首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
Familiar as it may seem, gravity remains a mystery to modern physics. Despite several decades of trying, scientists have failed
Familiar as it may seem, gravity remains a mystery to modern physics. Despite several decades of trying, scientists have failed
admin
2015-10-20
98
问题
Familiar as it may seem, gravity remains a mystery to modern physics. Despite several decades of trying, scientists have failed to fit Einstein’s general theory of relativity, which describes how gravity holds big objects together, with the quantum mechanics(an extension of statistical mechanics based on quantum theory)he pioneered, which describes the tiny fundamental particles of which matter consists and the forces by which they interact Recent discoveries have highlighted further problems.
Many physicists are therefore entertaining the idea that Einstein’s ideas about gravity must be wrong or at least incomplete. Showing exactly how and where the great man erred is the task of the scientists who gathered at the "Rethinking Gravity" conference at the University of Arizona in Tucson this week.
One way to test general relativity is to examine ever more closely the assumptions on which it rests, such as the equivalence principle: that gravity accelerates all objects at the same rate, regardless of their mass or composition. This principle was famously demonstrated by Galileo Galilei some 400 years ago when he simultaneously dropped cannon and musket balls, and balls made of gold, silver and wood, from the Tower of Pisa. Each appeared to hit the ground at the same time.
A more precise test requires a taller tower. In effect, researchers are sending balls all the way to the moon and back. Tom Murphy, of the University of California, San Diego, and his colleagues fire laser beams from the deserts of New Mexico at reflectors placed on the moon by American and Russian spacecraft in the late 1960s and early 1970s. They use a telescope to capture the small fraction of the light that returns. Because the speed of light is known, they can calculate the distance between the Earth and the moon from the time taken for light to pass through it.
According to general relativity, because the Earth and the moon orbit the sun, they should "fall" towards it at the same rate, in the same way as Galileo’s balls fell to the ground. By repeatedly measuring the distance between them, scientists can calculate the orbits of the Earth and the moon around the sun relative to each other. If the equivalence principle were violated, the moon’s orbit around the Earth would not appear straight, either towards or away from the sun. So far, Dr Murphy told the conference, these experiments have merely confirmed the equivalence principle to one part in 10 trillion. Dr Murphy and his colleagues hope that even more precise measurements could ultimately show general relativity to be only approximately correct. This would usher in a new revolution in physics.
Tom Murphy and his colleagues fire laser beams at reflectors on the moon with the aim to
选项
A、measure the distance between the moon and the Earth.
B、calculate the speed of light.
C、check how long it takes light to cross it.
D、prove the equivalence principle more accurately.
答案
D
解析
事实细节题,考查目的细节。根据Tom Murphy定位到第四段。该段紧承第三段,从该段首句Amore precise test requires a taller tower可知,下文所说的Tom Murphy和他的同事所做的激光实验是为了更精确地论证等效原理,故D项正确。
转载请注明原文地址:https://kaotiyun.com/show/HVzZ777K
0
考研英语一
相关试题推荐
TheElectromagneticRadiationAffectsOurLifeWhethermobilephonescancausecancerremainsanopenquestion.Buttheyare
TheElectromagneticRadiationAffectsOurLifeWhethermobilephonescancausecancerremainsanopenquestion.Buttheyare
Itisallverywelltoblametrafficjams,thecostofpetrolandthequickpaceofmodernlife,butmannersontheroadsarebe
Itisallverywelltoblametrafficjams,thecostofpetrolandthequickpaceofmodernlife,butmannersontheroadsarebe
Thequestionofwhereinsightscomefromhasbecomeahottopicinneuroscience,despitethefactthattheyarenoteasytoindu
Ifthereisonethingscientistshavetohear,itisthatthegameisover.Raisedonthebeliefofanendlessvoyageofdiscove
Ifthereisonethingscientistshavetohear,itisthatthegameisover.Raisedonthebeliefofanendlessvoyageofdiscove
随机试题
磺酰脲类药物中易引起不良反应较多的药物是:
A.选择偏倚B.信息偏倚C.混杂偏倚D.报告偏倚E.失访偏倚应用多因素分析可以控制的偏倚是
下列有关合同争议评审的说法,正确的有()。
防火防爆措施是综合性的措施,包括选用合理的电气设备,保持必要的防火间距,电气设备正常运行并有良好的通风,采用耐火设施,有完善的继电保护装置等技术措施。平面布置中,室外变、配电装置与堆场、可燃液体储罐和甲、乙类厂房库房的距离不应小于()m
如果你的某个同事“十一”要结婚,给你发来了请柬,但这位同事与你平日里很少有交往,你会()。
()是现场抢救中最简单、最合适的方法。
陆钦斯量杯实验说明定势具有()。
给定资料1.我国是世界第二草原大国,天然草原约占国土总面积的40%。作为我国陆地生态安全的重要屏障,草原在调节气候、涵养水源、保持水土、防风固沙等方面发挥着举足轻重的作用。我国的草地占国土总面积的40%左右,是现有农田的3倍,畜牧业发展潜力很大。
战略计划过程是企业及其各业务单位为生存和发展而制定长期总战略所采取的一系列重大步骤,主要包括()。
MyfatherservedinWorldWarII.
最新回复
(
0
)