(单词翻译:单击)
Scientists are always keeping an eye out for extraterrestrial life
科学家们一直在密切关注外星生命，
and finding friendly, intelligent life on another world? Kind of a dream.
寻找另一个世界的友好智慧生命？这有点儿梦幻。
But if we ever want a long-distance relationship with aliens, finding them is only half the battle.
但如果我们想要与外星人建立远距离关系的话，找到他们只成功了一半。
They also have to find us.
他们也要发现我们。
And according to a paper published online last month in the Monthly Notices of the Royal Astronomical Society,
上个月刊登在《皇家天文学会月报》上的一篇论文
that might not be so easy.
表明这可能并不容易。
The researchers based their calculations on what someone on another planet would see
研究人员进行推算的依据是，
if they tried to detect planets in our solar system using the main technique we use to detect planets in other star systems.
如果其他星球上的人用我们探测其他星系中的行星的主要技术，来探测我们太阳系中的行星，那他们会发现什么。
We've found more than three and a half thousand exoplanets since the first discoveries back in the late 80s and early 90s.
自80年代末90年代初以来，我们已经发现了三千五百多颗系外行星。
Scientists have a few different ways of detecting them, but by far the most successful is the transit method:
科学家有几种不同的探测方法，但目前最成功的是凌日变光观测法。
They watch to see if a star seems to get dimmer periodically,
他们观察恒星是否周期性变暗，
which can mean that there's something regularly passing in front of it. Like a planet.
这意味着有东西定期从它前面经过。比如行星。
It's such a simple technique that we've used transits to find three-quarters of the exoplanets we've discovered so far,
这技术很简单，我们用它找到的系外行星占已发现行星的四分之三，
but it has its limits, mainly, we can only use transits to find planets that pass between us and their stars.
但凌日法也有局限性，主要是我们只能利用它发现在地球和其主恒星之间经过的行星。
There are lots of exoplanets out there that we just can't detect using this method,
有很多系外行星用这种方法探测不到。
because their orbits don't line up right.
因为它们的轨道没有对齐。
That limitation would also apply for any aliens using the transit method to look for planets outside of their star systems.
这种局限性也适用于任何利用凌日法寻找系外行星的外星人。
They'd only be able to see us if they were in just the right place to spot Earth passing in front of the sun as we orbit.
只有他们处在合适的位置，能够看到地球在运转时从太阳前经过，才能看到我们。
So, the paper's authors used the size and locations of our solar system's planets
因此，论文的作者使用了我们太阳系行星的大小和位置，
to calculate where you'd be able to see them transit the sun, and what they found wasn't too encouraging:
来计算在哪里能看到他们经过太阳，但结果很不乐观：
From any random point in space, intelligent life would only have about a 2.5% chance
从太空的任意点，智慧生命只有2.5%的可能性
of being able to see any of the planets in our solar system transit the sun.
能够发现太阳系中任何经过太阳的行星。
And there's only about a 0.5% chance they'd be able to see the Earth, specifically.
特别地是，他们只有0.5%的可能性能够看到地球。
They'd have around a 0.2% chance of being able to see two planets, and a 0.02% of seeing three.
他们大约只有0.2%的可能性看到两颗行星，0.02%的可能性看到三颗行星。
Which aren't great odds.
几率不大。
But the authors didn't just do their calculations and end their paper with a "Forever Alone" meme.
但是作者们并没有仅做了计算就用一个“永远孤独”的模因来结束他们的论文。
They went through all of the known exoplanets and found about 65 in the right place to see one of the planets in our solar system,
他们审查了所有已知的系外行星，发现大约有65颗在能够看到太阳系行星的合适地点，
including 9 that could see Earth.
其中有9颗能够看到地球。
And based on what we know about how often different kinds of exoplanets form,
根据对不同种类的系外行星形成频率的了解，
they calculated that there might be around ten nearby, Earth-like planets that we can't see because they're at the wrong angle,
他们计算出了附近大约有10颗类地行星，但因为它们位置不合适，我们看不到。
but where you could see Earth transit the sun just fine.
但在那里你刚好可以看到地球经过太阳。
Of course, we don't actually know if there's extraterrestrial life out there,
当然。我们还不能确切地知道是否有地外生命，
let alone intelligent life that knows how to use the transit method to detect planets around other stars.
更别提知道如何利用凌日法探测其他恒星周围行星的智慧生命了。
But if there is another civilization out there wondering if it's alone in the universe,
但如果存在另一种文明，它想知道自己是否在宇宙中孤独的话，
at least now we know a little more about whether they'd be able to see us.
现在我们至少知道他们是否能看到我们了。
Meanwhile, we're also learning more about how galaxies work.
