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Good morning class, time to put on your tinfoil hats! The question of whether or not we are alone in the universe is something mankind has wondered for hundreds of years.

同学们早上好，请带上锡箔帽。我们在宇宙中是否孤独呢？这个问题人类已经思索了数百年。

Is there life outside of Earth, and what would even make that possible? Well, the following theories explain why aliens are most likely out there.

地球之外有生命吗外星生命为什么可能存在？接下来的理论将为你解释为什么外星人极有可能存在。

Here are 10 credible explanations of why aliens likely exist. Number 10 is the number of planets.

关于外星人的存在问题有十个可信的解释。第十，星球数量之繁多。

If we think of life as a phenomenon which requires a specific set of environmental factors to occur, then we can start to work out the probability of alien life in the universe. Temperature, material elements, chemistry, and stability, all of these things play their part.

如果我们将生命看作一种需要，在一系列特定环境条件下才能出现的现象，那么我们就能从这里入手探讨外星人存在的可能性了。温度、物质元素、化学成分、稳定性，这些都在人类存在中扮演着重要的角色。

But the biggest number one factor necessary for life as we know it is to have a celestial body, like a planet. You know, the perfect neighborhood for life to evolve.

但是我们知道生命存在所必需的首要因素是得有一个天体，比如说一颗行星。因为天体是生命进化的完美环境。

Previously, we were not exactly sure that planets around other stars, known as exoplanets, actually existed. But, with the development of the Kepler satellite, which can detect minuscule changes in a distant star's light when planets pass in front of it, astronomers have detected nearly 4000 planets so far.

以前，我们并不很确信那些围绕着其它星星的行星，也就是外星行星，真的存在。但是，随着开普勒卫星项目的推进，它能探测到当行星经过时那些遥远的星球的光芒里发生的一些细小的变化，目前，天文学家已探测的恒星接近四千颗。

So, in other words, planets are probably abundant, and that means that there are plenty of places for extraterrestrial life to call home. You know, now that I think about it, an alien world would probably be perfect.

换句话说，这些星球数量之繁多足以有可能在其中许多星球能让外星生命在此安家落户。所以我就在想外星世界那么完美无极限。

Why would they wanna come here with all the farting cows? It's a thing, Google it.

为什么外星人还要来地球接受汽车尾气的熏陶呢？问得好，上网搜一下吧。

Number nine is the age of the universe. In case you didn't know, the universe is about 13. 8 billion years old.

第九，宇宙之沧桑。我要普及一个常识宇宙大概有一百三十八亿岁了。

Our planet Earth has been around for about 4. 5 billion years of that, with the oldest evidence of life being 3. 9 billion years old. It wasn't until about 7 million years ago that the first hominoids evolved, and then finally, you get us, the homo sapien, just a few hundred thousand years ago.

而我们的地球大概四十五亿岁，生命最古老的证据可以追溯到三十九亿年前。直到七百万年前，最早的类人动物才开始进化，他们最终进化成我们现在的样子，也就是智人，这才是几十万年前的事儿。

But even within that time, recorded history is only about 10, 000 years old, probably because we didn't develop writing until about that time. Well, you know, that or there were numerous cataclysmic events that kept resetting our civilization.

但有记录的人类历史比这个时间还要短，才大约一万年，可能是因为一万年前人还不会书写吧。而大家都知道未来可能有无数的浩劫来重置人类的文明。

Mama, no! The point is, even if it takes 4 billion years to get civilization, the universe is way older than that.

妈呀！ 不！重点是，虽然人类文明史延续了四十亿年。

An extraterrestrial species could've become technologically advanced several times over during that time, so who knows how many alien cultures could be out there? They're probably looking at us right now like, "They're still using toilet paper? "They don't know about the shells."

但这点时间在沧桑的宇宙面前不值一提，在没有人类存在的宇宙里，外星生命可能已经在科技上领先人类好几倍了，谁知道那时究竟有多少外星文明呢？外星生命很可能在俯视着芸芸众生：“他们咋还在用厕纸？”“咋不用贝壳呢？”

Number eight is the theory of panspermia. A big challenge in science is to explore the conditions which led inanimate matter to become self-replicating, evolving through natural selection.

第八，胚种论。科学上的一个巨大挑战就是探索导致无机质自我复制的条件，也就是探索物竞天择带来的进化。

You know, that little thing called life. Most theories involve the early Earth environment, but one theory is a little different.

