In 1971 a young man who grew up very poor was travelling across the country, trying to make a new start for himself. Along the way he had completely run out of(用光) money and was forced to spend the night in his car. This continued until one morning, after a week of sleeping in his car, he walked nervously into a restaurant and ordered a big breakfast.

    After eating his first good meal in weeks, he found himself lying to the waiter, telling him he had lost his wallet. The waiter, who was also the owner, walked behind the chair where the young man had been sitting. He bent down, and came up with a $20 bill that looked as if it had fallen on the floor and said, “Son, you must have dropped this,” the owner said. The young man couldn't believe his luck! He quickly paid for the breakfast, left a tip, bought gas with the change, and headed West.

    On the way out of town, he began to understand what the owner did. Maybe nobody dropped the money at all. “Maybe that fellow just knew I was in trouble and he helped me in a way that didn't embarrass(使尴尬) me. So I just made a promise to help other people if I can.”

    Later, he worked very hard and became a rich man. Now he lives near Kansas City. Each year he gives away thousands of dollars. He is known as the “Secret Santa” because at Christmas time each year, he personally hands money out to those on the street and at restaurants. Last year, he gave more than $50,000 away in Kansas City.

    In 1880, fourteen-year-old Matthew Henson loved to hear sailors tell tales of their exciting lives at sea. The travel, the adventure, the danger, and the steady pay were all attracting young Henson. One day, he found a job as a cabin boy on a beautiful ship called the Katie Hinds. For the next five years, Henson sailed around the world. With the help of the ship's captain and other members of the crew, Henson learned mathematics, navigation, history, geography, and many other subjects. By the time he left the Katie Hinds in 1885, Henson was well educated and had become an excellent seaman.

    Unable to find work anywhere else, Henson took a job in a hat shop in Washington, D.C. One day in 1887, a man came in to buy a hat. The man, Robert Peary, asked the owner if he knew anyone with experience at sea. Peary would soon travel to South America for the U.S. government. He needed experienced men to accompany him. The shop owner knew about his young employee's skills and experience on ocean journeys, so he introduced Peary to Henson.

    Using his map-reading and sailing skills, Henson proved himself to be a worthy and smart seaman. Peary soon made Henson his assistant（助理）, and they became close friends. One day Peary told Henson about his real dream: to be the first man to stand on “the top of the world” at the North Pole. He asked Henson to help him make his dream come true. Over the next five years, the two explorers made two trips together to the Arctic. However, they were not able to reach the pole either time. The cold, wind, and ice were worse than either of them had ever imagined.

    In 1908, Peary and Henson were ready to make their final attempt at reaching the North Pole. Both men were over forty years old. The years of hardship in the arctic cold had made them suffer a lot. This would be their last chance. With four Inuit（因纽特）guides, they made a mad rush straight across the ice toward the pole. Peary's feet were injured and he had to be pulled on a dogsled. In April 1909, Henson's instruments showed they were standing at the North Pole. Together Henson and Peary planted the American flag in the snow.

    In later years, Robert Peary and Henson were greatly honored for their achievements. Today, the two friends and fellow explorers lie in heroes' graves not far apart in the Arlington National Cemetery.

    It was the last time Susan Butcher ran the Iditarod Trail Sled Dog Race in 1992. An hour into the race, Susan and her sled dog team sped down a hill and crashed into a fallen tree. Although hurt, Susan continued the difficult race.

    The Iditarod Race started in 1925 when a doctor in Nome, Alaska was desperately in need of medicine to stop the spread of a deadly disease. Only a hospital had what he needed, but it was 700 mile-away! In January, it was too dangerous to send a boat and too stormy for his tiny airplane. The only hope was to use several sled dog teams following a trail, called the Iditarod Trail. They passed the medicine from one sled team to another. Wind and snow did not stop the men and their dogs. The medicine was delivered in record time. The race follows the route of the famous medicine run. Over 1,000 miles long, it is considered the toughest race in the world.

    Susan Butcher was born in Cambridge, Massachusetts. In her teens Susan was given a Siberian husky dog and became very interested in huskies as sled dogs. After reading about the Iditarod Race, Susan moved to Alaska. She got several jobs to earn money to buy herself a sled and a team of huskies. After years of hard work and training, Susan achieved her dream of racing on the Iditarod Trail.

    In 1978, at the age of 24, Susan entered the race for the first time and became the first woman to finish in the top 20. In 1982 she came in second. In 1984 she was leading her team across a frozen waterway when they fell into the water. Her lead dog managed to pull Susan and the other dogs out of danger. Remarkably, she came in second.

