What is at the center of the universe?
宇宙的中心是什么？
It's an essential question that humans have been wondering about for centuries.
这是一个很重要的问题，几百年来，人们为此上下而求索。
But the journey toward an answer has been a strange one.
追寻答案的过程却是段奇异的旅程。
If you wanted to know the answer to this question in third century B.C.E. Greece,
如果你想知道公元三世纪希腊人给出的这个问题的答案，
you might look up at the night sky and trust what you see.
你可能就直接仰望夜空，然后相信所见即是。
That's what Aristotle, THE guy to ask back then, did.
这就是亚里士多德当时所做的。
He thought that since we're on Earth, looking up, it must be the center, right?
他认为既然我们在地球上，向天上看，那么地球就一定是宇宙的中心，不是吗？
For him, the sphere of the world was made up of four elements: Earth, water, air, and fire.
对他而言，这个球体世界的一切由四大元素所构成：土，水，空气和火。
These elements shifted around a nested set of solid crystalline spheres.
这些元素在一个包裹着固体晶状球核的套层中移动。
Each of the wandering stars, the planets, had their own crystal sphere.
每个浮于夜空的恒星和行星都有它们自己的晶状球核。
The rest of the universe and all of its stars were on the last crystal sphere.
宇宙剩下的部分和所有的星星构成了最后的晶状球核。
If you watch the sky change over time, you could see that this idea worked fine at explaining the motion you saw.
如果你观察天空随时间的变化，你可以发现这个理论能很好的用来解释你所看到的变化。
For centuries, this was central to how Europe and the Islamic world saw the universe.
几个世纪以来，这就是欧洲和伊斯兰世界的宇宙观的中心。
But in 1543, a guy named Copernicus proposed a different model.
但是在1543年，一个叫做哥白尼的人提出了一个不同的模型。
He believed that the sun was at the center of the universe.
他认为太阳才是宇宙的中心。
This radically new idea was hard for a lot of people to accept.
这个十分激进的新思想让大多数人难以接受。
After all, Aristotle's ideas made sense with what they could see, and they were pretty flattering to humans.
毕竟，毕竟亚里士多德的观点才符合他们看到的天体，并且这些观点也更加符合对人类本身的奉承。
But a series of subsequent discoveries made the sun-centric model hard to ignore.
但是一系列奇怪的发现让日心说无法被忽视。
First, Johannes Kepler pointed out that orbits aren't perfect circles or spheres.
首先，约翰尼斯·开普敦指出行星运动的轨道并不是完美的圆弧或者球型。
Then, Galileo's telescope caught Jupiter's moons orbiting around Jupiter, totally ignoring Earth.
之后，伽利略的望远镜发现木星也有围绕自己的月亮（卫星），完全与地球无关。
And then, Newton proposed the theory of universal gravitation, demonstrating that all objects are pulling on each other.
接着，牛顿提出了万有引力定律，说明了所有的物体都互相吸引。
Eventually, we had to let go of the idea that we were at the center of the universe.
最终，我们不得不放弃地球是宇宙中心的想法。

Shortly after Copernicus, in the 1580s, an Italian friar, Giordano Bruno,
哥白尼死后不久，在1580年，意大利修道士乔尔丹诺·布鲁诺
suggested the stars were suns that likely had their own planets and that the universe was infinite.
提出太阳这样的恒星都有自己的卫星，还有宇宙是无限的。
This idea didn't go over well. Bruno was burned at the stake for his radical suggestion.
这个理论推广得并不好。布鲁诺因为他激进的言论被烧死在刑柱上。
Centuries later, the philosopher Rene Descartes proposed that the universe was a series of whirlpools,
几个世纪之后，哲学家勒内·笛卡尔提出宇宙是一系列漩涡，
which he called vortices, and that each star was at the center of a whirlpool.
他称之为涡流，每个恒星都在一个漩涡的中心。
In time, we realized there were far more stars than Aristotle ever dreamed.
随着时间发展，我们发现星星的数量远多于亚里士多德所能想到的。
As astronomers like William Herschel got more and more advanced telescopes,
随着像威廉·赫歇尔这样的天文学家发明出更加先进的望远镜，
it became clear that our sun is actually one of many stars inside the Milky Way.
我们的太阳不过是银河里众多恒星之一，变得更清晰了。
And those smudges we see in the night sky?
而那些我们在夜空中看到的印迹呢？
They're other galaxies, just as vast as our Milky Way home.
他们是其他的星系，就和我们所在的银河一样广阔。
Maybe we're farther from the center than we ever realized.
也许我们和宇宙中心的距离比我们所知的要更遥远。
In the 1920s, astronomers studying the nebuli wanted to figure out how they were moving.
在20世纪20年代，天文学家研究星云，想弄明白它们的运动规律。
Based on the Doppler Effect, they expected to see blue shift for objects moving toward us, and red shift for ones moving away.
根据多普勒效应，天文学家猜想会在朝我们移动的星云中观察到蓝移现象，而远离的则会出现红移现象。
But all they saw was a red shift. Everything was moving away from us, fast.
但他们所有观测到的现象都是红移。所有星星都在以飞快的速度远离我们而去。
This observation is one of the pieces of evidence for what we now call the Big Bang Theory.
这些观测构成了现在被我们称之为大爆炸理论的证据之一。
According to this theory, all matter in the universe was once a singular, infinitely dense particle.
根据这个理论，宇宙中的所有物质最初都来源于一个单一的、密度极高的粒子。
In a sense, our piece of the universe was once at the center.
某种意义上可以说，我们所处的这部分宇宙曾经位于中心。
But this theory eliminates the whole idea of a center since there can't be a center to an infinite universe.
不过这个理论完全摧毁了中心论，因为无穷大的宇宙是不会有中心点的。
The Big Bang wasn't just an explosion in space; it was an explosion of space.
大爆炸并不只是空间当中的一次爆炸，而是一次空间本身的爆炸。
What each new discovery proves is that while our observations are limited,
每个新发现都证明，即使我们的观测的方式有限，
our ability to speculate and dream of what's out there isn't.
但我们探索和幻想更外面层的宇宙空间的能力是无限的。
What we think we know today can change tomorrow.
我们今天所认可的事实有可能明天就被改变。
As with many of the thinkers we just met,
就如我们刚谈到的那些思想家，
sometimes our wildest guesses lead to wonderful and humbling answers and propel us toward even more perplexing questions.
有些时候，人类最狂野的想象可以引领我们找到奇妙又震撼人心的答案，并促使我们向更加复杂的问题前进。