We're at a tipping point in human history, a species poised between gaining the stars and losing the planet we call home.
我们身处人类历史的转折点上，人类处在想获得其他星球，同时也在失去地球家园的尴尬境地。
Even in just the past few years, we've greatly expanded our knowledge of how Earth fits within the context of our universe.
即使是在过去短短几年的时间里，我们对地球是如何在宇宙中存在的认识已经有了大幅度的提升。
NASA's Kepler mission has discovered thousands of potential planets around other stars,
美国国家航空航天局的开普勒任务已经发现了围绕着其他恒星的数千颗潜在的行星，
indicating that Earth is but one of billions of planets in our galaxy.
这也表明了地球只是银河系中数十亿行星中的一颗。
Kepler is a space telescope that measures the subtle dimming of stars as planets pass in front of them,
开普勒是个太空望远镜，它可以发现行星在经过恒星前方发生“凌日现象”，
blocking just a little bit of that light from reaching us.
挡住到达我们这里的光时，光线发生的细微变化。
Kepler's data reveals planets' sizes as well as their distance from their parent star.
开普勒望远镜的数据揭示了行星的大小，以及它们与其母恒星之间的距离。
Together, this helps us understand whether these planets are small and rocky,
把这些综合起来，就可以帮助我们理解这些行星
like the terrestrial planets in our own Solar System, and also how much light they receive from their parent sun.
是否像太阳系中那些类地行星一样，体积小，而且岩石密布，以及我们从它们的母恒星那里得到了多少光。
In turn, this provides clues as to whether these planets that we discover might be habitable or not.
同时，这也能为我们判断已找到的那些行星是否适宜居住提供了一些线索。
Unfortunately, at the same time as we're discovering this treasure trove of potentially habitable worlds,
但不幸的是，在我们极力去探索潜在的宜居星球、这些“无主宝藏”的同时，
our own planet is sagging under the weight of humanity. 2014 was the hottest year on record.
我们自己的星球却正遭受着人类的破坏。2014年是有记录以来最热的一年。
Glaciers and sea ice that have been with us for millennia are now disappearing in a matter of decades.
冰川和海上的浮冰跟我们一起相处了几千年，但在过去几十年的时间里却正在逐渐消失。
These planetary-scale environmental changes that we have set in motion are rapidly outpacing our ability to alter their course.
这些我们所造成的全球性环境变化的速度，远远超过了我们拯救环境的速度。
But I'm not a climate scientist, I'm an astronomer.
但我不是气候学家，我是个天文学家。
I study planetary habitability as influenced by stars with the hopes of finding the places in the universe where we might discover life beyond our own planet.
我研究在恒星影响下行星的宜居性，希望可以在宇宙中找到除地球以外有生命存在的地方。
You could say that I look for choice alien real estate.
也可以说我是在寻找外星的房地产。
Now, as somebody who is deeply embedded in the search for life in the universe,
现在，作为一个刻苦钻研、想要找寻宇宙中的生命体的人，
I can tell you that the more you look for planets like Earth, the more you appreciate our own planet itself.
我可以告诉大家，你越想找到像地球一样的行星，你就会越珍惜我们自己的星球。
Each one of these new worlds invites a comparison between the newly discovered planet and the planets we know best: those of our own Solar System.
我们每发现一处“新大陆”，就会对这些新发现的星球和那些太阳系中我们最熟悉的行星做一个比较。

Consider our neighbor, Mars.
想想我们的邻居，火星。
Mars is small and rocky, and though it's a bit far from the Sun,
火星很小，表面布满岩石，虽然它离太阳有点远，
it might be considered a potentially habitable world if found by a mission like Kepler.
但如果从类似开普勒任务的角度来看，可能会认为它是个宜居的世界。
Indeed, it's possible that Mars was habitable in the past, and in part, this is why we study Mars so much.
事实上，火星在过去的确有可能是适宜居住的，这也是我们为什么对火星投入这么多研究精力的一部分原因。
Our rovers, like Curiosity, crawl across its surface, scratching for clues as to the origins of life as we know it.
我们的那些火星车，比如好奇者号，爬过火星的表面，寻找我们所知的生命起源的迹象。
Orbiters like the MAVEN mission sample the Martian atmosphere, trying to understand how Mars might have lost its past habitability.
进行“火星大气与挥发物演化任务”的人造卫星采集了火星的大气样本，试着了解火星是如何失去曾经的可居住性的。
Private spaceflight companies now offer not just a short trip to near space but the tantalizing possibility of living our lives on Mars.
