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Dark matter has been the go-to explanation for many scientists as to why there seems to be more gravitational influence in our universe than the gravity measured by visible matter.
许多科学家一直用暗物质解释，为什么我们宇宙中的引力影响，比可见物质测量的引力更强。
But what if there's no dark matter at all?
但是如果暗物质根本不存在呢？
The idea of dark matter was first proposed by Henri Poincaré in 1906.
暗物质的想法最初由亨利·庞加莱于1906年提出。
Then in 1933, evidence of dark matter was found by Fritz Zwicky while studying galaxy clusters.
随后在1933年，弗里茨·兹威基在研究星系团时发现了暗物质存在的证据。
And then more evidence of dark matter was found based on the calculations of rotational velocities in galaxies made by Vera Rubin in 1978.
然后薇拉·鲁宾在1978年计算出了银河的旋转速度，更多暗物质存在的证据得以发现。
Our universe is made up of less than 5% of visible matter---like stars, planets, galaxies you, me, everything we can see.
我们宇宙中的可见物不到5％ —— 就像星星，行星，星系，你，我，我们能看到的一切。
Everything else, is stuff we can't see which we call dark matter.
其他的一切，都是我们无法看到的，我们称之为暗物质。
And scientists think 95% of the matter in our universe is dark matter.
科学家们认为我们宇宙中95％的物质是暗物质。
Right now, Dark Matter is used to explain a few pesky things in astrophysics.
现在，人们用暗物质来解释天体物理学中一些讨厌的东西。
Why hot galaxy clusters don't blow themselves apart.
为什么热星系团不会自己炸开。
Why stars don't get flung out into space because of galaxy rotation.
为什么恒星不会因为星系旋转而被扔进太空。
And also, the temperature fluctuations of the CMB -- or cosmic microwave background radiation.
以及CMB或宇宙微波背景辐射的温度波动。
That said, there are theories that are trying to explain all this without assuming it's dark matter.
也就是说，有一些理论试图在不假设暗物质存在的情况下解释这一切。
These are: scale invariance and emergent gravity.
它们是：尺度不变性和新兴引力。
The empty space scale invariance theory says that properties of empty space should not change based on scale.
空间尺度不变性理论认为，空间的性质不应基于尺度而变化。
An astrophysicist looked back at the early equations of Einstein, and Newtonian Dynamics, and modified an acceleration term in Newton's law.
一位天体物理学家回顾了爱因斯坦早期计算出的方程以及牛顿动力学，改进了牛顿定律中的一个加速项。
With this change, the law could explain a new force.
伴随这种变化，牛律定律可以解释一种新的力。
This force can explain things that were explained by dark matter, such as holding a galaxy together that's spinning at high rotational velocities.
这种力可以解释暗物质所解释的东西，比如星系在高速旋转时仍能汇聚不散。
The only problem is, on Earth, this force can be up to billion times smaller than the force of gravity--making it difficult to measure.
唯一的问题是，在地球上，这个力比重力小几十亿倍，因此难以测量。
It doesn't explain gravitational lensing -- which is the bending of light-- or the temperature fluctuations of the CMB.
它不能解释引力透镜效应——就是光的弯曲或CMB温度波动。
The craziest, but to me the most interesting, is the holographic principle, which says that our entire universe can be described on an imaginary sphere that surrounds ordinary matter.
最疯狂的，但对我来说，也是最有趣的，那就是全息原理，即我们可以把全宇宙放在一个想象的球体中进行描述，普通物质环绕在球体周围。
It lead to the theory of emergent gravity.
这就引出了感应引力。
That is the idea that gravity arises (or emerges) through the presence of matter.
就是重力通过物质存在而增加（或出现）的想法。
This suggests this happens the same way temperature arises from the movement microscopic particles of matter.
这表明这与物质粒子微观运动产生热量的原理相同。
So, if gravity is formed this way then it can be used to explain gravitational phenomena again!
所以，如果重力是这样形成的，那么它就又可以被用来解释重力现象了！
Because something is keeping galaxies gravitationally bound.
因为某些东西正在保持星系的引力束缚。
It's possible that the force created in the emergent gravity theory does this!
可能的是，新兴引力理论中产生的力帮助做到了这点！
But it still doesn't explain the CMB temperatures...
但它仍然不能解释CMB的温度...
Scientists are still developing theories, like these, so they can explain things like the reason our universe hasn't blown apart because of invisible matter.
科学家仍在研究这类理论，从而解释像宇宙不会因为暗物质被吹散等问题。
And they think it might be because of a gravitational field that developed through the movement of visible matter in our universe.
他们认为原因可能是宇宙中可见物质运动产生了引力场。
It's all very complicated, and yet, epic.
这一切都很复杂，但也很壮丽。
At the moment, arguments for dark matter still stand tall above many of these other theories, but hey, maybe not forever.
目前，对于暗物质的争论仍然多于许多其他理论，但嘿，也许不是永远。
Plus, check out Trace's video about a new form of matter excitonium!
另外，您可以去特雷斯视频观看新物质——激子元素。
And one last fun fact: the holographic principle says we've always looked at life as 3 dimensions, but if we looked at it as 2 dimensions then MAYBE the universe is just a holographic projection of ourselves.
最后一个有趣的事实：全息原理说，我们一直把生命看作三个维度，但是如果我们把它看成两个维度，那么宇宙也许只是我们自己的全息投影。
Thanks for watching!
谢谢收看！
