19．Scientists said on Thursday they have for the first time detected gravitational （引力的） waves，ripples （漣波） in space and time hypothesized （假設） by physicist Albert Einstein a century ago，in a landmark discovery that opens a new window for studying the cosmos．
Discovering gravitational waves would be a huge deal for physics，cosmology，and our understanding of the universe at large．But if you're not a scientist studying one of the mentioned fields，it's possible you've never heard of these mysterious ripples．So what are gravitational waves and why is the discovery so significant？
Gravitational waves are disturbances in space-time，the very fabric of the universe，that travel at the speed of light．The waves are sent out by any mass that is changing speed or direction．The simplest example is a binary （二元的） system，where a pair of stars or compact objects （like black holes） orbit their common center of mass．
We can think of gravitational effects as curvatures （曲率） in space-time．Earth's gravity is constant and produces a static curve in space-time．A gravitational wave is a curvature that moves through space-time much like a water wave moves across the surface of a lake．It is generated only when masses are speeding up，slowing down or changing direction．
The new discovery was made by a group of more than 1，000scientists from universities around the United States as well as in 14other countries．Director David Reitze announced on Thursday at a press conference that they detected gravitational waves．
While opening a door to new ways to observe the universe，scientists said gravitational waves should help them gain knowledge about mysterious objects like black holes and neutron stars．The waves also may provide insight into the mysterious nature of the very early universe．
The scientists said that because gravitational waves are so radically （徹底地） different from electromagnetic waves they expect them to reveal big surprises about the universe．
21．Discovering gravitational waves would be a huge deal forC．
A．medicine．
B．literature．
C．cosmology．
D．philosophy．
22．The author explains the term of gravitational wavesD．
A．by classifying
B．by giving cause and effect
C．by making a comparison
D．by presenting a definition
23．The number of the countries that have scientists in the new discovery of gravitational waves isD．
A.12．
B.13．
C.14．
D.15．
24．What can be inferred from the last paragraph？A
A．Scientists can get further information about the universe by studying gravitational waves．
B．Scientists expect gravitational waves to reveal big surprises about the universe．
C．Gravitational waves are so radically different from electromagnetic waves．
D．Scientists from all the world work together to study the mystery of the solar system．
分析 科學家最近有了新發現，即引力波，并介紹了引力波的概念以及對于整個宇宙研究的重要作用．
解答 21-24CDDA
21．C 細節題．根據第二段開頭Discovering gravitational waves would be a huge deal for physics，cosmology可知，引力波的發現對于物理學以及宇宙學來說是一次巨大的事情，故選C．
22．D 細節題．從第三段的內容介紹可知，Gravitational waves are disturbances in space-time，the very fabric of the universe…作者主要告訴我們什么是引力波，即用定義的方法來呈現，故選D．
23．D 推理題．文章The new discovery was made by a group of more than 1，000scientists from universities around the United States as well as in 14other countries這句話提到引力波的發現除了美國還有其他14個國家，所以一共是15個國家，故選D．
24．A 推理題．根據最后一句話The scientists said that because gravitational waves are so radically （徹底地） different from electromagnetic waves they expect them to reveal big surprises about the universe．
得知，科學家期望通過引力波的研究能揭示關于宇宙更多的奧秘，故選A．
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