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.


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


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


The Moon. Luna. Our orbital buddy.


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


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.


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]


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


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.


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.


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


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.


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.



[1] Giant-impact hypothesis – Wikipedia

[2] Martian meteorite – Wikipedia

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