你看，那个渺小的东西就是生命的雏形。大部分相关理论都涉及到早期地球环境，但有个理论显得与众不同。

The theory of panspermia states that life didn't start on Earth, but instead was brought here. Now hold on, before you start to think that ancient aliens did it, panspermia actually refers to the transference of bacteria.

胚种论声称生命的起源不在地球，在地球之外。等一下，你千万别以为人类是古代时外星生命带到地球上的，因为胚种论实际上是细菌转移学说的引用。

Microscopic critters were hitchhiking on an asteroid or comet, which struck the Earth, depositing life into the seas billions of years ago. Furthermore, we know that volcanic eruptions or large impacts could feasibly throw out rocky debris into space.

即几十亿年前，微生物搭上了小行星或彗星的顺风车，但这个顺风车撞上了地球，而这些微生物被雪藏在了海底。还有，我们大家都知道火山喷发或者巨大的冲击力足以将岩石碎片抛掷到太空中。

This then spreads life further from planet to planet. So, it could very well be that we are the aliens ourselves and that countless worlds have been seeded, just like ours.

借此把生命传送到另一个星球上去。所以，很有可能人类就是外星人，因为外星人的种子洒满全宇宙，我们就是其中一粒啊。

Oh, I just realized what panspermia means. Get it, volcanoes just.

噢，我好像发现胚种论很污。明白了，火山爆发就是射……

That's inappropriate. Number seven are hydrothermal vents.

不太适合在这里说。第七，深海热泉喷口。

We know for a fact that life arose at least once here on Earth, and we can speculate about other planets and say it's likely that alien life exists, but we don't know that for a fact. However, by studying life here on Earth, we can increase our confidence.

我们可以确信地球上至少存在过一次生命，我们还能推测其他星球上可能有外星生命的存在，但是，我们不能百分之百保证。然而通过研究地球上的生命，我们就愈发有信心说外星生命是存在的。

Now, there are many planets that are nothing like Earth. In fact, most of them are quite different.

目前，许多星球跟地球是迥异的。可以说，这些星球和地球完全不同。

Many of them are too far from their stars to have temperatures needed for most life, like on Earth. In fact, some are called orphan planets and don't even orbit a star at all.

其中大多数星球离它们的恒星太远，所以星球上的温度很低，大多数地面生命都活不了。还有一些星球被称为“孤儿星球”，它们就算想公转也没有恒星。

But even these cold worlds may have life. You know, like ice people walking around.

但这些寒冷的行星上也可能存在生命。你懂的，结成冰块的人走来走去。

That's not what that means? Okay. Deep at the bottom of our oceans, there are hydrothermal vents, which spew heated gas and liquid from beneath the sea bed.

是我异想天开了吗？好吧。地球上的海底深处，存在深海热泉喷口泉口会喷出海床下面产生的热气或热液。

Around this heat source, a rich ecology of life has evolved without any sunlight at all. Astrobiologists hold out hope that even the remotest planets have such vents, and who knows what creeps around them?

以此热源为中心，在没有阳光的条件下，一个丰富的生态圈逐渐形成了。天体生物学家主张再遥远的星球也有深海热泉喷口，天知道这些生命是以什么形态存在的。

It's like a little club where all the alien life can get together and hang on the seabed. It's a lovely thought.

深海热泉喷口就像一个小型俱乐部，所有外星生命都聚集在这里，在海床上生生不息。这想法太可爱了。

Number six is the fertile solar system. We may not need to look very far to find extraterrestrial life if our own backyard is anything to go by.

第六，富饶的太阳系。如果后院有宝，我们就不用跑太远去找外星生命了。

There are several candidates for environments which could actually support life around our own solar system, including Mars and the moons of Jupiter and Saturn. While so far, Mars seems barren, there are telling signs that there may be life under the surface living in water.

太阳系里有几个候选星球，它们的条件基本上可以供养生命，包括火星、木星和土星的卫星。就目前所知，火星是贫瘠的，然而其地表以下的水中有生命存在的迹象。

Around Jupiter and Saturn, moons such as Enceladus, may have oceans of water underneath a thick crust of ice, warmed by the tidal forces of the huge gas giants they orbit. Some people have even suggested that there could be multicellular life, such as fish-like creatures down there.

