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专业八级改错练习－47
You stare at waterfall for a minute or two, then shift your gaze to its surrounding
专业八级改错练习－47
You stare at waterfall for a minute or two, then shift your gaze to its surrounding. What you now see appears to drift upward. You __1__ are board a train in a busy station when suddenly another train next __2__ to your starts moving forward. __3__ For a fraction of a second you feel that your train has lurched backward. These optical illusions occur because the brain is constantly matching its model of reality to signals from the body's sensors and interpret what must be happening – that your train __4__ might have moved, not the other; that downward motion is now __5__ normal, so a change from it must be perceived as upward motion.
The sensors that make this magic are two kinds. __6__ Each eye contains about 120 million rods, which provide somewhat blurry black and white vision. These are the windows of night vision; once adapted to the dark, they can detect a candle burnt __7__ ten miles away. Colorful vision in each eye comes from six to seven __8__ million structures called cones. Under ideal conditions, every cone can “see” the entire rainbow spectrum of visible colors, but one type of cone is most