私人太空旅行公司现在不仅仅提供近太空的短程旅行，还提供了可以在火星上居住的诱人的可能性。
But though these Martian vistas resemble the deserts of our own home world,
尽管火星上的这些远景看起来很像我们地球上的沙漠，
places that are tied in our imagination to ideas about pioneering and frontiers, compared to Earth Mars is a pretty terrible place to live.
那些一提到就会联想起拓荒者、边境等等的地方，但与地球相比，火星上的环境对于生命体来说简直太恶劣了。
Consider the extent to which we have not colonized the deserts of our own planet, places that are lush by comparison with Mars.
想想那些我们还没有征服的地球上的沙漠，相较于火星来说，沙漠可都算是“枝繁叶茂”了，
Even in the driest, highest places on Earth, the air is sweet and thick with oxygen exhaled from thousands of miles away by our rainforests.
即使在地球上最干燥海拔最高的地方，我们仍然能呼吸到数千英里外那些热带雨林生产出的新鲜的、富含氧气的空气。
I worry -- I worry that this excitement about colonizing Mars and other planets carries with it a long, dark shadow:
我担心--我担心殖民于火星和其他行星的激动之情会带来深远的负面影响：
the implication and belief by some that Mars will be there to save us from the self-inflicted destruction of the only truly habitable planet we know of, the Earth.
源于一些人的心理暗示和信仰--认为火星将会是我们自己把唯一真正宜居的行星--地球毁灭之后的“诺亚方舟”。
As much as I love interplanetary exploration, I deeply disagree with this idea.
这么说吧，我有多爱星际探索，我就有多反对这种想法。
There are many excellent reasons to go to Mars, but for anyone to tell you that Mars will be there to back up humanity
去火星有很多天花乱坠的理由，但如果有人跟你说火星是个人类生存地的备胎的话，
is like the captain of the Titanic telling you that the real party is happening later on the lifeboats. Thank you.
那就像泰坦尼克号的船长告诉你，“一会儿真正的派对将在救生船上展开”一样的胡扯。谢谢。
But the goals of interplanetary exploration and planetary preservation are not opposed to one another.
然而，事实上星际探索和保护星球这两个目标并不互相矛盾。
No, they're in fact two sides of the same goal: to understand, preserve and improve life into the future.
实际上，它们是同一个目标的两个方面：那就是了解、保护和改善生命，使生命延续。
The extreme environments of our own world are alien vistas. They're just closer to home.
我们星球上的极端环境就是外星的景象。只是它们离我们比较近而已。
If we can understand how to create and maintain habitable spaces out of hostile, inhospitable spaces here on Earth,
如果我们能知道如何在地球上十分恶劣、不宜居住的环境中创造并维持可居住的空间，
perhaps we can meet the needs of both preserving our own environment and moving beyond it.
也许我们就能满足既保护我们的环境，又“走出去”的双重需求了。
I leave you with a final thought experiment: Fermi's paradox.
最后我想给大家出一个思考题：“费米悖论”。
Many years ago, the physicist Enrico Fermi asked that,
许多年前，物理学家恩里科·费米提出了一个问题：
given the fact that our universe has been around for a very long time and we expect that there are many planets within it,
那就是，我们的宇宙存在了很长很长的时间是个事实，我们也知道宇宙中有无数的行星，
we should have found evidence for alien life by now. So where are they?
那我们现在应该已经找到外星生命存在的迹象了。可是它们在哪呢？
Well, one possible solution to Fermi's paradox is that,
“费米悖论”的一种可能的解释是这样的：
as civilizations become technologically advanced enough to consider living amongst the stars,
随着文明的进步，科技变得足够先进，能够开始考虑如何在宇宙中生存时，
they lose sight of how important it is to safeguard the home worlds that fostered that advancement to begin with.
人们也就会忽视保护自己的家园，这个孕育了高科技的地方的重要性。
It is hubris to believe that interplanetary colonization alone will save us from ourselves,
简单地迷信殖民于其他星球就可以拯救我们自己恐怕是自不量力，
but planetary preservation and interplanetary exploration can work together.
其实环境保护和星际探索这两项工作是可以结合着进行的。
If we truly believe in our ability to bend the hostile environments of Mars for human habitation,
如果我们对为了人类居住而改变火星恶劣环境的能力足够自信的话，
then we should be able to surmount the far easier task of preserving the habitability of the Earth. Thank you.
那我们更应该可以完成保护地球宜居性这个超级简单的任务。谢谢。