쉐도잉 연습: How Often do Asteroids Hit the Earth?: Crash Course Geology #20 - 영상으로 영어 말하기 배우기

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The sky is falling!

Sort of?

Our planet gets pummeled by about 48 .5 tons of space rocks every day.

That's a weight of seven and a half elephants falling from the heavens 24 -7.

Most of that cosmic debris is harmless.

It's so tiny it burns up in the atmosphere before it rains down on Earth.

But what about the really big rocks?

The asteroids that could wipe out life as we know it?

Truth is, they're out there, and they've collided with Earth before.

Today, let's talk straight about rocks from space.

They're at the top of my things to worry about list.

Hi, I'm Sage, and this is Crash Course Geology.

You've seen the movies.

An asteroid is headed straight for Earth.

Everybody panic, crunch for your lives.

Aw, thanks, Duane.

I really should go out on more movie auditions.

But despite all that drama and disaster, space rocks are sort of run -of -the -mill here on Earth, hitting its surface daily like a light drizzle.

Most of the time.

So what exactly are they? it.

Most space rocks are leftovers from the moment our solar system formed, some 4 .6 billion years ago.

We differentiate them in a few ways.

An asteroid is a rock that orbits the sun and is more than one meter across.

Basically, anything with a diameter longer than a baseball bat, but not big enough to be a planet with its own gravitational pull.

That's why asteroids are sometimes called a minor planet.

Mmm, burn!

Most asteroids hail from the asteroid belt, an area between Mars and Jupiter that's chock -full of space rocks, some of them hundreds of miles across.

A trip to the asteroid belt would be like, uh, what am I thinking of?

Oh, that video game where you dodge barrels that a gorilla throws at you.

Uh, Dwayne has just informed me that there's a video game literally called Asteroids, and apparently it's very famous.

Mm, my bad.

Now, when a space rock's diameter is less than a meter across, it's a meteoroid.

Usually, a meteoroid is a chunk of an asteroid that got blasted off during a collision with another asteroid.

You'd think that wouldn't happen with all that, you know, space, but it does.

So, big space rock?

Asteroid.

Small space rock?

Meteoroid.

And if a meteoroid leaves space and enters a planet's atmosphere, it becomes a meteor.

These are the flashes of light we spot in the sky and call shooting stars.

Meteors are little space rocks that burn up and vaporize into dust as they hurtle through the atmosphere.

If a piece of meteor doesn't completely obliterate before reaching the ground, it becomes something else.

A meteorite.

As for asteroids that enter the Earth's atmosphere or hit the surface, they're still called asteroids.

But here's some good news while our planet gets pelted by tons of space rocks every day, there's only one recorded instance of a meteorite actually striking a person.

In Alabama in 1954, a meteorite broke through Ann Hodge's roof, interrupted her nap, and left her a mean shiner on her thigh.

And most of the space rocks that hit Earth aren't big enough to completely wreck it.

If an asteroid less than 25 meters wide enters Earth's atmosphere, it's likely to burn up and disintegrate.

In fact, an asteroid the size of a car enters the atmosphere and explodes before reaching the surface almost every year.

That's what happened above Chelyabinsk, Russia in 2013, with an asteroid about two and a half times as long as a London bus.

It entered Earth's atmosphere and burned up 30 kilometers above the city, releasing 30 times more energy than the atomic bomb dropped on Hiroshima.

And the sound wave that followed was so powerful, it shattered windows across six cities, injuring 1 ,500 people.

So even asteroids that burn up can have an impact, especially if they're big.

An asteroid 140 meters wide hits the Earth roughly every 20 ,000 years.

That's big enough to wipe out a metro area or even whole U .S states.

An asteroid with the potential to cause global devastation and kill most living things is extremely rare, reaching us every 100 million years at most.

But it does happen.

And we know that because it's happened before.

Let's dig a little deeper.

Remember, 66 million years ago, an asteroid wider than Mount Everest is tall, hurtled through Earth's atmosphere.

And it didn't burst in midair.

It directly collided with our planet off the coast of what's now Mexico.

And the world changed.

In the first minute of impact, what's now known as the Chicxulub asteroid carved a crater over 20 kilometers deep into the ocean floor,

vaporizing some of the rocks and water around it.

Within three minutes, its sheer force caused the ground in the center of the crater to liquefy

and rebound up into a giant peak.

Then it collapsed again, sending out shockwaves in every direction.

That collapse dumped chunks of rock at the edges of the crater, forming a ring around the molten gap at the center.

And that's just the first thirty minutes.

Within an hour, the ocean surged over the molten crater where the water began churning and spitting up steam.

For a whole day, the ocean sloshed back and forth as rocks from the crater's rim toppled and stirred up water,

waves spitting them back onto the crater's rim.

Also, everything within 1 ,400 kilometers of the impact was on fire.

