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If there's two things I know about the universe it's that it's big and there's a lot of it.
如果关于宇宙，我有两点了解的话，那就是它广袤无垠，繁星点点。
So much in fact, that we didn't know where half of it was until recently.
事实上，直到近年，我们对宇宙中物质所在的了解尚不足半。
Now before you get your hopes up, I'm not talking about dark matter or dark energy,
现在，在你燃起希望前，（让我告诉你）我并不是在说暗物质或暗能量，
which combined make up over 95% of the universe.
这两者加起来占到宇宙空间的95%以上。
I know you're all as antsy as I am to find out what dark matter and dark energy really are, but that mystery remains unsolved.
我知道你同我一样，热切希望能够认识暗物质和暗能量，但这仍是个未解之谜。
No, I'm talking about plain old baryonic matter like you and me and everything we know.
不，我在这里谈论的是普通重子物质，正如你我，以及我们都知道的一切。
The stuff that makes up less than 5% of the universe.
这种物质在宇宙中的占比不足5%。
Turns out we couldn't even track THAT stuff down.
因此，我们根本无法对这种物质进行追踪。
That's not to say we didn't have a pretty good idea of where it was.
这并不是说我们不了解它的所在。
See the matter we could account for was where you'd expect it to be,
看看我们可以解释的物质，你会想到它在哪里，
bundled up in two trillion galaxies each with an average of hundreds of billions of stars across the observable universe.
它混迹在二万亿个星系里，在可见宇宙中，这里平均每个星系都包含有数千亿颗星星。
In between those galaxies we think are filaments of dark matter, linking them together in a mind-breakingly huge cosmic web.
在这些星系之间，我们认为是暗物质的细丝，将它们连接在一个无比巨大的宇宙网中。
We suspected the gravity of that dark matter also attracted regular matter too,
我们怀疑暗物质的引力同样也吸引着规则物质，
which had been turned into plasma after ultraviolet radiation from early stars separated atoms from their electrons.
早期恒星从它们的电子中分离出原子，在经受紫外辐射后，这些规则物质变成了等离子体。
This plasma is what's known as the WHIM, or Warm-Hot Intergalactic Medium.
这种等离子体被称作WHIM，或称“温热星系际介质”。
For a long time the problem was we couldn't see the WHIM, it was just too hard to detect.
很长一段时间以来，问题在于我们无法看到WHIM，它们实在难以察觉。
Until two separate teams found it using the Sunyaev-Zel'dovich effect.
直到两个独立的团队利用苏尼亚耶夫-泽尔多维奇效应，发现了它。
When photons pass through a plasma, they get shifted to a slightly higher energy level.
当光子穿过等离子体时，它们会跃迁到稍高能级上。
The effect is very tiny though, so the teams took data from hundreds of thousands to a million pairs of galaxies they figured would be connected by the WHIM,
但是这种效果极微，所以这两支团队，观测的星系对数从几十万到上百万不等，他们认为这些星系都与WHIM存在联系，
and stacked them up until the effect was noticeable.
并把它们叠加起来，直到效果显现。
Just like that, they found half the baryonic matter in the universe, and more evidence of a dark matter web.
就这样，他们发现了宇宙中一半的重子物质，为暗物质网搜寻到了更多证据。
So 5% down, 95% to go.
所以，已经有5%确定了，还有95%有待探索。
We're getting closer, guys!
我们越发接近真相了，伙计们！
If you liked this video subscribe so you don't miss more cool science matters.
如果你喜欢这个视频节目，就订阅吧，这样你就不会错过更多炫酷的科学问题了。
We keep coming up with new ways to look for dark matter, like with black holes and gravitational waves!
我们一直在寻找新的方法来寻找暗物质，比如通过黑洞和引力波!
By the way when we say baryonic matter, technically electrons don't count because they're leptons,
顺便说一下，当我们说到重子物质时，严格意义上讲，电子不能被算在内，因为它们是轻子，
but astronomers lump them in with protons and neutrons to make things simpler.
但为使事情简单，天文学家们将他们与质子和中子相提并论。
Thanks for watching Seeker!
感谢收看“探索者”节目！
