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It’s the kind of question that sort of breaks your brain when you even start to figure out how to think about it: what shape is the universe?
这个问题就是那种即便只是想想应该从那个角度去思考它都会让你大伤脑筋的问题，这个问题就是：宇宙到底是什么形状？
No one can be sure; until we can step outside of the universe and walk around it somehow -- we can’t actually do that ever --
除非我们站到宇宙外面沿着它的周围绕上一圈，不管怎么绕——实际上，这一点我们是做不到的——否则没人能给出肯定的答案，
the best we can do is take what we know to model the likeliest scenario.
我们能做的就是用我们已知的条件进行类似的情境模拟。
The idea of the shape of the universe comes down to the key insight from General Relativity that says mass warps space, and that objects moving through space have their paths curved.
归根结底，宇宙形状这一概念涉及的是广义相对论的核心见解：质量会使空间变形，太空中运动的物体的运动轨迹都是曲线。
Here’s a simple way to think about it: imagine there’s a bowling ball on a trampoline.
这点我们可以这么简单地理解：想象一张上面放了一个保龄球的蹦床。
That’s the sun warping space around it.
这个蹦床就是太阳周围的翘曲空间。
Now roll a marble past the bowling ball to mimic a planet in orbit.
现在我们在保龄球附近滚动一颗弹珠，用弹珠来模拟轨道上的行星。
From the marble’s perspective it's rolling in a straight line,
从弹珠的角度来看，它是沿着直线滚动的，
but we can see that its path is curved by the bowling ball depressing the trampoline.
但实际上，在挤压蹦床的保龄球的作用下，弹珠是沿着曲线滚动的。
Now imagine that the universe is a giant trampoline covered in bowling-ball stars, medicine-ball black holes, and little planet marbles.
现在想象一下，宇宙是一个巨大的蹦床，上面覆盖着保龄球一样的恒星，药丸一样的黑洞和弹珠一样的小行星。
This means that masses are warping space all over the place, and the combined force of all that mass has the capacity to shape the universe.
这就意味着各个位置的质量体都在挤压太空，而这些质量体的合力就决定了宇宙的形状。
So really, when we talk about the shape of the universe, we’re talking about the density of the universe.
所以，谈论宇宙形状时，我们谈论的其实是宇宙的密度。
The simplest shape to get your head around is the flat universe,
我们最容易理解的宇宙形状是扁平的形状，
which isn’t flat like a two dimensional piece of paper, it’s flat because it has no curvature.
这种扁平不同于二维纸张的那种扁平，宇宙之所以呈现出扁平的形状是因为它的曲率为0。
This is the shape the universe would take if it has the exact amount of mass to stop the universe expanding after an infinite time.
如果宇宙的质量足够大，能够在无数年之后让宇宙停止膨胀，宇宙就会变成这种形状。
It will have no bounds and expand forever, slowing but never stopping.
那时候的宇宙将会没有边界，还会不断膨胀，尽管膨胀速度会减慢但绝不会停止。
If the universe contains more mass -- more than critical mass so enough to stop its expansion — it will have a positive curvature.
如果宇宙包含的质量过大 - 超过足以阻止其膨胀的临界质量 - 宇宙将具有正曲率。
In this scenario the universe is closed and looks a little like a sphere.
在这种情况下，宇宙是封闭的，看起来有点像球体。
It would be finite but without a beginning or end.
虽然有限，但将没有起点，也没有终点。
Eventually, the mass will cause the universe to collapse back in on itself.
最终，宇宙的质量就会使其崩溃。
If, on the other extreme, the universe has insufficient mass to stop its expansion,
相反，如果宇宙不具有足够阻止其膨胀的质量，
it will have no bounds and expand forever in an open shape sort of like a saddle.
宇宙将会变得没有边界，并且以类似马鞍的形状一直膨胀下去。
So, which is it?
所以，到底会是哪种情况呢？
Well, current cosmological observations say the Universe should expand forever, so the positive curvature isn’t likely.
嗯，目前的宇宙观测表明宇宙应该会永远膨胀下去，所以正曲率是不太可能的。
but, it also doesn’t seem to have the right conditions for negative curvature.
然而，我们的宇宙似乎也不满足负曲率的条件。
Data from NASA’s Wilkinson Microwave Anisotropy Probe, mission of distant supernovae, show that the universe’s rate of expansion is accelerating,
探测遥远超新星的NASA威尔金森微波各向异性探测器的探测数据显示，宇宙膨胀的速度已经加快了，
but that rate is balanced by the mass of dark matter.
但暗物质的质量平衡了这一变化。
In short, the Universe is likely ever so nearly flat.
简而言之，宇宙可能永远都会非常接近扁平的状态。
But it’s possible that that’s the observable universe.
但这也可能只是可观察宇宙的形状。
Because the speed of light is a fixed value, we can only see 13.8 billion years back.
因为光速是一个固定值，我们只能看到138亿年前宇宙的形状。
It’s possible we just can’t detect a complete curvature with the instruments we have, or in ways that the laws of physics will allow.
根据当前的仪器或者物理定律，我们还是无法检测到完整的宇宙曲率也是可能的。
So while we all know the Earth isn’t flat… it looks like the universe almost is.
因此，尽管我们都知道地球不是扁平的......但貌似宇宙还真有可能是扁平的。
Thanks Domain.com for sponsering this episode of Seeker.
感谢Domain.com对本期《科学探索之旅》的大力支持。
When you buy a domain name from Domain.com,
在Domain.com购买一个域名，
you’re taking the first steps in creating an identity and vision for your brand.
就是为打造你自己的品牌创建了一个档案和一份愿景。
No domain extension will help tell your story like a .com or .net domain name.
而一个.com或者.net的域名远比其他域名更能帮你讲述你的故事。
Get 20% off Domain.com’s already affordable domain names and web hosting when you use coupon code SEEKER at checkout.
Domain.com网站的域名和虚拟主机价格都十分优惠，而且使用我们栏目的专属折扣码付款还能享折上八折优惠噢。
It’s been almost FOUR YEARS since I started here, and I’ve loved every single episode!
我已经加入这个栏目差不多四年了，我们的每一期节目我都非常喜欢！
Especially that awkward naked cold open and fun time with chimerism!
尤其是讲嵌合现象的赤果果，又尴尬又冷的那期节目！
but I’ve got some exciting new things in the works so I’m not going to be around Seeker as much.
但是，我已经接到了一些非常值得期待的新任务，所以最近可能不怎么会在咱们栏目露面了。
I’m still doing Vintage Space,
但是《复古空间》的节目我还是会继续做的，
so if you want to keep up with me and see what I’ve got going on -- and also tons of pete pics! --
所以，大家如果想了解我的动态，看看接下来我的工作 —— 还有海量的酷照的话——
be sure to follow me on YouTube as well as Twitter and Instagram.
一定要在YouTube，Twitter和Instagram上关注我噢。
And of course be sure to Subscribe for more Seeker.
当然了，还要订阅我们的《科学探索之旅》查看更多节目内容。
Thanks for watching and for four years of awesome science contact.
感谢大家的收看，以及大家四年来的大力支持。
