On May 23, 1989, Stefania Follini came out from a cave at Carlsbad, New Mexico. She hadn't seen the sun for eighteen and a half weeks. Stefania was in a research program, and the scientists in the program were studying body rhythms. In this experiment Stefania had spent 130days in a cave, 30 feet in depth.

    During her time in the cave, Stefania had been completely alone except for two white mice. Her living place had been very comfortable, but there had been nothing to tell her the time. She'd had no clocks or watches, no television or radio. There had been no natural light and the temperature had always been kept at 21℃.

    The results were very interesting. Stefania had been in the cave for over four months, but she thought she had been there for only two. Her body clock had changed. She hadn't kept to a 24-hour day, she had stayed awake for 20～25 hours and then had slept for 10 hours. She had eaten fewer meals and had lost 171bs in weight as a result! She had also become rather depressed.

    How had she spent her time in the cave? As part of the experiment she'd done some physical and mental tests. She'd recorded her daily activities and the results of the tests on a computer. This computer had been specially programmed for the project. Whenever she was free, she'd played cards, read books and listened to music. She'd also learned French from tapes.

    The experiment showed that our body clocks are affected by light and temperature. For example， the pattern of day and night makes us wake up and go to sleep. However, people are affected in different ways. Some people wake up naturally at 5:00 a.m., but others don't start to wake up till 9:00 or 10:00 a.m. This affects the whole daily rhythm. As a result the early risers are at their best in the late morning. The late risers, on the other hand, are tired during the day and only come to life in the afternoon or evening!

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    Tears ran down from my eyes as I saw the essay my high school English teacher had just handed back. A big F was written on top. I was hopeless. I was stupid !My face burned with shame when my classmates called me stupid.

    “I'm the only one who doesn't know my ABCs!” I sobbed to Mom.

    “I'll help,” she promised.

    Everyday I sat with her, but to me, cat looked like cta and red was reb. Frustrated, I would return to my bedroom and draw, filling the paper with houses, restaurants and offices.

    “When I grow up, I want my own store,” I told Mom , pointing to my drawings.

    “That's great!” she said, “ but first you have to learn to read.”

Later, I was diagnosed with dyslexia (失读症). So Mom took me to a learning centre, where I was given reading exercises. But I still had a hard time. Finally, I graduated, but I was afraid of my reading skills.

    “I'll never get a job !”  I cried to Mom later again.

    “Don't focus on what you can't do,” she comforted, “ Concentrate on what you really can.”

    But what can I do? I wondered. Suddenly, I thought of the drawings I'd made as a child and my dream of having my own store. I enjoyed sales so much that over the next few years, I tried my hand at other businesses. Today, I watch over seven branches. We have 187 employees and $15 million in sales.

    While I'll never be what my teachers might have wanted, I am a success--on my own terms. The other day a student sent me a card, reading: You gave me so much confidence. I hope to be like you when I am big. Tears of joy filled my eyes. This was my A, and I smiled.

    Will it matter if you don't take your breakfast? Recently a test was given in the United States. Those testes included people of different ages, from 12 to 83. During the experiment, these people were given all kinds of breakfast, and sometimes they got no breakfast at all. Special tests were set up to see how well their bodies worked when they had eaten a certain kind of breakfast. The results show that if a person eats a proper breakfast, he or she will work with better effort than if he or she has no breakfast. This fact appears to be especially true if a person works with his brains. If a student eats fruit, eggs, bread and milk before going to school, he will learn more quickly and listen with more attention in class. Contrary to what many people believe, people become so hungry at noon that they eat too much for lunch, and end up gaining weight instead of losing. You will probably lose more weight if you reduce other meals.

    Modern life is impossible without travelling. The fastest way of travelling is by plane. With a modern airline you can travel in one day to places which it took a month or more to get to hundred years ago.

    Travelling by train is slower than by plane, but it has its advantages. You can see the country you are travelling through. Modern trains have comfortable seats and dining-cars. They make even the longest journey enjoyable.

    Some people prefer to travel by sea when possible. There are large liners and river boats. You can visit many other countries and different parts of your country on them. Ships are not so fast as trains or planes, but travelling by sea is a very pleasant way to spend a holiday.

    Many people like to travel by car. You can make your own timetable. You can travel three or four hundred miles or only fifty or one hundred miles a day, just as you like. You can stop wherever you wish where there is something interesting to see, at good restaurant where you can enjoy a good meal, or at a hotel to spend the night. That is why travelling by car is popular for pleasure trips, while people usually take a train or plane when they are travelling on business.

    Philadelphia offers a ton of attractions that are suitable for people of every age and here are some family—friendly attractions.

    Spruce Street Harbor Park

    Spruce Street Harbor Park，one of the best urban beaches in American，is an outdoor heaven on the Delaware River waterfront. Visitors can relax in a hammock，play on the playgrounds，and play games like table tennis and giant chess. Don't miss out on the park at night，when colorful LED lights hanging from treetops make the entire area bright.

    Blue Cross RiverRink

    Offering ice skating in the winter and roller skating in the summer，Blue Cross RiverRink creates a fun，outdoor experience for the whole family. Visitors can play on the nine-hole mini-golf course during the summer，and enjoy eats and drinks from the on-site(现场的)bar and restaurant all year round.

    Sesame Place

    Big Bird，Elmo and the other stars of Sesame Street come out and play at Sesame Place，the only theme park in the nation starring the popular TV show's most lovable characters. A water park，interactive activities，parades，fireworks and shows add to the fun.

    Once Upon a Nation Storytelling Benches

    On summer days，uniformed and professional storytellers at 13 storytelling benches throughout Philadelphia's Historic District entertain visitors with true，free，three-to-five minute tales about the colonial(殖民的)era as part of Once Upon a Nation. Children can pick up a Story Flag at any storytelling bench，and then collect a star from every storyteller on their journeys. Flags with all the stars can get free rides on the Parx Liberty Carousel at Franklin Square.

    Many leading AI researchers think that in a matter of decades, artificial intelligence will be able to do not merely some of our jobs, but all of our jobs, forever transforming life on Earth.

    The reason why many regard this as science fiction is that we've traditionally thought of intelligence as something mysterious that can only exist in biological organisms, especially humans. But such an idea is unscientific.

    From my point of view as a physicist and AI researcher, intelligence is simply a certain kind of information-processing performed by elementary particles (基本粒子) moving around, and there is no law of physics that says one can't build machines more intelligent than us in all ways. This suggests that we've only seen the tip of the intelligence iceberg and that there is an amazing potential to unlock the full intelligence that is potential in nature and use it to help humanity.

    If we get it right, the upside is huge. Since everything we love about civilization is the product of intelligence, amplifying (扩大) our own intelligence with AI has the potential to solve tomorrow's toughest problems. For example, why risk our loved ones dying in traffic accidents that self-driving cars could prevent or dying of cancers that AI might help us find cures for? Why not increase productivity through automation (自动化) and use AI to accelerate our research and development of affordable sustainable (可持续的) energy?

    I'm optimistic that we can develop rapidly with advanced AI as long as we win the race between the growing power of our technology and the knowledge with which we manage it. But this requires giving up our outdated concept of learning form mistakes. That helped us win the race with less powerful technology: We messed up with fire and then invented fire extinguishers (灭火器), and we messed up with cars and then invented seat belts. However, it's an awful idea for more powerful technologies, such as nuclear weapons or superintelligent AI—where even a single mistake is unacceptable and we need to get things right the first time.