How the Grand Canyon (大峡谷) was created remains one of the geology's greatest mysteries. Some evidence suggests that the process was a gradual one in which the Colorado River (which runs through the canyon) slowly cut deeper and deeper into the ground over millions of years. But volcanic rock samples taken from the canyon now suggest that the canyon was down-cut instead.

    Down-cutting is when a flood of water rushes over a landscape (地形) with enough force to cut deeply into the ground and leaves behind a canyon. Such a flood is usually released when a natural or man-made dam (堤坝) bursts.

    Robert Webb, a research geologist, says natural dams seem to have formed and broken across the Colorado River several times during the last million years. The dams were built when lava(熔岩) from the eruptions of nearby volcanoes flowed into the river. The lava hardened into hard rocks and blocked the river, causing it to back up and form a lake. Each time the lake grew so huge that it broke the rock dam, releasing a flash flood that furthered the down-cutting process and deepened the canyon.

    Down-cutting is not just an earthly event. Satellite photos sent back from Mars suggest that the process has happened there, too, say many other researchers.

    The photos, taken by the Mars Global Surveyor, indicate that an enormous lake existed on Mars 3.5 billion years ago. The lake spilled into a large nearby hole. One edge of the hole broke, releasing a flash flood that quickly carved out a grand canyon.

    The existence of down-cutting on Mars is just one more piece of evidence that the cold, dry planet was once warm and wet.

    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.”

    Many animals recognize their food because they see it. So do humans. When you see an apple or a piece of chocolate you know that these are things you can eat. You can also use other senses when you choose your food. You may like it because if smells good or because it tastes good. You may dislike sonic types of food because they do not look, smell or taste very nice. Different animals use different senses to find and choose their food. A few animals depend on only one or their senses, while most animals use more than one sense.

    Although there are many different types of food, some animals spend their lives eating only one type. The giant panda eats only one particular type of bamboo. Other animals eat only one type of food even when given the choice. A kind of white butterfly will stay on the leaves of a cabbage, even though there are plenty of other vegetables in the garden. However, most animals have a more varied diet. The bear eats fruits and fish. The fox eats small animals, birds and fruits. The diet of these animals will be different depending on the season.

Humans have a very varied（广泛的）diet. We often eat food because we like it and not because it is good for us. In countries such as France and Britain, people eat foods with too much sugar. This makes them overweight, which is bad for their health. Eating too much red meat and animal products, such as butter, can also be bad for the health. Choosing the right food, therefore, has become an area of study in modern life.

    With more than 100,000 people aged 100 or over, Spain is the country with the greatest life expectancy after Japan. How do you live to 100? Here 4 of the country's centenarians (百岁老人) give their advice on staying youthful.

Francisco Nunez, 112

    He is from Bienvenida, Badajoz, southern Spain. Nunez lives with his daughter. He says he doesn't like the pensioners' (领养老金的人) daycare center because it's full of old people, whose negative attitude towards life affects him deeply sometimes. Despite his old age. he has always maintained (保持) a youthful outlook, and that is what has kept him going on.  Pedro Rodriguez, 106

    He lives in Cangas de Onis, Asturias, northern Spain. Rodriguez plays the piano every day in the living room of the flat where he lives with his wife who is nearly 20 years younger than him. Their daughters visit them often. His hobby is something that he feels has kept him young. "The nuns (修女) taught me how to play the piano as a child," he says.

    Maximino San Miguel, 102

    He lives in Leon, northern Spain. San Miguel discovered his passion (酷爱) for amateur dramatics at the age of 80 and has participated in many local productions. He didn't go to school as a child because he was sent to work as a shepherd (牧羊人). He prefers reading books about drawing and traveling. Now this hobby, he said, has kept him full of energy.  Pilar Fernandez, 101

    She lives with her daughter Pili, granddaughters Flori and Ana in Ambas, Asturias, northern Spain. Fernandez suffered hunger and hardship during the war years alongside her nine brothers and sisters. To avoid history repeating itself, she limited herself to just one child. "From pure fear, I didn't have anymore," says Fernandez. One of the best things for her health, she says, is tending livestock (家畜) and a vegetable garden.

    Have you ever been afraid to talk back when you were treated unfairly? Have you ever bought something just because the salesman talked you into it? Many people are afraid to speak out for their rights. Dr Robert Albert, author of Stand Up, Speak Out, and Talk Back thinks it's because their self-respect is low.

    But Albert and other scientists are doing something to help people help themselves. They offer "assertiveness training" courses A. T. for short. In the A. T. Course people learn that they have a right to be themselves. They learn to speak out and feel good about doing so. They learn to help themselves without hurting other people.

In one way, learning to speak out is to get rid of fear, a group taking an A. T. Course will help the shy person to lose his fear. But a. T. uses an even stronger motive— he needs to share. The shy person speaks out in the group because he wants to tell how he feels. Whether or not you speak up for yourself depends on your self-respect. If someone you face is more "important" than you, you may feel less of a person. You start to doubt your answers to problems. You can get to feel good about yourself. And once you do you can learn to speak out.

    Birdbrain has long been a term when laughing at somebody. The common opinion is that birds' brains are simple. But that opinion has increasingly been called into question because crows and parrots, among other birds, have shown behaviors as smart as that of chimpanzees.

    The conflict of simple brain and complex behavior has led some neuroscientists (神经学家) to create a new map of the birdbrain.

    Today, in the journal Nature Neuroscience Reviews, an international group of bird experts is showing their opinion. Nearly everything written in anatomy (解剖学) textbooks about the brains of birds is wrong, they say. The bird brain is as complex, and creative as any mammal brain, they argue, and it's time to use a more exact term that shows a new understanding of the anatomies of bird and mammal brains.

    "Names have a powerful influence on the experiments we do and the way we think," said Dr. Erich, a neuroscientist at Duke University and a leader of the Bird Brain Terms Association. "Old term has prevented scientific progress."

    The association of 29 scientists from six countries met for seven years to develop new, more exact names for structures in both bird and mammal brains. For example, the bird's seat of intelligence or its higher brain is now named the pallium (大脑皮层).

    "The change of terms is a great advance," said Dr. Jon Kaas, a leading expert in neuroanatomy at Vanderbih University. "It's hard to get scientists to agree about anything."

    Scientists have come to agree that birds are indeed smart, but those who study bird intelligence differ on how birds got that way. Experts are split into two warring camps. One holds that birds' brains make the same kinds of internal (内在的) connections as do mammal brains and that intelligence in both groups arises from these connections. The other holds that bird intelligence developed through increasing an old part of the mammal brain and using it in new ways and it questions how developed that intelligence is.