kind of big.

話しておきたい事があります

We'll start here.

重要な話です

Sixty-five million years ago --

始めましょう

(Laughter)

6500万年前

the dinosaurs had a bad day.

恐竜達には不運な1日でした

(Laughter)

（笑）

A chunk of rock six miles across,

直径10キロの大きな隕石が

moving something like 50 times the speed of a rifle bullet,

ライフル銃の

slammed into the Earth.

約50倍の速さで

It released its energy all at once,

地球に衝突しました

and it was an explosion that was mind-numbing.

そのエネルギーは一瞬で放射され

If you took every nuclear weapon ever built

大爆発し

at the height of the Cold War,

全てが終わりました

lumped them together,

冷戦の最中に造られた

and blew them up at the same time,

全ての核兵器を

that would be one one-millionth of the energy released at that moment.

集めて一度に

The dinosaurs had a really bad day.

爆発させたとしても

OK?

その隕石が衝突した時の

Now, a six-mile-wide rock is very large.

100万分の１のエネルギーにしかなりません

We all live here in Boulder.

恐竜達には本当に不運な1日でした

If you look out your window and see Longs Peak --

いいですか？

you're probably familiar with it --

直径10キロの隕石は非常に大きいです

now, scoop up Longs Peak and put it out in space.

我々はボルダーに住んでいます

Take ... Meeker, Mt. Meeker.

窓の外の

Lump that in there, and put that in space as well.

ロングスピークは 見慣れた景色です

And Mt. Everest. And K2.

では ロングスピークをすくい上げて

And the Indian peaks.

脇に置いておきます

Then you're starting to get an idea of how much rock we're talking about, OK?

ミーカー山もとって１つにまとめて

We know it was that big

エベレストとＫ２（山）

because of the impact it had and the crater it left.

インディアンピークスも

It hit in what we now know as Yucatan, the Gulf of Mexico.

一緒にしておきます

You can see here, there's the Yucatan Peninsula,

では考えてみましょう

if you recognize Cozumel off the east coast there.

いくつの山について話しましたか？

Here is how big of a crater was left.

その隕石が巨大だったのは

It was huge.

その衝撃やクレーターから明らかです

To give you a sense of the scale ... there you go.

隕石が落ちたのは

The scale here is 50 miles on top, a hundred kilometers on the bottom.

メキシコ湾のユカタンです

This thing was 300 kilometers across -- 200 miles --

こちらに見えるのが

an enormous crater that excavated out vast amounts of earth

ユカタン半島です　コスメル島は

that splashed around the globe and set fires all over the planet,

東海岸から離れたところにあります

threw up enough dust to block out the sun.

クレーターの大きさが見てとれますね

It wiped out 75 percent of all species on Earth.

巨大でした　規模を測ると

Now, not all asteroids are that big.

こちらですが

Some of them are smaller.

大きさは頂上が80キロで

Here is one that came in

ふもとは100キロです

over the United States in October of 1992.

直径300キロ（約200マイル）の

It came in on a Friday night.

巨大なクレーターは

Why is that important?

大量の大地を削って世界中に撒き散らし

Because back then, video cameras were just starting to become popular,

日光を遮る程の粉じんと共に

and parents would bring them to their kids' football games

地球全体を火の海にしてできました

to film their kids playing football.

地球上の全生物の75パーセントが

And since this came in on a Friday,

絶滅しました

they were able to get this great footage of this thing breaking up

全ての小惑星がこんなに大きい訳ではなく

as it came in over West Virginia, Maryland, Pennsylvania and New Jersey

小さいものもあります

until it did that

これは

to a car in New York.

1992年10月に

(Laughter)

アメリカに落下した隕石です

Now, this is not a 200-mile-wide crater,

金曜日の夜でした

but then again, you can see the rock, which is sitting right here,

なぜそれが重要か？

about the size of a football,

当時ビデオカメラは

that hit that car and did that damage.

普及し始めたばかりで

Now, this thing was probably about the size of a school bus

誰もがビデオカメラを携帯し

when it first came in.

