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
Before there were black holes and stars and galaxies, the universe went through a period just after the big bang known as the Da
Before there were black holes and stars and galaxies, the universe went through a period just after the big bang known as the Da
admin
2015-02-12
60
问题
Before there were black holes and stars and galaxies, the universe went through a period just after the big bang known as the Dark Age of the Universe that lasted until evolving structure ultimately led to the first stars. Jordi Miralda-Escude, an astronomer at Ohio State University in Columbus, describes the Dark Age as the epoch when the universe had become completely dark as it gradually cooled following the big bang and "all the matter that forms us today was spread around space and uniformly distributed."
Little differences in the density of matter that had been present since the beginning of the universe gradually grew larger as a result of gravitational attraction. Eventually the density was large enough to cause a gravitational collapse and the first star was born. These first stars, according to Miralda-Escude, were likely quite massive and when they exploded as supernovae they littered the universe with atoms heavier than hydrogen and helium which were required for the formation of planets in the next generation of stars. "In the beginning, the universe contained only hydrogen and helium, but at the present time planets like the Earth are made of heavier atoms," he said. "They all come from stars. So all the atomic nuclei on which life is based—except for hydrogen—were made in stars."
One of the curiosities Miralda-Escude is trying to pin down is when the first star was born after the Dark Age began. "Imagine you are an observer floating in space and looking through the universe in the Dark Age and around you it is completely dark," he said. "The temperature is decreasing so the cosmic background light has all shifted to infrared wavelengths, and there is nothing in visual light. Then, all of a sudden you see the first star appear in the distance."
Miralda-Escude estimates that the first visible star probably appeared about 75 million years after the big bang. Today, the universe is nearly 14 billion years old and contains billions of galaxies, each one with billions of stars.
What caused the differences in the density of matter to grow larger?
选项
A、Gravitational attraction.
B、Little differences in the density of matter.
C、The big bang.
D、Massive stars.
答案
A
解析
属事实细节题。第二段首句告诉我们,由于引力,物质密度的差别逐渐增大。
转载请注明原文地址:https://kaotiyun.com/show/2E74777K
0
考研英语一
相关试题推荐
TheGeneVariationCausesanAutismCommongeneticvariationsthatcancontributetoautismhavebeenreliablyidentifiedfo
TeachtheKidHowtoTalktoImproveSpeechChildrenwillhavelessonsonhowtospeakproperEnglishinformalsettings,un
CharacteristicMedicalTreatmentItisstartlinghowcommonthesechronicdiseaseslikecancerarewhenonelooksatthenum
TheRelationshipBetweenOurPersonalityandSiblingsForalongtime,researchershavetriedtonaildownjustwhatshapes
TheRelationshipBetweenOurPersonalityandSiblingsForalongtime,researchershavetriedtonaildownjustwhatshapes
TheOceanPollutesAdecisionbytheLondon-basedInternationalMaritimeOrganization(IMO)establishesanemissionscontrol
Attemptstounderstandtherelationshipbetweensocialbehaviorandhealthhavetheirorigininhistory.Dubos(1969)suggested
Throughoutthe19thcenturyandintothe20th,citizensoftheUnitedStatesmaintainedabiasagainstbigcities.Mostlivedon
Itisonlyinrecentyearsthatwehaverecognizedthat_____.Fromparagraph1wecaninferthatitisnowpossibleforwomen
Untilrecently,mostpopulationgrowthhasoccurredinrelativelydenseurbanenvironments.In【C1】______words,evenifwewerew
随机试题
Whatproductdotheysell?
胆红素主要来源于()。
中国人最常见的病毒性肝炎是()。
计入产品成本的费用包括()。
根据下列资料回答86~90题2007年全国粮食种植面积10533万公顷,比上半年增加70万公顷;棉花种植面积559公顷,增加7公顷;油料种植面积1094万公顷,减少60万公顷;糖料种植面积167万公顷,增加10万公顷。全国2007年粮食产量50
(2016河南)某人走失了一只小狗,于是开车沿路寻找,突然发现小狗沿路边往反方向走,车继续行30秒后,他下车去追小狗,如果他的速度比小狗快3倍、比车慢3/4,问他追上小狗需要多长时间?
甲是公安局局长,乙是公安局刑侦大队大队长,乙有一套闲置房子欲以市价1000万元出售,甲得知后让乙以500万元卖给自己,乙不得不照办。1个月后甲调到外省,乙极其后悔。关于本案下列说法正确的是()
国际格局走向多极化,是时代进步的要求,符合各国人民的利益。世界多极化格局有利于
______isaprincipalrepresentativeofTheLondonSchool.
书法和绘画在早期的皇权时代,书法和绘画是上层社会最为尊崇的艺术,大部分是由业余爱好者创作的,这些业余爱好者通常是有充足的闲暇时间来对笔法和画法进行技术和鉴赏完善的贵族和士大夫。书法被认为是最高等、最纯洁的绘画形式。晋朝时,人们开始欣赏绘画的美丽,
最新回复
(
0
)