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I am holding something remarkably old. It is older than any human artifact,
我拿着的是一个十分古老的东西。它比任何一个人工制品都要古老，
older than life on Earth, older than the continents and the oceans between them.
比地球上的生命古老，也比大陆和它们之间的海洋古老。
This was formed over four billion years ago in the earliest days of the solar system while the planets were still forming.
它形成于四十亿年前，在太阳系最初阶段行星还在形成的过程中。
This rusty lump of nickel and iron may not appear special, but when it is cut open,
这一块粗糙的镍铁合金看起来并不特殊，但它一旦被切开，
you can see that it is different from earthly metals. This pattern reveals metallic crystals that can only form out in space
你就会发现它与地球上的金属有很大不同。这种花纹意味着只能在外太空形成的金属晶体，
where molten metal can cool extremely slowly, a few degrees every million years.
在那里融化的金属能以极慢的速度冷却，每百万年下降几度。
This was once part of a much larger object, one of millions left over after the planets formed.
它曾经是一个巨大物体的一部分，是在星球形成后存留下来的百万块中的一个。
We call these objects asteroids. Asteroids are our oldest and most numerous cosmic neighbors.
我们称这些物体为小行星。小行星是我们已知的最古老数量最多的宇宙邻居。
This graphic shows near-Earth asteroids orbiting around the Sun, shown in yellow,
这张图显示了近地小行星绕太阳运行的轨道，用黄色标出的部分，
and swinging close to the Earth's orbit, shown in blue.
同时在地球轨道附近转动的行星，用蓝色标出。
The sizes of the Earth, Sun and asteroids have been greatly exaggerated so you can see them clearly.
关于地球，太阳以及小行星的大小被放大，所以大家能很清楚地看到。
Teams of scientists across the globe are searching for these objects,
全球许多科学家都在寻找这些东西，
discovering new ones every day, steadily mapping near-Earth space.
并且每天都有新的发现，稳定分布在近地空间。