子供達のフットボールの試合を撮りました

It broke up through atmospheric pressure,

金曜日に落下したことで

it crumbled, and then the pieces fell apart

この素晴しい映像が各地で撮影されました

and did some damage.

ウエストヴァージニア

Now, you wouldn't want that falling on your foot or your head,

メリーランド ペンシルバニア

because it would do that to it.

ニュージャージー

That would be bad.

ニューヨークの車にまで

But it won't wipe out, you know, all life on Earth, so that's fine.

（笑）

But it turns out, you don't need something six miles across

これは直径300キロもありませんね

to do a lot of damage.

しかしここにあるような

There is a median point between tiny rock and gigantic rock,

フットボール位の隕石でも

and in fact, if any of you have ever been to near Winslow, Arizona,

ぶつかると

there is a crater in the desert there that is so iconic

車が損傷しています

that it is actually called "Meteor Crater."

この隕石は恐らく元々は

To give you a sense of scale, this is about a mile wide.

スクールバス程の大きさでした

If you look up at the top, that's a parking lot,

それが大気圧で砕けて

and those are recreational vehicles right there.

粉々になり かけらが落下して

So it's about a mile across, 600 feet deep.

被害を与えたのでしょう

The object that formed this was probably about 30 to 50 yards across,

こんな隕石が足や頭の上に落ちてきたら

so roughly the size of Macky Auditorium here.

大変なことになりますね

It came in at speeds that were tremendous,

最悪でしょう

slammed into the ground, blew up,

しかし地球上の全ての生命が

and exploded with the energy of roughly a 20-megaton nuclear bomb --

絶滅する事は無いので大丈夫です

a very hefty bomb.

しかし直径10キロ無くても

This was 50,000 years ago,

大災害は起こり得るのです

so it may have wiped out a few buffalo or antelope,

隕石には小さなものと大きなものだけでなく

or something like that out in the desert,

中ぐらいの大きさを持つものもあります

but it probably would not have caused global devastation.

アリゾナのウィンズローに行くと

It turns out that these things don't have to hit the ground

砂漠の中に”アリゾナ隕石孔”と呼ばれる

to do a lot of damage.

非常に象徴的なクレーターがあります

Now, in 1908, over Siberia, near the Tunguska region --

規模を測ると 直径1.5キロです

for those of you who are Dan Aykroyd fans and saw "Ghostbusters,"

頂上は駐車場になっています

when he talked about the greatest cross-dimensional rift

RV車も停まっています

since the Siberia blast of 1909,

直径約1,5キロで深さ200メートルです

where he got the date wrong, but that's OK.

この隕石孔を形成した物体の大きさは

(Laughter)

およそ30～45メートル程で

It was 1908. That's fine. I can live with that.

このマッケイ公会堂位のサイズです

(Laughter)

それは驚異的な速さでやって来て

Another rock came into the Earth's atmosphere

地面に衝突し 粉々になり

and this one blew up above the ground,

およそ20メガトンの核爆弾のエネルギーで

several miles up above the surface of the Earth.

爆発しました

The heat from the explosion set fire to the forest below it,

非常に大きな爆弾です

and then the shock wave came down and knocked down trees

５万年前にその隕石は

for hundreds of square miles.

バッファローかアンテロープの様な生物を

This did a huge amount of damage.

砂漠から絶滅させました

And again, this was a rock probably roughly the size

しかし地球規模の災害の原因には

of this auditorium that we're sitting in.

ならなかった様ですね

In Meteor Crater, it was made of metal,

次の事例からは小惑星が衝突しなくても

and metal is much tougher, so it made it to the ground.

大災害が起こる事が分かります

The one over Tunguska was probably made of rock,

1908年のツングースカ大爆発ですが

and that's much more crumbly, so it blew up in the air.

”ゴーストバスターズ”を観ると

Either way, these are tremendous explosions -- 20 megatons.

ダン・エイクロイドが

Now, when these things blow up,

1909年のツングースカ大爆発以来の

they're not going to do global ecological damage.

