You have never seen him,but they're with you every time you fly.They record where you are going,how fast you're traveling and whether everything on your airplane is functioning normally.Their ability to withstand（经受得住）almost any disaster makes them seem like something out of a magic book.They're known as the black box.

    When planes fall from the sky,as a Yemeni airliner did on its way to Comoros Islands in the India ocean June 30,2009,the black box is the best bet for identifying what went wrong.So when a French submarine（潜水艇）detected the device's homing signal five days later,the discovery marked a huge step toward determining the cause of a tragedy in which 152 passengers were killed.

    In 1958,Australian scientist David Warren developed a flight-memory recorder that would track basic information like altitude and direction.That was the first mode for a black box,which became a requirement on all U.S.commercial flights by 1960.Early models often failed to withstand crashes,however,so in 1965 the device（装置）was completely redesigned and moved to the back of the plane-the area least affected bu impact-from its original position in the landing wells（起落架舱). The same year, the Federal Aviation Authority required that the boxes,which were never actually black,be painted orange or yellow to aid visibility.

    Modern airplanes have two black boxes: a voice recorder,which tracks pilots' conversations,and a flight-data recorder,which monitors fuel levels,engine noises and other operating functions that help investigators reconstruct the aircraft's final moments.Placed in an insulated ( 隔绝的) case and surrounded by a quarter-inch-thick panels of stainless steel,the boxes can withstand massive force and temperatures up to 2,000℉.When in deep water,they're also able to emit signals from depths of 20,000 ft.Experts believe the boxes from Air France Flight 447,which crashed near Brazil on June 1,2009,are in water nearly that deep,but statistics say they're still likely to turn up.In the approximately 20 deep-sea crashes over the past 30 years,only one plane's black boxes were never recovered.

    Climbers at Qomolangma are being asked to clean up after themselves.

Qomolangma has earned the nickname（绰号）the World's Highest Garbage Dump（垃圾场）.

    Climbing Qomolangma,the world's highest mountain,just becomes more challenging.The government of Nepal is telling climbers they cannot leave trash on the trails.Each climber will have to come down the mountain with at the least 18 pounds of garbage.That's the average amount of trash a climber leaves behind on Qomolangma.

    Officials say climbers are responsible for their own trash.“We are not asking climbers to pick up trash left by someone else,”said the Nepal Tourism Ministry.“We just want them to bring back what they took up.”

    More than 4,000 people have reached the 29,035-foot summit（顶峰）in more than 60 years.Leaving trash along the way helps climbers keep their bags light so they have energy to reach the summit.“The trash problem in Qomolangma is not new.”Burlakoti says.“When the people started to climb the mountain,they started to leave their garbage there.”They have left behind bottles,food boxes and equipment.

    The new rule came into effect in April,2014.To make sure it is followed,climbers will have to deposit money（交保证金）before they climb.Once they climb back down the mountain,officials will check climbers at a return camp to make sure they have the required 18 pounds of trash.If they do,their money will be returned to them.If they do not,climbers will not receive their deposit and they will not be given a permit the next time they want to climb Qomolangma.

    The goal is to make sure no more litter will be left on Qomolangma."As we offer Qomolangma to all the people of the world they should take responsibility to clean it."Burlakoti says,“After seeing the results from this,we will also apply this rule to other mountains.”

    My son has poliomyelitis (小儿麻痹)and he suffered from it a lot. When he was young, my wife and I took him to see so many doctors and got different kinds of treatments. But still, he couldn't walk like a normal kid.

    So he was laughed at by his peers for his walking style. His tears burnt our eyes like sulphuric acid (硫酸 ). Then, he became afraid of going to school. He wouldn't go anymore.

    One night, my wife had a breakdown and shouted at him, “I tell you, my kid, you might be like this forever. You are a freak in other people's eyes, and perhaps it would never change. But in my eyes, in your dad's eyes, you are not a freak! You are not! Even if you are, we love you and we will love you forever!” My son spoke nothing for two days. He didn't eat or sleep. We could read he was hurt. We hoped something wonderful would fall in our family. On the third morning, he struggled to walk to my car, with his school bag in his hand of course. He raised his head high and hugged me, saying “want to go to school. Nothing will beat me.”

    You know, from then on, he was never afraid of being mocked or despised anymore. If he couldn't avoid these looks, he chose to look at them in the eyes. Later, something nice really happened and my son went to MIT. When he was asked how he managed to bear the pressure, he said, “Because of my parents.”

    My dear fellows, if you care too much about how other people look at you or what their opinions are, you will never become what you want to be.

    Why does most of the world travel on the right side today? Theories differ but there's no doubt Napoleon was a major influence. The French have used the right since at least the late 18^th century. Some say that before the French Revolution, noblemen drove their carriages on the left, forcing the peasants to the right. Regardless of the origin, Napoleon brought right-hand traffic to the nations he conquered, including Russia, Switzerland and Germany. Hitler, in turn, ordered right-hand traffic in Czechoslovakia and Austria in the 1930s. Nations that escaped right-hand control, like Great Britain, followed their left-hand tradition.

    The U.S. has not always been a nation of right-hand drivers; earlier in its history, carriage and horse traffic travelled on the left, as it did in England. But by the late 1700s, people driving large wagons pulled by several pairs of horses began promoting a shift (改变) to the right. A driver would sit on the rear (后面的) left horse in order to wave his whip (鞭子) with his right hand; to see opposite traffic clearly, they travelled on the right.

    One of the final moves to firmly standardize traffic directions in the U.S. occurred in the 20^th century, when Henry Ford decided to mass-produce his cars with controls on the left (one reason, stated in 1908: the convenience for passengers exiting directly onto the edge, especially… if there is a lady to be considered). Once these rules were set, many countries eventually adjusted to the right-hand standard, including Canada in the 1920s, Sweden in 1967 and Burma in 1970. The U.K. and former colonies such as Australia and India are among the Western world's few remaining holdouts (坚持不变者). Several Asian nations, including Japan, use the left as well—though many places use both right-hand-drive and left-hand-drive cars.

Tunnels are passageways that are built under the ground. They can also be made under a sea or a river. Some tunnels are dug through high mountains.

For hundreds of years, tunnels have been built all over the world. People use these tunnels to travel from one place to another. Some tunnels are used as waterlanes. Coal and gemstones are also brought from under the ground through long tunnels.

In the past, people dug tunnels using picks and shovels. Rocks and soil were loaded into one-wheel barrows and then onto horses and carts. This work was very tiring.

Today, engineers do a lot of planning before they start to build a tunnel. They use computers to check the level of the water and the types of rock under the ground. When they are sure the area is safe, huge machines are used to dig out the soil.

These machines have an enormous cutting wheel at the front. The wheel slowly grinds (磨碎) through the rock and soil to make the tunnel. Soil that is not needed is carried away in large trucks. As the tunnel becomes longer, it is lined with huge pipes so the walls and roof do not callapse.

Long tunnels have powerful lights to help drivers see the road ahead. Water sprinklers (洒水装置) are fitted to help keep people safe if a fire breaks out in the tunnel.

In large cities, tunnels are built under very busy roads. , People can drive through these tunnels. This makes it quicker to travel to different parts of the city.

Some trains have to wind slowly and carefully over steep mountain slopes. But, in places where there are tunnels, trains can travel quickly through the mountain to reach the other side.