在木星和土星的卫星里，比如说“土卫二”之类的卫星这些星球上，厚厚的冰层下面可能有海水的存在，这些海水因星球转动时产生的巨大潮汐力而升温。一些人甚至推测这些寒冷星球上还可能有多细胞生命，比如说像鱼一样的生物。

If life has evolved several times across our own solar system, then this would again support the hypothesis that the universe should be teeming with life. You know, if there are infinite possibilities of civilizations, then that means that there are infinite possibilities of what they could look like.

如果在我们的太阳系中生命已经进化了好几次，那么这将再次证明这个假设：宇宙是生机勃勃的。然而，如果文明有无限种可能，那么这也意味着外星生命的长相一言难尽。

Maybe they have hands growing out their foreheads and something like that. It's gonna be a nightmare.

或许他们的手长在额头上之类的吧。简直是噩梦。

Number five is the resilience of life. The universe is a hazardous place, filled with radiation and extremes of temperature which would wipe out a person in a blink of an eye.

第五，生命的适应力。宇宙里危机四伏，充满辐射和极端的温度可以在眨眼之间让一个人消失。

But, when you look at the simple tardigrade, also known as a water bear, you realize just how resilient life can actually be, even when faced with the might of the universe. These microscopic animals can survive in mud volcanoes, and at the bottom of the ocean, and can even withstand anything between minus 272 and 150 degrees celsius.

但你去看看那些简单的缓步类动物，比如说水熊，你就会意识到生命的适应力到底有多强，即使在宇宙面前，这种恢复力也毫不逊色。这些微生物能在泥火山里生存，在海底存活，甚至能禁得起介于-272~150℃的温度。

It can even survive without food for 30 years, tolerate 1000 times more radiation than any other animal, and even survive in space. 30 years without food?

微生物甚至可以三十年不进食，其抗辐射能力比其他生物多一千倍，微生物甚至能在太空中生存。三十年不吃东西？

I go 30 minutes without food and I get hangry. And there are other lifeforms called extremophiles, which can thrive in even harsher environments.

我三十分钟不吃东西都会饿得发火。还有一种叫做“极端微生物”的生命形态，它们可以在更恶劣的环境中茁壮成长。

If life can be this resilient, then maybe there are all kinds of weird, almost indestructible creatures living out there in the vastness of space. And humans are definitely not one of them, because I just stub my toe and I cry like a baby.

如果生命力这么强大，那么在广阔的宇宙中可能生存着各种千奇百怪坚不可摧的生物。而人类肯定不会是独一无二的，因为我不小心踢到脚趾，都能哭得像个孩子。

Mm, fragile. Number four are the building blocks of life.

对，人很脆弱。第四，生命的构件。

Knowing the building blocks of life can help us identify where it might arise. For example, scientists theorize that the molecule hydroxylamine is a building block of life.

了解生命的构件能帮我们判断有生命存在的位置。比如说，科学家推测分子羟胺是生命的一个构件。

It's comprised of nitrogen, hydrogen, and oxygen, elements which are common here on Earth. And astronomers have detected it in abundance around a star just 1000 light-years from our solar system.

它由氮、氢、氧元素组成这些元素在地球上很常见。天文学家探测到大量的分子羟胺存在于距离我们的太阳系仅一千光年的一颗恒星上。

So, it's very possible that where we find the building blocks of life, hopefully we can find life itself. But there are also scientific models based on hypothetical biochemistry that state that life on other planets may use different building blocks.

所以这种情况是很有可能的：那些存在生命构件的地方，也有生命存在。此外，我们也有以生物化学假想为基础的科学模型模型提出，那些外星生命可能有不同的生命构件。

We're carbon-based lifeforms because there's a lot of carbon on Earth, but perhaps on another planet, something like silicon is the most abundant element, and therefore life could evolve from that. If that is the case, extraterrestrial life could exist in many more locations than we even imagine.

人体的主要构成元素是碳，因为地球上有很多碳，但或许在其他星球上就不是这样。其他星球上大量存在的可能是硅元素，那么外星生命就是以硅元素为基础的。如果真是这样的话，那有外星生命存在的地方将远远超出我们的想象。

Number three is natural selection. Evolution may mandate that there is extraterrestrial life out there, and not only that, but that there must be life which has technology and uses it to travel through space.

第三，物竞天择说。进化论指出外星生命是可能存在的，不仅如此，肯定还有一些掌握高科技的生命，他们能使用科技在太空中旅行。

Natural selection is the cornerstone principle of evolution. It's the idea of survival of the fittest, the idea that organisms adapt to their environments and eventually thrive because only the genetic mutations which make survival possible are actually passed on.

