earth.
24亿年前冰河从南北极开始蔓延
2.4 Billion Years Ago, Ice Creeps Out From The Poles.
阳光被冰雪反射
Instead Of Warming The Planet,
从而没法温暖地球
Sunlight Bounces Off The Ice,
气温下降
Temperatures Fall,
形成更多的冰进而让更多的阳光被反射到太空
Creating More Ice Which Bounces More Sunlight Back Into Space,
如此不断继续
And So On And So On
知道降温现象变得势不可挡
Until The Cooling Becomes Unstoppable.
冰河不断扩张
The Ice Marches On.
温度骤降
Temperatures Plunge.
蓝色星球彻底变白
The Blue Planet Turns White.
这就是雪地球时期
It's A Snowball Earth.
惊人的是这种现象可能不只发生一次
And Incredibly, This May've Happened Not Once
在接下来的几十亿年里至少发生了三次
But At Least Three Times Over The Following Billion Years
地球则继续绕日运行
As The Planet Lurched Around The Sun.
尽管这时期地球的环境极度险恶
But Throughout All Of This And Against All The Odds,
还是有些生物存活了下来
A Handful Of Species Clung To Life,
这一切要感谢火山
Thanks To Volcanoes.
虽然当时地球几乎被并覆盖了
Even In An Earth That Was Covered Almost Entirely By Ice,
但是火山还是能突破冰层
Volcanoes Would've Been Punching Through That.
所以火山周围会有小池塘
So You Certainly Have Pockets Of Water Lying About.
生命就可以存活
And Life Was Able To Carry On
然后熬过冰冻时期
And Get Through These Cold Periods.
在这时期
And The Whole Time,
让生命延续下去的火山
The Volcanoes That Help Sustain Life
一直在喷发出二氧化碳
Have Been Pumping Out Carbon Dioxide.
这种温室气体持续增加
As This Greenhouse Gas Increases,
大气层因而变暖
The Atmosphere Warms.
到了六亿四千万年前
Until 6♥4♥0 Million Years Ago,
最后一次重大的雪球地球期结束
The Last, Great Snowball Earth Ends.
生还者纷纷迎向新世界
And The Survivors Emerge Into A New World.
雪球地球时期结束后一切变得很有意思
After Snowball Earth Goes Away, Things Get Very Interesting.
地球出现了蓬勃生机
A Lot Of Opportunities Open Up For Life,
水开始流动并开始溶解
Water's Flowing, Ice Is Melting,
尚未分解的有机物开始累积
Organic Material Built Up That Hasn't Been Decomposing.
你可以想象那种万物齐发的情景
So You Can Imagine That There Will Be A Burst Of Development.
这时候
In The Meantime,
蓝藻细菌制♥造♥出更大量的氧气
Cyanobacteria Have Been Churning Out Ever More Oxygen.
其他生物必须学会呼吸氧气不然就必死无疑
Other Organisms Will Either Learn To Breathe It Or Die.
许多生物发现
Many Organisms Decided
氧气也有好处
That This Poison Could Be Useful,
它有能量
It's Energetic,
可以当作生物的能量来源
And That Allowed Them To Have An Energy Source
这种能量足以让生物
That Was So Powerful
发展出大型的复杂结构
That They Could Build Huge, Complex Structures --
接着动物出现了
Poof, Animals.
雪球地球是环境的浩劫
Snowball Earth Is An Environmental Disaster
却成就了演化
And An Evolutionary Triumph.
复杂生物纷纷出现
Complex Life Flourishes.
但这些生物多半无法演化下去
But Most Of These Creatures Will Never Evolve Beyond This Point.
有种因素让它们停止发展
Something Stops Them Dead.
这是宇宙中最强大的武器
It Is The Most Powerful Weapon In The Universe,
能够在一瞬间发动攻击
And It Strikes In The Blink Of An Eye.
尽管凶暴的宇宙危机重重
In A Violent Universe,
生命还是活了下来
Against All The Odds, Life Survives.
但是想象一下
But Consider This --
宇宙可以随时扣动扳机
At Any Moment, The Universe Could Pull The Trigger
从神秘的太空深处发射致命射线
On A Secret, Deep-space Death Ray,
毁灭地球的所有生物
Obliterating All Life On Earth.
在上世纪60年代之前没人知晓它的存在
And Until The 1960s, Nobody Even Knew It Existed.
1967年正值冷战的巅峰时期
1967 -- The Height Of The Cold War.
美国和苏联展开军备竞赛
The United States And Soviet Union raced To Outgun Each Other,
并且储备和测试核武器
Stockpiling And Testing Nuclear Weapons.
美国担心苏联有办法
America Was Worried That The Soviet Union
在太空测试核武器
Would Be Able To Test Nuclear Weapons In Space.
美国就连续发射卫星到太空
So What America Did Is Launch The Series Of Satellites
以寻找核试验一定会发出的
To Go Out Into Space And Look For The Tell-tale Flash
伽玛射线闪光
Of Gamma Rays From Nuclear Tests.
1967年7月2日