Obama, Lady Gaga and Steve Jobs—what do they have in common? They are, of course, all Americans. And according to a survey by social networking site baidu. com, they all best illustrate(举例说明) the word “cool”.

    But just what does it mean to say someone is “cool”? Most would answer that it is something to do with being independent-minded and not following the crowd.

    Yale University art professor Robert Farris Thompson says that the term “cool” goes back to 15th century West African philosophy. “Cool” relates to ideas of grace under pressure.

    “In Africa,” he writes, “coolness is a positive quality which combines calmness, silence, and life.”

    The modern idea of “cool” developed largely in the US in the period after World War II. “Post-war 'cool' was in part an expression of war-weariness (厌战情绪), . . . it went against the strict social rules of the time,” write sociologists Dick Pountain and David Robins in Cool Rules: Anatomy of an Attitude.

    But it was the American actor James Dean who became the symbol for “cool” in the hugely successful 1955 movie Rebel without a Cause. Dean plays a tough guy who disobeys his parents and the authorities. He always gets the girl, smokes cigarettes, wears a leather jacket and beats up bullies. In the movie, Dean showed what “cool” would mean to American young people for the next 60 years.

    Today the focus of “cool” has changed to athletics (体育运动) stars. Often in movies about schools, students gain popularity on the athletics field more than in the classroom. This can be seen quite clearly in movies like Varsity Blues and John Tucker Must Die.

    But many teenagers also think being smart is cool. Chess and other thinking games have been becoming more popular in schools.

    “Call it the Harry Potterization of America—a time when being smart is the new cool,” writes journalist Joe Sunnen.

    In 1941, science fiction writer Isaac Asimov stated the Three Laws of Robotics. These laws come from the world of science fiction, but the real world is catching up. A law firm gave Pittsburgh's Carnegie Mellon University $10 million to explore artificial intelligence. Peter Kalis, chairman of the law firm, K&L Gates, said the development of technology had led to questions that were never taken seriously before. What will happen when you make robots that are smart, independent thinkers and then try to limit their freedom?

    Researcher Kalis said, “One expert said we'll be at a point when we give an instruction to our robot to go to work in the morning and it turns around and says, 'I'd rather go to the beach.'” He said that one day we would want laws to keep our free-thinking robots from running wild.

    With the law firm's gift, the university will be able to explore problems now appearing within automated industries. “Take driverless cars for example,” Kalis said. “If there's an accident concerned with a driverless car, what policies do we have in place? What kind of insurance policies do they have?” In fact, people can take a ride in a driverless car in Pittsburgh where an American online transportation network company uses the city as a testing ground for the company's driverless cars.

    The problems go beyond self-driving cars and robots. Think about the next generation of smartphones, those chips fixed in televisions, computers, fridges, etc., and the ever-expanding collection of personal data being stored in the “cloud”. So can Asimov's Three Laws of Robotics be used in reality? Is it necessary to have a moral guideline that everyone can understand? Whatever it is, doing no harm should be the very first one.

    Are people less happy or more happy the older they get? A study found that people generally become happier and experience less worry after age 50. In fact, it found that by the age of 85, people are happier with their life than they were at 18.

    The finding came from a Gallup survey of more than 340,000 adults between the age of 18 and 85 in the United States.

    Arthur Stone in the Department of Psychiatry and Behavioral Science at Stony Brook University in New York led the study. His team found that levels of stress were highest among adults between the ages of 22 and 25. Stress levels dropped sharply after people reached their fifties.

    Happiness was highest among the youngest adults and those in their early seventies. But the people least likely to report feeling negative emotions were those in their seventies and eighties. The survey also found that men and women had similar emotional patterns as they grow older. However, women at all ages reported more sadness, stress and worry than men did.

    The researchers also considered possible influences like having young children, being unemployed or being single. But they found that influences like these did not affect the levels of happiness and well-being related to age.

    So why would happiness increase with age? One theory is that, as people get older, they become more thankful for what they have and have better control of their emotions. They also spend less time thinking about bad experiences.

    The original goal of the study was to confirm the popular belief that aging is connected with increased sleep problems. The survey did find an increase during middle age, especially in women. But except for that, people reported that they felt their sleep quality improved as they got older.

    A student is learning to speak British English. He wonders: Can I communicate with Americans? Can they understand me? Learners of English often ask: What are the differences between British and American English? How important are these differences?

    Certainly, there are some differences between British and American English. There are a few differences in grammar. For example, speakers of British English say "in hospital" and "Have you a pen?" Americans say "in the hospital" and 'Do you have a pen?' Pronunciation is sometimes different. Americans usually sound theirs in words like "bird" and "hurt". Speakers of British English do not sound theirs in these words. There are differences between British and American English in spelling and vocabulary. For example, "colour" and "honour" are British, "color" and "honor" are American.

    These differences in grammar, pronunciation, spelling and vocabulary are not important, however. For the most part, British and American English are the same language.

    American and British people both speak English of course. But sometimes it does not seem like the same language. In fact, there are some important differences between British English and American English.

    First of all, they sound very different. Often, Americans don't say each word separately. They say several words together. Americans may say "I dunno" instead of "I don't know". Or they may say "Whaddaya say?" instead of "What do you say?" However, the British are more careful in their speech. They usually say all the words and keep them separate.

    Sound is not the only difference between British English and American English. Words sometimes have different meanings too. Some American words are never used in England. The same thing is true of some British words in America. For example, the vocabulary for cars and driving is very different. Americans drive trucks, but in England people drive lorries.

    Many expressions are also different in the two countries. In England，if you are going to telephone your friends, you "phone them up". In America, you "give them a call". When you are saying goodbye in England you might say "Cheerio!" In America you might say "See you later."

    There're also some differences in grammar. For example, Americans usually use the helping verb "do" when they ask a question. They say "Do you have a storybook?" But the British often leave out the helping verb. They say "Have you a storybook?"

    All these differences can be confusing if you are learning English. But most languages are like this. Languages change over time. When people live in separate places, the languages change in different ways. This is what has happened to English. It can also happen to other languages, such as French. Many people in Canada speak French, but their French is very different from the French of France.

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.