【推荐1】Mars (火星) is a planet (行星). It is the fourth planet from the sun and is more than 200,000,000 kilometers from it. That is a very long way. Mars is also a very long way away from Earth but sometimes you can see it clearly at night. Most stars are white. But Mars is a little red. It is a very big planet. It is about half the size of Earth. The planet Earth has one moon. Mars has two moons. They are called Phobos and Deimos.

Long ago, the only way to study Mars was just to look at it. People with good eyes could see some things but not everything. Later on, it was easier, because scientists had telescopes (望远镜). They could see Mars come clearly. They learnt much more about Mars this way. In the twentieth century (世纪) things got even better. First of all, we had spacecraft. They flew close to Mars and sent back information. Then, they sent spacecraft to fly around Mars. Finally, spacecraft landed (着陆) on Mars.

Maybe one day a man will walk on Mars.

【推荐2】Hey! The people of the earth. Can you hear this radio message? Do not be afraid! We come in peace from another planet— and why not? We are your cousins. We are men, as you are. We have been here before.

You will see a huge spaceship, a few hours from now. We are flying towards the solar system (太阳系) almost as fast as this radio message. Your sun is already in sight. Our ancestors (祖先) and yours shared the sun ten million years ago. I’m sure you have forgotten your history while we have remembered ours.

Our ancestors lived on the Earth when dinosaurs were dying. Sadly, they could hardly save the beasts. Your planet was very warm then. Our ancestors believed it would make a nice home for them.

They were wrong. Though we were masters of space, we knew so little about the Earth.

For millions of summers — there were no winters in those ancient days — the Earth had rapid (飞速的) development. It took about thirty years to fly from one planet to another, so our ancestors seldom travelled in space. But they never felt lonely. They kept in touch with their relatives and friends on other planets. Three or four times every century, starships would call and bring them space news.

But two million years ago, the Earth began to change. The temperatures fell quickly. The ground was covered with snow and ice. At that time, however, our ancestors knew little about that. Those who had called the Earth their home believed there was just a strange disease spreading on the earth. The disease wouldn’t cause death to them, but it would bring much pain and do harm to men’s health.

A group of scientists discovered a gas called phosphine(磷化氢) on Venus(金星). That means there may be living things on the planet, which made many people start to imagine the talk between aliens and humans. A reporter from Washington Post wrote a letter to people of Earth on behalf of(代表) the citizens on Venus.

【推荐1】Eggshells are just thin, but you may be surprised at how strong they are. Let’s do an experiment.

What you need

● Four eggs   ● Sharp scissors（锋利的剪刀） ● Tape（胶带） ● An adult helper   ● A bowl

● Phone books or hardcover books

What you do

● Dig a hole in the small end of each egg and make it larger to pour the eggs into the bowl. Give the eggs to your helper— they are used for cooking. Wash and air-dry the shells.

● Stick the tape around each egg’s widest point; carefully break away shells between tape and hole.

● Put shells on the floor in a square and gently put a book on them. Add more books and see how strong the eggshells are.

What has happened

Eggshells are strong because they work the same way as an arch（拱门）. Put weight on one place, and the curving（弯曲的）shell spreads the force all around the egg. The strong wall of the shell supports the weak point.               

In ancient times, people usually wrote from right to left in vertical columns (竖列). But now, we write from left to right in horizontal rows. Why has it changed like this?

This has to do with the writing tools and habits that people had back then. Before paper was created, people wrote on bamboo slips. The thin slips were connected by small pieces of string (线). People wrote from top to bottom on one piece and then another. The slips were then connected together into one long passage.

After being connected, the slips were rolled up. While opening a roll, people usually held it with their right hand and opened it with their left hand. Therefore, it made more sense to start writing from the right-hand side.

Near the end of the Qing Dynasty (1644—1911), some people began to spread western ideas and suggested that Chinese people follow the Western writing habit. In 1917, linguist (语言学家) Qian Xuantong wrote a letter to the New Culture Movement leader Chen Duxiu, suggesting writing Chinese characters from left to right. He said that if we used our right hands to write, it would be easier to begin from the left. It would be more comfortable to read, too. However, this idea wasn’t widely accepted.

In the early 1950s, famous overseas Chinese businessman and philanthropist Chen Jiageng and Chinese writer Guo Moruo raised this suggestion again. Gradually, the texts of newspapers, magazines and books were printed in horizontal rows. People got used to writing from left to right in rows.

Have you ever stayed up late one night? Did you feel tired the next day? Did you feel bad-tempered? It is because your body missed its sleep! So why does a good night’s sleep make you feel better?   

Scientists have studied sleep to find the answer to this question. They have found some different reasons.

First, sleep helps your body stay healthy. Even though you are sleeping, your body is still active. Sleep gives your body a chance to repair itself.

Sleep also helps your body to rest. How? Your body does not need as much energy when it slows down. The beat of your heart and your breathing rate become slower, which lowers your body’s energy level. Your body needs rest after a busy day.

Sleep is important for your brain too. During the day your brain gathers information. At night while you are sleeping, your brain reviews everything that you did during the day. It saves some of your experiences so you can remember them. Some scientists think all this reviewing causes you to dream.

What happens if you do not have enough sleep? People who miss too much sleep have trouble paying attention. They make more mistakes in their work. Scientists believe that people who miss more than three days of sleep may become sick and even start seeing something that is not really there.

Students need between 8 and 10 hours of sleep each night. What can you do to help give your body a good night’s sleep?

Ways to help you sleep.

♦Run and play outside during the day. 

♦Drink a glass of milk before going to bed. 

♦Go to bed on time.

♦Read a book in bed.

♦Have a dark, quiet room.

Following these steps and you will begin to feel relaxed and happy. Nothing else will help your body like a good night’s sleep.

【推荐2】It might be fun to use your smartphone, but be careful. Too much screen time may be harmful to your health.

It is bad for your eyes. A researcher says the problem comes from the blue light that the screen gives out. Looking at a smartphone for a long time can cause eye strain (劳损), headaches and dry eyes. So it is a good idea to take a break every 15 minutes when you are using a smartphone.

Screen use can do harm to children’s brains. A new study shows that using screens too much can influence how children’s brains grow. If children use screens for more than one hour a day, they might have lower levels of white matter in their brains. White matter is a key to the development of language and reading skills. So it is wise to cut down the time of children using all kinds of screens.

Using screens too much will influence your sleep. According to a study, about 5% of the people between the ages of 13 and 64 use electronics before bed, especially the young people under 20. Doctors say that the light from those electronics at night may make you excited before you go to bed. Then it’s hard for you to get enough sleep. So you’d better turn off smartphones, TVs and other screens an hour before your bedtime.