题目内容
Invisibility Ring
Scientists can"t yet make an invisibility cloak like the one that Harry Potter uses. But， for the first time， they"ve constructed a simple cloaking device that makes itself and something placed inside it invisible to microwaves.
When a person "sees" an object， his or her eye senses many different waves of visible light as they bounce off the object. The eye and brain then work together to organize the sensations and reconstruct the object"s original shape. So， to make an object invisible， scientists have to keep waves from bouncing off it. And they have to make sure the object casts no shadow. Otherwise， the absence of reflected light on one side would give the object away.
Invisibility isn"t possible yet with waves of light that the human eye can see. But it is now possible with microwaves. Like visible light， microwaves are a form. of radiant energy. They are part of the electromagnetic spectrum， which also includes radio waves， infrared light， ultravioletmys， X rays， and gamma rays. The wave lengths of microwaves are shorter than those of radio waves but longer than those of visible light.
The scientists" new "invisibility device" is the size of a drink coaster and shaped likearing. The ring is made of a special material with unusual ability. When microwaves strike thering， very few bounce off it. Instead， they pass through the ring， which bends the waves all the way around until they reach the opposite side. The waves then return to their original paths.
To a detector set up to receive microwaves on the other side of the ring， it looks as if the waves never changed their paths as if there were no object in the way! So， the ring is effectively invisible.
When the researchers put a small copper loop inside the ring， it， too， is nearly invisible.
However， the cloaking device and anything inside it do cast a pale shadow. And the device works only for microwaves， not for visible light or any kind of electromagnetic radiation. So， Harry Potter"s invisibility cloak doesn"t have any real competition yet.
Harry Potter is mentioned in the passage， because scientists __________. 查看材料
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依据《湖南省实施＜中华人民共和国旅游法＞办法》的规定，政府及旅游主管部门和有关部门存在哪些行为，可以对直接负责的主管人员和直接责任人员依法给予行政处分？
设\(f(x)=sin\ x\)，则\(f^{(50)}(x)=\)\(-sin\ x\)________.
UFOs
Sixty years ago, a man named Kenneth Arnold saw something that we can still __________ (51)today-- something that changed popular culture for ever.
Flying his plane over mountains in the US state of Washington, he saw a line of strange objects, either crescent-shaped (月牙形的 ) or disc-like, flying __________ (52) the motion of a saucer (碟) skimming (飞速掠过) on water.
The media soon picked up on the story--the Flying Saucers were here! Was the earth being__________ (53) by creatures from another planet？ Soon, So many sightings were made that the US military began to __________ (54). It called these strange Objects UFOs--Unidentified Flying Objects, and that is how they are __________ (55)today.
Military investigations found no evidence of visitors from outer space. But that did not stop the true __________ (56). The military were __________ (57) up, they said. Or maybe it was because the travelers from space were of such superior intelligence __________ (58) they could hide from military analysts (分析家) .
People have always seen strange lights in the sky. In the past these were explained in __________ (59)ways. In a world where religion was less infuenfial and science fiction was popular, signs from God were replaced by visitors from other __________ (60).
The date of the first UFO sightings was also significant. In 1947, World War I! had just ended and the __________ (61) War was just beginning. Humanity seemed locked in endless conflicts.
Like generations before them, people looked __________ (62) the skies for help. But instead of seeking God, they looked for help from super-intelligent aliens (外星人) with __________ (63)technology. Belief in UFOs became the first religion of science.
However, even people who believe in UFOs are not quite sure why they visit the earth. The universe is a big place and it is __________ (64) to assume that there is life somewhere out there.
It is possible that aliens have worked out how to travel through space. Yet some people report that they have been taken by aliens and have had experiments __________ (65) on them. Why would anyone travel across half the universe to conduct medical experiments on people living in small towns in the United States？
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