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.

     Grace, usually known as the Home of Microsoft, is inside an office building in Redmond, Washington. Once you come into the building, you will feel that you're in a modern and future home.

      When you enter the building, Grace's voice, coming from a hidden speaker, tells you your messages. In the kitchen, you set a bag of flour(面粉) on a flat stone table. Grace sees what you're doing and makes a menu of flour-based foods on the table. Once you choose one, Grace gives you ingredients(配料).

There's also a notice board in the kitchen made of “intelligent(智能的) cloth” that works like a touch screen computer. You can deal with postcards and invitations and surf the net with the touch of a finger. The invitations could be encoded(编码). You can deal with them on the computer. It's part of Microsoft's Smart Personal Objects Technology, whose aim is to make every object more efficient(有效率的).

      “The day when your house becomes a member of your family is not far,” says Pam Heath, a manager of Microsoft. At the Andersen Windows Company, Jay Libby imagines that windows made of intelligent glass can be changed into TVs.

      “Nobody wants a television set,” says Libby. “What you want is the service it provides.” If the TV isn't improved, it will disappear in the future.

Home entertainment is one consideration for the future. At the Georgia Institute of Technology in Atlanta, scientists are designing systems that will allow old people to live better on their own. So Grandma's home can be cleverly designed to recognize(识别) her ways of waking, sleeping and movement. Family members will be told any change by their computers.

    Do you know when Earth Day is? It is on April 22nd, and it began in the US in 1970. Earth Day in our country began in the 1990s. Earth Day is a good time for people to think about what they can do to make the Earth clean and beautiful, because now the environment on Earth is getting worse and worse. In fact, there are many things we can do to protect our Earth.

    Plant trees.

    Planting more trees helps to reduce greenhouse gases (温室气体), stop the earth from running away and provide homes for animals.

    Don't waste.

    Do not waste water. Use both sides of paper when you write. Turn off the light when you leave. Take your cup with you. Take your own shopping bags to the supermarket. Stop using the plastic bags. Don't use any disposable things. We should save energy.

    Don't throw rubbish in the streets.

    When rainwater washes over the rubbish, it becomes polluted. The polluted water flows into the rivers and seas.

    Ride your bike or take a bus.

    Too many cars pollute the air and waste energy.

    Remember: Every day is Earth Day.

    We should protect the Earth every day, not just on Earth Day. The Earth is our home. Let's do our best to make the Earth cleaner and more beautiful.