了解宇宙是如何运行的（2010）

How the Universe Works S06E04

Part 2 Dec. 22, 2021, 7:22 p.m.

Neptune snowplows these bodies out.
这就柯伊伯带的成因
They because the Kuiper belt,
这个由数千个冰和岩石组成的小天体带
the band of thousands of small bodies of ice and rock
就在海王星的轨道之外
just beyond Neptune's orbit.
你可以把柯伊伯带的结构想象成
You can think of the structure of that Kuiper belt as, like,
谋杀现场墙上的血迹
blood splatter on the wall at a murder scene.
这是海王星猛烈向外移♥动♥时
It's the record of this really violent of Neptune
穿越太阳系的记录
migrating outward across the solar system.
但海王星的运动不只是
But Neptune's movement doesn't just fling
把这些小冰体抛到柯伊伯带
these small icy bodies out into the Kuiper belt.
它也使其中一些撞向太阳
It also sends some of them crashing in towards the Sun.
有些还轰炸了早期的地球
Some bombard the early Earth.
这是自太阳系诞生以来
It's the most violent time on our planet
地球上最猛烈的时期
since the birth of the solar system itself,
也就是太阳燃烧形成5亿年之后
500 million years after the Sun flared into life.
这被称为晚期重轰炸时期
It's called the late heavy bombardment.
在晚期重轰炸中
During the late heavy bombardment,
你会不断看到石头从天上掉下来
you had rocks literally falling down from the sky constantly.
这将是生命的最糟糕的时刻
This would've been a terrible time for life.
然而，这一连串的冰体
And yet, this cascade of icy bodies
也带来了生命所必需的东西
also brings something essential for life.
太阳系外♥围♥天体的一个特点
One characteristic of the outer solar system bodies
就是我们经常能发现有机物
is that we often find organics.
有机物为我们今天
Organics provide the basis
所发现的所有生物提供了基础
for all living organisms we find today.
它们是在早期太阳系尘埃颗粒表面
They're carbon-based molecules that form on the surface
形成的碳基分子
of dust grains in the early solar system.
岩质内行星在这些有机物成长的过程中会把它们卷走……
The rocky inner planets sweep up these organics as they grow...
但这些年轻行星焦灼的表面
But the scorched surfaces of the young planets
太不适合
are too inhospitable
这些脆弱的分子生存了
for many of these delicate molecules to survive.
然而，在这些海王星抛向早期地球的
Yet organics remain intact on the small, icy bodies
太阳系外♥围♥小型冰态天体上
of the outer solar system
有机物依然完好无损
that Neptune tosses towards the early Earth.
海王星是太阳系的宇宙传送服务员
Neptune was the solar system's cosmic delivery service.
远在天王星和海王星之外
As far away as Uranus and Neptune are,
太阳系外♥围♥冰巨星的存在
the existence of ice giants in the outer solar system
可能对今天地球的存在至关重要
may have been critical for the existence of Earth today.
这些冰巨行星所做的可能不仅仅是
And the ice giants may have done
为地球上的生命提供了动力
more than give life on Earth a kickstart.
他们可能阻止了
They may have prevented our planet
我们的星球被完全摧毁
from being completely destroyed.
冰巨人……天王星和海王星
The ice giants... Uranus and Neptune,
这两个遥远的巨行星
distant giant worlds
可能将生命元素带到地球上
that may have delivered the elements of life to Earth.
没有它们，我们的星球可能根本就不存在
Without them, our planet itself might not exist at all.
这些冰巨星是迷人的世界
These ice giants are fascinating worlds,
但它们可能比这更重要
but they may be even more important than that.
他们可能是我们在这里的原因
They might be the reason we're here.
大约40亿年前
Around 4 billion years ago,
年轻的地球受到
the young Earth is under threat
太阳系恶霸木星的威胁
from our solar system's bully, Jupiter.
木星位于多岩石的内行星
Positioned between the rocky inner planets
和巨大的外行星之间
and the giant outer ones,
木星主宰着整个太阳系
Jupiter dominates the solar system.
当你的太阳系中有一个像木星这样的庞然大物时
When you have a behemoth like Jupiter in your solar system,
它的行为在一定程度上决定了其他所有事物的行为
what it does determines in part what everything else does.
当木星和土星
As Jupiter and Saturn lock
锁定它们的引力之舞时
into their gravitational dance,
它们向外迁移，开始远离太阳
they migrate out, away from the Sun.
木星巨大的引力会把地球
Jupiter's immense gravity should pull Earth
和金星一起拉过来
and Venus along with it.
地球和金星的轨道
Earth and Venus' orbits should stretch
