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Think of the ocean on a calm day. Ignoring the rise and fall of the waves, you might imagine the surface was dead flat the whole way across. You’d be wrong. Hills and valleys are as much as a feature of the sea as the land, although on a much smaller scale. These undulations have a variety of causes. Tides, currents, eddies, winds, river flow and changes in salinity and temperature push the sea level up in some places and down in others by as much as 2 meters. Ever tried swimming uphill How do we map these oceanic hills and valleys First, we need to know what the planet would look like without them. This is where the geoid (大地水准面) comes in. It is a surface where the Earth’s gravitational potential is equal and which best fits the global mean sea level. It is approximately an ellipsoid, though uneven distribution of mass within the Earth means that it can vary from this ideal by up to 150 meters. The geoid represents the shape the sea surface would be if the oceans were net moving and affected only by gravity. Thus it can be used as a reference to measure any deviations in the ocean surface height that aren’t caused by gravity—the hills and valleys, for instance, or any regional increase in sea level. So how do you measure the geoid and the ocean’s irregular topography It’s complicated. Geophysicists calculate the geoid using data on variation in gravitational acceleration from several dozen satellites. The hills and valleys of the oceans are all very interesting, but can the geoid tell us anything more significant about the state of the planet It certainly can. Knowing accurately where the geoid lies and how the Ocean surface deviates from it will help meteorologists spot changes in Ocean currents associated with climate change. The circumpolar current around Antarctic is one they are particularly interested in. It can also predict local climate variations produced by events such as El Nino, El Nino keeps warm water that would normally move westwards close to the coast of South America, deprives Southeast Asia of its monsoon rains, and increases rainfall on the west coast of the Ametlca. Since temperature changes cause changes in sea level, geoid-watchers should be able to prepare us before it strikes. According to the passage, the word "geoid" probably means______.
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Which of the following is NOT true about the educational videos
To a large degree, the measure of our peace of mind is determined by how much we are able to live on the present moment. (31) of what happened yesterday or last year, and what may or may not happen tomorrow, the present moment is where you are—always! Without (32) , many of us have mastered the (33) art of spending much of our lives worrying about a (34) of things—all at once. We allow past problems and future concerns (35) your present moments, so much (36) we end up anxious, frustrated, depressed, and hopeless. On the flip side, we also postpone our gratification, our stated priorities, and our happiness, often (37) ourselves that "someday" will be much better than today. Unfortunately, the same mental dynamics (38) tell us to look toward the future will only repeat themselves so that "someday" never actually arrives. John Lennone once said, "Life is what is happening while we are busy making other plans." When we are busy making "other plans", our children are busy growing up, the people we love are moving away and dying, our bodies are getting out of shape, and our dreams are slipping (39) . In short, we miss out on life. Many people live as if life is a dress rehearsal for (40) later date. It isn’t. In fact, no one has a guarantee (41) he or she will be here tomorrow. Now (42) the only time we have, and the only time that we have any control (43) . When our attention is in the present moment, we (44) fear from our minds. Fear is the concern over (45) that might happen in the future—we won’t have enough money, our children will get into trouble, we will get old and die, whatever. (46) fear, the best strategy is to learn to bring your attention back to (47) . Mark Twain said, "I have been through some terrible things in life, some of which (48) happened." I don’t think I can say it any better. Practice (49) your attention on the here and now. Your effort will (50) great dividends.
The name Helen Keller has had special meaning for millions of people in all parts of the world. She could not see or hear. Yet Helen Keller was able to do so much with her days and years. Her success gave others hope. Helen Keller was born June twenty-seventh, eighteen eighty in a small town in northern Alabama. Her father, Arthur Keller, was a captain in the army of the South during the American Civil War. Her mother was his second wife. She was much younger than her husband. Helen was their first child. Until she was a year-and-one-half old, Helen Keller was just like any other child. She was very active. She began walking and talking early. Then, nineteen months after she was born, Helen became very sick. It was a strange sickness that made her completely blind and deaf. The doctor could not do anything for her. Her bright, happy world now was filled with silence and darkness. From that time until she was almost seven years old, Helen could communicate only by making signs with her hands. But she learned how to be active in her silent, dark environment. The young child had strong desires. She knew what she wanted to do. No one could stop her from doing it. More and more, she wanted to communicate with others. Making simple signs with her hands was not enough. Something was ready to explode inside of her because she could not make people understand her. She screamed and struggled when her mother tried to control her. When Helen was six, her father learned about a doctor in Baltimore, Maryland. The doctor had successfully treated people who were blind. Helen’s parents took her on the train to Baltimore. But the doctor said he could do nothing to help Helen. He suggested the Kellers get a teacher for the blind who could teach Helen to communicate. A teacher arrived from the Perkins Institution for the Blind in Boston. Her name was Annie Sullivan. She herself had once been almost completely blind. But she had regained her sight. At Perkins, she had learned the newest methods of teaching the blind. Annie Sullivan began by teaching Helen that everything had a name. The secret to the names was the letters that formed them. The job was long and difficult. Helen had to learn how to use her hands and fingers to speak for her. But she was not yet ready to learn. First, she had to be taught how to obey, and how to control her anger. Until she was 7 years old, she communicated with people only by______.
To a large degree, the measure of our peace of mind is determined by how much we are able to live on the present moment. (31) of what happened yesterday or last year, and what may or may not happen tomorrow, the present moment is where you are—always! Without (32) , many of us have mastered the (33) art of spending much of our lives worrying about a (34) of things—all at once. We allow past problems and future concerns (35) your present moments, so much (36) we end up anxious, frustrated, depressed, and hopeless. On the flip side, we also postpone our gratification, our stated priorities, and our happiness, often (37) ourselves that "someday" will be much better than today. Unfortunately, the same mental dynamics (38) tell us to look toward the future will only repeat themselves so that "someday" never actually arrives. John Lennone once said, "Life is what is happening while we are busy making other plans." When we are busy making "other plans", our children are busy growing up, the people we love are moving away and dying, our bodies are getting out of shape, and our dreams are slipping (39) . In short, we miss out on life. Many people live as if life is a dress rehearsal for (40) later date. It isn’t. In fact, no one has a guarantee (41) he or she will be here tomorrow. Now (42) the only time we have, and the only time that we have any control (43) . When our attention is in the present moment, we (44) fear from our minds. Fear is the concern over (45) that might happen in the future—we won’t have enough money, our children will get into trouble, we will get old and die, whatever. (46) fear, the best strategy is to learn to bring your attention back to (47) . Mark Twain said, "I have been through some terrible things in life, some of which (48) happened." I don’t think I can say it any better. Practice (49) your attention on the here and now. Your effort will (50) great dividends.
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