Coloring is an activity that children worldwide have long enjoyed. With a picture already made for them, kids simply chose a crayon, pencil or marker of their favorite color and fill it in. Today, it also becomes more and more popular among teenagers and even adults, who are enjoying relaxing hours of coloring. In December, five of the top ten best-selling books in the United States were coloring books.

    They are fun, but are coloring books good for you?

    The good feedback(反馈)from customers is encouraging. Trina Lucida, a popular artist creating coloring books, says that many of her customers are buying the coloring books for others who are sick or going through a hard time. She adds that the "big idea" behind her latest book is to encourage people to do something creative.

    Lucida is right, according to Allan Rohan, a psychology(心理学)professor. "Many customers think of coloring books as a new creative stage," he said in an interview, "but what's more important is that people spend time coloring in order to reduce stress after a long day." Research shows that coloring can reduce stress by guiding people to focus on(专注)one simple task. When a person is filling in a flower with a light purple color, he focuses on the flower and forgets about all his troubles in life.

    Experts add that coloring may relieve a certain kind of pain. Doing the coloring helps people relax their mind and calm down. Also, coloring helps people's brain in a healthy way. The shape of the drawing makes one side of the brain active, while the color of the drawing improves the other. Coloring can bring out your imagination and take you back to your childhood. Interesting, isn't it?

    "It's very relaxing," said Susan Jackson, a big fan of Lucida's coloring books. "Coloring frees my mind. And it's not just to try to fill blank(空白的)pages. The pictures make me happy and there is just something about them. So I'm saving the pictures I like best to the very end."

    If you put your history notes under your pillow and sleep on them the night before an exam, will you do any better in the exam? Most of us have hoped this might help. However, knowledge can't go through the pillow into your brain. But that doesn't mean you can't learn while you are asleep.

    Scientists aren't exactly sure how it works, but they have discovered that the brain can learn things during sleeping hours.

    In one experiment, researchers gave German speakers some Dutch words to learn. Then, they divide them into three groups. The researchers played the Dutch words for people in Group 1 while they were asleep, without telling these German speakers what they were doing. The sound was low. So it didn't wake them up, and only the newly introduced words were used.

    Another group listened to the same words while they were awake. The researchers found the people in Group 1 were better able to identify and translate the words later. This was true only for the words that were played while they slept. The third group listened to words when they walked. The walkers didn't have the same success remembering the words as the sleeping group.

    The researchers later found that people had more slow wave(慢波的) brain activity all over the night. They said that more slow waves made people have a better memory for the new words.

    As space science develops, man has learned more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success.

    Scientists have found out that the radiation(辐射) is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of the radiation from the sun and other stars, which is bad for their health. The harm of the radiation won't be found until their children even grandchildren are born. Some special medicine may work a little, but no really effective medicine has been found so far. Space rubbish is also thought to be a great danger to spacemen. It's reported that there were 9,000 man-made things flying in space. About 30% of these are satellites, 10% are spaceships, and the rest are space rubbish. An explosion(爆炸) in space in 1999 made a cloud of 300,000fragments, each at least 4mm in size. A small piece of these even knocked a spaceship window and caused some damage(损坏).

    Scientists are watching and reporting any possible danger all the time. They are working to deal with space rubbish. Although space is really dangerous, it interests many people on the earth. In the near future, it may become possible for people to spend a few days in a space hotel. People may even choose to leave the earth and live in space in a few years. So scientists are doing everything they can to help improve the space environment.

    Some people wonder why countries spend millions of dollars on space projects. They want to know how space research helps people on Earth. Actually, space technology helps people on Earth every day. This is called "spinoff technology". Spinoff technology is space technology that is now used on Earth.

    In early space programs, such as the Apollo missions(任务) of the 1960s and 1970s, and in the space shuttle missions today, scientists developed objects for the astronauts to use on the moon and in space. We now use some of these objects every day. For example, we have Quartz clocks and watches with an accuracy of one minute a year. We purify the water we drink with a water filter(过滤器) designed for the astronauts' use in space. The cordless, hand-held tools we use in our homes, such as cleaners, flashlights, drills, and irons came from the technology of these early space programs.

    On cold winter days, we can stay warm with battery - operated shoes and socks, and insulated(绝缘的) coats and jackets. All of these clothes are similar to the spacesuit designs that keep astronauts comfortable in the temperatures of the moon, and are spinoffs from space technology.

    These products are only a few examples of the many ways space technology helps us in our everyday life. No one knows how new spinoff technology from the International Space Station will help us in the future.

    Dinosaurs, one of the most successful groups of animals that have ever lived, evolved(进化) into many sizes and shapes. The word "dinosaur" was invented by Sir Richard Owen in 1842 to describe these "fearfully great reptiles(爬行动物) ".

    Some things to keep in mind about dinosaurs：

    ·Not everything big and dead is a dinosaur. Dinosaurs were a special group of reptiles. Although Pterosaurs(翼龙) were similar, they were not true dinosaurs.

    ·Not all dinosaurs lived at the same time. Different dinosaurs lived at different times. Although you can see Stegosaurus(剑龙) fought against Tyrannosaurus

(暴龙) in some movies like King Kong and Jurassic Park, no Stegosaurus ever saw a Tyrannosaurus. It's because Tyrannosaurus appeared on the Earth about 80 million years after Stegosaurus died out.