It's only a question of finding them.But now, there'sa new theory.

问题只是找没找到 但是现在有种新的理论

It's called the Rare Earth Theory.

像我们这样的星球可能很稀少这就是稀有地球理论

It says that simple life, like bacteria,

该理论认为像细菌一样的简单生命

the type of slime I'veseen in hot volcanic pools,may be common in the universe.

我曾在火山泥浆潭里看到的那种粘性物质 可能在宇宙随处可见

But for complex life like plants and animals to evolve

但是复杂生命像植物和动物如果进化

requires an extraordinary sequence of events.

则需要大量事件发生

A nd ha ving tra veiled the world to make this series,

在环游世界制作这个系列节目的时候

what strikes me most is the incredible good fortune

我最大的感触是地球

it's taken to make our planet a home for such rich and diverse life.

能够成为如此丰富多样生命的家 真是不可思议的好运气

To get an idea of just how lucky Earth has been,

为了能够明白地球有多么幸运

let me take you back to what I reckon is the most important day in Earth's history.

让我带你们回到 我所认为的地球历史上最重要的一天

This one day was responsible for much of what makes Earth so special.

让地球如此特别大部分原因归功于这一天

And yet, it was just a chance event.

但是，这只是偶然的事件