If we are observant(善于观察的), we can find that most of the flowers in nature are red, orange and yellow. If we have seen a black flower, it is a chance in a million. People have made census (统计) to colors of more than four thousand kinds of flowers and discovered that only eight of them are black. Why are black flowers so rare?

    As we know, sunlight is formed by seven different kinds of colored light. The wave length of each light changes, so the quantity of heat in each light changes, too. Flowers, especially their petals (花瓣) , are very weak and easy to the harm caused by high temperature. Black flowers can take in all the light waves, which cause the flowers to dry up in a high temperature. So the black flowers can hardly continue their lives. While red flowers, orange flowers and yellow ones can protect themselves from sunlight by reflecting（反射） the red light, orange light and yellow light, each of which has a large quantity of heat.

    That is why red, orange and yellow flowers are very common in nature while black flowers are so unusual.

    Planning to get away? Think passport first

    If you're planning to get away from it all this year, you should think passport first. Checking you have a valid passport before you book your trip takes minutes but could save you the trouble and cost of not being able to go.

    Renewing (更新) your passport before it runs out

    You can renew your passport up to 9 months before it can no longer be legally used. So take the time now and save the tears later.

    Applying for a passport for the first time

    Our eligibility (资格) checks mean that it takes a minimum of one week to issue (颁发) a passport. So make sure you don't leave it to the last minute, and apply in plenty of time.

    Help with your application is just around the corner

    Selected Post Office branches and World choice travel agents offer a Check and Send service that helps you with your application. It's convenient and you should receive your passport within 2 weeks.

    If you need to apply for or renew a passport, you can either:

    Pick up a Passport Application Form at Selected Post Office branches and World choice travel agents.

    Or call the Application Form Request line on 0901 4700 100 or visit www.passport.gov.uk

    If your need is urgent, call 0870 521 0410 for an appointment at one of our offices. We can't guarantee to see customers without an appointment.

    From 14th January a guaranteed same day (passport renewals only) or one week service will be available from passport public counters.

    Calls will be charged 60p per minute and the cost per call should not normally be more than 90p.

    Calls are charged at national rates.

    How does a sunset work? We love to look at one, but Jolanda Blackwell wanted her eighth-graders to really think about it and question.

    So Blackwell had her students watch a video of a sunset as part of a physics lesson on motion. "I asked them: ' So what's moving And why' " Blackwell says. Some thought the sun was moving; others knew that a sunset is the result of the Earth spinning around on its axis. "Usually, my biggest challenge is trying to keep them patient," she says. "They just have so many burning questions."

    "Every day, we meet new information," says Charan Ranganath, a psychologist. Ranganath was curious to know why we keep some information and forget other things. So he got 19 volunteers and asked them to review more than 100 questions. When the participants' curiosity was aroused, the parts of' their brains that regulate pleasure and reward lit up. Curious minds also showed increased activity in the brain, which is involved in greater memories.

    "Curious brains are better at learning not only about the subject at hand but also dull information. This is a phenomenon teachers can use in the classroom," says Evie Malaia, a professor. "Say a kid wants to be an astronaut," she says. NL Well, how do you link that goal with learning multiplication tables(乘法表)" "A teacher may choose to ask her class an interesting word problem that involves space exploration," Malaia says. Students may remember the answer to the word problem, but they'll also remember how they found the answer through multiplication.

    What Ranganath wants to know most is why some people seem naturally more curious than others. Lots of factors, including stress, aging and certain drugs  affect dopamine(多巴胺) processing in the brain. "If we could figure these things out, we could help those who may just seem bored," Ranganath says.

    Blackwell says she doesn't have to deal with that problem too often. She says her students love exploring the mysterious unknowns in science: What happens when a car crashes. How do rainbows work "I tell my kids there's no dumb questions," Blackwell says. "That's science: asking questions and seeking answers."

    Nisha Pradhan is worried. The recent college graduate just turns 21 and plans to live on her own. But she's afraid she won't be able to stay safe. That's because she isn't able to smell.

