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Scientists have long thought that Earth got its Moon when a Mars-sized object blasted into our developing planet.
长期以来，科学家们一直认为，一个火星大小的物体撞击地球时，地球就有了月球。
But for decades, different clues have called this hypothesis into question.
但几十年来，不同的线索让这一假设遭受质疑。
And last week, a paper published in the journal Science Advances is revealing a new twist: The Moon is emitting carbon.
上周，发表在《科学进展》杂志上的一篇论文揭示了一个新的扭转：月球正在排放碳。
Carbon should have boiled off the Moon a long time ago if it formed from a single violent collision.
如果月球是由一次剧烈的碰撞形成的话，那么碳应该在很久以前就从月球上蒸发掉了。
But it’s there—and it looks like it’s been there for billions of years… which hints that our lunar origin story is not as straightforward as we thought.
但月球现在确实还有碳——而且看起来它已经存在了几十亿年……这暗示着月球起源的故事并不像我们想象的那么简单。
The idea that the Moon is a blown-off chunk of the Earth is called the giant impact hypothesis, and early evidence for it came from the Apollo missions.
月球是地球爆炸后的一块碎片，这种观点被称为“巨大撞击假说”，它的早期证据来自阿波罗计划。
Apollo astronauts brought back rocks from the Moon that looked so much like Earth rocks that scientists reasoned they had to have come from here.
阿波罗号的宇航员从月球带回了一些岩石，这些岩石看起来非常像地球上的岩石，因此科学家推断它们一定来自地球。
The Moon rocks also appeared to be missing volatiles, which are elements and compounds with low boiling points, like carbon and hydrogen.
月球岩石似乎也没有挥发物，这些挥发物是低沸点的元素和化合物，比如碳和氢。
And that seemed to check out, because the intense heat from a giant impact should have vaporized any volatiles on the surface of the newborn Moon.
这似乎验证了那一假说，因为巨大撞击产生的强烈热量应该蒸发了新生月球表面的任何挥发物。
But in the study published last week, a team of physicists and planetary scientists from Japan used data from the Kaguya satellite to take a better look at the lunar surface.
但在上周发表的研究中，一组来自日本的物理学家和行星科学家利用“月亮女神”卫星的数据更好地观察了月球表面。
They looked through a year and a half of data from the late 2000s, when the satellite was operational—and that’s where they saw evidence of charged carbon atoms escaping from the surface.
他们查看了2000年代末卫星运行时一年半的数据，发现了带电荷的碳原子从月球表面逃逸的证据。
These charged atoms are called ions, and they form on the Moon when micrometeorites, sunlight, or charged solar particles hit the surface.
这些带电原子被称为离子，当微陨石、阳光或带电的太阳粒子撞击月球表面时，它们就会形成。
Any of those can knock electrons off atoms and kick the resulting ions out into space.
它们中的任何一种都可以将电子从原子中剥离，并将产生的离子反冲到太空中。
Previous satellites weren’t sensitive enough to detect those ions, but Kaguya was—and it detected more than anyone expected.
之前的卫星不够灵敏，无法探测到这些离子，但“月亮女神”做到了——而且它探测到的离子比任何人预期的都多。
In fact, the researchers were able to map carbon concentrations across the entire Moon, and they found that the amount of carbon in the ground varied by location.
事实上，研究人员能够绘制出整个月球的碳浓度图，他们发现月球表面的碳含量因地点而异。
Older surfaces emitted less carbon than younger surfaces, implying that the Moon started out with carbon and is gradually losing it to space, leaving older regions more depleted than younger ones.
较老的表面比较年轻的表面排放的碳更少，这意味着月球一开始是含碳的，然后逐渐向太空中流失，所以较老的区域比年轻区域的碳更容易耗尽。
The idea that carbon has just… been there all along raises a big challenge for the giant impact hypothesis.
碳一直存在的观点对“巨大撞击假说”提出了巨大的挑战。
Before we have a clear picture of how the Moon formed, scientists will have to explain how volatiles like carbon survived the event that created the Moon.
在我们清楚地了解月球是如何形成的之前，科学家必须解释像碳这样的挥发性物质是如何在月球形成的过程中保存下来的。
Some sort of collision is still the leading hypothesis for the Moon’s formation, but exactly what the circumstances were like is still up for debate.
某种形式的碰撞仍然是月球形成的主要假设，但具体是什么情况仍然存在争论。
While some scientists are working to better understand our own solar system, others are thinking about how to explore worlds way beyond it.
一些科学家正在努力更好地了解我们自己的太阳系，而另一些科学家则在思考如何探索太阳系之外的世界。
Last week, a paper in the journal Acta Astronautica laid out what it would take to create a laser-powered light sail, a type of probe that could one day be our best bet at visiting far-off worlds on human timescales.
