(
课件网) 英语说明文阅读理解 例题讲解 文章体裁：说明文 字数统计：347 主题：主要介绍了原子钟和正在研发中的 核钟（nuclear clock）的技术特点、工作原理 以及潜在的应用前景。 ①For the precise timekeeper, only an atomic clock will do. While the best quartz (石英) timepieces will lose a millisecond every six weeks, an atomic clock might not lose a thousandth of one in a decade. Such devices are accurate enough to drive everything from GPS and the internet to stock-market trading. However, researchers are now working on a successor: the nuclear clock. Ekkehard Peik, a pioneer in the field, says such a clock could be 1,000 times more accurate than today’s atomic clocks. ②Atomic clocks work by exciting the electrons around an atom’s nucleus (原子核) with incoming radiation of a specific frequency, with each wave cycle corresponding to a “tick.” Nuclear clocks would function similarly but would use the transitions of neutrons and protons (中子和质子) inside the nucleus. ③The most promising candidate nucleus is thorium-229, which uniquely, has a nuclear transition that lasers (激光) should be able to activate. The exact frequency at which this occurs, however, has long been unknown. Researchers Chuankun Zhang and Jun Ye, from the University of Colorado in Boulder, bypassed this challenge by developing a custom-built laser capable of generating a range of frequencies around the expected transition point. When they fired it at the target, one particular light stream matched the nuclear transition frequency. Although the system needs optimization, Zhang says, “It’s the first demonstration that all the components of a nuclear clock are here.” ④Because atomic clocks are already more than accurate enough for most practical uses, scientists are not aiming to replace them. Instead, they are more interested in the advantages of having two independent methods for measuring time, as beyond precise timekeeping, nuclear clocks could have broader applications in fundamental physics. One potential use is in testing Einstein’s theory of relativity, which suggests, among other things, that clocks should tick more slowly in stronger gravitational fields. If nuclear clocks show any differences in their response compared to atomic clocks under such conditions, it could motivate a rethinking of these well-established theories. 习题讲解 1. What do we know about atomic clocks A. They are less accurate than quartz timepieces. B. They are accurate enough for nearly all practical uses today. C. The difference between atomic and quartz clocks is insignificant. D. They are not reliable enough for technologies like GPS or stock trading. 细节理解题 习题讲解 A. They are less accurate than quartz timepieces.它们不如石英表准确。 ①For the precise timekeeper, only an atomic clock will do. While the best quartz (石英) timepieces will lose a millisecond every six weeks, an atomic clock might not lose a thousandth of one in a dec ... ...
