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太阳多层不同转速的谜题以及火星陨石的来源 – 译学馆
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太阳多层不同转速的谜题以及火星陨石的来源

The Sun's So Bright, It's Spinning Slower

对我们地球的居住者来说,很少有比太阳更加亘古持续的东西存在
For us Earthlings, there are few things as constant as the Sun.
但是太阳其实是一直在旋转着的…而且奇怪的是,它表面的大气层
But the Sun is actually spinning… and weirdly, the layer of gas at its surface spins slower
比下层的大气层旋转的更慢
than the gas beneath it.
我们现在已经掌握这个事实
We’ve known about this for a while.
差不多有30年了
Like, almost thirty years.
但科学家们一直没能对这个现象有个好的解释
But scientists have never had a great explanation for it.
目前,一组天文学家认为他们终于破解了这个谜题
But now, a team of astronomers thinks they have finally cracked the case.
他们认为外层大气移动的如此缓慢是因为
They think that outside layer could be moving more leisurely because the Sun is just so
太阳实在是太亮了
dang bright.
太阳光的作用就像是一道刹车
The light acts as a brake!
这一切都要说回到1980年间,当科学家们在研究一门与太阳有关的学科 叫
This all started back in the 1980s, when scientists were studying the Sun with something called
日震学
helioseismology.
这就好比地震学家观察地球上的震动波
It’s kind of like how seismologists monitor the waves moving through the Earth to learn
来研究地震一样
more about earthquakes.
在日震学当中,物理学家们可以通过震动来理解太阳上发生些什么
With helioseismology, physicists can use vibrations to understand what’s going on in the Sun.
通过这样的科学技术,他们可以观测到一个天文学家们已经了解了几个世纪的现象:
Using these techniques, they could see that the Sun’s equator rotates faster than the
太阳的赤道旋转的比两级更快
poles — something astronomers had known for centuries.
同时他们也观测到太阳表面比其下的气层旋转的更慢
They also saw that the solar surface rotates slower than the gas underneath it.
但现在的问题是:日震学只有在宏观上给予天文学家们一个好的观测
But here’s the thing: helioseismology is really only good at giving astronomers a really
比如在太阳横穿或者深度3000公里的一大块地方
big picture — what’s happening in chunks of the Sun like 3,000 kilometers across or
发生着什么
deep.
而且太阳表面总是因为各种不同原因而在不停的移动、变化着
And the Sun’s surface is constantly moving and changing for loads of different reasons.
所以科学家们知道太阳有不同速度多层结构的神秘现象
So, scientists knew about the different-layer, different-speed mystery, but didn’t have
却没有办法解释为什么
a way to explain it.
现在三十年过去了,天文学家们有了新的科学工具:
Now, three decades later, astronomers have a new tool: NASA’s Solar Dynamics Observatory
美国航空局太阳动力学观测卫星
satellite.
这是一个拥有10公里分辨率的卫星
This satellite lets them watch how the gases at the very edge of the Sun’s surface move,
让人们得以观测太阳表面极度边缘的地方大气是如何移动的
with a resolution of 10 kilometers.
收集了三年半的数据之后
Using three and a half years of data, the team tracked changes in the Sun’s outer
这个队伍追踪到了太阳外层的变化
layer.
并且,他们在一家叫物理检阅的杂志中发布了文章
And in a paper published in Physical Review Letters, they show that most of the slowdown
文中说明了大部分减速只在太阳表面外部70千米处发生,而不是整个太阳
happens in just the outer 70 kilometers of the solar surface, not the entire thing.
光正是从这特有的边缘中飞逸出宇宙空间
This very outer edge is where light escapes into space, and the researchers realized that
研究者们也意识到也许太阳光线正是让太阳本身减速旋转的原因
that sunlight itself might be what’s slowing down the Sun’s spin.
因为光线中的光子会从各种发光的东西中
That’s because photons of light have momentum, which they takes from whatever’s emitting
获得冲量
the light.
如果发光的东西像太阳表面那样向着一边移动的话
And if whatever’s emitting the light is moving sideways, like the Sun’s surface
光也会偷取那向着侧面的动量
does, light steals some of that sideways momentum, too.
光线中的每一个光子偷取一点小到无法计量的动量
Each photon of light steals an unimaginably small amount of momentum, but the Sun is really
但太阳极亮,它在其寿命中已经发出了很多的光子
bright, and it’s given off a lot of photons over its lifetime.
研究者经过计算,发现日光慢慢吸取的动量
The researchers did the math, and found that sunlight slowly siphoning off momentum can
正好可以解释太阳不同外层之间的不同移速
just about completely explain the difference in speeds between the Sun’s layers.