    Back home, her family do her smelling for her. She's moved in with them for now, but she's looking for a place of her own. “Now that I'm searching for ways or place to live as an independent person, I find that the sense of smell is important to how we live our lives,” Pradhan says.

    She says when she was a child she liked to eat and ate a lot. But there came a point where she lost interest in food.

    “One of the first things that people notice whenever they have a smell problem is that food doesn't taste right any more,” says Beverly Cowart, a researcher. That's because eating and smell go hand in hand. How food tastes often rely on what we smell. “When you lose your sense of smell, your whole sense of food flavors changed and reduced,” Cowart says, “You can still taste the basic tastes. What you're missing are the small distinctions.”

    “When I go out to eat I have often found that food is very tasteless to me. I never feel full,” she says. “I think a lot of us today like to pretend to be food lovers and we all like to talk about 'Oh, I think this could use a little bit more flavor,' or ‘I think this has a hint of meat,' I can't really participate in those conversations,” she says.

    Pradam thinks her smell loss also may have affected her memory. Pradhan may be on to something, according to biologist Paul Moore. “When smell signals come in, you feel about them first. And then you think about it and then the memory is laid down. So without the feel part, the thinking about its part doesn't come. And that means no new smell memory gets created.”

    In the ongoing battle between Tiger Moms, French Mamas, and everyone else who wants to know what is the best way to raise their kids, a new study adds evidence that the extreme Tiger-style may do more harm than good. Authoritarian parents are more likely to end up with disrespectful children with violent behaviors, the study found, compared to parents who listen to their kids with the goal of gaining trust.

    It was the first study to look at how parenting styles affect the way teens view their parents and, in turn, how they behave. The study considered three general styles of parenting. Authoritative parents are demanding and controlling while also being warm and sensitive to their children's needs. Authoritarian parents, on the contrary, are demanding and controlling without the appearance of caring, attachment and receptiveness. They take a "my way or the highway" approach to their kids. Permissive parents, the third group, have warm and receptive qualities, but they set few boundaries and carry out few rules.

    Using data on early 600 kids from an ongoing study of middle school and high school students in New Hampshire, researchers from the University of New Hampshire were able to find "my way or the highway" parenting with more violent behaviors like robbery, drug-taking, and attacking someone else with the intention of hurting or killing. Firm but loving parenting, on the other hand, led to fewer lawbreakers. Permissive parenting, surprisingly, didn't seem to make much of a difference either.

    To explain the link between parenting style and behavior in kids, the researchers suggested that what matters most is how reasonable kids think their parents' power is. This sense comes when kids trust that their parents are making the best decisions for them and believe that they need to do what their parents say even if they don't always like how their parents are treating them. When kids respect the power of their parents, the researchers reported in the journal of Adolescence, their behavior is better. Previous research has also linked firm but caring parenting with kids who have more self-control and independence.

    "When children consider their parents to be the reliable figure, they trust the parents and feel that they have a duty to do what their parents tell them to do," said lead researcher Pick Trinkner. "This is very important as the parent doesn't have to rely on a system of rewards and punishments to control behavior and the child is more likely to follow the rules when the parent is not physically present."

Friends play an important part in our lives, and although we may take friendship for granted, we often don't clearly understand how to make friends. While we get on well with a number of people, we are usually friends with only a very few — for example, the average among students is about 6 per person. In all the cases of friendly relationships, two people like one another and enjoy being together, but beyond that, the degree of intimacy between them and the reasons for their shared interests vary greatly. As we get to know people, we take into account things like age, race, economic condition, social position, and intelligence. Although these factors are not of great importance, it is more difficult to get on with people when there is a marked difference in age and background.

Some friendly relationships can be kept on argument and discussion, but it is usual for close friends to have similar ideas and beliefs, the same opinions and interests — they often talk about "being on the same wavelength". It generally takes time to reach this point. And the more intimately involved people become, the more they depend on one another. People who want to be friends have to learn to put up with annoying habits and to stand differences.

In contrast with marriage, there are no friendship ceremonies to strengthen the association between two people. But the supporting and understanding of each other that results from shared experiences and emotions does seem to create a powerful bond, which can overcome differences in background, and break down barriers of age, class or race.