You can tell a lot about people by looking at their hair – not just whether they brush, spray or blow-dry. Scientists have found a way to use hair to figure out where a person is from and where that person has been. The finding could help solve crimes, among other useful applications.

    Water is central to the new technique. The liquid makes up more than half an adult human's body weight. Our bodies break water down into hydrogen(氢) and oxygen. Atoms of these two elements end up in our tissues, fingernails, and hair.

    But not all water is the same. Hydrogen and oxygen atoms can vary in how much they weigh. In the case of hydrogen, for example, there are three types according to their weights. Each type is called a hydrogen isotope（同位素）. And depending on where you live, tap water contains different isotopes.

    Can hair record this information? That's what James R. Ehleringer, an environmental chemist at the University of Utah, wondered. To find it out, he and his colleagues collected hair from hair stylists in 65 cities across the United States. Even though people drink a lot of bottled water these days, the researchers have found that people's hair has the same isotopes as found in local tap water. That's probably because people usually cook their food with the local water.

    Authorities can now use the information to analyze hair samples from criminals or crime victims and narrow their search for clues. For example, one hair sample used in Ehleringer's study came from a man who had moved from San Francisco to Salt Lake City. As his hair grew, it reflected his change in location.

    Throughout history scientists have risked their health and their lives in their search for the truth.

    Sir Issac Newton, the seventeenth century scientist was very smart, but that didn't stop him from doing some pretty stupid things. In his laboratory in Cambridge, he often did the strangest experiments. Once, while testing how light passes through lenses (晶状体), he put a long needle into his eye, pushed it to the back, and then moved it around just to see what would happen. Luckily, there was no lasting bad effect. On another occasion, he stared at the sun, for as long as he could bear, to discover what effect this would have on his sight. To escape suffering permanent damage, he had to spend some days in a dark room before his eyes recovered.

    In the 1750s, the Swedish chemist Karl Scheele, was the first person to find a way to produce phosphorus (磷) He, in fact, discovered eight more chemical elements, including Chlorine (氯), though he didn't get any place for them. He was a very clever scientist, but he had a strange habit of tasting a little of every substance he studied. This risky practice finally caught up with him. In 1786, he was found dead in his laboratory, surrounded by a large number of dangerous chemicals, any of which might have been responsible for his death.

    Eugene Shoemaker was a respected geologist, he spent a large part of his life studying craters (陨石坑), and how they were formed, and later the research into the comments of the plane Jupiter. In 1997, he and his wife were in the Australian desert, where they went every year search for places where comets (彗星) might have hit the earth. While driving in the Tanam desert, one of the most open places in the world, another vehicle rushed into them, and Shoe maker died on the spot. Some of his ashes (骨灰) were sent to the moon by the Lunar Prospect or, a spacecraft, and he is the only person who has this honor.

    Charlie is a teacher and his wife, Maria is an artist. The night before last, just before the longest day of the year, Charlie was sitting in a deckchair enjoying the warm summer air when Maria touched his shoulder and he could tell immediately she was a little worried about something. He asked her what the matter was and she replied that there was a strange thing on the jacket that was hanging in the bedroom. They had both lived in the West Indies (西印度群岛) and had seen a lot of strange creatures in their house before. But now they were living in England and so Charlie just laughed and said he would have a look at the “thing”.

    He walked to the bedroom. He saw a jacket hanging in the bedroom and went up to it to have a closer look at the “thing”. The moment he touched it, the thing sprang into life. Now Charlie experiences fear like the rest of us but when this creature opened its wings, he jumped out of his skin and ran screaming from the room like a small child doing about 100 miles an hour.

    For a moment the next-door neighbours thought that Charlie was murdering his wife because of the noise they could hear. In fact, it was a bat that frightened Charlie.

Eventually Charlie managed to trap the bat in a box and took it to the garden to let the bat fly. Maria, who had been playing the guitar while Charlie was upstairs, asked Charlie if he had found out what the thing was. “Oh, nothing to worry about”, he said casually hoping that the terror could not be seen in his eyes, “it was just a bat.”

