英语必修三Unit 4 Astronomy课文翻译只是分享

<<<<<<

精品资料》

》

》

》

》

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

Bang

that

threw

matter

in

all

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.

<<<<<<

精品资料》