In its early history, Chicago had floods frequently, especially in the spring, making the streets so muddy that people, horses, and carts got stuck. An old joke that was popular at the time went something like this: A man is stuck up to his waist in a muddy Chicago street. Asked if he needs help, he replies,“No, thanks. I've got a good horse under me.”

    The city planners decided to build an underground drainage(排水) system, but there simply wasn't enough difference between the height of the ground level and the water level. The only two options were to lower the Chicago River or raise the city.

    An engineer named Ellis Chesbrough convinced the city that it had no choice but to build the pipes above ground and then cover them with dirt. This raised the level of the city's streets by as much as 12 feet.

    This of course created a new problem: dirt practically buried the first floors of every building in Chicago. Building owners were faced with a choice: either change the first floors of their buildings into basements, and the second stories into main floors, or hoist the entire bulidings to meet the new street level. Small wood-frame buildings could be lifted fairly easily. But what about large, heavy structures like the Tremont Hotel, which was a six-story brick building?

    That's where George Pullman came in. He had developed some house-moving skills successfully. To lift a big structure like Tremont Hotel, Pullman would place thousands of jackscrews(螺旋千斤顶) beneath the building's foundation. One man was assigned to operate each section of roughly 10 jackscrews. At Pullman's signal each man turned his jackscrew the same amount at the same time, thereby raising the building slowly and evenly. Astonishingly, the Tremont Hotel stayed open during the entire operation, and many of its guests didn't even notice anything was happening.

    Some people like to say that every problem has a solution. But in Chicago's early history, every engineering solution seemed to create a new problem. Now that Chicago's waste water was draining efficiently into the Chicago River, the city's next step was to clean the polluted river.

    The world has lost one of its brightest stars. British physicist Stephen dies on March 14, at the age of 76.

    Hawking is probably the world's most famous scientists after Albert Einstein. He is an expert on black holes. He has devoted his whole life to digging into the beginning (and the end) of the universe. “My goal is simple,” Hawking once said. “It is to completely understand the universe, why it is as it is and why it is there at all.”

    Hawking's achievements are even greater if you think about his disability. When he was 21, Hawking caught a bad illness that slowly stopped him form moving or talking. For a period of time, he had no way to communicate except by blinking（眨眼）. Later he sat on a wheelchair with a computer by his side. To communicate, he moved two fingers to control the computer's mouse. He selected his words from the screen, which were then spoken by a voice synthesizer（音响合成器）.

    “I have had the disease for most of my life,” Hawking once said. “Yet it has not stopped me from being successful at my work.”

    Though Hawking was a disabled man, he made great achievements. He received many awards and prizes for his work during his lifetime. This included winning the Albert Einstein Award, which stands for the highest achievement in theoretical physics.

    Despite the fact that he's no longer with us, his legacy will surely live on. As Sajid Javid, a UK government minister, put it, “A brief history on Earth; an eternity in the stars.”

    Some of the world's most significant problems never hit headlines. One example comes from agriculture. Food riots（暴动）and hunger make news. But the trend lying behind these matters is rarely talked about. This is the decrease in the growth in production of some of the world's major crops. A new study by the University of Minnesota and McGill University in Montreal looks at where, and how far, this decline is occurring.

    The authors take a vast number of data points for the four most important crops: rice, wheat, corn and soyabeans. They find that on between 24% and 39% of all harvested areas, the improvement inproduction that took place before the 1980s slowed down in the 1990s and 2000s.

    There are two worrying features of the slowdown. One is that it has been particularly sharp in the world's most populous countries, India and China. Their ability to feed themselves has been an important source of relative stability both within the countries and on world food markets. That self-sufficiency (自给自足) cannot be taken for granted if productions continue to slow down.

    Second, production growth has been lower in wheat and rice than in corn and soyabeans. This is problematic because wheat and rice are more important as foods, accounting for around half of all calories consumed. Corn and soyabeans are more important as feed grains. The authors note that "we have preferentially focused our crop improvement efforts on feeding animals and cars rather than on crops that feed people and are the basis of food security in much of the world."

    The report also states the more optimistic findings of another new paper which suggests that the world will not have to dig up a lot more land for farming in order to feed 9 billion people in 2050, as the Food and Agriculture Organisation has argued.

    Instead, it says, thanks to slowing population growth, land currently ploughed（犁）up for crops might be able to revert (回返) to forest or wilderness. This could happen. The trouble is that the prediction assumes continued improvements in productions, which may not actually happen.

    Field Trip Day

    On Friday, May 16, our class will take a field trip to North Park Zoo. The zoo has lions, elephants, and other interesting animals. Many of the animals we have been studying will be there for us to closely examine.

