Chuck McCarthy originally considered becoming a dog walker to earn some extra cash, but soon realized that the job required more than walking dogs on a leash. However, walking people didn't require much when they were out on walks. Chuck realized there was money to be made if he walked people around Los Angeles instead.

    It might sound like a joke, but The People Walker, as he calls himself, is very serious about his new job. For $7 per mile, he offers to walk with clients around L.A., listening to their problems or simply making conversations and offering them a sense of security. At 6-feet, 2-inches, and sporting a bulky figure and bushy beard, Chuck doesn't look like the kind of guy you'd want to mess with.

    Chuck's services are aimed at people who need a motivational boost to go walking, those who don't feel safe walking alone in some areas, and those who are afraid that people might see them walking by themselves and think that they have no friends. "I wear my The People Walker shirt upon request and on the first walk with a new client, so they can be 100% sure it's me," McCarthy says. However, he admits some people are a bit uncomfortable with this policy, as they don't necessarily want everyone to know that they're being walked.

    So far, Chuck McCarthy has already had another five people walkers employed, covering various areas, like downtown L.A., Hollywood, Eagle Rock, or Fairfax. Once he posted signs around the city, his phone started ringing and clients began rolling in. And with all the free publicity he has been getting in the press lately, more requests are coming.

    While he hopes that his acting career will pick up soon, in the meantime Chuck is very happy with his people walking business. After all, it's literally a walk in the park and it pays the bills.

    A team of engineers at Harvard University has been inspired by Nature to create the first robotic fly. The mechanical fly has become a platform for a series of new high-tech integrated systems. Designed to do what a fly does naturally, the tiny machine is the size of a fat housefly. Its mini wings allow it to stay in the air and perform controlled flight tasks.

     “It's extremely important for us to think about this as a whole system and not just the sum of a bunch of individual components (元件),” said Robert Wood, the Harvard engineering professor who has been working on the robotic fly project for over a decade. A few years ago, his team got the go-ahead to start piecing together the components. “The added difficulty with a project like this is that actually none of those components are off the shelf and so we have to develop them all on our own,” he said.

    They engineered a series of systems to start and drive the robotic fly. “The seemingly simple system which just moves the wings has a number of interdependencies on the individual components, each of which individually has to perform well, but then has to be matched well to everything it's connected to,” said Wood. The flight device was built into a set of power, computation, sensing and control systems. Wood says the success of the project proves that the flying robot with these tiny components can be built and manufactured.

    While this first robotic flyer is linked to a small, off-board power source, the goal is eventually to equip it with a built-in power source, so that it might someday perform data-gathering work at rescue sites, in farmers' fields or on the battlefield. “Basically it should be able to take off, land and fly around,” he said.

    Wood says the design offers a new way to study flight mechanics and control at insect-scale. Yet, the power, sensing and computation technologies on board could have much broader applications. “You can start thinking about using them to answer open scientific questions, you know, to study biology in ways that would be difficult with the animals, but using these robots instead,” he said. “So there are a lot of technologies and open interesting scientific questions that are really what drives us on a day to day basis.”

    In most parts of the world, many students help their schools make less pollution. They join “environment clubs”. In an environment club, people work together to make our environment clean.

    Here are some things students often do.

    No-garbage lunches. How much do you throw away after lunch? Environment clubs ask students to bring their lunches in bags that can be used again. Every week they will choose the classes that make the least garbage and report them to the whole school.

    No-car day. On a no-car day, nobody comes to school in a car. Not the students and not the teachers! Cars give pollution to our air, so remember: walk, jump, bike and run. Use your legs! It's lots of fun.

    Turn off the water! Did you know that some toilets can waste twenty to forty cubic (立方) meters of water an hour? In a year, it would fill a small river! In environment clubs, students mend those broken toilets. We love our environment. Let's work together to make it clean.

    Reports tell us that Americans work more and vacation less than people in other major industrial countries. Still, millions of Americans do try to get away from home for a week or two in the summer months. Some might even have the time and money to spend longer on vacation.

    For example, many retired Americans can be found driving around the United States in big recreational vehicles, known as R. V.'s. These serve as a home away from home. In fact, it might even be their only home as they see the country.

    Some American families get in their cars and drive to historic places like Colonial Williamsburg in Virginia. There, they can experience what life was like for early Americans. If that is not exciting enough, also in Williamsburg is a water park and an amusement park with rides.

    Other Americans visit national parks like Yellowstone or Yosemite out in the West. They want to spend time with nature. Or they take their vacation by a lake or the ocean. They might swim or fish. But many just want to sit and enjoy the feeling of doing nothing, except maybe read a book.

    Some families fly to other countries on vacation. Or they go on a cruise ship (大型游轮) and stop in different ports. Cruise ships are like floating cities.

    But not everyone goes someplace special on vacation. This might be the only time for people to work on things like home improvement projects. And while they do that, they might think of all the fun their friends are having.

    Weighing too much can damage your health, and obesity is a growing problem for both kids and adults around the world. Sleep might be one answer to the problem. A new study has found that elementary school students who slept too little were more likely to gain pounds.

    Past studies have shown a link between sleeping less and weighing more, but scientists have had a tough time determining "which came first, the chicken or the egg," says Julie C. Lumeng of the university of Michigan in Ann Arbor. In other words, it hasn't been clear whether kids who weigh too much have trouble sleeping, or whether sleeping less leads to weight gain. Both scenarios (可能出现的情况) seemed equally possible.

    To get a better idea of which causes which, Lumeng and her colleagues interviewed the parents of 785 third graders from around the United States. The parents answered questions about how well their kids slept that year. Three years later, the parents answered the same questions. By sixth grade, 18percent of kids involved in the study were obese.

    The scientists found no relationship between weight and the students' race or gender. It also didn't matter how strict their parents were, or whether they were boys or girls. Obesity struck all of these groups equally. Instead, sleep seemed to be the key factor. Over the three years of study, the children averaged a healthy 9. 5 hours of sleep a night. Some kids, however, slept a lot more or less than others.

    For the sixth graders, every hour of sleep above the 9. 5houraverage was linked to a 20 percent lower risk of being obese. Sleep appeared doubly important for the third graders. Every extra hour of sleep they got was linked to a 40 percent drop in obesity.

    In a world with limited land, water and other natural resources (资源), the harm from the traditional business model is on the rise. Actually, the past decades has seen more and more forests disappearing and globe becoming increasingly warm. People now realize that this unhealthy situation must be changed, and that we must be able to develop in sustainable (可持续的) ways. That means growth with low carbon(低碳) or development of sustainable products. In other words, we should keep the earth healthy while using its supply of natural resources.

    Today, sustainable development is a proper trend in many countries. According to a recent study, the global market for low-carbon energy will become three times bigger over the next decades. China, for example, has set its mind on leading that market, hoping to seize chances in the new round of the global energy revolution. It is now trying hard to make full use of wind and solar energy, and is spending a huge amount of money making electric cars and high-speed trains. In addition, we are also seeing great growth in the global markets for sustainable products such as palm oil (棕榈油)， which is produced without cutting down valuable rainforest. In recent years the markets for sustainable products have grown by more than 50%.

    Governments can fully develop the potential of these new markets. First, they can set high targets for reducing carbon emissions (排放) and targets for saving and reusing energy. Besides, stronger arrangement of public resources like forests can also help to speed up the development. Finally, governments can avoid the huge expenses that are taking us in the wrong direction, and redirecting some of those expenses can accelerate the change from traditional model to a sustainable one.

    The major challenge of this century is to find ways to meet the needs of growing population within the limits in this single planet. That is no small task, but it offers abundant new chances for sustainable product industries.