A strange thing happens to nearly everybody at night.They turn off the lights,pull up the covers and close their eyes.Six or seven sleeping hours later,they wake up again.Stange,isn't it?
Sleep puzzles scientists and doctors would rather talk about why one can not fall asleep.They are not so sure what causes sleep.The best conditions of sleep,they say,are good health and a meal neither too big nor too small.No worries and a comfortable place to sleep are important,too.They advise against two in one bed.Strange things happen during sleep.For example,you often move.You would feel tired if you didn't.You also dream.Part of your brain is still awake when you dream.Dreaming happens when the memory and imagination parts of your brain are still awake.Don't worry if you dream.
一共两段...sleep puzzles science这里开始是第2段