物竞天择说是进化论的基础原则。物竞天择的内容是：适者生存即只有那些适应生存环境的生物体才能最终存活下来，因为只有通过基因变异，生命才得以存活得以延续。

We see it throughout Earth. Millions of organisms adapted to their surrounding environments.

地球上物竞天择的例子数不胜数。无数生物体适应了周围的环境。

So, if we assume that some form of natural selection leads to simple life elsewhere, then that same process will, over billions of years, lead to creatures like ourselves who can change our environments. I would love to find out that there are aliens that survived on a volcanic planet.

如果我们假设，某种形式的物竞天择成就了他处的简单生命，那么漫长的几十亿年以来，同样的过程也会创造出像我们人类这样的生物，这些生物也有能力改变环境。我想知道有没有生活在火山星球上的外星生命。

Fire aliens! Sounds badass.

“火”星人！听起来好帅。

Number two is technology is king. Okay, we are now heading into some out-there ideas, but be brave and come with me on this journey.

第二，科技为王。接下来，我们要探讨一些非同寻常的概念，但是请勇敢地随我踏上征程吧。

I won't ask for much. Maybe your sanity, but that's about it.

我的要求不多。只需要你的理智，就是这样。

We are constantly innovating and creating new technologies, and those technologies then lead to other breakthroughs. There is a philosophical concept that we are merely the reproductive organs of technology, creating more of it until that technology can replicate itself and head out on its own.

我们不断创新科技，制造新科技，然后这些科技再引起其他突破。这是一个哲学概念，即我们只不过是科技的“生殖器官”，我们创造出更多科技直到这些科技可以自我复制，自己开始征程。

Yep, hand over your sanity please. Arthur C. Clark explored this idea that space is so vast that we wouldn't actually ever meet aliens, but instead, would encounter their technology.

好吧，请交出你的理智。亚瑟·C·克拉克曾提出一个想法：宇宙是如此的广袤，以至于我们不能真的相逢外星人，但我们可以遇见外星人的科技。

If there are aliens out there, they may be pieces of technology which replicate and explore the universe. In this way, one alien civilization could give birth to millions of others.

如果真的发现了外星生命，那么这些外星生命可能是科技碎片，可能是被复制出来以探索宇宙的科技碎片。按照这种逻辑，一种外星文明可以诞生成千上万的孩子。

And I'm fine with this, as long as they aren't the Terminator or the Borg. That would suck for us.

我觉得这样也不错，只要诞出的不是大反派“终结者”和“博格人”就行。是那样就太糟了。

And number one is the strong anthropic principle. The strong anthropic principle states that the reason we exist in this universe is because our universe makes life likely.

第一，强人择原理。强人择原理认为，我们之所以存在于宇宙中，是因为我们的宇宙让生命成为可能。

It's organized in such a way that all the laws of physics make sentient, intelligent, technology-building creatures probable at some point. The mathematician James England has even developed a mathematical theory which states that life has to happen, that it's as miraculous as a rock rolling down a hill.

从物理法则上看，宇宙的组织形式使其在某一时刻能创造出感性的，聪慧的能发展科技的生物。数学家詹姆斯·英格兰甚至创立了一个数学理论，用来说明生命是必然产生的，生命的产生就像岩石滚下山坡那样不可思议。

It will happen because our universe has all the right parameters to make it so. If this is the case, then it's very likely that we are not alone in the universe.

生命能够产生是因为我们的宇宙参数刚好使生命的发生成为可能。如果事实的确如此，那么很有可能我们人类在宇宙中不是独一无二的。

And now you know, you may take your tinfoil hats off, class. So, that was 10 credible explanations why aliens likely exist.

这节课就到这里，同学们可以摘下锡箔帽啦。以上就十个关于外星人可能存在的合理解释。

But if you guys enjoyed this, remember to give it a big thumbs up. Also, be sure to subscribe to my channel, and turn on notifications by clicking the little bell beside the subscribe button, so that you never miss a thing, because I release new videos all the time.

如果你喜欢本视频，别忘了给个大大的赞。还有，一定要订阅我的频道哦，请记得点击订阅按钮旁边的小铃铛，这样就能打开通知，不会错过任何精彩视频了，因为我会保持更新视频的。

Thank you guys for watching and I'll see you on the other side. Time to take off!

感谢大家的观看，下次再见。回家吃饭吧。