Up to two thirds of children don’t get as much sleep as they should do, and this can make them nervous and slow at school, scientists say.

So how long should children sleep each night? The answer is between 8 and 10 hours. If they don’t get enough sleep at night, they will have less energy the next day. Even losing one hour’s sleep a night can children do less well at school.

But the researchers say many children have missed out on 4, 500 hours of sleep by the time they are seven years old. They say that children miss sleep because they have TVs and computers in their rooms, and busy parents don’t read to their younger children at night any more. The traditional “bedtime story” helps children relax and fall asleep peacefully（平静地）. Children with TVs and computers in their bedrooms are more likely to sleep badly, and to get less than eight hours sleep.

German scientists think that your brain（大脑）keeps working while you’re asleep. To show that they were right, they gave two groups of people a problem to work out. One group went to sleep, and the other group stayed awake（醒着的）. The result? The people who slept worked out the problem more quickly, suggesting that their brains had been trying to find the answer while they were asleep.

So, make sure you get enough sleep tonight, and you’ll be at your best tomorrow!

It’s sad to learn that a whale has died in the ocean. However, that’s not the end for the whale. It has a lot to give to other sea animals after death.

When a whale dies, it quickly sinks to the bottom of the ocean floor. There, the whale carcass provides food and nutrients to deep—sea animals, which are often hungry for food. The remains can last for decades and create a complex ecosystem called a whale fall—an “oasis” of life in the deep sea.

Chinese scientists found a whale fall for the first time in the South China Sea during a deep-sea expedition carried out by oceanic research vessel Tansuo-1, which finished its expedition on April 2. Tansuo-1 carried the manned submersible Shenhai Yongshi, which can dive to a depth of 4, 500 meters.

The whale fall in the South China Sea is about three meters long. Scientists have found several species of shrimp and fish near the whale fall. Some fish have started to eat the whale’s tail. The whale fall might be quite recent and needs long-term observation, according to Xie Wei, a scientist who took part in the expedition.

The whale fall ecosystem can exist in the deep ocean because great pressure and cold temperatures there prevent the body from decomposing too quickly. But the depth also makes it hard for scientists to discover them. There are less than 50 known whale falls in the world.

By studying the whale fall, scientists can better understand how marine ecosystems support life and how to protect biodiversity resources in the deep sea.