Tornadoes(龙卷风) are one of the worst weather events on earth. Each year, tornadoes kill many people. The storms often carry homes, cars and trees from one place to another. And they can also destroy anything when they pass by.

      A tornado comes from a thunderstorm(雷雨) in the sky down to the ground. It is big at the top and small at the bottom.

      A tornado appears when winds in different directions meet in the cloud and begin to turn in circles. People can see tornadoes almost everywhere in the world. But most happen from late winter to middle summer. There is a second high season in November. During spring, warm air moves north and mixes with the cold air left from winter. In November, the opposite happens. Cold air moves south and mixes with the warm air left from summer.

      Tornadoes always come suddenly. Weather scientists have done something to predict(预测) tornadoes. But the storms often move too fast for people to protect themselves. Last year, tornadoes killed more than one hundred people in United States.

      Scientists say the best place to be in is a small room, without windows, in the middle the lowest part of a building when tornadoes come.

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A science fiction flying car looks like a normal car, but it is an aircraft (飞行器) that anybody can fly directly from any place to another without using roads or runways. Science fiction writers have written about flying cars for a long time. But now flying cars will soon fly out of the world of science fiction into our real world. And the dream of the science fiction writers will soon come true.

    The first-known sky car is the FSC-1. The FSC-1 looks like an expensive sports car. You can drive the FSC-1 on the road like a normal car. If you touch a button, its wings and propeller (螺旋桨) fold out and then it can take off, fly and land as an airplane. The owners of the FSC-1 can choose if they want to drive or fly.

Another flying car or sky car is the Moller Skycar M400. Although you can't drive it on the roads, it is small and easy to fly and can take off and land like a helicopter (直升飞机). Urban Aeronautics' X-Hawk is another type of sky car. It is expected to be available for about $3 million.

    Just like any new technology, flying cars have taken a long time to be developed. But some experts think the technology is far from what people imagine when they are sitting in traffic. It still needs to be improved.

    Why don't birds get lost on their long flights (飞行) from one place to another? Scientists have studied this puzzle for a long time. Now they're starting to fill in the blanks(空白).

    Not long ago, experiments showed that birds use the sun to guide them during daylight hours. How do birds fly at night? Tests with artificial stars, which are made by people, have proved that certain night-flying birds are able to follow the stars in their long-distance flights.

    They found a bird that spent its lifetime in a cage and never flew under a natural sky. But it was born with the ability to use the stars to look for the direction. This bird's cage was placed under the sky filled with artificial stars. Any change in the position of the artificial stars caused a change in the direction of the bird's flight. From the experiment, they found that the bird tried to fly in the same direction as those artificial stars moving under the natural sky.

    But the stars are of course birds' main ways of navigation (航行), when the stars are hidden by clouds, they can still find their way by such landmarks (路标) as river courses, mountain ranges (山脉), coast lines and so on. Because of this ability, people use the dove (鸽子) to send messages in some fields. For example, the doves were used to send messages in both World War I and World War II. During that time, thousands of doves were used to carry important messages in order to save the lives of many thousands of people. So it is also the symbol of peace.

    But when it's too dark to see these things, the doves are not able to find their way. They only circle helplessly and get lost.

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    You don't have to be a weatherman to tell people about the weather. If you notice the animals, the sky and the world around, you can predict weather on your own.

    Examine the moon or sun, but do not look at the sun directl or it will hurt your eyes seriously. If you see a ring around the sun or moon, then warm weather follows. A golden ring around the moon warns us that a storm is on the way. A watery yellow sunset is a sign that rain may be near. Feel the direction of the wind. A wind blowing from the east shows that a storm will probably happen. A wind from the west means a sunny day. Monitor the clouds. There are three things about clouds you should look for: movement, color, and change. As a rule , the higher the clouds, the better the weather.  And the lower the clouds , the worse the weather will be.

    The rainbow has a message, too. If you see the sun in the east and a rainbow in the west, the rain may be coming your way. If the sun is in the west and the rainbow is in the east, the rain will be moving away from you. Look at your shoes as you walk through the grass in the morning. If the grass is wet with dew (露珠), then you can expect dry weather. But if the grass is dry, then it will be wise of you to take your umbrella.

    Animals grow up（成长） in different ways. Some newborn（初生的） animals are helpless but their mothers protect them. A newborn kangaroo is very small. It is only a few centimeters（cm）long. It closes its eyes and doesn't have hair. It stays safe in its mother's pouch（育儿袋）for a long time.

    A newborn monkey can not walk. Its mother carries it everywhere.

    Other baby animals can walk soon after they're born. They learn to run with their mothers when danger is near. A baby zebra can run, an hour after it is born.

    Some baby animals are born in a place that is safe. Baby wolves are usually born in big holes with little light. Other baby animals are born in the open. A baby elephant is often born on open land.

    Some researchers explain how most people form their social groups with people of their age. Especially, as children and teenagers, even adults, people make their friends based on proximity (邻近) more than anything else. Even in a college classroom, the students may not make friends with those who have similar personalities and interests. It's the people they really sit next to. Clearly, who stands to you has the greatest influence on you. As Jim Rohn has widely said. "You are average (平均) of five people you spend the most little with."

    Over the past ten months, I've paid Ryan, it Famous writer of several bestselling books, to help with the book I'm writing. Working with him has shown me just how low my standards for my work are. For example, every time I send him a drab (草稿), he shows me how it could     be 10 times better, and he holds me to that standard.

      ▲   It's because that I don't know what I don't know. Working with Ryan has made me realize what is possible and what it takes to create something powerful.

    Like Ryan, my business partner Richard has wonderful ideas and far different experience than I have. He has written 36 New York Times Bestsellers. He's been speaking and doing events for 20 years. Richard always performs at high levels, and he is also very strict with me because my performance is a reflection (反映) on him. It's not a bad thing because it creates high pressure (压力) to help me make great progress in organizing author training.

    In a word, you need to stay with those people who can help you realize your level and potential. Staying with people who have higher standards is the fastest way for you to change. If you don't change your environment, your progress will be very slow. Who you stay with has huge importance. You can't ignore this.