Where did the Moon come from? A new theory | Sarah T. Stewart

翻译人员: Cissy Yun 校对人员: Carol Wang

Nobody likes to make a mistake.

没人喜欢犯错。

And I made a whopping one.

而我却犯了个惊天大错。

And figuring out what I did wrong led to a discovery

但弄清误点的过程 则让我有了一个发现，

that completely changes the way we think about the Earth and Moon.

它完全改变了我们对 地球和月球的看法。

I'm a planetary scientist,

我是一个行星科学家，

and my favorite thing to do is smash planets together.

我最爱做的事是：让行星相撞。

(Laughter)

（笑声）

In my lab, I can shoot at rocks using cannons like this one.

在我的实验室中，我可以用 这样的大炮击射岩石。

(Cannon shot)

（大炮射击）

(Laughter)

（笑声）

In my experiments, I can generate the extreme conditions

在实验中，我能模拟

行星形成时的极端环境。

during planet formation.

And with computer models, I can collide whole planets together

借助电脑模型，我可以 让所有的行星互相撞击，

to make them grow,

让它们重生，

or I can destroy them.

也可让它们毁灭。

(Laughter)

（笑声）

I want to understand how to make the Earth and the Moon

我想弄明白地球 和月球是如何形成的，

and why the Earth is so different from other planets.

而且地球为何 与其他行星如此不同。

The leading idea for the origin of the Earth and Moon

有关地球月球起源的主流观点

is called the "giant impact theory."

是“大碰撞理论”。

The theory states that a Mars-sized body struck the young Earth,

该理论认为，一个火星大小的 天体撞击了年轻的地球，

and the Moon formed from the debris disk around the planet.

而环绕行星周围的 碎屑盘形成了月球。

The theory can explain so many things about the Moon,

该理论能解释 有关月球的许多事，

but it has a huge flaw:

但它有一个巨大的瑕疵：

it predicts that the Moon is mostly made from the Mars-sized planet,

它预言月球的大部分构成 来自那个火星大小的行星，

that the Earth and the Moon are made from different materials.

即地球和月球 是由不同物质组成的。

But that's not what we see.

但这与我们的发现大相径庭。

The Earth and the Moon are actually like identical twins.

地球与月球其实 像一对孪生子。

The genetic code of planets is written in the isotopes of the elements.

行星的基因秘钥写在 它们的元素同位素中，

The Earth and Moon have identical isotopes.

而地球与月球 拥有相同的同位素。

That means that the Earth and Moon are made from the same materials.

这说明地球和月球 是由相同物质构成的。

It's really strange that the Earth and the Moon are twins.

地球和月球竟然是孪生子？ 这太怪了。

All of the planets are made from different materials,

所有行星都由不同的物质构成，

so they all have different isotopes,

所以它们都有不同的同位素，

they all have their own genetic code.

它们的基因秘钥也不一样。

No other planetary bodies have the same genetic relationship.

没有任何其他行星天体 有同样的基因关系。

Only the Earth and Moon are twins.

只有地球和月球是孪生子。

When I started working on the origin of the Moon,

当我开始研究月球起源时，

there were scientists that wanted to reject the whole idea of the giant impact.

已经有科学家尝试摈弃 “大碰撞理论”。

They didn't see any way for this theory to explain the special relationship

他们认为，该理论完全无法解释

地球与月球之间的特殊关系。

between the Earth and the Moon.

We were all trying to think of new ideas.

我们都在尝试找到新的想法。

The problem was, there weren't any better ideas.

但问题是，没有什么更好的想法，

All of the other ideas had even bigger flaws.

所有其他的想法漏洞更大。

So we were trying to rescue the giant impact theory.

因此，我们试图 去拯救“大碰撞理论”。

A young scientist in my group suggested that we try changing the spin

团队中的一位年轻科学家

建议我们尝试 改变大碰撞中的自转：

of the giant impact.

Maybe making the Earth spin faster could mix more material

也许将地球自转的速度提高后， 岩屑盘可以混入更多物质，

and explain the Moon.

并解释月球的成因。

The Mars-sized impactor had been chosen

选中火星大小的撞击物

because it could make the Moon

是因为它能够形成月球，

and make the length of Earth's day.

并形成地球上一天的时长。

People really liked that part of the model.

人们非常喜欢模型的这一部分。

But what if something else determined the length of Earth's day?

但是，倘若地球一天的时长 是由其他因素导致的呢？

Then there would be many more possible giant impacts that could make the Moon.

那么，很多其他可能的 大碰撞都有可能生成月球。

I was curious about what could happen,

我很好奇会发生什么情况，

so I tried simulating faster-spinning giant impacts,

所以，我模拟了行星转速 加快后的大碰撞实验，

and I found that it is possible

发现的确有可能

to make a disk out of the same mixture of materials as the planet.

