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We see this process in action when particles no larger than grains of sand
我們看到的實景 就是晚上的時候
burn up as they streak across the night sky.Shooting stars.
有像沙粒一樣大的亮光一閃而過 流星雨
One object that didn't burn up was Theia, Earth's twin.
地球早期和自己孿生星球的撞擊
Earth's early collision with its twinwas also vital for our planet in many other ways.
在其它方面也很重要
For a start, it probably resulted in Earth's core becoming larger.
一開始，地核變大
And because it's made of iron,
因為它是由鐵組成的
the churning of this huge metal core generates a powerful magnetic field.
這個巨大的金屬地核就產生了 巨大的磁場
It's possible to see this magnetic field at work.This is the aurora.
我們可以看到磁場如何發揮作用 這是極光
You're watching the magnetic field deflecting
你現在看到的就是地球磁場
the Sun's dangerous solar wind.
將太陽危險的太陽風扭曲
But the huge molten core contributes something else
但是這個巨大的融化內核
essential for life on Earth,
對地球生命還起到其它作用
a way of helping to regulate the planet's temperature.
這是調節地球溫度的一種方式
It's a remarkable system.
這是一個很了不起的系統