    Our class will be divided into six teams. Each team will have five students and one leader. The leaders are listed in the table.

    What You Need to Know

    The cost is $1.00 for students to enter the zoo. We will leave the school at 9:00 a.m. and return at 2:30 p.m.

    On the morning of the trip, the students will be divided into teams. One student from each team will receive a camera. The cameraman will take pictures of the team, the animals, and other fun sights at the zoo.

    All members should wear blue shirts. Be sure to wear comfortable shoes because we will be walking all day. Please bring a bag lunch and a drink. We will have a picnic at the park inside the zoo. Bring a healthy snack, such as a piece of fruit and a drink, for later in the day.

    When we are at the zoo, always remain with your team. Do not leave the team without asking permission from the team leader.

    Feeding the Animals

    The ONLY animals that students are allowed to feed are those in the children's Zoo. Special food can be bought at the zoo for 25 cents and given to these animals. Do not feed your lunch to them. It is not food for the animals.

Benefits and Problems of Genetic Engineering

    Plant breeding is the science of changing the characteristics of plants in order to produce desired ones. Genes in a plant are what determine what type of characteristics it will have. Plant breeders try to create a specific outcome of plants and potentially new plant varieties by changing the genes of the plants through breeding, which is making new plants from parents of different varieties or species.

    Actually, plant breeding has been practiced for thousands of years, since near the beginning of human civilization. It is practiced worldwide by individuals such as gardeners and farmers and by professional plant breeders employed by organizations such as government institutions, universities, crop-specific industry associations or research centers. They have crossbred plants to create the new types of plants that are, for example, bigger, stronger, or more attractive.

    Crossbreeding can take such a long time, however, and it is inaccurate. Now, we can change exact sections of Deoxyribonucleic acid (DNA), so the process is more accurate and faster. But people all over the world are arguing about its benefits and disadvantages. Some people use the technology to produce desired characteristics of plants and animals. Other people are concerned that the genetically engineered plants may harm the environment and worried that they may be dangerous for people to eat.

    There are many reasons for changing plants in this way. International development agencies believe that breeding new crops is important for ensuring food security by developing new varieties that are higher yielding(高产的), disease resistant, drought tolerant or regionally adapted to different environments and growing conditions. For example, some genetically engineered plants can live through frost or draught. As a result, famers can make more profit because fewer plants will die.

    Some genetically engineered plants are more nutritious. They have less fat, taste better or stay fresher than non-genetically engineered plants. This will allow people to buy better-quality fruit and vegetables.

    Some genetically engineered plants can resist natural pests such as viruses or insects. This reduces the amount of chemical needed to kill pests, which is helpful to the environment.

    However, genetically engineered plants can cause unexpected problems. Genetically engineered plants that resist pests may pass on that characteristic to a wild relative. This may cause the wild plant to spread fast, because pests are not naturally killing it.

    Genetically engineered plants can also harm animals. A type of corn has been developed which kills a species of insect that destroys it. The pollen (花粉) from this corn, however, can also kill monarch butterflies—the most beautiful of all butterflies, which do not harm the corn.

    To ensure the most adapted varieties are identified, advocates of organic breeding now promote the use of direct selection for many desired characteristics.

    Genetic engineering is a very new science and we have a lot to learn about the good it can do and the damage it can cause. The main concern is that not enough tests are being done to ensure it is safe.

The public footpath laid barely 20 meters from where I stood, promising a walk along the river, passing fields and through woodland, well away from any road. Yet there was something in my way—the River Thames.

I checked my map to see how to reach the path, but there was no other footpath that would lead me to the island on which it sat. It was only accessible by boat—kid's dream. Similar to a talent show, some performances are educational but mostly, they just make you laugh. Talent is irrelevant, and audience engagement through call and response is essential.

Away from phones and peers back home, social norms fade and space for self-exploration forms. Shy kids come out of their shells, and cool kids let_their_guard_down. They get to open up this door to a part of themselves that they wouldn't have felt safe to reveal at school or at home.

It's been a decade since my last performance as a camp counselor, and I never thought of skits from a skill-building perspective. But I now realize this rich camp tradition left a great impression on me. Through camp skits, I developed my sense of humor, built confidence in front of a crowd, and learned how to accept others for their quirks（怪癖）.

Maybe we can make our schools or communities more like summer camps by bringing the silliness of skits into our families and classrooms to reconnect with ourselves and each other. The next time you're sitting around a campfire with friends and family, give it a try. Embrace the discomfort and invite your loved ones to join in on the improvising（即兴创作）. And remember: the more funny noises and childlike humor, the better.