(单词翻译:单击)
The moon is our planet's constant, dependable companion.
月亮一直是地球的可靠伴侣。
Whether it's waxing, waning, or shining in its full glory, it always presents the same face to Earth: a mottled, monochrome landscape of black and white rocks.
无论月圆月缺，无论是亮是暗，月亮总是用同一面对着地球，那一面是黑白岩石组成的斑驳风景。
Depending on where you are in the world, you might see different things in that great inkblot in the sky.
世界上不同地方的人可以在天空中墨水一样的斑点中看到不一样的东西。
Some see the smiling face of the ‘Man in the Moon'.
有些人能看到“月亮上的人”的笑颜。
Others might see a rabbit stirring a pot of medicine.
有些人能看到玉兔在搅拌一壶药。
But whatever you make of it, that pattern is always the same.
但无论看到的是什么，模式总是一成不变的。
That's because the moon is tidally locked to the Earth:
这是因为月亮在潮汐作用下与地球锁定在了一起。
gravitational forces between the two have slowed the moon's spin, so it takes exactly the same amount of time to complete a full rotation as it does to orbit the Earth.
所谓潮汐作用就是月球和地球之间的引力作用减慢了月球的转速，所以月球自转的时间和围绕地球公转的时间差不多相等。
That's given us plenty of time to examine this side facing us, but nobody knew what was on the far side until relatively recently.
这就让我们有充足的时间来了解朝向地球的这一面，但大家都知道月球的另一面是怎样的。不过，最近我们有了突破。
Turns out it's very different from the side we normally see.
我们发现：月球的另一面跟我们通常看到的这一面是非常不同的。
And astronomers are still working to pin down how that happened.
天文学家依然在研究另一面经历过什么。
The mysterious, unseen side of the moon is sometimes called the dark side, thanks, Pink Floyd, but it isn't always dark.
月球的另一面因为不为人所看到，所以颇具神秘色彩。有时候，我们称之为月之暗面（这里要感谢平克•弗洛伊德乐队）。不过，这一面并不总是暗的。
During a new moon, and when all we can see from Earth are those toenail crescent slivers, the sun is positioned behind the moon, lighting up the far side and leaving the side facing us dark instead.
新月形成期间，地球上的人看到的只有月牙，因为太阳在月亮的后面，照亮着另一面。而朝向地球的这一面就成了暗面。
But it is dark from a knowledge point of view.
但据我们所知，那一面也是暗的。
Because of that rigid tidal locking, we'll never be able to see the far side from the surface of the Earth.
由于潮汐锁定的作用，地球上的我们永远也看不到月亮的另一面。
To do that, you have to physically fling something around the back of it.
要看到另一面，就要在另一面附近转悠。
Fortunately, 60 years ago, flinging things around the moon was an integral part of the space race.
所幸，60年前，在月球附近转悠已经成为太空竞赛的有机组成部分。
Although the US was the first to put an actual person on the moon, it was the Russians who led the space race at the beginning, and in 1959, their Luna 3 spacecraft became the first to visit and take pictures of the far side.
虽然每个是第一个实现载人登月的国家，但俄罗斯人才是在太空竞赛中领先的国家。1959年，月球3号成为第一个到访并拍摄月球另一面的航天器。
But you couldn't just snap a digital photo back then.
但那时候还不能即刻拍摄数码照片。
When Luna's cameras detected the sunlit far side of the moon, they took photos using actual physical film.
月球3号的摄像头探测到月球受太阳照射的另一面后，就用拍摄影片的方式拍摄了照片。
The negatives were then developed within the spacecraft and passed to a scanner, which shone a light through the image in 1000 horizontal lines and transmitted it back to Earth as an analog signal, like a fax.
航天器内部处理了底片，然后传送给扫描仪。接着，扫描仪通过1000条水平线来照射这张图片，并将其以模拟信号的形式发送回地球，就像发传真一样。
The image was blurry and low-res, which isn't too surprising if you remember what faxes used to be like.
图像不是很清晰，分辨率很低，这也在大家的意料之中，毕竟以前的传真，清晰度也不过如此。
But it was our first glimpse of a totally unknown lunar surface, and it was immediately obvious that the far side was completely different from the side we're used to seeing.
但这是人类第一次窥见月球完全不为人所知的另一面。而且显然另一面跟我们以前经常看到的这一面完全不同。
Where the near side is covered in dark patches, the far side was much brighter, with just two small black spots.
离我们近的这一面充满黑色的斑点，而另一面亮度更高，只有2个黑斑。
Since then, many more spacecraft have flung themselves around the moon to get a better look at its "dark side,"
从那以后，就有更多的航天器在月球附近转悠，从而更好地观测这一面，
and collected all kinds of data, from high resolution images to altitude and density readings.
同时收集各种数据，从高清图像到海拔和密度读数，不一而足。
And with all that data, scientists can now clearly see the differences between the near and far sides in incredible detail.
