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  3. The Inner Clock That Rules Our Lives Guess what time it is---without looking at your watch! The chances are you will be righ

The Inner Clock That Rules Our Lives Guess what time it is---without looking at your watch! The chances are you will be righ

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问题               The Inner Clock That Rules Our Lives
    Guess what time it is---without looking at your watch! The chances are you will be right within half an hour. Or try waking up at a particular time--without an alarm clock. You’ll probably be able to do that, too.
    Just about everyone can do these things, with a little practice, because the human body has its own built-in clocks.
    There is a complex series of interacting rhythms in nearly everything the human body does. It sleeps to a rhythm, eats to one, and even shows a rhythm in the electrical waves produced by the brain.
    Three main rhythmic cycles affect body time: the daily rhythms of the revolving earth; the monthly orbit of the moon around the earth; and the yearly journey of the earth around the sun,
    A Perfect Time Sense
    Not only mankind is affected by these great natural fides. All animals and plants feel them; too. Sometimes a body clock can keep accurate time to the precise minute, as in the case of the bean aphid (蚜虫), which can either lay eggs or produce live young, according to natural time that when the daylight lasts longer than 14 minutes, live offspring are born to take full advantage of the extra warmth. If the day is shorter, the aphid lays eggs to hatch at a later time.
Man’s time sense is both mental and physiological. He feels hungry every three to four hours. His brain cells show two-to-three-hour cycles of activity. Even dreams run in cycles. During dreaming, the eyes, even under closed eyelids, show rapid scanning movements. Measurements of this movement, during "rapid eye movement", or "REM", permit accurate timing of periods of dreaming. Based on this, man appears to dream in cycles of about 90 minutes.
    Circadian Rhythm
    Man’s natural rhythm of life is balanced between the length of the 24-hour solar day and the lunar day, which is 50 minutes longer. For this reason it is called the circadian (昼夜的) rhythm. Under normal conditions the circadian rhythm is constantly influenced by the rising and setting of the sun. But people isolated from outside stimuli--such as prisoners kept constantly in cells without natural light--revert automatically to a longer natural cycle.
    The circadian pattern seems to be controlled partly by the hypothalamus--an area in the base of the brain close to the pituitary (垂体) gland. The hypothalamus can regulate pituitary secretions, and thus, the activity of a number of other endocrine (内分泌) gland. Effects on the cortex of the adrenal (肾上腺) gland, and changes in release of an adrenal hormone called cortisol (皮质醇), appear to be especially important in certain kinds of rhythms. These mechanisms are highly adaptable.
    Most humans do have contact with natural stimuli, and their slightly shorter version of the circadian rhythm is vitally important to them. Temperature, blood pressure, pulse, breathing, and hormone activity all rise and fall in time with the world’s slow spin.
    A Cycle for Illness
    Similarly, ability, temper, and even resistance to infection are controlled by the circadian clock. This may be why some epileptics have seizures only at certain times of the day or why pregnant women get morning sickness.
    Experiments have shown that mice injected with pneumonia germs at 4 a.m. survive better than those injected at any other time of day. This could be important to humans. If vulnerability to disease is rhythmic, then response to vaccination is likely to be rhythmic, too.
    Circadian rhythms account for the difference between "owls", people who are wide awake at night and stay up late, and "larks", who rise early, do their best work in the morning, and go to bed early.
    Lark and Owl Patterns
    Both the lark people and the owl people have quite distinct rhythms, probably because of differences in the rhythm of their metabolism (新陈代谢). The variation is important in that it shows an important difference in rhythmic patterns in members of the same species. Surprisingly, although owls go to bed later than larks, both groups tend to get up at about the same time. In larks body temperature and efficiency rise more quickly, but by evening they have "peaked out"; whereas owls at that time are still building to their peak.
    Regular air travelers experience "jet lag"--feeling of bewilderment and lethargy (没有生气) when they make rapid journeys from one time zone to another. The phenomenon is caused by the individual’s circadian rhythm being out of step with clock time in his new part of the world. Gradually, he will adapt to new rhythms, but the process may take as long as a week.
    Oysters Sense the Moon
    A remarkable experiment with oysters (牡蛎) shows that their rhythm is extremely persistent. Oysters were taken from Long Island some 1,000 miles inland in a sealed and darkened tank. At first, they continued to follow their normal rhythm, opening and closing according to the cycle of the tides on their home beach. But after 15 days their rhythm changed--to what it would have been if the sea’s tides had washed over their new home.
    They opened when the moon--which controls the tides--reached its highest point over their new location. This occurred despite the fact that the oysters were kept in a light-free tank, at a constant temperature, thus ruling out responses to lunar light or temperature change. One possibility is that they were responding to subtle changes in atmospheric pressure caused by the moon’s gravitational pull.
    In human beings, birth and death follow cycles. Most babies are born--and most heart attacks occur--between midnight and 6 a.m. More babies are conceived in August and September than in February and March. And science has even confirmed some of the age-old beliefs of astrology (占星学).
    The Cosmic Rhythm
    The sun’ s own cycle-the 11-year rise and fall of sunspots, which are dark spots that can be seen on the sun at the same time as it hurls vast fountains of energy into space--also has its effects upon life. In the 1930s the Russian historian A. L. Tchijevsky claimed to have found a link between this cosmic rhythm and wars and epidemics (传染病) on earth.
    Maki Takata, a Japanese professor, discovered a relationship between human blood and the sun. He had developed a method by which gynecologists (妇科医生) could check the menstrual cycles of women. This involved comparative tests of the albumin in the blood of both sexes. In January 1938 hospitals throughout the world that used the "Takata reaction" reported that the results were changing for men as well as women. Takata cross-checked and analyzed the results for 20 years and discovered that they changed primarily when a group of sunspots passed across the center of the sun: that is, when the sun was pumping a concentrated stream of radiation toward the earth. The burst of hospital reports corresponded to a sudden surge in the sunspot cycle after several years of quiet.
     Takata also noticed that his test results showed a sudden change a few minutes before sunrise each day--as if the blood itself "foresaw" the break of day. "Man," Takata declared, "is a living sundial."
    He could just as well have been talking about animals or plants. Whatever and wherever it is, life seems completely in step with a cosmic clock.
For a person to recover from "jet lag", it may take______.
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答案as long as a week
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