虽然目前还不能确信这就是减速的主要原因
They still aren’t positive that this is the major cause of the slowdown, but it seems
但非常接近了
pretty likely.
但是别担心,太阳一时半会还不会停止旋转
And do not worry, the Sun won’t stop spinning any time soon.They checked, and a total slowdown
他们计算了,太阳的完全减速会花上比我们周围星球剩余50亿年还要长的多的时间
would take far longer than the five billion years our stellar neighbor has left.
下面,让我们谈谈NWA
Next, let’s talk about NWA.
不,不是嘻哈的那个NWA
No, not the hip-hop NWA.
也不是那家不再存在的航空公司
Not the airline — that doesn’t exist anymore.
而是那个石头
The rock version…
NWA 7635
NWA 7635.
这里的NWA代表着非洲西北,也就是那块石头被发现的地方
NWA stands, here, for Northwest Africa, because that’s where the rock was found.
但这不是一块普通的石头
But it’s no ordinary rock.
它来自火星
It’s from Mars.
一组科学家认为这个陨石证明了
And a group of scientists think this meteorite could be proof that at least one Martian volcano
火星上至少有一个火山持续喷涌岩浆超过了二十亿年
has been continuously spewing magma for more than two billion years.
这是在地球上前所未有的
That is unheard of on the Earth’s surface.
在这儿,我们有板块构造移动着所有大陆
Here, we have plate tectonics shifting everything around, so volcanoes would never really last
所以火山并不可能真正持续喷涌几十亿年
for more than a few million years.
NWA 7635 是科学家们在地球上发现的几百块陨石之一
NWA 7635 is one of about a hundred Mars rocks scientists have found on Earth, expelled from
它因为火星遭受撞击而被从火星表面铲除
the Martian surface by things crashing into it.
在它们来到地球的路程上,这些石头暴露在高能宇宙光线之下
On their way here, those rocks get exposed to high-energy cosmic rays that change some
使得组成它们的原子被转变为地球上所没有的同位素或元素
of their atoms into weird isotopes or elements that weren’t originally there.
它们在外太空漂浮的时间越长,它们包含的变异原子就越多
And the longer they’re floating out in space, the more weird atoms are in the rocks.
基于它们是由什么组成的以及它们在外太空待了多久
So based on what they’re made of and how long they were in space, scientists can tell
科学家们可以粗略计算出它们是何时离开火星的
roughly when they got kicked off Mars.
NWA 7635和另外10块被称为辉熔长石无球粒陨石的火山岩石非常相似
NWA 7635 is really similar to 10 other volcanic rocks called shergottites, which are Martian
也就是由特定元素及矿物组成的火星陨石
meteorites made up of certain elements and minerals.
特定一组的辉熔长石无球粒陨石大约在一百万年前被发射到宇宙中
This specific group of shergottites got launched into space about a million years ago and formed
并且在约3~6亿年前成型
about three to six hundred million years ago.
但是当研究者真正去查验NWA 7635的年龄时
But when these researchers actually checked NWA 7635’s age, they found that it’s not
他们发现它不是存在了几亿年…而是几近二十五亿年
a few hundred million years old… it’s nearly two and a half billion years old.
因为这些石头都是由同样的物质组成的,也就意味着
Because these rocks are all made of the same stuff, that means that there must have been
在同一个地点必定有一个火山或火山系统持续制造着新的火山岩石 超过二十亿年
a volcano or volcanic system making new rocks in the same spot for more than 2 billion years.
换句话说,它喷发了火星40%的历史!
In other words, it was erupting for over forty percent of Mars’s history!
并且那是一个持续喷涌的火山
And that is a persistent volcano.
许多科学家为了火星上是否有或有过板块构造论争辩了多年
Planetary scientists have argued for years about whether Mars has or ever had plate tectonics…
他们估计也会一直争辩下去
and they’ll probably keep arguing.
但NWA 7635表明了即使火星大陆板块会移动,估计也不会像地球那样
But NWA 7635 shows that even if the surface did shift around, it probably never worked
星球上每几亿年就显著的有不同变化
much like Earth, where the planet is significantly rearranged every couple hundred million years.
这项研究表明了我们并不总是需要飞越宇宙到红星上
And it just goes to show that we don’t always need to jet all the way over to the Red Planet
才能知道它的历史
to learn about its history.
陨石就这么向我们飞来!
The rocks just come to us!
尽管我们完全应该尽快到达那个星球上去
Though we should totally go to the rocks, as soon as possible.
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