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.

    Is there intelligent(有智力的) life on other planets(行星)? For years, scientists said "No." or "We don't know." But today this is changing. Seth Shostak and Alexandra Barnett are astronomers (天文学家). They believe intelligent life exists somewhere in the universe. They also think we will soon contact these beings(人；生物).

    Why do Shostak and Barnett think intelligent life exists on other planets? The first reason is time. Scientists believe the universe is about 12 billion years old. "This is long enough for other planets to have intelligent life," say Shostak and Barnett. The second reason is size——the universe is huge. "Tools like the Hubble Telescope (哈勃望远镜) have shown that there are at least 100 billion galaxies (银河系) ," says Shostak. "And our galaxy, the Milky Way, has at least 100 billion stars. Some planets going around these stars might be similar to Earth. "

    In the past, it was hard to look for signs of intelligent life in the universe. But now, powerful telescopes (高倍望远镜) allow scientists to discover smaller planets--the size of Mars or Earth--in other solar systems (太阳系).These planets might have intelligent life.

    Have beings from space already visited Earth? "Probably not," says Shostak. "It's a long way away. However, intelligent beings may contact us in other way, such as radio signals(信号). "In fact, they may be trying to communicate with us now, but we don't have the right tools to receive their messages. However, this is changing. By 2025, we could make contact with other life forms in our universe and we might help each other.

    Today people can use the phone to talk with others almost anywhere on the earth. But when you use the phone, you don't see the person you are talking with. That may change in the near future.

    Today some people are using a kind of telephone called the picture phone or vision phone. With it, two people who are talking can see each other.

    Picture phones can be useful when you have something to show the person you're calling.

    They may have other uses in the future. One day you may be able to ring up a library and ask to see a book. Then you'll be able to read the book right over your picture phone. Or you may be able to go shopping through your picture phone. If you see something in the newspaper that you think you want to buy, you'll go to your phone and call the shop. People at the shop will show you the thing you're interested in right over the phone. You'll be able to shop all over the town and never leave your room!

     The world itself is becoming much smaller by using modern traffic and morden communication means (工具). Life today is much easier than it was hundreds of years ago, but it has brought new problems. One of the biggest problems is pollution. To pollute means to make things dirty. Pollution comes in many ways. We see it, smell it, drink it and even heart it.

    Man has been polluting the earth. The more people have, the more pollution becomes. Many years ago, the problem was nor so serious because there were not so many people. When the land was used up or the river was dirty in one place, man moved to another place. But this is no longer true.

    Man is now slowly polluting the whole world.

    Air pollution is still the most serious. It's bad for all living things in the world, but it is not the only one kind of pollution, Water pollution kills our fish and pollutes our drinking water. Noise pollution makes us angry more easily.

    Many countries are making rules to fight pollution. They stop people from burning coal in houses and factories in the city, and from putting dirty smoke into the air. Pollution by sulfur dioxide (So₂) is now the most dangerous kind of air pollution. It is caused by heavy traffic. We are sure that if there are fewer people driving, there will be less air pollution.

    The earth is our home. We must take care of it. That means keeping the land, water and air clean. And we must pay attention to the rise in pollution at the same time.

    The world got a glimpse(一瞥) of one of the greatest mysteries of our universe(宇宙) on April 10.

    That′s when the first image of a black hole was shown to the public. The picture was created by a network of eight radio telescopes(射电望远镜).

    "We have seen what we thought was unseeable, "says Shep Doeleman. He led the effort to create the image.

    The black hole is at the center of galaxy (星系)named Messier 87, some 55 million light﹣years from the earth, and is 6.5 billion times the mass of the sun.

    The image shows the gas, dust, and stars that move around the black hole before disappearing into it. It does not truly show the black hole, because not even light can escape its gravity. Black holes, like vacuums, suck(吸)in everything that gets too close.