It was one of those terribly hot days in Baltimore. Needless to say, it was too hot to do anything outside. But it was also scorching in our apartment. This was 1962, and I would not live in a place with an air conditioner for another ten years. So my brother and I decided to leave the apartment to find someplace indoors. He suggested we could see a movie. It was a brilliant plan.

    Movie theaters were one of the few places you could sit all day and—most important —sit in air conditioning. In those days, you could buy one ticket and sit through two movies. Then, the theater would show the same two movies again. If you wanted to, you could sit through them twice. Most people did not do that, but the manager at our theater. Mr. Bellow did not mind if you did.

    That particular day, my brother and I sat through both movies twice, trying to escape the heat. We bought three bags of popcorn and three sodas each. Then, we sat and watched The Music Man followed by The Man Who Shot Liberty Valance. We'd already seen the second movie once before. It had been at the theater since January, because Mr. Bellow loved anything with John Wayne in it.

    We left the theater around 8, just before the evening shows began. But we returned the next day and saw the same two movies again, twice more. And we did it the next day too. Finally, on the fourth day, the heat wave broke.

    Still, to this day I can sing half the songs in The Music Man and recite half of John Wayne and Jimmy Stewart's dialogue from The Man Who Shot Liberty Valance! Those memories are some of the few I have of the heat wave of 1962. They're really memories of the screen, not memories of my life.

    I was at a dinner in London given in honor of one of the most celebrated English military (军事的)men of his time. I do not want to tell you his real name and titles. I will just call him Lieutenant General Lord Arthur Scoresby.

    I cannot describe my excitement when I saw this great and famous man. There he sat, the man himself, in person, all covered with medals. I could not take my eyes off him. He seemed to show the true mark of greatness. His fame had no effect on him. The hundreds of eyes watching him, the admiration of so many people, did not seem to make any difference to him.

    Next to me sat a clergyman(牧师), who was an old friend of mine. He was not always a clergyman. During the first half of his life he was a teacher in the military school at Woolwich. There was a strange look in his eye as he turned to me and said in a low voice-"privately-he is a complete fool." He meant, of course, the hero of our dinner.

    This came as a shock to me. I looked hard at my friend. I could not have been more surprised if he had said the same thing about Napoleon, or Socrates, or Solomon. But I was sure of two things about the clergyman. He always spoke the truth. And, his judgment of men was good. Therefore, I wanted to find out more about our hero as soon as I could.

    Some days later I got a chance to talk with the clergyman, and he told me more.

    If you want to travel from Xi'an to Chengdu by train, it will take about 16 hours. But starting this month, the new Xi'an-Chengdu high-speed railway will shorten this travel time to three hours.

    The 643-kilometer line is China's first high-speed railway to run through the Qinling Mountains, which form a natural boundary (分界线) between China's north and south. With a speed of 250 km per hour, it's also the first mountain-heavy train line to provide a 4G network. Along the way, the train passes through two areas for rare (稀有) wild animals — one for pandas and the other for crested ibises (朱鹮).

    To reduce the railway's influence on the animals, workers and experts have designed and built the railway to be environmentally friendly. There were 345 wild pandas living in the Qinling Mountains. China currently has 1,864 wild pandas in total, according to the Xinhua News Agency.

    To avoid disturbing the pandas, the railway was designed to run through tunnels (隧道) within the area. Protective shields (防护屏) are placed near the entrance of each tunnel to stop animals from going in.

    To protect the thousands of crested ibises that fly near one part of the railway, protective nets have been set up to make sure the birds will not fly into a train.

    The nets are about 32 km long and 4 meters high. Experts tested different shapes and materials for building the nets before making their final choice.

    In 1943, when I was 4, my parents moved from Coeur d'Alene, Idaho, to Fairbanks, Alaska, where adventure was never very far away.

    We arrived in the summer, just in time to enjoy the midnight sun. All that sunlight was fantastic for Mom's vegetable garden. Working in the garden at midnight tended to throw her timing off, so she didn't care much about my bedtime.

    Dad was a Railway Express agent and Mom was his clerk. That left me in a mess. I usually managed to find some trouble to get into. Once I had a little fire going in the dirt basement of a hotel. I had tried to light a barrel(桶) of paint but couldn't really get a good fire going. The smoke got pretty bad, though, and when 1 made my exit, a crowd and the police were there to greet me. The policemen took my matches and drove me home.