上周，《宇航学报》上的一篇论文阐述了如何制造激光驱动的光帆，这种探测器有朝一日可能成为我们按照人类的时间尺度访问遥远世界的最佳选择。
The idea behind a light sail is that light carries momentum, so you can physically push something through space just by shining a light on it.
光帆背后的想法是，光携带动量，所以你只需要在某个物体上发光，就可以真实地推动它在太空中移动。
After enough time, it could get going at a good fraction of the speed of light, meaning it could potentially reach neighboring star systems in a matter of decades—
只要时间够长，它可以以光速的一小部分速度前进，这意味着它有可能在几十年内到达邻近的恒星系统——
as opposed to the tens of thousands of years it would take a conventional probe.
而传统的探测器需要数万年的时间。
We’ve launched a few successful light sails already as proofs of concept, but those use sunlight, which just isn’t powerful enough to get a sail going at any significant speed.
作为概念的证明，我们已经成功地发射了一些光帆，但这些光帆使用的是阳光，它所携带的能量不足以让帆以任何显著的速度移动。
But the authors of this recent paper investigated what it would take to make a light sail that could reach another star.
但是最近这篇论文的作者研究了制造一个能到达另一颗恒星的光帆所需要的能量。
First of all, they calculated that it would take nearly the entire output of the Hoover Dam to power a laser that could push even a small light sail anywhere close to the speed of light.
首先，他们计算出，要想驱动哪怕只是很小的光帆以接近光速的速度飞行，几乎需要胡佛水坝的全部能量。
That’s… no laser pointer. Like, don’t get in the way of this thing.
那还是…没有激光笔的情况。比如，不要妨碍这件事。
One reason that number is so high is because researchers had to account for one important detail: special relativity.
这个数字如此之高，原因之一是研究人员必须解释一个重要的细节：狭义相对论。
Special relativity is Einstein’s theory of how space and time get distorted at high speeds, and because of this distortion,
狭义相对论是爱因斯坦关于空间和时间如何在高速下扭曲的理论，正是因为这种扭曲，
it will be harder to accelerate the sail the faster it goes.
帆航行得越快，它就越难加速。
As the sail goes faster, the laser will also have to shine at a higher frequency, because the light will appear stretched out from the ship’s perspective—
当帆的速度变快时，激光也必须以更高的频率照射，因为光线会从船的视角被拉长——
delivering less force than it would if the sail were moving much slower.
如果帆的速度变慢，所产生的力会更小。
The authors also sorted out some details about what a future light sail would look like.
作者还整理了一些关于未来光帆外观的细节。
It would need to be huge, to catch as much light as possible, but also light enough to be moved by a laser—so we’re talking just nanometers thick.
它得很大，这样才能捕捉到尽可能多的光，但也要足够轻才能被激光移动——所以我们谈论的可是纳米级的厚度。
Except, it also has to be strong… Oh, and it has to be reflective so that light bounces off, transferring as much momentum to the sail as possible.
此外，它还必须得强大。哦，它还得是能反光的，这样光线就会反射回来，把尽可能多的动量传递给帆。
So there are some hurdles to get past, which is why we’re not going to be making interstellar voyages anytime soon.
所以有一些障碍需要克服，这就是我们不能很快进行星际旅行的原因。
But just identifying those hurdles is a really important and also fascinating step.
但找到这些障碍是非常重要的一步，也是非常吸引人的一步。
And last month, a separate team of engineers published another paper in Acta Astronautica revealing a model for a super-light sail made of graphene.
上个月，另一个工程师团队在《宇航学报》上发表了另一篇论文，揭示了一个由石墨烯制成的超轻帆模型。
Now, it was only three millimeters wide, which is likely millions of times smaller than an interstellar probe would have to be, and scaling it up will come with its own problems.
现在，它的宽度只有3毫米，这可能比星际探测器的尺寸要小数百万倍，而且扩大它的尺寸会带来一些问题。
But! It demonstrated one way of making an efficient sail that could pick up momentum from light.
但是!它展示了一种制造高效帆的方法，可以从光中获取动量。
The researchers even tested it in a freefall chamber to see how it would fare in microgravity—and the sail sailed!
研究人员甚至在一个自由落体舱内进行了测试，看看它在微重力下的表现如何——结果帆起航了!
It’ll take some time and serious research before these things get past the proof-of-concept stage.
在这些东西通过概念验证阶段之前，需要一些时间和认真的研究。
But we’re shooting for the stars here, literally, and these are some of the first few steps toward getting us there.
但我们的目标可是恒星，以上所述只是我们到达恒星的一些最初的步骤。
Thanks for watching this episode of SciShow Space News!
感谢收看本期太空科学秀!
And if you want to learn more about how we might one day use sunlight to propel spaceships, we have an episode just for that!
如果你想了解更多关于我们将来如何利用阳光推动宇宙飞船的知识，我们有专门的的剧集哦。
