Researchers have discovered the first Earth-sized planet. It was first marked by NASA's Kepler telescope(望远镜) so it's called Kepler-186f. It lies about 500 light years from Earth and goes around its star. The planet is the right distance from its star for water: not too close or not too far. Water is one important condition that scientists guess is necessary for life. So it could have water and possible life. It's called a true Earth cousin.

"This planet is an Earth cousin, not an Earth twin," said Barclay, who is among a team of scientists reporting on the discovery in the magazine Science this week.

"It's very exciting to find a planet similar to the Earth," Barclay said, "It's not easy work because things change as we get more measurements."

Scientists don't know anything about the air of Kepler-186f, but it will be a task for future telescopes which can study for chemicals that have something to do with life.

    "It's possible for life to live in this planet, but that doesn't mean there is life in it," Barclay said.

So far, scientists have found nearly 1,800 planets in the universe.

"The past year has seen a lot of progress in the search for Earth-like planets. Kepler-186f is very important because it is the first planet that is the same temperature and is almost the same size as Earth," scientist David Charbonneau wrote in an email.

    What is a museum? A museum is a good place to keep old and beautiful things. A museum may be a place to learn about science and a place to find out about art or people or animals.

    What is inside a museum? Some museums have old cars and airplanes. Many museums have pictures and statues(雕塑). Others have rocks and old bones (骨头). One museum even has a real old street inside. It has shops and people's statues doing business. It looks so real that one might feel that he was back to the old time.

    Many cities have museums. Some very small towns have museums, too. Indianapolis has a children's museum. Children do not have to pay (付款) to get in. Children often go to the museum. They like to look at the dinosaur (恐龙)bones. They see a white bear ten feet tall.

    On Saturdays, Indianapolis children can hear talks about animals and trees. They see movies. They take hikes. They even learn to make things there.

    I am a little lion. My name is Nancy. I have a big head. I'm yellow. But my favorite colour is green. I like living in the forest. I like to eat little animals. But I live in the zoo now. I don't like the zoo. I get up in the cage（笼子） in the morning. I have breakfast, lunch and dinner in the cage. I go to bed in the cage in the evening, too. People watch me every day. Some boys hit（打） me with stones（石头）. I don't like them. They are not my friends. I can't go out. I want to go back to my friends in the forest. I want to live with them.

When you do your homework, you may often meet some problems. How do you solve them? Tom, a middle school student, would take out his smartphone, open a special app (应用) and search the problem. Answers soon appear on the screen. 

Nowadays, many students do homework with the help of the special apps like Tom. "It's convenient. You don't have to go out or wait for a tutor at home," Tom said. "You also learn by seeing how others work them out. It's very helpful and improves students' abilities," said John, another student. He said it was especially true for new types of homework. 

John's Chinese teacher often asks students to give speeches on great writers. When it comes to John's turn, he usually searches online, picks out certain stories and makes PPTs (演示文稿) . "I've become skilled at finding information online and using Microsoft Office," John said. 

However, many people think this trend (趋势) also brings up problems. Some students just copy the answers online without thinking. They become lazy. 

Head teacher Mr. Wang in Tom and John's school thinks that knowing how to use the Internet is important. The key is to have good self- control. "No matter how difficult the problem is, think about it by yourself first. Remember not to depend on the Internet too much," the teacher said. "Be sure to understand the reasons behind the answers, or you won't make progress. If you don't have confidence in your self- control, ask your parents for help."