Earthquake rescue (救援) robots experienced their final tests in Beijing, The inventors of this robot said with this robot, rescuers would be able to buy more time to save lives during an earthquake.

This kind of robot is able to fly. It's about three meters long, and it took about four years to develop the model. Its main function is to collect information from the air and send goods of up to 30 kilos to people trapped (困住) by an earthquake. It has an excellent camera which can provide very clear pictures. It can work day and night, and is also able to send the latest pictures from the quake area.

Dr. Qi Juntong, a researcher from Tsinghua University, said, "The most important character of this flying robot is that it doesn't need a control from faraway paces. We just set in it the information of the places where it should go, and then it takes of, and lands by itself. It flies as high as 30000 meters, and as fast as 100 kilometers per hour."

This robot has a different function一it can change as the environment changes. Its main job is to search for any signs of life in places where human rescuers are unable to go. The camera, also acting as a detector (探测器) that finds trapped people and detects harmful gases, is placed in the robot, which can work in the dark, With its 10 - mer - long pipe in the robot, people who are trapped in the fallen buildings will be able to get supplies including oxygen (氧气) and water.

Experts have said that the robots would enter production and serve as part of the national earthquake rescue team as soon as possible.

We see humans all around us. But when was the first human seen? Early humans did not leave behind any written records. However, they left behind many paintings on the walls of the caves(洞穴) where they lived. These paintings tell about their life, and we know these early humans walked on four limbs(四肢) like apes (猿). Also, they did not live at one place but moved from place to place in search of food and water.

Without any tools, early humans used stones, bones of animals, and sharp pieces of wood to dig, hunt and cut their food. They also used these to protect themselves from animals. Since stones were used to make tools, this age was called Stone Age.

With time going, tools made of bones and stones were replaced with metal(金属的) ones which were stronger, sharper, and long-lasting. Metals were also used for farming and making knives. Copper(铜) was the first metal to be used.

The first fire that early humans noticed was natural fire caused by lightning(闪电). With fire, early humans could now light up dark caves. They could keep themselves warm during cold weather and cook meat. Also the fire could drive animals away.

Early humans noticed new trees growing from the seeds(种子) that fell to the ground from the fruits. This gave them the idea that they could make their own food by planting seeds, which led to farming. With the beginning of farming, early humans began to settle down(定居). They moved out of the caves and lived on farms and near their fields together, then the first villages came up.

Raising animals was a big event in human history that changed the life of early humans. The wild dogs were probably the first animal to be raised. As time went, goats, sheep, cows, donkeys, and horses were kept, too. This led to herding(畜牧业). Milk, meat and wool came from these animals.

Scientists say they've developed a new system(系统). It can use "machine learning" to predict when and where lightning(闪电)will strike(闪击). The research was led by engineers from Switzerland.

European researchers have estimated(估算) between 6,000 and 24,000 people are killed by lightning worldwide each year. The strikes can also cause power cuts, destroy houses and start forest fires. For these reasons, some climate scientists have studied to develop methods to predict and control lightning. But no system has been created to effectively predict lightning.

The new system is being tested in the experiments(实验). It used a combination of data(数据资料) from weather stations and machine learning methods. The researchers developed a prediction model. It was trained to tell weather conditions that were possible to cause lightning.

The model was created with some data. The data was collected over a 12-year period from 12 Swiss weather stations in cities and mountain areas. The data related to(与……有关)four main surface conditions: air pressure, air temperature, relative humidity(相对湿度)and wind speed.

The atmospheric(大气的) data was put into a machine learning algorithm(计算程序), which compared it to records of lightning strikes. Researchers say the algorithm was then able to learn the conditions under which lightning happens.

Amirhossein Mostajabi is a PhD student who led the development of the new system. He said, "Common systems for collecting such data are slow and complex, and they require expensive collection equipment(设备)like radar or satellites (卫星)."

"Our system uses data that can be gotten from any weather station," Mostajabi said. "This will improve data collection in the areas which are not covered by radar and satellites or in places where communication systems have been cut," he added.

On a hot day, many people like to go to the beach. Some beaches, however, are not safe for swimming.

At some beaches, there are sharks in the water. So people put out shark nets. They help stop too many sharks from getting close to the beach. Sharks can still swim under or around the net. But if they try to swim through, they will get caught. Sharks can die if they are not cut free.

Shark nets don't just catch sharks. They can catch other animals, too. They have caught dolphins, stingrays and turtles. Even a whale has been caught in a shark net. I took many people to get it free.

Some animals are not so lucky. They are killed in the nets. One day, a whale was swimming with her calf. The calf got caught in a shark net. The mother whale tried to get the calf to come with her. The calf was caught in the net. It couldn't get free. The mother had to watch it die.

Many people think shark nets should not be used. Sharks are important to the ocean. They eat sick and dead fish, They help to keep the ocean clean. Sharks are the lions and the tigers of the sea.

Some people think there are other ways to keep beach safe for people Sharks potters are people who watch for sharks. They go to a high place Then they can look down on the beach. If they see a shark, a siren（汽笛）will sound. They put up a white flag Then people get out of the water.

After all, the water is a shark's home.