    In her fourth race, in 1985,a starving moose(驼鹿) attacked her dogs, killing two and injuring eleven. Susan had to leave the race. In 1986 Susan joined the race again. This time, she won. She won again in 1987. In 1988 she became the first person ever to win three Iditarod races in a row. Unbelievably, Susan won for the fourth time in 1990.

    A few weeks ago, I called an Uber to take me to the Boston airport for a flight home for the holidays. As I slid into the back seat of the car, the warm intonations(语调) of the driver's accent washed over me in a familiar way.

    I learned that he was a recent West African immigrant with a few young children, working hard to provide for his family. I could relate: I am the daughter of two Ethiopian immigrants who made their share of sacrifices to ensure my success. I told him I was on a college break and headed home to visit my parents. That's how he found out I go to Harvard. An approving eye glinted at me in the rearview window, and quickly, we crossed the boundaries of rider and driver. I became his daughter, all grown up — the product of his sacrifice.

    And then came the fateful question: "What do you study?" I answered "history and literature" and the pride in his voice faded, as I knew it might. I didn't even get to add "and African-American studies" before he cut in, his voice thick with disappointment, "All that work to get into Harvard, and you study history?"

    Here I was, his daughter, squandering the biggest opportunity of her life. He went on to deliver the age-old lecture that all immigrant kids know. We are to become doctors (or lawyers, if our parents are being generous) — to make money and send money back home. The unspoken demand, made across generations, which my Uber driver laid out plainly, is simple: Fulfill your role in the narrative(故事) of upward mobility so your children can do the same.

    I used to feel anxious and backed into a corner by the questioning, but now as a junior in college, I'm grateful for their support more than anything. This holiday season, I've promised myself I won't huff and get annoyed at their inquiries. I won't defensively respond with "but I plan to go to law school!" when I get unrequested advice. I'll just smile and nod, and enjoy the warmth of the occasion.

    Dogs are our best friends. That's especially true after a disaster, such as an earthquake. When buildings fall down, search and rescue dogs help find trapped people. Dogs' amazing noses can pick up the smell of survivors. Now scientists have developed an electronic tool that does the same thing. It's taking smell detection(探测) to a whole new level.

    The new invention is a sort of electronic nose, which can detect extremely low levels of many compounds(化合物) from people's skin. This isn't the first time engineers have developed such an object. Earlier models, however, have been bulky and expensive. They could not detect low levels of target compounds either. The new one is inexpensive and small enough to fit inside hand-held equipment.

    The electronic nose can detect extremely slight smell of more than one compound at the same time. "Being able to do this, in such a small object, is the significant discovery," says Sotiris E. Pratsinis, Professor of Process Engineering&Materials Science at the Swiss Federal Institute of Technology in Zurich. His team tested it in special spaces. They were like the small spaces where people might be trapped. Chemicals given off by the volunteers built up inside. The electronic equipment detected those compounds at unbelievably low levels.

The results were good news for the research team. But they may be not for our four-legged friends, who could soon be out of a job. "Ideally, this technology could replace search and rescue dogs," Pratsinis says.

    Stephen Taylor, an electrical engineer, agrees that the new technology has some benefits over dogs. Still, he thinks it may be too soon to have our trusty friends retire. He suspects, "I foresee that such an object could add to the fine work done by the dogs." Taylor also pointed out some potential limitations of the new invention. "E-noses are useful, but can be very likely to be affected by unstable readings and interruption," he says.

    Three men traveling on a train began a conversation about the world's greatest wonders.

    "In my opinion, "the first man said, "the Egyptian pyramids are the world's greatest wonder. Although they were built thousands of years ago, they are still standing. And remember: the people who built them had only simple tools. They did not have the kind of machinery that builders and engineers have today."

    "I agree that the pyramids in Egypt are wonderful," the second man said, "but I do not think they are the greatest wonder. I believe computers are more wonderful than the pyramids. They have taken people to the moon and brought them back safely. In seconds, they carry out mathematical calculations that would take a person a hundred years to do."

    He turned to the third man and asked, "What do you think is the greatest wonder in the world?"

    The third man thought for a long time, and then he said, "Well, I agree that the pyramids are wonderful, and I agree that computers are wonderful, too. However, in my opinion, the most wonderful thing in the world is this thermos."

    And he took a thermos out of his bag and held it up.

    The other two men were very surprised. "A thermos?" they exclaimed. "But that's a simple thing."

    "Oh, no, it's not," the third man said. "In the winter you put in a hot drink and it stays hot. In the summer you put in a cold drink and it stays cold. How does the thermos know whether it's winter or summer?"