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如何探究宇宙的历史 – 译学馆
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如何探究宇宙的历史

The history of the Universe in the blink of an eye

当你看着一样东西的时候
When you look at something,
你正在看着它的过去
you’re looking into the past.
看到这盆矮牵牛花了吗?
See this bowl of petunias?
你看到的其实是几分之一秒前的矮牵牛花
What you’re actually seeing is what the petunias looked like a tiny fraction of a second ago.
这是因为光以一定的速度运动
That’s because light has a finite speed.
以这颗星星为例
Take this star.
这颗星星发出的光要4年的时间才能到达地球
Its light takes four years to reach Earth.
所以我们只能看到4年前的星星
So we can only ever see it as it was four years ago.
如果你向宇宙更远处望去
The further you look out into space
你也会看到更久远的过去
the further back in time you see
天文学家就是利用这个规则来探索宇宙历史的
and astronomers can use this to explore the history of the Universe.
宇宙中充满电磁辐射
Space is full of electromagnetic radiation.
天文学家可以检测到附近星球产生的信号
Astronomers can detect signals from nearby stars…
其他星系产生的信号
…from other galaxies…
星系之间的间隙产生的信号
…from the gaps between galaxies…
乃至宇宙大爆炸时 宇宙本身产生的信号
…and from nearly the beginning of time itself.
所有这些信号发生于不同的距离 因此发生的时间也不同
All these signals are from different distancesand therefore different times.
但它们却同时到达观测点
But they all arrive at once.
混在一起 难以分辨
It’s kind of a mess.
所幸 天文学家有区分这些信号的方法
Luckily, astronomers have ways toseparate everything back out.
一个方法就是寻找隐藏在噪音中的特征信号:
And one way is to look for a special signalhidden in the noise:
21厘米谱线
the 21 centimeter line.
这一信号由宇宙中最常见的元素——氢产生
This signal is produced by the most commonelement in the Universe: hydrogen.
氢原子吸收并发出特定波长为21厘米的电磁波
Hydrogen atoms absorb and emit radiation at a specific wavelength of 21cm.
由于宇宙中到处都是氢
And because hydrogen’s pretty much everywhere,
所以21厘米谱线也应该遍布宇宙各处
the 21cm line should be too.
但事情不仅如此
But there’s more.
因为宇宙正在不断膨胀
Because the Universe is expanding,
电磁波的波长也会在运动过程中不断拉长
electromagnetic waves stretch as they travel across it.
星系距离我们的位置越远
The further away from us something is,
它的波长被拉伸的程度就越大
the more the waves stretch,
21厘米谱线也会发生这样的变化
including the 21cm line.
所以 通过检测这些微弱的信号
So by looking for that faint signal,
找出电磁波被拉伸了多大程度
and working out how much it’s been stretched,
天文学家就可以估算出他们探测的电磁波的产生时间
astronomers can start to put dates to thewaves they’re detecting.
每一个图层都来自宇宙历史中的不同时刻
Each of these layers comes from a different moment in the history of the Universe,
从上周四……到近乎时间起源之时
from last Thursday… back to almost thebeginning of time.
来自最远处发出的辐射
The radiation that has travelled the furthest,
也就是可见的最古老的那层辐射
the oldest visible layer,
是宇宙背景辐射
is the Cosmic Microwave Background.
这是宇宙大爆炸后产生的
This is the remnants of the first light
能够自由穿行宇宙的第一道光线的残留
that was able to travel freely through the universe after the Big Bang.
它们花了138亿年到达地球
It’s spent 13.8 billion years getting here
它们就像一道不透明的墙壁
and it’s like an opaque wall,
墙壁后的一切都无法看到
beyond which there’s nothing to see.
下一层是“暗物质时代”
Next came the dark ages,
氢原子散布在宇宙各处时
when hydrogen atoms spread out through space
并没有发生什么特别的事情
not really doing much.
直到宇宙中终于形成了第一批恒星
That is until the first stars formed,
随后是第一批星系
and then the first galaxies.
随着星系诞生 融合
As galaxies grew and merged,
它们开始影响周围空间中的氢原子
they started to affect the hydrogen atoms in the space around them,
使氢原子电离 并形成了这样的气泡形状
ionizing the atoms and formingbubble-like shapes
这时的21厘米谱线中出现了一道暗纹
which appear as dark gaps inthe usual 21cm glow.
天文学家们正在搭建新型望远镜
Astronomers are now building new telescopes
专门用来检测这些十亿年前的微弱电离气泡
specifically to detect these faint ionized bubbles from over a billion years ago.
他们希望找出隐藏在这些气泡中的
They hope that buried within these signals
有关宇宙最伟大奥秘的答案
could be answers to some of the Universe’sgreat mysteries,
比如暗物质的性质
like the nature of dark matter.
多亏了恒定的光速
Thanks to the finite speed of light
每当我们抬起头
every time we look up
都可以在眨眼间看到宇宙的历史
we see the history of the Universe in the blink of an eye.
而在21厘米谱线的帮助下
And with the 21cm line,
科学家可以着手探究隐藏在宇宙历史中的秘密了
scientists are starting to find the secrets hidden within.
宇宙的历史

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视频概述

从宇宙大爆炸到现在,天文学家如何分辨来自不同时间的辐射,又如何探究这些辐射中包含的信息呢?来看看他们是怎么做的吧!

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