2017大学英语四级考试阅读理解辅导练习2

>>英语四级仔细阅读练习：2017大学英语四级考试阅读理解辅导练习2

>>大学英语四级精品课程

The accuracy of cientific observations and calculations is always at the mercy of the scientist's timekeeping methods. For this reason,scientists are interested in devices that give promise of more precise timekeeping.

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 Einstein's 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 Einstein's theories

5.Implied but not stated:_______.

a.Precise timekeeping is essential in science

b.Scientists expect to disprove Einstein's relativity theories

c.Atomic clocks will be important in space flight

d.The rate of vibration of an atom never varies

译文：

科学观察和计算的准确性总是受到科学家计时方法的怜悯。因此，科学家对提供更精确计时的设备感兴趣。

科学家在寻求精确度时已经转向依赖于各种振动原子或分子的原子钟来提供它们的“滴答”。这是可能的，因为每种原子或分子都有自己的特征振动速率。例如，氨中的氮原子振动或“嘀嗒”一秒240亿次。

一个这样的原子钟是非常准确的，它将在3000年内失去不到一秒钟的时间。在诸如天文学这样的领域将是一个很大的改变，当加热到沸水的温度时，这是一个振荡每秒92亿次的铯原子。

用氨分子运行的原子钟可用于基于爱因斯坦相对论来检查预测的准确性，根据这一理论，运动时钟和休息时钟应保持时间不同。时钟可以以每小时18000英里的速度移动到轨道卫星上，将其时间读数传播到地面站，并将其与相似模型的读数进行比较。无论差异发生，将根据预测的差异进行检查。

答案:aabcc

关于英语四级仔细阅读的练习就先练习到这里，登录坦途网英语四级考试频道，为你提供更多英语四级阅读模拟试题，同时让你获得更多英语四级阅读技巧，为你的英语四级考试做好充足的准备。