18．It took 100years，but finally，scientists，from CalTech，MIT and the LIGO Scientific Collaboration，proved Albert Einstein's theory that gravitational（引力的） waves exist．The waves were predicted as part of Einstein's General Theory of Relativity nearly 100years ago．It was the theory of the physics behind the workings of our world and the universe．The idea was that the waves are like ripples in space，caused by some of the violent and energetic processes in the Universe．For example，two black holes crashing into each other．
What are these gravitational waves？Well，imagine throwing a rock into a pond．When the rock hits the flat surface of the water，it creates ripples or waves．Space time is like the surface of the water．So that means gravitational waves are like the ripples moving out from where the rock hits the water．It might be hard to understand，but those gravitational waves expand and contract space and time as they move through space．And when they get to the Earth，the waves pass through，and contract and expand the planet as the wave goes by．
It was Einstein who said these gravitational waves should be observable．But these are not huge waves．They are very，very small，which is why it took so long to find them．You cannot see them with your eyes．They are smaller than the size of an atom．
How did the scientists find them？For years，scientists have been watching two black holes in another galaxy faraway with the help of the Laser Interferometer Gravitational-Wave Observatory．The two were spinning around each other，moving closer and closer together．When they finally crashed into each other，it was with such power and force，that gravitational waves rang throughout the universe，like a giant bell．Those waves，traveling at the speed of light，finally reached the Earth，some 1.3billion years later．They are the same waves that the scientists announced this past week．
The National Science Foundation tweeted that each of the black holes was thought to be 29to 36times the mass of our sun．So，what does this discovery mean？Abhay Ashtekar，a Penn State physicist，who was not on the discovery team，said："Our understanding of the heavens changed dramatically．"
72．According to the 1st paragraph，we can learn thatA．
A．gravitational waves were part of Einstein's General Theory of Relativity
B．scientists proved that gravitational waves existed 100years ago
C．gravitational waves were the theory of the physics behind the universe
D．gravitational waves result from two black holes crashing into each other
73．From the passage we can know that the gravitational wavesD．
A．a(chǎn)re not supposed to be observed．
B．a(chǎn)re very huge．
C．a(chǎn)re easy to be found．
D．can't be seen with our eyes．
74．Why did scientists spend years watching two black holes？B
A．Because they wanted to see how the two black holes crashed into each other．
B．Because they wanted to find the gravitational waves．
C．Because they wanted to see the gravitational waves reach the Earth．
D．Because they wanted to know how black holes formed．
75．What can we infer from the passage？C
A．The discovery has no relation to Albert Einstein's theory
B．Throwing a rock into a pond can generate gravitational waves
C．The discovery will considerably affect people's understanding of universe
D．gravitational waves can't contract and expand the Earth．
分析 本文屬于說明文閱讀，作者通過這篇文章主要向我們描述了又一重大科學(xué)發(fā)現(xiàn)：首次測得引力（重力）波真實(shí)存在．
解答 72．A．判斷推理題．根據(jù)第一段的The waves were predicted as part of Einstein's General Theory of Relativity nearly 100 years ago可知重力波是愛因斯坦的相對理論的一部分．故選A．
73．D．細(xì)節(jié)理解題．根據(jù)第三段的You cannot see them with your eyes．They are smaller than the size of an atom你不能用鏡看到它們．它們比原子還�。蔬xD．
74．B．判斷推理題．通讀文章第四段，并根據(jù)第一句話的How did the scientists find them？For years，scientists have been watching two black holes in another galaxy faraway with the help of the Laser Interferometer Gravitational-Wave Observatory可知科學(xué)家們觀察兩個黑洞就是為了找到重力波的存在．故選B．
75．C．推理判斷題．根據(jù)文章最后一句話Our understanding of the heavens changed dramatically可知這個發(fā)現(xiàn)將極大地影響人們對宇宙的理解．故選C．
點(diǎn)評 考察學(xué)生的細(xì)節(jié)理解和推理判斷能力，做細(xì)節(jié)理解題時一定要找到文章中的原句，和題干進(jìn)行比較，再做出正確的選擇．在做推理判斷題不要以個人的主觀想象代替文章的事實(shí)，要根據(jù)文章事實(shí)進(jìn)行合乎邏輯的推理判斷．