    Mom and Dad were occupied in the garden and Dad told the police to keep me, and they did! I had a tour of the prison before Mom rescued me. I hadn't turned 5 yet.

    As I entered kindergarten, the serious cold began to set in. Would it surprise you to know that I soon left part of my tongue on a metal handrail at school?

    As for Leonhard Seppala, famous as a dog sledder, I think I knew him well because I was taken for a ride with his white dog team one Sunday. At the time I didn't realize what a superstar he was, but I do remember the ride well. I was wrapped (包裹) heavily and well sheltered from the freezing and blowing weather.

    In 1950, we moved back to Coeur d'Alene, but we got one more Alaskan adventure when Leonhard invited us eight years later by paying a visit to Idaho to attend a gathering of former neighbors of Alaska.

    People typically wash their hands seven times a day in the United States, but they do it at a far higher temperature than is necessary to kill germs, a new study says. The energy waste is equivalent to the fuel use of a small country. Amanda R. Carrico, a research assistant professor at the Vanderbilt Institute for Energy and Environment in Tennessee, told National Geographic that hand washing is often “a case where people act in ways that they think are in their best interest, but they in fact have inaccurate beliefs or outdated perceptions.”

    Carrico said, “It's certainly true that heat kills bacteria, but if you were going to use hot water to kill them it would have to be a way too hot for you to tolerate.”

Carrico said that after a review of the scientific literature, her team found “no evidence that using hot water that a person could stand would have any benefit in killing bacteria.” Even water as cold as 40°F (4.4℃) appeared to reduce bacteria as well as hotter water, if hands were scrubbed, rinsed(冲洗)and dried properly.

    Using hot water to wash hands is therefore unnecessary, as well as wasteful, Carrico said, particularly when it comes to the environment. According to her research, people use warm or hot water 64 percent of the time when they wash their hands. Using that number, Carrico's team calculated a significant impact on the planet.

    “Although the choice of water temperature during a single hand wash may appear unimportant, when multiplied by the nearly 800 billion hand washes performed by Americans each year, this practice results in more than 6 million metric tons of CO2 equivalent emissions annually,” she said.

    The researchers published their results in the July 2013 issue of International Journal of Consumer Studies. They recommended washing with water that is at a “comfortable” temperature, which they noted may be warmer in cold months and cooler in hot ones.

    There are two kinds of secrets: secrets of nature and secrets about people. Natural secrets exist all around us; to find them, one must study some undiscovered aspect of the physical world. Secrets about people are different: they are things that people don't know about themselves or things they hide because they don't want others to know. So when thinking about what kind of company to build, there are two distinct questions to ask: What secrets is nature not telling you? What secrets are people not telling you?

    It's easy to assume that natural secrets are the most important: the people who look for them can sound authoritative (权威的).This is why physics PhDs are difficult to work with—because they know the most basic truths, they think they know all truths. But does understanding electronic theory automatically make you a great marriage counselor? Does a gravity theorist know more about your business than you do? At PayPal, I once interviewed a physics PhD for an engineering job. Halfway through my first question, he shouted, "Stop! I already know what you're going to ask!" But he was wrong. It was the easiest no-hire decision I've ever made. Secrets about people are relatively overlooked. Maybe that's because you don^'t need a dozen years of higher education to ask the questions that uncover them: What are people not allowed to talk about? What is forbidden or taboo?

    The best place to look for secrets is where no one else is looking. Most people think only in terms of what they've been taught; schooling itself aims to spread basic wisdom. So you might ask: are there any fields that matter but haven't been standardized? Physics, for example, is a real major at all major universities, and it's set in its ways. The opposite of physics might be astrology, but astrology doesn't matter. What about something like nutrition? Nutrition matters for everybody, but you can't major in it at Harvard. Most top scientists go into other fields. Most of the big studies were done 30 or 40 years ago, and most are seriously flawed (有缺陷的). The food pyramid that told us to eat low fat and large amounts of grains was probably produced by Big Food(美国著名食品公司)than real science; its chief impact has been to worsen our obesity(肥胖)problem. There^'s plenty more to learn: we know more about the physics of far away stars than we know about human nutrition. It won't be easy, but it's not obviously impossible: exactly the kind of field that could produce secrets.