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Much of this work is funded by NASA. I think of the search for these asteroids as a giant public works project,
NASA支持着绝大部分该方面的工作。我把搜寻这些小行星看作一项大型公众项目，
but instead of building a highway, we're charting outer space, building an archive that will last for generations.
没有修建快速通道，恰恰相反，我们在绘制外太空图，建立一个能延传几代人的资料库。
These are the 1,556 near-Earth asteroids discovered just last year.
这些是仅去年一年被发现的1556个近地小行星。
And these are all of the known near-Earth asteroids, which at last count was 13,733.
这些则是已知的近地行星，它们的最新统计量为13733。
Each one has been imaged, cataloged and had its path around the Sun determined.
每一个都被拍照，分类并且确定了它绕太阳旋转的轨道。
Although it varies from asteroid to asteroid, the paths of most asteroids can be predicted for dozens of years.
虽然行星之间差异很多，但绝大多数行星在未来几十余年的轨道是可被预测的。
And the paths of some asteroids can be predicted with incredible precision.
而且一部分行星的轨道能被极其精准地预测。
For example, scientists at the Jet Propulsion Laboratory predicted where the asteroid Toutatis was going to be
举个例子，喷气推进实验室的科学家提前四年预测了
four years in advance to within 30 kilometers. In those four years, Toutatis traveled 8.5 billion kilometers.
图塔蒂斯小行星的运行轨迹，误差在30公里内。在那四年中，图塔蒂斯小行星运行了85亿公里。
That's a fractional precision of 0.000000004.
它的分级精度达到了0.000000004。
Now, the reason I have this beautiful asteroid fragment is because,
现在，我能拿到这块美丽的行星碎片是因为，
like all neighbors, asteroids sometimes drop by unexpectedly.
就像所有的邻居一样，行星有时也会毫无预兆地拜访。
Three years ago today, a small asteroid exploded over the city of Chelyabinsk, Russia.
三年前的今天，一个小行星在俄罗斯的车里雅宾斯克爆炸。
That object was about 19 meters across, or about as big as a convenience store.
那个东西有19米宽，或者说像一个便利店一样大。
Objects of this size hit the Earth every 50 years or so.
像这样大的物体每五十年左右撞击一次地球。