产生与行星物质相同的岩屑盘。

We were pretty excited.

我们都非常兴奋，

Maybe this was the way to explain the Moon.

也许，这可以解释月球起源。

The problem is, we also found that that's just not very likely.

问题是，我们也发现 这种可能性极小，

Most of the time, the disk is different from the planet,

因为多数情况下，岩屑盘 与行星的物质是不一样的，

and it looked like making our Moon this way

若如此形成了月球，

would be an astronomical coincidence,

看起来像是天文巧合。

and it was just hard for everyone to accept the idea

大家很难接受

that the Moon's special connection to Earth was an accident.

月球和地球的特殊关系 仅仅是一个巧合。

The giant impact theory was still in trouble,

“大碰撞理论”依然无法解释，

and we were still trying to figure out how to make the Moon.

我们仍在尝试 搞清月球的成因，

Then came the day when I realized my mistake.

直到有一天，我发现自己弄錯了。

My student and I were looking at the data from these fast-spinning giant impacts.

我和学生在研究行星高速 自转时大碰撞所产生的数据。

On that day, we weren't actually thinking about the Moon,

那一天，我们其实 没思考有关月球的事，

we were looking at the planet.

我们在观察那个行星。

The planet gets super-hot and partially vaporized

因为碰撞所产生的能量，

from the energy of the impact.

那个星球会变得超级热， 并会部分蒸发。

But the data didn't look like a planet.

但数据显示，不像是行星，

It looked really strange.

它看起来十分奇怪。

The planet was weirdly connected to the disk.

行星以一种奇怪的方式 与岩屑盘联结着。

I got that super-excited feeling

我忽然有了那种 超级兴奋的感觉：

when something really wrong might be something really interesting.

当某件事看起来很不对劲时， 极有可能是个有趣的发现。

In all of my calculations,

在所有的计算中，

I had assumed there was a planet with a separate disk around it.

我都假设行星被一个 分离的岩屑盘所环绕。

Calculating what was in the disk as how we tested

把计算岩屑盘的成分

whether an impact could make the Moon.

作为测试大碰撞 是否生成月球的方法。

But it didn't look that simple anymore.

但它看起来却不再那么简单，

We were making the mistake

我们犯的错在于

of thinking that a planet was always going to look like a planet.

认为行星总是 其终极状态的样子，

On that day, I knew that a giant impact was making something completely new.

直到那天，我才意识到大碰撞 创造出一种全新的天体。

I've had eureka moments.

我有过很多次“恍然大悟”的时刻，

This was not one of them.

但這次却不是。

(Laughter)

（笑声）

I really didn't know what was going on.

我完全不知道到底发生了什么。

I had this strange, new object in front of me

在我面前的是这个奇怪的新型天体,

and the challenge to try and figure it out.

我的挑战则是弄清它是什么。

What do you do when faced with the unknown?

当你面对未知物時， 你会怎么做？

How do you even start?

你该如何着手？

We questioned everything:

我们质疑所有事情：

What is a planet?

什么才是行星？

When is a planet no longer a planet anymore?

什么情况下， 行星就不再是行星了？

We played with new ideas.

我们玩索各种 脑洞大开的新想法。

We had to get rid of our old way of thinking,

我们得摒弃旧的思考方式，

and by playing, I could throw away all of the data,

因为“玩”的性质， 我可以忘却所有数据、

all of the rules of the real world,

扔掉所有现实中的条条框框、

and free my mind to explore.

让我的思想去自由地探索。

And by making a mental space

我先在大脑中创建一个

where I could try out outrageous ideas

让自己任意遐想的空间，

and then bring them back into the real world to test them,

然后再在现实世界中 去测试这些想法，

I could learn.

并从中学习。

And by playing, we learned so much.

通过玩索，我们受益匪浅。

I combined my lab experiments with computer models

我把实验与电脑模型结合起来，

and discovered that after most giant impacts,

发现在多数大碰撞之后，

the Earth is so hot, there's no surface.

地球会变得滚烫，没有地表。

There's just a deep layer of gas that gets denser and denser with depth.

地球只有一层厚厚的气体， 愈深密度愈高，

The Earth would have been like Jupiter.

这时的地球其实像木星一样，

There's nothing to stand on.

表面没有任何固体。

And that was just part of the problem.

但这只是问题的一部分，

I wanted to understand the whole problem.

而我想搞清整个问题。

I couldn't let go of the challenge to figure out what was really going on

我放手不了这个

弄清大碰撞到底 发生了什么的挑战，

in giant impacts.

It took almost two years

为此，我花了大约两年的时间

of throwing away old ideas

去摒弃老思维，

and building new ones

并筑建新理论，

that we understood the data

这些理论基于理解实验数据、

and knew what it meant for the Moon.

和弄清它对月球的影响。

I discovered a new type of astronomical object.

我发现了一种新型天文物体，

It's not a planet.

