The word“day” has two meanings. When we talk about the number of days in a year,  we are using “day” to mean 24 hours. But when we talk about day and night,  we are using“day” to mean the time between sunrise and sunset. Since the earth looks like a ball,  the sun can shine on only half of it at a time. Always one half of the earth is having day and the other half night. A place is moved from day into night and from night into day over and over by the spinning（旋转）of the earth. At the equator（赤道）day and night are sometimes the same length（长度）. They are each twelve hours long. The sun rises at 6 o'clock in the morning and sets at 6 o'clock in the evening. For six months the North Pole is tilted（倾斜）toward the sun. In those months the Northern Hemisphere（半球）gets more hours of sunlight than the Southern Hemisphere. Days are longer than nights. South of the equator nights are longer than days. For the other six months the North Pole is tilted away from the sun. Then the Southern Hemisphere gets more sunlight. Days are longer than nights. North of the equator nights are longer than days. Winter is the season of long nights. Summer is the season of long days.

    When you watch TV and play video games you make global warming(全球变暖) worse! To make electricity, fossil fuels(矿物燃料) are burned in big factories. But burning fossil fuels also makes greenhouse gases. This means that every time you use electricity you help make global warming worse!

    Cars are also making global warming worse. They burn fossil fuels in their engines, and send lots of greenhouse gases into the air.

    So what can we do to stop global warming?

    Try to use less electricity. First, turn off lights, your television, and your computer when you stop using them，You could also try to watch less TV. But you may find it hard to do these! Second, plant trees. Not only is it a fun thing to do, but it is also a great way to lower the number of greenhouse gases in the air. Trees take carbon dioxide(二氧化碳) out of the air when they grow. Last, don't throw away your rubbish, but try to recycle it. Because if rubbish is not recycled, it rots(腐烂) and makes a greenhouse gas called methane(甲烷). So try to recycle cans, bottles, plastic bags and newspapers. It'll make you feel great! And it'll help the Earth.

Dear friends,

    I am writing this letter to draw your attention to the disasters（灾难）these days. Too much rain destroyed the crops and washed the earth away. Sometimes it was too little and made plants dead. Also there was too much dust in the air. All these did great damage to our life.

    However, we made them! So it is time for us to try our best to save the Earth.

    The most important thing is to plant trees as many as possible. At the same time, we should stop cutting down trees and protect the forests. And we can save our planet through many other ways, such as saving water and using both sides of paper. Besides, don't keep TVs or computers on when you are not using them. When you leave a room, turn off the lights.

    A small action is very helpful to our planet. Please join us in the action of protecting the Earth. Let's start from the little things right around us.

Bruce

Leader of the Students' Union

    Technology is changing our ways of life. Robby Pepper is Italy's first robot gatekeeper. He can answer questions in Italian, English and German. He is placed at a hotel to help answer simple questions from visitors. A guest from Moldova, congratulated the robot on his skills. "He's like a real person. He's really good." She said. "He talked to me, and he shook my hand."

    Japan's Softbank Robotics created Robby. It can provide hotel guests with information they need, like where to find a restaurant and its hours of operation. The use of robots is growing in service industries like tourism. But they are expected to become more useful as better artificial intelligence, or AI, is developed.

    The International Federation of Robotics says about 79,000 professional service robots were sold last year. It expects up to 25 percent sales growth each year. There are many different kinds of artificial intelligence machines: learning robots, cleaning robots, medical robots and public relations robots.

    We have made some progress in the development of AI, but we still have a long way to go. Experts say people in the United States and Japan seem more welcoming to robots than people in Europe do. Shoppers at a store in Scotland got one robot, Softbank's Fabio Pepper, fired out Customers were not willing to talk to the robot. And a security robot in Washington DC made news last year when it rolled itself into a fountain*and could not get out.

    In Brescia, the Cayu car sore is using another Softbank Pepper robot to sell cars Named Cayuiki .the robot is programmed to give information on cars, playing games and collecting information. It is helping to bring in possible car buyers .But the head of the Cayu car store said, "To sell the cars, you still need human beings."