    A lifetime of active exercise will let you keep the body of a 20-year-old well into your 70s, scientists have found.

    The physical decline (衰退) thought to be an unavoidable part of ageing is actually the result of not exercising enough, according to the research, which found that regular cyclists kept the muscles, lungs, and even the immune system (免疫系统) of people years younger. Besides, many serious health problems could be prevented if people became more active, researchers insist.

    Janet Lord, a leading researcher, said, “Our findings prove the false belief that ageing automatically makes us weaker. We now have strong evidence that encouraging people to do regular exercise throughout their lives can solve the problem that we are living longer but not healthier.”

    She looked at 125 cyclists aged 55 to 79 who had been exercising regularly for 25 years and compared them with 75 ordinary people of a similar age and 55 people aged 20 to 36. On a series of physical measures, the cyclists showed no difference from people much younger in their immune systems and making T cells.

    Now Professor Lord aims to discover how much exercise people need to do to stay young. “You needn't work out a lot. It may be intensity (强度) that helps—like going up and down the stairs ten times a day.”

    While there is no magic method of staying mentally and physically fit in later life, the benefits of keeping active can never be ignored, whatever your age or state of health.

    My teacher, Mr. August J. Bachmann, was the most influential teacher I ever had.

    I had gotten into trouble in his class: Another student had pushed me for fun, and I became angry and began to hit him. Mr. Bachmann stopped the fight, but instead of sending me to the office, he sat me down and asked a simple question, "Penna, why are you wasting your life？Why aren't you going to college?"

    I didn't know anything about colleges or scholarships. No one had ever considered that a fatherless boy from the poorest neighborhood had a future. That day, instead of rushing off for lunch, he stayed and explained possible education options to me. At the end of our talk, he sent me to see a secretary who had a child at a state college. This was in 1962 at Emerson High School in Union City, New Jersey.

    Well, 55 years have passed, and what have I done with the knowledge he gave me？I gained a PhD from Fordham University when I was only 29.I taught English and social studies and then moved up the chain of command from teacher to principal(校长).

    I've sat on the board for Magnet Schools of America and represented that organization at the United Nations. I've won a number of great educational awards. But where would I be if a truly caring teacher had not taken the time out of his lunch period to speak to me? It was without question only his confidence in me that helped me forward.

    I have repaid his kindness hundreds of times by encouraging misguided youngsters to aim higher. If I have saved any children, it is because of him. If I have been a successful educator, it is because I had a great role model in Mr. Bachmann.

    Twenty years ago, I drove a taxi for a living. One night I went to pick up a passenger at 2:30 a.m. When I arrived to collect, I found the building was dark except for a single light in a ground floor window.

    I walked to the door and knocked, "Just a minute," answered a weak, elderly voice. After a long pause, the door opened. A small woman in her eighties stood before me. By her side was a small suitcase.

    I took the suitcase to the car, and then returned to help the woman. She took my arm and we walked slowly toward the car.

    She kept thanking me for my kindness. "It's nothing," I told her. "I just try to treat my passengers the way I would want my mother treated."

    "Oh, you're such a good man." She said. When we got into the taxi, she gave me an address, and then asked, "Could you drive through downtown?"

    "It's not the shortest way," I answered quickly.

    "Oh, I'm in no hurry," she said. "I'm on my way to a hospice(临终医院). I don't have any family left. The doctor says I don't have very long."

    I quietly reached over and shut off the meter(计价器).

    For the next two hours, we drove through the city. She showed me the building where she had once worked, the neighborhood where she had lived, and the furniture shop that had once been a ballroom where she had gone dancing as a girl.

    Sometimes she'd ask me to slow down in front of a particular building and would sit staring into the darkness, saying nothing.

    At dawn, she suddenly said," I'm tired. Let's go now."

    We drove in silence to the address she had given me.

    "How much do I owe you?" she asked.

    "Nothing." I said.

    "You have to make a living," she answered. "Oh, there are other passengers," I answered.

    Almost without thinking, I bent and gave her a hug. She held onto e tightly. Our hug ended with her remark, "You gave an old woman a little moment of joy."