Winter is very cold in many countries. It's easy for you and me to keep warm. If we are cold, we can just buy a warm coat or use a heater and we will feel better. But what about animals? How do they keep warm in winter?

    Some animals migrate(迁移). This means they travel to places where the weather is warmer. Many birds leave before the winter starts. They fly in groups. If they fly together, the trip will be safer. They like to migrate to the same places every year. Do you know how they can find the same places? Scientists say that birds use the sun, moon and stars to help them. Other animals like moose (麋鹿) also migrate. Fish and whales swim to warmer water.

    Some animals don't have leave their homes. They hibernate in winter. They fall into a very deep sleep. The animals' temperature drops and their breathing slows down. Before the winter, these animals must eat too much food that they get very fat. If they don't eat enough, they may die when they are hibernating.

    Imagine this. You come back from school and your robot housekeeper is already waiting for you at the door. He turns on the lights, air-conditioner and television. While you are having dinner, he cleans the floor. Before you go to sleep, he tells you the weather report, then reads you a bedtime story.

    Such thoughts are not just for stories. Now they can happen in the real world, as long as you have the robot Alpha 2. Alpha 2 was a star at the 2017 World Robot Conference(大会), which was held from August 23^rd to 27^th in Beijing. More than 150 universities and companies from across the world brought their robots to the event for show and sale. Some robots work in factories. Some robots go to outer space or under water for exploration. But the highlights(亮点)of the event were service robots.

    This kind of robot is the closest to our daily lives. From cleaning to teaching, music to sports, service robots have been used to do many kinds of jobs.

    Teo is a popular service robot, as well as an artist and music teacher. His 53 fingers help him play the piano well. He played John Lennon's song Imagine at the conference.

    There is another service robot called Bestic. It acts as a human arm to feed people with a spoon. It can be a good helper for little kids, the elderly and those with difficulties using their hands.

    The scientists believe that it may not be far when every family has at least one service robot.

    A hundred years ago, most people thought that human beings would never fly. And the idea of flying seemed crazy and dangerous. But as a new world full of new inventions（发明物）came, everyone was trying to break the old thoughts. So many inventors, like Orville and Wilbur Wright, tried to make a flying thing.

    Most plane inventors at that time were impulsive. They would think of an idea, make a plane as quickly as they could, and then try to fly it as soon as possible. All of them had the same result they took their planes home and they had no idea why they didn't work.

    However, the Wright brothers were much smarter inventors. They tested their ideas in smaller or safer ones before making a real plane. For example, the Wright brothers made a wind tunnel(隧道)to compare(比较)wing shape ideas. They also flew lots of kites to test their ideas. They studied the way birds fly through the air and tried to learn something from it when making their models. Finally, the Wright brothers felt they were ready to test their planes, but they needed to find the right place. They knew the right place to test their planes after writing to the US Weather Bureau for help. At last on December 17th, 1903, Orville and Wilbur tested the plane and they made it.

    The plane flied for twelve seconds and it traveled just 120 feet, but Orville and Wilbur were very happy. Their plane really worked! By the end of the day, both brothers had great successful flights(飞行), with Wilbur having a record of 852 feet in 59 seconds.

    Is there intelligent(有智力的)life on other planets? For years, scientists said "no." or "we don't know." But today this is changing. Seth Shostak and Alexandra Barnett are astronomers(天文学家). They believe intelligent life exists(存在)somewhere in the universe. They also think we will soon contact these beings(人;生物).

    Why do Shostak and Barnett think intelligent life exists on other planets? The first reason is time. Scientists believe the universe is about 12 billion years old. "This is long enough for other planets to have intelligent life," say Shostak and Barnett. The second reason is size—the universe is huge. "Tools like the Hubble Telescope(哈勃望远镜)have shown that there are at least 100 billion galaxies, " says Shostak. "And our galaxy, the Milky Way, has at least 100 billion stars. Some planets going around these stars might be similar to Earth."

    In the past, it was hard to look for signs of intelligent life in the universe. But now, powerful telescopes(高倍望远镜)allow scientists to discover smaller planets——the size of Mars or Earth—in other solar systems. These planets might have intelligent life.

    Have beings from space already visited Earth? "Probably not," says Shostak. "It's a long way away. However, intelligent beings may contact us in other way, such as radio signals(信号). In fact, they may be trying to communicate with us now, but we don't have the right tools to receive their messages. However, this is changing. By 2025, we could make contact with other life forms in our universe and we might help each other."

Mobile phones are becoming more and more popular not only with adults but also with students. However, they also have become a problem for middle schools in the last few years.

Some children have got mobile phones as Christmas or birthday gifts, and more will ask their parents to buy phones for them.

Many students like mobile phones because they are easy and quick. Some parents feel it convenient because they can get in touch with their children. Some teachers think using mobile phones is a distraction(分心的事)to students during school hours and mobile phones also give them much trouble in their classrooms. Sometimes students send phone messages to cheat(作弊)during exams. A new study says that some teenagers even hurt their fingers because of the over-use of mobile phones. They keep using mobile phones for more than ten hours during a day.

Many teachers suggest that students should not have phones at school, but if there is a good reason, they can leave their phones at the school office. Many people think they understand why parents would want their children to have them, but they agree school should let the students know when they can use their mobile phones.