25 trillion tons of debris had been hurled up into the sky, some of which landed far from the crater, setting fires ablaze all over the planet.

And there was a massive tsunami, with waves 1 .5 kilometers high.

The shockwave then triggered more tsunamis, earthquakes, and volcanic eruptions across the globe.

If that wasn't enough, the rocks vaporized by the asteroid's impact unleashed up to 325 gigatons of sulfur into the air,

creating toxic sulfuric acid.

This might have blocked the sun and chilled the climate for years

or tainted the rivers and oceans with showers of acid rain.

All told, these effects were eventually enough to kill roughly 75 % of all plants and animals on Earth, including the dinosaurs.

Except the very few that evolved into today's birds.

Those guys are resilient.

Can we just appreciate for a moment that human brain power can reconstruct a thing that happened millions of years ago, but I can't remember where I left my keys?

Has anyone seen my keys?

To be fair, it took decades of shared brain power to get to this level of detail.

In 1977, an American father and son team, Luis and Walter Alvarez, made a discovery.

In Italy, they found a very thin layer of clay sandwiched between rocks with tons of marine fossils, and rocks with barely any.

It turns out you can find this thin clay layer in rocks from the same time period all over the world.

The Alvarezes and their collaborators discovered that this layer is full of soot and iridium, an extremely rare metal on Earth, most often found in asteroids.

This was the first clue.

All that iridium must have been ejected from a space rock.

A really big space rock.

Today, that thin layer is called the Cretaceous -Paleogene boundary, or the KPG boundary for short.

It marks the moment about 66 million years ago

when a 12 -kilometer asteroid rammed into the planet and left a geological stamp.

The other big piece of evidence was the Chicxulub impact crater, which marks the spot where the asteroid hit just off the coast of what's now Mexico.

It's a whopping 180 kilometers wide and 900 meters deep, but it's also buried a kilometer below the surface, partially under the ocean.

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So it wasn't even discovered until the 1990s.

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Chicxulub?

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Can't see me.

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It's pretty much impossible to find evidence of asteroid impacts from that long ago.

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Erosion and plate tectonics are constantly exfoliating Earth in slo -mo, erasing the evidence.

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Like, the Fredafort impact structure in what's now South Africa marks

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a spot where an asteroid up to 25 kilometers wide slammed into the Earth a little over 2 billion years ago.

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But the main clue left behind isn't even a crater anymore.

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It's a dome, an area where the ground lifted after an asteroid obliterated the ground surrounding it.

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Hmm?

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Oh, yeah, Dwayne doesn't like that I use the word obliterated.

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If you're wondering how worried you should be about an asteroid doing the same thing to us, you're not alone.

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But I have more good news.

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We've got one thing the dinosaurs didn't have.

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What's that, Dwayne?

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Chapel Rhone?

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Well, yes, definitely.

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Oh, thumbs?

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I think you could argue Iguanodons did have thumbs but we're getting off track here.

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We've got one thing the dinosaurs didn't have, and that's human brain power.

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Remember how I said that before?

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That's foreshadowing, baby.

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Over the years, we've developed different ways of tracking asteroids, like their pizzas we never want delivered.

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Today, NASA uses powerful space telescopes to take pictures of asteroids' movements and calculate their orbits.

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And none of the asteroids big enough to be damaging—let me repeat, none of them— are on track to hit the Earth any time in the foreseeable future.

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If an asteroid does someday pose a threat, we'll know!

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And there's an organized effort to prepare for these risks if they ever arise.

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Every two years, NASA's planetary defense team leads a hypothetical tabletop exercise where key leaders

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and experts run through the what -ifs of a potential asteroid impact.

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Someone should tell them to play that asteroids game I just learned about.

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There's also ongoing research into redirecting an asteroid's path by crashing a spacecraft into it.

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And get this, we've done it!

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Like not in a movie, in real life!

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NASA sent a spacecraft on a one -way trip to smack into an asteroid.

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And it worked.

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The craft, called the Double Asteroid Redirection Test, or DART, had to travel for more than 10 months to reach the asteroid.

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But it successfully head -butted the 160 -meter rock onto a slightly different path.

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That's one small smack on an asteroid, one giant leap for humanity.

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So the sky is falling.

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But it's far more likely to be a shower of cosmic brownie sprinkles than a massive dino killer.

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At the time we're filming this, there are almost 1 .5 million asteroids in our solar system that we know of.

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But altogether, their total mass is less than that of our moon.

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And there's even more good news.

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The last time a large asteroid had a major impact, some life managed to survive, adapt, and evolve into new life forms,

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including a weird, complicated ape that's invented marbles like novelty socks, pizza with cheese in the crust,

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and ways of tracking asteroids before they become a threat.

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All right, can we strike asteroid impact from my things to worry about list?

