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 generally 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.
A VISIT TO THE MOON
Last month I was lucky enough to have a chance to make a trip into space with my friend Li Yanping, an astronomer. We visited the moon in our spaceship!
Before we left, Li Yanping explained to me that the force of gravity would change three times on our journey and that the first change would be the most powerful. Then we were off. As the rocket rose into the air, we were pushed back into our seats because we were trying to escape the pull of the earth ’s gravity. It was so hard that we could not say anything
to each other. Gradually the weight lessened and I was able to talk to him. “Why is the spaceship not falling back to the earth? On the earth if I fall from a tree I will fall to the ground. ”I asked. “We are too far from the earth now to feel its pull,”he explained, “so we feel as if no gravity at all. When we get closer to the moon, we shall feel its gravity pulling us, but
it will not be as strong a pull as the earth ’s.”I cheered up immediately and floated weightlessly around in our spaceship cabin watching the
earth become smaller and the moon larger.
When we got there, I wanted to explore immediately. “Come on,”I said. “If you are right, my weight will be less than on the earth because the moon is smaller and I will be able to move more freely. I might even grow taller if I stay here long enough. I shall certainly weigh less!”I laughed and climbed down the steps from the spaceship. But when I tried to step forward. I found I was carried twice as far as on the earth and fell over. “Oh dear,”I cried, “walking does need a bit of practice now that gravity has changed.”After a while I got the hang of it and we began to enjoy ourselves.
Leaving the moon’s gravity was not as painful as leaving the earth ’s. But returning to the earth was very frightening. We watched, amazed as fire broke out on the outside of the spaceship as the earth’s gravity increased. Again we were pushed hard into our seats as we came back to land. “That was very exhausting but very exciting too, ”I said. “Now I know much more about gravity! Do you think we could visit some stars next time?”“Of course,”he smiled, “which star would you like to go to?”
Unit 5 CANADA- “THE TRUE NORTH ”
A TRIP ON “THE TRUE NORTH”
Li Daiyu and her cousin Liu Qian were on a trip to Canada to visit their cousins in Montreal on the Atlantic coast. Rather than take the aeroplane all the way, they decided to fly to Vancouver and then take the train from west to east across Canada. The thought that they could cross the whole continent was exciting.
Their friend, Danny Lin, was waiting at the airport. He was going to take them and their baggage to catch“The True North”, the cross-Canada
train. On the way to the station, he chatted about their trip.“You’re going to see some great scenery. Going eastward, you’ll pass mountains and thousands of lakes and forests, as well as wide rivers and large cities. Some people have the idea that you can cross Canada in less than five days, but they forget the fact that Canada is 5,500 kilometres from coast to coast. Here in Vancouver, you’re in Canada’s warmest part. People say it is Canada’s most popular cities to live in. Its population is increasing rapidly. The coast north of Vancouver has some of the oldest and most beautiful forests in the world. It is so wet there that the trees
are extremely tall, some measuring over 90 metres”.
That afternoon aboard the train, the cousins settled down in their seats. Earlier that day, when they crossed the Rocky Mountains, they managed to catch sight of some mountain goats and even a grizzly bear and an eagle. Their next stop was Calgary, which is famous for the Calgary Stampede. Cowboys from all over the world come to compete in the Stampede. Many of them have a gift for riding wild horses and can win thousands of dollars in prizes.
After two days ’travel, the girls began to realize that Canada is quite empty. At school, they had learned that most Canadians live within a few hundred kilometres of the USA border, and Canada’s population is only slightly over thirty million, but now they were amazed to see such an empty country. They went through a wheat-growing province and saw farms that covered thousands of acres. After dinner, they were back in an urban area, the busy port city of Thunder Bay at the top of the Great Lakes. The girls were surprised at the fact that ocean ships can sail up the Great Lakes. Because of the Great Lakes, they learned, Canada has more fresh water than any other country in the world. In fact, it has one-third
of the world’s total fresh water, and much of it is in the Great Lakes. That night as they slept, the train rushed across the top of Lake Superior, through the great forests and southward towards Toronto.
“THE TRUE NORTH”FROM TORONTO TO MONTREAL
The next morning the bushes and maple trees outside their windows were
red, gold and orange, and there was frost on the ground, confirming that fall had arrived in Canada.
Around noon they arrived in Toronto, the biggest and most wealthy city in Canada. They were not leaving for Montreal until later, so they went on a tour of the city. They went up the tall CN Tower and looked across the lake. In the distance, they could see the misty cloud that rose from the great Niagara Falls, which is on the south side of the lake. The water flows into the Niagara River and over the falls on its way to
the sea.
They saw the covered stadium, home of several famous basketball teams. As they walked north from the harbour area, Li Daiyu said, “Lin Fei, one of my mother ’s old schoolmates, lives here. I should phone her from a telephone booth”.
They met Lin Fei around dusk in downtown Chinatown, one of the three in Toronto. Over dinner at a restaurant called The Pink Pearl, the cousins chatted with Lin Fei, who had moved to Canada many years earlier. “We can get good Cantonese food here,”Lin Fei told them, “because most of the Chinese people here come from South China, especially Hong Kong. It ’s too bad you can’t go as far as Ottawa, Canada’s capital. It’s approximately four hundred kilometres northeast of Toronto, so it would take too long.”
The train left late that night and arrived in Montreal at dawn the next morning. At the station, people everywhere were speaking French. There were signs and ads in French, but some of them had English words in smaller letters. “We don’tleave until this evening,”said Liu Qian. “Let’s go downtown. Old Montreal is close to the water.”They spent the afternoon in lovely shops and visiting artists in their workplaces beside the water. As they sat in a buffet restaurant looking over the broad St Lawrence River, a young man sat down with them.
“Hello, my name is Henri. I ’m a student at the university nearby,”he said, “and I was wondering where you are from.”The girls told him they were on a train trip across Canada and that they had only one day in Montreal. “That’s too bad,”he said. “Montreal is a city with wonderful restaurants and clubs. Most of us speak both English and French, but the
city has French culture and traditions. We love good coffee, good bread and good music”.
That night as the train was speeding along the St Lawrence River toward the Gulf of St Lawrence and down to the distant east coast, the cousins dreamed of French restaurants and red maple leaves.
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