超常現象だと言いますが

They're not going to do something like the dinosaur killer did.

間違っていますね 1908年です

They're just not big enough.

大丈夫　間違ってても生きていけます

But they will do global economic damage,

（笑）

because they don't have to hit, necessarily,

この時小惑星は大気圏に入ると

to do this kind of damage.

地上から数キロ上空で

They don't have to do global devastation.

爆発しました

If one of these things were to hit pretty much anywhere,

爆発による高熱で

it would cause a panic.

森は炎上し その空振で

But if it came over a city, an important city --

数千平方キロメートルの木々が

not that any city is more important than others,

なぎ倒されました

but some of them we depend on more on the global economic basis --

これは非常に大きな破壊規模でした

that could do a huge amount of damage to us as a civilization.

繰り返しますが これは恐らく

So, now that I've scared the crap out of you --

この公会堂位の小惑星の仕業でしょう

(Laughter)

アリゾナ隕石孔は鉄金を成分とした

what can we do about this?

とても頑丈な隕石が衝突した事で

This is a potential threat.

形成されました

Let me note that we have not had a giant impact like the dinosaur killer

ツングースカについては恐らく

for 65 million years.

とても砕けやすい小惑星の仕業で

They're very rare.

それ故に空中分解しました

The smaller ones happen more often,

いずれの事例も20メガトンの大爆発でした

but probably on the order of a millennium,

この位の規模の爆発では

every few centuries or every few thousand years.

地球規模で生態系に影響を及ぼすことはないでしょう

But it's still something to be aware of.

恐竜が絶滅したような事態には

Well, what do we do about them?

ならないでしょう

The first thing we have to do is find them.

それ程の破壊力はありません

This is an image of an asteroid that passed us in 2009.

しかし世界経済には損失を与えます

It's right here.

地表に衝突しなかったとしても

But you can see that it's extremely faint.

損失が出ることがあります

I don't know if you can see that in the back row.

地球規模の惨事になる必要はありません

These are just stars.

もし隕石がどこかに落ちてくるとしたら

This is a rock that was about 30 yards across,

パニックを引き起こすでしょう

so roughly the size of the ones that blew up over Tunguska

もしこれが最も重要な都市―

and hit Arizona 50,000 years ago.

どの都市もそれぞれ重要ですが

These things are faint.

世界経済を支えている都市に

They're hard to see, and the sky is really big.

隕石が降ったとすると

We have to find these things first.

我々の文明や生活に大きな影響が

Well, the good news is, we're looking for them.

あるでしょう

NASA has devoted money to this;

みなさん怖くなって震えてますね

the National Science Foundation and other countries

（笑）

are interested in doing this.

我々に何ができるでしょう？

We're building telescopes that are looking for the threat.

これは潜在的脅威です

That's a great first step. But what's the second step?

この6500万年の間 恐竜が絶滅したような

The second step is if we see one heading toward us, we have to stop it.

巨大衝突は起きていません

What do we do?

めったに無い事です

You've probably heard about the asteroid Apophis.

小さな隕石の衝突はしばしば起きますが

If you haven't yet, you will.

恐らくは1000年周期

If you've heard about the Mayan 2012 apocalypse,

数世紀から数千年に一度の出来事です

you're going to hear about Apophis,

それでも注意を向けるべき事です

because you're keyed in to all the doomsday networks, anyway.

さて 我々はどうしましょう？

(Laughter)

まずは見つける事です

Apophis is an asteroid that was discovered in 2004.

これは2009年に地球の近くを通った

It's roughly 250 [meters] across, so it's pretty big --

小惑星です

bigger than a football stadium.

ここです

And it's going to pass by the Earth in April of 2029.

とても見えづらいでしょう

And it's going to pass us so close

後方にあるものが見えるでしょうか

that it's actually going to come underneath our weather satellites.

