Many years ago, when I was fresh out of school and working in Denver, I was driving to my parents' home in Missouri for Christmas. I stopped at a gas station (加油站) about 50 miles from Oklahoma City, w I was planning to stop to visit a friend. While I was standing in line at the cash register (收款台), I said hello to an older couple w were also paying for gas.

    I took off, but had gone only a few miles when black smoke poured from the back of my car. I stopped and wondered w I should do. A car pulled up behind me. It was the couple I had spoken to at the gas station. They said they would take me to my friend's. We chatted on the way to the city, and when I got out of the car, the husband gave me his business card.

    I wrote him and his wife a thank-you note for helping me. Soon afterward, I r a Christmas present from them. Their note that came with it said that helping me had m their holiday meaningful.

    Years later, I drove to a meeting in a nearby town in the morning. In late afternoon I returned to my car and found that I'd left the lights on all day, and the battery (电池) was dead. Then I n that the Friendly Ford dealership—a shop selling cars—was right next door. I walked over and found two salesmen in the showroom.

    "Just how friendly is Friendly Ford?" I asked and explained my trouble. They quickly drove a pickup truck to my car and started it. They would a(no payment, so when I got home, I wrote them a note to say thanks. I received a letter back from one of the salesmen. No one had ever taken the time to write to him and say thank you, and it meant a lot, he said.

    "Thank you"—two powerful words. They're easy to say and mean so much.

    Greenwich (格林威治) is on the River Thames, five miles away from the middle of London, and it has a two-thousand-year history. The first English people were fishermen there, and they named the place Greenwich, meaning "green village". Later the English kings and queens lived at Greenwich in their beautiful palaces.

    The name of the earliest palace was Placentia. Its windows were made of glass—the first in England. Henry VIII lived there. He knew that England must be strong at sea. So he started two big ship yards (船坞) at Greenwich, and for 350 years the ships which were made there were the best in the world.

    But trouble was coming to Greenwich. In 1649, a war started in England and for eleven years there was no king. The men who had worked for him at Placentia decided to live in the palace themselves. They sold all its beautiful things, and bought small pieces of the palace garden with money. Finally the war ended and King Charles II came back. But Placentia was falling down. So King Charles built a new and bigger palace, which is now open to the public.

    At that time, Charles was worried about losing so many of its ships at sea; their sailors didn't know how to tell exactly where they were. So in 1678, Charles made John Flamsteed, the first astronomer (天文学家) in England, try to find the answers. Flamsteed worked in a new building on the high ground in Greenwich Park. From it with a telescope which he made 15 himself, Flamsteed could watch all around the sky. And he did, night after night, for twenty years. Continuing Flamsteed's work a hundred years later, an astronomer called Harrison finally made a clock which told the time at sea, and helped sailors to know where they were. You can see Harrison's clock, still working, in Greenwich's museum. Because of both men's work, every country in the world now tells its time by Greenwich time.