There are many different kinds of pollution in our world. It is very common to hear about pollution in the air and water, but have you ever heard of light pollution?

Light pollution is a man-made problem, and it has increased by 50% in the last 20 years. The bright lights in big cities make people’s life safer and easier. However, they have affected the health of people and animals around the world at the same time.

Everyone has their own natural sleep-wake cycles (周期). For many people, darkness is important to tell the body that it is time to relax and go to sleep. When there is too much light in the environment, the body produces less melatonin (褪黑激素), which makes sleeping difficult. Being in a bright environment at night can also increase worry and stress.

Our bright lights are harmful to many animals, too. Take birds for example. Birds use the light of the moon to migrate (迁徙), but with so much man-made light in the environment, they often get lost.

Many countries and groups have taken action against light pollution. There are some things that you can do for protection from light pollution. For example, stop using your electronic devices (设备) one or two hours before you go to sleep. Also, turn off lights that you are not using, especially those outside.

Anger is a kind of feeling. Many things can make you angry. When your teacher gives you too much homework, when your team loses an important game, when a friend borrows your favorite thing and then breaks it, you may get really angry.

Usually, your body will tell you when you are angry. For example, you breathe faster, your face turns red, and you may want to break something or hit(打) someone, but sometimes, you hide(隐藏) your anger. For example, you may hide it in your heart. The problem is that if you do this, you may get a headache or your stomach may hurt.

In fact, it’s not good to hide your anger, and it’s normal for you to get angry sometimes. But anger must be let out in the right way, without hurting others or yourself.

When you get angry, you can talk about it with other people. It’s helpful to talk about your anger with an adult, such as parents, a teacher, etc. When you talk about anger, those bad feelings can start to go away. Here are some other things you can do when you start to feel angry: talk to a good friend; count from 1 to 100; give someone a hug(拥抱); go for a bike ride; think about good things, etc.

Remember that how you act when you are angry can make everything better or worse. Don’t let your anger control you.

Many people wear face masks (口罩) when staying out these days. But do you know that they have a history of thousands of years?

The earliest face mask-like objects date back to the 6th century B.C. in Persia. According to the study, religious priests (宗教祭司) needed to wear masks when they honored ancestors. They thought the masks could cover their mouths and noses when they held outdoor ceremonies in front of the holy fire altar (圣火坛) to prevent from spitting out (吐口水) when they spoke, which showed their respect (尊敬) to the ancestors. Some people in the drawings of that time were wearing a piece of cloth over their faces. In the 14th century, a serious illness called the Black Death spread to many European countries. French doctor Charles invented a special mask. The mask looked like the head of a bird. It completely covered the wearer’s face. The wearer had to see through the glass in the mask. The medicine in the mask protected the wearer from illnesses. The face masks we use today were invented in China. In 1910, a serious illness spread in northeastern China. The Chinese medical scientist Wu Liande carried out research with very careful medical methods. He discovered that the illness could quickly spread through people’s breath. Then he invented “Wu’s mask” and advised people to wear it. Within four months, the illness was under control. Since it was cheap and easy to make, the mask was widely praised by the experts in the world.

Over the past few years, some scientists have tried to develop the face mask. Today, face masks are among the world’s best-selling products.