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
107
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
TakingRubbishThestretchofthePacificbetweenHawaiiandCaliforniaisvirtuallyempty.Therearenoislands,noshippin
TakingRubbishThestretchofthePacificbetweenHawaiiandCaliforniaisvirtuallyempty.Therearenoislands,noshippin
ThinJustByWayofSatisfyVaingloryNowomancanbetoorichortoothin.ThissayingoftenattributedtothelateDuchess
TheRelationshipBetweenOurPersonalityandSiblingsForalongtime,researchershavetriedtonaildownjustwhatshapes
Attemptstounderstandtherelationshipbetweensocialbehaviorandhealthhavetheirorigininhistory.Dubos(1969)suggested
Attemptstounderstandtherelationshipbetweensocialbehaviorandhealthhavetheirorigininhistory.Dubos(1969)suggested
Itmayturnoutthatthe"digitaldivide"—oneofthemostfashionablepoliticalslogansofrecentyearsislargelyfiction.Asy
Untilrecently,mostpopulationgrowthhasoccurredinrelativelydenseurbanenvironments.In【C1】______words,evenifwewerew
随机试题
关于路基雨期施工的说法,不正确的是()。
女性最常见的骨转移性肿瘤主要来源于()
色氨酸是
金融工具是指金融活动中以书面形式发行和流通的各种具有法律效力的凭证,它的特征有()。
在施工合同履行过程中,施工单位接受竣工付款证书后,应当认为()。
下列设备中,属于气体灭火系统的是()。
山东省是少数民族散杂居省份,世居少数民族有回族、满族、蒙古族。()
遵义会议是我们党历史上一次伟大的转折点。关于遵义会议,下列说法错误的是()。
显示器的主要技术指标之一是____________。
A、Buyanewspaper.B、Askfordirections.C、Standnearthestore.D、Helpothersmoreoften.B男士说:“但愿我能找到那个新的杂货店。它一定就在这附近。”女士回答道:“
最新回复
(
0
)