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Presently, it is directly above the server being mad at me because I corrected my order.

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You're not mad at me, are you, Katie?

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Next time, we'll learn how geology fuels our world.

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See you then.

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FOR YOU

이 레슨의 어휘와 말하기 포인트

이 영상에는 섀도잉할 문장 150개와 단어 1842개가 있습니다. 말하는 구간의 길이는 10:15입니다. 화자는 분당 약 180단어로 빠르게 말하므로 연음과 약하게 발음되는 소리가 많습니다. 영어에서 가장 많이 쓰이는 3,000단어에 속하는 단어가 75%뿐이라 어휘가 어려운 편입니다.

이 영상의 핵심 어휘

영상에 나오는 익혀 둘 만한 단어 15개를 발음, 뜻과 함께 정리했습니다.

단어	발음	뜻
asteroid 명사	/ˈæst(ə)ɹɔɪd/	소행성
atmosphere 명사	/ˈætməsˌfɪɹ/	대기, 대기권
crater 명사	/ˈkɹeɪ.tɚ/	충돌구, 크레이터
layer 명사	/ˈleɪ̯ɚ/	층
ton 명사	/tʌn/	톤
thin 형용사	/ˈθɪn/	가늘다, 얇다
meter 명사	/ˈmitəɹ/	계량기
dinosaur 명사	/ˈdaɪnəsoɹ/	공룡
metre 명사	/ˈmiːtəɹ/	미터, 메터
meteor 명사	/ˈmiːtiɚ/	유성, 류성
acid 명사	/ˈæsɪd/	산
pizza 명사	/ˈpi.tsə/	피자
belt 명사	/ˈbɛlt/	벨트, 허리띠
clay 명사	/kleɪ/	찰흙, 점토
clue 명사	/kluː/	실마리

영상에 나오는 구동사

단어	뜻
wipe out 동사	무찌르다

주의할 발음

화자는 they're, we've, didn't 같은 축약형과 약화된 형태를 31번 사용합니다. 들리는 대로 짧게 발음하세요.

“th” 소리: thin /ˈθɪn/, thumb /ˈθʌm/, thirty /ˈθɝti/, earthquake /ˈɝθkweɪk/, altogether /ɔl.tuˈɡɛð.ɚ/
“sh”와 “zh” 소리: flash /flæʃ/, partially /ˈpɑɹʃəli/, sheer /ʃɪɚ/, collision /kəˈlɪʒn̩/, audition /ɑˈdɪʃən/
긴 단어 — 강세 위치에 주의: diameter /daɪˈæmɪdɚ/, geology /d͡ʒɪˈɒl.ə.d͡ʒɪ/, complicated /ˈkɑm.plɪˌkeɪ.tɪd/, successfully /səkˈsɛs.fə.li/, humanity /hjuˈmænɪti/

이 영상으로 연습하는 방법

먼저 말하지 않고 영상을 끝까지 듣고 모르는 단어를 적어 둡니다.
0.75배속으로 한 문장씩 섀도잉을 시작하고, 익숙해지면 보통 속도로 돌아갑니다.
자신의 목소리를 녹음해 원본과 비교하고, asteroid, atmosphere, crater 같은 단어에 특히 주의합니다.

이 영상의 문법

화자가 가장 많이 쓰는 문형을 영상 속 실제 표현과 함께 정리했습니다.

문형	영상 속 표현
수동태 be + 과거분사 — 누가 하는지보다 무슨 일이 일어나는지에 초점	is headed · are sometimes called · had been hurled
현재완료 have/has + 과거분사 — 과거의 일이 지금도 관련이 있을 때	they've collided · You've seen · has just informed

쉐도잉이란? 영어 실력을 빠르게 키우는 과학적 방법

쉐도잉(Shadowing)은 원래 전문 통역사 훈련을 위해 개발된 언어 학습 기법으로, 다언어 학자인 Dr. Alexander Arguelles에 의해 대중화된 방법입니다. 핵심 원리는 간단하지만 매우 강력합니다: 원어민의 영어를 들으면서 1~2초의 짧은 지연으로 즉시 소리 내어 따라 말하는 것——마치 '그림자(shadow)'처럼 화자를 따라가는 것입니다. 문법 공부나 수동적인 청취와 달리, 쉐도잉은 뇌와 입 근육이 동시에 실시간으로 영어를 처리하고 재현하도록 훈련합니다. 연구에 따르면 이 방법은 발음 정확도, 억양, 리듬, 연음, 청취력, 말하기 유창성을 크게 향상시킵니다. IELTS 스피킹 준비와 자연스러운 영어 소통을 원하는 분들에게 특히 효과적입니다.

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쉐도잉 연습: How Often do Asteroids Hit the Earth?: Crash Course Geology #20 - 영상으로 영어 말하기 배우기

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