I am holding something remarkably old. It is older than any human artifact, older than life on Earth, older than the continents and the oceans between them. This was formed over four billion years ago in the earliest days of the solar system while the planets were still forming. This rusty lump of nickel and iron may not appear special, but when it is cut open ... you can see that it is different from earthly metals. This pattern reveals metallic crystals that can only form out in space where molten metal can cool extremely slowly, a few degrees every million years. This was once part of a much larger object, one of millions left over after the planets formed. We call these objects asteroids.
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, 比地球上的生命古老, 也比大陆和它们之间的海洋古老。 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。 这一块粗糙的镍铁合金看起来并不特殊, 但它一旦被切开... 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, 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。 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。 我们称这些物体为小行星。
Asteroids are our oldest and most numerous cosmic neighbors. This graphic shows near-Earth asteroids orbiting around the Sun, shown in yellow, and swinging close to the Earth's orbit, shown in blue. The sizes of the Earth, Sun and asteroids have been greatly exaggerated so you can see them clearly. Teams of scientists across the globe are searching for these objects, discovering new ones every day, steadily mapping near-Earth space. Much of this work is funded by NASA. I think of the search for these asteroids as a giant public works project, but instead of building a highway, we're charting outer space, building an archive that will last for generations.
小行星是我们已知的 最古老数量最多的宇宙邻居。 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, 同时在地球轨道附近转动的行星, 用蓝色标出。 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。 全球许多科学家都在寻找这些东西, 并且每天都有新的发现, 稳定分布在近地空间。 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, 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. And these are all of the known near-Earth asteroids, which at last count was 13,733. Each one has been imaged, cataloged and had its path around the Sun determined. Although it varies from asteroid to asteroid, the paths of most asteroids can be predicted for dozens of years. And the paths of some asteroids can be predicted with incredible precision. For example, scientists at the Jet Propulsion Laboratory predicted where the asteroid Toutatis was going to be four years in advance to within 30 kilometers. In those four years, Toutatis traveled 8.5 billion kilometers. That's a fractional precision of 0.000000004.
这些是仅去年一年 被发现的1556个近地小行星。 这些则是已知的近地行星, 它们的最新统计量为13733。 每一个都被拍照,分类 并且确定了它绕太阳旋转的轨道。 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。 而且一部分行星的轨道 能被极其精准地预测。 举个例子,喷气推进实验室的科学家 提前四年预测了 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。 它的分级精度 达到了0.000000004。
(Laughter)
(笑声)
Now, the reason I have this beautiful asteroid fragment is because, like all neighbors, asteroids sometimes drop by unexpectedly.
现在,我能拿到这块美丽的行星碎片是因为 就像所有的邻居一样, 行星有时也会毫无预兆地拜访。
(Laughter)
(笑声)
Three years ago today, a small asteroid exploded over the city of Chelyabinsk, Russia. That object was about 19 meters across, or about as big as a convenience store. Objects of this size hit the Earth every 50 years or so.
三年前的今天, 一个小行星在 俄罗斯的车里雅宾斯克爆炸。 那个东西有19米宽, 或者说像一个便利店一样大。 像这样大的物体 每五十年左右撞击一次地球。
66 million years ago, a much larger object hit the Earth, causing a massive extinction. 75 percent of plant and animal species were lost, including, sadly, the dinosaurs. That object was about 10 kilometers across, and 10 kilometers is roughly the cruising altitude of a 747 jet. So the next time you're in an airplane, snag a window seat, look out and imagine a rock so enormous that resting on the ground, it just grazes your wingtip. It's so wide that it takes your plane one full minute to fly past it. That's the size of the asteroid that hit the Earth.