应该会相互拉伸和重叠
and overlap with each other.
这将是一场即将发生的碰撞……
It's a collision waiting to happen...
……庆幸的是……它没有发生
...except... It didn't.
所以我们在地球上谈论这个事实
So by the fact that we're talking about this here on Earth
表明地球和金星
suggests that Earth and Venus
在太阳系早期并没有受到影响
didn't have an impact early in the solar system
而当时木星和土星正在迁移
when Jupiter and Saturn were migrating.
似乎有什么东西保护了我们
Something appears to have protected us.
科学家们认为，在木星
Scientists think something yanked Jupiter
有机会把地球和金星拉到碰撞轨道之前
into a different orbit before it had a chance to pull
有什么东西把木星拉到了不同的轨道上
Earth and Venus on a collision course.
但是是什么导致了木星的迁移
But what could cause such a large jump
有如此大的飞跃呢？
in Jupiter's migration?
此时，在这个故事中冰巨人出场了
This is where the ice giants enter the story.
让木星在迁移过程中有一个大的跳跃
Getting Jupiter to make a big jump in its migration
并不容易
is not easy,
所以最好方法就是让模拟器
and so the best way that the models have been able
真实再现这种跳跃
to actually recreate this jump is to have Jupiter
让木星将海王星大小的物体
actually eject something the size of Neptune
完全从太阳系中喷出
out of the solar system entirely.
木星有很大的引力
Jupiter has a lot of gravity,
如果你离它太近
and if you get too close to it,
在向木星坠落的过程中你就会被加速
you're going to be accelerated as you fall in towards Jupiter,
就有可能会这样把一颗行星
and it's possible that you can eject a planet
完全甩出太阳系
completely out of the solar system this way.
这就好比是弹弓
It's basically slingshotting it.
但是即便是对木星来说
But a planet the size of Neptune
海王星那么大的行星还是很重的
is heavy, even for Jupiter,
把它弹射出太阳系就会给木星
and slingshotting it out of the solar system
一个反作用力
gives Jupiter a kickback.
木星被位到新的轨道上，地球得救了
Jupiter is knocked into a new orbit, and Earth is saved.
但究竟是哪个冰巨人为我们牺牲了自己？
But which ice giant sacrificed itself for us?
海王星仍然在太阳系中
Neptune is still in the solar system,
当然还有天王星
and so is Uranus.
如果你用计算机模似器
If you use computer models
来预测行星的行为
to basically predict the behavior of the planets,
你会发现，如果从木星、土星
what you find is that if you start with Jupiter,
天王星和海王星开始，你不可能在不喷射
Saturn, Uranus and Neptune, you can't save the Earth
天王星或海王星的情况下来拯救地球
without ejecting either Uranus or Neptune,
但它们都在那里，所以我们知道这是不对的
but they're there, so we know that's not right.
然而，如果再加上第三颗冰巨星
However, if you add a third ice giant,
第五颗巨行星在模块器中
a fifth giant planet out there,
那一切就都能顺利进行了
then that actually makes everything work.
可以拯救地球了
You can save the Earth,
并让行星保持现在的状态
have the planets in their present configuration,
然后那个冰巨行星就会从太阳系中喷射出来
and that ice giant gets ejected from the solar system.
想象一下我们的太阳系
Imagine our solar system
一开始有三颗冰巨星
starting with three ice giants.
其中一个离木星太近了
One swings too close to Jupiter.
我们的太阳系恶霸把这个受害者
Our solar system's bully throws its victim clean
扔出了操场
out of the playground.
木星被这个冰巨行星的引力
Jupiter is pushed into a new orbit
推入新的轨道
by the ice giant's gravity.
地球摆脱了木星致命的引力
Earth is saved from Jupiter's deadly gravitational pull,
太阳系变成了我们今天所看到的
and the solar system becomes the safe
安全有序的地方
and orderly place we see today.
这里有个有趣的故事
So we have a funny story here.
这个可能存在于数十亿年前的
This ice giant that may have existed billions of years ago
冰巨行星将木星拉回了外太阳系
(之所以用“拉回”是因为之前木星
就在外太阳系，后来逐渐进入到
太阳系内，现在是回来原来的位置)
yanked Jupiter back into the outer solar system,
阻止了它摧毁地球
preventing it from destroying the Earth,
但与此同时，它为我们牺牲了自己
but in the meantime, it sacrificed itself for us,
被甩出了太阳系
getting ejected from the solar system.
我们必须感谢它让我们存在
We have to thank it for our existence,
只是它已经不在了
but it's not there anymore.
我们人类真的很幸运
We humans are really lucky.
如果恐龙没有灭绝，我们就不会在这里了
Had the dinosaurs not gone extinct, we wouldn't be here.