英语听力：自然百科 已知的宇宙 接触外星人(4)（在线收听）

Water allows the sand grains to flow to gather and intermingle and form more complex structures.

水可以使沙粒流动到一起并相互粘连并形成更复杂的结构。

In the same way, water acts like a cocktail mixer, allowing the atoms and molecules to come together, and also may form the building blocks of life.

水的作用就像鸡尾酒调酒师使得原子和分子来在一起最终形成构成生命的基本物质。

All that water was perfect for breeding life. Lots of it.

那些水十分适合哺育生命，许多生命。

It's estimated that since the emergence of earth’s first life form, 100 billion species have existed on the planet.

据估计自从地球上首个生命的诞生1000万个物种在地球上生存过。

Millions are alive right now.

现在有数百万种存在着。

And that fact alone tells scientists a lot as they combed the cosmos for alien life.

在宇宙中寻找外星生命的科学家从中学到了很多东西。

If we look for life in the universe, we have to understand they were coming in different shapes and sizes, and the same thing occurs here on earth.

如果我们在宇宙中寻找生命就必须明白生命的形状和体积有很多种形式，地球上的一样如此。

Take this handful of dirt. It's not just dirt.

就拿这捧土来说，这不只是土。

There is a lot going on here. There is an earth worm, going a little more, and there are these tiny little mites, zooming further, and there are these litter creatures called protozoa, and smaller still, there's bacteria, billions of them.

其中还包含了很多东西。那儿有只蚯蚓，再深入点，就看到了这些微小的螨虫，再放大一下，这些小东西叫做原生动物，再看更小点的，就是细菌了，有数百万个。

So you see, there really are a lot of living things in a handful of dirt and we should probably remember that if we ever go digging around on Alien worlds.

所以你看到这对土里的确有许多的生物，也许当我们在外星世界中，搜寻时也应该记住这一点。

Life isn't always something you can see with a naked eye.

并非所有生命都能用肉眼看到。

In these piles of dirt lie the secrets to our origins and scientists are keeping that in prospective when they search for life in the cosmos.

这堆土中蕴含着我们生命起源的秘密，科学家们搜寻宇宙时也时刻牢记这一点。

You have to be looking for that bacterium first, because that's gonna be far more common.

你必须先寻找细菌因为他们最为普遍但我们找不到。

If we don't find that, the chance of finding these hollow, again, gray ET guys is gonna be highly diminished.

那么我们发现外星人的机会也就微乎其微。

So are there other earths out there, capable of supporting ET or even bacteria?

那么到底还有没有其他“地球”可以支持外星人或着细菌的生存呢？

We are closer than ever to finding the answers, because scientists pick up the scent in this cosmic cut.

我们现在离找到答案比任何时候都要接近，因为科学家们在宇宙追捕中找到了踪迹。

In the hunt for alien life, scientists are focusing their efforts on finding small rocky planets like earth, but searching for another earth is like trying to find a needle in a million haystacks.

在搜寻外星生命的过程中科学家们专注于搜寻向地球一样的小型岩石行星，但是找寻另一个地球如同大海捞针。