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.
我手中拿的是一個非常古老的東西。 它比任何人造製品, 比地球上任何生命, 比任何陸地和大洋都要古老。 它是四十多億年前形成的。 那時還是太陽系的最早期, 眾星球還在形成。 這一塊生鏽的鎳鐵, 看起來可能沒有什麼特別之處。 但如果把它切開, 你會發現它與地球的金屬不同。 它的紋路顯示它是只能在 太空中形成的金屬晶體。 在太空中,熔化了的金屬, 可以以極慢的速度冷卻。 每幾百萬年,只冷卻幾度。 這是一個比它 大很多的物體的一部分。 星球形成後,它是 數百萬被遺落的物體之一。 我們把這些物體叫做小行星。
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.
小行星是我們宇宙鄰居裡 最古老和為數最多的。 這幅圖像展示了靠近地球的小行星 繞太陽運轉。 太陽是圖中黃色的那個。 它們活躍於地球繞行軌道附近, 地球軌道是圖中藍色部分。 為了讓大家看得清楚, 圖中的地球、太陽和小行星 都被放大了很多倍。 世界各地的科學家團隊 都在尋找這些物體。 他們每天發現新的小行星, 逐漸繪製著近地空間的地圖。 這項工作大部分是由 美國國家航空暨太空總署資助的。 我覺得,搜尋小行星的工作, 是極為浩大的公共工程項目, 我們為太空製圖, 而不是在建高速公路, 並建立著能夠世代延續的檔案。
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.
光是去年,科學家就發現了 1556 顆近地小行星。 圖上的這些,是我們已知的 全部近地小行星。 根據最近的統計, 總數是 13,733 顆。 每一顆小行星, 都已經被繪圖和編入目錄, 它繞太陽運行的軌跡, 也都已經被確定。 雖然每一顆小行星都不同, 它們大多數在未來幾十年的 運行軌跡都可以被預測。 有一些小行星的軌跡, 可以被無比精確地預測。 舉個例子來講, 噴氣推進實驗室的科學家們, 提前四年預測了 圖塔迪斯小行星的位置, 誤差小於 30 公里。 在這四年裡, 圖塔迪斯運行了 85 億公里 。 小數精度為 0.000000004。
(Laughter)
(笑聲)
Now, the reason I have this beautiful asteroid fragment is because, like all neighbors, asteroids sometimes drop by unexpectedly.
我之所以有手中 這塊美麗的小行星碎片, 是因為,像所有的人類鄰居一樣, 小行星有時候也會意外造訪。
(Laughter)
(笑聲)
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, 一顆小型的小行星在俄羅斯的 車里雅賓斯克市上方爆炸。 當時,這塊物體的 截面長度大約為 19 米, 和一個便利店的大小差不多。 大約每五十年, 就會有這樣體積的物體撞擊地球。
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.
六千六百萬年前, 一個還要大很多的物體撞擊了地球, 導致了大規模的生物滅絕。 百分之 75 的動植物 物種都徹底消失, 可悲的是,其中包括恐龍。 當時的物體截面長度 長達 10 公里。 10 公里差不多是一架 波音 747 的飛行高度。 你下次坐飛機的時候, 選一個臨窗的座位,然後想像一下 一顆巨石拔地而立, 和你的機翼擦身而過。 你的飛機需要飛整整一分鐘 才能越過它的寬度。 這就是撞擊地球的 那顆小行星的尺寸。
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.
在我們這個世代, 小行星才被認為 是我們星球的一個威脅。 那以後,我們才開始致力於 對這些物體進行搜尋和紀錄。 我非常幸運能夠參與這一個工作。 我是使用 NASA NEOWISE 望遠鏡的科學家團隊一員。 要知道,NEOWISE 並不是為搜尋小行星設計的。 它是為了能夠繞行地球 以遙望太陽系之外, 為了尋找最寒冷的星球和 最明亮的星系而設計的。 在七個月的既定壽命中, 它很出色地完成了任務。 但六年後的今天,它還在運轉。 我們將它的用途變成了 搜尋和研究小行星。 雖然它是個非常出色的 太空小機器人, 但現在它有些像二手車。 用於傳感器的製冷劑 很早以前就消耗殆盡了, 我們開玩笑說,空調壞了。 它的里程表上, 已經有了 9.2 億英里, 但它依然運行良好。 它每 11 秒就會拍一張天空的照片。 從我開始演講到現在, 它已經拍了 23 張照片了。
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 如此寶貴的原因之一是, 它是通過熱紅外線觀測天空的。 這意味著,NEOWISE 看到的 不是小行星折射的陽光, 而是它們放散發的熱量。 這種能力至關重要, 因為有些小行星暗如黑炭, 幾乎不可能被其他的望遠鏡觀測到。 但所有的小行星,無論明暗,
Astronomers are using every technique at their disposal
在 NEOWISE 的眼中, 都一樣熠熠閃耀。
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.
天文學家們正在利用他們所有的技術 來發現和研究小行星。 2010 年,一項歷史性的 里程碑得以樹立。 通過研究者的共同努力, 我們已經發現了超過 90% 截面長度大於一公里的小行星—— 這些物體足以給地球 帶來巨大的破壞。 但我們的工作還沒有結束, 一個横截長度大於 140 米的物體, 就足以摧毁一個中型國家。 至今,我們只發現了 25% 這種大小的。
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.
我們必須不停地 探索天空中的近地小行星。 我們是唯一能夠理解微積分 或者製造望遠鏡的物種。 我們知道如何找到這些物體。 這是我們的責任。 如果我們能夠在危險的 小行星出現早期就發現它們, 我們就可以把它 從原來的軌跡上推開。 不同於地震、颶風和火山爆發, 我們可以準確地預測和預防 小行星的衝擊。 我們現在需要做的是 繪製出近地的空間地圖。 我們必須繼續不停地探索天空。
Thank you.
謝謝各位。
(Applause)
(鼓掌)