初二上学期英语课文我要第三模块第二单元的课文.谁能给我?要外研版的!分好说.半小时之内!发上来!
初二上学期英语课文
我要第三模块第二单元的课文.谁能给我?要外研版的!分好说.半小时之内!发上来!
初二上学期英语课文我要第三模块第二单元的课文.谁能给我?要外研版的!分好说.半小时之内!发上来!
初二上学期英语课文
我要第三模块第二单元的课文.谁能给我?要外研版的!分好说.半小时之内!发上来!
ScientiststhinkthattherehasbeenlifeonEarthformillionsofyears.However,wehaven'tfoundlifeonotherplanetsyet.Whynot?
TheEarthisaplaneanditgoesaroundtheSun.SevenotherplanetsalsogoaroundtheSun.Noneofthemhasanenvironmentwithair,sopeopleandthingscannotgrow,TheSunanditsplanetsarecalledthesolarsystem.Thesolarsystemisasmallpartofourgalaxy.
Thestarsweseeatnightarethesunsinothersolarsystems.Therearemorethan200billionstarsinourgalaxy,calledtheMilkyWay,andourSunisonlyoneofthem.
Butscientistshavediscoveredmanyothergalaxiesintheuniverse.Theyarealongwayawayandtheirlighthastravelledformanyyearstoreachus.Itishardtounderdtandhowlargetheuniversis.
Sinentistshavesentlostofspacecrafttolookatotherplanetsinoursolarsystem,andsomespacecrafthavegonebeyondthesolarsystem.Howener,noonehasdiscoveredanylifeinspaceyet.
Butwhyhansnoonefromohterplanetssentusamessage?Havetheytriedtosendinformationtous?Withsomanyatarsintheuniverse,arewealone,oristherelifeoutthereinspace?Wedon'tknow...yet.