它不是行星，

It's made from planets.

但它来自于行星。

A planet is a body whose self-gravity

行星，是受强大自引力作用

is strong enough to give it its rounded shape.

而呈球状的星体。

It spins around all together.

它作为一个整体进行自转。

Make it hotter and spin it faster,

温度越高，自转速度就越快，

the equator gets bigger and bigger until it reaches a tipping point.

赤道会越变越大， 直至到达临界点。

Push past the tipping point,

一旦过了临界点，

and the material at the equator spreads into a disk.

在赤道附近的物质 会向外扩散形成岩屑盘，

It's now broken all the rules of being a planet.

此时，它也不再遵循 行星的所有规律。

It can't spin around together anymore,

它再也无法自转，

its shape keeps changing as it gets bigger and bigger;

随着不断变大， 其形状也会不断变化，

the planet has become something new.

行星变成了一种全新的天体。

We gave our discovery its name:

我们给这个发现起了个名字：

synestia.

索内斯蒂亚（synestia），

We named it after the goddess Hestia,

用女神赫斯提亚来命名它，

the Greek goddess of the hearth and home,

她是古希腊神话中的家炉之神，

because we think the Earth became one.

因为我们认为地球 就变成了这样的角色。

The prefix means "all together,"

词首“syn”意味着“一起”，

to emphasize the connection between all of the material.

强调了所有物质之间的联结。

A synestia is what a planet becomes

当热量和转速将行星推越了 球型天体的极限后，

when heat and spin push it over the limit of a spheroidal shape.

行星就变成了索内斯蒂亚。

Would you like to see a synestia?

你们想看看索内斯蒂亚吗？

(Cheers)

（欢呼）

In this visualization of one of my simulations,

这是其中的一个模拟视频，

the young Earth is already spinning quickly from a previous giant impact.

因为之前的一次碰撞， 年轻的地球在快速自转。

Its shape is deformed, but our planet would be recognizable

地球有些变形，但根据地表的水，

by the water on its surface.

我们还认得出它是地球。

The energy from the impact vaporizes the surface,

大碰撞带来的能量 让地球表层、水、大气层 、

the water, the atmosphere,

完全蒸发，

and mixes all of the gases together in just a few hours.

在短短几小时中， 所有的气体混合起来。

We discovered that many giant impacts make synestias,

我们发现许多大碰撞 会产生索内斯蒂亚，

but these burning, bright objects don't live very long.

但这些燃烧着的 炽热天体寿命不长。

They cool down, shrink and turn back into planets.

它们会降温，缩小， 并再次变回行星。

While rocky planets like Earth were growing,

在类似地球这样的 岩石行星在成长过程中，

they probably turned into synestias one or more times.

可能会一次或数次 变成索内斯蒂亚。

A synestia gives us a new way to solve the problem of the origin of the Moon.

索内斯蒂亚为我们解决 月球起源提供了新途径，

We propose that the Moon formed inside a huge, vaporous synestia.

我们提出，月球形成于一个 巨型、气化的索内斯蒂亚内部。

The Moon grew from magma rain

月球形成于

岩石蒸汽凝结 而产生的岩浆雨。

that condensed out of the rock vapor.

The Moon's special connection to Earth

月球与地球间的特殊联系

is because the Moon formed inside the Earth

是因为月球形成于地球内部，

when Earth was a synestia.

那时，地球还是一个索内斯蒂亚。

The Moon could have orbited inside the synestia for years,

月球在索内斯蒂亚内部 可能已公转了许久，

hidden from view.

但我们无法观察到它。

The Moon is revealed by the synestia cooling and shrinking

而当索内斯蒂亚冷却缩小 到月球公转轨道以内时，

inside of its orbit.

月球才出现在我们的视线中，

The synestia turns into planet Earth

只有经历了几百年的冷却后，

only after cooling for hundreds of years longer.

索内斯蒂亚才会变成地球。

In our new theory,

在我们的新理论中，

the giant impact makes a synestia,

大碰撞形成了索内斯蒂亚，

and the synestia divides into two new bodies,

而索内斯蒂亚分成两个新天体，

creating our isotopically identical Earth and Moon.

就是同位素相同的地球与月球。

Synestias have been created throughout the universe.

索内斯蒂亚在宇宙各处都在发生，

And we only just realized that by finding them in our imagination:

通过想象他们的存在，我们 才刚刚意识到这个现象：

What else am I missing in the world around me?

在我周围的世界中， 我还遗漏了什么？

What is hidden from my view by my own assumptions?

我自己的臆测 还妨碍我看到什么其他信息？

The next time you look at the Moon,

下一次你赏月时，

remember:

请记住:

the things you think you know

你认为自己知道的事，

may be the opportunity to discover something truly amazing.

也许正是让你发现真正 令人惊讶事情的好机会。

(Applause)

（掌声）