英语必修三Unit4Astronomy课文翻译

英语必修三

Unit 4 Astronomy

课文翻译

作者：未知

来源：尚学苑

2014-09-20

LIF HOW E BEGAN ON THE EARTH

No one knows exactly how the earth began, as it happened so long ago. However, according to

a widely accepted theory, the universe began with a

that, atoms began to form and combine to create stars and other bodies.

For several billion years after the

was to become was uncertain until between 4.5 and 3.8 billion years ago when the dust settled into

a solid globe. The earth became so violent that it was not clear whether the shape would last or not.

It exploded loudly with fire and rock. They were in time to produce carbon, nitrogen, water vapour

and other gases, which were to make the earths atmosphere. What is even more important is that

as the earth cooled down, water began to appear on its surface.

Water had also appeared on other planets like Mars but, unlike the earth, it had disappeared

later. It was not immediately obvious that water was to be fundamental to the development of life.

What many scientists believe is that the continued presence of water allowed the earth to dissolve

harmful gases and acids into the oceans and seas. This produced a chain reaction, which made it

possible for life to develop.

Many millions of years later, the first extremely small plants began to appear on the surface of

the water. They multiplied and filled the oceans and seas with oxygen, which encouraged the later

development of early shellfish and all sorts of fish. Next, green plants began to grow on land. They

were followed in time by land animals. Some were insects. Others, called amphibians, were able to

live on land as well as in the water. Later when the plants grew into forests, reptiles appeared for the

first time. They produced young enerally by laying eggs. After that, some huge animals, called

dinosaurs, developed. They laid eggs too and existed on the earth for more than 140 million years.

However,

65

million

years

ago

the

age

of

the

dinosaurs

ended.

Why

they

suddenly

disappeared

still

remains

a

mystery.

This

disappearance

made

possible

the

rise

of

mammals

on

the

earth.

These

animals were different from all life forms in the past, because they gave birth to young baby animals

and produced milk to feed them.

Finally about 2.6 million years ago some small clever animals, now with hands and feet,

appeared and spread all over the earth. Thus they have, in their turn, become the most important

animals on the planet. But they are not looking after the earth very well. They are putting too much

carbon dioxide into the atmosphere, which prevents heat from escaping from the earth into space.

As a result of this, many scientists believe the earth may become too hot to live on. So whether life

will continue on the earth for millions of years to come will depend on whether this problem can be

solved.

地球上生命的起源

没有人 确切知道地球是怎么样开始形成的，因为在很早很在以前地球就形成了。然而，

一种普遍为人们所接受的理论是：

宇宙起源于一次大爆炸，

这次大爆炸 将物质投射到四面八方。

然后，原子开始形成并结合成恒星和其他天体。

大爆炸后好几十亿年过去了，但地球还只是一团尘埃。随后它会变成什么没人能知道，

直到

38-45

亿年前，这团尘埃才慢慢地形成一个团体 的球状物。地球开始变得激烈动荡，不

知道这个固体形状是否 会继续存下去。它猛烈地爆炸喷出了烈火与岩石，最终产生了碳，

氮气，水蒸气和其他多种气体，

从而形成了地球的大气层。

更为重要的是，

地球冷却了下来，地

球的表面就开始出现了水。

在火星这些其他行星上都出现了水，

但和地球不同的是，

这些水后来都消失了。

水对于生命

的发展会起关键作用，

这一点在当时并不明显。

很多科学家相信，

由于地球上长期有水

存在，

使得地球得以把有害气体和酸性物质溶解在海洋里。

这就产生了一系列的反应，

使得生命

就有可能开始发展了。

好几百万年后，

水的表面开始出现了极小的植物。

他们繁殖起来就使得早期的海洋充满

了氧气，

这为早期的贝类及其他各种鱼类的发育进一步创造了条件。

接着，绿色植物开始出

现在陆地上。 随后，陆地上出现了动物，其中有一些是昆虫，另外一些叫两栖动物，他们既