六百六十万年前, 一个更大的物体撞击地球, 造成了物种大灭绝。 当时地球上百分之七十五的动植物消失, 包括不幸的恐龙。 那个物体有十千米宽, 而十千米是波音747的巡航高度。 所以下次当你坐飞机时, 抢一个靠窗的座位, 看着窗外想象一个如此巨大的石块 躺在地上, 它恰好擦过机翼。 它大到飞机需要整整一分钟 才能飞过它。 这是曾经撞击地球的小行星的大小。
It has only been within my lifetime that asteroids have been considered a credible threat to our planet. And since then, there's been a focused effort underway to discover and catalog these objects. I am lucky enough to be part of this effort. I'm part of a team of scientists that use NASA's NEOWISE telescope. Now, NEOWISE was not designed to find asteroids. It was designed to orbit the earth and look far beyond our solar system to seek out the coldest stars and the most luminous galaxies. And it did that very well for its designed lifetime of seven months. But today, six years later, it's still going. We've repurposed it to discover and study asteroids. And although it's a wonderful little space robot, these days it's kind of like a used car. The cryogen that used to refrigerate its sensors is long gone, so we joke that its air-conditioning is broken. It's got 920 million miles on the odometer, but it still runs great and reliably takes a photograph of the sky every 11 seconds. It's taken 23 photos since I began speaking to you.
这是小行星在我有生以来唯一一次 被视作我们星球的威胁。 从那以后,人们集中努力 发现并分类这些物体。 我很幸运成为这项工作的一员。 我是使用NASA的NEOWISE 望远镜科学家小组的成员。 现在,NEOWISE并不是 为了寻找小行星而设计的。 而是环绕地球运动 并观测太阳系外的情形, 寻找最冷的星球以及最亮的星系。 而且它在其七个月的预期寿命中 非常好的完成了工作。 但是现在,六年过去了, 它仍然在工作。 我们重新改造让它开始寻找并研究小行星。 虽然它是一个完美的太空机器人, 但是现在它更像一辆用过的汽车。 对其传感器进行降温 的制冷剂长时间供应不足, 所以我们开玩笑说 它的制冷系统已经损坏。 它的里程表上显示已经 运行了九亿两千万英里, 但它的状态依旧良好 并且稳定的在每十一秒 拍摄一张天空的照片。 从我开始和大家讲话到现在, 它已经拍了23张照片了。
One of the reasons NEOWISE is so valuable is that it sees the sky in the thermal infrared. That means that instead of seeing the sunlight that asteroids reflect, NEOWISE sees the heat that they emit. This is a vital capability since some asteroids are as dark as coal and can be difficult or impossible to spot with other telescopes. But all asteroids, light or dark, shine brightly for NEOWISE.
NEOWISE有这样高价值的原因之一便是 它使用红外感应观测天空。 这意味着NEOWISE看到的 是小行星辐射的热量 而不是它们反射的太阳光。 这是一项很重要的能力, 因为一些小行星像黑碳一样暗, 其他的探测器很难或 不可能发现这类行星。 但所有亮或暗的行星 对NEOWISE来说,都是发光的。
Astronomers are using every technique at their disposal to discover and study asteroids. In 2010, a historic milestone was reached. The community, together, discovered over 90 percent of asteroids bigger than one kilometer across -- objects capable of massive destruction to Earth. But the job's not done yet. An object 140 meters or bigger could decimate a medium-sized country. So far, we've only found 25 percent of those.
宇航员在使用一切可能的手段和技术 去寻找并研究小行星。 2010年,我们达到了一个里程碑。 参与的组织共同发现直径大于一公里的 百分之九十以上的小行星。 这些物体能对地球造成巨大破坏。 但是工作并没有结束。 一个140米宽或更大的物体 能够摧毁一座中型城市。 迄今为止,我们只找到了 它们中的四分之一。
We must keep searching the sky for near-Earth asteroids. We are the only species able to understand calculus or build telescopes. We know how to find these objects. This is our responsibility. If we found a hazardous asteroid with significant early warning, we could nudge it out of the way. Unlike earthquakes, hurricanes or volcanic eruptions, an asteroid impact can be precisely predicted and prevented. What we need to do now is map near-Earth space. We must keep searching the sky.
我们必须继续搜索天空, 寻找近地小行星。 我们是唯一能理解微积分 或制造望远镜的物种。 我们知道如何找到这些物体。 这是我们的责任。 如果我们发现一个极具危险性 的小行星并提前发出有效警告, 我们便可以把它推走。 不像地震,飓风或火山爆发, 行星所产生的影响是可以被准确预测 并预防的。 我们现在所需的是将 地球附近的太空准确标记。 所以,我们必须继续对天空的搜索。
Thank you.
谢谢。
(Applause)
(掌声)