Someday rocket ships will probably carry men on trips to the Moon or even to the planet Mars.
也许有一天宇宙飞船可以载人飞行到月球上或是火星上。
How would you like to go exploring in a rocket ship beyond the World's atmosphere out through empty, airless space?
你想乘一艘宇宙飞船飞出地球的大气层，到那空无一人、没有空气的太空中去探险吗？
How would you like to be the first Man in the Moon?
你想成为踏上月球的第一人吗？
You wouldn't find any living thing on the Moon, for the Moon is a dead, lifeless ball without any air on it at all.
你会发现月球上没有任何生物，因为月球是一个没有空气、没有生命的死星球。
But if your rocket got to Mars you would almost certainly find some living plants —and perhaps, who knows?—even some living animals.
但是如果宇宙飞船把你带到火星上去，也许你能发现一些活的植物，甚至会有活的动物，谁知道呢？
Some mountains are so high that their tops almost stick out of the ocean of air;
有些山非常高，高到山顶几乎都伸出了大气层；
at least there is so little air covering their tops that people can't go all the way to the top unless they take along canned air to breathe.
至少，山顶上空气非常稀薄，所以人们不带氧气罐就无法一直登到山顶。
You can't see air—you may think you can, but what you see is smoke or clouds, not air.
你看不到空气—也许你觉得自己能看到，但你看到的只是烟或云，而不是空气。
When air is moving, we call it wind. Then you can feel it when it blows your hat off, you can hear it when it bangs the shutters and whistles round the house;
空气流动的时候，我们称之为风。当风把你的帽子吹走的时候你可以感觉到它，当它撞着百叶窗，在房子外呼啸的时候你可以听到它。
but no one has ever seen air itself.
但是没有人看到过空气本身。
The world wasn't always as it is now. It was once a ball of fire—a huge burning ball.
世界并不总是现在这个样子的。它曾经是一个火球—一个巨大的燃烧的球。
That was millions of years ago, and of course long before there were any people or animals or plants on the world.
早在世界上人、动物或植物存在以前，它已经存在几百万年了。
But the fiery ball got cooler and cooler until it was no longer burning but a hot ball of rock.
但是这个大火球逐渐冷却，直到不再燃 烧，成为一个灼热的大石球。
There were then no oceans, no water on the World, for water won't stay on anything very hot
当时世界上没有海洋，没有水，因为水不能在任何热的东西上面停留，比如说一个热热的火炉，
it won't stay on a hot stove—it turns to steam when there is fire under it;
当下面有火的时候，水就会变成水蒸气。
so there were only clouds of steam, an ocean of steam, around the world.
所以当时的世界上只有大团大团的水蒸气，一个蒸汽的海洋笼罩着世界。