首页
登录
职称英语
For 150 years scientists have tried to determine the solar constant, the amo
For 150 years scientists have tried to determine the solar constant, the amo
游客
2025-04-02
25
管理
问题
For 150 years scientists have tried to determine the solar constant, the amount of solar constant energy that reaches the Earth. Yet, even in the most cloud-free regions of the planet, the solar constant cannot be measured precisely. Gas molecules and dust particles in the atmosphere absorb and scatter sunlight and prevent some wavelengths of the light from ever reaching the ground.
With the advent of satellites, however, scientists have finally been able to measure the Sun’s output without being impeded by the Earth’s atmosphere. Solar Max, a satellite from the National Aeronautics and Space Administration(NASA), has been measuring the Sun’s output since February 1980. Although a malfunction in the satellite’s control system limited its observation for a few years, the satellite was repaired in orbit by astronauts from the space-shuttle in 1984. Max’s observations indicate that the solar constant is not really constant after all. The satellite’s instruments have detected frequent, small variations in the Sun’s energy output, generally amounting to no more than 0. 05 percent of the Sun’s mean energy output and lasting from a few days to a few weeks. Scientists believe these fluctuations coincide with the appearance and disappearance of large groups of sunspots on the Sun’s disk. Sunspots are relatively dark regions on the Sun’s surface that have strong magnetic fields and a temperature about 2, 000 degrees Fahrenheit cooler than the rest of the Sun’s surface. Particularly large fluctuations in the solar constant have coincided with sightings of large sunspot groups. In 1980, for example, Solar Max’s instruments registered 0. 3 percent drop in the solar energy reaching the Earth. At that time a sunspot group covered about 0. 6 percent of the solar disk, an area 20 times larger than the Earth’s surface.
Long-term variations in the solar constant are more difficult to determine. Although Solar Max’s data have indicated a slow and steady decline in the Sun’s output, some scientists have thought that the satellite’s aging detectors might have become less sensitive over the years, thus falsely indicating a drop in the solar constant. This possibility was dismissed, however, by comparing Solar Max’s observations with data from a similar instrument operating on NASA’s Nimbus 7 weather satellite since 1978. [br] What does this passage mainly discuss?
选项
A、The components of the Earth’s atmosphere.
B、The launching of a weather satellite.
C、The measurement of variations in the solar constant.
D、The interaction of sunlight and air pollution.
答案
C
解析
主旨题。这篇文章主要讲的是太阳常数的测量方法,答案选C。
转载请注明原文地址:http://tihaiku.com/zcyy/4023604.html
相关试题推荐
Theworkintheofficewas______byaconstantstreamofvisitors.A、confusedB、ha
TheGreek’sloftyattitudetowardscientificresearch—andthescientists’co
TheGreek’sloftyattitudetowardscientificresearch—andthescientists’co
TheGreek’sloftyattitudetowardscientificresearch—andthescientists’co
Forseveralyears,scientistshavebeentestingasubstancecalledinterfero
Forseveralyears,scientistshavebeentestingasubstancecalledinterfero
Assumingthataconstanttravel-timebudget,geographicconstraintsandshor
Assumingthataconstanttravel-timebudget,geographicconstraintsandshor
Assumingthataconstanttravel-timebudget,geographicconstraintsandshor
Assumingthataconstanttravel-timebudget,geographicconstraintsandshor
随机试题
Whichofthefollowingisastativeverb(静态动词)?A、Step.B、Push.C、Run.D、Underst
[originaltext]W:Ifoundanexpensive-lookingringinthelockerroomthismorn
[originaltext]Anapplication,orapp,developedbyresearchersattheUnive
设A,B是n阶方阵,A≠0且AB=0,则(). A.|B|=0或|A|=
扩展法是鉴别词和短语的一个重要标准,“黑板”可以扩展为“黑的板”、“北京大学”可
小明是刚转入市一小的五年级学生,他在原学校时成绩优秀,总是班里的第一名,但来到新
按公路的使用任务、功能和适应的交通量对公路分级,可分为()。A.高速公路,一
国家机关及其公职人员在贯彻和实施法律的活动时要严格依照法定职权和程序,保证法律的
接种卡介苗后的PPD试验有逐年减弱倾向,一般逐渐消失的时间是A.5~10年 B
根据《危险化学品安全管理条例》的规定,下列关于剧毒化学品运输管理的说法,正确的是
最新回复
(
0
)