The population of the Earth is growing faster. It is important that we look after the Earth. We need it!
The Earth gives us a lot of things. We also give the Earth a lot, but some of the things are not good.
In nature, when something dies, other animals and plants get food from it. Every animal or plant gives food for other animals or plants. However, animals can't get food from many of the things that we ‘give' the Earth. Animals and plants can't eat metal, plastic and glass. These things will stay in the ground for many, many years.

Some rubbish is very dangerous for plants and animals. In some places, many animals live together. One animal makes food for many more animals. If we put rubbish and chemicals in the water, the plankton(浮游生物) can die. If there isn't any plankton, many animals have nothing to eat.
So what can we do? Don't leave any rubbish in the countryside! Don't make so much rubbish!

    Scientists have been experimenting with four-leg robots for years. They want to use robots to carry heavy things over difficult land.

    But providing enough power for those kinds of robots has been a problem. Now, that has changed. Engineers at MIT have designed a running robot that runs on batteries. Scientists say their robots will soon be able to run like cheetahs, the fastest land animals on Earth.

    One difficulty in designing these types of robots continues to be providing power. These machines are still quite heavy and they need a lot of power to run. But the cheetah-like robot designed by engineers at MIT is light enough m run on batteries. The robot weighs just 30 kilograms. The robot needs only about 700 watts of power to run. This robot can actually jump 40cm high and it can land very safely and then it can run. The robots limbs and other parts were made in a three-dimensional or 3D printer. A strong, light-weight material called Kevlar is used to make the robot's part stronger.

    But the development of MITs robot is not without its own set of problems. The robot's limbs must support heavy force, and sometimes they break.

    Scientists say the new technologies used on this robot may be used in the making of limbs for disabled persons and other machines. Some of those machines may help save humans from performing difficult and dangerous jobs.

    Fraser Island is in Queensland, Australia, about 200 kilometers north of Brisbane. It is about 120 kilometers long and 240 kilometers wide. It is a very important island because it is completely made of sand. In fact, it is the largest sand island in the world. There is no airport on the island, but there is a long beach along the east coast. Planes arrive and leave from here.

    The sand makes unusual shapes. There are hills made of sand called sand blows. Nothing grows on them. They move one or two meters a year from the northwest towards the southeast of the island, getting bigger and bigger. At other places on the island, such as Rainbow Gorge, The Cathedrals and Red Canyon, the sandy rocks have different colors. Sometimes the rocks are so brown that they turn the sea brown, like coffee.

    Surprisingly, the sandy island has a lot of different plants and animals. There are dark forests—eucalyptus woods, beautiful flowers and over a hundred lakes. There are many kinds of birds, like owls and curlews. There are many animals there, too, such as crocodiles, flying foxes and wild dogs called dingoes.

    About 500,000 people visit the island every year to see the island's beauty and nature. People enjoy camping and hiking（徒步）there. Unluckily, the visitors create problems. They damage plants and frighten animals. Their sun cream（防晒霜）makes the water dirty. So it is necessary to manage the visitors. For example, people may not use motor boats or go fishing in the lakes, and they need official papers to drive there.

    Scientists found that moderate (适度的) noise can make people more creative, The New York Times reported.

    Scientists did tests on students. They divided them into four groups. They then asked the students to do certain tasks involving creative thinking. But each group did the task with different volumes (音量) of background noise. They found that students did best when working under moderate noise—70 decibels (分贝). This is about the same volume of background noise in a cafe. Students did worse in low noise (50 dB). This is the volume of a quiet room. They did the poorest when in a high-noise (85 dB) environment. This is the noise level in a factory.

    Moderate noise can distract (分心) people just enough so that they think more creatively. "It helps you think outside the box," Raci Mehta, a lead researcher in the study, said to the Business Standard. On the one hand, working in a very quiet place can strengthen our focus. But it also stops

    us from thinking abstractly (抽象).

    "This is why if you are too focused on a problem and you can't solve it," said Mehta, "you leave it for some time and then come back to it and you'll get the solution."

    However, the scientists said that when you need to do detailed things, like proofreading (校对) a paper, a quiet place is better than a noisy one.

    In today's world, almost everyone knows that air pollution and water pollution are harmful to people's health. However, not all the people know that noise is also a kind of pollution, and that is harmful to human health, too.

    People who work and live under noisy conditions usually become deaf. Today, scientists believe that 10% of the workers in Britain are becoming deaf because of the noise where they work. Many of the workers who print newspapers and who weave cloth (织布) become deaf. Plenty of people living near airports also become deaf. Recently it was discovered that many teenagers in America could hear no better than 65-year-old persons, because these young people like to listen to pop music and most of pop music is a kind of noise. Besides, noise which is produced by jet planes or machines will make people's life difficult and unpleasant. It can make people ill or even drive them mad.

    It is said that a continuous noise of more than 85 decibels (分贝) can cause deafness. Now the governments in many countries have made laws to control noise and make it less than 85 decibels.

    In China, the government is trying to solve not only air and water pollution problems but also noise pollution problems.