【推荐2】Worn-out tires are no good for a car, right? But they can be good for another type of transportation: walking!

In Zimbabwe and in many other countries, old tires are not thrown away. Instead, craftsmen cut them up and make them into sandals (凉鞋). One of these craftsmen is Casper Mamutse, who runs a small sandal-making business just outside his house.

When Casper first saw a man named Issac wearing tire sandals, he thought they looked funny. So he asked Issac where he got them. Issac said he had made them himself. Casper decided to buy a pair of make his friends laugh, but his friends didn’t laugh. Instead, they wanted their own,” Finally, I asked him to teach me how to make tire sandals.”, says Casper.

For more than six months, Casper learned how to cut shape sloes (鞋底) from tires. To make the right size, Casper traces a shoe on the tire and cuts out a sole,” Cutting a tire with a knife requires as much brains as strength.” he says. “You have to use a lot of power and concentration of else you will cut your finger along with the tire.” After the sole is cut, Casper tears off the soft inside part of the tire and cuts it into strips (带状物). He attaches the strips to the sole for “belts”. From one tire, Casper can make about four pairs of sandals for adults or about six pairs for kids.

The Zimbabwe countryside is full of sharp stones. Unless you have thick soles, your shoes can be easily pierced (刺穿). But strong boots are expensive, and many people walk barefoot. But now they can get tire sandals, which are strong enough and much less expensive than leather shoes.

Fedzai, a 10-years-old boy, thinks that what his friends need now are not cars to take them to school, but shoes.” Going to school on foot instead of in a car does not bother me very much,” he says, “After all, we are still moving on tires.”

【推荐3】A team of engineers at Harvard University is trying to create the first robotic fly. 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.

“The added difficulty with a project like this is that actually none of its components(部件) is off the shelf and so we have to develop them all on our own,” said Robert Wood, a Harvard engineering professor.

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 interdependences(相互依赖) 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.

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.

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 on technologies and open interesting scientific questions that are really what drives us on a day to day basis.”

【推荐2】Yousuf and his family left their home in eastern Afghanistan eight years ago. They went to the city of Kabul to escape war, but they could not escape sadness. Five of Yousuf's children died in the Afghan capital, not from violence, but from air pollution.

Kabul has become one of the most polluted cities in the world. On many days, a mix of smog and smoke lies over the city. In some cases, families burn whatever they can to keep warm in cold weather. The air in their own homes then poisons them. Many years of war have worsened the damage to Afghanistan's environment. At the local Children's Hospital, doctors say they have seen the number of patients with pollution-related health problems increase. Saifullah Abassin, a doctor at the hospital, says his hospital ward(病房) can hold 10 patients but often has three times that number.

“Thirty years ago, it was a wish for people to come to Kabul and breathe its air,” said Ezatullah Sediqi, deputy director for the National Environmental Protection Agency. “But in the wars since, we lost all our urban infrastructure(基础设施) for water, electricity, public transportation, green areas, all these things.”

Kabul's environmental department has started a program to control old vehicles, one major source of pollution. City officials have called on people to use fuel instead of burning garbage for heat. But there are other steps officials need to take, such as passing a plan to stop unplanned development and creating more green spaces.

【推荐3】A recent experiment held in Japan shows that it is almost impossible for people to walk exactly straight for 60 meters. Tokyo University of Agriculture and Technology found 20 healthy men and asked them to walk as straight as possible to a target 60 meters away at normal speed. Each man had to walk on white paper fixed flat to the floor wearing wet coloured socks. The footprints revealed that all walked in a winding rather than a straight line. Researchers found that people readjust（重新调整)the direction of walking every few seconds. The amount of the winding differed from subject to subject. This suggests that none of us can walk in a strictly straight line. We walk in a winding way mainly because of a slight structural or functional imbalance of our limbs (四肢). Although we may start walking in a straight line, several steps afterwards we have changed direction.

Eyesight helps us to correct the direction of walking and leads you to the target. Your ears also help you walk. After turning around a lot with your eyes closed, you can hardly stand still, let alone walk straight.

It’s all because your ears help you balance. Inside your inner ear there is a structure which contains liquids. On the sides of the organ are many tiny hair-like structures that move around as the liquid flows. When you spin (旋转) the liquid inside also spins. The difference is that when you stop, the liquid continues to spin for a while. Dizziness (眩晕) is the result of these nerves in your ear. When you open your eyes, although your eyesight tells you to walk in a straight line, your brain will trust your ears more, and thus you walk in a curved line.