これらはただの星です

The Earth's gravity is going to bend the orbit of this thing so much

直径30メートル位なので

that if it's just right,

ツングースカやアリゾナに衝突した

if it passes through this region of space,

物体とほぼ同じ大きさでしょう

this kidney-bean-shaped region called the keyhole,

かすかにしか見えません

the Earth's gravity will bend it just enough that seven years later,

見えづらい上に 空は広大です

on April 13 -- which is a Friday, I'll note -- in the year 2036 --

我々はこれらを見逃してはなりません

(Laughter)

幸いな事に 我々は常に見張っています

you can't plan that kind of stuff --

NASAはこの監視に予算を充てています

(Laughter)

アメリカ国立科学財団や諸外国は

Apophis is going to hit us.

この事にとても関心を持っています

And it's 250 meters across, so it would do unbelievable damage.

これらの脅威を見つけ出すために

The good news is that the odds of it actually passing through this keyhole

我々は望遠鏡を作っています

and hitting us next go-around are one in a million, roughly --

重要な第一歩です　次に行う事は

very, very low odds.

地球に向かってきている物体を確認し

So I personally am not lying awake at night worrying about this at all.

食い止める事です　何をするか？

I don't think Apophis is a problem.

小惑星アポフィスをご存知でしょう

In fact, Apophis is a blessing in disguise,

知らなくてもいつか耳にします

because it woke us up to the dangers of these things.

2012年のマヤの予言についてご存知なら

This thing was discovered just a few years ago

アポフィスを知る事になるでしょう

and could hit us a few years from now.

地球の終末についての情報は

It won't, but it gives us a chance to study these kinds of asteroids.

互いに結び付いているのですから

We didn't really necessarily understand these keyholes, and now we do,

アポフィスは2004年に発見されました

and it turns out that's really important,

直径およそ250メートルの大きさで

because how do you stop an asteroid like this?

かなり大きいですね

Well, let me ask you:

フットボール競技場よりも大きい物体が

What happens if you're standing in the road and a car's headed for you?

2029年４月に地球の近くを通過します

What do you do?

どれ程近くかというと

You do this. Right? Move, and the car goes past you.

気象衛星よりも近くを通ると

But we can't move the Earth, at least not easily,

思われています

but we can move a small asteroid.

地球の引力はアポフィスの軌道を

And it turns out, we've even done it.

曲げてしまいます

In the year 2005, NASA launched a probe called Deep Impact,

もしアポフィスが この豆型の

which slammed a piece of itself into the nucleus of a comet.

”鍵穴”とよばれる場所を通過すると

Comets are very much like asteroids.

地球の重力で軌道が変わり

The purpose wasn't to push it out of the way;

そうすると

the purpose was to make a crater to excavate the material

7年後の2036年４月13日には…

and see what was underneath the surface of this comet,

ちなみに13日の金曜日ですね（笑）

which we learned quite a bit about.

―天体の動きに計画は立てられません―

We did move the comet a little tiny bit --

アポフィスが地球に衝突するでしょう

not very much, but that wasn't the point.

それは直径250メートルで

However, think about this:

衝撃は想像を超えるでしょう

This thing is orbiting the Sun at 10, 20 miles per second.

幸いな事に その確率ですが

We shot a space probe at it and hit it, OK?

鍵穴を通過して

Imagine how hard that must be, and we did it.

地球に衝突する確率は100万分の１です

That means we can do it again.

とても低い確率でなので個人的には

If we see an asteroid that's coming toward us, headed right for us,

心配で夜眠れない様な事はありません

and we have two years to go?

アポフィスは問題ではありません

Boom! We hit it.

アポフィスは不幸中の幸いです

You know, if you watch the movies --

こうしたことに対する我々の危機意識を

(Laughter)

目覚めさせたからです

you might think:

これはたった数年前に発見されたもので

Why don't we use a nuclear weapon?

数年後に衝突することもあり得ました

Well, you can try that, but the problem is timing.

実際には衝突しませんがこれを機に

Shoot a nuclear weapon at this thing,

この類の小惑星の調査が始まりました

you have to blow it up within a few milliseconds of tolerance,

以前は鍵穴のことなどわかりませんでしたが

or else you'll miss it.

今はわかっています

And there are a lot of other problems with that; it's very hard to do.