Earth was a tropical planet.

地球是一顆熱帶行星。

Behemoth and tiny dinosaurs alike roamed its lands, while reptiles and tentacled ammonites swept its seas.

巨獸和小恐龍在它的土地上肆虐，爬行動物和觸角瘤龍在它的海洋裡遊蕩。

But in an instant, everything would change.

但轉瞬間，一切都會改變。

A roughly 12-kilometer-wide asteroid was careening toward Earth at around 20 kilometers per second.

一顆大約 12 公里寬的小行星以每秒約 20 公里的速度向地球飛去。

From where the sauropod stood, there would have been no early warning signs.

從長腳類動物站立的位置看，不會有任何早期預警信號。

The asteroid barreled through Earth's atmosphere in a matter of seconds and struck the Yucatan submerged continental shelf.

小行星在幾秒鐘內穿過地球大氣層，擊中了尤卡坦半島的水下大陸架。

It exploded upon impact, instantaneously creating a 100-kilometer-wide hole and ejecting sedimentary and crystalline rocks.

它在撞擊時爆炸，瞬間形成了一個 100 公里寬的大洞，沉積岩和結晶岩噴射而出。

Within minutes, the impact crater, known today as Chicxulub, began collapsing inwards.

幾分鐘之內，這個今天被稱為奇克蘇盧布的撞擊坑開始向內坍塌。

Meanwhile, the base rebounded some 20 kilometers above the Earth's surface, then fell back down and moved outwards, creating a ring of mountains.

與此同時，基座在距地球表面約 20 公里處反彈，然後回落並向外移動，形成了一個山環。

The energy released from the asteroid's impact is estimated to have been several billion times that of a nuclear bomb.

據估計，小行星撞擊釋放的能量是核彈的幾十億倍。

The force sent seismic energy across the planet at a much greater magnitude than any earthquake a tectonic fault could ever produce.

這股力量在地球上產生的地震能量比構造斷層產生的任何地震都要大得多。

Massive landslides ensued, and a tsunami sped from the newly formed crater, potentially reaching 1,500 meters high.

隨之而來的是大規模的山體滑坡，海嘯從新形成的火山口噴湧而出，可能高達 1500 米。

Countless lives were extinguished, some instantly.

無數生命就此逝去，有些甚至是瞬間逝去。

All life within 1,500 kilometers of the impact site was incinerated, others right after by colossal waves, landslides, and hurricane-force winds.

撞擊地點周圍 1500 公里內的所有生物都被焚燬，其他生物也隨即被巨浪、山體滑坡和颶風摧毀。

But many organisms across the planet survived.

但是，地球上的許多生物倖存了下來。

It was what came next that would bring about the end for many species, including almost all dinosaurs.

接下來，許多物種，包括幾乎所有恐龍，都將走向滅亡。

This was just the beginning of one of the most devastating periods in the history of life on Earth.

這只是地球生命史上最具破壞性時期之一的開始。

When the asteroid struck, it sent hundreds of gigatons of carbon dioxide-rich limestone and sulfur-saturated sediments into the atmosphere.

當小行星撞擊地球時，它將數百億噸富含二氧化碳的石灰石和硫飽和沉積物送入大氣層。

The sulfur combined with water vapor to create sulfate aerosol.

硫與水蒸氣結合，形成硫酸鹽氣溶膠。

This plume of limestone dust, soot, and sulfate aerosols spread from the impact site at several kilometers per second, blanketing the globe in a matter of hours.

這股石灰岩塵埃、煙塵和硫酸鹽氣溶膠以每秒幾公里的速度從撞擊地點擴散開來，在幾個小時內就覆蓋了全球。

It's thought to have blocked the sun, plunging Earth into an extended period of darkness and dropping the temperature in many places by at least 25 degrees Celsius.

人們認為它擋住了太陽，使地球陷入長時間的黑暗，許多地方的氣溫至少下降了 25 攝氏度。

The asteroid's immediate impact was devastating, but it seems to have been the rapid climate change it triggered that ended the roughly 165 million year reign of the dinosaurs.

小行星的直接撞擊是毀滅性的，但似乎是它引發的快速氣候變化結束了恐龍大約 1.65 億年的統治。

Plants and plankton rapidly died, causing the collapse of food webs worldwide.

植物和浮游生物迅速死亡，導致全球食物網崩潰。

An estimated 75% of life on Earth went extinct, including almost all dinosaurs.

據估計，地球上有 75% 的生物滅絕了，其中包括幾乎所有的恐龍。

Small birds were the only kinds that remained, perhaps because they relied on hardy seeds that weathered the catastrophe.

小鳥是唯一倖存下來的鳥類，也許是因為它們依靠堅硬的種子抵禦了這場災難。

It's unclear why exactly the lifeforms that survived the extinction did.

目前還不清楚大滅絕中倖存下來的生命形式究竟是為什麼。

Many smaller organisms, like insects, persisted.

許多較小的生物，如昆蟲，依然存在。

So did early mammals, perhaps because of their ability to burrow and hibernate.

早期的哺乳動物也是如此，也許是因為它們具有鑽洞和冬眠的能力。

And photosynthetic lifeforms, like algae, that had ways of withstanding low-light conditions also survived.

而像藻類這樣有辦法抵禦弱光條件的光合生命體也存活了下來。

Traces of the asteroid scattered worldwide, and the scar of the Chicxulub crater attest to this period of monumental destruction.

小行星散落在世界各地的痕跡和奇克蘇盧布隕石坑的傷痕都證明了這一時期的巨大破壞。

So what are the chances of another Chicxulub happening?

那麼，再次發生奇克蘇魯伯事件的可能性有多大？

Space programs are continuously identifying and tracking near-Earth asteroids.

太空計劃正在不斷識別和跟蹤近地小行星。

Fortunately, the likelihood of one as large and cataclysmic striking in the next thousand or so years seems to be small, something like a 7 in a million chance.

幸運的是，在未來一千年左右的時間裡，發生如此大規模災難性事件的可能性似乎很小，大約只有百萬分之一的可能性。

However, we are facing the consequences of another kind of rapid climate change.

然而，我們正面臨著另一種快速氣候變化的後果。

This time, because of humanity's own emissions.

這一次，是因為人類自身的排放。

Animals are going extinct faster than ever in our history.

動物滅絕的速度比我們歷史上任何時候都快。

And people are being displaced from their homes.

人們流離失所。

But unlike the dinosaurs, we have the opportunity to avoid the large-scale devastation that will come if governments continue with the status quo.

但與恐龍不同的是，如果政府繼續維持現狀，我們就有機會避免大規模的破壞。

Fortunately, we've already proven our ability to make life-saving changes on a planetary scale.

幸運的是，我們已經證明，我們有能力在地球範圍內做出拯救生命的改變。

Watch this video to find out what happened to that hole in the ozone layer, and discover what role you can play in Earth's destiny at ed.ted.com slash earthschool.

觀看本視頻，瞭解臭氧層空洞的情況，並在 ed.ted.com slash earthschool 網站上了解您在地球命運中可以扮演的角色。