Dolphins(海豚) live in a dark underwater world. It's often impossible to see each other or anything else around them, so sound plays an important role in their survival. To communicate with each other, dolphins produce all kinds of sounds.

    Only other dolphins understand what the sounds mean. Scientists haven't uncovered their secret communication, except for one kind of whistle. It might last less than a second, but this whistle is a big deal. Why? Because these whistles are actually names of dolphins - and every dolphin has one. Scientists call these sounds a “signature whistle.” When other dolphins hear the whistle, they know which dolphin is calling.

    Dolphins often hunt by themselves but still need to stay connected to the group. Since they can't always see each other, dolphins use their signature whistles to check in with other dolphins hundreds of yards away. “In coastal areas, dolphins exchange whistles even when they're a third of a mile apart,” says Greg Campbell, who studies animals. That means dolphins shout out to group members that might be nearly five football fields away.

    What's amazing is who names the baby dolphin. Not the mother. Not an auntie dolphin or another group member. Scientists believe the baby dolphin itself comes up with the signature whistle. Like human babies, a baby dolphin plays with sounds throughout its first year. While testing its sound skills, a baby dolphin is doing something amazing. It's creating or figuring out its signature whistle. How or why it chooses its signature whistle is not clear. Studies show that most of the time the signature whistle is nothing like its mother's or group members' whistles.

    When the baby dolphin is about a year old, its signature whistle is set. It repeats it often so the other dolphins learn to recognize it.

    Deciphering(破译) dolphin names is just the beginning of figuring out what dolphins communicate about. Do they chat about sharks? Discuss the tides? Maybe they even have a name for people. Someday scientists are to decipher the rest of dolphins' communication.

    My 10-year-old Donna said, “Mom, I made a new friend at school today. Can she come over tomorrow?” Donna was a shy girl and I wanted her to make some friends to bring her out of her shell.

    “Sure, honey, that sounds great.” I said, thinking back to my own best friend, Lillian. We lived across the street from each other in Washington Heights, New York. We met at the age of 10, too. Like my daughter, I was shy, but Lillian drew me out. She was one of the friendliest people in school, with shiny black hair and a mile-wide smile.

    In senior high school, Lillian went on a trip to Florida. This was the first time we had to be away from each other for a few days. “I'll be back soon.” she told me. But three days later, Lillian's sister told me that she had fallen into a river and hadn't come out any more. Soon, my family moved to New Jersey. Whenever I thought of her, tears came into my eyes.

    The next day Donna brought her new friend home. “Hi, Mrs. Loggia.” the little girl said. Her hair was so shiny and black and she shot me a big smile. “My name is Laura.”

    My daughter's new friend was so much like Lillian. I was still puzzled (迷惑) when Laura's mom came to pick her up later that afternoon. I opened the door to let her in. “Judy!” she cried. “It's me, Lillian's sister, from Washington Heights.” Yes, my daughter's friend looked familiar. She was Lillian's niece.

    Lights out, phones on. Many teenagers reach for their smartphones or tablets at bedtime, but it may be a good idea to switch off before you hit the pillow.

    According to a study by researchers at Murdoch and Griffith Universities in Australia, using mobile devices late at night could harm teenagers' sleep and lead to an increased risk of mental health problems.

    The study was carried out on more than 1,000 Australian high school students aged between 13 and 16. It lasted four years as student participants moved from Year 8 to Year 11.

    During the study, students were asked what time of the night they received or sent text messages and phone calls, and how well they slept.

    The results are impressive. When the study started in Year 8, more than 85 percent of the students had a mobile pone and around one-third of these students never used phones after lights out. In contrast, 93 percent of Year 11 students had a mobile phone and only 22 percent of then had no late night mobile use when the study concluded four years later.

    As the levels of mobile phone use increased, there was a growth in poor sleep behavior among the students. Meanwhile, mental health problems also increased. Students in Year 8 who were more likely to use phones at night were found to have higher levels of depression (抑郁) and lower self-esteem (自尊心) one year later.

    Lynette Vernon, lead author of the study, explained that phones affect our sleep patterns because of the unnatural blue light they produce. This light could affect the level of hormones (荷尔蒙) in the body, disrupting (打乱) its balance.

     “The more you sit in bed and watch TV, play with your tablet, and play with your phone at three o'clock in the morning, the more these things affect the slow waves of your sleep pattern and give your poor quality sleep,” Mark Levi, a Sydney-based sleep doctor said.