与此同时，我们对星系运行有了更多的了解。
There's still a lot that astronomers don't quite understand about how galaxies form,
天文学家们对星系如何形成还有很多不理解的地方，
and one mystery is how they get their magnetic fields.
一个谜题是它们如何获得磁场的。
In a paper published this week in Nature Astronomy,
本周在《自然天文学》上发表的一篇论文中，
researchers reported the best-ever measurements of a distant galaxy's magnetic field,
研究人员报告了对遥远星系磁场的最好测量，
which are helping chip away at some of those unanswered questions.
这有助于我们解决一些悬而未决的问题。
Magnetic fields are really important for helping galaxies keep in order:
磁场对帮助星系保持秩序非常重要，
they help gravity maintain the galaxy's overall structure,
它们能帮引力维持星系的整体结构，
and they help gas clouds collapse to form stars.
也能帮气云坍缩形成恒星。
It's pretty hard to study magnetic fields from a distance, though,
不过，远距离研究磁场很难，
because they tend to be pretty weak, and we can't see them directly like we can see light.
因为它们相当微弱，我们不能像看光一样直接看到它们。
The problem is, distant galaxies are exactly the ones we need to study to figure out how today's magnetic fields came to be.
但问题是，遥远的星系正是我们需要研究的，以此来弄清楚如今的磁场是如何形成的。
They're so far away that their light has taken billions of years to get to Earth,
它们非常遥远，发出的光要经过数十亿年才能到达地球，
so they're like a window into the early universe.
所以它们就像进入早期宇宙的窗户。
Astronomers usually measure a galaxy's magnetic field by studying how it affects the light passing through it.
天文学家们经常通过研究星系磁场对经过它的光的影响来衡量它。
The technique works great for mapping nearby galaxies,
这一技术对于绘制附近的星系非常有效，
and even some distant galaxies with super-strong magnetic fields.
甚至对有超强磁场的遥远星系也有效。
But it doesn't work as well for distant galaxies with plain-old average magnetic fields,
但对有普通磁场的遥远星系来说就没效果了
and without knowing more about average galaxies, we can't really understand how most galaxies evolved.
如果对普通星系了解不多，我们就无法真正了解大多数星系是如何进化的。
So the authors of this new study decided to see how light from a really bright, distant galaxy, about 7.9 billion light-years away,
所以这项新研究的作者决定观察，来自大约79亿光年之外的遥远星系的明亮光
was affected by the magnetic field in a slightly closer, more average galaxy, around 4.6 billion light-years away.
是如何被46亿光年远的普通星系的磁场影响的。
All that bright light made smaller effects from the closer galaxy's magnetic field a lot easier to see,
那种明亮光让较近星系磁场的较小影响变得更容易看见
and because of the way these two galaxies were lined up with Earth,
正是因为这两个星系与地球在同一直线上，
the team was able to measure the magnetic field in the closer galaxy really precisely.
研究人员才得以极为精确地测量较近星系中的磁场。
That gave them the best picture yet of what galaxies' magnetic fields looked like in the early universe.
这向他们完美展示了早期宇宙的星系是什么样的。
For one thing, this galaxy's magnetic field was about as strong as the fields in today's galaxies,
一方面，这个磁场和如今的星系磁场一样强，
which tells us that galactic magnetic fields probably haven't changed too much over the last few billion years.
这表明银河磁场在过去的几十亿年里没有太大变化。
They also found the most distant evidence
他们发现的最遥远证据
yet for one of our best explanations of why galaxies have magnetic fields in the first place,
也给了我们星系一开始就有磁场的最好解释，
a dynamo, swirling gas and intense cosmic rays that sustain the galaxy's magnetic field by enhancing the smaller fields from things like stars.
一种发电机一样的旋涡气体和强烈的宇宙射线，通过增强较小的恒星磁场来维持星系磁场。
So, thanks to a couple of galaxies billions of light-years away,
所以，多亏了几十亿光年之外的星系，
we now know a little bit more about how the universe around us came to be.
使得我们对周围宇宙的形成有了更多的了解。
Thanks for watching this episode of SciShow Space News,
感谢您收看本期的太空科学秀，
and thank you especially to all of our patrons on Patreon who help make this show possible.
同时感谢Patreon对本节目的大力赞助。
If you want to help us keep making episodes like this, you can go to patreon.com/scishow.
如果你想我们继续做此节目，可以登陆patreon.com/scishow。
And if you just want to help us out by watching and sharing, that is also great.
如果你想通过观看和分享来支持我们也不错，
We are at youtube.com/scishowspace!
那就登录youtube.com/scishowspace来找我们吧！
