In their search for precision, scientists have turned to atomic clocks that depend on various vibrating atoms or molecules to supply their ticking .This is possible because each kind of atom or molecule has its own characteristic rate of vibration. The nitrogen atom in ammonia , for example, vibrates or ticks 24 billion times a second.
One such atomic clock is so accurate that it will probaly lose no more than a second in 3000 years. It will be of great improtance in fields such as astronomical is a sesium atom that vibrates 9.2 billion times a second when heated to the temperature of boiling water.
An atomic clock that operates with an ammonia molecue may be used to check the accuracy of predictions based on Einsteins relativity theories, according to which a clock in motion and a clock at rest should keep time differently. Placed in an orbiting satellite moving at a speed of 18000 miles an hour, the clock could broadcast its time readings to a ground station, where they would be compared with the readings on a similar model. Whatever differences develop would be checked against the differences predicted.
1.Scientists expect that the atomic clocks will be ______.
a.more precise
b.absolutely accurate
c.more durable
d.indestructible
2.The heart of the atomichron is _______.
a.acesium atom
b.an ammonia molecule
c.a nitrogen atom
d.a hydrogen
3.From theselection,we may assume that temperature changes_______.
a.affect only ammonia molecules
b.may affect the vibration rate of atoms
c.affect the speed at which atoms travel
d.do not affect atoms in any way
4.Identical atomic clocks may be used to check______.
a.the effect of outer space on an atomic clock
b.the actual speed of an orbiting satelite
c.the accuacy of predictions based on theories of relativity
d.all of Einsteins theories
5.Implied but not stated:_______.
a.Precise timekeeping is essential in science
b.Scientists expect to disprove Einsteins relativity theories
c.Atomic clocks will be important in space flight
d.The rate of vibration of an atom never varies
答案:aabcc
什么是“家庭软暴力”?
中国成语故事:自出机杼
中国传统民间故事:打邻家的儿子
昙花一现的潮流 fad
什么是“甜柠檬心理”?
同性婚姻 gayriage
中国成语故事:孰能生巧
中国传统民间故事:蓬蒙杀后羿
你是homedebtor吗?
中国成语故事:曲突图薪
什么是food porn(食物也色情?)
中国传统民间故事:役虎
补发工资 back pay
智能手机导致的“屏幕近视”
你知道什么是“金发姑娘原则”吗?
中国成语故事:捕鼠之猫
“拼图家庭”什么样?
中国成语故事:羿射不中
其貌不扬的eye broccoli
什么是“度假地婚礼”?
买完就退的deshoppers
什么是“朋友区间”?
两代人之间的“粗俗代沟”
中国成语故事:夜光之珠
“暖潮”英语怎么说?
中国成语故事:越人造车
什么是“安倍经济学”?
中国成语故事:治舟驾舟
中国成语故事:恐钟有声
你有“玛丽苏情结”吗?
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |