How Often do Asteroids Hit the Earth?: Crash Course Geology #20 · CrashCourse
了解太空岩石如何影响地球，包括陨石、小行星等。适合练习科普类英语表达和科学词汇。
The sky is falling!
天要塌下来了！
...Sort of?
……算是吧？
Our planet gets pummeled by about 48.5 tons of space rocks every day.
我们的星球每天会受到大约48.5吨太空岩石的撞击。
That’s the weight of seven and a half elephants falling from the heavens, 24/7.
这相当于七头半大象从天而降所产生的压力，而且这种压力是全天候（24小时/7天）持续存在的。
Most of that cosmic debris is harmless— it’s so tiny it burns up in the atmosphere before it rains down on Earth.
大部分这些宇宙碎片其实都是无害的；它们的体积非常微小，会在进入地球大气层之前就被烧毁，因此不会对地球造成任何危害。
But what about the really big rocks?
那么那些非常大的岩石呢？
The asteroids that could wipe out life as we know it?
那些有可能彻底摧毁我们所熟知的生命形式的小行星……
The truth is, they’re out there, and they’ve collided with Earth before.
事实上，这些物体确实存在于太空中，并且之前已经与地球发生过碰撞。
Today, let’s talk straight about rocks from space.
今天，我们就来直截了当地谈谈来自太空的岩石吧。
They’re at the top of my Things to Worry About List.
它们在我需要担心的问题清单上名列前茅。
Hi, I’m Sage, and this is Crash Course Geology.
大家好，我是Sage，这是《地质学速成课程》（Crash Course Geology）。
[THEME MUSIC] You’ve seen the movies.
[主题音乐] 你们都看过那些电影吧。
“An asteroid is headed straight for Earth!
一颗小行星正朝地球飞来！
Everyone panic!
所有人都惊慌失措了！
Run for your liiiiiiives!”
快逃命吧！
Thanks, Dwayne.
谢谢，德韦恩。
I really should go on more movie auditions.
我确实应该多去参加一些电影试镜活动。
But despite all that drama and disaster, space rocks are sort of…
但尽管发生了那么多戏剧性事件和灾难，太空岩石其实还是……
run of the mill here on Earth, hitting its surface daily like a light drizzle.
在地球上，这种现象非常普遍：每天都有微量的雨水降落到地表。
Most of the time.
大多数时候都是这样。
So…
那么……
what exactly are they?
它们到底是什么呢？
Most space rocks are leftovers from the moment our solar system formed, some 4.6 billion years ago.
大多数太空岩石都是太阳系形成时的遗留物，太阳系大约形成于46亿年前。
And we differentiate them in a few ways.
我们通过几种方式来区分它们。
An asteroid is a rock that orbits the sun and is more than one meter across.
小行星是一种围绕太阳运行的岩石，其直径超过一米。
Basically, anything with a diameter longer than a baseball bat, but not big enough to be a planet with its own gravitational pull.
基本上来说，任何直径大于棒球棒、但又不足以形成具有自身引力的行星的天体都属于这一范畴。
That’s why asteroids are sometimes called a minor planet.
这就是为什么小行星有时被称为“次级行星”（minor planet）。
Oooh, burn.
哦哦哦，真疼……
Most asteroids hail from the asteroid belt— an area between Mars and Jupiter that’s chock-full of space rocks,
大多数小行星都来自小行星带——这个位于火星和木星之间的区域里布满了太空岩石。
some of them hundreds of miles across.
其中一些区域的宽度达到了数百英里。
A trip to the asteroid belt would be like…
前往小行星带的一次旅行，将会像……
what am I thinking of?
我在想什么呢？
That video game where you dodge barrels that a gorilla throws at you?
就是那个游戏吧——玩家需要躲避大猩猩扔向自己的桶子……
Oh.
哦。
Dwayne has just informed me that there’s a video game literally called Asteroids, and apparently it’s very famous.
德韦恩刚刚告诉我，确实有一款名为《Asteroids》的电子游戏，而且这款游戏非常受欢迎。
My bad.
是我的错。
Now, when a space rock’s diameter is less than a meter across, it’s a meteoroid.
当一块太空岩石的直径小于一米时，它就被称作“流星体”（meteoroid）。
Usually, a meteoroid is a chunk of asteroid that got blasted off during a collision with another asteroid.
通常，流星体是小行星在与其他小行星碰撞时被炸飞出来的碎片。
You’d think that wouldn’t happen, with all that, y’know, space.
你可能会觉得这种事情不可能发生，毕竟有那么广阔的空间啊……
But it does.
但它确实如此。