有了这些数据，科学家现在就能清晰地看到这两面之间的诸多区别，而且可以看得很仔细。
As that blurry Luna 3 image suggested, while the near side is covered with vast plains of dark lava, the far side has very few.
月球3号发回的模糊图像显示，近地面上覆盖着黑色岩浆组成的广袤平原，但另一面上几乎没有。
Instead, it's a rugged cratered highland landscape of a type of light-colored rock that's rich in calcium.
相反，另一面上都是崎岖不平的高地，富含高钙的浅色岩石。
Elevation maps also reveal something that's not easy to see from the pictures: one of the largest craters in the solar system.
高度图显示了一些从图像上不容易看出的东西——这一面有太阳系里最大的火山口之一。
The South Pole-Aitken crater covers a huge area of the southern hemisphere on the far side, around 2500 kilometers in diameter and 13 kilometers deep.
南极–艾特肯火山口覆盖着这一面南半球的大片区域，直径近2500公里，深度达13公里。
And even more surprisingly, measurements of the density of rocks beneath the lunar surface showed that the moon's crust is up to 35 kilometers thicker on the far side, compared to the side that faces us.
更让人吃惊的是：人们对这一面地下岩石的密度进行测量后发现：月球近地面的地壳厚度比另一面多35公里。
That was surprising, to say the least.
这一点让人非常意外。
With the Earth and other rotating planets as examples, we had reason to think that you'd get the same kinds of features on all sides of a planetary body.
看到地球等环绕恒星运行的行星，我们就有理由认为所有行星的所有面都有一样的特征。
But it turns out that's not always a thing!
但结果却并非如此。
Today, with detailed images of planets and moons all over the solar system, we know that the idea of a two-faced world isn't unique.
如今，我们了解了太阳系里许多行星和卫星的精确图像后，就知道两面不同的星体并不是唯一的。
Mars has radically different northern and southern hemispheres, Pluto is adorned with a huge, heart-shaped birthmark over one side, and Iapetus, a moon of Saturn, is truly two-toned, with dark-colored dust smeared over one hemisphere of its icy white surface.
火星的南北半球迥然不同，冥王星的一面有巨大的心形胎记，土卫八的两个半球也是完全不同——其中一个半球雪白的冰层上覆盖着黑色的灰尘。
And yet, the reasons for the differences between the near and far sides of the moon remain something of a mystery.
至于月球的近地面和远地面为何会不同，我们暂不可知。
It's hard to reconstruct a 4.5 billion year history, even of our closest neighbor.
很难重塑一个有着45亿年历史的行星经历了什么，即便月球离我们最近。
But like most mysteries, scientists have some ideas!
但与大多数谜题相似，科学家总会有自己的猜想！
The difference in the number of lava plains, for instance, is probably tied to that uneven crust.
比如，熔岩平原数量不同很可能是因为地壳凹凸不平。
Some researchers think that in the early days of the solar system, while the Earth and Moon were still forming, a massive asteroid struck the thick crust on the far side, creating that gigantic South Pole-Aitken crater.
一些科学家认为，太阳系形成初期，在地球和月球还没有形成的时候，一颗质量巨大的小行星撞击了月球远地面厚重的地壳，从而产生了南极–艾特肯火山口。
Later impacts all over the moon left craters on the far side, but were able to pierce the thinner crust on the near side, unleashing a flood of lava that filled the craters they left behind.
后续月球远地面发生的一些冲击留下了其他火山口，但可以刺穿近地面稍薄一些的地壳，并释放出许多岩浆，填满了这些火山口。
The lava cooled, and the Earth-facing side of the moon was left with a permanent scar, its mottled face.
岩浆冷却后，近地面就留下了永远的伤疤，外表斑驳。
But that doesn't explain why the crust was thicker on one side in the first place, or why the South Pole impact didn't send the moon shooting off into space.
但这个猜想并不能解释地壳为何一开始就厚度不同的原因，也不能解释南极受到的影响为何没有将月球推到更远的地方。
With government agencies and private companies starting to set their sights on the moon again, hopefully we'll get more data that will help us figure that out.
现在，各政府机构和私营企业开始重新关注月球，希望我们能获得更多数据，解开这一迷题。
Luna 3's photos of the far side of the moon were probably the first major lunar revelation of the space age.
月球3号对月球远地面的拍摄很有可能是太空历史上第一次揭开月球面纱的重要里程碑。
But nearly 60 years later, we still have a blot more secrets to uncover.
但近60年后的今天，我们依然有很多谜题有待解开。
Thanks for watching this episode of SciShow Space!
感谢收看本期的《太空科学秀》！
And thanks especially to our community on patreon: your support is what allows us to keep diving into the amazingly weird history of space exploration and the most mind-boggling aspects of the universe.
尤其要感谢我们的忠实粉丝：你们的支持让我们可以持续探索光怪陆离的宇宙探索历史，揭开宇宙里让人伤脑筋的谜题。
If you're not yet a patron and want to learn more, you can check out patreon.com/scishow.
如果您还不是我们的粉丝并想了解更多的话，可以访问patreon.com/scishow。
