了解宇宙是如何运行的（2010）

How the Universe Works S08E01

Part 4 Jan. 30, 2022, 2:57 p.m.

that will change
the future trajectory
未来的轨迹
of that lone
roller derby skater.
而下一次
And the next time around,
可能会是一个巨大的失误也可能是正面撞击
it might be a wide miss
or it might be a head-on impact.
太阳系也是如此
Narrator: It's the same
in the solar system.
地球和月球的联合引力
The combined gravity
of the earth and moon
创造了所谓的引力锁眼
creates what's called
a gravitational keyhole,
一个引力最佳点
a gravitational sweet spot,
可以改变阿波菲斯的轨道
which could change
apophis' orbit.
这将改变这块岩石未来可能的轨迹
That will change the potential
future trajectory of this rock
可能使它完全无害
and might make it
totally harmless
或者可能增加
or might increase the chances
未来进一步撞击的机会
of an impact
even further in the future.
由于引力锁眼的存在
Narrator: Because of the
gravitational keyhole,
阿波菲斯在2068年
there's still a small chance
撞击地球的可能性仍然很小
that apophis will hit earth
in 2068.
普莱特:这是阿波菲斯教给我们的重要一课——
Plait: That is the important
lesson that apophis taught us --
你可能会错过地球
you can miss the earth,
但如果你穿过其中一个引力锁眼
but if you pass through
one of these keyholes,
过一段时间，你就会撞上地球
at some time later,
you will hit the earth.
我们现在知道，阿波菲斯将在2029年错过这个引力锁眼
Narrator: We now know apophis
will miss the keyhole in 2029,
但还有其他的引力锁眼和其他近距离通行
but there are other keyholes
and other close passes.
♪
阿波菲斯并不是唯一的威胁
apophis is not a lone threat.
据估计，有832500颗小行星
There are an estimated
832,500 asteroids
围绕太阳运行
orbiting the sun.
大多数小行星过着
Most asteroids live
their lives
非常平静的生活，越过火星轨道
perfectly peacefully
past the orbit of mars
或尾随木星的轨道，并不干扰其他星球
or trailing jupiter
and don't mind anybody else,
也不会造成任何麻烦，但有些小行星的轨道
don't cause any troubles,
but some asteroids
非常特殊
are on very particular orbits
它们穿过了地球轨道
that cross the orbit
of the earth.
这些小行星已经离开了
Narrator: These asteroids
have left the stable orbit
小行星带的稳定轨道
of the asteroid belt
进入了靠近我们的轨道
and moved into orbits
that get near our own.
这些小行星被称为近地小行星
These asteroids are called
near earth asteroids
简称 n.E.A.S
or n.E.A.S for short.
沃尔什:近地小行星的数量很有趣
Walsh: The near earth asteroid
population is interesting
而且有潜在的危险，因为它们
and potentially dangerous
because they are the ones
实际上是穿过地球的轨道
that actually cross
the orbit of the earth.
所以它们很有可能在未来的
So they're most likely
to have, at some point
某个时候与地球发生碰撞
in the future,
an impact with the earth.
大多数 n.E.A.S 对地球几乎没有威胁
Narrator: Most n.E.A.S pose
little or no threat to earth.
但我们已经探测到了超过2000个
But we've detected over 2,000,
包括1200英尺高的波菲斯
including the 1,200 foot apophis
that do.
这些叫做 p.H.A.S…
These are called p.H.A.S --
即有潜在危险的小行星
potentially hazardous asteroids.
近地小行星
The difference between
a near earth asteroid
和潜在危险小行星之间的区别在于距离和大小
and a potentially hazardous
asteroid is distance and size.
任何东西都可以接近地球
Anything can get near the earth,
可能在2000万英里（约3200万公里）之外
and that could be
20 million miles away,
类似这样的东西，可能是一颗近地小行星
something like that,
and be a near earth asteroid,
但有潜在危险的一颗可能会撞击我们
but a potentially hazardous one
can hit us,
它的大小足以造成破坏
and it's big enough
to do damage.
所以，在接下来的一百年左右的时间里
So something that over
the next hundred years or so
有可能袭击我们并对我们造成损害的东西——
has a chance of hitting us
and doing damage when it does --
就是一个潜在的危险物体
that's a potentially
hazardous object.
P.H.A.S 是指460英尺（约140米）或更大的小行星
Narrator: P.H.A.S are asteroids
that are 460 feet or larger
可能与地球相撞
that could collide with earth.
以一颗400英尺（约122米）长的小行星为例——如果击中
Take a 400-foot asteroid --
if it hits,
释放的能量相当于
it would release as much energy
3000颗广岛原♥子♥弹♥
as 3,000
hiroshima nuclear bombs.
2018年7月
Narrator: In July of 2018,
美国国家航♥空♥航♥天♥局(NASA)发布了一张地图
nasa published a map
上面有所有已知的 n.E.A.S 和 p.H.A.S
of all the known
n.E.A.S and p.H.A.S.
动画记录了它们
The animation tracks
their discovery
从1999年到2018年的发现
from 1999 through 2018.
每次我看到这个动画
Every time I look
at this animation,
我的心都会停止跳动
it does make my heart
stop a little bit
因为它看起来就像一群愤怒的蜜蜂
because it looks like
we're in the middle of a swarm
围着我们团团转
of angry bees
circling all around us.
1999年，我们发现了
Narrator: In 1999,
we'd identified
300个 n.E.A.S
under 300 n.E.A.S
分散在太阳系内部
scattered through
the inner solar system.
10年后，我们又发现了500个
10 years later,
we'd found 500 more.
到2018年，我们已经发现了18000颗近地小行星
By 2018, we'd discovered 18,000
near earth asteroids,
但我们估计还有数百万颗
but we estimate
there are millions out there.
似乎我们永远也找不全所有的小行星
It seems like we could
never find all the asteroids.
他们不会停下来
They just keep coming.
就像我们在和一群僵尸战斗
It's like we're fighting
an army of zombies.
僵尸以每小时6♥4♥000英里（约103000公里）的速度
Narrator: Zombies that keep
hurtling our way,
向我们飞奔而来
hitting the earth at up
to 6♥4♥,000 miles an hour.
这是非常非常快的速度
That is very, very fast.
比步♥枪♥子弹快多了
That is much faster
than a rifle bullet.
这就是它破坏力的关键所在
And that's the key
to its destructive power.
当一颗速度非常快、体积非常大的小行星撞击地球时
Narrator: When a really fast
and really large asteroid hits,
其影响是前所未有的
the impact is off the charts.
爆♥炸♥非常强烈
The blast is so intense,
可以融化甚至汽化岩石
it can melt
or even vaporize rock.
♪
2019年1月
narrator: January 2019,
月全食的时候
a total eclipse
of the moon.
天文学家把望远镜对准
Astronomers train
their telescopes
逐渐变暗的月球表面
on the darkening lunar surface.
它们捕捉到了
They capture a bright flash
持续约四分之一秒的闪光
that lasts around a quarter
of a second.
它被记录了下来当时有很多网络直播
It was recorded. There were
a lot of live webcasts
和类似的事情