It was 3:21 a.m. when nine-year-old Glenn Kreamer awoke to the smell of burning. Except for the cracking(爆烈声) of flames somewhere below there was not a sound in the two-storey house at Baldwin Long Island.

    With his father away on night duty at a local factory, Glenn was worried about the safety of his mother, his sister Karen, 14 and his 12-year-old brother Todd. He ran downstairs through the smoke-filled house to push and pull at Karen and Todd until they sat up. Then he helped each one through the house to the safety of the garden. There, his sister and brother, taking short and quick breaths and coughing, fell down onto the lawn.

    The nine-year-old boy raced back into the house and upstairs to his mother's room. He found it impossible to wake her up. Mrs. Kreamer, a victim of the smoke, was unconscious(昏厥的), and there was nobody to help Glenn carry her to the garden. But the boy remained calm and, as a fireman said later, "acted with all the self-control of a trained adult."

    On the bedroom telephone, luckily still working, Glenn called his father and, leaving Mr. Kreamer to telephone the fire brigade and ambulance service, got on with the task of saving his mother.

    First he filled a bucket with water from the bathroom and threw water over his mother and her bed. Then, with a wet cloth around his head he went back to the garden.

    He could hear the fire engine coming up, but how would the firemen find his mother in the smoke-filled house where flames had almost swallowed up the ground floor?

    Grasping firmly a ball of string(线) from the garage, Glenn raced back into the house and dashed upstairs to his mother's room. Tying one end of the string to her hand, he ran back, laying out the string as he went, through the hall and back out into the garden.

    Minutes later he was telling fire chief John Coughlan, "The string will lead you to mother." Mrs. Kreamer was carried to safety as the flames were breaking through her bedroom floor.

    Social change is more likely to occur in societies where there is a mixture of different kinds of people than in societies where people are similar in many ways. The simple reason for this is that there are more different ways of looking at things present in the first kind of society. There are more ideas, more disagreements in interest, and more groups and organizations with different beliefs. In addition, there is usually a greater worldly interest and greater tolerance in mixed societies. All these factors tend to promote social change by opening more areas of life to decision. In a society where people are quite similar in many ways, there are fewer occasions for people to see the need or the opportunity for change because everything seems to be the same. And although conditions may not be satisfactory, they are at least conventional and generally agreed.

    Within a society, social change is also likely to occur more frequently and more readily in the material aspects of the culture than in the non-material, for example, in technology rather than in values; in what has been learned later in life rather than what was learned early; in the less basic and less emotional aspects of society-than in their opposites; in the simple elements rather than in the complex ones; in form rather than in substance; and in elements that are acceptable to the culture rather than in strange elements.

    Furthermore, social change is easier if it is gradual. This is one reason why change has not come more quickly to Black Americans as compared to other American minorities, because of the sharp difference in appearance between them and white people.

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    If you have more questions, you may log in and post your questions here. We will solve your problems as soon as possible.

    The morning had been a disaster. My tooth was aching, and I'd been in an argument with a friend. Her words still hurt: “The trouble with you is that you won't put yourself in my place. Can't you see things from my point of view?” I shook my head stubbornly-and felt the ache in my tooth. I'd thought I could hold out till my dentist came back from holiday, but the pain was really unbearable. I started calling the dentists in the phone book, but no one could see me immediately. Finally, at about lunchtime, I got lucky.

    “If you come by right now,” the receptionist said, “the dentist will fit you in.”

    I took my purse and keys and rushed to my car. But suddenly I began to doubt about the dentist. What kind of dentist would be so eager to treat someone at such short notice? Why wasn't he as busy as the others?

    In the dentist's office, I sat down and looked around. I saw nothing but the bare walls and I became even more worried. The assistant noticed my nervousness and placed her warm hand over my ice-cold one.

    When I told her my fears, she laughed and said, “Don't worry. The dentist is very good.”

    “How long do I have to wait for him?” I asked impatiently.

    “Come on, he is coming. Just lie down and relax. And enjoy the artwork,” the assistant said.

    “The artwork?” I was puzzled.

    The chair went back. Suddenly I smiled. There was a beautiful picture, right where I could enjoy it: on the ceiling. How considerate the dentist was! At that moment, I began to understand what my friend meant by her words.

    What a relief!

    In 2016, designer Liz Ciokajlo received a task from the Museum of Modern Art (Moma) in New York: revisit the Moon Boot, a fluffy-looking snowshoe inspired by the footwear used by the Apollo astronauts.

    Launched in 1972 at the height of the lunar missions, the Moon Boot is an icon of the 20th Century's “plastic age” and the museum administrators wanted a new take on it.

    Ciokajlo set out to reimagine it. She knew only a biomaterial would work in a “post-plastic age”, but the designer also wanted a new destination to inspire it. Our generation's space travel obsession is not the Moon, she thought, but the red planet Mars. And Mars allows you to really think outside of the box.

    The task led her to an amazing biomaterial that had already attracted the attention of engineers innovating m building materials and of top space agencies like NASA and ESA. Her final design, a tall, female, rough-looking boot, can be made on board a spaceship with almost only human sweat and a few fungus spores (真菌孢子), ideal for a seven-month trip to Mars with limited check-in luggage.

    This magic biomaterial is mycelium (菌丝体), the vegetative part of the fungus It looks like amass of white thread-like structures, each called hyphae. Collectively, these threads are called mycelium and are the largest part of the fungus.

    Mycelium has amazing properties. It is a great recycler, as it feeds off a substrate to create more material, and has the potential of almost limitless growth in the right conditions. It can endure more pressure than conventional concrete without breaking. It is a known insulator and fire-retardant and could even provide radiation protection on space missions.

    On Earth it's currently used to create ceiling panels, leather, packaging materials and building materials, but in outer space it stands out for its architectural potential, says artist and engineer Maurizio Montalti, who has teamed up with Ciokajlo.

    For her revisited boot, Ciokajlo wanted to use the human body as the source for some of the building materials and decided to employ sweat. Reusing sweat is not entirely new in space exploration but a novelty approach for footwear. She thinks it might make astronauts feel closer to home during the long journey to Mars.

    The design is still hypothetical, because the real boot submitted for Moma and currently in display at the London Design Museum did use mycelium but not human sweat, as their deadline was too tight, but the science checks out.

    Photography（摄影） is a very popular art form. Anyone with a camera – or a mobile phone – can practice it. A picture communicates in a way that words often can't. As the photographer Destin Sparks put it, “Photography is the story I fail to put into words.” And there's no better chance to practice the art of photography than during our vacation time.

    Holiday photos have been a part of the culture of travelers for a long time. For decades, vacationers have made sure they've packed a camera along with bathing suits, Hawaiian shirts and sunglasses. A camera is an important holiday item. But over the last 10 years, photography has become much more popular. It's easy to capture ( 捕捉 ) still and moving pictures of places of interest, and it's also easy to show off these pictures on social media. Armed with their smart phones, tourists, this year more than ever, are capturing the beauty of our planet.

    Of course, travel companies have caught on to this. Trekksoft has an example of photo-tourism from the United States, a land with a vast choice of beautiful locations. Antelope Slot Canyon Tours in Arizona specializes in tours of the state's famous canyons（峡谷）, which gives photographers the chance to capture them on camera.

    Most of the tourists are able to make beautiful images with just their mobile phones. Still, help is on hand from the tour guide for those who aren't great at using their cameras. These tour guides have taken a course in photography in case the skills they've learned would help their customers.