英语听力：自然百科 已知的宇宙：外星生命 Alien_Contact-4
时间：2014-05-21 06:32:12
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（单词翻译）
Water allows the sand grains to flow to gather and intermingle and form more complex structures. In the same way, water acts like a cocktail1 mixer, allowing the atoms and molecules2 to come together, and also may form the building blocks of life.
All that water was perfect for breeding life. Lots of it. It's estimated that since the
emergence3 of earth’s first life form, 100 billion species have existed on the planet. Millions are alive right now. And that fact alone tells scientists a lot as they combed the
cosmos4 for alien life.
"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. Take this handful of dirt. It's not just dirt. There is a lot going on here. There is an earth worm, going a little more, and there are these tiny little
mites5,
zooming6 further, and there are these litter creatures called protozoa, and smaller still, there's bacteria, billions of them. 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."
Life isn't always something you can see with a naked eye. In these piles of dirt lie the secrets to our origins and scientists are keeping that in
prospective7 when they search for life in the cosmos.
"You have to be looking for that
bacterium8 first, because that's gonna be far more common. If we don't find that, the chance of finding these hollow, again, gray ET guys is gonna be highly diminished."
So are there other earths out there, capable of supporting ET or even bacteria? We are closer than ever to finding the answers, because scientists pick up the
scent9 in this cosmic cut.
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.
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