Smog is a big problem in many Chinese cities. But it seems that besides wearing a mask, few of us know what has caused the smog and what to do to beat it. In fact, burning too much coal and oil are the main causes of PM2.5 and smog (雾霾).

    To solve the problem, we should clean our coal and oil or replace them with cleaner energy such as natural gas. We ordinary people can do something to help control smog, too.

    What can we do to help beat the smog?

    Choose to take public transportation. Though many people have their own cars, they had better take public transportation, such as the subway or buses. If the destination (目的地) is not far away, you can also walk ________ ride a bike.

    Call the hotline 12369. You can call the number for complaints and questions about environmental issues. It is run by China's Ministry of Environmental Protection. If you call the number, some officers can come and try to solve the issues, so please remember it.

Report and resist pollutant source. If you find any pollutant source, take a picture of it and post it on your social media accounts. Remember to add “@local environmental departments” on weibo. Payattention to factories that pollute the environment and don't buy products from them.

    Our environment will become better if everyone is concerned (关注) with the environment. This is what we need in the future. So everyone can do something to beat smog.

Is there intelligent life on other planets? 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．

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 age at least 100 billion galaxies，”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 took 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．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．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 changin9．By 2025，we could make contact with other life forms in our universe and we might help each other．”

    In our daily life, robots are often found to do work that is too dangerous, boring, difficult, or dirty. And we often see kids play with toy robots.

    But what exactly is a robot? There are some important characteristics(特征) that a robot must have. These characteristics might help you to decide what is and what is not a robot. It will also help you to decide what you will need to build into a machine before it can be considered as a robot. A robot has these important characteristics.

    Sensing First of all, your robot would have to be able to sense the environment around it. 

    Give your robot sensors (传感器): light sensors( eyes ), touch sensors (hands), chemical sensors(nose), hearing sensors(ears) and taste sensors (tongue).

    Movement A robot needs to be able to move around its environment.  It can move on wheels, walk on legs or be driven by small engines(发动机). A robot can move either the whole body or just parts of it.

    Energy A robot needs to be able to power itself.  Some robots might power itself with sunlight, some might with electricity, while others with the battery(电池). The way your robot gets its energy will depend on what your robot needs to do.

    Intelligence A robot needs some kind of "smarts". A programmer is the person who gives the robot its "smarts". The robot will have to have a certain way to receive the program so that it knows what it is to do.

    How do you light up the night sky? The answer is by using electricity. But did you know that nature can glow (发光), too?

    Scientists have found many glowing living things. Most of them live in the ocean. Some use their lights to talk to each other. Others use them to hunt, to mate (交配) or to protect themselves. The vampire squid (幽灵蛸), for example, uses a cloud of light to scare enemies.

    Scientists around the world are looking at this kind of light for new ideas. In 2013, the US company Gleaux said it has created the world's first light-producing plant, the Daily Mail reported. It is a genetically-modified (转基因的) plant. It can glow like a firefly.

    Alexander Krichevsky, the company's founder (创始人), and other scientists hope that in the future, glowing plants could replace lamps and glowing trees could light up highways. Krichevsky also hopes the technology could be used in farming. Farmers could know when their crops need water or are ready to be picked if they glow.

    While Gleaux is working on glowing plants, the French company Glowee is trying to use glowing bacteria (细菌) to light up shop windows and street signs. It's the same type of bacteria that cause a type of squid to light up, New Scientist Online reported.

    "Our goal is to change the way we produce and use light," said Glowee founder Sandra Rey. "We want to help reduce the 19 percent of electricity consumption (消耗量) that is used to produce light.

    The name of our galaxy(星系), the Milky Way, comes from its appearance. It's a milky white band of glowing light that spreads across the night sky. If you look up at the evening sky, there's a good chance you will not be able to see what your grandmother saw when she was a little girl. A new study says that nearly 80 percent of people in North America can't see the Milky Way because of light pollution.

    The most light-polluted country in the world is Singapore where researchers found that people living in the country never have the chance to experience true darkness. Other countries with large percentages of people living under such skies include Qatar, Kuwait and the United Arab Emirates.

    Too much light has a direct influence on human physiology and behavior. It can also destroy our sleep cycle. What's more, it also influences wildlife. For example, baby turtles may not swim into the ocean because of street lights near shorelines.

    In the U.S., some communities have been taking action on light pollution but in developing countries, people still want to make bigger, brighter light, like LED lights. They can save energy, but on the other hand, they will increase light pollution rapidly in fact.

    There are still people that can remember when they used to be able to see the Milky Way, when they would walk outside at night, but those are becoming fewer and fewer.

    Nighttime natural scenery needs protection just like daytime scenery. Don't let the light pollution steal the chance to experience the wonder of a natural night sky from us.