    Based on the findings, the researchers suggested parents should focus on guiding their children's use of mobile devices.

    According to Vernon, the solution is not simply to ban teenagers from using their devices, but teach them better ways of using them

     “Back when they're aged 7 to 10, you have to be a role model. If you put your phone away at night and it doesn't go into your bedroom, it becomes normalizedin the household and you have a much easier job,” he told The Guardian.

    Dogs were living as companions to the early settlers of North America over 10,000 years ago. The oldest domestic dogs in the Americas were thought to be around 9500 years old. Angela Perri of Durham University, UK, and her colleagues have carried out fresh radiocarbon dating on the two dog skeletons that gave this date, discovered in the prehistoric Koster site in Illinois, and found they were even older: around 10,100 years old.

    A third dog from another Illinois site called Stilwell II was older still, at 10,190 years old. That makes it the oldest known domesticated dog in the Americas. The team concluded that all three dogs were domesticated as they skeletons were complete and unskinned, and so hadn't been butchered for food. They had also been carefully buried, evidence they were valued by their owners. The Stilwell II dog, which probably resembled a small English settler, was under what seemed to be the floor of a living area. It is unclear why it took so long for tame dogs to arrive in the Americas, given that they were domesticated at least 14,000 years ago in Eurasia. By this time, people were already moving into North America from Siberia; there is evidence some reached Chile 18,500 years ago. Geneticists have found signs of at least three waves of migration over the following millennia. There is no evidence that domestic dogs accompanied them. “We don't know if dogs were part of the first waves of immigration to the Americas" says Luc Janssens of Ghent University in Belgium. "It could be so, but no archaeological bones have yet been found." It is "overwhelmingly probable" that some of the early settlers did bring dogs to the Americas, but they may not have had "the time or the spiritual compulsion to bury them", says Pat Shipman of Pennsylvania State University.

    One silly question I simply can't stand is "How do you feel? Usually the question is asked of a man in action — a man on the go, walking along the street, or busily working at his desk. So what do you expect him to say? He'll probably say, "Fine, I'm all right," but "you've put a bug in his ear" — maybe now he's not sure. If you're a good friend, you may have seen something in his face, or his walk, that he overlooked that morning. It starts him worrying a little. First thing you know, he looks in a mirror to see if everything is all right, while you go merrily on your way asking someone else, "How do you feel?" Every question has its time and place. It's perfectly acceptable, for instance, to ask "How do you feel?" if you're visiting a close friend in the hospital. But if the fellow is walking on both legs, hurrying to catch a train, or sitting at his desk working, it's no time to ask him that silly question. When George Bernard Shaw, the famous writer of plays, was in his eighties, someone asked him, "How do you feel?" Shaw put him in his place. "When you reach my age," Shaw said, "either you feel all right or you're dead."

    Dr. John Wilkins was a natural philosopher who lived from 1614 until 1672. He was crazy about getting to the moon and meeting the people who surely lived there. Wilkins believed that anything as Earth-like as the moon must have been created by God for living beings, and he was determined to meet them — despite the fact that he was three centuries ahead of his time.

    In the 1600s, the scientific understanding of gravity and outer space was limited. Wilkins believed, like many 17th-century scientists, that there was no difference between the atmosphere of Earth and the conditions in space, and that Earth's pull was due to magnetism (磁力). It was only reasonable, then, that Wilkins believed a two-wheeled horse-drawn battle car with wings with enough speed could lift high enough off the ground to break free of Earth's magnetic pull and reach the moon.

    Then Wilkins moved on to more pressing issues with his remarkable ability to think of new ideas: How would travelers feed themselves during the journey? He theorized that the main cause of hunger was simply the act of working against gravity, so getting to the moon without being burdened by it would be able to be realized. There was some knowledge at that time about the fact that air gets thinner and colder the higher up you go, but he had a fix for that too, "moistened sponges (湿润的海绵) might help us against its thinness".

    By studying the way in which birds fly, which also happened to be part of the studies that led to planes and rockets centuries later, Wilkins put his theory to the test with the help of a colleague, Robert Hooke. Neither of the two ever recorded their attempts, but it's somewhat safe to say that it didn't work out. Hooke himself may have been the reason he gave up hope, in fact, since he was part of the team that discovered space was a place without oxygen.