了解宇宙是如何运行的（2010）

How the Universe Works S08E09

Part 5 Jan. 30, 2022, 2:59 p.m.

can have, you know,
a big influence over time.
♪
地球绕太阳的轨道
narrator:
Earth's orbit around the sun
只是我们更大的宇宙旅行的一部分
is just part of our
far larger cosmic journey.
♪
整个太阳系在银河系中飞驰
the entire solar system is
hurtling around the milky way,
♪
把我们带到我们不想去的地方
taking us places
we don't want to be.
有时候，我们的星球可能会
Sometimes our planet
might wander
误入一个本质上很糟糕的社区
into what's essentially
a bad neighborhood.
有什么危险在等着我们？
Narrator: What dangers await us?
这些区域会给地球上的生命
And could these neighborhoods
spell disaster
带来灾难吗？
for life on earth?
♪
♪
在过去的37亿年里
narrator: Over the last
3.7 billion years,
一系列的灭绝事件
a series of extinction events
wiped out
导致了将近95%的物种灭绝
almost 95 percent
of all species on earth.
[爆♥炸♥]
[ explosion ]
♪
现在的研究表明，地球的轨道
now research suggests
our planet's orbit
可能是部分原因
could be partly to blame,
但不是地球绕太阳的轨道
but not the earth's orbit
around the sun,
而是我们星球绕银河系更大、更长的旅程轨道
our planet's larger and longer
journey around the milky way.
我们的太阳系和太阳
Our solar system and our sun
is shooting through the galaxy
正以每小时53万英里的速度穿过银河系，围绕着银河系中心
at about 530,000 miles per hour
around the center of our galaxy.
这个星系的中心离我们大约26000光年远
And that center of the galaxy is
about 26,000 light-years away,
所以太阳要花两亿三千万年
so it should take the sun
about 230 million years
才能绕星系中心画出一个完整的轨道
to trace out one full orbit
around the center of the galaxy.
♪
尽管地球以每小时50万英里的速度
narrator: Despite racing
around the milky way
环绕银河系
at 1/2 million miles an hour,
但在地球的整个历史中，地球绕银河系的路程
earth has completed less than
20 laps of the galaxy
还不到20圈
in our planet's entire history,
而且事实证明，这个银河系之旅
and it turns out
this galactic ride
比看起来要复杂得多
is more complicated
than it seems.
现在，如果你看地球围绕太阳转
Now, if you look at the earth
going around the sun,
它定义了一个椭圆形
it defines an ellipse,
但这是一个平面，你会想
but that's a flat figure,
and you'd think,
“好吧，太阳可能也在一个平面上转圈”
"well, the sun probably goes
around in a plane, as well,"
但其实没那么简单
and it turns out
not that simple.
♪
太阳系的大部分质量
narrator: Most of the mass
of the solar system
都集中在太阳上
is concentrated in the sun,
所以地球和其他行星都平稳地绕着我们的恒星运行
so earth and the other planets
smoothly orbit our star.
♪
但是银河系的质量分布不均匀
but the mass of the milky way
is spread out unevenly.
这就改变了星系的引力
That changes the gravity
of the galaxy,
也就改变了星系中物体的运动方式，事实上
and so it changes how things
move in it, and in fact,
如果你让物体上下运动
if you give something a little
bit of an up or down motion,
它就会跟随着上下跳动
it'll bob up and down
as it goes around.
奥卢塞伊:骑在地球上就像骑在旋转木马上
Oluseyi: Riding the earth is
almost like riding a carousel.
当太阳和地球绕着银河系运行时
As the sun and the earth
go around the galaxy,
太阳也会有起落
the sun also goes up and down
就像你骑在一匹有杆子的马上一样
like you're on one of
those horses with the pole,
这样的运动
and so what this can do
可以把我们带进不同的星系环境
is take us into different
galactic environments.
♪
这种上下摆动的运动使地球和太阳系
narrator: This bobbing motion
takes earth and the solar system
在银河系的银道面上
on a 60,000-year journey
进行了长达6万年的上下运动
up and down through
the milky way's galactic plane.
♪
我们这样的轨道
our orbit also takes us
还带着我们穿过不同的星系邻居
through different
galactic neighborhoods.
♪
今天，我们将穿越银河系一个平静的郊区
today, we're traveling through
a calm suburb of the galaxy.
但有时候事情会有点不顺利
But sometimes things
get a little bumpy.
有时我们的太阳和地球
Sometimes our sun and our planet
might wander
可能会漫游到一个本质上不好的邻居
into what's essentially
a bad neighborhood.
你知道，也许这是一个
You know, maybe it's an area
有很多恒星正在形成的区域
where there's a lot of
star formation going on,
有很多年轻的恒星非常活跃
where there's a lot of young
stars that are very active,
或者这是一个有濒死恒星的地方
or maybe it's a location
where there are dying stars,
那里的东西会变得非常热
and things are about
to get really hot.
银河系中最糟糕的邻居
Narrator: The baddest
neighborhoods in the galaxy
可能就是旋臂
may be the spiral arms.
♪
这些充满气体的区域环绕银河系中心运行的速度
these gas-filled regions orbit
the galactic center
比地球慢很多
more slowly than the earth,
所以我们的行星大约
so our planet
passes through an arm
每1.5亿年穿过一条旋臂
roughly every 150 million years.
普雷特:这些旋臂是气体云倾向于聚焦的地方
Plait: These arms are where
gas clouds tend to hang out,
如果它们被压缩，就会形成很多恒星
and if they get compressed,
they form a lot of stars.
当它们形成大质量恒星时，就会形成明亮的蓝色恒星
When they form a lot of stars,
they make bright, blue stars.
它们不会持续很长时间，会以超新星的形式爆♥炸♥
And they don't last long,
and they blow up as supernovae.
♪
[爆♥炸♥]
[ explosion ]
所以当我们经过这些区域的时候
so it's possible that as we're
passing through these regions,
这些地方可能是你不想去的地方
these are places you might not
want to be in,
所以在遥远的过去
so in the distant past,
这可能会影响地球
this may have
affected the earth.
♪
当巨型恒星变成超新星时
narrator: When giant stars
go supernova,
恒星的外层会随着
the stars' outer layers
blast into space
♪
每秒两万英里的冲击波
along with a shock wave
冲入太空
traveling at
20,000 miles a second.
♪
超新星还会释放宇宙射线——
supernovas also release
cosmic rays --
“太空子弹”以接近
space bullets
that shoot across the galaxy
光速的速度穿过星系
at close to the speed of light.
♪
普雷特:你不会想太多接触这些射线的
plait: And you don't want to be
exposed to too many of them,
如果剂量足够大
but in high enough doses,
这些东西就会渗入我们的细胞，破坏我们的 DNA
these things penetrate our cells
and damage our dna
长♥期♥下去会对人体造成非常
and over the long-term can cause
really bad damage