With the approval of the Singapore government, a company called nuTonomy has become the first-ever to test self-driving cars with the public. Interested people could sign up for a free trial run at no cost. When they received an invitation from the company, they could book a ride on the driverless taxi service from their smartphones.Not surprisingly,the rides proved very popular,with dozens of customers eagerly trying out the cars each day.

    Driverless cars are a great option for those who do not know how to drive and for those who do not enjoy driving.Some researchers even believe that such cars can make road travel safer by reducing human errors.But since driving requires many of our senses to be on alert（高度警觉）, replacing that by machines is easier said than done.

    The environment in which cars operate is constantly changing—from roads and pedestrians to co-travelers. A driverless car needs special equipment to analyze its surroundings. Then, it must translate that information into a practical route and safe travel. To be truly autonomous, a car has to do this independently without human input. Today, some cars have a certain degree of autonomous functions. But even the completely automated vehicles still require a driver to take back control under uncertain conditions.

    The island city-state is well known for excellent roads and drivers who obey the rules. This has made it ideal for real-world testing and feedback. The government has encouraged research in autonomous vehicles, since it can improve safety and potentially reduce the traffic burden as well.

    That cold January night, I was growing sick of my life in San Francisco. There I was, walking home at one in the morning after a tiring practice at the theatre. With opening night only a week away, I was still learning my lines. I was having trouble dealing with my part-time job at the bank and my acting at night at the same time. As I walked, I thought seriously about giving up both acting and San Francisco. City life had become too much for me.

    As I walked down empty streets under tall buildings, I felt very small and cold. I began running, both to keep warm and to keep away from any possible robbers. Very few people were still out except a few sad-looking homeless people under blankets.

    About a block from my apartment, I heard a sound behind me. I turned quickly, half expecting to see someone with a knife or a gun. The street was empty. All I saw was a shining streetlight. Still, the noise had made me nervous, so I started to run faster. Not until I reached my apartment building and unlocked the door did I realize what the noise had been. It had been my wallet falling to the sidewalk.

    Suddenly I wasn't cold or tired anymore. I ran out of the door and back to where I'd heard the noise. Although I searched the sidewalk anxiously for fifteen minutes, my wallet was nowhere to be found. Just as I was about to give up the search, I heard the garbage truck(垃圾车) pull up to the sidewalk next to me. When a voice called from the inside,  "Alisa Camacho?" I thought I was dreaming. How could this man know my name? The door opened, and out jumped a small red-haired man with an amused look in his eye. "Is this what you're looking for?" he asked, holding up a small square shape.

    It was nearly 3 a.m. by the time I got into bed. I wouldn't get much sleep that night, but I had gotten my wallet back. I also had gotten back some enjoyment of city life. I realized that the city couldn't be a bad place as long as people were willing to help each other.

    Organic food, grown without artificial chemicals, is increasingly popular nowadays. Consumers (消费者) have been willing to pay up to twice as much for goods with organic labels (标签). However, if you think paying a little more for organic food gets you a more nutritious and safer product, then you'd better save your money. A study led by researchers at Stanford University says that organic products aren't necessarily more nutritious, and they're no less likely to suffer from disease-causing bacteria, either.

    For their new study, Smith-Spangler and her colleagues conducted a review of two categories（种类）of research, including 17 studies that compared health outcomes between consumers of organic against traditional food products, and 223 studies that analyzed(分析) the nutritional content of the foods, including key vitamins, minerals and fats.

    While the researchers found little difference in nutritional content, they did find that organic fruit and vegetables were 20% less likely to have chemicals remaining on the surfaces. Neither organic nor traditional foods showed levels of chemicals high enough to go beyond food safety standards(标准). And both organic and traditional meats, such as chicken and pork, were equally likely to be harmed by bacteria at very low rates. The researchers did find that organic milk and chicken contained higher levels of omega-3 fatty acids, a healthy fat also found in fish that can reduce the risk of heart disease. However, these nutritional differences were too small, and the researchers were unwilling to make much of them until further studies confirm the trends.

    Organic food is produced with fewer chemicals and more natural-growing practices, but that doesn't always translate into a more nutritious or healthier product. The U. S. Department of Agriculture (USDA) states that "whether you buy organic or not, finding the freshest foods available may have the biggest effect on taste." Fresh food is at least as good as anything marketed as organic.

