除了人造的卫星和太空垃圾外,可以说现在存在地球上的物质从地球形成开始就不会离开地球吗?Other than man-made satellites and space junks, can it be said that all matters and substances that were present during Earth’s creation have never left our planet?

【翻译自quora,作者 Jeffrey Naujok 】

Nope. Not even close.

不,完全不对。

Go outside, look up. See that shiny thing up there?

走到外面看看,看看外面什么东西在发光?

No, not the sun. Oh nuts, I forgot to specify, do this at night. The other shiny thing.

不是,不是太阳。我忘了说明,应该是在晚上出去看看,看看那些发光的东西。

The Moon. Luna. Our orbital buddy.

月亮,我们的卫星。

That, my friend, used to be part of the Earth.

这是我们的朋友,曾经也是地球的一部分。

You see, early on, when the Mother Earth was young, and hot, she attracted a friend named Theia who got just a little too close, if you know what I mean. Then bang, and nine months later, out popped little Luna.

你也看到了,当我们的地球母亲还很年轻,温度很高时,它用引力俘获了一个名叫“Theia”的离得很近的朋友。然后,砰!九个月后,小月亮就诞生了。

Okay, okay, enough with the bad analogies. This is known as the Giant Impactor Hypothesis, and it pretty much is the only origin theory of the Moon that explains almost everything we know about it and the origin of the Earth.[1]

好吧,好吧,这个比喻不恰当。这被称为“巨大冲击”假说,这是目前唯一能很好解释有关月球与地球起源的假说。

That’s a pretty big chunk of missing mass right off the bat.

地球失去的那块质量真的是很大。

Then there’s the rest of the impactors that have hit the Earth. Ever look at Manicougan, Canada on a map?

你曾在地图上看过加拿大的 Manicougan 吗?这儿还有那次事件留下来的影响。

Look familiar? Like a giant, 100 km wide impact crater? And that’s only 214 million years old. Before that Earth was really getting pounded.

看起来很像?像一个巨大的,100km宽的撞击坑?这只有2.14亿年的历史。这个时候盘古大陆还没解体。

Those kind of impacts toss off large quanties of rock to space. We know this because we can find pieces of the moon and even Mars in meteorites that land on Earth. [2]

这种冲击可以大量岩石从星球上(不一定是地球)抛向太空。 我们之所以知道这一点,是因为我们可以在地球上上找到那些来自月亮和火星的陨石。 [2]

And then chemicals like helium, which are derived from nuclear decay, and hydrogen, tend to bubble up to the top of the atmosphere, where Earth’s gravity is not enough to hold onto them, and the float off into space.

然后,诸如来自核衰变的氦气和氢之类的化学物质,往往会缓慢向上飘到达大气层的顶部,在那里地球的引力不足以吸引住它们,于是它们就漂浮到太空中。

Glancing meteors can also carry bits of the atmosphere off into space.

掠过的流星还可以将大气的一部分带入太空。

Coronal Mass Ejections that hit the Earth hard enough can temporarily collapse the magnetic fields of the Earth, exposing the top of the atmosphere to the solar wind, which will scour part of the atmosphere away.

撞击地球的 日冕物质喷发 足以暂时破坏地球的磁场,使大气层顶部暴露于太阳风中,从而冲走一部分大气层。

On the plus side, every day about 200 tons of various space dust, particles, and gasses fall down into Earth’s gravity well and add back to the mass of the Earth.

从好的方面来说,每天大约有200吨各种太空尘埃,微粒和气体掉入地球的引力井中,并重新组成地球的质量中。

And while most of the original mass is still here, it is constantly undergoing nuclear decay. When the Earth was young, there was a lot more nuclear material around, like Uranium 235, or probably even Neptunium and Plutonium. But those things aren’t stable, and now, 4.5 billion years later, we’ve got a lot of lead and palladium, comparatively, to the amount of actual fissile uranium and plutonium we have hanging around.

而且,尽管大多数一开始就有的质量仍然存在,但它一直在经历核衰变。 当地球还年轻时,有更多的核材料,例如铀235,甚至可能还有镎和钚。 但是这些情况并不稳定,现在,在45亿年后的现在,相较于我们拥有的铀和 钚, 我们现在拥有更多的大量的铅和钯。

And, of course, your question begs the other question, where did it all come from. The Earth is made of dead stars. So saying it’s never been “off the Earth” ignores the fact that it was off the Earth in the heart of stars, in other planets or asteroids, or created in the collision of neutron stars (see that gold ring on your finger? Neutron star collision) before it ever got to become part of the cloud that would collapse to become the solar system, a tiny fraction of which would become Earth.

当然,您的问的另一个问题是,它们都是从哪里来的。 地球是由死去的星组成的。 因此,说它从未离开地球就忽略了,那些物质会在地球刚开始形成时就离开地球,被其他星球或陨石带走,或者是在中子星碰撞时产生的(参见手指上的金戒指?这也是中子星碰撞形成的)变成云的一部分,然后崩溃成为太阳系,而其中的一小部分将成为地球。【??这段还没看懂】

You, me, and everything around you was born in the heart of dying stars. If that ain’t cool enough for you, I don’t know what is.

你,我和你周围的一切都是从死去的星星中诞生的。如果这还不够酷的话,那就没有酷的东西了。

Footnotes

[1] Giant-impact hypothesis – Wikipedia

[2] Martian meteorite – Wikipedia

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