評(píng)論
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Here are some images of clusters of galaxies.
這是一些星團(tuán)的照片。
They're exactly what they sound like.
正如聽上去一樣。
They are these huge collections of galaxies,
它們是一堆星系，
bound together by their mutual gravity.
由于互相的引力而吸引在一起。
So most of the points that you see on the screen are not individual stars,
你在屏幕上看到的大部分點(diǎn)，不是單獨(dú)的恒星，
but collections of stars, or galaxies.
而是一系列恒星，或者稱為星系。
Now, by showing you some of these images,
現(xiàn)在通過展示這些圖片，
I hope that you will quickly see that galaxy clusters are these beautiful objects,
希望你已經(jīng)看到星團(tuán)是很美麗的東西，
but more than that,
都不止于此，
I think galaxy clusters are mysterious,
我認(rèn)為星團(tuán)是神秘的，
they are surprising,
它們讓人驚奇，
and they're useful.
而且它們很有用。
Useful as the universe's most massive laboratories.
作為宇宙里最大的實(shí)驗(yàn)室，它們很有用。
And as laboratories, to describe galaxy clusters is to describe the experiments that you can do with them.
就像描述實(shí)驗(yàn)室一樣，要描述星團(tuán)，就要去描述你能夠通過它們做的實(shí)驗(yàn)。
And I think there are four major types,
我認(rèn)為那包括四種主要類型，
and the first type that I want to describe is probing the very big.
我想描述的第一類是去探測(cè)“極大”。
So, how big?
那么，是多大？
Well, here is an image of a particular galaxy cluster.
這里是某個(gè)星團(tuán)的一張照片。
It is so massive that the light passing through it is being bent, it's being distorted by the extreme gravity of this cluster.
它的質(zhì)量非常大，以至于光在經(jīng)過的時(shí)候，由于其引力的作用而變彎了。
And, in fact, if you look very carefully you'll be able to see rings around this cluster.
事實(shí)上，如果你仔細(xì)看，能夠看到這個(gè)星團(tuán)周圍的光環(huán)。
Now, to give you a number,
具體到數(shù)字，
this particular galaxy cluster has a mass of over one million billion suns.
這個(gè)星團(tuán)的質(zhì)量有超過10的15次方個(gè)太陽(yáng)那么大。
It's just mind-boggling how massive these systems can get.
這些系統(tǒng)質(zhì)量之巨大簡(jiǎn)直讓人瞠目結(jié)舌。
But more than their mass,
但除了巨大的質(zhì)量之外，
they have this additional feature.
他們還有其他特殊之處。
They are essentially isolated systems,
它們基本上可以算是孤立的系統(tǒng)，
so if we like, we can think of them as a scaled-down version of the entire universe.
如果愿意的話，我們可以將它們想象為整個(gè)宇宙的縮小版本。