    Brian Greene, a professor of physics and mathematics at Columbia University, has created an online science education platform. He tries to "build a bridge" with things you know about, and then "bring you across that bridge to the strange place of modern physics."

    Recently I had a chance to ask Greene about wormholes (a hole which some scientists think might exist, connecting parts of space and time that are not usually connected), time travel and other mysteries of the universe. I asked him a million-dollar question: What if I went through a wormhole and prevented my parents from meeting? "Most of us believe that the universe makes sense," Greene said. Although there are several interesting theories about time travel, he added, the laws of physics would probably prevent something so illogical from taking place. The good news is that the time paradox（悖论） is open for future physicists to solve.

    When asked how physics could become more exciting for kids, Greene said that books by Stephen Weinberg, Leonard Susskind, and other physicists, "make it a great time for people who want to learn about big ideas but aren't yet ready, perhaps, to learn math."

    When I pointed out that some students still might find physics boring, Greene said that the key is to teach them about things that are strange. "The basic stuff is important," Greene said. "But I think it's really important to also describe the more modern ideas, things like black holes and the Big Bang. If kids have those ideas in mind, then at least some of them will be excited to learn all the details．"

    Greene has followed Albert Einstein's lead in trying to solve the mysteries of the universe. Now he wants kids to do the same. As Greene said, physics is "not just a matter of solving problems in an exam." It's about experimenting, showing an interest in strange phenomena（现象）-- and having fun!

    Palaces are known for their beauty and splendor, but they offer little protection against attacks. It is easy to defend a fortress (堡垒),but fortresses are not designed with the comfort of a king or queen in mind. When it comes to structures that are both majestic and well-defended, the classic European castle is the best example of design. Across the ages castles changed, developed, and eventually fell out of use, but they still command the fascination of our culture.

    Castles were originally built in England by Norman invaders. In 1066. As William the Conqueror advanced through England, he defended key positions to secure the land he had taken. The castles he built allowed the Norman lords to draw back to safety when threatened by English rebellion. Castles also served as bases of operation for offensive attacks. Troops were summoned to（召集）, organized around, and deployed (部署) from castles. In this way castles served both offensive and defensive roles in military operations.

    Not limited to military purposes, castles also served as offices from which the lord would administer control over his kingdom. That is to say, the lord of the land would hold court in his castle. Those that were socially beneath the lord would come to report the affairs of the lands that they governed and pay tribute to the lord. They would address conflicts, handle business, feast, and enjoy festivities, In this way castles served as important social centers in medieval England. Castles also served as symbols of power. Built on important and noticeable sites overlooking the surrounding areas, castles constantly appeared in the background of many peasants' lives and served as a daily reminder of the lords strength.

    Now, castles no longer serve their original purposes. However, the remaining castles receive millions of visitors each year from those who wish to experience the glory of a time long passed.

    I believe in the power of science fiction, not just for its capacity to transform dreams into reality, but also for its power to bond together those who share a common vision of the future. For me, that's true for my relationship with my dad. Some fathers and sons bond over sports, fishing or hunting, but my dad and I bond over Star Trek. We tried a trip to Disney World, but one of my earliest memories wasn't Mickey, but a Klingon battle cruiser(巡洋) on the screen.

    Over the years, nearly every setting and situation has become far away for my dad and me. When it's warm at night, we're not driving along some dark streets in Indiana, but going at a slow speed with stars dimly shining. Both of us are thinking of them, without needing to say a word. All these visions of other universes have together created a private universe for my dad and me.

    Gene Rodenberry, creator of Star Trek, once said, " Science fiction is a way of thinking, a way of logic that bypasses(绕过)a lot of nonsense. It allows people to look directly at important subjects. "A lifetime of science fiction has influenced more than just my relationship with my dad, but has also helped me shape my own hopes for the future. I'm now a science writer.

    Yes, science fiction has made me into a "nerd"(书呆子), and it also has been a source of joy for my family, making me an optimist while enabling me to think critically about the danger of technology. Thank those authors who have shared their visions; the world and my family are better for it. Thank my dad, who is both the best storyteller and the best man I have ever known because he helped me realize the truth of Tennyson's words," Since I dipped into the future, I saw the vision of the world, and all the wonders that would be."