See a cellphone cover that you like on Taobao? Forget about placing an order, paying the bill online and waiting for days for it to be delivered to you. In the near future, you'll be able to get it in minutes just by hitting “print” on your computer.

    You might find it hard to believe that you could actually “print” an object like you would a picture. But it is not that hard to understand how it would work. Just as a traditional printer sprays ink onto paper line by line, modern 3D printers spread material onto a surface layer by layer, from the bottom to the top, gradually building up a shape.

    Instead of ink, the materials the 3D printer uses are mainly plastic, resin(树脂) and certain metals. The thinner each layer is—from a millimetre to less than the width of a hair—the smoother and finer the object will be.

    This may sound like a completely new technology, but the truth is that 3D printing has been around since the late 1980s. Back then, it was barely affordable for most people, so few knew about it.

    Last year, though, saw a big change in the 3D printing industry—printers became much cheaper. For example, 10 years ago a desktop 3D printer might have cost ￡20，000, while now they cost only about ￡1，000, according to the BBC.

    Taken out of the factory and introduced to more diverse and common uses, 3D printing can create just about anything you can think of—flutes , bikinis, jewelry, aircraft parts and even human organs. In fact, scientists from Cornell University in New York have just made an artificial ear using a 3D printer, according to Science Daily. The fake ear looks and acts exactly like a natural one.

    However, as 3D printing becomes more common, it may bring about certain problems—such as piracy. “Once you can download a coffee maker, or print out a new set of kitchen utensils (餐具) on your personal 3D printer, who will visit a retail  store again？” an expert in 3D printing told Forbes News. Even more frightening, what if anyone in the world could use a 3D printer to print out a fully functioning gun?

    A survey said the average Asian dad spent one minute a day with his children. I was shocked. I mean, a whole minute? Every day? Get real. Once a week maybe. The fact is, many Asian males are terrible at kid-related things. In fact, I am one of them.

    Child-rearing (养育) doesn't come naturally to guys. My mother knew the names of our teachers, best friends and crushes. My dad was only vaguely aware there were short people sharing the apartment. My mother bought healthy fresh food at the market every day. My dad would only go shopping when there was nothing in the fridge except a jar of butter. Then he'd buy beer. My mother always knew the right questions to ask our teachers. My dad would ask my English teacher if she could get us a discount on school fees. My mother served kid food to kids. My dad added chili sauce to everything, including our baby food.

    The truth is, mother have superpowers. My son fell off a wall once and hurt himself all over. I demanded someone bring me a computer so I could google what to do. My wife ignored me and did some sort of chanting(咏诵) phrase such as “Mummy kiss it better,” and cured 17 separate injuries in less than 15 seconds.

    Yes, mothers are incredible people, but they are not always correct. Yet honesty forces me to record the fact that mothers only know best 99.99 percent of the time. Here are some famous slip-ups.

    The mother of Bill Gates: “If you're going to drop out of college and hang out with your stupid friends, don't come running to me when you find yourself penniless.” The mother of Albert Einstein: “When you grow up, you'll find that sitting around thinking about the nature of time and space won't pay the grocery bills.” The mother of George W. Bush: “You'll never be like your dad, who became President of the United States and started his own war.”

    Sports can help us a lot. Taking exercises can make us strong. In collective（集体的）sports like basketball, volleyball or football, we will learn the importance of cooperation(合作). And sports can also help us relax after work or study.

    However, as the saying goes, "there are two sides of everything." Sometimes we may hurt other players or ourselves if we are not careful enough when participating(参加) in sports activities. What's more, too much or hard practice can be bad for our health.

    Sports can make us healthy both physically and psychologically(心理地). It is also a good way for people to know each other and can improve friendship between people. So long as we are careful enough, sports can do us nothing but good.

    American schools do not have separate classes for boys and girls. If boys want to cook or to sew, they can learn these things in classes that are no longer just for girls. If girls want to repair cars, they can now learn this in school. Most students like to have boys and girls on the same baseball team.

    Many boys and girls dress alike in school. They wear blue jeans and sport shirts. Some have long hair and some have short hair. Sometimes a boy has longer hair than a girl.

    Even the language is different. Students learn to say fire fighter instead of fireman, police officer instead of policeman, and letter carrier instead of mailman. A person does not need to be a man to fight a fire or to deliver the mail.

    Most people think that these changes are great. They give all people an equal chance to be happy and to do what they want to do with their lives. Fathers like to tell their sons that they can grow up to be president. Today, mothers can tell the same things to their daughters.

    Time talks. It speaks more plainly than words. Time communicates in many ways.

    Consider the different parts of the day, for example. The time of the day when something is done can give a special meaning to the event. It is not customary to telephone someone every early in the morning. If you telephone him early in the day, the time of the call shows that the matter is very important and requires immediate attention. If someone receives a call during sleeping hours, he assumes it is a matter of life or death. The time chosen for the call communicates its importance.

    In social life, time plays a very important part. In the United States, guests tend to feel they are not highly regarded if the invitation to a dinner party is extended only three or four days before the party date. But this is not true in all countries. In other areas of the world, it may be considered foolish to make an appointment too far in advance because plans which are made for a date more than a week away tend to be forgotten.

    The meaning of time differs in different parts of the world. Thus, misunderstandings often arise between people from cultures that treat time differently. Promptness(准时) is valued highly in American life, for example. If people are not prompt, they may be regarded as impolite or not fully responsible. In the U.S., no one would think of keeping a business partner waiting for an hour; it would be too impolite. A person who is five minutes late is expected to make a short apology.

    This way of treating time is quite different from that of several other cultures. This helps to explain the unfortunate experience of a certain agriculturist from the United States, assigned to duty in another country. After a long delay, the agriculturist was finally agreed an appointment with the Minister of Agriculture. Arriving a little before the appointed hour, the agriculturist waited. The hour came and passed. At this point he suggested to the secretary that perhaps the minister did not know he was waiting in the outer office. This gave him the feeling of having done something to solve the problem, but he had not. Twenty minutes passed, then thirty, then forty-five. To an American, that is the beginning of the "insult period". No matter what is said in apology, there is little that can remove the damage done by an hour's wait in an outer office. Yet in the country where this story took place, a forty-five-minute waiting period was not unusual.

    In the West, particularly in the United States, people tend to think of time as something fixed in nature. As a rule, Americans think of time as a road stretching into the future, along which one progresses. The road has many sections, which are to be kept separate— "one thing at a time". People who cannot plan events are not highly regarded. Thus, an American may feel angry when he has made an appointment with someone and then finds a lot of other things happening at the same time.

    Since time has such different meanings in different cultures, communication is often difficult. We will understand each other a little better if we can keep this fact in mind.

Many scientists today are convinced that life exists elsewhere in the universe—life probably much like that on our own planet. They reason in the following way.

    As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist.

    Life requires the right amount and kind of atmosphere. This eliminates(除去) all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere; a larger one would hold too much of it.

    Life also requires a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify.

    Finally, life could evolve(进化) only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away.

    If we suppose that every star in the universe has a family of planets, then how many planets might support life? First, eliminate those stars that are not like our sun. Next eliminate most of their planets; they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out.

    This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.